JP2013236020A - Solar battery manufacturing apparatus and manufacturing method of solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a solar battery manufacturing apparatus which arranges multiple substrates and concurrently performs processing on the multiple substrates and accurately measures a film thickness of a semiconductor film adhering to each substrate.SOLUTION: A solar battery manufacturing apparatus includes: a chamber 11; a substrate stage 12 and a substrate tray 13 that hold a substrate 111 in the chamber 11; thin film forming means forming a semiconductor film on the substrate 111 in the chamber 11; multiple lift pins 16 provided at through holes 12a, 13a, which are provided at the substrate stage 12 and the substrate tray 13 penetrating through the substrate stage 12 and the substrate tray 13 in a thickness direction, and supporting the substrate 111 so that the substrate 111 does not contact with the substrate stage 12 and the substrate tray 13; a mass measuring instrument 31 detecting loads applied to the lift pins 16 and thereby measuring the mass of the substrate 111; and a control part 32 causing the mass measuring instrument 31 to measure the reference mass of the substrate 111 before film formation and the mass of the substrate after the film formation.

Description

  The present invention relates to a solar cell manufacturing apparatus and a solar cell manufacturing method.

In recent years, heterojunction solar cells combining amorphous silicon (hereinafter referred to as a-Si) with single crystal silicon (hereinafter referred to as c-Si) have achieved a high conversion efficiency exceeding 20%, attracting attention. Yes. The feature of this solar cell is that i-type a-Si without a dopant at the junction formed by a-Si and c-Si (for example, p-type a-Si and n-type c-Si) having different conductivity. The purpose is to insert a thin film (passivation layer) (film thickness to 5.0 nm). As a result, the i-type a-Si layer having a large optical band gap forms a sharp junction at the heterointerface, and at the same time, the dopant material (boron, phosphorus, etc.) is prevented from being mixed with each other, and the carrier at the heterojunction interface To achieve a higher open circuit voltage (V _oc ).

In realizing such a heterojunction solar cell, the role of the process for forming the passivation layer (i-type a-Si film) is very important. A technique for forming a film with a target film thickness with high accuracy on -Si is desired. This is because when the thickness of the passivation layer is excessive with respect to the optimum value, the series electrical resistance component in the cell increases, and the fill factor (FF) decreases, and conversely, This is because when the thickness is insufficient with respect to the optimum value, the passivation effect becomes insufficient and V _oc decreases. Therefore, in a heterojunction solar cell, in order to stably realize high power generation efficiency among a plurality of deposition lots, the thickness variation of the passivation layer is ± 0.25 nm or less (± 5.0% of the target value). The following is required to be suppressed.

  By the way, conventionally, a thin film manufacturing apparatus capable of measuring the film thickness during the formation of a thin film on a substrate has been proposed (for example, see Patent Document 1). This patent document 1 describes a change in the total weight of a substrate holder and a substrate that occurs during thin film formation in a thin film manufacturing apparatus that has a substrate holder in a chamber and forms a thin film on the substrate held by the substrate holder. What has the structure provided with the balance which measures is disclosed. In this thin film manufacturing apparatus, by monitoring the mass during film formation, the total film adhesion amount to the substrate and the substrate holder can be grasped, and a thin film having a target film thickness (film adhesion amount) can be obtained. it can.

JP-A-8-8191

  The method of measuring the total mass of the substrate including the substrate holder and monitoring the film adhesion amount as in the conventional technique described above is the method of a-Si film (passivation layer or doping layer) in a heterojunction solar cell. It is also considered effective in manufacturing. However, the thickness of the a-Si film formed by the heterojunction solar cell is as very thin as ˜5.0 nm, which is several hundred μg, for example, in terms of the mass per 165 mm square substrate. On the other hand, the substrate holder generally has a meter angle size and a mass of several tens of kg. The chamber also has a meter angle so that about 9 to 16 substrates can be arranged and processed simultaneously. Thus, the mass of the substrate holder is about seven orders of magnitude higher than the amount of film attached to the substrate. That is, when it is going to manage the film thickness (film adhesion amount) of an a-Si film with the structure of the thin film manufacturing apparatus described in Patent Document 1, the film adhesion amount is buried in the measurement error of the mass of the substrate holder, There was a problem that control was not possible with high accuracy. Further, there is a problem that a mechanism for feedback when the film adhesion amount deviates from the target value is not provided, and high film thickness stability cannot be obtained.

  The present invention has been made in view of the above, and in a solar cell manufacturing apparatus capable of simultaneously processing a plurality of substrates arranged side by side, a solar cell manufacturing apparatus capable of accurately measuring the film thickness of a semiconductor film attached to the substrate And it aims at obtaining the manufacturing method of a solar cell.

  To achieve the above object, a solar cell manufacturing apparatus according to the present invention includes a chamber, substrate holding means for holding a semiconductor substrate in the chamber, and thin film formation for forming a semiconductor film on the semiconductor substrate in the chamber. And a plurality of substrate support members that are provided in a hole that penetrates in the thickness direction provided in the substrate holding means, and that support the semiconductor substrate without contacting the substrate holding means, and the substrate support member A mass measuring means for detecting the load and measuring the mass of the semiconductor substrate; and a control means for measuring a reference mass before film formation of the semiconductor substrate and a mass after film formation by the mass measurement means; It is characterized by providing.

