Process for suppressing boron penetration in BF2 + -implanted P+ -poly-Si gate using inductively-coupled nitrogen plasma

Claim 1

A process for suppressing boron penetration through a BF 2 + implanted p+ type polycrystalline Si gate region using an inductively coupled nitrogen plasma, said process comprising (a) growing a gate oxide layer on a silicon wafer substrate by steps of washing said silicon wafer, placing said substrate in a high temperature furnace, and introducing oxygen at temperatures of 900°-1000° C. to grow said oxide layer of 50-120 Å thickness; (b) carrying out an inductively coupled plasma treatment of said silicon wafer in nitrogen at a power of 100-300 W for 1-30 minutes to form a nitrided layer on said oxide layer providing an energy barrier substantially impenetrable by boron ions; (c) forming at least one layer of polycrystalline silicon of approximately 1000-3000 Å thickness on said nitrided layer and said oxide layer; (d) implanting BF 2 + ions at an energy of 30-70 keV in an amount of 1×10 15 to 1×10 16 atoms/cm 2 into said at least one layer of polycrystalline silicon to form a p+ type gate region; (e) washing said silicon wafer again; and (f) again placing said silicon wafer into said high temperature furnace, introducing one of nitrogen or oxygen at 800° to 1000° C., and annealing for 10-60 minutes.