CN104521002A - Solar cell manufacturing method - Google Patents

Solar cell manufacturing method Download PDF

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Publication number
CN104521002A
CN104521002A CN201280075188.5A CN201280075188A CN104521002A CN 104521002 A CN104521002 A CN 104521002A CN 201280075188 A CN201280075188 A CN 201280075188A CN 104521002 A CN104521002 A CN 104521002A
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slurry
semiconductor substrate
diffusion layer
silicon substrate
solar cell
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CN104521002B (en
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米泽雅人
西村邦彦
太田成人
森川浩昭
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Mitsubishi Electric Corp
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Mitsubishi Electric Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0216—Coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0216—Coatings
    • H01L31/02161—Coatings for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/02167—Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • H01L31/02168—Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells the coatings being antireflective or having enhancing optical properties for the solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/0256—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by the material
    • H01L31/0264—Inorganic materials
    • H01L31/028—Inorganic materials including, apart from doping material or other impurities, only elements of Group IV of the Periodic Table
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic Table
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/546—Polycrystalline silicon PV cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/547—Monocrystalline silicon PV cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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Abstract

The present application can easily realize a selective emitter structure by including the following steps: a first step that coats a portion of one surface of a first conductive-type semiconductor substrate (2) with a paste (21) that contains a second conductive-type impurity element; a second step that, inside a processing chamber, applies a first heat treatment to the semiconductor substrate in a gas atmosphere that does not contain the second conductive type impurity element and causes diffusion of the second conductive type impurity element from the paste to the lower region of the paste on the semiconductor substrate, thereby forming in the lower region of the paste on the semiconductor substrate a first impurity diffusion layer (3a) in which the second conductive type impurity element is diffused at a first concentration; and a third step that, inside the processing chamber, following the first heat treatment, applies a second heat treatment to the semiconductor substrate in a gas atmosphere that contains a dopant that contains the second conductive type impurity element and causes diffusion of the second conductive type impurity element from the gas containing the dopant to an exposed region not coated with paste on the one side of the semiconductor substrate, thereby forming on the exposed region a second impurity diffusion layer (3b) in which the second conductive type impurity element is diffused at a second concentration, which is lower than the first concentration.

Description

The manufacture method of solar cell
Technical field
The present invention relates to the manufacture method of solar cell.
Background technology
In general monocrystaline silicon solar cell or polysilicon solar cell, in order to be separated the charge carrier generated by irradiating sunray, need to form pn knot.Such as, when using p-type silicon substrate as substrate, by the sensitive surface side of Shi Lindeng 5 race Elements Diffusion to substrate, form N-shaped silicon layer in the sensitive surface side of substrate, thus form pn knot.The impurity element being diffused into substrate is in this wise called alloy.
That is, when using p-type monocrystalline silicon substrate or p-type polycrystalline silicon substrate as substrate, by at the temperature of 700 DEG C ~ about 1000 DEG C by the sensitive surface side of phosphorus system alloy thermal diffusion to substrate, thus form diffusion layer on two-sided whole of substrate.Then, remove the diffusion layer of unwanted part as required and form diffusion layer used for solar batteries.
In addition, when using N-shaped monocrystalline silicon substrate or N-shaped polycrystalline silicon substrate as substrate, form p-type silicon layer to the sensitive surface side of substrate in the sensitive surface side of substrate by Shi Pengdeng 3 race Elements Diffusion, thus form pn knot.
In addition, as the method for the photoelectric conversion efficiency of raising solar cell, the known sensitive surface side at substrate forms the method selecting emitter structure.So-called emitter structure is selected to be following structure: as in the monocrystalline silicon substrate of semiconductor or polycrystalline silicon substrate, the diffusion concentration of the alloy of the engaging zones with metal electrode engagement is set to the concentration higher than the diffusion concentration of the alloy in the region beyond this engaging zones, thus is easy to be joined together as the silicon substrate of semiconductor and metal electrode electricity.
In the sensitive surface side of substrate, the region beyond above-mentioned engaging zones is sensitive surface.The diffusion concentration of the alloy of sensitive surface is than low with the diffusion concentration of the alloy of the engaging zones of metal electrode engagement.Therefore, select emitter to there is combining again of the charge carrier of the impurity level that can reduce based on energy level and the advantage of light output electric current can be increased.
Formation method as such selection emitter structure proposes there is following method: use the ink discharge device coating agent that separately coating concentration of dopant is different or the different coating agent of alloy, formed by a heat treatment and select diffusion layer (for example, referring to patent documentation 1).In addition, also propose there is following method: use ink discharge device local change concentration of dopant and apply, formed by a heat treatment or laser irradiation locally etc. and select emitter structure (for example, referring to patent documentation 2, patent documentation 3).
Patent documentation 1: Japanese Unexamined Patent Publication 2004-221149 publication
Patent documentation 2: Japanese Unexamined Patent Publication 2003-224285 publication
Patent documentation 3: Japanese Unexamined Patent Application Publication 2005-506705 publication
Summary of the invention
But, according to above-mentioned prior art, have following problem: which kind of method all needs special device, or all need the operation implementing multiple complexity, and the maintenance of device is also difficult.The main cause that the manufacturing cost that these problems become solar cell rises.
In view of the above problems, the object of the invention is to obtain and can easily and at low cost manufacture the method for manufacturing solar battery having and select solar cell that emitter constructs, photoelectric conversion efficiency excellence.
In order to solve the problem and realize object, the feature of the manufacture method of solar cell of the present invention is, comprise: the first operation, to the slurry of the impurity element of part coating containing the second conduction type of the one side side of the semiconductor substrate of the first conduction type; Second operation, above-mentioned semiconductor substrate is implemented to the first heat treatment under the environment of the gas of the impurity element not containing the second conduction type in process chamber, make the impurity element of the second conduction type be diffused into the lower area of the above-mentioned slurry above-mentioned semiconductor substrate from above-mentioned slurry, thus form at the lower area of the above-mentioned slurry of above-mentioned semiconductor substrate the first impurity diffusion layer having spread the impurity element of the second conduction type with the first concentration; 3rd operation, in above-mentioned process chamber, then second heat treatment contained under the environment of dopant gas of the impurity element containing the second conduction type is implemented in above-mentioned first heat treatment to above-mentioned semiconductor substrate, make the impurity element of the second conduction type from the above-mentioned exposed area being diffused into the above-mentioned slurry of uncoated the one side side of above-mentioned semiconductor substrate containing dopant gas, thus formed with the second impurity diffusion layer having spread the impurity element of the second conduction type lower than the second concentration of above-mentioned first concentration in above-mentioned exposed area; 4th operation, removes above-mentioned slurry; 5th operation, above-mentioned first impurity diffusion layer forms sensitive surface lateral electrode; And the 6th operation, form rear side electrode in the another side side of above-mentioned semiconductor substrate.
According to the present invention, play and can easily and at low cost obtain the effect having and select solar cell that emitter constructs, photoelectric conversion efficiency excellence.
Accompanying drawing explanation
Fig. 1-1 is the plane graph of the schematic configuration of the solar cell that embodiments of the present invention are shown.
Fig. 1-2 is the important part sectional drawing of the schematic configuration of the solar cell that embodiments of the present invention are shown, is the important part sectional drawing at the line segment A-A place of Fig. 1-1.
