JP2013232607A - Solar battery cell manufacturing method and electrode forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode forming device of a solar battery cell capable of properly forming an electrode on a high concentration selective diffusion layer.SOLUTION: The electrode forming device comprises: a light intensity detection section having a light source 1 for radiating light including a wavelength region permeating through a semiconductor substrate 6 to the semiconductor substrate 6 on which a high concentration selective diffusion layer 7 is formed, and an optical sensor 2 for detecting intensity distribution of light permeating through the semiconductor substrate 6; an electrode formation section 5 forming an electrode on the semiconductor substrate 6; a movable stage 4 conveying the semiconductor substrate 6 to the light intensity detection section and the electrode formation section 5, and holding the semiconductor substrate 6 so that an electrode formation position to the semiconductor substrate 6 can be adjusted; and a computer 3 for identifying a position region of the high concentration selective diffusion layer 7 of the semiconductor substrate 6 from light intensity detection results of the optical sensor 2, and adjusting a position of the movable stage 4 at the electrode formation section 5 based on identification results.

Description

  The present invention relates to a method for manufacturing a solar battery cell and an electrode forming apparatus.

  At present, cost reduction is an important issue in the methods used to manufacture consumer solar cells, and therefore, a method combining a thermal diffusion method and a screen printing method is common. The details are as follows, for example.

First, a p-type silicon substrate obtained by slicing a single crystal silicon ingot pulled up by the Czochralski (CZ) method or a polycrystalline silicon ingot produced by a cast method by a multi-wire method is prepared. Next, after removing slice damage on the surface with an alkaline solution, fine unevenness (texture) having a maximum height of about 10 μm is formed on the surface, and an n-type diffusion layer is formed on the substrate surface by a thermal diffusion method. Further, TiO ₂ or SiN is deposited with a film thickness of, for example, about 70 nm on the light receiving surface to form an antireflection film. Next, a back electrode is formed by printing and baking a material mainly composed of aluminum over the entire back surface of the non-light-receiving surface using a screen printing method. On the other hand, the light-receiving surface electrode is formed by printing and baking a material mainly composed of silver in a comb-like shape having a width of about 100 to 200 μm, for example.

  As a method for manufacturing such a consumer solar cell, for example, in Japanese Patent Application Laid-Open No. 2004-193350 (Patent Document 1), a diffusion prevention film such as a silicon oxide film is grown on the surface of a semiconductor silicon substrate. Partly removed by a technique such as a photomask method, a diffusing agent containing a dopant is applied by a technique such as spin coating, and this is heat treated to form a high-concentration selective diffusion layer in the part from which the film is removed, It is disclosed that a low-concentration diffusion layer is formed in a portion where the film is not removed. The emitter diffusion layer composed of the high concentration selective diffusion layer and the low concentration diffusion layer is called a two-stage emitter.

  Further, regarding the light receiving surface side electrode, many common crystalline solar cells have an electrode structure formed by screen plate making with a pattern as shown in FIG. That is, as shown by 21 in FIG. 3, a plurality of electrodes corresponding to substantially parallel thin wire openings having a line width of about 100 to 200 μm and an interval of about 1.5 to 2.5 mm (generally these are finger electrodes). Is formed over the entire surface of the cell to collect power generated from the entire semiconductor substrate. In addition, when the electric charge collected by the finger electrodes is further collected in a form orthogonal to these finger electrodes to produce a solar cell module, power is transmitted to the outside of the solar cell module when connecting the solar cells. For the purpose of connecting the wiring, an electrode corresponding to a relatively thick opening having a width of about 1.0 to 3.0 mm shown in FIG. Called a bus bar electrode).

  Patent Document 1 discloses a method of forming an electrode only on a high concentration selective diffusion layer in order to increase conversion efficiency.

  In addition, in recent years, in order to improve the conversion efficiency of solar cells, a through hole (through hole) is formed directly below the finger electrode on the light receiving surface side in order to reduce the shadow loss of the light receiving surface side electrode as much as possible. Connected to the bus bar electrode on the back side through (generally referred to as a metal wrap through structure), or a structure that has no electrode on the light receiving surface side and an electrode only on the back side (generally a back surface)・ Solar cells (called contact structures) have been developed.

  Here, when producing a consumer high-efficiency solar cell having a high-concentration selective diffusion layer according to the disclosed example, for example, first, a high-concentration selective diffusion layer is formed by combining a photomask method, a spin coating method, and a thermal diffusion method. Then, a two-stage emitter structure composed of a low concentration diffusion layer is formed in the other portions, and then an electrode agent paste is screen printed on the high concentration selective diffusion layer to form an electrode.

  Conventionally, when manufacturing a solar cell as described above, the high-concentration selective diffusion layer previously formed on the semiconductor substrate is difficult to visually recognize in the post-process after the cleaning step, so the high-concentration selection In each step of forming the diffusion layer and the electrode, the distance from the edge of the semiconductor substrate is controlled to align the high concentration diffusion layer with the electrode.

