Plasma assisted growth of ultrathin nitrides on Si surfaces under ultrahigh vacuum conditions

Plasma assisted nitridation of Si is a very useful and easily controlled process for the direct in-situ deposition of pure silicon-nitride films on Si under ultrahigh vacuum conditions. The plasma used in the present work is formed by microwave dissociation of nitrogen gas. Under these circumstances an additional activation barrier to the formation of nitride exists which can be overcome by isothermal processing at temperatures from 300 deg. C and up. Room temperature growth of ultrathin silicon-nitride films on top of different substrates is also found to be possible through the use of dispersed atomic Si layers which react with the microwave excited nitrogen plasma at room temperature. Studies are undertaken with the Si(111) and Si(100) surfaces and the results for these two surfaces are compared. The conditions for the growth of amorphous versus microcrystalline films are established with a critical temperature around 500-600 deg. C