JPS62111416A - Method for forming monocrystalline thin film - Google Patents

Abstract

PURPOSE:To form a monocrystalline thin film without introducing a grain boundary or crystal defect by forming films in the shape of a convex lens transparent to a laser beam on a polycrystalline thin film, and applying a laser thereto. CONSTITUTION:On a polycrystalline thin film, a plurality of striped convex lenses composed of a film transparent to a laser light such as silicate glass or borophoscate glass, and scanning by a laser beam 4 is applied between a plurality of striped films 5. In the 10mum-wide region in the gap between the convex lenses, a recrystallized monocrystalline thin film can be formed which contains no grain boundary or crystal defect.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for forming a single crystal thin film.

BACKGROUND OF THE INVENTION In recent years, semiconductor circuit elements have become extremely dense and highly integrated, and their performance has become extremely high. However, it is predicted that two-dimensional integration will reach its limit in the near future, and three-dimensional circuit elements have been proposed that enable three-dimensional integration. In order to realize this three-dimensional circuit element, the method of forming a single-crystal thin film on a single-layer film has become a very important technology.

Hereinafter, a conventional method for forming a single crystal thin film as described above will be described with reference to the drawings.

FIG. 2 shows a cross-sectional view for explaining the steps of a conventional method for forming a single crystal thin film. In FIG. 2, 1 is an St substrate, 2 is a 5102 film, 3 is a polySt film, and 4 is a laser beam. In this method, the laser beam 4 is used to
When the Jsj film 3 is irradiated, the Bo1Jsi film 3 melts and when solidified again a single crystal thin film is obtained.

Problems to be Solved by the Invention However, in the above configuration, the intensity distribution of the laser beam 4 is a Gaussian distribution, and the temperature distribution of the irradiated area is also high at the center and low at the edges, so that the crystal Since the growth progresses from the edges of the irradiated area to the center, the formed recrystallized film is greatly influenced by both ends of the irradiated area, and has the disadvantage of containing many grain boundaries and microscopic crystal defects. .

In view of the above drawbacks, the present invention provides a method for forming a single crystal thin film that does not contain grain boundaries or crystal defects.

Means for Solving the Problems In order to solve the above problems, the method for forming a single crystal thin film of the present invention provides a method for forming a single crystal thin film by applying a film transparent to laser light to a convex lens on a polycrystalline film to be recrystallized. A plurality of lenses are formed in the shape of a convex lens, and a laser beam is irradiated between the convex lens-shaped films.

Function: In this configuration, the film formed on the polycrystalline film that is transparent to the laser beam acts as a laser beam prevention film and also has a lens effect, so that the film does not contain the laser beam. Since it collects light, it works to increase the temperature at the end. This film also functions to keep the ends warm during the cooling process.

Due to these two functions, crystal growth progresses from the center to the edges, and therefore, grain boundaries and crystal defects are introduced into the recrystallized film in the region between the convex lens-shaped films. It will not be done.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a process sectional view of a method for forming a single crystal thin film in an embodiment of the present invention. In Figure 1, 1
is a Si substrate, 2 is a SiO2 film, 3 is a poly-Si[,4
5 is a laser beam, and 5 is a borophosphate glass (BPSG) film. The manufacturing process will be briefly explained below. A P-type Si substrate 1 having a specific resistance of 6 Ω·cm and a (100) orientation is thermally oxidized at 1000° C. in wet Q2 for about 5 hours to grow an SiO2 film 2 with a thickness of about 1 μm. Subsequently, SiH4 gas is thermally decomposed at 600° C. using a low-pressure CVD apparatus to deposit a poly-Si film 3 with a thickness of about 0.5 μm. Thereafter, a BPSG film having a B# degree of 4 wt% and a P concentration of 4 wt% is deposited to a thickness of 0.5 μm at a total atmospheric pressure CV D f of 430°C. The BPSG film 5 is formed into lines (6 μm) and spaces (10 μm) using photolithography technology and dry etching.
m) to form a striped pattern with a width of 5 μm, and
Heat treatment was performed for three films in wet O2 at 50°C, and B
The PSG film 5 is flowed to form a striped lens. After this, the area between the striped lenses was scanned with a C'W argon laser. Laser power is aW
, the scanning speed was 10 crn/S.

As described above, according to this example, by forming a film transparent to laser light in the shape of a convex lens on a polycrystalline film and performing laser irradiation, particles can be formed in a region with a width of 10 μm in the gap between the convex lenses. A recrystallized single crystal thin film containing no fields or crystal defects can be formed.

Note that in this example, the lens under the polycrystalline film was formed of BPSG, but this is not limited to BPSG.
Any material may be used as long as it is transparent to laser light.

Effects of the Invention As described above, the present invention forms a film transparent to laser light in the shape of a convex lens on a polycrystalline thin film, and then irradiates the film with laser light, without introducing grain boundaries or crystal defects. A single crystal thin film can be formed, and its practical effects are impressive.

[Brief explanation of drawings]

FIG. 1 is a process cross-sectional view of a method for forming a single crystal thin film according to an embodiment of the present invention, and FIG. 2 is a process cross-sectional view of a conventional method for forming a single crystal thin film. 1...Si substrate, 2...SiO2 film, 3
...Poly-Si film, 4...Laser light, 6.
...BPSG film.

Claims (3)

[Claims] (1) A step of forming a plurality of striped convex lenses made of a film transparent to laser light on a polycrystalline thin film, and a step of scanning at least between the plurality of striped films with a laser light. A method for forming a single crystal thin film, comprising: (2) As a film transparent to laser light, silicate
A method for forming a single crystal thin film according to claim 1, characterized in that glass is used. (3) The method for forming a single crystal thin film according to claim 1, characterized in that borophosphate glass is used as the film transparent to laser light.