JP2012143787A - Thin film laser patterning method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To process a scribe region so as neither to damage a substrate nor to cause remaining of a film by preventing excessive energy in a superposed portion between processing spots in a thin film scribe using laser beam.SOLUTION: There are provided a thin film laser patterning method and a thin film laser patterning device which irradiate a thin film formed on a surface of a sample with pulsed laser beam while relatively scanning the pulsed laser beam on the surface of the sample, thereby partially removing the thin film from the surface of the sample. In the method and the device, the pulsed laser is formed so as to have the intensity distribution of a top hat shape which is asymmetrical to the relatively scanning direction. An irradiation region of the formed pulsed laser is irradiated with the pulsed laser beam while partly overlapping the region, thereby performing relative scanning, so that the thin film on the irradiated region is removed.

Description

  The present invention is generally applicable to a thin film patterning method and apparatus using laser light. Specifically, the present invention relates to a thin film laser patterning method and apparatus for cutting a conductive thin film or a silicon thin film at high speed and reliably in a process of forming a thin film solar cell that has been attracting attention in recent years.

  In thin-film solar cells using amorphous silicon or microcrystalline silicon, improvement in power generation efficiency is a major issue. For this reason, generally, a high voltage is obtained by dividing the power generation layer and the transparent conductive film into cells and connecting them in series. In this cell division, in order to minimize the area loss due to the removal of the film, it is required to divide the cells with high accuracy along a linear scribe region provided between the cells. As a method of dividing cells with high accuracy along the scribe region, there is a method of processing using a laser.

  A thin film processing optical system using a laser is disclosed in Patent Document 1. In order to make the processing shape uniform, the homogenizer is used to make the beam intensity distribution uniform and prevent beam decentering to improve uniformity.

  Patent Document 2 discloses a configuration in which a sample is irradiated with a different laser distribution intensity in order to improve the processing accuracy by the laser.

JP 2007-310368 A JP 2005-968 A

  In order to process the linear scribe region, a processing spot by a pulse laser such as a YAG laser may be irradiated so as to be continuous linearly. Here, in order to perform the insulation division of the transparent electrode satisfactorily, it is necessary to prevent damage to the underlying film and to prevent the film residue from occurring in the scribe region, and a uniform processed shape can be obtained. desirable. Patent Document 1 describes a method in which a laser energy distribution for each pulse is formed in a top hat and an image is transferred onto a workpiece with uniform power. However, in order to process a linear scribe region by this method, when the spots are continuously irradiated and connected in a straight line, an overlapping portion does not occur between the spots, and there is a gap between adjacent spots. The laser must be irradiated so that it does not occur. However, in practice, it is difficult to irradiate such a beam, and in actuality, irradiation is performed so that a part of adjacent beams overlap. However, in this case, in the method described in Patent Document 1, energy is excessive in the overlapping portion between spots, and damage to the base is likely to occur. In this case, impurities in the underlying glass adhere to the scribe part, causing insulation failure and shortening of life. In order to avoid this, if the interval between spots is increased, a film residue tends to occur at the boundary between spots. That is, the avoidance of damage to the base and the avoidance of the remaining film are complementary, and it is difficult to achieve both.

  Patent Document 2 describes that a spatial energy distribution of a laser beam is changed to a top hat distribution using a beam shaping unit. However, when a spot is continuously irradiated onto a workpiece and connected to a linear shape, There is no description of irradiating a laser beam without damaging the underlying film and without leaving a film residue in the scribe region.

  It is an object of the present invention to prevent excessive energy at the overlapping portion between processing spots in scribing using a thin film laser so as not to cause damage to the ground and to prevent film residue from occurring. An object of the present invention is to provide a thin film laser patterning method and apparatus capable of processing a scribe region.

In order to solve the above-described problems, in the present invention, a thin film is partially formed from the surface of a sample by irradiating the thin film formed on the surface of the sample with pulsed laser light while being scanned relative to the surface of the sample. In the thin-film laser patterning method, the pulse laser is shaped so as to have a top hat intensity distribution that is asymmetric with respect to the scanning direction, and the irradiated areas of the shaped pulse laser are partially overlapped. The thin film in the region scanned and irradiated relatively was removed by irradiating and relatively scanning.
In order to solve the above-described problems, in the present invention, a thin film laser patterning device includes a pulse laser light source that emits a pulse laser beam, stage means on which a sample can be placed and moved in a plane, and a pulse laser. It has an optical element that shapes the pulse laser beam emitted from the light source into a top hat shape in which the light intensity distribution in the cross section perpendicular to the optical axis of the pulse laser beam is asymmetric. The stage means is shaped into a top hat shape with an asymmetrical light intensity distribution by the optical elements of the beam irradiation optical system. The sample is moved so that the region on the sample irradiated with the pulsed laser beam is partially overlapped with the previously irradiated region. Beam irradiation optical system is to have a top-hat shape changing unit that changes an asymmetrical top hat shape of the light intensity distribution of the pulse laser beam in accordance with the moving direction of the sample by the stage unit.

