JP3265300B2 - Solder material for semiconductor device, semiconductor device using the same, and method of manufacturing the semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device has high heat resistance with low environmental loads using a die bonding material and in which the reliability of the semiconductor device is considered using this material and its manufacturing method, since the material that can be substituted for a lead/tin solder alloy out of consideration for the environment even in the field of a high power semiconductor device, such as a power transistor, is required. SOLUTION: A semiconductor element 1 is bonded to a substrate 2 or a heat sink using an alloy 3 that contains silver and copper and of which the primary component is tin. This alloy 3, for example, has the composition consisting of the silver of 8 to 15 weight percentage, the copper of 0.5 to 3 weight percentage, and the tin of 82 to 91.5 weight percentage, or has the composition consisting of the silver of 1 to 4 weight percentage, the copper of 4 to 6 weight percentage, and the tin of 90 to 95 weight percentage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder material for a semiconductor device, a semiconductor device using the same, and a method of manufacturing the same. More specifically, the present invention relates to a solder material suitable for a high-power semiconductor device and excellent reliability. And a method for manufacturing the same.

[0002]

2. Description of the Related Art Among semiconductor devices, in particular, a high power semiconductor device such as a power transistor which handles relatively large power has a semiconductor element (chip) mounted on a substrate having good heat conductivity such as copper as a heat sink. Joining with solder (die bonding). As the solder material, a low-temperature solder having a relatively low melting point (for example, 37% by weight of Pb and 63% by weight)
Pb-Sn alloy having a melting point of 183 ° C. containing Sn and high-temperature solder having a relatively high melting point (eg, 97% by weight of Pb)
And Pb-Sn having a melting point of 320 ° C. containing 3% by weight of Sn
Alloy). On the other hand, the junction temperature of the high-power semiconductor device is 150 ° C. in the absolute maximum rating, and the melting point of the low-temperature solder has a small margin and causes a problem in reliability. For this reason, a high-power semiconductor device usually uses high-temperature solder. The temperature at which the high power semiconductor device is solder-mounted on a printed circuit board is 240 ° C. for reflow mounting and 260 ° C. for flow mounting.
Since such a process temperature is higher than the melting point of the low-temperature solder of 180 ° C., a high-temperature solder is suitable as a solder material used for die bonding even in consideration of the processing temperature of solder mounting on a printed circuit board.

[0003] On the other hand, in recent years, from the viewpoint of environmental protection, a semiconductor device in which substances such as lead, antimony, and bromine having a large environmental load are reduced is desired. A high-temperature solder alloy (for example, an alloy containing 97% by weight of Pb and 3% by weight of Sn) used in a high-power semiconductor device in the future contains a lot of lead, and has a low environmental load. It cannot be reduced.

[0004]

The lead-free high-temperature solder includes an alloy mainly composed of aluminum (for example, 5th Symposium on "Microjoining and Assembling").
embly Technology in Electronics "February 4-5, 199
9, p305-308). However, this alloy is not practical as a die bonding material because of its poor wettability with semiconductor elements and substrates.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high-power semiconductor device having a low environmental load, excellent heat resistance at a junction between a semiconductor element and a substrate, and high reliability, and a method of manufacturing the same.

[0006]

In order to achieve the above object, a first semiconductor device of the present invention contains silver and copper,
A semiconductor element in which an element is formed on a semiconductor substrate and a heat sink or a substrate to be a heat sink are joined using an alloy containing tin as a main component. This alloy is
While having practical wettability, it has a high melting point and excellent heat resistance. Therefore, the reliability of the high power semiconductor device can be improved by using this alloy as the die bonding material.

In the above semiconductor device, it is preferable to use an alloy having a liquidus at 270 ° C. or higher. The maximum working temperature in consideration of the variability and the margin with respect to the temperature (240 to 260 ° C.) of solder mounting (flow mounting, reflow mounting) for mounting the semiconductor device of the present invention on a printed circuit board is as described above. For this reason, it is desired to assume about 270 ° C. Further, it is appropriate to assume about 10 seconds as the work time of the solder mounting. 270 ° C
According to the alloy having the liquidus in the above temperature range, it is possible to suppress the occurrence of poor adhesion in the solder mounting operation under such conditions.