  In this regard, in the disclosed example, since the high-concentration selective diffusion layer formed on the light-receiving surface side and the light-receiving surface-side electrode are overlapped, precise position measurement such as a CCD (Charge Coupled Device) camera is possible at the substrate edge. A manufacturing process that performs alignment using an apparatus is desirable.

  However, in the disclosed example, the method of forming the two-stage emitter and the method of forming the light receiving surface electrode are different, and the screen printing method itself, which is an electrode forming method, is excellent in cost and productivity, but the printing positioning accuracy is sufficiently high. Production is not high, such as printing press alignment accuracy, durability against continuous use of screen plate making, wear of squeegees and scrapers used in screen printing, changes in physical properties of electrode paste due to environmental changes such as temperature and humidity, etc. Due to various differences and variations in the process, there is a considerable misalignment between the high-concentration diffusion layer and the electrode formation position of the two-stage emitter. As a result, this misalignment location increased the contact resistance and decreased the photoelectric conversion efficiency of the solar battery cell.

  Therefore, conventionally, when forming the high-concentration selective diffusion layer, the variation width due to the manufacturing process is taken into account in advance, and the high-concentration selective diffusion layer is formed in a similar shape uniformly thicker than the finger electrode line width to be formed later. It was.

  However, the high-concentration selective diffusion layer (generally called a dead area) that is thicker than the finger electrode line width has more carrier recombination centers than the low-concentration diffusion layer. A photoelectric conversion efficiency falls and a highly efficient photovoltaic cell cannot be obtained. Conversely, if the finger electrode is made as thin as the line width, a highly efficient solar cell can be obtained if there is no misalignment with the electrode, but if the misalignment occurs, the photoelectric conversion efficiency is extremely reduced. There was a problem to do.

JP 2004-193350 A

  This invention is made | formed in view of the said situation, and it aims at providing the manufacturing method and electrode formation apparatus of a photovoltaic cell which can form an electrode appropriately on a high concentration selective diffusion layer.

In order to achieve the above object, the present invention provides the following solar cell manufacturing method and electrode forming apparatus.
[1] In a method for manufacturing a solar battery cell, wherein an emitter layer having a high-concentration selective diffusion layer having a predetermined pattern is formed on a semiconductor substrate, an antireflection film is formed thereon, and an electrode is further formed on the antireflection film. Irradiating a semiconductor substrate having a high-concentration selective diffusion layer of a predetermined pattern with light including a wavelength region that passes through the semiconductor substrate, and the intensity of the light transmitted through the semiconductor substrate or reflected by the semiconductor substrate The distribution is detected, and then the position area of the high-concentration selective diffusion layer is identified from the detected light intensity distribution, and then the electrode formed on the semiconductor substrate based on the position-area identification result of the high-concentration selective diffusion layer is detected. A method for manufacturing a solar cell, comprising determining a position region and forming the electrode in the position region.
[2] The method for producing a solar cell according to [1], wherein the electrode is formed by a screen printing method.
[3] The position region of the electrode in the semiconductor substrate is determined so that the overlap area of the position region of the identified high concentration selective diffusion layer and the position region of the electrode to be formed is maximized. The manufacturing method of the photovoltaic cell as described in 1] or [2].
[4] After forming the electrode on the semiconductor substrate, confirm the electrode formation position on the semiconductor substrate, and correct the electrode formation position on the next semiconductor substrate based on the confirmation result of the electrode formation position. The method for producing a solar battery cell according to any one of [1] to [3].
[5] The method for manufacturing a solar cell according to any one of [1] to [4], wherein the electrode is a finger electrode.
[6] A light source that irradiates a semiconductor substrate on which a high-concentration selective diffusion layer is formed with light including a wavelength region that is transmitted through the semiconductor substrate, and an intensity distribution of light that is transmitted through the semiconductor substrate or reflected by the semiconductor substrate A light intensity detecting unit having an optical sensor for detecting the light, an electrode forming unit for forming an electrode on the semiconductor substrate, and transporting the semiconductor substrate to the light intensity detecting unit and the electrode forming unit to form an electrode for the semiconductor substrate The position of the high-concentration selective diffusion layer in the semiconductor substrate is identified from the movable stage that holds the semiconductor substrate so that the position can be adjusted, and the light intensity detection result by the optical sensor. A control unit that adjusts the position of the movable stage; and a solar cell electrode forming apparatus.
[7] The electrode forming apparatus according to [6], wherein a wavelength range of light emitted from the light source and a detectable wavelength range of the optical sensor include 800 to 1200 nm.
[8] The electrode forming apparatus according to [6] or [7], wherein a distance between the optical sensor and the semiconductor substrate on the movable stage when detecting the light intensity distribution is 10 cm or less.
[9] The control unit adjusts the position of the movable stage in the electrode forming unit so that the overlap area of the position region of the identified high concentration selective diffusion layer and the position region of the electrode to be formed is maximized. The electrode forming apparatus according to any one of [6] to [8].
[10] The electrode forming apparatus according to any one of [6] to [9], wherein the optical sensor is a CCD image sensor.
[11] The control unit confirms an electrode formation position on the semiconductor substrate from an image obtained by imaging the semiconductor substrate on which the electrode has been formed by the optical sensor, and the next semiconductor based on the confirmation result of the electrode formation position. The electrode forming apparatus according to [10], wherein the electrode forming position on the substrate is corrected.

