JP3439179B2 - Laser etching method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a photovoltaic device in which a plurality of photoelectric conversion elements that generate electromotive force by light irradiation are electrically connected to each other, and a transparent electrode film, an amorphous semiconductor film, The present invention relates to a laser etching method for forming a separation groove for electrically insulating each photoelectric conversion region on a plane of a metal electrode film.

[0002]

2. Description of the Related Art In order to separate unit photoelectric conversion elements on a substrate such as a solar cell and connect them in series on the substrate, it is necessary to form a separation groove in an electrode film and a power generation film. In recent years, by using a laser scribing method that is excellent in fine workability as a processing method for forming the separation groove, the groove width is narrowed to increase the actual photoelectric conversion area per apparent battery area, thereby improving the overall conversion efficiency. The device to raise is made.

For example, in this method, N of wavelength 1.06 μm is used.
d: YAG laser is used to irradiate the processed portion with a beam diameter such that the groove width is about 50 μm, and the film to be processed is relatively moved in the separation groove forming direction and etched by the laser beam to form the groove. The portion of the film to be processed is removed.

In this processing method, the pattern of the cross section perpendicular to the optical path of the beam emitted from the laser oscillator has a circular shape, and the distribution of the laser intensity on its diameter is a Gaussian distribution shape, and the center has the strongest circle. It has a bell-shaped distribution that draws a skirt toward the periphery. Therefore, the shape of this distribution does not change even if the beam is focused by a lens in accordance with the width of the separation groove to form a circle of a planned diameter on the processing surface. This state is shown in FIG.

In FIG. 3A, reference numeral 31 is a planned target separation groove, 33 is a plan view of both sides of the separation groove etched by the conventional laser beam, 32 is a pattern on the processed surface of the conventional beam, R Is the beam diameter, D in FIG. 3B is the intensity distribution curve of the conventional laser seen on the AA ′ plane, Im is the maximum intensity value, and I is the average intensity value (∫D /
R), in FIG. 3 (c), 33 is a conventional separation groove processing cross section, 31 is a planned target processing cross section, F1 is a film to be processed, and F2 is a layer adjacent to the film to be processed.

That is, the beam diameter R is set according to the target (planned) value of the groove width, and the laser intensity is set to, for example, the average value I according to the material and the groove depth. Since it has the intensity distribution D as shown in FIG. 3 (b), the processed separation groove is finished in a cross section like (c) 33, and the finished cross section 31 is not finished. Further, since the center line of the separation groove is exposed to the maximum strength Im, the film F1 to be processed is processed.
Draw through the bottom of the planned separation groove.

This causes the adjacent layer film F2 to be melt-altered and the melt-altered substance to adhere to the periphery of the groove. This phenomenon deteriorates the adhesion when another film is further laminated on the adjacent layer film F2 exposed in the separation groove portion in the next step.

Further, since the section (c) 33 of the separation groove is exposed to the laser at the skirt portion of the intensity distribution, sufficient energy for vaporizing and evaporating the material cannot be given. When the grooved film is a semiconductor film, this energetically lacking portion undergoes melting or annealing without evaporating, and the groove wall surface becomes a state such as a partially doped single crystal. Remain. That is, the PIN junction appears to be short-circuited and the device characteristics are significantly deteriorated.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and a transparent electrode film, an amorphous semiconductor film or a metal electrode film is irradiated with a laser beam to flatten the film. In the method of forming a separation groove for separating in, the conventional laser scribing method overcomes the disadvantage inherently caused, and provides a photoelectric conversion device with excellent photoelectric conversion efficiency that does not deteriorate the device characteristics. For the purpose of provision. Further, another object is to provide a laser etching method having the above characteristics and having a high processing speed.

