JP2008192920A - Beam irradiator and beam irradiation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an alignment mark good by irradiating a laser beam to a first position with the power density and the irradiation time according to the intensity of the first position. <P>SOLUTION: In a beam irradiator, a processing object in which an amorphous silicon film is formed on a ground member is prepared. The intensity of the first position of the amorphous silicon film is detected. The alignment mark is formed by irradiating a laser beam 11 to the first position with the power density and the irradiation time according to the detected intensity of the first position. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a beam irradiation apparatus and a beam irradiation method having a function of forming an alignment mark by irradiating a laser beam.

  Various laser irradiation apparatuses are used for laser annealing (see, for example, Patent Document 1). An apparatus that can quickly, objectively and automatically determine beam irradiation conditions for forming a polycrystalline silicon film by irradiating a laser beam on an amorphous silicon film (see, for example, Patent Document 2), a laser In addition to annealing, an apparatus (for example, see Patent Document 3) that can form alignment marks is known.

A target of laser annealing is a processed substrate (amorphous silicon film) in which an amorphous silicon film is formed on an insulating thin film formed of SiO ₂ or SiN on one main surface of a glass substrate, for example. For example, prior to laser annealing, the alignment mark is formed by irradiating a processed substrate (amorphous silicon film) with a laser beam, for example, the same green laser beam as that used for laser annealing. However, the irradiation result of the laser beam for forming the alignment mark may vary depending on the processed substrate, and even on the same processed substrate, depending on the irradiation position of the beam.

  The absorption rate of the green laser beam absorbed by the amorphous silicon film varies depending on the film thickness of the amorphous silicon film or the insulating thin film, the film structure of the insulating thin film, and the like. For this reason, when there is a manufacturing error or film formation error on the processed substrate, the alignment mark does not form a predetermined shape due to insufficient heat input, or part of the amorphous silicon film due to excessive heat. Problems such as ablation are likely to occur. In addition, the film thickness of the amorphous silicon film varies greatly in the peripheral portion of the glass substrate, which is one of the causes that the alignment mark is not properly formed.

  The processed substrate is irradiated with a beam for forming at least two alignment marks (first mark and second mark). After the beam irradiation, the two beam irradiation positions are imaged and image processing is performed. Image processing is an operation for detecting positional deviation by performing processing such as binarization on the observation image at the beam irradiation position and matching with a pattern registered in advance.

  When the alignment mark is satisfactorily formed by laser beam irradiation, image processing is performed normally. When there is a problem such as an irradiation shape defect or ablation, the accuracy of image processing may be deteriorated, or pattern matching may fail in some cases. If image processing is normally performed at both of the two beam irradiation positions, the subsequent alignment of the processed substrate can be appropriately performed.

JP 2005-217267 A Japanese Patent Laid-Open No. 2002-8976 JP 2004-103628 A

  The objective of this invention is providing the beam irradiation apparatus which can form an alignment mark favorably.

  It is another object of the present invention to provide a beam irradiation method that can satisfactorily form alignment marks.

  According to one aspect of the present invention, a laser light source that emits a laser beam and a workpiece on which an amorphous silicon film is formed on a base member are held, and the workpiece is moved in response to an external signal. A stage, a luminance detector for detecting the luminance of the amorphous silicon film of the processing object held on the stage, and an optical system for irradiating the processing object held on the stage with a laser beam emitted from the laser light source The power density adjusting means capable of changing the power density of the laser beam at the irradiation position by receiving a signal from the outside, and the irradiation of the laser beam to the workpiece by receiving the signal from the outside. An optical system including at least one of irradiation time adjusting means capable of changing the time, and movement of the workpiece to be controlled on the stage The optical signal is transmitted so that an alignment mark is formed by irradiating a laser beam at a power density and an irradiation time corresponding to the detected luminance at a position where the luminance is detected by the luminance detector. There is provided a beam irradiation apparatus having a power density adjusting means included in the system and a control device for sending a signal for controlling at least one of the irradiation time adjusting means.

