JPWO2011027533A1 - Thin film solar cell manufacturing method and manufacturing apparatus thereof - Google Patents

Abstract

A thin-film solar cell manufacturing method and a manufacturing apparatus thereof capable of appropriately patterning a ZnO-based transparent conductive film. A method of manufacturing a thin-film solar cell according to an embodiment of the present invention forms an infrared pulsed laser beam having a cross-sectional intensity distribution in which the beam intensity in the peripheral part is higher than that in the central part, and is formed on a transparent substrate. The zinc oxide (ZnO) transparent conductive film is irradiated with the infrared pulse laser beam, and the infrared pulse laser beam is scanned while overlapping a part of the irradiation range. By using infrared pulsed laser light having such a cross-sectional intensity distribution, film residue at the boundary between the laser irradiation region and the non-irradiation region can be suppressed, and the shape of the boundary can be sharply formed. . Thereby, a zinc oxide type transparent conductive film can be appropriately patterned. In addition, a desired insulation resistance between adjacent conductive film patterns can be ensured. [Selection] Figure 1

Description

  The present invention relates to a method for manufacturing a thin film solar cell using a ZnO-based transparent conductive film as an electrode layer and a manufacturing apparatus therefor.

In general, a thin film solar cell is configured by laminating a transparent conductive film, a semiconductor layer as a power generation layer, and a metal film as a back electrode in this order on a transparent substrate such as glass. As the transparent conductive film, indium tin oxide (ITO), tin oxide (SnO ₂ ), zinc oxide (ZnO), or the like is usually used.

ITO is used in a wide range of fields because of its high conductivity, but it is disadvantageous in terms of cost. SnO ₂ is cheaper than ITO and has a low free electron concentration, so that a film with a high transmittance can be obtained. However, the conductivity is low and the plasma resistance is also low. On the other hand, ZnO is cheaper than ITO and has a resistivity comparable to that of ITO, and thus is regarded as a promising alternative material for ITO. In addition, ZnO is suitable as a transparent conductive film for thin film solar cells because it has high plasma resistance and high mobility, and thus has a high transmittance of long wavelength light. Furthermore, the carrier density of ZnO can be controlled by adding aluminum (Al), gallium (Ga), or the like. These zinc oxide-based materials are called AZO, GZO and the like.

  By the way, in a thin film solar cell, it is common to insulate and separate a plurality of power generation areas by patterning a laminated film using a laser and to connect the plurality of power generation areas in series. Specifically, a transparent conductive film is formed on a glass substrate and separated into strips. A semiconductor layer and a back electrode are sequentially stacked thereon, and then the semiconductor layer and the back electrode are patterned using a laser. At this time, the semiconductor layer and the back electrode are patterned so that the transparent electrode film of one cell including the transparent electrode film, the semiconductor layer, and the back electrode is in contact with the back electrode of another adjacent cell.

In general, a near-infrared laser is widely used for patterning the SnO ₂ film. For example, Patent Document 1, by intermittently irradiating a pulsed laser beam having a wavelength of 1064nm to SnO ₂ film, describes a method of forming a scribe groove on the SnO ₂ film. Patent Document 2 describes a method of patterning a transparent conductive film using a YAG laser having a wavelength of 1064 nm having a top flat type (energy intensity distribution is trapezoidal) cross-sectional intensity distribution.

JP 2002-141526 A Japanese Patent Laid-Open No. 10-258383

However, when the transparent conductive film is a ZnO-based transparent conductive material such as AZO, there is a problem that the transparent conductive film cannot be appropriately patterned when irradiated with laser light under the same irradiation conditions as the SnO ₂ film. According to the experiments by the present inventors, even if the irradiation conditions are appropriate for the SnO ₂ film, if the AZO film is irradiated with the laser light under the irradiation conditions, the film remains at the pattern boundary, and the AZO is appropriate. Can not be removed. Also, the pattern shape accuracy is poor, and it is very difficult to form a scribe groove with a desired processing width.

  In view of the circumstances as described above, an object of the present invention is to provide a method for manufacturing a thin-film solar cell and an apparatus for manufacturing the same, which can appropriately pattern a ZnO-based transparent conductive film.

  In order to achieve the above object, a method for manufacturing a thin-film solar cell according to an embodiment of the present invention includes forming infrared pulsed laser light having a cross-sectional intensity distribution in which the beam intensity in the peripheral part is higher than in the central part. By irradiating the zinc oxide (ZnO) -based transparent conductive film formed on the transparent substrate with the infrared pulse laser beam and scanning the infrared pulse laser beam while overlapping a part of the irradiation range, the transparent The conductive film is patterned.

In order to achieve the above object, a thin-film solar cell manufacturing apparatus according to an embodiment of the present invention is a thin-film solar cell manufacturing apparatus having a zinc oxide-based transparent conductive film formed on a transparent substrate, A laser light source, a stage, a moving mechanism, and a control unit are provided.
The laser light source emits infrared pulsed laser light having a cross-sectional intensity distribution in which the beam intensity in the peripheral part is higher than that in the central part.
The stage supports the transparent substrate.
The moving mechanism can move the stage in an in-plane direction of the transparent substrate.
The control unit controls the moving mechanism so that a part of the irradiation range of the infrared pulsed laser light on the transparent conductive film overlaps.

