WO2014082152A1 - Method for diffusing dopants into silicon wafers for manufacturing solar cells - Google Patents

Method for diffusing dopants into silicon wafers for manufacturing solar cells Download PDF

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Publication number
WO2014082152A1
WO2014082152A1 PCT/BR2013/000523 BR2013000523W WO2014082152A1 WO 2014082152 A1 WO2014082152 A1 WO 2014082152A1 BR 2013000523 W BR2013000523 W BR 2013000523W WO 2014082152 A1 WO2014082152 A1 WO 2014082152A1
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WIPO (PCT)
Prior art keywords
dopant
diffusion
process according
type dopant
solar cells
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PCT/BR2013/000523
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French (fr)
Portuguese (pt)
Inventor
Izete ZANESCO
Adriano MOEHLECKE
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União Brasileira De Educação E Assistência, Mantenedora Da Pucrs
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Publication of WO2014082152A1 publication Critical patent/WO2014082152A1/en

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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
    • H01L31/18—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 System
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/22—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
    • H01L21/2225—Diffusion sources
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/22—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
    • H01L21/225—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities using diffusion into or out of a solid from or into a solid phase, e.g. a doped oxide layer
    • H01L21/2251—Diffusion into or out of group IV semiconductors
    • H01L21/2254—Diffusion into or out of group IV semiconductors from or through or into an applied layer, e.g. photoresist, nitrides
    • H01L21/2255—Diffusion into or out of group IV semiconductors from or through or into an applied layer, e.g. photoresist, nitrides the applied layer comprising oxides only, e.g. P2O5, PSG, H3BO3, doped oxides
    • 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
    • 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

Definitions

  • the present invention is directed to a process for manufacturing solar cells by depositing and diffusing p-type dopant on one side of a silicon slide and another n-type dopant on the opposite side, using a silicate protective layer. p-doped face of the diffusion of the other n-type dopant. More specifically, the proposed process aims to use boron as p-type dopant and phosphorus as n-type dopant. This avoids the use of the specific oxidation, resin deposition and oxide attack processes required in conventional processes to protect one side of the diffusion being carried out on the other side of the silicon blade.
  • the present invention is in the field of electrical, energy and materials engineering.
  • Solar cells or photovoltaic cells are devices that directly convert solar energy into electrical energy. They do not generate waste during the conversion process, producing clean electricity.
  • Commercially the dominant technology is crystalline silicon cells, which are processed into silicon sheets. In this area, technological development is focused on increasing the efficiency of solar cells or reducing manufacturing costs. The present invention is focused on a solar cell manufacturing process with reduced production cost.
  • US 8,039,734 describes a method of manufacturing solar cell and solar cell pastes comprising these pastes.
  • the pastes comprise an initial metal component containing silver (Ag), a second component including zinc (Zn) and at least one additional component which may be selected from the group comprising boron, phosphorus, among others.
  • US 7,776,722 describes solar cell optimized emitting structures and methods of emitter formation comprising the steps of: depositing a dielectric layer on a substrate; transfer a pattern to the dielectric layer; implant an initial doping material; optionally implanting a second doping material; heat the substrate to redistribute the dopants and optionally form the metal mesh over the substrate.
  • the doping material may comprise arsenic (As), boron (B) or phosphorus (P).
  • the present invention is directed to a process for manufacturing solar cells by depositing and diffusing p-type dopant on one side of a silicon slide and another n-type dopant on the opposite side, using a silicate protective layer. p-type doping face of the other dopant of type n. More specifically, the proposed process aims at the use of boron as d-type d phosphorus and as n-type dopant.
  • the first dopant comprises a p-type dopant.
  • the p-type dopant comprises the boron element.
  • the second dopant comprises an n.
  • the n-type dopant comprises the phosphorus element.
  • the first dopant deposition step comprises spin-on, with evaporation of solvents in the temperature range of 100 ° C to 400 ° C.
  • the first dopant diffusion step comprises performing in a quartz tube furnace.
  • said furnace diffusion comprises being carried out in the temperature range of 700 ° C to 100 ° C.
  • said furnace diffusion comprises being performed between 5 min and 180 min.
  • the dilute hydrofluoric acid comprises a concentration in the range of 1% to 10%.
  • the silicate attack comprises the use of hydrofluoric acid with a concentration greater than 30%.
