JPS5833822A - Preparation of semiconductor substrate - Google Patents

Abstract

PURPOSE:To form stable single crystalline Si layer covering the whole area by irradiating light beam or electron beam to the polycrystalline or amorphous Si layer deposited on the silicon nitride film over the whole area. CONSTITUTION:The light beam or electron beam is irradiated to the polycrystalline or amorphous Si layer 3 entirely deposited on the Si nitride film 6 formed on the Si substrate 1 via the Si oxide film 2 formed as the basic layer. Thereby, the adequate region of power of irradiated beam used for stable single- crystallization for the whole area of the Si layer can be extended without disappearance of even a part of Si of the Si layer, because disappearance of silicon of the polycrystalline Si layer 3 can be prevented due to the existence of Si nitride film 6 between the Si oxide film 2 and the polycrystalline Si layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a semiconductor single crystal layer on an insulating film formed on a substrate. A semiconductor substrate on which a semiconductor single crystal layer is formed is called a "semiconductor substrate."

One method for increasing the operating speed and density of a semiconductor device is to reduce stray capacitance and narrow element spacing by forming element elements on an insulator. For this reason, K is
It is necessary to form a semiconductor single crystal on an insulator, and one conventional method for this purpose is to deposit polycrystalline silicon on a silicon oxide film, and then irradiate the surface with light from a flash lamp or a laser device. There is a method of heating the surface layer by irradiating it with electron beams to form a silicon single crystal layer. FIG. 1 shows a cross-sectional structure of a silicon substrate, which is a semiconductor substrate formed by such a method, at an intermediate manufacturing step. In Figure 1, ftl is a silicon substrate, (2) is a silicon oxide film, (3) is a polycrystalline silicon layer, (4) is a laser device, flash lamp or electron beam source, and (5) is a light beam or An irradiation beam consisting of an electron beam and irradiating a polycrystalline silicon layer +31K,
O) is a silicon substrate in an intermediate manufacturing process consisting of a silicon substrate 11), a silicon oxide film (2) and a polycrystalline silicon layer (3). The irradiation beam (5) typically scans the silicon substrate (100) optically, electrically, and/or optically to irradiate the entire surface of the silicon substrate (100).

The polycrystalline silicon layer (3) absorbs the radiation beam (61) and is heated. If the power of the radiation beam (6) is greater than a certain value, the polycrystalline silicon layer (3) melts and absorbs the radiation beam (61). Recrystallization occurs when heating is no longer achieved due to the movement or disappearance of 6).

If the power of the irradiation beam (5) is too large, the silicon in the polycrystalline silicon layer (3) will evaporate or scatter and disappear. is the illumination beam i with power in the appropriate range
ll must be used.

However, the appropriate power range of the irradiation beam (6) changes depending on the presence or absence of the underlying silicon oxide film (2) and its film thickness. If there is a structure due to this, the range of appropriate power becomes narrower. When sufficient power is irradiated to the part that is most difficult to melt, the polycrystalline silicon layer (6)
There was also a drawback that, when the easily melted parts were irradiated with appropriate power, the hard to melt parts did not melt and M crystallization was not possible.

This invention was made to eliminate the above-mentioned drawbacks, and uses polycrystalline or amorphous silicon deposited entirely on a silicon nitride film formed on a substrate with an underlying silicon oxide film interposed therebetween. By irradiating the layer with a light beam or an electron beam, it is possible to widen the appropriate value range of the power of the irradiation beam that can stably obtain a monocrystalline silicon layer over the entire surface without partially dissipating the silicon in the silicon layer. The purpose of this invention is to provide a method for manufacturing a semiconductor substrate that can be manufactured using the following methods.

Hereinafter, this originating TIA will be explained based on an example.