  According to the present invention, the position of the high-concentration selective diffusion layer of each semiconductor substrate is specified and the electrode is formed in accordance with this, so that the overlay accuracy between the high-concentration selective diffusion layer and the electrode is improved, and the solar cell A decrease in the conversion efficiency of the cell can be suppressed. Moreover, since the high concentration selective diffusion layer can be made as thin as the finger electrode line width, a solar cell having high conversion efficiency can be obtained.

It is the schematic which shows the structure of the electrode formation apparatus which concerns on this invention. It is a top view which shows the pattern of the exposure mask for high concentration selective diffusion layers. It is a top view which shows the pattern of screen plate making for light-receiving surface electrode formation.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiments.

Hereinafter, a method for producing a consumer-use high-efficiency solar cell using the electrode forming apparatus of the present invention will be described.
(Preparation of substrate)
Here, when the type of semiconductor substrate to be used (hereinafter also simply referred to as a substrate) is silicon, a single crystal substrate manufactured by the Czochralski (CZ) method or the float zone (FZ) method has higher performance. It is suitable for making the solar battery cell. The conductivity type may be N-type or P-type.

  In the case of a single crystal silicon substrate, the crystal plane orientation is preferably (100) when anisotropic etching with an alkaline solution is used when forming the following texture, but physical grinding is performed using a grinder or the like. In this case, other crystal plane orientations may be used. In addition, the substrate specific resistance is preferably, for example, 0.1 to 20 Ω · cm, and in particular, 0.5 to 3.0 Ω · cm is suitable for producing a high-performance solar cell.

  The thinner the substrate thickness, the lower the material cost. However, in the case of silicon, if it is too thin, the solar cell characteristics are lowered, the mechanical strength is also lowered, and the production yield is lowered. In order to maintain high solar cell characteristics and mechanical strength, a thickness of about 150 to 300 μm is desirable.

  As a method for removing damage from the substrate, a strong alkaline aqueous solution such as a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution can be used. The same object can be achieved with an aqueous acid solution such as hydrofluoric acid.

  Moreover, it is preferable to form the uneven | corrugated shape called a texture on the surface normally about a photovoltaic cell. The reason is that in order to reduce the reflectance of sunlight, it is necessary to cause the light receiving surface to perform reflection at least twice as much as possible. Therefore, the substrate is immersed in an aqueous solution containing sodium hydroxide and isopropyl alcohol at a concentration of 1 to 5% by mass and wet-etched to form random textures on both sides. The size of each of these peaks is about 1 to 20 μm. Other typical surface uneven structures include V-grooves and U-grooves. These can also be formed by using a grinding machine. Further, acid etching, reactive ion etching, or the like can be used as an alternative method for forming a random uneven structure.

(Formation of high concentration selective diffusion layer)
As in the above disclosed example, it is desirable to form a high-concentration selective diffusion layer immediately below the light-receiving surface electrode in order to produce a high-performance solar cell. Various methods for forming the high-concentration selective diffusion layer are disclosed. For example, a photomask method, a spin coating method, and a thermal diffusion method are exemplified as follows.

  First, the silicon substrate is heat-treated in an oxygen atmosphere at 850 to 950 ° C. for about 10 to 60 minutes to form a silicon oxide film with a thickness of about 10 to 30 nm. Next, a photoresist material is spin-coated on the light receiving surface side of the substrate, baking is performed, and the resist film is exposed and developed using a glass mask having a pattern overlapping the light receiving surface electrode. In this case, the photoresist material may be a positive type or a negative type. In the case of the positive type, the irradiated portion of the resist film is removed with an alkali developer, and in the case of the negative type, the non-irradiated portion is removed. preferable. Next, the silicon oxide film is removed only in a portion where the photoresist film is removed by development by dipping in an aqueous solution of about 5% by mass of hydrogen fluoride, and the remaining resist film is completely removed by acetone dipping and sulfuric acid boiling. Next, a coating agent containing a dopant such as phosphoric acid is spin-coated on the patterned silicon oxide film and baked.

  Next, as a heat treatment method, for example, the substrate can be put into a heat treatment furnace by grooving a boat and processed by a predetermined thermal profile. At this time, materials such as quartz and silicon carbide (SiC) can be used for the boat and the core tube used. Quartz is preferable in terms of purity and cost.

  The thermal profile differs depending on the type and concentration of the dopant contained in the diffusing agent, other components, the amount of diffusing agent applied to the substrate, and the like. For example, when a diffusing agent containing phosphorus is used, the treatment can be performed at 850 to 950 ° C. for about 10 to 120 minutes.

  Various types of gases can be used as the process gas during the diffusion heat treatment. For example, nitrogen and oxygen can be used when considering the purity and cost. The flow rate of the process gas varies depending on the capacity of the heat treatment furnace to be used. For example, when a furnace tube having an inner diameter of 150 to 350 mm and a length of about 1500 to 3500 mm is used, nitrogen is 5 to 40 L / min, oxygen is 0.025 to 0 The flow rate may be about 20 L / min.

