JPH08306861A - Chip resistor - Google Patents

Abstract

PURPOSE: To provide a rectangular contact area of an electrode and a resistor along facing lateral sides, and enable utilization of a lower layer of the electrode required as a bonding area, as a resistor via a second insulating layer, so as to increase the area of the resistor and improve efficiency of the resistor in a wafer. CONSTITUTION: A resistor layer 12 as a resistor is provided below a second insulating layer 21. A contact portion 22 is formed as a longitudinally large rectangle. An electrode 13 is extended on the second insulating layer 21 so as to secure the area of the electrode. Thus, since the resistor portion has a higher calorific value than the electrode portion, more heat can be radiated by a heat sink or a metal substrate provided below the resistor. The aluminum electrode 13 is provided on facing lateral sides of the rectangular resistor layer 12, and an aluminum thin wire 14 is bonded thereon. Thus, an efficient chip size of the chip resistor can be realized with redundant portions being unnecessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip resistor, and more particularly to a chip resistor having excellent heat dissipation and efficient size.

[0002]

2. Description of the Related Art Generally speaking, a chip component is a passive element by a technique such as screen printing on a ceramic substrate.
Resistors, capacitors, coils, etc. are formed and mounted on the hybrid substrate. For example, it is described in detail in IC mounting technology (second edition in 1981) issued by the Industrial Research Council.

The present application corresponds to the chip resistor of the above, and generally, a current is caused to generate a voltage at both ends, and this voltage is picked up and fed back to a circuit controlled via a control circuit or the like. And protects and controls the circuit. For example, JP
According to Japanese Patent Laid-Open No. 3-128675, a resistor is attached to the emitter side of the output transistor, and a current flowing through the resistor is detected to protect the output transistor.

What is called a chip resistor as described above is
Generally mounted on an insulating substrate such as a ceramic substrate,
This is not preferable in consideration of the temperature characteristics of the resistor itself, the thermal conductivity of the insulating substrate, and the like. In this publication, the Cu wiring itself attached to the metal substrate is utilized, and the thermal conductivity depends on the temperature of the metal substrate. The characteristics were compensated by mounting an element that compensates for the positive temperature characteristics.

Further, in order to reduce the loss, it is necessary for the resistor to have an extremely small resistance value, and since it is Cu as described above, the resistance value can be made small in a relatively narrow disposition area, and the metal substrate Therefore, the heat dissipation is good and an extra current can be flowed accordingly. However, when a part of the Cu wiring described above is used as a resistor, the Cu wiring has a variation in thickness in the rolling process for forming a foil shape, and the wiring is formed by sticking this on the entire surface of the substrate and then etching it. In addition, there is a problem that a highly accurate product cannot be obtained due to variations in etching and side etching. Further, the temperature coefficient of Cu is as high as about 4000 ppm, and it has been necessary to correct the variation of the resistance value due to the temperature change with, for example, a diode.

A chip resistor for forming a resistor on a substrate made of an insulating material such as a ceramic substrate can be easily mounted by an automatic die-bonding device or the like, but the thermal conductivity of the substrate itself is small and a large current can be applied. There was a problem that it was difficult to release the heat generated when flowing it to the outside. Therefore, Japanese Patent Application No. 7-119
No. 15 (see FIG. 5), an insulating film 2 is formed on a silicon semiconductor substrate 1, a resistance film 3 formed by a semiconductor technique is provided on the insulating film 2, and the silicon substrate 1 is attached to a heat sink 4 or a direct metal substrate 5. It was implemented and solved.

[0007]

The chip resistors adopting the semiconductor substrate 1 have a size of, for example, 4.2 mm in length and width, and are formed in large quantities in a matrix on a wafer. Therefore, the cost of one chip is determined by how many can be made on one wafer. On the other hand, in order to transfer the heat generated in the chip resistor to the heat sink 4 attached to the lower layer or the metal substrate 5 directly attached, the larger the area to which the chip resistor is connected, the better the chip size. There was a problem I had to do.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. Firstly, the resistive film is provided with a predetermined width along at least opposite sides of a rectangular shape. This is solved by having the second insulating layer, an electrode that is in contact with the resistance film exposed in the vicinity of the opposite side, and a thin metal wire that is in contact with the electrode.

Secondly, the aluminum thin wire is bonded with a length parallel to the pair of side edges of the resistor, and the length of the pair of side edges is equal to the electrode formed on the resistor and the aluminum thin wire. The solution is to make the connection length to and substantially equal. Thirdly, the length of the pair of sides is determined by the length of the connection length between the electrode and the aluminum thin wire plus a margin necessary for bonding.