  According to the present invention, it is possible to prevent damage due to excessive laser energy in scribing a thin film, and it is possible to scribe a thin film with high accuracy.

  In addition, when the present invention is applied to the cutting of cells of a thin-film solar battery, it has the effect of improving the insulation between unit cells and preventing impurities from being mixed into the film, thereby contributing to the improvement of reliability and life.

It is a figure which shows the processing principle in one Example of this invention. It is sectional drawing of the optical system which forms the top hat with which intensity distribution shown as comparison for demonstrating the principle in one Example of this invention is symmetrical. It is sectional drawing of the optical system which forms the top hat whose intensity distribution is asymmetrical for demonstrating the principle in one Example of this invention. It is sectional drawing of the optical system which forms the top hat whose intensity distribution is asymmetrical for demonstrating the principle in one Example of this invention. It is sectional drawing of the optical system which shows the structure of the imaging optical system in one Example of this invention. It is a block diagram which shows the structure and operation | movement of an outline | summary of the apparatus in one Example of this invention. It is a block diagram which shows the structure and operation | movement of an outline | summary of the apparatus in one Example of this invention. It is a top view of the beam irradiation area | region of the sample which shows the process shape in one Example of this invention. It is a top view of the beam irradiation area | region of the sample which shows the process shape in one Example of this invention. It is a perspective view of the thin film solar cell of the process target in one Example of this invention. It is a figure which shows the outline of the manufacturing process of the thin film solar cell of the process target in one Example of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a processing principle in one embodiment of the present invention. This figure shows the situation where the substrate is irradiated with laser light as seen from the cross-sectional direction. FIGS. 1A to 1C show processing by a top hat image (hereinafter referred to as a symmetric top hat image) in which the intensity distribution of a cross section perpendicular to the optical axis of the laser beam 2 is symmetric, and FIGS. Processing using a top hat image in which the intensity distribution of a cross section perpendicular to the optical axis of the laser beam 2 is asymmetrical (hereinafter referred to as an asymmetric top hat image) is shown. Each of (a), (d), and (g) shows the state of irradiation with the first pulse laser beam 2, (b), (e), and (h) show the state between pulses, and (c), (f) ) And (i) show the state of irradiation with the second pulse laser beam 2. In the figure, 2 is a laser beam, 810 is a glass substrate, 811 is a base film, 820 is a transparent conductive film, 821 is an irradiation region of the laser beam 2 on the transparent conductive film 820, and 822 is a transparent conductive film irradiated with the laser beam 2. A scribe region 820 is removed, and a damaged region 812 is generated in the base film 811. In addition, 201 to 203 shown at the lower side of the substrate in FIGS. 1A, 1C, 1D, 1F, 1G, and 1I are intensities in a cross section perpendicular to the optical axis of the laser beam 2. Show the distribution. Among these, Ea represents the processing threshold value of the transparent conductive film 820, and Eb represents the damage threshold value of the base film 811. In general, since the boiling point of the base film 811 is higher than that of the transparent conductive film 82, Eb is higher than Ea as illustrated.

  Hereinafter, description will be given in the order of the drawings. As shown in FIG. 1A, the cross-sectional intensity distribution of the laser beam 2 is the symmetrical top-hat image, and the cross-sectional intensity of the laser beam 2 is the base film 811 over the entire area 821 where the transparent conductive film 82 is irradiated. If the damage threshold value Eb is larger than the threshold value Eb, the first irradiation with the pulse laser 2 evaporates the transparent conductive film 820 in the entire irradiation region 821 to form a scribe region 822 as shown in FIG. The In the second irradiation of the pulse laser 2 shown in FIG. 1 (c), the glass substrate 810 is continuously moved in one direction on a table (not shown), and therefore, leftward from the first irradiation position by a certain distance. The part is overlapped with the region 821 irradiated with the first pulse laser beam, and the right end of the region 823 irradiated with the laser beam 2 is the first pulse laser beam. The transparent conductive film 820 formed by the irradiation is irradiated to the scribe region 822 where the underlying film 811 is exposed. In the case of a symmetric top hat image, the intensity of the entire beam exceeds the damage threshold value Eb of the base film 811, so that the portion of the scribe region 822 where the base film 811 is exposed is irradiated with the laser beam 2 below. A damaged area 812 is generated in the base film 811.

