JPS62159444A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a substrate which is improved in its heat dissipation by growing a silicon carbide by a CVD method on a silicon, polishing the silicon and forming the substrate which mainly contains the silicon carbide. CONSTITUTION:A silicon carbide 12 having 500mum of thickness is grown by a CVD method on a silicon substrate 11. The carbide 12 is not necessarily crystallized, but may be polycrystalline SiC. Then, the substrate 11 is mechanically or chemically polished. The mechanical polishing is by polishing powder, and the chemical polishing is by etchant such as caustic potash. Then, the substrate 11 which has wrong thermal conduction is formed thinly, and the carbide 12 having good thermal conduction is formed thickly. Thus, the substrate 11 which is improved in the heat dissipation is obtained.

Description

[Detailed Description of the Invention] [Summary] A substrate with a structure in which silicon carbide is grown on a silicon plate by chemical vapor deposition, and then the silicon plate is polished from the back side to stack a silicon layer on the silicon carbide. Alternatively, a substrate having a structure in which a silicon layer is buried in silicon carbide is created, and a semiconductor element is formed in the silicon layer. Such a substrate has good thermal conductivity.

[Industrial Field of Application] The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of forming a substrate.

As is well known, semiconductor devices such as ICs and LSIs are becoming extremely fine and highly integrated, and this is because the higher the integration, the higher the performance, such as high-speed operation.

However, the higher the degree of integration and density, the more heat generated during operation, and therefore sufficient consideration must be given to heat dissipation.

[Problems that the conventional technology and invention try to solve]
Conventionally, highly integrated and highly dense semiconductor devices such as LSIs are produced by attaching LSI elements formed on a silicon substrate to a substrate with good thermal conductivity, such as a diamond plate.
It has a structure that allows heat to dissipate easily. Such a structure is called a heat sink structure.

In addition, RC with a dielectric isolation structure is well known, in which semiconductor elements are separated by a dielectric, but as electronic equipment becomes more RC, ICs with high dielectric strength and high reliability are required, for example, for telephones. LS used in subscriber line circuits due to computerization
I (SLIC) requires a high withstand voltage of several hundred volts. The silicon substrate of such an IC is shown in Figures 3(a) to (
It is formed by the process shown in d).

First, as shown in FIG. 3(a), a silicon substrate 1 is selectively etched to form an island region 2. Then, as shown in FIG. By providing a mask on a silicon substrate with a plane orientation of (100) and performing selective anisotropic etching (referred to as V-cutting) using a caustic potash solution, the shape shown in the figure can be easily formed. Then,
As shown in Figure (b), the entire surface is thermally oxidized to a film thickness of 2 to 3.
A silicon oxide (Si02) film 3 having a thickness of μm is produced.

Next, as shown in FIG. 3 (C1), chemical vapor deposition (C
A polycrystalline silicon film 4 having a thickness of several hundred μm is deposited by the VD method. Next, as shown in FIG. 4(d), the silicon substrate 1 is mechanically or chemically polished to a film thickness of
A silicon island region 2 of about μm size is formed on a substrate formed on a polycrystalline silicon film 4 via a 5i02 film 3. Such a substrate as shown in FIG.
Since it is a bulk (crystalline substrate made by pulling or band-melting molten silicon using a seed) with few crystal defects, the semiconductor element formed in the island-like region can obtain a high breakdown voltage and is highly reliable. Become an IC.

However, since the substrate of the high voltage IC shown in FIG. 3 1d) is made of polycrystalline silicon, it has a disadvantage of insufficient thermal conductivity. Furthermore, when removing the silicon substrate 1 by polishing, there is a problem in that it is difficult to detect the end point of polishing because the silicon substrate and the polycrystalline silicon film are made of the same material.

In addition, in the former type of heat sink structure IC, the IC is mounted on a silicon substrate, and even if a plate with good thermal conductivity is closely attached, heat dissipation is not necessarily sufficient due to the thick silicon substrate. .

The present invention proposes a method for manufacturing a semiconductor device, that is, a method for manufacturing a substrate, for alleviating these problems and forming an IC with good heat dissipation.