Fig. 2 is the flow chart of an example of the manufacture method of solar cell for illustration of embodiments of the present invention.
Fig. 3-1 is the important part sectional drawing of an example of the manufacturing process of solar cell for illustration of embodiments of the present invention.
Fig. 3-2 is important part sectional drawings of an example of the manufacturing process of solar cell for illustration of embodiments of the present invention.
Fig. 3-3 is important part sectional drawings of an example of the manufacturing process of solar cell for illustration of embodiments of the present invention.
Fig. 3-4 is important part sectional drawings of an example of the manufacturing process of solar cell for illustration of embodiments of the present invention.
Fig. 3-5 is important part sectional drawings of an example of the manufacturing process of solar cell for illustration of embodiments of the present invention.
Fig. 3-6 is important part sectional drawings of an example of the manufacturing process of solar cell for illustration of embodiments of the present invention.
Fig. 3-7 is important part sectional drawings of an example of the manufacturing process of solar cell for illustration of embodiments of the present invention.
Fig. 4-1 is the plane picture of the important part before the resistance test that the screen printing plate employing stainless (steel) wire is shown under state (new product state).
Fig. 4-2 is plane pictures of the important part after the resistance test that the screen printing plate employing stainless (steel) wire is shown.
Fig. 5-1 is the plane picture of the important part before the resistance test that the screen printing plate employing resin web is shown under state (new product state).
Fig. 5-2 is plane pictures of the important part after the test that the screen printing plate B employing resin web is shown.
Fig. 6 is the figure of an example of the diffusion conditions that two stage continuous diffusing procedure (the first diffusing procedure and the second diffusing procedure) is shown.
Fig. 7-1 illustrates the phosphorous oxychloride (POCl based on during diffusing procedure 3) gas flow formation N-shaped impurity diffusion layer after the performance plot of change of square resistance of sensitive surface of p-type silicon substrate.
Fig. 7-2 be illustrate that width is arranged thermal diffusion furnace in p-type silicon substrate on the schematic diagram located.
Fig. 8 irradiates the state of light and the image that obtains with infrared camera Halogen lamp LED for shooting to the sensitive surface side defining the semiconductor substrate of antireflection film after forming the first N-shaped impurity diffusion layer and the second N-shaped impurity diffusion layer by two stage continuous diffusing procedure.
Fig. 9 is the image irradiating ultrared state with infrared camera miniature lamp for shooting to the sensitive surface side defining the semiconductor substrate of antireflection film after forming the first N-shaped impurity diffusion layer and the second N-shaped impurity diffusion layer by two stage continuous diffusing procedure and obtain.
(description of reference numerals)
1: solar cell; 2: semiconductor substrate (p-type silicon substrate); 3:n type impurity diffusion layer; 3a: the first N-shaped impurity diffusion layer; 3b: the second N-shaped impurity diffusion layer; 4: anti-reflection layer; 5: show silver-colored grid (grid) electrode; 6: show silver-colored bus electrode; 7: back of the body aluminium electrode; 8:p+ layer (BSF (Back Surface Field, back surface field)); 11: semiconductor substrate; 12: sensitive surface lateral electrode; 13: rear side electrode; 21: containing alloy slurry; 22 oxide-films; 31: stainless (steel) wire; 32: peristome; 33: resin web; 34: peristome; 51: thermal diffusion furnace; 52:p type silicon substrate.
Embodiment
Below, the execution mode of the manufacture method of solar cell of the present invention is described in detail based on accompanying drawing.In addition, the present invention is not limited to following describing, and suitably can change in the scope not departing from main idea of the present invention.In addition, in accompanying drawing shown below, for ease of understanding, the scaling of each parts is different from reality sometimes.Also be same between each width accompanying drawing.
Execution mode
Fig. 1-1 is the plane graph of the schematic configuration of the solar cell that embodiments of the present invention are shown.Fig. 1-2 is the important part sectional drawing of the schematic configuration of the solar cell that embodiments of the present invention are shown, is the important part sectional drawing at the line segment A-A place of Fig. 1-1.
In the solar cell 1 of execution mode, spread by phosphorus in the sensitive surface side of the semiconductor substrate 2 (hereinafter referred to as p-type silicon substrate 2) be made up of p-type silicon and form N-shaped impurity diffusion layer 3, forming the semiconductor substrate 11 with pn knot.In addition, N-shaped impurity diffusion layer 3 is formed the antireflection film 4 be made up of such as silicon nitride film (SiN film).In addition, can use in p-type monocrystalline silicon substrate or p-type polycrystalline silicon substrate as semiconductor substrate 2 a certain.In addition, as semiconductor substrate 2, be not limited to the silicon substrate of p-type, the silicon substrate of the polycrystalline of N-shaped or the monocrystalline silicon substrate of N-shaped can also be used.
In addition, in the sensitive surface side of p-type silicon substrate 2, the minute asperities (texture, texture) (not shown) of the texture structure being configured for sealing light is formed.Minute asperities (texture) be increased in sensitive surface the area of the light absorbed from outside, light is sealed structure in solar cell 1 by the reflectivity suppressed in sensitive surface, efficiency well.
Antireflection film 4 is made up of the silicon nitride film (SiN film) as dielectric film.In addition, antireflection film 4 is not limited to silicon nitride film (SiN film), can also use silicon oxide film (SiO 2film) or oxidation titanium film (TiO 2) dielectric film such as film formed.
In addition, at table silver grid (grid) electrode 5 of the multiple elongated strip of sensitive surface side spread configuration of semiconductor substrate 11, generally perpendicularly arrange table silver bus (bus) electrode 6 with this table silver gate electrode 5 conducting with this table silver gate electrode 5, each comfortable bottom surface sections is electrically connected with N-shaped impurity diffusion layer 3.Show silver-colored gate electrode 5 and Biao Yin bus electrode 6 is made up of ag material.
Show silver-colored gate electrode 5 there is the width of such as 70 μm ~ about 200 μm and configure substantially in parallel with the interval of such as about 2mm, the electricity that the inside of collection semiconductor substrate 11 sends.In addition, show silver-colored bus electrode 6 and there is the width of such as about 1mm ~ 3mm and often open configuration 2 ~ 4 in solar cell, the electricity collected by the silver-colored gate electrode 5 of table is fetched into outside.And, form the sensitive surface lateral electrode 12 as the first electrode in comb shape by the silver-colored gate electrode 5 of table and Biao Yin bus electrode 6.Sensitive surface lateral electrode 12 can cover the sunlight to semiconductor substrate 11 incidence, so it seems from the viewpoint improving generating efficiency, preferably reduce its area as much as possible, be generally configured to the table silver gate electrode 5 of comb shape such as Figure 1-1 and the table silver bus electrode 6 of strip.
The electrode material of the sensitive surface lateral electrode of silicon solar cell uses silver paste usually, and is added with such as nonex.Such glass is frit (frit) shape, such as formed with the composition of plumbous (Pb) 5 ~ 30wt%, boron (B) 5 ~ 10wt%, silicon (Si) 5 ~ 15wt%, oxygen (O) 30 ~ 60wt%, and, sometimes also mix the zinc (Zn) or cadmium (Cd) etc. of a few about wt%.Such nonex is dissolved by the heating of hundreds of DEG C (such as 800 DEG C), now has the character corroding silicon.In addition, generally in the manufacture method of system of crystallization silicon solar cell, use and utilize the characteristic of this glass frit (glass frit) to obtain the method for the electrical contact of silicon substrate and silver paste.
