JP2011088247A - Processing device of ingot for offering silicon substrate in which texture structure is formed, and processing method of ingot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystal silicon substrate with a texture structure efficiently and to form the texture structure without unevenness in a size of roughness. <P>SOLUTION: An ingot processing device is equipped with: an ingot holding section 3 for holding an ingot I; a slice electrode 21 for cutting the ingot I in a predetermined direction by liquating silicon from the ingot I; and texture forming electrode 31 for forming fine unevenness in a part of the surface by liquating the silicon from the surface from which the silicon is eluted to be exposed by the slice electrode 21. Furthermore, the ingot processing device is equipped with a moving mechanism 10 for moving the ingot holding section 3, or the slice electrode 21 and texture forming electrode 31 so that each of track of relative displacement of the slice electrode 21 and the texture forming electrode 31 with respect to ingot holding section 3 becomes parallel mutually. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ingot processing apparatus and an ingot processing method for providing a silicon substrate having a texture structure.

  Solar cells are attracting attention due to the recent increase in demand for clean energy. Crystalline silicon solar cells are currently the most manufactured and used solar cells for solar power generation. However, in order to further promote the spread, further cost reduction and improvement in conversion efficiency are indispensable.

  A crystalline silicon solar cell is manufactured by performing a plurality of processes on a monocrystalline or polycrystalline crystalline silicon substrate. The manufacturing process for crystal silicon substrates, which is currently common, is to refine and purify silicon into an ingot shape with few impurities and crystal defects by a crystallization method such as the casting method or Czochralski method. And it is comprised by each process of cutting out to plate shape from now. If the crystallization method selected at this time is a cast method, it becomes a polycrystalline silicon ingot, and if it is a Czochralski method, it becomes a single crystal silicon ingot. Conventionally, silicon ingots have been cut mechanically with wire saws, etc., but in order to reduce kerf loss (loss during processing) and reduce costs, chemicals using anodization are used. A technique has also been proposed (see Patent Document 1).

  In addition, as one method for improving the conversion efficiency, a technique for forming a texture structure having an uneven structure on the surface of a cut-out crystal silicon substrate is known. Since the texture structure scatters and multi-reflects light, the light use efficiency in the crystalline silicon solar cell can be improved.

  The formation of the texture structure will be described separately for a single crystal silicon substrate and a polycrystalline silicon substrate. In the case of a single crystal silicon substrate, a technique for forming a pyramid structure on the surface of the single crystal silicon substrate by wet etching using an alkaline solution such as KOH is known. This utilizes the etching rate difference in the crystal direction of single crystal silicon. However, in the case of a polycrystalline silicon substrate, since the crystal plane orientation of the polycrystalline silicon substrate is irregular, the texture structure cannot be formed uniformly, and the overall reflectance cannot be reduced effectively. In order to solve such a problem, a method of forming a texture structure on a polycrystalline silicon substrate by reactive ion etching has been proposed (see Patent Document 2 and Patent Document 3).

  A method of forming a texture structure on the surface of a crystalline silicon substrate by anodic oxidation has also been proposed. With anodization, a texture structure can be formed regardless of whether the silicon substrate is single crystal or polycrystal. Patent Document 4 discloses a technique in which anodization is performed with one surface of a crystalline silicon substrate facing a Pt electrode serving as a cathode in an electrolytic solution.

International Patent Publication WO2008 / 140058) JP-A-5-75152, JP-A-9-102625 JP-A-6-310741

  As described above, preparation of a crystalline silicon substrate having a texture structure requires a plurality of steps such as cutting out the crystalline silicon substrate from the silicon ingot and forming the texture structure on the crystalline silicon substrate. However, in the prior art, since each process is performed by a separate apparatus, there is a problem that the manufacturing process becomes complicated. In addition, after cutting a crystalline silicon substrate from a silicon ingot, in order to transfer the crystalline silicon substrate to an etching apparatus, an anodizing apparatus, or the like for forming a texture structure, it is necessary to carefully prevent damage to the crystalline silicon substrate. Transport is required, leading to increased costs and processing time.

  The present invention has been made in consideration of such points, and the work efficiency can be improved by omitting the labor of transporting the generated substrate between apparatuses, and the ingot processing apparatus and the ingot can be improved. An object is to provide a processing method.

An ingot processing apparatus according to the first aspect of the present invention is provided.
An ingot processing apparatus for processing an ingot by anodization,
A treatment tank for storing an electrolyte solution;
An ingot holding part for holding at least a part of the ingot so as to be immersed in the electrolytic solution;
Slicing electrodes that cut the ingot in a predetermined direction while forming slice sections facing each other by locally eluting silicon from the ingot;
A textured electrode that elutes silicon from the slice cross section to form minute irregularities in at least a part of the slice cross section;
A power supply device that causes a current to flow between the slice electrode and the textured electrode and the ingot by setting the ingot to a high potential with respect to the slice electrode and the textured electrode;
A moving mechanism for moving the ingot holding part or the slice electrode and the texture forming electrode so that the relative position of the slice electrode and the texture forming electrode with respect to the ingot holding part changes in the processing tank. When,
It has.

An ingot processing apparatus according to the second aspect of the present invention is provided.
An ingot processing apparatus for processing an ingot by anodization,
A treatment tank for storing an electrolyte solution;
An ingot holding part for holding at least a part of the ingot so as to be immersed in the electrolyte; and
A processing electrode for eluting silicon from the ingot;
A power supply device for causing a current to flow between the machining electrode and the ingot by setting the ingot to a high potential with respect to the machining electrode;
A moving mechanism for moving at least one of the ingot holding part and the processing electrode so that a relative position of the processing electrode with respect to the ingot holding part reciprocally changes in the processing tank;
A control device that controls at least one of the power supply device and the moving mechanism;
The control device, so that the current per unit time flowing between the machining electrode and the ingot on the return path is smaller than the current per unit time flowing between the machining electrode and the ingot on the forward path, It is configured to control at least one of the power supply device and the moving mechanism.

An ingot processing method for processing an ingot by anodization,
An immersion step of immersing at least a part of the ingot in an electrolytic solution;
Slicing step of cutting the ingot in a predetermined direction while forming slice sections facing each other by locally eluting silicon from the ingot;
By eluting silicon from the slice cross section to form a textured structure that forms minute irregularities in at least a part of the slice cross section, and
In the same processing tank, the slicing step and the texture structure forming step change the relative position between the ingot and the processing electrode, while making the ingot have a higher potential than the processing electrode. This is performed by passing a current between the ingot and the machining electrode.