  As a result, the portion where the oxide film is removed has a sheet resistance of 10Ω / □ to 100Ω / □, whereas the sheet resistance where the oxide film is present corresponds to the sheet resistance where there is no oxide film. Bigger than.

(Joining separation)
After the dopant is diffused by the above method or the like, for example, a junction separation process can be performed here. Junction separation means that the positive electrode and the negative electrode of a solar battery cell are connected by a dopant diffusion layer of the same conductivity type to prevent short-circuiting and deterioration of the characteristics. And the negative electrode are not connected by a dopant diffusion layer of the same conductivity type.

  As a bonding separation method, any method such as a method of etching a substrate such as dry etching or wet etching, a physical grinding method using a grinding machine, or an ablation method using a laser beam may be used. Further, it is not always necessary to perform the junction separation after the diffusion heat treatment.

(Glass layer removal)
A dopant glass layer (phosphorus glass in the case of phosphorus) is formed on the surface of the substrate subjected to the diffusion heat treatment and serves as a surface recombination center. Therefore, the dopant glass layer is removed using hydrogen fluoride or the like. Depending on the diffusing agent used, hydrogen fluoride alone may not be completely removed, so that general cleaning of the semiconductor may be continued. General cleaning includes cleaning using ammonia and aqueous hydrogen peroxide, cleaning using hydrochloric acid and aqueous hydrogen peroxide, and the like.

(Formation of surface protective layer and antireflection film)
Next, a surface protective film and an antireflection film are deposited on the emitter layer. The film types include silicon oxide film, silicon nitride film, aluminum oxide, titanium dioxide film, zinc oxide film, tin oxide film, etc., but the appropriate film type varies depending on the conductivity type of the emitter layer, and it is highly functional. In order to function as an antireflection film, the order of film formation and the film thickness are different. For example, by forming a silicon nitride film on the phosphorus diffusion layer using a direct plasma CVD apparatus having a frequency of 250 kHz, a surface protective film and antireflection film can be obtained. The film thickness of the silicon nitride film at this time is suitably 70 to 100 nm because it also serves as an antireflection film. In addition to the above, the formation method includes a remote plasma CVD method, a coating method, a vacuum deposition method, and the like. From an economical viewpoint, it is preferable to form the silicon nitride film as described above by the plasma CVD method. Furthermore, if a film having a refractive index between 1 and 2, such as a magnesium difluoride film, is formed on the antireflection film so that the total reflectance is minimized, the reflectance is further reduced. The current density is increased.

(Electrode formation)
Next, for example, using the electrode forming apparatus of the present invention as shown in FIG. 1, an electrode is formed on the light receiving surface side in the following procedure.

  As shown in FIG. 1, the electrode forming apparatus of the present invention includes a light source 1 for irradiating a semiconductor substrate 6 on which a high-concentration selective diffusion layer 7 is formed with light including a wavelength region that passes through the semiconductor substrate 6 and the semiconductor substrate. A light intensity detection unit having an optical sensor 2 for detecting an intensity distribution of light transmitted through 6, an electrode formation unit 5 for forming an electrode on the semiconductor substrate 6, and the semiconductor substrate 6 as the light intensity detection unit and the electrode. A movable stage 4 that is transported to the forming unit 5 and holds the semiconductor substrate 6 so that the electrode formation position with respect to the semiconductor substrate 6 can be adjusted, and a high-concentration selective diffusion layer in the semiconductor substrate 6 based on the light intensity detection result by the optical sensor 2 7, and a control unit (computer 3) that adjusts the position of the movable stage 4 in the electrode forming unit 5 based on the identification result.

  Here, the wavelength region of the light emitted from the light source 1 desirably includes a range of 800 to 1200 nm when a single crystal silicon substrate is used as the semiconductor substrate 6. This is because light having a wavelength shorter than that in the wavelength region may be absorbed by the single crystal silicon substrate and a sufficient transmitted light intensity may not be obtained, and light having a wavelength longer than the wavelength region may not be absorbed by the single crystal silicon. This is because the difference in transmitted light intensity between the high concentration selective diffusion layer 7 and other portions may not be sufficiently obtained.

  The optical sensor 2 is not particularly limited as long as it uses a light receiving element (photodiode) that can measure the intensity distribution of transmitted light or reflected light in a predetermined wavelength region from the semiconductor substrate 6. For example, a CCD image sensor (CCD It may be a digital camera equipped with an element. At this time, it is preferable that the detectable wavelength region of the light of the optical sensor 2 corresponds to the wavelength region of the light emitted from the light source 1 described above, for example, a wavelength region of 800 to 1200 nm is included as the detectable wavelength region.

  Further, in order to accurately overlap the high concentration selective diffusion layer 7 and the electrode to be formed over the entire surface of the semiconductor substrate 6, it is desirable to detect the light intensity distribution over the entire surface of the semiconductor substrate 6 by the optical sensor 2, and its resolution. The higher the better.