  According to the present invention, the mass before and after film formation of the semiconductor substrate supported by the substrate support member is measured by the mass measuring means. Therefore, even when a semiconductor film is manufactured on a plurality of substrates having a meter angle size, a plurality of semiconductor films are manufactured. Even a solar cell manufacturing apparatus that can process a plurality of substrates side by side has an effect that the film thickness of the semiconductor film attached to the substrate can be accurately measured.

1 is a cross-sectional view schematically showing an example of the configuration of a solar cell manufacturing apparatus according to Embodiment 1 of the present invention. FIG. 2 is a top view schematically showing the configuration of the substrate holding mechanism according to the first embodiment. FIG. 3 is a diagram illustrating an example of the mass-film thickness correspondence information. FIG. 4 is a flowchart showing an example of a processing procedure of the solar cell manufacturing method according to the first embodiment. FIG. 5-1 is a cross-sectional view illustrating an example of a film forming process performed by the solar cell manufacturing apparatus according to Embodiment 1. FIG. 5-2 is a cross-sectional view showing an example during the mass measurement process in the solar cell manufacturing apparatus according to Embodiment 1. FIG. 6 is a cross-sectional view schematically showing an example of the configuration of a double-sided heterojunction solar cell manufactured by a solar cell manufacturing apparatus. FIG. 7 is a diagram showing measured values of film thickness when a semiconductor film is formed by the solar cell manufacturing apparatus according to Embodiment 1 and the conventional solar cell manufacturing apparatus. FIG. 8 is a cross-sectional view schematically showing an example of the configuration of the solar cell manufacturing apparatus according to Embodiment 2 of the present invention. FIG. 9 is a diagram illustrating an example of plasma irradiation time-etching amount correspondence information. FIG. 10 is a flowchart showing an example of the processing procedure of the solar cell manufacturing method according to the second embodiment. FIG. 11 is a cross-sectional view showing an example of the mass measurement process in the solar cell manufacturing apparatus according to the second embodiment. FIG. 12 is a diagram showing measured values of film thickness when a semiconductor film is formed by the solar cell manufacturing apparatus according to Embodiments 1 and 2. FIG. 13 is a diagram illustrating an example of a result of power generation efficiency when a semiconductor film is formed by the solar cell manufacturing apparatus according to Embodiment 2 and the conventional solar cell manufacturing apparatus.

  Exemplary embodiments of a solar cell manufacturing apparatus and a solar cell manufacturing method according to 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.

Embodiment 1 FIG.
1 is a cross-sectional view schematically showing an example of the configuration of a solar cell manufacturing apparatus according to Embodiment 1 of the present invention. Here, a plasma CVD (Chemical Vapor Deposition) apparatus is taken as an example of the solar cell manufacturing apparatus. The solar cell manufacturing apparatus 10 includes a substrate stage 12 which is a substrate holding unit disposed via a support member 14 on a bottom surface in an airtightly configured chamber 11. On the substrate stage 12, a substrate tray 13 on which a c-Si substrate (hereinafter also simply referred to as a substrate) 111 to be processed is disposed is provided. The substrate tray 13 has a configuration capable of transporting the substrate 111 in a state where the substrate 111 is disposed at a predetermined position. In addition, a plurality of substrates 111 can be arranged on the substrate tray 13.

  Above the substrate tray 13, a shower head 17 is provided substantially parallel to the substrate placement surface of the substrate tray 13. Although not shown, the shower head 17 is supported on the inner surface of the chamber 11 via an insulating member. A power supply line 41 for supplying high frequency power is connected to the shower head 17, and a blocking capacitor 42, a matching unit 43, and a high frequency power supply 44 are connected to the power supply line 41. During film formation, high frequency power having a predetermined frequency is supplied from the high frequency power supply 44 to the shower head 17.

  A gas supply port 21 is provided on the upper surface of the chamber 11, and a raw material gas supply unit 23 is connected to the gas supply port 21 via a pipe 22. Here, when forming an a-Si film, the source gas supply unit 23 holds, for example, silane gas as a source gas. The pipe 22 is provided with a gas valve 24 for switching on / off of the source gas from the source gas supply unit 23, a mass flow controller (not shown) for controlling the flow rate of the source gas, and the like. A gas exhaust port 18 is provided below the chamber 11 (here, the bottom surface), and the gas in the chamber 11 is exhausted by exhaust means such as a vacuum pump (not shown).

  The substrate stage 12 and the substrate tray 13 of the solar cell manufacturing apparatus 10 according to the first embodiment are provided with a mass measuring mechanism that can measure the mass of the substrate 111 placed near the center of the substrate tray 13. 2A and 2B are top views schematically showing the configuration of the substrate holding mechanism according to Embodiment 1, wherein FIG. 2A is a top view of the substrate stage, and FIG. 2B is a top view of the substrate tray. Near the center of the substrate stage 12, a plurality of through holes 12 a that penetrates the substrate stage 12 in the thickness direction are provided. A plurality of through holes 13 a penetrating in the thickness direction are also provided at positions of the substrate tray 13 corresponding to the through holes 12 a of the substrate stage 12. And the lift pin 16 which is a board | substrate support member is inserted in the formation position of these through-holes 12a and 13a, The lower part is supported by the support member 14 with the expansion-contraction arm 15. FIG. The center positions of the through hole 13a of the substrate tray 13 and the through hole 12a of the substrate stage 12 are coincident with each other, so that the vertical movement of the lift pins 16 is not hindered. The telescopic arm 15 is contracted so that the upper end of the lift pin 16 coincides with the upper surface of the substrate tray 13 during film formation, and the telescopic arm 15 is configured to extend during mass measurement. Although the number of lift pins 16 (through holes in the substrate stage 12 and the substrate tray 13) is four here, the number is not limited as long as the number can support the substrate 111.

