TW201312643A - Forming an oxide layer on a flat conductive surface - Google Patents

Abstract

A method and apparatus for electrochemically forming an oxide layer on a flat conductive surface which involves positioning a working electrode bearing the flat conductive surface in opposed parallel spaced apart relation to a flat conductive surface of a counter electrode such that the flat conductive surface of the working electrode and the flat conductive surface of the counter electrode are generally opposed, horizontally oriented, and define a space therebetween. A volume of organic electrolyte solution containing chemicals for forming the oxide layer on the flat conductive surface of the working electrode is arranged to flood the flat conductive surface of the counter electrode surface and to occupy the space defined between the flat conductive surface of the working electrode and the flat conductive surface of the counter electrode such that at least the flat conductive surface of the counter electrode is in contact with the organic electrolyte solution and substantially only the flat conductive surface of the working electrode is in contact with the organic electrolyte solution. An electric current flows between substantially only the flat conductive surface of the counter electrode and substantially only the flat conductive surface of the working electrode, in the organic electrolyte solution, for a period of time and at a magnitude sufficient to cause the chemicals to form the oxide layer on the flat conductive surface of the working electrode.

Description

Technique for forming an oxide layer on a flat conductive surface Field of invention

This application is a summary of techniques for forming oxide layers on flat conductive surfaces such as semiconductor components and photovoltaic (PV) cells.

Background of the invention

Photovoltaic (PV) cells, and more particularly crystalline photovoltaic cells, generally have a side surface operative to receive light and a back side surface opposite the front side surface. The front side surface is part of an emitter of the photovoltaic cell and in which a plurality of electrical contacts are formed, and the back side surface has at least one electrical contact. The photovoltaic cells are connected to an external electrical circuit using electrical contacts on the front and back side surfaces.

In order to improve photovoltaic cell efficiency by reducing light reflection, the front side surface can be treated by wet chemical texturing and deposition of an anti-reflective coating. Antireflective coatings typically comprise an optically clear material having a thickness of from about 1.8 to about 2.3 and a thickness of from about 80 to 100 nm. The use of an anti-reflective coating and texturing system will reduce the initial light reflection from 38% to 8 to 12% on polycrystalline photovoltaic cells and to 5 to 7% on single crystal photovoltaic cells. A corresponding gain that results in photovoltaic cell efficiency.

For wafer solar cells, the most common type of anti-reflective coating is SiN ₄ deposited by atmospheric pressure chemical vapor deposition (APCVD) or plasma enhanced chemical vapor deposition (PECVD). Although virtually all photovoltaic cell manufacturing companies use this type of anti-reflective coating, these deposition techniques require high temperatures up to 700 ° C, high energy consumption, and expensive manufacturing equipment.

SiN ₄ anti-reflective coatings cannot be used to produce amorphous germanium photovoltaic cells and some types of hetero-junction photovoltaic cells because these types of cells cannot withstand processing temperatures above 300 °C. These types of photovoltaic cells use other types of anti-reflective coatings, such as conductive metal oxides, such as aluminum-doped zinc oxide Al:Zn _y O _x , fluorine-doped indium oxide F:In _y O _x , or tin-doped Indium oxide: In _x Sn _y O _z (also known as ITO). Transparent conductive oxides have been widely used in thin film photovoltaic cells and modules because they reduce light reflection and aid in establishing a low resistance electrical connection between the front or back side surface of the photovoltaic cell and the current collecting metallization pattern.

The normal system utilizes magnetron sputtering, evaporation, or chemical vapor deposition techniques for the industrial deposition of conductive metal oxide antireflective coatings on temperature sensitive photovoltaic cells. Although these techniques do not require high temperatures, they use expensive equipment and high vacuum processes, and provide only low production capacity and result in wasted expensive materials.

The use of SiN ₄ as an anti-reflective coating increases the efficiency of the photovoltaic cell due to lower light reflection and due to the built-in positive charge of the SiN ₄ layer. This built-in charge reflects a negative charge from the front surface of the p-type crystalline photovoltaic cell, which improves passivation due to reduced charge recombination. This improved passivation results in a photovoltaic cell efficiency gain.

If an Al ₂ O ₃ layer having a built-in negative charge of about 20 to 200 nm thickness is deposited on the back side of a p-type crystalline photovoltaic cell, a passivation quality similar to that of SiN ₄ can be achieved. This built-in negative charge reflects the negative charge generated by the photovoltaic cell when it is illuminated from the back surface of the solar cell. The aluminum oxide layer can be deposited by atomic layer deposition (ALD) techniques as described in the following documents: B. Hoex, J. Schmidt, P. Pohl, Van dersenden (MCM) Van de Sanden) and WMM Kessels under the name "Surface passivation by atomic layer deposition of Al ₂ O ₃ ", Journal of Applied Physics (PHYRITY OF PHYSICS) 104, p. 044903-1- 044903-12, 2008 documents; and G. Dingemans, W. Beyer, MCM van de Sanden, and WMM Kessels in the name "by Al Application of physical communication (APPLIED PHYSICS LETTERS) 97, 152106_2010 to the hydrogen induced decay of the Si interface of the ₂ O ₃ film and the SiO ₂ /Al ₂ O ₃ deposit. And deposited by RF magnetron sputtering, as described in the following documents: T. T. and Chiss (A. Cuevas) in the surface passivation of hydrogen in the spinel of sputtered alumina. The role of "PROGRESS IN PHOTOVOLTAICS: RESEARCH AND APPLICATIONS", 2011; 19: 320-325 documents. Unfortunately these technologies are quite expensive and do not provide sufficient production capacity.

If cost-effective technologies and equipment can be developed and delivered in volume production, the passivation effect of an Al ₂ O ₃ layer can be utilized to improve the efficiency of the wafer photovoltaic cell.

Efficient passivation of the germanium solar cell can be achieved by forming a passivation layer of yttria (SiO ₂ ) having a thickness of about 10 nm to 20 nm on the front and/or back surface of the solar cell. Efficient passivation occurs due to a strong decrease in the density of the Si interface. The SiO ₂ passivation layer can be formed by a thermal process at a very high temperature (~1050 ° C) or by a wet oxidation process at ~800 ° C in a humid atmosphere with H ₂ O, such as G. Dingemans, Vanderson. MCM van de Sanden, and WMM Kessels, in the name "Using an ultra-thin Al ₂ O ₃ cover film with a good Si surface passivation of low temperature SiO ₂ ", Phys. Status Solidi RRL 5, No. 1,22-24 (2011) is described in the document. Unfortunately, these processes are expensive, consume a lot of energy, and are not conducive to the high precision of SiO ₂ layer production to achieve the desired thickness and uniformity. Many efforts have been made to avoid the high temperatures (~1050 ° C) and long processing times required for the formation of hot SiO ₂ to prevent deterioration of the quality of the Si bulk. However, to date, it has been possible to produce significantly worse quality SiO ₂ layers and lower quality passivation of nitric acid oxidation (NAOS) and chemical vapor deposition (CVD), such as those obtained with thermally grown SiO ₂ . ) A low temperature alternative to achieve the best surface passivation efficiency.

An alternative method involves the use of an electroless plating technique to form a metal oxide layer, such as an aluminum oxide, zinc oxide or indium oxide layer, on a semiconductor substrate.

Named "Methods for Producing Zinc Oxide Thin Films, Methods for Producing Photovoltaic Components, and for Producing Semiconductor Components" issued to Masafumi Sano, Souraku-gun, Yuichi Sonoda US Patent No. 6,346,184 B1 describes a method for producing a zinc oxide film, wherein a current is passed through a conductive substrate immersed in an aqueous solution containing at least zinc ions and carboxylate ions, and a immersion in the aqueous solution. A thin film of zinc oxide is formed between the electrodes on the conductive substrate. This method stabilizes the formation of the zinc oxide film and improves the adhesion between the film and the substrate. The zinc oxide film is deposited on a cathode comprising an optically transparent or opaque substrate coated with, for example, indium oxide (In ₂ O ₃ ), indium tin oxide (In ₂ O ₃ + A transparent conductive material such as SnO ₂ ), zinc oxide (ZnO), or tin oxide (SnO ₂ ), which is deposited by sputtering, vacuum deposition, or chemical vapor deposition. The optically opaque conductive substrate on the cathode may be a flexible stainless steel film coated with a thickness of 0.15 mm of silver and or a layer of conductive zinc oxide. The back side of the stainless steel film is covered with an electrically insulating film to prevent electroplating of the zinc oxide layer thereon. A metal foil can be used as an opaque conductive substrate. This patent discloses that a 4-N purity zinc plate is used as the anode. The aqueous electrolyte solution described is an aqueous ammonia solution of zinc hydroxide, zinc oxalate or zinc oxide having a hydrogen ion index (pH) of a concentration of 0.001 to 3.0 mol/L and a pH between 8 and pH 12.5.

A method of forming an indium oxide film by an electrodeposition process or an electrodeless deposition process, a substrate provided with the indium oxide for a semiconductor element, and a semiconductor element provided with the substrate are issued. Arao), Nara, Katsumi Nakagwa, and Yukiko Iwasaki, U.S. Patent No. 6,110,347, the disclosure of which is incorporated herein by reference. The substrate and an auxiliary electrode are immersed in an aqueous solution containing at least nitrate and indium ions and cause an electric current to flow between the substrate and the auxiliary electrode, thereby causing an indium oxide film to be formed on the substrate. Further, a film forming method for forming indium oxide on a substrate by an electrodeless deposition process using an aqueous solution, and a substrate for a semiconductor element, and a photovoltaic element produced by the film forming method are provided. In the described process, the negative cathode electrode can be made of any conductive metal or alloy. For example, the cathode can be a 0.12 mm thick stainless steel plate having a back surface covered with an insulating tape to protect it from indium oxide deposition. The positive anode electrode can be made of a 0.2 mm thick platinum plate of 4-N purity. The electrolyte can be an aqueous solution containing indium nitrate and sucrose or dextrin. Please note that the electrolyte must always be stirred by a magnetic stirrer.

A method for forming a thin zinc oxide film, and a method for producing a semiconductor device substrate and a photovoltaic element using an indium oxide film is disclosed in U.S. Patent No. 6,133,061 to Yuichi Sonoda. A method of forming a film of zinc oxide on a conductive substrate by electrode position from an aqueous solution while preventing deposition of the film on the back surface of the substrate. More specifically, a film deposition preventing electrode for preventing deposition of a film on the back surface of the substrate is provided in an aqueous solution containing nitrate ions, and an electric current is supplied so that the auxiliary electrode is at a higher potential than the substrate. The substrate is at a higher potential than the film deposition preventing electrode. This method can be applied to a process for preparing a solar cell. Unfortunately, this method requires the use of a third auxiliary electrode to protect the back side of the conductive substrate from undesirable electrochemical treatment.

The methods described in U.S. Patent Nos. 6,346,184, 6,110,347 and 6,133,061 have several disadvantages. While these methods permit the deposition of a zinc oxide film on a metal or semiconductor conductive substrate, it requires electrical insulation on the back side of the substrate to prevent zinc oxide from depositing thereon. Moreover, the above method requires continued stirring of the electrolyte solution during deposition. In addition, the use of aqueous electrolyte solutions requires careful pH control in a narrow range to prevent precipitation of zinc/indium hydroxide in higher pH values and to avoid dissolution of zinc/indium from the substrate at lower pH. Hydroxide/oxide. Moreover, the method disclosed in the above U.S. Patent may not provide a reliable technique for controlling film thickness in situ.

Yet another disadvantage of the above patents is the use of an aqueous electrolyte solution. It is known that the deposition of ZnO film from an aqueous zinc salt solution will be accompanied by the formation of hydroxides which degrade the quality of the ZnO film, [S. Peulon, D. Lincot, oxidation from oxidized aqueous zinc chloride solution). Study on the mechanical action of cathodic electrodeposition of zinc and zinc hydroxychloride membranes], J. Electrochem. Soc., 45 (1998), 864-874], high temperature is required in aqueous pools ( 60 to 85 ° C) to shift the equilibrium balance of a hydroxide/oxide reaction to the preferred formation of oxides [D. Chu, Y. Masuda, T. Ohji ), and K. Kato, shape-controlled growth of electrodeposited In(OH) ₃ /In ₂ O ₃ nanostructures, Langmuir 2010, 26(18), 14814-14820]. Higher temperature (65 to 85 ° C) electrodeposition of the indium oxide/hydroxide from the aqueous solution of the indium salt does not prevent preferential growth of the indium hydroxide nanostructure. Further, it is necessary to dry at 80 ° C for 10 hours and at 300 ° C for 30 minutes to obtain indium oxide by dehydration of indium hydroxide.

Summary of invention

In accordance with an aspect of the invention, a method for electrochemically forming an oxide layer on a flat conductive surface is provided. The method involves positioning a working electrode supporting the flat conductive surface in a relatively parallel spaced relationship with respect to a flat conductive surface of an auxiliary electrode such that the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode are summarized Relatively and horizontally oriented and defining a space therebetween. The method further involves causing an organic electrolyte solution containing one of the chemicals used to form an oxide layer on the flat conductive surface of the working electrode, flooding the flat conductive surface of the auxiliary electrode surface, and occupying the flat conductive surface of the working electrode and assisting The space defined between the flat conductive surfaces of the electrodes is such that at least the flat conductive surface of the auxiliary electrode is in contact with the organic electrolyte solution and substantially only the flat conductive surface of the working electrode is in contact with the organic electrolyte solution. The method further involves causing a current in the organic electrolyte solution to flow between a flat conductive surface of substantially only the auxiliary electrode and a substantially flat conductive surface of the working electrode only for a period of time sufficient to cause a chemical at the working electrode A strength of the oxide layer formed on the flat conductive surface is the same.

The method may involve causing the volume of the organic electrolyte solution to occupy a space defined between the flat auxiliary electrode surface and the flat conductive surface of the working electrode, and may involve holding the working electrode such that substantially only the flat conductive surface of the working electrode is in contact with the organic electrolyte solution, However, the overall working electrode is not immersed in the organic electrolyte solution.

The retaining system can include a substantial portion of one side of the working electrode that is opposite the flat conductive surface of the working electrode from contacting the electrolyte solution.

