JPS5931226B2 - semiconductor equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called SOS (silicon on sapphire) type semiconductor device in which single crystal silicon is grown on an insulating substrate such as a sapphire substrate and elements are formed in the single crystal silicon. .

Conventionally, when creating a semiconductor device using a 505 substrate, after silicon is grown on a sapphire substrate, a process of diffusing impurities such as donors and acceptors into the silicon is performed several times. Due to the high temperature, the aluminum in the sapphire substrate also diffuses into the silicon, which can change the properties of the silicon, especially its electrical conductivity and conductivity type. Therefore, the conditions for allowing the donor and acceptor impurities diffused into the silicon to reach the sapphire from the silicon surface are severely restricted, creating great difficulties in device fabrication. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a 505 type semiconductor device which eliminates the above-mentioned drawbacks.

The semiconductor device of the present invention is formed by implanting an insulating substrate such as a sapphire substrate, a semiconductor layer such as silicon grown on the insulating substrate, and a layer formed between the insulating substrate and the semiconductor layer. It is characterized by having an oxide layer such as a silicon dioxide film. According to the semiconductor device of the present invention, the silicon dioxide film existing between the sapphire substrate and the silicon layer acts as a barrier to aluminum diffusing into the silicon from the sapphire substrate during high-temperature processes, thereby preventing aluminum from diffusing into the silicon. suppress.

Therefore, the properties of silicon are not changed by aluminum, and therefore the temperature can be increased to diffuse donor and acceptor type impurities from the silicon surface.
Time also has the great advantage of allowing sufficient time for the donor and acceptor impurities to reach the sapphire substrate. Next, in order to better understand the above-mentioned features of this invention, the following will explain them using figures. Referring to FIG. 1, a conventional 505 type semiconductor device, taking a MOS type element as an example, grows a silicon layer 102 on a sapphire substrate 101 as shown in FIG. A step of selectively diffusing impurities into the source region 104 and drain region 105 by thermal diffusion using the silicon film 103 as a mask is performed, and as shown in FIG.
1, a silicon layer 102, a source region 104, a drain region 105, a silicon dioxide film 106 that becomes a gate film, a silicon dioxide film IOT, IOT', and a silicon dioxide film covering other parts of the silicon layer 102. It has a structure consisting of metal wirings 108, 109, and 110.

In this conventional SOS type semiconductor device, when impurities are diffused into the source region 104 and drain region 105, aluminum also diffuses into the silicon layer 102 from the sapphire substrate 101, as shown in FIG.

For this reason, the silicon layer 102 tends to become strongly P-type from the portion close to the sapphire substrate 101. For this reason, if the element incorporated in the SOS type semiconductor device is an n-channel MOS transistor, the threshold voltage, the withstand voltage between the source 104 and the drain 105, etc. There is a drawback that the characteristics vary greatly and the reliability is significantly impaired.Also, when the MOS transistor is a P-channel, the part of the silicon layer 102 near the sapphire substrate 101 is inverted to the P type. In the end, the source 104 and drain 105 were always electrically conductive, resulting in a fatal defect in that they did not function as a transistor at all. Referring to FIG. 2, the SOS type semiconductor device of the present invention first grows a silicon layer 202 on a sapphire substrate 201 as shown in FIG.
Oxygen ions are implanted into a region 203 close to 1.