On the other hand, at the back side (with the face of sensitive surface opposition side) of semiconductor substrate 11, the back of the body aluminium electrode 7 be made up of aluminum is provided with throughout whole ground.And, form rear side electrode by back of the body aluminium electrode 7.
In addition, the p+ layer (BSF (Back Surface Field, back surface field)) 8 containing high concentration impurities is formed with in the skin section of the rear side of semiconductor substrate 11.P+ layer (BSF) 8 is arranged to obtain BSF effect, utilizes the electric field being with structure to improve p-type layer (semiconductor substrate 2) electron concentration, the electronics in p-type layer (semiconductor substrate 2) is not buried in oblivion.
And, in the solar cell 1 of execution mode, be formed with two kinds of layers as N-shaped impurity diffusion layer 3, thus form selection emitter structure.That is, in the skin section of the sensitive surface side of p-type silicon substrate 2, being formed with diffusion in high concentration at the lower area of sensitive surface lateral electrode 12 and near zone thereof has high concentration impurity diffusion layer (low resistance diffusion layer) the i.e. first N-shaped impurity diffusion layer 3a of N-shaped impurity.In addition, in the skin section of the sensitive surface side of p-type silicon substrate 2, do not forming the region of the first N-shaped impurity diffusion layer 3a, spreading low concentration impurity diffusion layer (high resistance diffusion layer) the i.e. second N-shaped impurity diffusion layer 3b of the impurity having N-shaped with being formed with low concentration.
Therefore, if set the Impurity Diffusion concentration of the first N-shaped impurity diffusion layer 3a as the first diffusion concentration, if the Impurity Diffusion concentration of the second N-shaped impurity diffusion layer 3b is the second diffusion concentration, then the second diffusion concentration is less than the first diffusion concentration.In addition, if set the resistance value of the first N-shaped impurity diffusion layer 3a as the first resistance value, if the resistance value of the second N-shaped impurity diffusion layer 3b is the second resistance value, then the second resistance value is greater than the first resistance value.
Above-mentioned sensitive surface lateral electrode 12 is formed on the first N-shaped impurity diffusion layer 3a.In addition, the region not forming sensitive surface lateral electrode 12 in the first N-shaped impurity diffusion layer 3a and the region being formed with the second N-shaped impurity diffusion layer 3b become the sensitive surface that light incides solar cell 1.
The solar cell 1 of the execution mode below formed like that, be formed with the first N-shaped impurity diffusion layer 3a that resistance is low in the bottom of the sensitive surface lateral electrode 12 of sensitive surface side, thus reduce the resistance (contact resistance) between p-type silicon substrate 2 and sensitive surface lateral electrode 12.In addition, the region in addition of sensitive surface side is formed with the second low N-shaped impurity diffusion layer 3b of impurity concentration, thus reduces electronics and occur and the recombination velocity buried in oblivion.Therefore, the solar cell 1 of execution mode has the selection emitter structure be made up of the first N-shaped impurity diffusion layer 3a and the second N-shaped impurity diffusion layer 3b.
Next, the manufacture method of the solar cell 1 of execution mode is described.Fig. 2 is the flow chart of an example of the manufacture method of solar cell for illustration of embodiments of the present invention.Fig. 3-1 ~ Fig. 3-7 is important part sectional drawings of an example of the manufacturing process of solar cell for illustration of embodiments of the present invention.
(silicon substrate preparatory process)
First, prepare such as the p-type silicon substrate 2 the most often used towards civil solar battery as semiconductor substrate.P-type silicon substrate 2 with band saw or multi-wire saw etc. by the monocrystal silicon of the silicon of cooling curing melting or polycrystal silicon ingot with saw blade cutting or be sliced into desired size and thickness manufactures, so damage when surface leaves section.Therefore, first, also take into account and remove this damage layer, and p-type silicon substrate 2 is impregnated in acid or warmed-up aqueous slkali, such as be impregnated in sodium hydrate aqueous solution or potassium hydroxide aqueous solution and carry out etched surfaces, thus removal occurs when cutting out silicon substrate and is present in the damage field of the near surface of p-type silicon substrate 2.The thickness removing the silicon substrate after damage is such as 180 μm, and overall dimension is 156mm × 156mm.
In addition, although be illustrated for the silicon substrate of p-type here, silicon substrate both can be p-type also can be N-shaped.In addition, silicon substrate both can be polycrystalline silicon substrate also can be monocrystalline silicon.
(texture formation process)
In addition, while removal damage, or after being connected on removal damage, minute asperities is formed as texture structure on the surface of the sensitive surface side of p-type silicon substrate 2.The solution being used in 80 DEG C ~ about 90 DEG C of the isopropyl alcohol (IPA) that with the addition of several ~ tens wt% in potassium hydroxide (KOH) aqueous solution of such as a few wt% carries out the anisotropic etching of p-type silicon substrate 2, forms pyramidal minute asperities (texture) on the surface of the sensitive surface side of p-type silicon substrate 2.Such texture structure is formed by the sensitive surface side at semiconductor substrate, the multipath reflection of light can be produced on the surface of solar cell, the light inciding solar cell is absorbed efficiently the inside of silicon substrate, can effectively reduce reflectivity and improve conversion efficiency.In general, by employing the anisotropic etching on the surface of the p-type silicon substrate 2 of alkali, the texture structure of random cone shape is formed.
In addition, in the manufacture method of the solar cell of present embodiment, about formation method and the shape of texture structure, be not particularly limited.Such as also can make any one method in waiting with the following method: use the aqueous alkali containing isopropyl alcohol or mainly comprise the method for acid etching of mixed liquor of hydrofluoric acid, nitric acid; P-type silicon substrate 2 surface forming part be provided with the mask material of opening, by obtaining the method for honeycomb structure or reverse taper structure across the surface being etched in p-type silicon substrate 2 of this mask material; Or employ the method for reactant gas etching (RIE:Reactive Ion Etching, reactive ion etching).
(working procedure of coating containing alloy slurry)
Next, in order to form high concentration impurity diffusion layer (low resistance diffusion layer) i.e. the first N-shaped impurity diffusion layer 3a selected in emitter structure, use silk screen print method apply on a face of p-type silicon substrate 2 formed as the coating agent containing diffuse source contain alloy slurry 21 (Fig. 3-1, step S10).At this, owing to employing p-type silicon substrate 2, thus in order to use such as phosphorus to use as alloy containing phosphorus compound containing alloy slurry 21.In addition, as alloy, 5 race's elements beyond dephosphorization, can also be used.In addition, when using N-shaped silicon substrate as silicon substrate, use containing such as Peng Deng 3 race element as alloy containing alloy slurry.
At this, do not distil be used in the thermal diffusion temperature (heat treatment temperature) of the first following diffusing procedure containing alloy slurry 21 under yet and do not burn (burning up) and the resin slurry of non-acid neutrality.Contain alloy slurry 21 as such, can use such as diffusion slurry YT-2100-N used for solar batteries (Hitachi Chemical Co., Ltd.'s manufacture).Below, the situation employing this diffusion slurry YT-2100-N used for solar batteries (Hitachi Chemical Co., Ltd.'s manufacture) and be used as containing alloy slurry 21 is described.
