JP2756136B2 - Method for manufacturing semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the bulking of crystal grain at a neck part, and prevent the generation of neck-cut by connecting one end portion of a bonding wire of high purity gold containing specified wt.% of germanium and calcium to the outer terminal of a semiconductor chip, and connecting the other end-portion to a lead. CONSTITUTION:The connection side of a covered wire 5 to a first bonding side is subjected to conduction connection by ball bonding by forming a ball 5A1; on the outer hand, by thermosonic bonding, the connection to a second bonding side is subjected to conduction connection as a second bonding part 5A2, without previously eliminating a covered film 58. Material of a gold wire 5A of the covered wire 5 is high purity gold (Au) of e.g. 99.99wt.% or more which contains 0.03-0.3wt.% germanium-(Ge) and 0.0005-0.01wt.% calcium-(Ca). Thereby the bulking of crystal grain at a neck part at the time of ball forma tion can be prevented, and the generation of neck-cut can be prevented.

Description

The present invention relates to a technique for manufacturing a semiconductor device using a bonding wire for a semiconductor element, and more particularly, to a so-called ball bonding method for connecting a chip electrode and a lead of the semiconductor element. The present invention relates to a semiconductor device manufacturing technique for performing wire bonding using a method.

[Conventional technology]

As a bonding wire used for manufacturing a semiconductor device, a wire made of gold (Au) is widely used. In particular, a so-called ball bonding technique has been widely employed for electrically connecting electrodes of a semiconductor chip and inner leads in a resin-sealed semiconductor device. In this technology, a gold ball is formed at the tip of the supply side of the gold wire, the gold ball is bonded to the electrode of the semiconductor chip by using thermocompression bonding or thermocompression together with ultrasonic vibration, and the rear end side of the gold wire is heated. This is a technique in which ultrasonic vibration is used in combination with compression bonding or thermocompression bonding to join the inner leads to make electrical connection.

By the way, the gold wire used for the resin-encapsulated semiconductor device has a total purity of gold (Au) of 99.99% by weight or more, intentional additive element and inevitable element after the purification of gold is 0.01% by weight or less. It has a certain composition. The purpose of intentionally adding an element to a gold wire is mainly to improve mechanical properties such as breaking load and elongation, improve heat resistance, and improve bonding properties.

Conventionally, gold wire is intentionally germanium (Ge),
An example of modifying and improving a gold wire by adding calcium (Ca) is disclosed in, for example,
-76556 and JP-A-56-96844.

[Problems to be solved by the invention]

The above-described conventional technique is characterized by deterioration of mechanical strength caused by coarsening of crystal grains in a neck portion directly above the ball due to heat influence during formation of a gold wire ball, disconnection or reduction in life of the neck portion in a temperature cycle test, and fatigue disconnection. Or the instability of the bond loop shape of the gold wire due to lack of mechanical strength, short-circuiting due to contact between adjacent wires, short-circuiting due to contact between the wire and the end of the semiconductor chip, etc. However, no satisfactory and effective improvements have yet been obtained.

Then, the present inventors conducted further intensive research and found that the following was found.

 One is the problem of the fatigue life of gold wires.

That is, when the resin-encapsulated semiconductor device undergoes a temperature change, the gold wire is pulled and receives a strong stress due to the difference in the coefficient of thermal expansion between the gold wire and the resin that are in close contact with each other inside the semiconductor device. By repeatedly receiving the temperature change (temperature cycle), it has been found that in the conventional gold wire, stress is concentrated on the neck portion immediately above the ball when ball bonding is performed, and fatigue disconnection easily occurs. This means that when forming a ball at the tip of a gold wire by a method such as arc discharge or hydrogen flame,
The biggest factor is considered to be that the neck portion is affected by heat and the crystal grains in that portion are coarsened and the difference in crystal grain size from the portion following the neck portion occurs.

However, in the above-described conventional technology, the content of elements such as germanium and calcium contained in the gold wire was not optimal, and thus it cannot be said that the prevention of neck breakage has always been successful.

Second, there is a problem of securing mechanical properties such as breaking load and elongation of the gold wire.

That is, in the conventional gold wire, the elongation rate of the gold wire is increased by performing heat treatment, and the stress in the neck portion is removed.
Increasing the elongation rate of the gold wire significantly reduces the breaking load and causes a problem that the bonding operation becomes inferior.

Third, there is a problem associated with long-distance bonding and thinning.

That is, phenomena such as a reduction in the distance between adjacent bonding wires due to the recent increase in the density of semiconductor devices and an increase in the distance between the external terminals of the semiconductor chip and the inner leads are added. The problem of short-circuit due to contact between adjacent wires, or short-circuit due to contact between the wires and the end of the semiconductor chip, which is caused by the flow of the resin material, easily occurs.

In addition, since long-distance bonding is required in a multi-pin semiconductor device, it is desired to reduce the thickness of the wires and to make the gold balls small.

An object of the present invention is to provide a semiconductor device manufacturing technique capable of extending the fatigue life of a gold wire, preventing a so-called neck break, and improving the reliability of the semiconductor device.

Another object of the present invention is to provide a semiconductor device manufacturing technique suitable for increasing the number of pins (increase in the number of terminals) and increasing the degree of integration of the semiconductor device.

Another object of the present invention is to provide a breaking load of a gold wire,
An object of the present invention is to provide a semiconductor device manufacturing technique capable of securing mechanical properties such as elongation.

Still another object of the present invention is to provide a technique for manufacturing a semiconductor device suitable for long-distance bonding.

Still another object of the present invention is to provide a semiconductor device manufacturing technique suitable for realizing thinning.

Still another object of the present invention is to provide a semiconductor device manufacturing technique suitable for performing ball bonding of a gold wire.

Still another object of the present invention is to provide a semiconductor device manufacturing technique suitable for realizing a small ball at the time of performing ball bonding of a gold wire.

Still another object of the present invention is to provide a semiconductor device manufacturing technique capable of improving the reliability of wire bonding.

The above and other objects and novel features of the present invention are as follows.
It will be apparent from the description of this specification and the accompanying drawings.

[Means for solving the problem]

The outline of a representative invention among the inventions disclosed in the present application will be briefly described as follows.

That is, the manufacturing method of the semiconductor device of the present invention is 99.99
Wire bonding is performed using a bonding wire containing 0.03 to 0.3% by weight of germanium and 0.0005 to 0.01% by weight of calcium in high purity gold of at least% by weight.

The contents of germanium and calcium are each 0.05-
It can be 0.15% by weight and 0.001 to 0.003% by weight.

The bonding wire used in the present invention is a coated wire covered with a coating film made of an insulating material to which a predetermined amount of a coloring agent has been added.

Further, a heat-resistant polyurethane resin can be used as the insulating material.

[Action]

According to the above-described semiconductor device manufacturing technique of the present invention, 0.03 to 0.3% by weight of germanium and 0.0005 to 0.01% by weight of calcium to be contained in a bonding wire are combined with each other and with high-purity gold of 99.99% by weight or more. By acting synergistically, it is possible to effectively extend the fatigue life of the gold wire, to prevent coarsening of crystal grains at the neck portion during ball formation, and to prevent the occurrence of neck breakage. Thereby, the reliability of the semiconductor device can be improved.

In addition, by covering the semiconductor element ball of the present invention with an insulating material, defects such as short-circuiting between wires due to contact between wires, chip short-circuiting due to contact with a chip end, and tab short-circuiting due to contact with a tab. This eliminates the occurrence of long-distance bonding and thinning.

Further, the bonding wire for a semiconductor element of the present invention has a breaking load of 15 to 30 kg / mm ² and an elongation of 10 to 25%, so that the mechanical properties are improved and excellent bonding performance is exhibited. Can be.

In addition, the heat-resistant polyurethane used for coating the gold wire in the present invention can be bonded by decomposing its urethane bond even at the bonding temperature during normal wire bonding or ultrasonic vibration energy. Reliable bonding can be obtained by using both pressure bonding and ultrasonic vibration or by ultrasonic vibration. In this case, if local heating of the bonding site is used together, more reliable wire bonding can be performed. Then, by adding a coloring agent to the coating film, it is possible to visually confirm melting and peeling of the coating film.

Next, the heat-resistant polyurethane used for the coating film of the coated wire in the present invention will be further described. The heat-resistant polyurethane is obtained by reacting a polyol component and an isocyanate, and has a structural unit derived from terephthalic acid in a molecular skeleton. This heat-resistant polyurethane is obtained by using a polymer component mainly composed of a terephthalic acid-based polyol containing active hydrogen, and isocyanate. Here, “consists of a main component” is intended to include a case where the whole is composed only of a main component.

Terephthalic acid-based polyol containing the active hydrogen, terephthalic acid and polyhydric alcohol, using OH / COO
It can be obtained by a conventional esterification reaction with H = 1.2-30 and a reaction temperature of 70-250 ° C. In general, those having an average molecular weight of 30 to 10,000 and having about 100 to 500 hydroxyl groups and having hydroxyl groups at both ends of the molecular difference are used.

Raw materials constituting such a terephthalic acid-based polyol include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol,
Hexane glycol, butane glycol, glycerin,
Aliphatic glycols such as trimethylolpropane, hexanetriol and pentaerythritol;
In addition, polyhydric alcohols such as 1,4-dimethylolbenzene can be mentioned. In particular, it is preferable to use ethylene glycol, propylene glycol, and glycerin.

Terephthalic acid is used as the dicarboxylic acid. If necessary, amic acid and imidic acid can be used in combination.

 The structural formula of the imidic acid is as follows.

Further, dibasic acids such as isophthalic acid, orthophthalic acid, succinic acid, adipic acid and sebacic acid, and 1,2,3,4-butanetetracarboxylic acid, cyclopentanetetracarboxylic acid, ethylene Polybasic acids such as tetracarboxylic acid, pyromellitic acid and trimellitic acid may be used in combination.

As the isocyanate to be reacted with the terephthalic acid-based polyol, the isocyanate group of a polyvalent isocyanate having at least two isocyanate groups in one molecule such as toluylene diisocyanate and xylylene diisocyanate is converted into a compound having active hydrogen, for example, phenol. , Caprolactam and those blocked with methyl ethyl ketone oxime.
Such isocyanates are stabilized. Further, a compound obtained by reacting the above polyvalent isocyanate compound with a polyhydric alcohol such as trimethylolpropane, hexanetriol, or butanediol and blocking with a compound having active hydrogen is also used.

Examples of the isocyanate compound, manufactured by Nippon Polyurethane Co., Millionate MS-50, Coronate 2501,250
3,2505, Coronate AP-St, Death Module CT-St and the like. It is preferable to use a polyisocyanate having a molecular weight of about 300 to 10,000.

The present invention provides a coating composition in which a gold wire of a wire body is insulated by forming a coating composition using the above-described raw materials, coating the coating composition on a gold wire of the wire body, and forming a film having a thickness of several μm. A semiconductor device is manufactured using wires.

The coating composition used in the present invention is prepared by adding an isocyanate group in the stabilized isocyanate in an amount of 0.4 to 4.0 equivalents, preferably 0.9 to 2.0 equivalents, and a required amount of an effect-promoting catalyst per equivalent of the hydroxyl group of the polyol component to induce an appropriate amount of the catalyst. It can be obtained by adding a solvent (phenols, glycol ethers, naphtha, etc.) to make the solid content usually 10 to 30% by weight. At this time, if necessary, an appropriate amount of an additive such as an appearance improving agent and a dye can be blended.

In the present invention, the isocyanate group of the stabilized isocyanate is 0.4 to 0.4 per hydroxyl equivalent of the polyol component.
The reason for adding 4.0 equivalents is that if it is less than 0.4 equivalents, the crazing characteristics of the resulting insulated wire will decrease, while the wear resistance of the coating film exceeding 4.0 equivalents will be inferior. The effect promoting catalyst added at the time of preparing the coating composition is preferably 0.1 to 10 parts by weight per 100 parts by weight of the polyol component. If this is less than 0.1 part by weight, the tendency of the film-forming ability to deteriorate with the decrease in curing acceleration and curing is seen,
Conversely, if the amount exceeds 10 parts by weight, the heat-resistant polyurethane bonding wire obtained will have reduced thermal degradation characteristics.

Examples of the curing acceleration catalyst include metal carboxylic acids, amino acids, and phenolic acids. Specific examples include naphthenic acid, octenoic acid, zinc salts of persatic acid, iron salts, copper salts, manganese salts, and cobalt salts. , Tin salts and 1,8 diazabicyclo (5,4,0) undecene-7,2,4,6 tris (dimethylaminomethyl) phenol.

