JPH0760869B2 - High thermal conductivity insulating substrate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high thermal conductive insulating substrate.

[Problems to be solved by the conventional technology / invention] With the development of ICs, LSIs, etc., electronic circuits have become smaller, highly integrated, and have higher output, and the packaging density of semiconductor elements has also become higher. . With such high integration, high output, and high density of semiconductor elements, the number of elements per chip is increasing year by year, and the amount of heat generation per chip is also increasing. Since this increase in the amount of heat generation has a great influence on the reliability of the semiconductor element, there is a strong demand for a high thermal conductivity packaging material. Further, in the hybrid IC, the heat-generating components come to coexist in the same package, and a high thermal conductive insulating substrate is required to further promote high-density mounting.

As a substrate that satisfies such needs, AlN, SiC, BeO
There is a high thermal conductive insulating substrate and hitaseram (SiC type) formed from etc., but both substrates are expensive, and BeO substrates are toxic. BeO as a sintering aid for SiC substrates
AlN, which has a large dielectric constant at high frequencies,
The manufactured substrate has the drawback that it is weak against water and alkali.

In addition, although there is a thermal spray substrate as a metal base substrate, this substrate has poor surface smoothness, and in the current thermal spray technology, high thermal conductivity diamond, diamond-like carbon, and
It has the drawback that it cannot form SiC.

Furthermore, ion beam method, plasma CVD method, thermal CVD method on crystalline silicon substrate, Mo substrate, W substrate and diamond substrate.
Although there are reports on forming diamond and diamond-like carbon by the CVD method, electron beam CVD method, etc., they are highly versatile and have high thermal conductivity, and are cheaper than Al substrates, Al-Si substrates, Cu substrates, Cu alloy substrates. No formation of diamond or diamond-like carbon on it has been reported.

It is an object of the present invention to provide a high thermal conductive insulating substrate that solves the above problems of the present invention.

[Means for Solving Problems] The present invention relates to a high thermal conductive metal substrate made of Cu, a Cu alloy, Al or an Al alloy with a thickness of at least 500 Å to 3 μm.
An intermediate layer made of an amorphous silicon carbide-based material with a Vickers hardness of 1000 or more is arranged, and further on it, crystallized silicon carbide, amorphous silicon carbide containing crystallized silicon carbide fine particles, diamond, diamond-like carbon, cubic crystal -BN or hexagonal-BN has a thermal conductivity of 0.35cal / cm ・ sec ・
It relates to an insulating substrate having a high thermal conductivity of ℃ or higher.

Example As shown in FIG. 1, the high thermal conductive insulating substrate of the present invention is
An intermediate layer (2) is provided on at least a part of a high heat conductive metal substrate (1), and a heat conductive insulating layer (3) is further provided thereon.

The high thermal conductivity metal substrate, Cu, Cu alloy, Al or Al-Al such as Al-Si has a thermal conductivity of 0.35ca
Any metal substrate having a high thermal conductivity of l / cm · sec · ° C or higher can be used without particular limitation.

Providing an intermediate layer on at least a part of a high thermal conductive metal substrate means that an intermediate layer having a desired size and shape is provided on a desired portion where a thermal conductive insulating layer needs to be provided on the high thermal conductive metal substrate. The intermediate layer may be formed on one side or both sides of the high thermal conductivity metal substrate, or may be patterned on a part of the intermediate layer to form the intermediate layer.

The role of the intermediate layer in the present invention has two major roles.

First, since the high thermal conductivity metal forming the substrate has a large coefficient of thermal expansion, when a thermally conductive insulating layer having a small coefficient of thermal expansion is directly formed on the metal substrate, cracks and cracks are likely to occur. The presence of the intermediate layer serves as a buffer layer and makes cracks and cracks less likely to occur.

Secondly, it can be used as a substrate on which an insulating layer made of crystallized silicon carbide having high thermal conductivity, amorphous silicon carbide containing crystallized silicon carbide fine particles, diamond, diamond-like carbon or the like can be formed.