It is a process flow explaining the manufacturing method of the thin film solar cell which concerns on one Embodiment of this invention. It is principal part sectional drawing of each process explaining the manufacturing process of the said thin film solar cell. It is a top view which shows schematic structure of the manufacturing apparatus of the thin film solar cell which concerns on one Embodiment of this invention. It is a front view which shows schematic structure of the said manufacturing apparatus. It is a schematic block diagram of the infrared pulse laser light source with which the said manufacturing apparatus is equipped. It is a figure which shows an example of the optical characteristic of the glass material used as a transparent substrate which comprises the said thin film solar cell, (A) shows the transmittance | permeability characteristic of white plate glass, (B) shows the transmittance | permeability characteristic of soda-lime glass, respectively. ing. It is a figure which shows an example of the optical characteristic of the AZO film | membrane used as a transparent conductive film which comprises the said thin film solar cell. (A) is a figure which shows typically the cross-sectional intensity distribution of the infrared pulsed laser beam which concerns on a comparative example, (B) is the SEM photograph of the AZO film processed using the laser beam which has the cross-sectional intensity distribution It is. (A) is a figure which shows typically the cross-sectional intensity distribution of the infrared pulse pulse laser beam used in one Embodiment of this invention, (B) is processed using the laser beam which has the cross-sectional intensity distribution. 3 is an SEM photograph of an AZO film. FIG. 10 is an optical micrograph of each sample of an AZO film processed using an infrared pulse laser beam having a cross-sectional intensity distribution shown in FIG. (A) is an SEM photograph showing an example of a conductive byproduct generated when an AZO film is processed using infrared pulsed laser light, and (B) is a state after cleaning with an alkaline cleaning liquid. It is a SEM photograph which shows. FIG. 10 is an SEM photograph of each sample of an AZO film processed using an infrared pulse laser beam having a pulse width of about 72 ns having the cross-sectional intensity distribution shown in FIG. FIG. 10 is an SEM photograph of each sample of an AZO film processed using an infrared pulse laser beam having a pulse width of about 32 ns having the cross-sectional intensity distribution shown in FIG.

  The manufacturing method of the thin film solar cell which concerns on one Embodiment of this invention includes forming the infrared pulsed laser beam which has cross-sectional intensity distribution whose beam intensity of a peripheral part is higher than a center part. By irradiating the zinc oxide (ZnO) -based transparent conductive film formed on the transparent substrate with the infrared pulse laser beam and scanning the infrared pulse laser beam while overlapping a part of the irradiation range, the transparent The conductive film is patterned.

  By using the infrared pulsed laser beam having the cross-sectional intensity distribution as described above, compared to the case of using the infrared pulsed laser light having a cross-sectional intensity distribution such as a Gaussian distribution in which the beam intensity at the central part is higher than the peripheral part. The film residue at the boundary between the laser irradiation region and the non-irradiation region can be suppressed, and the shape of the boundary can be sharply formed. Thereby, it becomes possible to pattern a zinc oxide type transparent conductive film appropriately. In addition, by scanning the laser beam while overlapping a part of the irradiation range, it is possible to secure a desired insulation resistance between adjacent conductive film patterns.

  The infrared pulse laser beam having the cross-sectional intensity distribution can be formed by an appropriate method. For example, an optical fiber that forms a laser beam having a higher beam intensity at the peripheral part than at the central part can be used.

  The transparent substrate is typically composed of a glass substrate having a high infrared transmittance. The infrared pulse laser beam can be appropriately determined according to the optical characteristics of the material constituting the transparent conductive film, and a near infrared laser having a wavelength of 1000 nm to 1500 nm is used. Since the glass substrate has a relatively high near-infrared transmittance, the transparent conductive film can be patterned by allowing laser light to enter from the substrate side. By making the laser beam incident from the substrate side, it is possible to avoid the removal material from the transparent conductive film from adhering to the laser irradiation source.

  The transparent conductive film is not limited to a binary system of ZnO. For example, a ternary system material such as AZO to which aluminum is added or GZO to which gallium is added may be used.

  The overlap rate (overlap rate) of the irradiation range can be set as appropriate, for example, 10% or more and 70% or less. When the overlap rate is less than 10%, it is difficult to ensure a desired insulation resistance between adjacent patterns. On the other hand, if the overlap ratio exceeds 70%, conductive by-products are generated in the laser irradiation region, and the insulation resistance between patterns decreases. The overlap rate can be controlled by the scanning speed of the infrared pulse laser beam with respect to the transparent conductive film, the pulse repetition frequency of the laser beam, and the like.

  The method for manufacturing the thin-film solar cell may further include a step of forming a semiconductor layer on the transparent conductive film and a step of forming a metal film on the semiconductor layer. Since the transparent conductive film can be appropriately patterned as described above, a highly reliable thin film solar cell can be manufactured.

  The method for manufacturing the thin-film solar cell may further include a step of cleaning the patterned transparent conductive film with an alkaline cleaning liquid. Thereby, the conductive by-product produced | generated in the laser irradiation area | region is removed, and the insulation defect between adjacent patterns can be prevented.

A thin-film solar cell manufacturing apparatus according to an embodiment of the present invention is a thin-film solar cell manufacturing apparatus having a zinc oxide-based transparent conductive film formed on a transparent substrate, and includes a laser light source, a stage, and a movement A mechanism and a control unit.
The laser light source emits infrared pulsed laser light having a cross-sectional intensity distribution in which the beam intensity in the peripheral part is higher than that in the central part.
The stage supports the transparent substrate.
The moving mechanism can move the stage in an in-plane direction of the transparent substrate.
The control unit controls the moving mechanism so that a part of the irradiation range of the infrared pulsed laser light on the transparent conductive film overlaps.

  In the manufacturing apparatus, the laser light source patterns the transparent conductive film on the transparent substrate by irradiating the transparent substrate placed on the stage with the infrared pulse laser beam having the cross-sectional intensity distribution. The control unit controls the movement of the stage by the moving mechanism so that a part of the irradiation range of the infrared pulse laser beam on the transparent conductive film overlaps.

