JP3823166B2 - Electrolytic etching method, photovoltaic device manufacturing method, and photovoltaic device defect processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of performing partial etching or pattern etching using an electrolytic reaction.
[0002]
[Prior art]
Conventionally, as a method for etching a metal or a transparent conductive film, there is a chemical etching method disclosed in, for example, Japanese Patent Application Laid-Open No. 55-108779, US Pat. No. 4,419,530. In this method, first, a positive pattern is formed by silk screen printing or photoresist, and then a metal corresponding to a negative part (exposed part) or a transparent conductive film is treated with an etching solution such as a ferric chloride solution or nitric acid. Is the method.
[0003]
However, in the chemical etching method, it is necessary to perform a process such as applying or removing a resist on an object to be etched, which complicates the process and increases the processing cost. Further, depending on the type of the object to be etched, a long processing time is required because of a low reaction rate. In addition, since non-contact processing cannot be performed, there is a problem in that the yield decreases.
[0004]
On the other hand, when an electrolytic reaction is used, in order to perform partial etching or patterning, a resist is applied to an object to be etched, and after the pretreatment for obtaining a pattern by exposure and curing, electrolytic etching is performed. Here, it is necessary to remove the used resist after etching. For example, Japanese Patent Application Laid-Open No. Sho 62-290900 discloses a method in which a resist pattern is brought into close contact with a conductive film, immersed in an aqueous hydrochloric acid solution, energized, and a portion other than the resist is patterned, and the resist is removed to complete the etching. Has been. Specifically, a flat electrode is used as a counter electrode, and an electrolytic process is performed with a power source in an electrolytic solution to form a desired pattern on an object to be etched.
[0005]
However, in this method, non-contact processing is possible at the time of electrolysis, but it is completely non-processed in the pre-process and post-process in the same way as chemical etching in that a pre-treatment resist coating and post-treatment resist stripping are necessary. There is a problem that the contact processing cannot be performed and the processing cost cannot be reduced, and there are many processes, resulting in a decrease in yield. In addition, if bubbles generated during electrolysis stay in the resist pattern, there is a problem that patterning cannot be performed accurately.
[0006]
Further, as a method of not pre-treating the resist pattern on the object to be etched side, JP-A-5-93300 discloses that a probe electrode is inserted into a capillary having a tip opening, and the peripheral surface of the tip opening and the working electrode. A method is disclosed in which electrolysis is performed while a small gap is placed between the surface of the solid object to be processed and the electrolyte solution flows through the opening at the tip.
[0007]
However, in such a method, it is possible to perform patterning processing on an object to be etched without pretreatment without contact, but because of the pinpoint etching technique, it is difficult to control the pattern because the liquid spreads in the plane direction. There is. In addition, there is a problem that edge portion sagging and processing time become long when applied to a wide range of patterning. Furthermore, depending on the type of the object to be etched and the electrolytic solution, the amount of gas generated during electrolysis is large, and the gas generated at the beginning of the reaction becomes bubbles and stays between the object to be etched and the electrode. Therefore, there is a problem that the patterning line is broken or hooked because the electrolytic reaction is hindered in the portion where the staying bubbles are present.
[0008]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide an electrolytic etching method that solves the above-mentioned conventional problems, is non-contact with an object to be etched, can be reduced in cost, has fewer steps, and can further improve patterning accuracy. And
[0009]
[Means for Solving the Problems]
As a result of intensive investigations on etching methods utilizing reduction, oxidation, and dissolution phenomena by electrochemical reactions of metals and transparent conductive films, the present invention has found conditions for improving etching accuracy, and without causing side effects such as peeling. An etching method capable of performing a long-term stable treatment has been completed by adding further detailed examination to the knowledge obtained by the present inventors.
[0010]
  The essence of the etching process is an electrochemical reaction between the object to be etched and the etching electrode.The object to be etched is a conductive layer provided on the semiconductor layer,The electrolyte is an aqueous solution containing a Lewis acid or a Lewis base.And containing polyethylene glycol or polypropylene glycol as an additive that lowers the surface tension of the electrolyte,Contact angle of electrolyte to the object to be etchedBut70 ° or lessIsTherefore, the influence of bubbles generated during electrolysis can be controlled. As a result, the problem of etching defects such as disconnection and hooking of the patterning line is solved. Further, it can be used for manufacturing a photovoltaic device, and it is possible to manufacture a device having high characteristics, yield, and reliability.
[0011]
[Action]
The present invention has been completed based on these findings, and the operation of the present invention will be described below.
[0012]
By reducing the surface tension of the electrolytic solution and adjusting the contact angle of the electrolytic solution with respect to the object to be etched to 70 ° or less, preferably 10 ° to 70 °, a large amount of gas is generated by the electrolytic reaction and bubbles are increased. In the meantime, the bubbles are too fine and easily aggregated to prevent the aggregates of the bubbles from staying.
[0013]
When an electrochemical reaction is performed between the object to be etched and the etching electrode, by reducing the surface tension of the electrolyte solution, bubbles generated by the generated gas can be broken or suppressed, and large bubbles are formed with the object to be etched. It is possible to control residence at any part between the electrodes. As a result, it is possible to effectively perform electrolytic etching.
[0014]
By adding 0.01% to 10% by weight of the additive material to the total weight of the electrolyte, it is possible to achieve good patterning by electrolytic etching without inhibiting the electrolytic reaction while controlling the retention of bubbles. It becomes.
[0015]
The surface tension can be effectively reduced by adding at least one of polyethylene glycol, polypropylene glycol, acetylene alcohol, ethanol and their copolymers, and surfactants to the electrolyte as a substance that reduces the surface tension. it can. As a result, foam retention can be suppressed.
