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.<>