[0010]

In the first place, the most important point is how to efficiently determine the size in order to transfer the heat generated in the resistor to the heat transfer means provided in the lower layer. As will be described later, when a current is applied, for example, in FIG. 10, the electrode that is in direct contact with the resistance film has a lower surface temperature than the resistance film. Therefore, the area of the electrode that contacts the resistor as much as possible is
It is necessary to make the necessary minimum necessary for the current to flow. However, the area required for bonding is required for the electrode. Therefore, an electrode is placed on the second insulating film to secure an area necessary for bonding, while the contact portion between the resistor and the electrode required for the flowing current has a predetermined area along the opposite side edges. The second insulating film is processed by etching so as to make contact with a certain width. Therefore, the contact area between the electrode and the resistor can be minimized and the second
The lower layer of the insulating film can be used as a resistor. Therefore, the area of the high temperature resistor can be increased, more heat can be transmitted to the heat transfer means provided in the lower layer, and the size of the chip resistor is not limited to the extra portion (T shown in FIG. The required vertical and horizontal margins of fine lines are not required, and an efficient chip size can be achieved.

Secondly, the main part of the chip resistor which generates heat is the exposed region which is not covered with the electrodes as described above, and the electrode part does not generate heat. Therefore, the electrode portion in contact with the aluminum thin wire is necessary as a portion for supplying a current to the resistor, but the electrode portion not in contact with the thin wire is difficult to work as a main current supplying portion, and the resistor It is also difficult to serve as the main medium for transmitting the heat generated by the heat sink to the heat sink or the substrate below. Therefore, the utilization efficiency of the chip is improved by making the lengths of the pair of sides substantially equal to the contact length between the electrode formed on the resistor and the aluminum thin wire.

Thirdly, since a slight margin is required for the size of the electrode for bonding, the length of the pair of sides is set to the connection length between the electrode and the aluminum thin wire. Good bonding can be achieved by determining the length including the margin required for bonding.

[0013]

EXAMPLES Before explaining the examples of the present invention,
The reason for using silicon will be described. Normal IC
The use of silicon wafers used in the manufacturing process or defective wafers discharged in the manufacturing process, which can be produced in large quantities by ordinary semiconductor technology within the wafer, and is also discarded as substrates to be formed. Since you can use, you can significantly reduce the cost. In addition, a resistor is formed on a wafer by ordinary semiconductor technology, and it is used as a substrate (heat sink) having a higher thermal conductivity than an insulating substrate such as ceramic, and is mounted by an automounter like a semiconductor chip. . Therefore,
It can be automatically mounted as shown in Fig. 2 by supplying it from the manufacturer on a wafer-by-wafer basis, directly on a metal substrate or with a heat sink attached.

Here, the case of employing a defective wafer will be briefly described. For example, the manufacturing process of a bipolar IC will be roughly described as follows. First (1)
Preparation of P-type substrate, (2) Surface oxidation, (3) Forming an inlet in a part of this oxide film, (4) N + buried layer formation, (5) Oxide film removal, (6) N-type Formation of epi layer,
(7) Oxidation of epi layer surface, (8) Formation of oxide film at isolation inlet, (9) Diffusion of isolation,
(10) Base inlet and base diffusion, (11)
There are 14 steps including formation and diffusion of an emitter introduction port, (12) oxide film removal, (13) oxide film formation, (14) contact port formation, and (14) metal formation.

Generally, when forming a passive element, it is preferable that the surface is flat. Therefore, (1) to (2),
Those that have become defective in the steps (5) to (7) and (12) are preferable. That is, an insulating film and /
Alternatively, this is because the epitaxial layer is formed, but since there is no unevenness for the introduction port or the contact, the wafer surface is flat.

In the MOSIC manufacturing process, (1) P
Preparation of mold substrate, (2) whole surface oxidation, (3) whole surface formation of silicon nitride film, (4) removal of the nitride film for locos oxidation, (5) locos oxidation using the nitride film as an oxidation resistant mask,
(6) Removal of nitride film and oxide film, (7) Formation of gate oxide film, (8) Forming gate, forming source / drain by self-aligning with gate, (9) Forming insulating film by CVD on entire surface, There are 11 steps of (10) contact formation and (11) metal formation.

