Classifications

• • 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
  • H01L31/022441—Electrode arrangements specially adapted for back-contact solar cells
  • H01L31/02245—Electrode arrangements specially adapted for back-contact solar cells for metallisation wrap-through [MWT] type solar cells
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
  • C30B29/02—Elements
  • C30B29/06—Silicon
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B31/00—Diffusion or doping processes for single crystals or homogeneous polycrystalline material with defined structure; Apparatus therefor
  • C30B31/06—Diffusion or doping processes for single crystals or homogeneous polycrystalline material with defined structure; Apparatus therefor by contacting with diffusion material in the gaseous state
  • C30B31/18—Controlling or regulating
  • C30B31/185—Pattern diffusion, e.g. by using masks
• • 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
  • 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
  • H01L31/02—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
  • H01L31/022441—Electrode arrangements specially adapted for back-contact solar cells
  • H01L31/022458—Electrode arrangements specially adapted for back-contact solar cells for emitter wrap-through [EWT] type solar cells, e.g. interdigitated emitter-base back-contacts
• • 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
  • H01L31/0236—Special surface textures
  • H01L31/02363—Special surface textures of the semiconductor body itself, e.g. textured active layers
• • 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
  • H01L31/04—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 adapted as photovoltaic [PV] conversion devices
  • H01L31/06—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 adapted as photovoltaic [PV] conversion devices characterised by potential barriers
• • 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
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24802—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]
  • Y10T428/24917—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.] including metal layer

Definitions

• the present invention relates to a novel process for the preparation of printable, low to high viscosity oxide media, and their use in solar cell manufacturing, as well as the improved lifetime products produced using these novel media.
• a silicon wafer (monocrystalline, multicrystalline or quasi-monocrystalline, p- or n-type base doping) is freed of adherent saw damage by means of an etching process and "simultaneously", usually in the same etching bath, texturized in this case, the creation of a preferred Surface (texture) as a result of the etching step or simply to understand the targeted, but not particularly oriented roughening of the wafer surface
• the aforementioned etching solutions for treating the silicon wafers typically consist of dilute potassium hydroxide solution to which isopropyl alcohol has been added as solvent. Instead, other alcohols having a higher vapor pressure or higher boiling point than isopropyl alcohol may be added, provided that the desired etching result can be achieved thereby.
• the desired etch result is a morphology that is randomly-etched, or rather etched out of the original surface.
• Pyramids is characterized by square base.
• density the density
• the height and thus base area of the pyramids can be influenced by a suitable choice of the above-mentioned constituents of the etching solution, the etching temperature and the residence time of the wafers in the etching basin.
• Temperature range of 70 - ⁇ 90 ° C performed, with ⁇ tzabträge of up to 10 pm per wafer side can be achieved.
• the etching solution may consist of potassium hydroxide solution with an average concentration (10-15%).
• this etching technique is hardly used in industrial practice. More often becomes one
• Etching solution consisting of nitric acid, hydrofluoric acid and water used.
• This etching solution can be modified by various additives such as sulfuric acid, phosphoric acid, acetic acid, N-methylpyrrolidone and also surfactants, which u. a.
• Wetting properties of the etching solution and their etch rate can be specifically influenced.
• These acid etch mixtures produce a morphology of interstitially arranged etch pits on the surface.
• the etching is typically carried out at temperatures in the range between 4 ° C to ⁇ 10 ° C and the ⁇ tzabtrag is here usually 4 ⁇ to 6 ⁇ .
• the wafers are placed in a tube furnace in a controlled atmosphere quartz glass tube consisting of dried nitrogen, dried oxygen and phosphoryl chloride, exposed.
• the wafers are introduced at temperatures between 600 and 700 ° C in the quartz glass tube.
• the gas mixture is transported through the quartz glass tube.
• the phosphoryl chloride decomposes into a vapor, consisting of phosphorus oxide (eg P205) and chlorine gas, the vapor of phosphorus oxide is deposited among other things on the wafer surfaces (occupancy).
• the silicon surface is oxidized at these temperatures to form a thin oxide layer. In this layer, the deposited phosphorus oxide is embedded, resulting in a mixed oxide of silicon dioxide and phosphorus oxide on the wafer surface.