  According to the ingot processing apparatus and the ingot processing method of the present invention, the ingot can be cut and the texture structure can be formed in the slice cross section formed in the ingot in the same processing tank. For this reason, it is possible to save the labor of transporting the generated substrate between apparatuses, and it is possible to improve work efficiency.

The conceptual diagram which shows the aspect which is processing the ingot by the ingot processing apparatus by 1st embodiment of this invention. The bottom view of the slice electrode and texture formation electrode by 1st embodiment of this invention. The side view of the slice electrode and texture formation electrode by 1st embodiment of this invention. Side sectional drawing of the aspect which is processing the ingot by the ingot processing apparatus by 1st embodiment of this invention. Sectional drawing of the structure where a part of slice electrode is coated with the insulating film in 1st embodiment of this invention. The bottom view of the slice electrode and texture formation electrode by the modification of 1st embodiment of this invention. The side view of the slice electrode and texture formation electrode by the modification of 1st embodiment of this invention. Side sectional drawing of the aspect which is processing the ingot by the ingot processing apparatus by the modification of 1st embodiment of this invention. Sectional drawing of the structure where the insulating film coat has adhered to a part of texture formation electrode in the modification of 1st embodiment of this invention. Sectional drawing of the structure where the insulating structure has adhered to a part of texture formation electrode in the modification of 1st embodiment of this invention. The perspective view of the slice electrode by the second embodiment of this invention, a texture formation electrode, and an insulating member support body. Side sectional drawing of the aspect which is processing the ingot by the ingot processing apparatus by 2nd embodiment of this invention. The side view of the slice electrode and texture formation electrode by the modification of 2nd embodiment of this invention. The bottom view of the processing electrode and schematic diagram of a power supply by 3rd embodiment of this invention. The side view of the processing electrode by 3rd embodiment of this invention. Side sectional drawing of the aspect which has cut | disconnected the ingot by the ingot processing apparatus by 3rd embodiment of this invention. Side sectional drawing of the aspect which has formed the texture structure in the cross section of the ingot by the ingot processing apparatus by 3rd embodiment of this invention.

First Embodiment Hereinafter, a first embodiment of an ingot processing device and an ingot processing method according to the present invention will be described with reference to the drawings. Here, FIG. 1 thru | or FIG. 7B is a figure which shows 1st embodiment of this invention.

  The ingot processing apparatus shown in FIG. 1 processes the silicon ingot I by anodic oxidation, so that the processing tank 1 storing the electrolytic solution E and at least a part of the silicon ingot I are immersed in the electrolytic solution E. A silicon ingot holding portion 3 that holds the silicon ingot, and a slice electrode 21 that cuts the silicon ingot I downward (predetermined direction) while forming slice sections facing each other by locally eluting silicon from the silicon ingot I. And a texture-forming electrode 31 that further elutes silicon from the slice cross section to form minute irregularities in at least a part of the slice cross section.

  In the present embodiment, the processing electrode is configured by the slice electrode 21 and the texture forming electrode 31. Further, in the present application, the slice cross section means a surface of the silicon ingot I that is exposed when silicon is eluted by the slice electrode 21.

  By the way, as electrolyte solution E, what diluted hydrofluoric acid (HF) with alcohol solvents, such as IPA, can be used, for example. Moreover, although this embodiment demonstrates using a silicon ingot as the ingot I which is a to-be-processed object, it is not restricted to this.

  In the silicon ingot processing apparatus shown in FIG. 1, the current between the slice electrode 21 and the texture forming electrode 31 and the silicon ingot I is increased by setting the silicon ingot I to a high potential with respect to the slice electrode 21 and the texture forming electrode 31. , The relative positional change trajectory of the slice electrode 21 with respect to the silicon ingot holding part 3, and the relative positional change trajectory of the texture forming electrode 31 with respect to the silicon ingot holding part 3 are parallel to each other. A moving mechanism 10 is also provided for moving the slice electrode 21 and the texture forming electrode 31 so as to coincide with each other.

  Among these, as shown in FIG. 1, the moving mechanism 10 includes a vertical axis 11 extending in the vertical direction, and a slice electrode support 22 and a texture formation electrode support 32 described later on the slice electrode 21 and the texture formation electrode 31. The lifting member 12 has a lifting member 12 that can freely move up and down the vertical shaft 11. The lifting member 12 can also remain at a predetermined height.

  Next, details of the slice electrode 21, the slice electrode support 22, the texture forming electrode 31, the texture forming electrode support 32, and the elevating member 12 will be described with reference to FIGS. 2A and 2B. 2A is a bottom view looking up from below, and FIG. 2B is a side view.

  As shown in FIGS. 2A and 2B, the plurality of slice electrodes 21 are provided with slice electrode supports 22 that support the slice electrodes 21. Here, the slice electrode 21 and the slice electrode support 22 are integrated, and not only the slice electrode 21 but also the slice electrode support 22 is formed of a conductor. For this reason, the slice electrode 21 and the slice electrode support 22 can be energized integrally.

  The plurality of texture forming electrodes 31 are provided with a texture forming electrode support 32 that supports the texture forming electrode 31. Here, the texture forming electrode 31 and the texture forming electrode support 32 are integrated, and not only the texture forming electrode 31 but also the texture forming electrode support 32 is formed of a conductor. For this reason, the texture-forming electrode 31 and the texture-forming electrode support 32 can be energized integrally. Note that platinum, tungsten, or the like can be used as the conductor.

  As shown in FIG. 2A, when the slice electrode support 22 is viewed from the bottom side, it has a frame shape, and the slice electrode support 22 holds both ends of the plurality of slice electrodes 21 at predetermined intervals. is doing.

  Similarly to the slice electrode support 22, the textured electrode support 32 also has a frame shape, and the textured electrode support 32 has a predetermined interval between both ends of the plurality of textured electrodes 31. And hold. In FIG. 2A, the textured electrode 31 and the textured electrode support 32 are not shown because they are hidden behind the slice electrode 21 and the slice electrode support 22, respectively.

  Further, as shown in FIG. 1, the slice electrode support 22 that supports the slice electrode 21 and the texture formation electrode support 32 that supports the texture formation electrode 31 are fixed to the elevating member 12 at a predetermined interval. Yes. Therefore, the moving mechanism 10 can be moved while keeping the distance between the slice electrode 21 and the texture forming electrode 31 constant.