  • the process for manufacturing dopant-diffusing solar cells on silicon slides further comprises the steps of:
  • Figure 1A shows the steps of the silicon solar cell manufacturing process of the present invention.
  • Figure 1B presents the steps of the process of manufacturing silicon solar cells with n + pp + and or p + nn + conventional structure 1.
  • Figure 1C shows the steps of the manufacturing process of silicon solar cells with n + pp + and or p + nn + conventional structure 2.
  • the present invention provides a novel method of producing solar cells from silicon slides by diffusing boron (or other p-type dopant) and phosphorus (or other n-type dopant) into the silicon slide without using silicon oxide layer and processes using photosensitive resin.
  • silicon oxide is grown Thermally on both sides of a silicon blade, resin is deposited on one side and the oxide layer on the other side is attacked. In this way, one side will be protected by an oxide layer. In the face without oxide, dopant diffusion occurs in the silicon blade and in the face with oxide it is avoided.
  • boron or other p-type dopant
  • a silicate layer is difficult to attack with hydrofluoric acid diluted in deionized water.
  • the slide is submerged in dilute hydrofluoric acid and the S1O2 layer is removed only on the non-boron-doped face, leaving the borosilicate layer, which protects the surface from phosphorus diffusion. .
  • steps of the manufacturing process of boron doping solar cells (or other p-type dopant) are avoided, reducing the production cost.
  • the present invention is understood as solar cells, devices that convert solar energy into electrical energy through the photovoltaic effect.
  • n + pp + frame solar cell technology is based on the formation of the p + region with aluminum paste and conveyor belt diffusion.
  • Another type of dopant to form the p + region is boron, which produces better quality p + regions when compared to aluminum.
  • boron is used as p + dopant because this region remains transparent to solar radiation after the diffusion process, a fact that does not occur when aluminum is used as a dopant.
  • boron diffusion (or other p-type dopant) is performed by deposition of spin-on boron dopant liquid, typical of the semiconductor device industry, on one side of the silicon slide and diffusion is performed on oven with quartz tube.
  • a boron-containing liquid called a doping liquid
  • a doping liquid is dripped onto the silicon blade and rotated with angular velocities from 1000 rpm to 5000 rpm, causing the doping liquid to spread evenly over the blade surface.
  • This process is called spin-on and the equipment where the process is performed is called spinner.
  • the slide is removed from this equipment and placed to evaporate the solvents at a temperature of 100 ° C to 400 ° C for periods of time from 02 min to 40 min. In this process, the solvents are evaporated and the dopant boron remains on the silicon slide.
  • the slides are introduced in a quartz tube electric oven at temperatures of 700 ° C to 1,100 ° C, with boron diffusion occurring on the silicon slides only on the face where it was deposited.
  • oxidation, resin deposition and oxide attack are performed only on the face on which phosphorus will be diffused.
  • the resin should be removed with acetone, isopropanol (optional) and deionized water.
  • Phosphorus diffusion is performed in a quartz tube and after extraction of phosphorosilicates and oxides, the doping liquid with boron is deposited by spin-on and the boron is diffused.
  • the proposed process does not use photosensitive resin, buffer hydrofluoric acid and acetone, which reduces the production cost.
  • photosensitive resin buffer hydrofluoric acid and acetone
  • fewer process steps are required, contributing to lower manufacturing costs by reducing hours of human resources and consumption of electricity, high purity gases and chemicals.

Abstract

The present invention describes a new method for manufacturing solar cells from silicon wafers by diffusion of boron (or another p-type dopant) and phosphorus (or another n-type dopant) into these wafers, a silicate layer being used to protect the face containing boron (or another p-type dopant) from the diffusion of phosphorus (or another n-type dopant). The thermal step for growing the silicon oxide layer and the use of a resin for protecting one of the faces while the oxides are etched with hydrofluoric acid are dispensed with. The invention therefore is advantageous in that it dispenses with the use of photosensitive resin, buffering hydrofluoric acid and acetone, and with at least four steps of solar cell manufacturing methods. It thus reduces manpower/hours and the consumption of electricity, high-purity gases and chemicals, thus lowering production costs in comparison with conventional methods.

