JPH04238686A - Laser beam machine and processing method thereof - Google Patents

Abstract

PURPOSE:To increase the throughput of Laser beam processing and to decrease the number of positioning times of a mask as well as to enhance processing accuracy by setting the beam size of a laser beam at a proper size to increase an energy density and projecting this laser beam to the mask. CONSTITUTION:The laser beam 11 is collimated into collimated beams of light of the cross-sectional area having the area smaller than the vertical and horizontal lengths of the processing pattern range of the mask. The collimated beams of light are projected and scanned perpendicularly to the processing pattern surface. The collimated beams of light are formed to the sectional shape smaller than the aperture diameter of a projecting optical system 29 for projecting these beams to a sample 15. Further, when the collimated beams of light are made incident in parallel with the optical axis of the projecting optical system 29, the exit light thereof is made to emerge in parallel with the optical axis of the projecting optical system 29. In addition, the collimated beams of light are scanned by an operating mirror 26 which is provided at the focal position of the incident optical system 29 of the mask 12 and chanegs its angle around twin axes.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an optical system for laser processing, and in particular, it projects a large area of a processing pattern formed on a mask surface onto a sample surface at once, thereby efficiently processing the sample surface. This invention relates to a laser processing device and a processing method for the same.

0002

[Prior Art] Conventional laser processing methods scan and irradiate a sample surface with a narrowly focused laser beam with high energy density to locally remove the processed area by heating or chemical action.
I was trying to process it. In addition, in the March 1990 issue of Joytech magazine, pages 16-20 entitled "Excimer laser processing system and its applications," a patterned mask was set in the optical path of the excimer laser. It is described that the above-mentioned excimer laser beam is irradiated all at once, and the transmitted light beam is reduced and projected to process the sample surface at once. Furthermore, Japanese Patent Application Laid-Open No. 64-44294 discloses that the cross-sectional shape of the laser beam is set to an elongated shape that is longer than the pattern width of the mask, and the laser beam is swept vertically on the mask, and the emitted light is reduced and projected to illuminate the sample surface. Processing is disclosed.

0003

[Problems to be Solved by the Invention] In the method described in Joytech magazine, if the sample does not have photoreactivity due to laser energy, there is a threshold for the energy density that can process the sample surface. When the area is expanded to increase the area that can be processed at one time, there is a problem in that the energy density decreases and processing becomes impossible. Furthermore, in the method described in JP-A-64-44294, processing unevenness occurs because it is difficult to maintain a uniform energy density within the elongated beam. Since the scanning angle is only in one direction, it is inconvenient that the pattern on the mask cannot be scanned to any desired position as needed. SUMMARY OF THE INVENTION An object of the present invention is to provide a laser processing apparatus and a processing method therefor which eliminate the drawbacks of the prior art by allowing a laser beam of a suitable cross-sectional area to arbitrarily scan a mask.

0004

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention uses a laser beam as a parallel beam whose cross-sectional area is smaller than the vertical and horizontal lengths of the processing pattern range of the mask. is irradiated perpendicularly to the surface of the processed pattern and scanned. For this reason, the cross-sectional shape of the parallel light is made smaller than the aperture of the projection optical system for projecting the light onto the sample, and furthermore, when the parallel light is incident parallel to the optical axis of the projection optical system, the output light is emitted parallel to the optical axis of the projection optical system. In addition, the parallel light is scanned by a scanning mirror that changes angle around two axes provided at the focal point of the incident optical system of the mask, or a polygon mirror that can rotate around an axis perpendicular to the optical axis of the parallel light. Make it.

Further, the scanning mirror is mounted so that the parallel light enters the mask at right angles, and is moved parallel to the mask. In addition, the parallel light enters through the opening of the XY table, irradiates the mask above it, reflects the light passing through the mask and enters the projection optical system, and further reflects the emitted light to make the XY table The sample above is irradiated, and the parallel light is caused to scan the mask by moving the XY table.

[0006] Further, a cover glass made of, for example, transparent quartz glass is placed opposite to the mask with a gap maintained above the mask, and a cooling gas is allowed to flow through the gap. Furthermore, an excimer laser is used as a laser light source. Further, the sample is hermetically sealed in a vacuum container, the sample is processed by irradiating a laser beam from the outside through the airtight window, and the sample is further plasma cleaned in the vacuum container. In addition, the XY table is moved outside the projection range of the projection optical system and the processed pattern of the sample is inspected with an inspection light beam,
The processing defects will be corrected.

