Evergreen Solar, Inc.

1366 Technologies Inc.

Max Era, Inc.

Richard Lee Wallace, Jr

Ralf Jonczyk

Emanuel Michael Sachs

Scott Reitsma

Weidong Huang

G D Stephen Hudelson

Eerik Torm Hantsoo

Adam M Lorenz

David S Harvey

Christine Richardson

Daniel Doble

Andrew M Gabor

Adam L Lorenz

A main crucible of molten semiconductor is replenished from a supply crucible maintained such that there are always two phases of solid and liquid semiconductor within the supply crucible. Heat added to melt the solid material results in the solid material changing phase to liquid, but will not result in any significant elevation in temperature of the liquid within the supply crucible. The temperature excursions are advantageously small, being less than that which would cause problems with the formed product. The solid product material acts as a sort of temperature buffer, to maintain the supply liquid temperature automatically and passively at or very near to the phase transition temperature. For silicon, excursions are kept to less than 90&#xb0; C., and even as small as 50&#xb0; C. The methods also are useful with germanium. Prior art silicon methods that entirely melt the semiconductor experience excursions exceeding 100&#xb0; C.

Method for maintaining contained volume of molten material from which material is depleted and replenished

Semi-conductor wafers with thin and thicker regions at controlled locations may be for Photovoltaics. The interior may be less than 180 microns or thinner, to 50 microns, with a thicker portion, at 180-250 microns. Thin wafers have higher efficiency. A thicker perimeter provides handling strength. Thicker stripes, landings and islands are for metallization coupling. Wafers may be made directly from a melt upon a template with regions of different heat extraction propensity arranged to correspond to locations of relative thicknesses. Interstitial oxygen is less than 6&#xd7;10atoms/cc, preferably less than 2&#xd7;10, total oxygen less than 8.75&#xd7;10atoms/cc, preferably less than 5.25&#xd7;10. Thicker regions form adjacent template regions having relatively higher heat extraction propensity; thinner regions adjacent regions with lesser extraction propensity. Thicker template regions have higher extraction propensity. Functional materials upon the template also have differing extraction propensities.

Methods and apparati for making thin semi-conductor wafers with locally controlled regions that are relatively thicker than other regions and such wafers

A pressure differential can be applied across a mold sheet and a semiconductor (e.g. silicon) wafer (e.g. for solar cell) is formed thereon. Relaxation of the pressure differential can allow release of the wafer. The mold sheet may be cooler than the melt. Heat is extracted through the thickness of the forming wafer. The temperature of the solidifying body is substantially uniform across its width, resulting in low stresses and dislocation density and higher crystallographic quality. The mold sheet can allow flow of gas through it. The melt can be introduced to the sheet by: full area contact with the top of a melt; traversing a partial area contact of melt with the mold sheet, whether horizontal or vertical, or in between; and by dipping the mold into a melt. The grain size can be controlled by many means.

Apparati for fabricating thin semiconductor bodies from molten material

A pressure differential is applied across a mold sheet and a semiconductor (e.g. silicon) wafer (e.g. for solar cell) is formed thereon. Relaxation of the pressure differential allows release of the wafer. The mold sheet may be cooler than the melt. Heat is extracted almost exclusively through the thickness of the forming wafer. The liquid and solid interface is substantially parallel to the mold sheet. The temperature of the solidifying body is substantially uniform across its width, resulting in low stresses and dislocation density and higher crystallographic quality. The mold sheet must allow flow of gas through it. The melt can be introduced to the sheet by: full area contact with the top of a melt; traversing a partial area contact of melt with the mold sheet, whether horizontal or vertical, or in between; and by dipping the mold into a melt. The grain size can be controlled by many means.

Selected methods for efficiently making thin semiconductor bodies from molten material for solar cells and the like

Methods exploiting a Self Aligned Cell (SAC) architecture for doping purposes, use the architecture to direct the deposition and application of either a dopant or a diffusion retarder. Doping is provided in regions that will become metallization for conducting fingers. Dopant may be treated directly into metallization grooves. Or, diffusion retarder may be provided in non-groove locations, and dopant may be provided over some or all of the entire wafer surface. Dopant and metal automatically go where desired, and in register with each other. The SAC architecture also includes concave surfaces for light absorbing regions of a cell, to reduce reflection of light energy, which regions may also be treated with dopant in the concavities, to result in semi-conductor emitter lines. Alternatively, diffusion retarder may be treated into the concavities, leaving upper tips of ridges between the concavities exposed, thereby subject to deeper doping.

Methods to pattern diffusion layers in solar cells and solar cells made by such methods

Methods for efficiently making thin semiconductor bodies from molten material for solar cells and the like

A ribbon crystal pulling furnace has a base insulation and a liner insulation removably connected to the base insulation. At least a portion of the liner insulation forms an interior for containing a crucible.

Removable thermal control for ribbon crystal pulling furnaces

A string for use in a string ribbon crystal has a base portion with a refractory material, and an externally exposed layer radially outward of the refractory material. The base portion has a coefficient of thermal expansion that is generally matched with the coefficient of thermal expansion for silicon. The externally exposed layer has a contact angle with silicon of between about 15 and 120 degrees.

Ribbon crystal having reduced wetting string

A method of growing ribbon crystal provides a crucible containing molten material, and passes at least two strings through the molten material to produce a partially formed ribbon crystal. The method then directs a fluid to a given portion of the partially formed ribbon crystal to convectively cool the given portion.

Method and apparatus for growing a ribbon crystal with localized cooling

Reduced wetting string for ribbon crystal

Methods and apparatus for concurrent growth of multiple crystalline ribbons from a single crucible employ meniscus shapers to facilitate continuous growth of discrete and substantially flat crystalline ribbons having controlled width.

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Acton, MA, United States of America

Richard Lee Wallace, Jr