JP2013143491A - Apparatus and method for substrate surface treatment and manufacturing method of solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate surface treatment apparatus which improves the stability and the uniformity of the treatment on a surface of each substrate and stably achieves a treatment process in the substrate surface treatment apparatus performing the treatment on the substrates in a horizontal transfer method.SOLUTION: A substrate surface treatment apparatus 10A includes: a treatment tank 11 where a treatment liquid for performing treatment on a surface of a substrate 70 is accumulated; transfer rollers 13, each of which has a rotation shaft located at an upper part of the treatment tank 11 and arranged in a direction perpendicular to a transfer direction of the substrate 70 and rotates while contacting with a lower surface of the substrate 70 to transfer the substrate 70; and a treatment liquid temperature control part adjusting the treatment liquid in the treatment tank 11 to a predetermined temperature. The substrate surface treatment apparatus 10A includes a transfer roller temperature control part 51 which adjusts temperatures of the transfer rollers 13 so that the temperatures of the transfer rollers 13 becomes equivalent to a temperature of the treatment liquid.

Description

  The present invention relates to a substrate surface treatment apparatus and method, and a solar cell manufacturing method.

  In the manufacturing process of a semiconductor device, many chemical surface treatments are performed on a substrate to constitute a device. Chemical surface treatments for substrates include dry processes using reactive gases and wet processes using chemical chemicals, but they are wet in that the cost of the equipment used can be kept low. Many processes are used. In addition, this wet process includes single-wafer processing in which only one surface of a flat substrate is brought into contact with a processing solution. For example, cleaning, removal of a surface-modified layer, and thinning of a glass substrate, silicon wafer, etc. It is often used for surface shape processing and plating treatment. Therefore, conventionally, various single wafer processing type substrate surface processing apparatuses have been proposed (see, for example, Patent Documents 1 and 2).

  Patent Document 1 includes a plurality of transport rollers that are partly immersed in a processing liquid accommodated in a processing liquid tank and that are rotatably provided on the upper part of the processing liquid tank. A substrate surface processing apparatus having a structure in which the length of the substrate is equal to or greater than the substrate width and a groove is provided at least on the surface of the substrate in contact with the substrate. With such a structure, the processing liquid is brought into contact with the lower surface of the substrate while the substrate is transported by the transport roller, and the gas generated at that time is easily removed through the groove of the transport roller.

  Further, Patent Document 2 discloses that an electrolytic current is applied to the processing side surface of the product by applying an external current while keeping the upper contact surface in a dry state and immersing the processing side surface in the processing liquid. An in-line type electrical contact device for performing processing and / or wet chemical processing is disclosed. Here, the transport device having the upper and lower transport and / or contact means is configured to lower the liquid level by providing a downcomer in the region of the upper contact. Thereby, even when the product does not exist in the region of the contact, the upper contact is prevented from coming into contact with the processing liquid and getting wet.

JP 2006-196781 A Special table 2010-539324 gazette

  However, the substrate surface processing apparatus disclosed in Patent Document 1 has a problem in that the transport roller is heated and the surface temperature of the transport roller becomes high due to the reaction between the substrate to be etched and the etching solution. Further, in the in-line type electrical contact device disclosed in Patent Document 2, since the plating electrode is heated by energization, the plating is performed at the contact portion and the non-contact portion of the substrate to be plated and the plating electrode. There was a problem that a film quality difference occurred in the film.

  The present invention has been made in view of the above, and in a substrate surface processing apparatus for processing a substrate by a horizontal conveyance method, it is possible to improve the stability and uniformity of processing in the substrate surface and stably realize a processing process. An object of the present invention is to obtain a substrate surface treatment apparatus and method that can be used. Another object of the present invention is to obtain a solar cell manufacturing method using this substrate surface treatment method.

  In order to achieve the above object, a substrate surface processing apparatus according to the present invention includes a processing tank for storing a processing liquid for processing a substrate surface, and a rotating shaft in a direction perpendicular to the substrate transport direction at an upper part of the processing tank. A substrate surface treatment comprising: a transport unit configured to rotate and transport the substrate while being in contact with a lower surface of the substrate; and a processing liquid temperature adjusting unit configured to adjust the processing liquid in the processing tank to a predetermined temperature. The apparatus is characterized by further comprising a temperature adjusting means for adjusting the temperature of the transfer means so that the temperature of the transfer means becomes equal to the temperature of the treatment liquid.

  According to the present invention, it is possible to improve the stability and uniformity of the processing in the substrate surface by controlling the temperature of the transport roller in the horizontal transport type substrate surface processing apparatus, and stably reproduce the processing process. It has an effect that it can be realized with good performance.

