JP2000049263A - Heat sink and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sink in which stripping of a thin diamond film layer from a substrate can be suppressed. SOLUTION: The heat sink 50 comprises a substrate 51 containing a metal having low coefficient of thermal expansion and Cu and having surface roughness R1 of 1-5 μm, an intermediate layer 52 formed on the surface 54 of the substrate 51, and a thin diamond film layer 53 formed on the surface of the intermediate layer 52.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat sink and a method of manufacturing the same, and more particularly, to a laser diode,
PU (central processing unit), MPU (micropro
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat sink on which a semiconductor element having a relatively large amount of heat, such as a heat sink unit and a high-frequency amplifier element, is mounted.

[0002]

BACKGROUND OF THE INVENTION Diamond is known to have the highest thermal conductivity of any material. Studies have been made to apply this diamond to heat sinks for mounting semiconductor elements. As a heat sink using diamond, a heat sink made entirely of diamond and a heat sink having a diamond film formed on a metal substrate have been developed.

[0003] Since natural diamonds are rare and artificial diamonds are expensive, the cost increases as the amount of diamonds in the heat sink increases. Therefore, a heat sink made entirely of diamond,
A semiconductor element that generates high heat, such as a high-power laser, and is used only for applications in which the original performance cannot be exhibited due to insufficient heat removal with a substitute, or for which the cost is not estimated at the research stage. A heat sink in which a diamond film is formed on a metal substrate is used for a product requiring cost reduction.

When a metal is used for a part of the heat sink, the heat conductivity is reduced as compared with the case where the heat sink is composed of diamond alone, but the price is reduced. Therefore, the price and performance of the heat sink are almost proportional, and generally, the heat sink having higher thermal conductivity is more expensive. Therefore, a heat sink which is not so expensive and has a high thermal conductivity is desired.

[0005] In order to meet such demands, a heat sink having a laminated structure in which a diamond thin film is stacked on a metal having good thermal conductivity is described in, for example, Japanese Patent Application Laid-Open No. Hei 5-326767.

[0006]

In the heat sink described in the above-mentioned publication, copper or copper-tungsten alloy which is a metal having good heat conductivity is described as a material of the substrate. Since these materials have high thermal conductivity and are relatively inexpensive even among metal materials, they are suitable as heat sink materials.

[0007] However, New Diamond Vol.10 No.3
(34) As described in pp.26-27, copper in the substrate does not form carbides, and copper does not absorb carbon and does not form a solid solution with carbon. There is a problem that it is difficult to form a thin film with good adhesion.

In addition, if the difference between the coefficient of thermal expansion of the substrate and the coefficient of thermal expansion of diamond is small, even if the heat sink becomes high temperature, only the stress is generated inside the diamond thin film and the heat sink does not warp. Since the coefficient of thermal expansion of the sintered body containing copper is larger than that of diamond,
There is a problem that the heat sink is warped.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a heat sink capable of forming a diamond thin film on a substrate having good heat conductivity with good adhesion. It is an object of the present invention to provide a manufacturing method thereof.

Another object of the present invention is to provide a heat sink capable of suppressing the occurrence of warpage and a method of manufacturing the same.

[0011]

According to the present invention, there is provided a heat sink comprising a metal having a low coefficient of thermal expansion and Cu, having a surface roughness _RZ of 1 μm or more and 5 μm or less, and a heat sink formed on the surface of the substrate. And a diamond thin film layer formed on the surface of the intermediate layer.

In the heat sink configured as described above, since the surface roughness R _Z of the substrate is set to an optimum range of 1 μm or more and 5 μm or less, the substrate and the intermediate layer formed on this surface are Adhesion is improved.

Further, the adhesion between the intermediate layer and the diamond thin film is high. As a result, the adhesion between the substrate and the diamond thin film layer increases. Furthermore, even when the difference between the coefficient of thermal expansion of the substrate and the coefficient of thermal expansion of the diamond thin film layer is large, an intermediate layer exists between the substrate and the diamond thin film layer. Warpage can be prevented.