  Infrared pulsed laser light having a cross-sectional intensity distribution such as a Gaussian distribution having a central beam intensity higher than the peripheral part by using an infrared pulsed laser light having a cross-sectional intensity distribution with a higher beam intensity in the peripheral part than in the central part Compared with the case of using the film, it is possible to suppress the film residue at the boundary between the laser irradiation region and the non-irradiation region, and to form the shape of the boundary sharply. Thereby, it becomes possible to pattern a zinc oxide type transparent conductive film appropriately. In addition, by scanning the laser beam while overlapping a part of the irradiation range, it is possible to secure a desired insulation resistance between adjacent conductive film patterns.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Manufacturing process of thin film solar cell]
First, the outline of the manufacturing process of the thin film solar cell according to the present embodiment will be described. FIG. 1 is a process flow for explaining a method of manufacturing a thin film solar cell, and FIG.

  A thin film solar cell module is an integrated body of a plurality of solar cells fabricated on a transparent substrate having translucency. The solar cell includes a transparent conductive film (first electrode layer) formed on a substrate, a semiconductor layer formed on the transparent conductive film, and a metal film (second electrode) formed on the semiconductor layer. The electrode layer has a laminated structure. The transparent conductive film, the semiconductor layer, and the metal film are formed by a vapor deposition method such as a CVD method or a sputtering method. After the formation of each layer, each layer is laser scribed on the surface of the substrate in order to separate the element into a plurality of cells, and adjacent solar cells are connected in series or in parallel. Then, a thin film solar cell module is manufactured through the removal process of the said laminated film located in the edge part of a board | substrate, the resin sealing process of the board | substrate whole surface, etc.

  1 and 2, first, a transparent conductive film 11 is formed on a glass substrate 10 (step ST1, FIG. 2 (A)).

  The glass substrate 10 is made of a transparent material that transmits light having a wavelength of 300 nm or more. Glass includes soda-lime glass, white plate glass, blue plate glass, borosilicate glass, and the like. The size of the glass substrate 10 is not particularly limited, and is, for example, 1300 mm long, 1100 mm wide, and 4 mm thick.

  The transparent conductive film 11 uses a zinc oxide-based material, not only ZnO, but also a zinc oxide-based material (AZO) in which aluminum (Al) is added to ZnO, and zinc oxide in which gallium (Ga) is added to ZnO. A system material (GZO) or the like is applicable. In particular, AZO and GZO are excellent in plasma resistance, and both conductivity and transmittance in the near infrared region are high. In the present embodiment, the transparent conductive film 11 is composed of an AZO film. The transparent conductive film 11 is formed with a thickness of, for example, about 800 nm by a sputtering method, but is not limited thereto.

  If necessary, the transparent conductive film 11 may have a predetermined texture on the surface thereof. Thereby, since the surface area of the transparent conductive film 11 increases, it becomes possible to improve the light transmission efficiency and the adhesiveness with an upper layer (semiconductor layer). As the texture forming method, for example, an etching process using an aqueous ammonium salt solution can be employed.

  Next, a step of patterning the transparent conductive film 11 is performed by irradiating a predetermined region of the transparent conductive film 11 on the glass substrate 10 with a laser beam (step ST2, FIG. 2B).

  In this embodiment, as will be described later, the transparent conductive film 11 is irradiated with infrared pulse laser light, and the transparent conductive film 11 is scanned with the infrared pulse laser light while overlapping a part of the irradiation range. One separation groove 11a is formed. The individual transparent conductive films 11 on the glass substrate 10 are electrically insulated by the separation grooves 11a. Further, the infrared pulse laser beam is irradiated from the glass substrate 10 side toward the transparent conductive film 11. Thereby, contamination of the laser irradiation part by the processing waste (dust) of the transparent conductive film 11 can be prevented.

  Then, the process of wash | cleaning the process area | region of the transparent conductive film 11 with a washing | cleaning liquid is performed (step ST3). This step is intended to remove the conductive decomposition product of the transparent conductive film generated in the laser light irradiation region. As the cleaning liquid, for example, an acid or alkaline aqueous solution is used. When an acid aqueous solution is used as the cleaning liquid, hydrochloric acid, acetic acid, sulfuric acid, hydrofluoric acid, etc. are used. By this step, it is possible to avoid an insulation failure of the separation groove 11a. In addition, when the production | generation of the said decomposition product does not become a problem, it is also possible to abbreviate | omit the said process.

  Next, the semiconductor layer 12 is formed on the glass substrate 10 (step ST4, FIG. 2C).

  The semiconductor layer 12 is formed so as to cover the transparent conductive film 11 and the first separation groove 11a. In the present embodiment, the semiconductor layer 12 has a structure in which p-type, i-type, and n-type amorphous silicon (a-Si: H) films, to which hydrogen is added, are sequentially stacked. These amorphous silicon layers are formed by a plasma CVD method. The thickness of the p-type amorphous silicon layer (a-Si: Hp) is, for example, 5 nm to 20 nm, the thickness of the i-type amorphous silicon layer (a-Si: Hi) is, for example, 100 nm to 600 nm, and the n-type amorphous silicon layer ( The film thickness of a-Si: Hn) is, for example, several tens of nm.

  Then, the process of patterning the semiconductor layer 12 is performed by irradiating a predetermined area | region of the semiconductor layer 12 on the glass substrate 10 with a laser beam (step ST5, FIG.2 (D)).

  In the present embodiment, the semiconductor layer 12 is irradiated with green pulse laser light, and the green pulse laser light is scanned while overlapping a part of the irradiation range, thereby forming the second separation groove 12a in the semiconductor layer 12. To do. The second separation groove 12a is formed so as to be adjacent to the first separation groove 11a, for example, as shown in the figure, but is not limited to this. The laser light is irradiated from the glass substrate 10 side as described above.

  Next, a metal film 13 is formed on the glass substrate 10 (step ST6, FIG. 2E).

