JPH0529507A - Substrate for semiconductor - Google Patents

Abstract

(57) [Summary] [Object] It is an object of the present invention to provide a highly reliable semiconductor substrate that includes a heat dissipation plate having excellent thermal conductivity, has few cracks and warps, and has high reliability. [Structure] A semiconductor substrate according to the present invention is a multilayer substrate 1a formed of an aluminum nitride sintered body, and this multilayer substrate 1a.
A heat dissipation plate 2a for transmitting heat generated from the semiconductor element 3 arranged in
a is copper plates 8a and 8a on both sides of the molybdenum plate 7a, respectively.
It is characterized in that it is formed of a composite material 9a that is integrally joined. The thickness of the molybdenum plate 7a and the copper plates 8a, 8a is preferably set within the range of 0.03 to 0.3 mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor substrate which constitutes an electronic device or the like, and in particular, it has a heat dissipation plate, so that it has excellent heat dissipation characteristics. The present invention relates to a highly reliable semiconductor substrate capable of preventing peeling.

[0002]

2. Description of the Related Art Conventionally generally used semiconductor substrates are formed by laminating a plurality of sheets of alumina (Al ₂ O ₃ ) green sheet as an insulating material on which desired circuit patterns and the like are printed. It further comprises a fired multilayer substrate and a heat radiating plate for rapidly transmitting heat generated from the semiconductor IC chips arranged on the multilayer substrate to a cooling unit such as a heat sink. As the heat dissipation plate, a Cu / W alloy obtained by alloying 10% to 20% Cu (copper) in tungsten (W) is used, and the thermal expansion coefficient of this Cu / W alloy is almost equal to that of alumina (Al ₂ O ₃ ) is set equal to. Therefore, even when a Cu / W alloy heat dissipation plate is integrally joined to the multilayer substrate by brazing or when the semiconductor chip generates heat during the operation of the electronic device, the multilayer substrate is cracked or peeled due to thermal stress. There are few things.

By the way, in recent years, there has been a strong demand for higher speed, smaller size, and higher integration and performance of electronic devices and power devices using semiconductors. For example, a high speed (ECL) ceramic multilayer substrate having an operating speed of about 50 to 100 ns has been developed. For semiconductor substrates that are becoming mainstream and are used in bipolar devices that consume a large amount of power and generate a large amount of heat, there is a demand for a thermal design that allows the heat generated from the semiconductor chips to be more efficiently discharged to the outside of the system. .

[0004]

However, although alumina (Al ₂ O ₃ ) generally used as a conventional ceramic material for multilayer substrates has excellent electrical and mechanical properties, it has a high thermal conductivity. (K) is 17W /
Since it has a low difficulty of about m · k, it is not suitable for a high speed and high power consumption device. Therefore, compared with alumina, beryllia (B
eO) or aluminum nitride (AlN) may be used.

However, beryllia has a problem because it emits a toxic gas in the raw material preparation process, and as an alternative material, it has a thermal conductivity almost equal to that of BeO, and an aluminum nitride sintered body having a particularly excellent thermal conductivity. Is attracting attention.

However, when a conventional heat dissipation plate made of a Cu / W alloy is brazed to this aluminum nitride sintered body, the aluminum nitride multilayer substrate tends to crack or the heat dissipation plate is largely warped. There is. That is, the conventional Cu / W alloy heat dissipation plate is set to have the same thermal expansion coefficient as that of alumina, and when bonded to an aluminum nitride multilayer substrate, the thermal expansion coefficients of both members are greatly different. However, thermal stress is generated, which causes cracks and warpage.

When the content of Cu is set to about 8% or less in order to reduce the difference in thermal expansion, bonding can be performed without cracking, but the thermal conductivity is sharply reduced. There is a point.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a highly reliable semiconductor substrate provided with a heat dissipation plate having excellent thermal conductivity and having few cracks and warps. To aim.

[0009]

In order to achieve the above object, the present invention provides a multilayer substrate formed of an aluminum nitride sintered body and a heat dissipation plate for transmitting heat generated from a semiconductor element arranged on the multilayer substrate. In the provided semiconductor substrate,
The heat dissipation plate is characterized by being formed of a composite material in which copper plates are integrally bonded to both surfaces of a molybdenum plate.

The thickness of the molybdenum plate and each copper plate may be set within the range of 0.03 to 0.3 mm.

In the present invention, the multilayer substrate is formed by alternately stacking a plurality of aluminum nitride sintered bodies as an insulating layer and a metallized layer, and has a thermal conductivity K of 170 W / m.multidot.
k or more, and the coefficient of thermal expansion in the temperature range from room temperature to 500 ° C. is 5 to 6 × 10 ⁻⁶ / ° C. A heat sink made of metal is integrally bonded to the multilayer substrate to manufacture a semiconductor substrate.

The heat radiating plate is joined to the insulating portion or metallized portion made of aluminum nitride by using various brazing materials. In addition, in order to improve the familiarity between the heat sink and the brazing filler metal and increase the joint strength, a thickness of 1 to 5 μm is previously formed on the joint surface of the heat sink.
It is preferable to form a plating layer of Ni, Au, or the like.