• This mixed oxide is called phosphosilicate glass (PSG).
• PSG phosphosilicate glass
• the mixed oxide serves the silicon wafer as a diffusion source, wherein in the course of diffusion, the phosphorus oxide diffuses in the direction of the interface between PSG glass and silicon wafer and is reduced there by reaction with the silicon at the wafer surface (silicothermally) to phosphorus.
• the resulting phosphor has a solubility which is orders of magnitude greater in silicon than in the glass matrix from which it is formed, and thus dissolves preferentially in silicon due to the very high segregation coefficient.
• the phosphorus in silicon diffuses along the concentration gradient into the volume of silicon. In this diffusion process, concentration gradients of the order of 105 between typical
• a PSG layer is formed, which typically has a layer thickness of 40 to 60 nm. in the
• the drive-in phase follows. This can be decoupled from the assignment phase, but is conveniently conveniently in time directly to the Occupancy coupled and therefore usually takes place at the same temperature.
• the composition of the gas mixture is adjusted so that the further supply of phosphoryl chloride is suppressed.
• the surface of the silicon is further oxidized by the oxygen contained in the gas mixture, whereby a phosphorus depleted silicon dioxide layer is also generated between the actual doping source, the phosphorus oxide highly enriched PSG glass and the silicon wafer
• the tube furnace is automatically cooled and the wafers can be removed from the process tube at temperatures between 600 ° C to 700 ° C.
• Composition of the gas atmosphere used for doping the formation of a so-called boron skin can be detected on the wafers.
• This boron skin is dependent on various influencing factors: decisive for the doping atmosphere, the temperature, the doping time, the
• Pretreatment were subjected (for example, their structuring with diffusion-inhibiting and / or -unterbindenden layers and
• Dopant sources eg, boron oxide and boron nitride
• Doping sources for example, dilute solutions of phosphoric or boric acid, as well as sol-gel-based systems or solutions of polymeric Borazilitatien can be used.
• Solvents from the aforementioned doping media is usually followed by a treatment at high temperature, while those unwanted and interfering, but the formulation-related, additives are either "burned" and / or pyrolyzed.The removal of solvents and the burn-out may, but need not, occur simultaneously.
• the coated substrates usually pass through a continuous furnace at temperatures between 800 ° C and 1000 ° C, to shorten the cycle time, the temperatures in comparison to
• Gas phase diffusion in the tube furnace can be slightly increased.
• the prevailing in the continuous furnace gas atmosphere can according to the
• Nitrogen dry air, a mixture of dry oxygen and dry nitrogen and / or, depending on the design of the furnace to be passed, zones of one and the other of the above
• Driving the dopant can in principle be decoupled from each other.
• the wafers present after the doping are coated on both sides with more or less glass on both sides of the surface. More or less in this case refers to modifications that can be applied in the context of the doping process: double-sided diffusion vs. quasi one-sided diffusion mediated by back-to-back arrangement of two wafers in a parking space of the process boats used.
• the latter variant allows a predominantly one-sided doping, but does not completely prevent the diffusion on the back.
• the wafers are on the one hand transhipped in batches in wet process boats and with their help in a solution of dilute hydrofluoric acid, typically 2% to 5%, immersed and left in this until either the surface is completely removed from the glasses, or Process cycle has expired, which is a sum parameter from the necessary ⁇ tzdauer and the automatic process automation represents.
• the complete removal of the glasses can be determined, for example, by the complete dewetting of the silicon wafer surface by the dilute aqueous hydrofluoric acid solution.
• the complete removal of a PSG glass is achieved under these process conditions, for example with 2% hydrofluoric acid solution within 210 seconds at room temperature.
• the etching of corresponding BSG glasses is slower and requires longer process times and possibly also higher concentrations of the hydrofluoric acid used. After etching, the wafers are rinsed with water.
• the etching of the glasses on the wafer surfaces can also be carried out in a horizontally operating method in which the wafers are introduced in a constant flow into an etching system in which the wafers pass through the corresponding process tanks horizontally (inline system).
• the wafers are conveyed on rollers and rollers either through the process tanks and the etching solutions contained therein or the etching media are transported onto the wafer surfaces by means of roller application.
