JP4709563B2 - Manufacturing method of semiconductor device - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor device in which a semiconductor element is soldered and bonded to a substrate, and more particularly to a method capable of satisfactorily bonding to a substrate having a large surface roughness.

  In recent years, the application field of semiconductor light-emitting devices (hereinafter referred to as “LED: Light Emitting Diode”) has dramatically increased due to progress in process technology related to gallium nitride (GaN) -based compound semiconductors and technology related to phosphors. It is expanding.

  In particular, semiconductor light-emitting devices that combine LEDs that can emit light in the wavelength band from ultraviolet light to visible light and appropriate phosphors can produce white light with excellent color rendering, so backlights and buttons for liquid crystal displays Applications to lighting and various lighting of automobiles are increasing. In addition, development of high-power semiconductor light-emitting devices used as light sources for flashlights and camera flashes is also underway.

  In recent years, a new package in which a plurality of LED chips are mounted in one package as shown in FIG. 22 has been commercialized. In this package, a plurality of chips 200 are die mounted on a ceramic substrate 100.

  When the LED chip 200 having a junction down structure is die-mounted on the ceramic substrate 100, as shown in FIG. 23, the electrode surface 101 of the ceramic substrate 100 has a rough Rz of about 3 to 7 μm. The solder film 102 having a thickness of 3 μm (see, for example, Patent Document 1) cannot absorb the roughness of the electrode surface 101 of the ceramic substrate 100 and may cause poor bonding.

In order to solve this problem, a method is conceivable in which the thickness of the solder film 102 is made approximately the same as the roughness of the electrode surface 101 of the ceramic substrate 100. However, since the surface roughness of the ceramic substrate 100 also varies, when the LED chip 200 is die-mounted on the electrode surface 101 with a small variation, the molten solder protrudes to the side surface of the LED chip, and the side wall of the LED chip 200 There is a problem of contact.
JP 2003-234482 A

  The above-described semiconductor device manufacturing method has the following problems. That is, when the LED chip 200 having the junction down structure is die-mounted on the ceramic substrate 100 as described above, the electrode surface 101 of the ceramic substrate 100 is as rough as Rz 3 to 7 μm, so that the solder film 102 having a thickness of 2 to 3 μm is formed. If it is placed as it is, as shown in FIG. 24, the roughness cannot be reduced and a gap remains. For this reason, bubbles 111 are likely to be generated from this portion. If bubbles 111 remain in the solidified solder material, there is a problem that heat is not easily released from the heated LED chip 200 to the ceramic substrate 100 side. In addition, when cracks occur in the solder, there are problems in terms of reliability, such as the cracks tend to develop in the bubbles and the connection resistance increases.

  In order to solve this problem, there is a method of making the thickness of the solder film as high as the roughness of the electrode surface, but it is difficult to increase the thickness of the solder film generated by vapor deposition or sputtering from the viewpoint of cost. .

  In addition, even when the solder film can be formed thick, the surface roughness of the wiring board also varies, so when die-mounted on an electrode with small variations, conventional bonding in which the chip is mounted by pressure heating In the system, since the melted solder protrudes to the side surface of the chip and comes into contact with the side wall, there is a problem that the difficulty of the process becomes high.

  For this reason, the manufacturing method which implement | achieves a good solder joint to the connection base material with rough electrode surfaces, such as a ceramic, at low cost using the semiconductor element in which the solder film thickness of 2-3 micrometers was formed in the connection electrode is required. It has become.

  Therefore, the present invention provides a method for manufacturing a semiconductor device that can achieve high-reliability and good bonding at low cost even when a semiconductor element is bonded to a substrate having a rough surface such as a ceramic substrate. It is intended to provide.

  In order to solve the above-mentioned problems and achieve the object, a semiconductor device manufacturing method of the present invention is configured as follows.

