JPH10321776A - Radiator member for semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiator member which is low in thermal expansion coefficient and superior in thermal conductivity characteristic. SOLUTION: This radiator member is made by sintering a powder green compact of a mixture of AlN powder coated with wetting-property improving metal and metal powder having high thermal conductivity, and has a structure such that gaps between AlN powder particles are filled with the high thermal- conductivity metal. AlN powder may be formed in the form of plurality of layers of the wetting property improving metal and high thermal-conductivity metal or may be coated with an alloy or mixture of such metals. In this case, the coated AlN powder may be made into a green compact and sintered as it is. The high thermal-conductivity metal is a metal of Cu, Al, Ag or an alloy thereof. The wetting-property improving metal is a metal of Y, Ti, Zr or Hf, or an alloy thereof. Since gaps between the AlN power particles are filled with the high thermal-conductivity metal, the raditor member can exhibit high thermal conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat radiating member having a small coefficient of thermal expansion and a large thermal conductivity, such as a heat sink or a semiconductor substrate.

[0002]

2. Description of the Related Art As a substrate for mounting a semiconductor element, a small thermal expansion relatively close to that of the semiconductor element is used in order to prevent cracks due to thermal stress from being generated at a bonding interface between the mounted semiconductor element and the substrate. Metal materials such as W, Mo, and Kovar having a high modulus, and ceramic materials such as Al ₂ O ₃ , AlN, and BeO are used. Further, a substrate for mounting a semiconductor element is required to have good thermal conductivity in order to dissipate heat generated in the semiconductor element and maintain the semiconductor element at a temperature equal to or lower than a rated temperature. Therefore, various types of Cu alloys are sometimes used for a substrate that requires particularly high thermal conductivity. Thermal conductivity is also required for a heat sink or a radiation fin that dissipates heat generated in the semiconductor element to the outside. In the following description, a semiconductor element mounting substrate, a heat sink, a radiating fin, and the like are collectively referred to as a radiating member.

Meanwhile, in response to recent advances in semiconductor integration technology, the size and density of semiconductor elements have been increased. With the increase in size and density of semiconductor elements, the amount of heat generated in the semiconductor elements has also increased considerably, and the required characteristics of heat dissipating members have become more severe. To meet this demand, for example, Japanese Patent Application Laid-Open No. 50-62776
In the publication, a method is disclosed in which a composite sintered body made of a metal such as Cu or Ag having excellent thermal conductivity and W, Mo or the like having a low coefficient of thermal expansion is interposed between the Si element and the Cu terminal plate. ing. Japanese Patent Application Laid-Open No. Sho 59-21032 discloses that a material obtained by infiltrating Cu into a W powder sintered body by an infiltration method is used as a substrate for mounting a semiconductor element.
In a heat dissipating member in which Cu, Ag, etc. are combined with W, Mo, etc., by changing the content of Cu, Ag, etc.,
The coefficient of thermal expansion and the coefficient of thermal conductivity can be set arbitrarily. Utilizing this advantage, the material of the semiconductor device to be mounted,
Optimal heat radiation members according to the shape of the package, the size of the substrate, and the like are manufactured and widely used.

[0004]

However, recent innovations in semiconductor integrated technology have been remarkable, and there has been a strong demand for the development of heat radiating members having better heat radiating characteristics than conventional ones. Incidentally, a commercially available heat radiation member composed of 30% by weight of Cu and 70% by weight of W has a thermal expansion coefficient of about 7.5 × 10 ⁻⁶ / ° C. and a thermal conductivity of about 140 W / m · K. . In addition, 30 weight Cu
The radiating member composed of and 70% by weight Mo has a thermal expansion coefficient of about 9.5 × 10 ⁻⁶ / ° C. and a thermal conductivity of about 230 W / m / K. On the other hand, the thermal expansion coefficient of the heat radiation member required at present is 8.0 × 10 ⁻⁶ / ° C. or less, and the thermal conductivity is about 200
W / m · K or more. Thus, the coefficient of thermal expansion is small,
The heat dissipating member having a large thermal conductivity is made of conventional W, Mo and Cu,
It cannot be manufactured in combination with Ag. In addition, it is also required that the material for the heat dissipating member has a specific gravity as small as possible and a large area thin plate can be processed by rolling. The present invention
It has been devised to meet such a demand. By mixing and sintering AlN powder having a low coefficient of thermal expansion close to that of a semiconductor element, heat radiation having a small coefficient of thermal expansion and a large coefficient of thermal conductivity is achieved. An object is to provide a member.

