JP3194118B2 - Semiconductor device and method of manufacturing semiconductor component used in the semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a semiconductor component used in a semiconductor device, and more particularly to a mounting substrate on which a semiconductor element such as an IC is mounted.

[0002]

2. Description of the Related Art Conventionally, heat sinks as mounting substrates for mounting semiconductor elements such as ICs have been proposed one after another.
It is actually used in packages for housing semiconductor chips. At present, most of the mounting boards (hereinafter, referred to as heat sinks) of semiconductor devices proposed have a thermal expansion coefficient of silicon (Si) or gallium arsenide (GaAs).
s) and the like, so as to approach the thermal expansion coefficient of the semiconductor material forming the semiconductor element. This is to avoid destruction of the semiconductor chip due to a difference in the coefficient of thermal expansion between the semiconductor chip and the heat sink. With this in mind,
Molybdenum (M
o), a high melting point metal such as tungsten (W) is used as a material for the heat sink.

[0003] From such a background, Japanese Patent Publication No. 2-3186
No. 3 discloses that the thermal expansion coefficient is set to 9 × 10 ⁻⁶ / K or less in order to match the thermal expansion coefficient between the semiconductor chip and the heat sink.

On the other hand, in recent years, it has been desired to reduce the weight of semiconductor chips and heat sinks and to reduce the cost of semiconductor devices by mass production. However, refractory metals such as molybdenum and tungsten generally have a high density, and the use of the refractory metal makes the heat sink heavy and expensive. That is, the use of a high melting point metal is not suitable for the demand for weight reduction and cost reduction. Japanese Patent Publication No. 3-36304 discloses a method of impregnating a high-melting-point metal porous body with copper in order to reduce the weight and cost.

[0005]

However, in the next generation, a mounting substrate for mounting a semiconductor element is
There is a strong demand for a light-weight and one that does not impair the function, and the characteristics of the mounting board that satisfies the demand include a thermal conductivity of at least 200 W / m · K, preferably 230 W / m.
-A range of not less than K, which is not significantly larger than the currently most promising copper, in other words, 10 g
/ Cm ³ or less. However, as shown in FIG. 6, when the rigidity and workability are taken into consideration, none of the above-mentioned conventional devices satisfy these requirements.

Here, as shown in FIG. 6, aluminum (Al) and silicon carbide (SiC) are superior in terms of density, but the former is too large in thermal expansion and the latter is brittle and practically endurable in processing. There is a serious problem that can not be done.

[0007] In the future technical trend, there is a strong demand for a mounting substrate which can be reduced in weight and cost, and on which a device having a plurality of elements or a plurality of functions can be mounted. Therefore, for example, the size of a piece of the mounting substrate, which is 10 to 30 mm and sometimes 40 mm as in the related art, is expected to be twice as large as that of the related art in the future.

However, since aluminum has a large thermal expansion, if the substrate area is large, there is a problem that the substrate is deformed by high heat, such as warping.
Also, silicon carbide is brittle and cannot withstand practical processing.

On the other hand, a copper substrate has good thermal conductivity and is particularly effective for a module generating high heat. However, since handling after assembly is troublesome and it is difficult to make the whole thin, it is necessary to provide external pins separately. In particular, in the case of a multi-chip module having a very large area (for example, a large one having a size of 100 to 200 mm), deformation such as warping of a substrate due to high heat is inevitable and the reliability of the module itself is not reduced. It will impair the nature. Therefore, it is expected that copper substrates will be insufficiently compatible with the progress of high integration.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor which has a large area, is free from deformation such as warpage even when high heat is applied to a mounting substrate on which a plurality of elements are mounted, and can be reduced in weight and cost. It is to provide a device.

Another object of the present invention is to improve the workability and improve the IC
An object of the present invention is to provide a semiconductor device having characteristics suitable for a package.

Still another object of the present invention is to provide a method for manufacturing a semiconductor component as a mounting substrate having the above characteristics.

[0013]

According to the present invention, there is provided, as a means for mounting a semiconductor element, a semiconductor device including a semiconductor component comprising a first metal made of molybdenum or tungsten and a second metal made of copper. The semiconductor component has a thermal conductivity of 200 W / m · K or more, a density of 10 g / cm 3 or less, and a Young's modulus of 14,000 kg / mm 2 or more; The semiconductor component is subjected to warm pressing at 300 ° C. or more, so that the semiconductor component is formed to have a stepped shape including a substrate portion and a protruding portion protruding from a plate surface of the substrate portion. A semiconductor device characterized by the following.