The insulative coated bonding wire used in the present invention can be obtained by applying the coating composition as described above on the surface of the gold wire of the wire body and baking it with a conventional baking coating device.

The coating and baking conditions vary depending on the amounts of the polyol component, the stabilized isocyanate, the polymerization initiator and the curing accelerator, but are usually about 200 to 300 ° C. for about 4 to 100 seconds. In short, baking is performed at a temperature and for a time sufficient to substantially complete the curing reaction of the coating composition.

The insulating coated bonding wire thus obtained has an insulating coating film made of heat-resistant polyurethane formed on the outer periphery of the gold wire of the wire body made of gold, copper or aluminum.

In this case, a composite coating film structure using the insulating coating film and another insulating coating film in combination may be used. This composite coating film, after forming the insulating coating film of the present invention described above,
It is obtained by further forming a second insulating coating film on the insulating coating film. In this case, the thickness of the second insulating coating film is not more than twice the thickness of the insulating coating film of the present invention,
Preferably, it is set to 0.5 times or less. Examples of the material for forming the second insulating coating film include a polyamide resin, a special polyester resin, and a special epoxy resin.

Hereinafter, the configuration and operation of the present invention will be described together with an example in which the present invention is applied to a semiconductor manufacturing technique used for a resin-encapsulated semiconductor device.

In all the drawings for describing the embodiments, components having the same function are denoted by the same reference numerals, and redundant description thereof will be omitted.

Embodiment 1 FIG. 1 is a half sectional view of a resin-sealed semiconductor device using a bonding wire according to an embodiment of the present invention, FIG. 2 is a schematic enlarged sectional view of a wire bonding portion, and FIG. FIG. 4 is a schematic configuration diagram of a wire bonding apparatus that can be used in the present invention, FIG. 4 is a perspective view of a main part thereof, FIG. 5 is a partial cross-sectional view showing a specific configuration of a main part of the wire bonding apparatus, and FIG. The figure is a plan view as seen from the direction of arrow VI in FIG.
FIG. 8 is a sectional view taken along the line VII-VII of FIG. 6, FIG. 8 is a schematic diagram showing the principle of ball formation, FIG. 9 is an exploded perspective view of the spool of the wire bonding apparatus, FIG.
FIG. 11 is an enlarged perspective view of a main part of the spool, FIG. 11 is a schematic plan view of a local heating unit for wire bonding, FIG. 12 is a plan view showing an example of wire bonding, and FIG. FIG. 14 is an enlarged partial cross-sectional view showing a chip short-circuit state, FIG. 15 is a partial cross-sectional view showing a tab touch state of a covering wire, and FIG.
FIG. 17 is an enlarged partial cross-sectional view showing a tab short state, FIG. 17 is a graph showing the short-circuit rate between the semiconductor chip and the coated wire with respect to the temperature cycle in the present invention, and FIG. 6 is a graph showing the short-circuit rate with the graph.

The semiconductor device of this embodiment is an example of a resin-encapsulated semiconductor device 1, and its semiconductor chip 2 can be configured as a semiconductor integrated circuit element such as a memory, a gate array, a microprocessor, and a MOS logic.

The semiconductor chip 2 includes a substrate 2A made of, for example, silicon (Si) and a passivation film 2B on the top thereof.
And an external terminal (bonding pad) 2C exposed from the opening of the passivation film 2B. The semiconductor chip 2 is joined to the tab 3A of the lead 3 by a joining material 4 such as a silver (Ag) paste.

On the other hand, the external terminals 2C of the semiconductor chip 2 are electrically connected to the inner leads 3B of the leads 3 by conductive wires. In this embodiment, the covering wires 5 are used as the conductive wires. This coated wire 5 is a gold wire
It has a structure in which an insulating coating film 5B is applied to the surface of 5A.

The material of the gold wire 5A of the covering wire 5 is, for example, 99.99
Gold (Au) with a high purity of at least 0.005% by weight contains 0.03-0.3% by weight of germanium (Ge) and 0.0005-0.01% by weight of calcium (Ca).
It is contained in the range of 01 to 0.01% by weight.

The contents of germanium and calcium are each 0.
Better results can be obtained when the content is 0.05 to 0.15% by weight and 0.001 to 0.003% by weight.

The germanium is the elongation of the gold wire 5A, the breaking load,
It is a useful element that can increase the yield strength and can prevent stress concentration at the neck by increasing its elongation. However, if the content is less than 0.03% by weight, the effect of improving the elongation and the like is small and practical Does not reach.

On the other hand, if the germanium content exceeds 0.03% by weight, the ball shape during bonding is not stable and the ball hardness becomes too large, resulting in poor connection and chip breakage, which is not practical.

However, the germanium has a useful range (0.03 to 0.
(3% by weight), the recrystallization temperature of the metal wire 5A is lowered, which results in coarsening of the crystal grains at the neck portion during ball formation, which has an adverse effect on the prevention of neck breakage.

Therefore, in the present invention, calcium is used together with germanium.

Calcium is useful for raising the recrystallization temperature of the metal wire 5A to increase the heat resistance and suppressing the coarsening of crystal grains,
It is also a useful element for increasing the breaking load.

However, when the content of calcium is less than 0.0005% by weight, the usefulness is low, and when the content exceeds 0.01% by weight,
The ball shape during bonding is not stable and the ball hardness is large, causing chip cracks, etc., and also causing the elongation rate of the metal wire 5A to decrease, causing the drawability to decrease, and the practicality. Inferior to

Therefore, the contents of germanium and calcium are preferably in the above-mentioned range or in the optimum range.

The coating film 5B of the coating wire 5 is obtained by reacting a polyol component with an isocyanate, as described above and in detail later, and is made of a heat-resistant polyurethane having a molecular skeleton containing a structural unit derived from terephthalic acid. It becomes.

The coated wire 5 of the present embodiment has its first (first =
1St) The bonding side, that is, the connection side between the external terminal 2C of the semiconductor chip 2 and one end of the covering wire 5 is a ball 5A ₁
The connection between the second (2 = 2nd) bonding side, that is, the connection between the inner lead 3B of the lead 3 and the other end of the covering wire 5 is made by thermocompression bonding and ultrasonic vibration while the conductive connection is made by ball bonding due to the formation of It is conductively connected as second bonding portion 5A ₂ without prior removal of the coating film 5B by a so-called thermo-sonic bonding.

The semiconductor chip 2 thus pellet-bonded and wire-bonded and the tab of the lead 3 are formed.
3A, the inner lead 3B, and the covering wire 5 are sealed with a resin material 6 such as an epoxy resin, for example.
Only the outer leads 3C protrude outside the resin material 6.

Next, the configuration and operation of the wire bonding apparatus for bonding the covered wire 5 in the present embodiment will be described mainly with reference to FIGS.

The wire bonding apparatus is configured as a so-called ball bonding apparatus. The ball bonding apparatus is configured to supply the covering wire 5 wound around the spool 11 to the bonding section 12 as shown in FIG. Have been.

That is, the supply of the covering wire 5 from the spool 11 to the bonding section 12 is performed through the tensioner 13, the wire guide member 14, the wire clamper 15, and the bonding tool (capillary) 16.

The resin-sealed semiconductor device 1 before resin sealing, which is configured as shown in FIG. 3 and FIG. Then, as shown in FIG. 3, the resin-encapsulated semiconductor device 1 before resin encapsulation is mounted on a semiconductor device support base (semiconductor device mounting table) 17 of a bonding apparatus.
It is supported by.

An external terminal 2C of the semiconductor chip 2 has a coating wire 5
Covering layer 5B at one end connects the ball 5A _1, which is formed of gold wire 5A which is exposed is removed. Ball 5A ₁ is adapted to compared to the diameter of gold wire 5A is composed of a large diameter, for example, about 2 to 3 times. The inner lead 3B of the lead 3 is connected to a gold wire 5A at the other end of the covered wire 5 that is exposed by breaking the coating film 5B at the other end of the covered wire 5 at the connection portion. That is, the other end side of the covering wire 5 is configured so that substantially only the covering film 5B at the connection portion with the lead 3 is removed, and the other covering film 5B remains. The coating film 5B on the other end side of the coating wire 5
As will be described later, the destruction can be performed by ultrasonic vibration, appropriate pressurization, and appropriate heating (energy) provided by the bonding tool 16.

As described above, in the resin-encapsulated semiconductor device 1 using the covering wire 5, the ball 5A formed by the gold wire 5A on one end side of the covering wire 5 is attached to the external terminal 2C of the semiconductor chip 2.
₁ and contact the inner lead 3B of the lead 3 with the gold wire on the other end side of the coated wire 5 in which the coating film 5B of the contact portion is broken.
By connecting 5A, the size of the ball 5A ₁ is large, so that the contact area between the external terminal 2C of the semiconductor chip 2 and the gold wire 5A of the coating wire 5 can be increased, and the bondability between the two can be improved. At the same time, the other end of the covered wire 5 other than the portion connected to the inner lead portion 3B of the lead 3 is covered with a covering film 5B, and the other end of the covered wire 5 adjacent to the other end of the covered wire 5 Can be reduced, so that the interval between the leads 3 can be reduced, and the number of terminals of the resin-encapsulated semiconductor device 1 (so-called multi-pin) can be increased.

The feed direction of the distal end portion of the bonding tool 16 and the insulated wire 5 (ball 5A ₁ forming portion), as shown in the FIGS. 3 and 4, during the formation of the ball 5A _1, is coated on the covering member 18A It is configured as follows. The covering member 18A is configured to rotate in the direction of arrow A shown in FIG. That is, the covering member 18A is connected to the ball 5A ₁
At the time of forming, the bonding tool 16 is inserted from the tool insertion opening 18B by a rotation operation in the direction of arrow A, and is covered.

This covering member 18A is shown in FIG. 5 (partial sectional view showing a specific configuration, corresponding to a section taken along the line VV in FIG. 6), FIG. 6 (from the direction of arrow VI in FIG. 5). FIG. 7 (a cross-sectional view taken along the line VII-VII in FIG. 6).
It is configured as shown in FIG. Covering member 18A is described below, during the formation of the ball 5A _1, the coating film 5B in the bonding portion 12 in blowing the melt up the coating film 5B are configured so as not to scatter. In addition, the coating member 18A is configured to easily hold an antioxidant coating gas atmosphere (shield gas atmosphere) when the gold wire 5A of the coating wire 5 is formed of an easily oxidizable material such as Cu or Al. I have. Covering member 18
A is formed of, for example, stainless steel. Further, the covering member 18A is a state of formation of balls 5A _1, etc. coated wire 5 so the operator can confirm, may be formed of a glass material having transparency.

As shown in FIGS. 3, 4 and 5, an electric torch (arc electrode) 18D is provided on the bottom of the covering member 18A.
Is provided. The electric torch 18D is brought close to the gold wire 5A on the tip side on the supply side of the covering wire 5 as shown in FIG. 8 (a schematic configuration diagram illustrating the principle of ball formation), and an arc Ac is generated between the two. It is configured to form a ball 5A ₁ Te. The electric torch 18D is formed of, for example, tungsten (W) that can withstand high temperatures.

Electric torch 18D is a suction device 1 made of conductive material
It is connected to the arc generator 20 via a suction pipe 18E to the pipe 9. The suction tube 18E is made of, for example, stainless steel, and fixes the electric torch 18D with an adhesive metal layer such as an Ag-Cu brazing material interposed therebetween. The suction tube 18E is fixed to the covering member 18A with the holding member 18F interposed therebetween.
That is, the electric torch 18D, the suction tube 18E and the covering member 18A
And are integrally formed.

The electric torch 18D, as can be separated from the coated wire proximate the distal end of the supply side of the 5, the supply path of the covered wire 5 during the bonding process when forming a ball 5A ₁ as described above, in FIG. 4 It is configured to be able to move in the direction of arrow A shown. The moving device for moving the electric torch 18D mainly includes a support member 18G for supporting the electric torch 18D with a suction pipe 18E and an insulating member 18H interposed therebetween,
It comprises a crankshaft 18I for rotating 18G in the direction of arrow A, and a drive source 18K for rotating this crankshaft 18I. The rotation of the crankshaft 18I is performed by the movement of the shaft 18J of the drive source 18K in the direction of the arrow B connected to the crank portion. Drive source 18K is formed of, for example, an electromagnetic solenoid. Although not shown, the crankshaft 18I is rotatably supported by the bonding apparatus main body. In addition,
The movement of the electric torch 18D and the movement of the covering member 18A are substantially the same because they are integrally formed.