(1) In a method of manufacturing a semiconductor device in which a terminal of a semiconductor element is joined to a connection electrode of a substrate, a step of thermocompression bonding a metal bulk material to the connection electrode with ultrasonic waves and a contact surface of the metal bulk material are flat. A step of flattening by pressing with a tool, a step of heating the substrate, a semiconductor element having a solder film formed on the terminal is mounted on the substrate, the solder film is melted, and the terminal and the connection are connected and a step of bonding the electrode, in the step of the flattening, the ultrasonic vibrations perpendicular to the load direction of said tool, and characterized in that it applied to the two-way direction orthogonal to each other.

(2) In a method of manufacturing a semiconductor device in which a terminal of a semiconductor element is joined to a connection electrode of a substrate, a step of ultrasonically bonding a gold-tin metal bulk material to the connection electrode together with the ultrasonic contact with the metal bulk material A step of flattening by pressing with a tool having a flat surface, a step of heating the substrate, a semiconductor element having a tin-based metal film formed on the terminal is mounted on the substrate, and the metal film is melted and a step of joining the said terminal and the connection electrode, in the step of the flattening, the ultrasonic vibrations perpendicular to the load direction of said tool, and, applying the two-way direction orthogonal to each other It is characterized by.

(3) In a method for manufacturing a semiconductor device in which a terminal of a semiconductor element is bonded to a connection electrode of a substrate, a step of thermocompression bonding a metal bulk material to the connection electrode with ultrasonic waves and a contact surface of the metal bulk material are flat. A step of flattening by pressing with a tool, and a step of thermocompression bonding a semiconductor element having a metal film formed on the terminal to the substrate by using ultrasonic vibration. the ultrasonic vibration orthogonal to the load direction of said tool, and characterized in that it applied to the two-way direction orthogonal to each other.

  According to the present invention, even when a semiconductor element is bonded to a substrate having a rough surface such as a ceramic substrate, high reliability and good bonding can be realized at low cost.

  1-3 is a figure which shows an example of LED30 applied to each embodiment of this invention, Comprising: FIG. 1 is a top view, FIG. 2 is a side view, FIG. 3 is a bottom view. FIG. 4 is a plan view showing a ceramic substrate 40 similarly applied to each embodiment.

  The LED 30 is a double-sided electrode LED having a junction-down structure, and has a quadrangular frustum-shaped chip body 31 formed of a Si compound. The chip size of the die mount surface (lower side in FIG. 2) is 0.3 mm square, and the opposite surface (upper side in FIG. 2) is 0.2 mm square.

  A wire bonding pad 32 is provided on the upper surface 31a of the chip body 31, an epitaxial layer 33 is formed on the lower surface 31b, and a terminal electrode 34 is formed on the lower surface. In the terminal electrode 34, a Ni film is formed on the barrier metal, and a gold-tin solder film for bonding is formed to a thickness of 2.0 μm.

  In order to prevent a short circuit failure due to solder creeping up, the size of the terminal electrode 34 is smaller than the chip area, for example, 0.2 mm square. In a region other than the terminal electrode 34 on the lower surface 31b of the chip body 31, a passivation film 35 is formed of polyimide.

  The ceramic substrate 40 includes a base material 41 made of an alumina material, and a wiring 42 formed of tungsten is provided on the base material 41. The size of the base material 41 is, for example, 5.0 mm square and a thickness of 0.3 mm. On the tungsten surface of the wiring 42, Ni is electrolytically plated with a thickness of 5.0 μm, and gold is electrolytically plated on the Ni with a thickness of 0.5 μm. Further, a connection electrode 43 is formed on a part of the wiring 42. The wiring width is formed wider than the terminal electrode 34 of the LED 30 and is, for example, 0.4 mm. Since the base material 41 of the ceramic substrate 40 is formed by firing, the surface of the connection electrode 43 is rough, and the Rz is around 7.0 μm.

