AVS 53rd International Symposium
    Thin Film Tuesday Sessions
       Session TF+SS-TuA

Paper TF+SS-TuA6
Mechanistic Details of TiN Atomic Layer Deposition (ALD) Processes

Tuesday, November 14, 2006, 3:40 pm, Room 2022

Session: Surface Functionalization for Selective Area ALD
Presenter: F. Zaera, University of California, Riverside
Authors: H. Tiznado, University of California, Riverside
F. Zaera, University of California, Riverside
Correspondent: Click to Email
The reaction mechanisms of atomic layer deposition (ALD) processes have been characterized by a combination of surface sensitive techniques. In this talk our study of the deposition of TiN films from TiCl@sub 4@ and ammonia will be used to illustrate the power of this approach. First, each of the two half steps comprising the ALD process was studied independently. It was found that exposure of the surface to TiCl@sub 4@ leads to the initial deposition of titanium in the +3 oxidation state; only at a later stage most of it appears in the +4 state expected for TiCl@sub 4@. Also, the Cl:Ti final ratio at the end of the TiCl@sub 4@ deposition reaches a value of ~ 3.5, indicating some chlorine removal. Subsequent treatment with ammonia removes most of the remaining Cl and deposits the required nitrogen, as expected. Nevertheless, some chlorine is still seen on the surface, most likely because of HCl readsorption. The buildup of thicker films was tested by performing multiple cycles with alternating exposures to TiCl@sub 4@ and NH@sub 3@. Similar films could be deposited on glass and on W, Ni and Cu foils. Interestingly, depth-profiling studies show that the resulting film consists of a Ti@sub 3@N@sub 4@ layer on top of TiN. This suggests that the reduction of titanium takes place during the exposure of the surface to TiCl@sub 4@, not NH@sub 3@, and that it is the first reaction of the cycle the rate limiting in the whole ALD process.