FIG. 1 is a diagram schematically showing a schematic configuration of the substrate surface treatment apparatus according to the first embodiment. FIG. 2 is a flowchart showing an example of the procedure of the solar cell manufacturing method according to the first embodiment. FIG. 3-1 is a cross-sectional view schematically showing an example of a processing procedure of the solar cell manufacturing method according to Embodiment 1 (Part 1). 3-2 is sectional drawing which shows typically an example of the process sequence of the manufacturing method of the solar cell by Embodiment 1 (the 2). FIG. 4 is a diagram schematically showing a schematic configuration of the substrate surface treatment apparatus according to the second embodiment. FIG. 5 is a flowchart showing an example of the procedure of the solar cell manufacturing method according to the second embodiment. FIG. 6-1 is a cross-sectional view schematically showing an example of a processing procedure of the solar cell manufacturing method according to the second embodiment (No. 1). 6-2 is sectional drawing which shows typically an example of the process sequence of the manufacturing method of the solar cell by Embodiment 2 (the 2).

  Exemplary embodiments of a substrate surface treatment apparatus and method and a method for manufacturing a solar cell according to embodiments of the present invention will be explained below in detail with reference to the accompanying drawings. Note that the present invention is not limited to these embodiments. In addition, the cross-sectional view showing the manufacturing process of the solar cell used in the following embodiments is a schematic one, and the relationship between the layer thickness and the width, the ratio of the thickness of each layer, etc. is different from the actual one There is.

Embodiment 1 FIG.
FIG. 1 is a diagram schematically showing a schematic configuration of the substrate surface treatment apparatus according to the first embodiment. Here, an example of an etching apparatus that performs etching of one main surface of the substrate will be described as the substrate surface processing apparatus 10A.

  The substrate surface processing apparatus 10A is disposed in parallel with a predetermined interval at a top of the processing tank 11 for storing the etching liquid 12A and the upper part of the processing tank 11, and the lower surface of the substrate 70 to be etched is brought into contact with the etching liquid 12A. And a transport roller 13 for transport.

  A replenishment tank 31 for replenishing the processing tank 11 with the etching solution 12 </ b> A is connected to the processing tank 11 through a pipe 21 and a circulation pump 22. The processing tank 11 is provided inside an outer tank 41 that collects the etching solution 12A overflowing from the processing tank 11. A discharge port 42 is provided in the lower part of the outer tub 41, and is connected to the supply tank 31 via a pipe 43. The lower surface of the outer tank 41 has an inclination toward the discharge port 42, for example, and the etching solution 12A overflowing from the processing tank 11 is supplied to the replenishing tank 31 by natural fall.

  Temperature control pipes 14 and 32 are provided in the processing tank 11 and the replenishment tank 31, respectively. The etching liquid 12A is supplied to the temperature control pipes 14 and 32 at a predetermined temperature by a processing liquid temperature control unit (not shown). The temperature adjusting liquid whose temperature is adjusted to flow is flowed. The temperature adjustment pipes 14 and 32 have a loop structure via the treatment liquid temperature control unit, and the temperature adjustment liquid whose temperature is adjusted by the treatment liquid temperature control unit is circulated. The temperature adjusting liquid is appropriately selected according to the heating or cooling of the etching solution, and for example, water can be used.

  The transport roller 13 has a rotation shaft in a direction perpendicular to the transport direction of the substrate 70 and is rotated in a predetermined direction by a driving mechanism (not shown). Here, the length of the transport roller 13 in the rotation axis direction is equal to or greater than the width in the direction orthogonal to the transport direction of the substrate 70. Further, the transport roller 13 is provided with a transport roller temperature adjusting mechanism that maintains the surface temperature of the transport roller 13 at a predetermined temperature. Here, the conveyance roller temperature control mechanism stores the temperature adjustment liquid 52 that adjusts the temperature of the conveyance roller 13 at a predetermined temperature and can deliver the temperature adjustment liquid 52, and the conveyance roller temperature control unit 51. And a pipe 53 that connects the conveyance roller 13. The pipe 53 is connected to the transport roller 13 located at both ends in the transport direction. Further, a pipe (not shown) is connected between the transport rollers 13 so that the temperature adjusting liquid 52 flows in order in the transport rollers 13. The inside of the transport roller 13 has a double structure so that the temperature adjusting liquid 52 can flow, and a flow path through which the temperature adjusting liquid 52 flows is formed. This flow path is connected to a pipe 53 and a pipe (not shown). Further, a temperature measuring unit (not shown) such as a thermocouple is provided in the vicinity of the surface of the transport roller 13, and the result is output to the transport roller temperature control unit 51.