  The support member 14 is provided with a mass measuring device 31 such as a load cell that measures a load applied to the telescopic arm 15 connected to the lift pin 16. By detecting the load applied to the mass measuring device 31 by the substrate 111 placed on the lift pin 16 via the telescopic arm 15, the mass of the substrate 111 on the lift pin 16 can be accurately measured. The mass measuring device 31 is connected to the control unit 32 outside the chamber 11, and outputs the measured mass value of the substrate 111 to the control unit 32 as measurement value data. In the first embodiment, the mass to be measured is only one substrate 111 to be processed and does not include a member for holding the substrate 111. Therefore, the thin film to be measured is compared with the conventional example. It becomes possible to accurately measure the amount of adhesion.

  The control unit 32 controls the film forming process in the solar cell manufacturing apparatus 10. Specifically, after the a-Si film is formed for a predetermined time, the a-Si film formed on the substrate 111 using the measurement value data from the mass measuring device 31 is formed. The thickness is obtained by calculation to determine whether the target film thickness has been reached. If the target film thickness has been reached, the process is terminated.If the target film thickness has not been reached, the necessary film thickness from the current film thickness to the target film thickness is obtained. The film processing time is calculated, and the film forming process is executed again. Such processing is repeatedly executed until the target film thickness is reached. In order to execute such processing, the control unit 32 includes a mass measurement unit 321, a mass storage unit 322, a film formation time calculation unit 323, a mass-film thickness correspondence information storage unit 324, and a film formation processing unit. 325.

  The mass measuring unit 321 performs a process of measuring the mass of the substrate 111 before and after the film forming process. For example, at the time of mass measurement, the extendable arm 15 is extended and the mass measuring device 31 measures the mass of the substrate 111 supported by the lift pins 16. Thereby, the film thickness of the semiconductor film formed on the substrate 111 can be grasped with high accuracy in-line.

  The mass storage unit 322 stores the measurement value data of the mass detected by the mass measuring device 31 when the mass measurement process is executed by the mass measurement unit 321. The mass measured before film formation is called initial mass, and the mass measured after film formation is called mass after film formation. Here, the initial mass and the post-film formation mass are stored, but only the initial mass may be stored.

  The film formation time calculation unit 323 sets the film formation time for setting the semiconductor film (a-Si film) as a target film thickness value (hereinafter referred to as a target film thickness value) as the current estimated film of the semiconductor film. The thickness is calculated using the thickness value (hereinafter referred to as the estimated film thickness value), the target film thickness value, and the film forming speed. Specifically, the mass of the semiconductor film attached to the surface of the substrate 111 by film formation is determined from the difference between the mass after film formation of the mass storage unit 322 and the initial mass, and the mass in the mass-film thickness correspondence information storage unit 324 is quantified. -The film thickness of the semiconductor film corresponding to the mass calculated using the film thickness correspondence information is obtained, and this is used as the estimated film thickness value. Then, the difference between the target film thickness value and the estimated film thickness value is calculated. As a result, a deviation from the target value of the semiconductor film formed on the substrate 111 can be grasped in-line with high accuracy. If this difference is within the predetermined range, the film forming time is 0, that is, the film forming is completed, and if this difference is larger than the predetermined range, the value obtained by dividing the difference by the film forming speed. Is set as the film forming time, and is passed to the film forming processing unit 325. If the film forming process is not performed, for example, a film forming time for forming a semiconductor film having a target film thickness value is set in advance, and this set film forming time is set in the film forming processing unit 325. Can be passed.

  The mass-film thickness correspondence information storage unit 324 indicates the relationship between the mass and the film thickness of the semiconductor film attached to the substrate 111 when the semiconductor film is formed on the substrate 111 to be formed. Store information. FIG. 3 is a diagram illustrating an example of the mass-film thickness correspondence information. In this figure, the horizontal axis represents the mass (μg) of the semiconductor film attached to the substrate 111, and the vertical axis represents the thickness (nm) of the semiconductor film attached to the substrate 111. This mass-thickness correspondence information is obtained by previously obtaining a plurality of combinations of the film thickness value obtained by measuring the formed semiconductor film by ellipsometry and the mass value of the semiconductor film at that time.

  The film formation processing unit 325 contracts the telescopic arm 15 connected to the lift pin 16 to a state during film formation, sets the inside of the chamber 11 to a predetermined degree of vacuum, supplies the source gas into the chamber 11, and performs a shower. A high-frequency power is applied to the head 17 to turn the raw material gas into plasma, and a film forming process is performed to form a film. When film formation is performed on the substrate 111 for the first time, film formation processing is performed for a predetermined film formation time, and when film formation is performed for the second and subsequent times on the semiconductor film on the substrate 111, film formation is performed. The film formation process is performed only for the film formation time calculated by the time calculation unit 323.