  In this embodiment, the elevating member 12 supports the slice electrode support 22 and the textured electrode support 32 from the left side of FIGS. 2A and 2B. Here, since the elevating member 12 is formed of an insulator, the slice electrode support 22 and the textured electrode support 32 can be electrically insulated from each other. Although the slice electrode support 22 and the textured electrode support 32 can be configured to be conductive, the current flowing through the slice electrode 21 and the textured electrode 31 can be finely controlled by insulating each other. become.

  Further, as shown in FIG. 1, the silicon ingot I is held in the silicon ingot holding unit 3 and immersed in the electrolytic solution E stored in the processing tank 1. At this time, since it is sufficient that only the reaction part is immersed, it is not necessary that all of the silicon ingot I is immersed. The silicon ingot holding unit 3 is connected to the anode (+) of the power supply device 40, while the slice electrode support 22 and the texture forming electrode support 32 are connected to the cathode of the power supply device 40 (−).

  If a large current is required for the slice electrode 21, the slice electrode 21 can be a rectangular parallelepiped extending in the vertical direction as shown in FIG. At this time, in order to prevent an excessive anodic oxidation reaction by the side surface portion of the slice electrode 21, only the front end portion is exposed and the side surface portion and the upper end portion may be covered with the insulator 26. According to such an aspect, not only can the current supplied to the slice electrode 21 be efficiently used, but also the kerf loss can be reduced by suppressing unnecessary anodizing reaction at the side surface portion.

  In the present embodiment, the number, width, and arrangement interval of the texture forming electrodes 31 are the same as those of the slice electrodes 21. When viewed from the side as shown in FIG. 21 is disposed immediately above. That is, since the elevating member 12 moves vertically downward along the vertical axis 11 during the processing step, the trajectory of the relative position change of the texture forming electrode 31 with respect to the silicon ingot holding part 3 is the silicon ingot of the slice electrode 21. This coincides with the trajectory of the relative position change with respect to the holding unit 3.

  Next, processing steps in the first embodiment will be described. The basis of this embodiment is a phenomenon called anodic oxidation. In FIG. 3, the slice electrode support 22 and the textured electrode support 32 are not shown in order to easily understand the reaction in the processing step.

  First, the silicon ingot I is immersed in the electrolytic solution E stored in the processing tank 1 (immersion step) (see FIG. 3).

  Next, the elevating member 12 moves the slice electrode support 22 and the textured electrode support 32 downward. At this time, a voltage is applied so that the silicon ingot I has a higher potential than the slice electrode 21 and the texture forming electrode 31 (see FIG. 1). For this reason, in a slice process and a texture structure forming process described later, a current flows in a state where the silicon ingot I is at a higher potential than the slice electrode 21 and the texture forming electrode 31.

Next, when the slice electrode 21 approaches the silicon ingot I to some extent, a current flows to the cathode side through the silicon ingot I and the electrolytic solution E, and a hole current flows toward the upper surface of the silicon ingot I. When the hole current reaches the contact surface _If (see FIG. 3) between the electrolyte E and the silicon ingot I, the anodic oxidation reaction in which silicon atoms (silicon) on the contact surface _If is eluted into the electrolyte E. Occurs, and the silicon ingot I is cut downward (predetermined direction). At this time, silicon atoms (silicon) are locally eluted from the silicon ingot I, and as a result, the silicon ingot I is cut downward (predetermined direction) while forming slice sections facing each other ( Slicing process).

  Here, the moving mechanism 10 moves the slice electrode 21 vertically downward relative to the silicon ingot I by an amount corresponding to the depression of the silicon ingot I due to the elution of silicon atoms. By repeating this, the silicon ingot I can be cut vertically downward by the slice electrode 21. At this time, after waiting for the silicon ingot I to sink to some extent, the slice electrode 21 may be moved vertically downward with respect to the silicon ingot I, or the slice electrode 21 may be continuously moved. Good.

  By the way, when the silicon ingot I is cut by the slice electrode 21, a slight gap is formed between the slice electrode 21 and the slice cross section. This is because an anodic oxidation reaction occurs not only below the slice electrode 21 but also in the silicon ingot I located obliquely downward or laterally. For this reason, by controlling the moving speed of the slice electrode 21 in the vertical downward direction so that the distance d between the slice electrode 21 and the slice cross section is constant, a crystalline silicon substrate (substrate) having a uniform thickness is obtained. be able to.

  Further, the anodic oxidation reaction can be controlled by arbitrarily changing the current flowing through the slice electrode 21, and the cutting speed and the gap formed between the slice electrode 21 and the slice cross section can be optimized. it can. The current can be changed depending on the magnitude of the voltage applied from the power supply device 40, and can also be controlled by the shape of the slice electrode 21 such as the material and thickness. In order to control the anodic oxidation reaction, it may be designed appropriately in view of desired kerf loss and throughput.

  Although affected by the concentration of the electrolytic solution E and the resistance of the silicon ingot I, stable slicing can be performed when the current is in the range of 100 mA to 200 mA per unit length (1 cm) of the electrode.

As described above, when silicon atoms (silicon) are eluted from the silicon ingot I and slice sections facing each other are formed, silicon atoms (silicon) are eluted from the slice sections, so that at least a part of the slice sections is minute. Unevenness is formed (formation process of texture structure). More specifically, the texture forming electrode 31 is passed between the slice cross sections facing each other so as to follow the slice electrode 21, and at this time, silicon atoms can be eluted from the slice cross section. As a result, an textured region I _t consisting of fine irregularities slice section is formed.

  The reaction performed in the texture structure forming process is also an anodic oxidation reaction. At this time, a small current is passed through the texture forming electrode 31 compared to the current passed through the slice electrode 21 (in other words, the current per unit time flowing through the slice electrode 21 in the slicing step is the texture structure). The current per unit time flowing through the texture forming electrode 31 in the forming step is larger).

  As described above, the minute irregularities formed in the slice cross section by the anodic oxidation reaction may be slightly different in individual size when viewed locally, but function sufficiently as a texture structure for solar cells when viewed macroscopically. It has the uniformity so that.

  In the present embodiment, the slice electrode support 22 and the texture forming electrode support 32 are fixed to the elevating member 12 at a predetermined interval, and therefore the distance between the slice electrode 21 and the texture forming electrode 31. Thus, the relative position with respect to the silicon ingot I is changed while being kept constant.

