Motorola Corporation

Solavolt International

Ralph J Ellis

Kalluri R Sarma

Richard W Gurtler

Israel A Lesk

Ronald N Legge

Aslan Baghdadi

A method is disclosed for improving the crystallinity of semiconductor ribbon material while increasing the material throughput and decreasing energy requirements. The crystallinity of a ribbon of semiconductor material can be improved by forming a localized molten zone in the material and sweeping this molten zone along the length of the material. As the molten zone refreezes, the material is locally recrystallized with enhanced grain size. In accordance with the invention, two ribbons are positioned back-to-back with a slight spacing between the ribbons. Energy sources are focused on the outer surfaces of the two ribbons to create a molten zone in each of the ribbons. Because of the close proximity between the ribbons, much of the energy reradiated from each molten zone is absorbed by the adjacent ribbon. The molten zones are then swept along both of the ribbons to simultaneously cause crystal improvement in both ribbons. The total energy input required for recrystallizing two ribbons is only slightly greater than the energy required to recrystallize one ribbon. Further improvements in the process are achieved by positioning a thermal diffuser between the two ribbons and/or staggering the relative positions of the molten zones.

Method for improving crystallinity of semiconductor ribbon

A method is provided for semiconductor ribbon-to-ribbon conversion in a rigid edge mode. A combination carrier and mask is provided by which the ribbon is secured during the conversion process. The carrier holds the ribbon and simultaneously masks the edges of the ribbon from the heating effects of an impinging energy beam. The energy beam, such as a laser or electron beam, impinges on the ribbon and creates a molten zone which extends through the thickness of the ribbon. During the growth process, the molten zone is caused to move along the length of the ribbon. The mask prevents melting of the extreme edge portions of the ribbon and thus allows a rapid growth rate and a stable molten zone without sophisticated electronic equipment to gate the energy beam at the ribbon edges.

Method for semiconductor ribbon-to-ribbon conversion

Apparatus is provided for semiconductor ribbon-to-ribbon conversion in a rigid edge mode. A combination carrier and mask is provided by which the ribbon is secured during the conversion process. The carrier holds the ribbon and simultaneously masks the edges of the ribbon from the heating effects of an impinging energy beam. The energy beam, such as a laser or electron beam, impinges on the ribbon and creates a molten zone which extends through the thickness of the ribbon. During the growth process, the molten zone is caused to move along the length of the ribbon. The mask prevents melting of the extreme edge portions of the ribbon and thus allows a rapid growth rate and a stable molten zone without sophisticated electronic equipment to gate the energy beam at the ribbon edges.

Apparatus for semiconductor ribbon-to-ribbon conversion

A method of producing a sheet of semiconductor material directly usable for the production of solar cells is disclosed. The method comprises establishing a molten region at an edge of a sheet of semiconductor material, moving the molten region across the sheet to create a path of elongated crystal grains, establishing a molten zone along a portion of the path of the elongated crystal grains and parallel thereto, and causing the molten zone to travel in a direction transverse to the path of elongated crystal grains.

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Mesa, AZ, United States of America

Ralph J Ellis