Method for making an integrated circuit device including a graded, grown, high quality gate oxide layer and a nitride layer

Abstract

A method for making an integrated circuit device includes forming source and drain regions in a semiconductor substrate and defining a channel region therebetween, forming a graded, grown, gate oxide layer adjacent the channel region, forming a nitride layer adjacent the gate oxide layer, and forming a gate electrode layer adjacent the nitride layer. The gate oxide layer may be formed by growing a first oxide portion by upwardly ramping the channel region to a first temperature lower than a glass transition temperature, and exposing the channel region to an oxidizing ambient at the first temperature and for a first time period. A second oxide portion may be grown between the first oxide portion and the channel region by exposing the channel region to an oxidizing ambient at a second temperature higher than the glass transition temperature for a second time period so that the second oxide portion has a thickness in a range of about 2% to about 75% of a total thickness of the gate oxide layer. Forming the nitride layer may include forming a non-stoichiometric nitride layer, and the nitride layer is preferably formed to have a thickness of less than about 15 Å. The nitride layer reduces penetration of a dopant, such as boron, into the gate oxide layer.