[0016]
By combining the electrolytic etching process and the patterning process, a process with a high processing speed can be performed without being affected by the temperature of the processing solution.
[0017]
By combining electrolytic etching and mask etching, patterning including a curve or the like becomes possible.
[0018]
By forming the etching electrode in a desired etching pattern, non-contact patterning becomes possible.
[0019]
Since the electrolyte solution contains Lewis acid or Lewis base, and exchanges electron pairs, it becomes a charge carrier, so that the electrolytic reaction can be promoted without generating many hydrogen ions. Generation of problematic bubbles can be reduced.
[0020]
By using an electrolytic solution as an aqueous solution, the volatility is low, and it is difficult to be affected by evaporation and the like, and a continuous process can be easily performed.
[0021]
By supplying a direct current, a pulse, or an alternating current between the etching electrode and the object to be etched, the line width and the processing time can be controlled.
[0022]
By performing water cleaning and heat treatment of the object to be etched after the etching process, the additive substance does not react with the object to be etched, and side effects such as peeling do not occur.
[0023]
By using the substrate to be etched as a substrate on which a transparent conductive film is deposited, the electrolytic etching of the present invention can be used for manufacturing various devices such as solar cells, photosensitive devices, light emitting devices, and liquid crystal displays.
[0024]
By making the object to be etched a substrate for a photovoltaic device having at least one of a metal layer and a transparent conductive film, precise and accurate patterning can be obtained, and a photovoltaic device with high appearance, characteristics and reliability can be obtained. It is done.
[0025]
Since the object to be etched is a photovoltaic element having a semiconductor layer provided on a substrate and a conductive layer provided on the semiconductor layer, high-accuracy photovoltaics can be obtained because highly accurate etching is possible. The device can be manufactured.
[0026]
By reducing the conductive layer around the short circuit by the electrolytic etching method of the present invention, the conductive layer on the short circuit can be selectively etched, and the performance of the photovoltaic device can be recovered.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
In the following, exemplary embodiments of the present invention will be described.
[0028]
(Patterning processing)
The electrolytic etching method of the present invention will be described taking patterning as an example.
[0029]
In the electrolytic etching method of the present invention, various electrolytic solutions can be used, the reaction proceeds at room temperature, and it is not necessary to supply heat from the outside. During electrolysis, the constituents of the object to be etched are ionized by reduction or oxidation reaction and dissolved in the electrolyte simultaneously with the generation of gas.
[0030]
In order to perform patterning by electrolytic etching, a mask is formed by applying a resist to an object to be etched, or a portion without a mask is etched, or the electrode side is formed in a shape for patterning in advance, and lines of electric force are applied. There is a method of controlling to form a desired patterning line.
[0031]
FIG. 1a) shows a method for performing electrolytic etching by forming a mask on an object to be etched. Here, 101 is an object to be etched, 102 is a mask, 103 is an etching electrode, 104 is an electrolytic solution, 105 is a power source, 106 is a controller for controlling conditions such as voltage, current, and time, and 107 is an electrolytic cell. Here, only the non-mask portion can be subjected to etching patterning by an electrolytic reaction.
[0032]
FIG. 1b) shows a method of performing electrolytic etching by patterning the electrode side and further providing a gap. Here, the etching electrode 103 is provided with a gap 110 formed by patterning and cutting a 1 mm-thick silicone rubber sheet.
[0033]
FIG. 1c) shows a method of performing electrolytic etching by patterning the electrode side to form an auxiliary electrode and controlling electric lines of force. The etching electrode 111 has a working electrode 112 and an auxiliary electrode 113, and a pattern is formed by each of the electrodes. An insulating material 114 is provided between the working electrode 112 and the auxiliary electrode 113.
[0034]
The current that flows between the etching electrode and the object to be etched is not particularly limited, but it is preferable to control the line width and the processing time by appropriately selecting a direct current, a pulse, or an alternating current to flow.
[0035]
In addition, after the etching process is completed, the object to be etched is washed with water and subjected to heat treatment, so that the substance contained in the electrolytic solution does not remain in the object to be etched and does not react. In this case, it is preferable that no side effects such as peeling occur due to part of the layer being eroded.
[0036]
The object to be etched is not particularly limited, but a substrate on which a transparent conductive film is deposited, a metal layer, a photovoltaic element substrate having at least one of the transparent conductive film, at least a semiconductor layer provided on the substrate, and the semiconductor layer And a photovoltaic device having a transparent electrode layer provided on the substrate.
[0037]
Conventionally, in any of the methods of FIGS. 1a) to 1c), gas generated during electrolytic etching becomes bubbles and partially stays.
[0038]
In FIG. 1 a), bubbles stay on the edge of the mask 102 formed on the object to be etched 101. Here, there is a risk that uniformity cannot be obtained until the etching is completed due to the influence of bubbles generated in the initial stage of etching.
[0039]
In FIGS. 1b) and 1c), bubbles may stay on the patterned electrode side, which is fatal.
[0040]
That is, in FIG. 1b), after etching the object to be etched by an electrolytic reaction, bubbles remain in the patterned portion of the electrode 103 and the gap between the gap 110 when the next object to be etched is etched. That is, bubbles stay between the etching electrode 103 and the object to be etched 101, so that the electrochemical reaction does not proceed there. Therefore, the patterning line becomes non-uniform, and when there is a large amount of bubbles, line breakage may occur. The effect of this phenomenon becomes significant by accumulating the amount of accumulated bubbles by repeating the number of etching processes.