  As described above, in the present embodiment, each texture forming electrode 31 forms a texture structure while following each slice electrode 21. That is, the trajectory of the relative position change of the slice electrode 21 with respect to the silicon ingot holding part 3 in the slicing process and the trajectory of the relative position change of the texture forming electrode 31 with respect to the silicon ingot holding part 3 in the texture structure forming process. , Not only parallel to each other, but also coincide with each other.

  Since the slice electrode 21 cuts the silicon ingot I while keeping the gap between the slice cross section at a constant distance d, the distance d is also kept constant between the texture forming electrode 31 and the slice cross section. In this respect, since the formation of the texture structure is also an anodic oxidation reaction, if the distance between the texture forming electrode 31 and the slice cross section is always constant, the anodic oxidation reaction can be performed uniformly over the entire slice cross section. It is possible to form a minute uneven texture structure having a uniform size without unevenness on the entire cross-section.

  By the way, it is known that the size of the unevenness formed in the slice cross section is proportional to the magnitude of the current flowing through the texture forming electrode 31. Although it is influenced by the concentration of the electrolyte E and the moving speed of the textured electrode 31, if the current flowing through the textured electrode 31 is controlled from 10 mA to 50 mA per unit length (1 cm) of the electrode, sunlight is The size can be made small enough to function sufficiently for scattering and multiple reflection. In this embodiment, the textured electrode support 32 and the slice electrode support 22 are integrally supported by the elevating member 12. For this reason, the current flowing through the texture forming electrode 31 may be controlled in consideration of the cutting speed of the silicon ingot I by the slice electrode 21. It is said that the diameter of the textured recess is preferably 2 microns or less, but of course, it may be adjusted according to the target specification of the completed solar cell.

  As a method of adjusting the current, for example, it is conceivable to change the cross-sectional area of the texture forming electrode 31 or use a material having a resistivity different from that of the slice electrode 21 as the material of the texture forming electrode 31.

  In this embodiment, a mode in which the same power supply device 40 is connected is used. However, the present invention is not limited to this, and the power supply devices connected to the texture forming electrode 31 and the slice electrode 21 are different power sources. It is also possible to adjust the current flowing through the texture forming electrode 31 as a device.

  In this embodiment, the width of each texture-forming electrode 31 is the same as that of each slice electrode 21, but the width of the texture-forming electrode 31 is smaller than that of the slice electrode 21 in order to suppress the anodic oxidation reaction. You may make it small equally on either side.

  In the present embodiment, as shown in FIG. 2B, the slice electrodes 21 and the texture forming electrodes 31 are arranged in pairs in the vertical direction, but a plurality of texture forming electrodes 31 are arranged in the vertical direction. Also good. For example, two texture forming electrodes may be arranged in the vertical direction so as to follow the slice electrode 21. In this case, the current may be controlled so that the first (lower) texture-forming electrode forms a relatively large unevenness, and the second (upper) texture-forming electrode that follows forms a smaller unevenness. it can. This is preferable because the size of the texture structure unevenness can be controlled more accurately. Further, the unevenness of the texture structure to be formed can be achieved by making the current flowing through the textured electrode 31 into a pulse shape, adding irregularities to the shape of the textured electrode 31, or slightly moving the textured electrode 31 up and down. May be controlled.

  In the present embodiment, the processing is performed by fixing the silicon ingot I on the silicon ingot holding unit 3 and moving the slice electrode 21 and the texture forming electrode 31, but is not limited thereto. The slice electrode 21 and the texture forming electrode 31 may be fixed, and the silicon ingot holding part 3 may be moved upward in the electrolytic solution E, or the silicon electrode is held while the slice electrode 21 and the texture forming electrode 31 are moved downward. The part 3 may be moved upward in the electrolytic solution E.

  In the present embodiment, the silicon ingot holding part 3 also serves as an electrode for connecting the silicon ingot I to the anode of the power supply device 40, but is not limited thereto. In addition to the silicon ingot holding unit 3, an electrode in which the silicon ingot I is connected to the anode side of the power supply device 40 may be provided. In this case, the role of the silicon ingot holding part 3 is only to hold a part of the silicon ingot I in the electrolytic solution E.

  Moreover, in this embodiment, although the silicon ingot holding | maintenance part 3 is provided separately from the processing tank 1, it is not restricted to this. The silicon ingot I may be held by the bottom of the processing tank 1 so that the bottom of the processing tank 1 also serves as the silicon ingot holding part 3 as long as it can be stably held during processing.

  In the present embodiment, the slice electrode support 22 and the textured electrode support 32 are integrally fixed to the elevating member 12 to move the slice electrode 21 and the textured electrode 31 simultaneously. However, the present invention is not limited to this. Absent. It is also possible to individually control the slice electrode support 22 and the textured electrode support 32 by attaching them to separate lifting members. In this way, since it is not necessary to match the speed at which the silicon ingot I is cut and the speed at which the texture structure is formed on the slice cross section, the degree of freedom in design is improved. At this time, if the descent start time and the descent speed of the texture forming electrode 31 are adjusted so as to coincide with the scheduled time to complete the cutting of the silicon ingot I by the slice electrode 21, the texture structure is only formed after the cutting is completed. The processing time can be eliminated. Even in this case, if the trajectory of the slice electrode 21 and the texture forming electrode 31 is designed to be the same, a uniform texture structure can be formed over the entire slice cross section. It is desirable to share the lifting shaft 11.

  Even if the slice electrode 21 cuts the silicon ingot I to the end, the texture forming electrode 31 stops in the middle of the slice cross section. For this reason, it is desirable that the interval between the slice electrode 21 and the texture forming electrode 31 be about the length of the region where the solar cell element is not formed in the peripheral portion of the crystalline silicon substrate. By doing in this way, the remaining area | region can be made into the area | region where a solar cell element is not formed, and it is because it will not become a problem even if the texture structure is not formed.

In the embodiment described above, since the texture forming electrodes 31 are arranged corresponding to all the slice electrodes 21, texture structures are formed on both the front and back surfaces of the resulting crystalline silicon substrate. On the other hand, when it is desired to form a texture structure only on one side of the crystalline silicon substrate, every other texture forming electrode 31 may be arranged with respect to the slice electrode 21 as shown in FIGS. 5A and 5B. In this case, as shown in FIG. 6, a pair of slice section containing textured regions I _t, a pair of slice sections of the textured structure is not formed so that the alternating. 5A is a bottom view of the slice electrode 21 and the texture forming electrode 31, and FIG. 5B is a side view of the slice electrode 21 and the texture forming electrode 31.