[0007]

[Operation] The processing pattern is scanned by parallel light from a laser whose cross-sectional area falls within the processing pattern of the mask, and the sample surface is processed by the passing light. The parallel light is produced by a scanning mirror that changes angle around two axes provided at the focal point of the incident optical system of the mask, or a polygon mirror that can rotate around an axis perpendicular to the optical axis of the parallel light, or the second parallel light. The light beam is scanned by a scanning mirror or the like that moves parallel to the light beam, and after passing through the mask, the light beam is incident parallel to the optical axis of the projection optical system, and is emitted parallel to the same optical axis. In another scanning method of the present invention, the parallel light is incident on a mask attached to the opening of the XY table, and the passing light is reflected twice through the projection optical system to reach the sample on the XY table. Irradiate and process.

[0008] Furthermore, the mask is cooled by flowing a cooling gas over the mask, and the cooling gas is sealed with a cover glass. Furthermore, an excimer laser is used as a light source to increase the energy density of the parallel light. Further, the sample is hermetically sealed in a vacuum container, and the sample is processed by guiding a laser beam through an airtight window, and at the same time, plasma of oxygen gas is generated to remove the process-affected layer and the adhering process layer. Further, the XY table is moved outside the projection range of the projection optical system to inspect the processed pattern of the sample using the inspection light beam, and correct any processing defects.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram illustrating the basic operation of a laser processing optical system and processing method according to the present invention. In FIG. 1, a laser beam 11 that is incident on a mask 12 at a right angle and parallel to an optical axis 18 is focused by a lens 13 at the position of its pupil 14, and a projection lens (projection optical system) 1
3, the laser beam is emitted parallel to the optical axis 18, and the sample 18, which is placed so as to be struck at right angles, is irradiated with this emitted laser beam. In this state, when the laser beam 11 is scanned, for example, in the direction of the arrow 16 by optical or mechanical means, the laser beam exiting the projection lens 13 moves on the sample surface in the direction of the arrow 17. In order to perform the above scanning, the laser beam 11 has a cross-sectional area smaller than the aperture area of the projection optical system.
Further, in order to improve processing efficiency, the cross-sectional area is set to such an extent that a wide area portion of the processing pattern on the mask 12 can be projected all at once. Thereby, the sample surface can be processed quickly with a beam size corresponding to the magnification of the lens 13 with less distortion of the projected image.

[Embodiment 1] FIG. 2 is a diagram showing an example of the practical configuration of FIG.
The energy value of the laser beam emitted by the laser beam is adjusted by the energy adjustment optical system 22, and is incident on the energy density distribution adjustment optical system 25 via mirrors 23 and 24. The energy density distribution adjusting optical system 25 acts to equalize the energy density distribution within the cross section, and the emitted light is scanned by the scanning mirror 26 and enters the input optical system 29 . Since the scanning mirror 26 can be rotated around two axes by motors 27 and 28, the reflection angle of the beam can be controlled arbitrarily, for example in the X and Y directions.

Although the scanning mirror 26 is a plane mirror, scanning can be performed similarly by rotating a polygonal mirror whose angle with respect to the incident laser beam changes around one axis by a motor, and at the same time controlling the beam scanning speed. be able to. The cross-sectional area of this laser beam is smaller than the aperture of the incident optical system 29 and the area of the processed pattern on the mask 12.

FIG. 3 shows the output beam from the input optical system 29.
FIG. 2 is a configuration diagram of a telecentric optical system used to avoid optical distortion of a projected image caused by the beam. In FIG. 3, by making the distance between the scanning mirror 26 and the input optical system 29 equal to the focal length f of the input optical system 29, the laser beam 11 exiting the input optical system 29 is always relative to the optical axis of this optical system. become parallel. Further, since the optical axes of the input optical system 29 and the projection lens 13 are made to coincide with each other, and the laser beam 11 that is incident parallel to the optical axis of the projection lens 13 is focused at the position of the pupil of the projection lens 13, the laser beam exiting the projection lens 13 is The beam is also always parallel to the optical axis of this projection lens 13.

When the laser beam 11 is scanned by the scanning mirror 26 under the above optical system so as to cover the entire area of the processing pattern on the mask 12, the surface of the sample 15 is exposed to the laser beam that has passed through the projection lens 13. The beam scans, and the processed pattern image of the mask 12 is accurately projected without distortion. Further, the energy density of the projection laser beam is adjusted by the energy density adjusting optical system 22 so that it exceeds a threshold value necessary for processing the sample.

[Embodiment 2] FIG. 4 is a diagram illustrating another laser beam scanning method according to the present invention. In FIG. 4, the laser beam exiting the energy distribution adjusting optical system 25 enters an input optical system 29 as parallel light, and a motor 36 moves a stage 37 on which a scanning mirror 26 tilted at 45 degrees is mounted on an optical axis 40. When the mirror 26 moves in the direction, the processing pattern on the mask 12 is projected onto the sample surface along the moving direction of the mirror 26, and the sample surface is processed. In this way, after machining in one direction by mirror movement, the motors 38, 3
By changing the relative positions of the mask 12 and the sample 15 using 9, 31, and 32, and repeating the same process, the entire area of the processing pattern on the mask is projected onto the sample surface, and processing according to the pattern is performed.

