JPS6394657A - Method and apparatus of laser processing - Google Patents

Abstract

PURPOSE:To subject a silicon substrate to a scribing process free from chipping and sticking melted substances by a method wherein an optical system for monitoring a laser processing part is provided at the position opposite to a carbon dioxide gas laser beam with the processed object between and beat-reactive etchant is made to act upon the processed surface of the silicon substrate only and the carton dioxide laser beam is applied from the opposite side of the processed surface. CONSTITUTION:Heat-reactive etchant 15 is contacted with the processed surface 14 of a silicon substrate 11 which is fixed to a vessel 12 with adhesive 13. A laser is oscillated by a carbon dioxide laser oscillator 16 and the carbon dioxide laser beam 19 is converged on the etchant 15 contacted with the processed surface of the substrate 11 by a lens 18. Therefore, the part of the etchant on which the laser beam 19 is converged is activated and etches the contacted processed surface 14 of the substrate 11 selectively. The bottom surface of the vessel 12 is made of parallel flat plane glass and a visible light source 20, a semitransparent mirror 21 and a converging lens 22 are provided on the side opposite to the carbon dioxide laser beam 19 with the silicon substrate 11 between and the processed position of the silicon substrate 11 is directly monitored.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a laser processing method and a processing device, and in particular to a laser processing method and a processing device that can process silicon substrates with good chipping, γ-ping, and good scrubbing and iving without melt deposits. Regarding processing equipment.

[Prior Art] Methods for scribing a silicon substrate include a method using a rotating grindstone (dicing) and a method using an AG laser (laser scribing).

Since die sinking is a mechanical process, it has the disadvantage that chipping occurs on the scribe surface of the silicon substrate. In addition, a YAG laser was used... In the scribing, the laser irradiation part is heated, melted, and evaporated to perform thermal processing (N Secret Work Handbook, No. 8).
edition, pp. 1551-1556). For this reason, there is a drawback that the molten material remains attached to the scribe surface.

1. Problems to be Solved by the Invention] As mentioned above, in the conventional scribing processing method for silicon substrates, chipping occurs in dicing using a grindstone, resulting in defects; There is a problem in laser scribing that the molten material adheres to the substrate surface and contaminates it.

[Means for Solving the Problems] The laser processing method of the first invention applies a heat-reactive chloride/socinda solution only to the processing surface of a silicon substrate, and emits a carbon dioxide laser beam from the reflective surface of the processing surface. This is a laser processing method characterized by irradiation. Further, in the laser processing apparatus of the second invention, the observation optical system of the laser processing section, which includes a visible light source, a semi-transparent mirror, and a condensing lens, is arranged on the opposite side of the carbon dioxide laser beam with the workpiece in between. This is a distinctive laser processing device.

Effect] When a heat-reactive etching liquid is applied only to the processed surface of the silicon substrate, and a carbon dioxide laser beam is irradiated from the opposite side to the processed surface, the carbon dioxide laser beam passes through the silicon substrate and interacts with the processed surface of the silicon substrate. Absorbed by the contacting heat-reactive etching solution. Therefore, when a carbon dioxide laser beam is focused on the thermally reactive etching liquid in contact with the processed surface of the silicon substrate, the etching liquid absorbs the laser and becomes high in temperature, and the processed surface of the silicon substrate near the laser irradiation area is selectively etched.

In addition, by placing the laser processing part observation optical system consisting of a visible light source, a semi-transparent mirror, and a condensing lens on the opposite side of the carbon dioxide laser beam across the silicon substrate, with the beam axis aligned, the silicon substrate processing surface can be The laser irradiation position and processed shape can be observed, and scribing can be performed at the desired position.

〔Example〕

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

FIG. 1 is a configuration diagram showing an embodiment of a laser processing apparatus of the present invention. The silicon substrate 11 is fixed to the container 12 with an adhesive 13, for example. The bottom surface of the container 12 is made of parallel plane glass. A potassium hydroxide aqueous solution (concentration 30
% weight ratio). A laser (laser power 20W) is oscillated from the carbon dioxide laser oscillator 16 and the mirror 17
The direction of the laser beam is changed by changing the direction of the laser beam, and the carbon dioxide laser beam 19 is focused by the lens 18 onto the etching liquid 15 in contact with the processed surface 14 (lower surface) of the silicon substrate 11 .