As shown in FIG. 4, the arc generator 20 mainly includes a capacitor C ₁ , a storage capacitor C ₂ , a thyristor D for generating an arc activated by a trigger, and a resistor R. DC power supply DC is, for example, -1000 to -3000 [V]
It is configured to supply a voltage of a negative polarity of the order. The DC power supply DC is connected to the electric torch 18D via a thyristor D, a resistor R and the like. The reference potential GND is, for example, a ground potential (= 0 [V]). V is a voltmeter and A is an ammeter.

As will be described in detail later, the gold wire 5A of the covering wire 5 has an end wound around the spool 11 connected to the reference potential GND. As a result, when forming a ball 5A ₁ to the distal end portion of the covered wire 5 with electric torch 18D, FIG. 3, as shown in FIG. 4 and FIG. 8, an electric torch 18D negative potential (-), coated wire The gold wire 5A at the end in the supply direction of 5 can be set to a positive potential (+).

Thus, in the bonding apparatus to generate arc Ac, forming a ball 5A ₁ to the distal end portion of the covered wire 5 between the gold wire 5A and the arc electrode 18D of the distal end portion of the covered wire 5, gold coated wire 5 By connecting the wire 5A to a positive potential (+) and connecting the electric torch 18D to a negative potential (-), the arc Ac generated between the gold wire 5A of the coated wire 5 and the electric torch 18D is generated. Since the position can be stabilized as compared with the case of the opposite polarity, it is possible to reduce the arc Ac from creeping toward the rear end side of the gold wire 5A of the covering wire 5. The reduction in the crawling of the arc Ac can reduce the melting of the coating film 5B of the coating wire 5 and prevent the generation of spheres of the insulating coating film.

It should be noted that the present invention provides a reference potential GND such that the gold wire 5A of the covering wire 5 has a positive potential with respect to the electric torch 18D.
The gold wire 5A of the covering wire 5 may be connected to a higher or lower voltage.

The spool 11 around which the coating wire 5 is wound,
It is configured as shown in FIGS. 4 and 9 (an exploded perspective view of a main part). The spool 11 is formed by, for example, performing alumite treatment on a surface of a cylindrical aluminum metal. The alumite treatment is performed to improve mechanical strength and prevent scratches. As described above, the spool 11 has an insulating property because it is anodized.

The spool 11 is attached to a spool holder 21,
The spool holder 21 is attached to the bonding apparatus main body 10 by a rotation shaft 21A.

The spool holder 21 is made of, for example, stainless steel so that at least a part thereof has conductivity.

The spool 11 is provided with a connection terminal 11A, as shown in FIGS. 9 and 10 (enlarged perspective views of essential parts). The connection terminal 11A is provided in a dotted shape on a side surface portion (flange) of the spool 11 that comes into contact with a conductive portion of the spool holder 21.

As shown in FIG. 10, the connection terminal 11A is configured such that a conductor 11Ab is provided on an insulator 11Aa, and a connection metal part 11Ac is provided on the conductor 11Ab. The insulator 11Aa is electrically separated from the conductor 11Ab and the spool 11 reliably, and furthermore, is made of, for example, a polyimide resin so as to have an appropriate elasticity so that the connection metal portion 11Ac can be reliably brought into contact with the spool holder 21. Form. The conductor 11Ab includes a connection metal part 11Ac for connecting the gold wire 5A of the covering wire 5 and a spool holder.
It is made of, for example, a Cu foil so that the connection metal portion 11Ac in contact with 21 can be reliably connected. The connection metal part 11Ac is formed of a conductive paste, solder, or the like.

The connection terminal 11A has a notch formed in the side surface (flange) of the spool 11 and a gold wire 5A at the end of the covering wire 5 on the opposite side to the side supplied to the bonding portion 12,
That is, it is configured to connect the gold wire 5A at the winding start end of the covering wire 5. The gold wire 5A is connected to the connection terminal 11A by the connection metal part 11Ac. The coating film 5B on the surface of the gold wire 5A at the beginning of winding of the coating wire 5 is
Heat or remove chemically. The connection terminal 11A, that is, the gold wire 5A of the covering wire 5 is connected to the reference potential GND through the spool holder 21, its rotating shaft 21A and the bonding apparatus main body 10. The reference potential GND is the same potential as the reference potential GND of the arc generator 20.

In this manner, the spool 11 is provided with the connection terminal 11A for connection to the reference potential GND, and the connection terminal is connected to the gold wire 5A at the start end of the covering wire 5 so that the reference wire is passed through the spool holder 21 or the like. Since it can be connected to the potential GND, the gold wire 5A of the covering wire 5 can be reliably connected to the reference potential GND.

The gold wire 5A of the covering wire 5 is connected to the reference potential GND.
By being connected to, at the time of formation of the ball 5A _1, sufficiently securing a potential difference between the electric torch 18D and gold wire 5A of coated wire 5 on the supply side, arcing Ac can be improved since, it is possible to reliably form a ball 5A _1.

As shown in FIGS. 3 and 4, the bonding tool 16 is supported by a bonding head (digital bonding head) 22 via a bonding arm 16A. Although not shown, the bonding arm 16A has a built-in ultrasonic vibration device, and is configured to ultrasonically vibrate the bonding tool 16. The bonding head 22 is supported by a base 24 with an XY table 23 interposed. The bonding head 22
A moving device capable of moving the bonding arm 16A in the vertical direction (the direction of arrow C) is provided so that the bonding tool 16 can be moved toward and away from the bonding section 12. The moving device mainly includes a guide member 22A, an arm moving member
22B, a female screw member 22C, a male screw member 22D, and a motor 22E. The guide member 22A is configured to move the arm moving member 22B in the direction of arrow C. The motor 22E is configured to rotate the male screw member 22D, move the female screw member 22C fitted with the male screw member 22D in the direction of arrow C by this rotation, and move the arm moving member 22B in the direction of arrow C by this movement. Have been.

Bonding arm 1 supported by arm moving member 22B
6A is configured to rotate around a rotation shaft 22F. The rotation of the bonding arm 16A about the rotation axis 22F is controlled by the elastic member 22G. This elastic member 22G
The rotation control is configured to prevent the bonding unit 12 from being pressed more than necessary when the bonding tool 16 comes into contact with the bonding unit 12, and to prevent damage or destruction of the bonding unit 12. I have.

The wire clamper 15 can hold the covering wire 5 and is configured to control the supply of the covering wire 5. The wire clamper 15 is provided on the bonding arm 16A with the clamper arm 15A interposed.

The wire guide member 14 is configured to guide the covered wire 5 supplied from the spool 11 to the bonding section 12. The wire guide member 14 is provided on the clamper arm 15A.

As shown in FIGS. 3 and 8, in the vicinity of the leading end of the covering wire 5 in the supply direction and in the vicinity of the supply path of the covering wire 5 between the bonding tool 16 and the bonding portion 12, as shown in FIGS. A fluid spray nozzle 18C of the fluid spray device 25 is provided. Fluid spray nozzles 18C, when forming a ball 5A ₁ gold wire 5A of the distal end portion of the supply direction of coated wire 5, fluid Gs from the fluid spray device 25 to the forming portion (gold wires 5A and the coating film 5B) Is configured to be sprayed. Fluid Gs blown out from fluid spray nozzle 18C
As shown in FIG. 8, when forming a ball 5A ₁ gold wire 5A of the distal end portion of the covered wire 5, blow coating film 5B rising melted by heat generated by the arc Ac (5Ba) as It is configured.

The fluid spray nozzle 18C may basically spray the fluid Gs to the tip of the bonding tool 16, that is, the tip of the coating wire 5 as described above. In the present embodiment, the fluid spray nozzle 18C is provided on the coating member 18A. ing. As shown in FIG. 4 to FIG. 7, the fluid spray nozzle 18C is provided with a fluid from the rear end side to the front end side of the coated wire 5 to reduce the melting of the coating film 5B. It is configured to spray Gs. The fluid spray nozzle 18C
Is preferably not attached to the bonding tool 16. When the fluid spray nozzle 18C is attached to the bonding tool 16, the weight of the bonding tool 16 increases,
Since the load of the ultrasonic vibration increases, the bondability of the connection portion decreases.

As the fluid Gs, a gas such as N ₂ , H ₂ , He, Ar, or air is used. As shown in FIG. 8, a fluid spraying device (fluid source) 25 supplies a cooling device 25 A, a flow meter 25 B, The fluid is supplied to the fluid spray nozzle 18C via the pipe 25C.

The cooling device 25A is configured to actively cool the fluid Gs below normal temperature. The cooling device 25A is configured by, for example, an electronic cooling device using the Peltier effect. The fluid transfer pipe 25C is shown in a simplified form in FIG. 8, but is configured to cover at least the space between the cooling device 25A and the supply port of the fluid spray nozzle 18C with a heat insulating material 25D. That is, the heat insulating material 25D is the fluid cooled by the cooling device 25A.
It is configured not to change the temperature of Gs during the movement of the fluid transport pipe 25C (to increase the cooling efficiency).

Further, in the vicinity of the leading end of the coating wire 5 in the supply direction, and at a position facing the fluid spray nozzle 18C around the melted portion of the coating film 5B of the coating wire 5,
A suction tube 18E connected to the suction device 19 is provided. As described above, the suction pipe 18E is also used as a conductor for connecting the electric torch 18D and the arc generator 20, but mainly the melting of the coated wire 5 blown off by the fluid spray noise 18C. It is configured to suck the coated film 5Ba. The coating film 5Ba sucked by the suction tube 18E is
The suction is performed by the suction device 19.

Further, in the present embodiment, only the inner lead 3B of the lead 3 is higher than the other parts in order to more securely bond (second bond) the other end of the covered wire 5 to the inner lead 3B of the lead 3. As shown in FIGS. 2 and 11, a ceramic heater 26 for locally heating to a temperature is provided in a square ring shape. The sign
26A is a power supply line to the rectangular ring-shaped heater 26 for local heating.

Next, the wire bonding method of this embodiment will be briefly described.

First, as shown in FIG. 3, FIG. 4, FIG. 5, and FIG. 8, the bonding tool 16 and the leading end portion of the coating wire 5 protruding toward the pressing surface thereof in the supply direction are coated with a coating member 18A.
Cover with. This coating is performed by moving the coating member 18A in the direction of arrow A by the moving device operated by the driving source 18K. Further, by performing the coating with the coating member 18A, the electric torch 18D, the fluid spray nozzle
18C can be placed near the tip of the coated wire 5 respectively.

Then, as shown in FIG. 8 to generate an arc Ac between the gold wire 5A and the electric torch 18D of the distal end portion of the supply direction of coated wire 5, to form a ball 5A ₁ by the gold wire 5A. By arc Ac heat forming the ball 5A _1,
The insulating coating film 5B at the distal end in the supply direction of the coating wire 5 melts. That is, the coating film 5B at the distal end in the supply direction of the coating wire 5 is removed, and the gold wire 5A is exposed.

Formation of the ball 5A ₁ is carried out in the shortest possible time. Short, yet high energy to form a ball 5A ₁ in (current, each of the higher voltage region), the coating film 5 of the covered wire 5
The melting amount of B becomes smaller. Thus, the ball 5A ₁
Is performed for a short time and with high energy, as described above, stabilizes the generation of the arc Ac, that is, the electric torch D
Is set to a negative potential (-) and the gold wire 5A of the covering wire 5 is set to a positive potential (+).

Then, when forming the ball 5A _1, the covering member 18A
The fluid Gs is sprayed from the fluid spraying device 25 by the fluid spraying nozzle 18C whose position is set together with the coating film 5B in which the coating wire 5 melts.
And the coating film 5B is blown off as shown in FIG. The blown coating film 5Ba is sucked by the suction device 19 through the suction pipe 18E, and is removed out of the system.

The fluid Gs from the fluid spray nozzle 18C is cooled to, for example, about 0 to -10 [° C.] by the cooling device 25A shown in FIG. Fluid Gs from fluid spray nozzle 18C
The lower the temperature is, the smaller the melting amount of the coating film 5B of the coating wire 5 is. That is, the fluid Gs cooled by the cooling device 25A
Can actively cool the gold wire 5A, the coating film 5B, the bonding tool 16 and the like of the coating wire 5, so that the coating film 5B of only the arc Ac generating portion is melted and the other portions are coated. The film 5B is not melted, and as a result, the amount of the coating film 5B that has melted can be reduced.

Next, the covering member 18A and the electric torch 1
8D, and each of the fluid spray nozzles 18C is moved in the direction of arrow A (the direction opposite to the above).

