JPS62154650A - Insulating substrate having high thermal conductivity and manufacture thereof - Google Patents

Abstract

PURPOSE:To be able the use of a substrate as a hybrid IC substrate or a substrate for a high frequency high power transistor by preparing the substrate by providing an insulating layer having a large thermal conductivity on a single crystal silicon or a polycrystalline silicon substrate to make it to be of a high thermal conductivity and a low permittivity. CONSTITUTION:A silicon substrate 1 is set at an RF applying electrode 2 side, a DC voltage is applied through a high frequency choke coil 3, and a magnetic field B is applied to the vicinity of the substrate in a direction perpendicular to an electric field, i.e., parallel to the surface of the substrate. The substrate is heated to 200-300 deg.C to discharge with both DC and RF mixture. H2, CH4, SiH4 are fed as reaction gases from a gas inlet 4, an RF power is applied and a DC voltage is applied. The pressure of a reaction chamber is 0.3-5Torr, and a silicon carbide film having approx. 3-5mum is obtained in approx. 1hr of reaction time.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a highly thermally conductive insulating substrate and a method for manufacturing the same.

[Problems to be solved by conventional technology/invention] IC,
With the development of LSI and other technologies, electronic circuits are becoming smaller, more highly integrated, and have higher output, and the packaging density of semiconductor elements is also increasing. As semiconductor devices become more highly integrated, have higher output power, and become more dense, the number of devices per chip is increasing year by year, and the amount of heat generated per chip is also increasing.

This increase in heat generation has a significant effect on the reliability of semiconductor devices, and therefore there is an increasing demand for packaging materials with high thermal conductivity. Also, in hybrid IC,
Heat-generating components are now coexisting in the same package, and in order to further promote high-density packaging, highly thermally conductive insulating substrates are becoming necessary.

Furthermore, when considering actually mounting an element, it is important that the coefficient of thermal expansion is close to that of the element, other package constituent materials, and circuit board.

As a substrate that satisfies both of the above, MN, Hitaceram Si
Ceramic substrates such as C and BeO are being considered, but
Both are expensive, and BcO is toxic, and Hitaceram SIC uses BeO as a sintering aid.
There is a problem that the dielectric constant at high frequencies is as large as about 40 at I MHz, and MN has drawbacks such as poor stability against water or alkali.

The present invention is a high thermal conductivity insulating substrate having a coefficient of thermal expansion close to that of an element or other package constituent material or circuit board, the substrate being made of NN1 Hitaracem SiC.

The object of the present invention is to provide an insulating substrate that does not have the drawbacks of ceramic substrates such as BeO.

[Means for solving problems]

The present invention was made based on the discovery that the above problems can be solved by using a substrate in which the surface of a single crystal silicon or polycrystalline silicon substrate is coated with an insulating layer that has a high thermal conductivity and a low dielectric constant at high frequencies. A highly thermally conductive insulating substrate in which at least a portion of the surface of a single-crystal silicon or polycrystalline silicon substrate is covered with an insulating layer having high thermal conductivity; When manufacturing a highly thermally conductive insulating substrate covered with an insulating layer with high thermal conductivity, a single crystal silicon or polycrystalline silicon substrate is set on the RF injection electrode side, and a DC voltage and RF power are applied to this electrode. The present invention relates to a method for manufacturing a highly thermally conductive insulating substrate, which is characterized by forming an insulating layer by applying a magnetic field parallel to the surface of the substrate.

〔Example〕

The single crystal silicon or polycrystalline silicon substrate used in the present invention is made of single crystal silicon or polycrystalline silicon having a thermal conductivity of 50 W/m·K or more, for example, 10
~200mmφ or 10~200mm opening thickness 0
．． It refers to a substrate having a shape of 1 to 2 mm.

In the present invention, at least a portion of the surface of the substrate is covered with an insulating layer having high thermal conductivity.

Coating at least a part of the surface means that at least a necessary part is covered, and there is no particular limitation on the proportion of the substrate surface to be covered, and it may be the entire substrate surface or only a small part. Good too.