First N-shaped impurity diffusion layer 3a forms sensitive surface lateral electrode 12 by operation below, thus realizes the electrical contact of the first N-shaped impurity diffusion layer 3a and sensitive surface lateral electrode 12.Configuration error is there is when forming sensitive surface lateral electrode 12.Therefore, the profile that the forming position of the sensitive surface lateral electrode 12 of the first N-shaped impurity diffusion layer 3a in the face of p-type silicon substrate 2 to have had compared with the profile of sensitive surface lateral electrode 12 slightly to outside broadening, thus be formed as the shape larger than this sensitive surface lateral electrode 12.
Specifically, the screen printing plate that the width design of use peristome must be wider than the width of sensitive surface lateral electrode 12 carries out the silk screen printing containing alloy slurry 21.Such as, when the formation width of sensitive surface lateral electrode is 100 μm, consider the position deviation of sensitive surface lateral electrode 12, the width containing alloy slurry 21 is set to 250 μm.
When corresponding to that gate electrode width is 100 μm, gate electrode length is 153mm, gate electrode number is the screen printing plate of the structure of 70, aperture area is about 2.2cm 2.In this situation, be about 50mg for the use amount containing alloy slurry 21 in the printing of the p-type silicon substrate 2 of 1.
The specification of the screen printing plate that the silk screen printing containing alloy slurry 21 in present embodiment uses such as described below.In addition, the screen printing plate for the formation of the first N-shaped impurity diffusion layer 3a is shown here, this first N-shaped impurity diffusion layer 3a is formed in the forming position of the table silver gate electrode 5 in sensitive surface lateral electrode 12.
(the screen printing plate A containing alloy slurry: gate electrode forming position is used)
Net: stainless (steel) wire #290
Stainless (steel) wire linear diameter: 20 μm
A/F: 250 μm
Opening length: 153.5mm
(the screen printing plate B containing alloy slurry: gate electrode forming position is used)
Net: resin web #420
Resin web linear diameter: 27 μm
A/F: 250 μm
Opening length: 153.5mm
At this, the resistance test result that research obtains the impact that screen printing plate A and screen printing plate B causes as the YT-2100-N used containing alloy slurry 21 is described.In resistance test, YT-2100-N to be placed on screen printing plate and after placing 24 hours, with alcohol washes, to check feel state and apparent condition.
Fig. 4-1 is the plane picture of the important part before the resistance test that the screen printing plate A employing stainless (steel) wire is shown under state (new product state).(a) of Fig. 4-1 to be multiplying power be image of 50 times, (b) of Fig. 4-1 to be multiplying power be image of 200 times.Fig. 4-2 is plane pictures of the important part after the resistance test that the screen printing plate A employing stainless (steel) wire is shown.(a) of Fig. 4-2 to be multiplying powers be image of 50 times, (b) of Fig. 4-2 to be multiplying powers be image of 200 times.The surface state of the periphery of the peristome 32 of the forming surface side (opposition side of emulsion applicator surface) of the stainless (steel) wire 31 that screen printing plate A loads slurry has been shown in Fig. 4-1 and Fig. 4-2.
Fig. 5-1 is the plane picture of the important part before the resistance test that the screen printing plate B employing resin web is shown under state (new product state).(a) of Fig. 5-1 to be multiplying power be image of 50 times, (b) of Fig. 5-1 to be multiplying power be image of 200 times.Fig. 5-2 is plane pictures of the important part after the test that the screen printing plate B employing resin web is shown.(a) of Fig. 5-2 to be multiplying powers be image of 50 times, (b) of Fig. 5-2 to be multiplying powers be image of 200 times.The surface state of the periphery of the peristome 34 of the forming surface side (opposition side of emulsion applicator surface) of the resin web 31 that screen printing plate B loads slurry has been shown in Fig. 5-1 and Fig. 5-2.
To employ stainless (steel) wire 31 screen printing plate A resistance test after state confirm time, the same before confirming feel state and apparent condition and resistance test as shown in the Fig. 4-2 like that.In addition, for the screen printing plate A after resistance test, do not see yet and change in size and distortion occur.Therefore, the impact that YT-2100-N causes screen printing plate A is not seen.
In addition, to employ resin web 33 screen printing plate B resistance test after state confirm time, as shown in Fig. 5-2, confirm feel state the same with before resistance test with apparent condition.In addition, for the screen printing plate B after resistance test, do not see yet and change in size and distortion occur.Therefore, the impact that YT-2100-N causes screen printing plate B is not seen.
At use Acid Slurry as containing alloy slurry 21, the stainless (steel) wire on screen printing plate or resin web can be corroded.But, in present embodiment, owing to using non-acid resinene slurry as containing alloy slurry 21, so the corrosion of screen printing plate can be prevented.
The scraper plate used as the silk screen printing containing alloy slurry 21 can use the scraper plate of general polyurethane rubber and the scraper plate of silicon rubber.At this, the resistance test result that research obtains the impact that scraper plate causes as the YT-2100-N used containing alloy slurry 21 is described.In resistance test, putting in the YT-2100-N in container, the scraper plate test film A that the part burying the scraper plate cutting out polyurethane rubber underground obtains and cut out the part of scraper plate of silicon rubber and the scraper plate test film B that obtains after placing 24 hours, with alcohol washes, check feel state and apparent condition.
When state after the resistance test of the scraper plate test film A to polyurethane rubber confirms, confirm feel state the same with before resistance test with apparent condition.In addition, for the scraper plate test film A after resistance test, do not see yet and change in size and distortion occur.Therefore, the impact that the scraper plate of YT-2100-N on polyurethane rubber causes is not seen.
When state after the resistance test of the scraper plate test film B to silicon rubber confirms, confirm feel state the same with before resistance test with apparent condition.In addition, for the scraper plate test film B after resistance test, do not see yet and change in size and distortion occur.Therefore, the impact that the scraper plate of YT-2100-N on silicon rubber causes is not seen.
When employ Acid Slurry as containing alloy slurry 21, the scraper plate of polyurethane rubber system or silicon rubber can be corroded.But, in present embodiment, owing to using non-acid resinene slurry as containing alloy slurry 21, so the corrosion of scraper plate can be prevented.
Low containing the viscosity under the static condition of alloy slurry 21 when, if will be configured on screen printing plate containing alloy slurry 21, then continue to launch on screen printing plate containing alloy slurry 21.Therefore, when carrying out the continuous printing containing the printing of alloy slurry 21 continuously to multiple p-type silicon substrate 2, the wide scraper that the frame that preferred use reaches screen printing plate is such.In addition, also can the little frame preventing from launching containing alloy slurry 21 be set in the inner side of the frame of screen printing plate.In addition, in order to improve containing the viscosity itself under the static condition of alloy slurry 21, such as, also thixotropic agent can be added in slurry.