[0008] More specifically, in the semiconductor device, specifically, the alloy contains 8 to 15% by weight of silver and 0.5 to 3% by weight of copper, and the balance is substantially composed of tin. Silver 1
It is preferable to have any composition selected from the composition B containing 4% by weight and 4 to 6% by weight of copper, and the balance substantially consisting of tin. The present invention relates to this preferred composition at 270 ° C.
A semiconductor device having the above liquidus and used for bonding a semiconductor element provided in the semiconductor device to a heat sink or a substrate serving as a heat sink is also included.

However, in the above compositions A and B, a part of tin may be replaced by another metal in a range of 2% by weight or less. The metal that can be substituted is not particularly limited as long as the object of the present invention is achieved, and examples thereof include Ge and Pd. The metal that replaces part of tin may include other metals that are inevitably mixed. In the present specification, even when a part of tin is replaced by another metal in a range of 2% by weight or less, it corresponds to a case where the remainder substantially consists of tin.

Preferably, the semiconductor device is formed so as to cover at least the alloy and contains a thermosetting resin having a glass transition temperature of 150 ° C. or higher. The glass transition temperature of the thermosetting resin may be raised from less than 150 ° C. to 150 ° C. or more by performing at least one treatment selected from heat treatment, ultraviolet irradiation, and electron beam irradiation after molding. According to these preferred examples, the adhesive strength between the substrate and the resin is improved. Therefore, the movement of the partially liquefied alloy is suppressed, and the heat resistance of the semiconductor device is improved.

A second semiconductor device according to the present invention is a semiconductor device comprising a semiconductor element having elements formed on a semiconductor substrate, a heat sink, and a circuit board having a metal film formed on a surface of a heat sink in a predetermined pattern. The semiconductor element is joined to the heat sink by a first alloy containing silver and copper and containing tin as a main component, and the heat sink is made of a second alloy having a melting point lower than that of the first alloy. It is characterized by being bonded on a metal film. This semiconductor device also
The use of the first alloy which has a high melting point and excellent heat resistance while having practical wettability enhances reliability.

In the above second semiconductor device, 270
It is preferable to use a first alloy having a liquidus line at a temperature of at least 0 ° C.
% By weight, with the balance being substantially tin, and composition B comprising 1-4% by weight of silver and 4-6% by weight of copper, with the balance being substantially tin. It is preferable to have the following composition.

Further, in the second semiconductor device,
It is preferable to include a thermosetting resin formed so as to cover at least the first alloy and having a glass transition temperature of 150 ° C. or higher. Further, after the molding, the glass transition temperature of the thermosetting resin may be increased from less than 150 ° C. to 150 ° C. or more by performing at least one treatment selected from heat treatment, ultraviolet irradiation, and electron beam irradiation.

A first method of manufacturing a semiconductor device according to the present invention includes a step of bonding a semiconductor element to a heat sink or a substrate serving as a heat sink by using an alloy containing silver and copper and containing tin as a main component. A step of molding a thermosetting resin so as to cover the alloy and at least one treatment selected from heat treatment, ultraviolet irradiation, and electron beam irradiation are performed to reduce the glass transition temperature of the thermosetting resin to 15 degrees.
Raising the temperature from less than 0 ° C. to 150 ° C. or more.

In the above manufacturing method, it is preferable to raise the glass transition temperature of the thermosetting resin from less than 150 ° C. to 150 ° C. or more by heat treatment at 200 ° C. or less.

In a second method of manufacturing a semiconductor device according to the present invention, there is provided a circuit board comprising: a semiconductor element having an element formed on a semiconductor substrate; a heat sink; and a metal film having a predetermined pattern formed on a surface of a heat sink. A method of manufacturing a semiconductor device, comprising: a first material containing silver and copper and containing tin as a main component.
After the semiconductor element is joined to the heat sink by the alloy of the above, the heat sink is joined to the metal film by a second alloy having a melting point lower than that of the first alloy.

