Sidewall Oxidation of Polycrystalline-Silicon Gate

Evidence is presented demonstrating that sidewall oxidation, a processing step needed for device reliability, can lead to gate oxide thickening in short-channel devices. This increase in thickness is the result of encroachment of bird’s beaks from the edges of the gate structure into the channel region. The encroachment can be reduced by increasing oxidation temperature and/or using a dry ambient. With a judicious choice of polysilicon sidewall oxidation conditions, minimum gate-to-drain overlap capacitance and adequate device reliability can be achieved. © 1989 IEEE