The reason why the surface roughness R _Z of the substrate is 1 μm or more and 5 μm or less is that if the roughness R _Z is less than 1 μm, the adhesion between the substrate and the intermediate layer becomes small, and the roughness R Z _Z
Is more than 5 μm, since irregularities are formed on the surface of the diamond thin film layer formed on this surface, which is not preferable.

The substrate is made of a Cu-W sintered body, Cu-M
It is preferably at least one type of sintered body selected from the group consisting of an o-sintered body and a Cu-W-Mo sintered body.

The intermediate layer is made of Ti, TiC, TiN,
Si, SiC, Si ₃ N ₄ , AlN, Al ₂ O ₃ , V,
Cr, Mn, Mo, In, Sn, Hf, Ta, Ir, N
It is preferable to include at least one selected from the group consisting of i, Pt, and Au.

Further, the intermediate layer is formed on the first substrate formed on the substrate.
An intermediate layer and a second intermediate layer formed on the first intermediate layer are provided, and the first intermediate layer and the second intermediate layer are preferably made of different materials.

Further, the first intermediate layer is made of Ti, TiC and
Including at least one selected from the group consisting of TiN,
The second intermediate layer is made of Si, SiC, Si_Three N_Four , AlN and
Al _Two O_Three At least one selected from the group consisting of
Preferably.

In this case, the first intermediate layer contains Ti, TiC or TiN which has high adhesion to the substrate, and the second intermediate layer has Si, SiC, Si which has high adhesion to diamond.
_Since 3N ₄ , AlN or Al ₂ O ₃ is contained, the adhesion between the diamond thin film layer and the substrate can be improved.

Further, when two or more kinds of materials are laminated in the specific order or alternately as the intermediate layer, a material having good adhesion to copper can be used rather than using a material having relatively good adhesion to both copper and diamond. A material having good adhesion to diamond and diamond can be used, and the adhesion between the diamond thin film and the substrate can be further improved. Also, by alternately laminating a plurality of layers, the adhesion between the two types of materials selected for the intermediate layer can be improved.

The thickness of the intermediate layer is preferably 10 μm or less. If the thickness of the intermediate layer exceeds 10 μm, the adhesiveness between the substrate and the diamond thin film layer will be deteriorated, and the thermal conductivity will decrease, and the thermal conductivity of the heat sink will decrease.

The surface of the intermediate layer in contact with the diamond thin film layer is preferably subjected to a scratching treatment.

According to a method of manufacturing a heat sink according to the present invention, a step of performing a surface roughening treatment on a surface of a substrate containing a metal having a low coefficient of thermal expansion and Cu, and an step of forming an intermediate layer on the surface of the substrate subjected to the surface roughening treatment Forming a diamond thin film layer on the surface of the intermediate layer.

According to the method of manufacturing a heat sink having such a process, the intermediate layer is formed on the surface of the substrate.
Copper on the surface of the substrate is covered by the intermediate layer, and a diamond thin film layer is formed on the intermediate layer. Therefore, the diamond does not come into direct contact with the copper of the substrate, and the intermediate layer and the diamond thin film layer are bonded to each other, so that the adhesion between the diamond thin film layer and the substrate is improved.

Further, even when the difference between the coefficient of thermal expansion of the diamond thin film layer and the coefficient of thermal expansion of the substrate is large, the warp of the heat sink can be suppressed by the intermediate layer acting as a buffer layer.

Further, roughening treatment step preferably comprises a roughness R _Z of the surface of the substrate and 1μm or 5μm or less.

[0027] The roughness R _Z of the surface was 1μm or 5μm or less, is less than R _Z is 1μm adhesion between the intermediate layer and the substrate is reduced, the diamond thin-film layer when R _Z is more than 5μm This is because irregularities are formed on the surface, which is not preferable.

