JP2964547B2 - Method for forming SOI substrate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for forming an SOI substrate which is a kind of SI substrate required for forming a semiconductor device.

(Prior Art) Conventionally, as a method of forming an SOI substrate using a vapor phase growth method having excellent crystallinity, for example, a method described in J. of electrochem.
c.), Volume 130, p. 1571, Epitaxial Lateral Overgrowth
th), and a method called tunnel epitaxy as shown in the 50th Annual Meeting of the Japan Society of Applied Physics, Proceedings of Lectures, Second Volume, page 588 (28a-C-8).

(Problems to be Solved by the Invention) In the epitaxial lateral overgrowth of the prior art, when epitaxial growth is signaled laterally from the seed region onto SiO ₂ , the growth rate in the film thickness direction and the lateral growth are increased. Since it is difficult to make a large difference in the speed, the film thickness increases as the lateral growth proceeds, and it is difficult to obtain a thin SOI (single crystal Si on SiO ₂ ) region with a large area.

Tunnel epitaxy uses epitaxial lateral
Overgrowth can overcome such disadvantages. In tunnel epitaxy, crystal growth proceeds laterally in a tunnel region sandwiched between upper and lower portions of SiO ₂ . In this method, the SOI film thickness is precisely controlled by the height of the tunnel, so it is possible to form a thin SOI with a large area.However, if the length of the tunnel from the seed becomes longer when forming the tunnel, ,
Will block the tunnel upper SiO ₂ layer in contact with the lower SiO ₂ film deflection, it can not be introduced in the deposition gas. Therefore,
The disadvantage is that the resulting SOI area is limited by limiting the length of the tunnel that can be formed.

(Means for Solving the Problems) According to the present invention, a step of forming a SiO ₂ film on the surface of a Si substrate,
A step of forming the SiO ₂ film, a step of removing a partial region of the SiO ₂ film to expose the Si substrate, and a step of epitaxially growing Si only in the region where the Si substrate is exposed, a growth surface and a SiO ₂ film surface. a step height of a seed so as to be substantially the same, a step of patterning a polycrystalline Si, Si ₃ N
₍₄₎ depositing a film, removing a part of the Si ₃ N ₄ film to form a window, and introducing HCl gas from the window to form a polycrystalline S
A method for forming an SOI substrate, comprising the step of removing i and the step of introducing a growth gas containing Si from the window and growing epitaxial Si on the SiO ₂ film from the seed by introducing a growth gas, is obtained.

By (action) or less present invention describes the action to be possible to form a SOI large area compared to use the top of the tunnel SiO ₂ film.

In the present invention, a Si ₃ N ₄ film is used instead of the upper SiO ₂ film of tunnel epitaxy. The Si ₃ N ₄ film is harder and less thermally deformed than the SiO ₂ film. Therefore, using a Si ₃ N ₄ film makes it possible to form a tunnel at a longer distance from the seed than when using an SiO ₂ film, and as a result, it is possible to form a larger-area SOI Becomes

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic sectional view for explaining an embodiment of the present invention. Three types of S of plane orientation (100), (110), and (111)
on the i-substrate 10, SiO ₂ by dry or wet oxidation and LPCVD method substrate temperature 500 to 900 ° C. of the substrate temperature of 900 to 1100 ° C.
A film 20 having a thickness of 0.2 to 0.8 μm was formed, and a partial region of the SiO ₂ film was opened by ordinary photolithography and dry etching to form a seed 30 (FIG. 1A). Next, an epitaxial Si 130 was selectively grown only in the seed region until the surface of the epitaxial growth and the surface of the SiO ₂ film became almost the same height (FIG. 1B). Growth is based on SiH ₂ Cl ₂ (SiH
₄ or Si ₂ H ₆ ) / HCl / H ₂ mixed gas at a substrate temperature of 800 to 50 ° C. Next, LPCVD of polycrystalline Si240
After patterning by depositing 0.05 to 0.6 μm by the method, an Si ₃ N ₄ film 250 is further deposited on the entire surface by 0.1 to 0.5 μm. Thereafter, a gas introduction window 260 was formed at a position 5 to 50 μm away from the seed by a normal dry etching technique (FIG. 1C). For comparison, a film using an SiO ₂ film instead of the Si ₃ N ₄ film shown in FIG. 1C was also formed at the same time. Then HCl
Removes polycrystalline Si by gas etching using
A tunnel 370 having SiO ₂ and an upper portion sandwiched by Si ₃ N ₄ was obtained (No. 1).
Figure (d). Finally, epitaxial growth is performed in the tunnel under the same selective growth conditions as in FIG.
80 was obtained (FIG. 1 (e)). The obtained SOI is SEM and STM
Was observed and evaluated from the cross section direction.

As a result, if the height of the tunnel is 0.05 μm, after gas etching with HCl is completed, the material of the upper part of the tunnel is 15 μm or more when SiO ₂ is used and the material of the tunnel is 25 μm or more when the material is Si ₃ N _4. Was in a collapsed state and SOI could not be formed. When the height of the tunnel is 0.5 μm, the material at the top of the tunnel is SiO ₂
In the case of Si ₃ N _{4 having} a thickness of 30 μm or more, a similar phenomenon was observed. Thus, it was confirmed that a larger area SOI could be formed by changing the material of the upper part of the tunnel from SiO ₂ to Si ₃ N ₄ .

(Effects of the Invention) As described above, according to the present invention, it becomes possible to obtain a tunnel epitaxy technique capable of forming a SOI of a larger area than a conventional technique, and it becomes possible to supply a substrate for forming a high-performance SiLSI. Was.

[Brief description of the drawings]

1 (a) to 1 (e) are schematic sectional views for explaining an embodiment of the present invention. 10 ...... Si substrate, 20 ...... SiO ₂ film, 30 ...... seed, 130 ...... epitaxial Si, 240 ...... polycrystalline Si, 250 ...... Si ₃ N ₄ film, 260 ...... gas introduction window, 370 ...... Tunnel, 480 …… SOI area

Claims (1)

(57) [Claims] A step of forming an SiO ₂ film on a surface of a Si substrate;
Removing a part of the SiO ₂ film to expose the Si substrate, and epitaxially growing Si only in the exposed region of the Si substrate to seed the growth surface and the SiO ₂ film surface so that the height is almost the same. Forming a pattern, depositing and patterning polycrystalline Si, depositing a Si ₃ N ₄ film, forming a window by removing a partial region of the Si ₃ N ₄ film, HC from window
l gas to remove polycrystalline Si, and S
introducing a growth gas containing i to grow epitaxial Si on the SiO ₂ film from the seed.