JPS6172549A - Processing optical system for laser marking - Google Patents

Abstract

PURPOSE:To provide the titled apparatus used in a semiconductive process generating no scattering of the molten lump of a processing material and enhancing marking quality, constituted by specially modulating laser beam by providing a mask having a plurality of specific opening parts in laser beam. CONSTITUTION:The titled optical system is constituted of a beam expander 8, a scanning optical system 9 forming a pattern and a processing lens 10 and the mask 8 has a plurality of circular opening parts 8a each having a size 1/20-1/5 the diameter of laser beam and the opening parts 8a are arranged so as to be symmetric or at random to an optical axis in 1/4 rotary symmetric arrangement. The mask 8 is provided to a processing surface in the vicinity of a galvano emitting port at a position forming beam intensity distribution corresponding to opening positions. Because a processing cross-section takes a shape showing a high beam scattering property wherein the pitch of the valley 12 and crest 12b of a bottom part is 5-50mum and a depth is 2,500Angstrom -1mum and marking easy to look a character is formed.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a processing optical system in a laser marking device,
More specifically, the optical system is designed to improve the quality of marking by spatially modulating the laser beam.

(Prior Art) Laser marking devices used in semiconductor processes mark patterns such as letters and management numbers on the surface of semiconductors at high speed and in a non-contact manner.

FIG. 3 shows an example of the configuration of this device.

The laser beam output from the oscillator 1 is changed in direction by a reflecting mirror 2, passes through a beam expander 3 that widens the beam width, and enters an optical scanner 4. After the pattern is formed with the optical scanner 4,
The machined surface 6 is reached.

This laser processing, which also includes laser marking, is a type of thermal processing, and is a process in which the surface of the material to be processed melts or instantly evaporates by absorbing laser light, causing the molten mass to scatter, that is, to scatter dust. be.

Normally, laser marking is performed on semiconductor wafers before polishing, so even if dust scatters, it will be removed during the subsequent polishing process and will not form an interlayer. In some cases, the molten lumps may scratch the surface of the sea urchin, impair the adhesion of the mask during photo-etching, or cause abnormal vapor phase growth with the molten lumps as the core during the epitaxial vapor growth process. It becomes a problem.

(Problems to be Solved by the Invention) In order to solve this problem, there is a need to develop a marking method that does not cause any visible dust scattering.

To achieve this kind of marking, it is necessary to suppress the laser output by using an attenuation filter while the laser output is stable, changing the magnification of the beam expander, or performing processing at a position where the focal plane 1 is shifted. A marking method that does not scatter dust can be considered.

With these markings, it is possible to obtain the line width and character size, which are the first factors that determine the visibility of printed characters, but since the shape of the processed cross section becomes smooth, it is difficult to see from a specific angle. This has the disadvantage that sufficient light scattering at the processed cross section, which is the second condition that determines the legibility of characters, cannot be obtained, making the printed characters difficult to see.

SUMMARY OF THE INVENTION An object of the present invention is to provide a processing optical system for a laser marking device that does not cause dust scattering and allows printed characters to be easily seen.

(Means for solving the problem) In order to achieve the above object, the processing optical system for laser marking according to the present invention includes a laser light source, an expander for expanding a laser beam emitted from the laser light source, and a laser marking processing optical system for laser marking according to the present invention. The laser marking device includes a scanning optical system for scanning the laser beam, and a processing lens.
A mask having a plurality of apertures arranged so as to have 74-rotation symmetrical positions and each having a size of 1/20 or more and 1/5 or less of the laser beam is provided, and the opening positions of the apertures are set on the processing surface. The structure is configured to provide a light intensity distribution corresponding to .

According to the above configuration, a light-scattering cross-sectional structure with many unevenness can be formed in the processed groove to increase the light-scattering property, thereby making it possible to make the printed characters easier to see.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 2 is a perspective view showing an embodiment of the processing optical system according to the present invention, in which the beam expander 7 and the mask 8 are arranged with openings for giving spatial modulation to the laser beam.
, a scanning optical system 9 for forming patterns such as letters on a processing surface, and a processing lens 10.

The mask 8 has a plurality of circular or rectangular apertures 8a, and the apertures 8a are arranged in a 1/4 rotation pair, arranged symmetrically about the optical axis, or arranged randomly. It is. The mask 8 is provided near the galvano exit opening at a position where a light intensity distribution corresponding to the opening position is formed on the processing surface.

The size of the apertures 8a arranged at 1/4 rotation symmetrical positions is such that the diameter of the beam emitted from the beam expander 7 is 5.
When it is oblique, one side or diameter is 0.25-1. Om
(1/!O~”15).

FIG. 2 shows the structure of a processed cross section obtained with the processing optical system configured in this manner. Grooves 12 are formed by the laser beam, and the pitch between valleys 12a and peaks 12b at the bottom is approximately 5.
μm to 50 μm, and the depth is 2500 to 1 μm.

The pitch of the peaks and valleys is not necessarily uniform, resulting in a shape with high light scattering properties.

(Effects of the Invention) As described above in detail, according to the processing optical system according to the present invention, there is no scattering of dust due to scattering of the molten lump of the processing material, and markings with easy-to-read characters can be realized.

Furthermore, since there is no need to use a laser with high optical output, not only the laser generator to be mounted can be made smaller, but also the marking machine can be made smaller.

In terms of safety, there is an advantage that during laser marking, the intensity of the laser light scattered or reflected from the processed surface is relatively small and noisy, so that visible damage is reduced.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the processing optical system according to the present invention, FIG. 2 is a diagram showing an example of a light-scattering cross-sectional structure of a processed section created by the optical system of the present invention, and FIG. 3 is a diagram showing a conventional scanning method. FIG. 2 is a block diagram of a marker optical system. 1... Excavator 2... Reflector 3... Beam expander 4.9... Galvano type optic 4 Cal scanner 5.10
...Processing lens 1j 6.11...Processing surface 7...
Beam expander 8... Masko 1 time 2 Figure; -12-l--6

Claims (1)

[Claims] a laser light source, an expander that expands the laser beam emitted from the laser light source, and a scanning optical system that scans the laser beam from the expander;
In the laser marking device including a processing lens, in the laser beam near the expander exit port, the laser marking device is arranged so as to have a 1/4 rotation symmetrical position with respect to the laser beam optical axis, and has individual sizes. is the laser beam 2
Processing optics for laser marking, characterized in that by providing a mask having a plurality of openings of 1/0 or more and 1/5 or less, a light intensity distribution corresponding to the opening position of the mask is given to the processing surface. system.