  7A and 7B are cross-sectional views of the texture forming electrode 31 according to a modification of the present embodiment. As shown in FIGS. 7A and 7B, the texture forming electrode 31 is provided with insulating portions 36 a and 36 b that cover the side surfaces of the texture forming electrode 31 asymmetrically.

  More specifically, in FIG. 7A, a part of the texture forming electrode 31 is coated with an insulating film coat (insulating part) 36a by sputtering, vapor deposition polymerization or the like. With such a structure, even if the texture forming electrodes 31 are not arranged every other with respect to the slice electrode 21, the texture structure is formed only on one side surface of the slice cross section in the texture structure forming step. Can be formed. Furthermore, since the texture structure surfaces of the crystal silicon substrate after being cut out all face in the same direction, the effort to align the orientation of the crystal silicon substrate in the subsequent transport process of the crystal silicon substrate, the processing process of the crystal silicon substrate, etc. Can be omitted.

  If the anodic oxidation reaction on the other surface cannot be sufficiently suppressed only by the insulating film coat 36a, a larger insulating structure (insulating portion) 36b that prevents wraparound may be mounted as shown in FIG. 7B.

  As described above, according to the present embodiment, the texture structure can be formed simultaneously with the cutting of the silicon ingot I in the same processing tank 1. For this reason, compared with the case where it was processed separately until now, it is not necessary to adjust the position again in each processing, and the labor of transporting the generated crystalline silicon substrate (substrate) between apparatuses can be saved. Work efficiency can be greatly improved. Furthermore, regardless of whether the processing target is a single crystal silicon ingot or a polycrystalline silicon ingot, the cutting of the silicon ingot I and the formation of the texture structure can be performed collectively.

  Incidentally, the crystalline silicon substrate (substrate) is generally supplied to the solar cell manufacturer by the crystalline silicon substrate manufacturer in the state of the substrate. Then, the solar cell manufacturer who receives the provision of the crystalline silicon substrate forms a texture structure on the surface as necessary. Therefore, the cutting of the silicon ingot and the formation of the texture structure are originally performed by different vendors. In this regard, as a result of intensive studies by the present inventors, it has been conceived that these treatments are performed collectively in the same treatment tank 1. Therefore, the invention according to the present embodiment contributes to reducing the manufacturing cost of the entire solar cell, and its significance is very large.

  In order to form a texture structure according to the conventional technique, anodization is performed by disposing one surface of a crystalline silicon substrate opposite to a flat cathode in an electrolytic solution. However, the present inventors have found that the prior art has a problem that unevenness is likely to occur in the size of the textured unevenness in the crystal silicon substrate surface. This is because if the crystalline silicon substrate is distorted, the flat cathode and the crystalline silicon substrate cannot be made sufficiently parallel. That is, if there is a place where the distance from the cathode is different in the plane of the crystalline silicon substrate, the anodic oxidation reaction proceeds only where the distance is short. Crystalline silicon substrates used in the solar cell manufacturing process are rarely completely flat, and it becomes increasingly difficult to improve the accuracy of flatness as the size of the substrate increases. Further, even if the crystalline silicon substrate is sufficiently flat, it is a very troublesome operation to arrange the crystalline silicon substrate in parallel with high accuracy with respect to the flat cathode.

  In this respect, according to the present embodiment, the texture forming electrode 31 moves on the same or parallel trajectory of the slice electrode 21, so that the distance between the texture forming electrode 31 and the slice cross section is kept constant. A structure is formed. Therefore, the anodic oxidation reaction can be performed uniformly over the entire slice cross section, and a substrate having a texture structure with no unevenness in the size of the unevenness can be obtained.

  That is, in the present embodiment, the in-plane uniformity of the size of the unevenness of the texture structure depends on the parallelism between the slice electrode 21 and the texture forming electrode 31 included in the processing apparatus, and individual crystals as in the prior art. It does not depend on the flatness of the silicon substrate. For this reason, as long as the parallelism between the slice electrode 21 and the texture forming electrode 31 can be made with high accuracy, it is possible to mass-produce crystal silicon substrates having a texture structure with high in-plane uniformity with high reproducibility.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS. The second embodiment is the same in that a phenomenon called anodization is used, but the second embodiment is different from the first embodiment in the shapes of the slice electrode 21 and the texture forming electrode 31. In FIG. 8, 21 'is a slice electrode, 31' is a textured electrode, 51 is an insulating member, 52 is an insulating member support, 29 is a slice electrode current supply line, and 39 is a textured electrode current supply line.

  In the second embodiment shown in FIGS. 8 to 10, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

The slice electrode 21 ′ and the texture forming electrode 31 ′ are fixed with a predetermined interval in the vertical direction by the insulating member 51 for each pair. 'Although a rectangular parallelepiped, the distal end portion 21' individual slices electrode 21 is covered with an insulating member 51 with the exception of the _t. On the other hand, the texture forming electrode 31 ′ has a lower part fixed to the insulating member 51, but the side surface portion is exposed.

  The insulating member 51 used here is obtained by forming grooves in a resin material by machining, and is obtained by fixing the slice electrode 21 ′ and the texture forming electrode 31 ′ to the insulating member 51 with an adhesive. The slice electrode 21 ′ and the texture forming electrode 31 ′ are arranged with high accuracy in the cutting direction of the silicon ingot I. By doing so, in the processing step, the trajectory of the relative position change of the texture forming electrode 31 ′ with respect to the silicon ingot holding portion 3 is the trajectory of the relative position change of the slice electrode 21 ′ with respect to the silicon ingot holding portion 3. Can be matched.

  The insulating member support (electrode holding member) 52 shown in FIG. 8 has a frame shape, and aligns and holds a plurality of insulating members 51 at predetermined intervals. By such insulating member support 52 and insulating member 51, each slice electrode 21 'and each texture forming electrode 31' can be held together in a state of being electrically insulated from each other. Similar to the first embodiment, the interval between the slice electrode 21 ′ and the texture forming electrode 31 ′ may be set to be equal to or shorter than the length of the region where the solar cell element is not formed in the peripheral portion of the crystalline silicon substrate.

  A slice electrode current supply line 29 and a textured electrode current supply line 39 connected to the cathode (−) of the power supply device 40 are disposed on the insulating member support 52. The slice electrode current supply line 29 and the texture forming electrode current supply line 39 are supplied with current from the slice electrode 21 'and the texture forming electrode 31', respectively. The insulating member support 52 is held by the elevating member 12. The elevating member 12 moves up and down along the vertical axis 11 as in the first embodiment.