In other words, when forming the insulating layer, normally, Prosma CV
The D method is used.In this method, the temperature of the substrate surface rises due to collisions with ions, etc., and it is difficult for the film to adhere due to the difference in the coefficient of thermal expansion between the high thermal conductivity metal and the insulating layer. However, if left at room temperature, the attached film may peel off. Further, sputtering occurs due to collision of ions, particularly hydrogen ions. In the case of a substrate made of Cu, Cu alloy, Al, or Al alloy having a large spatter rate, sputtering proceeds more than film deposition, and the film does not adhere.

However, when the intermediate layer is present, a problem due to a difference in coefficient of thermal expansion due to temperature rise on the substrate surface, a problem due to sputtering due to ions, etc. are less likely to occur, and a high thermal conductive insulating layer can be formed.

The material forming the intermediate layer has structural flexibility, can reduce the difference in thermal expansion coefficient between the high thermal conductive metal substrate and the thermal conductive insulating layer, good insulating Vickers hardness 1000 The above amorphous silicon carbide-based materials are mentioned, and an intermediate layer having a thickness of 500 Å to 3 μm is formed by using one or more of these materials as a constituent material.

If the film thickness is less than 500Å, the difference in coefficient of thermal expansion may not be sufficiently relaxed, or the high thermal conductive insulating layer may not be easily formed. If it exceeds 3 μm, the thermal conductivity of the intermediate layer is affected, and the thermal conductivity of the entire substrate of the present invention tends to be lowered.

Examples of the amorphous silicon carbide-based material forming the intermediate layer include a-Si _x C _1-x , a-Si _{x + y} C _1-x N _1-y ,
a-Si _{x + y} C _1-x O _1-y , a-Si _{x + y} C _1-x Ge _1-y (said x, y
Is 0.001 ≤ x <1 and 0.001 ≤ x + y ≤ 1), etc., or these amorphous silicon carbide based materials contain at least one of hydrogen and halogen group elements. Among them, those with a Vickers hardness of 1000 or more are used.These are used because they have a large structural flexibility and effectively reduce the difference in the coefficient of thermal expansion between the high thermal conductive metal substrate and the thermal conductive insulating layer. It is preferable from the standpoints of good adhesion and high adhesion.

As the reaction gas used when forming the intermediate layer made of an amorphous silicone carbide-based material, for example, SiH ₄ , Si
_{2 H 6, SiF 4, SiH} 3 F, gas stingray-containing compounds such as SiCl _4, etc. _{CH 4, C 2 H 4,} CF 4, C 2 H 2, C 6 H 6, C 6 H 3 F 3 Hydrocarbon-based or halogenated hydrocarbon-based gases, NH ₃ , N ₂ , N
Gases of nitrogen-containing compounds such as F ₃ and Ge such as GeH ₄ and GeF _4.
Gases containing compounds, O ₂ , H ₂ O gas, etc. can be mentioned,
It is not limited to these. Also as a dilution gas
H ₂ , Ar, He or the like may be used.

A DC discharge in which a negative high voltage is applied to the substrate is used as an intermediate layer more suitable for forming the high thermal conductive insulating layer on the intermediate layer.
Amorphous silicon carbide-based materials with a Vickers hardness of 1000 or more formed by the plasma CVD method of mixing both RF discharges are excellent. It is particularly excellent in terms of heat resistance and resistance to spattering. When manufacturing this amorphous silicon carbide, it is recommended to use H ₂ , CH ₄ , SiH ₄ , and CF ₄ from the viewpoint of productivity ( It is preferable in that the film is attached only when desired.

It is suitable that the amorphous silicon carbide used for forming the intermediate layer contains 20 atom% or more of hydrogen or halogen atoms in the film. On the other hand, amorphous silicon carbide containing crystallized silicon carbide fine particles is suitable for the heat conductive insulating layer.