  The operation of the substrate surface processing apparatus 10A having such a structure will be described. The temperature adjusting liquid whose temperature is controlled by the processing liquid temperature control unit is flowed to the temperature adjusting pipe 32, and the etching liquid 12A stored in the replenishing tank 31 is controlled to have a predetermined temperature. When the temperature reaches a predetermined temperature, the etching solution 12A is sent from the replenishing tank 31 to the processing tank 11 by the circulation pump 22. Also in the processing tank 11, the temperature adjusting liquid whose temperature is controlled by the processing liquid temperature control unit is caused to flow through the temperature adjusting pipe 14, and the etching liquid 12 </ b> A in the processing tank 11 is controlled to have a predetermined temperature.

  Thereafter, the substrate 70 is horizontally placed on the plurality of transport rollers 13 arranged on the transport roller 13 with the surface to be etched facing downward. When the transport roller 13 is rotated, the substrate 70 moves on the transport roller 13. At this time, in the region between the transport rollers 13, the lower surface of the substrate 70 comes into contact with the etching solution 12A, and etching is performed. Here, the rotational speed of the transport roller 13 is determined so that the lower surface of the substrate 70 is etched by a desired amount before the substrate 70 transported by the transport roller 13 crosses the distance in the transport direction of the processing tank 11. Is done.

  Even during the etching, the temperature of the etching solution 12A in the processing tank 11 is controlled to be a predetermined temperature. Further, the etching solution 12A is supplied from the replenishing tank 31 to the processing tank 11, but the amount exceeding the capacity of the processing tank 11 overflows from the upper part of the processing tank 11 and flows into the outer tank 41. The etching solution 12 </ b> A that has flowed into the outer tank 41 returns from the discharge port 42 to the replenishment tank 31 through the pipe 43. Then, the temperature is adjusted again in the replenishing tank 31 and the process of being supplied to the processing tank 11 by the circulation pump 22 is repeated.

  By the way, during etching, the surface temperature of the transport roller 13 gradually increases due to the etching reaction heat between the substrate 70 and the etching solution 12A, which becomes an unstable factor of the etching rate. Therefore, the temperature of the conveying roller 13 measured by the temperature measuring unit is fed back, and the conveying roller temperature control unit 51 controls the temperature of the temperature adjusting liquid 52 so that the temperature of the conveying roller 13 becomes a predetermined temperature, and piping. It is sent out to the conveyance roller 13 through 53. The sent temperature adjusting liquid 52 passes through the inside of each conveying roller 13 and returns to the conveying roller temperature control unit 51 again via the pipe 53. In this way, the temperature of the surface of the transport roller 13 is made to substantially match the temperature of the etching solution 12A.

  In FIG. 1, an inline type substrate surface treatment apparatus has a structure in which the temperature of the conveyance roller 13 is collectively controlled by one conveyance roller temperature control unit 51. In such an apparatus, when the substrate 70 is continuously inserted at a predetermined interval, the temperature rise of the transport roller 13 is constant between the transport rollers 13, and thus the temperature controllability of the transport roller 13 is related. There is no problem.

  In the example of FIG. 1, the transport roller 13 is collectively controlled by one transport roller temperature control unit 51, but the transport roller temperature for each transport roller 13 or for each block in units of a plurality of transport rollers. The control unit 51 may be installed. The individual control as described above can perform the temperature control of the transport roller 13 with higher accuracy. However, in this case, it is necessary to install a plurality of transport roller temperature control units 51.

  Next, a method for manufacturing a solar cell using such an etching apparatus will be described. FIG. 2 is a flowchart showing an example of the procedure of the solar cell manufacturing method according to Embodiment 1, and FIGS. 3-1 to 3-2 are examples of the processing procedure of the solar cell manufacturing method according to Embodiment 1. It is sectional drawing which shows this typically.

  First, as shown in FIG. 3A, a P-type single crystal silicon substrate 112 doped with boron (B) having a specific resistance of about 2 Ω · cm as a single crystal semiconductor substrate is prepared. Next, the single crystal silicon substrate 112 is dipped in an alkaline solution heated to 70 ° C., for example, in an aqueous solution of about 10% sodium hydroxide for 10 minutes, and the substrate surface is etched and washed (step S11). As a result, the substrate surface cleaning is performed at the same time as removing the damaged region generated near the substrate surface during substrate slicing.

  Next, anisotropic etching is performed at about 80 ° C. for 5 minutes in a mixed solution of an alkaline solution, for example, the same 10% aqueous sodium hydroxide solution as above, and an alcohol solution, for example, a solution to which about 1% of isopropyl alcohol is added. The texture structure is formed on the surface of the single crystal silicon substrate 112 (step S12). In the drawing, the illustration of the texture structure is omitted.

