AVS 52nd International Symposium
    Electronic Materials and Processing Monday Sessions
       Session EM-MoA

Paper EM-MoA3
DFT Investigation of the Initiation of HfO@sub2@ ALD on H-Si(100)-2x1 and Nitrided Si Surfaces

Monday, October 31, 2005, 2:40 pm, Room 309

Session: High-k Dielectric Growth and Processing
Presenter: Y. Xu, Stanford University
Authors: Y. Xu, Stanford University
C.B. Musgrave, Stanford University
Correspondent: Click to Email
Atomistic mechanisms for the initiation of atomic layer deposition (ALD) of hafnium oxide (HfO@sub2@) on hydrogen terminated and nitrided silicon surfaces were investigated using density functional theory (DFT). There are two possible pathways for the reaction of the precursor Hf[N(CH@sub3@)@sub2@]@sub4@ and Si-H surfaces. One is to form a Si-Hf bond through a ligand exchange mechanism. One H atom from the Si-H* surface site and one N(CH@sub3@)@sub2@ group of the precursor combine through a four-centered transition state to form NH(CH@sub3@)@sub2@, which subsequently desorbs. The second pathway is one H atom will be transferred from Si-H surfaces to one CH@sub3@ group from precursor to form Si-N-Hf bond. Alternatively, Hf[N(CH@sub3@)@sub2@]@sub4@ and residual water in the reactor can react to form Hf[N(CH@sub3@)]@subx@(OH)@suby@. Subsequently, Hf[N(CH@sub3@)]@subx@(OH)@suby@ can react with Si-H* to form Si-O-Hf structures of the reacted precursor. This reaction is more kinetically favorable than both of the reaction of Hf[N(CH@sub3@)@sub2@]@sub4@ with Si-H surfaces and it is important for understanding the interface structure between silicon surface and HfO@sub2@ films. We have also investigated the reactions of Hf precursors with the nitrided Si(100) surface and found that alkylamide precursors can react with SiNH* sites to initiate ALD whereas HfCl@sub4@ reactions with the nitrided surface are kinetically unfavorable.