After the intermediate layer is formed, the heat conductive insulating layer to be further formed is made of a material having good thermal conductivity, such as crystallized silicon carbide, amorphous silicon carbide containing crystallized silicon carbide fine particles, diamond, diamond. Carbon, cubic-BN, and hexagonal-BN are mentioned, and one or more of these materials are preferable, and the film thickness is 5000Å to 100.
μm, preferably electric conductivity 10 ⁻⁹ (Ω · cm) ⁻¹ or less, more preferably 10 ⁻¹⁰ (Ω · cm) ⁻¹ or less, preferably withstand voltage 20 V / μm or more, more preferably 40 V / μm or more. A thermally conductive insulating layer is formed.

The thermally conductive insulating layer is also formed by the ion beam method or the thermal CVD method, but if the area is made larger, the plasma is used.
It is better to use the CVD method. Research on diamond and diamond-like thin films using the microwave plasma CVD method is intensive, but from the viewpoint of easier and larger area,
DC discharge plasma CVD method, RF discharge plasma CVD method, DC discharge
The plasma CVD method of mixing both with RF discharge is suitable. Important for forming the thermally conductive insulating layer is to place the substrate on the cathode and dilute the source gas with hydrogen.

A more suitable method is a plasma CV of a mixture of both DC discharge and RF discharge in which a magnetic field orthogonal to the electric field exists on the substrate.
The D method is mentioned, and when a film is formed by this method, a higher heat conductive insulating film is formed. Also in this method, it is important to place the substrate on the cathode and dilute the source gas with hydrogen. The reason why the heat conductive insulating layer is formed by this method is that crystallization proceeds further. This crystallization is achieved by appropriately adjusting the magnetic field strength and the electric field strength to control the energy distribution of electrons and generating a large amount of hydrogen radicals.

From the viewpoint of thermal conductivity, crystallized silicon carbide has a larger thermal conductivity than amorphous silicon carbide, and diamond has a larger thermal conductivity than diamond-like carbon.

Next, the method for producing the substrate of the present invention will be described based on preferred embodiments.

On the cathode side of the device as shown in Fig. 2, the thickness of 0.2-5mm
Set Cu substrate or Al substrate, H ₂ gas 50 ~ 200SCCM, S
A mixed gas of 10 to 50 SCCM of iH ₄ gas and 10 to 50 SCCM of CH ₄ gas was introduced from the gas inlet (7), the reaction chamber pressure was 0.1 to 5 Torr, DC.
Voltage −100V to −2KV, current 0.14 to 10mA / cm ² , RF power 10
Approximately 3000 Å of amorphous silicon carbide is applied by plasma CVD method of applying both DC discharge and RF discharge by applying ~ 500 mW / cm ^2.
Deposit about 2 μm. In addition, DC voltage is DC power supply (4)
Is applied to the electrode (6) via the high frequency choke coil (5).

The adhesion of the film to be adhered is 20 to 100 kg / cm ² , and the surface Vickers hardness is as large as 1000 to 3000. In addition, the film contains 1 to 30 atm% of hydrogen, and has structural flexibility.

Next, on this intermediate layer, a device which is almost the same as the device shown in FIG. 2 except that a magnetic field is applied in the direction perpendicular to the electric field on the cathode on which the substrate is set, A silicon carbide layer is formed as a layer to a thickness of 5000Å to 30 μm.

As the reactive _{gas, H 2 50~200SCCM, CH 4 5~30SCCM} , SiH
₄ 10 to 60 SCCM flow, reaction chamber pressure 0.1 to 10 Torr, magnetic field strength 10
0 ~ 1000 gauss, DC voltage -150V ~ -1KV, DC current 0.5 ~ 15m
A / cm ² , RF power 50 to 1000 mW / cm ² applied, DC discharge, RF
Discharge A mixed discharge of both is generated to form a film at a substrate temperature of 200 to 800 ° C. The deposition rate is 1 to 15Å / sec.

