Investigation and characterization of silicon concentration in N-free anti-reflective layer films

In the 28 nm high voltage flow, the N-free anti-reflective layer (NFARL) taking the place of silicon oxide as Poly hard mask (HM) film can achieve more vertical profile for Poly. However, there is (Ni, Pt)Si impurity generated on the top of the NFARL film after nickel silicide process. In this paper, the effects of silicon (Si) concentration on the characteristic, Poly profile and purity of NFARL films were systematically investigated by experimental techniques. With increasing of Si concentration, the refractive index n and extinction coefficient k of films increase monotonically. The transmission electron microscopy (TEM) measurements indicate (Ni, Pt)Si impurity can't be formed on the top of the NFARL film for the lowest Si concentration, because there is no C-Si bond in the film.