[0005]

In order to achieve the object, a heat radiating member for a semiconductor device according to the present invention is formed by sintering a mixed powder compact of an AlN powder coated with a wettability improving metal and a high thermal conductive metal. Wherein the particle gaps of the AlN powder particles have a structure filled with a highly thermally conductive metal. The AlN powder may be coated in multiple layers with a wettability improving metal and a high thermal conductivity metal, or with an alloy or mixture of a wettability improving metal and a high thermal conductivity metal.
In this case, the coated AlN powder can be directly compacted and sintered. As the high thermal conductive metal, a single metal of Cu, Al, Ag or an alloy thereof is used. As the wettability improving metal, Y, T
A single metal of i, Zr, Hf or an alloy thereof is used.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS AlN exhibits a low coefficient of thermal expansion close to that of a semiconductor element and has good thermal conductivity. Utilizing such physical properties, the AlN sintered body is used as a high-performance heat dissipation member for semiconductors, such as a VHF band power amplification module, a high-voltage / large-current switching module, a module for opto-electronics, and a ceramic package substrate for microwaves. Widely used for applications. However, JP
JP-A-127267, JP-A-60-71575, JP-A-61-10071, JP-A-63-27
As described in JP-A-7570 and JP-A-63-277573, in order to produce a product having a high thermal conductivity of 230 W / m · K or more, it is necessary to use an N ₂ gas atmosphere.
It is necessary to sinter at a very high temperature of 1850 ° C. for 10 hours in a carbon container for a long time. Further, it was necessary to control the amount of oxygen contained as an impurity in the sintered body to 1000 ppm or less. Moreover, since the AlN sintered body has no ductility and cannot be processed into a thin plate by rolling, it is currently mainly used only for small and special applications.

The reason why the sintering temperature of AlN is so high is that
This is because an oxide such as Y ₂ O _{3 having a} high melting point (melting point: 2410 ° C.) or CaO (melting point: 2572 ° C.) is used as a sintering aid. Further, the amount of impurity oxygen in the sintered body is 10
When the content exceeds 00 ppm, the Y-Al
It is considered that one of the causes is that oxygen that cannot be completely trapped in the -O compound or the Ca-Al-O compound forms a solid solution in the crystal lattice of AlN, thereby significantly lowering the thermal conductivity. The present inventors have found that if AlN powder particles having a small specific gravity can be filled with a relatively low-melting-point metal such as Cu, Al, or Ag, which has excellent spreadability, without a gap, the coefficient of thermal expansion can be kept at a considerably low value. It was considered that the thermal conductivity could be further improved in this state, and that a large-area heat radiation member could be manufactured by sintering or rolling at a lower temperature. However, AlN powder particles,
It has no wettability to molten metals such as Cu, Al and Ag, and the sintering reaction does not proceed simply by mixing these powders.

In order to improve the wettability of AlN powder, in the present invention, a single metal of Y, Ti, Zr, Hf (hereinafter referred to as a wettability improving metal), these metal elements and Cu, Al, A
g (hereinafter, referred to as a high thermal conductive metal), AlN powder is previously coated as an alloy, a mixture, or in a multilayer form. The improvement of the wettability of AlN powder by metal elements such as Y, Ti, Zr, Hf is described in “Ceramics Joining Engineering”, (Nov. 15, 1996, published by Nikkan Kogyo Shimbun, Shinya Iwamoto, Yuichi Suga), p. . In the present invention, a sintered body suitable for a heat dissipating member for a semiconductor element is manufactured by utilizing this improvement in wettability.
The weight ratio of the wettability improving metal to the AlN powder particles is 1 to
When adjusted to the range of 10% by weight, a continuous coating layer is formed on the surface of the AlN powder particles, and substantially the entire surface of the powder particles is covered with the wettability improving metal. Therefore,
In the sintered body prepared using the coated AlN powder, the metal phase of the high thermal conductive metal is reliably interposed between the individual AlN powder particles, and the AlN powder particles are not directly adjacent to each other. Therefore, the bonding strength of the sintered body is significantly improved.

