AVS 53rd International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS2-MoM

Paper PS2-MoM11
Influence of Stopping Layer Nature on Poly-Si/Metal Gate Patterning Process

Monday, November 13, 2006, 11:20 am, Room 2011

Session: Advanced Gate Fabrication
Presenter: V. Paraschiv, IMEC, Belgium
Authors: V. Paraschiv, IMEC, Belgium
D. Shamiryan, IMEC, Belgium
M. Demand, IMEC, Belgium
S. Beckx, IMEC, Belgium
C.G.N. Lee, LAM Research
G. Kota, LAM Research
W. Boullart, IMEC, Belgium
Correspondent: Click to Email
TiN or TaN layers are introduced between poly-Si electrode and the gate dielectric to solve the poly-Si depletion and boron diffusion issues. Although a minimal change is introduced we show that this modification has a significant impact on poly-Si etch due to the nature of the layer underneath the poly-Si electrode (dielectric or metallic). The etch was carried out in a Lam Research Versys2300 etch reactor. Poly-Si gate etch includes main etch (ME), soft landing (SL) and over etch (OE).@footnote 1@ SL is critical since it has to stop on SiO2 and has to keep a straight gate profile. For conventional (poly-Si/SiO2) gate stack the etch time after end point (EP), during SL, defines the bottom profile since the SiO2 starts accumulating positive charges inducing ions deflection at the bottom of the gate.@footnote 2@ The deflected ions remove the poly-Si foot present at the moment of EP. Conventional gate etch could not remove the poly-Si foot when stopping on metal, apparently due to lack of charge accumulation and the corresponding ion deflection. Although, the metallic layer can be oxidized by O2 present in the SL etch chemistry, the bottom power required for ion deflection is too low and results in damaging the top gate profile, due to hard mask charging effect (negatively charged oxide hard mask deflects ions distorting gate profile).@footnote 3@ Changing the ME chemistry from HBr/Cl2/CF4/O2 to SF6/CH2F2/N2 provides better passivation of poly-Si sidewalls allowing a SL step with a very low bottom power (65V) that removes the poly-Si foot without affecting the top profile. Although both TiN and TaN are conductive, it is more difficult to remove the poly-Si foot when stopping on TiN due to their different oxidation behavior. @FootnoteText@ @footnote 1@ E. Pargon et al., J. Vac. Sci. Technol. B 23(5), 1913 (2005).@footnote 2@ G. S. Hwang et al., J. Vac. Sci. Technol. B. 15, 70 (1997).@footnote 3@ D. Shamiryan et al., J. Vac. Sci. Technol. B, 23 2194 (2005).