• the typical residence time of the wafers in the case of etching the PSG glass is about 90 seconds, and the hydrofluoric acid used is somewhat more concentrated than in the batch process
• the concentration of hydrofluoric acid is typically 5%.
• the tank temperature compared to the
• edge insulation - glass etching is a process engineering necessity, which results from the system-inherent characteristics of the double-sided diffusion, even with intentional unilateral back-to-back diffusion.
• the front and back of the solar cell are parasitic and parasitic
• the wafers are unilaterally via an etching solution
• etching solution consisting of nitric acid and hydrofluoric acid.
• the etching solution may contain as minor constituents, for example, sulfuric acid or phosphoric acid.
• the etching solution is imparted via rollers to the
• the etching removal typically achieved with these methods amounts to approximately 1 ⁇ m silicon (including the glass layer present on the surface to be treated).
• the glass layer remaining on the opposite side of the wafer serves as a mask before
• edge isolation can also be done with the help of
• Plasma etching processes are performed. This plasma etching is then usually carried out before the glass etching. For this purpose, several wafers are stacked on each other and the outer edges become the plasma
• the plasma is filled with fluorinated gases, for example
• Tetrafluoromethane fed.
• the glass etching is then generally carried out.
• Solar cells with an anti-reflection coating which usually consists of amorphous and hydrogen-rich silicon nitride.
• Antireflection coatings are conceivable. Possible coatings may include titanium dioxide, magnesium fluoride, tin dioxide and / or
• the coating of the Waferoberfl surface with the above-mentioned silicon nitride fulfilled in essentially two functions: on the one hand, due to the numerous incorporated positive charges, the layer creates an electric field that can keep charge carriers in the silicon away from the surface and the recombination speed of these charge carriers at the
• this layer depending on its optical parameters, such as refractive index and layer thickness, this layer generates a reflection-reducing property which contributes to the fact that more light can be coupled into the later solar cell. Both effects can increase the conversion efficiency of the solar cell.
• the antireflection reduction is most pronounced in the wavelength range of the light of 600 nm.
• the directional and non-directional reflection shows a value of about 1% to 3% of the originally incident light (perpendicular incidence to the surface normal of the silicon wafer).
• the above-mentioned silicon nitride films are currently deposited on the surface generally by direct PECVD method.
• a gas atmosphere of argon is ignited a plasma, in which silane and ammonia are introduced.
• the silane and the ammonia are converted in the plasma by ionic and radical reactions to silicon nitride and thereby deposited on the wafer surface.
• the properties of the layers can z. B. adjusted and controlled by the individual gas flows of the reactants.
• the deposition of the above-mentioned silicon nitride layers can also be carried out using hydrogen as the carrier gas and / or the reactants alone. Typical deposition temperatures are in the range between 300 ° C to 400 ° C.
• Alternative deposition methods may be, for example, LPCVD and / or sputtering.
• Silicon nitride coated wafer surface the front electrode are defined.
• the electrode has been established using the screen printing method using metallic
• the sum of the residual constituents results from the rheological aids necessary for formulating the paste, such as, for example, solvents, binders and thickeners.
• the silver paste contains a special Glasfrit mixture, mostly oxides and mixed oxides based on
• the glass frit fulfills essentially two functions: on the one hand it serves as a bonding agent between the wafer surface and the mass of the silver particles to be sintered, on the other hand it is responsible for the penetration of the silicon nitride covering layer in order to enable the direct ohmic contact to the underlying silicon.
• the penetration of the silicon nitride takes place via an etching process with subsequent diffusion of silver present dissolved in the glass frit matrix into the silicon surface, whereby the ohmic contact formation is achieved.
• the silver paste is deposited by screen printing on the wafer surface and then dried at temperatures of about 200 ° C to 300 ° C for a few minutes. For the sake of completeness, it should be mentioned that double-printing processes also find industrial application, which make it possible to print on an electrode grid generated during the first printing step, a congruent second.
• Silver metallization increases, which can positively influence the conductivity in the electrode grid.
• the solvents contained in the paste are expelled from the paste.
• the printed wafer passes through a continuous furnace.
• Such an oven generally has several heating zones, which can be independently controlled and tempered.
