AVS 47th International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS1-ThA

Paper PS1-ThA8
The Relationship between Deprotection and Film Thickness Loss during Plasma Etching of Chemically Amplified Resists

Thursday, October 5, 2000, 4:20 pm, Room 310

Session: Plasma-Surface Interactions II
Presenter: A.P. Mahorowala, IBM T.J. Watson Research Center
Authors: A.P. Mahorowala, IBM T.J. Watson Research Center
D.R. Medeiros, IBM T.J. Watson Research Center
Correspondent: Click to Email
Positive-tone chemically amplified (CA) resists provide the sensitivity, contrast and resolution necessary to print state-of-the-art sub-wavelength features using KrF (248 nm) and more recently ArF (193 nm) lithography. These materials are also being looked at for printing sub-100 nm features with F@sub 2@ (157 nm) and next-generation lithography technologies such as EUV (13 nm) and E-beam projection lithography (EPL). Beyond the desired exposure-induced reactions, the acid-catalyzed deprotection reactions responsible for the solubility differential can also occur in unexposed resist areas when etched in a plasma due to uv-exposure, high energy ion bombardment, plasma composition and elevated substrate temperatures. Deprotection has been associated with resist mass loss and film shrinkage during plasma etch that can adversely affect the tight resist budget. In this paper, we determine the film thickness loss during etching of several unexposed CA resists in a variety of plasmas while simultaneously monitoring the film composition by FTIR. These results will be compared with theoretical predictions based on well-known deprotection mechanisms. It will be demonstrated that the acidic nature of certain plasmas such as Cl@sub 2@/O@sub 2@ can deprotect the resist film even in the absence of a photoacid generator (PAG). It will also be shown that the nature of the resist polymer and the identity of the deprotection products directly influence resist mass loss and etch rate linearity both of which can be controlled by careful selection of resist materials.