  5-10 is sectional drawing which shows typically the LED manufacturing method based on the 1st Embodiment of this invention, FIG. 11 is a graph which shows a heating profile. A gold wire having a purity of 99.99% and a wire diameter of 25 μm was used as a metal wire for forming a metal bump (metal bulk material). Moreover, the rosin type flux which has the activity power of RMA was used for the flux.

  First, the ceramic substrate 40 is heated to 250 ° C., a 70 μm gold ball formed at the tip of the gold wire is pressurized with a load of 0.6 N using a capillary, and an ultrasonic vibration with an amplitude of 1.0 μm is applied for 30 ms. Apply. Thereby, the gold bump (metal bulk material) 50 is joined on the connection electrode 43 (FIG. 5). A capillary made of alumina ceramic is used. Instead of forming the gold bump, metal (metal bulk material) may be supplied to the connection electrode 43 by wedge bonding.

  Next, the ceramic substrate 40 is heated to 200 ° C., and a flattening tool 60 having a surface roughness Ra of 0.1 μm and a flatness of 1.0 μm is pressed with a load of 10 N per bump to form a flat surface of 250 μmφ (FIG. 6). ). The flattening tool 60 is formed of, for example, a cemented carbide D30, and the tip is coated with an artificial diamond that is vapor-phase grown.

  By pressing with the flattening tool 60, Ni plated on the surface of the connection electrode 43 is also deformed, and a flat surface having a diameter of 250 μm can be formed. Further, by applying ultrasonic vibration having an amplitude of 2.0 μm to the flattening tool 60 and flattening the gold bump 50, the gold bump 50 that has been spread is solid-phase diffused with gold plated on the connection electrode 43. As a result, better bonding can be ensured.

  Furthermore, by applying ultrasonic waves in the load application direction of the flattening tool 60, the gold bumps 50 can be spread out concentrically. When the amplitude is applied in a direction orthogonal to the load direction, the gold bump 50 is expanded in the amplitude direction, and the flat surface becomes elliptical. As a countermeasure, it is possible to form a flattened surface close to a perfect circle by dividing the flattening process into two steps and applying ultrasonic waves in two directions perpendicular to each other in the surface direction of the ceramic substrate 40. It is.

  After planarization, the flux 51 is supplied onto the gold bump 50 by dispensing (FIG. 7), and the LED 30 is mounted with a load of 0.5 N (FIG. 8). After the LED 30 is mounted, the ceramic substrate 40 is passed through a reflow furnace, and the gold-tin solder film formed on the terminal electrode 34 is melted and soldered (FIG. 9). In the heating profile, for example, as shown in FIG. 11, the temperature is raised from room temperature to 300 ° C. at a constant rate in 60 seconds and then cooled. After the reflow, the sample is immersed in isopropyl alcohol, and 38 kHz ultrasonic waves are applied for 15 minutes to clean the residue of the flux 51, thereby completing the die mounting process (FIG. 10).

  As described above, according to the manufacturing method of the semiconductor device according to the first embodiment, when the LED 30 is mounted on the ceramic substrate 40 having a rough surface, a thick solder film cannot be formed on the terminal electrode 34 on the LED 30 side. Even in such a case, by supplying a metal bulk material that is sufficient and free of bubbles from the gold bump 50 or the like, the roughness of the ceramic substrate 40 can be alleviated, and poor bonding due to generation of voids during reflow melting is prevented. can do.

Note that the flux 51 is not supplied after the flattening of the gold bump 50, and the ceramic substrate 40 is heated to a temperature higher than the melting point of the gold-tin solder film of the terminal electrode 34, and a reducing atmosphere of N ₂ 95% + H ₂ 5%. The semiconductor element 30 may be mounted on the ceramic substrate 40 below. In this case as well, it is possible to carry out a good solder joint.

