Defect engineering in polycrystalline silicon using ultrasound

Ultrasonic vibrations introduced into bulk or thin-film semiconductors stimulate defect reactions beneficial for electronic materials and devices. This type of semiconductor processing ultrasound treatment (UST) - initially developed in compound semiconductors was recently successfully applied to Si based materials. The analysis of UST effects is performed within a general scenario of three-step point defect gettering: (a) release, (b) diffusion, and (c) capture. As a demonstrating vehicle of UST mechanisms, the experimental data on ultrasonically enhanced diffusion of the atomic hydrogen in thin poly-Si films are discussed. UST applied to plasma hydrogenated films improves homogeneity of recombination and transport properties. Ultrasound promotes a passivation of grain boundary defects as revealed using spatially resolved photoluminescence, sheet resistance, and atomic force microscopy. The results favor a mechanism of trap-limited hydrogen diffusion facilitated by the ultrasound. UST application for electronic devices is discussed.