Description

Relatório Descritivo de Patente de Invenção  Patent Invention Descriptive Report
PROCESSO DE DIFUSÃO DE DOPANTES EM LÂMINAS DE SILÍCIO PARA A FABRICAÇÃO DE CÉLULAS SOLARES Campo da Invenção  DOCUMENT DIFFUSION PROCESS IN SILICON BLADES FOR MANUFACTURE OF SOLAR CELLS Field of Invention
A presente invenção tem como objetivo um processo de fabricação de células solares por meio da deposição e difusão de dopante tipo p em uma face de uma lâmina de silício e outro dopante tipo n na face oposta, com o uso de uma camada de silicato para proteção da face com dopante tipo p da difusão do outro dopante do tipo n. Mais especificamente, o processo proposto visa o uso de boro como dopante tipo p e fósforo como dopante tipo n. Desta forma, evita-se o uso de processos de oxidação específicos, deposição de resina e ataque de óxidos, necessários em processos convencionais com a função de proteger uma das faces da difusão que está sendo realizada na outra face da lâmina de silício. A presente invenção se situa no campo da engenharia elétrica, de energia e materiais.  The present invention is directed to a process for manufacturing solar cells by depositing and diffusing p-type dopant on one side of a silicon slide and another n-type dopant on the opposite side, using a silicate protective layer. p-doped face of the diffusion of the other n-type dopant. More specifically, the proposed process aims to use boron as p-type dopant and phosphorus as n-type dopant. This avoids the use of the specific oxidation, resin deposition and oxide attack processes required in conventional processes to protect one side of the diffusion being carried out on the other side of the silicon blade. The present invention is in the field of electrical, energy and materials engineering.
Antecedentes da Invenção Background of the Invention
As células solares ou células fotovoltaicas são dispositivos que convertem diretamente energia solar em energia elétrica. Não geram resíduos durante o processo de conversão, produzindo energia elétrica de forma limpa. Comercialmente a tecnologia dominante é a de células de silício cristalino, que são processadas em lâminas de silício. Nesta área, o desenvolvimento tecnológico está focado no aumento da eficiência das células solares ou na redução do custo de fabricação. A presente invenção está focada em um processo de fabricação de células solares com redução do custo de produção.  Solar cells or photovoltaic cells are devices that directly convert solar energy into electrical energy. They do not generate waste during the conversion process, producing clean electricity. Commercially the dominant technology is crystalline silicon cells, which are processed into silicon sheets. In this area, technological development is focused on increasing the efficiency of solar cells or reducing manufacturing costs. The present invention is focused on a solar cell manufacturing process with reduced production cost.
A busca na literatura científica e patentária apontou alguns documentos relevantes para a presente invenção, os quais serão descritos a seguir.  The search in the scientific and patent literature has pointed out some relevant documents for the present invention, which will be described below.
O documento US 8,039,734 descreve um método de fabricação de pastas para células solares e células solares compreendendo estas pastas. As pastas compreendem um componente inicial com metais contendo prata (Ag), um segundo componente incluindo zinco (Zn) e pelo menos um componente adicional que pode ser escolhido do grupo que compreende boro, fósforo, entre outros. US 8,039,734 describes a method of manufacturing solar cell and solar cell pastes comprising these pastes. The pastes comprise an initial metal component containing silver (Ag), a second component including zinc (Zn) and at least one additional component which may be selected from the group comprising boron, phosphorus, among others.
O referido documento US 8,039, 734 não antecipa a invenção, uma vez que, apesar de citar o uso de boro e fósforo em uma pasta que será usada em um eletrodo, o mesmo discorre sobre pastas contendo Ag como base e em D1 nada é dito a respeito da ausência de resina para proteção da fase oposta e nem o uso da técnica de spin-on, conforme descrito pela invenção.  The aforementioned US 8,039,734 does not anticipate the invention, since, although citing the use of boron and phosphorus in a paste to be used in an electrode, it discusses pastes containing Ag as a base and in D1 nothing is said. regarding the absence of resin for protection of the opposite phase nor the use of the spin-on technique as described by the invention.