  According to another aspect of the present invention, (a) a step of preparing an object to be processed in which an amorphous silicon film is formed on a base member; and (b) a luminance at a first position of the amorphous silicon film. And (c) forming an alignment mark by irradiating the first position with a laser beam at a power density and irradiation time corresponding to the luminance of the first position detected in step (b). There is provided a beam irradiation method.

  ADVANTAGE OF THE INVENTION According to this invention, the beam irradiation apparatus which can form an alignment mark favorably can be provided.

  Further, it is possible to provide a beam irradiation method that can satisfactorily form alignment marks.

  The beam irradiation apparatus according to the embodiment will be described with reference to FIGS.

  FIG. 1A is a schematic diagram illustrating a beam irradiation apparatus according to an embodiment.

  The laser light sources 10a and 10b are Nd: YAG lasers that receive a trigger signal transmitted from the control device 24 and emit a continuous wave laser beam of the second harmonic (wavelength 532 nm). From the laser light sources 10a and 10b, for example, laser beams 11a and 11b each of which is linearly polarized light are emitted, and after passing through mechanical shutters 13a and 13b and variable attenuators 30a and 30b, an electro-optic modulator (EOM) 12a, 12b.

  The mechanical shutters 13a and 13b receive control signals sent from the control device 24, and switch between passing and shielding of the incident laser beams 11a and 11b.

  The variable attenuators 30a and 30b receive the control signal sent from the control device 24, adjust the energy of the incident laser beams 11a and 11b, and emit the adjusted signals.

  The EOMs 12a and 12b rotate the polarization plane of the incident light according to the voltage value applied by the control device 24. The EOM 12a rotates the polarization plane of the laser beam 11a so that the laser beam 11a becomes S-polarized light with respect to the polarization beam splitter 15. The EOM 12b rotates the polarization plane of the laser beam 11b so that the laser beam 11b becomes P-polarized light with respect to the polarization beam splitter 15. The laser beams 11 a and 11 b emitted from the EOMs 12 a and 12 b are reflected by the folding mirror 14 a arranged as necessary and enter the polarization beam splitter 15.

  The polarization beam splitter 15 transmits incident P-polarized light and reflects S-polarized light. The laser beams 11 a and 11 b are superimposed on the same optical axis by the polarization beam splitter 15 and are emitted from the polarization beam splitter 15 as the laser beam 11.

  The laser beam 11 emitted from the polarization beam splitter 15 propagates through the optical path X or the optical path Y, and enters the mask 19 having a translucent region pattern. The mask 19 is held by a mask moving mechanism 20 so as to be movable in a direction intersecting the optical axis of the laser beam 11, for example, a direction orthogonal thereto. The mask 19 is moved by sending a control signal from the control device 24 to the mask moving mechanism 20.

  The cross-sectional shape of the laser beam 11 is shaped by the mask 19, and the processed substrate 27 placed on the stage 26, for example, the XYθ stage, is irradiated through the imaging optical system 21. On the surface of the processed substrate 27, the imaging optical system 21 forms an image of the cross section of the laser beam 11 at the position of the mask 19.

The processed substrate 27 is a substrate in which an amorphous silicon film is formed on one main surface of a glass substrate via an insulating thin film formed of SiO ₂ or SiN. For example, the orientation length is 920 mm and the lateral length is 730 mm, and one of four corners of the rectangle is cut to form an orientation flat. The stage 26 can move the processed substrate 27 within the placement surface in response to a control signal from the control device 24. Laser annealing is performed by irradiating the amorphous silicon film of the processed substrate 27 with the laser beam 11. Further, for example, prior to laser annealing, alignment marks are also formed by irradiation with the laser beam 11.

  The switchable mirrors 16 a and 16 b receive a control signal from the control device 24 and switch whether the laser beam 11 emitted from the polarization beam splitter 15 is introduced into the optical path X or the optical path Y. When the switchable mirrors 16 a and 16 b are not disposed on the optical path of the laser beam 11, the laser beam 11 travels along the optical path X, and when disposed on the optical path of the laser beam 11, the laser beam 11 travels along the optical path Y.

  On the optical path X, the folding mirrors 14b and 14c and the DOE 17 are disposed, and the laser beam 11 is introduced into the optical path X when laser annealing is performed. On the optical path Y, folding mirrors 14d and 14e and a DOE 18 are arranged, and the laser beam 11 is introduced into the optical path Y when forming an alignment mark.

