JPH04258152A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To make a polishing stopper pattern later at an SOI substrate, which has a rather thick Si layer, and make a film SOI by the filming by polishing. CONSTITUTION:In an Si substrate (SOI substrate), equipped with a first Si film 3 through the first SiO2 film made by ZMR method, a first aperture 4 and a second aperture 7 are made partially, and a second Si film 8 is grown selectively by CVD method. Then, by thermal oxidation, a third SiO2 film 9 is made on the second Si film 8, and using a polishing plate and an abrasive, the first Si film 3 is filmed by polishing with the third SiO2 film 9 as a stopper.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to SOI (Silicon
The present invention relates to a method for manufacturing an on-insulator type semiconductor device.

0002

2. Description of the Related Art In recent years, SOI type semiconductor devices have been put into practical use as they have advantages over semiconductor devices fabricated on Si substrates in terms of radiation resistance and high speed. S.O.
In general, type I semiconductor devices have little superiority over semiconductor devices formed on Si substrates unless the thickness of the Si film is less than about 0.2 μm. However, ZMR (Zone M
elting Recrystallization)
SOI substrates formed by the bonding method and bonding method generally have a film thickness of 0.
．． The thickness is 5 μm or more, and the uniformity of the film thickness is also poor. It was extremely difficult to reduce the thickness of this film by polishing in terms of film thickness control. Therefore, there has been a method in which a polishing stopper pattern is formed in advance, and then an SOI film is formed using a ZMR method or a bonding method, and the film is made thinner by polishing.

FIG. 4 shows a conventional polishing stopper pattern and Z
This shows a method for forming a thin film SOI using the MR method. In FIG. 4, 101 is a Si substrate, 102 is a SiO2
103 is a polishing stopper pattern, 104 is a non-single crystal Si film, and 105 is a single crystal Si film.

The operation of the method for forming a thin film SOI using the polishing stopper pattern constructed as described above and the ZMR method will be described below.

First, as shown in FIG. 4(a), a Si substrate 10 is
SiO2 with polishing stopper pattern 103 on 1
A film 102 is formed, and a non-single crystal Si film 10 is further formed thereon.
form 4. Next, as shown in Fig. 4(b), the non-single crystal S
The i-film 104 is melted and recrystallized by a linear heater 106,
A single crystal Si film 105 is formed.

Next, as shown in FIG. 4C, the monocrystalline Si film 105 is polished using an abrasive and a polishing plate until the polishing stopper pattern 103 is exposed, thereby reducing its thickness. By selecting an abrasive that has a fast polishing rate for Si and hardly removes SiO2, the polishing rate becomes extremely slow when the polishing stopper pattern 103 is exposed, and a single crystal Si film with a uniform thickness over the entire wafer surface can be formed. It is.

[0007]

[Problems to be Solved by the Invention] However, in the above-mentioned configuration, since the polishing stopper pattern exists as a step on the base layer during recrystallization using the ZMR method, for example,
Problems include crystal defects occurring around the polishing stopper pattern in the recrystallized SOI layer, and because the polishing stopper pattern is formed before recrystallization, the device layout is restricted by the polishing stopper pattern after recrystallization. It had a point. In addition, when polishing an SOI plate without a polishing stopper pattern to make it thin, the SOI
There was a problem in that the thickness of the I layer could not be accurately controlled.

In view of the above-mentioned problems, the present invention has been developed to form a polishing stopper pattern afterwards so as not to adversely affect the crystallinity of the SOI layer.
It is an object of the present invention to provide a method for manufacturing a semiconductor device in which an OI substrate can also be thinned with good controllability of film thickness.

[0009]

[Means for Solving the Problems] In order to solve the above problems, a method for manufacturing a semiconductor device according to the present invention includes a first SiO2
A step of providing a first opening in the first Si film so that the surface of the first SiO2 film is exposed by photomask method and dry etching in a Si substrate provided with a first Si film via the film. forming a second SiO2 film on the first Si film by thermal oxidation, and exposing the Si substrate to the oxidation-resistant mask film and the first SiO2 film in the first opening; a step of providing a second opening smaller than the first opening; a step of selectively growing a second Si film in the second opening by CVD; and a step of growing the second Si film by thermal oxidation. A third SiO2 layer is applied to the film so that the surface thereof is at least higher than the surface of the first SiO2 film.
a step of forming a film; and a step of forming a film on the surface of the first Si film.
and polishing the first Si film using a polishing plate and an abrasive material until the surface of the first Si film is approximately at the same height as the surface of the third SiO film. It is equipped with a process.

0010

[Operation] According to the above-described structure, the present invention uses an SOI layer to form a polishing stopper pattern after forming an SOI layer.
This does not affect the crystallinity of the layer, and it is possible to form a polishing stopper pattern later on a thick film SOI without a polishing stopper pattern to make the film thinner.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a semiconductor device according to an embodiment of the present invention will be described below with reference to the drawings. Figure 1, Figure 2
1A and 1B are process cross-sectional views showing a method for manufacturing a semiconductor device according to claim 1 of the present invention.

In FIG. 1, 1 is a Si substrate, 2 is a first SiO2 film, 3 is a first Si film, 4 is a first opening, and 5 is a first SiO2 film.
6 is a second SiO2 film, and 6 is an oxidation-resistant mask film.

In FIG. 1(a), a Si substrate, ie, an SOI substrate, is provided with a first Si film 3 via a first SiO2 film 2.
FIG. 3 is a cross-sectional view of the substrate. This SOI substrate is formed using a ZMR method, a bonding method, a SIMOX method, etc., and the film thickness of the first SiO2 film 2 is about 0.2 μm to 2 μm, and the film thickness of the first Si film 3 is The thickness is approximately 0.1 μm to 4 μm.