The carbon dioxide gas ν-the beam 19 has the property of transmitting through the silicon substrate 11 and being absorbed by the potassium hydroxide aqueous solution 1,
Therefore, the part of the etching solution focused by one carbon dioxide gas laser beam is thermally activated, and the part of the etching solution that is in contact with the silicon substrate 1
The processed surface 14 of No. 1 is selectively etched.

At this time, since the silicon substrate 11 does not transmit visible light, the processed portion 14 located below cannot be directly observed from above. Therefore, the bottom surface of the container 12 is made of parallel plane glass, and the processed portion 1 of the silicon substrate 11 is observed from below. A visible light source (wavelength 0.6 μm, halogen lamp) 20 and a semi-transparent mirror 21 are located on the reflection side of the carbon dioxide laser beam 19 across the silicon substrate 11 (workpiece), that is, below the bottom surface (parallel plane glass) of the container 12. The 8-lens barrel 23 in which the condensing lens 22 is held and arranged is held on the XYZ stage 24, and the condensing position of the visible light 25 can be adjusted.
The processing position of step 1 can be directly observed.

Wavelength 0.6μ from visible light source (halogen lamp) 20
m of visible light passes through the semi-transparent mirror 21 and is focused by the lens 22 onto the processed surface 14 of the silicon substrate 11. In this case, visible light with a wavelength of 0.6 μIn is transmitted through the potassium hydroxide aqueous solution. The reflected light from the processed surface is reflected by the semi-transparent mirror 21, enters the camera 20, and is observed on the television monitor 27. During machining, the vibrator 28, the heat exchanger 29, and the pump 30 circulate the machining/soching fluid. Mobile platform 3
By moving the silicon substrate 11 using 1, scribing processing can be performed.

The carbon dioxide laser power was 20 W, and the silicon substrate was moved at a speed of 5 Il/sec using the moving table 31 to relatively scan the beam. As a result, a groove with a width of 70 μm and a depth of 350 μm was formed on the processed surface of the silicon substrate. There were no chippings or melted deposits in the processed grooves, and a good scribing process was achieved.

In this example, the carbon dioxide laser beam was placed above and the observation optical system was placed below with the silicon substrate 11 in between, but as shown in FIG. The observation optical system visible light 25 and the carbon dioxide laser beam 19 may be arranged on the left and right sides, respectively.

Further, as a method of fixing the silicon substrate to the container, other methods such as pressure contact using a sealing rubber may be used as long as the etching solution is not leaked from the fixing portion.

〔Effect of the invention〕

As described above, by the processing method of the present invention, it is possible to perform good scribing processing on a silicon substrate without chi-sobbing or melt deposits.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a laser processing apparatus showing one embodiment of the present invention, and FIG. 2 is a cross-sectional view showing an example of the arrangement of a carbon dioxide laser beam, a silicon substrate, and an observation optical system in another embodiment of the present invention. . ]1...Silicon substrate, 12.12A...Container, 1
3... Adhesive, 14... Processed surface, 15... Etching liquid, 16... Carbon dioxide laser oscillator, 17...
Mirror, 18... Lens, I9... Carbon dioxide laser beam, 20... Visible light source, 21... Semi-transparent mirror, 22... Lens, 23... Lens barrel, 24... XY
Z stage, 25...Visible light, 26...Camera, 2
7...TV monitor, 28...pipe, 29...
Tank, 3o...bona, 31...mobile platform. Figure 1 Figure 2 I

Claims (2)

[Claims] (1) A method for laser processing a silicon substrate, characterized in that a heat-reactive etching solution is applied only to the processed surface of the silicon substrate, and a carbon dioxide laser beam is irradiated from a reflective surface of the processed surface. (2) In a laser processing device that processes a workpiece by irradiating a carbon dioxide laser beam, the observation optical system of the laser processing section, which consists of a visible light source, a semi-transparent mirror, and a condensing lens, is placed between the workpiece and the carbon dioxide laser beam. A laser processing device characterized by being placed on the opposite side of a beam.