JPS60127294A - Device for modifying shape of beam - Google Patents

Abstract

PURPOSE:To form a high-quality single crystal film having large crystal particle size, by dividing a light beam into ordinary ray and extraordinary ray with a birefringence plate, and placing an element to deflect the direction of the polarization plane of ordinary ray or extraordinary ray by a specific angle to the emission side of the birefringence plate. CONSTITUTION:The laser beam 1 is divided into the ordinary ray 3 and the extraordinary ray 4 by passing through the birefringence plate 2. The ordinary ray 3 is a linearly polarized light having an electric field oscillating perpendicular to the plane of the paper, and the extraordinary ray 4 is a linearly polarized light having an electric field oscillating parallel to the plane of the paper. The plane of polarization of the ordinary ray 3 is different from that of the extraordinary ray 4 by 90 deg.. Accordingly, when the phase of the extraordinary ray is shifted by 180 deg. by passing the ray through the half- wave plate 5, the plane of polarization of the extraordinary ray is deflected by 90 deg., and the extraordinary ray 4 is converted to the linearly polarized light 6 having an electric field oscillating perpendicular to the plane of paper similar to the ordinary ray 3. An ordinary ray 3 and a linearly polarized ray 6 having the same plane of polarization can be obtained by this process, and the obtained light beam has double-humped cross-section.

Description

[Detailed Description of the Invention] The present invention relates to a laser heating method for heating a sample substrate using a laser beam, and it is possible to easily obtain a laser beam shape particularly suitable for forming a single crystal film. Relating to a beam shaper.

The single-crystal film formation method using a laser beam, developed from the annealing of silicon ion-implanted layers, is expected to be applied to three-dimensional integrated circuits and display device integrated circuits. The above polycrystalline or amorphous (1) single crystallization of licon, i.e. 5os (s 1 conon
8apphire), 80I (5ilicon
It has been actively researched as a process technology such as oninsul'ator.

However, in the formation of such a surface single crystal film, conventionally,
Because it was difficult to control the nuclei of crystal growth, it was only possible to obtain large crystal grains. The reason for this is that the normally used laser beam has a circular shape and its intensity distribution is a Gaussian distribution that is stronger at the center. This is because solidification is delayed in the center of the area compared to the surrounding area, and many microcrystalline nuclei generated around the irradiated area grow independently without any context. It is possible to use a laser beam with a bimodal cross-sectional shape by dividing the laser beam into two, an ordinary ray and an extraordinary ray, by transmitting the laser beam through a birefringent plate. By using a beam, (2) Since the irradiation dose is small in the central part of the irradiated area, cooling and solidification occur more quickly than in the vicinity, and as a result of this assimilation,
Large crystal grains can now be obtained because the crystal growth progresses toward the center or edge.

However, using this bimodal laser beam has the following drawbacks. That is, since the polarization planes of the ordinary ray and the extraordinary ray differ by 90 degrees, the vibration directions of their respective electric fields are shifted by 90 degrees. As a result, the crystallinity of crystal grains obtained with ordinary light is different from the crystallinity of crystal grains obtained with extraordinary light, resulting in a problem that crystallinity becomes non-uniform within large crystal grains.

SUMMARY OF THE INVENTION An object of the present invention is to provide a beam shaper that can eliminate the above-mentioned drawbacks and produce a high-quality single crystal film with large crystal grains.

In the beam shape shaper of the present invention, the direction of the plane of polarization of either the ordinary ray or the extraordinary ray is set at 90° on the exit side of the birefringent plate that divides the light beam into two, an ordinary ray and an extraordinary ray.
(3)

Next, the present invention will be explained in detail using the drawings.

The figure shows an embodiment of the present invention. In the figure, a laser beam 1 passes through a birefringent plate 2 and is split into an ordinary ray 3 and an extraordinary ray 4. This ordinary ray 3 is linearly polarized light having an electric field vibrating perpendicular to the plane of the paper, and this extraordinary ray 4 is linearly polarized light having an electric field vibrating parallel to the plane of the paper. That is, the polarization plane of the ordinary ray 3 and the polarization plane of the extraordinary ray 4 differ by 90°. Therefore, by transmitting the extraordinary ray 4 through the 1/2 wavelength plate 5 (of course, the ordinary ray 3 may be used instead of the extraordinary ray 4 by transmitting it through the 1A wavelength plate 5), the extraordinary ray 4 is gives a phase difference of 4° and the extraordinary ray 4
The plane of polarization is changed by 90 degrees to convert it into a linearly polarized light ray 6 that has an electric field that oscillates perpendicular to the plane of the paper, similar to the ordinary ray 3.

As a result, the ordinary ray 3 and the above-mentioned linearly polarized ray 6 having the same plane of polarization are obtained, and the cross-sectional shape of the beam becomes bimodal.

In this example, a 1/2 wavelength plate was used as an element that changes the direction of the polarization plane by 90 degrees, but it is not limited to this, and any element that can change the polarization plane by 90 degrees may be used.For example, an electro-optic plate can be used. It is also possible to use a crystal and adjust it by an externally applied electric field. When we tried to make a single crystal of a polysilicon film using a laser beam formed using this invention, we found that the wavelength was 515 nm.
, when the irradiation power is 10 W and the scanning speed is 8 tM/s, the width is 2.
A silicon single crystal film having uniform crystallinity of 00 μm and 1 mm in length was formed. Note that on the surface of this polysilicon film, a protective layer consisting of an 8isN4 film with a thickness of about 115-0 nm and a phosphosilicate glass film with a thickness of about 1 μm was provided in advance, as is usually done. There is a thickness of 60 mm between the polysilicon film and the substrate.
An insulating film layer made of 5i02 with a thickness of about 0 nm was provided.

As described above, according to the present invention, it is possible to easily form a laser beam suitable for forming high-quality single crystal films with large crystal grains.

[Brief explanation of the drawing]

The figure shows an embodiment of the present invention. In the figure, 1 is a laser beam, 2 is a birefringent plate, 3 is an ordinary ray, 4 is an extraordinary ray, 5 is a half-wave plate, and 6 is a 0, which is a ray of light with linear polarization

Claims (1)

[Claims] The device is characterized in that an element for changing the direction of the plane of polarization of either the ordinary ray or the extraordinary ray by 'i90' is provided on the output side of the birefringent plate that splits the light beam into two, an ordinary ray and an extraordinary ray. Beam shape former.