In addition, must form the first N-shaped impurity diffusion layer 3a as described above with the shape larger than sensitive surface lateral electrode 12, this first N-shaped impurity diffusion layer 3a is formed with sensitive surface lateral electrode 12.Therefore, the area of application containing alloy slurry 21 also must set larger than the forming region of sensitive surface lateral electrode 12.Therefore, the area of the peristome of screen printing plate is also large than the area of the peristome forming sensitive surface lateral electrode 12 screen printing plate used.If the peristome of screen printing plate is large, then employing the low slurry of the viscosity under static condition as when containing alloy slurry 21, even between presswork withholding period, sometimes also drip from peristome containing alloy slurry 21.In this case, in containing the printing of alloy slurry 21, produce contamination, and the printing containing alloy slurry 21 under the pattern expected cannot be realized.
Contain in the printing of alloy slurry 21 at such, as the countermeasure of staiing, can enumerate and peristome large for the area in screen printing plate segmentation is cut and is set to shape of slit.Such as, when the application width of the first N-shaped impurity diffusion layer 3a be 250 μm, namely the A/F of screen printing plate is 250 μm, the width of peristome entirety is set to 250 μm, and segmentation cuts open oral area in the direction of the width, and peristome is set to shape of slit.Thus, can not printing quality be affected, and low the dripping from peristome containing alloy slurry 21 of the viscosity under static condition can be prevented.
In addition, when silk screen printing, the pollution of the p-type silicon substrate 2 preferably preventing life-span inhibiting factor (life time killer) from causing.Particularly, for the transfer system of the p-type silicon substrate 2 in screen process press, mounting p-type silicon substrate 2 workbench, other with the contact site of p-type silicon substrate, eliminate the existence of life-span inhibiting factor such as metal impurities as much as possible.
In addition, after silk screen printing used containing alloy slurry 21 can use when electrode is formed containing discarding as combustiblerefuse in the same manner as aluminum slurry.
In addition, although what illustrate is use silk screen print method to apply containing the coating process of alloy slurry 21 as to p-type silicon substrate 2 herein, the coating process containing alloy slurry 21 is not limited to silk screen print method.
(drying process containing alloy slurry)
After containing the printing of alloy slurry 21, carry out the drying process (step S10) making this contain alloy slurry 21 drying.After containing the printing of alloy slurry 21, when slow containing the rate of drying of alloy slurry 21, the printed patterns that printed contamination containing alloy slurry 21 and can not get is expected.Therefore, preferably promptly carry out the drying containing alloy slurry 21, such as, preferably use infrared heater etc. to improve temperature containing alloy slurry 21 to make it dry.
Such as, when containing when containing terpinol as solvent in alloy slurry 21, preferably make containing alloy slurry 21 dry with the temperature of more than 200 DEG C.Such as, when containing when containing ethyl cellulose as resinous principle in alloy slurry 21, in order to make ethyl cellulose burn, make containing alloy slurry 21 dry at the temperature preferably more than 400 DEG C.In addition, though to have made lower than the temperature of 400 DEG C containing alloy slurry 21 drying when, owing to can ethyl cellulose be made to burn in diffusing procedure afterwards, so also no problem.
Containing the drying of alloy slurry 21 preferably under the state of open system, carry out under the horizontal state be namely available at the superjacent air space of the printing surface containing alloy slurry 21 of p-type silicon substrate 2.When the state overlapping in the vertical direction with the interarea of p-type silicon substrate 2 has carried out the drying containing alloy slurry 21, be attached to the reason other p-type silicon substrate 2 becoming characteristic of solar cell deterioration after volatilizing again containing the terpinol contained in alloy slurry 21 (solvent) etc.
In addition, if carry out the drying containing alloy slurry 21 under airtight state, such as, be attached to containing the terpinol (solvent) etc. contained in alloy slurry 21 reason p-type silicon substrate 2 becoming characteristic of solar cell deterioration after volatilizing again.
When drying containing alloy slurry 21 cannot be carried out in open system by superimposed for p-type silicon substrate 2 and drying, preferably the interval between p-type silicon substrate 2 is established wider, make dry air circulate by force.Thereby, it is possible to prevent the volatile ingredients such as terpinol (solvent) to be attached to again on p-type silicon substrate 2.In addition, when making dry air circulate by force, preferably the flow set of the dry air of circulation is obtained larger.By the flow set of dry air is obtained larger, can make containing alloy slurry 21 dry quickly, and can reliably prevent the volatile ingredients such as terpinol (solvent) to be attached to p-type silicon substrate 2 again.
(the first diffusing procedure)
After containing alloy slurry 21 drying, p-type silicon substrate 2 is put into thermal diffusion furnace, carry out thermal diffusion operation i.e. the first diffusing procedure (the first heat treatment) (Fig. 3-2, the step S20) based on the alloy (phosphorus) containing alloy slurry 21.This first diffusing procedure is the first stage in two stage continuous diffusing procedure.
First diffusing procedure is in thermal diffusion furnace, makes such as nitrogen (N 2), oxygen (O 2), the mist (N of nitrogen and oxygen 2/ O 2), to carry out under the ambient condition of the circulation such as air.The flow of environmental gas is not particularly limited.In addition, the flow-rate ratio of each gas when mist is also not particularly limited, and can be arbitrary flow.Such as, with the mist (N of nitrogen and oxygen 2/ O 2) flow be N 2: 5.7SLM, O 2: 0.6SLM carries out.That is, in the first diffusing procedure, do not use phosphorous oxychloride (POCl 3), except containing alloy slurry 21, there is not the diffuse source of alloy (phosphorus).In addition, the first diffusing procedure keeps carrying out to 10 minutes for 5 minutes with the temperature of such as 870 DEG C ~ 940 DEG C.Therefore, in p-type silicon substrate 2, only the thermal diffusion carrying out alloy (phosphorus) containing the bottom in the region of alloy slurry 21 is being printed with.Thus, in the face of p-type silicon substrate 2, in region slightly to outer expandable of the profile of the forming region than sensitive surface lateral electrode 12, only carry out the diffusion of alloy (phosphorus).
By this first diffusing procedure, alloy (phosphorus) from containing alloy slurry 21 to the surface of p-type silicon substrate 2 should containing (with the first diffusion concentration) thermal diffusion and form the first N-shaped impurity diffusion layer 3a in high concentration of the lower area of the printing zone of alloy slurry 21.The region that the profile that 1n type impurity diffusion layer 3a is formed in the forming region of sensitive surface lateral electrode 12 frequently in the face of p-type silicon substrate 2 expands slightly to outside, becomes lower area and the near zone thereof of sensitive surface lateral electrode 12 in solar cell 1.
In addition, in the first diffusing procedure with containing oxygen (O 2) condition when having carried out thermal diffusion, the region of not printing containing alloy slurry 21 in the surface of p-type silicon substrate 2, is formed with thin oxide-film 22 because of impact during thermal diffusion on surface.
In addition, containing after alloy slurry 21 drying, need p-type silicon substrate 2 to put into thermal diffusion furnace fast.After the drying containing alloy slurry 21 absorb the moisture etc. in air when, be also deployed into the region beyond printing zone containing alloy slurry 21, the printed patterns expected will be destroyed.Therefore, especially should be noted that the moisture absorption containing alloy slurry 21 in the season that humidity is high.