• the wafers are heated to temperatures up to about 950 ° C. However, the single wafer is typically exposed to this peak temperature for only a few seconds. During the remaining run-up phase, the wafer has temperatures of 600 ° C to 800 ° C. In these Temperatures are contained in the silver paste contained organic impurities such as binder, and the etching of the
• Silicon nitride layer is initiated. During the short time interval of the prevailing peak temperatures, contact formation occurs.
• the front electrode grid consists of thin fingers
• the rear bus buses are also usually by means of
• the back electrode is defined following the pressure of the bus buses.
• the electrode material is made of aluminum, which is why Definition of the electrode an aluminum-containing paste by screen printing on the remaining free area of the wafer back with a
• Edge distance ⁇ 1mm is printed.
• the remaining components are those already mentioned under point 5 (such as solvents, binders, etc.).
• the aluminum paste is bonded to the wafer during co-firing by causing the aluminum particles to start to melt during heating and remove silicon from the wafer in the wafer
• the melt mixture acts as a dopant source and gives aluminum to the silicon (solubility limit: 0.016 atomic percent), whereby the silicon is p + doped as a result of this drive-in.
• a eutectic mixture of aluminum and silicon which solidifies at 577 ° C. and has a composition with a mole fraction of 0.12 Si, is deposited on the wafer surface, inter alia.
• This potential wall is generally referred to as the back surface field or back surface field.
• edge isolation of the wafer has not already been carried out as described under point 3, this is typically carried out after co-firing with the aid of laser beam methods.
• a laser beam is directed to the front of the solar cell and the front p-n junction is severed by means of the energy coupled in by this beam.
• This trench with a depth of up to 15 ⁇ due to
• this laser trench is 30 pm to 60 pm wide and about 200 pm away from the edge of the solar cell.
• solar cell architectures with both n-type and p-type base material. These solar cell types include PERT solar cells
• Diffusion barriers are deposited on the silicon wafers before depositing the glasses to define the areas to be doped. A similar effect can be achieved with diffraction barriers, if you need different dopings on the front and back of a wafer. If the diffusion barrier consists of materials which are deposited by means of PVD and CVD methods, as in the case of conventional barrier materials consisting of silicon dioxide,
• Silicon nitride or, for example, silicon oxynitride is the case, they must be subjected to structuring in order to produce differently doped regions on a wafer surface in a subsequent process step.
• Phosphoryl chloride and / or boron tribromide do not allow to selectively generate local dopants and / or locally different dopants on silicon wafers.
• the creation of such structures is only possible by the use of known doping technologies by costly and expensive structuring of the substrates. When structuring different dopants and / or locally different dopants on silicon wafers.
• the object of the present invention is thus to provide suitable, inexpensive media, by means of which protective layers can be introduced against unwanted diffusion in simple printing technologies.
• the two to fourfold symmetrically and / or asymmetrically substituted alkoxysilanes and alkoxyalkylsilanes used in the sol-gel synthesis for the condensation can have saturated, unsaturated branched, unbranched aliphatic, alicyclic and aromatic radicals individually or different of these radicals, which in turn can be used at any position
• Alkoxy radical or alkyl radical can be functionalized by heteroatoms selected from the group O, N, S, Cl, Br.
• the anhydrous sol-gel synthesis for the preparation of high-viscosity oxide media in the presence of strong carboxylic acids are preferably acids selected from the group of formic acid, acetic acid, oxalic acid, trifluoroacetic acid, mono-, di- and trichloroacetic acid, glyoxylic acid, tartaric acid, maleic acid, malonic acid, pyruvic acid, malic acid, 2-oxoglutaric acid.
• Oxide media based on hybrid sols and or gels are obtained when alcoholates / esters, acetates, hydroxides or oxides are used in their preparation of aluminum, germanium, zinc, tin, titanium, zirconium, or lead, and mixtures thereof.
• the oxide medium is dissolved to a highly viscous, approximately glassy mass, which is then brought back into solution either by addition of a suitable solvent or solvent mixture or with the aid of intensive shearing
• Thickeners are formulated. Furthermore, a stable mixture can be prepared in this way, which is storage stable for a period of at least three months. Particularly good properties have the printable high-viscosity media, if to improve the stability
• Oxide media "capping agent" selected from the group
• Acetoxytrialkylsilane, Alkoxytrialkylsilane, Halogentrialkylsilane and derivatives thereof are added.
