JPH06268115A - Manufacture of heat radiating substrate for semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a heat radiating substrate composed of such a homogeneous clad material that the film thickness ratio can be selected within a wide range and has a uniform coefficient of thermal expansion, and then, no strain is generated in the material by sticking a second member composed of Cu or Ti to both surfaces of a first member composed of W or Mo by the hot uniaxial working method. CONSTITUTION:At the time of manufacturing the title heat radiating substrate for mounting or holding a semiconductor chip, a second member 1 composed of copper or titanium is stuck to counterposed one main surfaces of first members 2 composed of tungsten or molybdenum and facing each other by the hot uniaxial working method. For example, after performing acid cleaning or displacement cleaning on the surfaces of a Cu plate 1 and Mo plate 2, the plates 1 and 2 are set in a hot press by putting the plates 1 and 2 upon another. Then the plates 1 and 2 are heated to 600 deg.C in an Ar gas atmosphere and, after 30 minutes, the plates 1 and 2 are gradually cooled while the plates 1 and 2 are pressed against another with a pressure of 350kgf/cm<2> by means of a punch 5 and die 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a heat dissipation board for a semiconductor device for mounting or holding a semiconductor element, and more specifically, manufacturing a clad material used for the heat dissipation board of a package for mounting a semiconductor element. It is about the method.

[0002]

2. Description of the Related Art A semiconductor element supporting electrode material or a semiconductor element mounting substrate has a heat dissipation effect matching thermal expansion with a semiconductor element as a semiconductor integrated circuit device (IC) has higher density and higher output. What is expensive is required. In addition to the semiconductor element, a substrate having a thermal expansion coefficient close to that of the package material is desired. Alternatively, a substrate having a controlled coefficient of thermal expansion different from these materials is desired in consideration of a balance of thermal expansion after being assembled with a packaging material, a brazing material, a terminal, and the like. Further, considering the coefficient of thermal expansion, it is desirable to use a material that is as light as possible, and it is also required for the material of the substrate that the processing, brazing and plating necessary for assembling the package are easy.
In some cases, the material of the substrate requires chemical resistance.

As materials satisfying some of the above requirements, composite materials of copper / molybdenum, copper / tungsten, titanium / molybdenum, etc. have been proposed. However, molybdenum (Mo) is used from the viewpoint of workability required for assembly, brazing property with package material, chemical resistance, etc.
It is strongly desired to provide a high-quality clad-type heat dissipation substrate material in which copper (Cu) or titanium (Ti) is used as a base material of tungsten or tungsten (W) as a base material.

Conventionally, these clad materials are manufactured by a rolling method. Unlike a composite material containing a non-metal, in a typical metal clad material made of a metal-based composite material having ductility, its production and secondary working can be performed by plastic working. Therefore, the production of the metal clad material by the rolling method is suitable for mass production. In particular, as is clear from Japanese Patent No. 1458686, the metal clad material can be easily manufactured by hot rolling.

However, when the metal clad material is manufactured by the rolling method, if the difference in the thickness (hereinafter referred to as the layer thickness) between the base material forming the clad material and the laminated material is large, a uniform layer thickness ratio is obtained. It is difficult to obtain it in a stable manner, and a solution for it is required.

[0006]

As described above, for example, the clad material can be easily manufactured by the rolling method within a range in which the difference in the layer thickness of Cu / Mo / Cu or Cu / W / Cu is small. Incidentally, the layer thickness ratio of the Cu / Mo / Cu or Cu / W / Cu clad material produced by the conventional rolling method is in the range of 1: 5: 1 to 2: 1: 2.

Further, since different kinds of metals having remarkably different deformation resistances are processed at the same time (which cannot be pressure-bonded without processing), the processing is performed outside the above-mentioned Cu / Mo / Cu or Cu / W / Cu layer thickness ratio range. In many cases, undulations or colonies of the Mo layer or W layer are formed along with the progress of.

FIG. 8 is a sectional view schematically showing the undulations or colonies of the Mo layer or W layer. As shown in FIG. 8A, the undulation of the Mo layer (material) or the W layer (material) 2 sandwiched between the Cu layers (material) 1, that is, a partial macroscopic shear band is formed. . Further, as shown in FIG. 8B, the Mo layer or W layer 2 is divided to form a colony. When undulations or colonies of the Mo layer or W layer are formed in this way, the coefficient of thermal expansion of the clad material becomes nonuniform, and the clad material itself is distorted. As a result, such a clad material cannot be used as a material for the heat dissipation substrate that requires high reliability.