FIG. 1(b) shows an SOI substrate having such a structure.
As shown in FIG. 2, a first opening 4 is formed using a photomask and dry etching method so that the surface of the first SiO2 film 2 is exposed. Although the shape of the first opening 4 is not limited, for example, forming it in a lattice shape is convenient for later polishing. Appropriately, one side of the grating is several tens of micrometers to several hundred micrometers. Further, the width is approximately several μm to several tens of μm.

Next, as shown in FIG. 1C, a second SiO2 film 5 is formed on the first Si film 3 by thermal oxidation, and then a CVD-SiN film, for example, is deposited as an oxidation-resistant mask film 6. The thickness of the second SiO2 film 5 is from 2 nm to 100 nm.
The thickness of the SiN film is approximately 10 nm to 200 nm.

Next, as shown in FIG. 1D, a second opening 7 is formed using a photomask and dry etching so that the Si substrate 1 is exposed in the first opening 4. As shown in FIG. Second
The shape of the opening 7 is similar to the shape of the first opening 4, but
The width thereof is made narrower than the first opening 4 by several μm.

Next, as shown in FIG. 1(e), a second Si film 8 is selectively formed in the second opening 7 by CVD. The film thickness of this second Si film 8 is finally the same as that of the first Si film 3.
The thickness of the first SiO2 film 2 is set to be the same as that of the first SiO2 film 2, although the thickness of the first SiO2 film 2 is determined here. That is, the first
The surfaces of the SiO2 film 2 and the second Si film 8 are made to be at the same height.

Next, as shown in FIG. 2(a), a third SiO2 film 9 is formed on the second Si film 8 by thermal oxidation. Third
The film thickness of the SiO2 film 9 varies depending on the target film thickness of the first Si film 3 and the film thicknesses of the first SiO2 film 2 and the second Si film 8. When the film thicknesses of the film 2 and the second Si film 8 are equal, it is expressed by (Equation 1).

[0019]

Equation (1) is derived from the fact that the thermally oxidized SiO2 film interface subsides by 45% of the SiO2 film thickness downward and rises by 55% upward relative to the initial Si film surface. For example, if the target thickness of the first Si film 3 is 50 nm, the second Si film 8 has a thickness of 9 nm.
A thermal oxide film, that is, a third SiO2 film 9 of 0.9 nm is formed.

Next, as shown in FIG. 2(b), a resist 10 is left so as to hide the third SiO2 film 9 by a photomask process.

Next, as shown in FIG. 2C, the oxidation-resistant mask film 6 and the second SiO2 film 5 are removed by wet etching or dry etching.

Next, as shown in FIG. 2(d), the first Si film 3 is polished using a polishing plate 11 and an abrasive to make it thin. As the abrasive material, a material whose polishing speed is very fast for Si and very slow for SiO2 is used, such as an amine aqueous solution. As the first Si film is made thinner and thinner in this way, the surface of the third SiO2 film 9 comes into contact with the polishing plate 11 (see FIG. 2e). Then, since the polishing speed of the SiO2 film is very slow, the polishing cannot proceed any further, and the polishing of the first Si film also stops automatically. Finally, the thickness of the first Si film 3 is determined by the height of the surface of the third SiO2 film 9 and the thickness of the first SiO2 film 3.
This is equal to the difference in height between the surfaces of the two films 2.

After polishing is completed, the result is as shown in FIG. 3, and semiconductor elements such as MOS transistors are formed on the thinned first Si film 3.

Note that the oxidation-resistant mask film 6 other than the SiO2 film
The formation of is not necessarily necessary, and the subsequent steps are exactly the same except that when forming the third SiO2 film 9, the second SiO2 film 5 becomes thicker and the first Si film becomes thinner.

[0025]

Effects of the Invention As described above, the present invention provides a polishing stopper pattern after forming an SOI layer.
It does not adversely affect the crystallinity of the layer, and even an SOI substrate that does not have a polishing stopper pattern can be polished into a thin film.

[Brief explanation of the drawing]

FIG. 1 is a partial process cross-sectional view of a method for manufacturing a semiconductor device in an embodiment of the present invention.

FIG. 2 is a partial process cross-sectional view of a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a semiconductor device formed according to the same example.

FIG. 4 is a process sectional view illustrating a conventional example.

[Explanation of symbols]

1 Si substrate 2 First SiO2 film 3 First Si film 4 First opening 5 Second SiO2 film 6 Oxidation-resistant mask film 7 Second opening 8 Second Si film 9 Third SiO2 film 10 Recipe 11 Polishing plate

Claims (1)

[Claims] 1. In a Si substrate provided with a first Si film via a first SiO2 film, a surface of the first SiO2 film is exposed to the first Si film by a photomask method and dry etching. a step of forming a second SiO2 film on the first Si film by thermal oxidation; and a step of forming a second SiO2 film on the first Si film in the first opening; a step of providing a second opening in the film through which the Si substrate is exposed and which is smaller than the first opening; and selectively forming a second S into the second opening by a CVD method.
The step of growing an i film and thermal oxidation
forming a third SiO2 film on the film so that its surface is at least higher than the first SiO2 film surface; removing the second SiO2 film on the first Si film surface; and a polishing plate. and polishing the first Si film using an abrasive until the surface of the first Si film is approximately at the same height as the surface of the third SiO2 film.