The protection system may be configured to hold a rear side of the working electrode against a holding surface supporting a sealing member, the sealing member being operatively configured to contact a working electrode rear side adjacent an outer peripheral edge of the working electrode rear side .

Holding the working electrode against the holding surface system can include causing a negative pressure to occur adjacent the back side of the working electrode, such that the ring chamber pressure presses the back side of the working electrode against the seal.

Creating a negative pressure may involve providing a vacuum adjacent the seal.

The flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode are separately separated by a distance which facilitates adhesion of the organic electrolyte solution to the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode due to the capillary force of the organic electrolyte solution.

Positioning the working electrode system can involve positioning the working electrode such that the flat conductive surface of the working electrode is between about 0.1% and about 20% of the length of the working electrode from the flat conductive surface of the auxiliary electrode.

Positioning the working electrode system relative to the flat conductive surface of the auxiliary electrode can involve holding the auxiliary electrode in a substantially horizontal orientation in a container operatively configured to contain the organic electrolyte solution and holding the working electrode in the container, The auxiliary electrodes are distributed separately, thus defining a space between the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode.

The flat conductive surface that causes the volume of organic electrolyte solution to flood the auxiliary electrode can involve incorporating a predetermined volume of organic electrolyte solution into the container.

Incorporating the predetermined volume of the organic electrolyte solution may involve passing the predetermined volume through an opening in the auxiliary electrode that is conductive to a space between the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode.

Passing the predetermined volume through an opening may involve pumping the predetermined volume of organic electrolyte solution from a reservoir through the opening.

The method can involve draining the organic electrolyte solution after the oxide layer is formed to a desired thickness on the flat conductive surface of the working electrode.

The chemical system can involve an oxygen supply sufficient to permit formation of the oxide layer to a desired thickness.

The oxygen supply system can involve dissolved oxygen or at least one oxygen precursor.

The oxygen supply system can involve at least one oxygen precursor, and the at least one oxygen precursor system can involve at least one of dissolved nitrate, nitrite, hydrogen peroxide, and traces of water.

Anode reaction

The working electrode can be formed from a material, and the oxide layer can be an oxide of the material, and causing the current flow system to involve causing current to flow in a direction that causes the working electrode to function as an anode.

The method can involve agitating the organic electrolyte solution as the current flows.

The agitation system can involve causing a first-rate defined space between the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode.

The organic electrolyte solution may be protic, and the chemical may include at least one of methanol, ethanol, isopropanol, ethylene glycol, and tetrahydrofuran methanol.

The organic electrolyte solution may be aprotic, and the chemical may include at least one of N-methylacetamide and acetonitrile.

The organic electrolyte solution and the working and auxiliary electrodes can be generally maintained at a constant temperature between about 15 ° C and about 90 ° C.

The causing current flow may involve maintaining the current at a level that is at least sufficient to maintain oxide formation on the working electrode as oxide formation occurs and resistance is formed to the current.

The method can involve terminating the flow of current when the current flow meets a discriminant criterion.

The discrimination criteria may include a condition that the oxide layer has a predetermined thickness.

The current can have a current density of from about 1 mA/cm ² to about 100 mA/cm ² .

Cathodic reaction

The oxide layer can be a metal oxide layer, and causing the current flow system can involve causing current to flow in a direction such that the working electrode acts as a cathode, and the organic electrolyte solution can include at least one ion source of the metal.

The method may involve determining a predetermined volume based on the desired thickness of the metal oxide to be plated on the flat conductive surface of the cathode and based on the concentration of the ion source of the metal and the volume of the organic electrolyte solution.

The oxide layer can comprise a metal oxide film of aluminum oxide, and the ion source of the metal can comprise at least one dissolved aluminum salt or at least one aluminate or at least one dissolved aluminum salt or at least one aluminate combination.

The oxide layer may comprise a metal oxide film of indium oxide, and the ion source of the metal may comprise at least one dissolved indium salt.

The oxide layer may comprise a metal oxide film of zinc oxide, and the ion source of the metal may involve at least one dissolved zinc salt or at least one zincate or at least one dissolved zinc salt or at least one zincate combination.

The oxide layer may comprise a metal oxide film of one of aluminum-doped zinc oxide, and the ion source of the metal may involve at least one dissolved zinc salt and at least one dissolved aluminum salt.

The oxide layer may comprise a metal oxide film of indium-doped zinc oxide, and the ion source of the metal may involve at least one dissolved zinc salt and at least one dissolved indium salt.

The oxide layer may comprise a metal oxide film comprising chlorine-doped zinc oxide, and the ion source of the metal may involve at least one dissolved zinc salt, and the organic electrolyte solution may involve at least one dissolved chloride.

The oxide layer may comprise a tin-doped indium oxide metal oxide film, and the metal ion source may involve at least one dissolved indium salt and at least one dissolved tin salt.

The method can involve maintaining the organic electrolyte solution stationary while the current is flowing.

The organic electrolyte solution may be protic, and the chemical may include at least one of methanol, ethanol, propanol, isopropanol, ethylene glycol, and glycerin.

The organic electrolyte solution may be aprotic, and the chemical may include at least one of dimethyl hydrazine (DMSO) and propylene carbonate.

The organic electrolyte solution and the working and auxiliary electrodes can be maintained at a temperature between about 15 ° C and about 90 ° C.

The method can involve terminating the flow of current when a predetermined coulomb number has passed through the organic electrolyte solution.

The predetermined coulomb number may be sufficient to cause the ion supply of substantially all of the metal in the electrolyte solution to be depleted from the organic electrolyte solution and oxidized on the flat conductive surface of the working electrode to facilitate the creation of the oxide layer to a desired thickness.

Maintaining the current at one level may involve maintaining the current at one of the current densities between about 0.1 mA/cm ² and about 100 mA/cm ² in the organic electrolyte solution.

The current can be maintained at a level that produces a current concentration between about 1 mA/cm ³ and about 1000 mA/cm ³ in the organic electrolyte solution.

The method can involve discharging an organic electrolyte solution that substantially depletes metal ions after the flat conductive surface of the cathode has been plated with metal oxide to a desired thickness.

Anode reaction applied to a semiconductor wafer

The working electrode can be a semiconductor wafer, the flat conductive surface can be on a front side or a back side of the semiconductor wafer, and the oxide layer can be a semiconductor oxide layer. The semiconductor oxide layer can be formed directly on the flat conductive surface of the working electrode or can be formed via a metal oxide layer that has been formed thereon.

The semiconductor wafer can include an n-type crystalline semiconductor wafer or a p-type crystalline semiconductor wafer.

The flat conductive surface may be on an n-type portion or a p-type portion of the crystalline semiconductor wafer, or the flat conductive surface may be located on an n-type portion or a p-type portion of the crystalline semiconductor wafer On the metal oxide layer.

The method can further include exposing the flat conductive surface of the working electrode to light at least a portion of a period of time during which the current can flow.

Exposing the flat conductive surface of the working electrode to the light system can involve incorporating light into the space between the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode.

Incorporating light into the space may involve incorporating light through an opening in the auxiliary electrode or incorporating light through at least a portion of at least one peripheral edge of the space.

Cathodic reaction applied to a semiconductor wafer

The working electrode can be a semiconductor wafer, the flat conductive surface of the working electrode can be on a front side or a back side of the semiconductor wafer, and the oxide can be a metal oxide. The metal oxide can be formed directly on the flat conductive surface or can be formed on a layer of semiconductor oxide that is already on the flat conductive surface.

The flat conductive surface of the working electrode semiconductor wafer can relate to an n-type portion or a p-type portion of a crystalline photovoltaic cell.

The method can further include exposing the flat conductive surface of the working electrode to light at least a portion of a period of time during which the current flows.

Exposing the flat conductive surface of the working electrode to the light system can involve incorporating light into the space between the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode.

Incorporating light into the space may involve incorporating light through an opening in the auxiliary electrode or incorporating light through at least a portion of at least one peripheral edge of the space.

In accordance with another aspect of the invention, an apparatus for electrochemically forming an oxide layer on a flat conductive surface is provided. The apparatus includes a container operatively configured to hold an organic electrolyte solution having a volume of a chemical for forming an oxide layer, and an auxiliary electrode having a flat conduction in a substantially horizontal orientation in the container The surface causes the organic electrolyte solution to flood the flat conductive surface of the auxiliary electrode. The apparatus further includes a working electrode holder for holding a working electrode supporting the flat conductive surface, the oxide layer being formed on the flat conductive surface in a general horizontal orientation opposite, parallel and spaced apart from the auxiliary electrode, Thus a space is defined between the flat conductive surface of the auxiliary electrode and the flat conductive surface of the working electrode. At least a portion of the organic electrolyte solution can occupy the space and contact the flat conductive surface of the auxiliary electrode and the flat conductive surface of the working electrode. The apparatus further includes a DC current source operatively configured to be coupled to the auxiliary electrode and the working electrode to cause a current to flow between the auxiliary electrode and the working electrode to cause the working electrode to act as at least a portion of the organic electrolyte solution An anode or as a cathode.

The working electrode holder can be operatively configured to hold the working electrode so that only the flat conductive surface of the working electrode is in contact with the organic electrolyte solution, but the entire working electrode is not immersed in the organic electrolyte solution.

The working electrode holder can include a protector operatively configured to protect a substantial portion of one side of the working electrode from contact with the electrolyte solution.

The protector can include a retaining surface that supports a seal that is configured to contact the rear side of the working electrode adjacent an outer peripheral edge of a rear side of the working electrode.

The working electrode holder may include means for causing a negative pressure to occur adjacent to the rear side of the working electrode, such that the ring chamber pressure presses the back side of the working electrode against the seal with a force sufficient to prevent leakage of the electrolyte solution through the seal .

The means for creating a negative pressure may include a vacuum opening adjacent the seal.

The working electrode holder can be operatively configured to separate the flat conductive surface of the working electrode from the flat conductive surface of the auxiliary electrode to facilitate adhesion of the organic electrolyte solution to the flat conductive surface of the working electrode due to the capillary force of the organic electrolyte solution and the auxiliary The distance from the flat conductive surface of the electrode.

The working electrode holder can be operatively configured to position the working electrode such that the flat conductive surface of the working electrode is between about 0.1% and about 20% of the length of the working electrode.

The auxiliary electrode may include a graphite plate, a gas carbon plate, or a graphite fabric, or a platinum plate.

The apparatus can include means for incorporating a predetermined volume of organic electrolyte solution into the container.

The measure for incorporating the predetermined volume of the organic electrolyte solution may include an opening in the auxiliary electrode through which the predetermined volume is introduced into the container.

The measure for incorporating the predetermined volume of the organic electrolyte solution can include a pump operatively configured to pump the predetermined volume of organic electrolyte solution from a reservoir and through the opening.

The apparatus can include a row of ports operatively configured to discharge the organic electrolyte after the oxide layer is formed to a desired thickness on the flat conductive surface of the working electrode.

The chemical can include an oxygen supply sufficient to permit formation of the oxide layer to a desired thickness.

The oxygen supply can include dissolved oxygen or at least one oxygen precursor.

The oxygen supply may include at least one oxygen precursor, and the at least one oxygen precursor may include at least one of dissolved nitrate, nitrite, hydrogen peroxide, and traces of water.

Anode reaction

The DC current supply system can be operatively configured to cause current to flow in a direction in which the working electrode acts as an anode.

The device can include means for agitating the electrolyte as the current flows.

The means for agitation may include measures for causing the volume of electrolyte solution to flow through the space defined between the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode.

The organic electrolyte solution may be protic, and the chemical may include at least one of methanol, ethanol, isopropanol, ethylene glycol, and tetrahydrofuran methanol.

The organic electrolyte solution may be aprotic, and the chemical may include at least one of N-methylacetamide and acetonitrile.

The apparatus can include means for maintaining the organic electrolyte solution, the working electrode, and the auxiliary electrode at a constant temperature between about 15 ° C and about 90 ° C.

The DC current supply system can include means for maintaining the current at a level that is at least sufficient to maintain oxide formation as oxide formation occurs and resistance is formed to the current.

The apparatus can include means for terminating the flow of current when the current flow meets a discriminant criterion.

The discrimination criteria may include a condition that the oxide layer has a predetermined thickness.

The DC current supply system can include a measure to maintain the current in a concentration of between about 1 mA/cm ² and about 100 mA/cm ² in the organic electrolyte solution of the volume.

Cathodic reaction

The oxide layer can be a metal oxide layer, and the electrolyte solution can include at least one ion source of the metal, and the DC current source can be operatively configured to cause current to flow in the direction of the working electrode as a cathode. in.

The predetermined volume of electrolyte solution may be sufficient to ensure that the flat conductive surface of the auxiliary electrode and the flat conductive surface of the working electrode will contact the electrolyte solution. The predetermined volume may have a concentration of metal ions sufficient to plate a metal oxide to a desired thickness of the metal oxide layer on the flat conductive surface of the working electrode.

The metal oxide layer can comprise alumina, and the ion source of the metal can comprise at least one dissolved aluminum salt or at least one aluminate or at least one dissolved aluminum salt or at least one aluminate combination.

The metal oxide layer can include indium oxide, and the ion source of the metal can include at least one dissolved indium salt.

The metal oxide layer can comprise zinc oxide, and the ion source of the metal can comprise at least one dissolved zinc salt or at least one zincate or at least one dissolved zinc salt or at least one zincate combination.

The metal oxide layer can include aluminum-doped zinc oxide, and the ion source of the metal can include at least one dissolved zinc salt and at least one dissolved aluminum salt.

The metal oxide layer can include indium-doped zinc oxide, and the metal ion source can include at least one dissolved zinc salt and at least one dissolved indium salt.

The metal oxide layer may include chlorine-doped zinc oxide, and the ion source of the metal may include at least one dissolved zinc salt, and the organic electrolyte solution may include at least one dissolved chloride.

The metal oxide layer can include tin-doped indium oxide, and the ion source of the metal can include at least one dissolved indium salt and at least one dissolved tin salt.

The organic electrolyte solution can remain stationary while the current is flowing.

The organic electrolyte solution may be protic, and the chemical may include at least one of methanol, ethanol, propanol, isopropanol, ethylene glycol, and glycerin.