The above-mentioned problems also occur in a rolled clad material having two layers or four layers or more.

As a material for the semiconductor element supporting electrode or the semiconductor element mounting substrate, a clad material having a three-layer structure and having a Cu layer positioned outside is often used because of ease of plating and brazing. .

Therefore, an object of the present invention is to manufacture a heat dissipation substrate for a semiconductor device, which can have a layer thickness ratio in a wide range, has a uniform coefficient of thermal expansion and does not generate distortion and is made of a homogeneous clad material. Is.

[0012]

[Means for Solving the Problems and Their Effects] The inventors of the present application have conducted extensive studies to solve the above problems, and as a result, in the clad materials such as Cu / Mo / Cu and Cu / W / Cu Without adding plastic deformation, for example,
As a method of producing a homogeneous clad material that does not generate the above-described strain and undergoes almost no rolling process, a method of heating while applying a static uniaxial pressure to the entire surface of the clad material has been developed. The inventor of the present application has found that a clad material having high quality and high reliability can be obtained by this method.

That is, in the method for manufacturing a heat dissipation substrate for a semiconductor device according to the present invention, copper and titanium are formed on one main surface and the other main surface of the first member, which is made of one of tungsten and molybdenum, facing each other. This is a method of joining the second member made of either metal by a hot uniaxial working method.

Examples of the apparatus used in the manufacturing method of the present invention include a hot press and a hot isostatic press.

According to the manufacturing method of the present invention, it is possible to manufacture a heat dissipation substrate as a pressure-bonded composite material by combining a base material of various sizes and a bonding material. Further, according to the manufacturing method of the present invention, the ratio of the layer thicknesses of the clad material can be set in a wide range. Therefore, the coefficient of thermal expansion of the clad material can be controlled within a wide range. Further, although the base material is a refractory metal having a large deformation resistance, the manufacturing method of the present invention enables the composite material and the base material to be composited by a slight and uniform deformation of only the composite material. Therefore, it is possible to manufacture a heat dissipation substrate that is homogeneous and has little distortion. In the manufacturing method of the present invention, strain is hardly introduced in the manufacturing process. Therefore, warpage or distortion does not occur during or after the package is assembled, and a high-quality package can be manufactured.

The manufacturing method of the present invention will be described below by taking the case where molybdenum (Mo) is used as the base material and copper (Cu) is used as the bonding material as an example.

First, the joint surface of molybdenum as the first member (base material) and copper as the second member (composite material) is subjected to acid cleaning by a doppling method to remove surface oxides. Next, after performing acid substitution cleaning using alcohol or acetone, the copper material and the molybdenum material are directly laminated. Alternatively, the surface of the molybdenum material is plated with copper, nickel, or a combination thereof, and then the copper material and the molybdenum material are stacked.
By performing this plating treatment, it becomes possible to reduce the heating temperature at the time of pressure heating and joining in the subsequent step.

The thickness of the first member (base material) is preferably 10 μm or more and 0.3 mm or less. A substrate having a thickness of less than 10 μm has no substantial effect on controlling the thermal expansion of a practical heat dissipation substrate. Also, when the thickness of the base material exceeds 0.3 mm, the second heat sharing function is shared.
This is because it becomes difficult for the member (combining material) to exhibit its function.

Then, the laminated base material and the laminated material are heated while being pressurized. The heating temperature is preferably in the range of 300 ° C to 800 ° C. If the heating temperature is less than 300 ° C,
The base material and the mating material necessary for bonding are not sufficiently familiar, and sufficient bonding cannot be obtained between them. The heating temperature is 8
If it exceeds 00 ° C, the laminated material is largely deformed, and it becomes difficult to control the layer thickness.

The pressure applied to the laminated base material and the laminated material is preferably in the range of 200 to 1000 kgf / cm ² . If the pressure is less than 200 kgf / cm ² , the adhesion between the base material and the bonding material necessary for bonding and the interfacial reaction do not proceed. Further, even if a pressure of 1000 kgf / cm ² is applied, improvement in the adhesion between the base material and the laminated material cannot be expected.

It is desirable that the cooling after the heating and pressure welding be as slow as possible in order to facilitate the release of strain. Also,
In order not to cause deformation during cooling, it is desirable to avoid rapid cooling at least and to lower the cooling rate within 10 ° C / min.