The energy implanted at this time is the grown silicon layer 2.
Although it varies depending on the thickness of 02, if the thickness is about 1μ, about 150Kev is appropriate. Next, as shown in Figure b, by heating the SOS substrate into which oxygen has been implanted, a silicon oxide film 204 is formed between the sapphire substrate 201 and the silicon layer 202. The oxygen implanted at this time partially forms silicon oxide due to its high energy, and is distributed at a high concentration in the region 203 of the silicon layer, so high temperature heat treatment is not required at most. A temperature below 900°C is sufficient. Therefore, when the silicon oxide film 204 is formed, the sapphire substrate 201
The diffusion of aluminum into the silicon layer 202 is ignored. Thereafter, as shown in Fig. c, after selectively leaving the silicon layer 202, impurities are diffused into the source region 206 and drain region 207 using the silicon dioxide film 205 as a mask. At this time, the silicon layer 202 and the sapphire substrate 20
Since the silicon oxide film 204 is interposed between the sapphire substrate 201 and the silicon layer 202, diffusion of aluminum from the sapphire substrate 201 to the silicon layer 202 is suppressed. Therefore, a sapphire substrate 201, a silicon layer 202, a silicon layer 2 as shown in FIG.
Oxide film layer 2 interposed between 02 and sapphire substrate 201
04, source region 206, drain region 207, gate film 208, silicon dioxide film 209, 209' covering the surface of silicon layer 202 other than the gate film, and metal wiring 210
, 211, 212 of the first embodiment of the present invention.
Get an S-type semiconductor device. SO of the first embodiment of this invention
According to the S-type semiconductor device, since the oxide film 204 is interposed between the sapphire substrate 201 and the silicon layer 202, and there is no diffusion of aluminum from the sapphire substrate 201 into the silicon layer 202, the electrical conductivity of the silicon layer 202 and impurities are reduced. The concentration does not change and therefore the threshold voltage, source 20
This has the great advantage that various electrical characteristics such as withstand voltage between the drain 207 and the drain 207 can be kept stable.

Referring to FIG. 3, in the SOS type semiconductor device according to the second embodiment of the present invention, a silicon layer 302 is first grown on a sapphire substrate 301 as shown in FIG.
After the surface of silicon dioxide 302 is covered with silicon dioxide films 303 and 303', oxygen ions are implanted into a portion 304 of the silicon layer 302.

Thereafter, as shown in Figure b, the silicon layer 302 is selectively left and the silicon layer 304 into which oxygen has been implanted is covered with a silicon dioxide film 305, and impurities are diffused into the source region 306 and drain region 307, and at the same time the sapphire substrate 301 is An oxide film 308 is formed between the silicon layer 302 and the silicon layer 302. Next, a sub-↑ia substrate 301 and a silicon layer 30 grown thereon as shown in Fig. c are prepared in the same manner as a normal SOS type semiconductor device incorporating a MOS type element.
2, a source region 306, a drain region 307, a silicon oxide film 308 and a gate film 309 interposed between the sapphire substrate 301 and the silicon layer 302, and a silicon dioxide film 310 covering the surface of the silicon layer 302 other than the gate portion.
, 310' and metal wirings 311, 312, 313. According to this second embodiment, the oxide film 308 interposed between the sapphire substrate 301 and the silicon layer 302
is only a portion below the gate film 309, so the crystal structure of the silicon layer 302 that is disturbed when oxygen ions are implanted into the silicon layer 304 in FIG. Since the crystal lattice of the sapphire substrate 301 exists nearby, it has the advantage that recovery is easy and an SOS type semiconductor device with better performance can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view for explaining a conventional SOS type semiconductor device, FIG. 2 is a sectional view for explaining a first embodiment of the present invention, and FIG. 3 is a second embodiment of the present invention. FIG. 2 is a sectional view for explaining. 101, 201, 301 are sapphire substrates, 102, 2
02, 302 are silicon layers, 103, 104, 104'
, 205, 209, 209', 303, 303', 30
5, 306, 306' are silicon dioxide films, 104, 2
06, 306 are source regions, 105, 207, 307 are drain regions, 106, 208, 309 are gate films, 2
04, 308 is a silicon oxide film, 108, 109, 11
0,210,211,212,311,312,313
is metal wiring.

Claims (1)

[Claims] 1. A single-crystal insulating substrate having a property that contains as a constituent element an element that serves as a conductivity type-determining impurity for a semiconductor layer provided thereon, and a semiconductor oxide layer formed on the single-crystal insulating substrate; A semiconductor device comprising: a single crystal semiconductor layer existing on the oxide layer; and an element or a part of the element is formed within the single crystal semiconductor layer.