FIG. 2 is a diagram showing a cross-sectional structure of a silicon substrate in an intermediate manufacturing step of an embodiment of the method for manufacturing a semiconductor substrate according to the present invention. In Figure 2, +11 is a silicon substrate,
(2) is a silicon oxide film with a thickness of approximately 5000 A formed by thermally oxidizing the surface of the silicon substrate (1), and (6) is a silicon oxide film formed by plasma OvD on the silicon oxide film (2).
A silicon nitride film with a thickness of about 50 OA deposited by
3) t; t Polycrystalline silicon N with a thickness of 400 OA formed entirely on the silicon nitride film (6) by low pressure OVD method, (looa) h Silicon substrate (1), silicon oxide film (2), silicon It is a silicon substrate consisting of nitride (61) and a polycrystalline silicon layer (3).

The polycrystalline silicon layer (3) of the silicon substrate (100) shown in FIG. When irradiation was performed while scanning with an um argon laser at a scanning speed of 10 cm and 77 g, melting occurred at a power of about 10 W, and part of the silicon in the polycrystalline silicon layer (3) disappeared at 11 W. but,
In the silicon substrate (1001!L) shown in Fig. 2, the silicon nitride film (6) is interposed between the silicon oxide film (2) and the polycrystalline silicon layer (3), so it is the same as the case in Fig. 1. When the beam diameter and scanning speed are set to l.

Melting occurs with the power of W, and silicon in the polycrystalline silicon layer (3) does not disappear even with the power of 12 W.

FIG. 3 is a diagram showing a cross-sectional structure of a silicon substrate in an intermediate manufacturing step of an application example of the embodiment described using FIG. 2. In FIG. 3, the same reference numerals as in FIG. 2 represent the same parts as those shown in FIG. , (6a) is a silicon nitride film formed on the surface of the part of the silicon substrate (1) where the silicon oxide film (2a) is not formed and over the surface of the silicon oxide film (2a), (1001)) is Silicon substrate (1
), a silicon substrate consisting of a silicon oxide film (2aχ silicon nitride film (6a) and a polycrystalline silicon layer (3)).

For the silicon substrate (xo6b) shown in FIG. 3, in order to melt the polycrystalline silicon layer (3) on the left side,
Since a power of 11 W is required using an argon laser under the same conditions as in the embodiment described using FIG. 2, a polycrystalline silicon layer (loob) is 3) It is possible to stably recrystallize the entire surface to obtain a silicon single crystal layer.

In the above embodiment, the case of recrystallization by laser beam irradiation is shown, but the polycrystalline silicon layer may be single-crystallized by light beam irradiation with a flash lamp or electron beam irradiation.

Further, in the above embodiment, a case was described in which a polycrystalline silicon layer produced by a low pressure OVD method was made into a single crystal, but a polycrystalline or amorphous silicon layer produced by a normal pressure OVD method was used. can also be made into a single crystal in the same way.

As detailed above, in the method for manufacturing a semiconductor substrate according to the present invention, polycrystalline or amorphous silicon is formed entirely on a silicon nitride film formed on the substrate via a silicon oxide film. Since the layer is irradiated with a light beam or an electron beam to form a single crystal, the irradiation beam is used to stabilize and form a single crystal over the entire surface of the silicon layer without causing part of the silicon to disappear. The appropriate range of power can be expanded.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a cross-sectional structure of a silicon substrate in an intermediate manufacturing step of a conventional semiconductor substrate manufacturing method, and FIG. 2 is a cross-sectional view of a silicon substrate in an intermediate manufacturing step of an embodiment of a semiconductor substrate back manufacturing method according to the present invention. FIG. 3 is a diagram showing a cross-sectional structure of a silicon substrate in an intermediate manufacturing step of an application example of the present invention. In the figure, (1) is a silicon substrate (substrate), (21
. (2a) is silicon oxide film, (31Fi polycrystalline silicon layer (silicon layer), +61, (6a) is silicon 7
Nitride film, (100), (looa), (100b)
is a silicon substrate. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] +11 A polycrystalline or amorphous silicon layer formed entirely on a silicon nitride film formed on a substrate via a silicon oxide film is irradiated with a light beam or an electron beam to make the silicon layer into a single crystal. A method for manufacturing a semiconductor substrate, characterized in that: