Ebara Solar, Inc.

Ebara Corporation

Daniel L Meier

Hubert P Davis

Ruth A Garcia

Jalal Salami

Joyce A Jessup

Gregory T Neugebauer

Philip J Simpson

Robert P Stoehr

Edward V Macuga

Edgar L Kochka

Akio Shibata

The present invention provides a system and method for creating self-doping contacts to silicon devices in which the contact metal is coated with a layer of dopant and subjected to high temperature, thereby alloying the silver with the silicon and simultaneously doping the silicon substrate and forming a low-resistance ohmic contact to it. A self-doping negative contact may be formed from unalloyed silver which may be applied to the silicon substrate by either sputtering, screen printing a paste or evaporation. The silver is coated with a layer of dopant. Once applied, the silver, substrate and dopant are heated to a temperature above the Ag&mdash;Si eutectic temperature (but below the melting point of silicon). The silver liquefies more than a eutectic proportion of the silicon substrate. The temperature is then decreased towards the eutectic temperature. As the temperature is decreased, the molten silicon reforms through liquid-phase epitaxy and while so doing dopant atoms are incorporated into the re-grown silicon lattice. Once the temperature drops below the silver-silicon eutectic temperature the silicon which has not already been reincorporated into the substrate through epitaxial re-growth forms a solid-phase alloy with the silver. This alloy of silver and silicon is the final contact material, and is composed of eutectic proportions of silicon and silver. Under eutectic proportions there is significantly more silver than silicon in the final contact material, thereby insuring good electrical conductivity of the final contact material.

Method and apparatus for self-doping contacts to a semiconductor

The present invention provides a system for self-doping contacts to silicon devices in which the contact metal is coated with a layer of dopant and subjected to high temperature, thereby alloying the silver with the silicon and simultaneously doping the silicon substrate and forming a low-resistance ohmic contact to it. The silver is coated with a layer of dopant. Once applied, the silver, substrate and dopant are heated to a temperature above the Ag&mdash;Si eutectic temperature (but below the melting point of silicon). The silver liquefies more than a eutectic proportion of the silicon substrate. This alloy of silver and silicon is the final contact material, and is composed of eutectic proportions of silicon and silver. Under eutectic proportions there is significantly more silver than silicon in the final contact material, thereby insuring good electrical conductivity of the final contact material.

Apparatus for self-doping contacts to a semiconductor

Method for self-doping contacts to a semiconductor

A process for dendritic web growth is described. The process includes providing a melt, growing a dendritic web crystal from the melt, replenishing the melt during the step of growing the dendritic web crystal, and applying a magnetic field to the melt during the step of growing the dendritic web crystal. An apparatus for stabilizing dendritic web growth is also described. The apparatus includes a crucible including a feed compartment for receiving pellets to facilitate melt replenishment and a growth compartment designed to hold a melt for dendritic web growth. The apparatus further includes a magnetic field generator configured to provide a magnetic field during dendritic web growth.

Method for stabilizing dendritic web crystal growth

System for stabilizing dendritic web crystal growth

A process for fabricating a solar cell is described. The process includes: (1) providing a base layer, (2) fabricating an emitter layer of p-type conductivity on a same side as the non-illuminated surface of the base layer to provide a strongly doped p-type emitter layer and a p-n junction between the n-type base layer and the p-type emitter layer. The base layer of the present invention has n-type conductivity and is defined by an illuminated surface and a non-illuminated surface. The illuminated surface has light energy impinging thereon when the solar cell is exposed to the light energy and the non-illuminated surface is opposite the illuminated surface.

Aluminum alloy back junction solar cell and a process for fabrication thereof

A self-doping electrode to silicon is formed primarily from a metal (major component) which forms a eutectic with silicon. A p-type dopant (for a positive electrode) or an n-type dopant (for a negative electrode) is alloyed with the major component. The alloy of major component and dopant is applied to a silicon substrate. Once applied, the alloy and substrate are heated to a temperature above the major component-silicon eutectic temperature such that the major component liquefies more than a eutectic proportion of the silicon substrate. The temperature is then decreased towards the eutectic temperature permitting molten silicon to reform through liquid-phase epitaxy and while so doing incorporate dopant atoms into its regrown lattice. Once the temperature drops below the major component-silicon eutectic temperature the silicon, which has not already regrown into the lattice, forms a solid-phase alloy with the major component and the remaining unused dopant. This alloy of major component, silicon and unused dopant is the final contact material. Alternatively, a self-doping electrode may be formed from an unalloyed metal applied to a silicon substrate. The metal and substrate are heated to a temperature above the metal-silicon eutectic temperature in an ambient gas into which a source of vaporized dopant atoms has been introduced. Dopant atoms in the ambient gas are absorbed by the molten mixture of metal-silicon to a much greater extent than they are absorbed by the solid silicon substrate surfaces. The temperature is then decreased to below the metal-silicon eutectic temperature. During this temperature decrease, the doped regrown silicon layer and the metal-silicon alloy final contact material are created in the same process as described above.

Method and apparatus for self-doping negative and positive electrodes for silicon solar cells and other devices

A solar cell having self-aligned metal electrodes and underlying relatively deep emitter regions joined by relatively shallow emitter regions under the surface not covered by the electrodes is formed in a semiconductive substrate by forming relatively shallow p+ and n+ diffusion regions on the front and back surfaces, respectively, of a silicon semiconductive substrate, screen printing aluminum onto the front surface of the substrate in a desired electrode pattern, heat treating the developing cell to form the relatively deep p+ type emitter regions underneath the electrode pattern, while growing an oxide passivation layer over the uncovered portions of the substrate surface, applying an antireflective coating to the front surface in the regions not covered by the electrodes, and screen printing silver over the electrodes on the front surface and over the back surface of the solar cell.

Structure and fabrication process for self-aligned locally deep-diffused

An improved solar cell design and method of fabrication that primarily uses two materials, n-type doped silicon and aluminum to form a p-n alloy junction back contact solar cell. The aluminum alloy junctions are placed on the back (unilluminated) side of the cell, thereby combining the desirable features of aluminum (as a dopant, contact metal and light reflector), with the advantages of a back contact cell. The cell design and method of fabrication includes such features as surface texturing, front and back surface field minority carrier mirrors, surface passivation using oxidation layers, use of Al contacts as light reflectors, intrinsic protection against reverse bias due to contiguous n.sup.+ and p.sup.+ regions, and an improved bus bar contact design suitable for interconnecting cells using a surface mount technology. An improved method of ohmic contact formation uses a self-alignment technique for forming the ohmic contacts.

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Pittsburgh, PA, United States of America

Daniel L Meier