AVS 51st International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS2-TuM

Paper PS2-TuM8
The Control of Electrode Impedance, Gas-Injection and Wafer-Temperature Radial Profile and their Effects on Poly-Gate Etching Performance

Tuesday, November 16, 2004, 10:40 am, Room 213B

Session: New Gate Conductor Etching
Presenter: M.H. Hagihara, TEL
Authors: M.H. Hagihara, TEL
L.C. Chen, TEL
F.H. Higuchi, TEL
Y.T. Tsukamoto, TEL
K.I. Inazawa, TEL
T.T. Tatsumi, Sony
A.K. Kawashima, Sony
Correspondent: Click to Email
The etch rate and CD radial uniformity can be effectively optimized by controlling the radial profile of the inlet gas, the plasma parameters and the wafer temperature. A 2-zone ESC is used to control the wafer temperature radial profile. The ion energy and electron density (n@sub e@) radial distribution are controlled by the wafer-electrode's VHF impedance. The variable impedance is achieved by a series LC circuit where a variable capacitor is used. SCCM POLY source-plasma is generated by 60MHz VHF power while the 13.56MHz wafer-bias accelerates the ions. The passage of the 60MHz electron towards the wafer-electrode and hence, the n@sub e@ radial profile, is strongly effected by the wafer-electrode's 60MHz impedance. In addition to the wafer-electrode's 13.56MHz bias power, the ion energy is also effected by its 60MHz impedance. The etcher is also equipped with a 2-zone gas showerhead providing radial distribution control of the neutral species. Etch data were taken for 4 poly-gate steps: fluorocarbon-based BARC etching, fluorocarbon TEOS hard mask open, fluorocarbon-based high-dope poly etching and HBr-based poly etching. A radial SW (Surface Wave) probe is used to measure the radial n@sub e@ directly above the wafer at various 60MHz impedance settings. Etch rate, XSEM profile and top-down CD uniformity are also recorded for various VHF impedance settings, 2-zone gas injection ratios and various 2-zone ESC temperature settings. Provision of these additional control knobs significantly improve the uniformity of the etch results.