Examples of materials for forming an insulating layer having a high thermal conductivity, preferably 50 W/ll1·K or more, more preferably 100 W/ll1·K or more, include diamond, diamond-like carbon, silicon carbide, and non-silicon. Crystalline silicon carbide, c-BN, h-BN,
M, N, etc., and using one or more of these,
Preferably the film thickness is 1 to 50%, more preferably 2 to 20%
An insulating layer of the hot pot is formed. When an insulating layer is formed using two or more types of materials, a composite insulating layer may be used.

When the material forming the insulating layer is diamond-like carbon, a material containing one or both of silicon or germanium atoms in a range of 9 atm% or less has a small internal stress, a large adhesion force, and is more effective. It is preferable because it has physical properties close to those of diamond, and is 0.1 to 4 atm.
It is more preferable that the content be within the range of %. Note that if the amount of silicon or germanium in the film exceeds 9 atm %, the thermal conductivity decreases.

Regarding this effect of a trace amount of 91% Ge, the details are currently unknown, but it is likely that the sp of <5tSGe
It is thought that the three orbits are effective in nucleation of diamond.

A patent application has already been filed for a hard carbon film containing trace amounts of 81 and Ge.

When the material forming the insulating layer is amorphous silicon carbide, it is preferable that the material contains at least one of hydrogen atoms and halogen group elements in a range of 30 atm% or less from the viewpoint of high thermal conductivity. 0,1~LOat
More preferably, the content is in the range of m%.

The insulating layer as described above usually has an electrical resistivity of 10 8 (Ω·mark) or more and a withstand voltage of 20 V/body or more, and is preferably used as an insulating substrate.

Next, a method for manufacturing the highly thermally conductive insulating substrate of the present invention will be explained.

There are no particular limitations on the method for forming an insulating layer on the surface of a single-crystal silicon or polycrystalline silicon substrate, and any method can be applied as long as an insulating layer made of the above-mentioned materials can be formed.

A specific example of such a method is a DC discharge plasma C which is suitable for forming an insulating layer made of diamond, diamond-like carbon, silicon carbide, amorphous silicon carbide, hexagonal BN, cubic BN, etc.
Examples include the VD method, the RF discharge plasma CVD method, the plasma CVD method in which both DC discharge and RF discharge are mixed, and the plasma CVD method in which both DC discharge and φRF discharge are mixed in a magnetic field perpendicular to the electric field. In particular, when forming an insulating layer made of diamond, diamond-like carbon, silicon carbide, or amorphous silicon carbide, plasma C is a mixture of both DC discharge and RF discharge with a magnetic field perpendicular to the electric field on the substrate.
It is preferable to apply the VD method because a film with more crystallinity and excellent thermal conductivity can be produced at high speed.

A specific method for manufacturing a highly thermally conductive insulating substrate using a plasma CVD method that combines both DC discharge and RF discharge with a magnetic field perpendicular to the electric field on the substrate is as shown in Figure 1. A single crystal silicon or polycrystal silicon substrate (1) is set on the electrode ('2J side), and a DC voltage is applied to this electrode through a high frequency choke coil (3).
Applying a DC voltage of preferably -150 to -600,
RF power, preferably 100~400w (140~
Apply an RF power of 560+llW/cJ), preferably a reaction pressure of 0.1 to 20 Torr, and a reaction pressure of 200 to 35 Torr.
An example of this method is to form an insulating layer at a substrate temperature of 0° C. while applying a magnetic field (B), preferably a magnetic field (13) of 100 to 1000 Gauss, parallel to the substrate surface.

The substrate of the present invention manufactured in this way has a thermal conductivity of 50 W/m·K or more, preferably Lt 100 W/a+
・K or more, surface Vickers hardness is 500 or more, preferably 1500 or more, more preferably 2000 or more, electrical insulation is IXLO9Ω・c, although it varies depending on the type of insulating layer.
m or more, the dielectric constant at I MHz is 20 or less (15 or less in the case of silicon carbide), and the dielectric loss at I MHz is 0.02 or less.