When the ratio of the metal for improving the wettability to the AlN powder is less than 1% by weight, the coating layer formed on the surface of the AlN powder particles tends to be striped or dotted. In the sintered body obtained using such an AlN powder, a portion in which AlN powder particles are directly adjacent to each other is observed without intervening a metal phase of a highly thermally conductive metal. In this portion, internal defects such as pinholes are likely to occur. Conversely, when the proportion of the wettability improving metal exceeds 10% by weight, the effects of Y, Ti, Zr, Hf, etc. on the properties of the obtained sintered body appear greatly, and the coefficient of thermal expansion is larger than that of the semiconductor element. Significantly increased. As a result, cracks and the like due to thermal stress are likely to occur at the bonding interface between the semiconductor element and the heat dissipation member that repeatedly rises and falls in temperature. Al coated with wettability improving metal
The N powder particles need to have a particle size of 1 to 10 μm in order to efficiently exert the effect of the continuous coating layer. When the particle size of the AlN powder particles is less than 1 μm, A
The agglomeration of the 1N powder particles is so severe that it is difficult to form a uniform coating layer on the individual AlN powder particles. Conversely, if the particle size of the AlN powder particles exceeds 10 μm, the coating layer to be formed on the individual AlN powder particles becomes thicker, so that the thickness of the coating becomes uneven, and the surface of the coating tends to become uneven, and the powder flow Practical problems such as fluctuations in properties and apparent specific gravity occur.

Al coated with a wettability improving metal
By changing the mixing ratio of the N powder particles and the high thermal conductive metal, the coefficient of thermal expansion and thermal conductivity of the target sintered body can be variously adjusted. Powders such as artificial diamond and cubic BN can be used in addition to AlN powder.
Ceramic powders such as iC, TiC, CrC, WC, TiN, and Si ₃ N ₄ generally have a small coefficient of thermal expansion,
Since the thermal conductivity is extremely poor, it cannot be used as a heat radiating member. The wettability improving metal is coated on the AlN powder particles by a sputtering method, an ion plating method, a vacuum evaporation method, a CVD method, or the like. Among them, the powder sputtering method is most suitable. In a method other than the sputtering method, Y
(Melting point: 1526 ° C), Ti (melting point: 1670 ° C), Zr
(Melting point: 1852 ° C.), Hf (melting point: 2227 ° C.), etc.
(Melting point: 1085 ° C), Al (melting point: 660 ° C), Ag
(Melting point: 961 ° C.) and an alloy of a wettability improving metal and the like with a constant composition are extremely difficult to coat. The coating of the AlN powder by the sputtering method can be easily performed by using a powder sputtering apparatus developed by the present inventors. As this type of powder sputtering apparatus, for example, there is an apparatus (Japanese Patent Laid-Open No. 2-153068) for sputtering metal onto a powder fluidized bed formed by rotation of a rotary container charged with powder.

Al coated with wettability improving metal
The N powder is mixed with a highly thermally conductive metal and sintered by any of the following methods. (1) AlN pre-coated with a wettability improving metal
The powder is mixed with one or more kinds of high thermal conductive metals, compacted, and compacted in a hydrogen gas atmosphere at 800 ° C. to 12 ° C.
Heat to 00 ° C. (2) The surface of the AlN powder is coated as a first layer with a wettability improving metal, and the first layer is coated with a highly thermally conductive metal to form a second layer. The obtained two-layer composite powder is compacted, and 800 to 1200 in a hydrogen gas atmosphere.
Heat to ° C. (3) Al previously coated on the surface of AlN powder with an alloy or a mixture of a wettability improving metal and a high thermal conductive metal
N powder is compacted in a hydrogen gas atmosphere at 800 ° C to 1 ° C.
Heat to 200 ° C.

