Twin Creeks Technologies, Inc.

Gtat Corporation

Aditya Agarwal

Srinivasan Sivaram

Christopher John Petti

S Brad Herner

Thomas Parrill

Steven M Zuniga

Andrew J Nagengast

Kathy Jackson

Derek G Aqui

Keenan Leon Guerrero

Orion Leland

Harish Kumar Bolla

Robert D Tolles

Michael A Vyvoda

Gopal Prabhu

A donor wafer, for example of silicon, has an irregular surface following cleaving of a lamina from the surface, for example by exfoliation following implant of hydrogen and/or helium ions to define a cleave plane. Pinholes in the lamina leave column asperities at the exfoliated surface of the donor wafer, and the beveled edge may leave an edge asperity which fails to exfoliate. To prepare the surface of the donor wafer for reuse, mechanical grinding removes the column and edge asperities, and minimal additional thickness. Following cleaning, growth and removal of an oxide layer at the surface rounds remaining peaks. The smoothed surface is well adapted to bonding to a receiver element and exfoliation of a new lamina. A variety of devices may be fabricated from the lamina, for example a photovoltaic cell.

Method for preparing a donor surface for reuse

A very thin photovoltaic cell is formed by implanting gas ions below the surface of a donor body such as a semiconductor wafer. Ion implantation defines a cleave plane, and a subsequent step exfoliates a thin lamina from the wafer at the cleave plane. A photovoltaic cell, or all or a portion of the base or emitter of a photovoltaic cell, is formed within the lamina. In preferred embodiments, the wafer is affixed to a receiver before the cleaving step. Electrical contact can be formed to both surfaces of the lamina, or to one surface only.

Method to form a photovoltaic cell comprising a thin lamina

A system for simultaneously treating multiple workpieces is configured with sites, configured to hold respective workpieces, affixed on a rotatable base. Each site has a shelf accommodating an interior space and may be positioned by base rotation in alignment with a station of fixed location. Each station is equipped with an active component. The active components are movable simultaneously within respective stations into the respective interior spaces of respective aligned sites.

Apparatus and method for simultaneous treatment of multiple workpieces

Ion implanters are especially suited to meet process dose and energy demands associated with fabricating photovoltaic devices by ion implantation followed by cleaving.

Ion implanter for photovoltaic cell fabrication

A system for simultaneously treating multiple workpieces is configured with treatment sites, configured to hold respective workpieces, fixed on a rotatable base. Treatment stations are equipped with respective active components operable simultaneously to treat respective workpieces identically on respective aligned treatment sites. For loading and unloading the treatment sites are rotated through distinct loading and unloading stations of the treatment stations which allow loading of a second batch while a first batch is being unloaded.

A method is described to create a thin semiconductor lamina adhered to a ceramic body. The method includes defining a cleave plane in a semiconductor donor body, applying a ceramic mixture to a first face of the semiconductor body, the ceramic mixture including ceramic powder and a binder, curing the ceramic mixture to form a ceramic body, and cleaving a lamina from the semiconductor donor body at the cleave plane, the lamina remaining adhered to the ceramic body. Forming the ceramic body this way allows outgassing of volatiles during the curing step. Devices can be formed in the lamina, including photovoltaic devices. The ceramic body and lamina can withstand high processing temperatures. In some embodiments, the ceramic body may be conductive.

Formed ceramic receiver element adhered to a semiconductor lamina

Methods for bonding a donor wafer to a receiver element and transferring a lamina from the donor wafer to the receiver element are disclosed herein. The donor wafer may be, for example, a monocrystalline silicon wafer with a thickness of from about 300 microns to about 1000 microns, and the lamina may be may be less than 100 microns thick. The receiver element may be composed of, for example, metal or glass, and the receiver element may have dissimilar thermal expansion properties from the lamina. Although the lamina and the receiver element may have dissimilar thermal expansion properties, the methods disclosed herein maintain the integrity of the bond between the lamina and the receiver element.

Methods of transferring a lamina to a receiver element

In some embodiments, a method of forming a photovoltaic cell includes (1) forming a cleave plane in a donor body so as to define a lamina to be bonded to a receiver element and exfoliated from the donor body; (2) prior to bonding, pre-heating the donor body without the receiver element to a temperature of greater than about 200&#xb0; C. for a first time period that is less than a time period required for exfoliation of the lamina from the donor body; (3) cooling the donor body after pre-heating the donor body; (4) bonding the donor body to the receiver element; and (5) heating the bonded donor body and receiver element for a second time period so as to complete the exfoliation of the lamina from the donor body. Numerous other aspects are provided.

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Sunnyvale, CA, United States of America

Aditya Agarwal