  12 to 15 are cross-sectional views schematically showing a method for manufacturing a semiconductor device according to the second embodiment of the present invention. In the present embodiment, the metal film 52 is used in place of the gold bump 50 when the flat film-like metal bulk material described above is formed (FIG. 12). The metal film 52 has a purity of 99.99% and is formed to have a 250 μm square and a 10 μm thickness with one side 50 μm larger than the terminal electrode 34. The gold thin film 52 is mounted on the heated connection electrode 43, and is pressed using the planarizing tool 60 while applying ultrasonic waves (FIG. 13). After flattening, the flux 51 is supplied onto the gold thin film 52 by dispensing, and the LED 30 is mounted with a load of 0.5 N (FIG. 14). After the LED 30 is mounted, the ceramic substrate 40 is passed through a reflow furnace, and the gold-tin solder film formed on the terminal electrode 34 is melted and soldered. After reflow, the sample is immersed in isopropyl alcohol, and 38 kHz ultrasonic waves are applied for 15 minutes to clean the residue of the flux 51, thereby completing the die mount process (FIG. 15).

  In the method of manufacturing the semiconductor device according to the second embodiment, it is possible to form a metal flattening film that can be satisfactorily soldered similarly to the method of manufacturing the semiconductor device according to the first embodiment described above. It is.

  16 to 18 are cross-sectional views schematically showing a method for manufacturing a semiconductor device according to the third embodiment of the present invention. Note that a tin-based solder film is formed on the terminal electrode 34 of the LED 30.

  In the present embodiment, a gold-tin eutectic alloy bump 53 is formed on the connection electrode 43 (FIG. 16). Next, the flux 51 is dropped on the gold-tin eutectic alloy bump 53 (FIG. 17), the terminal electrode 34 is aligned with the connection electrode 43, and the LED 30 is mounted. Next, heating is performed in a reflow furnace, and the tin-based solder film on the gold-tin eutectic alloy bump 53 and the terminal electrode 34 is melted and soldered (FIG. 18). This is because by increasing the ratio of tin in the solder material sufficiently, the time is increased from the liquid phase to the solid phase so that bubbles can be easily removed. Therefore, solder joining with less bubbles is possible. Finally, the flux residue is washed to complete the solder bonding between the chip and the substrate.

  Further, according to the present embodiment, since the gold-tin eutectic alloy bump 53 formed on the connection electrode 43 can be melted, a metal film other than solder, such as Au or Ni, is formed on the terminal electrode 34. Even if it is a film | membrane, favorable soldering can be performed.

  In the above-described process, the gold-tin eutectic alloy bump 53 is not flattened, but the gold-tin eutectic alloy bump 53 is flattened using the flattening tool 60 as in the first embodiment. Also good. Thereby, it is possible to reduce the damage which the connection electrode 43 receives when mounting the LED 30.

  19 to 21 are cross-sectional views schematically showing a method for manufacturing a semiconductor device according to the fourth embodiment of the present invention. Note that a gold film having a thickness of 0.1 μm is formed on the terminal electrode 34 of the LED 30 by sputtering or vapor deposition.

  In this manufacturing method, as in the semiconductor manufacturing method according to the first embodiment described above, the gold bumps 50 are formed (FIG. 19), and after the gold bumps 50 are planarized (FIG. 20), the temperature is increased to 200.degree. The LED 30 is adsorbed on the heated substrate with the bonding tool 61, and is pressurized for 30 ms with a load of 4N while applying ultrasonic vibration with an amplitude of 1.0 μm (FIG. 21). Thereby, in the gold film of the terminal electrode 34 and the gold bump 50, solid phase diffusion of gold and gold is performed, and good bonding can be ensured. Note that the bonding tool 61 is made of a cemented carbide D30, as with the planarization tool 60, and the tip is coated with an artificial diamond that is vapor-phase grown.

  In the method of manufacturing the semiconductor device according to the fourth embodiment, it is possible to form a metal flattening film that can be satisfactorily soldered in the same manner as in the method of manufacturing the semiconductor device according to the first embodiment described above. It is.