The obtained sintered body is rolled to a required thickness at a reduction of 50% or more. 50% reduction
By setting as described above, the sintered body is consolidated and the toughness is improved. The density of the consolidated sintered body increases to substantially the theoretical density. Since the sintered body has a structure in which the space between the AlN powder particles is filled with the high thermal conductive metal without any gap, the generation of defects such as cracks due to rolling in the structure after rolling is also suppressed. You. The rolled sintered body is subjected to punching, bending, etc., depending on the application.
The heat radiation member has a predetermined shape. Here, excellent workability is developed due to the consolidated structure, and defects such as chipping and breakage do not occur at the time of punching or bending, and the target shape is processed with high accuracy. The processed product has a flat and dense surface. Therefore, the adhesion of the electroless nickel plating layer formed prior to the mounting of the element is also improved.

The specific gravity of the heat radiation member according to the present invention is 4 to 5
Which is an extremely low value as compared with the conventional heat dissipation member. By the way, the specific gravity of the heat radiating member of 30 wt% Cu-70 wt% W is 16.2. 30 wt% Cu-70 wt% Mo.
Has a specific gravity of 9.8, which is heavier than the heat radiating member of the present invention. The price per unit weight of AlN powder is almost the same as the price of W powder or Mo powder, but the specific gravity of AlN powder is 3.3, the specific gravity of W powder is 19.3, and the specific gravity of Mo powder is 10%. 2. Very light compared to 2. Therefore, when converted to the price per unit volume,
The raw material price is extremely low, 1/6 to 1/3.

[0014]

【Example】

Example 1 A commercially available AlN powder (TOY manufactured by Toyo Aluminum Co., Ltd.) was used using a powder sputtering apparatus developed by the present inventors (see Japanese Patent Application Laid-Open No. 2-153068).
(ALNITE-US, average particle size 1.4 μm)
% By weight of Y was coated. Coating powder 75
g and 25 g of commercially available Cu powder (average particle size: 1.0 μm manufactured by Fukuda Metal Foil Powder Co., Ltd.) are sufficiently mixed, and the pressure is 5 ton / cm.
² was compacted. The green compact is placed in a hydrogen gas atmosphere for 120 minutes.
Sintering was performed by maintaining the temperature at 0 ° C. for 1 hour. The obtained sintered body is cold-rolled at a cross-sectional reduction rate of 50% to a thickness of 0.5 mm.
Into a plate shape. Example 2: As in Example 1, AlN powder was coated with 4% by weight of Ti. 80 g of the coating powder and 20 g of a commercially available Al powder (average particle size: 10.0 μm, manufactured by Toyo Aluminum Co., Ltd.) were sufficiently mixed, compacted, and then sintered at 800 ° C. for 1 hour in a hydrogen gas atmosphere. The obtained sintered body was cold-rolled at a cross-sectional reduction rate of 50% to form a plate having a thickness of 0.5 mm.

Example 3 As in Example 1, AlN powder was coated with 7% by weight of Zr. After sufficiently mixing 85 g of the coating powder and 15 g of a commercially available Ag powder (average particle size: 3.0 μm, manufactured by Kojundo Chemical Laboratory Co., Ltd.), the mixture is compacted, and then sintered at 1100 ° C. for 1 hour in a hydrogen gas atmosphere. Tied. The obtained sintered body was subjected to a cross-sectional reduction rate of 50.
%, And formed into a plate having a thickness of 0.5 mm. Example 4: As in Example 1, 10% by weight of AlN powder
Hf. 90 g of the coating powder and a commercially available Ag-Cu alloy powder (Ag 72 wt% -Cu 28 wt%, manufactured by Nippon Atomize Processing Co., Ltd.
(0 μm), 10 g were sufficiently mixed, compacted, and sintered at 900 ° C. for 1 hour in a hydrogen gas atmosphere. The obtained sintered body is cold-rolled at a cross-sectional reduction rate of 50%,
It was formed into a plate having a thickness of 0.5 mm.

