JPH0282518A - Manufacture of semiconductor single crystal layer - Google Patents

Abstract

PURPOSE:To contrive improvement and the like of characteristics of an element by forming grooves in a silicon thin film in the direction that is parallel to a beam scanning direction and separating silicon thin film into several parts before performing a fusion-recrystallization process, thereby forming a protective insulating film in the grooves and on the silicon thin film. CONSTITUTION:An SiO2 film 11 of 2mum thickness is deposited on a face-oriented single crystal silicon substrate 10 by a CVD process and then, an opening 12 which acts as a seed in the case where recrystallization is performed is formed by the use of the water solution of ammonium fluoride. Then a polycrystal silicon film 13 of 0.4mum thickness is deposited on the SiO2 film 11 and in the opening 12 by the CVD process in which the thermal decomposition of silane is used. Subsequently, grooves 14 are formed in the silicon film 13 by the use of reactive ion etching to separate the polycrystal silicon film 13 into stripes in such a way that each stripe is 30mum or less in width and the stripes are spaced about 2mum apart. The manufacturing work of this element is thus completed by forming an SiO2 film 15 of 0.5mum thickness on the silicon film as a protective insulating film. Therefore, no silicon is cohesive when it is molten through the irradiation of electron beam.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a technique for forming a semiconductor single crystal layer on an insulating film, and particularly to a method for manufacturing a thin semiconductor single crystal layer (thickness of 4000 Å or less).

(Prior art) Conventionally, S OI (Slicon On In5ul)
To manufacture a semiconductor single crystal layer such as a silicon substrate, a polycrystalline silicon film 43 deposited on an insulating film 41 on a silicon substrate 40 is melted by scanning an energy beam 46 as shown in FIG. A method is used in which the silicon film 43 is made into a single crystal by lateral epitaxial growth using the silicon film 40 as a seed crystal. At this time, silicon single crystal layer 4
In order to ensure the uniformity of the polycrystalline silicon film 43, the polycrystalline silicon film 43 is generally formed to have a thickness of 6000 Å or more. Further, a protective insulating film 45 is formed on the polycrystalline silicon film 43 to prevent silicon from evaporating or the like.

On the other hand, when forming an element, the thinner the semiconductor single crystal layer is, the better the characteristics of the element will be.
The single crystal layer of 000 Å or more is made thinner by etching. However, the etching method has the problem that it is difficult to control the film thickness, and that element characteristics deteriorate due to damage caused by etching.

As a method of obtaining a single crystal layer of 4000 Å or less, which is expected to improve device characteristics, a method of recrystallizing a silicon thin film of 4000 Å or less from the beginning maintains uniformity of the film thickness and does not cause crystal defects later. It is preferable from the following points.

However, when melting and recrystallizing a polycrystalline silicon film using an energy beam, if the thickness of the molten silicon is less than 4000 Å, agglomeration of the molten silicon is likely to occur due to surface tension or the like. Therefore, the problem arises that the molten silicon may peel off, making it difficult to continue the lateral epitaxial crystal growth.

(Problem to be Solved by the Invention) Conventionally, when manufacturing a silicon single crystal layer on an insulating film, when the silicon thin film before recrystallization becomes thin, the silicon layer peels off due to agglomeration of molten silicon, etc. Therefore, it has been difficult to manufacture a thin (less than 4000 Å) silicon single crystal layer on an insulating film.

The present invention has been made in consideration of the above circumstances. [Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to separate a silicon thin film to be made into a single crystal into strips and hold it with an insulating film. By increasing the force, the energy beam can melt and melt silicon without agglomerating it.
It consists in recrystallization.

That is, the present invention provides a method for manufacturing a semiconductor single crystal layer in which a polycrystalline or amorphous silicon thin film deposited on a silicon substrate via an interlayer insulating film is melted and recrystallized by scanning with an energy beam such as an electron beam. In this step, before the melting recrystallization step by scanning the energy beam, grooves are formed in the silicon thin film in a direction parallel to the beam scanning direction to separate the thin film into strips, and the silicon thin film is formed in the grooves and on the silicon thin film. This method involves forming a protective insulating film.