The organic electrolyte solution may be aprotic, and the chemical may include at least one of dimethyl hydrazine (DMSO) and propylene carbonate.

The apparatus can include means for maintaining the organic electrolyte solution, the working electrode, and the auxiliary electrode at a temperature between about 15 ° C and about 90 ° C.

The apparatus can include means for terminating the flow of current when a predetermined number of coulombs has passed through the organic electrolyte solution.

The predetermined coulomb number may be sufficient to cause the ion supply of substantially all of the metal in the electrolyte solution to be depleted from the organic electrolyte solution and oxidized on the flat conductive surface of the working electrode to facilitate the creation of the oxide layer to a desired thickness.

The measure of maintaining the current at a certain level may include a measure for maintaining the current in a current density of between about 0.1 mA/cm ² and about 100 mA/cm ² in the organic electrolyte solution.

The means for maintaining the current may include a measure for maintaining the current in the organic electrolyte solution to produce a current concentration between about 100 mA/cm ³ and about 1000 mA/cm ³ .

The apparatus can include means for discharging an organic electrolyte solution that substantially depletes metal ions after the flat conductive surface of the cathode has been plated with metal oxide to a desired thickness.

Anode reaction applied to a semiconductor wafer

The working electrode can comprise a semiconductor wafer, the flat conductive surface can be on a front side or a back side of the semiconductor wafer, and the oxide layer can be a semiconductor oxide layer. The semiconductor oxide layer can be formed directly on the flat conductive surface of the working electrode or can be formed via a metal oxide layer that has been formed thereon.

The semiconductor wafer can include an n-type crystalline semiconductor wafer or a p-type crystalline semiconductor wafer.

The flat conductive surface may be on an n-type portion or a p-type portion of the crystalline semiconductor wafer, or the flat conductive surface may be located on an n-type portion or a p-type portion of the crystalline semiconductor wafer On the metal oxide layer.

The apparatus can further include means for exposing the flat conductive surface of the working electrode to light at least a portion of a period of time during which the current flows.

The means for exposing the flat conductive surface of the working electrode to light can include measures to incorporate light into the space between the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode.

The means for incorporating light into the space may include a light transmissive portion in the auxiliary electrode to permit light to pass through the light transmissive portion and impinge on the flat conductive surface of the working electrode.

The means for incorporating light can include a light transmissive portion formed in the container for enclosing light into the space via at least a portion of at least one peripheral edge of the space.

Cathodic reaction applied to a semiconductor wafer

The working electrode can be a semiconductor wafer, the flat conductive surface of the working electrode can be on a front side or a back side of the semiconductor wafer, and the oxide can be a metal oxide. The metal oxide can be formed directly on the flat conductive surface or can be formed on a layer of semiconductor oxide that is already on the flat conductive surface. The planar conductive surface of the working electrode can be on one of the semiconductor oxide layers on a front or back side of the semiconductor wafer.

The planar conductive surface of the working electrode semiconductor wafer can comprise an n-type portion or a p-type portion of a crystalline photovoltaic cell.

The apparatus can further include means for exposing the flat conductive surface of the working electrode to light at least a portion of a period of time during which the current flows.

The means for exposing the flat conductive surface of the working electrode to light may include means for incorporating light into the space between the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode.

The means for incorporating light into the space may include a light transmissive portion in the auxiliary electrode to permit light to pass through the light transmissive portion and impinge on the flat conductive surface of the working electrode.

The means for incorporating light can include a light transmissive portion formed in the container for enclosing light into the space via at least a portion of at least one peripheral edge of the space.

Other aspects and features of the present invention will become apparent to those skilled in the <RTIgt;

Simple illustration

In the drawings showing the embodiments of the present invention: FIG. 1 is a simplified perspective view of an apparatus for forming an oxide layer on a flat conductive surface according to a first embodiment of the present invention; FIG. 2 is a first diagram A cross-sectional view of a portion of the device showing a holder in a position where the formation of the oxide is operable; FIG. 3 is a top plan view of the container portion of the apparatus shown in FIG. 1; Figure 2 is a bottom perspective view of the container portion; Figure 5 is a simplified oblique view of the working electrode holder of the device shown in Figure 1; Figure 6 is the working electrode holder shown in Figure 4 FIG. 7 is a simplified cross-sectional view of the working electrode holder shown in FIG. 4, the working electrode holder holding a plate having a flat conductive surface on which an oxide layer is to be formed; Figure is a cross-sectional view of a portion of the apparatus shown in Figure 1 showing a holder in an alternative position in which an oxide layer can be formed; Figure 9 is a simplified illustration of a portion of the apparatus according to the second embodiment Cross-sectional view, which is used to form a The oxide layer is on a p-type semiconductor surface; and Fig. 10 is a simplified cross-sectional view of a portion of the device according to the third embodiment for forming an oxide layer on a p-type semiconductor surface.

Detailed description of the preferred embodiment

Referring to Figure 1, an apparatus for forming an oxide layer on a flat conductive surface is shown generally at 10. Referring to Figures 1 and 2, apparatus 10 includes a container 12 operatively configured to contain an organic electrolyte solution containing a volume 14 of a chemical used to form an oxide layer. The apparatus further includes an auxiliary electrode 16 having a flat conductive surface 18 that is oriented generally horizontally within the container 12 such that the organic electrolyte solution of the volume 14 floods the flat conductive surface 18 of the auxiliary electrode 16.

The device 10 further includes a working electrode holder 20 for holding a working electrode 22 supporting a flat conductive surface 24 on which an oxide layer will be formed. Referring to Figure 2, the working electrode holders 20 are held in opposite, parallel and spaced apart orientations for the auxiliary electrodes 16 to maintain the working electrode 22 in a substantially horizontal orientation. A spacer 26 is thus defined between the flat conductive surface 18 of the auxiliary electrode 16 and the flat conductive surface 24 of the working electrode 22. At least a portion of the volume 14 of the organic electrolyte solution occupies the space 26 and is provided in a sufficient amount to simultaneously contact the flat conductive surface 18 of the auxiliary electrode 16 and the flat conductive surface 24 of the working electrode 22.

Referring again to Figure 1, device 10 further includes a DC current source 30 operatively configured to be coupled to auxiliary electrode 16 and working electrode 22 to cause a current to flow between the auxiliary electrode and the working electrode to cause a working electrode Selectively as one of the anodes of the organic electrolyte solution contacting the volume or as a cathode. The polarity of the DC current supply source 30 determines whether the working electrode 22 acts as an anode or as a cathode.

Working electrode 22 can be made of any conductive material that is capable of reacting with oxygen to form an oxide on its flat conductive surface 24. The oxide of the material of the working electrode 22 can be referred to as a simple oxide. If the working electrode 22 is an iron plate, for example, the simple oxide may be iron oxide. If the working electrode 22 is a crystalline semiconductor wafer, the simple oxide will be yttrium oxide. The polarity of the working electrode 22 can be utilized to be at a positive potential relative to the auxiliary electrode 16 to form a simple oxide.

Similarly, a polarity of the direct current source 30 can be set such that the working electrode has a negative polarity with respect to the auxiliary electrode 16, whereby a metal oxide is formed on the flat conductive surface 24 of the working electrode 22. Depending on whether a simple oxide or a metal oxide will be formed on the flat conductive surface 24, a different organic electrolyte solution is used.

In the depicted embodiment, the working electrode 22 is a semiconductor wafer, and the working electrode 22 has a positive potential relative to the auxiliary electrode 16 by causing the polarity of the DC current source 30 to form a semiconductor oxide. The material is on the flat conductive surface 24 of the semiconductor material itself or has been formed underneath a metal oxide layer on the semiconductor material. Alternatively, by causing the DC current source 30 polarity to be set such that the auxiliary electrode 16 has a positive potential relative to the working electrode 22, a metal oxide layer can be formed on the flat conductive surface 24 of the working electrode 22 or formed at the working electrode. The flat conductive surface is on one of the semiconductor oxide layers. Depending on whether a semiconducting oxide or a metal oxide will be formed on the flat conductive surface 24, a different organic electrolyte solution is used.

Referring to Figure 2, whether a simple oxide layer is to be formed or a metal oxide layer will be formed, the electrolyte solution of the volume 14 includes a chemical 32 that facilitates an electrolytic reaction, and the chemical includes an oxygen supply source 34. If a metal oxide layer is to be formed, the chemical system includes an oxygen supply source and further includes a metal ion supply source 36.

Referring again to Figure 1, the device 10 is described in more detail. In the illustrated embodiment, the container 12 is formed as a top portion of a table 40. The container 12 is generally rectangular in shape and has a bottom portion 42 and a peripheral wall 44 extending upwardly from a periphery of the bottom portion 42. For example, the bottom portion 42 and the peripheral riser 44 are formed from a chemically resistant material such as Teflon, polycarbonate, polystyrene or glass.

The bottom portion 42 is formed with a rectangular recess 46 for receiving and holding the auxiliary electrode 16. For example, the auxiliary electrode 16 is formed of a carbon graphite plate or a glass graphite plate or a graphite fabric material or a platinum plate and has a flat conductive surface 18. A recess 46 is formed in the bottom portion 42 such that the flat conductive surface 18 of the auxiliary electrode 16 is generally coplanar with the bottom portion 42, which is generally horizontally oriented in the illustrated embodiment.

Referring to FIG. 3, the auxiliary electrode 16 is connected to a connector 90 by a conductor 92 to facilitate easy electrical connection to the auxiliary electrode 16. Referring again to FIG. 1, the connector 90 is connected by a wire 94 to a corresponding connector 96 of the DC current source 30. The working electrode 22 is similarly connected to a direct current source 30. Therefore, the working electrode 22, the electrolyte solution of the volume 14, and the auxiliary electrode 16 are formed in a series circuit with the current supply source 30. Therefore, the DC current source 30 provides a DC current supply and includes an automatic control circuit 31 that selectively adjusts the polarity applied across one of the auxiliary electrode 16 and the working electrode 18 and is adjustable The potential increases, decreases, or maintains a current through a series circuit comprising the working electrode 22, the electrolyte solution of the volume 14, and the auxiliary electrode 16. In addition, the automatic control circuit 31 can determine whether a specific criterion is met, such as whether the resistance of the serial circuit has reached a predetermined current flowing in the tandem circuit, and at that time, the automatic control circuit 31 is selectively closed. Break current supply.

Distribution system

The auxiliary electrode 16 has a centrally disposed opening 48, and the bottom portion 42 of the container 12 has an aligned opening (not shown) that is aligned with the centrally disposed opening 48 that is operable to incorporate the organic electrolyte of the volume 14. The solution is placed into the container 12.

The electrolyte solution of this volume 14 is provided by a dispensing system, generally indicated at 60. In the illustrated embodiment, the dispensing system 60 includes a first reservoir 62 operatively configured to receive a rinse solution 64, and a first pump 66 for pumping a first from the first reservoir A volume of rinsing solution is coupled into the feed conduit 68 that is coupled to the opening 48 by a flexible feed conduit 70.

The dispensing system 60 further includes a second reservoir 72 operatively configured to receive a first electrolyte solution 74, and a second pump 76 for pumping a predetermined volume from the second reservoir 72 An electrolyte solution 74 is passed into the feed conduit 68 and through the opening 48.

The dispensing system 60 further includes a third reservoir 78 operatively configured to receive a second electrolyte solution 80, and a third pump 81 for pumping a predetermined volume from the third reservoir 78 The two electrolyte solution 80 is passed into the feed conduit 68 and through the opening 48.

A controller 82 is provided to selectively operate the first, second or third pump (66, 76, 81) to selectively pump the flushing solution 64 or a predetermined volume of the first or second electrolyte solution (74, 80) The feed conduit 50 is passed through the opening 48 to flood the flat conductive surface 18 of the auxiliary electrode 16 to be used as part of an electrolytic cell with the working electrode 22 in the container 12.

For example, the rinsing solution 64 can include an organic solvent or water.

The first and second electrolyte solutions 74, 80 are configured to facilitate use of the working electrode 22 as an anode or cathode, respectively, to suit the type of oxide layer that will be formed. Each of the first and second electrolyte solutions 74, 80 includes a chemical comprising an oxygen supply sufficient to permit formation of the oxide layer to a desired thickness. The oxygen supply system can include at least one of dissolved oxygen or at least one oxygen precursor such as dissolved nitrate, nitrite, hydrogen peroxide, and traces of water. The concentration of the dissolved oxygen precursor in the electrochemical process used to form the oxide layer should be selected such that the electrolyte dispensed into the volume within the vessel 12 is provided with at least sufficient source oxygen to facilitate formation of a desired An oxide layer of thickness.

The controller 82 selectively causes a first predetermined volume of the first electrolyte solution 74 to be incorporated into the vessel 12 and causes the current source 30 to be configured to cause the working electrode 22 to act as an anode. The first predetermined volume must be sufficient to ensure that the flat conductive surface 18 of the auxiliary electrode 16 and the flat conductive surface 24 of the working electrode 22 are in contact with the first predetermined volume of the first electrolyte solution 74. With the working electrode 22 as the anode, the oxide formed on the flat conductive surface 24 of the working electrode 22 will be the oxide of the material from which the working electrode is made, i.e., a simple oxide. Thus, for example, if the working electrode 22 is a germanium semiconductor wafer, when the first electrolyte solution 74 is used and the current supply source 30 causes the working electrode 22 to have a positive potential relative to the auxiliary electrode 16, the ruthenium oxide layer can be formed in It has a flat conductive surface or has formed under one of the metal oxide layers thereon.

If the working electrode 22 is used as the anode, the organic electrolyte solution may be protonic, and the chemical in the first electrolyte solution 74 may include at least one of methanol, ethanol, isopropanol, ethylene glycol, and tetrahydrofuran methanol. Alternatively, the first electrolyte solution 74 can be aprotic, and the chemical can include at least one of N-methylacetamide and acetonitrile.

