Spectroscopic Ellipsometry Sensors for Advanced Processing of Thin-Film CIS Photovoltaics

Thin-film technologies have found significant application today, particularly in the area of thin-film electronics (high temperature superconductors, magnetic storage media, flat-panel displays, photovoltaics), protective coatings (thermal, corrosion, wear), and optically transparent "smart" coatings. ITN Energy Systems, Inc. (ITN/ES) has products in advanced power generation, storage, and distribution using thin-film power generation via photovoltaics, fuel cells, batteries, and thermoelectrics and is the technical lead/commercialization arm of a DARPA Vapor Phase Manufacturing (VPM) consortium to apply intelligent processing sensors and techniques to complex thin-film copper-indium-diselenide (CIS). Critical to the success of this program is the ability to isolate a given material attribute in situ to monitor critical material properties, such as composition and stoichiometry for films such as CIS. Ellipsometry, particularly multiwavelength ellipsometry, has the potential for monitoring film deposition and growth and providing a means for in situ process control. Overall objective of the proposed work is to develop an in situ method for process control of CIS photovoltaics based on spectroscopic ellipsometry and to improve analysis algorithms for the handling of ellipsometric data. Specific objectives for Phase 1 of this program are to 1) construct a multiwavelength parallel-detector spectroscopic ellipsometer system, 2) study properties of CIS films, 3) correlate these data with ellipsometric data of the same films, and 4) identify which film(s) and process(es) will be considered in a Phase 2 program.