According to the present invention, the copper content is 40% by weight or more, the thermal conductivity is 200W / m · K or more, and the density is 10g.
/ Cm ³ or less, and Young's modulus 14,000 kg / mm ²
A method for producing a semiconductor component having the above characteristics, comprising mixing molybdenum or tungsten and copper, kneading an organic binder, and extruding to obtain a sintered material for the semiconductor component. Is obtained.

[0015]

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing one embodiment of a semiconductor device according to the present invention. In FIG. 1, a plurality of semiconductor elements (hereinafter referred to as IC chips) 1 and a plurality of lead frames 5 are mounted on a mounting substrate 6. A plurality of lead terminals 3 are arranged in parallel in the front and back directions in the figure, and each lead terminal 3 is connected to the IC chip 1 via a lead wire 2. Further, an insulating material 4 is provided between the mounting substrate 6 and the lead terminals 3. The insulating material 4 is, for example, a polyimide film.

When copper is used as the material of the mounting substrate having such a large area, since copper is flexible (soft and easily bendable), desired characteristics as it is, that is, deformation of the substrate such as warpage, etc. However, it does not have such characteristics as to make the thermal expansion coefficient between the IC chip and the mounting substrate equal, and cannot be satisfied as a material which is inexpensive enough for general use. Therefore, the inventors of the present invention have studied how to manufacture a semiconductor component as a mounting substrate having the above characteristics based on a composite material of molybdenum and tungsten, which are high-melting metals close to the expansion coefficient of an IC chip. Considered from the manufacturing method. Hereinafter, a method for manufacturing a semiconductor component having the above characteristics will be described. Hereinafter, the semiconductor component is referred to as a mounting substrate.

The present inventors have already announced that copper powder and molybdenum powder can be mixed, sintered and then rolled to produce a high-precision mounting substrate (Powder and Powder Metallurgy Association Fall Meeting 1993). It is a well-known fact. However, this is a problem in terms of cost, particularly because hot rolling is easily broken, and the Young's modulus, which is one index of deformation resistance, has not been solved.

The present inventors knead a mixture of copper powder and molybdenum powder together with an organic binder, and convert the kneaded material into a high-density, high-viscosity slurry having a thickness of 0.5 to 4 mm, preferably 1 to 1.5 mm. By extruding with a thickness, debinding and sintering, only a cold rolling is performed on a sintered body of 2.5 mm or less, and a cold rolling is performed on a sintered body of 2.5 mm or more after hot rolling. It has been found that a substrate material having no surface irregularities, chips, or wrinkles on the surface of the mounting substrate and having excellent surface roughness can be produced extremely easily and at a much lower cost than before. As shown in Table 2, the rolled plate or mounting substrate obtained by this method had a Vickers hardness of 80 Hv or more, was extremely dense, and had an elongation of 15% or more. Further, even if the deformation is caused by distortion such as heat generation, since the generation local part is elongated and absorbs the distortion, there is no deformation such as warpage that affects the IC chip mounted on the mounting substrate.

Here, when copper is less than 40% by weight,
Sintering was insufficient and a sufficiently dense product could not be obtained by rolling. When the content of copper is 90% by weight or more, the effect on the characteristics cannot be expected much as compared with the use of copper itself.
Therefore, it is meaningless because only the material containing molybdenum and tungsten is expensive and no material advantage is obtained.

Hereinafter, characteristics of the mounting substrate manufactured by the above method will be described. 4 and 5 and Tables 1 to 3
When the weight percentage of copper with respect to molybdenum is 40% by weight, 60% by weight, 90% by weight, and 100% by weight, a series of steps for manufacturing a mounting substrate, which will be described in detail later,
It shows the results of measuring various characteristics when the conditions in the mixing step, the sintering step, the rolling step and the like are unified. When the weight% of copper is 40%, 60%, and 90% by weight, as shown in FIGS. 4, 5 and Table 1, the density is 10 g / cm 3 or less, and the Young's modulus is 1
4000 kg / mm ² or more, and the thermal conductivity is 23
0 W / m · K or more. In other words, with this characteristic, even when heat is generated, deformation such as warpage that does not affect the elements mounted on the mounting substrate occurs.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

With respect to the hardness of the mounting substrate, as shown in Table 2, in the case of a mixture of copper and molybdenum, copper was 40% by weight.
When the Vickers hardness is 182, when the copper is 60% by weight, the Vickers hardness is 132, when the copper is 90% by weight, the Vickers hardness is 85, when the copper is 100% by weight, the Vickers hardness is 50 to 70, It can be seen that all have high rigidity. The Vickers hardness is an index of the rigidity of the mounting substrate.