Preferably, the roughening step is performed by machining. In this case, the entire surface of the substrate can be uniformly subjected to a roughening treatment by machining.

Preferably, the roughening step is performed by etching. In this case, since microscopic unevenness is formed on the surface of the substrate by the etching, the adhesion between the substrate and the intermediate layer can be further improved.

It is preferable that the method of manufacturing the heat sink includes a step of performing a damaging treatment on the surface of the intermediate layer prior to the formation of the diamond thin film layer.

In this case, since diamond nuclei are easily generated from scratches on the surface of the intermediate layer, many diamond nuclei are generated on the surface of the substrate, so that the growth of the diamond thin film layer is accelerated and the thickness of the diamond thin film layer is uniform. Becomes

[0032] Preferably, the damaging treatment includes damaging the surface of the intermediate layer using diamond. In this case, when the surface of the substrate is scratched, the diamond adheres to the surface of the substrate, so that the diamond becomes a nucleus when forming the diamond thin film layer. Therefore, the growth of the diamond thin film layer can be further promoted.

The diamond thin film layer is formed on the substrate by a vapor phase synthesis method.
Hot filament CVD (chemical vapor deposition)
Any known method such as a plasma CVD method, a flame method, or the like may be used.

[0034]

(Example 1) FIG. 1 shows a hot filament CV for vapor phase synthesis of diamond used in Example 1 of the present invention.
It is a schematic diagram of D apparatus. Referring to FIG. 1, a hot filament CVD apparatus 1 includes a reaction vessel 21 and a gas inlet 22.
, A gas outlet 23, an AC power supply 24, a tungsten filament 25, a substrate holder 27, a cooling water inlet 28, and a cooling water outlet 29.

The reaction vessel 21 is provided with a gas inlet 22 for introducing a raw material gas and a gas outlet 23 for discharging a raw material gas or a gas generated from the raw material gas.

In the reaction vessel 21, a tungsten filament 25 is provided. The tungsten filament 25 is connected to the AC power supply 24,
4 causes the tungsten filament 25 to glow red when a current flows through the tungsten filament 25.

Below the tungsten filament 25, a molybdenum substrate holder 2 for mounting a substrate
7 are provided. The temperature of the tungsten filament 25 rises due to red heating, so that the substrate holder 27 also rises in temperature. A cooling water inlet 28 for introducing cooling water for cooling the substrate holder 27 and a cooling water outlet 29 for discharging the cooling water are provided on the substrate holder 27.

A Cu-W sintered body having a Cu content of 10% by weight and a length × width × thickness of 12 mm × 12 mm × 0.1 mm.
A 6 mm substrate was prepared. The surface of the substrate was cut and roughened to make the surface roughness R _Z of the substrate 3.4 μm. It is to be noted that the R _Z JIS (Japanese Industrial St
andards) means ten-point average roughness.

AlN having a thickness of 5 μm was deposited as an intermediate layer on the roughened surface. After the surface of the intermediate layer was subjected to a scratching treatment with diamond particles, the substrate 26 was placed on the substrate holding table 27 shown in FIG. Thereafter, a current is passed from the AC power supply 24 to the tungsten filament 25,
The temperature of the tungsten filament 25 was set to about 2050 ° C.

Next, a mixed gas having a methane concentration of 1 mol% was introduced into the reaction vessel 21 from the gas inlet 22. A diamond thin film layer was synthesized on the substrate 26 over 40 hours while maintaining the pressure in the reaction vessel 21 at 70 Torr. The thickness of the diamond thin film layer was 24 μm. The warpage of the diamond thin film layer was 3 μm.

After polishing the surface of the diamond thin film layer to a mirror surface, the length × width × thickness is 2 mm × 1 mm × 0.6 m
The diamond thin film layer did not peel off from the substrate even when the substrate was cut so as to obtain m. Thereafter, the substrate was metallized to produce a heat sink.