The next, the pressing surface of the bonding tool 16, drawing the ball 5A ₁ formed at the tip portion of the feed direction of the coated wire 5.

Then, in this state, go to approximate the bonding tool 16 to the bonding portion 12, as shown the bonding tool 16 by a broken line in FIG. 2, the ball 5A ₁ formed at the tip portion of the feed direction of the coated wire 5 It is connected to the external terminal 2C of the semiconductor chip 2 (first bonding: 1st). Connection of the ball 5A ₁ is performed in the ultrasonic vibration and / or thermal compression bonding tool 16 (may be either one).

Next, as shown in FIG. 2, the gold wire 5A at the rear end of the covered wire 5 is connected to the inner lead 3B of the lead 3 by the bonding tool 16 (second bonding: 2
nd). The connection on the rear end side of the covered wire 5 is performed by ultrasonic vibration and thermocompression bonding of the bonding tool 16 (the former may be used alone).
Do with. Thus, the rear end of the insulated wire 5 and the inner leads 3B at second bonding portion 5A _2, are firmly wedge bonding.

The connection at the rear end side of the coated wire 5 is such that the coated wire 5 at the connection portion is coated in advance with the coating film 5B, but the coating film 5B only at the connection portion is formed by ultrasonic vibration of the bonding tool 16. It is destroyed and the gold wire 5A is exposed. Although there is a slight change depending on the energy of the ultrasonic vibration of the bonding tool 16 and the thermocompression force, the coating film 5B of the coating wire 5 is preferably, for example, about 0.2 to 3 [μm] thick. When the thickness of the coating film 5B of the coating wire 5 is too small, the withstand voltage as the insulating coating film is small. If the thickness of the coating film 5B of the coating wire 5 is too large, the coating film 5B is less likely to be broken by the ultrasonic vibration of the bonding tool 16, and the coating film 5B has a predetermined value. If it exceeds, the coating film 5B will not be destroyed, so that a connection failure between the gold wire 5A of the coating wire 5 and the inner lead 3B of the lead 3 will occur.

In this embodiment, as a material of the gold wire 5A of the covering wire 5, for example, gold (Au) having a high purity of 99.99% by weight or more, germanium (Ge) of 0.03 to 0.3% by weight,
Since the material containing 0.0005 to 0.01% by weight of calcium (Ca) is used, germanium and calcium act synergistically with each other and with high-purity gold, so that the fatigue life of the gold wire 5A Can be effectively extended, and the crystal grains at the neck portion can be prevented from becoming coarse during the formation of the ball, and the occurrence of neck break can be prevented.

That is, the micrograph of the bonding wire
As shown in FIG. 51 (the present invention) and FIG. 52 (prior art), in the bonding wire of the present invention (FIG. 51), the coarsening of the crystal grains in the neck portion can be prevented even in the ball forming state. This can prevent neck breakage.

On the other hand, in the prior art (FIG. 52), the neck portion of the bonding wire is easily cut off due to the coarsening of the crystal grains in the neck portion.

In this embodiment, when the other end of the covered wire 5 is bonded (second bonding), only the inner lead 3B of the lead 3 is locally heated by the heater 26 to a temperature which is particularly higher than the other portions. Since the heating and division of the covering film 5B are further promoted, the bondability of the second bonding can be improved, and strong wire bonding can be performed.

Thereafter, the bonding tool 16 is separated (at this time, the covering wire 5 is cut), thereby completing one bonding step of the covering wire 5 as shown in FIG.

Thus, in bonding technique to form a ball 5A ₁ to the distal end portion of the coated wire 5, in the vicinity of the distal end portion of the covered wire 5, the fluid spray nozzle 18C (fluid spray for spraying a fluid Gs at the tip portion of the insulated wire 5 Part of device 25)
Is provided, the coating film 5B, which melts the coating wire 5, can be blown off, so that it is possible to prevent the sphere of the insulating coating film 5B from being formed on the coating wire 5. As a result, the coated wire 5 is prevented from being caught by the bonding tool 16 due to the sphere of the insulating coating film 5B, and the coated wire 5 can be drawn to the pressing surface of the bonding tool 16, so that ball bonding is performed. And bonding defects can be prevented.

Further, a bonding technique to form a ball 5A ₁ to the distal end portion of the covered wire 5, wherein the fluid spray nozzle 18C
(A part of the fluid spraying device 25) is provided, and a suction pipe for sucking a coating film 5B of the coated wire 5 blown off by blowing the fluid Gs from the fluid spray nozzle 18C near the tip of the coated wire 5. By providing 18E (suction device 19), the coating film 5B, which melts, of the coating wire 5 is blown off, and the sphere of the coating film 5B is prevented from being formed on the coating wire 5,
As described above, the bonding failure can be prevented and the blown coating film 5Ba can be bonded to the bonding portion 12
Since it is not scattered, bonding defects caused by the scattered coating film 5Ba can be prevented. The bonding failure caused by the scattered coating film 5Ba is, for example, that the coating film 5Ba scatters between the external terminal 2C of the semiconductor chip 2 or the inner lead 3B of the lead 3 and the gold wire 5A of the coating wire 5. However, this is a case where conduction failure occurs between the two.

Further, a bonding technique to form a ball 5A ₁ to the distal end portion of the covered wire 5, wherein the fluid spray nozzle 18C
By providing a (fluid spraying device 25) and a cooling device 25A for cooling the fluid Gs of the fluid spraying nozzle 18C, melting of the insulating coating film 5B of the coated wire 5 is significantly reduced and melted. Even in this case, since the coating film 5B can be blown off, it is possible to prevent the sphere of the coating film 5B from being formed on the coating wire 5 and prevent the bonding failure as described above.

Further, the coating in the bonding technique using a wire 5 to form a ball 5A ₁ on the distal end side of the feed direction of the coated wire 5, the external terminal 2C of the semiconductor chip 2 to the ball 5A ₁
And the rear end side of the coating wire 5 in the supply direction is brought into contact with the inner lead 3B of the lead 3, and the coating film 5B at the contact portion is broken, and the gold wire on the other end side of the coating wire 5
By connecting 5A to the inner lead 3B of the lead 3, the coating film 5B can be removed without using a coating film removing torch for removing the coating film 5B on the rear end side of the coated wire 5. Therefore, it is possible to reduce the coating film removing torch, its moving device, control device, and the like. As a result, the structure of the bonding apparatus can be simplified.

In particular, in the semiconductor device 1 of the present embodiment, a heat-resistant polyurethane containing a structural unit derived from terephthalic acid in the molecular skeleton is used as the insulating coating film 5B of the coating wire 5 by reacting a polyol component with an isocyanate. As a result, it is possible to reliably prevent a tab short, a chip short, or a short between wires due to film destruction caused by thermal differentiation of the coating film 5B.

That is, after bonding the covering wire 5 as described above, a resin molding operation is performed with the resin material 6 to manufacture the resin-encapsulated semiconductor device 1. For example, as shown in FIG. When the distance between the external terminal 2C of the chip 2 and the bonding portion of the inner lead 3B of the lead 3 is long, as shown in FIG.
A so-called chip touch state in which the silicon wire of the semiconductor chip 2 contacts with the so-called chip touch state, or a so-called tab touch state in which the covering wire 5 and the tab 3A contact each other as shown in FIG.
Further, a so-called wire-to-wire touch state where the coated wires 5 come into contact with each other may occur. Such a wire touch phenomenon is likely to occur particularly when the wire length becomes 2.5 mm or more, or when the size of the tab 3A is larger than the size of the semiconductor chip 2.

When such a wire touch phenomenon occurs, for example, as shown in FIG. 14, the coating film 5B of the coating wire 5 is broken by thermal deterioration caused by heat generation from the semiconductor chip 2, and the gold wire 5A becomes Directly contact with the semiconductor chip 2 to cause a chip short failure with the semiconductor chip 2 or a tab short failure with the tab 3A as shown in FIG. May occur.

However, in the semiconductor device 1 of the present embodiment, as described above, since the coating film 5B of the coating wire 5 is made of a special heat-resistant polyurethane, it is temporarily assumed that the chip touch, the tab touch or the wire Even if a touch state occurs, it is possible to reliably prevent a short circuit from occurring.

In order to confirm the neck breaking prevention effect and the short failure prevention effect obtained by such a bonding wire for a semiconductor element according to the present invention, an experimental result obtained by the present inventors on a semiconductor device after resin sealing is used as an experimental example. This will be described below. Parts in the experimental examples indicate parts by weight.

Experimental Example 1 Germanium (Ge) and calcium (Ca) were added to 99.99% by weight of gold (Au), melt-cast, and subjected to wire drawing to produce a bonding gold wire having a wire diameter of 25 μm. The mechanical properties such as the elongation percentage and the breaking load of the gold wire were measured, and a bonding operation was performed using the measured mechanical properties.

The resulting bonding properties, along with the mechanical properties, are shown in Table 1 by germanium and calcium content.

As is clear from Table 1, 0.09.99% by weight of gold
By containing 3 to 0.3% by weight of germanium and 0.0005 to 0.01% by weight of calcium, the mechanical properties such as the breaking load of the gold wire are improved, and at the time of bonding, the neck portion and the arch portion (second from the neck portion) It was confirmed that the uniformity of the crystal grains in the portion (the portion extending in a loop toward the bonding side) was ensured, the neck was cut, and the bonding characteristics could be improved.

In particular, the content of germanium and calcium respectively
Even better results are obtained with 0.05-0.15% by weight and 0.001-0.003% by weight.

Experimental Example 2 Using the gold wire obtained in Experimental Example 1, the breaking load [kg / mm ² ] and the elongation [%] were measured to confirm the fatigue strength. The wire diameter of the gold wire was 25 [μm].

As a result, the fatigue strength of the gold wire itself was as shown in FIG. 45 regardless of the formation of the gold ball, and the fatigue strength of the neck portion after the formation of the gold ball was as shown in FIG. 46.

As is clear from FIG. 45, the gold wire of the present invention has superior fatigue strength as compared with the conventional one, and particularly, the content of germanium is 0.1% by weight, and the content of calcium is 0.1% by weight.
The best breaking load and elongation were obtained at 0.002% by weight. And the breaking load is 15-30 kg / mm ² , the elongation 10-25
%, Especially good results were obtained.

Regarding the fatigue strength of the neck, as shown in FIG. 46,
Good results have been obtained with the present invention. In the measurement of the fatigue strength of the neck portion, the gold wire was connected to the positive electrode, the torch electrode was connected to the negative electrode, the distance between the gold wire and the torch electrode was 0.5 mm, and a gold ball was formed at the tip of the gold wire. One used. Then, the breaking load and the elongation of this sample gold wire were measured by a Tensilon tensile tester under the measurement conditions of a sample gold wire length of 13 mm and a pulling speed of 2 mm / min.

Further, as apparent from FIG. 46, the breaking load and the elongation of the neck portion are hardly affected by the heat treatment temperature of the gold wire.

Experimental Example 3 In order to test the fatigue strength of the gold wire, particularly its neck, the gold wire after forming the gold ball was bonded to the fixed portion only at the gold ball portion (1st bonding side), and the other end of the gold wire was mercury. And the gold wire was clamped by a clamper at a position of a predetermined length from the bonding portion, and the clamper was repeatedly vibrated with a predetermined displacement (amplitude) to detect breakage due to fatigue of the gold wire.

The results of the fatigue test are as shown in FIG. 47, and it was confirmed that the gold wire of the present invention had extremely excellent fatigue resistance.

Experimental Example 4 The change in the fatigue strength of the gold wire due to the difference in the polarity of the discharge when forming the ball of the gold wire was measured.

The discharge in this test was a positive electrode discharge in which the wire was negative (-) and the torch electrode was positive (+), and conversely, a negative electrode discharge in which the wire was positive and the torch electrode was negative. . The discharge conditions for the positive electrode discharge and the negative electrode discharge were set so that the ball diameter was 60 μm, the respective discharge currents were 3 mA and 15 mA, and the discharge time was 6.0 msec.
And 6.5 msec, and the discharge voltage was 1200 V
Met.

The fatigue test after ball formation was performed in the same manner as in Experimental Example 3.

The experiment was performed on two types of gold wire, respectively, and the results of each are shown in FIGS. 48 and 49.

As is clear from these figures, in any case, the wire fatigue strength is approximately doubled by changing from the positive electrode discharge to the negative electrode discharge. Further, in the negative electrode discharge, the difference in fatigue strength between both types is almost eliminated.

Thus, it was found that the difference in the polarity of the discharge during the formation of the gold wire ball had a great effect on the fatigue strength, and that the negative electrode discharge had about twice the fatigue life of the gold ball neck.