This method is functionally the same as the first embodiment in that it can project a wide area, but since the mirror can only be moved in the direction of the optical axis 40, the throughput is slightly reduced. Since it is sufficient to keep the angle of 26 constant at all times, it is possible to obtain the advantages of easy control and simple structure.

[Embodiment 3] Next, FIG. 5 is a diagram showing another embodiment of the present invention in which the mask pattern of the mask 15 can be transferred only by moving the XY table 30. Note that in this embodiment, the projection magnification of the projection optical system is 1:1.
Applicable in the case of In FIG. 5, the XY table 30
A parallel laser beam 11 is incident at right angles from the lower part of the mask 12 attached to the opening 42 provided in the opening 42, is reflected by the first mirror 43, and is transmitted parallel to the optical axis of the projection lens 13 shown in FIG. The output light is sent to the second mirror 44.
The direction is further changed by irradiating the sample 15 on the XY table 30, and the processed pattern of the mask 12 is projected onto the sample surface. In this state, the XY table 30 is moved so that the laser beam 11 can scan the entire pattern of the mask 12.

[Embodiment 4] FIG. 6 shows the structure of a cooling mask that is effective in preventing damage and thermal deformation of the mask 12 caused by heating caused by high energy density laser beam irradiation in the laser processing of the present invention. FIG. Figure 6
, a transparent cover glass 46 is placed on top of the mask 12.
The mask 12 is irradiated with the laser beam 11 through the cover glass 46, and the beam passing through the gap between the mask patterns 46 is taken out. At this time, by flowing the cooling gas 47 into the gap between the cover glass 46 and the mask 12, the mask 12 is efficiently cooled, and at the same time, scattering of the laser beam due to fluctuations of the cooling gas 47 can be prevented.

The materials for the mask 12 and the cover glass 46 only need to be transparent to the wavelength of the laser beam used, but when using an excimer laser with a wavelength of 248 nm, it is preferable to use quartz glass. In addition, processing pattern 45
A dielectric material with high reflectivity or a high melting point metal should be used for this purpose. Further, as the cooling gas, helium gas having high thermal conductivity is suitable, but rare gases such as argon gas and nitrogen gas, or inert gases may also be used. It goes without saying that the mask shown in FIG. 6 may be reversed so that the pattern 45 is on the lower side.

[Embodiment 5] FIG. 7 is a diagram showing an apparatus of the present invention that can perform laser processing while removing a damaged layer and a contaminant layer due to processing waste, which are often a problem in such laser processing methods. Yes, it can be applied when processing organic films using an excimer laser. In FIG. 7, the vacuum container 4 loaded on the XY table 30
A sample 15 is placed inside the chamber 8, and a vacuum pump is connected to the exhaust hole 49 to bring the inside into a vacuum state. Next, while applying a voltage between electrodes 50 and 51 provided on both sides of the sample 15, oxygen gas is injected between the electrodes to generate oxygen plasma 52, and the laser beam 11 is irradiated onto the sample through a window 53 made of quartz glass. Then, a predetermined laser process is performed on the surface of the sample 15, and at the same time, the process-affected layer generated by this process can be removed by plasma cleaning. Note that this plasma cleaning may be performed after laser processing.

[Embodiment 6] FIG. 8 is a block diagram of a laser apparatus of the present invention capable of repairing processing defects caused by the laser processing described above. The processing defects described above are caused by locally unprocessed portions or processing residues remaining due to pattern defects in the mask 12, the thickness of the sample 15, variations in laser energy, and the like. In FIG. 8, the XY table 30 after laser processing is moved to the position indicated by the dotted line using the methods described above to inspect and correct the processing defects.

The laser beam from the laser oscillator 21 is split by a half mirror 54, focused by a focusing optical system 56, and irradiated through the half mirror 55 onto the sample 15 after the movement. The reflected light from the sample 15 is reflected by a half mirror 55 and enters an image pickup tube 57, and is inspected for defects by a pattern inspection device 58. At this time, if there is a processing defect, the XY table 30 is moved and the laser beam is applied to the processing defect part of the sample 15, and the energy density and beam size are adjusted appropriately according to the material of the sample and the defect size. Set and remove defective parts. As a result, the final yield of laser processing can be improved to approximately 100%. Note that the light beams for inspection and defect removal may be provided separately and independently.