• Oxide media are particularly suitable for the production of diffusion barriers in processing processes of silicon wafers for photovoltaic,
• microelectronic, micromechanical and micro-optical applications can be easily by spin or dip coating, drop casting, curtain or slot dye coating, screen or flexoprinting, gravure, ink-jet or aerosol jet printing, offset printing, Microcontact printing, electrohydrodynamic dispensing, roller or spray coating, ultrasonic spray coating, pipe jetting, laser transfer printing, pad printing or rotary screen printing, but preferably with screenprinting (Screen printing) and can be used for the production of PERC, PERL, PERT, IBC solar cells and others, the
• Solar cells may have other architectural features such as MWT, EWT, Selective Emitter, Selective Front Surface Field, Selective Back Side Field and Bifaciality.
• the oxide media are very well suited for the production of thin, dense glass layers, which act as a sodium and potassium diffusion barrier in the LCD technology as a result of a thermal treatment.
• they are suitable for producing thin, dense glass layers on the cover glass of a display, consisting of doped S1O2 and / or mixed oxides, which can be derived on the above-mentioned possible hybrid sols, the diffusion of ions from the cover glass in the
• the printed on the surface of the silicon wafer oxide medium in a temperature range between 50 ° C and 950 ° C, preferably between 50 ° C and 700 ° C, more preferably between 50 ° C and 400 ° C, simultaneously or sequentially, using one or more, to be carried out sequentially Temper Colouren (tempering by means of a step function) and / or an annealing ramp, dried and compacted for glazing, whereby a grip and abrasion resistant layer is formed with a thickness of up to 500 nm.
• the oxide media according to the invention can be printed on hydrophilic and / or hydrophobic silicon surfaces and subsequently converted into diffusion barriers.
• silicon wafers are printed with the high-viscosity oxide media and the printed layers are thermally densified. Furthermore, it is possible to obtain hydrophobic silicon wafer surfaces after removal of the applied oxide media by the inventive oxide media after printing, drying, and compacting and / or doping by temperature treatment, the resulting glass layers with an acid mixture containing hydrofluoric acid and optionally
• Phosphoric acid are etched, wherein the etching mixture used as Etching agent hydrofluoric acid in a concentration of 0.001 to 10 wt .-% or 0.001 to 10 wt .-% hydrofluoric acid and 0.001 to 10 wt .-% phosphoric acid in the mixture.
• printable high-viscosity oxide media can be produced by condensing di- to tetra-substituted alkoxysilanes with strong carboxylic acids in an anhydrous sol-gel-based synthesis and preparing highly viscous media (pastes) by controlled gelation.
• Alkoxyalkylsilanene be condensed with strong carboxylic acids and pasty and highly viscous printable pastes are prepared by controlled gelation, which are printed as diffusion barriers.
• the highly viscous paste can be screen printed onto the surface of a wafer, then dried and then thermally compacted. This densification of the material printed on wafer is usually done in one
• the drying and densification can be done in one process step.
• the diffusion barriers produced in this way are oxide layers which, however, can serve not only as diffusion barriers but also as etch barriers or else as so-called etching resist in the production of solar cells.
• optionally compacted paste acts in the context of the production of solar cells as a temporary etching barrier against hydrofluoric, wet-chemical etching, as well as their vapors or hydrofluoric acid vapor mixtures, but also in plasma etching with fluorine-containing precursors or reactive ion etching.
• unbranched aliphatic, alicyclic and aromatic radicals which in turn may be functionalized at any position of the alkoxide radical by heteroatoms selected from the group O, N, S, Cl, Br.
• the condensation reaction takes place, as stated above, in the presence of strong carboxylic acids.
• carboxylic acids are organic acids of the general formula to understand in which the chemical and physical properties on the one hand clearly determined by the carboxy group, since the
• the acidity of the carboxylic acids is higher when at the alpha-C atom
• Substituent with an electron-withdrawing (-I-effect) is present, such as. B. in corresponding halogenated acids or in dicarboxylic acids.