  The metal film 13 is formed so as to cover the semiconductor layer 12 and the second separation groove 12a. Thereby, the transparent conductive film 11 and the metal film 13 are electrically connected via the separation groove 12a. In the present embodiment, the metal film 13 is made of a metal material having a relatively high reflectivity, such as aluminum or silver. The film thickness of the metal film 13 is not specifically limited, For example, you may be several hundred nm-several micrometers.

  Subsequently, a process of patterning the metal film 13 is performed by irradiating a predetermined region of the metal film 13 on the glass substrate 10 with a laser beam (step ST7, FIG. 2F).

  In the present embodiment, the metal film 13 is irradiated with green pulse laser light, and the green pulse laser light is scanned while overlapping a part of the irradiation range, thereby forming the third separation groove 13a in the metal film 13. To do. The third separation groove 13a is formed so as to be adjacent to the second separation groove 12a, for example, as shown in the figure, but of course not limited thereto. The laser beam is irradiated from the glass substrate 10 side as described above, and the metal film 13 is removed together with the semiconductor layer 12 located in the formation region of the separation groove 13a. Thereby, the solar cell module 15 in which a plurality of solar cells are connected in series on the glass substrate 10 is produced.

[Configuration of laser processing equipment]
Next, the configuration of a laser processing apparatus (laser scribing apparatus) used for patterning the transparent conductive film 11, the semiconductor layer 12, and the metal film 13 will be described. The said processing apparatus respond | corresponds to one Embodiment of the manufacturing apparatus of the thin film solar cell which concerns on this embodiment.

  3 and 4 are a plan view and a front view showing a schematic configuration of the laser processing apparatus 20 according to the present embodiment. In each figure, the X-axis and Y-axis directions are plane directions orthogonal to each other, and the Z-axis direction represents the height direction.

  The laser processing apparatus 20 includes a base 21 and a stage 22 for supporting the substrate S. The stage 22 supports the lower surface periphery of the substrate S. Between the base 21 and the stage 22, a pair of guide rails 23X for moving the stage 22 along the X-axis direction in the figure is laid. A linear motor is used as a drive source for the stage 22, but is not limited thereto, and may be a ball screw unit or the like. The guide rails 23X, the drive source, and the like constitute a moving mechanism for the stage 22. The stage 22 supports the substrate S that is subjected to patterning.

  The substrate S may be the glass substrate 10 on which the transparent conductive film 11 is formed, or the glass substrate 10 on which the semiconductor layer 12 or the metal film 13 is formed. The substrate S is disposed on the stage 22 with the surface (back side) opposite to the surface on which the transparent conductive film 11 and the like are formed facing upward. The stage 22 may include an alignment mechanism that positions the substrate S at a predetermined position, a holding mechanism that holds the substrate S, a lifter pin that assists in transferring the substrate S to the upper surface of the stage 22, and the like.

  A gantry 24 having a longitudinal direction in the Y-axis direction is installed above the base 21. The gantry 24 is fixed to the base 21 via a pair of leg portions 25. The gantry 24 is provided with a laser light source unit 26 that irradiates the substrate S on the stage 22 with laser light. A pair of guide rails 23Y extending in the Y-axis direction are laid on the upper surface of the gantry 24, and the laser light source unit 26 is movable in the Y-axis direction in the drawing under the guide action of these guide rails 23Y. Is done. A linear motor is used as the drive source of the laser light source unit 26, but the present invention is not limited to this, and a ball screw unit or the like may be used. The guide rails 23Y, the drive source, and the like constitute a moving mechanism of the laser light source unit 26.

  The laser processing apparatus 20 includes a control unit 28. The control unit 28 controls the movement of the stage 22 in the X-axis direction relative to the base 21 and the movement of the laser light source unit 26 relative to the gantry 24 in the Y-axis direction and the Z-axis direction. The laser processing apparatus 20 can perform laser processing on the substrate S on the stage 22 according to a predetermined control sequence.

  The laser light source unit 26 is configured as a multi-laser light source unit in which a plurality of laser light sources are arranged in the Y-axis direction. In the present embodiment, three infrared pulse laser light sources 26r, three green pulse laser light sources 26g, Are configured in combination. As shown in FIG. 4, the laser light sources of the respective colors are alternately arranged. Although not shown, each laser light source is configured to be movable along the Z-axis direction.

  FIG. 5 is a schematic configuration diagram of the laser light sources 26r and 26g. The laser light sources 26r and 26g include an oscillator 31, an optical fiber 32, a collimator lens 33, an isolator 34, an expander 35, and a condenser lens 36.

  The laser light generated in the oscillator 31 is transmitted in the optical fiber 32 and enters the collimator lens 33 from the exit end of the optical fiber 32. The laser light incident on the collimator lens 33 is converted into parallel light by the collimator lens 33, passes through the isolator 34, and enters the expander 35. The isolator 34 is for preventing, for example, laser light reflected on the condenser lens 36 or the substrate S from returning to the optical fiber 32 side. The laser beam that has passed through the isolator 34 is adjusted to an appropriate beam diameter by the expander 35, and then condensed on the processing target film on the substrate S by the condenser lens 36.

The expander 35 is a variable magnification type, and adjusts the spot diameter d of the focused beam at the substrate irradiation position. The spot diameter d [mm] is D as the diameter of the beam incident on the expander 35, m as the magnification of the expander 35, f as the focal length of the condenser lens 36, λ as the wavelength of light, and M ^{2 as} the beam quality. Then, it can be expressed by the following formula.
d = (M ² × 4 × λ × f) / (π × m × D) (1)

The spot diameter d can be appropriately set according to the constituent material, thickness, pattern width, pattern accuracy, etc. of the transparent conductive film, and the spot diameter d when processing the AZO film is 30 μm or more and 100 μm or less. For example, if M ² = 2, λ = 1064 [nm], f = 150 [mm], D = 1.2 [mm], and m = 7, the spot diameter d is about 48 μm.