In the second manufacturing method, after the heat sink is bonded to the metal film, a thermosetting resin is further formed so as to cover at least the semiconductor element, the first alloy, and the heat sink; It is preferable to include a step of raising the glass transition temperature of the thermosetting resin from less than 150 ° C. to 150 ° C. or more by performing at least one treatment selected from irradiation and electron beam irradiation.

In this case, it is preferable to raise the glass transition temperature of the thermosetting resin from less than 150 ° C. to 150 ° C. or more by heat treatment at 200 ° C. or less.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the high power semiconductor device of the present invention will be described below. (First Embodiment) FIG. 1 is a cross-sectional view of one embodiment of the semiconductor device of the present invention. In this semiconductor device, a semiconductor element (chip) 1 is composed of a substrate 2 made of copper as a heat sink.
(Die bonding) via an alloy 3.

The substrate serving as a heat sink is as follows:
Metals other than copper may be used as long as they have high thermal conductivity. Further, if the semiconductor element 1 can be joined,
For example, a multilayer structure in which a metal film having high heat conductivity is formed on a dielectric surface having high heat conductivity, such as a copper foil formed on the surface of alumina, may be used as the substrate 2.

The semiconductor device 1 is a device in which a device is formed on a semiconductor substrate, for example, a device in which a predetermined circuit pattern is formed on a semiconductor substrate. The semiconductor element 1 is electrically connected to the external electrode 4 by a thin metal wire 5. Further, the entire semiconductor element 1 is sealed with a molding resin 6.
As shown in the figure, the resin 6 is formed so as to cover the alloy 3 and the fine metal wires 5. Thus, a high-power semiconductor device such as a power transistor is configured.

The alloy used for die bonding is an alloy containing silver and copper and mainly containing tin. As described above, this alloy preferably has a liquidus at a temperature of 270 ° C. or higher. It also contains 8 to 15% by weight of silver and 0.5 to 3% by weight of copper, or 1 to 4% by weight.
Of silver and tin containing 4 to 6% by weight of copper.

As described above, such an alloy may contain a small amount of impurities, but the specific composition is 8 to 15% by weight of silver and 0.5 to 3% by weight of copper. And composition b comprising 82 to 91.5% by weight of tin, 1 to 4% by weight of silver, 4 to 6% by weight of copper, and 90 to 95% by weight of tin.

Table 1 shows the solidus and liquidus temperatures of the alloys belonging to the above composition ranges.

(Table 1) ――――――――――――――――――――――――――――――― Solder composition (% by weight) Characteristics in melting point diagram (℃) silver copper tin composition solidus liquidus --------------------------------- a ₁ 8. _{0 0.5 91.5 221 282 a 2 8.0} 3.0 89.0 221 282 a 3 15.0 0.5 84.5 221 341 a 4 15.0 3.0 82.0 221 340 b 1 _{1.0 4.0 95.0 227 283 b 2 4.0} 4.0 92.0 227 282 b 3 1.0 6.0 93.0 227 380 b 4 4.0 6.0 90.0 227 380 ―――――――――――――――――――――――――――――――――

The solidus temperature of the alloys shown in Table 1 is 270
The liquidus temperature is below 270 ° C (280-400 ° C). Such characteristics are suitable as a die bonding material.

When the compositions a and b are compared, the composition a is preferable in terms of workability because the fluctuation of the melting point due to the variation in silver concentration is small, and the composition b is preferable in terms of resistance to thermal fatigue.

At the assumed solder mounting operation temperature (270 ° C.), the above alloy is in a state where a liquid phase and a solid phase are mixed. In general, the liquefied alloy flows out of the bonding portion and leaves voids, which lowers the reliability of the semiconductor device. However, in the above alloy, since the volume change between the liquid phase and the solid phase is relatively small (that is, the difference in specific gravity is small), even when a part of the alloy liquefies, the outflow of the liquid itself can be suppressed.