In addition, it has been found that the negative electrode discharge has an advantage that the shape of the gold ball is more stable.

Experimental Example 5 First, the raw materials as shown in Table 2 below were blended in the ratio as shown in the same table, and this was put in a 500 cc flask.
A thermometer and the above condenser were attached and reacted to obtain three types of terephthalic acid-based polyols P1-, P-2, and P-3. The ratio of terephthalic acid to ethylene glycol and the reaction time at this time are also shown in Table 2. The end point of the above synthesis reaction was determined based on theoretical reaction water and an acid value of 5 or less. In this case, a reduced pressure reaction was performed as needed.

Using the three types of terephthalic acid-based polyols P-1, P-2, P-3 obtained as described above and commercially available polyols, these polyol components and isocyanate components are shown in Table 3 below. A coating composition was prepared by blending at such a ratio. Then, the coating composition thus obtained was diluted to a concentration of 10% using a solvent, and 2 μm
Apply at least 175 ° C for 21 minutes, then 170 ° C
For 2 hours to form an insulating film made of heat-resistant polyurethane, followed by wire drawing. The composition and coating film properties in this case are shown in Table 3 below.

Next, using the heat-resistant polyurethane-coated wire obtained as described above, the semiconductor chip wire-bonded as described above is molded with a resin material, and FIG. 13 (chip touch state) and FIG. 15 (tab touch state). A semiconductor device corresponding to the touch state shown in Fig. 1 was manufactured, a temperature cycle test of MIL-883B was conducted, and a short-circuit rate with a semiconductor device using a commercially available polyurethane-coated wire was compared to evaluate the improvement of the present invention. did.

The results of this comparative experiment were as shown in FIG. 17 and FIG. That is, FIG. 17 shows the short-circuit rate between the semiconductor chip and the coated wire in the chip touch state as shown in FIG. 13. As is clear from FIG. 17, the semiconductor using the heat-resistant polyurethane-coated wire of the present invention was used. In the device, a remarkable short-circuit rate, that is, a chip short-circuit preventing effect was confirmed as compared with a semiconductor device using a commercially available polyurethane-coated wire.

FIG. 18 shows the short-circuit rate between the tab and the coated wire in the tab chip state as shown in FIG. 15, but also in this case, the semiconductor device using the heat-resistant polyurethane-coated wire of the present invention has a remarkable short-circuit. Rate, that is, a tab short prevention effect was obtained.

Next, the present inventors compared the heat-resistant polyurethane-coated wire according to the present invention and a commercially available polyurethane-coated wire in a wire state before resin sealing under the test conditions described below,
The wear strength and the deterioration rate of the coating film were evaluated. The results of these experiments and other various experiments are described below in Experimental Examples 6 to 10.
19 to 25 will be described.

Experimental Example 6 Experimental conditions were represented by a model diagram shown in FIG. That is, a fixed load (1 g) is hung on the lower end of the insulated wire 5 whose outer surface is coated with an insulating coating film (heat-resistant polyurethane of the present invention or commercially available polyurethane) 5B to make a vertically suspended state, The tab 3A of the lead frame is brought into contact with the coated wire 5 at the edge thereof at a contact angle α = 45 degrees, and is pressed against the coated wire 5 in a horizontal direction from the side opposite to the tab edge contact portion with a load W ₁ (0.65 g). By applying force and oscillating the tab 3A vertically by 20 μm,
The wear of the coating film 5B was evaluated.

Here, the amplitude (vibration) frequency Nf until the coating film 5B wears and breaks is defined as a wear strength and evaluated.

In addition, the heat resistance of the coating film 5B is high temperature storage (150-200 ° C,
(0 to 1000 hours).

As a result, it has been found that, in the case of polyurethane, thermal degradation can be greatly suppressed by imidizing the polyurethane, and the temperature cycle life T∞ can be significantly improved.

 Hereinafter, these experimental results will be specifically described.

First, FIGS. 20 and 21 show the thermal deterioration of the wear strength of the coating film 5B at 150 ° C. and 175 ° C., respectively (reduction of the number of coating film breakage after 100 hours). As is apparent from these figures, in the case of the coating film using the heat-resistant polyurethane of the present invention, the wear strength Nf even after the high-temperature leaving time has elapsed.
Was found to be small, and the deterioration of the coating film was very small. In particular, it was found that the fact that the rate of deterioration of the coating film 5B in reducing the number of times the coating film was destroyed after 150 to 175 ° C for 100 hours (Hrs) was within 20% was an extremely advantageous characteristic for the coated wire.

Experimental Example 7 Next, FIG. 22 shows the experimental results of the relationship between the temperature (horizontal axis) and the deterioration rate, that is, the deterioration rate [ΔNf / 100Hrs] (= N ₀ −N ₁₀₀ / 100Hrs) (vertical axis). is there. Also in this figure, in the case of the heat-resistant polyurethane-coated wire of the present invention,
It is understood that the deterioration rate is much smaller than that of the commercially available polyurethane.

Experimental Example 8 Next, FIG. 23 shows the imidization rate (horizontal axis) and the deterioration rate of the coating film, that is, the deterioration rate (vertical axis on the left), and the peel strength of the second (2nd) bonding of the coated wire (vertical axis on the right). It is an experimental result showing the relationship with.

The peel strength of the 2nd bonding was determined by the inventors of the present invention using a heat-resistant polyurethane-coated wire having a diameter of φ = 25 μm and bonding the inner film 3B to the inner lead 3B without previously peeling the coating film 5B as shown in FIG. This is the result of performing.

As is clear from FIG. 23, the imidization ratio of the coating film is about
1/3 is preferable for both the deterioration rate (deterioration rate) and the peel strength.

In particular, in the case of the heat-resistant polyurethane-coated wire of the present invention,
Since the peel strength of the 2nd bonding part was large, the reliability of bonding was high and an extremely advantageous result was obtained.

Experimental Example 9 Further, FIG. 24 shows the experimental results on the temperature cycle amplitude (−55 to 150 ° C.) and the temperature cycle life of the coated wire. As is clear from the figure, the service life T の of the coating film made of a commercially available polyurethane is about 400, while that of the heat-resistant polyurethane of the present invention is greatly improved to 4000 or more.

Experimental Example 10 FIG. 25 is a graph showing the results of an experiment on the effect of the presence or absence of a coloring agent on the coating film of a coated wire on the deterioration rate (deterioration rate).

According to the knowledge of the present inventors, when performing bonding using the covered wire 5, for example, when forming a ball, since the thickness of the covering film 5B is very thin, it is checked whether or not the coating film 5B melts or peels. Is very difficult to do,
At least it's impossible with the naked eye. Thus, the present inventors have found that if a coloring agent such as oil scarlet is added to the coating film 5B, the melt-up or peeling thereof can be visually confirmed (for example, by using an electron microscope), and it is extremely useful. It is.

However, if the amount of the coloring agent added is too large, the deterioration rate (deterioration rate) of the coating film increases, and the present inventors conducted various experiments on the appropriate amount, and as a result, Is shown in FIG.

As is clear from the experimental results shown in FIG. 25, when the amount of the colorant added is too large, the deterioration rate (deterioration rate) of the coating film increases, while when the amount is too small, the above-mentioned results are obtained. The merit of adding such a coloring agent is lost. So, in light of these two conflicting requirements,
As a result of extensive studies by the present inventors, the amount of the coloring agent (in this example, oil scarlet) was 2.0% by weight or less,
In particular, it became clear that 0.5% by weight to 2.0% by weight was optimal. By adding a colorant to the coating film in this range, the advantage that the coating film can be visually confirmed as melting or peeling from the coating wire while preventing the characteristics of the coating film from being impaired is obtained. Can be

The present inventors have obtained the following findings through Experimental Example 5 and further Experimental Examples 6 to 10 and various other experiments, studies, studies, and confirmations.

That is, as described above, the use of the heat-resistant polyurethane having the above composition of the present invention as the coating film of the coated wire is extremely useful for the thermal deterioration of the coating film, the bonding property, and the improvement of the peeling strength of the bonding.

In addition to this, as apparent from, for example, Experimental Example 6, the thermal degradation (degradation rate) of the coating film, that is, the abrasion test under the experimental conditions shown in FIG. It is extremely important to use a material that can reduce the degradation rate within 20% in reducing the number of times the coating film is destroyed after 100 hours at 150 ° C. to 175 ° C. as a constituent material of the coating film.

In addition, as a characteristic to be provided as a coating film, it is also very important that the coated wire does not cause a problem in bonding property when the coated wire is put to practical use in a wire bonding operation. The present inventors have conducted intensive research on this point, and found that the coating film is formed, for example, when forming a ball in ball bonding, or when removing the coating film by heating.
It has been found that it is important to configure the material with non-carbonizing properties.

The reason is as follows. That is, the coating film melts immediately above the ball when the ball is formed or when the coating film is removed by heating, but when the coating film is carbonized, it is not decomposed due to the heating temperature at that time, for example, a high temperature of 1060 ° C. At the same time. As a result, the carbonized coating film adheres and remains on the gold wire just above the ball, so that the carbonized coating film is supplied through the capillary when bonding with a bonding tool. And makes it difficult or impossible for the coated wire to pass through the capillary. On the other hand, if the adhered carbonized coating film falls on the integrated circuit forming surface of the semiconductor chip for some reason, the carbide has conductivity, and the dropped object causes an electrical short-circuit failure of the integrated circuit. It is. In addition, the coated wire with carbide adhered to, for example, the second lead to the inner lead
It has been found that bonding also causes bonding failure.

Considering such facts comprehensively, as the coating film of the coated wire, the deterioration rate under the above-mentioned predetermined conditions, ie, 150 ° C. to 175 ° C., in reducing the number of times of coating film destruction after 100 hours It is extremely important that these two requirements, that is, a material exhibiting non-carbonization when the deterioration rate is within 20% and when the ball is formed or the coating film is removed by heating, are extremely important. It has been confirmed by the inventors that very satisfactory results are obtained as a coated wire.

According to the study results of the present inventors, not only the heat-resistant polyurethane having the above-described composition, but also those satisfying these two requirements, the material satisfying these two requirements is the heat-resistant urethane of the above-described composition. The material is not limited to the above, and a heat-resistant polyurethane having another composition, or a material other than the heat-resistant polyurethane, can be used as the material of the preferable coating film.

In this regard, among polyurethanes, commercially available polyurethanes and formals satisfy the requirement of non-carbonization, but are not suitable as coating films because the above-mentioned deterioration rate exceeds 20%.

On the other hand, polyimide, polyamide, nylon, polyester, polyamide imide, polyester imide, and the like exhibit carbonization during ball formation or when the coating film is removed by heating, and are therefore unsuitable for use as a coating film for a coating wire. It became clear.

Next, the present invention will be further described with reference to FIGS. 26 to 30 showing other various embodiments of the wire bonding method which can be used in the present invention.

Example 2 In the embodiment of FIG. 26, as an example of another wire bonding method included in the present invention, first the coated wire 5 (1st) bonding side likewise ball bonding using balls 5A ₁ as in Example 1 The second (2nd) bonding side is the second bonding part 5A
As shown in FIG. ₂₂ , the coating film 5B is removed in advance before the second bonding, and the second bonding is performed by thermocompression bonding and / or an ultrasonic vibration method.

Then Example 3, in the embodiment of Figure 27, in addition to second bonding portion 5A ₂ are bonded without removing the same coating film 5B to Example 1, also the first bonding side rather than ball bonding by the ball, the coating film 5B and the first bonding by thermocompression and / or ultrasonic vibration method without prior removal, to form the first bonding portion 5A _11.

Therefore, in the present embodiment, the same bonding method is used for both the first and second bonding.

Example 4 Further, examples of FIG. 28 is first bonding portion 5A ₁₁ are the same as in Example 3, like-second bonding portion 5A ₂₂ Example 2, previously removed covering film 5B Is bonded.

Example 5 In the embodiment of Figure 29, as the first bonding portion 5A _12, the previously removed the bonding method of the coating film 5B, similarly second bonding portion 5A ₂ and Examples 1 and 3, the coating The bonding is performed without removing the film 5B.

Example 6 Further, in the embodiment of Figure 30, the bonding gold wires 5A the state in which the previously removed covering film 5B of the first bonding portion 5A ₁₂ and second bonding portion 5A ₂₂ in a non-ball forming method Here is an example.

Embodiment 7 FIG. 31 is a partial sectional view showing a wire bonding portion according to another embodiment of the present invention.