  Here, as described above, the substrate S is placed on the stage 22 with its film-forming surface facing the lower side opposite to the laser light source unit 26. Accordingly, the dust generated from the laser light irradiation region does not scatter to the laser light source unit 26 side, so that the laser light emission port is not contaminated by the dust adhesion. Thereby, since the maintenance cycle of the laser light source unit 26 can be lengthened, a stable laser emission function is ensured over a long period of time. In order to suppress reattachment of dust to the substrate S, the laser processing apparatus 20 is provided with a dust collection unit 27 that collects dust generated from the substrate S. The dust suction port of the dust collection unit 27 is provided on the upper surface of the stage 22 facing the lower surface of the substrate S, for example.

  Next, details of the infrared pulse laser light source 26r constituting the laser light source unit 26 will be described.

  The infrared pulse laser light source 26r oscillates near-infrared laser light having a wavelength of 1000 nm or more and 1500 nm or less and emits it toward the substrate S. The infrared pulse laser light source is mainly used for patterning the transparent conductive film 11 formed on the substrate S. The oscillation wavelength is appropriately set according to the optical characteristics of the glass substrate 10 constituting the substrate S and the transparent conductive film 11 which is a film to be processed. In this embodiment, the transparent conductive film 11 is irradiated with laser light through the glass substrate 10 to process the transparent conductive film 11. Accordingly, the laser light is required to have optical characteristics such as high transmission characteristics with respect to the glass substrate 10 and high absorption characteristics with respect to the transparent conductive film 11.

  FIG. 6 shows the wavelength dependence characteristics of the transmittance measured for a glass material applicable to the glass substrate 10. FIG. 6A shows the transmittance characteristics of white plate glass, and FIG. 6B shows the transmittance characteristics of soda lime glass. On the other hand, FIG. 7 shows an example of the wavelength dependence characteristics of the transmittance and reflectance of an AZO film applicable to the transparent conductive film 11. As a measurement sample, an AZO film having a film thickness of 7000 mm (700 nm) and a sheet resistance of 4.3Ω / □ was used.

  As shown in FIG. 7, the AZO film has both low transmittance and reflectance in the ultraviolet region (wavelength of 400 nm or less), and therefore it is possible to efficiently process the AZO film using ultraviolet laser light. I understand. However, as shown in FIGS. 6A and 6B, the glass substrate 10 has a relatively high light absorptance in the ultraviolet region, and the AZO film (transparent conductive film) is irradiated with laser light from the glass substrate 10 side. When processing the film 11), the glass substrate 10 may be damaged such as cracks. On the other hand, as shown in FIG. 7, the AZO film has a relatively high reflectance of light having a wavelength of 1500 nm or more, and it is very difficult to efficiently process the AZO film with laser light in this wavelength region. Therefore, in the present embodiment, a laser beam having a wavelength of 1000 nm or more and 1500 nm or less, which is a wavelength region in which both the transmittance and the reflectance of the AZO film are relatively low, is used.

  Next, the cross-sectional intensity distribution (beam profile) of the infrared laser beam for processing the AZO film will be described.

In general laser processing, laser light having a cross-sectional intensity distribution (beam profile) in which the beam intensity in the central part is higher than that in the peripheral part is used. As a comparative example, FIG. 8A schematically shows a typical cross-sectional intensity distribution (beam profile) of laser light in the case of patterning the SnO ₂ film. FIG. 8B is an SEM (scanning electron microscope) photograph of a laser irradiation region when an AZO film having a thickness of 700 nm is patterned with the beam profile shown in FIG. In the drawing, the right side is a laser irradiation region, and the left side is a non-irradiation region. The laser irradiation conditions were a laser oscillation wavelength of 1064 nm, a laser irradiation power of 8.37 W (9.6 J / cm ² ), a laser scanning speed of 1000 mm / s, a pulse width of 72 ns, and a processing width of 58.8 μm.

When the transparent conductive film is a ZnO-based transparent conductive material such as AZO, the transparent conductive film cannot be appropriately patterned when irradiated with laser light under the same irradiation conditions as the SnO ₂ film. As shown in FIG. 8B, it can be seen that the AZO film remains in the laser irradiation region on the right side of the drawing. In this case, the laser irradiation region does not perform an insulating separation function between patterns as a separation groove.

Therefore, in this embodiment, the AZO film is patterned using infrared pulsed laser light having a cross-sectional intensity distribution (beam profile) in which the beam intensity in the peripheral part is higher than that in the central part. FIG. 9A schematically shows an example of a cross-sectional intensity distribution of the infrared pulse laser beam used in the present embodiment. FIG. 9B is a SEM (scanning electron microscope) photograph of a laser irradiation region when an AZO film having a thickness of 700 nm is patterned with the beam profile shown in FIG. 9A. In the drawing, the right side is a laser irradiation region, and the left side is a non-irradiation region. The laser irradiation conditions were a laser oscillation wavelength of 1064 nm, a laser irradiation power of 8.37 W (9.6 J / cm ² ), a laser scanning speed of 1000 mm / s, a pulse width of 72 ns, and a processing width of 44.6 μm.

  By using an infrared pulse laser beam having a cross-sectional intensity distribution as shown in FIG. 9A, compared to using an infrared pulse laser beam having a cross-sectional intensity distribution as shown in FIG. 8A, It is possible to suppress the film residue at the boundary between the laser irradiation region and the non-irradiation region. The intensity ratio between the beam peripheral part and the beam central part is not particularly limited as long as the beam intensity at the peripheral part is higher than the beam intensity at the central part.

  According to the present embodiment, the shape of the boundary portion can be formed sharper than in the comparative example (FIG. 8B) (FIG. 9B). In addition, regardless of the same laser irradiation conditions, the laser beam having the beam profile shown in FIG. 9A can reduce the processing width. These effects are considered to be due to the fact that the processing efficiency of the outer peripheral portion of the cross section of the laser beam (beam) is enhanced by the fact that the beam intensity in the peripheral portion is higher than that in the central portion. From the above, according to the present embodiment, the AZO film can be appropriately patterned, and a fine pattern can be formed with high accuracy.