(Function) When a silicon thin film is made into a single crystal, if a wide area of the thin film is melted by an energy beam, the silicon thin film with a thickness of 6000 Å or less tends to aggregate due to surface tension or the like. In the present invention, it is a characteristic diagram showing the yield rate when a SiFCON single crystal layer is formed by scanning with an electron beam using a conventional method using grooves in a silicon thin film. The non-defective rate is the rate at which a predetermined element is formed on a manufactured silicon single crystal layer and the element exhibits an acceptable performance or higher. From this figure, the film thickness is 6
When the thickness is less than 000 Å, the yield rate decreases, and the film thickness is 4000 Å.
As you can see below, the non-defective product rate is extremely low. This decrease in the yield rate is due to interruption of lateral epitaxial growth due to aggregation of silicon. Note that even if various conditions of the electron beam are changed, the above characteristic curve only slightly slides left and right, and the shape of the characteristic curve hardly changes.

In addition, the gap between silicon thin films, which had a very low yield rate with a film thickness of 4,000 Å or less, has been reduced to 4,000 Å or less by reducing the gap to 2 μm or less, which does not change the thermal conditions when melting silicon. Single crystallization of a silicon thin film with a thickness of 6000 Å or more can be performed stably in the same way as single crystallization of a silicon thin film with a thickness of 6000 Å or more.

FIG. 3(a) shows that as the thickness of the polycrystalline silicon film decreases, the yield rate decreases, and when the thickness is 50 μm or more, there is not much difference from the conventional method. However, if the width is less than 30μm, 1009
It can be seen that the good product rate is close to 6.

Therefore, the present invention is particularly effective for melt recrystallization of silicon thin films with a thickness of 4000 Å or less, and it is desirable that the width of the separated silicon thin film is 30 μm or less.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a sectional view showing a sample structure for explaining a method according to an embodiment of the present invention. To form this sample, first, a CVD process was performed on a single crystal silicon substrate 10 with a plane orientation (100).
A 5 in 2 film (interlayer insulating film) 11 having a thickness of 2 μm is deposited by a method, and an opening 12 that will serve as a seed during recrystallization is formed in this St, 2 film 11 using an ammonium fluoride aqueous solution. Then, CVD using thermal decomposition of silane (SiH4)
By the method, a thickness is
A 0.4 μm polycrystalline silicon film (silicon thin film) 13 is deposited. Next, grooves 14 are formed in the silicon film 13 using reactive ion etching, and the polycrystalline silicon film 13 is
is divided into stripes with a width of 30 μm or less (for example, 20 μm) and an interval of about 2 μm. Furthermore, this is realized by forming a 5in2 film 15 with a thickness of 0.5 μm as a protective insulating film thereon.

When this sample is scanned with an electron beam (energy beam) 16 in the direction of the arrow in the figure, the polycrystalline silicon film 13 separated into stripes melts and recrystallizes, thereby forming a silicon single crystal layer 17. be done. At this time, molten silicon did not aggregate and it was possible to stably continue lateral epitaxial growth from the opening 12.

As the electron beam 16, a pseudo-linear beam obtained by deflecting a point beam at high speed in a direction perpendicular to the scanning direction was used (T,
Hamasaki et al., J., Appl., Ph.
ys, 59 (1986) 2971. ), i.e. 38
The half width is approximately 150 μm due to the MHz amplitude modulated sine wave.
By deflecting the spot beam in one direction at high speed,
The spot beam is pseudo-linearized to a length of about 5 mm, and a modulation wave with a computer-controlled waveform is used for amplitude modulation to equalize the longitudinal intensity distribution of the linearized beam at a frequency of 10 KHz. there was. This linearized electron beam was scanned in a direction perpendicular to the linearized beam at a beam acceleration voltage of 12 KV, a beam current of 9.5 mA, and a scanning speed of 100+ua/s.