Further, depending on the surface shape of the clad material, distortion occurs during the pressure contact. To make it easier to release the distortion,
It is desirable to provide a semicircular cutout on the outer peripheral portion of the board surface shape of the clad material.

FIG. 6 is a plan view showing the board surface shape of the clad material. For example, by providing a semi-circular cutout on the outer peripheral portion of the diameter D = 200 mm, the strain generated during the pressure welding is easily released.

The purity of copper material and molybdenum material are both 9
If it is about 9.9% or more, there is no problem in design.

The thickness of the base material and the bonding material is basically the thickness of the heat dissipation substrate (hereinafter referred to as the total thickness) of 0.3 to 3.0 mm converted into a desired composition ratio. To make the total thickness of the final product to the desired value, add an etching allowance (for example, a thickness of about 10 μm) for removing the mold release agent of the hot press mold during heating and pressure welding. Set.

For example, with a total thickness of 1.0 mm, Cu / Mo /
When manufacturing a heat dissipation substrate with a Cu layer thickness ratio of 5: 1: 5, a Mo base material with a thickness of 0.090 mm and a thickness of 0.460 m
The Cu composite material of m is superposed with the composition of Cu / Mo / Cu. At this time, it should be noted that the formation of an oxide layer on the surface of the base material or the composite material is suppressed.

In order to lower the heating temperature at the time of pressure contact and improve the bondability, it is effective to bond both the base material and the bonding material with the third layer having good wettability interposed therebetween.
For the third layer, for example, a Cu or Ni plating layer is effective. In addition to this, it is also possible to use vapor phase coating such as vapor deposition as a method of forming the third layer. The thickness of the third layer is 1
It is preferably 0 μm or less. The thickness of the third layer is 10
When the thickness exceeds μm, the amount of the metal forming the third layer diffused into the composite material increases, and the thermal conductivity of the composite material itself decreases.

For applications in which the surface roughness of the clad material in the joined state is not suitable for package assembly, the outer circumference of the clad material is washed and then the surface roughness is reduced to 0. It is necessary to correct it precisely to about 1 μmRa.

As described above, according to the present invention, a layer thickness ratio of 1: 9: 1 to 5: 1: 5, which is conventionally impossible to manufacture, a variation in the thickness of the substrate ± 3/100, and a warp of 0. 5mm / 300mm
It is possible to produce a clad material within the range. For example, when the structure of the clad material is Cu / Mo / Cu and the layer thickness ratio is 1: 9: 1 to 5: 1: 5, the range of the coefficient of thermal expansion is 6 × 10 ^{−6 to} 16 × 10 ^−. It can be controlled in a wide range of ⁶ / K.

Further, the deviation of the thickness of the base material after being made into the clad material can be controlled to a value which is considerably smaller than that in the case of the rolling method.

FIG. 7 is a cross-sectional view used to explain the deviation of the thickness of the base material. t ₀ indicates the thickness of the base material before rolling or before hot uniaxial working, and t ₁ and t ₂ indicate the thickness of the base material after rolling or after hot uniaxial working. In FIG. 7, the copper (Cu) material 1 is joined to both surfaces of the molybdenum (Mo) material 2. The deviation S is represented by the following formula.

S = (t ₀ × 100) / (t ₁ or t ₂ ) The value of the deviation S is 20 to 30% according to the rolling method, but up to about 5% according to the manufacturing method of the present invention. Get smaller.

As described above, the pressure-bonded composite material of the present invention is exemplified by the case where molybdenum (Mo) is used as the base material and copper (Cu) is used as the bonding material.
That is, the manufacturing method of the heat dissipation substrate made of the clad material has been described. When titanium (Ti) is used as the bonding material, tungsten (W) is used as the base material and copper (Cu) or titanium (Ti) is used as the bonding material. Also in this case, a highly reliable clad material can be obtained by the same manufacturing method.

[0034]

EXAMPLES Example 1 Diameter 200 mm and thickness 0.4 produced by rolling method
A 65 mm Cu plate and the same diameter as the Cu plate but with a thickness of 0.09
A 0 mm Mo plate was prepared. After cleaning the surface of each of the Cu plate and Mo plate with an HF / HNO ₃ solution, hot pure water,
The acid was replaced and washed with acetone. After that, C
u / Mo / Cu were superposed in this order, and the superposed plate was set in a hot press as shown in FIG.