As shown in Table 3, the elongation of the mounting substrate is 16.1% when copper is 40% by weight.
When the copper is 60% by weight, the elongation is 27.1%. When the copper is 90% by weight, the elongation is 46.5%. When the copper is 100% by weight, the elongation is 54%. As described above, it can be seen that it is extremely dense.

In view of the above characteristics, the composite material of copper and molybdenum has a higher thermal conductivity than molybdenum and is more rigid than copper. It can also be expected to be used for electrical parts and the like to be made into semiconductor devices used in places where there is.

Here, a particularly important point in the manufacturing method for obtaining the above characteristics is that a sintered material having a thickness close to a desired plate thickness is extruded with a high-density, high-viscosity slurry, and is slightly rolled after sintering. The point is to finish with. Further, it is important to select a binder having good wettability as a binder to be kneaded with copper and molybdenum powder. As a result of various investigations, as a binder to be kneaded with the copper and molybdenum mixed powder, it was found that a binder (organic binder) obtained by adding a nonionic surfactant to soft wax was optimal. As a result of kneading the copper molybdenum powder using a binder obtained by adding a nonionic surfactant to soft wax,
A desired sintered material (green body) was obtained.

Specifically, a paraffinic soft wax having a HLB (hydrophilic-lipophilic balance) value of 4-12 as a nonionic surfactant is added. In this case, paraffin soft wax and HLB
The total amount of both of the nonionic surfactants having a value of 4 to 12 needs to be 13% by weight or less. When this binder was used, no cracking occurred in the green body, so that extrusion without cracking and with a small residual carbon amount was possible. Therefore, high-density and high-viscosity slurry extrusion can be performed, and a sheet thickness close to that of a sintered material can be manufactured.

It has been confirmed that those having an HLB value of 4 or less are sticky, and those having an HLB value of more than 12 have high hygroscopicity and are difficult to manage and operate.

A methylcellulose / propylene glycol / water binder often used in ceramic extrusion is advantageous in terms of industrial production in terms of equipment safety.
Although it is possible to extrude, it is difficult to dissolve the methylcellulose, so that it is difficult to obtain stability of drying and debinding.

Here, a first embodiment of the method of manufacturing a mounting board according to the present invention will be described. Alcohol wet mixing of 1670 g (corresponding to 40% by weight of copper) of electrolytic copper powder with 2500 g of molybdenum Mo powder having a particle size of 3 μm was performed for 20 hours using an attritor containing balls. Next, after removing and drying the alcohol, 400 g of soft wax (melting point: 120 F) and 15 g of surfactant Emulgen 903 (commercially available) were mixed in a screw-type rotating twin-arm kneader and kneaded for 10 hours. Thereafter, the whole amount was discharged, and the kneaded material was again loaded in a kneader and kneaded for 10 hours to obtain a green body. Thereafter, the green body was extruded to a thickness of 1.5 mm. After binder removal at 400 ° C. in the molded body 5 vol% H ₂ -N ₂ gas atmosphere, in H ₂ 12
Sintered at 50 ° C. for 1 hour.

Next, the sintered body is cold-rolled at a rolling reduction of 10% or less, then annealed at 900 ° C. for 15 minutes, and cold-rolled again at a rolling reduction of 10% or less to obtain a thickness of 1. 0m
m was obtained. The obtained mirror-finished plate was cut into a piece of 25 mm by punching and press working to obtain a mounting substrate. This mounting substrate was good without chipping. The surface roughness of this mounting substrate is Ra 0.3 μm, and the density is 9.
It was 6 g / cm ³ . When physical properties were measured, Vickers hardness was 178, elongation was 15.5%, and thermal expansion coefficient was 9.3 × 1.
0 ^-6 / K, thermal conductivity 235 W / m · K, Young's modulus 195
It was 00 kg / mm ² .