  As shown in FIG. 9A, the infrared pulse laser light source 26r of the present embodiment irradiates infrared pulse laser light having a cross-sectional intensity distribution in which the beam intensity in the peripheral part is higher than that in the central part. The laser beam is generated by the oscillator 31 and the optical fiber 32. As the oscillator 31, a fiber pulse laser oscillator is used.

  This type of laser oscillator has a fiber laser medium and an excitation light source. The excitation light source emits excitation light to the fiber laser medium. The pulse width of the laser light is controlled by the emission timing of the excitation light. In particular, it is possible to easily realize a minute pulse width of several tens of ns. The fiber laser medium mainly uses a fiber in which rare earth ions are added to the core as a gain medium, and can perform optical amplification over a wider band than a crystal medium such as a YAG crystal. The laser light emitted from the fiber laser medium has a plurality of modes having different cross-sectional intensity distributions, and a desired single-mode laser light is output by adjusting the core diameter and fiber length of the optical fiber 32. . In the present embodiment, the laser light emitted from the oscillator 31 has a multimode in which an LP01 mode having an intensity peak at the center and an LP11 mode having a peak intensity at the periphery are mixed. The core diameter and the fiber length are set so that the desired LP11 mode laser beam is selectively output while the LP01 mode laser beam is appropriately attenuated during the transmission process.

  The control unit 28 controls the movement of the stage 22 so that a part of the irradiation range of the infrared pulse laser beam on the transparent conductive film 11 overlaps. The overlap rate (overlap rate) of the irradiation range can be set as appropriate, and can be, for example, 10% or more and 70% or less. When the overlap rate is less than 10%, it is difficult to ensure a desired insulation resistance between adjacent patterns. On the other hand, if the overlap ratio exceeds 70%, conductive by-products are generated in the laser irradiation region, and the insulation resistance between patterns decreases. The overlap rate can be controlled by the scanning speed of the infrared pulse laser beam with respect to the transparent conductive film, the pulse repetition frequency of the laser beam, and the like.

The overlap rate can be expressed by the following equation.
Overlap ratio = {(d−V / f) / d} × 100 [%] (2)
Here, d is the spot diameter [mm], V is the moving speed [mm / s] of the substrate (stage), and f is the pulse repetition frequency [Hz]. The overlap rate can be arbitrarily controlled by changing the spot diameter d, the moving speed V of the stage 22, and the pulse repetition frequency f. For example, when the pulse repetition frequency f is 30 kHz and the spot diameter d is 48 μm, the moving speed V is controlled in the range of 144 mm / s to 1008 mm / s.

  FIG. 10 is an optical micrograph of each sample showing a laser irradiation region when an AZO film having a thickness of 700 nm is irradiated with infrared pulse laser light with different overlap ratios. The laser irradiation conditions were an oscillation wavelength of 1064 nm, an irradiation power of 8.8 W, and a repetition frequency of 49 kHz, and the overlap rate was adjusted by the moving speed of the substrate (stage). In the sample A1 shown in FIG. 10A, the moving speed is 2.0 m / s (overlap ratio 14%), and in the sample B1 shown in FIG. 10B, the moving speed is 1.5 m / s (overlap ratio 35). %). In the sample C1 shown in FIG. 10C, the moving speed is 1.0 m / s (overlap rate 57%), and in the sample D1 shown in FIG. 10D, the moving speed is 0.5 m / s (overlap rate 78). %). And about each sample, the linear resistance between two adjacent patterns isolate | separated in the laser irradiation area | region was measured. The measured values of Samples A1 to D1 were 5 MΩ, “OL”, “OL”, and 2 MΩ, respectively. “OL” means a resistance value (overload, overload) exceeding the measurement limit of the measuring instrument. For measurement, a digital insulation resistance meter “MY40” manufactured by Yokogawa Meter & Instruments Co., Ltd. was used.

  Comparing samples A1 to C1, it can be seen that samples B1 and C1 have higher insulation resistance than sample A1, so that the withstand voltage increases as the overlap ratio increases. In addition, when the overlap rate is extremely low (for example, less than 10%), a desired insulation resistance (MΩ or more) may not be ensured. Further, when comparing the sample A1 and the sample D1, it was confirmed that the sample D1 having a higher overlap ratio had a lower insulation resistance. This is considered to be because when the overlap ratio is excessively large (for example, more than 70%), conductive by-products are generated in the laser irradiation region, and the insulating characteristics between patterns are deteriorated. This type of by-product is likely to occur when a zinc oxide-based material is processed with a laser having a wavelength band of 1000 to 1500 nm.

  On the other hand, the by-product can be removed by washing the patterned AZO film with an alkaline aqueous solution. FIG. 11A is an SEM photograph showing a state immediately after laser irradiation of an AZO film sample patterned under predetermined conditions, and FIG. 11B is an SEM photograph showing a state after the sample is washed with an alkaline aqueous solution. It is. In FIG. 11A, the presence of by-products is confirmed in the laser irradiation region. However, as shown in FIG. 11B, it was confirmed that the laser irradiation region was cleaned after cleaning. As the cleaning liquid, for example, a potassium hydroxide solution (aqueous solution) can be used.

  Next, the irradiation power and pulse width of infrared pulse laser light will be described.