  Next, processing steps according to the second embodiment will be described. In FIG. 9, the insulating member support 52 is omitted for easy understanding of the reaction in the treatment process.

  First, the silicon ingot I is immersed in the electrolytic solution E in the electrolytic solution E stored in the treatment tank 1 (immersion step) (see FIG. 9).

  Next, the elevating member 12 moves the slice electrode support 22 and the textured electrode support 32 downward.

Next, when the slice electrode 21 approaches the silicon ingot I to some extent, a current flows to the cathode side through the silicon ingot I and the electrolytic solution E, and a hole current flows toward the upper surface of the silicon ingot I. When the hole current reaches the contact surface _If between the electrolytic solution E and the silicon ingot I, an anodic oxidation reaction in which silicon atoms on the contact surface _If elute into the electrolytic solution E occurs, and the downward direction (predetermined The silicon ingot I is cut in the direction). At this time, silicon atoms (silicon) are locally eluted from the silicon ingot I, and as a result, the silicon ingot I is cut downward (predetermined direction) while forming slice sections facing each other ( Slicing process).

Here, _t 'tip 21 of the' slice electrode 21 is opposed to the contact surface I _f of the electrolyte E in the bottom of the slice lines and the silicon ingot I. 'Although a rectangular parallelepiped, the distal end portion 21' individual slices electrode 21 because except _t are coating with an insulating member 51, the anodic oxidation reaction is performed only in the vicinity of the contact surface I _f. For this reason, not only can the current supplied to the slice electrode 21 ′ be efficiently used, but also the kerf loss can be reduced by suppressing unnecessary anodizing reaction at the side surface portion. Similar to the first embodiment, a crystal silicon substrate having a uniform thickness can be obtained by adjusting the distance of the gap formed between the slice electrode 21 ′ and the slice cross section to be constant.

As described above, when silicon atoms (silicon) are eluted from the silicon ingot I and slice sections facing each other are formed, silicon atoms (silicon) are eluted from the slice sections, so that at least a part of the slice sections is minute. Unevenness is formed (formation process of texture structure). More specifically, the texture forming electrode 31 ′ is passed between the slice sections facing each other so as to follow the slice electrode 21 ′, and at this time, silicon atoms can be eluted from the slice section. As a result, an textured region I _t consisting of fine irregularities slice section is formed.

  Here, the texture forming electrode 31 'moves vertically downward along the same trajectory as the slice electrode 21'. Accordingly, if the distance between the slice electrode 21 ′ and the slice cross section is constant, the distance between the texture forming electrode 31 ′ and the slice cross section in the texture forming step is always constant, and the anodic oxidation reaction is performed over the entire slice cross section. As a result, it is possible to form a minute uneven texture structure having a uniform size without unevenness on the entire slice cross section.

  In the present embodiment, the widths of the individual texture forming electrodes 31 ′ and the individual slice electrodes 21 ′ are the same. However, as described in the first embodiment, since the current flowing through the texture forming electrode 31 ′ may be smaller than the current flowing through the slice electrode 21 ′, in order to suppress the anodic oxidation reaction by the texture forming electrode 31 ′. The lateral width of the texture forming electrode 31 ′ may be made to be equal to the left and right of the slice electrode 21 ′.

  In the present embodiment, the slice electrodes 21 ′ and the texture forming electrodes 31 ′ are arranged in pairs in the vertical direction, but a plurality of texture forming electrodes 31 ′ may be arranged in the vertical direction. For example, two texture forming electrodes are arranged in the vertical direction so as to follow the slice electrode 21 ′ and fixed by an insulating member. The current is controlled so that the first (lower side) textured electrode forms a relatively large irregularity, and the second (upper side) textured electrode that follows further forms a smaller irregularity. In this way, the size of the texture structure unevenness can be controlled more accurately. Alternatively, the size of the texture structure to be formed may be controlled by making the current flowing through the texture forming electrode 31 ′ into a pulse shape or adding irregularities to the shape of the texture forming electrode 31 ′.

  In the present embodiment, the processing is performed by fixing the silicon ingot I on the silicon ingot holding portion 3 and moving the slice electrode 21 ′ and the texture forming electrode 31 ′, but the present invention is not limited to this. The slice electrode 21 ′ and the texture forming electrode 31 ′ may be fixed, and the silicon ingot holding part 3 may be moved upward in the electrolyte E, or the slice electrode 21 ′ and the texture forming electrode 31 ′ may be moved downward. The silicon ingot holding part 3 may be moved upward in the electrolytic solution E.

  In the present embodiment, the silicon ingot holding part 3 also serves as an electrode for connecting the silicon ingot I to the anode of the power supply device 40, but is not limited thereto. In addition to the silicon ingot holding unit 3, an electrode in which the silicon ingot I is connected to the anode side of the power supply device 40 may be provided. In this case, the role of the silicon ingot holding part 3 is only to hold a part of the silicon ingot I in the electrolytic solution E.

  Further, in this embodiment, the silicon ingot holding unit 3 is provided separately from the processing tank 1, but the present invention is not limited to this, and the bottom of the processing tank 1 can be used as long as it can be stably held during processing. The silicon ingot I may be held by the bottom of the processing tank 1 also serving as the silicon ingot holding unit 3.

  In the present embodiment, since the texture forming electrode 31 ′ is arranged corresponding to each slice electrode 21 ′, a texture structure is formed in all slice cross sections. On the other hand, when a texture structure is required only on one side of the crystalline silicon substrate, the crystalline silicon in which the texture structure is formed only on one side by arranging every other texture forming electrode 31 ′. A substrate can be obtained. Furthermore, as shown in FIG. 10, if one surface of the texture forming electrode 31 ′ is covered with an insulating film 56, only one surface is formed, as in the embodiment shown in FIGS. 7A and 7B of the first embodiment. The crystalline silicon substrate on which the texture structure is formed can be obtained in a state where they all face the same direction.

  As described above, in the second embodiment, the slice electrode 21 ′ and the textured electrode 31 ′ are integrally held by the insulating member support (electrode holding member) 52 while being electrically insulated from each other. In addition to the effect obtained in the first embodiment, the effect that the device configuration can be simplified can be obtained.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS. 11A to 12B. The third embodiment is the same as the first embodiment and the second embodiment in that the phenomenon of anodic oxidation is used, but the relative position change between the silicon ingot I and the processing electrode 61 is performed in a reciprocating manner. More specifically, the slicing process is performed in the forward path, and the texture structure forming process is performed in the backward path. This embodiment is different from the first embodiment and the second embodiment in that the slice electrode 21 and the texture forming electrode 31 are not separately provided.