(the second diffusing procedure)
After the first diffusing procedure terminates, then carry out based on phosphorous oxychloride (POCl 3) thermal diffusion operation i.e. the second diffusing procedure (the second heat treatment) (Fig. 3-3, the step S30) of alloy (phosphorus).That is, p-type silicon substrate 2 is not taken out from thermal diffusion furnace, and after the first diffusing procedure, then carry out the second diffusing procedure (continuous DIFFUSION TREATMENT).This second diffusing procedure is the second stage in two stage continuous diffusing procedure.
Second diffusing procedure there is phosphorous oxychloride (POCl in thermal diffusion furnace 3) gas when to carry out.That is, the first diffusing procedure is not containing phosphorous oxychloride (POCl 3) environmental condition under carry out thermal diffusion, and the second diffusing procedure contains phosphorous oxychloride (POCl in the diffuse source as alloy (phosphorus) 3) environmental condition under carry out thermal diffusion.The flow of environmental gas is not particularly limited, and suitably sets according to each conditions such as diffusion concentration, diffusion temperature, diffusion times.In addition, from the first diffusing procedure 870 DEG C ~ 900 DEG C of temperature are dropped to such as 800 DEG C ~ 840 DEG C and keep carrying out for 10 minutes ~ 20 minutes by the second diffusing procedure.
By this second diffusing procedure, alloy (phosphorus) forms the second N-shaped impurity diffusion layer 3b with the concentration (the second diffusion concentration) lower than the first N-shaped impurity diffusion layer 3a to the exposed area thermal diffusion of region, i.e. the p-type silicon substrate 2 except containing the printing zone of alloy slurry 21 in the surface of p-type silicon substrate 2.Second N-shaped impurity diffusion layer 3b becomes the sensitive surface of incident light in solar cell 1.In addition, the surface of the p-type silicon substrate 2 after just completing the second diffusing procedure, is formed with the nature of glass (phosphosilicate glass, the PSG:phospho-silicate glass) layer (not shown) being deposited in surface during DIFFUSION TREATMENT.
Fig. 6 is the figure of an example of the diffusion conditions that two stage continuous diffusing procedure (the 1st diffusing procedure and the 2nd diffusing procedure) is shown.In figure 6, transverse axis illustrates the processing time in two stage continuous diffusing procedure, and the longitudinal axis illustrates the treatment temperature (in stove design temperature) (DEG C) in two stage continuous diffusing procedure.
In addition, in the first diffusing procedure with containing oxygen (O 2) condition when having carried out thermal diffusion, the region of not printing containing alloy slurry 21 in the surface of p-type silicon substrate 2, is formed with thin oxide-film 22 because of impact during thermal diffusion on surface.That is, form the region of the second N-shaped impurity diffusion layer 3b when the second diffusing procedure on the surface of p-type silicon substrate 2, be formed with thin oxide-film when the beginning of the second diffusing procedure.Therefore, the diffusion conditions of the second diffusing procedure changes according to the formational situation of this oxide-film 22.Particularly, at the oxygen (O that the first diffusing procedure is 100% 2) environment under when carrying out, oxide-film 22 is formed thicker, and in the second diffusing procedure, alloy (phosphorus) is difficult to diffusion, so should be noted that.Therefore, each condition such as flow, diffusion temperature, diffusion time adjusting environmental gas is needed.
In the second diffusing procedure, when adjusting the diffusion conditions of square resistance of the sensitive surface for obtaining expectation, need to pay attention to following item.The p-type silicon substrate 2 printed containing alloy slurry 21 is being carried out based on phosphorous oxychloride (POCl 3) the diffusion of phosphorus when, if diffusion conditions (temperature, pressure, flow etc.) is set to existing only based on phosphorous oxychloride (POCl by what do not use containing alloy slurry 21 on a silicon substrate 3) the diffusion of phosphorus to form the situation of N-shaped impurity diffusion layer identical, then the square resistance forming the sensitive surface after N-shaped impurity diffusion layer raises.
Its reason is, when the second diffusing procedure, consumes phosphorous oxychloride (POCl by the alloy slurry 21 that contains be printed on p-type silicon substrate 2 3).Therefore, in the second diffusing procedure, owing to consuming the phosphorous oxychloride (POCl of the amount proportional with the quantity of the p-type silicon substrate 2 putting into thermal diffusion furnace 3), so need to pay attention to this point when the diffusion conditions of adjustment second diffusing procedure.
As the method that can prevent the square resistance of the sensitive surface formed in this wise after N-shaped impurity diffusion layer from raising, following method can be enumerated.That is, with not print containing alloy slurry 21 on a silicon substrate existing based on phosphorous oxychloride (POCl 3) diffusion time compare, increase the phosphorous oxychloride (POCl of same treatment quantity 3) flow of gas.
Fig. 7-1 be when diffusing procedure is shown based on phosphorous oxychloride (POCl 3) gas flow formation N-shaped impurity diffusion layer after the performance plot of change of square resistance of sensitive surface of p-type silicon substrate 52.In Fig. 7-1, transverse axis illustrates the allocation position of the p-type silicon substrate 52 in the thermal diffusion furnace 51 that width is arranged, and the longitudinal axis illustrates the square resistance (Ω/) of the sensitive surface of the p-type silicon substrate 52 after diffusing procedure.Fig. 7-2 be illustrate that width is arranged thermal diffusion furnace in 51 p-type silicon substrate 52 on the schematic diagram located.Number on p-type silicon substrate 52 in Fig. 7-2 corresponds to the number (locating) of the transverse axis in Fig. 7-1.
◇ mark in Fig. 7-1 represent to do not print carry out containing the p-type silicon substrate 52 of alloy slurry existing only based on phosphorous oxychloride (POCl 3) the data of sample 1 of phosphorus diffusion.△ mark in Fig. 7-1 represents having printed the data of having carried out the sample 2 spread based on the phosphorus of above-mentioned two stage continuous diffusing procedure (the first diffusing procedure and the second diffusing procedure) containing the p-type silicon substrate 52 of alloy slurry.Phosphorous oxychloride (POCl in second diffusing procedure of sample 2 3) flow identical with the situation of sample 1.Zero mark in Fig. 7-1 represents having printed the data of having carried out the sample 3 spread based on the phosphorus of above-mentioned two stage continuous diffusing procedure (the first diffusing procedure and the second diffusing procedure) containing the p-type silicon substrate 52 of alloy slurry.Phosphorous oxychloride (POCl in second diffusing procedure of sample 3 3) flow-rate ratio sample 1 increase.
In this thermal diffusion furnace 51, import phosphorous oxychloride (POCl from the left end side Fig. 7-2 3) gas, be vented from right-hand member side.P-type silicon substrate 52 every tens with the state vacating predetermined distance is in the horizontal direction one group and longitudinally configure.And, on the bearing of trend of thermal diffusion furnace 51, vacate predetermined distance by multiple groups and configure.In addition, herein, in thermal diffusion furnace 51, put into hundreds of open p-type silicon substrate 52 and spread continuously.Wherein, fasten in illustrated pass, having illustrated the p-type silicon substrate 52 of the amount of 7 groups from the left end in thermal diffusion furnace in 51 in Fig. 7-1 and Fig. 7-2.