Next, a second embodiment of the method of manufacturing a mounting board according to the present invention will be described. In the same manner as in the first embodiment, molybdenum powder 1500 g, copper powder 3500 g
(Equivalent to 70% by weight of copper) and 5 g of nickel (Ni) as a sintering aid were mixed, and the mixture was kneaded with the binder to obtain a green body. Thereafter, the green body was extruded to a thickness of 2.4 mm. After that, the binder was removed in the same manner as in Example 1, and sintering was performed at 1050 ° C. for 1 hour in H ₂ . 850 ° C
After hot rolling for 15 minutes at a thickness of 1.98 mm, cold rolling was further performed to obtain a mirror surface plate having a thickness of 1.86 mm.

Next, a warm sizing machine was set at 350 ° C., and 0.2 mm grooves (squares) were formed.
As shown in FIG.
At 8 mm, a mounting board having a good appearance was obtained. Finally, a piece of the mounting substrate was cut out by a slitter so as to have a length of 100 mm and finished. A semiconductor device including this mounting substrate is as shown in FIG.

The characteristics of the mounting substrate for this semiconductor module are as follows: density 9.3 g / cm ³ , Vickers hardness 125, elongation 25.0%, coefficient of thermal expansion 13.8 × 10 ^-6 / K, thermal conductivity 260 W / m・ K, Young's modulus 16,000 kg / mm ²
Met. In addition, the thickness of the plate is 1 m with a composition of only copper and molybdenum.
m, the Vickers hardness was 122 and the thermal conductivity was 300 W / m · K.

When the warp was actually measured with respect to the length of one piece of 100 mm, it was 20 μm, which was smaller and better than that of pure copper.

Next, a third embodiment of the method of manufacturing a mounting board according to the present invention will be described. In the same manner as in the first embodiment, molybdenum powder 3000 g, electrolytic copper powder 2000
g (corresponding to 40% by weight of copper) was mixed, and the mixture was kneaded with the binder to obtain a green body. Thereafter, the green body was extruded to a thickness of 2.5 mm. After that, the binder was removed in the same manner as in Example 1, and sintering was performed at 1250 ° C. for 1 hour in H ₂ . After heating this sintered material at 900 ° C. for 15 minutes, the sintered body was subjected to hot rolling at a rolling reduction of 10% or less, and further, repeated heating and rolling to finish to a sheet thickness of 1.0 mm. Then, after annealing at 850 ° C. for 20 minutes in a reducing atmosphere, a 0.5 mm-thick mirror body was obtained by cold rolling. The obtained mirror-finished plate was cut into a piece of 25 mm by punching and press working to obtain a mounting substrate. This mounting substrate was good without chipping. The surface roughness of the mounting substrate is Ra0.
3 μm and a density of 9.6 g / cm ³ . When physical properties were measured, Vickers hardness 182, elongation 15%,
Thermal expansion coefficient 9.1 × 10 ^-6 / K, thermal conductivity 230 W / m
· K, was a Young's modulus 19000kg / mm ^2.

Next, a fourth embodiment of the method for manufacturing a mounting board according to the present invention will be described. In the same manner as in the first embodiment, molybdenum powder 1500 g, electrolytic copper powder 3500
g (corresponding to 70% by weight of copper) were mixed, and the mixture was kneaded with the binder to obtain a green body. Thereafter, the green body was extruded to a thickness of 2.5 mm. After that, the binder was removed in the same manner as in Example 1, and sintering was performed at 1070 ° C. for 1 hour in H ₂ . After heating this sintered material at 850 ° C. for 15 minutes, the sintered body was subjected to hot rolling at a rolling reduction of 10% or less, and further, heating and rolling were repeated to finish to a sheet thickness of 1.0 mm. Then, after annealing at 850 ° C. for 20 minutes in a reducing atmosphere, a 0.5 mm-thick mirror body was obtained by cold rolling. The obtained mirror-finished plate was cut into 6 mm pieces by punching and pressing to obtain a mounting substrate. This mounting substrate was good without chipping. The surface roughness of the mounting substrate is Ra0.3.
μm and a density of 9.3 g / cm ³ . When the physical properties were measured, the Vickers hardness was 122, the elongation was 28%, the thermal expansion coefficient was 13.6 × 10 ⁻⁶ / K, and the thermal conductivity was 298 W / m.
· K, was a Young's modulus 15500kg / mm ^2.

