JP2912211B2 - Semiconductor substrate material and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for melting a filler metal such as Cu or Ag in a semiconductor substrate material suitable for an integrated circuit, in particular, a sintered body of a high melting point metal powder such as W or Mo. about the semiconductor substrate materials soaked.

[0002]

2. Description of the Related Art Conventionally, as a semiconductor substrate (heat sink) for an integrated circuit, there is a Cu-based, Mo-based or W-based one, all of which are plated with Ni and joined to a ceramic package component or a semiconductor element.

However, a Cu substrate has high heat conductivity and excellent heat dissipation, but has a coefficient of thermal expansion several times larger than that of a ceramic envelope material or a semiconductor element. However, there is a disadvantage that distortion due to a difference in thermal expansion promotes deterioration of a brazed portion. on the other hand,
A substrate made of W or Mo has a relatively low coefficient of thermal expansion and is a material excellent in reliability at the time of brazing, but has a drawback that thermal conductivity is low and heat radiation is poor. Therefore, C
Attempts have been made to combine u with W or Mo to obtain a semiconductor substrate material having excellent characteristics utilizing the respective advantages.

As a method of compounding Cu and W or Mo, W is infiltrated by a technique of powder metallurgy.
Alternatively, there is a method of infiltrating Cu into a Mo powder sintered body, or a method of joining with a clad. However,
The latter method of joining with a clad requires precise machining because the dimensional accuracy is not obtained, a highly reliable joining cannot be expected, and the cost is high, and the W or Mo ingot from the sintered ingot is used. It is difficult to obtain a long material at the time of rolling, and furthermore, there is a drawback that mechanical bonding with Cu becomes difficult due to the presence of a strong oxide film.
As described in JP-B-3-36304, JP-B-3-36305, and JP-A-6-13494, the infiltration method has been widely adopted.

[0005]

However, the application of the infiltration method requires a complicated process and a Cu content of 20% by weight.
In the following cases, the required density cannot be obtained with the green compact, and it is necessary to adjust the density by shrinkage during sintering. In this case, it is difficult to control the heating conditions and it is difficult to obtain a predetermined shrink state, and the density and dimensions after shrinkage vary,
It affects the coefficient of thermal expansion and the thermal conductivity, which causes variations in quality.

The problem to be solved in the present invention is to infiltrate a filler metal such as Cu or Ag into a semiconductor substrate material suitable for an integrated circuit, in particular, a sintered body of a high melting point metal powder such as W or Mo. It is an object of the present invention to improve the heat dissipation efficiency and the coefficient of thermal expansion, the uniformity of the density, and the dimensional accuracy of the semiconductor substrate material.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a high melting point metal.
Large particles and small particles, or large particles and medium particles
It consists of a combination of small particles and large particles and small particles.
Material in which filler metal is infiltrated into a sintered body in which the particles are mutually dispersed
A semiconductor substrate material consisting of

[0008] The particle size configuration of the high-melting-point metal powder, the powder 70 to 85% by volume and the balance of the large element group having an average particle diameter 7~15μm of small children groups having an average particle size of 0.5~1.0μm powder It means either, or large child group <br/> of powder having an average particle size of 7~15μm and 60-80% by volume and the particle diameter 0.5-1.0
10-25 volume% of powder of small children groups [mu] m, by a structure comprising the remainder of the powder group Chutsubu element group having an average particle diameter of 2-4 [mu] m, the filling rate is 60-80% of the theoretical density pressure It shall be the powder.

As the high melting point metal powder, W powder or M powder is used.
o powder, furthermore, a mixed powder of W and Mo having different particle sizes or their metals can be used. As a filler for infiltration, the melting point is much lower than that of the high melting point metal, and the high melting point metal and the compound are used. , Ag, Al with good thermal conductivity
Alternatively, these alloys can be used. Small particles can fill the gaps between the large particles and increase the density of the compact,
Further, by incorporating medium particles, shrinkage during sintering can be further suppressed, and dimensional accuracy can be improved.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The semiconductor substrate of the present invention is prepared by filling a high-melting metal powder having the above-mentioned composition with a wax for improving powder fluidity in a molding die, and compression-molding the same to a theoretical density of 65%. %, And then calcined at 800 ° C for dewaxing, then calcined at 1000 to 1200 ° C, and then filled at 1000 to 1200 ° C for infiltration at a temperature at which the infiltrating filler dissolves. It is obtained by infiltrating the material into the secondary pre-sintered body.