The heat radiating plate is made of a composite material such as a clad material in which a Cu plate having a predetermined thickness is attached to both sides of a Mo plate. Since Cu plates, which are the same material, are arranged on both sides of the composite material having a three-layer structure, the composite material itself is less likely to warp due to temperature change. In addition, since a Mo plate having a coefficient of thermal expansion similar to that of the aluminum nitride multilayer substrate is installed as a core material and the Cu plates arranged on both sides of the Mo plate are restrained from thermal expansion, thermal stress acting on the multilayer substrate is relaxed. It becomes possible to do. Therefore, when a conventional Cu / W radiator plate is brazed to a multilayer substrate, cracks and warpage are less likely to occur.

Further, M constituting a heat dissipation plate made of a composite material
The thicknesses of the o-plate and the Cu-plate have a great influence on the strength and thermal conductivity of the entire semiconductor substrate.
It is recommended to set it within the range of 3 mm. That is, the thickness is 0.03
When the thickness is less than mm, the function of reinforcing the substrate is deteriorated, while when the thickness is more than 0.3 mm, the heat conductivity of the heat dissipation plate is decreased, and the heat dissipation is deteriorated. A composite heat dissipation plate within the above thickness range can be brazed and bonded to a multilayer substrate without causing cracks or warpage. The thinner the Mo plate and the Cu plate are, the higher the thermal conductivity is, and the thermal conductivity K of the heat dissipation plate in the plate thickness range is 200 to 260 W / m · k, which is almost the same as that of the aluminum nitride multilayer substrate. Equivalent value.

[0015]

According to the semiconductor substrate having the above structure, since the heat dissipation plate is formed of the composite material in which the copper plates are integrally bonded to both surfaces of the Mo plate, the thermal stress generated on the copper plate having a large coefficient of thermal expansion is prevented. It is possible to obtain a heat sink that can be absorbed by the Mo plate and has a coefficient of thermal expansion close to that of an aluminum nitride multilayer substrate while maintaining high thermal conductivity as a whole of the heat sink. Therefore, it is possible to obtain a highly reliable semiconductor substrate in which cracks are less likely to occur in the multilayer substrate when the heat sink is joined. Further, since the copper plates having the same coefficient of thermal expansion are bonded to both surfaces of the Mo plate, the heat dissipation plate is less likely to warp.

[0016]

Embodiments of the present invention will now be described with reference to the accompanying drawings. 1 to 4 are cross-sectional views showing first to fourth embodiments of the semiconductor substrate according to the present invention.
FIG. 4 is a cross-sectional view showing the structure of a heat dissipation plate used in each example.

[0017] Example 1 Figure 1 and aluminum nitride multilayer substrate 1a for use in semiconductor substrate of the first embodiment shown in FIG. 6 with the following steps 10
0 pieces were manufactured.

That is, a powder containing AIN raw material powder and 3% by weight of yttrium oxide (Y ₂ O ₃ ) as a normal pressure sintering aid was slurried to obtain a slurry. Next, after molding the obtained slurry into a green sheet (GS) with a thickness of 0.7 mm by the doctor blade method, a large number of blanks are punched out so that one side is 53 mm and a square shape is formed, and further a wiring pattern is printed. Wiring parts such as electrode pads and wire bonding pads were printed with a conductive paste mainly composed of tungsten (W).

Then, a plurality of green sheets are integrally laminated by thermocompression bonding to form a laminated body having a thickness of 3 mm, and after degreasing,
Sintering was carried out by heating in an N ₂ gas atmosphere at a temperature of 1800 ° C. for 6 hours to obtain a sintered body having a square shape with a side of 42 mm and a thickness of 2 mm.

On the other hand, as shown in FIG. 5, as a core material, a 0.13 mm thick Mo plate 7a has a thickness of 0.1 mm on each side.
The rolled composite material 9a in which the Cu plates 8a and 8a were clad was punched out to manufacture a large number of square heat dissipation plates 2a each having a side of 25 mm. Next, after directly bonding the LSI circuit element 3 to the heat dissipation plate 2a, the heat dissipation plate 2a is further formed on the peripheral edge of the hollow portion of the multilayer substrate 1a.
Bonding was performed using a silver brazing material 5 on a. The temperature at the time of joining is 8
The temperature was set to 00 to 850 ° C. Then, in order to measure the rate of occurrence of cracks and warpage in the multilayer substrate 1a when the heat sink 2a is joined, a substrate for each semiconductor is measured with a metal microscope with a magnification of 100 times and a scanning electron microscope (SEM) with a magnification of 2000 times. Was observed.

A thermal shock test (TCT) of 500 cycles was performed on each semiconductor substrate. The test condition is -5
The operation of holding each of the three temperatures of 5 ° C., room temperature (RT) and 150 ° C. for 10 minutes was set as one cycle. In addition, a thermal shock test for one cycle was also performed in which the temperature was raised from room temperature (RT) to 450 ° C. and held for 10 minutes and returned to room temperature (RT). The rate of warpage of the heat sink 2a was counted and the results shown in Table 1 were obtained.