In this embodiment, the coating film of the coating wire 5 has a composite coating structure. That is, the outer surface of the covering wire 5 is covered with the covering film 5B made of the above-described heat-resistant polyurethane, and the outer surface of the covering film 5B is further covered with a second covering film 5C made of another insulating material. This is an example of coating with.

As the material of the second coating film 5C, as described above, a polyamide resin, a special polyester resin, a special epoxy resin, or the like can be used. For the purpose of improving the slipperiness of the coated wire in the capillary using nylon or the like, a second coating film can be applied.

The thickness of the coating film 5C in FIG. 2 is 2 times the thickness of the coating film 5B.
It can be less than or equal to 0.5 times, preferably less than or equal to 0.5 times.

[Embodiment 8] Fig. 32 is an explanatory view showing a route of a covering wire from a wire spool to a bonding tool in a wire bonding apparatus as an assembling apparatus used in another embodiment of the present invention, and Fig. 33 is an airbag. FIG. 34 is a partially cutaway perspective view showing the structure of the tensioner, FIG. 34 is a side view showing the inner peripheral surface shape of the airbag tensioner, FIG. 35 is a schematic sectional view showing a clamper, and FIG. 36 is a clamper 37 is an enlarged perspective view showing the vicinity, FIG. 37 is a schematic plan view showing a driving mechanism of the clamper, FIG. 38 is a schematic cross-sectional view of a conventional clamper for comparison with FIG. 35, and FIG. , FIG. 40 is an explanatory plan view of a lead frame showing a wire bonding state according to the present embodiment, and FIG. 41 is a resin sealing obtained by the present embodiment. It is an overall cross sectional view of a type semiconductor device 33.

In this embodiment, the structure of the wire bonding apparatus itself is almost the same as that shown in FIG. 2 in the first embodiment, but in this embodiment, the wire bonding apparatus is provided between the wire spool 11 and the bonding tool 16. It is characterized in that the static elimination means is different.

That is, the coated wire 5 supplied from the wire spool 11 is inserted into the bonding tool 16 via the airbag tensioner 31, the sprocket 14, and the clamper 32.

The airbag tensioner 31 has a pair of guide plates 31A as shown in FIG. This guide plate 3
1A may be an aluminum alloy surface that has been subjected to alumite treatment. However, by forming at least the contact surface with the coated wire 5 with a conductive metal, a structure that can prevent charging of the coated wire 5 at the time of contact. ing. Further, not only the contact surface but also the entire guide plate 31A may be made of stainless steel or the like.

As shown in FIG. 34, a plurality of projections 31B are formed on the surface of the guide plate 31A of the present embodiment on the wire passage space 31G side, as shown in FIG. Such a protrusion 31B
As a technique for obtaining the structure of the above, by using a processing technique such as pressing, the inner peripheral surface of the guide plate 31A may be processed into a protruding shape, or may be joined to the inner peripheral surface of the guide plate 31A formed flat. The rod-shaped member may be fixed using a means such as bonding.

As described above, in the present embodiment, by providing the protrusion 31B extending in the direction substantially perpendicular to the direction in which the covering wire 5 passes on the inner peripheral surface of the guide plate 31A, the covering when passing through the airbag tensioner 31 is provided. The contact between the outer peripheral surface of the wire 5 and the inner peripheral surface of the guide plate 31A is substantially in a point contact state, and by reducing the contact area, friction can be suppressed and the outer peripheral surface of the covered wire 5 can be prevented from being charged.

A metal adapter 31D connected to a fluid supply pipe 31C is mounted on one longitudinal end of both guide plates 31A, and a fluid outlet 31E is opened on an end surface of the adapter 31D. A flat spacer 3 is provided around the fluid outlet 31E.
1F is formed so as to protrude, and the width of the wire passage space 31G is determined by the thickness of the spacer 31F. The width of such a wire passage space 31G varies depending on the diameter of the covering wire 5 used or the height of the projection 31B from the inner surface of the guide plate 31A, but is about 1 mm in the present embodiment.

The fluid supply pipe 31C connected to the adapter 31D is connected to a fluid supply source 31H. The fluid supply source 31H has, for example, a built-in corona discharge means 31H1, so that ion-separated ion gas is supplied from the outlet 31E of the adapter 31D to the wire passage space 31G as a current eliminator Cs2. ing.

Therefore, according to the present embodiment, the supply of the current eliminator Gs2 to the wire passage space 31G causes the airbag tensioner 3
It is possible to apply the back tension of the coated wire 5 which is the original purpose, and at the same time, to remove the electrostatic charge of the coated wire 5. Further, as described above, the contact between the covering wire 5 and the airbag tensioner 31 is substantially point contact due to the structure of the projection 31B on the inner peripheral surface of the guide plate 31A. Of the outer peripheral surface is also suppressed.

The clamper 32 located below the airbag tensioner 31 has a pair of clamper arms 32A as shown in FIGS. 36 and 37, and the clamper arm 32A passes through a shaft support 32B. The front end side can be opened and closed by the operation of the cam mechanism 32C engaged at the rear end side (FIG. 37). The pair of clamper arms 32A1, 3A
2A2 is normally urged by a spring 32D or the like in a direction in which the tip is closed, and the cam mechanism 32C is actuated from this state to cause the clamper arm 32A to operate.
The distal ends of 1, 32A2 are configured to move away from each other so that the clamper 32 can be opened.

A first clamper chip 32E1, which is made of a hard metal such as stainless steel and whose surface is mirror-finished by chrome plating or the like, is fixed inside the tip of one clamper arm 32A1 (fixed side). At the approximate center of the chip surface of the first clamper chip 32E1, an outlet 32F of a current eliminator Gs2 as shown in FIGS. 35 and 36 is provided.
32F is communicated with the fluid supply tube 31C connected to a fluid supply source 31H, for example, ion gas or the spraying of neutralizing fluid Gs2 such as N ₂ gas, it is possible. The fluid supply source 31H incorporates the corona discharge means 31H1 as described in the description of the airbag tensioner 31 described above.

A leaf spring-like sub-arm 32G having a predetermined elasticity is attached to the tip of the other clamper arm 32A2 (movable side) with its base fixed with screws 32H or the like. A second clamper chip 32E2 made of ruby or the like is fixed. The second clamper chip 32E2 is detachable from the clamper arm 32A2 in units of sub-arms 32G.
This can be exchanged in units of 32G. With the structure of the leaf spring-like sub arm 32G, the covering wire 5
The load applied to the side surface of the covered wire 5 at the time of clamping is controlled to prevent the covered wire 5 from being damaged.

Note that a chip-shaped stopper 32J is fixed to the back side of the second clamper chip 32E2, that is, to the inner end of the movable clamper arm 32A2.

The positional relationship between the clamper 32 and the covering wire 5 is as follows.
As shown in FIG. 36 and FIG. 36, the covering wire 5 from the sprocket 14 to the bonding tool 16
The second clamper chips 32E1 and 32E2 are arranged so as to pass through substantially the center between the opposing chip surfaces. Here, as shown in FIG. 35, a current eliminator Gs2 is constantly blown out from an outlet 32F opened on the chip surface of the first clamper chip 32E1, and this current eliminator Gs2, for example, The ion gas passes through the coating wire 5 and the chip surface of the second clamper tip 32E2, so that the coating wire 5 and the second clamper tip 32
Static electricity charged on the chip surface of E2 is removed. Addition to the above ion gas as neutralization fluid Gs2 According to experiments by the present inventors, also obtained a neutralizing effect by blowing N ₂ gas or the like has been confirmed.

Note that the outlet 32F need not always be arranged at the center of the clamper chip surface of the first clamper chip 32E1 if static elimination is performed only on the chip surface of the clamper chip 32E2. It is possible to blow the current eliminator Gs2 also to the side surface of the wire 5. As a result, it is possible to remove static electricity from the covered wire 5 and to scatter and remove the adsorbed foreign matter 5D such as a small side adhered to the side surface of the covered wire 5, and to clean the covered wire 5. For this reason, in the present embodiment, it is possible to effectively prevent clogging and the like in the bonding tool 16 caused by the adsorbed foreign matter 5D adsorbed on the coated wire 5, and as a result of extending the maintenance cycle of the bonding tool 16, the efficiency is improved. It is also possible to realize the production of the resin-encapsulated semiconductor device 33. In the eighth embodiment, as described above,
Since the electrostatic charging of the ruby clamper chip 32E2 attached to the tip of G is effectively prevented, the coated wire 5 is adsorbed and curled by the clamper chip 32E2 before insertion into the bonding tool 16. Can be prevented. That is, in the prior art, as shown in FIG. 38, the covering wire 5 is attracted to the clamper chip 32E2 due to the electrostatic charging of the clamper chip 32E2, and even when the clamper 32 is opened. The covered wire 5 remained curled. When this is inserted into the bonding tool 16 and wire bonding is performed, the ball shape also affects the wire bonding loop shape, and the bonding strength between the external terminal 2C (bonding pad) or the inner lead 33B and the coated wire 5 is reduced. As a result, the wire flow at the time of resin molding due to lowering or a loop abnormality has resulted. In addition, since the coated wire 5 is attracted to the charged clamper chip 32E2, the coated wire 5 is not smoothly fed from the bonding tool 16 during wire bonding, and the bonding tool 16 is lowered when the bonding tool 16 is lowered. As a result, an extra resistance force is added to the wire 16, and when the wire 5 is stretched while the wire 5 is pulled out from the tip of the bonding tool 16, a breakage of the wire 5 or an abnormal loop may occur. was there.
In this regard, according to the eighth embodiment, the clamper chip 32
Since the static elimination of E2 is reliably performed, the coated wire 5 is prevented from being attracted to the clamper chip surface, and as a result, the coated wire 5 is straight and smooth as shown in FIGS. 35 and 36. To the bonding tool 16.

For this reason, a bonding failure due to a loop abnormality due to disconnection or curling of the covered wire 5 is effectively prevented. According to the study of the present inventors, the adsorption of the covered wire 5 due to the electrification of the clamper chip 32E2 (No.
FIG. 38) is a phenomenon that occurs remarkably in the covered wire 5 having the same structure as that described in the first embodiment, but is not limited to such a covered wire 5, and bare gold (Au) and aluminum ( It has been found that the possibility of occurrence is high even when a wire such as Al) or copper (Cu) is used as a bonding wire.

Next, the structure of the resin-sealed semiconductor device 33 assembled in the eighth embodiment will be briefly described.

In the eighth embodiment, the resin-encapsulated semiconductor device 33
Is provided in a state before assembly, that is, in a state of the lead frame 33A. FIG. 40 shows a state in which wire bonding has already been completed. For convenience, the structure of the inner lead 33B of the lead frame 33A will be described with reference to FIG. As shown in the figure, the lead frame 33A is provided with inner leads extending in four directions in a plane 4 in a non-contact manner with the tab 33D centered on a tab 33D supported substantially at the center by a tab suspension lead 33C. 33B. The respective inner leads 33B are in a state of being connected to each other by a frame (not shown) at a further outer peripheral portion shown in FIG. Such a lead frame 33A
Is obtained by pressing or etching a plate-like member having a thickness of about 0.15 mm such as Kovar, 42 alloy or nickel alloy into a shape shown in FIG.

As shown in FIG. 39, the semiconductor chip 2 is fixed on the tab 33D via a bonding material 4 such as a silver paste, a silicon paste, or a gold foil applied to a thickness of about 30 μm. Although not shown in detail, a microprocessor, a logic circuit, or the like is formed in an upper layer of the semiconductor chip 2 through an oxidation / diffusion process using a photoresist technique. Briefly describing the schematic configuration of each layer inside the semiconductor chip 2, a silicon oxide film 2A2 of about 0.45 μm is formed on an upper layer of a chip substrate 2A1 made of silicon (Si) having a thickness of about 400 μm. On the upper layer, a PSG film 2A3 as an interlayer insulating film is 0.3μ.
It is formed with a thickness of about m. On the uppermost layer, a passivation film 2B as a protective film is deposited with a thickness of about 1.2 μm, a part of which is opened and has a thickness of 0.8 μm made of aluminum (Al) partially provided in the lower layer.
A degree of external terminal 2C exposes its upper surface to the outside.

Next, a wire bonding procedure according to the present embodiment will be described. In the following description, it is assumed that the structure of the wire bonding apparatus other than that shown in FIG. 32 is the same as that of FIG. 3 described in the first embodiment.

First, when the lead frame 33A is fixed at a predetermined position on the stage surface of the bonding stage 17, the heat of the heater 26 built in the bonding stage 17 is transmitted to the lead frame 33A, and the lead frame 33A and the semiconductor chip 2 Is increased to a predetermined bonding condition temperature.