As described above, since the substrate surface is preferably flat, the wafers that are defective in (1) to (3) are preferable. In addition to the preferred steps described above, glass or the like may be first formed on the uneven wafer to make it flat, or the uneven surface may be etched to make it flat. First, a description will be given with reference to FIGS. A first insulating layer 11 is formed on the surface of the silicon substrate 10. The insulating layer 11 is, for example, a thermal oxide film, a silicon oxide film or a silicon nitride film formed by CVD, or another insulating layer. On the insulating layer 11, tantalum nitride or a resistance film 1 in which Cr-Ni-Mn is laminated in this order
2 are provided. The resistance film may be made of other materials, such as polysilicon, but is not preferable because of its temperature characteristics. If possible, those having less temperature characteristics are preferable. The tantalum nitride content is about 50 ppm / degree.

Further, here, a rectangular silicon substrate 10 is used.
A resistance film is formed on the entire surface and the shape is exactly the same. This is the same so that the number of wafers taken in the wafer is large, but since the silicon substrate itself also acts as a kind of heat sink, it may be larger than the resistor. Then, the second insulating layer 21 is provided on the resistor 12. The present application only needs to have a predetermined width along the opposite sides of the contact portion between the electrode 13 and the resistance film 12 shown by 22, and even if the second insulating film is provided on the entire surface, it is the same as the present application. Alternatively, only the bonding portion may be provided. In the case of the present application, since the insulating film 21 is not provided, more heat can be released from here to the passivation film provided thereon, or to the external atmosphere in contact with this portion if not provided.

The feature of the present invention resides in that a resistance film acting as a resistor is provided under the second insulating film. That is, the contact portion 22 is realized by changing the width and thickness of the contact portion 22 according to the electric current to be passed, and is formed as a vertically long rectangle. Since this portion is insufficient as a wire bonding area, the electrode 13 is extended on the second insulating film 21 to secure the area of the electrode. Therefore, a resistor can be formed in the lower layer of the second insulating film 21, and more heat-generating resistor portions can be arranged as compared with FIG.

That is, as shown in FIGS. 7 to 10 (which will be described later), since the resistor portion has a larger amount of heat generation than the electrode portion, the area of this portion can be increased, and the heat sink or the metal provided below it. More heat can be released to the substrate. Electrodes 13, 13 made of aluminum are provided on opposite sides of the rectangular resistor film 12, and aluminum thin wires 14 are ultrasonically bonded on the electrodes 13, 13. Other than this, the thin wire may be copper or gold, or an alloy mainly containing them. Considering the supply of electric current, the contact form as shown in FIG. 1 having a large contact area is preferable. Although not shown in the figure, the other end of the thin wire is electrically connected to the wiring forming the circuit provided on the metal substrate.

The above chip resistor is fixed to a heat sink made of a metal having excellent heat conduction, for example, copper. As a fixing method, soldering or fixing with a silver paste 16 can be considered, and a back surface electrode in which tantalum / palladium / nickel / gold is laminated is provided on the back surface of the silicon substrate 10 in consideration of the fixing strength. In the present invention, the metal substrate 17
Is a substrate mainly having a wiring pattern 18 provided thereon, and a heat sink having a chip resistor mounted thereon is fixed to one of the lands via a solder 19.

Here, the metal substrate 17 may be copper or aluminum, on which an insulating resin 20 such as polyimide is provided.
The wiring pattern is fixed by hot pressing via. A polyimide or silicon nitride film is passivated on the chip resistor for the purpose of passivation, and silicone or the like including the heat sink 15 is potted. The groove provided in the heat sink 15 bites this potting resin to prevent resin peeling.

Next, description will be made with reference to FIGS. 3 and 4. Similarly to the above, the insulating layer 11 is formed on the surface of the silicon substrate 10.
Are formed. This insulating layer is, for example, a thermal oxide film, C
A silicon oxide film or a silicon nitride film by VD, other insulating layers, and the like. On the insulating layer 11, a resistance film 12 is provided in which tantalum nitride or Cr-Ni-Mn is laminated in this order. The resistance film may be made of other materials, such as polysilicon, but is not preferable because of its temperature characteristics. If possible, those having less temperature characteristics are preferable. The tantalum nitride content is about 50 ppm / degree.

Further, here, a rectangular silicon substrate 10 is used.
A resistance film is formed on the entire surface and the shape is exactly the same. This is the same so that the number of wafers taken in the wafer is large, but since the silicon substrate itself also acts as a kind of heat sink, it may be larger than the resistor. If this is done, heat will be generated mainly in the exposed resistance film, which will be described later, so the non-overlapping portion of the resistor is less likely to act as a medium for heat transfer than the overlapping portion, but at least it is better than at least the metal substrate. I can tell a lot.