Similarly, controller 82 can alternatively operate third pump 81 to cause a second predetermined volume of second electrolyte solution 80 to be incorporated into vessel 12 and cause current source 30 to be configured to cause working electrode 22 to act as a cathode. The second predetermined volume of the second electrolyte solution 80 must be sufficient to ensure that the flat conductive surface 18 of the auxiliary electrode 16 and the flat conductive surface 24 of the working electrode 22 are in contact with the second predetermined volume of the second electrolyte solution 80.

In this embodiment where the working electrode 22 is a germanium semiconductor wafer, when the second electrolyte solution 80 is used and the current supply source 30 causes the working electrode 22 to have a negative potential relative to the auxiliary electrode 16, a metal oxide layer will It is formed on its flat conductive surface 24 or on a layer of semiconducting oxide that has been formed on its flat conductive surface.

The second electrolyte solution 80 can be protic, and the chemical can include at least one of methanol, ethanol, propanol, isopropanol, ethylene glycol, and glycerin. Alternatively, the second electrolyte solution 90 can be aprotic, and the chemical can include at least one of dimethyl hydrazine (DMSO) and propylene carbonate.

Also, the second electrolyte solution 80 includes an ion source of at least one metal to facilitate formation of a metal oxide layer on the flat conductive surface 24 of the working electrode 22 or a simple oxide layer formed on the flat conductive surface 24. on. The source of ions for the metal in the second predetermined volume must be sufficient to facilitate formation of the metal oxide layer on the flat conductive surface 24 of the working electrode 22 to a desired thickness.

If an aluminum oxide layer is intended to be formed on a PV cell, for example, the metal ion source may comprise at least one dissolved aluminum salt or at least one aluminate or at least one dissolved aluminum salt or at least one aluminate combination . The dissolved aluminum salt can be selected, for example, from a nitrate, a chloride, or a sulfate. The organic electrolyte solution may contain from 0.0001Eq/L (gram equivalent/liter) to 0.1Eq/L of aluminum or from 0.0001Eq/L of aluminum to a saturated solution concentration to 4in to 8in (10.16cm) in a photovoltaic (PV) battery. An aluminum oxide film having a thickness of from about 10 nm to about 200 nm is produced on the square to 20.32 cm).

If the indium oxide layer is to be formed on a PV cell, the ion source of the metal may include at least one dissolved indium salt. The at least one dissolved indium salt may be selected, for example, from a nitrate, a chloride, or a sulfate. The organic electrolyte solution may contain from 0.0001Eq/L (gram equivalent/liter) to 0.1Eq/L of indium or from 0.0001Eq/L of indium to a saturated solution concentration to 4in to 8in (10.16cm) in a photovoltaic (PV) battery. An indium oxide film having a thickness of about 50 nm to about 130 nm is produced on the square to 20.32 cm).

If the zinc oxide layer is to be formed on a PV cell, the ion source of the metal may comprise at least one dissolved zinc salt or at least one zincate or at least one dissolved zinc salt or at least one zincate combination. The at least one dissolved zinc salt may be selected, for example, from a nitrate, a chloride, or a sulfate. The organic electrolyte solution may contain from 0.0001Eq/L (gram equivalent/liter) to 0.1Eq/L zinc or from 0.0001Eq/L zinc to a saturated solution concentration to 4in to 8in (10.16cm) in a photovoltaic (PV) battery. A zinc oxide film having a thickness of from about 50 nm to about 130 nm is produced on the square to 20.32 cm).

If an aluminum-doped zinc oxide layer is to be formed on a PV cell, the metal ion source system can include at least one dissolved zinc salt and at least one dissolved aluminum salt. The dissolved zinc salt may be selected, for example, from a nitrate, a chloride, or a sulfate. The dissolved aluminum salt can be selected, for example, from a nitrate, a chloride, or a sulfate. The organic electrolyte solution may contain a gram equivalent of zinc and aluminum in a ratio of about 500/1 to 3:1 to produce a ratio of about 80 nm to about 4 in a 10 to 8 in. (10.16 cm to 20.32 cm) square of a photovoltaic (PV) cell. An aluminum-doped zinc oxide film having a thickness of 100 nm.

If an indium doped zinc oxide layer is to be formed on a PV cell, the metal ion source may comprise at least one dissolved zinc salt and at least one dissolved indium salt. The dissolved zinc salt may be selected, for example, from a nitrate, a chloride, or a sulfate, and at least one dissolved indium salt may be selected, for example, from a nitrate, a chloride, or a sulfate. The organic electrolyte solution may contain a gram equivalent of zinc and indium in a ratio of between about 200/1 and 5:1 to produce a thickness of from about 50 nm to about 4 in a 8 in. (10.16 cm to 20.32 cm) square on a photovoltaic (PV) cell. Indium-doped zinc oxide film having a thickness of 130 nm.

If a chlorine-doped zinc oxide layer is to be formed on a PV cell, the metal ion source system can include at least one dissolved zinc salt and at least one dissolved chloride. At least one zinc salt may be selected, for example, from a nitrate, a chloride, or a sulfate. The organic electrolyte solution may contain from 0.0001Eq/L (gram equivalent/liter) to 0.1Eq/L of zinc or from 0.0001Eq/L of zinc to a saturated solution concentration and from 0.001Eq/L to 0.1Eq/L of chloride or From a 0.001Eq/L chloride to a saturated solution concentration, a chlorine-doped zinc oxide film having a thickness of from about 50 nm to about 130 nm is produced on a 4 in to 8 in (10.16 cm to 20.32 cm) square of a photovoltaic (PV) cell. .

If a tin-doped indium oxide layer is to be formed on a PV cell, the ion source of the metal may include at least one dissolved indium salt and at least one dissolved tin salt. The dissolved indium salt may be selected, for example, from a nitrate, a chloride, or a sulfate, and at least one dissolved tin salt may be selected, for example, from a nitrate, a chloride, or a sulfate. The organic electrolyte solution may contain a gram equivalent of zinc and indium in a ratio of about 200/1 to 1:1 to produce a ratio of about 50 nm to about 4 in a 4 to 8 in (10.16 cm to 20.32 cm) square of a photovoltaic (PV) cell. A tin-doped indium oxide film having a thickness of 130 nm.

The controller 82 and the direct current source 30 are electrically connected to each other to ensure that the first predetermined volume of the first electrolyte solution 74 is introduced into the container 12 before causing a current to flow therein in a direction in which the working electrode 22 is the anode. And ensuring that the second predetermined volume of the second electrolyte solution 80 is introduced into the container 12 before causing a current to flow therein in a direction in which the working electrode 22 serves as a cathode, and that the container 12 is flushed before and after subsequent use. The solution 64 is rinsed and, with each successive use, a new predetermined volume of the first or second electrolyte solution 74 or 80 is incorporated into the container 12 without contamination from previous use.

Referring again to Figure 3, in order to facilitate rinsing the container of used electrolyte solution, the bottom portion 42 of the container 12 has a discharge passage 100 extending adjacent the auxiliary electrode 16 along the peripheral boundary of the bottom portion. The discharge passage 100 is electrically connected to a discharge opening 102. The discharge passage 100 is suitably sloped to direct the liquid (i.e., the rinsing solution 64, or the first or second electrolyte solution 74 or 80, respectively) into the discharge opening 102.

Referring to Fig. 4, a solenoid valve 104 is attached to the bottom side of the container 12 and is electrically connected to the discharge opening 102 and a discharge conduit 106. The solenoid valve 104 is selectively opened and closed by a controller (82 of Fig. 1) to discharge the flushing solution 64 or any first or second electrolyte solution (74, 80) from the container 12 or to accommodate flushing. The solution or first or second electrolyte solution (74, 80) is in vessel 12, as desired. Thus, when the first or second electrolyte solution (74, 80) is incorporated into the vessel 12 and during an electrolysis operation, the solenoid valve 104 remains closed and is opened after an electrolysis operation to discharge spent electrolyte from the vessel 12. The solution, and/or when the rinse solution 64 is incorporated into the container 12, is used for rinsing. The controller 82 discharge passage 100, the discharge opening 102, and the solenoid valve 104 cooperate to discharge the electrolyte solution from the vessel 12 to a designated collector after a plating cycle has been completed. Separate collectors may be provided to collect respective volumes of rinse solution 64, first electrolyte solution 74 and second electrolyte solution, and may provide a suitable valve actuation system to selectively direct the liquid received in discharge opening 102 to Appropriate collector.

Referring again to Figure 1, the table 40 includes a support member 110 extending upwardly from the container 12. A slidable collar 112 is coupled to the support member 110, the slidable collar 112 being operable to slide over the support member and slide relative to the support member in a vertical direction as indicated by arrow 114. A stop 116 can be securely fastened to the support 110 and can be used to limit the movement of the slidable collar 112 in the vertical direction. The slidable collar 112 is coupled to a chuck mount 118 for fastening a working electrode holder 120. The mount 118 is a movement that allows the working electrode holder 120 to be oriented in the direction of the arrow 122 in a direction orthogonal to the direction of movement of the slidable collar 162 shown by arrow 114. The mount 118 has a clip 124 for holding the working electrode holder 120 and provides vertical adjustment of the working electrode holder relative to the mount 118. Of course, the working arm holder 120 can alternatively be positioned in the location described herein using a robotic arm.

Referring to Figure 5, in this embodiment, the apparatus includes means for maintaining the electrolyte solution, working electrode 22 and auxiliary electrode 16 at a temperature between about 15 ° C and about 90 ° C and having an accuracy of about ± 1 ° C. . These measures include forming a working electrode holder 120 to include a conductive plate 130, which in this embodiment includes a metal plate having an aluminum thickness of approximately 2 cm, but the plate may alternatively be, for example, stainless steel, silver or platinum or Other metals or metal alloys are made and they may have a different thickness. The plate 130 is formed with a plurality of channels 132 that are sealed by the plugs 134 and that are conductive to the first and second tube connectors 136 and 138 on a top surface 164 of the metal sheet 130.

Referring again to Figure 1, the supply and exhaust pipes 140 and 142 are coupled to the first and second pipe connectors 136 and 138, respectively. The discharge tube 142 is electrically connected to a liquid heater 144, and a pump 146 is electrically connected to the heater via a pump conduit 148. The operation of pump 146 causes the pump to draw hot liquid from heater 91 via pump conduit 148 and cause it to pass through supply tube 140 to first tube connector 136 and then through passage 132 and away from second tube connector 138 into the discharge tube. 142 is returned to liquid heater 144. The configuration of the passage 132 and the tubular connectors 86 and 88 permits thermal fluid, such as water, to be pumped from the first tubular connector 86 through the passage 132 to the second tubular connector 88, for example, to provide a flow of hot fluid through the plate. 80 maintains the working electrode 22 held by it at a generally constant temperature. For example, the hot fluid can be water or a 50/50 mixture of water and glycol antifreeze. Other thermal fluids that are compatible with the metal used to form the plate 130 may alternatively be used. Alternatively, the plate 130 can be electrically heated.

Referring again to FIG. 5, the working electrode holder 120 has a riser member 150 secured to the plate 130 by an electrically insulating mount 152 that electrically insulates the riser member 150 from the plate 130. Referring to Fig. 1, the upright member 150 is held by the clip 124 to mount the working electrode holder 120 thereto.

Referring to Figure 6, a bottom side surface 160 of the panel 130 is shown. The plate has an aperture 162 extending therethrough between a top surface 164 of the panel as shown in Figure 5 and a bottom side surface 160 of the panel as shown in Figure 6. The bottom side surface 160 is cut (e.g., by a milling machine) having a vacuum supply passage 166 that conducts through the aperture 162 and conducts around a peripheral boundary extending from the bottom side surface 160. Peripheral passage 168. Referring to Figures 5 and 6, the aperture 162 is electrically connected to a vacuum hose connector 170, which is connected to a vacuum hose 172 as shown in Figure 1, and the vacuum hose 172 is attached to a table. Vacuum pump 174 on 40.

Referring to Figures 1 and 6, when the vacuum pump 174 is activated, a vacuum is applied to the aperture 162 and conducts through the passages 166 and 168, particularly when a working electrode 22 is placed in close proximity to the bottom side surface 160.

Referring to Fig. 5, in the illustrated embodiment, the vacuum hose connector 170 is metallic and the plate 130 is metallic. The vacuum hose connector 170 has screw threads to connect it to the plate 130, and since the vacuum hose connectors and plates are metallic, they are in electrical contact with one another. A loop 171 of an electrical terminal lug 173 is received over the screw threads of the vacuum hose connector 170 prior to screwing the vacuum hose connector into the aperture 162 in the plate 130. Referring to Figures 1 and 5, a wire 175 connected to the electrical terminal lug 173 is electrically coupled to a second terminal 177 of the DC current source 30. The use of the metallic plate 130 and the metallic vacuum hose connector 170 facilitates the easy electrical connection of the wires 175 to the plate 130. Of course, any other suitable method of attaching a wire to a board can be used.

Referring to Fig. 6, the bottom side surface 160 also has a peripheral groove 181 which holds, for example, a rubber seal 182 formed of a soft rubber material such as silicone rubber. One of the regions 184 delimited by the peripheral groove 181 is predetermined to have the same shape as the working electrode 22 held by the working electrode holder 120 but is slightly smaller. The peripheral groove 181 is formed and the rubber seal 182 is sized to have a width of between about 1 mm and 3 mm and a thickness of between about 0.1 mm to about 1 mm such that the rubber seal protrudes from the bottom side surface 160 of the plate 130. Not more than about 0.1 mm to about 0.5 mm, as clearly shown in Figure 7. The entire surface of the panel 130 - except for the region 184 delimited by the peripheral trench and rubber seal 182 - is pre-anodized deep to protect these surfaces. This anodization forms an electrically insulating layer and causes these surfaces to be chemically inert to the first and second electrolyte solutions 74 and 78 and to the rinsing solution 64. Or, for example, these surfaces may be pre-coated with an inert coating such as Teflon (Teflon ). Therefore, as explained above, when the working electrode 22 and the auxiliary electrode 16 are placed in contact with the first or second electrolyte solution 74 or 80 and current is conducted therethrough, the plate 130 is not involved in the electrochemical reaction that occurs. Region 184 is not pre-anodized and maintains conductivity to facilitate electrical connection of working electrode 22 to plate 130.