  Note that the moving mechanism 10 of the present embodiment has a relative positional change trajectory of the machining electrode 61 relative to the silicon ingot holding part 3 in the forward path and a relative positional change of the machining electrode 61 relative to the silicon ingot holding part 3 in the return path. The machining electrode 61 is moved so that the tracks are parallel to each other and coincide with each other.

  In the present embodiment, the current per unit time flowing between the machining electrode 61 and the silicon ingot I in the return path is smaller than the current per unit time flowing between the machining electrode 61 and the silicon ingot I in the forward path. Thus, a control device 45 that controls the power supply device 41 is provided.

  In the third embodiment shown in FIGS. 11A to 12B, the same parts as those in the first embodiment and the second embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. 11A is a bottom view of the processing electrode 61, the processing electrode support 62, and the elevating member 12 as viewed from below, and FIG. 11B is a side view.

  As shown in FIG. 11A, the processing electrode support 62 has a frame shape when viewed from the bottom surface side, and supports both ends of the plurality of processing electrodes 61 at predetermined intervals. Since the processing electrode support 62 is also formed of a conductor like the processing electrode 61, both the processing electrode support 62 and the processing electrode 61 can be energized integrally. As the conductor, platinum, tungsten, or the like can be used as described above. The power supply device 41 to which the machining electrode support 62 is connected has a variable resistance, and can raise and lower the voltage. The processing electrode support 62 is held by the elevating member 12 from the left side of FIGS. 11A and 11B.

  Next, processing steps according to the third embodiment will be described with reference to FIGS. 12A and 12B. In FIG. 12A and FIG. 12B, the processing electrode support 62 is omitted for easy understanding of the reaction in the processing step. The elevating member 12 is movable up and down along the vertical axis 11 as in the first embodiment and the second embodiment.

  First, the silicon ingot I is immersed in the electrolytic solution E in the electrolytic solution E stored in the processing tank 1 (immersion step) (see FIG. 12A).

  Next, the processing electrode 61 is moved vertically downward by the elevating member 12 with respect to the silicon ingot I holding body 3 connected to the anode (+) of the power supply device 41 (see the arrow in FIG. 12A). . At this time, since the processing electrode 61 performs the same role as the slice electrode 21 of the first embodiment and the second embodiment, the silicon ingot I is cut. By adjusting the moving speed of the machining electrode 61 and the power supply device 41, the optimum slicing speed and kerf loss can be achieved. At this time, similarly to the first embodiment and the second embodiment, if the distance of the gap formed between the processing electrode 61 and the slice cross section is adjusted to be constant, the crystalline silicon substrate having a uniform thickness Can be obtained.

  When the processing electrode 61 reaches the lower end of the silicon ingot I and the slicing process is completed, the process proceeds to a texture structure forming process. In other words, the elevating member 12 moves the processing electrode 61 in the opposite direction to the slicing step, that is, vertically upward (see the arrow in FIG. 12B), thereby forming a texture structure in the slice cross section. At this time, the power supply device 41 is adjusted by the control device 45 so that a current small enough to form a minute unevenness in the slice cross section flows.

  In this manner, the slicing step and the texture structure forming step can be performed by reciprocating the processing electrode 61 up and down. Since the elevating member 12 reciprocates along the vertical axis 11, the trajectory of the relative position change of the machining electrode 61 with respect to the silicon ingot holding part 3 in the slicing process and the silicon ingot holding part of the machining electrode 61 in the texture structure forming process. 3 are not only parallel to each other but also coincide with each other. Therefore, if the distance of the gap formed between the processing electrode 61 and the slice cross section is constant, the distance between the processing electrode 61 and the slice cross section in the texture forming process is always constant. For this reason, even in this embodiment, the anodic oxidation reaction can be performed uniformly over the entire slice cross section, and as a result, a minute uneven texture structure having a uniform size can be formed on the entire slice cross section. Can do.

  In the present embodiment, the control device 45 controls the power supply device 41 to change the magnitude of the current flowing through the processing electrode 61 in the slicing process and the texture structure forming process. However, the present invention is not limited to this. The control device 45 may change the moving speed of the machining electrode 61, or the current flowing through the machining electrode 61 can be adjusted by adding a resistor in the circuit.

  In the present embodiment, the silicon ingot I is fixed on the silicon ingot holding unit 3 and the processing electrode is moved, but the present invention is not limited to this. The processing electrode 61 may be fixed and the silicon ingot holding part 3 may be moved upward in the electrolytic solution E.

  In the present embodiment, the silicon ingot holding unit 3 also serves as an electrode for connecting the silicon ingot I to the anode of the power supply device 41, but is not limited thereto. In addition to the silicon ingot holding unit 3, an electrode in which the silicon ingot I is connected to the anode side of the power supply device 41 may be provided. In this case, the role of the silicon ingot holding part 3 is only to hold a part of the silicon ingot I in the electrolytic solution E.

  Further, in this embodiment, the silicon ingot holding unit 3 is provided separately from the processing tank 1, but the present invention is not limited to this, and the bottom of the processing tank 1 can be used as long as it can be stably held during processing. The silicon ingot I may be held by the bottom of the processing tank 1 also serving as the silicon ingot holding unit 3.

  By the way, in each embodiment mentioned above, although demonstrated using the rectangular parallelepiped silicon ingot I, it is not restricted to this. The silicon ingot processing apparatus according to the present invention can also be used for processing a single crystal silicon ingot having a cylindrical shape.

  Moreover, in each embodiment mentioned above, the trajectory of the relative position change with respect to the silicon ingot holding part 3 of the processing electrode in the slicing process, and the relative position change of the processing electrode with respect to the silicon ingot holding part 3 in the formation process of the texture structure Are described using a mode in which the orbits are parallel to each other and coincide with each other. However, the present invention is not limited to this. For example, the trajectory of the relative position change of the machining electrode with respect to the silicon ingot holding portion 3 in the slicing process and the trajectory of the relative position change of the machining electrode with respect to the silicon ingot holding portion 3 in the texture structure forming process are parallel to each other. It may be an aspect that does not coincide with each other. Such an aspect is useful when a texture structure is formed only on one side of slice sections facing each other.