  As described above, since the lift pins 16 are lowered during film formation, the semiconductor film does not adhere to the side surfaces of the lift pins 16 but adheres only to the substrate 111. As a result, the mass of the semiconductor film measured by the mass measuring device 31 can be only the amount attached to the substrate 111.

  Next, a method for forming a solar cell in such a solar cell manufacturing apparatus 10 will be described. FIG. 4 is a flowchart illustrating an example of a processing procedure of the solar cell manufacturing method according to the first embodiment, and FIG. 5A illustrates an example of a film forming process performed by the solar cell manufacturing apparatus according to the first embodiment. FIG. 5-2 is a cross-sectional view illustrating an example of the mass measurement process performed by the solar cell manufacturing apparatus according to Embodiment 1. Moreover, FIG. 6 is sectional drawing which shows typically an example of a structure of the double-sided heterojunction solar cell manufactured with a solar cell manufacturing apparatus. In FIG. 6, the relationship between the thickness and width of the layers, the ratio of the thicknesses of the layers, and the like may be different from the actual ones.

  First, the structure of a double-sided heterojunction solar cell manufactured by the solar cell manufacturing apparatus 10 will be described with reference to FIG. The double-sided heterojunction solar cell 100 is a main power generation layer on the first surface serving as the light-receiving surface of the first conductivity type c-Si substrate 111, and a substantially intrinsic i-type a-Si layer 112; The conductive type a-Si layer 113 and the first transparent conductive layer 114 made of a transparent conductive material are stacked. That is, this double-sided heterojunction solar cell 100 includes an i-type a-Si layer 112 between the first conductivity type c-Si substrate 111 and the second conductivity type a-Si layer 113 in order to improve the pn junction characteristics. It has a heterojunction provided. The i-type a-Si layer 112 includes a first conductivity type impurity contained in the first conductivity type c-Si substrate 111 and a second conductivity type impurity contained in the second conductivity type a-Si layer 113. It also has a passivation function to suppress the mutual diffusion. A comb-shaped first collector electrode 115 is formed on the first transparent conductive layer 114.

  Further, on the second surface facing the first surface of the first conductivity type c-Si substrate 111, a BSF (Back Surface Field) layer 116, a second transparent conductive layer 117 made of a transparent conductive material, and Are stacked. The BSF layer 116 has a BSF structure in which an i-type a-Si layer 1161 and a first conductivity-type Si layer 1162 are sequentially stacked on a first conductivity-type c-Si substrate 111. Carrier recombination on the second transparent conductive layer 117 side in the conductive c-Si substrate 111 is prevented. A second collector electrode 118 is also formed on the second transparent conductive layer 117.

  In such a double-sided heterojunction solar cell 100, the thickness of the i-type a-Si layer 112 is required to be precisely controlled to about 5 nm. Therefore, in the first embodiment, a solar cell manufacturing apparatus 10 for forming a semiconductor film which is the i-type a-Si layer 112 in FIG. 6 and a solar cell manufacturing method will be described.

  First, the substrate 111 is placed at a predetermined position on the substrate tray 13 (step S11), the substrate tray 13 is transferred into the chamber 11, and the substrate tray 13 is placed on the substrate stage 12. At this time, alignment is performed so that the positions of the through holes 12a of the substrate stage 12 and the through holes 13a of the substrate tray 13 coincide. At this time, one substrate arranged on the substrate tray 13 (in this example, the substrate 111 at the center of the substrate tray 13) is arranged on the position where the lift pins 16 are arranged. Next, the chamber 11 is evacuated by an evacuation means such as a vacuum pump (step S12) to obtain a predetermined degree of vacuum. Thereafter, the mass measurement unit 321 of the control unit 32 performs a mass measurement process on the substrate 111. Specifically, the mass measuring device 31 measures the mass of the substrate 111 disposed on the lift pins 16 (step S13), outputs the value to the control unit 32 as measurement value data, and receives it in the mass storage unit 322. The measured value data is stored as the initial mass (step S14).

  Next, a film forming process is performed by the film forming process unit 325 (step S15, FIG. 5-1). As shown in FIG. 5A, the telescopic arm 15 is folded so that the upper end of the lift pin 16 coincides with the upper surface of the substrate tray 13. Next, a raw material gas (for example, silane gas) 231 from the raw material gas supply unit 23 is sent to the chamber 11 through the pipe 22 and distributedly supplied onto the substrate 111 through the shower head 17. When the source gas 231 is supplied, the substrate stage 12 is grounded, and high frequency power is applied to the shower head 17 from the high frequency power supply 44, thereby generating a source gas plasma 232, and a semiconductor film (a -Si layer 112) is formed. This state is maintained for a predetermined film forming time, that is, a film forming time corresponding to the target film thickness value. After a preset film forming time has elapsed, the supply of high-frequency power to the shower head 17 is stopped and the source gas plasma 232 is extinguished. Further, the supply of the source gas 231 into the chamber 11 is stopped, the inside of the chamber 11 is evacuated through the gas exhaust port 18, and the film forming process is terminated.

  Thereafter, the mass measurement unit 321 executes mass measurement processing (step S16, FIG. 5-2). As shown in FIG. 5B, in the mass measurement process, the extendable arm 15 is extended, the lift pins 16 are raised, the substrate 111 on which the semiconductor film is formed is lifted, and the mass of the substrate 111 is measured by the mass measuring device 31. . And the mass measuring device 31 outputs this measured mass to the control part 32 as measurement value data, and the control part 32 acquires the received measurement value data as mass after film forming (step S17). At this time, the mass after film formation may be stored in the mass storage unit 322.