  The mask 19 has a region on which the laser beam 11 traveling on the optical path X is incident and a region on which the laser beam 11 traveling on the optical path Y is incident.

  The mask moving mechanism 20 moves the mask 19 in synchronization with the insertion of the switchable mirrors 16a and 16b onto the optical path, and changes the position on the mask 19 where the laser beam 11 is incident.

  The illumination light source 22 is projection-type illumination that illuminates the processed substrate 27. The CCD camera 23 images the surface of the processed substrate 27 and transmits, for example, image data including the luminance of the surface of the processed substrate 27 (amorphous silicon film) to the control device 24. The control device 24 controls the irradiation conditions of the laser beam onto the processed substrate 27 based on the transmitted imaging data so as to be optimized, for example. For example, the voltage applied to the EOMs 12 a and 12 b is controlled by the control device 24 so that the laser beam 11 is shielded from being emitted from the polarization beam splitter 15 toward the optical path X or Y, and the laser irradiated on the processing substrate 27. The irradiation time of the beam 11 is controlled.

  The control device 24 includes a storage device 25, for example, a memory. In the storage device 25, information for determining the irradiation conditions when the processed substrate 27 is irradiated with the laser beam 11, for example, the brightness of the amorphous silicon film necessary for forming a good alignment mark, the processed substrate, The relationship between the power density of the laser beam 11 incident on the laser beam 27 and the irradiation time of the laser beam 11 is stored.

  Reference is made to FIG. The laser beam 11 emitted from the polarization beam splitter 15 and introduced into the optical path X is reflected by the folding mirrors 14 b and 14 c, diffracted by the DOE 17, and enters the mask 19. The DOE 17 forms an image at the position of the mask 19 with a long beam, for example.

  As shown in FIG. 1B, light is shielded at both ends in the length direction of the long laser beam 11 at a position on the mask 19 where the laser beam 11 traveling along the optical path X and diffracted by the DOE 17 is incident. A region is provided, and both end portions in the length direction of the incident laser beam 11 are cut and emitted.

  FIG. 1C shows a cross-sectional shape of the laser beam 11 shaped and emitted by the mask 19. The laser beam 11 is shaped into a long beam and is emitted from the mask 19. The laser beam 11 is irradiated onto the processed substrate 27 (amorphous silicon film) so that this shape is imaged, and laser annealing is performed. The beam size on the irradiation surface is, for example, 1.3 mm in the length direction (long direction) and 4.0 μm in the width direction (short direction).

During laser annealing, beam irradiation is performed so that the power density of the irradiated surface is, for example, 300 to 600 kW / cm ² . Beam irradiation is performed while moving the processed substrate 27 by the stage 26 at, for example, 150 to 1000 mm / sec and scanning the laser beam 11 in the width direction of the long shape (scanning the stage 26). The stage 26 is installed, for example, so that the width direction of the long beam and the Y-axis direction of the stage 26 are parallel to each other.

  Reference is made to FIG. The laser beam 11 emitted from the polarization beam splitter 15 and introduced into the optical path Y by the switchable mirror 16a is reflected by the folding mirrors 14d and 14e, diffracted by the DOE 18, reflected by the switchable mirror 16b, and masked. 19 enters. The DOE 18 images the laser beam 11 at the position of the mask 19 in a size and shape different from the DOE 17, for example, a rectangular shape.

  For example, a circular through hole 19a is provided at a position on the mask 19 where the laser beam 11 traveling along the optical path Y and diffracted by the DOE 18 is incident. The through hole 19a may be a cross (cross shape) or a T (tee) shape.

  FIG. 1E shows an example of a cross-sectional shape of the laser beam 11 that is shaped and emitted by the mask 19. The laser beam 11 is shaped into a beam having a circular cross section and is emitted from the mask 19. The laser beam 11 is irradiated onto the processed substrate 27 (amorphous silicon film) so that this shape is imaged, and alignment marks are formed. The beam size on the irradiation surface is, for example, 60 μm in diameter.