Alternatively, a brass plate can be substituted for the aluminum plate 130. The surface of the brass plate exposed to the electrolyte can be coated with Teflon (Teflon Or other coatings that are chemically inert to the first and second electrolyte solutions 74, 80 and the rinsing solution 64. If a brass plate is used, the region 184 delimited by the peripheral trenches 181 can be silver plated to provide good electrical contact with the working electrode 22, for example. The use of a brass plate may be the most suitable version for the production of the device.

operating

Referring to Figures 1 and 7, in order to use the apparatus 10, an article system having an oxide layer formed thereon is led to the vicinity of the bottom side surface 160 of the plate 130, and then the vacuum pump 174 is activated. The object is intended to be generally planar in shape and in this embodiment is a semiconductor wafer or photovoltaic cell. In other embodiments, other conductive or semi-conducting planar objects may similarly act as the object. The term "conducting" as used herein in connection with an object on which an oxide layer is to be formed is meant to include both conductive and semi-conductive materials.

The object has a backside surface 180 and supports a flat planar conductive surface 24 on which an oxide layer will be formed, on one side of the object opposite the backside surface 180. The back side surface 180 is drawn into contact with the bottom side surface 160 of the plate 130 by a vacuum that is conducted through the aperture 162 to the passage 168 (and 166 shown in FIG. 6). The vacuum that is conducted to the passages 166 and 168 creates a negative pressure between the back side surface 180 and the plate 130, so that the back side surface 180 is held against the bottom side surface 160 of the plate 130 by the annular chamber air pressure. The object should have the proper dimensions and be carefully positioned relative to the bottom side surface 160 prior to actuation of the vacuum pump (174) so that the rubber seal 182 will contact the back side surface 180 adjacent the outer edge of the object, as in the seventh As shown, most of the backside surface 180 is located within the region 184 that is delimited by the rubber seal 182. The annular chamber air pressure presses the object against the rubber seal 182 to effectively seal the region 184 of the backside surface 180 delimited by the rubber seal 182. Thus, when the device is in use, the rubber seal 182 will serve to protect the region 184 of the backside surface 180 demarcated by the rubber seal from contact with the electrolyte.

Since the rubber seal 182 protrudes from the bottom side surface 160 only a small amount, and since the seal extends adjacent to the peripheral edge of the object, the object is held in a relatively flat planar condition, but a central inner portion of the object 183 will experience a large vacuum due to proximity to aperture 162. The central inner portion 183 will flex and will be drawn mechanically and electrically into contact with the underside surface 160 of the plate 130. Since the board 130 is electrically connected to the second terminal 177 of the DC current source, when the object is electrically contacted to the bottom side surface 160 of the board 130, it is also electrically connected via the lead 175 connected to the vacuum hose connector 170. Sexual contact with the DC current source 30. As the object is secured to and in electrical contact with the working electrode holder 120, the system becomes the working electrode 22.

Referring to Figures 1 and 2, as the working electrode 22 is in place, the slidable collar 112 slides down the support member 110 until the flat conductive surface 24 of the working electrode 22 and the flat conductive surface 18 of the auxiliary electrode 16 are parallel and separate. Separate and define the space 26 between them. The auxiliary electrode 16 and the working electrode 22 are oriented horizontally, as are the flat conductive surface 18 of the auxiliary electrode and the flat conductive surface 24 of the working electrode. In this embodiment, the working electrode 22 is positioned such that the flat conductive surface 24 of the working electrode is away from the flat conductive surface 18 of the auxiliary electrode 16 by a distance 190. For example, the distance 190 can be between about 0.1% and about 20% of the length 192 of the working electrode 22.

For example, if the working electrode 22 is a semiconductor wafer or a photovoltaic cell, it may have the shape of a square rectangular plate having a side length of 15 cm, and thus the distance 190 may be predefined as, for example, between about 0.15 mm and about 30 mm. Ideally, the clip 124 and the slidable collar 112 are designed to accommodate the flat conductive surface 24 of the working electrode 22 and the flat conductive surface 18 of the auxiliary electrode 16 in a range between about 0.15 mm and about 30 mm. The separation between the two is adapted to the size of the working electrode 22. The clip 124 can be pre-set to provide the predetermined distance 190 between the flat conductive surface 24 of the working electrode 22 and the flat conductive surface 18 of the auxiliary electrode 16 when the slidable collar 112 rests against the stop 116.

As the working electrode 22 is positioned in a tight, parallel spaced apart relationship as shown in FIG. 2, the controller 82 shown in FIG. 1 operates the first or second pump 76 or 81 to dispense a first predetermined volume. Or the second electrolyte solution 74 or 80 to the space 26 between the flat conductive surface 18 of the auxiliary electrode 16 and the flat conductive surface 24 of the working electrode 22 such that the flat conductive surface 18 is immersed in the electrolyte solution and substantially only the working electrode 22 The flat conductive surface 24 is in contact with the electrolyte solution. Since the rubber seal 182 prevents the organic electrolyte solution from contacting the back side surface 180 of the working electrode 22, the working electrode 22 is not completely immersed in the organic electrolyte solution. Moreover, in the illustrated embodiment, since the flat conductive surface 18 of the auxiliary electrode 16 and the flat conductive surface 24 of the working electrode 22 are closely spaced apart, the adhesion of the electrolyte to the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode Occurs due to the capillary force of the electrolyte. Therefore, in this embodiment, only a small amount of electrolyte solution is required to facilitate the electrolytic reaction that occurs when current is passed through the electrolyte.

Alternatively, as shown in Fig. 8, a larger spacing may be employed between the flat conductive surface 24 of the working electrode 22 and the flat conductive surface 18 of the auxiliary electrode 16, but in this embodiment, the electrolyte solution (74 or 80) The capillary force does not maintain the electrolyte solution in the space between the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode. This embodiment uses a relatively large amount of electrolyte solution (74 or 80). In order to maintain a minimum volume of electrolyte solution (74 or 80) used, it may be desirable to have an inner side surface 194 of the peripheral riser 44 slightly larger than the working electrode 22. For example, the peripheral riser may be formed such that a distance 196 or spacing between any edge 198 of the working electrode 22 and an inner side surface 194 of an adjacent portion of the peripheral riser 44 may be between about 8 mm and about 10 mm or at least sufficient to accommodate The width of a discharge passage 100 between the edge 198 of the working electrode 22 and an inner side surface 194 of an adjacent portion of the peripheral riser wall 44. Alternatively, the peripheral riser wall 44 can be overcut to provide space for the discharge passage adjacent the edge 198 of the working electrode 22 while occupying a space immediately above the discharge passage to maintain the required electrolyte volume to a minimum.

As the working electrode 22 is positioned in the container 12, as shown in Figures 7 or 8, the container is first rinsed with the rinsing solution 64 to remove any contaminants. To achieve this effect, the controller 82 actuates the solenoid valve 104 to open it to facilitate discharge and actuation of the first pump 66 to pump a continuous stream of rinsing solution through the opening 48 into between the working electrode 22 and the auxiliary electrode 16. Within space 26.

After rinsing, the container 12 is ready to receive a volume of electrolyte solution. The particular electrolyte to be received in the vessel 12 is selected depending on whether a simple oxide layer comprising oxides of the material comprising the working electrode is intended to be formed on the conductive surface 24 or a metal oxide layer is intended to be formed on the conductive surface. Solution. If the working electrode is a semiconductor wafer of a PV cell and if a simple oxide layer is to be formed, the conductive surface 24 of the material forming the working electrode may be virgin or may already have a metallic oxidation formed thereon. Things. If the working electrode is a semiconductor wafer or PV cell and if a metallic oxide layer is to be formed, the conductive surface 24 of the material forming the working electrode may be native or may already have a simple oxide layer formed thereon.

Using the working electrode as the anode

If the working electrode is a semiconductor wafer of a PV cell and a simple oxide layer is to be formed on a native conductive surface of the working electrode 22 or under a metal oxide layer formed on the native conductive surface, the controller 82 Actuating the second pump 76 to cause it to pump a first predetermined volume of the first electrolyte solution 74 into the feed conduit 68, through the flexible feed conduit 70 and through the opening 48 formed in the auxiliary electrode 16, such that The predetermined volume is incorporated into the container 12 and a portion of the first predetermined volume is located in and in electrical contact with the space 26 between the flat conductive surface 18 of the auxiliary electrode 16 and the flat conductive surface 24 of the working electrode 22.

If the spacing between the auxiliary electrode 16 and the working electrode 22 is as shown in Fig. 2, the first predetermined volume will be smaller than if the interval is as shown in Fig. 8. Thus, the first electrolyte solution 74 will have to be organized to have a concentration of one of the oxygen precursors suitable for use in conjunction with the dissolution of the selected embodiment, so that the first predetermined volume will have sufficient dissolved oxygen to facilitate at least the oxide layer to grow to The thickness you want.

The backside surface 180 of the working electrode 22 is protected from exposure by the seal 182 to the first electrolyte solution 74, and thus only the flat conductive surface 24 of the working electrode is exposed to the first electrolyte solution 74 and will participate in the electrolytic reaction. Since the surface of the plate 130 exposed to the electrolyte is pre-anodized or pre-coated with a chemically resistant material, the material of the plate does not participate in the electrolytic reaction.

As the flat conductive surface 24 of the working electrode 24 and the flat conductive surface 18 of the auxiliary electrode 16 are in contact with the first electrolyte solution 74, the controller 82 actuates the current supply source 30 such that the working electrode 22 is positive with respect to the auxiliary electrode 16 (+ The potential, the auxiliary electrode 16 is at a negative (-) potential with respect to the working electrode. This causes a current to flow through the first predetermined volume of the first electrolyte solution 74 between the working electrode 22 and the auxiliary electrode 16 and provides an electrochemical decomposition of the oxygen precursor. For example, if the oxygen precursor is water, the water is broken into hydrogen ions H ⁺ and oxygen ions O ^2- . The oxygen ion migrates to the flat conductive surface 24 of the working electrode 22 and the surface is oxidized, thereby forming an oxide on the surfaces. At the same time, the hydrogen ionic conductive migration to the planar surface 16 of the auxiliary electrode 18, where it is reduced in the formation of hydrogen gas H _2.

The depth at which the semiconductor oxide is formed in the planar conductive surface 24 may increase as the potential between the working electrode and the auxiliary electrode increases and increases with time, and vice versa, and thus may be controlled by the automatic control circuit 31 .

In the illustrated embodiment, as oxide formation occurs and an increased resistance is provided for current flow, the automatic control circuit 31 maintains the current at least sufficient to maintain one level of oxide formation. For example, as the resistance provided by the formation of the semiconductor oxide layer increases, the automatic control circuit 31 can increase the potential between the working electrode 22 and the auxiliary electrode 16 to maintain the current at a given level. Alternatively, as the oxide layer is formed, the automatic control circuit 31 may cause an increase or decrease in current. Knowing the applied voltage and maintaining the current, the automatic control circuit 31 monitors the increased resistance provided by the formation of the oxide layer until reaching a target resistance associated with a semiconductor oxide layer of a target thickness. At this time, the automatic control circuit 31 turns off the current supply source 30. Therefore, substantially, when the current meets a discriminating criterion, the automatic control circuit 31 terminates the flow of the current. In the described embodiment, the criterion is such that the current must be impressed by a resistance of a target value of a semiconductor oxide layer representing a target thickness.

Alternatively, the discriminant criteria may include a time measurement in which the discriminant criterion is met when a quasi-applied current has been applied to a boundary of a target time amount for a semiconductor oxide layer representing a target thickness.

For example, the automatic control circuit 31 can be configured to maintain a current at one of the current densities between about 1 mA/cm ² and about 100 mA/cm ² in the electrolyte solution 74 of the first predetermined volume.

During formation of the semiconductor oxide layer on the working electrode 22, the first predetermined volume of the first electrolyte solution 74 is agitated while the current is flowing. The agitation can be provided by causing one of the first predetermined volumes of electrolyte solution 74 to flow, so that the electrolyte solution does not stagnate or stand still. The vibratory motion can be transferred to the auxiliary electrode 16 using a vibrator on the table 40 and ultimately transferred to the first predetermined volume of electrolyte solution 74 in contact therewith such that the first predetermined volume of electrolyte solution 74 passes through the flat of the working electrode 22 The space 26 defined between the conductive surface 24 and the flat conductive surface 18 of the auxiliary electrode 16 is used to effect this effect. Alternatively, the container 12 can be configured to have a circulation pump (not shown) to circulate a first predetermined volume of electrolyte solution 74 between the flat conductive surface 24 of the working electrode 22 and the flat conductive surface 18 of the auxiliary electrode 16. Defined space 26.

As previously described, it is desirable to pump the hot fluid through the working electrode holder by maintaining the hot fluid in the heater 144 at a temperature in the range of between about 15 ° C to about 90 ° C and operating the pump 146 The plate 130 of 120 maintains the electrolyte solutions 74, 80, the working electrode 22 and the auxiliary electrode 16 at a constant temperature between about 15 ° C and about 90 ° C.

Under the above conditions, a semiconductor oxide layer is formed on the flat conductive surface 24 of the working electrode 22. Once the semiconductor oxide layer has reached the desired thickness, the current supply source 30 is turned off and the controller 82 actuates the solenoid valve 104 and then actuates the first pump 66 to dispense a volume of the rinsing solution 64 through the aperture 162 and into the container. 12 inside. The surviving dispensing of the rinsing solution 64 flushes the used first predetermined volume of the first electrolyte solution 74 from the vessel 12 and into a sump for recovery or at least detoxification.

After a rinse cycle, for example, the working electrode 22 can then be lifted away from the vessel 12 by the working electrode holder 120 and passed to a separate material handling device (not shown) for further processing such as annealing. Alternatively, the separate material handling device may simply flip the working electrode 22 upside down and start the process again, and the surface on which the semiconductor oxide layer has just been formed becomes vacuum-attached to the backside surface 180 of the working electrode holder 120. And the side that was previously the backside surface 180 is ready for a cycle of electrolysis as described above to form a layer of semiconducting oxide on the backside surface 180 that was previously the working electrode.

Alternatively, the flat conductive surface that has just been anodized by the above process may be formed by forming a metal oxide layer on the just-formed semiconductor oxide layer as described below, or the backside surface may form a metal oxide layer as follows.