[0022] was prepared a large number of semiconductor substrate illustrated in FIGS. 2 and 6 as Example 2 Example 2. As this semiconductor substrate, a multilayer substrate 1b having a hollow portion 6b with a bottom is used, and the LSI circuit element 3 is insulated from a heat radiating plate 2b, and the heat radiating plate 2b is a metallized layer 4b formed on the upper surface of the multilayer substrate 1b. Manufactured under the same condition process as in Example 1 except that the entire surface was brazed and bonded using the Ag brazing material 5. Then, in the same manner as in Example 1, the occurrence rates of cracking and warpage were measured during joining and after each thermal shock test, and the results shown in Table 1 were obtained.

Example 3 Hollow part 6a prepared in Example 1 as Example 3
3 and 7, the Ti-based brazing material (solder alloy) 10 is used to integrally braze the heat dissipation plate 2b at a temperature of 850 to 950 ° C. on the upper surface of the multilayer substrate 1a having the structure shown in FIGS. Many substrates were manufactured.

Here, the heat radiating plate 2b is, as shown in FIG.
As a core material, a rolled composite material 9b having 0.15 mm thick Cu plates 8b, 8b clad on both sides of a 0.17 mm thick Mo plate 7b was punched out to form a square shape with one side of 25 mm.

Regarding each semiconductor substrate, Example 1
Similarly to the above, the occurrence ratio of cracks and the like at the time of joining the heat sink 2b and after each thermal shock test was investigated.

[0026] upper surface of the multilayer substrate 1b having a hollow portion 6b bottomed prepared in Example 2 Example 4 Example 4, the heat radiating plate 2b prepared in Example 3 using a Ti-based brazing material 10 A large number of semiconductor substrates shown in FIGS. 4 and 7 were manufactured by integrally brazing and joining. This semiconductor substrate has the LSI circuit element 3 and the heat sink 2b.
Is formed by bonding the entire surface of the heat dissipation plate 2b to the upper surface of the multilayer substrate 1b made of aluminum nitride.

Then, in the same manner as in Example 1, each semiconductor substrate was subjected to a thermal shock test and the like, and the rate of occurrence of cracks and warpage was measured.

Comparative Example 1 As Comparative Example 1, a large number of semiconductor substrates having the same structure and dimensions as in Example 1 were prepared except that a conventional Cu / W alloy heat sink was used, and cracks and warpage occurred. The ratio was investigated and the results shown in Table 1 below were obtained.

[0029]

[Table 1]

As is clear from the results shown in Table 1, in the semiconductor substrates according to Examples 1 to 4, the multi-layer substrate was cracked without impairing the characteristics of the aluminum nitride substrate having high thermal conductivity. It has become clear that the heat sink can be joined to the heat sink without warping or the like, and the heat sink can be mounted on an electronic device or the like that generates a larger amount of heat.

On the other hand, in Comparative Example 1, since the difference in thermal expansion between the multilayer substrate and the heat sink is significant, cracking or warpage is likely to occur at the time of joining the heat sinks or due to thermal shock, resulting in a decrease in both product yield and reliability. It turned out that it could not be put to practical use.

[0032]

As described above, according to the semiconductor substrate of the present invention, since the heat dissipation plate is formed of the composite material in which the copper plates are integrally bonded to both surfaces of the Mo plate, the copper plate having a large coefficient of thermal expansion can be obtained. The generated heat stress can be absorbed by the Mo plate, and a heat sink having a coefficient of thermal expansion close to that of an aluminum nitride multilayer substrate can be obtained while maintaining high thermal conductivity as a whole of the heat sink. Therefore, it is possible to obtain a highly reliable semiconductor substrate in which cracks are less likely to occur in the multilayer substrate when the heat sink is joined. Further, since the copper plates having the same coefficient of thermal expansion are bonded to both surfaces of the Mo plate, the heat dissipation plate is less likely to warp.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of a semiconductor substrate according to the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing a third embodiment of the present invention.

FIG. 4 is a sectional view showing a fourth embodiment of the present invention.

FIG. 5 is a cross-sectional view showing the structure of a heat dissipation plate used in each example.

FIG. 6 is a plan view of the semiconductor substrate shown in FIGS.

FIG. 7 is a plan view of the semiconductor substrate shown in FIGS.

[Explanation of symbols]

1a, 1b Multilayer substrate 2a heat sink 3 LSI circuit element 4a, 4b Metallized layer (metallized layer) 5 Silver brazing material 6a, 6b hollow part 7a, 7b Mo plate 8a, 8b Cu plate 9a, 9b Rolled composite material 10 Ti-based brazing material

Claims (2)

[Claims] 1. A semiconductor substrate comprising a multi-layer substrate made of an aluminum nitride sintered body and a heat-dissipating plate for transmitting heat generated from a semiconductor element arranged on the multi-layer substrate, wherein the heat-dissipating plate is a molybdenum plate. A semiconductor substrate, which is formed of a composite material in which copper plates are integrally bonded to both surfaces. 2. A molybdenum plate and each copper plate having a thickness of 0.
The substrate for semiconductor according to claim 1, wherein the substrate is set within a range of 03 to 0.3 mm.