JPS5824947B2 - Hand tie souchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device having a porous silicon oxide film obtained by oxidizing a porous silicon film obtained by an anodic reaction in hydrofluoric acid.

Conventionally, a porous silicon oxide film obtained by making the silicon surface porous in hydrofluoric acid as described above and thermally oxidizing the porous silicon film in an oxidizing atmosphere has a high oxidation rate. It has been used to form thick oxide films in semiconductor devices because it is much faster to form a thick oxide film than that of a single-crystal silicon substrate.

However, stress tends to occur between the porous silicon oxide film obtained by oxidizing this porous silicon film and the silicon substrate, and between the porous silicon oxide film and the single crystal silicon substrate. There is a porous silicon layer that is not completely oxidized, so if there is a pn junction in contact with the porous silicon oxide film,
A major drawback is that the leakage current in the reverse direction of the pn junction can become very large.

Therefore, the present invention provides a semiconductor device that eliminates the above-mentioned drawbacks.

A semiconductor device and a method for manufacturing the same of the present invention include forming a silicon oxide film obtained by oxidizing single crystal silicon between a porous silicon oxide film and a single crystal silicon substrate, and forming a silicon oxide film obtained by oxidizing single crystal silicon in contact with the silicon oxide film. -The structure forms an n-junction.

In the device of this invention, the p-n junction is in contact with a silicon oxide film obtained by oxidizing single crystal silicon, so leakage current in the opposite direction of the p-n junction is caused by strain and remaining porous holes. Since it is hardly affected by the quality silicon film, it is possible to reduce the amount to a very small amount.

Furthermore, the oxide film in areas that require a deep oxide film, such as areas where no elements are formed, is a porous silicon oxide film, which allows the oxide film to be sufficiently thick and deep. This has the great advantage that the capacitance between the wiring on the silicon oxide film and the silicon substrate can be greatly reduced.

Next, the present invention will be explained using drawings in order to better understand the present invention.

Referring to FIG. 1, in a device using a conventional porous silicon oxide film, a porous silicon oxide film 102 is obtained by selectively making P-type silicon 101 porous and then oxidizing it. The structure is such that an n-type silicon layer 103, which is part of a circuit element, etc., is formed in contact with this porous silicon oxide film 102.

A pn junction 104 formed between a p-type silicon substrate 101 and an n-type silicon region 103 is in contact with a porous silicon oxide film 102.

The P-type silicon region 105 near this porous silicon oxide film 102 receives stress when the porous silicon film is oxidized, and is therefore susceptible to the resulting defects, and the porous silicon is completely replaced by the porous silicon oxide film. It remains unchanged at 102.

Therefore, when a reverse bias is applied between the P-type substrate 101 and the n-type silicon region 103, the p-n junction 104
There are serious drawbacks in that a large leakage current occurs in the region 106 where the voltage falls within the region 105, and the breakdown voltage in the reverse direction is also low.

Referring to FIG. 2, in one embodiment of the present invention, a P-type silicon substrate 2 is used in a semiconductor device using a porous silicon film.
A porous silicon oxide film 202 obtained by selectively making 01 porous and distributing it, and P-type silicon, which is single crystal silicon, located around the porous silicon oxide film 202. After a silicon dioxide film 203 obtained by oxidizing the substrate 201 is formed, an n-type silicon region 2 is formed.
04 is formed.

According to the semiconductor device according to the embodiment of the present invention, p-
The n-junction 205 is not in contact with the porous silicon oxide film 202 but is in contact with the silicon dioxide film 203.

That is, since it does not directly contact the silicon region 206 where there are many defects and porous silicon, the pn.
This has the great advantage of being able to reduce the leakage current of the junction 205 and not reducing the breakdown voltage.

Referring to FIG. 3, one embodiment of the present invention is illustrated in a MOSFET.
For example, it can be realized as follows.

In other words, as shown in Figure a, a nitride film 302 is selectively disposed on a P-type silicon substrate 301, and the portions not covered with the nitride film 302 are made porous and then oxidized to form a porous silicon oxide film. 303°303' and at the same time, the nitride film 3 is formed.
02 and converts the silicon dioxide film 304 into a nitride film 30.
Form on top of 2.

Next, as shown in the same figure, using the silicon dioxide film 304 as a mask, the porous silicon oxide film 303 is
After etching and removing the area in contact with 303', the silicon under the removed nitride film is oxidized to form silicon dioxide films 305 and 305'.

After that, as shown in FIG. C, an oxide film 304 and a nitride film 302
After removing the MOS transistors, a source region 306, a drain region 307, and a gate oxide film 308 are formed in the same manner as in the normal MOS transistor manufacturing method, and finally, metal wirings are formed to be connected to the source region 306, drain region 307, and gate oxide film 308, respectively. 309.310.311.

In the MOS transistor according to the embodiment of the present invention, the source region 306 and the drain region 307 are in contact with silicon dioxide films 305 and 305' obtained by oxidizing single crystal silicon, respectively, and the porous silicon oxide films 303 and 303 are in contact with silicon dioxide films 305 and 305' obtained by oxidizing single crystal silicon. '
It has the advantage that the leakage current is small because it is not in contact with the

Furthermore, when aligning the source region 306 and the drain region 307 when forming them, even if the misalignment becomes large, the source region 306 and the drain region 307 do not come into direct contact with the porous silicon oxide films 303 and 303'. There is also a margin for metal wiring 309, 310 and 3.
11 is mostly thick porous silicon oxide film 303, 30
3', it has the great advantage that the capacitance between these metal wirings and the P-type silicon substrate 301 can be greatly reduced.

The present invention can be very effectively implemented in a MOS integrated circuit including MOS transistors.

In particular, the capacitance between the metal wiring 309, 310, 311 and the P-type silicon substrate 301 can be reduced, and the leakage current between the source region 306, the drain region 307 and the P-type silicon substrate 301 can be reduced. This has the great advantage of greatly improving the switching characteristics and retention characteristics of a semiconductor memory device incorporating a MOS (MOS) transistor.

The present invention is not limited to the above-mentioned MOS transistors and MOS integrated circuit devices, but can also be effectively implemented in bipolar integrated circuits.

In other words, bipolar integrated circuits that use a porous silicon oxide film for isolation with low junction capacitance do not require a high-temperature, long-duration diffusion process, and therefore are less prone to surface crystal disorder and abnormal diffusion of impurities. However, the bipolar integrated circuit according to the present invention does not impair the conventional effects, has small stray capacitance between the metal wiring and the semiconductor substrate, has small junction capacitance based on the PN junction, and has low leakage current. small bipolar integrated circuits can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view for explaining a conventional semiconductor device, and FIGS. 2 and 3 are sectional views for explaining a semiconductor device of the present invention. 101.20L3 (N...P-type silicon substrate,
102.202, 303, 303'... Porous silicon oxide film, 103, 204... N-type silicon layer, 104, 205... p-n junction, 1
06, 206... P-type silicon region near porous silicon oxide film, 203, 304, 305, 305
'...Silicon dioxide film, 306...
Source region, 301...Drain region, 308
・・・・・・Gate film, 309°310, 311...
...It is metal wiring.

Claims (1)

[Claims] 1. A semiconductor device comprising a single-crystal semiconductor oxide surrounding a porous semiconductor oxide, and a PN junction surface in contact with a side surface of the single-crystal semiconductor oxide.