  Moreover, although each embodiment mentioned above demonstrated using the aspect processed with the silicon ingot I being fixed to the horizontal direction in the processing tank 1, it is not restricted to this. For example, if the silicon ingot I can be moved in the horizontal direction by a belt conveyor or the like in the processing tank 1, the slicing step and the texture structure forming step can be performed at different locations in the same processing layer 1. it can. Of course, in the slicing step and the texture structure forming step, if the trajectory of the relative position change of each processing electrode with respect to the silicon ingot holding part 3 is parallel, the texture structure having a uniform uneven size in the slice cross section is obtained. Can be formed.

  In the above description, the method of controlling the anodic oxidation reaction by covering a part of the slice electrode 21 and the texture forming electrode 31 with an insulating film has been shown. However, the region of the electrode covered with the insulating film is appropriately changed according to the electrode shape and the target numerical value of the processing step, and therefore should not be broadly interpreted without being limited to the drawings exemplified in the embodiments. It is.

1 treatment tank 3 ingot holder 10 moving mechanism 21, 21 'slice electrodes 21' _t tip 22 slices electrode support 26 insulators 31, 31 'texturing electrode 32 texturing electrode support 36a, 36b the insulating portion 40 power supply 41 Power supply device 45 Control device 51 Insulating member 52 Insulating member support (electrode holding member)
61 machining electrode E electrolyte I ingot _{I f} contact surface _{I t} textured regions

Claims (18)

An ingot processing apparatus for processing an ingot by anodization,
A treatment tank for storing an electrolyte solution;
An ingot holding part for holding at least a part of the ingot so as to be immersed in the electrolytic solution;
Slicing electrodes that cut the ingot in a predetermined direction while forming slice sections facing each other by locally eluting silicon from the ingot;
A textured electrode that elutes silicon from the slice cross section to form minute irregularities in at least a part of the slice cross section;
A power supply device that causes a current to flow between the slice electrode and the textured electrode and the ingot by setting the ingot to a high potential with respect to the slice electrode and the textured electrode;
A moving mechanism for moving the ingot holding part or the slice electrode and the texture forming electrode so that the relative position of the slice electrode and the texture forming electrode with respect to the ingot holding part changes in the processing tank. When,
An ingot processing apparatus comprising:   The trajectory of relative position change of the slice electrode with respect to the ingot holding portion and the trajectory of relative position change of the texture forming electrode with respect to the ingot holding portion are parallel to each other. 2. The ingot processing device according to 1.   The trajectory of the relative position change of the slice electrode with respect to the ingot holding portion and the trajectory of the relative position change of the textured electrode with respect to the ingot holding portion coincide with each other. The ingot processing device according to claim 1.   4. The ingot processing device according to claim 1, wherein the moving mechanism moves the distance between the slice electrode and the texture forming electrode while keeping the distance constant. 5.   The ingot processing apparatus according to claim 4, further comprising an electrode holding member that holds the slice electrode and the textured electrode integrally while being electrically insulated from each other.   6. The ingot processing apparatus according to claim 1, wherein the texture forming electrode is provided with an insulating portion that asymmetrically overlaps a side surface of the texture forming electrode. 7. An ingot processing apparatus for processing an ingot by anodization,
A treatment tank for storing an electrolyte solution;
An ingot holding part for holding at least a part of the ingot so as to be immersed in the electrolyte; and
A processing electrode for eluting silicon from the ingot;
A power supply device for causing a current to flow between the machining electrode and the ingot by setting the ingot to a high potential with respect to the machining electrode;
A moving mechanism for moving at least one of the ingot holding part and the processing electrode so that a relative position of the processing electrode with respect to the ingot holding part reciprocally changes in the processing tank;
A control device that controls at least one of the power supply device and the moving mechanism;
The control device is configured such that the current per unit time flowing between the machining electrode and the ingot on the return path is smaller than the current per unit time flowing between the machining electrode and the ingot on the forward path. An ingot processing device that controls at least one of the power supply device and the moving mechanism.   The trajectory of the relative position change of the machining electrode with respect to the ingot holding portion in the forward path and the trajectory of the relative position change of the machining electrode with respect to the ingot holding portion in the backward path are parallel to each other. The ingot processing device according to claim 7.   The trajectory of the relative position change of the machining electrode with respect to the ingot holding portion in the forward path and the trajectory of the relative position change of the machining electrode with respect to the ingot holding portion in the backward path are characterized by matching each other. The ingot processing device according to claim 8. An ingot processing method for processing an ingot by anodization,
An immersion step of immersing at least a part of the ingot in an electrolytic solution;
Slicing step of cutting the ingot in a predetermined direction while forming slice sections facing each other by locally eluting silicon from the ingot;
By eluting silicon from the slice cross section to form a textured structure that forms minute irregularities in at least a part of the slice cross section, and
In the same processing tank, the slicing step and the texture structure forming step change the relative position between the ingot and the processing electrode, while making the ingot have a higher potential than the processing electrode. A method for processing an ingot, which is performed by passing an electric current between the ingot and the processing electrode.   The trajectory of the relative position change of the machining electrode with respect to the ingot holding portion in the slicing step and the trajectory of the relative position change of the machining electrode with respect to the ingot holding portion in the texture structure forming step are parallel to each other. The ingot processing method according to claim 10, wherein:   The current per unit time flowing in the processing electrode in the slicing step is larger than the current per unit time flowing in the processing electrode in the texture structure forming step. Ingot processing method.   The trajectory of the relative position change of the machining electrode with respect to the ingot holding portion in the slicing step and the trajectory of the relative position change of the machining electrode with respect to the ingot holding portion in the forming step of the texture structure are mutually coincident. The ingot processing method according to claim 10, wherein the ingot is processed. The processing electrode has a slice electrode and a textured electrode formed separately from the slice electrode,
The slicing step is performed using the slice electrode,
The ingot processing method according to any one of claims 10 to 13, wherein the texture structure forming step is performed using the texture forming electrode.   In the slicing step and the texture structure forming step, the slice electrode and the texture forming electrode are moved while a distance between the slice electrode and the texture forming electrode is kept constant. The ingot processing method according to claim 14.   The ingot processing method according to claim 15, wherein the slice electrode and the texture forming electrode are electrically insulated and held together by an electrode holding member. The textured electrode is provided with an insulating portion that asymmetrically overlaps the side surface of the textured electrode,
The ingot processing method according to any one of claims 14 to 16, wherein in the texture structure forming step, a texture structure is formed only on one surface of the slice cross sections facing each other. The relative position change of the machining electrode with respect to the ingot holding part is performed reciprocally,
The slicing process is performed in the outward path,
14. The ingot processing method according to claim 10, wherein the texture structure forming step is performed in a return path.

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