LIGHTLY DOPED DRAIN PROFILE OPTIMIZATION WITH HIGH ENERGY IMPLANTS

摘要

After growth of a thin oxide on a silicon semiconductor body, and formation of a gate thereover, a blanket layer of oxide is deposited over the resulting structure, this oxide layer having, as measured from the surface of the silicon body, relatively thick regions adjacent the sides of the gate and relatively thin regions extending therefrom. Upon implant of ions, the relatively thick regions block ions from passing therethrough into the semiconductor body, while the relatively thin regions allow passage of ions therethrough into the body. After drivein of the ions, the thick layer of oxide is isotopically etched to take a substantially uniform layer therefrom over the entire surface of the thick oxide layer, so that the thick regions thereof are reduced in width. Upon a subsequent ion implant step, the thick regions, now reduced in width from the sides of the gate, block passage of ions therethrough, while the thin regions allow ions therethrough into the silicon body. This process may be continued as chosen to form desired source and drain profile.