Thereafter, as shown in FIG. 3B, the single crystal silicon substrate 112 is put into a thermal oxidation furnace and heated in an atmosphere of phosphorus (P) as an N-type impurity, and the single crystal silicon substrate 112 is heated. An N + layer 113 is formed by diffusing phosphorus on the surface and inverting the conductivity type. Here, a semiconductor PN junction region is formed on the surface of the single crystal silicon substrate 112 by heating at about 900 ° C. for about 20 minutes in a phosphorus oxychloride (POCl ₃ ) gas atmosphere (step S 13). Next, the phosphor glass film formed on the surface of the single crystal silicon substrate 112 is removed by immersing it in a 5% hydrofluoric acid aqueous solution for about 5 minutes.

  After that, as shown in FIG. 3C, an antireflection film 114 is formed on one main surface (hereinafter referred to as a surface) of the single crystal silicon substrate 112 (step S14). As the antireflection film 114, a silicon nitride film formed by a plasma CVD (Chemical Vapor Deposition) method using silane, ammonia, and nitrogen gas as source gases can be used. The film thickness and refractive index of the silicon nitride film can be set to values that suppress light reflection. For example, the refractive index can be about 2.0 and the film thickness can be about 80 nm.

  Next, as shown in FIG. 3D, the N + layer 113 on the other main surface (hereinafter referred to as the back surface) of the single crystal silicon substrate 112 is removed by etching (step S15). At this time, for example, the substrate surface treatment apparatus 10A shown in FIG. 1 can be used. For example, a solution obtained by mixing a 50% aqueous solution of hydrofluoric acid and a 60% aqueous solution of nitric acid at a ratio of 1: 1 can be used as the etching solution 12A when manufacturing a solar cell including the single crystal silicon substrate 112. When the single crystal silicon substrate 112 is etched using this etching solution 12A, by setting the temperature to about 15 ° C., the stability of the etching rate is increased and control is facilitated. Therefore, the processing liquid temperature control unit (not shown) is used for adjusting the temperature adjusting liquid adjusted to a predetermined temperature so that the temperature of the etching liquid 12A in the processing tank 11 and the replenishing tank 31 is about 15 ° C. Circulate through the pipes 14 and 32.

  Further, since the temperature of the etching solution 12A is about 15 ° C., the conveyance roller temperature control unit 51 is adjusted to a predetermined temperature so that the temperature of the conveyance roller 13 is also about the same as the temperature of the etching solution 12A. The adjustment liquid 52 is sent out through the pipe 53 and circulated between the transport rollers 13. As the temperature adjusting liquid 52 that flows through the flow path in the transport roller 13, for example, an antifreeze liquid in which about 50% alcohol is added to pure water can be used.

  The single crystal silicon substrate 112 is placed on the transport roller 13 provided in the upper part of the processing tank 11 filled with the etching solution 12A so that the back surface is on the lower side, and is transported by the transport roller 13. As a result, the back surface of the single crystal silicon substrate 112 comes into contact with the etching solution 12A, and the N + layer 113 on the back surface is etched and removed.

  When continuously processing a 156 mm square solar cell substrate at 10 mm intervals, when the conveyance speed is 0.5 m / sec and the roller interval is 50 mm pitch, the temperature of the conveyance roller temperature control unit 51 is 7 When set to ° C., the surface temperature of the conveying roller 13 can be kept at 15 ° C. When such a conventional apparatus that does not have the temperature control function of the transport roller 13 is used, the surface temperature of the transport roller 13 is gradually increased by the etching reaction heat between the single crystal silicon substrate 112 and the etching solution 12A. This becomes an unstable factor of the etching rate. As a result, the N + layer 113 may not be removed.

  Next, as shown in FIG. 3-2 (a), a paste mixed with aluminum is printed on the back surface of the single crystal silicon substrate 112 by a screen printing method to form the back surface side electrode layer 116a (step S16). Further, as shown in FIG. 3B, a paste mixed with silver is printed on the surface of the single crystal silicon substrate 112 in a comb shape by a screen printing method to form the light receiving surface side electrode layer 115a (step S17). ).

  Then, as shown in FIG. 3-2 (c), the single crystal silicon substrate 112 is baked (step S18). The firing process is performed, for example, in an air atmosphere at 800 to 900 ° C., the light receiving surface side electrode 115 is formed on the front surface, and the back surface side electrode 116 is formed on the back surface. At this time, although not shown, the light receiving surface side electrode 115 penetrates the antireflection film 114 and contacts the N + layer 113 at the junction. As a result, the N + layer 113 can obtain a good resistive junction with the light receiving surface side electrode 115. Further, a part of aluminum diffuses into the single crystal silicon substrate 112 from the paste mixed with aluminum formed on the back surface, and a P + layer 117 having a BSF (Back Surface Field) function is formed on the back surface side of the single crystal silicon substrate 112. It is formed. Through the above steps, the solar cell 111 is manufactured.

