The Effect of Phosphorus Doping on Tin Oxide Films Made by the Oxidation of Phosphine and Tetramethyltin: I . Growth and Etching Properties

Abstract

This paper describes the growth and etching characteristics of phosphorusdoped tin oxide films, prepared by the simultaneous oxidation of tetramethyltin (TMT) and phosphine gas in the 400°–500°C range. Both the growth and etch rates of these films are found to be relatively constant until the P/Sn ratio exceeds 3.2%, at which point they fall off and eventually become negligible. In addition, films grown by this technique are found to undergo a rapid transition from the polycrystalline to the amorphous state when their P/Sn ratio exceeds 3.2%. Possible mechanisms for this behavior are outlined, based on the relative strength of the P‒O and Sn‒O bonds and on the network former properties of . It is proposed that the mechanism of film growth and dopant incorporation is the direct (and independent) reaction of phosphine and TMT with oxygen adsorbed on the substrate surface. The transport properties of these films are discussed in a companion paper.