Nitrogen Profile Engineering in Thin Gate Oxides

摘要

In order to prevent boron penetration in PMOS ransistors without degrading channel mobility, it is necessary to engineer the distribution of nitrogen introduced into the gate oxide. We have investigated methods of engineering this distribution using nitric oxide (NO) gas in an RTP system to thermally nitride ultra-thin gate oxides. In one approach, the gate oxide is simultaneously grown and nitrided in a mixture of nitric oxide and oxygen. For a 40 A film, SIMS depth profiling shows that this process moves the nitrogen peak into the bulk of the oxide away from the oxide silicon interface. In another approach, an 11 A chemical oxide produced by a standard pre-furnace wet clean is nitrided in NO at 800 deg. C. This film is subsequently reoxidized in either oxygen or steam. For an 1100 deg. C., 120 sec RTP reoxidation in oxygen, the final film thickenss is 41 A. The nitrogen has a peak concentration of 5 at.