Known according to Fig. 7-2, by the phosphorous oxychloride (POCl in the second diffusing procedure 3) flow be set to identical with the situation of sample 1 and carried out sample 2 of two stage continuous diffusing procedure (the first diffusing procedure and the second diffusing procedure) when, along with at phosphorous oxychloride (POCl 3) circulating direction on advance, the square resistance forming the sensitive surface of the p-type silicon substrate 52 after N-shaped impurity diffusion layer raises.Its reason is, when the second diffusing procedure, consumes phosphorous oxychloride (POCl by the alloy slurry 21 that contains be printed on p-type silicon substrate 52 3).
On the other hand, by the phosphorous oxychloride (POCl in the second diffusing procedure 3) flow be set to when to increase than the situation of sample 1 and to have carried out sample 3 of two stage continuous diffusing procedure (the first diffusing procedure and the second diffusing procedure), in whole p-type silicon substrates 52, the square resistance of sensitive surface has almost no change, and obtains roughly uniform square resistance.Therefore, by increasing the phosphorous oxychloride (POCl of the second diffusing procedure in two stage continuous diffusing procedure 3) flow of gas, in the square resistance forming the sensitive surface after N-shaped impurity diffusion layer, obtain stable and that uniformity is high value.
As the phosphorous oxychloride (POCl in the second such diffusing procedure 3) example of increment of flow of gas, such as, for uncoated containing alloy slurry 21 p-type silicon substrate only based on phosphorous oxychloride (POCl 3) diffusion conditions (flow condition) be N 2: 5.8SLM, O 2: 0.9SLM, POCl 3: when 1.5SLM, be set to N by for the diffusion conditions (flow condition) be coated with containing in the second diffusing procedure of the p-type silicon substrate of alloy slurry 21 2: 5.8SLM, O 2: 0.9SLM, POCl 3: 2.0SLM.In addition, herein, phosphorous oxychloride (POCl when being processed together by the p-type silicon substrate of 100 is shown 3) flow of gas.
In addition, even if after the second diffusing procedure terminates, also should be noted that the moisture absorption containing alloy slurry 21.Containing alloy slurry 21 moisture absorption easier than the nature of glass on the surface being formed in p-type silicon substrate 2.When the vitreous layer (solidfied material after phosphorus compound dissolving) of the residue containing alloy slurry 21 after terminating as the second diffusing procedure absorbs the moisture etc. in air, residue containing alloy slurry 21 is deployed into the region beyond printing zone, stretches out from the printed patterns expected.In this case, the removal being formed in the vitreous layer on the surface of p-type silicon substrate 2 becomes uneven, but also impacts the uniformity of antireflection film 4 afterwards.Therefore, especially should be noted that the moisture absorption containing alloy slurry 21 in the season that humidity is high, need to implement subsequent handling rapidly after the second diffusing procedure terminates.
(pn separation circuit)
Then, be separated (Fig. 3-4, step S40) to make the back of the body aluminium electrode 7 as p-type electrode formed in subsequent handling carry out pn with sensitive surface lateral electrode 12 electric insulation as n-type electrode.N-shaped impurity diffusion layer 3 is formed at the surface uniform of p-type silicon substrate 2, so surface and the back side are in the state be electrically connected.Therefore, when defining back of the body aluminium electrode 7 (p-type electrode) and sensitive surface lateral electrode 12 (n-type electrode) when keeping such state, back of the body aluminium electrode 7 (p-type electrode) is electrically connected with sensitive surface lateral electrode 12 (n-type electrode).In order to cut off this electrical connection, by dry ecthing etch remove be formed in the end region of p-type silicon substrate 2 the second N-shaped impurity diffusion layer 3b and carry out pn separation.The additive method carried out as the impact in order to remove this second N-shaped impurity diffusion layer 3b, utilizes laser to carry out the method for end face separation in addition.
(vitreous layer removing step)
Then, p-type silicon substrate 2 is impregnated in such as hydrofluoric acid solution, then, carries out washing process, remove the vitreous layer (Fig. 3-5, step S50) on the surface being formed in p-type silicon substrate 2 in the second diffusing procedure thus.Thereby, it is possible to obtain the semiconductor substrate 11 by forming pn knot as the semiconductor substrate 2 be made up of p-type silicon of the first conductive type layer and the N-shaped impurity diffusion layer 3 as the second conductive type layer of sensitive surface side that is formed in this semiconductor substrate 2.In addition, as N-shaped impurity diffusion layer 3, the selection emitter structure be made up of the first N-shaped impurity diffusion layer 3a and the second N-shaped impurity diffusion layer 3b can be obtained in the sensitive surface side of p-type silicon substrate 2.
Now, as the vitreous layer (phosphorus compound dissolve after solidfied material) of the residue containing alloy slurry 21, remain, so need specially to remove due to thicker than the vitreous layer on the second N-shaped impurity diffusion layer 3b.When the vitreous layer caused containing alloy slurry 21 remains in the surface of p-type silicon substrate 2, antireflection film 4 gonorrhoea when forming antireflection film 4.So the reflectivity on antireflection film 4 raises, that is, anti-reflection effect disappears, and the generation electric current in solar cell 1 reduces.The removal of the vitreous layer caused containing alloy slurry 21 preferably uses bubble (bubbling) or Ultrasonic Cleaning in the lump when washing process.
In addition, the vitreous layer comprised containing the residue of alloy slurry 21 can be discharged as common plant drainage.
(antireflection film formation process)
Then, in order to improve photoelectric conversion efficiency, such as silicon nitride (SiN) film is formed and as antireflection film 4 (Fig. 3-6, step S60) using uniform thickness in the sensitive surface side (N-shaped impurity diffusion layer 3 side) of semiconductor substrate 11.The thickness of antireflection film 4 and refractive index are set as the value that light can be suppressed to reflect.The formation of antireflection film 4 uses such as plasma CVD method, and uses silane (SiH 4) gas and ammonia (NH 3) mist as raw material.In addition, as antireflection film 4, also can the different two-layer above film of stacked refractive index.In addition, the formation method of antireflection film 4, except plasma CVD method, also can use vapour deposition method, thermal cvd etc.In addition, should be noted that the antireflection film 4 formed in this wise is insulators, the words only forming sensitive surface electrode 12 thereon can not work as solar cell.
(electrode forming process)
Then, electrode (step S70) is formed by silk screen printing.First, sensitive surface lateral electrode 12 (before firing) is made.Namely, by silk screen printing at semiconductor substrate 11 as on the antireflection film 4 of sensitive surface, after containing the electrode material slurry (silver paste) of silver and glass frit by the shape coating showing silver-colored gate electrode 5 and Biao Yin bus electrode 6, make electrode material slurry drying.Then, after the electrode material slurry (aluminum slurry) be coated with containing aluminium in the whole face of the rear side of semiconductor substrate 11 by silk screen printing, electrode material slurry drying is made.
Herein, sensitive surface lateral electrode 12 contraposition on the first N-shaped impurity diffusion layer 3a is formed, but identifies that the region of the first N-shaped impurity diffusion layer 3a and the second N-shaped impurity diffusion layer 3b is difficult in the sensitive surface side forming the semiconductor substrate 11 after antireflection film 4.Fig. 8 irradiates the state of light and the image that obtains with infrared camera Halogen lamp LED for shooting to the sensitive surface side defining the semiconductor substrate 11 of antireflection film 4 after forming the first N-shaped impurity diffusion layer 3a and the second N-shaped impurity diffusion layer 3b by two stage continuous diffusing procedure (the first diffusing procedure and the second diffusing procedure).As shown in Figure 8, when having irradiated Halogen lamp LED, the region of clear identification first N-shaped impurity diffusion layer 3a and the second N-shaped impurity diffusion layer 3b has been difficult.Therefore, in this case, the positional precision of printing silver paste worsens.
