JPH02208920A - Soi structure forming method - Google Patents

Abstract

PURPOSE:To extend the distance of growth in lateral direction, and to form a single crystal Si film having low density of impurities by a method wherein undoped amorphous Si film is formed on a P-doped amorphous Si film, and an annealing treatment is conducted thereon. CONSTITUTION:An SiO2 film, having an aperture part 2' where a part of surface of a substrate 1 is exposed, is formed on a single crystal Si substrate 1, a first P-doped a-Si film 3 is deposited thereon, a second undoped a-Si film 4 is deposited on the a-Si film 3, and an annealing treatment is conducted. As a result, the crystal orientation is inherited, an a-Si film 3 is solid-phase grown, and a single crystal Si film 4' is formed. As the solid-phase growing process is conducted at a relatively low temperature, an automatic doping of impurities on the a-Si film 4 is suppressed, and after the extension of growth distance in lateral direction has been contrived by P-doping, a single crystal Si film 4', having low density of impurities on the surface, can be formed.

Description

[Detailed Description of the Invention] A) Industrial Field of Application The present invention is directed to silicon on
The present invention relates to a method of forming a Si film using an in-phase growth method.

(Example) Conventional technology A structure in which a single crystal S1 layer is formed on an insulating layer (including an insulating substrate) is called an SOI structure, which allows for easy element isolation in a narrow area and allows for higher integration and higher speed. iir#, also known as nanano. Furthermore, research and development are being actively conducted on semiconductor integrated circuits (ICs) because they offer improved characteristics compared to conventional semiconductor integrated circuits (ICs) in which elements are fabricated on a Si substrate.

There is an in-phase growth method to form a single crystal Si film on an insulating layer, and this method involves growing an insulating film on the side of a single crystal Si substrate by exposing a part of the Si substrate surface onto the insulating film as a seed. Amorphous Si (hereinafter a-5) is formed on the seed and insulating film.
By depositing a film (referred to as i) and annealing it at a low temperature of about 600'C, the a-3i film is made into a single crystal by growing in phase in the lateral direction of i.

One way to extend the lateral growth distance in solid phase growth is to implant P+ ions at a high concentration into the a-3i film on the insulating film and then perform an annealing process (Exte
Abstracts of the 16t
h Conference on 5olid 5t
ateDevices and Materials
, Kobe, 1984. I) p, 507-51
(see 0).

c) 5! However, in order to increase the lateral growth distance, P4 ions are doped at a high concentration of 3 x 10"an-", so the impurity (P) in the solid phase grown single crystal Si film is ) concentration became extremely high, making it difficult to fabricate a semiconductor device on this solid-phase grown single crystal 5iill.

It is also being considered to epitaxially grow a single crystal Si film on a solid-phase grown single crystal Si film doped with P at a substrate temperature of about 800°C to form a Si film with a low impurity concentration. However, due to auto-doping during epitaxial growth and solid-phase diffusion during the process of forming a bare metal, the impurity concentration on the surface of the epitaxially grown Si film exceeds I x IQ cm-', and as expected, one semiconductor It was unsuitable for making devices.

Means for Solving the Problems The present invention provides a step of forming an insulating layer on a single crystal Si base having an opening through which a part of the surface of the single crystal Si base is exposed; A step of forming a first a-3i film doped with P on the exposed surface of the single crystal Si base and the insulating layer, and a second *-3i film doped with no impurity on the first a-S i H. 8i film forming step and the first
This is a method for forming a SOttlI structure, which comprises an Il step in which a second a-5i film and a second a-5i film are annealed and grown in the same phase.

e) Forming a second a-Si film not doped with impurities on the first a-Si film doped with action (2);
When these a-3i films are annealed and grown as solid Flls, they inherit the crystal orientation of the single-crystal Si base and become the first a-3i films.
The film is grown in solid phase and then a second a-8i film is grown in solid phase. Since solid-phase growth is a relatively low-temperature process, the second
Autodoping of impurities in the a-5i film is difficult to occur, and a single crystal Si film with a low impurity concentration on one surface is formed by increasing the lateral growth distance by P doping.

f) Embodiment FIGS. 1A to 1E show schematic diagrams of a first embodiment of the present invention. In this embodiment, a single-crystal Si substrate is used on a single-crystal Si base, but a single-crystal Si film formed on the substrate may also be used.

(1) is a single-crystal Si substrate with a (100) plane as the main surface, and a SiO* film (2) with a thickness of about 1000 layers is coated by CVIJ on its surface as an insulating layer. (The SiOs film may be formed by direct thermal oxidation of the 81 substrate.) (FIG. 1A).