The range of the sintering temperature in the above embodiment is from 1000 ° C. to 1400 ° C., preferably from 1050 ° C.
1300 ° C. This is because, at 1000 ° C. or lower, the finished mounting substrate cannot be densified, and when the temperature exceeds 1400 ° C., the elution of copper rapidly increases, contamination in the furnace becomes severe, and a mounting substrate having the above characteristics cannot be obtained. It is.

The wet mixing time of copper and molybdenum is preferably 5 to 40 hours, and the next kneading time is preferably 1 to 10 hours.

Although the above embodiment is based on the mixing of copper powder and molybdenum powder, the characteristics similar to the above characteristics can be obtained by mixing copper powder and tungsten powder.

Since this material obtained in the above embodiment can be punched, it can be used also for the lead terminal 3 shown in FIG. In this case, since the lead terminal 3 having the above characteristics has rigidity, it is more resistant to an external impact than a conventional lead terminal made of copper. In addition, since the mounting substrate and the lead wires are made of the same material, there is an advantage that the semiconductor module can be processed in the same process until the punching process in the manufacture.

[0043]

According to the present invention, the mounting substrate as a semiconductor component has a thermal conductivity of 200 W / m · K or more and a density of 10 g.
/ Cm ³ or less, Young's modulus 14,000 kg / mm ² or more, elongation 15% or more, Vickers hardness 80 or more. Even if high heat is applied, deformation of the warp or the like does not occur, and further, weight reduction and cost reduction can be achieved, and workability can be improved.

When a material obtained by the manufacturing method according to the present invention is used for a lead terminal as a semiconductor component, the lead terminal has high rigidity against an external impact, thereby improving the reliability of the semiconductor device. In the manufacture of a semiconductor device, there is an advantage that processing can be performed in the same process until before punching.

[Brief description of the drawings]

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

FIG. 2A is a plan view showing a structure of a mounting board according to the present invention, and FIG. 2B is a cross-sectional view of the mounting board of FIG. 2A.

FIG. 3 is a cross-sectional view illustrating one embodiment of a semiconductor device including the mounting substrate illustrated in FIG. 2;

FIG. 4 is a graph showing the density of copper, which is a raw material of a mounting substrate according to the present invention, with respect to% by weight.

FIG. 5A is a graph showing the coefficient of thermal expansion of the mounting substrate according to the present invention with respect to the weight% of copper;
(B) is a graph showing the thermal conductivity of the mounting substrate according to the present invention with respect to the weight% of copper.

FIG. 6 (a) is a diagram showing various heat dissipation materials as viewed from density and thermal conductivity, and FIG. 6 (b) is a diagram showing various heat dissipation materials as viewed from density and thermal expansion coefficient. It is.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 IC chip 2 Lead wire 3 Lead terminal 4 Insulating material 5 Lead frame 6 Mounting board

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-180534 (JP, A) JP-A-4-333265 (JP, A) JP-A 7-153878 (JP, A) Patent 2717895 (JP, A B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) B22F 3/00-3/26 H01L 23/12-23/14 H01L 23/373

Claims (4)

(57) [Claims] 1. A semiconductor device including a semiconductor component comprising a first metal made of molybdenum or tungsten and a second metal made of copper as means for mounting a semiconductor element, wherein the second metal is 40% by weight. The semiconductor component has a thermal conductivity of 200 W / m · K or more, a density of 10 g / cm 3 or less, and a Young's modulus of 14,000 k.
g / mm2 or more, and 300
A semiconductor, wherein the semiconductor component is formed so as to exhibit a stepped shape composed of a substrate portion and a projecting portion projecting from a plate surface of the substrate portion by performing warm pressing at a temperature of not less than ℃. apparatus. 2. The semiconductor device according to claim 1, wherein the semiconductor component has a Vickers hardness of 80 or more and an elongation of 15% or more. 3. The sintered material for a semiconductor component is obtained by mixing the first metal and the second metal, kneading an organic binder, and extrusion molding. The manufacturing method of the semiconductor component described in the above. 4. After producing a sintered material by the production method according to claim 3, the sintered material is sintered, and the sintered body is subjected to cold rolling or hot rolling and cold rolling. A method of manufacturing a semiconductor component, characterized by being manufactured by the above method.