Varian Semiconductor Equipment Associates, Inc.

Nicholas Pt Bateman

Atul Gupta

Benjamin B Riordon

John W Graff

Joseph C Olson

Charles T Carlson

Bon-Woong Koo

Peter F Kurunczi

Timothy J Miller

Deepak Arabagatte Ramappa

Vikram M Bhosle

John A Frontiero

Svetlana Radovanov

Paul J Murphy

Russell J Low

Christopher R Hatem

Robert J Mitchell

Kevin M Daniels

Steven M Anella

Paul Sullivan

Christopher J Leavitt

Min-Sung Jeon

An apparatus and methods of improving the ion beam quality of a halogen-based source gas are disclosed. Unexpectedly, the introduction of a noble gas, such as argon, to an ion source chamber may increase the percentage of desirable ion species, while decreasing the amount of contaminants and halogen-containing ions. This is especially beneficial in non-mass analyzed implanters, where all ions are implanted into the workpiece. In one embodiment, a first source gas, comprising a dopant and a halogen is introduced into an ion source chamber, a second source gas comprising a hydride, and a third source gas comprising a noble gas are also introduced. The combination of these three source gases produces an ion beam having a higher percentage of pure dopant ions than would occur if the third source gas were not used.

Boron implanting using a co-gas

A method for improving the ion beam quality in an ion implanter is disclosed. In some ion implantation systems, contaminants from the ion source are extracted with the desired ions, introducing contaminants to the workpiece. These contaminants may be impurities in the ion source chamber. This problem is exacerbated when mass analysis of the extracted ion beam is not performed, and is further exaggerated when the desired feedgas includes a halogen. The introduction of a diluent gas in the ion chamber may reduce the deleterious effects of the halogen on the inner surfaces of the chamber, reducing contaminants in the extracted ion beam. In some embodiments, the diluent gas may be germane or silane.

Method of improving ion beam quality in an implant system

Methods of forming a passivation layer on a workpiece are disclosed. These methods utilize a SiC forming polymer to form the passivation layer. In addition, while the polymer is being heated to form SiC, a second result, such as annealing of the underlying workpiece, or firing of the metal contacts is achieved. For example, the workpiece may be implanted prior to coating it with the polymer. When the workpiece is heated, SiC is formed and the workpiece is annealed. In another embodiment, a workpiece is coating with the SiC forming polymer and metal pattern is applied to the polymer. The firing of workpiece causes the metal contacts to form and also forms SiC on the workpiece.

Passivation layer for workpieces formed from a polymer

An improved method of fabricating an interdigitated back contact (IBC) solar cell is disclosed. A first mask is used to perform a patterned ion implantation of n-type dopant to create the back surface field. A second mask is then used to create the p-type emitter on the same surface. The second mask may be aligned to the n-type implant, and may be used in a plurality of orientations to create the desired p-type emitter. In some embodiments, a p-type blanket implant is performed as well. In some embodiments, a doping gradient is created.

Method of creating two dimensional doping patterns in solar cells

Methods of doping a solar cell, particularly a point contact solar cell, are disclosed. One surface of a solar cell may require portions to be n-doped, while other portions are p-doped. At least one lithography step can be eliminated by the use of a blanket doping of species having one conductivity and a patterned counterdoping process of species having the opposite conductivity. The areas doped during the patterned implant receive a sufficient dose so as to completely reverse the effect of the blanket doping and achieve a conductivity that is opposite the blanket doping. In some embodiments, counterdoped lines are also used to reduce lateral series resistance of the majority carriers.

Doping pattern for point contact solar cells

An improved method of tilting a mask to perform a pattern implant of a substrate is disclosed. The mask has a plurality of apertures, and is placed between the ion source and the substrate. The mask and substrate are tilted at a first angle relative to the incoming ion beam. After the substrate is exposed to the ion beam, the mask and substrate are tilted at a second angle relative to the ion beam and a subsequent implant step is performed. Through the selection of the aperture size and shape, the cross-section of the mask, the distance between the mask and the substrate and the number of implant steps, a variety of implant patterns may be created. In some embodiments, the implant pattern includes heavily doped horizontal stripes with lighter doped regions between the stripes. In some embodiments, the implant pattern includes a grid of heavily doped regions.

Angled multi-step masking for patterned implantation

An improved method of doping a substrate is disclosed. The method is particularly beneficial to the creation of interdigitated back contact (IBC) solar cells. A paste having a dopant of a first conductivity is applied to the surface of the substrate. This paste serves as a mask for a subsequent ion implantation step, allowing ions of a dopant having an opposite conductivity to be introduced to the portions of the substrate which are exposed. After the ions are implanted, the mask can be removed and the dopants may be activated. Methods of using an aluminum-based and phosphorus-based paste are disclosed.

Self-aligned ion implantation for IBC solar cells

A method of tailoring the dopant profile of a substrate by utilizing two different dopants, each having a different diffusivity is disclosed. The substrate may be, for example, a solar cell. By introducing two different dopants, such as by ion implantation, furnace diffusion, or paste, it is possible to create the desired dopant profile. In addition, the dopants may be introduced simultaneously, partially simultaneously, or sequentially. Dopant pairs preferably consist of one lighter species and one heavier species, where the lighter species has a greater diffusivity. For example, dopant pairs such as boron and gallium, boron and indium, phosphorus and arsenic, and phosphorus and antimony, can be utilized.

Use of dopants with different diffusivities for solar cell manufacture

A system and method of exposing photoresist on the surface of the solar cell to light so as to create an appropriate mask is disclosed. A microcavity array is used to expose the photoresist to UV light in a pattern that matches the desired pattern on the solar cell. Microcavity arrays consist of an array of cavities, which may include tens of thousands of cavities. When an appropriate potential is applied to an electrode, a plasma is formed in the activated cavity. If the cavity contains a suitable gaseous environment, these activated cavities will emit light in the near ultraviolet spectrum. By properly configuring the locations of the activated cavities, a UV source may be created that exposes the photoresist in a desired pattern. The desired pattern can be created by selectively activating cavities, disabling certain cavities, or filling certain cavities so that they cannot create a plasma.

Use of patterned UV source for photolithography

An improved, lower cost method of processing substrates, such as to create solar cells is disclosed. In addition, a modified substrate carrier is disclosed. The carriers typically used to carry the substrates are modified so as to serve as shadow masks for a patterned implant. In some embodiments, various patterns can be created using the carriers such that different process steps can be performed on the substrate by changing the carrier or the position with the carrier. In addition, since the alignment of the substrate to the carrier is critical, the carrier may contain alignment features to insure that the substrate is positioned properly on the carrier. In some embodiments, gravity is used to hold the substrate on the carrier, and therefore, the ions are directed so that the ion beam travels upward toward the bottom side of the carrier.

Integrated shadow mask/carrier for patterned ion implantation

The manufacture of solar cells is simplified and cost reduced through by performing successive ion implants, without an intervening thermal cycle. In addition to reducing process time, the use of chained ion implantations may also improve the performance of the solar cell. In another embodiment, two different species are successively implanted without breaking vacuum. In another embodiment, the substrate is implanted, then flipped such that it can be and implanted on both sides before being annealed. In yet another embodiment, one or more different masks are applied and successive implantations are performed without breaking the vacuum condition, thereby reducing the process time.

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Reading, MA, United States of America

Nicholas Pt Bateman