  Next, the control unit 32 calculates the mass of the semiconductor film formed using the post-film formation mass and the initial mass (step S18), and uses the mass-film thickness correspondence information from the mass of the semiconductor film. The thickness of the semiconductor film to be obtained is acquired (step S19). The method for determining the film thickness of the semiconductor film is to calculate the difference between the post-film formation mass and the initial mass and quantify the mass of the semiconductor film adhering to the surface of the substrate 111. And the film thickness of a semiconductor film is estimated from the mass of this semiconductor film using the mass-film thickness correspondence information of FIG.

  Next, the film formation time calculation unit 323 of the control unit 32 compares the estimated film thickness value of the semiconductor film with a preset target film thickness value, and the estimated film thickness value is within a predetermined range with respect to the target film thickness value. (Step S20). As the predetermined range, for example, a range of ± 5.0% with respect to the target film thickness value can be set. If the estimated film thickness value is not within the predetermined range with respect to the target film thickness value, here the estimated film thickness value is smaller than the target film thickness value beyond the predetermined range (No in step S20). In this case, the film formation time calculation unit 323 calculates a film thickness value corresponding to the shortage, and calculates a film formation time necessary to compensate for the shortage (step S21). For example, the film forming time can be obtained by calculating the difference between the target film thickness value and the estimated film thickness value and dividing the difference by the film forming speed during the film forming process. Then, the control part 32 returns to step S15, and performs the film forming process during the film forming time calculated in step S21. Thereafter, the above-described processing is performed.

  On the other hand, when the estimated film thickness value is within the predetermined range with respect to the target film thickness value (Yes in step S20), the semiconductor film adheres to the substrate 111 by the thickness of the target film thickness value. As a result, a process of unloading the substrate 111 in the chamber 11 is performed (step S22). That is, the above process is repeatedly executed until the estimated film thickness value reaches the target film thickness value. The solar cell manufacturing method is thus completed.

  FIG. 7 is a diagram showing measured values of film thickness when a semiconductor film is formed by the solar cell manufacturing apparatus according to Embodiment 1 and the conventional solar cell manufacturing apparatus. In this figure, the abscissa indicates the number of semiconductor film depositions (number of lots), and the ordinate indicates the film thickness (nm) of the semiconductor film formed on the substrate 111. Here, nine semiconductor films are continuously formed by the solar cell manufacturing apparatus 10 described above, and a measured value that is an actual film thickness measured by ellipsometry is indicated by a black triangle. In addition, as a comparative example, nine semiconductor films were similarly formed by the method described in Patent Document 1, and the measured values, which are actual film thicknesses measured by ellipsometry, are indicated by black circles. . Here, film formation is performed under the same conditions with a target film thickness value of 5.0 nm. As shown in FIG. 7, in the comparative example, the variation in film thickness is ± 13.2% in Max-Min. However, in the method according to the first embodiment, the variation in film thickness is ± 6.7. %.

  In the first embodiment, the thickness of the semiconductor film attached to the surface of the substrate 111 is estimated by measuring the mass of the substrate 111 before and after film formation, and is insufficient with respect to the target film thickness value. Estimated the film thickness value of the shortage and implemented additional film formation. As a result, when a semiconductor film is formed on the meter-size substrate 111, the film thickness variation between a plurality of different film forming lots is suppressed to about half of the conventional film thickness, and the film thickness to be formed is stabilized. It is possible to realize the process that has been performed. In particular, even when a silicon film of several nm is formed on a silicon substrate for solar cells, the amount of adhesion can be accurately measured. Then, by forming a conductive silicon film with a controlled film thickness on the silicon substrate, it is possible to greatly suppress variation in performance when manufacturing solar cells, and to improve yield.

  In the method according to the first embodiment, only the mass of the substrate 111 is measured, and the mass of the substrate holding member such as the substrate tray 13 is not a measurement target. Therefore, it is possible to avoid the film adhesion amount, which has been a problem in Patent Document 1, from being buried in the measurement error of the mass of the substrate holding member. As a result, the film adhesion amount can be controlled with high accuracy.

Embodiment 2. FIG.
In Embodiment 1, although the process when the estimated film thickness value calculated | required from the mass measured with the mass measuring device is below a target film thickness value was demonstrated, the estimated film thickness value may exceed a target film thickness value. is there. Therefore, in the second embodiment, a solar cell manufacturing apparatus and a solar cell film forming method when the estimated film thickness value exceeds the target film thickness value will be described.

  FIG. 8 is a cross-sectional view schematically showing an example of the configuration of the solar cell manufacturing apparatus according to Embodiment 2 of the present invention. Here again, a plasma CVD apparatus is taken as an example of a solar cell manufacturing apparatus. This solar cell manufacturing apparatus 10 </ b> A has a configuration in which an etching gas supply unit 25 is further provided in the pipe 22 connected to the gas supply port 21 in the solar cell manufacturing apparatus 10 of the first embodiment. When an a-Si film is used as the semiconductor film, hydrogen gas can be used as an etching gas. The piping 22 connected to the etching gas supply unit 25 is also provided with a gas valve 24 that switches on / off the etching gas from the etching gas supply unit 25, a mass flow controller (not shown) that controls the flow rate of the etching gas, and the like. The control unit 32 further includes a plasma irradiation time / etching amount correspondence information storage unit 326, an etching time calculation unit 327, and an etching processing unit 328.

