Environmentally benign vacuum deposition with air-to-vacuum-to-air technology

Abstract

The deposition of thin films and coatings frequently results in the generation of toxic waste, volatile organic compounds, or large amounts of waste water and sludge. Vapor deposition in vacuum offers a more environmentally benign alternative, but is not prevalent outside of the microelectronics industry due to economic reasons. However, vacuum coating could be more widely accepted, and could potentially replace nonvacuum deposition methods, if either the cycle time or costs associated with vacuum coating were reduced. In order to reduce the cycle time for vacuum deposition, a robust system for continuous air-to-vacuum-to-air (AVA) transportation of discreet substrates has been developed and constructed in this study. This technology allows the insertion of discrete components into vacuum at high rates, without the need for venting the deposition chamber. Substrates have been repeatedly transported from atmosphere to 10⁻⁵ Torr in under a second. The capability of the AVA technology was studied through the deposition and characterization of CdS and CdTe films and photovoltaic devices. With the AVA technology, the need for venting the vacuum chamber to insert the substrates and subsequent pumping of the system for deposition is eliminated. The AVA technology could be applied to the processing of silicon wafers, compact disks, optical components, solar cells, cutting tools, and fasteners.