In order to further suppress the outflow of a part of the liquefied alloy, it is preferable that the glass transition temperature (Tg) of the molding resin is high. The thermal expansion coefficient of the molding resin becomes larger on the high temperature side after Tg. Therefore, by increasing the Tg, the amount of thermal expansion during solder mounting can be suppressed as compared with the case where the Tg is low, so that in the solder mounting operation, the gap between the molding resin and the substrate serving as a heat sink, and The gap between the molding resin and the semiconductor element can be reduced. That is, by increasing Tg, it is possible to suppress a decrease in the sealing ability of the molding resin during solder mounting.

Considering the assumed soldering operation temperature and time (10 seconds), the preferable T
g is 150 ° C. or higher. The molding resin generally has a Tg by heat treatment, or by irradiation with ultraviolet rays or electron beams.
Can be higher.

For example, Table 2 shows changes in the glass transition temperature when an epoxy resin (orthocresol novolak) having a glass transition temperature of 140 ° C. is heat-treated under various conditions. This heat treatment was performed after molding the epoxy resin so that the semiconductor element was sealed as shown in FIG. The molding conditions of the thermosetting resin were 180 ° C., 9
This was performed by clamping the mold for 0 second.

(Table 2) Heat treatment conditions Glass transition temperature (° C) Conditions Temperature (° C) Time (hours) _{) --------------------------- h 0 - - 140 h} 1 160 24 155 h 2 180 16 175 h 3 200 6 190 - ------------------------- * h ₀ shows the case is not performed to a heat treatment.

As shown in Table 2, the heat treatment at 160 to 200 ° C. changed the glass transition temperature from 140 ° C. to 15 to 5 ° C.
It was confirmed that the temperature rose by 0 ° C. The heat treatment time is preferably at least 6 hours.

However, if the heat treatment is performed at a temperature exceeding 200 ° C., the alloy used as the die bonding material may be oxidized and the reliability of the semiconductor device may be reduced. Therefore, the heat treatment is preferably performed at a temperature of 200 ° C. or lower in a temperature range in which the glass transition temperature of the thermosetting resin increases.

Next, a semiconductor device having a configuration similar to that shown in FIG. 1 was manufactured using the alloys shown in Table 1 and applying the heat treatment conditions shown in Table 2. Specifically, a 1 mm diameter solder wire made of an alloy shown in Table 1 is pressed and melted on a substrate (copper lead frame) 2 heated to 300 ° C., and a 3 mm square semiconductor element 1 is pressed on the melted alloy. After that, the alloy was solidified. Thereafter, the thin metal wire 5 was connected to the external electrode 4 and the entire semiconductor element 1 was sealed with the molding resin 6 to complete the semiconductor device shown in FIG.

Each of the obtained semiconductor devices was subjected to a heat resistance test and a dissolution test. Here, the heat resistance test is 27
The thermal resistance (ΔVbe) after immersion in a lead / tin alloy (an alloy containing 37% by weight of Pb and 63% by weight of Sn) held at 0 ° C. for 10 seconds was measured. 30%
Those which were higher than the above were judged to be defective. Heat resistance test is 1 for each
The test was performed on 0 semiconductor devices.

The dissolution test used was a dissolution test based on the notification of the Environment Agency No. 13. In this dissolution test, the lead is immersed in a nitric acid aqueous solution having a pH of 6 and the lead concentration is measured by an atomic absorption method or the like (however, the measurement limit is 0.05 ppm).
Is).

The results are shown in Table 3. Table 3 shows alloy c (4.0% by weight silver, 0.5% by weight copper, 95.5% by weight).
Tin), alloy d (96.5 wt% tin, 3.5 wt% silver),
The results using alloy e (97% by weight lead, 3% tin) are also shown.