[Means for solving the problem] The purpose is to grow silicon carbide (SzC; insulator) on a silicon plate by CVD method, and then polish the silicon plate to form a silicon layer on the silicon carbide. A process of forming a substrate with a structure provided with, or
Silicon carbide is grown by a CVD method on a silicon plate provided with an island-like region, and then the silicon plate is polished to form a substrate having a structure in which the island-like region is buried as a silicon layer in the silicon carbide. This is achieved by a method of manufacturing a semiconductor device that includes the steps of:

[Operation] That is, in the present invention, silicon carbide is grown on silicon by the CVD method, and the silicon is polished to form a substrate mainly made of silicon carbide (insulator).

In this case, silicon, which has poor heat transfer properties, becomes thinner, and silicon carbide, which has good thermal conductivity, becomes thicker, improving heat dissipation.

[Example] Hereinafter, embodiments will be described in detail with reference to the drawings.

FIGS. 1A to 1C show cross-sectional views in the order of the formation process of an embodiment of the present invention, and show a conventional heat sink structure I.
This is a method of forming a substrate in place of C.

FIG. 1(a) shows a silicon substrate 11 with a film thickness of about 600 μm.
Next, as shown in FIG. Polycrystalline SiC may be used.The growth conditions are as follows: Using a known CVD device, the substrate is heated to 1360°C, and silicon tetrachloride (SiC1a) is used as a reaction gas.
) and propane (COH8), or monosilane (S
iH4) and propane (C3H[l) are introduced to grow at normal pressure.

Next, as shown in FIG. 1C, the silicon substrate 11 is mechanically or chemically polished to form a silicon layer 11 having a thickness of about 100 μm. Mechanical polishing is polishing with abrasive powder, and chemical polishing is polishing with an etching agent such as caustic potash.

In this way, if a semiconductor element is formed on the silicon layer 11 on the substrate shown in FIG.

Next, FIGS. 2(a) to 2(dl) show sequential cross-sectional views of the forming steps of another embodiment according to the present invention, which is a method of forming a substrate in place of the high voltage IC described in FIG. 3.

Figure 2 [a] shows a silicon substrate 21 with a film thickness of about 600 μm.
Then, as shown in FIG. 2('b), the silicon substrate 21 is selectively anisotropically etched using a mask (not shown) to form island regions 22.

Next, as shown in FIG. 2(C), silicon carbide 23 with a thickness of 500 μm is grown thereon by CVD. The growth conditions are similar to the example described in FIG. Next, as shown in FIG. 3(d), the silicon substrate 21 is mechanically or chemically polished and removed, resulting in a film thickness of approximately 5.
Only the island-like regions 22 of 0 μm are left. At this time, in this polishing step, since the hardness of silicon carbide is higher than that of silicon, it becomes very easy to detect the end point of polishing.

When a semiconductor element is formed on the substrate shown in FIG. 2(d) created in this way, the result is shown in FIG. 3(C).
Because the substrate has better thermal conductivity than the substrate shown in
The reliability of C is further improved.

[Effects of the Invention] As is clear from the above description, according to the present invention, a substrate with good thermal conductivity can be obtained, so that a high-density IC can be made even more reliable.

[Brief explanation of drawings]

Figures 1 (a) to (C) and Figures 2 (a) to (d) are cross-sectional views in the order of forming steps of the embodiment according to the present invention, and Figures 3 fa) to (d) are sectional views in order of forming steps in the conventional example. FIG. In the figure, 1, 11.21 is a silicon substrate, 2.22 is an island region, 3 is a 5i02 film, 4 is a polycrystalline silicon film, 12, 23 is a silicon carpaiton 1 ball 4-KB74H; ■Shira Lro ('Process 1ヅQ15S1UdeJ@(T)flit Figure n≦EJfi lJ7? S 'F', 'F'i' I
i”II $ffiGo IID (1) @ Figure 2 Open-circuit high T glue + 'tilt trace diagram @ Figure 3

Claims (2)

[Claims] (1) A step of growing silicon carbide on a silicon plate by chemical vapor deposition, and then polishing the silicon plate to form a substrate having a structure in which a silicon layer is provided on the silicon carbide. A method of manufacturing a semiconductor device, characterized in that: (2) Silicon carbide is grown by chemical vapor deposition on a silicon plate provided with island-like regions, and then the silicon plate is polished to form the island-like regions as a silicon layer within the silicon carbide. A method for manufacturing a semiconductor device, comprising the step of forming a substrate with a buried structure.