FIG. 2 is a schematic sectional view of a heat sink obtained according to the above-described steps. Referring to FIG. 2, heat sink 50 includes a substrate 51, an intermediate layer 52 made of AlN formed on surface 54 of substrate 51, and a diamond thin film layer 53.

When an InP laser diode was installed on the heat sink 50, the laser diode oscillated. This implies that the heat sink can be sufficiently put to practical use.

Example 2 A Cu—W sintered body having a Cu content of 15% by weight and a length × width × thickness of 10 mm × 1
A substrate of 0 mm × 0.6 mm was prepared. The surface of the substrate was subjected to a surface roughening treatment by cutting, so that the surface roughness R _Z of the surface of the substrate was set to 1.2 μm. 2 μm thick SiC was deposited as an intermediate layer on the roughened surface. The surface of the intermediate layer of the substrate was scratched with fine diamond particles.

Thereafter, the substrate 26 was placed on the substrate holder 27 shown in FIG. The temperature of the tungsten filament 25 was set to about 2100 ° C., and a mixed gas having a methane concentration of 1 mol% was flowed from the gas inlet 22 into the reaction vessel 21. The pressure in the reaction vessel 21 was set to 70 Torr.

Under these conditions, a diamond thin film layer was formed on the substrate 26 for 40 hours. The thickness of the diamond thin film layer was 22 μm. The warpage of the diamond thin film layer was 2.5 μm. After polishing the surface of the diamond thin film layer to a mirror surface, the length × width × thickness is 2 mm × 1 mm
Even when the substrate was cut to a size of × 0.6 mm, the diamond thin film layer did not peel off from the substrate.

Thereafter, the surface of the substrate opposite to the surface on which the diamond thin film layer was formed was polished and metallized to produce a heat sink. In this heat sink
When the P laser diode was installed, the laser diode oscillated. From this, it can be said that this heat sink can be put to practical use.

(Embodiment 3) FIG. 3 is a schematic diagram of a microwave plasma CVD apparatus of the diamond vapor phase synthesis method used in Embodiment 3. Referring to FIG. 3, microwave plasma CVD apparatus 100 includes a substrate holder 101, a microwave power supply 104, a tuner 105, a waveguide 106,
A reaction vessel 107, an outlet 108, an inlet 109,
And a plunger 110.

A substrate holder 101 for holding a substrate in the reaction vessel 107 is provided. In the reaction vessel 107,
An inlet 109 for introducing a raw material gas, and an outlet 108 for discharging the raw material gas and a gas formed by the reaction.
Is provided. The outlet 108 is connected to a vacuum pump. Microwave power supply 104 and isolator (not shown)
And the tuner 105 constitute a microwave generator. The reaction vessel 107 is constituted by a quartz tube.

The microwave generated from the microwave generator goes to the plunger 110 via the waveguide 106. Since the reaction vessel 107 is provided in the middle of the waveguide 106, plasma surrounded by a dotted line 103 is generated in the reaction vessel 107. Since the position where the plasma is generated is the position where the reaction vessel 107 and the waveguide 106 intersect, the substrate holding table 101 is installed near the intersection.

The Cu content is 10% by weight and is made of a Cu—Mo sintered body, and the length × width × thickness is 15 mm × 15 mm × 1
mm substrate was prepared. The surface of the substrate is subjected to a surface roughening treatment by etching so that the surface roughness R _Z of the substrate is 1.7.
μm. 2.1μ thick on the roughened surface
m was deposited as an intermediate layer. After the surface of the intermediate layer was subjected to a treatment of damaging diamond particles, the substrate was placed on the substrate holding table 101 of the microwave plasma CVD apparatus 100 described above.

