High Ge Content SiGe Selective Processes for Source/Drain in Manufacturing the Next Generations of pMOS Transistors

Selectivity of different SiGe processes toward oxide and nitride has been studied on both: blanket and patterned Si wafers. Three different precursors: silane, dichlorosilane and disilane were used for SiGe growth. It was found that the growth of SiGe with Ge content higher than 35% was intrinsically selective toward SiO2; SiGe with any Ge content, up to pure Ge, could not be grown selectively toward nitride; in order to get selectivity toward nitride, an etching gas should be used and its amount in the gas phase decreases with an increase of the Ge content.