Cathodic reaction

If it is desired to form a metal oxide layer on a native conductive surface of the working electrode 22 or a semiconductor oxide layer that has been formed on the native conductive surface, the controller 82 actuates the third pump 81 to cause it A second predetermined volume of the second electrolyte solution 80 is pumped into the feed conduit 68, past the flexible feed conduit 70 and through the opening 48 formed in the auxiliary electrode 16 such that the second predetermined volume is incorporated into the container 12, thus partially The second predetermined volume is located in the space 26 and is received between and in electrical contact with the flat conductive surface 18 of the auxiliary electrode 16 and the flat conductive surface 24 of the working electrode 22.

If the auxiliary electrode 16 and the working electrode 22 are as shown in Fig. 2, the second predetermined volume will be smaller than if the interval is as shown in Fig. 8. Thus, the second electrolyte solution 80 will have to be configured to have a dissolved oxygen precursor suitable for use in conjunction with one of the selected embodiments, so that the second predetermined volume will have sufficient dissolved oxygen precursor to facilitate metal oxide layer growth. To the desired thickness.

Further, the concentration of the metal source in the second predetermined volume of the electrolyte solution 80 is selected, so that when substantially all of the metal ions of the metal source are depleted from the second predetermined volume of the electrolyte solution 80, the flat conduction formed at the working electrode 130 The metal oxide on the surface of the surface 24 has a thickness corresponding to the amount of metal source in the volume of the electrolyte solution contained in the container 12. Therefore, in order to produce a suitable second electrolyte solution, it is determined how many moles of dissolved metal ions will be required to form the metal oxide layer to have a target thickness, and to ensure that at least this amount of dissolved metal ions appears in the second predetermined The volume of the second electrolyte solution 80.

The backside surface 180 of the working electrode 22 is protected by the seal 182 without exposure to the second electrolyte solution 80, and thus only the flat conductive surface 24 of the working electrode is substantially exposed to the second electrolyte solution 80 and will participate in the electrolytic reaction.

As the flat conductive surface 24 of the working electrode 22 and the flat conductive surface 18 of the auxiliary electrode 16 contact the second electrolyte solution 80, the controller 82 actuates the current supply source 30 such that the working electrode 22 is negative relative to the auxiliary electrode 16 (- The potential, the auxiliary electrode 16 is at a positive (+) potential with respect to the working electrode. This causes a current to flow through the second predetermined volume of the second electrolyte solution 80 between the working electrode 22 and the auxiliary electrode 16 and provides an electron source for the reduction of the dissolved oxygen or oxygen precursor and for the conductive surface of the working electrode 22. The vicinity of 24 interacts with metal ions dissolved in the solution. This causes the metal oxide to precipitate directly on the flat conductive surface 24 of the working electrode 22.

The growth rate of the metal oxide may increase or decrease as the current density in the second electrolyte solution 80 increases or decreases and thus may be controlled by the automatic control circuit 31. The growth rate of the metal oxide can also be controlled by the temperature of the second electrolyte solution 80.

As the number of metal ions in the second electrolyte precipitates as a metal oxide on the flat conductive surface 24, the thickness of the metal oxide layer on the flat conductive surface increases and the second electrolyte solution becomes depleted of metal ions. When the second electrolyte solution substantially depletes the metal ions, the metal oxide layer will have a specific thickness. In order to ensure that substantially all of the metal ions have been depleted from the second electrolyte solution, a sufficient number of coulombs is provided by the current. A coulomb counter can be used to measure the number of coulombs that have passed through the electrolyte, or a time integral of the current can be calculated to provide a coulomb number. A calibration curve can be generated prior to the production run that depicts the specified current, metal ion concentration, and oxide layer thickness vs. coulomb or time at different temperatures and for different surfaces, such as p-type or n-type crystalline semiconductor surfaces, It is also used to determine the appropriate metal ion concentration, temperature, current, and time parameters for the production run to produce a desired thickness of the metal oxide layer.

In the illustrated embodiment, the automatic control circuit 31 maintains the current at least one level sufficient to maintain metal oxide formation as the metal oxide layer occurs. Forming a metal oxide layer can constitute an electrical resistance to the current. The automatic control circuit 31 increases the potential between the working electrode 22 and the auxiliary electrode 16 to maintain the current at a given level as the resistance formed by the formation of the metal oxide layer increases. Alternatively, the automatic control circuit 31 may cause an increase or decrease in current as the metal oxide layer is formed. Regardless of whether the current is increased or decreased or maintained constant, when a predetermined coulomb number has passed through the second electrolyte solution 80, the automatic control circuit 31 terminates the flow of current sufficient to ensure substantially all metal ions of the second electrolyte solution. The source has been depleted from the second electrolyte solution and oxidized on the flat conductive surface of the working electrode 22 to form a metal oxide layer to a desired thickness. In the depicted embodiment, the time integral of the current is a predetermined coulomb number of electrons that have passed through the second electrolyte solution 80, which is a target thickness of the metal oxide layer.

The automatic control circuit 31 can control the current to produce a current density in the second predetermined volume of the second electrolyte solution having a number of stages from about 0.1 mA/cm ² to about 100 mA/cm ² . The optimum current density is selected to be in a range corresponding to a preferential deposition of a particular metal oxide and a potential competitive reaction to eliminate metal deposition. For example, a suitable current density for depositing alumina may be in a range between about 1 mA/cm ² to about 5 mA/cm ² .

In the embodiment illustrated in FIG. 2, due to the short separation distance 190 between the flat conductive surface 24 of the working electrode 22 and the flat conductive surface 18 of the auxiliary electrode 16, it is possible to have a range of about 1 mA/cm ³ to about 1000 mA/cm ³ . And preferably a high current concentration in the range of about 10 mA/cm ³ to about 100 mA/cm ³ .

During the formation of the metal oxide layer on the working electrode 22, it is not desirable to agitate the second predetermined volume of the second electrolyte solution 80 while the current is flowing, and to maintain the second predetermined volume of the second electrolyte solution stationary.

As previously indicated, the second predetermined volume is desirably maintained by maintaining the hot fluid in the heater 144 at a temperature within this range and operating the pump 146 to pump the hot fluid through the plate 130 of the working electrode holder 120. The second electrolyte solution 80, the working electrode 22 and the auxiliary electrode 16 are maintained at a constant temperature between about 15 ° C and about 90 ° C.

The thickness of the metal oxide layer formed on the flat conductive surface 24 is controlled by the amount of dissolved metal ions in the second electrolyte solution 80 that is subjected to a sufficient number of Coulombs of electrons passing through the second electrolyte solution 80. Thus, it has been known that there must be sufficient volume to ensure that the flat conductive surface 24 of the working electrode 22 and the flat conductive surface 18 of the auxiliary electrode 16 will contact the second electrolyte solution, which must first be determined to form the metal oxide layer to the desired thickness. The desired number of moles of dissolved metal ions, and then the concentration of dissolved metal ions required in the second predetermined volume of the second electrolyte solution. This provides very precise control of the thickness of the metal oxide layer and provides nearly 100% utilization of all metal ions in the second electrolyte solution 80.

When substantially sufficient Coulomb number has passed through the second electrolyte solution 80 and substantially all of the metal ions of the metal supply source in the second predetermined volume of the second electrolyte solution 80 are exhausted from the second electrolyte solution and formed on the flat conductive surface of the working electrode 22 When a metal oxide film of a desired thickness is formed on 24, a resistance to the current flow is constituted by the metal oxide layer and is detected by the automatic control circuit 31. In response, the automatic control circuit 31 turns off the current supply source 30. Once the current supply source 30 is turned off, the controller 82 actuates the solenoid valve 104 and then actuates the first pump 66 to dispense a volume of irrigation solution through the opening 48 and into the container 12. The surviving dispensing of the rinsing solution flushes the used second predetermined volume of the second electrolyte solution from the vessel 12 and into a sump for recovery or at least detoxification.

For example, the vacuum pump 108 can then be turned off and the working electrode 22 having a metal oxide plated surface at this time dropped onto a material handling device (not shown) for further processing stages, such as annealing, to release the vacuum. .

After the working electrode 22 has been removed for further processing and the depleted electrolyte has been discharged from the vessel 12, the apparatus 10 is then ready to receive another working electrode supported by a flat conductive surface on which a metal oxide will be formed. Or the working electrode 22 can be flipped over and reattached to the working electrode holder 120 by the surface on which the metal oxide layer has just been formed, and the back side surface 180 can be exposed for the metal oxide layer according to the above process form.

With the above process, a semiconductor oxide layer can be formed on a surface of a native semiconductor, and a metal oxide layer can be formed on the semiconductor oxide layer. In this case, the formation of the metal oxide layer should be performed while the semiconducting oxide layer is still "wet" - that is, just formed and before any annealing.

Similarly, with the above process, a metal oxide layer can be formed directly on the surface of a native semiconductor, and a semiconductor oxide layer can be formed after a metal oxide layer has been formed. In this case, the formation of the semiconductor oxide layer should be performed while the metal oxide layer is still "wet".

It has been discovered that the semiconductor oxide layer penetrates the planar conductive surface and grows into the surface as the semiconductor oxide layer is formed. This effect occurs whether the semiconductor oxide layer is formed on a native surface of the semiconductor material or a metal oxide layer has been formed on the native surface by the above process.

It is also desirable to form the desired semiconductor oxide layer and metal oxide layer on the front and/or back surface prior to any annealing. The final layer needs to be annealed to form the desired crystal structure from the semiconductor oxide or metal oxide of the above process.

Depending on the chemical composition and thickness of the semiconductor oxide or plated metal oxide, the annealing may be carried out at a temperature in the range of from about 300 ° C to about 700 ° C in an air atmosphere or in a particular gas atmosphere. A particular gas atmosphere for this purpose may include, for example, a gas consisting of from about 3% to about 10% hydrogen and the balance being nitrogen or an inert gas. The annealing process can take, for example, from about 15 minutes to about 2 hours.

The above described apparatus is particularly well suited for forming metal oxides on semiconductor components such as photovoltaic cells. In this example, the flat conductive surface 24 of the working electrode 22 is a surface of an n-type or p-type semiconductor substrate, and the device 10 is formed on the surface of the n-type or p-type semiconductor substrate. A simple oxide film or a metal oxide film. These films can be used to passivate and improve the optical quality of the surface of a semiconductor substrate.

In one embodiment, a minimum oxide film is plated onto a p-type Si crystalline wafer using the process described above. The second electrolyte is a saturated solution of AlCl ₃ in isopropanol. The electrolyte was maintained at a temperature of about 30 ° C and the current density was about 0.25 mA / cm ² for 2 minutes. X-ray diffraction analysis (not shown) exhibits one of the k-Al ₂ O ₃ forms of transitional alumina with typical peaks at 2θ ₁ = 32.903 degrees (more dense) and 2θ ₂ = 32.092 (less dense). The surface area of the working electrode 22 is 100 cm ² . The distance 190 between the flat conductive surface 24 of the working electrode 22 and the flat conductive surface 18 of the auxiliary electrode 16 is 1 mm. The concentration of aluminum ions is 0.005 Eq/L (gram equivalent/liter).

Referring to Figure 9, if the working electrode 22 is a p-type semiconductor substrate and a direct current source causes current to flow such that the working electrode acts as a cathode, causing the metal oxide to be plated on the flat conductive surface 24, or if the working electrode 22 is An n-type semiconductor substrate and a direct current source causes current to flow such that the working electrode acts as an anode to cause a semiconductor oxide layer to be formed on the flat conductive surface, which can be illuminated or incorporated into the working electrode by the current flowing The flat conductive surface 24 of 22 enhances the oxide formation process. To make this effect, for example, the distance 190 between the flat conductive surface 24 of the working electrode 22 and the flat conductive surface 18 of the auxiliary electrode 16 can be set to approximately 3 cm, and the volume of the first or second electrolyte solution 74, 80 is increased. To ensure that the flat conductive surface 24 and the flat conductive surface 18 are still in contact with the electrolyte solution. To achieve this effect, the peripheral wall 44 of the container 12 is heightened and provided with a light transparent window 220 made of a glass of polystyrene for incorporating light 222 produced by an external light source (not shown). Window 220 passes through electrolyte solutions 74, 80 and onto flat conductive surface 24 of working electrode 22.

Referring to Fig. 10, in another embodiment, an opening such as shown at 230 may be provided in the auxiliary electrode 16, and by causing the bottom portion 42 of the container 12 to be transparent using a glass such as polystyrene. The material is formed to reduce the distance 190. A light source 232 can be placed under the container 12 such that light can pass through the bottom portion 42 of the container and through the opening 230 of the auxiliary electrode 16 and through the volume of the electrolyte solution to reach the flat conductive surface 24 of the working electrode 22.

The above apparatus and method provide for the distance between the flat conductive surface 24 of the working electrode 22 and the flat conductive surface 18 of the auxiliary electrode 16, the amount of electrolyte solution, and the amount of dissolved metal salt and other chemical components in the electrolyte solution. Precision control. This enables precise control of the thickness of the semiconductor oxide and metal oxide formed on the surface of the object, which will have particular advantages when the object is, for example, a semiconductor substrate for a PV cell. Furthermore, since the distance between the flat conductive surface 24 of the working electrode 22 and the flat conductive surface 18 of the auxiliary electrode 16 is relatively small, the electrolyte solution constitutes a relatively small resistance, which enables a low current while achieving a high current density. This results in very low heat generation in the electrolyte solution and produces only small convective motion within the electrolyte, which is particularly advantageous when forming metal oxides on the surface of semiconductors such as wafer wafers used in photovoltaic cells.

In addition, the above apparatus and method avoid separate electrical insulation on the back side of the working electrode due to the sealing effect of the rubber seal on the working electrode holder, and the above method and apparatus provide a second in a given plating operation. The nearly 100% utilization of metal ions in the volume of the electrolyte. Finally, the above apparatus and method allow for only a small change in the electrolyte solution and a small change in current direction, and the same device can be selectively used to form semiconductor oxide and metal on the same conductive surface of a semiconductor wafer or a PV cell. Oxide.