After the polycrystalline silicon film 13 was made into a single crystal in this manner, the uppermost 5i02 film 15 was removed using 10% hydrofluoric acid. At this time, the 5in2 film 11 under the recrystallized silicon single crystal layer 17 is not etched, and the film thickness is 0.4 μm.
It was possible to obtain a silicon single crystal layer 17 of m. In addition,
Substantially similar results were obtained even when the polycrystalline silicon film 13 had a thickness of 3000, 2000, or 1000.

Thus, according to the method of this embodiment, the polycrystalline silicon film 13
Since grooves 14 are provided to separate the corrugated film 13 into strips and each strip of silicon film 13 is held by the 5i02 film 15, aggregation of silicon will not occur during melting by electron beam irradiation. Therefore, even a thin polycrystalline silicon film with a thickness of 4000 Å or less can be stably turned into a single crystal like a silicon film with a thickness of 6000 Å or more. Furthermore, compared to the conventional method in which etching is performed to reduce the film thickness after single crystallization, this method has advantages such as better uniformity of the film thickness of the silicon single crystal layer and no damage caused by etching.

FIG. 2 is a sectional view for explaining another embodiment of the method of the present invention. Note that the same parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

This embodiment differs from the previously described embodiments in the pattern of the grooves formed in the silicon thin film. That is, a groove 24 basically parallel to the beam scanning direction is formed in the polycrystalline silicon film 13, and a portion of this groove 24 is formed in a meandering manner. As a result, the silicon film 13 separated into strips forms a continuous pattern of irregular width.

When such a sample was beam annealed in the same manner as in the previous example, the polycrystalline silicon film 13 could be stably made into a single crystal without causing silicon aggregation. Therefore, this embodiment also provides the same effects as the previous embodiment. In addition, in this embodiment, depending on the area occupied by elements to be formed later on the recrystallized silicon single crystal layer 17,
By determining the separation pattern of the polycrystalline silicon film 13, it is also possible to make effective use of the chip area.

Note that the present invention is limited to the above-described embodiments, but it is also possible to use a light beam instead of an electron beam.

Furthermore, a silicon nitride film can be used instead of the silicon oxide film as the interlayer insulating film or the protective insulating film. Furthermore, hot phosphoric acid or the like can be used instead of hydrofluoric acid for etching the insulating film. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, the silicon thin film to be single-crystalized is separated into strips and the holding power of the insulating film is increased, thereby preventing the silicon from agglomerating (uniformly using an energy beam). It can be melted and recrystallized.

Therefore, a thin (4000 Å or less) silicon single crystal layer can be manufactured on the insulating film, which can contribute to improving device performance.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a sample structure for explaining one embodiment of the method of the present invention, FIG. 2 is a cross-sectional view for explaining another embodiment of the method of the present invention, and FIG. 3 is a recon film ( 14.24...Groove, 15...5in2 film (protective insulating film), 16...Electron beam, 17...Silicon single crystal layer.

Claims (3)

[Claims] (1) A method for manufacturing a semiconductor single crystal layer in which a polycrystalline or amorphous silicon thin film deposited on a silicon substrate via an interlayer insulating film is melted and recrystallized by scanning an energy beam, Before the step of converting into silicon, a groove is formed in the silicon thin film in a direction parallel to the beam scanning direction to separate the thin film into strips, and a protective insulating film is formed in the groove and on the silicon thin film. A method for manufacturing a semiconductor single crystal layer. (2) The thickness of the silicon thin film is set to 4000 Å or less, and the width of each silicon thin film separated into strips is set to 3
2. The method for manufacturing a semiconductor single crystal layer according to claim 1, wherein the distance is set to 0 μm or less and the interval is set to 2 μm or less. (3) The method for manufacturing a semiconductor single crystal layer according to claim 1, wherein a pseudo-linear electron beam is used as the energy beam.