  As described above, in the first embodiment, the temperature of the transport roller 13 that transports the substrate 70 during etching is controlled to be equal to the temperature of the etching solution 12A. As a result, the stability of the etching rate is increased, the stability and uniformity of processing within the substrate surface can be improved, and the controllability of the etching process can be increased.

  Further, if this substrate surface treatment apparatus 10A is used, for example, for removing the N + layer 113 on the back surface of the solar battery cell, the high performance solar cell in which the N + layer 113 on the back surface side is removed more reliably and inexpensively than in the past. It has the effect that a battery cell can be obtained.

Embodiment 2. FIG.
FIG. 4 is a diagram schematically showing a schematic configuration of the substrate surface treatment apparatus according to the second embodiment. Here, a plating apparatus that performs plating on one main surface of the substrate 70 will be described as an example of the substrate surface processing apparatus 10B.

  The substrate surface processing apparatus 10B is arranged in parallel with a predetermined interval at the upper part of the processing tank 11 for storing the plating solution 12B and the processing tank 11, and makes the lower surface of the substrate 70 to be plated contact the plating solution 12B. And a transport roller 13 for transport.

  A supply tank 31 for supplying the plating solution 12 </ b> B to the processing tank 11 is connected to the processing tank 11 through a pipe 21 and a circulation pump 22. The processing tank 11 is provided inside an outer tank 41 that collects the plating solution 12B overflowing from the processing tank 11. A discharge port 42 is provided in the lower part of the outer tub 41, and is connected to the supply tank 31 via a pipe 43. The lower surface of the outer tank 41 has an inclination toward the discharge port 42, for example, and the plating solution 12B overflowing from the processing tank 11 is supplied to the replenishing tank 31 by natural fall.

  A temperature adjusting heater 15 is provided in the processing tank 11, and the temperature adjusting heater 15 controls the temperature of the plating solution 12B by controlling the current to the temperature adjusting heater 15 to control the temperature of the plating solution 12B (not shown). Parts are connected.

  In addition, a circulation line heater 23 for heating the plating solution 12 </ b> B supplied to the treatment tank 11 by the circulation pump 22 is provided in the pipe 21 connecting the replenishment tank 31 and the treatment tank 11. The circulation line heater 23 also adjusts the temperature of the plating solution 12B to a predetermined temperature. In the example of FIG. 4, both the temperature control heater 15 and the circulation line heater 23 are provided. However, the heating method of the plating solution 12B is not limited to this, and various methods are used. be able to. For example, a configuration in which only one of the temperature adjustment heater 15 and the circulation line heater 23 is provided, or the temperature adjustment heater 15 is not provided in the treatment tank 11, but the treatment tank 11 is arranged from the outer peripheral portion. A method of heating may be used.

  The transport roller 13 has a rotation shaft in a direction perpendicular to the transport direction of the substrate 70 and is rotated in a predetermined direction by a driving mechanism (not shown). Here, the length of the transport roller 13 in the rotation axis direction is equal to or greater than the width in the direction orthogonal to the transport direction of the substrate 70. A plating electrode 130 is provided on the outer periphery of the transport roller 13. The plating electrode 130 includes a core material 131 of an electrode material, and a conductive protection film 132 provided on the surface of the core material 131 to prevent the substrate 70 to be transported from coming into contact and being damaged. A metal material (conductive material) having corrosion resistance to the plating solution 12B is used as the core material 131, and a conductive soft material containing a large amount of carbon having a thickness of 1 mm, for example, is used as the conductive protective film 132. Can do. Examples of such a soft material include conductive rubber and conductive soft resin. The plating electrode 130 of each conveyance roller 13 is connected to the plating power source 61 via the plating electrode wire 62.

  Further, the transport roller 13 is provided with a transport roller temperature adjusting mechanism that maintains the surface temperature of the transport roller 13 at a predetermined temperature. Here, the conveyance roller temperature control mechanism stores the temperature adjustment liquid 52 that adjusts the temperature of the conveyance roller 13 at a predetermined temperature and can deliver the temperature adjustment liquid 52, and the conveyance roller temperature control unit 51. And a pipe 53 that connects the conveyance roller 13. The pipe 53 is connected to the transport roller 13 located at both ends in the transport direction. Further, a pipe (not shown) is connected between the transport rollers 13 so that the temperature adjusting liquid 52 flows in order in the transport rollers 13. The inside of the transport roller 13 has a double structure so that the temperature adjusting liquid 52 can flow, and a flow path through which the temperature adjusting liquid 52 flows is formed. This flow path is connected to a pipe 53 and a pipe (not shown). Further, a temperature measuring unit (not shown) such as a thermocouple is provided in the vicinity of the surface of the transport roller 13 (plating electrode 130), and the result is output to the transport roller temperature control unit 51. The temperature adjusting liquid 52 preferably has a specific resistance of 10 MΩcm or more in order to prevent leakage current from the plating electrode 130. However, when the insulation between the plating electrode 130 and the temperature adjusting liquid 52 is sufficiently ensured, the temperature adjusting liquid 52 having a specific resistance of less than 10 MΩcm may be used.