When the alignment mark is formed, beam irradiation is performed so that the power density of the irradiated surface becomes, for example, 10 to 100 kW / cm ² . The beam irradiation time is, for example, 300 μsec to 1000 msec.

  Hereinafter, the laser annealing method according to the embodiment will be described.

  The processed substrate 27 is placed on the stage 26 by being mechanically positioned, for example, at an appropriate position where the vertical direction of the processed substrate 27 is parallel to the Y-axis direction of the stage 26.

  Perform substrate edge correction. The substrate end face correction is a step of detecting how much the processed substrate 27 mechanically positioned and placed on the stage 26 is actually deviated from the target value. If the amount of deviation exceeds a predetermined value (when mechanical positioning is unsuccessful), an error occurs and the subsequent steps are not performed.

  While illuminating the processed substrate 27 with the illumination light source 22, the CCD camera 23 images the amorphous silicon film at the position where the alignment mark (first mark and second mark) is formed on the processed substrate 27, and transmits the image data to the control device 24. . The control device 24 detects the brightness of the amorphous silicon film at the first mark formation position and the second mark formation position from the transmitted image data.

  The film thickness of the amorphous silicon film roughly corresponds to the brightness (luminance) of the film on the image processing screen. Further, the absorption factor of the second harmonic of the Nd: YAG laser varies greatly depending on the film thickness of the amorphous silicon film. When illuminated with projection-type illumination (illumination light source 22), the higher the absorption rate of the second harmonic of the Nd: YAG laser, the darker the image processing screen looks (the luminance is lower). For this reason, the beam irradiation conditions for forming the alignment mark satisfactorily can be determined based on the detected luminance.

  In the storage device 25 of the control device 24, an appropriate beam irradiation condition corresponding to the brightness of the image of the amorphous silicon film (the power density of the laser beam 11 which can form the alignment mark satisfactorily, for example, is incident on the processing substrate 27). And the irradiation time of the laser beam 11) are stored. Based on the information stored in the storage device 25, the control device 24 applies the laser beam 11 to the amorphous silicon film at the alignment mark (first mark and second mark) formation position under the beam irradiation conditions corresponding to the detected luminance. Incident light is formed to form an alignment mark. In order to realize an appropriate beam irradiation condition, the control device 24 sends a control voltage to, for example, the EOMs 12a and 12b to shield the laser beam 11 and control the irradiation time of the laser beam 11 irradiated to the processing substrate 27. To do. Further, the power density of the laser beam 11 irradiated to the processed substrate 27 is controlled using the variable attenuators 30a and 30b.

  As described above, when forming the alignment mark, the switchable mirrors 16a and 16b are inserted into the optical path of the laser beam 11, the laser beam 11 is introduced into the optical path Y, and the mask is moved by the mask moving mechanism 20. The laser beam 11 is incident on a position on the mask provided with the circular through hole 19a.

  After the laser beam 11 is irradiated to the alignment mark (first mark and second mark) formation position of the processed substrate 27, the amorphous silicon film at the position is imaged by the CCD camera 23, and the imaging data is transmitted to the control device 24. Then, image processing of the first mark formation position and the second mark formation position is performed.

  Prior to mark formation, the brightness (luminance) of the amorphous silicon film at the formation position is detected, and the laser beam is emitted under appropriate irradiation conditions determined based on the detected brightness (luminance). Good alignment marks are formed at both positions. For this reason, image processing is normally performed.

  The switchable mirrors 16a and 16b are removed from the optical path of the laser beam 11, the laser beam 11 is introduced into the optical path X, and laser annealing is performed. The mask 19 is moved so that the light shielding regions are disposed at both ends in the length direction of the long laser beam 11 at positions on the mask 19 where the DOE 17 forms an image with the beam having a long shape.

  In the long laser beam 11 having a length direction of 1.3 mm and a width direction of 4.0 μm, the width direction of the laser beam 11 and the longitudinal direction of the processed substrate 27 (the Y axis direction of the stage 26) are substantially parallel. In this manner, the light is incident on the amorphous silicon film of the processed substrate 27 and laser annealing is performed. The stage 26 moves the processed substrate 27 in the Y-axis direction at a constant speed of 200 to 1000 mm / sec.