  The plasma irradiation time-etching amount correspondence information storage unit 326 shows the relationship between the etching time and the etching amount when the semiconductor film (a-Si layer 112) is etched with the etching gas (hydrogen gas). Stores correspondence information. FIG. 9 is a diagram illustrating an example of plasma irradiation time-etching amount correspondence information. In this figure, the horizontal axis represents the plasma irradiation time (s) of the etching gas (here, hydrogen), and the vertical axis represents the amount of etching (etching amount) (nm) of the semiconductor film. This plasma irradiation time-etching amount correspondence information is obtained in advance by experiments.

  When the estimated film thickness value exceeds the target film thickness value, the etching time calculation unit 327 calculates an etching time necessary to remove the excess film thickness. Specifically, the mass of the semiconductor film attached to the surface of the substrate 111 by film formation is determined from the difference between the mass after film formation of the mass storage unit 322 and the initial mass, and the mass in the mass-film thickness correspondence information storage unit 324 is quantified. -The film thickness of the semiconductor film corresponding to the mass calculated using the film thickness correspondence information is obtained, and this is used as the estimated film thickness value. Then, the difference between the target film thickness value and the estimated film thickness value is calculated, and when the estimated film thickness value is larger than the target film thickness value beyond a predetermined range, the estimated film thickness value and the target film thickness value are And the hydrogen plasma irradiation time corresponding to this film thickness value is acquired from the plasma irradiation time-etching amount correspondence information. Then, this acquired time is set as an etching time, and is passed to the etching processing unit 328.

  The etching processing unit 328 performs control so that the processing for etching the substrate 111 is executed only for the etching time acquired from the etching time calculation unit 327. In addition, the same code | symbol is attached | subjected to the component same as Embodiment 1, and the description is abbreviate | omitted.

  Below, the manufacturing method of the solar cell in such a solar cell manufacturing apparatus 10A is demonstrated. FIG. 10 is a flowchart showing an example of the processing procedure of the solar cell manufacturing method according to the second embodiment, and FIG. 11 is a cross-sectional view showing an example of the mass measurement process in the solar cell manufacturing apparatus according to the second embodiment. It is.

  As described in steps S11 to S20 in FIG. 4 of the first embodiment, the substrate 111 is transferred into the chamber 11 and the mass of the substrate 111 on which the lift pins 16 are located is measured, and then a semiconductor film is formed on the substrate 111. Then, the mass of the substrate 111 where the lift pins 16 are located is measured, and the estimated film thickness value of the semiconductor film formed on the substrate 111 is within a predetermined range with respect to the target film thickness value based on the measurement result. (Steps S31 to S40, FIG. 11). Since this process has been described in the first embodiment, a description thereof will be omitted.

  When the estimated film thickness value is larger than the target film thickness value within a predetermined range (No in step S40), the etching time calculation unit 327 calculates the film thickness value corresponding to the excess amount. Then, the etching time required to remove the excess is calculated (step S41). For example, the etching time calculation unit 327 calculates the difference between the estimated film thickness value and the target film thickness value of the semiconductor film, and obtains the etching time corresponding to the difference from the plasma irradiation time-etching amount correspondence information. Then, this etching time is passed to the etching processing unit 328.

  Next, the etching processing unit 328 of the control unit 32 performs etching processing of the semiconductor film formed on the substrate 111 during the obtained etching time (step S42, FIG. 8). As shown in FIG. 8, an etching gas 251 (for example, hydrogen gas) from the etching gas supply unit 25 is sent to the chamber 11 through the pipe 22 and is distributedly supplied onto the substrate 111 through the shower head 17. When the etching gas 251 is supplied, the substrate stage 12 is grounded, and a high frequency power is applied to the shower head 17 from the high frequency power supply 44, thereby generating an etching gas plasma 252, which generates a semiconductor film on the substrate 111. Etch the surface. After the calculated etching time has elapsed, the supply of the high frequency power to the shower head 17 is stopped and the etching gas plasma 252 is extinguished. Further, the supply of the etching gas 251 into the chamber 11 is stopped, and the inside of the chamber 11 is evacuated through the gas exhaust port 18 to finish the etching process. Thereafter, the process returns to step S36 (FIG. 10).

  On the other hand, when the estimated film thickness value is within the predetermined range with respect to the target film thickness value in Step S40 (Yes in Step S40), the semiconductor film on the substrate 111 has the target thickness. Thus, the substrate 111 in the chamber 11 is unloaded (step S43). That is, the above process is repeatedly executed until the estimated film thickness value reaches the target film thickness value. The solar cell manufacturing method is thus completed.

  Here, the case where the estimated film thickness value is larger than the target film thickness value beyond a predetermined range has been described for the case where the excessive film thickness is removed by etching. In combination, when the estimated film thickness value is small beyond the predetermined range from the target film thickness value, a semiconductor film having an insufficient film thickness is formed by the method of the first embodiment. By removing the excessive semiconductor film by the method of Embodiment Mode 2, the semiconductor film thickness can be controlled with higher accuracy.