[0041]
In FIG. 1c), bubbles stay on the etching electrode side as in FIG. 1b). Here, when bubbles stay in the working electrode 112 in a form of adhering bubbles, the electric lines of force cannot be controlled according to a desired pattern, resulting in uneven patterning lines and occurrence of disconnection. In either case, bubbles can be removed by an ultrasonic generator, liquid circulation, wiper, etc., but the effect is not sufficient depending on the amount of gas generated. Also, the more complicated the pattern, the more likely the bubbles will stay at the edge of the pattern.
[0042]
According to the present invention, it is possible to suppress or prevent the retention of bubbles due to the gas generated during the electrolytic reaction, which is a problem here.
[0043]
In the electrolytic etching method of the present invention, the contact angle of the electrolytic solution to the object to be etched is 70 ° or less, preferably 10 ° to 70 °. If the contact angle of the electrolytic solution to the object to be etched is 70 ° or less, the surface tension of the electrolytic solution is reduced to show defoaming properties. If the contact angle is 10 ° or more, fine bubbles are aggregated and aggregated. Continuously stable patterning can be performed without gradually staying.
[0044]
The electrolytic solution preferably contains an additive substance (additive) that lowers the surface tension. The inclusion of such an additive substance is preferable because the electrolyte solution can have a bubble-breaking property that destroys bubbles once generated and a bubble-suppressing property that suppresses the generation of bubbles in the electrolyte solution.
[0045]
In order to maintain the effect stably without inhibiting the electrochemical reaction, the content of the additive substance is preferably 0.01 wt% to 10 wt% of the entire electrolytic solution.
[0046]
By selecting an additive having a high expandability (dispersibility) to the electrolyte and a low surface tension, the foam breaking property can be exhibited. Further, by selecting one having a low solubility in the electrolytic solution and a low surface tension, it is possible to exhibit foam suppression. That is, as a more effective additive, the surface tension is small, the expansibility (dispersibility) is large, and the solubility is small.
[0047]
  When an acid or base or an aqueous solution thereof is used as the electrolytic solution, it is necessary to select an additive.Additives that are polyethylene glycol and polypropylene glycol areIt can be used in one or two mixed systems.Liquid or solidHowever, in view of the influence of the post-electrolysis treatment remaining on the object to be etched, a liquid with high solubility is desirable.
[0048]
Further, in order to process a semiconductor element such as a photovoltaic element substrate, it is necessary that there is no residue on the substrate surface. That is, in the case of a composite multilayer thin film, if the additive remains, there is a risk that a part of the layer is eroded and peeling occurs.
[0049]
Specifically, at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, acetylene alcohol, ethanol or a copolymer thereof and a surfactant is effective. Among these, polyethylene glycol and polypropylene glycol are suitable because they are low in volatility and are not evaporated during the electrolytic treatment and lose their effects even when long-term continuous treatment is performed.
[0050]
  Here, the electrolyte is used as a medium for causing an electrochemical reaction.Yes, an aqueous solution containing Lewis acid or Lewis baseCan be used.
[0051]
Here, by containing a Lewis acid or a Lewis base in the electrolytic solution, and making a charge carrier by exchanging electron pairs, the electrolytic reaction can be promoted without generating many hydrogen ions, and thus It is preferable because it is possible to reduce the generation of bubbles which are problematic during etching. Specific examples of Lewis acids and Lewis bases to be included in the electrolyte include acids and bases such as sulfuric acid, nitric acid, hydrochloric acid, and ammonia, sodium chloride, potassium chloride, aluminum chloride, zinc chloride, tin chloride, ferric chloride, sodium nitrate A solution obtained by dissolving a salt such as potassium nitrate in a solvent is used.
[0052]
In addition, it is preferable that the electrolytic solution is an aqueous solution of the above acid, base, or salt, since it has low volatility and is not easily affected by evaporation and the like, and a continuous process can be easily performed.
[0053]
(Manufacture of photovoltaic elements)
A photovoltaic device can be produced by etching a conductive layer provided on a semiconductor layer such as a transparent electrode layer by the electrolytic etching method of the present invention.
[0054]
An example of a photovoltaic device that can be produced by the present invention is shown in FIG. FIG. 3 shows an amorphous solar cell 300, which has a plurality of semiconductor layers 303, 313, and 323 having nip junctions that generate a current flow in response to absorption of incident light. Reference numeral 303 denotes a bottom cell, 313 denotes a middle cell, and 323 denotes a top cell. Reference numeral 301 denotes a substrate that supports the solar cell body, 302 denotes a lower electrode layer, 304 denotes a transparent electrode layer, and 305 denotes a grid electrode used as a collecting electrode. FIG. 3 shows an amorphous silicon solar cell in which light is incident from the side opposite to the substrate, but the photovoltaic element manufactured in the present invention is not limited to a photovoltaic element having a specific structure or shape.
[0055]
Hereinafter, each component will be described.
[0056]
<Substrate 301>
The substrate 301 is a substrate that mechanically supports the semiconductor layers 303, 313, and 323 in the case of a solar cell having a multilayer thin film structure such as amorphous silicon, and may be used as an electrode at the same time. The substrate is a conductive substrate, for example, a metal member such as a stainless steel substrate or tin metal foil, or an insulating substrate such as glass or synthetic polymer resin, or a conductive film is deposited on at least a part of the insulating substrate. Use things.
[0057]
<Lower electrode layer 302>
The lower electrode layer 302 is one electrode for taking out the electric power generated by the semiconductor layers 303, 313, and 323. In the case where a conductive substrate is used as the substrate 302, the lower electrode layer 302 is not essential. The semiconductor layer 303 is required to have a work relationship that forms an ohmic contact. The surface of the lower electrode layer may be textured to cause irregular reflection of light to improve Jsc.