  When the laser annealing step (vertical processing) for scanning the laser beam 11 along the vertical direction of the processed substrate 27 is completed, laser annealing (horizontal processing) for scanning the laser beam 11 along the horizontal direction of the processed substrate 27 is performed.

  The processed substrate 27 is once paid out, and the orientation of the substrate is rotated by 90 ° and placed on the stage 26 again. The processed substrate 27 is mechanically positioned and placed at an appropriate position where the lateral direction is parallel to the Y-axis direction of the stage 26.

  When the substrate end face correction is not performed and the error is not determined, image processing of the alignment marks (first mark and second mark) formed prior to the vertical processing is performed, and the position of the alignment mark is read into the control device 24.

  The control device 24 performs angle correction on the basis of the read alignment mark so that the beam scanning direction on the processed substrate 27 is orthogonal to the vertical processing already performed and the horizontal processing to be performed in the future. The scanning direction (scanning angle) is determined. The angle correction includes deviation correction of the substrate placement angle during vertical processing and horizontal processing, and correction of laser pointing stability.

  Laser beams 11a and 11b are emitted from the laser light sources 10a and 10b, and lateral processing is performed. The laser beam 11 is scanned in a direction perpendicular to the vertical processing (direction corrected with reference to the alignment mark), and laser annealing is completed.

  As mentioned above, although this invention was demonstrated along the Example, this invention is not limited to these.

  For example, in the embodiment, the image captured by the CCD camera is processed and the irradiation condition of the beam is determined. However, the present invention is not limited to the CCD camera, and an apparatus capable of detecting the intensity (luminance) of reflected light from the amorphous silicon film is used. Thus, an appropriate beam irradiation condition can be determined.

  It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like are possible.

  It can be suitably used for laser processing in general, particularly laser annealing.

(A)-(E) is a figure for demonstrating the beam irradiation apparatus by an Example.

Explanation of symbols

10a, 10b Laser light source 11, 11a, 11b Laser beam 12a, 12b EOM
13a, 13b Mechanical shutters 14a-14e Folding mirror 15 Polarizing beam splitters 16a, 16b Switchable mirrors 17, 18 DOE
DESCRIPTION OF SYMBOLS 19 Mask 19a Through-hole 20 Mask moving mechanism 21 Imaging optical system 22 Illumination light source 23 CCD camera 24 Control apparatus 25 Memory | storage device 26 Stage 27 Processed substrate 30a, 30b Variable attenuator

Claims (3)

A laser light source for emitting a laser beam;
A stage for holding a processing target in which an amorphous silicon film is formed on a base member, and moving the processing target in response to an external signal;
A luminance detector for detecting the luminance of the amorphous silicon film of the processing object held on the stage;
An optical system that irradiates a workpiece held on the stage with a laser beam emitted from the laser light source, and can change the power density of the laser beam at the irradiation position by receiving an external signal. An optical system including at least one of a power density adjusting unit, and an irradiation time adjusting unit capable of changing the irradiation time of the laser beam on the object to be processed in response to an external signal;
A signal for controlling the movement of the workpiece is sent to the stage, and a laser beam is irradiated to the position where the luminance is detected by the luminance detector at a power density and irradiation time corresponding to the detected luminance. And a beam irradiation apparatus having a control device for sending a signal for controlling at least one of the power density adjusting means and the irradiation time adjusting means included in the optical system so that an alignment mark is formed. (A) preparing a processing object in which an amorphous silicon film is formed on a base member;
(B) detecting the luminance of the first position of the amorphous silicon film;
(C) forming an alignment mark by irradiating the first position with a laser beam at a power density and irradiation time corresponding to the luminance of the first position detected in the step (b). Beam irradiation method. In the step (b), the brightness of a second position different from the first position of the amorphous silicon film is detected,
In the step (c), an alignment mark is formed by irradiating the second position with a laser beam at a power density and irradiation time corresponding to the luminance at the second position,
Furthermore, the beam irradiation method includes a step of rotating the workpiece and performing alignment with reference to the alignment marks formed at the first and second positions.

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