Optimization of plasma etch processes using evolutionary search methods with in-situ diagnostics

This paper presents several approaches that have been used to control, optimize and characterize a low pressure (10–300 mTorr) plasma processing system. Methods such as contour following and differential evolution have been used to find contours of DC bias, total ion flux, ion energy flux, quadrupole mass spectrum (QMS) intensity ratios and line intensity ratios of the optical emission spectrum (OES) in argon and nitrogen plasmas. A mapping for a 4 × 4 multi-dimensional parameter space is also presented, in which the relationship between four control parameters (power, pressure, mass flow rates of two supplied gases) and four measurement outputs (DC bias, ion flux, QMS ratios and OES line intensity ratios) is determined in a plasma etching process. The use of these methods significantly reduces the time needed to re-configure the processing system and will benefit transfer of processes between different systems. A similar approach has also been used to find quickly an optimum condition for directional etching of a silicon wafer.

[1]  Tadahiro Ohmi,et al.  Anisotropic etching of n+ polycrystalline silicon with high selectivity using a chlorine and nitrogen plasma in an ultraclean electron cyclotron resonance etcher , 1990 .

[2]  J. Roberts,et al.  Optical Emission Spectroscopy on the Gaseous Electronics Conference RF Reference Cell , 1995, Journal of research of the National Institute of Standards and Technology.

[3]  Anisotropic etching of deep trench for silicon monolithic microwave integrated circuit , 1993 .

[4]  Jean-Paul Booth,et al.  Measurements of characteristic transients of planar electrostatic probes in cold plasmas , 2000 .

[5]  P. Kopperschmidt,et al.  Multichannel process monitor for real-time film thickness and rate measurements in dry etching and deposition , 1998 .

[6]  R. Boswell,et al.  Transient RF self-bias in electropositive and electronegative plasmas , 2003 .

[7]  Adrian A. Hopgood,et al.  Fuzzy logic in a blackboard system for controlling plasma deposition processes , 1998, Artif. Intell. Eng..

[8]  Tadahiro Ohmi,et al.  Directional etching of Si with perfect selectivity to SiO2 using an ultraclean electron cyclotron resonance plasma , 1990 .

[9]  R. Storn,et al.  Differential Evolution - A simple and efficient adaptive scheme for global optimization over continuous spaces , 2004 .

[10]  E. Aydil,et al.  Real-time monitoring of surface chemistry during plasma processing , 1994 .

[11]  Edgar Voges,et al.  Reactive ion etching of silicon submicron-sized trenches in SF6/C2Cl3F3 plasma , 1995 .

[12]  Adrian A. Hopgood,et al.  DARBS: A Distributed Blackboard System , 2001 .

[13]  T. Ohmi,et al.  Inversion from selective homoepitaxy of Si to selective Si film deposition on SiO2 using an ultraclean electron cyclotron resonance plasma , 1992 .

[14]  Roger A. Haas,et al.  Plasma Stability of Electric Discharges in Molecular Gases , 1973 .

[15]  Tae Seon Kim,et al.  Optimization of via formation in photosensitive dielectric layers using neural networks and genetic algorithms , 1999 .