Then, stripe-shaped openings (2゛) are formed in the <100> direction of the single crystal 81 substrate (1).

11'7. (2) A pattern is formed using photolithography technology (FIG. 1B).

Next, an a-5i film is formed over the entire surface by CVD.

First, cleaning the surface on which the a-5i film is formed, especially the surface of the single crystal Si substrate rt) exposed at the opening (2°) (i.e., seed, hereinafter referred to as seed (1')). Do this. The substrate is installed in a low pressure CVD apparatus (not shown), and 1
The substrate temperature was raised to approximately 550°C in a vacuum chamber on a 0-'T orr stage, and while the temperature was maintained, Ar gas was introduced into the reaction chamber (
Flow rate 150cc7 n+in, Ar partial pressure 65mT
orr) L, 13.56 MHz using RF oscillator
Ar plasma is generated by applying RF. The RF high output at this time is about 5 (1 W) (70 W). Then, a negative voltage of about 50 to 100 V is applied to the substrate to cause Ar+ ions to collide with the surface to perform sputter cleaning. The sputtering time required for cleaning is 5
It takes about a minute.

When cleaning with Ar+ ions is completed, t'r
r gas, RF high power bias application is stopped, and Sl[1,
The P-doped first
The a-Si film (3) is deposited (FIG. 1C).

At this time, the substrate temperature is maintained at 550° C., and a film thickness of about 5000 layers is deposited at a deposition rate of about 100 layers/min.

After forming the first a-3i film (3) for about 5,000 people, P
Stop the supply of H, gas, and apply SiH, gas for 200 s (・c
By flowing only ffl, the second a-5 illi (4) which is not doped with impurities (non-doped) is connected to the first a-5
i-film (3) (FIG. 1D).

At this time, the substrate temperature was maintained at 550°C, and If
At an f-A rate of about 250 layers/min, a thickness of about 5000 layers is deposited to form the desired device.

After the formation of the second a-8i film (4), the 5it-
1. Stop the gas supply and supply only nitrogen gas to 11z'mi.
The substrate temperature was raised to 6)1)°C and held for 12 hours for annealing.'2

Through this annealing treatment, first, the first a-Si film (3) inherits the crystal orientation of the seed (1') (the crystal orientation of the single crystal 81 substrate (1)) and grows in a solid phase to form +B crystals. S model 3°). Since the first a-5i film (3) is doped with P, the lateral growth distance is long, and the single crystal S (3°) grows in phase over a wide area. Next, a second a-8illi (4) is grown in solid phase using the solid phase grown single crystal Si film (3') as a seed, and the single crystal Si film (3') is then grown in solid phase.
A single crystal Si film (4°) having approximately the same width as 3) is formed (FIG. 1E).

In solid phase growth, since the substrate temperature is about 600°C, impurity doping from the single crystal Si film (3') (first a-5i film) to the single crystal Si film (4'') does not occur much. Therefore, the single crystal Si film (4°) has a low impurity concentration.

g) Effects of the Invention As is clear from the above description, the present invention is to form a second a-3r film not doped with impurities on a first a-5i film doped with P, and then perform an annealing treatment. By doping with P, the lateral growth distance of the a-Si film model is extended, and a single crystal Si film with a large area is obtained, and a single crystal Sr film with a low impurity concentration is obtained. Further, it is possible to provide a substrate with a Sol structure suitable for manufacturing semiconductor elements, and it can contribute to higher integration and improved characteristics in semiconductor integrated circuits.

[Brief explanation of the drawing]

FIGS. 1A to 1E are process explanatory diagrams of an embodiment of the present invention. (1)...Single crystal Si substrate (single crystal Si base) (l゛)...Seed, (2)...Sin, film (insulation 11.
λ), (2°)...opening part, (3)...first a-
51 film, (3゛)...Single crystal Si film, (4)...Second a-3i film, (4')...Single crystal Si film Applicant Sanyo Oki Co., Ltd. Representative Patent attorney Master Takuji Nishino and 2 others

Claims (1)

[Claims] (1) Forming an insulating layer on a single-crystal Si base having an opening through which a part of the surface of the single-crystal Si base is exposed; a step of forming a first amorphous Si film doped with P on the insulating layer; a step of forming a second amorphous Si film not doped with impurities on the first amorphous Si film; . A method for forming an SOI structure, comprising the steps of annealing a first amorphous Si film and a second amorphous Si film to grow them in a solid phase.