  Next, the case of an asymmetric top hat image in which the intensity distribution of the cross section of the laser beam 2 is as shown by 202 will be described with reference to FIGS. These three cases show a case where the processing proceeds from the right side to the left side of the drawing. The intensity distribution 202 of the laser beam 2 ′ is set to be lower than the damage threshold value Eb of the base film 811 on the right side. However, since the intensity exceeds the processing threshold value Ea of the transparent conductive film 820 over the entire cross section perpendicular to the optical axis of the laser beam 2 ′, the first pulse laser is irradiated as shown in FIG. Thus, as shown in FIG. 1E, the transparent conductive film 820 in the irradiation region 821 ′ evaporates to form a scribe region 822 ′, as in the case of the symmetrical top hat image described in FIG. The same. The second pulse laser beam 2 ′ is irradiated at a position 823 ′ that is shifted from the first irradiation position 821 ′ to the left by a certain distance and partially overlaps the region 821 ′ irradiated with the first pulse laser beam. Done. At the right end of the region 823 ′ irradiated with the laser beam 2 ′ by the second irradiation, the transparent conductive film 820 is evaporated by the first irradiation of the pulse laser beam 2 ′, and the base film 811 is exposed. However, the intensity of the pulse laser beam 2 ′ irradiated on the exposed base film 811 is lower than the damage threshold Eb of the base film 811. Therefore, even if the laser beam 2 ′ having an intensity distribution like 202 is irradiated to the scribe region 822 ′ formed by the first pulse laser irradiation, the exposed base film 811 is not damaged.

  1 (g) to (i) show a case in which processing proceeds from the left side to the right side of the drawing, contrary to the case of FIGS. 1 (d) to (f). The intensity distribution 203 of the laser beam 2 ″ is reversed from the case of FIGS. 1D to 1F. In this case, the processing direction (the scanning direction of the laser beams 2 ′ and 2 ″ with respect to the glass substrate 810) is. Except for the opposite, the processing principle is exactly the same as in the case of FIGS. That is, as shown in FIG. 1G, a pulse laser 2 ″ having an intensity distribution as shown in 203 is irradiated to the region 821 ″ on the transparent conductive film 820 by the first irradiation, and FIG. As shown, the transparent conductive film 820 in the region 821 ″ irradiated with the pulse laser 2 ″ is evaporated to form a scribe region 822 ″, and a part of the base film 811 is exposed. Is irradiated with a pulse laser 2 ″ on a region 823 ″ overlapping with the first irradiation region 821 ″. At this time, the pulse laser 2 ″ is irradiated to the base film 811 exposed to the scribe region 822 ″ formed by the first pulse laser 2 ″ irradiation. The pulse laser 2 ″ has an intensity distribution as indicated by 203. The beam intensity of the pulse laser 2 ″ irradiated to the exposed underlayer 811 is lower than the damage threshold value Eb of the underlayer 811. Therefore, the first irradiation with the pulse laser 2 ″ is performed. Even if the formed scribe region 822 ″ is irradiated with the laser beam 2 ″ having an intensity distribution like 203, the exposed base film 811 is not damaged.

  Therefore, the transparent conductive film 820 can be selected without causing damage to the underlying film 811 even if the processing proceeds in either the left or right direction by simply reversing the intensity distribution of the asymmetric top hat image as 202 and 203. Can be processed automatically.

  2 to 4 show the principle of the asymmetric top hat forming optical system. In this example, an optical system using a diffractive optical element is shown. In each figure, 7 is a diffractive optical element, 71 is an inner region, 72 is an outer region, and 2 is a laser beam.

  Prior to the asymmetric top hat image, the principle of forming the symmetric top hat image will be described with reference to FIG. Laser light 2 emitted from a light source (not shown) on the left side of FIG. 2A travels in the direction of the arrow in the state of parallel light and enters the diffractive optical element 7. In this example, the diffractive optical element 7 is composed of two regions having different optical characteristics, an inner region 71 and an outer region 72, and the focal lengths of the diffractive optical element 7 are different from each other at fi and fo. That is, it can be interpreted that the spherical aberration is intentionally created.