[0010]

SUMMARY OF THE INVENTION The present invention is a laser for an irradiation section.
-The beam pattern is elliptical and the major axis of the ellipse is a separation groove.
After shaping into a beam that matches the direction center line,
Beam intensity in the direction perpendicular to the separation groove direction (beam movement direction)
Cut off the bottom of the distribution according to the separation groove width
A cut-off means is arranged to make the laser beam intensity distribution of the irradiation portion on the film different in the separation groove forming direction and the direction perpendicular thereto, and the separation groove direction is Gaussian distribution, and the direction perpendicular to the separation groove forming direction is substantially rectangular. Characterized by having a distribution, preferably the cut-off means is a rectangular slit,
Align the long side center line of the slit with the long axis of the ellipse.
The elliptical laser pattern
The longer side direction of the longer than the major axis of the laser pattern,
The short side is set to be narrower than the short diameter of the laser pattern .

As is well known, in such processing, the laser to be used repeats pulsed irradiation with respect to the time axis,
The movement stroke and timing are controlled for each pulse to relatively move the beam in the separation groove forming direction. As described above, since the beam cross section or irradiation surface has a circle or an outer periphery close to it, in order to perform etching in the groove forming direction uniformly at the processing depth and up to the set depth, the head and tail of the beam pattern in the moving direction should be used. Move with a slight overlap. Therefore, the laser intensity of the superposed portion becomes the combined value of that portion of the front and rear beams, and becomes stronger. Since it is not preferable that this is more than the limit, which leads to a penetration phenomenon, it is preferable in the present invention that the vicinity of the pattern contour in the moving direction has an intensity distribution that attenuates toward the vicinity of the contour, that is, a normal Gaussian distribution. The above-mentioned beam superposition is usually 10 to 20% of the beam length in the moving direction, but in order to reduce the influence on the underlying film, the laser output is higher than the laser energy density required for removing the film to be etched. 2 to 5 in the same place by reducing the beam overlap and setting the beam overlap to 50% or more.
Often times irradiation is performed. In this case, if the Gaussian distribution is present in the moving direction, the beam portion of weak intensity is first irradiated and then the strong portion is gradually irradiated.
This is very convenient because it has a small effect on the underlying film.

On the other hand, the intensity distribution of the beam pattern in the direction of movement, that is, in the direction perpendicular to the separation groove direction, drops sharply on both sides of the separation groove, and the average energy in the perpendicular direction is close to the maximum value of the distribution. With the shape, it is possible to effectively prevent the difficulties as encountered in the above-mentioned prior art, that is, the phenomenon of penetration in the beam pattern intensity distribution max portion (center) and the phenomenon of remaining untranspirationd altered portions on both sides of the separation groove. Of. That is, in the present invention, the distribution form is a distribution close to a rectangle.

Further, according to the present invention, after the laser beam pattern of the irradiation portion is elliptical and the major axis of the ellipse is shaped into a beam which coincides with the center line of the separation groove forming direction, a beam in a direction perpendicular to the separation groove direction is formed in the optical path. It is also characterized in that a cutoff means for cutting off the skirt portion of the intensity distribution is arranged.

The present inventors have separately proposed a method of making the irradiation pattern of the laser beam in the laser scribing method into an ellipse. According to this, the irradiation drawing length of the beam in the processing direction is increased while the energy density is the same, and the processing speed is increased. However, the present invention also employs the method, and is required by the present invention. For the distribution in the perpendicular direction, the arc portion having the major axis of the ellipse as the chord is cut at both sides of the separation groove.

As a result, the beam intensity distribution in the processing direction is Gaussian, and the beam intensity distribution is close to a rectangle at the right angle, and the processing speed is high.

Further, the present invention is also characterized in that the cut-off means is a rectangular slit, and the center line of the slit in the long side direction coincides with the long axis of the ellipse.

That is, as one of the cut-off means, in the present invention, a slit such as a light-shielding plate having a rectangular opening is placed in the optical path to cut the beam at the foot of the Gaussian distribution, and the intensity in the right-angled direction is the separation groove. The distribution is sharply cut off on the shore. The opening width is a value determined by the separation groove width.