Example 5: As in Example 1, commercially available Al
N powder (TOYALNI manufactured by Toyo Aluminum Co., Ltd.)
TE-UF, average particle size of 2.0 μm) is coated as a first layer with 1% by weight of Y and further 25% by weight of C
u to form a second layer on the first layer.
A pressure of 5 ton /
After compacting at a pressure of 1200 cm ² ,
Sintering was carried out by holding at 1 ° C. for 1 hour. Next, the sintered body was cold-rolled at a cross-sectional reduction rate of 50% to form a plate having a thickness of 0.5 mm. Example 6: As in Example 5, AlN powder was coated as a first layer with 4% by weight of Ti and further as a second layer with 20% by weight of Al. After 100 g of the obtained two-layer coating powder was compacted, it was sintered by being kept at 800 ° C. for 1 hour in a hydrogen gas atmosphere. Next, the sintered body is cold-rolled at a cross-sectional reduction rate of 50%,
It was formed into a plate having a thickness of 0.5 mm.

Example 7: As in Example 5, AlN powder was coated as a first layer with 7% by weight of Zr and further as a second layer with 15% by weight of Ag. After 100 g of the obtained two-layer coating powder was compacted, it was sintered at 1100 ° C. for 1 hour in a hydrogen gas atmosphere. Next, the sintered body was reduced in cross-section reduction rate by 50%.
To form a plate having a thickness of 0.5 mm. Example 8: As in Example 5, AlN powder was coated as a first layer with 10% by weight of Hf, and as a second layer, a 10% by weight Ag-Cu alloy (Ag 72% by weight, Cu
28% by weight). After 100 g of the obtained two-layer coating powder was compacted, it was sintered at 900 ° C. for 1 hour in a hydrogen gas atmosphere. Next, the sintered body was cold-rolled at a cross-sectional reduction rate of 50% to form a plate having a thickness of 0.5 mm.

Example 9: As in Example 1, commercially available Al
N powder (TOYALNI manufactured by Toyo Aluminum Co., Ltd.)
74 g of TE-UM, average particle size 6.5 μm) were coated with 26 g of a Cu—Y alloy (Cu 96.2 wt%, Y 3.8 wt%). After 100 g of the coating powder was compacted, it was sintered at 1200 ° C. for 1 hour in a hydrogen gas atmosphere. Next, the sintered body was reduced in cross-sectional reduction rate by 5%.
It was cold rolled at 0% and formed into a plate having a thickness of 0.5 mm. Example 10: As in Example 9, 76 g of AlN powder
It coated with 24 g of 1-Ti alloy (83.3 weight% of Al, 16.7 weight% of Ti). Coating powder 10
After 0 g was compacted, it was sintered by holding it at 800 ° C. for 1 hour in a hydrogen gas atmosphere. Next, the sintered body was cold-rolled at a cross-sectional reduction rate of 50% to form a plate having a thickness of 0.5 mm.

Example 11: In the same manner as in Example 9, 78 g of AlN powder was mixed with an Ag-Zr alloy (68.2% by weight of Ag, Zr
31.8% by weight). After 100 g of the coating powder was compacted, it was sintered at 1100 ° C. for 1 hour in a hydrogen gas atmosphere. Next, the sintered body was cold-rolled at a cross-sectional reduction rate of 50% to form a plate having a thickness of 0.5 mm. Example 12: As in Example 9, 80 g of AlN powder was
f-Ag-Cu alloy (Hf 50.0% by weight, Ag36.
(0% by weight, Cu 14.0% by weight). After 100 g of the coating powder was compacted, it was sintered by holding it at 900 ° C. for 1 hour in a hydrogen gas atmosphere. Next, the sintered body was cold-rolled at a cross-sectional reduction rate of 50% to form a plate having a thickness of 0.5 mm.