  Note that the digital camera as the optical sensor 2 may include a short wavelength filter, a long wavelength filter, or the like, depending on the optical characteristics of an imaging element such as a CCD element included. This is for selectively detecting the light transmitted through the semiconductor substrate 6 and cutting the light in the wavelength region serving as a noise component so that the position region of the high concentration selective diffusion layer 7 can be identified.

  The number of digital cameras used is not necessarily one, and a plurality of cameras may be used at the same time in consideration of the optical magnification and resolution of the lens. It is also possible to shoot only a part of it at multiple locations.

  In the configuration example shown in FIG. 1, the light source 1 is installed on the first plane side (lower side in the figure) of the semiconductor substrate 6, and the optical sensor 2 is installed on the second plane side (upper side in the figure) of the semiconductor substrate 6. The incident light 8 emitted from the light source 1 is transmitted through the semiconductor substrate 6 and the transmitted light 9 is detected by the optical sensor 2. Both the light source 1 and the optical sensor 2 are installed on the second plane side of the semiconductor substrate 6, the incident light 8 irradiated from the light source 1 is reflected by the semiconductor substrate 6, and the reflected light is reflected by the optical sensor 2. It is good also as a structure to detect.

  The computer 3 is connected to the optical sensor 2, the movable stage 4, and the electrode forming unit 5 so that they can communicate with each other and can be controlled. Further, from the viewpoint of productivity, the computer 3 processes the light intensity distribution detected by the optical sensor 2 (including an image captured by a digital camera when the optical sensor 2 is a digital camera) in as short a time as possible (image processing). It is desirable to include a computing element capable of).

  The movable stage 4 moves to any position of the light intensity detection unit and the electrode formation unit 5 under the control of the computer 3 while holding the semiconductor substrate 6. Although the movable stage 4 depends on the electrode forming method employed in the electrode forming portion 5, it is desirable that the movable stage 4 has sufficient rigidity for stable electrode formation and can be repeatedly moved with high accuracy to any position. Is desirable. Further, the light from the light source 1 is irradiated on the semiconductor substrate 6 and the light transmitted through the semiconductor substrate 6 can be detected by the optical sensor 2 on all or part of the contact portion with the semiconductor substrate 6 on the movable stage 4. What is provided with the window material of the raw material which can permeate | transmit the light of the light source 1 is desirable. Any material may be used for the window material as long as it transmits light in the wavelength region of the light source 1. For example, plastic such as quartz or acrylic resin can be used.

  In addition, it is desirable that the distance between the optical sensor 2 and the semiconductor substrate 6 on the movable stage 4 can be set within a distance of 10 cm. If the distance between the two is set at a distance of 10 cm or more, depending on the texture structure of the semiconductor substrate 6 and the pattern of the high concentration selective diffusion layer 7, it may be difficult to recognize the pattern of the high concentration selective diffusion layer 7. . Therefore, by reducing the distance between the semiconductor substrate 6 fixed on the movable stage 4 and the optical sensor 2 in this way, the influence of light scattering due to the texture structure of the semiconductor substrate 6 can be reduced, and pattern recognition is possible. It becomes.

An example of a specific procedure for forming the light receiving surface electrode is as follows. Here, a case where the optical sensor 2 is a digital camera will be described.
(Procedure 1) First, as a preparation stage, the single crystal silicon substrate is prepared in advance as a dummy substrate, the dummy substrate is vacuum-adsorbed and fixed on the movable stage 4 placed at the initial setting position, and the movable stage 4 is attached to the electrode. It moves to the formation part 5, and electrode formation is performed.

  The electrode forming method of the electrode forming portion 5 performed here may be a screen printing method generally used as an electrode forming method of a solar battery cell, but may be an intaglio printing method, an ink jet printing method, or other printing. The method may be used. Note that electrode forming methods such as vapor deposition are not suitable for the present invention because of the property of forming electrodes on the entire surface of the substrate 6. The screen printing method is desirable in terms of cost and productivity.

(Procedure 2) Next, the movable stage 4 is moved below the optical sensor 2 of the light intensity detection unit, an electrode pattern actually printed is photographed, and the image image is processed by the computer 3, whereby the electrode is processed. The pattern is recognized and stored as the position area information of the electrode formed on the semiconductor substrate in the case of the movable stage position arranged this time in the electrode forming unit 5.

(Procedure 3) Next, as a printing stage, the semiconductor substrate 6 having the high-concentration selective diffusion layer 7 on the light receiving surface side is vacuum-adsorbed and fixed on the movable stage 4 from the non-light receiving surface side. High density selection is achieved by irradiating light from the light source 1 from the light receiving surface side, detecting the intensity distribution of the light transmitted through the semiconductor substrate 6 by the optical sensor 2 installed above the light receiving surface side, and performing image processing by the computer 3 The position area of the diffusion layer 7 is identified. In this case, since the high-concentration selective diffusion layer 7 absorbs light transmitted through the semiconductor substrate 6, a region having a relatively low intensity is identified as the high-concentration selective diffusion layer 7 as a light intensity distribution on the detected semiconductor substrate surface. The

  In addition, when light from the light source is irradiated from the light receiving surface side of the semiconductor substrate 6 and the intensity distribution of the reflected light is detected by the optical sensor 2, the light is reflected by the high-density selective reflection layer 7, so that the light is detected. A region having a relatively high intensity as the light intensity distribution on the semiconductor substrate surface is identified as the high concentration selective diffusion layer 7.