In addition, the coefficient of thermal expansion is
It is suitable for hybrid IC substrate materials for thick film circuits that require high-temperature processing, and is extremely stable against acids and alkalis.

Hereinafter, the present invention will be explained based on examples.

Examples 1 to 2 A SiC film was produced on single crystal silicon using a plasma CVD apparatus as shown in FIG.

LOOX toox 0.5mm silicon substrate (
1) was set on the RF injection electrode (2) side as shown in FIG.

DC voltage was applied through a high frequency choke coil (3). A magnetic field (B) was applied near the substrate in a direction perpendicular to the electric field, that is, parallel to the silicon substrate surface.

The magnetic field strength was 100-500 Gauss. The substrate temperature was heated to 200 to 300°C using this device, and DC was applied.

A mixed discharge of both RF was generated. As a reaction gas, H2
-100~200900M, CH4=20~80SC
CM, S i H4-10~809CCM is flowed from the gas inlet (4), R, F power is 100~300W (1
40 to 420 mW/cJ) and set the DC voltage to -1.
50 to -400v was applied. Reaction chamber pressure is 0.3-5T
It was orr. Approximately 3 to 5 silicon carbide membranes were replaced in a reaction time of approximately 1 hour.

As a result of X-ray diffraction analysis, the obtained film was found to contain microcrystalline β-8iC.
It turned out to be. IR measurements of the film show that there is absorption of hydrogen bonded to silicon and carbon in the film.
The hydrogen content in the membrane was 1-15 ato+%.

Table 1 shows various properties of an example of the obtained film.

The film thickness is approximately 5 mm. The films shown in Table 1 have carbon contents of 40 atm % and 6 atIn %, respectively.

The values of various properties change depending on the amount of silicon and carbon in the film, and as a tendency, when the amount of carbon exceeds 50 atm %, hardness increases, but thermal conductivity decreases.

The reason why the obtained insulating substrate has a lower dielectric constant than high thermal conductivity SiC obtained by normal sintering is that it is not SIC, completely crystalline or polycrystalline, but amorphous silicon containing hydrogen. This is thought to be because it has a structure consisting of both carbide and crystalline SiC, and the dielectric constant is low due to the amorphous portion containing hydrogen, and the thermal conductivity is good due to the crystalline portion.

Example 3 An insulating substrate was produced in the same manner as in Example 1 using a normal RF plasma CVD apparatus (equipment without magnetic field and DC power supply). The resulting film is amorphous and contains carbon ff14.
As shown in Table 1, the properties of the film in the case of 0 atm% are very good insulating properties, and the thermal conductivity is 50 to 90 W.
/1Il・K.

Example 4 Film formation was performed using the same apparatus as in Example 1.

Magnetic field strength (B) 300-1000 Gauss, substrate temperature 250-350°C, H2-100-30 as reaction gas
Using 0SCCM, CH4-1~IO3CCM, RF power 100~400W (140~560+++W/
ci), DC voltage -200 to -eoov, and reaction chamber pressure 0.1 to 20 Torr.

Compared to Example 1, the experimental conditions were I? l'power, DC
The difference was that both voltages were higher and CH4 was diluted to 10% by volume or less with H2.

Approximately 3 to 5 cups of diamond-like carbon film were replaced in a reaction time of 2 hours. The surface Vickers hardness of the obtained film is 6000.
~8000, a value close to that of natural diamond. Furthermore, TED (electron diffraction) analysis of the film confirmed the formation of diamond particles. The films produced differed considerably depending on the conditions. Relatively low concentration of methane (5% by volume)
Table 1 shows the properties of the pentagonal film produced using the following methods. The adhesion hardness was as low as 20 to 50 kg/cJ.

Example 5 Under the same conditions as Example 4, 0.1 to 7% by weight of silane gas or 0% germanium hydride gas was added to methane gas.
．． A diamond-like carbon film was produced by adding 1 to 5% by volume.