[0058]
Examples of the material of the lower electrode layer 302 include Al, Ag, Pt, ZnO, and In₂O_ThreeIn addition, a metal body or alloy such as ITO (indium tin oxide) or AlSi, transparent conductive oxide (TCO), or the like is used.
[0059]
As a manufacturing method of the lower electrode layer 302, methods such as plating, vapor deposition, and sputtering can be used.
[0060]
Here, it is important for improving the characteristics of the photovoltaic element that the lower electrode layer 302 includes a metal layer or a metal alloy layer having high conductivity and high reflection. However, if the metal layer and the semiconductor layer 303 are directly stacked, alloying at the interface may increase the series resistance, so a metal layer or a metal alloy layer and a transparent conductive oxide layer are sequentially stacked on the substrate 301. The configuration described above is preferably used.
[0061]
<Semiconductor layers 303, 313, 323>
Taking an amorphous silicon solar cell as an example of the semiconductor layer, the semiconductor material constituting the i layer may be a so-called group IV or group IV amorphous silicon semiconductor such as a-Si, a-SiGe, or a-SiC. Is mentioned. The semiconductor material constituting the p layer or the n layer can be obtained by doping a valence electron controlling agent into the semiconductor material constituting the i layer described above. As a valence electron controlling agent for obtaining a p-type semiconductor, a compound containing a Group III element is used. Examples of Group III elements include B, Al, Ga, and In. As a valence electron controlling agent for obtaining an n-type semiconductor, a compound containing a Group V element is used. Examples of Group V elements include P, N, As, and Sb.
[0062]
As a method for forming the amorphous silicon semiconductor layer, a known method such as an evaporation method, a sputtering method, an RF plasma method, a microwave plasma CVD method, an ECR method, a thermal CVD method, or an LPCVD method is used as desired. Moreover, in order to obtain a large area, a method of forming a film by continuously transporting the substrate by a roll-to-roll method is used.
[0063]
The present invention is not only for manufacturing a cell having a single semiconductor junction, but also for manufacturing a so-called tandem cell in which two or more semiconductor junctions are stacked for the purpose of improving spectral sensitivity and voltage, and a triple cell as shown in FIG. Can be used.
[0064]
<Transparent electrode layer 304>
The transparent electrode layer 304 is an electrode for taking out electromotive force generated in the semiconductor layers 303, 313, and 323. The transparent electrode layer 304 forms a pair with the lower electrode layer 302 and is also called an upper electrode. The transparent electrode layer is necessary in the case of a semiconductor having a high sheet resistance such as an amorphous silicon solar cell. Moreover, since it is located on the light incident side, it needs to be transparent.
[0065]
The transparent electrode layer 304 preferably has a light transmittance of 85% or more in order to efficiently absorb light from the sun, a fluorescent lamp, or the like into the semiconductor layers 303, 313, and 323. In order to allow the current generated by light to flow in a direction parallel to the semiconductor layers 303, 313, and 323, it is necessary to reduce the sheet resistance, and preferably 100Ω / □ or less.
[0066]
As a material having such characteristics, SnO₂, In₂O_Three, ZnO, CdO, CdSnO_FourMetal oxides such as ITO and the like can be used, and these are preferably used as the material of the transparent electrode layer 304.
[0067]
<Collector electrode 305>
The current collecting electrode 305 takes out the electromotive force generated in the semiconductor layers 303, 313, and 323 by the transparent electrode layer 304, and further collects current. The collecting electrode 305 is formed in a comb shape, and a suitable width, pitch, and the like are designed and determined from the sheet resistance of the transparent electrode layer 304. The collector electrode 305 is required to have a low specific resistance so as not to be a series resistance of the solar cell.
[0068]
As a method for forming the collector electrode 305, specifically, a metal such as Ag, Ni, Al, Ti, Cr, W, or Cu is powdered and mixed with a polymer binder or solvent to obtain a paste. Examples thereof include a method of forming, a method of directly forming by vapor deposition, a soldering method, a plating method, and a method of laying the metal in the form of a wire.
[0069]
(Defect processing of photovoltaic elements)
FIG. 5 shows a cross-sectional view of a photovoltaic device 500 that has been subjected to defect processing. In FIG. 5, 501 is a substrate, 502 is a lower electrode layer, 503 is a bottom cell, 513 is a middle cell, 523 is a top cell, 504 is a transparent electrode layer, 505 is a collecting electrode (grid electrode), 506 is a defective portion, and 507 is This is a part with high resistance.
[0070]
Generally, the total thickness of the semiconductor layers 503, 513, and 523 deposited is a thin film layer of about 4000 mm. For this reason, when there are protrusions and foreign matters from above and below, it is difficult to sufficiently cover them by deposition.
[0071]
For example, when stainless steel is used for the substrate 501 and the semiconductor layers 503, 513, and 523 are continuously deposited thereon, even if the surface of the substrate 501 is processed smoothly, protrusions, depressions, and distortion are eliminated at all. It is difficult. In addition, mechanical dents and scratches are not a little generated from the back side of the substrate 501 during conveyance during continuous film formation. For this reason, a defect occurs due to unevenness of 1 μm or more and mechanical damage to the semiconductor layers 503, 513, and 523.