According to the X-ray diffraction analysis method, most of the produced films are usually β-SiC crystal form, and IR spectrum analysis shows a slight amount of hydrogen in the films (stretching of C-H and Si-H). There is a small absorption in the wavenumber corresponding to the mode).

Large thermal conductivity of the silicon carbide formation is important to proceed by crystallization, as the film forming conditions, diluting with H _2, to adjust the magnetic field, electric field, the electron energy distribution by three parameters of pressure This is very important.

The thermal conductivity of the fabricated substrate near room temperature is
When using a Cu substrate, it is greatly related to the thickness of the insulating film and the crystallinity of the film, but it is 0.35 to 0.90 cal / cm ・ sec ・ ° C.
The value is almost the same, and there is no decrease in the thermal conductivity around 100 ° C, which is almost the same value. Surface Vickers hardness is 2000-35
It is possible to obtain the same value as 00, which is almost equivalent to single crystal β-SiC. The electric conductivity is 10 ^-12 (Ωcm) ^-1 or less, and the withstand voltage is 50.
~ 200V / μm. In addition, thermal cycle test (-55 ℃
X 30 minutes, 150 ° C x 30 minutes) is 1 cycle, and peeling of the mother body from the Cu substrate after 1000 cycles is usually not seen at all, and the adhesion strength is the same as before the test, ²⁰ to 100 kg / cm ^2. . The peeling in the adhesion test occurs not between the intermediate layer and the insulating layer but between the intermediate layer and the metal substrate. The surface roughness Ra (center line average roughness) of the insulating substrate is 0.1 μm.
The following is also suitable for a thin film circuit substrate.

The substrate of the present invention produced in this manner has a high thermal conductivity because the intermediate layer and the thermally conductive insulating layer formed on the substrate have a small film thickness and the thermally conductive insulating layer has a high thermal conductivity. It has an excellent conductivity of 0.35 cal / cm · sec · ° C or higher, which is close to that of a metal substrate with high thermal conductivity.

Further, the thermal expansion coefficient of the heat conductive insulating layer, the insulating layer is from crystalline silicon carbide, amorphous silicon carbide containing crystalline silicon carbide fine particles, diamond, diamond-like carbon, cubic-BN, hexagonal-BN, etc. Since it is almost the same as silicon when it is formed, it is characterized in that it does not lead to deterioration in device performance due to the difference in thermal expansion coefficient. Furthermore, when the thermally conductive insulating layer is formed by the plasma CVD method, a film having extremely excellent surface smoothness can be obtained.

Next, the high thermal conductive insulating substrate of the present invention will be described based on examples.

Example 1 A Cu substrate having a thickness of 1 mm was set on the cathode side of the apparatus as shown in FIG. 2, and a mixed gas of H ₂ gas 100 SCCM, SiH ₄ gas 30 SCCM, CH ₄ gas 30 SCCM was introduced from the gas introduction port (7). Then, a reaction chamber pressure of 1.0 Torr, a DC voltage of −600 V, a current of 5 mA / cm ² , and an RF power of 50 mW / cm ² were applied, and amorphous silicon carbide was removed by plasma CVD with a mixture of DC discharge and RF discharge. About 1 μm was deposited. The DC voltage was applied to the electrode (6) from the DC power supply (4) through the high frequency choke coil (5).

The adhesion of the deposited film was 50 kg / cm ² , and the surface Vickers hardness was as high as 1500. In addition, the film contained 18 atm% of hydrogen and had structural flexibility.

Next, on this intermediate layer, a device which is almost the same as the device shown in FIG. 2 except that a magnetic field is applied in the direction perpendicular to the electric field on the cathode on which the substrate is set, A silicon carbide layer was formed as a layer.

As reaction gas, H ₂ 150SCCM, CH ₄ 20SCCM, SiH ₄ 30SCCM
Flow, reaction chamber pressure 1.0 Torr, magnetic field strength 600 gauss, DC voltage −400 V, DC current 7 mA / cm ² , RF power 500 mW / cm ² ,
A substrate temperature of 30
The film was formed at 0 ° C. The deposition rate was 5Å / sec and the film thickness was 5 μm.