FIG. 1 is a schematic view showing the structure of a hot press used for hot uniaxial processing in the manufacturing method of the present invention. The laminated material (Cu / Mo / Cu) 3 is Cu material 1 and M
It is composed of o material 2. The Cu material 1 is superposed on both sides of the Mo material 2. Spacers 4 are provided between the overlapping materials 3.
Is provided. The upper punch 5 and the lower punch 6 are arranged so that pressure is applied to the superposed material 3 via the spacer 4. A side mold 7 and a guide ring 8 are provided so as to surround the outer peripheral portions of the overlapping material 3 and the spacer 4. The side mold 7 and the guide ring 8 are provided on the inner peripheral surface of the guide mold 9. A heater 10 is provided outside the guide mold 9.

In the hot press shown in FIG.
On the contact portions of the spacer 4 and the guide ring 8 with the overlapping material 3, a thin film of BN powder dispersed in alcohol was applied. After degassing the inside of the furnace under vacuum, argon (Ar) gas was introduced, vacuum degassing was again carried out, and argon gas was introduced. After that, the pressure inside the furnace was reduced to 5 Torr and then heated to a temperature of 600 ° C. At this time, the pressing force was kept at 350 kgf / cm ² by the upper punch 5 and the lower punch 6. In that state, it was gradually cooled after 30 minutes.

Argon gas was introduced into the furnace when the temperature was cooled to 200 ° C., and the pressure applied by the upper and lower punches was released when the temperature was cooled to 100 ° C.

Cu / Mo / taken out from the hot press
In the Cu clad material, BN remained on the surface layer, and after slightly etching using HNO ₃ , the thickness of the clad material was measured and found to be 1.02 mm.
Lapping treatment is performed on both sides of the clad material at the same time using # 8000 abrasive grains, and the thickness of the clad material is 1.00 mm.
I chose The cross section of the clad material thus obtained is schematically shown in FIG. The clad material 30 is M as a base material.
o material 2 and Cu material 1 as a bonding material bonded to both surfaces thereof
Composed of and.

The shear strength of the obtained clad material is measured according to JISZ.
When measured based on -3192, the shear strength was 30 kgf / mm ² or more. Since the standard of the shear strength of a general copper clad material is set to 10 kgf / mm ² or more, it was confirmed that the bonding strength of the clad material obtained by the manufacturing method of the present invention satisfies this condition.

The thermal conductivity and thermal expansion coefficient of the obtained clad material were measured. FIG. 3 is a graph showing these measurement results.

In FIG. 3A, the horizontal axis represents Cu / Mo /
The mass% of Cu in the Cu clad material is shown, and the vertical axis shows the thermal conductivity (W / mK). The white circle plot is K
-Z (heat conductivity in the thickness direction) is shown, and a black circle plot shows K-xy (heat conductivity in a plane orthogonal to the thickness direction). The ratio shown in the graph is Cu: M
The value of the layer thickness ratio of o: Cu is shown.

In FIG. 3B, the horizontal axis represents the mass% of Cu in the Cu / Mo / Cu clad material, and the vertical axis represents the thermal expansion coefficient (10 ⁻⁶ / K). The white circle plot is α-
xy (coefficient of thermal expansion in a plane orthogonal to the thickness direction) is shown.

As is apparent from FIG. 3, when the manufacturing method of the present invention is used, the layer thickness ratio of the clad material can be set in a wide range, so that both the thermal expansion coefficient and the thermal conductivity can be set in a wide range. It becomes possible to control.

Next, the obtained clad material was punched into a planar shape of 25 mm square by a die floating method,
The outer peripheral portion was plated with nickel having a thickness of 2 μm. In the outer peripheral portion, cracks, uneven plating, etc. did not occur, and a heat dissipation board having a good appearance was obtained.

Further, an adhesion strength test in solder wetting was carried out using a 20 mm square flat heat dissipation substrate obtained by the above punching. Ag brazing was used as the brazing material.

FIG. 4 is a schematic view showing an apparatus for evaluating the adhesion strength of plating on the heat dissipation board obtained by the present invention. The heat dissipation board 30 (20
(mm square shape) was set between the two jigs 50 and 60. The surface area of the jigs 50 and 60 facing the heat dissipation board 30 was 30 mm × 30 mm. Heat dissipation board 30 and jig 50
, And the Ag brazing material 70 was provided between the heat dissipation board 30 and the jig 60, and the heat dissipation board 3 was brazed to the jigs 50 and 60. In this state, the jigs 50 and 6 are arranged in the thickness direction of the heat dissipation board 30, that is, in the direction shown by the arrow in FIG.
When 0 was pulled vertically, it fractured at the portion of the Mo material forming the heat dissipation substrate 30. From this, it is understood that the adhesion strength of the plating to the heat dissipation substrate obtained by the present invention also satisfies the general standard of 5 kgf / mm ² or more and is sufficiently high.