[0072]
For example, when the height of the protrusion is large from the surface of the substrate 501, the substrate 501 to the lower electrode layer 502 are not covered with the semiconductor layers 503, 513, and 523, and the transparent electrode layer 504 is directly laminated on the substrate 501 to the lower electrode layer 502. Contact will cause shunts and shorts. In addition, when dust or the like is deposited during film formation of the semiconductor layers 503, 513, and 523, not-formed portions of the semiconductor layers 503, 513, and 523 are formed or peeled off, which causes pinholes. The transparent electrode layer 504 is directly laminated on the lower electrode layer 502 to the substrate 501 to cause a shunt or short circuit.
[0073]
The presence of these defects affects the voltage characteristics at low illumination. That is, the photovoltaic current of the photovoltaic element increases directly with increasing illumination, but the resulting electromotive voltage increases exponentially. That is, when the electromotive force is high in illuminance, the brightness is extremely 100 mW / cm.²Under a strong light source, there is almost no difference regardless of the degree of the defect, but as the illuminance decreases, the difference between the presence and absence of the defect appears. This tendency becomes more prominent from an illuminance of 1000 Lux or less. For this reason, it is important to eliminate the influence of defects in a room or in an environment where sunlight is difficult to gather.
[0074]
According to the defect processing method of the present invention, the high-resistance portion 507 is formed on a part of the transparent electrode layer 504 on the defect portion 506 of the semiconductor layers 503, 513, and 523 in the photovoltaic element 500. As a result, the current path to the defective portion 506 is blocked. At this time, since the resistance of the transparent electrode layer 504 is increased only in the vicinity of the defect portion 506, the resistivity itself of the transparent electrode layer 504 does not increase, and therefore the series resistance of the entire photovoltaic element does not increase.
[0075]
FIG. 6 shows an example of the defect processing apparatus of the present invention. 600 is a photovoltaic device, 601 is a substrate, 602 is a lower electrode layer, 603 is a semiconductor layer in which a p layer is deposited on the uppermost layer (left side in the figure), 604 is a transparent electrode layer, 606 is a defect portion, and 617 is an electrolysis A tank, 614 represents an electrolytic solution, 613 represents a counter electrode (etching electrode), and 615 represents a power source.
[0076]
In the present invention, the formation of the high resistance portion 507 in FIG. 5 described above is achieved by reducing a part of the transparent electrode layer 604. The photovoltaic element 600 is immersed in the electrolytic cell 617, connected to the negative electrode side of the power source 615, and the etching electrode 613 is connected to the positive electrode side. That is, a bias voltage is applied to the photovoltaic element 600 in the forward direction. At this time, when a bias is applied between the electrodes, current flows preferentially through the defect portion 606 having a low resistivity, using the electrolytic solution 614 as a medium.
[0077]
At this time, nascent hydrogen is generated on the photovoltaic element 600 side which is the cathode side, and the transparent electrode layer 604 formed around the defect portion 606, that is, above the defect portion 606 is chemically reacted. That is, the transparent electrode layer 604 made of a metal oxide is reduced. Simultaneously with this reduction reaction, dissolution of the reaction product into the electrolytic solution 614 begins, and the transparent electrode layer 604 of the dissolved portion is lost, and substantially becomes a defect from the lateral direction via the transparent electrode layer 604. The path of the leakage current that flows in is cut off. The amount of oxygen generated at this time varies depending on the type and concentration of the electrolytic solution, and the type and manufacturing conditions of the transparent electrode layer 604.
[0078]
According to the present invention, it is possible to reduce bubbles generated at the time of defect processing, and it is possible to form a high resistance portion only in the upper part near the defect portion. Since the high resistance portion is formed in a very small range, the influence on the series resistance can be reduced, and furthermore, the spotted portion is small and small, not only in terms of performance, In terms of appearance, the yield can be improved.
[0079]
The above electrolysis can also be performed by irradiating the photovoltaic element 600 with light in an electrolytic solution. At this time, the electromotive voltage itself generated by the photovoltaic element 600 by light becomes an applied bias, and the bias condition can be controlled by the intensity of the irradiated light.
[0080]
【Example】
Examples of the present invention will be described in detail below, but the present invention is not limited to these examples.
[0081]
  Example 1<Reference example>)
  Patterning by etching of the transparent conductive film was performed using the electrolytic etching apparatus shown in FIG.
[0082]
In this example, the working electrode 112 constituting the etching electrode 111 is a Pt plate having a thickness of 0.8 mm, the auxiliary electrode 113 is SUS304 having a thickness of 2.0 mm, and the insulating material 114 is 0.2 mm in thickness. These glass epoxy resin plates were used in combination. At this time, the electrode surface (the surface closest to the object to be etched 101 at the time of electrolytic etching) was smoothed by polishing.
[0083]
First, a 31 cm × 31 cm square SUS304 substrate that had been sufficiently degreased and washed was placed in a vapor deposition apparatus, and 750 mm of ITO film was deposited to produce an object to be etched 101.
[0084]
Next, the etching electrode 111 and the object to be etched 101 were set in the electrolysis apparatus 100. At that time, the ITO film side of the object to be etched 101 and the smoothed surface of the etching electrode 111 were made to face each other. Further, the working electrode 112 was set as the anode side, and the auxiliary electrode 113 and the object to be etched 101 were connected as the cathode side to the power source 105. Further, a contact spacer made of Teflon was provided to adjust the gap between the etching electrode 111 and the object to be etched 101 to 0.4 mm.