  FIGS. 2B to 2E show the principle of forming a top hat image. (B) to (e) show image formation at distances Wd, fo, and fi on the incident side and the diffractive optical element exit side of the diffractive optical element 7, respectively. The incident side laser beam 210 is divided into an inner region 213 and outer regions 211 and 212 as shown in FIG. On the emission side, the light from each region is condensed into fi and fo, and the light from the inner region 71 and the light from the outer region 72 have the sharpest and highest peak intensity at these distances. That is, at the position of fo, as shown in FIG. 2D, components 232 and 233 emitted from the outer region of the diffraction grating 7 have the sharpest and highest peak intensity, and components emitted from this and the inner region. 231 and the combined light flux 230, and at the position fi, the component 241 emitted from the inner region of the diffraction grating 7 has the sharpest and highest peak intensity as shown in FIG. A light beam 240 is obtained by combining the components 242 and 243 emitted from the region. Here, since fo is closer to fi, the light emitted from the diffraction grating 7 before the fo is the peak intensity 221 of the light emitted from the inner region 71 of the diffraction grating 7 as shown in FIG. Accordingly, there is a position WD where the modulus of the peak intensities 222 and 223 of the light emitted from the outer region 72 is increased. Therefore, a top hat image is formed at this position. This distance from the diffractive optical element 7 to the position of WD is usually called the working distance of the diffractive optical element 7.

  Similar to the above, the principle of forming an asymmetric top hat image will be described with reference to FIG. FIG. 3A shows the optical axis of the laser beam 2 incident on the diffractive optical element 7 shifted downward as compared with FIG. That is, as shown in FIG. 3B, in the light beam 310 of the laser 2 incident on the diffractive optical element 7, the component 311 is incident on the inner region 71 of the diffractive optical element 7 and the component 312 is outside the diffractive optical element 7. It enters the region 72. Therefore, in this case, the light incident on the inner region 71 decreases and the light incident on the outer region 72 increases. As a result, as shown in FIG. 3C, the intensity of the top hat image 320 formed at the position of WD increases with the lower component 322 and decreases with the upper component 321. In this way, an asymmetric top hat image 320 is formed.

  FIG. 4A shows a case where the optical axis of the laser beam 2 is shifted in the direction opposite to that in FIG. In this case, as shown in FIG. 4B, in the light beam 410 of the laser 2 incident on the diffractive optical element 7, the component 411 enters the inner region 71 of the diffractive optical element 7, and the component 412 The light enters the outer region 72. As a result, as shown in FIG. 4C, the intensity of the top hat image 420 formed at the position of WD increases with the upper component 422 and decreases with the lower component 421.

  Therefore, the tilt direction of the asymmetric top hat image can be switched by merely shifting the optical axis of the laser beam 2 up and down with respect to the diffractive optical element 7.

  As described above, according to this embodiment, an asymmetric top hat image can be formed using a diffractive optical element, and irradiation as described with reference to (d) to (i) of FIG. 1 is performed. Thus, it is possible to selectively process only the transparent conductive film 820 on the surface without damaging the base film 811.

  In the above description, the laser beam is scanned linearly on the transparent conductive film 820. However, the present invention is not limited to this, and the laser beam is scanned on a thin film in a circular or arbitrary locus. The thin film can be selectively processed into a circular shape or an arbitrary shape.

  Although not shown in this example, an asymmetric top hat can be obtained by similarly shifting the optical axis in the case of a top hat optical system using an aspheric lens.

  In the above-described formation of the asymmetric top hat image, the diffractive optical element 7 having different optical characteristics is used in the inner region 71 and the outer region 72. However, a normal condensing light is used instead of the diffractive optical element 7. Using a lens, a laser beam 2 having a Gaussian distribution as shown in FIG. 2B, for example, is shifted with respect to the optical axis of the condenser lens as described in FIG. 3 or FIG. May be made incident. In this case, the light emitted from the condensing lens has an asymmetric intensity distribution on the WD surface due to coma aberration of the condensing lens, an asymmetric Gaussian image is formed, and the glass substrate 810 having the transparent conductive film 820 formed on the base film 811 is formed. By performing the irradiation as described in FIGS. 1D to 1I, it is possible to selectively process only the transparent conductive film 820 on the surface without damaging the base film 811.