O documento US 7,776,722 descreve estruturas emissoras otimizadas em células solares e métodos de formação de emissores compreendendo as etapas de: depositar uma camada dielétrica sobre um substrato; transferir um padrão para a camada dielétrica; implantar um material dopante inicial; opcionalmente implantar um segundo material dopante; aquecer o substrato para redistribuir os dopantes e opcionalmente formar a malha metálica sobre o substrato. Nestas etapas, o material dopante pode compreender arsénio (As), boro (B) ou fósforo (P).  US 7,776,722 describes solar cell optimized emitting structures and methods of emitter formation comprising the steps of: depositing a dielectric layer on a substrate; transfer a pattern to the dielectric layer; implant an initial doping material; optionally implanting a second doping material; heat the substrate to redistribute the dopants and optionally form the metal mesh over the substrate. At these stages, the doping material may comprise arsenic (As), boron (B) or phosphorus (P).
O referido documento US 7,776,722 não antecipa a presente invenção uma vez que, apesar de citar o uso de boro ou fósforo como possíveis dopantes, nada é dito a respeito da ausência de óxido de silício e resina para proteção de uma das faces e nem o uso da técnica de spin-on para deposição de dopantes.  Said US 7,776,722 does not anticipate the present invention since, although citing the use of boron or phosphorus as possible dopants, nothing is said about the absence of silicon oxide and resin to protect one side and the use spin-on technique for doping deposition.
Do que se depreende da literatura pesquisada, não foram encontrados documentos antecipando ou sugerindo os ensinamentos da presente invenção, de forma que a solução aqui proposta possui novidade e atividade inventiva frente ao estado da técnica.  From what can be inferred from the researched literature, no documents were found anticipating or suggesting the teachings of the present invention, so that the solution proposed here has novelty and inventive activity in relation to the state of the art.
Sumário da Invenção Summary of the Invention
A presente invenção tem como objetivo um processo de fabricação de células solares por meio da deposição e difusão de dopante tipo p em uma face de uma lâmina de silício e outro dopante tipo n na face oposta, com o uso de uma camada de silicato para proteção da face com dopante tipo p da difusão do outro dopante do tipo n. Mais especificamente, o processo proposto visa o uso de boro como dopante tipo p e fósforo como dopante tipo n. The present invention is directed to a process for manufacturing solar cells by depositing and diffusing p-type dopant on one side of a silicon slide and another n-type dopant on the opposite side, using a silicate protective layer. p-type doping face of the other dopant of type n. More specifically, the proposed process aims at the use of boron as d-type d phosphorus and as n-type dopant.
É, portanto, objeto da presente invenção processo de difusão de dopantes em lâminas de silício para a fabricação de células solares compreendendo as etapas de:  It is, therefore, an object of the present invention to provide a silicon-blade dopant diffusion process for manufacturing solar cells comprising the steps of:
a. ataque anisotrópico ou de texturação;  The. anisotropic or textural attack;
b. limpeza RCA;  B. RCA cleaning;
c. deposição do primeiro dopante;  ç. deposition of the first dopant;
d. difusão do primeiro dopante;  d. diffusion of the first dopant;
e. ataque de Si02 na face sem dopagem em ácido fluorídrico diluído; f. limpeza RCA; and. Si0 2 attack on the face without doping in dilute hydrofluoric acid; f. RCA cleaning;
g. difusão do segundo dopante;  g. diffusion of the second dopant;
h. ataque de silicatos em ácido fluorídrico;  H. silicate attack on hydrofluoric acid;
Em uma realização preferencial, o primeiro dopante compreende um dopante do tipo p.  In a preferred embodiment, the first dopant comprises a p-type dopant.
Em uma realização preferencial, o dopante do tipo p compreende o elemento boro.  In a preferred embodiment, the p-type dopant comprises the boron element.
Em uma realização preferencial, o segundo dopante compreende um dopante do tipo n.  In a preferred embodiment, the second dopant comprises an n.
Em uma realização preferencial, o dopante do tipo n compreende o elemento fósforo.  In a preferred embodiment, the n-type dopant comprises the phosphorus element.
Em uma realização preferencial, a etapa de deposição do primeiro dopante compreende ser realizada por spin-on, com evaporação dos solventes na faixa de temperatura de 100 °C a 400 °C.  In a preferred embodiment, the first dopant deposition step comprises spin-on, with evaporation of solvents in the temperature range of 100 ° C to 400 ° C.
Em uma realização preferencial, a etapa de difusão do primeiro dopante compreende a realização em um forno com tubo de quartzo.  In a preferred embodiment, the first dopant diffusion step comprises performing in a quartz tube furnace.
Em uma realização preferencial, a dita difusão no forno compreende ser realizada na faixa de temperatura de 700 °C a 1 00 °C.  In a preferred embodiment, said furnace diffusion comprises being carried out in the temperature range of 700 ° C to 100 ° C.