  FIG. 12 is a diagram showing measured values of film thickness when a semiconductor film is formed by the solar cell manufacturing apparatus according to Embodiments 1 and 2. In this figure, the horizontal axis indicates the number of semiconductor film depositions (number of lots), and the vertical axis indicates the film thickness (nm) of the semiconductor film. Here, nine semiconductor films are continuously formed by the solar cell manufacturing apparatus 10A described in the second embodiment, and a measured value that is an actual film thickness measured by ellipsometry is indicated by a black square mark. . Also, in this figure, nine semiconductor films are similarly formed in succession by the solar cell manufacturing apparatus 10 described in the first embodiment, and the measured value which is the actual film thickness measured by ellipsometry is painted black. This is indicated by a triangle. Here, film formation is performed under the same conditions with a target film thickness of 5.0 nm. As shown in FIG. 12, in the first embodiment, the variation in film thickness is ± 6.7% in Max-Min, but in the method according to the second embodiment, the variation in film thickness is ± 3. It can be reduced to 0.0%.

  Next, the double-sided heterojunction solar cell in which the i-type a-Si layer 112 is formed by the solar cell manufacturing apparatus 10A of Embodiment 2 and the double-sided heterojunction solar cell in which the i-type a-Si layer 112 is formed by a conventional method Comparison of power generation efficiency will be described. FIG. 13 is a diagram illustrating an example of a result of power generation efficiency when a semiconductor film is formed by the solar cell manufacturing apparatus according to Embodiment 2 and the conventional solar cell manufacturing apparatus. In this figure, the horizontal axis indicates the number of semiconductor film depositions (number of lots), and the vertical axis indicates the power generation efficiency of the obtained solar cell. Further, in this figure, the power generation efficiency in each case is normalized with the highest power generation efficiency. Furthermore, the power generation efficiency of a double-sided heterojunction solar cell in which nine i-type a-Si layers 112 are continuously formed by the solar cell manufacturing apparatus 10A according to Embodiment 2 is indicated by black square marks. Further, as a comparative example, the power generation efficiency of a double-sided heterojunction solar cell in which nine i-type a-Si layers 112 are similarly continuously formed by the method described in Patent Document 1 is indicated by black circles. As shown in FIG. 13, in the comparative example, the variation in the power generation efficiency between lots is ± 6.0% in Max-Min. However, in the method according to the second embodiment, the power generation efficiency between lots. The variation can be reduced to ± 1.7%.

  In Embodiment 2, the film thickness value of the semiconductor film adhering to the surface of the substrate 111 is estimated by measuring the mass of the substrate 111 before and after film formation. Then, the film thickness value of the excess was estimated and the etching process was performed. Accordingly, when a semiconductor film is formed on the meter-sized substrate 111, the film thickness variation among a plurality of different film forming lots is suppressed to ½ or less compared to the case of the first embodiment, It has the effect that the process which stabilized the film thickness to form into a film | membrane can be implement | achieved. In addition, since variation between lots of semiconductor films can be suppressed, when manufacturing a double-sided heterojunction solar cell using this semiconductor film as the i-type a-Si layer 112, compared to the case of Patent Document 1. In addition, a solar cell having high power generation efficiency can be obtained stably.

  In the above description, the mass measuring device 31 is provided on the support member 14 in the chamber 11 and the lift pins 16 are moved up and down. However, the mass having the lift pins 16 below the substrate stage 12 on which the substrate tray 13 is installed. You may make it provide the mechanism which arrange | positions the measuring device 31 and moves up and down with the mass measuring device 31. FIG. That is, the telescopic arm 15 that moves the lift pin 16 up and down may be under the mass measuring device 31. Even with such a method, the weight change of the silicon substrate can be measured with high accuracy in the same manner as described above.

  In the above description, the mass measuring device 31 is provided in the chamber 11 (film forming chamber). However, a vacuum container continuous with the film forming chamber may be provided, and similar mass measurement may be performed in the vacuum container. For example, the mass measurement device 31 may be provided in a substrate transfer chamber for transferring the substrate tray 13 to the chamber 11 while keeping the chamber 11 in a vacuum, and mass measurement may be performed. Further, the etching of the film may be performed in a processing chamber different from the chamber 11 (film forming chamber) in which the film is formed.

  In the above description, the plasma CVD apparatus is described as an example of the solar cell manufacturing apparatus, but is not limited to this. For example, even in a film forming apparatus that forms a semiconductor film constituting another solar cell, such as a sputtering apparatus, the same effect can be obtained by applying the above-described configuration.

