JPH0265162A - Metal substrate for integrated circuits - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention mainly relates to a metal substrate for an integrated circuit, which is intended to improve the degree of integration of semiconductor elements.

[Prior Art] Currently, the most widely used substrate material for ICs and LSIs is alumina (A1203) ceramics. This is based on the conditions required for the substrate material, such as high electrical resistance, high dielectric strength, low dielectric constant, sufficient mechanical strength, heat resistance, good thermal conductivity, and chemical stability. This is because it satisfies the following conditions in a well-balanced manner, such as high moisture content and no hygroscopicity.

However, current semiconductor technology is rapidly developing from LSI to VLSI, and with this development, there is an increasing demand for child circuits to have multiple functions, higher performance, smaller size, lighter weight, and lower cost. are doing.

Under such circumstances, it has been pointed out that the use of Al2O3 has the following problems.

■Due to low thermal conductivity, the amount of heat generated increases as semiconductor devices become more highly integrated.

(2) Since there is a large difference in coefficient of thermal expansion from Si used in semiconductor chips, there is a risk that the Si chip will peel off if the amount of heat generated increases, and the heat dissipation structure to prevent this will become complicated.

Furthermore, the number of parts is large, leading to high costs.

■Radioactive elements contained in A I 2 Oa, such as U
.

The concentration of Th etc. is higher than the concentration of Mo used in semiconductor elements and wiring.
, which is orders of magnitude higher than that in AI gold metal, causes soft errors due to α-ray radiation.

■The substrate cannot be made large, making it difficult to achieve high integration.

Here is an example of the use of alumina ceramics substrate material.
The I package is shown in Figure 4. In the figure, 1 is an LSI chip, 2 is a molybdenum base to which the LSI chip 1 is fully bonded, and 3 is a copper stud having aluminum fins 4 for heat radiation, which are joined to the molybdenum base 2. 5 is alumina M, NZ, and the periphery of the molybdenum base 2 inserted into the central hole 6 is joined and supported via a Kovar member 7. 8 is the lead frame of LSI chip 1, 9
is an alumina cap for protecting the LSI chip 1, and is sealed to the alumina substrate 5 with a sealing glass 10.

As shown in FIG. 4, it is clearly seen that the heat dissipation structure becomes complicated in the case of an alumina substrate.

Therefore, as a solution to the above problem, conventional methods have been to use a ceramic sintered body of silicon carbide (S i C) or aluminum nitride (AIN), or to use a metal substrate coated with an insulating layer. is proposed.

In the case of SiC, it has been found that when BeO is added as a sintering aid, a sintered body with high thermal conductivity and high electrical insulation can be obtained, and the reliability of bonding by the metallization method is also high. However, SiC has a high dielectric constant, which limits its application in high frequency ranges. Further, since the SiC sintered body is manufactured by hot pressing, there are problems such as difficulty in improving flatness, difficulty in mass production, and difficulty in increasing the size of the substrate.

Next, AIN is a high-strength, highly electrically insulating material that theoretically has a thermal conductivity of 320 W/m-, but in the past, only materials with low thermal conductivity could be manufactured, but recently AIN It has become possible to manufacture sintered bodies with a temperature exceeding /m-K. However, it lacks stability due to the concentration of impurities in the raw material powder, and since it is a hot press sintered body, it has the same problems as SiC described above. Furthermore, the range of thermal expansion coefficients is large, and there remains a problem in compatibility with Si.

Next, in the case of metal substrates, the insulating layer is generally made of epoxy resin,
Since it is made of glass epoxy resin, polyimide film, etc., it has a problem of poor dielectric strength and heat resistance.

[Problems to be Solved by the Invention] As described above, conventional substrate materials have had difficulties in achieving high integration of semiconductor elements and the accompanying high heat dissipation.

Furthermore, in the case of hot-pressed sintered bodies, it is not possible to stably produce large substrates, which limits high integration.

In order to solve the above-mentioned conventional problems, the present invention provides heat dissipation,
The purpose of this invention is to obtain a metal substrate that is highly mass-producible and allows the substrate to be made larger.

[Means for Solving the Problems] A metal substrate for an integrated circuit according to the present invention is formed by depositing a thin film of cubic boron nitride (c-BN) on the surface of a metal plate by vapor deposition. The vapor deposition method is PVD method or CV
Method D is used. Generally, AI or Cu-based materials are used for the metal plate, but electromagnetic shielding becomes possible when a magnetic material is used.

