Effect of nitride sidewall spacer process on boron dose loss in ultrashallow junction formation

A nitride spacer with an underlying deposited tetraethoxysilane oxide, that behaves as a convenient etch stop layer, is a popular choice for sidewall spacer in modern complementary metal–oxide– semiconductor process flows. In this work we have investigated the effect of the silicon nitride spacer process on the boron profile in silicon and the related dose loss of B from the Si into the silicon dioxide. This is reflected as a dramatic decrease in the junction depth. We find that the silicon nitride influences the concentration of hydrogen in the silicon dioxide during the final source/drain anneal. The presence of H enhances the diffusivity of B in the silicon dioxide and thereby results in a significant dose loss from the Si into the silicon dioxide. In this work we have shown this dose loss can be lowered by altering the silicon nitride stoichiometry. © 2004 American Vacuum Society. @DOI: 10.1116/1.1642645#