(Procedure 4) Next, using the movable stage 4, the electrode formation position of the semiconductor substrate 6 with respect to the high concentration diffusion layer 7 is aligned, and the electrode is formed. That is, the semiconductor substrate 6 is slid to a predetermined position below the electrode forming portion 5 (position of the movable stage 4 indicated by a dotted line in FIG. 1), and then electrode formation is performed.

  The alignment here means a semiconductor substrate in which the overlapping area of the position region of the high-concentration selective diffusion layer 7 identified by the computer 3 within the field of view of the optical sensor 2 and the position region of the electrode to be formed is maximized. 6 is obtained by moving the semiconductor substrate 6 to the electrode printing position of the electrode forming portion 5 so that the electrode is formed in the position region of the electrode in the target semiconductor substrate 6. As a result, the electrode can be formed by accurately aligning with the high concentration selective diffusion layer 7.

  In addition, after electrode printing, the movable stage 4 is slid under the optical sensor 2, the actually formed electrode is photographed, and image processing is performed by the computer 3, so that the electrode is formed on the semiconductor substrate 6 at the current movable stage position. It is desirable to recognize the position area of the recognized electrode, store the recognized position area information of the electrode as an electrode formation position, and apply it when aligning the semiconductor substrate 6 to be processed next time. It is preferable to update and correct the electrode formation position by this procedure every time the electrode is formed or every time a predetermined number of electrodes are formed. Thereby, the position shift of the high concentration selective diffusion layer and the electrode due to the variation in the position of the electrode formed in the electrode forming portion 5 can be suppressed.

(Procedure 5) Next, an electrode paste containing silver or aluminum is formed on the non-light-receiving surface side of the semiconductor substrate 6 by a screen printing method or the like.
(Procedure 6) Next, baking is performed with a predetermined thermal profile of about 700 to 850 ° C. to simultaneously form a light receiving surface electrode and a non-light receiving surface electrode.

  In the above example, a structure having a two-stage emitter structure on the light-receiving surface side, which is a general method for producing a high-efficiency solar cell for consumer use, has been described. In addition, the metal wrap-through structure and the back- It goes without saying that the present invention can also be applied to a solar cell having a contact structure when aligning a high concentration selective diffusion layer and an electrode.

  Examples of the present invention will be described below. In addition, this invention is not limited to the content of this Example.

[Example 1]
In the method for manufacturing a solar battery cell, a solar battery cell sample was manufactured under the following conditions.
(Preparation of semiconductor substrate 6)
The crystal is a boron-doped p-type single crystal manufactured by the CZ method, an as-sliced specific resistance of 0.5 to 3.0 Ω · cm, a plane orientation (100), a thickness of 200 μm, a 156 mm square silicon substrate, 1000 sheets are prepared. Then, it was immersed in a 40% by mass sodium hydroxide aqueous solution, the damaged layer was removed by etching, and a random texture was formed on both sides by the wet etching method described above.
(Formation of high concentration selective diffusion layer 7)
The substrate was dry oxidized at 900 ° C. for 30 minutes in an oxygen atmosphere to form a silicon oxide film with a thickness of 15 nm.
Next, a positive photoresist material was spin-coated on the light-receiving surface side of the substrate, baked at 100 ° C. for 20 minutes, and the resist film was exposed and developed using a glass mask having a pattern as shown in FIG. . The number of fine lines in the pattern of FIG. 2 at the time of exposure is 78, the length is 154 mm, the distance between the fine lines is 2.0 mm, and the opening width of the fine lines is 200 μm. The distance from the substrate edge on the side to the center of the first fine line pattern was 1000 μm.
Next, the silicon oxide film was removed only in the portion where the photoresist was removed by development by dipping in a 5% by mass hydrogen fluoride aqueous solution, and the remaining resist film was completely removed by acetone dipping and sulfuric acid boiling.
Next, a coating agent containing phosphoric acid was spin-coated on the patterned silicon oxide film and baked at 80 ° C. for 3 minutes.
Next, a diffusion heat treatment was performed at 900 ° C. for 40 minutes to form a high concentration selective diffusion layer 7.
(Joining separation)
Next, the outer peripheral part of the substrate was etched by several μm using a plasma etching apparatus to perform junction separation.
(Glass layer removal)
Next, the phosphor glass formed on the surface was etched with hydrofluoric acid, washed with a mixed solution of ammonia and hydrogen peroxide, and dried.
(Formation of surface protective layer and antireflection film)
Next, using a direct plasma CVD apparatus having a frequency of 250 kHz, a silicon nitride film having a thickness of 100 nm was formed on the substrate surface in an atmosphere of 450 ° C.