(Table 3) ―――――――――――――――――――――――――――― Sample alloy Heat treatment condition No. of heat-resistant test failure Elution test (pieces) _{(ppm) ------------------------------ 1 a 1 h} 0 8 <0.05 2 a 1 h 1 0 < _{0.05 3 a 2 h 1 0 <} 0.05 4 a 3 h 3 0 <0.05 5 a 4 h 0 6 <0.05 6 a 4 h 3 0 <0.05 7 b 1 h 0 4 < _{0.05 8 b 1 h 1 0 <} 0.05 9 b 2 h 1 0 <0.05 10 b 3 h 1 0 <0.05 11 b 4 h 0 3 <0.05 12 b 4 h 3 0 < _{0.05 13 c h 0 9 <0.05} 14 c h 1 7 <0.05 15 d h 0 8 <0.05 16 eh ₁₀ 33 ――――――――――――――――――――――――――――――

Further, using a silver / copper / tin ternary alloy in which the concentration of silver is changed in the range of 5 to 20% by weight and the concentration of copper is changed in the range of 0 to 7% by weight, A semiconductor device was manufactured and a heat resistance test was performed. The number of tests was 10 for each as described above, and the heat treatment conditions were h _{2 in} Table _2.
Was applied. Table 4 shows the results.

(Table 4) (Number of defectives) ―――――――――――――――――――――――――― Copper content (% by weight) Silver content ( 0 0.5 1 3 5 7 ―――――――――――――――――――――――――― 5 4 -2---8 3 0 0 0 0 0 10 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0 ... ... --- The balance consists essentially of tin.

As shown in Table 4, the silver content was 8% by weight or more,
Good results were obtained in the range containing 0.5% by weight or more of copper. However, when silver is contained in an amount exceeding 15% by weight, it is necessary to perform a die bonding operation at a high temperature, and the product yield may be reduced. On the other hand, when copper is excessively contained, workability extremely deteriorates. Therefore, the range of the composition a is preferable. It is better to use less expensive silver. From such a viewpoint, in the composition a, the silver content may be limited to less than 10% by weight.

Of the test examples shown in Table 4, the bonding portion of a semiconductor device manufactured using an alloy containing 10% by weight of silver, 1% by weight of copper, and 89% by weight of tin was bonded before and after the heat resistance test. X
A fluoroscopic image was taken. The results are shown in FIG.

On the other hand, for the semiconductor device of Sample 15 in Table 3 (using an alloy containing 3.5% by weight of silver and 96.5% by weight of tin), an X-ray fluoroscopic image of the bonded portion was similarly taken. The results are shown in FIG.

10% by weight of silver, 1% by weight of copper and 89% of tin
In the case of using an alloy containing 3.5% by weight, there is almost no difference in the cross-sectional state of the bonded portion before and after the heat resistance test (FIG. 2). When used, the shape of the voids present in the bonded portion has changed significantly (FIG. 3). This indicates that the alloy containing 3.5% by weight of silver and 96.5% by weight of tin melted and fluidized during the heat resistance test.

Further, using a silver / copper / tin ternary alloy in which silver is changed in the range of 0 to 5% by weight and copper in the range of 3 to 7% by weight, the substrate is formed in the same manner as described above. (Copper lead frame) to fabricate a semiconductor device.
After performing a heat resistance test at 70 ° C. for 10 seconds, a heat cycle test was further performed.

The heat cycle test was conducted at -65 ° C. and 15 ° C. in the liquid phase.
The test was repeated at 0 ° C. for 5 minutes each time. After a predetermined number of cycles, the sample was taken out and irradiated with soft X-rays to form a transmission image in the same manner as described above. Then, the density of the transmitted image was image-analyzed, and the ratio of the light-colored portion viewed in a plane was measured to obtain the crack occurrence rate. Further, the number of cycles until the crack occurrence rate reached 40% was measured and defined as a heat cycle life. Here, the number of tests was 10 each, and h2 in Table ₂ was applied as the heat treatment condition of the sealing resin. Table 5 shows the test results.

(Table 5) (Thermal cycle life; times) ―――――――――――――――――――――――――― Copper content (% by weight) Silver Content (% by weight) 3.0 4.0 5.0 6.0 7.0 ―――――――――――――――――――――――――― 0 − − 700 − − 1.0 − 1000 1000 800 − 1.5 − 1000 1000 1000 − 2.0 − 1200 1200 1200 − 3.0 700 1500 1500 1500 700 700 4.0 − 1200 1500 1200 − 5.0 − − 700 − − ―――――――――――――――――――――――――― * The balance consists essentially of tin.