The film produced under the above conditions was β-
It was a crystal form of SiC.

The thermal conductivity of the fabricated substrate near room temperature is 0.70 cal / cm ・ se.
It was almost the same as c · ° C, and there was no decrease in thermal conductivity around 100 ° C. Surface Vickers hardness is 32
The value of 00 was almost the same as that of single crystal β-SiC. The electric conductivity was 10 ⁻¹⁴ (Ω · cm) ⁻¹ or less, and the withstand voltage was 1 KV.
In addition, thermal cycle test (-55 ℃ × 30 minutes, 150 ℃ × 30
Min) as one cycle, no peeling of the mother material from the Cu substrate was observed after 100 cycles, and the adhesion hardness was 50 kg / cm ^2, which was the same as before the test. The peeling in the adhesion test occurred not between the intermediate layer and the insulating layer but between the intermediate layer and the metal substrate. The surface roughness Ra (center line average roughness) of the insulating substrate was 0.1 μm or less, and was suitable for a thin film circuit substrate.

Example 2 A Cu substrate provided with an amorphous silicon carbide layer having a thickness of 5000Å as an intermediate layer was set in the same apparatus as shown in FIG. 2 in the same manner as in Example 1. In this case as well, Example 1
Similarly to the above, a magnetic field perpendicular to the electric field was made to exist on the substrate set on the cathode. CH ₄ 3SCCM, CF ₄ 1 as reaction gas
Introduced SCCM, H ₂ 200 SCCM, reaction chamber pressure 7 Torr, magnetic field strength
700 gauss, DC voltage −300V, DC current 15mA / cm ² , RF power 2
50mW / cm ² was applied and a mixed discharge of DC discharge and RF discharge was performed. At this time, the substrate temperature was raised to 400 ° C. by heating from the outside. The deposition rate was 3Å / sec and the film thickness was 5 μm.

The Vickers hardness of the produced film was 8000, which was very large, which was almost equal to that of natural diamond. The presence of hydrogen was not seen in the IR spectrum analysis. According to transmission electron diffraction (TED), diamond (111), (22
A ring corresponding to (0) was obtained. The produced film was a so-called diamond-like carbon film.

The thermal conductivity of the fabricated substrate near room temperature is 0.75 cal / cm ・ se.
It was as large as c · ° C, and there was no decrease in thermal conductivity at 100 ° C.
The electric conductivity is 10 ^-14 (Ωcm) ^-1 , and the withstand voltage is about 1 kV.
There was no peeling in the heat cycle test, and the adhesive strength was 100 kg / cm ^2, which was the same as before the test.

Comparative Example 1 An experiment was conducted using the same apparatus as in Example 1. A copper substrate is used as the substrate, and H ₂ 150SCCM, CH ₄ 20 is used as the reactive gas.
SCCM, SiH ₄ 30SCCM flow, reaction pressure 1.0 Torr, magnetic field strength 6
I tried to form silicon carbide, which is an insulating layer, to have a thickness of 5 μm under the conditions of 00 gauss, DC voltage of −400 V, and RF power of 500 mW / cm ² , but I wondered if the copper, which is the substrate, was sputtered. A uniform and continuous film was not obtained, a particulate product was obtained, and there was no insulation.

Comparative Example 2 An experiment was conducted using the same device as in Example 1. A copper substrate was used as the substrate, and H ₂ 100SCCM, SiH ₄ 3 as the reactive gas.
A flow rate of 0 SCCM was applied to deposit 0.5 μm of amorphous silicon as an intermediate layer under the conditions of reaction pressure of 1.0 Torr, DC voltage of −300 V, and RF power of 50 mW / cm ² . The adhesion of the attached film is 10k
The surface Vickers hardness was 600 at g / cm ² .