Electrodes 13, 13 made of aluminum are provided on opposite sides of the rectangular resistor film 12, and aluminum thin wires 14 are ultrasonically bonded on the electrodes 13, 13. Other than this, the thin wire may be copper or gold, or an alloy mainly containing them, but in consideration of current supply, a contact form having a large contact area as shown in FIG. 1 is preferable. Although not shown in the figure, the other end of the thin wire is electrically connected to the wiring forming the circuit provided on the metal substrate.

The chip resistor described above is fixed to a heat sink made of a metal having excellent heat conduction, for example, copper. As a fixing method, soldering or fixing with a silver paste 16 can be considered, and a back surface electrode in which tantalum / palladium / nickel / gold is laminated is provided on the back surface of the silicon substrate 10 in consideration of the fixing strength. In the present invention, the metal substrate 17
Is a substrate mainly having a wiring pattern 18 provided thereon, and a heat sink having a chip resistor mounted thereon is fixed to one of the lands via a solder 19.

Here, the metal substrate 17 may be copper or aluminum, on which an insulating resin 20 such as polyimide is provided.
The wiring pattern is fixed by hot pressing via. A polyimide or silicon nitride film is passivated on the chip resistor for the purpose of passivation, and silicone or the like including the heat sink 15 is potted. The groove provided in the heat sink 15 bites this potting resin to prevent resin peeling.

As described above, the temperature coefficient TCR of the resistor
Is approximately ± 50 PPM and can be realized as a resistor of several mmΩ. 1989 Science Book of Volume 62, 47
According to page 7, alumina has 21 κ at room temperature, polyethylene has about 0.25, silicon has 168 κ at 0 degrees, aluminum has 236 κ at 0 degrees, and Cu has 403 κ at 0 degrees. Here, the unit of κ is W / (m · K). Needless to say, since it is arranged on the silicon substrate 10, it has a better heat dissipation property than the resistor formed on the insulating substrate.

The feature of the present invention is that the thin metal wire 14 and the electrode 13 are provided.
There is a relationship between the contact size with and the size of the chip resistor. This will be described below with reference to FIGS. 5 and 7 to 10. As shown in FIG. 5, in the case of a square size, for example, 4.2 mm square, and the electrode is provided long except for the contact portion of the thin metal wire, the portion indicated by T in FIG. 5 has a problem in terms of efficient shape. I found out that there is. The width of the electrode is 0.5 mm, and the diameter of the thin aluminum wire is 300 μm.

The tortuous lines in FIGS. 7 to 10 show the temperature distribution when viewed by thermovision.
The resistance value is, for example, 10 ohms. The currents in the figure are 1.0 amp, 1.5 amp, 1.8 amp, and
It is 2.0 amps. As a whole, it was found that the exposed portion of the resistor, which did not overlap the electrode, had a higher surface temperature than the portion provided with the electrode. That is, since the resistance value of the electrode portion is almost zero and the exposed portion has the resistance value, there is a difference in temperature between the region where the electrode is present and the resistance film exposed region. For example, in FIG. 7, the area surrounded by the line a is about 51 degrees, and the area surrounded by the lines a and b is
At about 49 degrees, the area surrounded by the line b and the chip periphery was about 46. That is, there is a difference of about 5 degrees.

On the other hand, in FIG. 10, the part surrounded by the line a is 127.5 degrees, the area surrounded by the lines a and b is 125 degrees, and the area surrounded by the line b and the chip periphery is 110 degrees. There is a difference of 27.5 degrees between the electrode part and the exposed part. Here, a region T that does not overlap the thin line shown in FIG.
Is a portion that is difficult to act as a main current path that flows in or out of the thin wire. Moreover, considering the surface temperature, the temperature of the electrode portion is low, and the amount of heat transferred to the heat sink or the metal substrate is smaller than that of the high heat portion. Therefore, since it is a portion that is hard to work as a medium through which an electric current flows and is hard to work in terms of heat dissipation, if this portion is removed, the chip area becomes smaller and an efficient number of wafers can be obtained. However, if the T portion is removed in FIG. 5, the shape is + and the efficiency is poor.

Therefore, as shown in FIG. 3, if the vertical length of the rectangular resistor is determined by the contact length between the thin metal wire 14 and the electrode, the T portion can be removed and the wafer has a rectangular shape. It can be arranged efficiently and efficiently without any gaps. However, since a certain margin is actually required for the bonding work, the vertical length is determined by the size including this margin.