  The asymmetric top hat image described with reference to FIGS. 3 and 4 has been described with the configuration in which the light emitted from the diffractive optical element 7 formed concentrically is irradiated to the glass substrate 810 as it is. For example, the glass substrate 810 may be irradiated with a light-shielding mask that shields the periphery and formed into a rhombus or an ellipse.

  FIG. 5 shows an asymmetric top hat relay optical system for forming an asymmetric top hat image. In the configuration shown in FIG. 5, reference numeral 2 denotes a laser that proceeds in the direction of the arrow. 7 is a diffractive optical element, 8 is a relay lens, and 9 is a condenser lens. In this optical system, the working distance WD of the diffractive optical element 7, the focal length f8 of the relay lens 8, and the focal length f9 of the condensing lens 9 are set to substantially equal values. Therefore, the asymmetric top hat image formed by the diffractive optical element 7 is transferred to the position of the focal length f9 of the condenser lens 9 at the same magnification. In the figure, the solid line indicates the case where the optical axis of the laser beam 2 is aligned with the diffractive optical element 7, and the dotted line is the case where the optical axis of the laser 2 is shifted from the diffractive optical element 7. As in the case described with reference to FIGS. 2 to 4, the former forms a symmetric top hat image and the latter forms an asymmetric top hat image at a distance WD from the diffractive optical element 7. Further, the light emitted from the relay lens 8 becomes parallel light and enters the condenser lens 9, and a symmetric top hat image or an asymmetric top hat image is formed again at a distance of f9 from the condenser lens 9. Since the light emitted from the relay lens 8 is parallel light, the formation position of the asymmetric top hat image can be changed by changing the distance between the relay lens 8 and the condenser lens 9. It is also possible to change the size of the top hat image by changing one or both of the values of f8 and f9.

  As described above, the position and size of the asymmetric top hat image obtained by using the optical system as shown in FIG. 5 can be varied as necessary.

  6 and 7 show the configuration and operation of a thin film laser patterning apparatus. In FIG. 6, 1 is a laser light source, 2 is a laser emitted from the laser light source 1, 3 is a beam collimator, 4a to 4e are mirrors, 7 is a diffractive optical element, 73 is a diffractive optical element scanning mechanism, 8 is a relay lens, 9a to 9d are condensing lenses, 10a to 10c are beam splitters, 21a to 21d are branched laser beams, 810 is a glass substrate, and 821 and 822 are scribe regions. Although details are not shown in the figure, a base film 811 is formed on a glass substrate 810, and a transparent electrode film 820 is formed thereon in advance.

  The operation of this embodiment will be described in detail with reference to FIG. The laser light 2 generated from the laser light source 1 is improved in parallelism by the beam collimator 3, and then the optical path is bent by the mirror 4 a and enters the diffractive optical element 7. The top hat image formed thereby is transferred by the relay lens 8 and the condenser lenses 9a to 9d in the same manner as described in FIG. In the configuration shown in FIG. 6, by inserting half beam splitters 10a to 10c between the relay lens 8 and the condenser lenses 9a to 9d, four branch lasers 21a to 21d are formed, and the condenser lens 9a is formed. A top hat image is formed for each of .about.9d. By performing positioning so that the image positions of the condenser lenses 9a to 9d are on the surface of the glass substrate 810, it is possible to simultaneously form the scribe regions 821 with the top hat images at the four locations on the glass substrate 810. The top hat image at this time has an intensity distribution characteristic having a peak in the traveling direction of the laser beam 2 or the glass substrate 810 as shown by 202 used for irradiation in FIGS. . Thereby, for example, high-efficiency processing is possible even if the glass substrate 810 has a large size of 5.5G.

  Here, the diffractive optical element 7 is scanned in the x direction by the diffractive optical element scanning mechanism 73. As a result, a top hat image asymmetric in the x direction is formed on the exit side of the diffractive optical element 7. Further, as described with reference to FIG. 5, the asymmetric top hat image is transferred by the relay lens 8 and the condenser lenses 9a to 9d, and a top hat image that is asymmetric in the direction is formed under the condenser lenses 9a to 9d. Is done. As shown by the arrows in the figure, the glass substrate 810 is scanned in the x direction, and the bottom formed on the glass substrate 810 is continuously irradiated with an asymmetric top hat image partially overlapped in the same direction. Only the transparent electrode film 820 on the substrate can be selectively removed without damaging the base film 811.

