AVS 56th International Symposium & Exhibition
    Plasma Science and Technology Tuesday Sessions
       Session PS-TuA

Paper PS-TuA8
193 nm Photoresist Roughening in Plasmas: VUV Photons and Synergistic Mechanisms

Tuesday, November 10, 2009, 4:20 pm, Room A1

Session: Fundamentals of Plasma-Surface Interactions I
Presenter: M.J. Titus, University of California, Berkeley
Authors: M.J. Titus, University of California, Berkeley
D.G. Nest, University of California, Berkeley
D.B. Graves, University of California, Berkeley
Correspondent: Click to Email
Plasmas can either roughen or smooth 193 nm photoresist (PR), but little is known about mechanisms or controlling variables. We report measurements of 193 nm PR roughness as a function of ion energy, substrate temperature, VUV fluence, and photon-to-ion flux ratio, in a well-diagnosed inductively coupled Ar plasma. Comparisons are made to analogous vacuum beam experiments. We seek to answer the question: what “knobs” control surface texture? We focus special attention on the role of VUV photons and their synergistic interactions with other plasma effects. Fourier transform infrared (FTIR) transmission measurements as a function of VUV photon fluence demonstrate that VUV-induced bond breaking occurs over a period of time. We present a model based on the idea that VUV photons initially deplete near-surface O-containing bonds, leading to deeper, subsequent penetration and more bond losses, until the remaining near-surface C - C bonds are able to absorb the incident radiation. Fitted model photo-absorption cross sections compare well with literature values. The model is tested and shown to be valid by comparing to measurements of VUV lamp exposures in a vacuum beam system and in the Ar ICP.