AVS 49th International Symposium
    Plasma Science Monday Sessions
       Session PS-MoM

Paper PS-MoM5
Impact of Chemistry and Mask Nature on Critical Dimension Control of Gate Etch Processes

Monday, November 4, 2002, 9:40 am, Room C-105

Session: Conductor Etch I
Presenter: X. Detter, STMicroelectronics, France
Authors: X. Detter, STMicroelectronics, France
G. Cunge, CNRS/LTM, France
E. Pargon, CNRS/LTM, France
L. Vallier, CNRS/LTM, France
O. Joubert, CNRS/LTM, France
R. Palla, STMicroelectronics, France
I. Thomas-Boutherin, STMicroelectronics, France
Correspondent: Click to Email
During a CMOS gate etch process, requirements in terms of Critical Dimension (CD) bias and microloading are more and more severe. Since gate etch processes are composed of several steps (resist trimming, BARC and probably hard mask opening, poly-silicon main etch step, soft landing step (to preserve the gate oxide) and over-etch step), a good understanding of the mechanisms influencing the CD deviation is necessary for each of them. During a classical poly-silicon gate etch process, passivation layer deposition on the gate sidewalls is known to be one source of CD microloading and the main source of CD bias for isolated patterns. However, as the aspect ratio is increasing, the profile evolution is more complicated and may be influenced by loading and shadowing effects as well as charging effects. Indeed, the passivation layer formation results from deposition of inhibitors and etching by radicals which are both strongly influenced by the nature of the mask and total aspect ratio of the structure. In this talk, we present a study of profile evolution during the poly-silicon etch steps with a resist and an oxide hard mask. Aspect ratio dependent etching and passivation layer deposition mechanisms are investigated for chemistries used in today’s gate etch processes : HBr/Cl@sub 2@/O@sub 2@ and HBr/Cl@sub2@/O@sub2@/CF@sub4@. Loading and shadowing effects induced by the mask are more precisely investigated (in a range of aspect ratio varying from less than 0.1 to more than 3 and a minimal space between lines of 60 nm). A correlation with X-ray Photoelectron Spectroscopy analysis of passivation layers composition and emission spectroscopy of by-products present in the gas phase is also performed. Finally, the limits of the current processes and potential strategies for future gate etch processes are discussed.