  FIG. 7 shows a state where the glass substrate 810 is scanned in the left direction (−X direction) and then scanned in the reverse right direction (+ X direction) in the same apparatus as FIG. 6. That is, after the scribe region 821 is formed from the left end to the right end of the substrate, the glass substrate 810 is continuously moved in the opposite direction (+ X direction) after shifting by a predetermined pitch in the y direction, and the scribe region is formed on the glass substrate 810. 822 is formed partway. As can be seen from a comparison with FIG. 6, the diffractive optical element 7 is driven by the diffractive element driving mechanism 73 and is arranged on the opposite side to the case of FIG. 6 with respect to the optical axis of the laser light 2. Therefore, the asymmetric top hat image has a shape inclined in the opposite direction to the case of FIG. That is, the top hat image at this time has an intensity distribution characteristic having a peak in the traveling direction of the laser beam 2 or the glass substrate 810 as shown by 203 used in the irradiation in FIGS. ing.

Subsequently, each time the glass substrate 810 is reciprocated in the x direction, the diffractive optical element 7 moves alternately to the left and right with respect to the laser beam 2. This operation is continued until the scribe regions 821, 822,... Are formed on the entire surface of the glass substrate 810. As described above, it is possible to selectively process only the transparent conductive film 820 over the entire surface of the glass substrate 810 without damaging the base film 811 formed on the glass substrate 810. Further, since processing with an asymmetric top hat can be performed in both the reciprocating directions of the substrate, high-quality processing without loss of time and no removal of any scribe region is possible.
Although not shown in the drawing, the same result can be obtained in principle by moving the relay lens 8 or the condensing lenses 9a to 9d to the left and right instead of moving the diffractive optical element 7 to the left and right. Is obvious.

  FIGS. 8A and 8B show shapes of the scribe regions 821 and 822 of the transparent conductive film 820 processed by the apparatus described with reference to FIGS. 6 and 7 when viewed from the substrate surface side. 6A shows a scribe region 821 which is processed by moving the glass substrate 810 in the direction shown by the arrow in FIG. 6, that is, from the right to the left in the drawing, in the apparatus configuration shown in FIG. 6, and FIG. 7 is a scribe region 822 processed by moving the glass substrate 810 in the direction indicated by the arrow in FIG. 7, that is, from the left to the right in the drawing. In other words, (a) moves the laser spot from the left to the right relative to the glass substrate 810 as shown by the arrow, and (b) moves the laser spot from the right to the left relative to the glass substrate 810. It is a thing. In either case, although the processing direction is different, the transparent conductive film 820 is removed smoothly by irradiating the laser beam having the intensity distributions 202 and 203 as described in FIGS. Scribe regions 821 and 822 are formed.

  On the other hand, FIG. 8C shows the scribing regions 821 and 822 of the transparent conductive film 820 when the glass substrate 810 is processed with the laser beam 2 having a symmetric top hat beam profile without using the method of the present invention. Is a shape seen from the substrate surface side. A black area 811 indicates a damaged area generated in the base film 811 formed on the glass substrate 810. As shown in the drawing, a damaged region 811 of the glass substrate 810 is generated at a place where the laser spots are overlapped with each other. This is because the energy becomes excessive at the location where the laser spot is superimposed.

Regarding the intensity distribution in the direction perpendicular to the moving direction, that is, the vertical direction in the figure, the case of the present invention shown in FIGS. 8A and 8B and the conventional case shown in FIG. Are symmetric top-hat shapes.
When the beam scanning method of FIGS. 8A and 8B according to the present embodiment is compared with (c) in the case of a top hat shape with a simple beam intensity distribution, the top hat is asymmetric with respect to the beam scanning direction. The effect of molding into a shape is clear.

  As described above, according to this embodiment, it is possible to selectively process only the film on the substrate without damaging the glass substrate.

  FIG. 9 is a view showing a modification of the asymmetric top hat shape. In the laser beam described with reference to FIG. 8, the shape of the cross section perpendicular to the optical axis of the laser beam of the asymmetric top hat image is circular, but in the present embodiment, this is a square asymmetric top hat image. In addition, regarding the direction perpendicular to the moving direction, that is, the vertical direction in the figure, the top hat shape is symmetric as in the conventional case. This is because the diffractive optical element 7 is replaced with a type that forms a square top hat in the apparatus shown in FIGS. 2 to 7 or a mask for forming a square asymmetric top hat image is provided on the exit side of the diffractive optical element 7. Can be implemented. Also in this embodiment, the damage to the glass substrate can be prevented at the place where the laser spot is superimposed, which is exactly the same as the case described with reference to FIG. Further, it is obvious that the present method can be applied not only to a square but also to a rectangular spot or a rhombus or ellipse spot described above. In general, the shape of the laser spot is selected depending on the property of the material and the target processing quality, but the processing method according to the present invention can be applied to any spot shape.