[Function] The metal substrate according to the present invention has a thin film of c-BN coated on the surface of the metal plate by vapor deposition.

Since no c-BN molded product has been obtained to date that has the potential for practical use, the high thermal conductivity and electrical insulation properties of c-BN can be effectively utilized. -The metal plate has the mechanical strength as a blade support. Furthermore, a heat dissipation section such as an Al fin can be directly bonded to the metal plate, and this together with the increase in the heat dissipation area due to the metal plate provides high heat dissipation.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an enlarged sectional view showing an embodiment of a metal substrate according to the present invention. In the figure, 11 is a metal substrate as a whole, and 12 is a metal plate having the strength to support a semiconductor element, etc., and the material thereof is not particularly limited. Generally AI
, Cu-based materials are used, but electromagnetic shielding becomes possible by using magnetic materials. The thickness of the metal plate 12 is 1 mm.
It is enough. 13 is a thin film of c-BN deposited on one side of the metal plate 12 by vapor deposition, and the film thickness is about 10 μm. A PVD method or a CVD method is used as the vapor deposition method. For example, it can be deposited using a laser PVD method.

Since the c-BN film 13 is a highly pure thin film obtained by the above-mentioned vapor deposition method, it has been confirmed that its thermal conductivity reaches more than 500 W/m-.

This is a considerably large value compared to the 17 W/m- of Al2O3, and high heat dissipation can be achieved. Needless to say, it has sufficiently high electrical insulation properties and dielectric strength. Further, by employing the above-described vapor deposition method, highly reliable metal substrates can be stably mass-produced, and the size of the substrate can be increased.

Therefore, combined with the increase in the heat dissipation area of the present metal substrate 11, this suggests that high integration of semiconductor elements is possible. Furthermore, since the c-BN film 13 does not contain impurities that emit alpha rays, there is no possibility of soft errors occurring.

FIG. 2 is a diagram showing the peel strength of the c-BN film as described above (in the case of a film thickness of 10 μm) in relation to the heat generation density.

It can be seen from FIG. 2 that it can function satisfactorily with a heat generation density of 14 W/eI# or less.

FIG. 3 is a sectional view showing an example of an LSI package constructed using this metal substrate. As mentioned above, since the c-BN film 13 of this metal substrate has high thermal conductivity, LSI
The chip 1 can be directly fixed on the c-BN film 13 with full bonding. Furthermore, the AI fins 4 can also be directly fixed to the metal plate 12. The fixing method used is fusion welding, brazing, etc. Although the cap 9 is a mullite cap in this embodiment, it may also be an alumina cap. Alternatively, a configuration similar to that of the present metal substrate 11 may be used.

The cap 9 and the metal substrate 11 are sealed together by a sealing glass 10 at the middle of the drawer of the lid frame 8, as in the conventional example.

As is clear from the configuration shown in FIG. 3, when this metal substrate 11 is used, the structure of the heat dissipation portion of the AI fin 4 becomes extremely simple compared to that shown in FIG. 4 which shows a conventional example.

[Effects of the Invention] As described above, according to the present invention, by depositing a high-purity c-BN film, a large-sized metal substrate with high thermal conductivity can be obtained. It is possible to increase the integration of elements. The degree of integration is improved by at least one order of magnitude compared to the conventional one. Also, LSI, V
Since LSI etc. can be directly mounted, the heat dissipation structure is extremely simple, and the number of parts is small, contributing to cost reduction. Of course, it has great advantages, such as being able to be mass-produced, making it possible to make large-sized boards, and being able to stably supply highly reliable boards.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view showing one embodiment of the present invention, FIG. 2 is a diagram showing the relationship between peel strength and heat generation density of the c-BN film of the above embodiment, and FIG. 3 is a metal substrate of the present invention. FIG. 4 is a sectional view showing an example of the use of a conventional alumina substrate. 11...Metal substrate 12...Metal plate 13...c-BN film ¥1 Figure 2 Density fW/cm2) Agent Patent attorney Muneharu Sasaki

Claims (2)

[Claims] (1) A metal substrate for an integrated circuit, characterized in that a thin film of cubic boron nitride is deposited on the surface of a metal plate. (2) The metal substrate for an integrated circuit according to claim 1, wherein the cubic boron nitride thin film is deposited by a PVD method or a CVD method.