Em uma realização preferencial, a dita difusão no forno compreende ser realizada entre 5 min e 180 min.  In a preferred embodiment, said furnace diffusion comprises being performed between 5 min and 180 min.
Em uma realização preferencial, o ácido fluorídrico diluído compreende uma concentração na faixa de 1% a 10%. In a preferred embodiment, the dilute hydrofluoric acid comprises a concentration in the range of 1% to 10%.
Em uma realização preferencial, o ataque de silicatos compreende o uso de ácido fluorídrico com concentração maior que 30%.  In a preferred embodiment, the silicate attack comprises the use of hydrofluoric acid with a concentration greater than 30%.
Em uma realização preferencial, o processo para a fabricação de células solares com difusão de dopantes em lâminas de silício compreende adicionalmente as etapas de:  In a preferred embodiment, the process for manufacturing dopant-diffusing solar cells on silicon slides further comprises the steps of:
a. limpeza RCA e/ou deposição de camada de passivação; b. deposição de filme antirreflexo (AR);  The. RCA cleaning and / or passivation layer deposition; B. antireflective film (AR) deposition;
c. metalização e  ç. metallization and
d. isolamento de borda.  d. edge insulation.
Estes e outros objetos da invenção serão imediatamente valorizados pelos versados na arte e pelas empresas com interesses no segmento, e serão descritos em detalhes suficientes para sua reprodução na descrição a seguir. Breve Descrição das Figuras  These and other objects of the invention will be immediately appreciated by those skilled in the art and companies having an interest in the segment, and will be described in sufficient detail for their reproduction in the following description. Brief Description of the Figures
Figura 1A apresenta as etapas do processo de fabricação de células solares de silício da presente invenção.  Figure 1A shows the steps of the silicon solar cell manufacturing process of the present invention.
Figura 1 B apresenta as etapas do processo de fabricação de células solares de silício com estrutura n+pp+ e ou p+nn+ convencional 1. Figure 1B presents the steps of the process of manufacturing silicon solar cells with n + pp + and or p + nn + conventional structure 1.
Figura 1C apresenta as etapas do processo de fabricação de células solares de silício com estrutura n+pp+ e ou p+nn+ convencional 2. Figure 1C shows the steps of the manufacturing process of silicon solar cells with n + pp + and or p + nn + conventional structure 2.
Descrição Detalhada da Invenção Detailed Description of the Invention
Os exemplos aqui mostrados têm o intuito somente de exemplificar uma das inúmeras maneiras de se realizar a invenção, contudo, sem limitar o escopo da mesma.  The examples shown herein are intended solely to exemplify one of the numerous ways of carrying out the invention, however, without limiting the scope thereof.
A presente invenção proporciona um novo método de produção de células solares, a partir de lâminas de silício, por meio da difusão de boro (ou outro dopante tipo p) e fósforo (ou outro dopante tipo n) na lâmina de silício, sem a utilização de camada de óxido de silício e de processos que usam resina fotossensível. Em processos convencionais, o óxido de silício é crescido termicamente sobre ambas as faces de uma lâmina de silício, deposita-se resina em uma das faces e se ataca a camada de óxido da outra face. Deste modo, uma das faces ficará protegida por uma camada de óxido. Na face sem óxido, ocorre a difusão do dopante na lâmina de silício e na face com óxido a mesma é evitada. The present invention provides a novel method of producing solar cells from silicon slides by diffusing boron (or other p-type dopant) and phosphorus (or other n-type dopant) into the silicon slide without using silicon oxide layer and processes using photosensitive resin. In conventional processes, silicon oxide is grown Thermally on both sides of a silicon blade, resin is deposited on one side and the oxide layer on the other side is attacked. In this way, one side will be protected by an oxide layer. In the face without oxide, dopant diffusion occurs in the silicon blade and in the face with oxide it is avoided.
