A novel sacrificial gate stack process for suppression of boron penetration in p-MOSFET with shallow BF2-implanted source/drain extension

A novel process flow employing a sacrificial tetraethyl orthosilicate/polyc rystalline silicon (TEOS/poly-Si) gate stark is proposed for fabricating fl uorine-enhanced-boron-penetration-free p-channel metal oxide semiconductor field effect transistors (p-MOSFET's) with shallow BF2-implanted source/dra in (SID) extension, With the presence of the sacrificial TEOS/poly-Si gate stark as the mask during the shallow BF2 implant, the incorporated fluorine atoms are trapped in the sacrificial TEOS top layer and can be subsequentl y removed. The new process thus offers a unique opportunity of achieving an ultra shallow SID extension characteristic of the BF2 shallow implant, whi le not suffering from any fluorine-enhanced boron penetration normally acco mpanying the BF2 implant. Excellent transistor performance with improved ga te oxide integrity has been successfully demonstrated on p-MOSFET's fabrica ted with the new process flow.