Linear source technology review for CIGS co-evaporation on glass and flexible substrates

The highest efficiency copper, indium, gallium and selenium (CIGS) devices have been produced using thermal deposition methods on a variety of substrate materials including glass and stainless steel foils. There are several advantages of thermal deposition; process flexibility, inexpensive raw materials and high average efficiency. The disadvantages of thermal deposition have been low deposition rates, control complexity and the lack of commercially available large area deposition systems. Pursuit of the thermal deposition method has been difficult with multiple point Knudsen Cells (sources) due to the costs, source-to-source variability, flux rate stability over time, and the number of simultaneous control loops required for feedback monitoring and control. Veeco's linear metal source technology answers these challenges by creating an array of adjustable, distributed point sources from a single, temperature-controlled crucible for each element integrated into one heated body which can evaporate up to three different elements. This technology has been scaled for applications requiring 0.35 meter (m), 0.6 m, 1.0 m, and 1.2 m deposition widths. The primary focus of this paper will be the metal linear source operating conditions and performance results based on lab and production system deposition testing in glass and roll-to-roll (web) stainless steel CIGS production systems manufactured by Veeco Solar Equipment.