  The operation of the substrate surface processing apparatus 10B having such a structure will be described. The plating solution 12B stored in the replenishing tank 31 is sent from the replenishing tank 31 to the treatment tank 11 by the circulation pump 22. At this time, the plating solution 12B is heated to a predetermined temperature by the circulation line heater 23. Also in the processing tank 11, the temperature control heater 15 is heated by the processing liquid temperature control unit, and the plating liquid 12B in the processing tank 11 is controlled to have a predetermined temperature.

  Further, the plating solution 12B is continuously supplied from the replenishing tank 31 to the processing tank 11, but the amount exceeding the capacity of the processing tank 11 overflows from the upper part of the processing tank 11 and flows into the outer tank 41. The plating solution 12 </ b> B that has flowed into the outer tank 41 returns to the supply tank 31 from the discharge port 42 via the pipe 43. And the process of being heated and supplied to the processing tank 11 with the circulation pump 22 from the replenishment tank 31 is repeated.

  Thereafter, the substrate 70 that is conductive or conductive is placed horizontally on the plurality of transport rollers 13 with the surface to be plated facing down on the transport rollers 13. . When the transport roller 13 is rotated, the substrate 70 moves on the transport roller 13. Then, an electric current is applied from the plating power source 61 to the plating electrode 130 of each transport roller 13 through the plating electrode wire 62 to perform electrolytic plating. At this time, when the plating electrode 130 and the lower surface of the substrate 70 are in contact with each other, a current flows through the substrate 70, and a plating film is formed on the lower surface of the substrate 70. During the plating, the temperature of the plating solution 12B in the treatment tank 11 is controlled by the treatment solution temperature controller and the temperature adjustment heater 15 so that the temperature becomes a predetermined temperature. Here, the transport roller 13 is formed such that a plating film having a desired thickness is formed on the lower surface of the substrate 70 before the substrate 70 transported by the transport roller 13 crosses the distance in the transport direction of the processing tank 11. Is determined.

  By the way, during plating, since the plating electrode 130 is heated by energization, a temperature difference may occur between the contact portion and the non-contact portion of the substrate 70 with the plating electrode 130, and there may be a difference in the film quality of the plating film. . Therefore, the temperature of the conveyance roller 13 measured by the temperature measurement unit is fed back, and the conveyance roller temperature control unit 51 adjusts the temperature of the temperature adjustment liquid 52 so that the temperature of the conveyance roller 13 is substantially the same as the plating solution 12B. Controlled and sent to the conveyance roller 13 via the pipe 53. The sent temperature adjusting liquid 52 passes through the inside of each conveying roller 13 and returns to the conveying roller temperature control unit 51 again via the pipe 53. In this way, the temperature of the surface of the conveying roller 13 is made to substantially coincide with the temperature of the plating solution 12B.

  In FIG. 4, an inline type substrate surface treatment apparatus has a structure in which the temperature of the conveyance roller 13 is collectively controlled by one conveyance roller temperature control unit 51. In such an apparatus, when the substrate 70 is continuously inserted at a predetermined interval, the temperature rise of the transport roller 13 is constant between the transport rollers 13, and thus the temperature controllability of the transport roller 13 is related. There is no problem.

  In the example of FIG. 4, the transport roller 13 is collectively controlled by one transport roller temperature control unit 51, but the transport roller temperature is set for each transport roller 13 or for each block having a plurality of blocks. The control unit 51 may be installed. The individual control as described above can perform the temperature control of the transport roller 13 with higher accuracy. However, in this case, it is necessary to install a plurality of transport roller temperature control units 51.

  Further, in the example of FIG. 4, the temperature control of the plating electrode 130 is performed by circulating the temperature adjusting liquid 52 inside the transport roller 13, but the Peltier element and the temperature measuring element are included in the plating electrode 130. In addition, the plating electrode 130 may be directly temperature controlled.

  Next, a method for manufacturing a solar cell using such an etching apparatus will be described. FIG. 5 is a flowchart showing an example of the procedure of the solar cell manufacturing method according to the second embodiment. FIGS. 6-1 to 6-2 are examples of the processing procedure of the solar cell manufacturing method according to the second embodiment. It is sectional drawing which shows this typically.