  FIG. 10A shows a configuration of a thin film solar cell. The thin film solar cell has a stacked structure in which an amorphous photoelectric conversion film 830 is formed on a glass substrate 810 so as to be sandwiched between a transparent electrode film 820 and a back electrode film 840.

  Further, as shown in the figure, this thin-film solar cell is formed by electrically connecting a plurality of unit cells composed of an amorphous photoelectric conversion film 830, a transparent electrode screen 820, and a back electrode film 840 stacked on a glass substrate 810. Utilizes a phenomenon in which an electromotive force generated by the amorphous photoelectric conversion film 830 is generated between the transparent electrode film 820 and the back electrode film 840 of each unit cell by being excited by sunlight. is doing. Therefore, an electromotive force obtained by adding the electromotive forces of the unit cells appears as an output voltage of the solar cell between the electrodes at both ends of the plurality of unit cells connected in series.

  In order to obtain a structure in which a plurality of unit cells are integrated in this manner, thin film solar cells are manufactured by laminating each thin film layer while patterning using a laser scribing method.

  The scribe regions 821, 822, and 823 formed on the transparent conductive film 820 are formed by processing laser light having a wavelength of 1064 nm into an asymmetric top hat image. Similarly to the fourth embodiment, the scribe area 821 is processed from the lower left to the upper right, the scribe area 822 is processed from the upper right to the lower left, and the scribe area 823 is processed from the lower left to the upper right. Even if processing is performed while reciprocating the substrate in this way, as described in Example 4, by alternately reversing the inclination direction of the asymmetric top hat image, high-quality processing without any damage to the glass substrate in any scribe region Is possible.

  The manufacturing process will be specifically described with reference to FIG. 10B. First, (a) a glass substrate 810 is prepared, and (b) a transparent electrode film 820 is formed on the main surface of the glass substrate 810. (C) The first scribe regions 821, 822,... Are formed on the transparent electrode film 820 by removing the transparent electrode film 820 at a predetermined pitch (unit cell pitch: d) by irradiating and scanning with a laser. Then, the transparent electrode film 820 is insulated and divided into strips. In this process, a 1064 nm asymmetric top hat image is used as the laser light. Thereby, the transparent electrode film 820 can be selectively removed without damaging the glass substrate 810.

  Next, (d) an amorphous photoelectric conversion film 830 is stacked on the laser-processed transparent electrode film 820, and (e) a first scribe film formed on the previously formed transparent electrode film 820. .., By irradiating a laser to a region shifted from the region overlapping with the regions 821, 822,... And removing the amorphous photoelectric conversion film 830 at a predetermined pitch d, thereby adding a second to the amorphous photoelectric conversion film 830. Are formed, and the amorphous photoelectric conversion film 830 is insulated and divided into strips. In this process, a 532 nm asymmetric top hat image is used as laser light. Thereby, the amorphous photoelectric conversion film 830 can be selectively removed without damaging the transparent conductive film 820.

  Further, (f) a back electrode film 840 is laminated on the laser-processed amorphous photoelectric conversion film 830, and (g) second scribe regions 831, 832... Formed on the amorphous photoelectric conversion film 830. A third scribe region 841, 842,... Is formed in the back electrode film 840 by irradiating the laser at a predetermined pitch d and scanning the region shifted from the overlapping region with a predetermined pitch d to remove the back electrode film 840. The back electrode film 840 is insulated and divided into strips. In this process, a 532 nm asymmetric top hat image is used as laser light. Thereby, the back electrode film 840 can be selectively removed without damaging the transparent conductive film 820.

Same as general solar cell. The back electrode film 840 is electrically connected to the transparent electrode film 820 through second scribe regions 831, 832,... Formed in the amorphous photoelectric conversion film 830. According to the present invention, the transparent electrode film 820, the amorphous photoelectric conversion film 830, and the back electrode film 840 are each selectively removed, and other films are not removed in the same scribe region. Thus, high power generation efficiency can be obtained. In addition, since damage to the glass substrate 810 and other films can be prevented, mixing of impurities that cause deterioration can also be prevented.
As described above, according to the present invention, a high-performance and highly reliable solar cell can be manufactured.

