Abstract: An ion implanter has an implant wheel with a plurality of wafer carriers distributed about a periphery of the wheel. Each wafer carrier has a heat sink for removing heat from a wafer on the carrier during the implant process by thermal contact between the wafer and the heat sink. A respective wafer lift structure on each carrier is moveable between first and second positions, with the wafer supported spaced away from the heat sink and in thermal contact with the heat sink respectively. The lift structure is operated to move between the first and second positions wheel the implant is rotating. This allows control of wafer temperature during the implant process by adjusting the thermal contact between wafers and heat sinks.

Abstract: A donor silicon wafer may be bonded to a substrate and a lamina cleaved from the donor wafer. A photovoltaic cell may be formed from the lamina bonded to the substrate. An intermetal stack is described that is optimized for use in such a cell. The intermetal stack may include a transparent conductive oxide layer serving as a quarter-wave plate, a low resistance layer, an adhesion layer to help adhesion to the receiver element, and may also include a barrier layer to prevent or impede unwanted diffusion within the stack.

Abstract: A photovoltaic cell is described having emitter portions formed at both a light-facing surface and a back surface of the cell. In some embodiments, heavily doped emitter regions extend between the front and back emitter regions, connecting them electrically. Use of this structure is particularly well-adapted to a cell formed by implanting a semiconductor donor body with hydrogen and/or helium ions, affixing the donor body to a receiver element, cleaving a lamina from the donor body, and completing fabrication of a photovoltaic cell comprising the lamina. The emitter portion formed at the unbonded surface may comprise amorphous silicon. The lamina may be thin, for example 10 microns thick or less.

Abstract: A novel surface texturing provides improved light-trapping characteristics for photovoltaic cells. The surface is asymmetric and includes shallow slopes at between about 5 and about 30 degrees from horizontal as well as steeper slopes at about 70 degrees or more from horizontal. It is advantageously used as either the front or back surface of a thin semiconductor lamina, for example between about 1 and about 20 microns thick, which comprises at least the base or emitter of a photovoltaic cell. In embodiments of the present invention, the shallow slopes are formed using imprint photolithography.

Abstract: Ion implanters incorporating multibeam ion sources are used to meet process dose and energy demands associated with fabricating a thin lamina for use in photovoltaic devices. The thin lamina are formed by ion implantation followed by cleaving.

Abstract: A donor silicon wafer may be bonded to a substrate and a lamina cleaved from the donor wafer. A photovoltaic cell may be formed from the lamina bonded to the substrate. An intermetal stack is described that is optimized for use in such a cell. The intermetal stack may include a titanium layer in contact with the lamina, which reacts to form titanium silicide, a non-reactive barrier layer to check the silicide reaction, a low-resistance layer, and an adhesion layer to help adhesion to the receiver element.

Abstract: A voltage supply incorporates two voltage supplies connected in a mirror-image series arrangement to generate a DC voltage between the respective common terminals of the voltage supplies.

Abstract: A hydrogen ion implanter for the exfoliation of silicon from silicon wafers uses a large scan wheel carrying 50+ wafers around its periphery and rotating about an axis. In one embodiment, the axis of rotation of the wheel is fixed and the wheel is formed with tensioned spokes supporting a rim carrying the wafer supports. The spokes may be used for carrying cooling fluid to and from the wafer supports. In one embodiment, a ribbon beam of hydrogen ions is directed down on a peripheral edge of the wheel. The ribbon beam extends over the full radial width of wafers on the wheel.

Abstract: A hydrogen ion implanter for the exfoliation of silicon from silicon wafers uses a large scan wheel carrying 50+ wafers around its periphery and rotating about an axis. In one embodiment, the axis of rotation of the wheel is fixed and a ribbon beam of hydrogen ions is directed down on a peripheral edge of the wheel. The ribbon beam extends over the full radial width of wafers on the wheel. The beam is generated by an ion source providing an extracted ribbon beam having at least 100 mm major cross-sectional diameter. The ribbon beam may be passed through a 90° bending magnet which bends the beam in the plane of the ribbon. The magnet provides intensity correction across the ribbon to compensate for the dependency on the radial distance from the wheel axis of the speed at which parts of the wafers pass through the ribbon beam.