• carboxylic acids from the group of formic acid, acetic acid, oxalic acid, trifluoroacetic acid, mono-, di- and Trichloroacetic acid, glyoxylic acid, tartaric acid, maleic acid, maionic acid, pyruvic acid, malic acid and 2-oxoglutaric particularly suitable for use in the inventive method.
• the oxide medium is dissolved to a highly viscous mass and the product obtained, either by addition of a suitable solvent or solvent mixture, again dissolved or transformed by means of intensive shear mixing devices in a sol state and due to partial or complete structural recovery (gelation) to recover a homogeneous gel.
• the process according to the invention has proven to be particularly advantageous in that the formulation of the highly viscous oxide medium takes place without the addition of thickening agents. In this way, a stable mixture is prepared which is stable for a period of at least three months. If during production the oxide media "capping agent" (capping agent), selected from the group
• Acetoxytrialkylsilane, Alkoxytrialkylsilane, Halogentrialkylsilane and their derivatives are added, this leads to an improvement in the stability of the resulting media.
• the added "capping agent" need not necessarily be involved in the condensation and gelling reaction, but their time of addition can also be chosen so that they can be stirred into the resulting paste mass after gelation, the capping agent with in the reactive end groups contained in the network, such as, for example, silanol groups, are chemically reacted off and thus deprive them of further uncontrolled and undesirable condensation events
• Oxide media are particularly well suited for use as printable media for the production of diffusion barriers in the processing of silicon wafers for photovoltaic, microelectronic, micromechanical and micro-optical applications.
• the oxide media produced according to the invention can be produced by spin coating or dip coating, drop casting, curtain or slot dye coating, screen printing or flexoprinting, gravure, ink Jet or Aerosol Jet Printing, Offset Printing, Micro Contact Printing, Electrohydrodynamic Dispensing, Roller or Spray Coating, Ultrasonic Spray Coating, Pipe Jetting, Laser Transfer Printing, Päd Printing or rotary screen printing can be printed, the printing is preferably done by screen printing ,
• Correspondingly prepared oxide media are particularly well suited for the production of PERC, PERL, PERT, IBC solar cells (BJBC or BCBJ) and others, where the solar cells further architectural features, such as MWT, EWT, selective emitter, selective front surface field, selective Back Surface Field and Bifacialität or for the production of thin, dense glass layers, which act as a sodium and potassium diffusion barrier in the LCD technology due to a thermal treatment, in particular for the production of thin, dense glass layers on the cover glass of a display consisting of doped SiO 2 , which prevent the diffusion of ions from the cover glass into the liquid-crystalline phase.
• the present invention also relates to the novel oxide media prepared according to the invention, which have been prepared by the process described above and which contain binary or ternary systems from the group S1O2-Al2O3 and / or mixtures of higher degrees resulting from the use of alcoholates / Esters, acetates, hydroxides or oxides of aluminum, germanium, zinc, tin, titanium, zirconium or lead during manufacture.
• Maskants, complex and chelating agents in a sub- fully stoichiometric ratio on the one hand sterically stabilize and on the other hand specifically influence and control in terms of their condensation and gelling rate but also in terms of rheological properties.
• Chelating agents are contained in the patent applications WO 2012/119686 A, WO2012119685 A1 and WO2012119684 A. The content of these publications is therefore included in the disclosure of the present application.
• the oxide media By means of the oxide media thus obtained, it is possible to produce on silicon wafers, a grip and abrasion resistant layer. This result is achieved by placing the oxide medium on hydrophilic wafers to produce a
• hydrophilic wafers are to be understood as those, for example, with an oxide film
• Hydrophilic silicon wafer surfaces are to be understood as those surfaces which are freed of oxides by a cleaning step with suitable ammonium fluoride or HF solutions and have hydrophobic properties due to terminal H or F. However, these also include wafer surfaces which have hydrophobic properties by deposition of a few atomic layers of thick silane layers (deposition in a saturated atmosphere of hexamethyldisilazane (HDMS)).