[0085]
A sulfuric acid aqueous solution was used as the electrolytic solution 107. The concentration was adjusted to 1.0 wt% and the conductivity was adjusted to 25 mS / cm. As an additive, polyethylene glycol having a molecular weight of 400 was added at 1.0 wt% and sufficiently stirred. The contact angle of the electrolytic solution with respect to the surface of the object to be etched 101 was 56 ° when measured using a wettability determination device (CONTACT-ANGLE METER, manufactured by Kyowa Interface Science Co., Ltd.). A direct current power source was used as the power source 105. The controller 108 was used to adjust a constant current of 20 A to flow for 0.2 seconds, and electrolytic treatment was performed. Similarly, 100 samples were etched. During electrolysis, gas generation was observed from the surface of the object 101 to be etched. After electrolytic treatment, the patterned uneven surface on the surface of the etching electrode 111 was observed from the side, but no retention of bubbles was confirmed.
[0086]
Thereafter, the object to be etched 101 was taken out of the electrolytic solution 107, washed with pure water, dried, and then observed with an optical microscope. As a result, uniform patterning of 30 cm × 30 cm square and a line width of 0.2 mm was performed. In addition, no etching defects such as overhang were found in the etched portion of the patterning.
[0087]
(Comparative Example 1)
For comparison, the transparent conductive film was patterned by etching in the same manner as in Example 1 except that no additive was added to the electrolytic solution 107.
[0088]
The contact angle of the electrolyte was measured and found to be 87 °. When the generation of gas from the surface of the etching object 101 during electrolysis was observed, it was observed that many very large bubbles were generated. Further, after the electrolytic treatment, the patterned uneven surface on the surface of the etching electrode 111 was observed from the side, and it was clear that the retention of bubbles increased as the number of etching was repeated.
[0089]
Thereafter, the object to be etched 101 was taken out from the electrolytic solution 107, washed with pure water, dried, and then observed with an optical microscope. As a result, the width of the patterning line was found to be 0.2 mm ± 0.1 mm on average. Further, as the number of times of etching was repeated, a part where no line was formed (disconnection) was observed. In addition, sag and rounding were observed on the etched portion of patterning.
[0090]
  Example 2<Reference example>)
  100 samples were patterned by electrolytic etching of the transparent conductive film in the same manner as in Example 1 except that polypropylene glycol was used as the additive to be added to the electrolytic solution. Polypropylene glycol used as an additive had a molecular weight of 400, and the addition amount was 1.0 wt%.
[0091]
Here, the contact angle of the electrolytic solution 107 was measured and found to be 44 °. After the electrolytic treatment, the object to be etched 101 was taken out from the electrolytic solution 107, washed with pure water, dried, and then observed with an optical microscope. As in Example 1, 30 cm × 30 cm square, line width 0.2 mm ± 0.05 mm The uniform patterning was performed. In addition, no etching defects such as overhang were found in the etched portion of the patterning.
[0092]
  Example 3<Reference example>)
  100 samples were patterned by electrolytic etching of the transparent conductive film in the same manner as in Example 1 except that ethanol was used as the additive to be added to the electrolytic solution. The amount of ethanol used as an additive was 9.0 wt%.
[0093]
Here, the contact angle of the electrolytic solution 107 was measured and found to be 50 °.
[0094]
After the electrolytic treatment, the object to be etched 101 was taken out from the electrolytic solution 107, washed with pure water, dried, and then observed with an optical microscope. As in Example 1, 30 cm × 30 cm square, line width 0.2 mm ± 0.05 mm The uniform patterning was performed. In addition, no etching defects such as overhang were found in the etched portion of the patterning.
[0095]
  Example 4<Reference example>)
  100 samples were patterned by electrolytic etching of the transparent conductive film in the same manner as in Example 1 except that the additive to be added to the electrolytic solution was a surfactant.
[0096]
The surfactant used as an additive is fluorine-based (RfSO_ThreeKRf: C_nF_{2n + 1}  ^-A surfactant having a structure) was used, and the addition amount was 0.1 wt%.
[0097]
Here, the contact angle of the electrolytic solution 107 was measured and found to be 28 °.
[0098]
After the electrolytic treatment, the object to be etched 101 was taken out from the electrolytic solution 107, washed with pure water, dried, and observed with an optical microscope. As in Example 1, 30 cm × 30 cm square, line width 0.2 mm ± 0.05 mm The uniform patterning was performed. In addition, no etching defects such as overhang were found in the etched portion of the patterning.
[0099]
  Example 5<Reference example>)
  100 samples were patterned by electrolytic etching of the transparent conductive film in the same manner as in Example 1 except that the current applied during the electrolytic treatment was pulsed.
[0100]
The power source 105 was a pulse power source, and a pulse current of 0.05 A and a pulse width of 0.2 seconds was applied 20 times at 0.1 second intervals.
[0101]
After the electrolytic treatment, the object to be etched 101 is taken out from the electrolytic solution 107, washed with pure water, dried, and observed under an optical microscope. As a result, an etching line having an average of 30 cm × 30 cm square and a line width of 0.2 mm is obtained. It was. In addition, no etching defects such as overhang were found in the etched portion of the patterning.
[0102]
(Example 6)
When an amorphous solar cell having a pin junction triple cell structure as shown in FIG. 3 was manufactured, patterning by etching of the transparent electrode layer was performed using the electrolytic etching apparatus shown in FIG. 1-c). Details are shown below.
[0103]
First, a stainless steel (SUS430BA) substrate 301 having a roll thickness of 0.15 mm and a width of 360 mm that has been sufficiently ultrasonically cleaned with acetone and isopropanol is placed in a DC magnetron sputtering apparatus, and a layer thickness of 0. 4 μm of Ag was deposited, and then ZnO was deposited at a substrate temperature of 350 ° C. and 0.4 μm to form the lower electrode layer 302 having a two-layer structure.
[0104]
Next, the substrate was taken out from the DC sputtering apparatus, and an n-type semiconductor layer, an i-type semiconductor layer, and a p-type semiconductor layer were formed in this order by the following method to form a bottom cell 303. The following method was repeated in the same manner to form the middle cell 313 and the top cell 323, thereby forming a semiconductor layer.
