JP2550998B2 - Method for forming single crystal silicon film - Google Patents

Description

The present invention relates to a method for forming a single crystal silicon film, in particular, a so-called SOI technique for forming a single crystal silicon film on an insulating film or an insulator such as an insulating substrate. The present invention relates to a method for forming a single crystal silicon film.

[Outline of Invention]

The present invention relates to a method for forming a single crystal silicon film by so-called SOI, in which nitrogen or carbon is contained in the insulator, but the first and third layers are formed of silicon layers containing 20 atomic% or less of these. , A single crystal silicon layer is sequentially formed so as to be arranged above and below a second layer made of an amorphous silicon layer, and heat treatment is performed to crystallize the single crystal silicon layer. A silicon film is obtained.

[Conventional technology]

So-called SOI technology for forming a silicon single crystal film on an insulating film or an insulating material such as an insulating substrate is disclosed in, for example, Semiconductor World (Semiconducto) published by Press Journal.
1985.4, pp. 108-115, the SOI technology has been rapidly put to practical use in the manufacture of various semiconductor devices.

As described above, when a single crystal silicon layer is formed by the SOI technique, when the recrystallization method by annealing, that is, heat treatment is used, the silicon layer is peeled off at the time of heat treatment, or ball-up, that is, graininess or agglomeration occurs and crystallinity or In order to prevent the deterioration of the film state, a SiO ₂ layer is formed as a cap layer on the silicon.
Lamination with a Si ₃ N ₄ layer is performed. Alternatively, a sandwich structure in which a Si ₃ N ₄ layer having a thickness of 50 Å or less is arranged above and below a silicon layer, and a SiO ₂ layer having a thickness of, for example, 2 μm is formed on the sandwich structure.
A layer, further the Si ₃ N ₄ layer cap layer of thickness 600Å deposited formed thereon, Si ₃ N ₄ containing nitrogen N of the sandwich structure
The layer improves the so-called wetting with the underlying SiO ₂ in the molten state during the recrystallization annealing of silicon, and effectively prevents graining or agglomeration of the silicon layer due to peeling, etc. Proposals for forming a so-called cap layer for forming a film have been described, for example, in Materiality Research Society Symposium Proceedings Vol. 53, 1986 Materialials Research.
Society Pages 45-51 (Materials Research Society
Symposium Proceeding Vol.53,1986, Materials Resear
ch Society) and pp. 53-58.

However, such a cap layer is provided and annealing for recrystallization thereof is performed, for example, an excimer laser (ultraviolet wavelength
(249 nm), the Si ₃ N ₄ film as the cap layer has a high absorption of this excimer laser light, so that the melting for crystallization in the silicon layer is not performed effectively, and the former method However, since the effect of improving the wettability of nitrogen N cannot be obtained, it is difficult to obtain the effect of preventing the formation of granular or agglomerated so-called agglomeration of the silicon layer. Further, when the sandwich structure of Si ₃ N ₄ of the latter method described above is adopted, although the above-mentioned agglomeration prevention effect can be obtained, in this case Si ₃ N 4
_{Since four} layers are used, the N content is as large as 57 atomic%, and it is difficult to control the film thickness, so that it is substantially difficult to control the total amount of nitrogen N. There is something. When such a large amount of nitrogen N is contained, it acts as a donor, so that the obtained single crystal silicon layer tends to be n-type, and when the amount of nitrogen N is large, the dangling bond is increased. The presence of a large amount of Al causes the inconvenience of preventing the appearance of, for example, a single crystal silicon layer having a (100) crystal plane. Further, if the thickness of the nitride film becomes large, problems such as cracks during annealing of itself will occur.

Further, it is conceivable to use carbon C instead of nitrogen N described above, but in this case also, although the inconvenience of the above-described action as the donor is avoided, the same problem remains with respect to other problems.

[Problems to be solved by the invention]

The present invention solves the above-mentioned problems and provides a method for forming a single crystal silicon film by SOI having good film properties and crystallinity with good controllability and reproducibility.

[Means for solving the problem]

In the present invention, the insulator (11) contains nitrogen or carbon in an amount of 20 atomic% or less, that is, Si _1-x N _x or Si _1-x C.
_A first layer (1) made of an amorphous silicon layer of _x (both 0 <x0.2) and a second layer (2) made of an amorphous silicon layer substantially not containing N or C. And a third layer (3) consisting of an amorphous silicon layer of Si _1-x N _x or Si _1-x C _x (both 0 <x0.2) containing 20 atomic% or less of nitrogen or carbon. Each layer (1) to (3) is formed by low-pressure vapor deposition CVD sequentially and continuously, that is, only by adjusting or changing the supply of the source gas in the same reaction chamber, and then heat treatment, that is, annealing treatment is performed to form the layers. (1)-(3)
Is recrystallized to form a single crystal silicon layer.

[Action]

According to the above-described method of the present invention, the layers (1), (2) and (3) are formed continuously, that is, only by the change of the raw material gas in the same reaction chamber. Therefore, between the layers (1) to (3) The generation and mixing of foreign matter is avoided, and the interfaces of the layers are formed well. Further, the silicon nitride layers (1) and (3) can surely control the mixing amount of nitrogen N and the thickness thereof, and the nitrogen content is set to 20 atomic% or less. The generation rate of dangling bonds can be reduced, a crystal plane having excellent film properties and crystallinity can be generated, and unnecessary generation of donors due to the presence of a large amount of nitrogen N can be avoided. Furthermore, it is possible to prevent the film thickness of both silicon nitride layers (1) and (3) from becoming larger than necessary, and to avoid the problem of cracks during heating.