Comparative Example 1: 74 g of a commercially available AlN powder (TOYALNITE-US, manufactured by Toyo Aluminum Co., Ltd., average particle size: 1.4 μm) was converted to 74 g of a commercially available Y powder (average particle size: 10.0 μm, manufactured by Kojundo Chemical Laboratory Co., Ltd.) 1 g and commercially available C
After sufficiently mixing with 25 g of the u powder and compacting at a pressure of 5 ton / cm ² , sintering was attempted by holding the mixture at 1200 ° C. for 1 hour in a hydrogen gas atmosphere. Comparative Example 2: In the same manner as in Comparative Example 1, 76 g of AlN powder was replaced with a commercially available Ti powder (manufactured by Kojundo Chemical Laboratory Co., Ltd., having an average particle size of 1).
0.0 μm), sufficiently mixed with 4 g of commercially available Al powder and 20 g of commercially available Al powder, and then compacted.
Sintering was attempted by holding for a time.

Comparative Example 3: As in Comparative Example 1, 78 g of AlN powder was mixed with 7 g of commercially available Zr powder (average particle size 8.0 μm, manufactured by Kojundo Chemical Laboratory Co., Ltd.) and 15 g of commercially available Ag powder.
And then compacted, and then pressed in a hydrogen gas atmosphere for 1 hour.
Sintering was attempted by holding at 100 ° C. for 1 hour. Comparative Example 4: As in Comparative Example 1, 80 g of AlN powder was prepared by using a commercially available Hf powder (manufactured by Kojundo Chemical Laboratory Co., Ltd., average particle size: 1).
0.0 μm) 10 g, commercially available Ag powder 7.2 g and commercially available Cu powder 2.8 g were sufficiently mixed, compacted, and then sintered at 900 ° C. for 1 hour in a hydrogen gas atmosphere. Was. When the thermal conductivity of each of the sintered bodies obtained in the above examples was measured, as shown in Table 1, each of the sintered bodies had a thermal conductivity of 20%.
It showed a high thermal conductivity of 0 W / m · K or more. The coefficient of thermal expansion showed a low value of 8.0 × 10 ⁻⁶ / ° C. or less. From these results, it can be seen that it can be used as a heat dissipation member for a semiconductor package having excellent heat dissipation characteristics. On the other hand, in the comparative example using the AlN powder not subjected to the surface treatment, the AlN powder particles did not wet at all with the molten metal such as Cu, Al, and Ag, and thus did not become a sintered body.

[0022]

[0023]

As described above, the heat radiating member for a semiconductor element of the present invention is obtained by mixing AlN powder coated with a wettability improving metal with a high thermal conductive metal, compacting the mixture, and sintering the resultant. Therefore, it has a structure in which the gaps between the AlN powder particles are filled with a highly thermally conductive metal. Therefore, A
It is used as a heat dissipating member suitable for a semiconductor element substrate, a heat sink, a heat dissipating fin, and the like, which utilize the inherent low coefficient of thermal expansion and high thermal conductivity of 1N and tend to generate a large amount of heat as performance increases.

Claims (5)

[Claims] 1. Al coated with a wettability improving metal
A heat-dissipating member for a semiconductor device, comprising a sintered compact of a mixed powder of N powder and a high thermal conductive metal, wherein the AlN powder particles have a structure filled with a high thermal conductive metal. 2. A sintered compact of a powder compact of AlN powder coated in multiple layers with a wettability improving metal and a highly conductive metal, wherein a gap between the Al powder particles is filled with a highly thermally conductive metal. Heat dissipating member for semiconductor elements having a textured structure. 3. A powder compact of AlN powder coated with an alloy or a mixture of a wettability improving metal and a highly conductive metal is sintered, and a gap between the Al powder particles is made of a highly thermally conductive metal. A heat dissipating member for a semiconductor element having a filled structure. 4. The heat radiation for a semiconductor element using one or more selected from the group consisting of a single metal of Cu, Al, and Ag or an alloy thereof as the high thermal conductive metal according to claim 1. Element. 5. The method according to claim 1, wherein one or more selected from a single metal of Y, Ti, Zr and Hf or an alloy thereof.
3. A heat-dissipating member for a semiconductor element used as the wettability improving metal according to any one of the above items 3.