JPH024559B2 - - Google Patents

Description

Detailed Description of the Invention The present invention involves growing a polycrystalline layer such as polysilicon or an amorphous layer on a thermal oxide film provided on a single-crystal silicon substrate, and growing the polycrystalline layer or the amorphous layer in a single layer. The present invention relates to a single crystallization method for crystallization, and particularly to a method for single crystallizing a silicon wafer to obtain a single crystal layer over a wide area.

It is well known that single crystallization is achieved by irradiating an amorphous silicon layer or a polycrystalline silicon layer with an energy beam such as a pulsed laser.

Furthermore, forming a single crystal layer on an oxide film substrate is known as disclosed by Smith et al. in Appl. Phys. Lett. 35 1979.71. In the experiment by Smith et al., polycrystalline silicon was patterned into stripes (2 μm wide x 20 μm long) on an oxide film (SiO ₂ ), and a CW argon ( ^Ar It was shown that when the stripe is scanned and melted in the length direction, it easily becomes a single crystal with a (100) plane orientation even though there is no seed crystal (crystal nucleus). However, it was not always possible to obtain (100), and it was not possible to form a single crystal over a wide area.

On the other hand, when polycrystalline silicon is in contact with a single crystal such as a silicon substrate, it begins to melt from that part, and the polycrystalline silicon on the oxide film (SiO ₂ ) also forms a single crystal with the same crystal orientation as the original single crystal. It is also known that it can be grown. A conventional example of such lateral epitaxy is shown in the first example.
This will be explained based on the diagram.

In FIG. 1, a thermal oxide film (SiO ₂ ) is obtained on a single crystal wafer 1 of a P-type silicon substrate (100) by heat treatment (1000° C. for 40 minutes). The oxide film 2 is 0.5
Form to ~1μ thickness. Next, a window 3 is formed in the oxide film by photo-etching or the like, and CVD (chemical vapor deposition) is performed on the wafer 1 and the oxide film 2 in which the single crystal surface of the silicon substrate is partially exposed.
The polycrystalline silicon A is grown to a thickness of about 0.5μ by the method, and then by irradiating and scanning the CW argon laser 5 in the X-axis direction, the polycrystalline layer 4 is grown using the window opening 3 as a seed. Through crystallization, the polycrystalline layer on the oxide film 2 is also converted into a single crystalline layer having the same plane orientation as the silicon substrate 1, 100. When using the above-mentioned single crystallization method, single crystallization progresses only in the very vicinity of the window opening 3, and there is a drawback that single crystallization cannot be performed over a wide area.

For example, for solar photovoltaic and VLSI substrates, there is a requirement to grow single crystal silicon over a wide oxide film range.

If the conventional method shown in FIG. 1 is used to form a single crystal over such a wide area, window openings must be provided all over the wafer, making it impossible to pattern many patterns on the wafer. It creates a defect that disappears.

The present invention provides a method for single-crystallizing a silicon wafer that eliminates the above-mentioned drawbacks, and is characterized by forming an insulating layer on a single-crystal silicon wafer, and forming a plurality of adjacent layers on the insulating layer. A striped polycrystalline layer or an amorphous layer is provided, and the striped polycrystalline layer or amorphous layer is irradiated parallel to the striped polycrystalline layer or the amorphous layer. The amorphous layer is made into a single crystal,
This method includes a step of growing a polycrystalline layer or an amorphous layer again on the entire surface of the wafer, irradiating it with energy rays, and scanning it to make the entire surface of the insulating layer into a single crystal.

Hereinafter, details of one embodiment of the present invention will be explained with reference to FIGS. 2 and 3.

As shown in FIG. 2A, a silicon single crystal P-type substrate 1
An oxide film 2 of silicon dioxide (SiO ₂ ) is grown to a thickness of about 1 μm on the 00 wafer 1 by heat treatment. (FIG. 2B) Next, as shown in FIG. 3A, window openings are patterned on the scribe line 3a. FIG. 2C shows a cross section taken along the line A-A in FIG. 3A, and the scribe line 3a may be exposed up to the surface of the single crystal nucleus of the substrate 1, or may be patterned halfway through, for example, by hydrofluoric acid etching. The oxide film 2 is etched with a liquid.

Next, polycrystalline silicon 4a having a thickness of 2000 Å is grown on the entire surface of the patterned insulating oxide film 2 as shown in FIG. 3A by CVD (FIG. 2D). Next, the polycrystalline silicon layer 4a is patterned as shown in FIG. 3B. That is, the stripes 4a are selectively etched using a nitric-fluoric acid-based etching solution, for example, with a width of 2 .mu.m and an interval of 2 .mu.m between the stripes.

The BB cross section of FIG. 3B is the cross-sectional view shown in FIG. 2E, and the stripes 4a are patterned in a direction perpendicular to the core opened on the scribe line,
and parallel to the stripe, i.e. stripe 4a
An energy line 5 such as a pulsed or CW argon laser is scanned along the X-axis direction. In this way, the stripe 4a becomes a single crystal with the same orientation as the wafer 1. That is, the window opening 3 on the scribe line
A striped polycrystalline silicon layer 4a arranged perpendicularly to the line of the nucleus with a as a nucleus is single-crystallized to become a striped single-crystalline layer. Next, as shown in FIG. 2F, a polycrystalline silicon layer 6 is grown in a vapor phase to a thickness of 3000 Å over the entire surface of the wafer including the striped single crystal layer 4a, and is irradiated with an energy beam 5. The scanning direction in this case may be parallel to the stripes or perpendicular to them. That is, in this case, the single crystal serving as the nucleus is formed in the stripe 4a shape at the lower end of the polycrystalline layer 6, so when the polycrystalline layer melts and becomes single crystal by energy beam irradiation, the nucleus is at the lower end. Therefore, the entire surface 100 can be easily made into a single crystal. Moreover, in this case, the polycrystalline layer 6 is melted and redissolved, so that the surface is made smooth.

As described above, the present invention has the feature that a polycrystalline layer or an amorphous layer on an insulating oxide film can be made into a single crystal over a wide range and the surface can be made flat.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a wafer for explaining the conventional method for single crystallizing a silicon wafer, and FIGS. 2 A to F are each step of the wafer for explaining the method for single crystallizing a silicon wafer of the present invention. FIGS. 3A and 3B are plan views showing each process of the wafer for explaining the method for single crystallizing a silicon wafer of the present invention. 1... Wafer, 2... Oxide film, 3... Window opening, 4...
Polycrystalline silicon layer, 5... Energy beam such as laser, 3a... Window opening provided in scribe line,
4a...Striped polycrystalline silicon.

Claims (1)

[Claims] 1. An insulating layer is formed on a single crystal silicon wafer, and a plurality of adjacent striped polycrystalline layers or amorphous layers are provided on the insulating layer, and parallel to the striped polycrystalline layers or amorphous layers. The striped polycrystalline layer or amorphous layer is made into a single crystal by the energy beams irradiated and scanned, and then the polycrystalline layer or amorphous layer is grown again on the entire surface of the wafer, and then the energy beams are applied. A method for single-crystallizing a silicon wafer, comprising the steps of irradiating and scanning to single-crystallize the entire surface of an insulating layer.