In the present invention, the first and third Si _1-x N _x or S
In the i _1-x C _x layers (1) and (3), _x 0.2 means that when N exceeds 20 atomic%, dangling bonds are generated when a large amount of N or C mentioned above is mixed. In the case of N, a problem as a donor arises.

〔Example〕

For example, an amorphous silicon nitride Si _1-x N _x : H layer (1) is formed on an insulator (11) made of quartz, from 300 Å to 20 Å
Of 50 Å or less, preferably 50 Å or less, and then an amorphous Si: H layer (2) is formed thereon to have a thickness of 0.5 μm or less, and then the above-mentioned first A silicon nitride layer (3) having the same composition and thickness range as the silicon nitride layer (1) of No. 1 is continuously formed by the plasma CVD method or the photo CVD method.

The raw material gas of each of these layers (1) to (3) is used as a raw material for nitrogen N in N ₂ or NH 3 as an Ar or H ₂ carrier gas.
₃ and SiH ₄ or Si ₂ H ₆ as a raw material of silicon Si are vapor-deposited by vapor phase growth while changing the mixed amounts of these raw material gases at the required ratios.

Then, heat treatment is performed at 400 to 500 ° C. for 5 to 10 hours in an N ₂ atmosphere to discharge hydrogen H contained in each layer (1) to (3).

Then, as shown in FIG. 2, a SiN layer (5) is formed on the silicon nitride layer (3) as a capping layer through a SiO ₂ layer (4) of, for example, 1 μm or more, for example, 2 μm.
Å Apply to a thickness of about.

Then, when a single crystal layer is partially formed with a required pattern in a semiconductor device to be finally manufactured, each silicon layer (5) (3) (2)
The unnecessary portion of (1) is removed by plasma etching or the like to form a silicon layer having a predetermined pattern on the quartz insulator (11), and then heat treatment, that is, annealing, for example, zone melting method or continuous wave laser beam or pulse laser. Light, for example, pulse excimer laser light is irradiated to obtain a single crystal silicon layer in which the amorphous layers (1) to (3) are recrystallized.

Thereafter, if necessary, the SiO ₂ layer (4) and the SiN layer (5) as a capping layer are removed by etching to manufacture various semiconductors, for example, transistors and other semiconductor elements are formed to obtain a desired semiconductor device.

In the above example, each layer (1), (3),
(5) is the case of forming a layer containing nitrogen N, but Si _(1-x) C
It is also possible to set _x (0 <C0.2).

In addition, in the above-mentioned example, the case where the single crystal silicon film is formed on the insulator (11) made of a quartz substrate has been described, but the present invention is not limited to the quartz substrate and can be applied to various other insulating substrates. As a substrate, a SiO ₂ underlayer is formed on a single crystal substrate such as single crystal silicon or sapphire, a window is opened in this SiO ₂ underlayer, a silicon layer is formed on this, and the single crystal substrate is seeded. The present invention can be applied to various well-known SOIs, such as a method of growing a single crystal from this.

[Effects of the Invention] As described above, in the present invention, the method of mixing N or C into the amorphous silicon layer by CVD to obtain the single crystal layer is adopted, so that the amount of the mixing is accurately controlled. Therefore, it is excellent in reproducibility, and since each layer (1) to (3) is formed by continuous CVD, it is possible to avoid the inclusion of unnecessary contaminants at the interface of each layer, and to achieve high quality crystallization. It is easy to avoid such inconveniences, and because each of the layers (1) to (3) is an amorphous silicon layer, energy absorption efficiency can be easily increased when, for example, irradiation with excimer laser light is performed during annealing. It is melted, which brings about an effect that good quality recrystallization can be performed. Further, the content of N or C in each silicon (1) and (3) layer is small,
Further, since the thickness can be surely controlled, it is possible to avoid unnecessarily mixing a large amount of N or C, and for example, the amount of dangling bonds is increased or cracks are generated during annealing. This avoids the inconvenience. Further, many effects can be brought about, such as generation of a donor when nitrogen N is present in a large amount, that is, prevention of n-type conversion of the single crystal silicon layer.

The above-mentioned effect is obtained when the mixing amount of carbon or nitrogen in the first and third layers (1) and (3) is 0 <x0.2, or more effectively, the thickness is If the thickness of these layers (1) and (3) is less than 20Å, controllability problems may occur. Therefore, it is desirable that the thickness is 300Å to 20Å.

[Brief description of drawings]

FIG. 1 and FIG. 2 are schematic linear enlarged cross-sectional views of respective steps for explaining the method for forming a single crystal silicon film according to the present invention. (11) is an insulator, (1) and (3) are first and third layers made of amorphous silicon containing N or C, and (2) is a second layer made of amorphous silicon. .

Claims (1)

(57) [Claims] 1. A first layer comprising an amorphous silicon layer containing nitrogen or carbon at 20 atomic% or less, a second layer comprising an amorphous silicon layer, and 20 nitrogen or carbon on an insulator. A single crystal silicon layer is formed by sequentially and continuously forming a third layer made of an amorphous silicon layer containing not more than atomic% and crystallizing the first to third layers by heat treatment. And a method for forming a single crystal silicon film.