The temperature of the substrate 102 was set at 850 ° C., and a mixed gas having a methane concentration of 3 mol% was introduced from the inlet 109 into the reaction vessel 107. When the pressure in the reaction vessel 107 is 140
Torr was maintained. Under these conditions, the substrate 1
02, a diamond thin film layer was synthesized. The thickness of the diamond thin film layer was 22 μm, and the warpage of the diamond thin film layer was 4 μm.

After the surface of the diamond thin film layer was polished to a mirror surface, the diamond thin film layer was not peeled from the substrate even when the substrate was cut so as to be 2 mm × 1 mm × 1 mm thick. . Thereafter, the surface of the substrate opposite to the surface on which the diamond thin film layer was formed was polished and metallized to produce a heat sink. When an InP laser diode was set on this heat sink, the laser diode oscillated. This shows that this heat sink can be sufficiently used practically.

Example 4 A Cu—W sintered body having a Cu content of 15% by weight and a length × width × thickness of 10 mm × 1
A substrate of 0 mm × 0.3 mm was prepared. The surface of the substrate was subjected to a surface roughening treatment by etching to make the surface roughness R _Z of the substrate 1 μm. Three layers of Ti, TiN and AlN were laminated in this order as intermediate layers on the surface of the substrate subjected to the surface roughening treatment. The thickness of the above-mentioned intermediate layer composed of three layers is 1.
It was 4 μm.

After the surface of the intermediate layer was subjected to a diamond-damaging treatment, the substrate was placed on a substrate holder 101 of a microwave plasma CVD apparatus 100 shown in FIG. The temperature of the substrate 102 was set to 850 ° C., and a mixed gas having a methane concentration of 3.5 mol% was introduced into the reaction vessel 107 from the inlet 109. The pressure in the reaction vessel 107 was set to 140 Torr. Under these conditions, a diamond thin film layer was synthesized on the substrate 102 over 20 hours. The thickness of the diamond thin film layer is 25 μm, and the warpage of the diamond thin film layer is 2.7 μm.
m.

After polishing the surface of the diamond thin film layer to a mirror surface, the length × width × thickness is 2 mm × 1 mm × 0.3 mm
The diamond thin film layer did not peel off from the substrate even when the substrate was cut such that Thereafter, the surface of the substrate opposite to the surface on which the diamond thin film layer was formed was polished and metallized to produce a heat sink. When the InP laser diode was set on this heat sink, the laser diode oscillated. This shows that this heat sink can be sufficiently used practically.

(Example 5) A Cu-W sintered body having a Cu content of 10% by weight and a length x width x thickness of 10 mm x 1
A substrate of 0 mm × 0.6 mm was prepared. Was 1.1μm roughness R _Z of the surface of the substrate is subjected to surface roughening treatment on the surface of the substrate by machining using a dicing saw. 0.5 μm thick Ti was deposited on the surface of the substrate subjected to the surface roughening treatment. 20 nm thick TiN on Ti and 2 nm thick
50 nm of 0 nm AlN were alternately laminated. Ti, TiN and AlN constitute an intermediate layer.

After the surface of the intermediate layer was subjected to a scratching treatment with fine diamond particles, the substrate was placed on the substrate holding table 27 of the hot filament CVD apparatus 1 shown in FIG. The temperature of the tungsten filament was set to about 2100 ° C., and a mixed gas having a methane concentration of 1 mol% was flowed into the reaction vessel 21 from the gas inlet 22. The pressure inside the reaction vessel 21 is set to 70 Torr.
r. Under these conditions, a diamond thin film layer was synthesized on the substrate 26 over 40 hours. The thickness of the diamond thin film layer is 20 μm, and the warpage of the diamond thin film layer is 2.5 μm.
μm.

After the surface of the diamond thin film layer is polished to a mirror surface, the diamond thin film layer is not peeled from the substrate even when the substrate is cut so that the length × width × thickness becomes 2 mm × 1 mm × 0.6 mm. Was. Thereafter, the surface of the substrate was polished to reduce the thickness of the substrate to 0.3 mm, and then the substrate was metallized to produce a heat sink. When the InP laser diode was set on this heat sink, the laser diode oscillated. This shows that this heat sink can be sufficiently used practically.