While the invention has been described and illustrated with respect to the specific embodiments of the present invention

10. . . Device for forming an oxide layer on a flat conductive surface

12. . . container

14. . . Volume

16. . . Auxiliary electrode

18. . . Flat conductive surface of the auxiliary electrode 16

20,120. . . Working electrode holder

twenty two. . . Working electrode

twenty four. . . Flat conductive surface of working electrode 22

26. . . Spacer

30. . . DC current supply

31. . . Automatic control circuit

32. . . Chemicals that facilitate electrolysis

34. . . Oxygen supply

36. . . Metal ion source

40. . . Table

42. . . The bottom portion of the container 12

44. . . Peripheral wall

46. . . Rectangular recess

48. . . Opening

60. . . Distribution system

62. . . First reservoir

64. . . Flushing solution

66. . . First pump

68. . . Feeding catheter

70. . . Flexible feed conduit

72. . . Second reservoir

74. . . First electrolyte solution

76. . . Second pump

78. . . Third receptacle

80. . . Second electrolyte solution

81. . . Third pump

82. . . Controller

86,136. . . First pipe connector

88,138. . . Second pipe connector

90,96. . . Connector

91. . . Heater

92. . . conductor

94,175. . . wire

100. . . Discharge path

102. . . Discharge opening

104. . . The electromagnetic valve

106. . . Discharge conduit

108,174. . . Vacuum pump

110. . . supporting item

112. . . Slidable collar

114,122. . . arrow

116. . . Stopper

118. . . Chuck mount

124. . . Clip

130. . . Conductive plate

132. . . aisle

134. . . Plug

140. . . Supply tube

142. . . Drain pipe

144. . . Liquid heater

146. . . Pump

148. . . Pump conduit

150. . . Vertical member

152. . . Electrically insulated mount

160. . . Bottom side surface of plate 130

162. . . Aperture

164. . . Top surface of metal plate 130

166. . . Vacuum supply path

168. . . Peripheral access

170. . . Vacuum hose connector

171. . . Ring of electric terminal lug 173

172. . . Vacuum hose

173. . . Electric terminal lug

174. . . Vacuum pump

175. . . wire

177. . . Second terminal

180. . . Back side surface of the object

181. . . Peripheral trench

182. . . Rubber seal

183. . . Central inner part of the object

184. . . The area delimited by the peripheral groove 181, the area delimited by the rubber seal 182

190. . . The distance between the flat conductive surface 24 of the working electrode and the flat conductive surface 18 of the auxiliary electrode 16

192. . . Length of working electrode 22

194. . . Inner side surface of the peripheral wall 44

196. . . Distance between edge 198 and inner side surface 194

198. . . Edge of working electrode 22

220. . . Light transparent window

222. . . Light generated by an external light source

230. . . Opening

232. . . light source

1 is a simplified perspective view of a device for forming an oxide layer on a flat conductive surface in accordance with a first embodiment of the present invention;

Figure 2 is a cross-sectional view of a portion of the apparatus of Figure 1, showing a holder in a position where the formation of the oxide is operable;

Figure 3 is a top plan view of the container portion of one of the devices shown in Figure 1;

Figure 4 is a bottom perspective view of the container portion shown in Figure 2;

Figure 5 is a simplified top perspective view of the working electrode holder of one of the devices shown in Figure 1;

Figure 6 is a bottom plan view of the working electrode holder shown in Figure 4;

Figure 7 is a simplified cross-sectional view of the working electrode holder shown in Figure 4, the working electrode holder holding a plate having a flat conductive surface on which an oxide layer is to be formed;

Figure 8 is a cross-sectional view of a portion of the apparatus shown in Figure 1, showing a holder in an alternative position in which an oxide layer can be formed;

Figure 9 is a simplified cross-sectional view of a portion of a device according to a second embodiment for forming an oxide layer on a p-type semiconductor surface;

Figure 10 is a simplified cross-sectional view of a portion of a device in accordance with a third embodiment for forming an oxide layer on a p-type semiconductor surface.

10. . . Device for forming an oxide layer on a flat conductive surface

12. . . container

14. . . Volume

16. . . Auxiliary electrode

18. . . Flat conductive surface of the auxiliary electrode 16

20,120. . . Working electrode holder

twenty two. . . Working electrode

twenty four. . . Flat conductive surface of working electrode 22

30. . . DC current supply

31. . . Automatic control circuit

40. . . Table

42. . . The bottom portion of the container 12

44. . . Peripheral wall

46. . . Rectangular recess

48. . . Opening

60. . . Distribution system

62. . . First reservoir

64. . . Flushing solution

66. . . First pump

68. . . Feeding catheter

70. . . Flexible feed conduit

72. . . Second reservoir

74. . . First electrolyte solution

76. . . Second pump

78. . . Third receptacle

80. . . Second electrolyte solution

81. . . Third pump

82. . . Controller

90,96. . . Connector

94,175. . . wire

100. . . Discharge path

102. . . Discharge opening

106. . . Discharge conduit

110. . . supporting item

112. . . Slidable collar

114,122. . . arrow

116. . . Stopper

118. . . Chuck mount

124. . . Clip

136. . . First pipe connector

138. . . Second pipe connector

140. . . Supply tube

142. . . Drain pipe

144. . . Liquid heater

146. . . Pump

148. . . Pump conduit

150. . . Vertical member

160. . . Bottom side surface of plate 130

170. . . Vacuum hose connector

172. . . Vacuum hose

173. . . Electric terminal lug

174. . . Vacuum pump

175. . . wire

177. . . Second terminal

180. . . Back side surface of the object

Claims (112)

