Method to reduce field oxide loss from etches

摘要

The present invention provides a method of manufacturing a high nitrogen (N) content oxynitride layer 34A 34B over field oxide regions. The oxynitride layer 34A 34B prevents subsequent etches from forming recesses in the field oxide regions 30 and planarizes the surface. The method begins by forming a field oxide region 30 an isolation area in the substrate 22. A high N content oxynitride protection layer 34A 34B (an etch barrier) is then formed surrounding (over and under) the field oxide layer 30. The high N content oxynitride protection layer 34A 34B is formed by heating (e.g., annealing) the substrate in a gas environment comprising ammonia. The high N content oxynitride layer is preferably formed by rapidly thermally annealing the substrate at temperature between about 825 DEG and 875 DEG C. in an ammonia containing environment with a partial pressure of between about 0.5 and 1.2 kg/cm2 . The top high N content oxynitride layer 34A over the central area of the field is preferably removed while the top and bottom high content oxynitride layers 34A 34B remain at the periphery of the field oxide.