[0011]

EXAMPLE In this example, W was used as a high melting point metal,
An example in which Cu is used as a filling metal and applied to the production of a semiconductor substrate will be described.

Example 1 Large particle powder 80 having an average particle diameter of 8 μm as a large particle group
1% by weight of paraffin wax was added to 20% by volume of W powder of small particles having an average particle diameter of 1 μm as a small particle group, and mixed in a mixer for 1 hour. The obtained powder was subjected to 98, 196 and 29 using a powder molding press.
Emboss with pressure of 4MPa, length 40mm x width 40mm
A green compact having a thickness of 3 mm was obtained. FIG. 1 shows the density of this green compact. The horizontal axis represents the content of 1 μm W powder in the mixed powder of W powder having an average particle size of 1 μm and W powder having an average particle size of 8 μm, and the vertical axis represents the content. The obtained density is shown by% with respect to the theoretical density. As shown in FIG.
The density of the green compact of Pa was 11.78 g / cm ³ , which was 61% of the theoretical density. This green compact in H ₂ gas-80
0 to ° C shall dewaxing calcined 1 further also in in H ₂ gas
It was heated to 100 ° C. and calcined secondarily. This temporary sintered body did not shrink or deform, and had a density at the time of compacting. Pure copper in an amount sufficient to infiltrate the pre-sintered body as it was was heated to 1100 ° C. in H ₂ gas to infiltrate the pure copper. The density of the obtained substrate material is 1
5.25 g / cm ³ and the copper content was 21%. The variation was 0.03 g / cm ³ , the σ _n-1 variance was 0.0051, the dimensional variation in the vertical direction was 0.05 mm, and the σ _n-1 was 0.0087.

On the other hand, as a comparative example, the substrate material manufactured using W powder having an average particle diameter of 3 μm as in the past had a density variation of 0.17 g / cm ³ and a σ
_n-1 was 0.025, the dimensional variation in the vertical direction was 0.13 mm, and σ _n-1 was 0.025.

According to the present invention, the press forming pressure is set to 95 to 300.
By setting to MPa, the density of the green compact is set to 6
It can be adjusted freely from 0 to 80%.

FIG. 2 is a microscopic photograph showing the alloy structures of the present invention (a) and the comparative example (b) which is a conventional product. The following can be seen from this microscopic photograph. (A) shows a densely packed state in which small particles enter between large particles in W particles,
In the case of (b), since the required filling cannot be obtained only by filling, the density is increased by neck growth, which is the second stage of sintering, and the required density is obtained. Therefore, (b)
After sintering, shrinkage of several percent or more occurs. Moreover, in the neck growth process, there is a possibility that vacancies may be independent (closed pores), which may cause a problem of causing material defects after infiltration. In the present invention, such a problem does not occur because the pressed state is maintained.

Example 2 A large particle size powder 76 having an average particle diameter of 8 μm as a large particle group.
% By volume, and 19% by volume of a small particle size powder having an average particle size of 1 μm as a small particle group, and 4% as an average particle size as a medium particle group.
1 wt% of paraffin wax was added to W powder composed of 5% by volume of μm intermediate particles, and mixed in a mixer for 1 hour. The obtained powder was converted to 294 using a powder molding press.
It was embossed with a pressure of MPa to obtain a green compact having a length of 40 mm, a width of 40 mm and a thickness of 3 mm. FIG. 3 shows the density of this green compact, in which the horizontal axis indicates the content of intermediate particles having an average particle size of 4 μm in the particle constitution, and the vertical axis indicates the obtained density in% of the theoretical density. As shown in the figure, the density of this green compact was 14.67 g / cm ³ , which was 76% of the theoretical density. The green compact was dewaxed calcined at 800 ° C in in H ₂ gas, further, also with H ₂ aerial, 120
It was heated to 0 ° C. and calcined secondarily. This temporary sintered body had no shrinkage or deformation and had a density at the time of compacting. Pure copper in an amount sufficient for infiltration was placed on the pre-sintered body as it was, and heated to 1100 ° C. in H ₂ gas to infiltrate the pure copper. The density of the obtained substrate material is 16.2
It was 5 g / cm ³ and the copper content was 15%. The variation in the density is 0.05 g / cm ³ , the σ _n-1 is 0.0059, and the dimensional variation in the vertical direction is 0.
05 mm and σ _n-1 was 0.0084.

