JPS5919332A - Emitting method for laser beam - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for irradiating a laser beam with uniform irradiation energy density.

In recent years, lasers have been applied to many fields. For example, in fields such as the manufacturing of integrated circuit elements such as LSI and VLSI, and laser annealing, laser beams are applied to a wide area with uniform irradiation energy. It is desired to irradiate with high density.

The laser beam is circular and its energy density has a Gaussian distribution, which can be detected using a complex optical system.
Various attempts have been made to convert the laser beam into a laser beam with a uniform energy density distribution (Laser Foc
us Oct, p3'l, /9g/). Figure 1 shows
An example of an optical system for a typical conventional laser beam irradiation method is shown. Laser beam l is irradiated onto split mirror 2, and λ
Split reflected beam 1. A and lB are reflected by λ cylindrical concave mirrors 3A and aB, and recombined on the irradiation surface 4. As shown in FIG. 1A, the reflected beam LA,
in consists of half-bell-shaped parts (half Gaussian distribution shape), parts with low energy density overlap and compensate each other, and the recombined beam has energy density in the X direction as shown in Figure λ BVC three-dimensionally. The beam becomes a rectangular beam that is uniform but not uniform in the Y direction (Gaussian distribution). Then, by moving this beam in the Y direction or moving the irradiation surface in the Y direction, it is possible to irradiate a belt-shaped region with a width W with a uniform irradiation energy density.

However, the conventional irradiation method shown in FIG. 1 has a problem in that the irradiation area cannot be irradiated with uniform energy density unless the beam or irradiation surface is moved. Furthermore, since an assembly of three mirrors is used, the optical system is not integrated and its adjustment is not particularly easy, and there is no effect if the beam incidence position is shifted due to mechanical vibrations, etc. There are problems such as easy acceptance.

The present invention aims to solve these problems, and will be described in detail below with reference to the accompanying drawings. FIG. 3 is a diagram explaining the principle of the irradiation method of the present invention.

By making the laser beam σ incident on the center of the pyramid-shaped four-sided prism 5, it is divided into two parts. Each portion 1A to l is bent II' in the direction of the central axis 6.
i', they overlap on the irradiation surface 4, and a rectangular area with -side l is irradiated with uniform irradiation energy density. By adjusting the distance between the four-sided prism 5 and the irradiation surface 4, the side l changes, and the optimum irradiation conditions (conditions where the non-uniformity of energy density takes a minimum value with high energy utilization efficiency) can be obtained. .

Let a be the spot size of a circular laser beam with a Gaussian distribution (when the energy density of the beam has a Gaussian distribution, the beam radius where the energy density reaches its peak value) is a, and the distance from the beam center be r. Then, the irradiation energy density Z is 2 z=A-eXpC-2 [-T)]...
(1) A is expressed by an arbitrary constant. As shown in Figs. An arbitrary point P is expressed by the following equation as the X and y coordinates.

Therefore, the irradiation energy density at point P is (1)
From equation (2), it is expressed as follows.

FIG. 5 is a three-dimensional representation of an example of a rectangular recombined beam calculated using equation (3).

Tasoshi, a-6-9, 11 = g cm, '//a = 8/Otsu de Heru.

FIG. 4 shows the uniformity of beam irradiation energy density and energy utilization efficiency (recombined beam energy/original beam energy) obtained by the present invention. As shown in the figure, the non-uniformity of the irradiation energy density at that time takes a minimum value at ζ-/, / and the energy utilization efficiency is about qllot.

Here, the degree of non-uniformity is the maximum value (Imax) of the difference (Imax-Imin) between the maximum value (Imax) and minimum value (Imin) of the energy density of the recombined beam.
means the percentage of

Note that by projecting and enlarging/reducing the optimized irradiation surface using a lens system, it is possible to obtain a uniform irradiation surface with a desired area.

As detailed above, the present invention can efficiently irradiate a laser beam with uniform irradiation energy density by simply using seven four-sided prisms, and the optical system is extremely simple.
It is easy to operate because it is only necessary to adjust the distance from the four-sided prism to the irradiation surface. Furthermore, since no mirror is used, even if the beams are incident on the center of the four-sided prism at an angle, there will be almost no problem in recombining the beams. In particular, since there is no need to sweep the beam or move the irradiation surface,
It has the advantage that it can also be applied to irradiation with a glucose laser beam.

The pyramid-shaped four-sided prism used in the present invention is
As shown in FIG. 7, it is sufficient to have a square pyramidal surface 5A, and the shape of the bottom surface 5B may be circular, square, oval, etc., and may be appropriately selected depending on the purpose. Also, the incidence of the beam on the four-sided prism is not limited to the bottom side as shown in Figure 3.
A similar recombined beam can be obtained even if the beam is incident from the square pyramid surface side.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the optical system of the conventional laser beam irradiation method, Figure A is a diagram showing the energy density distribution of the recombined beam obtained in Figure 1, and Figure B is a perspective view of Figure A. Figure 3 is a diagram showing an example of the optical system of the laser beam irradiation method of the present invention, Figure q A and B are explanatory diagrams of the recombined beam obtained by the present invention, and Figure S is an illustration of the recombined beam obtained by the present invention. A perspective view showing an example of the energy density distribution of the recombined beam,
Figure 4 shows the recombined beam obtained by the present invention, code in the upper figure = 1...Laser beam, ■A
~ID ・・・・・・・・・Divided beam, 2
・・・・・・・・・Split mirror, 4(・・・・・・・・・
...Irradiation surface, 5...Pyramid-shaped four-sided prism, 6...Central axis, l...One side of the rectangle of the recombined beam ,a
・・・・・・・・・ Gaussian distributed laser beam spot size. Patent applicant RIKEN

Claims (1)

[Claims] /) A laser beam is incident on the center of a pyramid-shaped four-sided prism, divided into four parts, and each laser beam is refracted in the direction of the central axis and emitted, and then recombined into a square shape on the irradiation surface. A laser beam irradiation method characterized by irradiation with a laser beam. , 2) The irradiation surface from the tetrahedral prism is selected so that the ratio of one side l of the rectangle of the recombined laser beam to the spot size a of the laser beam is /, /. Laser beam irradiation method described in section.