AVS 47th International Symposium
    Material Characterization Tuesday Sessions
       Session MC-TuP

Paper MC-TuP8
Characterization of Si Distribution at the Tungsten / Titanium Nitride Interface Using Secondary Ion Mass Spectrometry - An Investigation of the Dynamic Response of a Chemical Vapor Deposition Chamber

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: C.M. Jones, Advanced Micro Devices
Authors: C.M. Jones, Advanced Micro Devices
J. Zhao, Advanced Micro Devices
Correspondent: Click to Email
In sub-micron MOS IC processing, tungsten lines or contact (via) plugs are formed by blanket chemical vapor deposited tungsten thin film fill into the narrow SiO@sub 2@ trenches or small contact openings on the titanium nitride (TiN) layer with the underlying structure. The blanket CVD tungsten thin film is typically accomplished as the following: a thin nucleation layer (~50nm) is grown by silane (SiH@sub 4@) reduction of tungsten hexafluoride (WF@sub 6@), and the bulk deposition is accomplished via hydrogen (H@sub 2@) reduction of WF@sub 6@. The TiN layer serves as an adhesion layer that promotes uniform W growth as well as a diffusion barrier between W and underlying Si or silicide layers. For the common CVD deposition chamber, such as a batch-processing machine, the deposition process parameters, such as gas flow, temperature and pressure, are monitored in the inlets of the chamber usually at a distance from the wafer surface where the reaction takes place. The small SiH@sub 4@ gas flow that controls the Si concentration in the nucleation layer, in particular, will have certain modulating effects from the chamber, in terms of time and concentration, in the course of transport. In the present work, simultaneous SiH@sub 4@ and H@sub 2@ reduction of WF@sub 6@ formed the tungsten nucleation layer with a nominal thickness of 60nm. A two-step SiH@sub 4@ gas flow scheme was used to determine the effects of magnitude and duration of SiH@sub 4@ flow on the Si concentration at the W/TiN interface. The results amply demonstrate that SIMS analysis can be used to evaluate the deposition process so as to meet the fill and barrier protection requirements for narrow trench or small via. Issues of SIMS analysis such as depth resolution, interference from molecular ions, memory effect, and quantification are discussed.