On the other hand, as a comparative example, in the case of a substrate material manufactured by using a powder whose particle size is substantially the same as the conventional one and has a mean particle size of 3 μm and a substantially normal distribution, the variation in density is 0.13 g / cm ^3. Σ _n-1 was 0.031, the dimensional variation in the vertical direction was 0.12 mm, and σ _n-1 was 0.024.

Example 3 A powder having an average particle diameter of 3 μm as a medium particle group and a powder having an average particle diameter of 1 μm as a small particle group were set as an equal volume percentage of a powder having an average particle diameter of 12 μm. 1 wt% of paraffin wax was added to the W powder having the changed content, and mixed for 1 hour in a mixer. The obtained powder was stamped with a pressure of 294 μPa using a powder molding press to obtain a green compact having a length of 40 mm, a width of 40 mm and a thickness of 3 mm.

FIG. 3 shows the density of the green compact.
On the horizontal axis, the content of the large particle powder having an average particle diameter of 12 μm,
The vertical axis indicates the obtained density by% with respect to the theoretical density. When the content of the large particle group is 70% by volume, and the content of the medium particle group and the small particle group is 15% by volume, respectively,
The density of the green compact is 15.2 g / cm ³ and the theoretical density is 79%
The maximum density was shown.

The green compact was dewaxed at 800 ° C. in a hydrogen stream, and further depressed at 1200 ° C. in the same hydrogen stream.
Was calcined secondarily. This calcined body did not shrink or deform and had a density at the time of compacting. As it is, place a sufficient amount of pure copper on this calcined body, and put it in hydrogen
The infiltration treatment was performed by heating to 1100 ° C. The density of the obtained infiltrated body was 17.1 g / cm ³ , the variation in the density was ± 0.05 g / cm ³ , the σ _n-1 was 0.057, and the vertical dimension Variation is 0.05
mm and σ _n-1 were 0.0084.

Next, the powders used in Examples 1, 2 and 3 were embossed at various pressures so that the copper content after infiltration was 10%, 15%, 20%, 30% and A substrate material was prepared under the same conditions as those of the example, with a green compact of 40% by weight, and the conditions of primary temporary sintering, secondary temporary sintering and infiltration.

FIG. 4 and FIG. 5 show the relationship between the copper content of the substrate material obtained by the above method and the thermal expansion coefficient and thermal conductivity.

As Comparative Example 1, by changing the pressure and the preliminary sintering conditions with W powder having a particle size of only 1 μm,
After the infiltration, the pre-sintered body having a copper content of 10% by weight, 15% by weight, 20% by weight, 30% by weight and 40% by weight is infiltrated, and the substrate material is infiltrated under the same conditions as the infiltration material. Produced.

W of 3 μm particle size used in the conventional example of Comparative Example 2
In the case of powder, a substrate material was prepared in the same manner as described above. In Comparative Example 3, the first temporary sintering, the second temporary sintering, and the sintering were carried out under the same conditions as in the example, using a W powder having a particle diameter of only 8 μm and being pressed under various pressures. Soaked copper content 2
0%, 30% and 40% by weight of the substrate material are shown.

From these figures, it can be seen that when comparing the examples of the present invention and the comparative examples, the 1 μm particle size has a smaller thermal expansion coefficient and a smaller thermal conductivity than the 8 μm particle size.
In the case of the particle size of the embodiment of the present invention and the particle size of the conventional example, it is in the middle. This is because the characteristics of the substrate material using the large particles and the characteristics of the substrate material using the small particles in the thermal expansion coefficient and the thermal conductivity of the present invention were moderated. It is considered that the coefficient of expansion and the thermal conductivity increase. Therefore, Example 1 having a high content ratio of large particles
However, among the products of the present invention, the thermal expansion coefficient and the thermal conductivity are the largest. Example 2 and Example 3 cannot be uniquely compared due to the difference in the average particle diameter and the mixing ratio of the large particles, but it is considered that the effect of the particle diameter had a relatively large effect in the comparison in the present case. In Example 3, the thermal expansion coefficient and the thermal conductivity tend to be larger.