As shown in Table 5, the composition containing 1 to 4% by weight of silver and 4 to 6% by weight of copper, and the balance substantially consisting of tin, had a good thermal cycle number of 800 to 1500. . Among them, silver 2-4% by weight and copper 4-6% by weight
And the balance substantially consisting of tin, the number of thermal cycles was even better, from 1200 to 1500. On the other hand, when the composition is out of the above range, the number of heat cycles is 10
00 or less.

In a semiconductor device in which an element such as an IC chip having a significantly different coefficient of thermal expansion and a substrate such as a copper lead frame are joined by a solder material, a large temperature cycle is required particularly when heat is generated from the element. Therefore, it is desired to have good thermal cycle characteristics as described above.

(Second Embodiment) In the first embodiment,
One embodiment of a high-power semiconductor device such as a power transistor in which a semiconductor element (chip) 1 is bonded to a substrate 2 serving as a heat sink (FIG. 1) has been described. In the present embodiment, a semiconductor element (chip) and passive elements such as resistors and capacitors are mounted on a circuit board provided with pattern wiring like a power module, and at least the semiconductor element is sealed with a resin. One embodiment of a power semiconductor device is described.

As shown in FIG. 4, in a circuit board 17 used in the semiconductor device of the present embodiment, a first copper foil 12 is formed in a predetermined pattern on a substrate 11 made of aluminum serving as a heat sink. I have. Then, a first insulating film 13 is formed on the substrate 11 so as to substantially cover the first copper foil 12. However, an opening 14 is provided in a part of the first insulating film 13, and a part of the first copper foil 12 is exposed from the opening 14. Further, on the first insulating film 13,
The second copper foil 15 is formed in a predetermined pattern. A second insulating film 16 is formed on the second copper foil 15 except for a region where the electronic component 22 is mounted and a region where wire bonding is performed. Thus, the circuit board 17 is formed by sequentially forming the first copper foil 12, the first insulating film 13, the second copper foil 15, and the second insulating film 16 on the substrate 11. In this circuit board 17, the first copper foil 12 is for dissipating heat generated in the semiconductor element 20 and the like mounted thereon to the board 11 side. Second copper foil 1
5 is a circuit wiring.

An example of a method for manufacturing a semiconductor device using the circuit board 17 will be described below. First, a semiconductor element (chip) 2 in which elements such as power transistors are formed on a semiconductor substrate on a heat sink 19 made of copper prepared separately.
0 by the first alloy 21 (die bonding)
I do. As in the first embodiment, another metal may be used as the heat sink 19 as long as it has a high thermal conductivity. Further, if the semiconductor element 20 can be joined,
For example, a multilayer structure in which a metal film having a high thermal conductivity is formed on the surface of a dielectric having a high thermal conductivity, such as a copper foil formed on the surface of alumina, may be used as the heat sink 19.

As the first alloy 21, the high-temperature solder described in the first embodiment is used. Specifically, examples of the first alloy 21 include an alloy containing silver and copper and containing tin as a main component. This alloy preferably has a liquidus at a temperature of 270 ° C. or higher.

As such an alloy, the same alloy as described above, for example, a composition a comprising 8 to 15% by weight of silver, 0.5 to 3% by weight of copper and 82 to 91.5% by weight of tin is used. Alloy, or 1-4 wt% copper, and 90-95
Alloys having a composition b consisting of wt.% Tin can be used.

Next, low-temperature solder (for example, Pb of 37% by weight) is applied to the opening 14 where the first copper foil 12 is exposed.
And Pb-S having a melting point of 183 ° C. containing 63% by weight of Sn
The heat sink 19 is joined by the second alloy 18 made of n alloy). At this time, at the same time, the electronic component 22
And a second alloy 1 made of a low-temperature solder on the second copper foil 15.
8 to join. The reason why a material having a lower melting point than the first alloy is used as the second alloy is to prevent the second alloy 18 that bonds the heat sink 19 and the semiconductor element 20 from being melted.