  First, as shown in FIG. 6A, a P-type single crystal silicon substrate 112 doped with boron (B) having a specific resistance of about 2 Ω · cm as a single crystal semiconductor substrate is prepared. Next, the single crystal silicon substrate 112 is immersed in an alkaline solution heated to 70 ° C., for example, in an aqueous solution of about 10% sodium hydroxide for 10 minutes to etch and clean the substrate surface (step S31). As a result, the substrate surface cleaning is performed at the same time as removing the damaged region generated near the substrate surface during substrate slicing.

  Next, anisotropic etching is performed at about 80 ° C. for 5 minutes in a mixed solution of an alkaline solution, for example, the same 10% aqueous sodium hydroxide solution as above, and an alcohol solution, for example, a solution to which about 1% of isopropyl alcohol is added. The texture structure is formed on the surface of the single crystal silicon substrate 112 (step S32). In the drawing, the illustration of the texture structure is omitted.

  After that, as shown in FIG. 6B, the single crystal silicon substrate 112 is put into a thermal oxidation furnace and heated in an atmosphere of phosphorus (P) as an N-type impurity. An N + layer 113 is formed by diffusing phosphorus on the surface and inverting the conductivity type. Here, a semiconductor PN junction region is formed on the surface of the single crystal silicon substrate 112 by heating for about 20 minutes at about 900 ° C. in a phosphorus oxychloride gas atmosphere (step S33). Next, the phosphor glass film formed on the surface of the single crystal silicon substrate 112 is removed by immersing it in a 5% hydrofluoric acid aqueous solution for about 5 minutes.

  Thereafter, as shown in FIG. 6C, an antireflection film 114 is formed on one main surface (hereinafter referred to as a surface) of the single crystal silicon substrate 112 (step S34). As the antireflection film 114, a silicon nitride film formed by a plasma CVD method using silane, ammonia, and nitrogen gas as source gases can be used. The film thickness and refractive index of the silicon nitride film can be set to values that suppress light reflection. For example, the refractive index can be about 2.0 and the film thickness can be about 80 nm.

  Next, as shown in FIG. 6D, a back side electrode 116 made of a Ni plating film is formed on the N + layer 113 on the other main surface (hereinafter referred to as the back side) of the single crystal silicon substrate 112 (see FIG. 6D). Step S35). At this time, for example, the substrate surface treatment apparatus 10B shown in FIG. 4 can be used. As the plating solution 12B, for example, Ni plating solution “Melbright (registered trademark) EF-220 (trade name)” manufactured by Meltex Co., Ltd. can be used. The plating solution 12B is preferably used at a temperature of about 50 ° C. Therefore, the treatment liquid temperature control unit (not shown) controls the temperature of the temperature adjusting heater 15 and the circulation line heater 23 so that the temperature of the plating solution 12B in the treatment tank 11 is about 50 ° C. Further, when Ni plating is performed at 50 ° C. using this plating solution 12B, a current of about 5 A / line (in the case of 10 V) is applied to the conveying roller 13 from the plating power source 61 through the plating electrode wire 62. Can be applied. The core 131 of the plating electrode 130 is preferably a structure having corrosion resistance against an acidic plating solution, and is made of, for example, Ti.

  Further, since the temperature of the plating solution 12B is about 50 ° C., the conveyance roller temperature control unit 51 is adjusted to a predetermined temperature so that the temperature of the conveyance roller 13 is also about the same as the temperature of the plating solution 12B. The adjustment liquid 52 is sent out through the pipe 53 and circulated between the transport rollers 13. For example, pure water can be used as the temperature adjusting liquid 52 that flows through the flow path in the transport roller 13, but an antifreeze liquid in which alcohol is added to pure water can also be used.

  The single crystal silicon substrate 112 is placed on the transport roller 13 provided on the upper portion of the processing tank 11 filled with such a plating solution 12B so that the back surface is on the lower side, and is transported by the transport roller 13. As a result, the back surface of the single crystal silicon substrate 112 comes into contact with the plating solution 12B, and the back surface side electrode 116 made of a Ni plating film is formed on the N + layer 113.

  When continuously processing a 156 mm square solar cell substrate at 10 mm intervals, when the conveyance speed is 0.5 m / sec and the roller interval is 50 mm pitch, the temperature of the conveyance roller temperature control unit 51 is 42. When set to ° C., the surface temperature of the plating electrode 130 can be kept at 50 ° C. When such a temperature control function of the plating electrode 130 does not exist, the plating electrode 130 is heated by energization, so that there is a difference in film quality between the plating film at the contact portion and the non-contact portion of the substrate 70 with the plating electrode 130. Will occur.