(Electrode formation)
Next, a screen having the pattern shown in FIG. 3 on the light receiving surface side is used using the electrode forming apparatus having the apparatus configuration shown in FIG. 1 having the digital camera 2 as the optical sensor 2 and the screen printer as the electrode forming unit 5. Using plate making, alignment is performed according to the following procedure so that the high-concentration selective diffusion layer 7 and the finger electrode pattern are accurately overlapped, and an electrode paste mainly composed of silver is screen-printed at 15 ° C. at 15 ° C. Dried for minutes. The number of finger electrode patterns in the pattern of FIG. 3 is 78, the length is 154 mm, the interval is 2.0 mm, the opening width is 100 μm, the number of bus bar electrode patterns is 3, the length is 154 mm, and the interval is 38.5 mm. The opening width was 1500 μm.

((Alignment and printing procedure))
<Preparation stage>
First, the single crystal silicon substrate was prepared as a dummy substrate, and the dummy substrate was vacuum-sucked and fixed on the movable stage 4 placed at the initial setting position.
Next, the movable stage 4 was slid to the reference position under the screen printer (image forming unit 5) to print the electrode paste.
Next, the movable stage 4 is slid under the digital camera (optical sensor 2), the actually printed electrode pattern is photographed, and the computer 3 performs image processing so that the electrode pattern on the dummy substrate is recognized, and the electrode It was stored as the formation position (positional data (reference position area) data of the electrodes on the substrate when formed at the reference printing position of the screen printing machine).

<Printing stage>
Next, the semiconductor substrate 6 having the high concentration selective diffusion layer 7 on the light receiving surface side was fixed on the movable stage 4 by vacuum suction on the non-light receiving surface side.
Next, the digital camera installed at the upper side of the light receiving surface is irradiated with light including a wavelength region of 800 to 1200 nm using the light source 1 from the non-light receiving surface side of the semiconductor substrate 6 having the high concentration selective diffusion layer 7. Then, the light transmitted through the semiconductor substrate 6 was detected, and the computer 3 performed image processing to identify the position area of the high concentration selective diffusion layer 7.
Next, using the movable stage 4, the stored electrode formation position and the high-concentration diffusion layer 7 were aligned, and the semiconductor substrate 6 was slid under the screen printing machine. Here, first, the position region (target position region) of the electrode on the semiconductor substrate 6 where the overlapping area of the position region of the high concentration selective diffusion layer 7 identified by the computer 3 and the position region of the electrode to be formed is maximized. Next, based on the stored reference position area of the electrode and the target position area determined this time, a slide amount from the reference print position of the screen printing machine, that is, a target print position is obtained, and the target print is performed by the computer 3. The movable stage 4 was moved to the position. Next, an electrode paste was printed on the semiconductor substrate 6 by a screen printer.

Next, an electrode paste containing silver was printed on the bus bar portion on the non-light-receiving surface side of the semiconductor substrate 6, and an electrode paste containing aluminum was printed on the entire surface other than that, and dried at 200 ° C. for 15 minutes.
Next, the light-receiving surface electrode and the non-light-receiving surface electrode were formed simultaneously by baking with a baking profile having a peak portion of 780 ° C. for 10 seconds.

[Example 2]
In Example 1, the following procedure is added after the printing procedure of the electrode forming step on the light receiving surface side to perform update correction of the electrode forming position. Otherwise, the electrode is formed under the same conditions as in Example 1, and the solar cell A cell sample was prepared.
<Electrode printing position update correction>
After electrode printing, the movable stage 4 is slid under the digital camera, the electrode positions actually formed are photographed, and image processing is performed by the computer 3, thereby the position area of the electrodes formed on the semiconductor substrate 6 is determined. Recognized and stored as an electrode formation position (position area data (corrected reference position area) data of the electrode on the substrate when formed at the target printing position of the screen printer).
The electrode formation position data was updated and corrected by the above procedure, and applied to the alignment in the printing stage of the electrode formation process of the semiconductor substrate 6 to be processed next.

[Comparative example] (Conventional method: Edge alignment method)
In Example 1, instead of the electrode forming apparatus of FIG. 1, a screen printing machine having a conventional alignment mechanism was used, and other than that, electrodes were formed under the same conditions as in Example 1 to produce a solar cell sample. . In the electrode forming step on the light receiving surface side, as a conventional edge alignment method, the high-concentration selective diffusion layer and the finger electrode pattern were aligned by the following procedure, and screen printing was performed.

((Alignment and printing procedure))
<Preparation stage>
First, the single crystal silicon substrate was prepared as a dummy substrate, and the dummy substrate was vacuum-sucked and fixed on a movable stage placed at an initial setting position.
Next, the edge portion of the dummy substrate was observed with a digital camera, and the movable stage was moved so that the edge portion of the dummy substrate was at a designated position in the visual field of the digital camera (hereinafter, this position is referred to as an edge designated position). .)
Next, the movable stage was slid under the screen printer to print the electrode paste.
Next, the distance from the substrate edge on the reference side to the center of the first finger electrode pattern of the electrode pattern printed on the dummy substrate is measured using an optical microscope, and the movable stage is set so that this distance becomes 1000 μm. The position was finely adjusted from the edge designation position, and printing of the dummy substrate, confirmation of the printing position, and fine adjustment of the movable stage position were repeated and stored as the electrode formation position.
<Printing stage>
Next, a semiconductor substrate having a high-concentration selective diffusion layer on the light receiving surface side was fixed by vacuum-adsorbing the non-light receiving surface side on the movable stage.
Next, alignment was performed at the stored electrode formation position using the movable stage.
Next, the movable stage was slid under the screen printer to print the electrode paste.