Na presente invenção, com a difusão de boro (ou outro dopante tipo p), cujo dopante foi depositado por spin-on, forma-se uma camada de silicato, difícil de atacar com ácido fluorídrico diluído em água deionizada. Após a difusão de boro (ou outro dopante tipo p), a lâmina é submersa em ácido fluorídrico diluído e é retirada a camada de S1O2 somente na face sem dopagem com boro, permanecendo a camada de borosilicato, que protege a superfície da difusão de fósforo. Desta forma, são evitadas etapas do processo de fabricação de células solares com dopagem com boro (ou outro dopante tipo p), reduzindo o custo de produção.  In the present invention, with the diffusion of boron (or other p-type dopant), whose dopant was deposited by spin-on, a silicate layer is difficult to attack with hydrofluoric acid diluted in deionized water. After boron diffusion (or other p-type dopant), the slide is submerged in dilute hydrofluoric acid and the S1O2 layer is removed only on the non-boron-doped face, leaving the borosilicate layer, which protects the surface from phosphorus diffusion. . In this way, steps of the manufacturing process of boron doping solar cells (or other p-type dopant) are avoided, reducing the production cost.
Células solares  Solar cells
A presente invenção entende como células solares, dispositivos que convertem energia solar em energia elétrica por meio do efeito fotovoltaico.  The present invention is understood as solar cells, devices that convert solar energy into electrical energy through the photovoltaic effect.
A tecnologia padrão da indústria atual de células solares com estrutura n+pp+ está baseada na formação da região p+ com pasta de alumínio e difusão em forno de esteira. Outro tipo de dopante para formar a região p+ (emissor ou campo retrodifusor) é o boro, que produz regiões p+ de melhor qualidade quando comparadas ao alumínio. Em células solares com estrutura p+nn+, usa- se boro como dopante p+ porque esta região permanece transparente à radiação solar após o processo de difusão, fato que não ocorre quando o alumínio é usado como dopante. Today's industry-standard n + pp + frame solar cell technology is based on the formation of the p + region with aluminum paste and conveyor belt diffusion. Another type of dopant to form the p + region (emitter or retrodiffuser field) is boron, which produces better quality p + regions when compared to aluminum. In solar cells with p + nn + structure, boron is used as p + dopant because this region remains transparent to solar radiation after the diffusion process, a fact that does not occur when aluminum is used as a dopant.
No processo apresentado, a difusão de boro (ou outro dopante tipo p) é realizada pela deposição de líquido dopante com boro por spin-on, típico da indústria de dispositivos semicondutores, em uma das faces da lâmina de silício e a difusão é realizada em forno com tubo de quartzo.  In the process presented, boron diffusion (or other p-type dopant) is performed by deposition of spin-on boron dopant liquid, typical of the semiconductor device industry, on one side of the silicon slide and diffusion is performed on oven with quartz tube.
Um líquido que contém boro, denominado de líquido dopante, é gotejado sobre a lâmina de silício e esta é colocada em movimento de rotação com velocidades angulares de 1000 rpm a 5000 rpm, fazendo com que o líquido dopante se espalhe uniformemente sobre a superfície da lâmina. Este processo é denominado de spin-on e o equipamento onde se realiza o processo é chamado de spinner. A lâmina é retirada deste equipamento e colocada para evaporar os solventes em temperatura de 100 °C a 400 °C, por períodos de tempo de 02 min a 40 min. Neste processo, os solventes são evaporados, permanecendo sobre a lâmina de silício o dopante boro. As lâminas são introduzidas em forno elétrico com tubo de quartzo, a temperaturas de 700 °C a 1 100 °C, ocorrendo a difusão de boro nas lâminas de silício somente na face onde o mesmo foi depositado. A boron-containing liquid, called a doping liquid, is dripped onto the silicon blade and rotated with angular velocities from 1000 rpm to 5000 rpm, causing the doping liquid to spread evenly over the blade surface. This process is called spin-on and the equipment where the process is performed is called spinner. The slide is removed from this equipment and placed to evaporate the solvents at a temperature of 100 ° C to 400 ° C for periods of time from 02 min to 40 min. In this process, the solvents are evaporated and the dopant boron remains on the silicon slide. The slides are introduced in a quartz tube electric oven at temperatures of 700 ° C to 1,100 ° C, with boron diffusion occurring on the silicon slides only on the face where it was deposited.