[0105]
The inside of the deposition chamber (vacuum chamber) that can be depressurized was depressurized to a predetermined initial pressure. Source gas SiH in the deposition chamber_Four, Dilution gas H₂Was introduced and evacuated by a vacuum pump. Here, BF is used as a dopant gas to form a p-type semiconductor layer._ThreeAs a dopant gas for forming an n-type semiconductor layer (other dopant gases can also be used)_Three(Other dopant gases can also be used). The substrate temperature was controlled by a heater. When depositing the i-type semiconductor layer, microwaves oscillated by a microwave power source were guided by an introduction tube and introduced into the deposition chamber through a dielectric window (in this example, alumina ceramics were used). The frequency of the microwave is 2.45 GHz, the substrate temperature in the deposition chamber is 300 ° C., the internal pressure is 10 mTorr, and the power is 0.1 W / cm.^ThreeIt was. In addition, an RF high frequency was applied to the plate electrode during the deposition of the n-type semiconductor layer and the p-type semiconductor layer. The frequency of the RF high frequency is 13.45 MHz, the substrate temperature in the deposition chamber is 200 ° C., the internal pressure is 1 Torr, and the RF power is 0.01 W / cm.^ThreeIt was.
[0106]
The bottom cell 303 has an n-type semiconductor layer 250 Å, an i-type semiconductor layer 1050 Å, and a p-type semiconductor layer 100 Å, and a middle cell 313 has an n-type semiconductor layer 600 Å, an i-type semiconductor layer 1450 Å, a p-type semiconductor layer 100 Å, and a top cell. In H.323, an n-type semiconductor layer 100 Å, an i-type semiconductor layer 1000 Å, and a p-type semiconductor layer 100 Å were used.
[0107]
Next, an ITO film was formed as a transparent electrode layer 304 on the substrate on which the semiconductor layer was formed by using a DC magnetron sputtering method (film formation temperature: 170 ° C., film thickness: 730 mm). The transparent electrode layer 304 has an antireflection function. The substrate formed up to the transparent electrode layer 304 is hereinafter referred to as a solar cell.
[0108]
Next, this solar cell substrate was cut to 360 mm × 260 mm, and the patterning shown in FIG. 2 was performed on the transparent electrode layer 304 in the same manner as in Example 1 using the electrolytic etching apparatus shown in FIG. . 201 is an etching line.
[0109]
Subsequently, a carbon paste is coated on a copper wire, placed at a pitch of 5 mm, and heat-pressed at 200 ° C. for 1 minute to form a collecting electrode 305 on the transparent electrode layer 304, as shown in FIG. A solar cell 300 was obtained. 100 solar cells were manufactured in the same manner. The initial characteristics of these solar cells 300 were evaluated as follows.
[0110]
First, the voltage-current characteristics in the dark state were measured, and the shunt resistance was obtained from the slope near the origin. The average was 100 kΩ · cm.²And there was no shunt. Further, when the surface of the substrate subjected to the etching treatment was analyzed with an XMA apparatus, no residual element of the additive was confirmed.
[0111]
Next, as shown in FIG. 4-a), the solar cell 400 having a half area was obtained by being divided by a press cutter on the center line. When the shunt resistance of each of the divided solar cells 400 was measured, the average was 98 kΩ · cm.²Even after being divided, no shunt occurred. 100mW / cm in 1.5AM global solar spectrum²When the solar cell characteristics were measured using a pseudo solar light source (manufactured by SRIRE Co., Ltd.) and the photoelectric conversion efficiency was determined, a good value of 9.0% ± 0.2% was obtained on average.
[0112]
Further, when the portion patterned by electrolytic etching was observed under an optical microscope, there was no disconnection or etching failure, and a uniform etching line was obtained.
[0113]
Next, the divided solar cells 400 were connected in series as shown in FIG. At this time, the copper foil 403 was used for the series connection, and the solder 404 was used for the positive current collector 401 of the right solar cell and the negative stainless steel portion 402 of the left solar cell. Further, the plus side extraction electrode 405 was soldered to the current collector of the left solar cell, and the minus side extraction electrode 406 was soldered to the stainless portion of the right solar cell. These serialized solar cells were laminated as follows to form a module. First, an insulating film having an EVA (ethylene vinyl acetate) resin on both sides, a glass nonwoven fabric, the above-mentioned solar electric device, an EVA resin sheet, and a fluororesin film were laminated on a galvalume steel plate, and were laminated by thermocompression bonding using a vacuum laminator.
[0114]
Furthermore, the reliability of this modularized solar cell (hereinafter referred to as “solar cell module”) based on the temperature and humidity cycle test A-2 defined in the environmental test method and durability test method of the crystalline solar cell module of Japanese Industrial Standard C8917. A test was conducted.
[0115]
First, the solar cell module was put into a thermo-hygrostat whose temperature and humidity can be controlled, and a cycle test in which the temperature was changed between −40 ° C. and + 85 ° C. was repeated 20 times. When the photoelectric conversion efficiency of the solar cell module after the test was measured by the method described above, an initial photoelectric conversion efficiency of 98.0% was obtained on average. Moreover, peeling of the semiconductor layer and the laminating agent of the solar cell was not observed by appearance observation.
[0116]
As described above, in this example, patterning accuracy can be improved by etching, and a solar cell excellent in initial characteristics and reliability can be manufactured.