Table 1 shows the properties of the film prepared by adding 0.5% by volume of silane gas.

Silicon was present in the film at 1aU% (defined as ff1 by ESCA).

This diamond-like carbon film containing a small amount of silicon had very low internal stress, and compared to a film that did not contain silicon, its adhesion was several times higher and its electrical insulation properties were improved.

[Margins below] [Effects of the Invention] The substrate of the present invention, in which an insulating layer with high thermal conductivity is provided on a single-crystal silicon or polycrystalline silicon substrate, has high thermal conductivity and low dielectric constant, so it can be used as a hybrid IC substrate, Used as a substrate for high-frequency high-power transformer sister.

[Brief explanation of drawings]

Figure 1 shows the plasma C used to manufacture the substrate of the present invention.
FIG. 2 is an explanatory diagram regarding a VD device. (Main symbols in drawings) (1) Silicon substrate

Claims (1)

[Scope of Claims] 1. A highly thermally conductive insulating substrate in which at least a portion of the surface of a single-crystal silicon or polycrystalline silicon substrate is covered with an insulating layer having high thermal conductivity. 2 The insulating layer with high thermal conductivity is one or two of diamond, diamond-like carbon, silicon carbide, amorphous silicon carbide, c-BN, h-BN, and AlN.
The substrate according to claim 1, which is a layer consisting of at least one species. 3. The substrate according to claim 2, wherein the diamond-like carbon contains 9 atm % or less of at least one of silicon and germanium atoms. 4. The substrate according to claim 2, wherein the amorphous silicon carbide contains at least one of a hydrogen atom and a halogen group element. 5 The insulating layer with high thermal conductivity has an electrical resistivity of 10^8 (
3. The substrate according to claim 1 or 2, which has a withstand voltage of 20 V/μm at a dielectric strength of 20 V/μm. 6. The substrate according to claim 1, wherein the high thermal conductivity insulating substrate has a thermal conductivity of 50 W/m·K or more. 7 The thermal conductivity of the high thermal conductive insulating substrate is 100 W/m・K
The substrate according to claim 1, which is the above. 8 The surface Vickers hardness of the highly thermally conductive insulating substrate is 500.
The substrate according to claim 1 or 2, which is the above. 9 The surface Vickers hardness of the highly thermally conductive insulating substrate is 150.
3. The substrate according to claim 1 or 2, wherein the number is 0 or more. 10. The substrate according to claim 1, which has a dielectric constant of 20 or less at 1 MHz and a dielectric loss of 0.02 or less at 1 MHz. 11 The insulating layer with high thermal conductivity is
Claim 1 obtained by VD method, RF discharge plasma CVD method, plasma CVD method with a mixture of DC discharge and RF discharge, or plasma CVD method with a mixture of DC discharge and RF discharge with a magnetic field perpendicular to the electric field, or The substrate according to item 2. 12. The substrate according to claim 2, wherein diamond, diamond-like carbon, amorphous silicon carbide, and silicon carbide are obtained by a DC and RF discharge mixed plasma CVD method with a magnetic field perpendicular to an electric field on the substrate. 13 When manufacturing a highly thermally conductive insulating substrate in which at least a portion of the surface of a single-crystal silicon or polycrystalline silicon substrate is covered with an insulating layer having high thermal conductivity, the single-crystal silicon or polycrystalline silicon substrate is placed on the RF input electrode side. A method for manufacturing a highly thermally conductive insulating substrate, which comprises: setting the electrodes, applying a DC voltage and RF power to the electrodes, and applying a magnetic field parallel to the substrate surface to form an insulating layer. 14 The insulating layer is -150 to -600V to the RF input electrode set on the single crystal silicon or polycrystal silicon substrate.
DC voltage and 100~400W (140~560m
An RF power of W/cm^2) was applied, a magnetic field of 100 to 1000 Gauss was applied parallel to the substrate surface, and a reaction pressure of 0.
The manufacturing method according to claim 13, which is formed at a temperature of 1 to 20 Torr and a substrate temperature of 200 to 350°C.