Como o silicato do dopante tipo p formado é mais resistente ao ataque em ácido fluorídrico diluído em água deionizada do que uma camada de óxido de silício, as lâminas são imersas nesta solução para atacar somente o óxido formado na face em que não foi depositado boro, para prepará-la para a difusão de fósforo. Deste modo, uma das faces permanece coberta com silicato e na outra, sem óxido, ocorrerá a difusão de fósforo no passo térmico subsequente. Foi provado que o borosilicato protege a face com boro da difusão de fósforo com POCI3 em forno com tubo de quartzo. Desta forma, além de não utilizar resina fotossensível, ácido fluorídrico tampão para atacar a camada de óxido e acetona para dissolver a resina, são reduzidas 4 etapas do processo de fabricação convencional 2 e 9 etapas do processo convencional 1 , conforme mostra a Figura 1. Since the p-type dopant silicate formed is more resistant to attack in hydrochloric acid diluted in deionized water than a silicon oxide layer, the blades are immersed in this solution to attack only the oxide formed on the non-boron face, to prepare it for phosphorus diffusion. In this way, one side remains covered with silicate and the other without oxide, phosphorus diffusion will occur in the subsequent thermal step. Borosilicate has been proven to protect the boron face from phosphorus diffusion with POCI 3 in a quartz tube furnace. Thus, in addition to not using photosensitive resin, hydrofluoric acid buffer to attack the oxide layer and acetone to dissolve the resin, 4 steps of conventional manufacturing process 2 and 9 steps of conventional process 1 are reduced, as shown in Figure 1.
No processo convencional 1 , para evitar a entrada de fósforo em ambas as faces da célula solar, é necessária a realização de oxidação, deposição de resina e ataque do óxido (com ácido fluorídrico tampão, HF+NH4F) somente na face em que será difundido o fósforo. Depois do ataque de óxidos, a resina deve ser removida com acetona, isopropanol (opcional) e água deionizada. Para proteger a face com fósforo da difusão de boro, outra oxidação é realizada, seguida de deposição de resina e ataque do óxido na face em que será depositado boro. Novamente, deve-se proceder a remoção da resina com uso de acetona, isopropanol (opcional) e água deionizada. Neste caso, a difusão de boro padrão é realizada em forno com tubo de quartzo com o dopante BBr3. In the conventional process 1, to prevent phosphorus from entering both sides of the solar cell, oxidation, resin deposition and oxide attack (with hydrofluoric acid buffer, HF + NH 4 F) is required only on the face where the phosphorus will be diffused. After oxide attack, the resin should be removed with acetone, isopropanol (optional) and deionized water. To protect the phosphorus face from boron diffusion, another oxidation is performed, followed by resin deposition and attack of the oxide on the face where boron will be deposited. Again, resin must be removed using acetone, isopropanol (optional) and deionized water. In this case, the Standard boron diffusion is performed in a quartz tube furnace with BBr 3 dopant.
No processo convencional 2, é realizada a oxidação, deposição de resina e ataque do óxido (com ácido fluorídrico tampão) somente na face em que será difundido fósforo. Da mesma forma que no processo convencional 1 , a resina deve ser removida com acetona, isopropanol (opcional) e água deionizada. Procede-se com a difusão de fósforo em tubo de quartzo e depois da extração dos fosforosilicatos e óxidos, deposita-se o líquido dopante com boro por spin-on e se realiza a difusão de boro.  In conventional process 2, oxidation, resin deposition and oxide attack (with buffer hydrofluoric acid) are performed only on the face on which phosphorus will be diffused. As with conventional process 1, the resin should be removed with acetone, isopropanol (optional) and deionized water. Phosphorus diffusion is performed in a quartz tube and after extraction of phosphorosilicates and oxides, the doping liquid with boron is deposited by spin-on and the boron is diffused.
No processo proposto não se utiliza resina fotossensível, ácido fluorídrico tampão e acetona, o que diminui o custo de produção. Além disto, para produzir as mesmas células solares dopadas com boro (ou outro dopante tipo p) e fósforo (ou outro dopante tipo n), é necessário um menor número de etapas do processo, contribuindo para a diminuição dos custos de fabricação pela redução em horas de recursos humanos e consumo de energia elétrica, gases de alta pureza e produtos químicos.  The proposed process does not use photosensitive resin, buffer hydrofluoric acid and acetone, which reduces the production cost. In addition, to produce the same boron-doped (or other p-type dopant) and phosphorous (or other n-type dopant) solar cells, fewer process steps are required, contributing to lower manufacturing costs by reducing hours of human resources and consumption of electricity, high purity gases and chemicals.