Although the present invention has been described above, the embodiment shown here can be variously modified. First, a Cu—W sintered body, a Cu—Mo sintered body, or a Cu—W—Mo sintered body can be adopted as a substrate. Further, as the intermediate layer, those other than those described in this embodiment can be used.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0062]

According to the present invention, a heat sink having high adhesion between the diamond thin film layer and the substrate can be obtained. Further, a heat sink with less warpage can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a hot filament CVD apparatus for vapor phase synthesis of diamond used in the present invention.

FIG. 2 is a schematic sectional view of a heat sink obtained by the present invention.

FIG. 3 is a schematic view of a microwave plasma CVD apparatus for diamond vapor phase synthesis used in the present invention.

[Explanation of symbols]

 Reference Signs List 50 heat sink 51 substrate 52 intermediate layer 53 diamond thin film layer 54 surface

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiyuki Yamamoto 1-1-1 Konyangkita, Itami-shi, Hyogo F-term in Sumitomo Electric Industries, Ltd. Itami Works 5F036 AA01 BB01 BD01 BD13 BD16

Claims (13)

[Claims] 1. A substrate containing a metal having a low coefficient of thermal expansion and Cu and having a surface roughness R _Z of 1 μm or more and 5 μm or less, an intermediate layer formed on the surface of the substrate, and a surface of the intermediate layer. And a diamond thin film layer formed on the heat sink. 2. The method according to claim 1, wherein the substrate is a Cu-W sintered body, Cu-M
The heat sink according to claim 1, wherein the heat sink is at least one kind of sintered body selected from the group consisting of an o sintered body and a Cu-W-Mo sintered body. 3. The intermediate layer includes Ti, TiC, TiN,
Si, SiC, Si _Three N_Four , AlN, Al_Two O_Three , V,
Cr, Mn, Mo, In, Sn, Hf, Ta, Ir, N
at least one selected from the group consisting of i, Pt and Au
The heat sink according to claim 1, wherein the heat sink includes one kind. 4. The intermediate layer includes a first intermediate layer formed on the substrate, and a second intermediate layer formed on the first intermediate layer, wherein the first intermediate layer and the second intermediate layer are provided. The heat sink according to claim 3, wherein a material of the heat sink is different from that of the intermediate layer. 5. The first intermediate layer comprises Ti, TiC and
Including at least one selected from the group consisting of TiN,
The second intermediate layer is made of Si, SiC, Si_Three N _Four , AlN
And Al_Two O_Three At least one selected from the group consisting of
5. The heat sink of claim 4, comprising a seed. 6. The heat sink according to claim 1, wherein said intermediate layer has a thickness of 10 μm or less. 7. The surface of the intermediate layer in contact with the diamond thin film layer is subjected to a scratching treatment.
7. The heat sink according to any one of 6. 8. A step of performing a surface roughening treatment on a surface of a substrate containing a metal having a low coefficient of thermal expansion and Cu; a step of forming an intermediate layer on the surface of the substrate having been subjected to the surface roughening treatment; Forming a diamond thin film layer on the surface of the heat sink. 9. The roughening step includes setting a surface roughness R _Z of the substrate to 1 μm or more and 5 μm or less.
A method for manufacturing the heat sink according to claim 8. 10. The method for manufacturing a heat sink according to claim 9, wherein the roughening step is performed by machining. 11. The method for manufacturing a heat sink according to claim 9, wherein the roughening step is performed by etching. 12. The method for manufacturing a heat sink according to claim 8, further comprising, before forming the diamond thin film layer, performing a process of damaging the surface of the intermediate layer. 13. The method for manufacturing a heat sink according to claim 12, wherein the damaging treatment includes damaging the surface of the intermediate layer using diamond.