The characteristics of the solar battery cell produced as described above were measured with a current-voltage measuring machine using artificial sunlight having an air mass of 1.5.
Table 1 shows the average value and standard deviation of the solar cell characteristics of each 1000 solar cells produced in the examples and comparative examples.

As shown in Table 1, in Example 1, the fill factor significantly increased and the standard deviation decreased compared to the comparative example. This is presumably because the position accuracy of the high-concentration selective diffusion layer 7 in each semiconductor substrate 6 is specified and the electrodes are formed in accordance with this, thereby improving the accuracy of electrode superposition.
In addition, compared with Example 1, Example 2 further increased the fill factor and reduced the standard deviation. This is presumably because the electrode formation accuracy was further improved by confirming the electrode formation position after each electrode formation of the individual semiconductor substrate 6 and performing update correction each time.

1 Light source 2 Optical sensor 3 Computer (control unit)
DESCRIPTION OF SYMBOLS 4 Movable stage 5 Electrode formation part 6 Semiconductor substrate 7 High concentration selective diffusion layer 8 Incident light 9 Transmitted light 10 Glass mask 11 Mask pattern 20 Screen plate making 21 Finger electrode pattern 22 Busbar electrode pattern

Claims (11)

  In a method for manufacturing a solar cell, an emitter layer having a high-density selective diffusion layer having a predetermined pattern is formed on a semiconductor substrate, an antireflection film is formed thereon, and an electrode is further formed on the antireflection film. A semiconductor substrate having a high concentration selective diffusion layer is irradiated with light including a wavelength region that passes through the semiconductor substrate, and the intensity distribution of the light transmitted through the semiconductor substrate or reflected by the semiconductor substrate is detected. Then, the position region of the high concentration selective diffusion layer is identified from the detected light intensity distribution, and the position region of the electrode formed on the semiconductor substrate is then determined based on the position region identification result of the high concentration selective diffusion layer. A method of manufacturing a solar battery cell, comprising: determining and forming the electrode in the position region.   The method for manufacturing a solar cell according to claim 1, wherein the electrode is formed by a screen printing method.   The position region of the electrode in the semiconductor substrate is determined so that the overlap area of the position region of the identified high concentration selective diffusion layer and the position region of the electrode to be formed is maximized. The manufacturing method of the photovoltaic cell of 2.   After forming the electrode on the semiconductor substrate, the electrode formation position on the semiconductor substrate is confirmed, and the electrode formation position on the next semiconductor substrate is corrected based on the confirmation result of the electrode formation position. The manufacturing method of the photovoltaic cell of any one of Claims 1-3.   The said electrode is a finger electrode, The manufacturing method of the photovoltaic cell of any one of Claims 1-4 characterized by the above-mentioned.   A light source that irradiates a semiconductor substrate on which a high-concentration selective diffusion layer is formed with light including a wavelength region that passes through the semiconductor substrate, and an intensity distribution of light that is transmitted through the semiconductor substrate or reflected by the semiconductor substrate. A light intensity detection unit having an optical sensor, an electrode formation unit for forming an electrode on the semiconductor substrate, and transporting the semiconductor substrate to the light intensity detection unit and the electrode formation unit to adjust an electrode formation position with respect to the semiconductor substrate The position of the high concentration selective diffusion layer in the semiconductor substrate is identified from the movable stage holding the semiconductor substrate and the light intensity detection result by the optical sensor, and the movable stage of the electrode forming unit is identified based on the identification result. And a control unit that adjusts the position of the solar cell electrode forming apparatus.   The electrode forming apparatus according to claim 6, wherein a wavelength region of light emitted from the light source and a detectable wavelength region of the optical sensor include 800 to 1200 nm.   The electrode forming apparatus according to claim 6 or 7, wherein a distance between the optical sensor and the semiconductor substrate on the movable stage when detecting the light intensity distribution is 10 cm or less.   The control unit adjusts the position of the movable stage in the electrode forming unit so that the overlapping area of the identified position region of the high concentration selective diffusion layer and the position region of the electrode to be formed is maximized. Item 9. The electrode forming apparatus according to any one of Items 6 to 8.   The electrode forming apparatus according to claim 6, wherein the optical sensor is a CCD image sensor.   The control unit confirms an electrode formation position on the semiconductor substrate from an image obtained by imaging the semiconductor substrate after electrode formation by the optical sensor, and an electrode on the next semiconductor substrate based on a confirmation result of the electrode formation position The electrode forming apparatus according to claim 10, wherein the forming position is corrected.

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