Effect of strain on p-channel metal-oxide-semiconductor field-effect-transistor current enhancement using stress-modulated silicon nitride films

The stress in chemical-vapor-deposited silicon nitride films (∼100 nm thick) is modulated by an ion implantation technique. The tensile-strained silicon nitride film is deposited on the back and front sides of a Si wafer. After implantation of P+, As+, Sb+, or B F2+ ion species, the stress of the silicon nitride film becomes compressive on the front side. It can be explained by strain relaxation of Si-N bond on the front side and highly tensile-strained Si-N bond on the back side of wafer. The compressive stress is increased with a double-implantation process because of more atomic collisions in the silicon nitride film, as well as more strain relaxation of Si-N bond on the front side of wafer. After a thermal annealing process, the compressive stress in the silicon nitride film with P+, As+, or Sb+ implantation is reduced, while compressive stress is increased for B F2+ ion implantation due to formation of the B-N bond in silicon nitride film. To justify the stress-modulated silicon nitride film by the ion implantation technique, the p -channel metal-oxide-semiconductor field-effect transistor (p -MOSFET) is fabricated. The drive current of a p -MOSFET is improved by 7-13% for implanted silicon nitride films, due to the compressive strain-induced effective mass lowering in the channel.