DESCRIPTION OF SYMBOLS 10,10A Solar cell manufacturing apparatus 11 Chamber 12 Substrate stage 12a, 13a Through hole 13 Substrate tray 14 Support member 15 Telescopic arm 16 Lift pin 17 Shower head 18 Gas exhaust port 21 Gas supply port 22 Pipe 23 Raw material gas supply unit 24 Gas valve 25 Etching Gas supply unit 31 Mass measuring device 32 Control unit 41 Feeding line 42 Blocking capacitor 43 Matching unit 44 High frequency power source 100 Double-sided heterojunction solar cell 111 c-Si substrate 112 i-type a-Si layer 113 Second conductivity type a-Si layer 114 Transparent conductive layer 115,118 Collector electrode 116 BSF layer 117 Transparent conductive layer 321 Mass measurement unit 322 Mass storage unit 323 Film formation time calculation unit 324 Mass-film thickness correspondence information storage unit 325 Film formation processing unit 326 Plasma irradiation time-etching amount Correspondence Distribution storage unit 327 etching time calculator 328 etching unit 1161 i-type a-Si layer 1162 first conductivity type Si layer

Claims (10)

A chamber;
Substrate holding means for holding a semiconductor substrate in the chamber;
Thin film forming means for forming a semiconductor film on the semiconductor substrate in the chamber;
A plurality of substrate support members that are provided in a hole penetrating in the thickness direction provided in the substrate holding means, and support the semiconductor substrate without contacting the substrate holding means;
A mass measuring means for detecting a load applied to the substrate support member and measuring a mass of the semiconductor substrate;
Control means for measuring a reference mass before film formation of the semiconductor substrate and a mass after film formation by the mass measurement means;
A solar cell manufacturing apparatus comprising:   The control means estimates the thickness of the semiconductor film deposited on the semiconductor substrate from the difference between the reference mass before film formation measured by the mass measurement means and the mass after film formation. The solar cell manufacturing apparatus according to claim 1.   The control means uses the mass-film thickness correspondence information indicating a correspondence relationship between the mass of the semiconductor film attached to the semiconductor substrate and the thickness of the semiconductor film attached to the surface of the semiconductor substrate, and the reference mass The solar cell manufacturing apparatus according to claim 2, wherein an estimated film thickness value of the semiconductor film corresponding to a difference between the thickness of the semiconductor film and the mass after the film formation is obtained.   In the case where the estimated film thickness value of the semiconductor film is smaller than the target film thickness value, the control means determines the difference between the target film thickness value and the estimated film thickness value, and film formation by the thin film forming means. The film forming time for the insufficient film thickness is calculated using the speed, and the additional film forming process of the semiconductor film by the thin film forming unit is executed for the film forming time for the insufficient film thickness. The solar cell manufacturing apparatus according to claim 3. Etching means for etching the semiconductor film;
The control means, when the estimated film thickness value of the semiconductor film is larger than the target film thickness value, the difference between the estimated film thickness value and the target film thickness value, the etching rate by the etching means, 5. The solar cell manufacturing according to claim 3, wherein an etching time for removing an excess film thickness is calculated using the step of etching the semiconductor film by the etching means for the etching time. apparatus. A chamber;
Substrate holding means for holding a semiconductor substrate in the chamber;
Thin film forming means for forming a semiconductor film on the semiconductor substrate in the chamber;
A plurality of substrate support members that are provided in a hole penetrating in the thickness direction provided in the substrate holding means, and support the semiconductor substrate without contacting the substrate holding means;
A mass measuring means for detecting a load applied to the substrate support member and measuring a mass of the semiconductor substrate;
A solar cell manufacturing method in a solar cell manufacturing apparatus comprising:
A pre-film formation mass measurement step of measuring a reference mass before film formation of the semiconductor substrate supported by the substrate support member by the mass measuring means;
A film forming step of forming the semiconductor film on the semiconductor substrate by the thin film forming means;
A post-film formation mass measurement step of measuring the mass of the semiconductor substrate after film formation with the mass measurement means;
The manufacturing method of the solar cell characterized by including.   The film thickness estimation step of estimating a thickness of the semiconductor film deposited on the semiconductor substrate from a difference between a reference mass before the film formation and a mass after the film formation is further included. The manufacturing method of the solar cell of description.   In the film thickness estimation step, using the mass-film thickness correspondence information indicating the correspondence between the mass of the semiconductor film attached to the semiconductor substrate and the thickness of the semiconductor film attached to the surface of the semiconductor substrate, The method for manufacturing a solar cell according to claim 7, wherein an estimated film thickness value of the semiconductor film corresponding to a difference between a reference mass and a mass after the film formation is obtained. A film thickness comparison step for comparing the estimated film thickness value with a target film thickness value of the semiconductor film;
When the estimated film thickness value of the semiconductor film is smaller than the target film thickness value, a difference between the target film thickness value and the estimated film thickness value and a film forming speed by the thin film forming unit are used. A film forming time calculating step for calculating a film forming time for the insufficient film thickness,
An additional film forming process step of performing an additional film forming process of the semiconductor film by the thin film forming means for a film forming time corresponding to the insufficient film thickness;
Further including
The solar cell according to claim 8, wherein the additional film forming process is repeatedly executed from the film thickness comparison process until the estimated film thickness value falls within a predetermined range with respect to the target film thickness value. Manufacturing method. The solar cell manufacturing apparatus further includes etching means for etching the semiconductor film,
A film thickness comparison step for comparing the estimated film thickness value with a target film thickness value of the semiconductor film;
When the estimated film thickness value of the semiconductor film is larger than the target film thickness value, the difference between the estimated film thickness value and the target film thickness value and the etching rate by the etching means are excessive. An etching time calculating step for calculating an etching time for the film thickness;
An etching step of performing an etching process of the semiconductor film by the etching means for the etching time;
Further including
The method for manufacturing a solar cell according to claim 8, wherein the etching process is repeatedly executed from the film thickness comparison process until the estimated film thickness value falls within a predetermined range with respect to the target film thickness value. .

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