Subsequently, the semiconductor element 20 is electrically connected to the second copper foil 15 which is a circuit wiring by a thin metal wire 23 made of an aluminum wire.
9, a molding resin 25 made of an epoxy resin (orthocresol novolak) is provided on the circuit board 17 so as to cover the semiconductor element 20 and the thin metal wires 23. As the molding resin 25, a resin molded in advance by clamping at 180 ° C. for 90 seconds is used. Thereafter, the molding resin 25 is formed so as to cover the heat sink 19, the semiconductor element 20, and the fine metal wire 23.
The gel 24 is injected and poured into the gap between the substrate and the circuit board 17. Gel 24 for protecting semiconductor element 20 and fine metal wire 23
For example, a silicone gel can be used.

The glass transition temperature of this epoxy resin is 14
0 ° C. Thereafter, heat treatment is performed at a temperature selected from the range of 160 to 180 ° C. (the upper limit is a temperature at which the low-temperature solder does not melt), thereby increasing the glass transition temperature of the epoxy resin and dehydrating and condensing the silicone gel to form a silicon-based resin. It is a cured resin. Thus, the semiconductor element 20 and the heat sink 19 are sealed with the silicone-based cured resin and the molding resin 25. As the heat treatment, conditions similar to those described above, for example, 160 ° C. for 10 hours may be applied. Thus, the semiconductor device shown in FIG. 4 is completed.

In the second embodiment, two layers of copper foil are provided on the substrate 11, a heat sink on which a semiconductor element is mounted is bonded to the first layer of copper foil, and the second layer of copper foil is connected to the circuit wiring. However, the present invention is not limited to this mode, and the heat sink may be bonded to the first and second layers by directly contacting the second-layer copper foil with the substrate 11. Further, a heat sink may be bonded only to the second layer. Further, three or more layers of copper foil may be used. Although aluminum is used as the substrate, the substrate is not limited to metal as long as it has good heat dissipation, and a dielectric such as alumina, zirconia, or sapphire may be used.

[0060]

As described above, according to the present invention,
By bonding a semiconductor element to a substrate using an alloy containing silver and copper and containing tin as a main component, a high-power semiconductor device with low environmental load, excellent heat resistance, and high reliability is provided. be able to.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device of the present invention.

FIG. 2 is a drawing substituting an X-ray transmission photograph obtained by observing an example of a semiconductor device of the present invention before (a) and after (b) a heat resistance test is performed.

FIG. 3 is a drawing substituting an X-ray transmission photograph obtained by observing a conventional semiconductor device before (a) and after (b) a heat resistance test is performed.

FIG. 4 is a cross-sectional view illustrating another embodiment of the semiconductor device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1,20 Semiconductor element 2,11 Substrate 3 Alloy 4 External electrode 5,23 Fine metal wire 6,25 Molding resin 12,15 Copper foil 13,16 Insulating film 17 Circuit board 18 Second alloy 19 Heat sink 21 First alloy 22 Electronic components 24 (liquid) gel

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takatoshi Arikawa 8-5-1 Shimorenzaku, Mitaka-shi, Tokyo Tanaka Denshi Kogyo Co., Ltd. Mitaka factory (56) References JP-A-52-6468 (JP, A) JP-A-59-149041 (JP, A) JP-A-61-181135 (JP, A) JP-A-11-354687 (JP, A) JP-A-8-148647 (JP, A) JP-A-9-232340 (JP, A) JP-A-11-347785 (JP, A) JP-A-2000-151095 (JP, A) JP-A-2001-35978 (JP, A) JP-A-2001-121285 (JP, A) JP-A 2001- 138088 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/52 H01L 23/40 H01L 23/48 B23K 35/26

Claims (16)