  In each of the above-described embodiments, the case where the terminal of the semiconductor element is bonded to the connection electrode of the substrate has been described. However, the present invention can also be applied to so-called die bonding for simply bonding the semiconductor element on the substrate.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The top view which shows the semiconductor light-emitting device used for each embodiment of this invention. The side view which shows the semiconductor light-emitting device. The bottom view which shows the same semiconductor light-emitting device. The top view which shows the ceramic substrate used for the embodiment. Sectional drawing which shows typically the process of the manufacturing method of the semiconductor device which concerns on the 1st Embodiment of this invention. Sectional drawing which shows the same process typically. Sectional drawing which shows the same process typically. Sectional drawing which shows the same process typically. Sectional drawing which shows the same process typically. Sectional drawing which shows the same process typically. The graph which shows the reflow heating profile in the same process. Sectional drawing which shows typically the process of the manufacturing method of the semiconductor device which concerns on the 2nd Embodiment of this invention. Sectional drawing which shows the same process typically. Sectional drawing which shows the same process typically. Sectional drawing which shows the same process typically. Sectional drawing which shows typically the process of the manufacturing method of the semiconductor device which concerns on the 3rd Embodiment of this invention. Sectional drawing which shows the same process typically. Sectional drawing which shows the same process typically. Sectional drawing which shows typically the process of the manufacturing method of the semiconductor device which concerns on the 4th Embodiment of this invention. Sectional drawing which shows the same process typically. Sectional drawing which shows the same process typically. The perspective view of the semiconductor device of the new package which mounted the some LED chip which concerns on a prior art example in one package. The block diagram of the semiconductor device which uses the ceramic substrate with the rough electrode surface which concerns on a prior art example. The block diagram of the semiconductor device which the bubble entered into the junction part which concerns on a prior art example.

Explanation of symbols

  30 ... LED, 34 ... terminal electrode, 40 ... ceramic substrate, 43 ... connection electrode, 50 ... gold bump, 51 ... flux, 52 ... metal film, 53 ... gold-tin eutectic alloy bump, 60 ... flattening tool, 61 ... Bonding tool.

Claims (3)

In a method for manufacturing a semiconductor device in which a terminal of a semiconductor element is bonded to a connection electrode of a substrate,
A step of thermocompression bonding of a metal bulk material to the connection electrode with ultrasonic waves;
The metal bulk material is flattened by pressing with a tool having a flat contact surface;
Heating the substrate;
Mounting a semiconductor element having a solder film formed on the terminal on the substrate, melting the solder film, and joining the terminal and the connection electrode;
In the step of the flattening, the ultrasonic vibrations perpendicular to the load Direction of the tool, and a method of manufacturing a semiconductor device, which comprises applying to the two-way direction orthogonal to each other. In a method for manufacturing a semiconductor device in which a terminal of a semiconductor element is bonded to a connection electrode of a substrate,
A step of thermocompression bonding a gold-tin metal bulk material to the connection electrode with ultrasonic waves;
The metal bulk material is flattened by pressing with a tool having a flat contact surface;
Heating the substrate;
Mounting a semiconductor element in which a tin-based metal film is formed on the terminal on the substrate, melting the metal film, and joining the terminal and the connection electrode;
In the step of the flattening, the ultrasonic vibrations perpendicular to the load Direction of the tool, and a method of manufacturing a semiconductor device, which comprises applying to the two-way direction orthogonal to each other In a method for manufacturing a semiconductor device in which a terminal of a semiconductor element is bonded to a connection electrode of a substrate,
A step of thermocompression bonding of a metal bulk material to the connection electrode with ultrasonic waves;
The metal bulk material is flattened by pressing with a tool having a flat contact surface;
The substrate is provided with a step of thermocompression bonding a semiconductor element having a metal film formed on the terminal together with ultrasonic vibration,
In the step of the flattening, the ultrasonic vibrations perpendicular to the load Direction of the tool, and a method of manufacturing a semiconductor device, which comprises applying to the two-way direction orthogonal to each other.

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