Submillimeter spectroscopic diagnostics in semiconductor processing plasmas Yaser H. Helal, Christopher F. Neese, Frank C. De Lucia Department of Physics The Ohio State University Paul R. Ewing, Phillip J. Stout, Michael D. Armacost Applied Materials June 17, 2014

Spectroscopy and industrial plasmas Submillimeter spectroscopy of plasmas is a well established technique Typical pressure of semiconductor plasma reactors (1-100 mtorr) is especially advantageous Many common molecules in processing plasmas have been studied and can be found in literature Many molecules are cataloged in astrophysical databases (JPL, Cologne, …)

Semiconductor Chip

Semiconductor Processing Cleaning Deposition Lithography Etching

QuickSyn Synthesizer 9.3 – 13.9 GHz QuickSyn Synthesizer 9.2 – 13.9 GHz VDI Receiver x54 VDI Transmitter x54 +40db Diode Detector Lock-In Amplifier A/D PC LO IF GHz (Amplifiers) Component Diagram Phase Shifter (FM) ~40 kHz

Application Technique Develop a spectroscopic catalog of molecules found in industrial plasmas Build “Snippets” from catalog – Jump to frequency of spectral line and sweep through width of line Using synthesizers’ frequency agility to focus on useful spectral lines Develop spectral scan strategy based on species of interest and make measurements quickly

Transceiver

Measured spectra with OSU test plasma reactor Initial tests at OSU With O 2 Without O 2

Applied Materials Reactor

Cl 2, HBr, O 2 plasma on polysilicon Feed gases are the fuel of reactions SiO (from wafer reaction), HCl and HBr found.

N 2, CH 2 F 2, SF 6 plasma on Si See CF 2, CS, NH 3 Do not see CF, H 2 S, H 2 CS, CH 2 F 2 (depleted in plasma)

N 2, CH 2 F 2, SF 6 plasma on Si (cont.) See NS, HCN, FCN, not CN

NH 3 plasma NH 3 abundance decreases with increasing power NH 2 observed

NH 2 measured A wider NH 2 snippet shows 3 lines surrounding the center we used from Splatalogue

NH 2 measured Hyperfine splitting resolved by Müller et al. and available in Cologne Database

NH 3 and NH 2 measurable in an NH 3 pulsed plasma Pulsed Plasma

Flow Ratio

Power + Pressure Suggests that a larger fraction of NH 3 is dissociated as pressure increases

Summary Prototype for a packaged submillimeter spectrometer Need for an expanded catalog applicable to industrial plasma products Submillimeter spectroscopy allows for the ability to compare how densities correlate with flow, power, pressure, and feed gas

Acknowledgements Jennifer A. Holt, OSU Mark A. Patrick, OSU Wei Liu, AM This work is supported by Semiconductor Research Corporation (SRC) through Texas Analog Center of Excellence at the University of Texas at Dallas (Task ID: )