The present invention is further characterized in that the elliptical pattern of the laser beam is created by arranging a cylindrical lens in the optical path of the laser beam. That is, the beam emitted from the laser oscillator is once diverged by the cylindrical concave lens, and when the ratio of the major axis and the minor axis is reached, the beam is made parallel by the cylindrical convex lens.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be exemplarily described in detail below with reference to the drawings. However, the types, shapes, relative arrangements, etc. of the constituent devices described in this embodiment are merely examples of explanation, not the intention to limit the scope of the present invention thereto, unless otherwise specified. .

FIG. 2 shows a laser etching apparatus used in the method of the present invention. 21 is a YAG laser oscillator, 22
Is a laser beam, 23 is a cylindrical concave lens, 2
4 is a cylindrical convex lens, 25 is a mirror, 26 is an objective lens, 27 is a substrate, 28 is a slit, and 29 is an XY stage.

A laser having a wavelength suitable for the material of the film to be processed from the YAG laser oscillator 21 and an output suitable for the material of the film to be processed, the separation groove depth, and the separation groove width R, for example, 10 k
Extract a pulse wave of Hz frequency. The laser beam is shaped by the cylindrical concave lens 23 and the cylindrical convex lens 24 into an elliptical beam cross section. The long side direction of the beam coincides with the ellipse long axis direction, and a rectangular slit 28 with its center line aligned is placed at the center of the optical axis to cut the Gaussian distribution skirt around the beam. The direction of this beam is changed by 90 degrees by the mirror 25, and an image is formed on the surface of the film to be processed on the substrate 27 by the objective lens 26. Then, XY
The stage 29 is moved relatively at a speed and a moving distance according to the pulse frequency and the pattern superimposition degree so that the beam advances in the separation groove forming direction, and the separation groove forming process is achieved.

FIG. 1 is a view of a first embodiment of the method of the present invention carried out by using the apparatus of FIG. 2, in which a rectangular slit is arranged on the optical path of an elliptical beam pattern as viewed from the rear of the optical path. is there. Reference numeral 10 is a slit pattern, and 12 is an elliptical beam pattern. 12 is obtained by forming a beam pattern with a cylindrical lens system described later. 10
Is a light-shielding plate provided with an opening as shown.

(B) shows that the separation groove is scribed using the beam pattern obtained by the above optical system and having the distribution skirt cut off in the direction (AA 'cross section) perpendicular to the separation groove forming direction. Indicated. 11 is the plan separation Mizogishi, 1
Reference numeral 3 indicates a processed separation groove bank, R indicates a separation groove width, and an arrow indicates a direction in which the beam pattern relatively moves. Although only one pulse of the laser beam is shown in the figure, the beam is moved by overlapping the front and rear of the pulsed beam by 20%.

In (c), when the intensity distribution D of the above pattern in the AA 'cross section is viewed, a Gaussian curve still remains in the central portion of the distribution intensity curve, but a sharp intensity drop occurs almost vertically on the separation trench. It shows that the distribution is substantially rectangular according to the present invention. Therefore, within the separation groove width R, the strength within the average value, which is the desired strength, is maintained, so that the punch-through phenomenon does not occur. This is shown in (d).

In FIG. 1D, F1 is the film to be processed, F2 is the adjacent layer film, and it can be seen that sharp scribing is possible with the film to be processed F1 and the adjacent layer film F2 is not affected. Therefore, since there is no defective portion of the adjacent layer film F2 and adhesion of the molten residue of the adjacent layer film F2, the adhesion of the film formed in the subsequent step is improved. Then, the sharp change in the strength at the separation trench prevented the migration of the semiconductor layer. Thus, the photoelectric conversion efficiency of the photoelectric conversion device in which the photoelectric conversion regions obtained by alternately repeating the overlaying and scribing of the electrode film and the semiconductor layer film on the substrate were connected in series was good.