[0022]

Effects of the Invention According to the present invention, the beam size of the laser beam is set to an appropriate size, the energy density is increased, and the laser beam is projected onto the mask, so that the laser beam can be used effectively. Since a large area of the laser beam can be projected all at once, the throughput of laser processing can be increased. Furthermore, since the number of times of mask alignment can be reduced, processing accuracy can be improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the basic operation of a projection optical system according to the present invention.

FIG. 2 is a configuration diagram of a laser processing apparatus according to the present invention.

FIG. 3 is a configuration diagram of a dual telecentric optical system used in the present invention.

FIG. 4 is another configuration diagram of the laser processing apparatus according to the present invention.

FIG. 5 is a diagram illustrating the configuration of another laser processing apparatus according to the present invention.

FIG. 6 is a structural diagram of a mask cooling device according to the present invention.

FIG. 7 is an explanatory diagram of a sample plasma cleaning apparatus according to the present invention.

FIG. 8 is a configuration diagram of a laser processing apparatus with a sample inspection and correction mechanism according to the present invention.

[Explanation of symbols]

11 Laser beam 12 Mask 13 Projection lens 14 Pupils 15 Sample 18 Optical axis 26 Mirror 29 Input optical system 30 XY stage 35 Rail guide 37 Stage 43 Reflector 45 pattern 46 Cover glass 47 Cooling gas 48 Vacuum container 50 electrode 52 Plasma 53 Window 54 Half mirror 57 Image tube 58 Pattern inspection device

Claims (14)

[Claims] 1. A laser processing device that irradiates a mask with laser light and projects the transmitted light onto a sample for processing,
beam shaping means for converting the laser beam into parallel light having a cross-sectional area smaller than the vertical and horizontal lengths of the processed pattern range of the mask; and irradiating the parallel light at right angles to the processed pattern surface. 1. A laser processing device comprising: means for moving and scanning. 2. The method according to claim 1, further comprising a projection optical system for projecting the parallel light onto the sample, wherein the cross-sectional area of the parallel light is made smaller than the aperture of the projection optical system by the beam shaping means. . The laser processing apparatus further characterized in that the projection optical system emits the emitted light parallel to the optical axis when the parallel light is incident parallel to the optical axis of the projection optical system. 3. Claims 1 and 2, further comprising: a scanning mirror that moves and scans the parallel light; and an incident optical system that irradiates the mask with reflected light from the scanning mirror; A laser processing device characterized in that it is provided at a focal point of a system. 4. A laser processing apparatus according to claim 3, further comprising means for changing the angle of said scanning mirror around two axes. 5. According to claim 3, said scanning mirror is mounted so that said parallel light is incident on said mask at right angles, and further provided with means for moving said scanning mirror parallel to said mask. Laser processing equipment. 6. The laser processing apparatus according to claim 3, wherein the traveling mirror is a polygon mirror that can rotate around an axis perpendicular to the optical axis of the parallel light. 7. According to claims 1 and 2, an opening for placing the mask on the XY table on which the sample is placed, and reflecting the parallel light that is incident through the opening and passes through the mask. A first mirror is provided to direct the reflected light from the first mirror into the projection optical system, and a second mirror is provided to reflect the emitted light, and the reflected light from the second mirror is directed to the sample. A laser processing apparatus characterized in that the laser beam is irradiated and the parallel light scans the mask by moving the XY table. 8. A laser processing apparatus according to claim 1, wherein the mask includes a pattern formed of a dielectric or reflective metal film on a transparent glass plate. 9. The laser processing apparatus according to claim 1, further comprising a cover glass facing the mask with a gap therebetween, and a cooling gas flowing through the gap. 10. A laser processing apparatus according to claim 9, wherein said cover glass is a translucent quartz glass plate. 11. A laser processing apparatus according to claim 1, wherein an excimer laser is used as a laser light source. 12. In claim 11, a vacuum container is provided, the vacuum container having an airtight window for introducing the laser beam from the outside and a plasma cleaning mechanism for plasma cleaning inside the window,
A laser processing apparatus characterized in that the sample is hermetically sealed in the vacuum container, the sample is processed by irradiating the laser beam through the airtight window, and the sample is further plasma cleaned. 13. According to any one of claims 1 to 12, means for moving the XY table outside the projection range of the projection optical system; means for generating an inspection light beam; Putter to inspect the pattern after processing
1. A laser processing method, comprising: inspection means for inspecting the sample; and means for correcting processing defects in the sample using the inspection light beam. 14. A laser processing method in which a mask is irradiated with laser light and a sample is processed using the transmitted light, comprising:
The laser beam is a parallel beam whose cross-sectional area is smaller than the vertical and horizontal lengths of the processing pattern range, and the parallel light is irradiated perpendicularly to the processing pattern surface for scanning. Laser processing method.