For example, the length of L (from the head to the neck of the thin wire) depends on the bonding tool, but the length of the thin wire is 2 to 2.
The margin required in the vertical and horizontal directions from the contact portion between the resistor and the electrode is three times, and the margin required for the tool is about 10 microns. Therefore, the vertical size of the electrode is the sum of the contact length (2 to 3 times the wire diameter) and the vertical total of 20 microns, and the horizontal is the contact area of 1.2 to 1.5 times the wire diameter. A total width of 20 microns is required as a margin for the width.

However, in FIG. 3, the thin wire extends from the upper side and contacts at one place on the left and right, but depending on the current capacity, two thin wires extend from the upper side and the lower side, respectively, and there are two places on one electrode. May be connected. In this case, the required margin (at least 10 microns or more) is added between the two wires extending from above and below twice the size described above.

Once the vertical size is determined, the area of the resistor is determined by the desired resistance value and the amount of heat generated by the flowing current, and the horizontal size is determined by this area. It is possible to form a resistor by determining the specific resistance and thickness of the. This series of calculations enables efficient design of the chip shape. Further, as described above, if the resistors and the silicon substrate have the same size, the number of the taken resistors can be made efficient, so that a low cost can be realized.

[0036]

As is apparent from the above description, the first
In addition, since the contact area between the electrode and the resistor is provided in a rectangular shape along the opposite sides, the lower layer of the electrode required as a bonding area can be utilized as the resistor through the second insulating film. Conventionally, since the electrodes are in contact with each other over the entire surface, the amount of heat generated is small, but since the lower layer of the second insulating layer can be utilized as a resistor, the amount of heat generated can be increased. In other words, the area of the resistor in the heat generating part can be expanded,
Since the area can be expanded, more heat can be transferred to the heat transfer means provided in the lower layer. That is, if the chip size is the same as the conventional one and the current and resistance values are the same, the second
More heat can be transferred to the lower portion by the amount of the resistor provided in the insulating film.

Secondly, the main part of the chip resistor that generates heat is the exposed region that is not covered by the electrode, and the part of the electrode that does not generate much heat. Therefore, the electrode part that is in contact with the thin aluminum wire is necessary as a part that supplies current to the resistor, but the electrode part that is not in contact with the thin wire does not work mainly as a current supplying part, and It does not serve as a main medium for transmitting the heat generated by the heat sink to the heat sink or the substrate below. Therefore, the utilization efficiency of the chip is improved by making the lengths of the pair of sides substantially equal to the contact length between the electrode formed on the resistor and the aluminum thin wire. Therefore, if it is formed in the wafer with this appropriate shape, a large number of chips can be efficiently arranged, and the cost can be reduced.

Thirdly, since a slight margin is required for the size of the electrode for bonding, the length of the pair of sides is set to the connection length between the electrode and the aluminum thin wire. By determining the length including the margin necessary for bonding, good bonding can be achieved, and the yield is also improved.

[Brief description of drawings]

FIG. 1 is a plan view illustrating a chip resistor of the present invention.

FIG. 2 is a cross-sectional view of FIG.

FIG. 3 is a plan view illustrating a chip resistor of the present invention.

4 is a cross-sectional view of FIG.

FIG. 5 is a plan view illustrating a conventional chip resistor.

FIG. 6 is a sectional view of FIG. 5;

FIG. 7 is a diagram illustrating a surface temperature of a chip resistor.

FIG. 8 is a diagram illustrating a surface temperature of a chip resistor.

FIG. 9 is a diagram illustrating a surface temperature of a chip resistor.

FIG. 10 is a diagram illustrating a surface temperature of a chip resistor.

Claims (3)

[Claims] 1. A first insulating layer provided on a semiconductor substrate mainly composed of substantially rectangular silicon, a resistance film provided via the insulating layer, and at least opposite sides of the rectangular shape. A second insulating layer provided so as to expose the resistance film with a predetermined width along the side, an electrode contacting the resistance film exposed in the vicinity of the opposite side, and a contact with the electrode. And a thin metal wire. 2. An insulating layer provided on a semiconductor substrate mainly made of substantially rectangular silicon, and a rectangular resistance film provided on the entire surface of the substantially semiconductor substrate facing the insulating layer are opposed to each other. An electrode suitable for aluminum bonding provided on a pair of sides, and at least an aluminum thin wire bonded to the electrode, the aluminum thin wire is bonded with a length parallel to the pair of sides, The chip resistor, wherein the length of the pair of sides is substantially equal to the connection length between the electrode and the aluminum thin wire. 3. The chip resistor according to claim 2, wherein the length of the pair of sides is a connection length between the electrode and the thin aluminum wire plus a margin necessary for the bonding.