Abstract: A semiconductor donor body such as a wafer is implanted with ions to form a cleave plane. The donor wafer is affixed to a polyimide receiver element, for example by applying polyimide in liquid form to the donor wafer, then curing, or by affixing the donor wafer to a preformed polyimide sheet. Annealing causes a lamina to cleave from the donor wafer at the cleave plane. The resulting adhered lamina and polyimide body are not adhered to another rigid substrate and can be jointly flexed.

Abstract: A semiconductor donor body such as a wafer is implanted with ions to form a cleave plane. The donor wafer is affixed to a polyimide receiver element, for example by applying polyimide in liquid form to the donor wafer, then curing, or by affixing the donor wafer to a preformed polyimide sheet. Annealing causes a lamina to cleave from the donor wafer at the cleave plane. The resulting adhered lamina and polyimide body are not adhered to another rigid substrate and can be jointly flexed.

Abstract: A hydrogen ion implanter for the exfoliation of silicon from silicon wafers uses a large scan wheel carrying 50+ wafers around its periphery and rotating about an axis. In one embodiment, the axis of rotation of the wheel is fixed and a ribbon beam of hydrogen ions is directed down on a peripheral edge of the wheel. The ribbon beam extends over the full radial width of wafers on the wheel. The beam is generated by an ion source providing an extracted ribbon beam having at least 100 mm major cross-sectional diameter. The ion source may use core-less saddle type coils to provide a uniform field confining the plasma in the ion source. The ribbon beam may be passed through a 90° bending magnet which bends the beam in the plane of the ribbon.

Abstract: A hydrogen ion implanter for the exfoliation of silicon from silicon wafers uses a large scan wheel carrying 50+ wafers around its periphery and rotating about an axis. In one embodiment, the axis of rotation of the wheel is fixed and the wheel is formed with tensioned spokes supporting a rim carrying the wafer supports. The spokes may be used for carrying cooling fluid to and from the wafer supports. Detachable connections in the cooling fluid conduits in the vacuum chamber may comprise tandem seals with an intermediate chamber between them which can be vented outside the vacuum chamber, or independently vacuum pumped. In one embodiment, a ribbon beam of hydrogen ions is directed down on a peripheral edge of the wheel. The ribbon beam extends over the full radial width of wafers on the wheel.

Abstract: In aspects of the present invention, a method is disclosed to form a lamina having opposing first and second surfaces. Heavily doped contact regions extend from the first surface to the second surface. Generally the lamina is formed by affixing a semiconductor donor body to a receiver element, then cleaving the lamina from the semiconductor donor body wherein the lamina remains affixed to the receiver element. In the present invention, the heavily doped contact regions are formed by doping the semiconductor donor body before cleaving of the lamina. A photovoltaic cell comprising the lamina is then fabricated. By forming the heavily doped contact regions before bonding to the receiver element and cleaving, post-bonding high-temperature steps can be avoided, which may be advantageous.

Abstract: Ions are implanted into a silicon donor body, defining a cleave plane. A first surface of the donor body is affixed to a receiver element, and a lamina is exfoliated at the cleave plane, creating a second surface of the lamina. There is damaged silicon at the second surface, which will compromise the efficiency of a photovoltaic cell formed from the lamina. A selective etchant, having an etch rate which is positively correlated with the concentration of structural defects in silicon, is used to remove the damaged silicon at the second surface, while removing very little of the relatively undamaged lamina.

Abstract: 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.

Abstract: 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.

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

Abstract: A sequence of series-connected transformers for transmitting power to high voltages incorporates an applied voltage distribution to maintain each transformer in the sequence below its withstanding voltage.

Abstract: A photovoltaic assembly comprises a thin semiconductor lamina and a receiver element, where the receiver element serves as a superstrate in the completed device. The photovoltaic assembly includes a photovoltaic cell. The photovoltaic cell is a back-contact cell; photocurrent passes into and out of the back surface of the cell, but does not pass through the light-facing surface. The lamina is typically substantially crystalline and has a thickness less than about 100 microns, in some embodiments 10 microns or less.