A method for electrochemically forming an oxide layer on a flat conductive surface, the method comprising the steps of: positioning a supportive planar conductive surface in a relatively parallel spaced relationship relative to a flat conductive surface of an auxiliary electrode Working the electrode such that the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode are generally oriented relatively horizontally and defining a space therebetween; causing the oxidation to be formed on the flat conductive surface for the working electrode a volume of organic electrolyte solution of one of the chemicals of the layer, submerging the flat conductive surface of the auxiliary electrode surface and occupying the space defined between the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode such that at least a flat conductive surface of the auxiliary electrode is in contact with the organic electrolyte solution, and substantially only the flat conductive surface of the working electrode is in contact with the organic electrolyte solution; and causing a current in the organic electrolyte solution to be substantially flat only of the auxiliary electrode Conductive surface and substance only the working electrode During Tan flow between the conductive surface of a period of time sufficient to cause lines and such a strength of the chemically formed oxide layer on whom a flat conductive surface of the working electrode. The method of claim 1, wherein the organic electrolyte solution causing the volume occupies the space defined between the surface of the flat auxiliary electrode and the flat conductive surface of the working electrode comprises holding the working electrode so that only the The flat conductive surface of the working electrode is in contact with the organic electrolyte solution, but the integral working electrode is not immersed in the organic electrolyte solution. The method of claim 2, wherein the retaining system comprises a substantial portion of one side of the working electrode opposite the flat conductive surface of the working electrode that is not in contact with the electrolyte solution. The method of claim 3, wherein the protection comprises holding a rear side of the working electrode against a holding surface supporting a sealing member, the sealing member being operatively configured to contact the working electrode An outer peripheral edge of the rear side is adjacent to the rear side of the working electrode. The method of claim 4, wherein the holding the working electrode against the holding surface comprises causing a negative pressure to occur adjacent to a rear side of the working electrode such that the annular chamber pressure is the rear side of the working electrode Press against the seal. The method of claim 5, wherein the causing the negative pressure comprises providing a vacuum adjacent the seal. The method of any one of claims 1 to 6, wherein the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode are separately separated by a distance due to the capillary force of the organic electrolyte solution The organic electrolyte solution is adhered to the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode. The method of any one of claims 1 to 7, wherein the positioning the working electrode comprises positioning the working electrode such that a flat conductive surface of the working electrode is spaced apart from a flat conductive surface of the auxiliary electrode The length is between about 0.1% and about 20%. The method of any one of clauses 1 to 8, wherein the positioning of the working electrode relative to the flat conductive surface of the auxiliary electrode comprises holding the auxiliary electrode in an operative manner in a substantially horizontal orientation In order to accommodate the container of the organic electrolyte solution, and the working electrode is held in the container and distributed separately from the auxiliary electrode, the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode are defined space. The method of claim 9 wherein the organic electrolyte solution causing the volume floods the flat conductive surface of the auxiliary electrode comprises incorporating a predetermined volume of the organic electrolyte solution into the container. The method of claim 10, wherein the incorporating the predetermined volume of the organic electrolyte solution comprises passing the predetermined volume through an opening in the auxiliary electrode, the opening being conductive to the flat conductive surface of the working electrode and the auxiliary This space between the flat conductive surfaces of the electrodes. The method of claim 11, wherein the passing of the predetermined volume through an opening comprises pumping the predetermined volume of organic electrolyte solution from a reservoir through the opening. The method of any one of claims 1 to 12, further comprising discharging the organic electrolyte solution after the oxide layer is formed to a desired thickness on the flat conductive surface of the working electrode. The method of any one of claims 1 to 13, wherein the chemical system comprises an oxygen supply sufficient to permit formation of the oxide layer to a desired thickness. The method of claim 14, wherein the oxygen source comprises dissolved oxygen or at least one oxygen precursor. The method of claim 15, wherein the oxygen source comprises at least one oxygen precursor, and wherein the at least one oxygen precursor comprises dissolved nitrate, nitrite, hydrogen peroxide, and traces of water. At least one of them. The method of any one of clauses 14 to 16, wherein the working electrode is formed of a material, and wherein the oxide layer is an oxide of the material, and wherein the current flow system is included This current is caused to flow in a direction in which the working electrode acts as an anode. The method of any one of claims 1 to 17, further comprising agitating the organic electrolyte solution while the current is flowing. The method of claim 18, wherein the agitation system comprises a space defined between the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode that causes the organic electrolyte solution to pass. The method of any one of claims 17 to 19, wherein the organic electrolyte solution is protic, and the chemical systems include methanol, ethanol, isopropanol, ethylene glycol, and tetrahydrofuran. At least one of methanol. The method of any one of claims 17 to 19, wherein the organic electrolyte solution is aprotic, and the chemical system comprises at least one of N-methylacetamide and acetonitrile. By. The method of any one of clauses 17 to 21, wherein the organic electrolyte solution and the working electrode and the auxiliary electrode are generally maintained at a constant temperature between about 15 ° C and about 90 ° C. The method of any one of clauses 17 to 22, wherein the causing the current flow comprises maintaining the current at a level sufficient to maintain the working electrode as oxide formation occurs and resistance is formed to the current The level of oxide formation. The method of any one of claims 17 to 23, further comprising terminating the flow of the current when the current of the current conforms to a criterion. The method of claim 24, wherein the criterion comprises a condition that the oxide layer has a predetermined thickness. The method of any one of claims 17 to 25, wherein the current has a current density in the organic electrolyte solution of between about 1 mA/cm ² and about 100 mA/cm ² . The method of any one of claims 1 to 16, wherein the oxide layer is a metal oxide layer, and wherein causing the current flow system to cause the current to flow in a working electrode as a In the direction of the cathode, and wherein the organic electrolyte solution comprises at least one ion source of the metal. The method of claim 27, further comprising, based on a desired thickness of the metal oxide to be plated on the flat conductive surface of the cathode, and a concentration of the ion source of the metal and the organic The predetermined volume is determined based on a volume of the electrolyte solution. The method of claim 27, wherein the oxide layer comprises a metal oxide film comprising aluminum oxide, and wherein the ion source of the metal comprises at least one dissolved aluminum salt or at least one aluminate or At least one combination of an aluminum salt or at least one aluminate is dissolved. The method of claim 27, wherein the oxide layer comprises a metal oxide film comprising indium oxide, and wherein the ion source of the metal comprises at least one dissolved indium salt. The method of claim 27, wherein the oxide layer comprises a metal oxide film comprising zinc oxide, and wherein the ion source of the metal comprises at least one dissolved zinc salt or at least one zinc salt or At least one combination of a zinc salt or at least one zincate is dissolved. The method of claim 27, wherein the oxide layer comprises a metal oxide film comprising aluminum-doped zinc oxide, and wherein the ion source of the metal comprises at least one dissolved zinc salt and at least one dissolved aluminum salt. The method of claim 27, wherein the oxide layer comprises a metal oxide film comprising indium doped zinc oxide, and wherein the ion source of the metal comprises at least one dissolved zinc salt and at least one dissolved indium salt. The method of claim 27, wherein the oxide layer comprises a metal oxide film comprising chlorine-doped zinc oxide, and wherein the ion source of the metal comprises at least one dissolved zinc salt, and wherein the organic The electrolyte solution contains at least one dissolved chloride. The method of claim 27, wherein the oxide layer comprises a metal oxide film comprising tin-doped indium oxide, and wherein the ion source of the metal comprises at least one dissolved indium salt and at least one dissolved tin salt. The method of any one of claims 27 to 35, further comprising maintaining the organic electrolyte solution stationary while the current is flowing. The method of any one of claims 27 to 36, wherein the organic electrolyte solution is protonic, and wherein the chemical systems include methanol, ethanol, propanol, isopropanol, ethylene glycol, and At least one of glycerin. The method of any one of claims 27 to 36, wherein the organic electrolyte solution is aprotic, and wherein the chemical system comprises at least at least dimethyl hydrazine (DMSO) and propylene carbonate. One. The method of any one of claims 27 to 38, wherein the organic electrolyte solution and the working electrode and the auxiliary electrode are maintained at a temperature between about 15 ° C and about 90 ° C. The method of any one of claims 27 to 39, further comprising terminating the flow of the current when a predetermined number of coulombs has passed through the organic electrolyte solution. The method of claim 40, wherein the predetermined coulomb number is sufficient to cause substantially all of the ion source of the metal in the electrolyte solution to be depleted from the organic electrolyte solution and oxidized on the flat conductive surface of the working electrode It is advantageous to produce the oxide layer to a desired thickness. The method of claim 41, wherein maintaining the current at a one-dimensional system comprises maintaining the current at a level between about 0.1 mA/cm ² and about 100 mA/cm ² in the organic electrolyte solution. One of the current densities. The method of any one of claims 27 to 42, wherein the current is maintained at a level of a current concentration between about 1 mA/cm ³ and about 1000 mA/cm ³ in the organic electrolyte solution. . The method of any one of claims 41 to 43 further comprising discharging substantially exhausting the metal ions after the flat conductive surface of the cathode has been plated by the metal oxide to the desired thickness The organic electrolyte solution. A method for forming an oxide layer on a semiconductor wafer, the method comprising the method of any one of claims 1 to 26, wherein the working electrode comprises the semiconductor wafer, the flat conductive surface system Located on a front side or a back side of the semiconductor wafer and the oxide layer is a semiconductor oxide layer. The method of claim 45, wherein the semiconductor wafer comprises an n-type crystalline semiconductor wafer or a p-type crystalline semiconductor wafer. The method of claim 46, wherein the flat conductive surface is on an n-type portion or a p-type portion of the crystalline semiconductor wafer, or wherein the flat conductive surface is located in the crystalline semiconductor crystal On a metal oxide layer on an n-type portion or a p-type portion of the circle. The method of claim 46, wherein the method further comprises exposing the flat conductive surface of the working electrode to light at least a portion of a period of time during which the current flows. The method of claim 48, wherein exposing the flat conductive surface of the working electrode to the light system comprises enclosing light into the space between the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode. The method of claim 49, wherein the incorporating light into the space comprises incorporating light through an opening in the auxiliary electrode or incorporating light through at least a portion of at least one peripheral edge of the space. A method for forming a metal oxide layer on a semiconductor wafer, the method comprising the method of any one of claims 27 to 44, wherein the working electrode comprises the semiconductor wafer, the working electrode The flat conductive surface is on a front side or a back side of the semiconductor wafer, or wherein the flat conductive surface of the working electrode is on one of the semiconductor oxide layers on a front side or a back side of the semiconductor wafer. The method of claim 51, wherein the flat conductive surface of the working electrode semiconductor wafer comprises an n-type portion or a p-type portion of a crystalline photovoltaic cell. The method of claim 51, wherein the method further comprises exposing the flat conductive surface of the working electrode to light at least a portion of a period of time during which the current flows. The method of claim 53, wherein exposing the flat conductive surface of the working electrode to the light system comprises incorporating light into the space between the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode. The method of claim 54, wherein the incorporating light into the space comprises incorporating light through an opening in the auxiliary electrode or incorporating light through at least a portion of at least one peripheral edge of the space. An apparatus for electrochemically forming an oxide layer on a flat conductive surface, the apparatus comprising: a container operatively configured to contain an organic electrolyte solution containing a volume of a chemical used to form the oxide layer An auxiliary electrode having a flat conductive surface oriented substantially horizontally in the container such that the organic electrolyte solution floods the flat conductive surface of the auxiliary electrode; a working electrode holder for holding a support for the flat a working electrode of a conductive surface, the oxide layer being formed on the flat conductive surface in a general horizontal orientation opposite, parallel and spaced apart from the auxiliary electrode such that a space is defined by the planar conductive surface of the auxiliary electrode Between the flat conductive surfaces of the working electrode, wherein at least a portion of the organic electrolyte solution can occupy the space and contact the flat conductive surface of the auxiliary electrode and the flat conductive surface of the working electrode; a direct current source for the operative group Constructed to connect to the auxiliary electrode and the working electrode to cause a current to flow to the auxiliary Between the electrode and the working electrode, to cause the working electrode as an anode or as a cathode in the organic electrolyte solution at least a portion. The device of claim 56, wherein the working electrode holder is operatively configured to hold the working electrode, so that only the flat conductive surface of the working electrode is in contact with the organic electrolyte solution, but the overall operation The electrode is not immersed in the organic electrolyte solution. The device of claim 57, wherein the working electrode holder comprises a protector operatively configured to protect a substantial portion of one side of the working electrode from contacting the organic electrolyte solution . The device of claim 58 wherein the protector comprises a retaining surface supporting a seal operatively configured to be adjacent the outer peripheral edge of one of the rear sides of the working electrode Contact a back side of the working electrode. The device of claim 59, wherein the working electrode holder comprises means for causing a negative pressure to occur adjacent to the rear side of the working electrode, so that the ring chamber pressure is sufficient to prevent leakage of the electrolyte solution. The force of the seal presses the rear side of the working electrode against the seal. The device of claim 60, wherein the means for causing a negative pressure comprises a vacuum opening adjacent the seal. The device of any one of claims 56 to 61, wherein the working electrode holder is operatively configured to separate a flat conductive surface of the working electrode from a flat conductive surface of the auxiliary electrode to facilitate the organic The electrolyte solution adheres to the distance between the flat conductive surface of the working electrode and the flat conductive surface of the auxiliary electrode due to the capillary force of the organic electrolyte solution. The device of any one of claims 56 to 62, wherein the working electrode holder is operatively configured to position the working electrode such that a flat conductive surface of the working electrode is spaced apart from a flat conductive surface of the auxiliary electrode Between about 0.1% and about 20% of the length of the working electrode. The apparatus of any one of claims 56 to 63, wherein the auxiliary electrode comprises a graphite plate, a gas carbon plate, or a graphite fabric, or a platinum plate. The device of claim 64, further comprising means for incorporating the predetermined volume of the organic electrolyte solution into the container. The device of claim 65, wherein the means for incorporating the predetermined volume of the organic electrolyte solution comprises an opening in the auxiliary electrode through which the predetermined volume is introduced into the container. The device of claim 66, wherein the means for incorporating the predetermined volume of the organic electrolyte solution comprises a pump operatively configured to pump the predetermined volume of organic electrolyte from a reservoir The solution passes through the opening. The apparatus of any one of claims 56 to 67, further comprising a row of ports operatively configured to form the oxide layer on the flat conductive surface of the working electrode to a The organic electrolyte is discharged after the thickness is desired. The apparatus of any one of claims 56 to 68, wherein the chemical system comprises an oxygen supply source sufficient to permit formation of the oxide layer to a desired thickness. The device of claim 69, wherein the oxygen source comprises dissolved oxygen or at least one oxygen precursor. The apparatus of claim 70, wherein the oxygen source comprises at least one oxygen precursor, and wherein the at least one oxygen precursor comprises dissolved nitrate, nitrite, hydrogen peroxide, and traces of water. At least one of them. The apparatus of any one of claims 56 to 71, wherein the direct current source is operatively configured to cause the current to flow in a direction in which the working electrode acts as an anode. The device of any one of claims 56 to 72, further comprising means for agitating the electrolyte when the current flows. The device of claim 73, wherein the means for agitating comprises defining a flow of an organic electrolyte solution for causing the volume to pass between a flat conductive surface of the working electrode and a flat conductive surface of the auxiliary electrode The device of this space. The apparatus of any one of claims 72 to 74, wherein the organic electrolyte solution is protonic, and the chemical system comprises methanol, ethanol, isopropanol, ethylene glycol, and tetrahydrofuran methanol. At least one. The apparatus of any one of claims 72 to 74, wherein the organic electrolyte solution is aprotic, and the chemical system comprises at least one of N-methylacetamide and acetonitrile. The device of any one of claims 72 to 76, further comprising a device for maintaining the organic electrolyte solution, the working electrode and the auxiliary electrode at a constant temperature between about 15 ° C and about 90 ° C. . The apparatus of any one of claims 72 to 77, wherein the direct current source is configured to maintain the current at a level sufficient to maintain an oxide as oxide formation occurs and resistance is formed for the current The level of the device formed. The device of any one of claims 72 to 78, further comprising means for terminating the flow of the current when the current of the current conforms to a criterion. The apparatus of claim 79, wherein the criterion comprises a condition that the oxide layer has a predetermined thickness. The apparatus of any one of claims 72 to 80, wherein the direct current source is configured to maintain the current in the organic electrolyte solution of the volume to cause from about 1 mA/cm ² to about 100 mA/cm. A device with a current density between ² . The apparatus of any one of claims 56 to 71, wherein the oxide layer is a metal oxide layer, wherein the electrolyte solution comprises at least one ion source of metal, and wherein the direct current source is The operatively configured to cause the current to flow in a direction that causes the working electrode to act as a cathode. The apparatus of claim 82, wherein the predetermined volume of electrolyte solution is sufficient to ensure that a flat conductive surface of the auxiliary electrode and a flat conductive surface of the working electrode are in contact with the electrolyte solution, and wherein the predetermined volume has Sufficient to plate the metal oxide to a metal ion of a desired thickness of the metal oxide layer on the flat conductive surface of the working electrode. The device of claim 82, wherein the metal oxide layer comprises alumina, and wherein the ion source of the metal comprises at least one dissolved aluminum salt or at least one aluminate or the at least one dissolved aluminum salt Or a combination of at least one aluminate. The device of claim 82, wherein the metal oxide layer comprises indium oxide, and wherein the ion source of the metal comprises at least one dissolved indium salt. The device of claim 82, wherein the metal oxide layer comprises zinc oxide, and wherein the ion source of the metal comprises at least one dissolved zinc salt or at least one zinc salt or the at least one dissolved zinc salt or At least one combination of zinc salts. The device of claim 82, wherein the metal oxide layer comprises aluminum-doped zinc oxide, and wherein the ion source of the metal comprises at least one dissolved zinc salt and at least one dissolved aluminum salt. The device of claim 82, wherein the metal oxide layer comprises indium-doped zinc oxide, and wherein the ion source of the metal comprises at least one dissolved zinc salt and at least one dissolved indium salt. The device of claim 82, wherein the metal oxide layer comprises chlorine-doped zinc oxide, and wherein the ion source of the metal comprises at least one dissolved zinc salt, and wherein the organic electrolyte solution comprises at least one Dissolve chloride. The device of claim 82, wherein the metal oxide layer comprises tin-doped indium oxide, and wherein the ion source of the metal comprises at least one dissolved indium salt and at least one dissolved tin salt. The apparatus of any one of claims 82 to 90, wherein the organic electrolyte solution is maintained stationary while the current is flowing. The apparatus of any one of claims 82 to 91, wherein the organic electrolyte solution is protonic, and wherein the chemical systems include methanol, ethanol, propanol, isopropanol, ethylene glycol, and At least one of glycerin. The apparatus of any one of claims 82 to 92, wherein the organic electrolyte solution is aprotic, and wherein the chemical system comprises at least at least dimethyl hydrazine (DMSO) and propylene carbonate. One. The device of any one of claims 82 to 93, further comprising means for maintaining the organic electrolyte solution, the working electrode and the auxiliary electrode at a temperature between about 15 ° C and about 90 ° C. The apparatus of any one of claims 82 to 94, further comprising means for terminating the flow of the current when a predetermined number of coulombs has passed through the organic electrolyte solution. The apparatus of claim 95, wherein the predetermined coulomb number is sufficient to cause substantially all of the metal source of the metal in the organic electrolyte solution to be depleted from the organic electrolyte solution and oxidized to the flat conductive surface of the working electrode Upper to facilitate the production of the oxide layer to a desired thickness. The device of claim 96, wherein the means for maintaining the current at a predetermined level comprises maintaining the current to produce about 0.1 mA/cm ² to about 100 mA in the organic electrolyte solution. A device with a current density between cm ² . The device of any one of claims 82 to 97, wherein the means for maintaining the current comprises means for maintaining the current in the organic electrolyte solution to produce from about 100 mA/cm ³ to about 1000 mA / A device with a current concentration between cm ³ . The apparatus of any one of claims 82 to 98, further comprising for substantially exhausting the metal after the flat conductive surface of the cathode has been plated by the metal oxide to the desired thickness A device of the organic electrolyte solution of ions. An apparatus for forming an oxide layer on a semiconductor wafer, the apparatus comprising the apparatus of any one of claims 56 to 71, wherein the working electrode comprises the semiconductor wafer, the flat conductive surface system Located on a front side or a back side of the semiconductor wafer, and the oxide layer is a semiconductor oxide layer. The device of claim 100, wherein the semiconductor wafer comprises an n-type crystalline semiconductor wafer or a p-type crystalline semiconductor wafer. The device of claim 101, wherein the flat conductive surface is on an n-type portion or a p-type portion of the crystalline semiconductor wafer, or wherein the flat conductive surface is located in the crystalline semiconductor crystal On a metal oxide layer on an n-type portion or a p-type portion of the circle. The device of claim 101, wherein the device further comprises means for exposing the flat conductive surface of the working electrode to light at least a portion of a period of time during which the current flows. The device of claim 103, wherein the means for exposing the flat conductive surface of the working electrode to light comprises a flat conductive surface for incorporating light into the working electrode and a flat conductive surface of the auxiliary electrode The device within this space. The device of claim 104, wherein the means for incorporating light into the space comprises a light transmissive portion of the auxiliary electrode to permit light to pass through the light transmissive portion and impact the flat of the working electrode On the conductive surface. The device of claim 104, wherein the means for incorporating light comprises a light transmissive portion formed in the container for allowing light to be incorporated into the space via at least a portion of at least one peripheral edge of the space . An apparatus for forming a metal oxide layer on a semiconductor wafer, the apparatus comprising the apparatus of any one of claims 82 to 99, wherein the working electrode comprises the semiconductor wafer, the working electrode The flat conductive surface is on a front side or a back side of the semiconductor wafer, or wherein the flat conductive surface of the working electrode is on a semiconductor oxide layer on a front side or a back side of the semiconductor wafer. The device of claim 107, wherein the flat conductive surface of the working electrode semiconductor wafer comprises an n-type portion or a p-type portion of a crystalline photovoltaic cell. The device of claim 107, wherein the device further comprises means for exposing the flat conductive surface of the working electrode to light at least a portion of a period of time during which the current flows. The device of claim 109, wherein the means for exposing the flat conductive surface of the working electrode to light comprises a flat conductive surface for incorporating light into the working electrode and a flat conductive surface of the auxiliary electrode. The device within this space. The device of claim 109, wherein the means for incorporating light into the space comprises a light transmissive portion of the auxiliary electrode to permit light to pass through the light transmissive portion and impact the flat of the working electrode On the conductive surface. The device of claim 109, wherein the means for incorporating light comprises a light transmissive portion formed in the container for allowing light to be incorporated into the space via at least a portion of at least one peripheral edge of the space .