Si Surface Cleaning by Si2H6–H2 Gas Etching and Its Effects on Solid-Phase Epitaxy

Abstract
Si surface cleaning with Si2H6–H2 was studied for lateral solid-phase epitaxy (L-SPE) of CVD a-Si films. The cleaning was performed at 850°C, which is considerably lower than the previously-reported H2-cleaning temperature (1100°C). This is because etching of native oxide is enhanced by a reaction between oxide and Si-atoms dissociated from Si2H6. The effects of Si2H6-cleaning on L-SPE were studied using a Si (100) wafer with SiO2 stripes. After Si2H6-cleaning or H2-cleaning at 850°C, CVD a-Si films are deposited on the wafers, then crystallized by annealing (575°C). An H2-cleaned sample showed imperfect L-SPE because of a residual native-oxide layer at the a-Si / substrate interface. In the Si2H6-cleaned sample, the native-oxide layer was removed, and L-SPE growth was observed uniformly in the wafer. Si2H6-cleaning at 850°C is applicable for substrates with abrupt impurity distribution.