Plasma deposition of amorphous semiconductors at microwave frequencies

Abstract

Apparatus and method for plasma deposition of thin film photovoltaic materials at microwave frequencies. The apparatus avoids unintended deposition on windows or other microwave transmission elements that couple microwave energy to deposition species. The apparatus includes a microwave applicator with one or more conduits passing therethrough that carry deposition species. The applicator transfers microwave energy to the deposition species to activate or energize them to a reactive state. The conduits physically isolate deposition species that would react or otherwise combine to form a thin film material at the point of microwave power transfer and deliver the microwave-excited species to a deposition chamber. One or more supplemental material streams may be delivered directly to the deposition chamber without passing through the microwave applicator and may combine with deposition species exiting the one or more conduits to form a thin film material. Precursors for the microwave-excited deposition species include fluorinated forms of silicon. Precursors delivered as supplemental material streams include hydrogenated forms of silicon. The invention allows for the ultrafast formation of silicon-containing amorphous semiconductors that exhibit high mobility, low porosity, little or no Staebler-Wronski degradation, and low defect concentration.