25 m diameter produced by the above method
A heat-dissipating substrate of Cu / Mo / Cu clad material having a thickness of 1 mm and a thickness of 1 mm was incorporated into an alumina ceramic package by brazing. FIG. 5 is a sectional view showing the configuration of a semiconductor device using the heat dissipation substrate of the present invention.

The heat dissipation substrate 30 has a semiconductor element mounting portion 31. The ceramic frame 11 made of alumina is brazed onto the heat dissipation substrate 30. Pin terminals 12 are provided on the ceramic frame 11.

According to FIG. 5, a semiconductor device was constructed using the heat dissipation substrate of the present invention. The thermal expansion matching between the heat dissipation substrate of the present invention and the semiconductor element or the package material was examined. As a result, it was found that there was no distortion or crack of the package and peeling of the joint, and it was excellent as a heat dissipation substrate.

Example 2 A Mo plate and a Cu plate were prepared in the same manner as in Example 1. After forming a Cu plating layer with a thickness of 3 μm on the surface of the Mo plate,
A Cu / Mo / Cu clad material was produced by the same procedure as in Example 1. The clad material joined at a pressing force of 500 kgf / cm ² and a heating temperature of 500 ° C. had a shear strength of 30 kgf / mm ² or more according to JIS Z-3192, and had a high joining strength. Also, as for the punching property, a good clad material was obtained as in Example 1.

Example 3 Example 1 in which a nickel plating layer was formed to a thickness of 5 μm
Mo plate with the same dimensions as the above, diameter 200 mm, thickness 0.46
Using a 5 mm Ti plate, Ti was prepared in the same manner as in Example 1.
A / Mo / Ti clad material was produced. Cu / Mo / Cu
Similar to the clad material, the shear strength according to JIS Z-3192 was 30 kgf / mm ² or more, and the same favorable punching as in Example 1 could be performed.

This clad material was also incorporated into a ceramic package in the same manner as in Example 1 and evaluated as a semiconductor device. As a result, it was found that a heat dissipation board that is well suited to the assembly atmosphere of the package and the brazing material and that has a sufficiently high quality and high reliability can be obtained even if the Ti material is used as the bonding material.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a hot press as an example of an apparatus used in a manufacturing method of the present invention.

FIG. 2 is a schematic view showing a cross-sectional structure of a heat dissipation board obtained by the present invention.

FIG. 3 is a graph showing the characteristics of thermal conductivity and thermal expansion coefficient of the heat dissipation board obtained by the present invention.

FIG. 4 is a schematic diagram showing an apparatus for evaluating the adhesion strength of plating to the heat dissipation board obtained by the present invention.

FIG. 5 is a cross-sectional view showing an example of a semiconductor device incorporating a heat dissipation substrate obtained by the present invention.

FIG. 6 is a plan view showing an example of a board surface shape of a clad material used for facilitating release of strain generated during pressure welding in the manufacturing method of the present invention.

FIG. 7 is a cross-sectional view for explaining a deviation in thickness of a base material before and after processing of a clad material.

FIG. 8 is a schematic view showing a cross section of a clad material obtained by a conventional rolling method.

[Explanation of symbols]

 1 Cu Material (Ladding Material) 2 Mo Material (Base Material) 3 Laminating Material 5 Upper Punch 6 Lower Punch 10 Heater 30 Heat Dissipating Board (Clad Material)

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tadashi Arikawa 2 Iwase Koshi-cho, Toyama City, Toyama Prefecture Tokyo Dan Gusten Co., Ltd. Toyama Works (72) Inventor Akira Ichida 2 Iwase Koshi-cho, Toyama City, Toyama Prefecture Gusten Co., Ltd. Toyama Works (72) Inventor Kenichiro Shibata 1-1-1 Kunyokita, Itami City, Hyogo Prefecture Sumitomo Electric Industries Itami Works Co., Ltd.

Claims (1)

[Claims] 1. A method for manufacturing a heat dissipation substrate for a semiconductor device for mounting or holding a semiconductor element, wherein one main surface and the other main surface of a first member made of a metal of either tungsten or molybdenum facing each other. To
A method for manufacturing a heat dissipation substrate for a semiconductor device, comprising joining a second member made of a metal of copper or titanium by a hot uniaxial working method.