Harmonic monitoring of the switched silicon etched process

• Published in: Journal of physics. D, Applied physics Vol. 36; no. 17; pp. 2146 - 2151
• Main Authors: Law, V J, Thornhill, N F, Kenyon, A J, Pagliarani, A, Lee, K, Watkins, M, Lea, L
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 07.09.2003; Institute of Physics
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Physics; Surface cleaning, etching, patterning; Surface treatments; Design; Time dependence; Harmonics; Radiofrequency amplifiers; Data processing; Silicon; Digital image; Chemical etching; Experimental study; Real time; Monitoring
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/36/17/319

A new non-invasive radio frequency technique for real-time monitoring of the STS ASE deep silicon etch process, or other forms of the Bosch switched etch process, is reported. The technique interrogates the plasma-generated harmonic and sideband noise floor level, which is a sensitive probe of the plasma. Using a narrow resolution bandwidth (9kHz) spectral information discriminating between the alternating cyclo-C4F8 passivation step and the SF6 etch step is clearly and easily visualized. The real-time feedback has the potential to allow characterization and control of the plasma process, both from run-to-run and day-to-day. This measurement technique may provide a path to the understanding of passivation and etching of silicon, and a means of automated process feedback control. The technique is likely to find application in many other processes, as it provides a real-time evolving characteristic signature that may be used to characterize new processes.