FIGS. 12A to 12D are SEM photographs of each sample showing a laser irradiation region when an AZO film having a thickness of 700 nm is irradiated with infrared pulsed laser light with different irradiation powers. The laser irradiation conditions were an oscillation wavelength of 1064 nm, a repetition frequency of 50 kHz, a moving speed of the substrate (stage) of 1000 mm / s, an overlap rate of 56%, and a pulse width of about 72 ns. In sample A2 shown in FIG. 12A, the irradiation power is 3.82 W (4.4 J / cm ² ), and in sample B2 shown in FIG. 12B, the irradiation power is 6.10 W (7.0 J / cm ² ). It was. In the sample C2 shown in FIG. 12C, the irradiation power is 8.37 W (9.61 J / cm ² ), and in the sample D2 shown in FIG. 12D, the irradiation power is 10.79 W (12.4 J / cm ² ). It was.

  Although it was confirmed that all of the samples A2 to D2 can ensure the desired insulation resistance, the shape accuracy at the pattern boundary is low. In other words, the boundary between the laser irradiation region and the non-irradiation region cannot be formed sharply. It is considered that the collapse of the shape of the boundary portion is related to the melting of the AZO film at the boundary portion and the swell due thereto. In the samples A2 to D2 irradiated with the pulse width of 72 ns, the variation in the shape at the boundary portion is remarkable for the sample D1 having a relatively large irradiation power. The processing widths of Samples A2 to D2 were 37 μm, 42.5 μm, 45.6 μm, and 46.1 μm, respectively, and it was confirmed that the processing width increased as the irradiation power increased.

On the other hand, FIGS. 13A to 13D are SEM photographs of each AZO film sample when irradiated with infrared pulse laser light under a condition of a pulse width of about 32 ns. The oscillation wavelength was 1064 nm, the repetition frequency was 50 kHz, the moving speed of the substrate (stage) was 1000 mm / s, and the overlap rate was 56%. In sample A3 shown in FIG. 13A, the irradiation power is 1.43 W (1.6 J / cm ² ), and in sample B3 shown in FIG. 13B, the irradiation power is 2.50 W (2.9 J / cm ² ). It was. In the sample C3 shown in FIG. 13C, the irradiation power is 3.62 W (4.2 J / cm ² ), and in the sample D3 shown in FIG. 13D, the irradiation power is 4.76 W (5.5 J / cm ² ). It was.

  Regarding sample A3, since the irradiation power was too low, the AZO film on the laser irradiation region could not be completely removed, and the desired function as a pattern separation groove could not be obtained. For samples B3, C3, and D3, the desired insulation resistance can be ensured between the patterns, and the boundary between the laser irradiation region and the non-irradiation region can be formed with moderate sharpness, and the AZO film rises at the boundary. It was also confirmed that it can be suppressed. The processing widths of Samples A3 to D3 were 28.2 μm, 37.7 μm, 41.0 μm, and 43.1 μm, respectively.

From the experimental results shown in FIGS. 12 and 13, the longer the pulse width and the greater the irradiation power, the more the energy is applied to the AZO film, the more the AZO film melts, and the shape collapse due to the bulge becomes noticeable. I understand. Therefore, by optimizing the irradiation power according to the size of the pulse width, it is possible to prevent a decrease in pattern shape accuracy while ensuring the desired insulation resistance. Irradiation power when the pulse width is about 33 ns (energy density) can be, for example, 2.0 J / cm ² or more 12 J / cm ² or less.

The infrared pulse laser light source 26r has been described above. On the other hand, the green pulse laser light source 26g is not limited in laser characteristics as long as the semiconductor layer 12 and the metal film 13 can be patterned. As the green laser light emitted from the laser light source 26g, for example, a second harmonic (532 nm) of an Nd-YAG laser (1064 nm) can be used. The beam profile of the green laser light may have a Gaussian distribution as shown in FIG. 8A, or a cross section in which the beam intensity in the peripheral part is higher than that in the central part as shown in FIG. 8B. It may be an intensity distribution. Typical irradiation conditions of the green pulse laser beam, the step of patterning the semiconductor layer 12 is 0.5~1.3J / cm ^2, in the step of patterning the metal film 13 is 0.5~1.3J / cm ² It is.

  Next, the operation of the laser processing apparatus 20 of the present embodiment configured as described above will be described.

  As shown in FIG. 2A, the glass substrate 10 (FIG. 2A) on which the transparent conductive film 11 is formed as the substrate S is on the stage 22 with the film formation surface of the transparent conductive film 11 facing downward. Placed on. The control unit 28 moves the laser light source unit 26 in the Y-axis direction and the Z-axis direction, thereby positioning the infrared pulse laser light source 26r to the irradiation position with respect to the substrate S. Next, the control unit 28 simultaneously irradiates the substrate S with infrared pulse laser light from each infrared pulse laser light source 26r while moving the stage in the X-axis direction at a predetermined constant speed. The moving speed of the stage 22 is controlled by the control unit 28 so that the laser beam is scanned at a predetermined overlap rate. Thereby, a plurality of first separation grooves 11a (FIG. 2B) are simultaneously formed in the transparent conductive film 11.

  In the present embodiment, the infrared pulse laser light source 26r emits a randomly polarized laser beam having an oscillation wavelength of 1064 nm, an output of 3.6 W, a repetition frequency of 30 kHz, and a pulse width of 33 ns (nanoseconds) from the oscillator 31. The overlap ratio of the laser light is adjusted to a range of 10% to 70% in the above-described manner.

  The control unit 28 reciprocates the stage 22 in the X axis direction. The first separation groove 11a is formed during the movement of the stage 22 in the X-axis direction. The control unit 28 moves the laser light source unit 26 by a predetermined distance in the Y-axis direction, and positions the laser light source unit 26 to the next irradiation position with respect to the substrate S. The movement control of the laser light source unit 26 in the Y-axis direction is executed when the stage 22 is turned back in the movement direction. Then, a new separation groove 11 a is formed in the transparent conductive film 11 again by the same operation as described above. By repeating the above operation a predetermined number of times, a plurality of separation grooves 11 a are formed in the transparent conductive film 11.