  Thereafter, as shown in FIG. 6A, a paste mixed with silver is printed on the surface of the single crystal silicon substrate 112 in a comb shape by a screen printing method to form the light receiving surface side electrode layer 115a (step S36). ). Then, as shown in FIG. 6B, the single crystal silicon substrate 112 is baked (step S37). The firing process is performed, for example, in an air atmosphere at 800 to 900 ° C., and the light receiving surface side electrode 115 is formed on the surface. At this time, although not shown, the light receiving surface side electrode 115 penetrates the antireflection film 114 and contacts the N + layer 113 at the junction. As a result, the N + layer 113 can obtain a good resistive junction with the light receiving surface side electrode 115. Through the above steps, the solar cell 111 is manufactured.

  As described above, in the second embodiment, the temperature of the transport roller 13 that transports the substrate 70 during plating is controlled to be equal to the temperature of the plating solution 12B. As a result, the stability at the time of plating film formation is increased, the stability and uniformity of processing within the substrate surface can be increased, and the controllability of the plating process can be enhanced.

  Further, if this substrate surface treatment apparatus 10B is used, for example, for forming the back side electrode 116 on the N + layer 113 on the back side of the solar battery cell, the N + layer 113 on the back side can be reliably and inexpensively compared with the conventional case. There is an effect that a high-performance solar battery cell having a Ni film formed thereon as the back electrode 116 can be obtained.

  In the first and second embodiments, the case where a solar cell is manufactured using a single crystal silicon substrate has been described. However, a polycrystalline silicon substrate may be used or another semiconductor material such as germanium or gallium arsenide may be used. A single crystal substrate or a polycrystalline substrate may be used.

10A, 10B Substrate surface treatment device 11 Processing tank 12A Etching solution 12B Plating solution 13 Transport roller 14, 32 Temperature control pipe 15 Temperature control heater 21, 43, 53 Pipe 22 Circulation pump 23 Circulation line heater 31 Supply tank 41 Outer tank 42 Discharge port 51 Transport roller temperature controller 52 Temperature adjusting liquid 61 Plating power supply 62 Plating electrode wire 70 Substrate 111 Solar cell 112 Single crystal silicon substrate 113 N + layer 114 Antireflection film 115 Light receiving surface side electrode 115a Light receiving surface side electrode layer 116 Back side electrode 116a Back side electrode layer 117 P + layer 130 Plating electrode 131 Core material 132 Conductive protective film

Claims (8)

A processing tank for storing a processing solution for processing the substrate surface;
A transport unit that has a rotating shaft in a direction perpendicular to a transport direction of the substrate at an upper portion of the processing tank, and transports the substrate by rotating while contacting a lower surface of the substrate;
Treatment liquid temperature adjusting means for adjusting the treatment liquid in the treatment tank to a predetermined temperature;
In a substrate surface treatment apparatus comprising:
A substrate surface processing apparatus comprising temperature adjusting means for adjusting the temperature of the transfer means so that the temperature of the transfer means is equal to the temperature of the processing liquid. The transport means comprises an electrode member made of a conductive material on the surface,
The substrate surface treatment apparatus according to claim 1, further comprising power supply means for supplying a current to the electrode member via a wiring. The electrode member is
A core made of a conductive material;
A conductive protective film made of a conductive soft material and provided on the surface of the core material;
The substrate surface treatment apparatus according to claim 2, comprising: The conveying means is a conveying roller having a flow path for temperature adjusting liquid inside,
The temperature adjusting means stores the temperature adjusting liquid while maintaining a predetermined temperature, and supplies the temperature adjusting liquid to the flow path in the transport roller via a pipe. 4. The substrate surface processing apparatus according to any one of 3 above. A treatment liquid supply step of supplying a treatment liquid adjusted to a predetermined temperature to the treatment tank;
A transporting step of transporting the substrate while bringing the lower surface of the substrate into contact with the processing liquid by transporting means provided on the processing tank and having a rotation axis in a direction perpendicular to the transporting direction of the substrate;
A temperature adjusting step for adjusting the temperature of the conveying means so that the temperature of the conveying means is equal to the temperature of the treatment liquid;
A substrate surface treatment method comprising: The transport means comprises an electrode member made of a conductive material on the surface,
The substrate surface treatment method according to claim 5, wherein in the transporting step, a current is passed through the electrode member through a wiring to form a plating film on the lower surface of the substrate.   A solar cell is manufactured using the semiconductor substrate which processed the surface using the substrate surface processing method of Claim 5, The manufacturing method of the solar cell characterized by the above-mentioned.   A method for manufacturing a solar cell, comprising forming an electrode made of a plating film on a semiconductor substrate using the substrate surface treatment method according to claim 6.

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