Subsequently, the XY table 23 is operated to activate the bonding head.
The bonding tool 16 is stopped at a position immediately above the semiconductor chip 2 on the lead frame 33A by moving the bonding tool 22 by a predetermined amount.

At this time, the clamper 32 is in a state of holding the covering wire 5 from the side surface, and the covering wire 5 is in a state where the position is fixed thereby.

Subsequently, as shown in FIG. 8, the electric torch 18D
Fig. 8 (Simulated configuration diagram illustrating the principle of forming the ball 5A1)
As shown in the figure, the ball is brought close to the gold wire 5A on the tip side on the supply side of the coated wire 5 and an arc Ac is generated between the two.
5A1 is formed. Subsequently, ultrasonic vibration is applied to the bonding tool 16 and the tip of the bonding tool 16 is pressed against the external terminal 2C of the semiconductor chip 2, whereby a synergistic effect between the heating of the heater 26 and the ultrasonic vibration is obtained. , The ball 5A1 is bonded to the external terminal 2C (1st bonding).

Next, when the cam mechanism 32C of the clamper 32 is operated, the respective clamper arms 32A1 and 32A2 are opened, and the covered wire 5 is released from the clamper 32.

At this time, in this embodiment, the static electricity charged in the other clamper chip 32E2 is reliably removed by blowing the current eliminator Gs2 from the outlet 32F of the one clamper chip 32E1, so The curling wire 5 is not substantially curled as shown in FIG.
It is possible to be inserted.

In this state, the vertically moving block in the bonding head 22
When the XY table 23 and the XY table 23 are moved by a predetermined amount in the respective directions, the bonding tool 16 moves the coating wire 5 so as to draw a loop while feeding the coating wire 5 from the tip thereof, and a predetermined inner lead is formed. Stops just above 33B (see Figure 39). At this time, the coated wire 5 sent out from the tip of the bonding tool 16 is supplied from the wire spool 11 and is supplied to the airbag tensioner 31.
In addition, it reaches the bonding tool 16 via the clamper 32. During this time, as shown in FIGS. 33 and 35, the current eliminator Gs is blown (blown) in the airbag tensioner 31 and the clamper 32. During this time, in the eighth embodiment, the continuous application of the ultrasonic vibration to the bonding tool 16 as described in the first embodiment may be performed, or the application of the ultrasonic vibration may be stopped except during the bonding. .

Next, when the vertical movement block 22B is moved downward again, the tip of the bonding tool 16 lands on the surface of the inner lead 33B while the covered wire 5 is drawn out from the tip.

Subsequently, when the vertical movement block 22B is moved downward again, the tip of the bonding tool 16 lands on the surface of the inner lead 33B with the covering wire 5 pulled out from the tip. Here, when the ultrasonic oscillation mechanism 22H is operated and ultrasonic vibration is applied to the tip of the bonding tool 16 again, the coating applied to the abdomen of the coating wire 5 derived from the bonding tool 16 is applied. The portion of the film 5B is rubbed against the surface of the inner lead 33B, and the ultrasonic energy causes a part of the coating film 5B to be broken / removed, so that the internal gold wire 5A comes into contact with the surface of the inner lead 33B. By continuing the application of ultrasonic vibration in this state, the gold wire 5A and the inner lead 33B are joined as shown in FIG. 39 (2nd bonding).

Next, the clamper 32 is closed and the bonding tool 16 is closed.
When the covering wire 5 is clamped above and the upward and downward movement block 22B is further moved, the covering wire 5 is cut between the bonding portion of the covering wire 5 and the bonding tool 16 to complete one cycle. The wire bonding operation is completed.

The wire bonding process of this embodiment is completed by repeating the above-described wire bonding operation for all the external terminals 2C (bonding pads) on the semiconductor chip 2 and the corresponding inner leads 33B for a predetermined cycle.

As described above, in the eighth embodiment, the airbag tensioner
Since the coated wire 5 is neutralized by the current eliminator Gs2 from the base 31 and the clamper chip 32E2 is neutralized to remove the adsorbed foreign matter 5D and the like, the coated wire 5 is disconnected during wire bonding. , Loop abnormalities and clogging of the bonding tool are reliably prevented.

As described above, in the eighth embodiment, since wire bonding using the covered wire 5 can be substantially realized,
Cross-bonding and the like at the portion indicated by a in the figure are also possible, and a highly functional and highly integrated microprocessor or logic element can be realized.

In FIG. 40, since the covered wire 5 is wire-bonded while straddling the tab suspending lead 33C at the location indicated by b in FIG. 40, there is a possibility that the covering wire 5 and the tab suspending lead 33C may come into contact with each other. high. However, even in the case where the coated wire 5 comes into contact with the tab suspension lead 33C, in the eighth embodiment, the coating film 5B is connected to the tab suspension lead 33C.
Electrical short circuit is prevented only by contact with As described above, in the eighth embodiment, wire bonding, which was difficult with the conventional bare gold wire, can also be realized.

After the completion of the wire bonding process as described above, the lead frame 33A is placed in a mold (not shown),
The package body 33E of the resin-encapsulated semiconductor device 33 is injected by injecting a high-pressure synthetic resin in a molten state into the mold.
(See FIG. 41). At this time, if there is an abnormality such as curl in the loop shape of the bonded covered wire 5, contact (wire short) between the covered wires 5 by the injection pressure of the synthetic resin, the covering wire 5 and the tab
The possibility of causing a defect such as contact with 33D (tab short) increases. However, according to the present embodiment, in the wire bonding step, as described above, static elimination of the coated wire 5 by the airbag tensioner 31 and static elimination of the clamper chip 32E2 are performed. In this case, the adsorption of the covered wire 5 and the attachment of foreign matter are effectively prevented, so that a bonding failure such as disconnection and an abnormal shape of the wire loop due to these are prevented, and highly reliable wire bonding is realized.

After the injected synthetic resin is cooled and hardened as described above, the lead frame 33A on which the package body 33E is formed is taken out of the mold.

Next, the outer lead 3 protruding from the package body 33E
3G is electrically divided and processed into an independent state, and by further bending the outer lead 33G at a predetermined angle,
A resin-sealed semiconductor device 33 shown in FIG. 41 is obtained.

[Embodiment 9] The energy of the ultrasonic vibration to the bonding tool 16 can be variably controlled according to the bonding site, purpose, etc. other than the example in the above embodiment.

FIGS. 50 (a) and 50 (b) show the application state of ultrasonic vibration energy to the bonding tool and the operation state of the bonding tool in another embodiment of the present invention.

As is clear from the figure, by providing a control unit (not shown) in the ultrasonic oscillation mechanism 22E, the first bonding to the external terminal 2C (first electrode) of the semiconductor chip 2 and the inner lead 3B (first The ultrasonic energy (power) can be controlled to an optimum state between the time of the second bonding to the second electrode and the second bonding.

That is, first, the external terminals 2C of the semiconductor chip 2
During 1s or bonding, to the ultrasonic oscillation mechanism 22E, as indicated by S1, applying a first ultrasonic vibration of the power P _1.

Next, the bonding tool 16 is moved to the second bonding position to the inner lead 3B. At this time, the ultrasonic vibration to the bonding tool 16 may be returned to the initial value indicated by the power P _0. As indicated by Sx, application of ultrasonic vibration to the moving bonding tool 16 can be continued with, for example, ultrasonic vibration energy of power Px.

As described above, by continuously applying the ultrasonic vibration energy to the moving bonding tool 16, the suction of the coated wire 5 in the bonding tool 16 is prevented, and the wire feed from the tip of the bonding tool 16 is prevented. Since the coating wire 5 is smooth, deformation such as bending of the coating wire 5 due to the suction of the coating wire 5 is prevented, and a loop abnormality is also suppressed. Also, by applying ultrasonic vibration to the bonding tool 16 before landing on the inner lead 3B, the coating film 5B is removed simultaneously with landing, so that a more reliable coating film removal can be achieved. It is possible.

Bonding tool 16 is lowered after moving above the inner leads 3B, the bonding tool 16 lands on the inner lead 3B, the bonding tool 16 is the power P ₂ as shown in S2 in the ultrasonic vibration energy of the second ultrasonic Vibration is applied. Thereby, the abdomen of the covering wire 5 led out from the tip of the bonding tool 16 is slid on a predetermined portion of the inner lead 3B, and the covering film 5B at that portion is mechanically broken and removed, and the gold wire is removed. 5A is exposed.

The destruction and removal of the coating film 5 by the second ultrasonic vibration energy can be performed at a position other than the second bonding position of the inner lead 3B. In that case, the bonding tool 16 generates the second ultrasonic vibration. While continuing, it is moved from the coating film removal position to the second bonding portion 5A22 of the inner lead 3B, and then the bonding tool 16
A third ultrasonic vibration is applied as shown by S3. As a result, due to the synergistic effect with the heating by the heater, the gold wire exposed at the distal end of the covered wire 5 becomes the inner lead 3B.
Is securely bonded on the second bonding portion 5A22.

The first (S1) and second (S2) in this embodiment as described above.
The third and third (S3), and the transition of the ultrasonic energy due to the ultrasonic vibration of Sx and the corresponding operation such as raising and lowering of the bonding tool 16 are respectively shown in the third.
50 (a) and (b). In the figure, the first and third ultrasonic vibrations (S1, S3) are necessary for bonding the gold wire 5A to the external terminal 2C or the inner lead 3B, and the second ultrasonic vibration (S2) Is necessary for the destruction of the coating film 5B, and the ultrasonic vibration (Sx) is
This is necessary to prevent the coated wire 5 from being attracted inside the bonding tool 16 and to smoothly feed the wire and break the coating film.

According to the study by the present inventors, the ultrasonic energy necessary for breaking / removing the coating film 5B is not always at the level of the ultrasonic energy necessary for wire bonding, and the ultrasonic energy and the like are not necessarily the same at the time of bonding. It has been found that those with lower frequencies are more effective than those of.

Also, the ultrasonic energy required to prevent the coated wire 5 from being attracted inside the bonding tool 16 may not be at the same level as the ultrasonic energy required for wire bonding.

Therefore, in this embodiment, as shown in FIGS. 50 (a) and 50 (b), by controlling the ultrasonic oscillator so as to obtain the optimum ultrasonic energy output for the purpose of applying the ultrasonic vibration, the efficiency is improved. It is possible to remove the coating film 5B and bond the gold wire 5A to the external terminal 2C and the inner lead 3B. Although the level of the ultrasonic energy in the first and third ultrasonic vibrations (S1 and S3) is set to be equal in FIG.
Different levels of ultrasonic energy may be changed.

As described above, in the present embodiment, the control unit variably controls the ultrasonic energy of the ultrasonic oscillator,
It is possible to efficiently remove the coating film 5B and improve the bonding reliability.

Further, in the present embodiment, if the part where the coating film 5B is removed and the part where the wire bonding is performed are separated on the inner lead 3B, the wire bonding part is kept clean and the coating film 5B Bonding failure due to contamination of sides and the like can be prevented.

Further, when the coating film 5B is removed, the surface of the inner lead 3B is formed of an uneven surface, etc.
The remaining of the coating film 5B can be reliably prevented, and the bonding strength between the gold wire 5A and the inner lead 3B can be increased.

Ultrasonic vibration (Sx) for the moving bonding tool 16 from the 1st bonding to the 2nd bonding
Need not be continuously performed during the entire movement of the movement, for example, 2n from the point indicated by Tx in FIG. 50 (a).
Bonding tool 16-2 as a pre-stage for d-bonding
It can be performed during descent to the nd bonding point.

Prior to the first bonding, when applying one end of the covered wire 5 to form the ball 5A1, or after forming the ball, as shown by Sp in FIG. By applying the ultrasonic vibration energy of
The feeding of the covering wire 5 from the wire is further facilitated. Since the coated wire 5 immediately after the formation of the ball is particularly difficult to be sent out due to the softening of the resin material of the coating film 5B, smoothing out of the wire is extremely useful.

Although the invention made by the inventor has been specifically described based on the first to ninth embodiments, the present invention is not limited to the above-described embodiment, and can be variously modified without departing from the gist thereof. Needless to say.

For example, the present invention is not limited to only a covered wire, but can be applied to a bonding wire consisting of only a bare wire. In any case, the bonding temperature is, for example, 160 to 300 ° C.

Further, a semiconductor device to which the present invention can be applied is shown in FIGS.
The present invention is not limited to the examples shown in FIGS. 12, 40 and 41 and can be widely applied to, for example, semiconductor devices shown in FIGS. 42, 43 and 44.