  According to this embodiment, the transparent conductive film 11 made of AZO is patterned using infrared pulsed laser light having a cross-sectional intensity distribution in which the beam intensity in the peripheral part is higher than that in the central part. Thereby, the film residue in the boundary part of a laser irradiation area | region and a non-irradiation area | region can be suppressed, and it becomes possible to form the said boundary part in a sharp shape. As a result, the processing accuracy of the separation groove 11a is increased, and a transparent conductive film pattern having a desired insulation resistance can be formed.

  After the formation of the separation groove 11a, the transparent conductive film 11 is cleaned with an alkaline cleaning liquid. Thereby, the conductive by-product produced | generated in the formation area of the isolation | separation groove | channel 11a is removed, and the insulation characteristic of the isolation | separation groove | channel 11a can be ensured. In this cleaning step, a method of immersing the substrate S in a cleaning solution may be employed, or a method of cleaning the transparent conductive film 11 by spraying or spin coating may be employed. In addition, implementation of this washing | cleaning process is arbitrary and can be abbreviate | omitted as needed.

  The laser processing apparatus 20 of this embodiment can also be used for the patterning process of the semiconductor layer 12 and the metal film 13. In patterning the semiconductor layer 12 and the metal film 13, a green pulse laser light source 26g is used. Then, a plurality of separation grooves 12a and 13a (FIGS. 2D and 2F) are formed at predetermined positions for the semiconductor layer 12 and the metal film 13 by the same operation as described above.

  According to the present embodiment, in the patterning process of the transparent conductive film 11, the separation groove 11a is appropriately formed by optimizing the irradiation conditions (beam profile, overlap rate, pulse width, irradiation energy, etc.) as described above. As a result of being formed, it is possible to stably manufacture a solar cell module having a desired insulation resistance between desired adjacent cells. In particular, since the rising due to melting of the transparent conductive film at the edge portion of the separation groove 11 a can be suppressed, the coverage of the semiconductor layer 12 with respect to the transparent conductive film 11 is enhanced, and the electrical property between the transparent conductive film 11 and the metal film 13 is increased. It is possible to effectively prevent a short circuit.

  Moreover, according to the laser processing apparatus 20, since the separation grooves 11a, 12a, and 13a can be formed, it is possible to apply to all laser scribing processes with one apparatus. In addition, since the laser light source unit 26 includes a plurality of infrared pulse laser light sources 26r and green pulse laser light sources 26g, the efficiency of the patterning process can be improved by simultaneously using the plurality of laser light sources. Can improve productivity.

  As mentioned above, although embodiment of this invention was described, of course, this invention is not limited to this, A various deformation | transformation is possible based on the technical idea of this invention.

  For example, in the above embodiment, the laser processing apparatus 20 according to the present invention is used in the process of forming the separation grooves 11a, 12a, and 13a. Further, the transparent conductive film, semiconductor layer, and metal film formed on the peripheral edge of the substrate. The apparatus may also be applied to an edge deration process for removing the laminated film made of.

  In the above embodiment, the case where the constituent material of the transparent conductive film 11 is an AZO film has been described as an example. However, the present invention is not limited to this, and other materials such as GZO and IGZO (indium-gallium-zinc oxide) are used. The present invention can also be applied to a transparent conductive film made of a zinc oxide-based material.

DESCRIPTION OF SYMBOLS 10 ... Glass substrate 11 ... Transparent electrically conductive film 11a ... 1st separation groove 12 ... Semiconductor layer 12a ... 2nd separation groove 13 ... Metal film 13a ... 3rd separation groove 15 ... Solar cell module 20 ... Laser processing apparatus 21 ... Base 22 ... Stage 23X, 23Y ... Guide rail 24 ... Gantry 26 ... Laser light source unit 26r ... Infrared pulse laser light source 26g ... Green pulse laser light source 28 ... Control unit 31 ... Oscillator 32 ... Optical fiber 33 ... Collimator lens 34 ... Isolator 35 ... Expander 36 ... Condensing lens

Claims (7)

Infrared pulsed laser light having a cross-sectional intensity distribution with a higher beam intensity in the peripheral part than in the central part is formed,
The zinc oxide-based transparent conductive film formed on the transparent substrate is irradiated with the infrared pulsed laser light, and the transparent conductive film is scanned by scanning the infrared pulsed laser light while overlapping a part of the irradiation range. Patterning A method of manufacturing a thin film solar cell. It is a manufacturing method of the thin film solar cell of Claim 1, Comprising: Furthermore,
Forming a semiconductor layer on the transparent conductive film;
A method for manufacturing a thin-film solar cell, comprising forming a metal film on the semiconductor layer. It is a manufacturing method of the thin film solar cell of Claim 2,
The transparent conductive film is a zinc oxide-based material containing aluminum as an additive element. It is a manufacturing method of the thin film solar cell according to claim 3,
The infrared pulsed laser beam has a wavelength of 1000 nm to 1500 nm. It is a manufacturing method of the thin film solar cell of Claim 1, Comprising: Furthermore,
A method for manufacturing a thin film solar cell, wherein the patterned transparent conductive film is washed. A thin-film solar cell manufacturing apparatus having a zinc oxide-based transparent conductive film formed on a transparent substrate,
A laser light source that emits infrared pulsed laser light having a cross-sectional intensity distribution in which the beam intensity in the peripheral part is higher than that in the central part;
A stage for supporting the transparent substrate;
A moving mechanism capable of moving the stage in an in-plane direction of the transparent substrate;
An apparatus for manufacturing a thin-film solar cell, comprising: a control unit that controls the moving mechanism so that a part of an irradiation range of the infrared pulsed laser light on the transparent conductive film overlaps. It is a manufacturing apparatus of the thin film solar cell of Claim 6, Comprising:
The laser light source includes an optical fiber that forms a laser beam having the cross-sectional intensity distribution.