Therefore, in the present embodiment, with infrared camera shooting, ultrared state is irradiated to the sensitive surface side defining the semiconductor substrate 11 of antireflection film 4 after forming the first N-shaped impurity diffusion layer 3a and the second N-shaped impurity diffusion layer 3b by two stage continuous diffusing procedure (the first diffusing procedure and the second diffusing procedure).Thereby, it is possible to identify the first N-shaped impurity diffusion layer 3a and the second N-shaped impurity diffusion layer 3b.Thereby, it is possible to precision prints silver paste on the second N-shaped impurity diffusion layer 3b excellently.
Fig. 9 irradiates ultrared state and the image obtained with infrared camera miniature lamp for shooting to the sensitive surface side defining the semiconductor substrate 11 of antireflection film 4 after forming the first N-shaped impurity diffusion layer 3a and the second N-shaped impurity diffusion layer 3b by two stage continuous diffusing procedure (the first diffusing procedure and the second diffusing procedure).As shown in Figure 9, by taking under irradiating ultrared state to the sensitive surface side of semiconductor substrate 11 with infrared camera, the region of the first N-shaped impurity diffusion layer 3a and the second N-shaped impurity diffusion layer 3b can be identified.In Fig. 9, the first N-shaped impurity diffusion layer 3a is taken into saturate wire.
Then, by firing the sensitive surface side of semiconductor substrate 11 and the electrode slurry of rear side with the temperature of 600 DEG C ~ about 900 DEG C, such as 760 DEG C in atmospheric environment simultaneously, in the face side of semiconductor substrate 11, by the glass material comprised in silver paste, during antireflection film 4 melting, ag material contacts with silicon and solidifies.Thus, obtain the table silver gate electrode 5 and Biao Yin bus electrode 6 as sensitive surface lateral electrode 12, and the conducting (Fig. 3-7) between the silicon that ensure that sensitive surface lateral electrode 12 and semiconductor substrate 11.Such technique is also referred to as burns (Fire-through) method.
In addition, aluminum slurry also with the pasc reaction of semiconductor substrate 11 and obtain carrying on the back aluminium electrode 7, and form p+ layer 8 immediately below back of the body aluminium electrode 7.In addition, illustrate only the silver-colored gate electrode 5 of table and back of the body aluminium electrode 7 in figure, eliminate the record showing silver-colored bus electrode 6.
By implementing above such operation, the solar cell 1 of the present embodiment as shown in Fig. 1-1 and Fig. 1-2 can be made.In addition, also slurry as electrode material can be exchanged to the configuration sequence of semiconductor substrate 11 in sensitive surface side and rear side.
In addition, the situation of to carry out pn and being separated between the second diffusing procedure is removed with vitreous layer has been shown in above-mentioned, but also after formation electrode, such as, can have carried out the separating treatment of the end of pn knot to the endmost surface irradiating laser of p-type silicon substrate 2.
As described above, in the present embodiment, by coating on p-type silicon substrate containing alloy slurry 21, under containing the state not having the diffuse source of alloy (phosphorus) except alloy slurry 21, implementing the first diffusing procedure, thus forming the first N-shaped impurity diffusion layer 3a.And, after the first diffusing procedure, p-type silicon substrate 2 is not taken out from thermal diffusion furnace, implement with phosphorous oxychloride (POCl 3) as the second diffusing procedure of the diffuse source of alloy (phosphorus), form the second N-shaped impurity diffusion layer 3b thus.That is, without the need to by p-type silicon substrate 2 from thermal diffusion furnace take out can implement to employ containing alloy slurry 21 the first diffusing procedure and employ phosphorous oxychloride (POCl 3) the two stage continuous diffusing procedure of the second diffusing procedure.Thereby, it is possible to implement the DIFFUSION TREATMENT of alloy (phosphorus) efficiently, thus easily separately make the first N-shaped impurity diffusion layer 3a and the second N-shaped impurity diffusion layer 3b formed select emitter structure.Thus, without the need to using special device, and just can easily and at low cost form selection emitter structure without the need to the operation implementing multiple complexity.
Therefore, according to the present embodiment, the solar cell of the photoelectric conversion efficiency excellence achieved based on the reduction of the contact resistance selected between the sensitive surface lateral electrode of emitter structure and N-shaped impurity diffusion layer, the raising of output current, the raising of open circuit voltage (Voc) can be formed easily and at low cost.
In addition, by forming multiple solar cell with the structure illustrated in above-mentioned execution mode, and adjacent solar cell being electrically connected in serial or parallel connection mode each other, the solar module of photoelectric conversion efficiency excellence can be realized.In this case, such as, the sensitive surface lateral electrode of a side in adjacent solar cell is electrically connected with the rear side electrode of the opposing party.
As described above, the manufacture method of solar cell of the present invention is useful for the situation of the solar cell manufacturing easily and at low cost photoelectric conversion efficiency excellence.

Claims (5)

1. a manufacture method for solar cell, is characterized in that, comprising:
First operation, to the slurry of the impurity element of part coating containing the second conduction type of the one side side of the semiconductor substrate of the first conduction type;
Second operation, described semiconductor substrate is implemented to the first heat treatment under the environment of the gas of the impurity element not containing the second conduction type in process chamber, make the impurity element of the second conduction type be diffused into the lower area of the described slurry described semiconductor substrate from described slurry, thus form at the lower area of the described slurry of described semiconductor substrate the first impurity diffusion layer having spread the impurity element of the second conduction type with the first concentration;
3rd operation, in described process chamber, then second heat treatment contained under the environment of dopant gas of the impurity element containing the second conduction type is implemented in described first heat treatment to described semiconductor substrate, make the impurity element of the second conduction type from the described exposed area being diffused into the one side side of described semiconductor substrate described in uncoated slurry containing dopant gas, thus formed with the second impurity diffusion layer having spread the impurity element of the second conduction type lower than the second concentration of described first concentration in described exposed area;
4th operation, removes described slurry;
5th operation, described first impurity diffusion layer forms sensitive surface lateral electrode; And
6th operation, forms rear side electrode in the another side side of described semiconductor substrate.
2. the manufacture method of solar cell according to claim 1, is characterized in that,
In described first operation, print neutral described slurry by silk screen printing.
3. the manufacture method of solar cell according to claim 1 and 2, is characterized in that,
Do not distil under the heat treatment temperature of described slurry in described first heat treatment and do not burn up.
4. the manufacture method of solar cell as claimed in any of claims 1 to 3, is characterized in that,
In described 4th operation, removed by etching simultaneously and be deposited in the compound of the described impurity element on described second impurity diffusion layer and described slurry in described 3rd operation.
5. the manufacture method of the solar cell according to any one in Claims 1-4, is characterized in that,
Described semiconductor substrate is p-type silicon substrate, and described impurity element is phosphorus.
CN201280075188.5A 2012-08-09 2012-08-09 The manufacture method of solaode Expired - Fee Related CN104521002B (en)

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