Claims

Reivindicações PROCESSO DE DIFUSÃO DE DOPANTES EM LÂMINAS DE SILÍCIO PARA A FABRICAÇÃO DE CÉLULAS SOLARES Claims DISTRIBUTION PROCESS OF SILENT BLADES FOR THE MANUFACTURE OF SOLAR CELLS
1. Processo de difusão de dopantes em lâminas de silício para a fabricação de células solares caracterizado por compreender as etapas de: 1. Silicon lamina dopant diffusion process for the manufacture of solar cells, comprising the steps of:
a. ataque anisotrópico ou de texturação;  The. anisotropic or textural attack;
b. limpeza RCA;  B. RCA cleaning;
c. deposição do primeiro dopante;  ç. deposition of the first dopant;
d. difusão do primeiro dopante;  d. diffusion of the first dopant;
e. ataque de S1O2 na face sem dopagem em ácido fluorídrico diluído; f. limpeza RCA; and. S1O 2 attack on the face without doping in dilute hydrofluoric acid; f. RCA cleaning;
g. difusão do segundo dopante;  g. diffusion of the second dopant;
h. ataque de silicatos em ácido fluorídrico;  H. silicate attack on hydrofluoric acid;
2. Processo, de acordo com a reivindicação 1 , caracterizado pelo processo para fabricação de células solares com difusão de dopantes em lâminas de silício por compreender adicionalmente as etapas de: a. limpeza RCA e/ou deposição de camada de passivação;  Process according to Claim 1, characterized in that the process for manufacturing dopant-diffused solar cells on silicon slides further comprises the steps of: a. RCA cleaning and / or passivation layer deposition;
b. deposição de filme antirreflexo (AR);  B. antireflective film (AR) deposition;
c. metalização e  ç. metallization and
d. isolamento de borda.  d. edge insulation.
3. Processo, de acordo com a reivindicação 1 , caracterizado pelo primeiro dopante ser um dopante do tipo p.  Process according to Claim 1, characterized in that the first dopant is a p-type dopant.
4. Processo, de acordo com a reivindicação 3, caracterizado pelo dopante do tipo p ser o elemento boro.  Process according to Claim 3, characterized in that the p-type dopant is the boron element.
5. Processo, de acordo com a reivindicação 1 , caracterizado pelo segundo dopante ser um dopante do tipo n.  Process according to Claim 1, characterized in that the second dopant is an n-type dopant.
6. Processo, de acordo com a reivindicação 5, caracterizado pelo dopante do tipo n ser o elemento fósforo.  Process according to Claim 5, characterized in that the n-type dopant is the phosphorus element.
7. Processo, de acordo com a reivindicação 1 , caracterizado pela etapa de deposição do primeiro dopante ser realizada por spin-on, com evaporação de solventes na faixa de temperatura entre 100 °C e 400 °C.Process according to Claim 1, characterized in that the step of deposition of the first dopant is carried out by spin-on with evaporation of solvents in the temperature range 100 ° C to 400 ° C.
8. Processo, de acordo com a reivindicação 1 , caracterizado pela etapa de difusão do primeiro dopante ser realizada em um forno com tubo de quartzo. Process according to Claim 1, characterized in that the diffusion step of the first dopant is carried out in a quartz tube furnace.
9. Processo, de acordo com a reivindicação 1 , caracterizado pela dita difusão no forno com tubo de quartzo ser realizada na faixa de temperatura de 700 °C a 1100 °C.  Process according to Claim 1, characterized in that said diffusion in the quartz tube furnace is carried out in the temperature range of 700 ° C to 1100 ° C.
10. Processo, de acordo com a reivindicação 1 , caracterizado pela dita difusão no forno com tubo de quartzo compreender a faixa de duração de 5 min a 180 min.  Process according to claim 1, characterized in that said diffusion in the quartz tube furnace comprises the duration range of 5 min to 180 min.
11. Processo, de acordo com a reivindicação 1 , caracterizado pelo ácido fluorídrico diluído compreender uma concentração entre 1 % a 10%. Process according to Claim 1, characterized in that the dilute hydrofluoric acid comprises a concentration between 1% and 10%.
12. Processo, de acordo com reinvindicação 1 , caracterizado pelo ataque de silicatos ser realizado com ácido fluorídrico com concentração maior que 30%. Process according to Claim 1, characterized in that the silicate attack is carried out with hydrofluoric acid with a concentration greater than 30%.
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