[0026]

As described above, the laser etching method according to the present invention overcomes the disadvantages inherent in the conventional laser scribing method and provides a photoelectric conversion device having excellent photoelectric conversion efficiency without deteriorating the device characteristics. It is also possible to provide a laser etching method having the above characteristics and having a high processing speed.

[Brief description of drawings]

1A is a conceptual diagram in which a rectangular slit is arranged on an optical path of an elliptical beam pattern, and FIG. 1B is a conceptual diagram in which a separation groove is etched by irradiating a laser beam having a beam pattern of the present invention. , (C) is a diagram showing a substantially rectangular intensity distribution in the direction perpendicular to the separation groove exhibited by the beam pattern of the present invention, and (d) is a schematic view of the separation groove shape processed by the method of the present invention.

FIG. 2 is a schematic view of an example of a laser etching apparatus used in the method of the present invention.

FIG. 3 (a) is a schematic diagram in which a separation groove is etched by a conventional method, and FIG. 3 (b) is a diagram showing a substantially rectangular intensity distribution in a direction perpendicular to the separation groove, which is exhibited by the beam pattern of the present invention,
(C) is a schematic view of a separation groove shape processed by a conventional method.

[Explanation of symbols]

10 slit pattern 11 planned separation groove bank 12 elliptical beam pattern 13 post-processing separation groove bank D laser intensity distribution Im in the direction perpendicular to the separation groove max value I in laser intensity distribution perpendicular to the separation groove I average in laser intensity distribution in the direction perpendicular to the separation groove Value R Separation groove width F1 Processed film F2 Adjacent layer film 21 YAG laser oscillator 22 Oscillation laser beam 23 Cylindrical concave lens 24 Cylindrical convex lens 25 Mirror 26 Objective lens 27 Workpiece 28 Slit 29 XY stage 31 Planned separation groove bank 32 Circular beam pattern 22 Separation groove after processing

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Yamauchi 1-1-1, Satinoura-machi, Nagasaki City Mitsubishi Heavy Industries Ltd. Nagasaki Shipyard (56) Reference JP-A-62-40986 (JP, A) JP 61-259524 (JP, A) JP-A 10-52780 (JP, A) JP-A 2-137687 (JP, A) JP-A 63-179581 (JP, A) JP-A 3-64043 (JP , A) JP-A-4-94174 (JP, A) JP-A-2000-124488 (JP, A) JP-A-63-153514 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) ) H01L 31/04-31/078 B23K 26/00-26/18

Claims (2)

(57) [Claims] 1. A transparent substrate having a laminated film of a conductive transparent electrode film, an amorphous semiconductor film, and a metal electrode film, which is separated on a substrate in module units, and the separated modules are connected in series on the substrate. A method for manufacturing a photovoltaic device connected to a transparent electrode film, an amorphous semiconductor film, or a metal electrode film is irradiated with a laser beam to form a separation groove for separating the film in a plane. And the laser beam pattern of the irradiation part is elliptical and the length of the ellipse is long.
After forming a beam whose axis matches the center line of the separation groove,
The tail of the beam intensity distribution in the direction perpendicular to the separation groove direction in the optical path
A cut-off that cuts off the field part according to the separation groove width.
Means to disperse the laser beam intensity distribution of the irradiation part on the film in the direction of the separation groove and the direction perpendicular to the separation groove.
A laser etching method characterized in that the forming direction is a Gaussian distribution and the direction perpendicular to the separation groove direction is a substantially rectangular distribution. Wherein said cut-off means is a rectangular slit, the longitudinal direction center line of the slit Rutotomoni to match the long axis of the ellipse, the elliptical laser pattern
In contrast, the longer side of the slit is the major axis of the laser pattern.
Longer, with the shorter side narrower than the shorter diameter of the laser pattern
Laser etching method according to claim 1, wherein the setting the.