[0117]
(Example 7)
When manufacturing an amorphous solar cell having a pin junction type torpull cell structure as shown in FIG. 5, patterning is performed by etching the transparent conductive film using the electrolytic etching apparatus shown in FIG. After that, defect processing was performed using the defect processing apparatus shown in FIG.
[0118]
The electrolyte used for the defect treatment was the same as in Example 6, and the electrolysis conditions were controlled by a DC power supply in sequence, and a DC voltage of 4.5 V was applied for 2 seconds. Thereafter, the patterned solar cell 600 was taken out of the electrolytic solution 614, washed with pure water, and dried.
[0119]
Subsequently, the carbon paste is coated on a copper wire, placed at a pitch of 5 mm, and heat-pressed at 200 ° C. for 1 minute to form a current collecting electrode 505 on the transparent electrode layer 504, as shown in FIG. A solar cell 500 was obtained. 100 solar cells were manufactured in the same manner.
[0120]
When the initial characteristics of these solar cells 500 were evaluated in the same manner as in Example 6, the shunt resistance averaged 698 kΩ · cm.²As a result, an even better value of 9.4% ± 0.2% on average was obtained. In addition, no extreme speckled portion was observed by appearance observation.
[0121]
【The invention's effect】
As described above, according to the present invention, it is possible to perform patterning with excellent selectivity even with a precise pattern without being affected by bubbles generated during electrolytic etching. Furthermore, the etching process can be simplified.
[0122]
In addition, according to the present invention, it is possible to provide a photoelectric conversion element having good characteristics in which problems such as shunting and poor appearance are solved.
[0123]
In addition, according to the present invention, since the defect processing of the photovoltaic element is performed by electrolytic etching, it is possible to perform defect processing that is non-contact and causes little damage to the photovoltaic element.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an electrolytic etching apparatus according to the present invention.
FIG. 2 is a schematic view showing an example of an etching pattern when etching is performed using the electrolytic apparatus shown in FIG.
FIG. 3 is a schematic cross-sectional view showing an example of a solar cell manufactured using the present invention.
FIG. 4 is a schematic diagram showing an example in which solar cells manufactured using the present invention are divided and connected in series.
FIG. 5 is a schematic cross-sectional view of a solar cell subjected to defect processing using the present invention.
FIG. 6 is a schematic view showing a defect processing apparatus according to the present invention.
[Explanation of symbols]
100 Electrolytic etching equipment
101 Object to be etched
102 mask
103, 111, 613 Etching electrode
104, 614 electrolyte
105, 615 Power supply
106 controller
107,617 Electrolyzer
110 gap
112 working electrode
113 Auxiliary electrode
114 Insulation material
201 Etching line
300, 500, 600 photovoltaic elements
301, 501, 601 substrate
302, 502, 602 Lower electrode layer
303, 503 Bottom cell
313, 513 Middle cell
323, 523 Top cell
304, 504, 604 Transparent electrode layer
305, 505 Current collecting electrode
400 Solar cell divided
401 Current collector on the positive side
402 Current collector on the negative side
403 copper foil
404 Solder
405 Positive extraction electrode
406 Negative extraction electrode
506, 606 Defective part
507 High resistance part
603 Semiconductor layer

Claims (14)

In the method of etching the object to be etched by an electrochemical reaction via an electrolytic solution between the object to be etched and the etching electrode, the object to be etched is a conductive layer provided on the semiconductor layer, electrolytic solution I aqueous der including Lewis acid or Lewis base, and containing polyethylene glycol or polypropylene glycol as additive agents to reduce the surface tension of the electrolytic solution, the contact angle of the electrolytic solution for該被etching object is An electrolytic etching method characterized by being 70 ° or less.   The electrolytic etching method according to claim 1, wherein a contact angle of the electrolytic solution with respect to the object to be etched is 10 ° or more. Electrolytic etching method according to claim 1 or 2 content of said additive material is characterized by a 0.01 wt% 10 wt%. Electrolytic etching method according to any one of claims 1 to 3, characterized in that performing the patterning by the etching process. 5. The electrolytic etching method according to claim 4 , wherein a mask is provided on the object to be etched, and a portion of the object to be etched that is not covered with the mask is etched. The electrolytic etching method according to claim 4 , wherein the etching electrode is a patterned electrode. Electrolytic etching method according to any one of claims 1 to 6, DC, characterized by energizing by passing a pulse or alternating current between the object to be etched and the etching electrode. The electrolytic etching method according to any one of claims 1 to 7 , wherein after the etching process is completed, the object to be etched is washed with water and heated. Electrolytic etching method according to any one of claims 1-8, wherein said conductive layer is a transparent conductive film or a metal layer. Claim 1, wherein the object to be etched, characterized in that a transparent electrode layer of the photovoltaic device having at least a semiconductor layer provided on the substrate and the transparent electrode layer provided on said semiconductor layer The electrolytic etching method according to any one of 8 . A method of manufacturing a photovoltaic device having at least a semiconductor layer provided on a substrate and said semiconductor layer conductive provided on layer, said conductive layer by electrolytic etching method according to claim 1-8 A method for producing a photovoltaic device, comprising a step of etching. The method of manufacturing a photovoltaic element according to claim 11 , wherein the conductive layer is a transparent electrode layer. A defect in a photovoltaic device having at least a semiconductor layer provided on a substrate and a conductive layer provided on the semiconductor layer, and having a short circuit that electrically short-circuits the conductive layer and the substrate through the semiconductor layer a processing method, the defect processing method of a photovoltaic device characterized by reducing the conductive layer near shorting path by electrolytic etching method according to claim 1-8. The defect processing method for a photovoltaic element according to claim 13 , wherein the conductive layer is a transparent electrode layer.

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