• HDMS hexamethyldisilazane
• the production of the diffusion barriers can be carried out in a process wherein the oxide medium printed on the surface, which
• this process for the production of grip- and abrasion-resistant layers can be characterized by
• a) silicon wafers are printed with the oxide media to produce the desired diffusion barriers, the printed layer dried, and if necessary. Compressed, and the thus coated wafers are exposed to downstream diffusion with dopants, the latter printable sol-gel-based oxide dopants, other printable Doping inks and / or pastes or doped APCVD and / or PECVD glasses and dopants from the conventional
• the treated wafers are freed by etching from the residues of the dopants and the one-sided diffusion barrier and then the printable oxide media as a diffusion barrier over the entire surface on one side printed on the opposite in step a) wafer side, dried and if necessary, be compacted, and which is subjected to the now unprotected with the diffusion barrier wafer side of further diffusion, wherein the doping media used meet the criteria mentioned in a), or
• silicon wafers with the printable oxide media are printed on one side over the entire surface, the oxide medium is dried and optionally compacted, and the opposite wafer side is coated with the same printable oxide medium using a structured print pattern, the oxide medium is dried and / or compacted, and the wafers coated in this way be subjected to a downstream diffusion with doping media, wherein the doping media used meet the criteria mentioned in a), whereby in the unprotected areas of the wafer a
• Process control are freed by etching of the residues of the dopants and the one-sided diffusion barrier, and then the printable oxide media on the patterned doped wafer side in a complementary negative pressure pattern to that which was used under point c) applied, printed, dried and possibly. Compressed followed by downstream diffusion with doping media, with those used
• Dottermedie meet the criteria mentioned in a), which creates a doping in the unprotected areas of the wafer, while the printable oxide medium protected areas are not doped,
• Diffusion barrier results, which acts diffusion-inhibiting on subsequently deposited doping, wherein the doping media used meet the criteria mentioned in a), and thus the Dose of the dopant, which is delivered to the substrate, is controlled.
• the layers produced according to the invention which are obtained by applying the highly viscous sol-gel oxide media on silicon wafers and after their thermal compaction, act as a diffusion barrier against phosphorus and boron diffusion.
• the mentioned doping media must be thermally activated and made to diffuse.
• the activation can be carried out in various ways, such as by heating in ovens, the loading of which is carried out batchwise or continuously with substrates, by irradiation of the substrate with laser radiation or high-energy lamps, preferably halogen lamps.
• Oxide media their drying, and compression and / or doping by thermal treatment resulting glass layers with a
• the dried and compacted doping glasses can furthermore be removed from the wafer surface with the following etching mixtures:
• buffered hydrofluoric acid mixtures BHF
• buffered oxide etch mixtures etching mixtures consisting of hydrofluoric and nitric acid, such as the so-called p-etching, R-etching, S-etching, or etchant mixtures consisting of hydrofluoric acid and sulfuric acid, the aforementioned list not claims to be complete.
• binders to be added for formulating pastes are generally extremely difficult to even impossible to clean up chemically or by to free their cargo of metallic trace elements.
• the cost of their cleaning is high and is due to the high cost out of all proportion to the claim of creating a cost-effective and thus competitive, for example, screen-printable diffusion barrier for silicon wafers.
• these adjuvants represent a constant source of unavoidable contamination by the unwanted
• these problems can be solved by the present invention described, namely by printable, viscous oxide media according to the invention, which can be prepared by a sol-gel process.
• these oxide media can also be produced as printable doping media by appropriate additions.
• a suitably adapted process and optimized synthesis approaches enable the production of printable oxide media.
• novel media can be synthesized on the basis of the sol-gel process and, if necessary, can be further formulated.
• the synthesis of the sol and / or gel can be achieved by adding
• Condensation initiators e.g. controlled by a strong carboxylic acid, excluding water.
• the viscosity can be controlled via the stoichiometry of the addition, for example the carboxylic acid.
• a superstoichiometric addition of the degree of crosslinking of the silica particles can be adjusted in this way, whereby a highly swollen and printable network, ie a pasty gel, can arise, which can be applied by means of various printing processes on surfaces, preferably on silicon wafer surfaces.
• Suitable printing methods can be the following:
• the printing is done by means of screen printing.