Next, H ₂ 150SCCM, CH ₄ 20 was added as a reaction gas on the intermediate layer.
SCCM, SiH ₄ 30SCCM flow, reaction pressure 1.0 Torr, magnetic field strength 6
00 Gauss, DC voltage -400 V, amorphous silicon carbide, which is an insulating film by RF power 500 mW / cm ² following condition 5
μm deposited.

According to the X-ray diffraction analysis method, the obtained insulating layer was
It was a film containing SiC.

The thermal conductivity of the manufactured substrate is 0.2 cal / cm ・ sec ・ ° C.
And the adhesive force was 10 kg / cm ² . Furthermore, the heat cycle test (-55 ° C x 30 minutes, 150 ° C x 30 minutes) was set as one cycle, and 1
When the test was performed for 000 cycles, peeling between the formed film and the Cu substrate occurred.

EFFECTS OF THE INVENTION Since the high thermal conductive insulating substrate of the present invention has the heat conductive insulating layer formed after the specific intermediate layer is provided on the high thermal conductive metal substrate, the thermal conductivity is stable and has high adhesion strength. A conductive insulating layer is attached to the metal substrate. Moreover, since the substrate of the present invention has high thermal conductivity and insulating properties and high hardness, it can be suitably used for applications such as electronic parts such as hybrid IC substrates. Further, the substrate of the present invention can be manufactured on an industrial scale.

[Brief description of drawings]

FIG. 1 is an explanatory view of a high thermal conductive insulating substrate of the present invention,
FIG. 2 is an explanatory diagram regarding a step of forming an intermediate layer on a high thermal conductive metal substrate. (Main symbols in the drawings) (1): High thermal conductive metal substrate (2): Intermediate layer (3): Thermal conductive insulating layer

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location H01B 19/00 321 4232-5G H05K 1/05 A (56) Reference JP-A-58-103156 (JP, A) ) JP-A-55-99793 (JP, A) JP-A-50-40116 (JP, A) JP-A-56-105627 (JP, A) JP-A-56-130466 (JP, A) JP-A-57- 56036 (JP, A) JP 58-132920 (JP, A)

Claims (5)

[Claims] 1. A high thermal conductive metal substrate made of Cu, a Cu alloy, Al or an Al alloy having a thickness of 500Å to 3 μ at least in a part thereof.
m, an intermediate layer made of an amorphous silicon carbide-based material having a Vickers hardness of 1000 or more is arranged, and further on it, crystalline silicon carbide, amorphous silicon carbide containing crystalline silicon carbide fine particles, diamond, diamond-like carbon, The thermal conductivity is 0.35 cal / cm ・ se with a thermally conductive insulating layer made of cubic-BN or hexagonal-BN.
High thermal conductivity insulating substrate with a temperature of c ° C or higher. 2. An amorphous silicon carbide based material having a Vickers hardness of 1000 or more in the intermediate layer is a-Si _x C _1-x or a-Si _{x + y.}
C _1-x N _1-y , a-Si _{x + y} C _1-x O _1-y , a-Si _{x + y} C _1-x Ge
_1-y (both x and y are 0.0001 ≦ x <1 and 0.001 ≦ x
+ Y ≦ 1), which is an amorphous silicon carbide based material containing at least one of
Substrate according to item. 3. An amorphous silicon carbide-based material having a Vickers hardness of 1000 or more is a-Si _x C _1-x or a-Si _{x + y} C.
_1-x N _1-y , a-Si _{x + y} C _1-x O _1-y , a-Si _{x + y} C _1-x Ge _1-y (both x and y are 0.001 ≦ x <1 At 0.001 ≦ x + y ≦ 1
The substrate according to claim 2, which is a material containing at least one of hydrogen and a halogen group element. 4. The thermal conductive insulating layer has an electric conductivity of 10 ⁻⁹ (Ω · c).
The substrate according to claim ^{1, having a} m) ^-1 or less and a withstand voltage of 20 V / μm or more. 5. The heat conductive insulating layer has a film thickness of 5000Å to 100 μm.
The substrate according to claim 1, wherein