  In this embodiment, the transparent electrode film 820, the amorphous photoelectric conversion film 830, and the back electrode film 840 are processed by the asymmetric top hat image, but only a part of the films is processed by the asymmetric top hat image. Of course it is also possible.

  The present invention can of course be used for processing of a solar cell substrate, but can be applied to a general device manufacturing apparatus created by processing a film formed on a large substrate such as a liquid crystal display element.

DESCRIPTION OF SYMBOLS 1 ... Laser light source 2 ... Laser beam 3 ... Beam collimator 4a, 4b, 4c, 4d, 4e ... Mirror 7 ... Diffractive optical element 71 ... Inner area | region 72 ... Outer area | region 73 ... Diffraction optical element scanning mechanism 8 ... Relay lens 9a, 9b, 9c, 9d ... Objective lens 10a, 10b, 10c ... Half beam splitter 810 ... Glass substrate 811 ... Damage area 820 ... Transparent electrode film 821, 822, 823 ... Scribe region 830 ... Amorphous photoelectric conversion film 831, 832, 833 ... Scribe region 840 ... Back electrode film 841, 842, 843 ..Scribe area

Claims (8)

  A method for partially removing the thin film from the surface of the sample by irradiating a thin film formed on the surface of the sample with a pulsed laser beam while scanning with respect to the surface of the sample. The pulse laser is shaped so as to have a top hat shape intensity distribution that is asymmetric with respect to the relatively scanning direction, and the irradiation region of the shaped pulse laser is irradiated while partially overlapping, and the relative scanning is performed. A thin film laser patterning method, wherein the thin film in the region irradiated by scanning relatively is removed.   2. The thin film laser patterning method according to claim 1, wherein the intensity distribution in the direction of scanning the asymmetric top hat-shaped intensity distribution relative to the surface of the sample is in the direction of the relative scanning. A thin film laser patterning method, wherein the thin film laser patterning method is characterized in that the film is shaped so as to be stronger than a rear strength.   3. The thin film laser processing method according to claim 2, wherein the intensity behind the relative scanning direction in the asymmetric top hat intensity distribution is a threshold value at which a material under the thin film to be removed is processed. A thin film laser patterning method characterized by being lower than power. 4. The thin film laser processing method according to claim 1, wherein the relative scanning is performed by irradiating the formed pulse laser while partially overlapping an irradiation region of the pulsed laser. The shaped pulse laser in front of the relatively scanning direction irradiates the thin film formed on the surface of the sample, and the shaped pulse laser in the rear of the scanning direction relative to the surface of the sample is A thin film laser patterning method comprising irradiating a lower surface of the thin film exposed by removing the thin film.   A pulse laser light source for emitting a pulse laser beam; stage means for placing a sample and moving in a plane; and a pulse laser beam emitted from the pulse laser light source within a cross section perpendicular to the optical axis of the beam. A beam irradiation optical system for irradiating the sample with a pulsed laser beam shaped into a top hat shape having an asymmetric light intensity distribution by the optical element. The stage means is a region where the region on the sample irradiated with the pulse laser beam shaped into a top hat shape in which the light intensity distribution is asymmetric by the optical element of the beam irradiation optical system is sequentially irradiated last time. The beam irradiation optical system moves the sample in accordance with the moving direction of the sample by the stage means. Scan the laser beam in a thin film laser patterning apparatus characterized by having a top hat shape changing unit for changing the asymmetrical top hat shape of the light intensity distribution. 6. The thin film laser patterning apparatus according to claim 5, wherein the beam irradiation optical system converts the pulse laser beam so that a light intensity distribution in a cross section perpendicular to the optical axis of the beam has a top hat shape. A thin film laser patterning apparatus comprising a diffractive optical element or an aspheric lens as an element. 6. The thin film laser patterning device according to claim 5, wherein the beam irradiation optical system further includes a relay lens and an objective lens, and the optical intensity distribution in the cross section perpendicular to the optical axis of the beam is top in the optical element. A thin film laser patterning apparatus, wherein an image of a pulsed laser beam converted into a hat shape is re-imaged on the sample by a combination of the relay lens and objective lens.   6. The thin-film laser patterning device according to claim 5, wherein the top hat shape changing unit of the beam irradiation optical system is configured so that the optical element has an optical axis relative to the optical axis of the pulse laser beam according to the moving direction of the sample by the stage means. A thin film laser patterning apparatus, wherein the top hat shape is changed by switching positions.

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