When the examples of the present invention and the comparative examples are viewed, the difference in the thermal conductivity is larger than the difference in the coefficient of thermal expansion. This indicates that the product of the present invention has a higher thermal expansion coefficient than the conventional product even when the composition is adjusted to the same thermal expansion as that of the conventional product, indicating a more excellent state. Further, by adjusting the ratio of the large, medium, and small particle groups, the density of the green compact can be increased to 80% of the theoretical density. For example, when a conventional material requires a coefficient of thermal expansion when the copper content is 20% by weight or more, Example 1 of the present invention can obtain a substrate material having better thermal conductivity,
On the other hand, Example 2 of the present invention further requires Example 3 when the thermal expansion coefficient at 15% by weight to 20% by weight of the conventional material difficult to manufacture in Example 1 of the present invention is required.
In the case where the thermal expansion coefficient is required at 10% by weight to 15% by weight of the conventional material which is difficult to manufacture even in Example 2, a substrate material having a higher thermal conductivity than the conventional example can be obtained.

[0027]

According to the present invention, the following effects can be obtained. (1) Shrinkage sintering for size adjustment is not required, and shrinkage after infiltration of the green compact can be reduced to almost zero, so that machining for finishing is not required. it can. (2) The density (filling rate) can be controlled at the stage of pressing the green compact, and the composition variation of the product can be reduced. (3) Although the number of thermal expansion coefficients is slightly increased by using large particles, the thermal conductivity is increased, and as a result, a semiconductor substrate having better thermal conductivity can be obtained. (4) Since the variation in the composition is small, the variation in the coefficient of thermal expansion and the variation in the thermal conductivity is also small, and a high-quality semiconductor substrate can be obtained.

[Brief description of the drawings]

FIG. 1 shows the relationship between the particle size configuration and the density of an obtained green compact, and shows an example of a particle size configuration composed of a combination of a large particle group and a small particle group.

FIG. 2A shows an alloy structure of the present invention, and FIG.
Indicates the alloy structure of the comparative example.

FIG. 3 shows the relationship between the particle size configuration and the density of the obtained green compact by an example of a particle size configuration including a combination of a large particle group, an intermediate particle group, and a small particle group.

FIG. 4 shows a thermal expansion coefficient of the obtained semiconductor substrate together with a comparative example.

FIG. 5 shows the thermal conductivity of the obtained semiconductor substrate together with a comparative example.

Claims (2)

(57) [Claims] 1. A refractory large particle group of metal and a small particle group and unions
The large particles and the small particles are mutually dispersed.
Presintered body filler metal to a semiconductor substrate material comprising a composite material infiltrated, the refractory metal is W Oh Rui I from M o Oh Rui W and Mo
Ri, Filling metal is Cu or Ag, or Al or an alloy, the average particle diameter of the large particle group is the 7～15Myu m, an average particle diameter of 0.5~1.0μm small particles powder And the large particle group is composed of 60 to 80 % by volume , and the balance is the small particle group
Semiconductor substrate materials, characterized in that it. 2. A combination of a large particle group, a medium particle group, and a small particle group of a high melting point metal,
A semiconductor substrate material of a composite material in which the particles infiltrated the filler metal to the temporary sintered dispersed in each other, the refractory metal is W Oh Rui I from M o Oh Rui W and Mo
Ri, Filling metal is Cu or Ag, or Al or an alloy, the average particle diameter of the large particle group is the 7～15Myu m, an average particle size of the medium particles is 2～4Myu m, and, the average particle diameter of the small particle group is a <br/> in 0.5～1.0Myu m, and, the large particle group 60 to 80 volume percent and a small particle group accounts for 10 to 25 volume%, the balance being A semiconductor substrate material comprising a group of medium particles.