(57) [Claims] 1 to 8% by weight of silver and 0.5 to 3% by weight of copper
Any composition selected from the composition A containing 1 to 4% by weight of silver and 4 to 6% by weight of copper and the balance being substantially composed of tin. A solder material for a semiconductor device, comprising an alloy having a liquidus of 270 ° C. or higher and used for joining a semiconductor element provided in the semiconductor device to a heat sink or a substrate serving as a heat sink. 2. A semiconductor device wherein a semiconductor element having an element formed on a semiconductor substrate and a heat sink or a substrate serving as a heat sink are joined by using an alloy containing silver and copper and containing tin as a main component. . 3. The semiconductor device according to claim 2, wherein an alloy having a liquidus at 270 ° C. or higher is used. 4. An alloy comprising 8 to 15% by weight of silver and 0.5 to 0.5% by weight of copper.
3% by weight, with the balance being substantially tin.
4. The semiconductor device according to claim 2, wherein the semiconductor device has any composition selected from the composition B containing 1 to 4% by weight of silver and 4 to 6% by weight of copper, and the balance substantially consisting of tin. 5. 5. Molded so as to cover at least the alloy,
The semiconductor device according to claim 2, further comprising a thermosetting resin having a glass transition temperature of 150 ° C. or higher. 6. The glass transition temperature of a thermosetting resin is increased from less than 150 ° C. to 150 ° C. or more by performing at least one treatment selected from heat treatment, ultraviolet irradiation, and electron beam irradiation after molding. 6. The semiconductor device according to 5. 7. A semiconductor device comprising: a semiconductor element in which an element is formed on a semiconductor substrate; a heat sink; and a circuit board in which a metal film is formed in a predetermined pattern on a surface of a heat sink, comprising silver and copper. The semiconductor element is joined to the heat sink by a first alloy mainly containing tin,
A semiconductor device, wherein the heat sink is joined to the metal film by a second alloy having a lower melting point than the first alloy. 8. The semiconductor device according to claim 7, wherein a first alloy having a liquidus at 270 ° C. or higher is used. 9. A composition A wherein the first alloy comprises 8 to 15% by weight of silver and 0.5 to 3% by weight of copper, the balance being substantially tin, and 1 to 4% by weight of silver and copper 9. The semiconductor device according to claim 7, wherein the semiconductor device has any composition selected from the composition B containing 4 to 6% by weight, and the balance substantially consisting of tin. 10. The semiconductor device according to claim 7, further comprising a thermosetting resin formed so as to cover at least the first alloy and having a glass transition temperature of 150 ° C. or higher. 11. The glass transition temperature of the thermosetting resin is increased from less than 150 ° C. to 150 ° C. or more by performing at least one treatment selected from heat treatment, ultraviolet irradiation, and electron beam irradiation after molding. The semiconductor device according to claim 10. 12. A step of joining a semiconductor element having an element formed on a semiconductor substrate to a heat sink or a substrate serving as a heat sink using an alloy containing silver and copper and containing tin as a main component, and a heat treatment so as to cover at least the alloy. A step of forming a curable resin, and a step of raising the glass transition temperature of the thermosetting resin from less than 150 ° C. to 150 ° C. or more by performing at least one treatment selected from heat treatment, ultraviolet irradiation, and electron beam irradiation. A method for manufacturing a semiconductor device, comprising: 13. The method according to claim 12, wherein the glass transition temperature of the thermosetting resin is increased from less than 150 ° C. to 150 ° C. or more by heat treatment at 200 ° C. or less. 14. A method of manufacturing a semiconductor device comprising: a semiconductor element having an element formed on a semiconductor substrate; a heat sink; and a circuit board having a metal film having a predetermined pattern formed on a surface of a heat sink, After joining the semiconductor element to the heat sink with a first alloy containing silver and copper and containing tin as a main component, the heat sink is made of the metal with a second alloy having a melting point lower than that of the first alloy. A method for manufacturing a semiconductor device, comprising bonding to a film. 15. A step of forming a thermosetting resin so as to cover at least the semiconductor element, the first alloy, and the heat sink after joining the heat sink to the metal film, and selecting from a heat treatment, an ultraviolet irradiation, and an electron beam irradiation. The method of manufacturing a semiconductor device according to claim 14, further comprising: increasing a glass transition temperature of the thermosetting resin from less than 150 ° C. to 150 ° C. or more by performing at least one treatment. 16. The method according to claim 15, wherein the glass transition temperature of the thermosetting resin is increased from less than 150 ° C. to 150 ° C. or more by heat treatment at 200 ° C. or less.