• the properties of the high-viscosity media according to the invention can be adjusted in a more targeted manner, so that they are optimally suitable for special printing processes and for application to specific surfaces, with which they can interact intensively. In this way, properties such as surface tension, viscosity, wetting behavior, drying behavior and adhesion ability can be adjusted in a targeted manner.
• properties such as surface tension, viscosity, wetting behavior, drying behavior and adhesion ability can be adjusted in a targeted manner.
• particulate additives eg aluminum hydroxides and
• particulate additives eg aluminum hydroxides and
• each printing and coating method has its own requirements for the composition to be printed.
• each printing and coating method has its own requirements for the composition to be printed.
• Printing method individually set parameters such as the
• the printable media in addition to their application for the production of diffusion barriers as scratch protection and corrosion protection layers, eg.
• photovoltaic components are in particular solar cells and modules.
• applications in the electronics industry are characterized by the use of said pastes in the exemplified but not exhaustively enumerated fields Thin-film solar cells made of thin-film solar modules, production of organic solar cells, production of printed circuits and
• TFT thin-film transistors
• LCD liquid-crystal displays
• OLED organic light-emitting diodes
• the following screening and printing parameters are used: 280 mesh, 25 ⁇ m thread strength (stainless steel), covering angle 22.5 °, 8-12 ⁇ m emulsion thickness over fabric.
• the jump is 1, 1 mm and the squeegee pressure 1 bar.
• the print layout corresponds to a square with 2 cm edge length. After printing, the wafers are dried on a hot plate at 300 ° C for 2 minutes. The result is a grip and abrasion resistant, interference colors having layer. The layer is easy to etch and remove with dilute hydrofluoric acid (5%). After etching, the previously printed surface is hydrophilic.
• the following screening and printing parameters are used: 280 mesh, 25 ⁇ m thread strength (stainless steel), covering angle 22.5 °, 8-12 ⁇ m emulsion thickness over fabric. Of the Bounce is 1, 1 mm and the squeegee pressure 1 bar.
• the print layout corresponds to a square with 2 cm edge length. After printing, the wafers are dried on a hot plate at 300 ° C for 2 minutes. The result is a grip and abrasion resistant, interference colors having layer. The layer is easy to etch and remove with dilute hydrofluoric acid (5%). After etching, the previously printed surface is hydrophilic.
• Aluminum triisopropylate introduced. The mixture is left for a further 30 minutes at this temperature, allowed to cool slightly and then post-treated on a rotary evaporator at 60 ° C, creating a
• the print layout corresponds to a square with 2 cm edge length. After printing, the wafers are dried on a hot plate at 300 ° C for 2 minutes (gripping and abrasion resistant) and then with a sol-gel-based phosphorus doping ink by spraying from a
• the layer of doping ink is also dried at 300 ° C for 2 minutes on a hotplate.
• the coated wafer is then treated at 900 ° C for 10 minutes in a muffle furnace and then freed from the vitrified layers by etching with dilute hydrofluoric acid.
• the four-point measurement determines a sheet resistance of 67 ohms / sqr on average, while the layer resistance in the protected region is 145 ohms / sqr. The determination of
• Sheet resistances of the previously described coatings on the opposite wafer surface are on average 142 ohms / sq.
• Aluminum triisopropylate introduced. The mixture is left for a further 30 minutes at this temperature, allowed to cool slightly and then post-treated on a rotary evaporator at 60 ° C, creating a
• the paste is printed on one side polished silicon wafer (p-type, 525 pm thick).
• the following screening and printing parameters are used: mesh number 165 cm "1 , 27 pm thread thickness (polyester),
• the wafers are dried on a hot plate at 300 ° C for 2 minutes (gripping and abrasion resistant) and then with a sol-gel-based phosphorus doping ink by spraying from a spray bottle and then spin coating at 2000 U / min for 30 s coated.
• the layer of doping ink is also dried at 300 ° C for 2 minutes on a hotplate.
• the coated wafer is treated at 900 ° C for 10 minutes in a muffle furnace and then freed from the vitrified layers by etching with dilute hydrofluoric acid.
• Wafer surface is on average 139 ohms / sqr.

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• 2013
  • 2013-12-18 US US14/655,839 patent/US20150340518A1/en not_active Abandoned
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