In the examples of these various semiconductor devices, FIG.
42, as well as the memory type semiconductor device shown in FIG. 43, also in the logic type semiconductor device shown in FIGS. 40 and 41,
Both insulated wires and bare wires can be used as bonding wires.

Also, in the logic type semiconductor device shown in FIGS. 11 and 44, a covered wire is advantageous for preventing a wire short, but a bare wire can be used as a matter of course.

When a bare wire is used as the bonding wire, the fluid supply pipe 31C for blowing off the coating material in the above embodiment can be omitted.

In addition, although the case where the blowing of the current eliminator Gs2 from the outlet 32F is always performed during the wire bonding has been described, the blowing cycle may be controlled for a predetermined time. It should be noted that the wire 5
When reinserting into the bonding tool 16,
It goes without saying that the blowing of the current eliminator Gs2 from F is stopped.

In addition, in each embodiment, ion gas subjected to ion separation by corona discharge as the current eliminator Gs2 for blowing,
Alternatively, the method using N ₂ gas has been described. However, the present invention is not limited to these.
It is known that there are radiation irradiation with rays, irradiation of ultraviolet rays, etc., and it is also known that the charge can be removed by spraying a liquid such as water, and a charge removing means using these may be used.

Further, a material for forming the coating film 5B or 5C,
For example, the types and compositions of the polyol component, isocyanate, terephthalic acid, and compounds thereof, and the additives are not limited to those described above.

Further, the bonding tool 16 is not limited to a capillary, and a knife-shaped wedge may be used.

In the above description, the case where the invention made by the present inventor is mainly applied to a wire bonding apparatus of a combined use type of so-called thermocompression bonding and ultrasonic bonding, which is a field of application, has been described, but is not limited thereto. For example, the present invention can be applied to an ultrasonic bonding type wire bonding apparatus.

In the above description, the case where the invention made by the present inventor is mainly applied to a resin-encapsulated semiconductor device as a field of application has been described. However, the present invention is not limited to this. The present invention can be widely applied to various semiconductor devices such as devices and manufacturing techniques thereof.

〔The invention's effect〕

The effects obtained by the representative inventions among the inventions disclosed in the present application will be briefly described as follows.

(1). In the method of manufacturing a semiconductor device according to the present invention, 0.03 to 0.3% by weight of germanium and 0.0005 to 0.01% by weight of calcium contained in a bonding wire are synergistically formed with each other and with a high-purity metal of 99.99% by weight or more. By effectively acting, the fatigue life of the metal wire can be effectively extended, and the reliability of the semiconductor device can be improved.

(2). According to the above (1), it is possible to prevent the crystal grains at the neck portion from becoming coarse during the formation of the ball, and thus to prevent the occurrence of neck breakage.

(3). According to the above (1), mechanical characteristics such as a breaking load of the metal wire and reliability of bonding can be improved.

(4). In addition, by making the contents of germanium and calcium 0.05 to 0.15% by weight and 0.001 to 0.003% by weight, respectively, better fatigue life extension effect and / or neck grain coarsening prevention (neck break prevention) effect. And so on.

(5). In addition, since the bonding wire for a semiconductor element of the present invention is covered with a coating film made of an insulating material to which a coloring agent is added, not only can the melting and peeling of the coating film be visually confirmed. In addition, it is possible to eliminate problems such as short-circuit between wires due to contact between wires, chip short-circuit due to contact with a chip end, and tab short-circuit due to contact with a tab.

(6). According to the above (5), long-distance bonding, thinning, small ball, and the like can be performed.

(7). According to the above (5) and (6), it is possible to increase the number of pins of the semiconductor device (to increase the number of terminals), and to achieve higher integration of the semiconductor device.

(8). In addition, the heat-resistant polyurethane used for coating the metal wire in the present invention can be bonded by decomposing the urethane bond even at the bonding temperature or ultrasonic vibration energy during normal wire bonding. Reliable bonding can be obtained by using both pressure bonding and ultrasonic vibration or by ultrasonic vibration. In this case, if local heating of the bonding site is used together, more reliable wire bonding can be performed.

[Brief description of the drawings]

FIG. 1 is a half sectional view of a resin-sealed semiconductor device using a bonding wire, which is one embodiment of a method of manufacturing a semiconductor device according to the present invention. FIG. 2 is a schematic enlarged sectional view of a wire bonding portion. FIG. 4 is a schematic configuration diagram of a wire bonding apparatus that can be used in the present invention. FIG. 4 is a perspective view of a main part of the wire bonding apparatus. FIG. 5 is a partial cross-sectional view showing a specific configuration of a main part of the wire bonding apparatus. FIG. 6 is a plan view as seen from the direction of arrow VI in FIG. 5, FIG. 7 is a sectional view taken along section line VII-VII in FIG. 6, FIG. 9 is an exploded perspective view of a main part of a spool of the wire bonding apparatus, FIG. 10 is an enlarged perspective view of a main part of the spool, FIG. 11 is a schematic plan view of a local heating unit for wire bonding, and FIG. Plan view showing an example of wire bonding, FIG. 3 is a partial cross-sectional view showing a chip touch state of the coated wire, FIG. 14 is an enlarged partial cross-sectional view showing the chip shorted state, FIG. 15 is a partial cross-sectional view showing a tab touch state of the coated wire, and FIG. 16 is a tab FIG. 17 is an enlarged partial cross-sectional view showing a short-circuit state, FIG. 17 is a diagram showing a short-circuit rate between a semiconductor chip and a coated wire with respect to a temperature cycle in the present invention, and FIG. 18 is a short-circuit between a tab and a coated wire with a temperature cycle in the present invention. FIG. 19 is a model diagram showing experimental conditions used for evaluating the coating film of the coated wire used in the present invention, and FIGS. 20 and 21 are wear of the coating film in the present invention, respectively. FIG. 22 shows the results of a comparative experiment of strength, FIG. 22 shows the results of an experiment on the relationship between temperature and degradation rate in the present invention, and FIG. 23 shows the imidization rate (horizontal axis) and degradation rate of the coating film. Ie poor Fig. 24 shows the experimental results on the relationship between the rate (left vertical axis) and the peel strength of the second (2nd) bonding of the coated wire (right vertical axis). Fig. 24 shows the temperature cycle amplitude and temperature cycle life of the coated wire. FIG. 25 is a view showing the experimental results of the present invention, FIG. 25 is a view showing the influence on the deterioration rate (deterioration rate) by the presence or absence of a coloring agent to the coating film of the coated wire, and FIGS. 26 to 31 are the present invention. FIG. 32 is a partial cross-sectional view for explaining a wire bonding state in Examples 2 to 7 of the present invention. FIG. 32 is an explanatory diagram showing a route of a covered wire from a wire spool to a bonding tool in a wire bonding apparatus according to Example 8 of the present invention. 33 is a perspective view showing a structure of the airbag tensioner according to the eighth embodiment with a part cut away, and FIG. 34 shows an inner peripheral surface shape of the airbag tensioner according to the eighth embodiment. FIG. 35 is a schematic sectional view showing the clamper of the eighth embodiment, FIG. 36 is an enlarged perspective view showing the vicinity of the clamper, FIG. 37 is a schematic plan view showing the drive mechanism of the clamper, FIG. FIG. 39 is a schematic sectional view of a conventional clamper for comparison with FIG. 35, FIG. 39 is an explanatory sectional view showing a wire bonding state in the eighth embodiment, and FIG. 40 is a lead showing a wire bonding state in the eighth embodiment. FIG. 41 is an explanatory plan view showing a frame. FIG. 41 is an overall sectional view of a resin-encapsulated semiconductor device obtained according to an eighth embodiment. FIGS. 42 to 44 show various embodiments of a semiconductor device to which the present invention can be applied. FIGS. 45 and 46 are diagrams showing experimental results of breaking load and elongation of the gold wire in the present invention, FIGS. 47 to 49 are diagrams showing results of a fatigue strength test of the gold wire in the present invention, Fig. 50 (a), (b) FIG. 51 is a view showing the state of application of ultrasonic energy to the bonding tool and the operating state of the bonding tool in Embodiment 9 of the present invention. FIG. 51 is a micrograph showing the metal structure of the neck portion of the bonding wire according to the present invention. It is a microscope photograph similarly showing the metal structure of the neck part of the bonding wire in the prior art. 1 ... resin-encapsulated semiconductor device, 2 ... semiconductor chip, 2A
…… Substrate, 2A1 …… Chip substrate, silicon oxide film 2A2, 2A
3 ... PSG film, 2B ... Passivation film, 2C ... External terminal (bonding pad), 3 ... Lead, 3A ... Tab, 3B ... Inner lead, 4 ... Bonding material, 5 ... Coated wire, 5A …… Gold wire, 5A1 …… Ball, 5A11, 5A12…
... 1st bonding part, 5A2, 5A22 ... 2nd bonding part, 5B, 5Ba ... coating film, 5C ... second coating film, 5D ... adsorption foreign material, 6 ... resin material, 10 ... bonding Device body,
11 Wire spool, 11A Connection terminal, 11Aa Insulator, 11Ab Conductor, 11Ac Connection metal part, 12
Bonding part, 13 ... tensioner, 14 ... sprocket, 15 ... clamper, 16 ... bonding tool (capillary), 16A ... bonding arm, 16B ... through hole, 16C ... conductive material, 17 ... bonding Stage, 18A …… Coating member, 18B …… Tool insertion slot, 18C ……
Cooling fluid spray nozzle, 18D: electric torch (arc electrode), 18E: suction tube, 18F: clamping member, 18G: support member, 18H: insulating member, 18I: crankshaft, 18J ...
Shaft, 18K Drive source, 19 Suction device, 20 Arc generator, 21 Spool holder, 21A Rotary shaft, 22 Bonding head (digital bonding head), 22A Guide member, 22B ... vertical movement block, 22C ... female screw member, 22D ... male screw member, 22E ...
Motor, 22F ... Rotary shaft, 22G ... Elastic member, 22H ... Ultrasonic oscillation mechanism, 23 ... XY table, 24 ... Base, 25 ...
Cooling fluid spray device (fluid source), 25A …… Cooling device, 25B…
… Flow meter, 25C …… Fluid transfer pipe, 25D …… Insulation material, 25E…
... Corona discharge means, 26 ... Heater, 26A ... Feed line, 31
…… Airbag tensioner, 31A …… Guide plate, 31B ……
Projection, 31C …… Fluid supply pipe, 31D …… Adapter, 31E ……
Fluid outlet, 31F ... spacer, 31G ... wire passage space, 31H ... fluid supply source, 31H1 ... corona discharge means, 32
…… Clamper, 32A1, 32A2 …… Clamper arm, 32B ……
Shaft support, 32C ... Cam mechanism, 32D ... Spring, 32E1 ... First
The second clamper chip, 32E2 ... 32E2
F …… Outlet, 32G …… Sub arm, 32H …… Screw, 32J…
... Stopper, 33 ... Resin-sealed semiconductor device, 33A ... Lead frame, 33B ... Inner lead, 33C ... Tab suspension lead, 33D ... Tab, 33E ... Package body, 33G
…… Outer lead, C1 …… Capacitor, C2 …… Storage capacitor, D …… Arc thyristor, R …… Resistance, DC… DC power supply, GND …… Reference potential, Gs …… Cooling fluid, Gs2… ... current eliminator, V ... voltmeter, A ... ammeter.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-290836 (JP, A) JP-A-61-194735 (JP, A) JP-A-57-162438 (JP, A) JP-A-2- 304944 (JP, A) JP-A-2-26347 (JP, A) JP-A-2-304943 (JP, A) JP-A-2-266541 (JP, A) JP-B-57-34659 (JP, B2) Special Publication 7-19788 (JP, B2) Special Publication 7-19789 (JP, B2)

Claims (3)

(57) [Claims] 1. A method of manufacturing a semiconductor device comprising connecting an external terminal of a semiconductor chip and a lead with a bonding wire, wherein the bonding wire has a purity of 99.99% by weight or more and gold of 0.03 to 0.3%. % Of germanium and 0.0005 to 0.01% by weight of calcium, and the bonding wire is covered with a coating film made of an insulating material to which a predetermined amount of a coloring agent is added, and one end of the bonding wire is connected to the semiconductor chip. And connecting the other end to a lead. 2. The method according to claim 1, wherein said insulating material is made of a heat-resistant polyurethane resin. 3. The method for manufacturing a semiconductor device according to claim 1, wherein a second insulating coating film is provided on said coating film.