1. 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

2. 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, …)

3. Semiconductor Chip http://www.mikeseeman.com/index.php?id=engineering/research

4. Semiconductor Processing http://www.atp.nist.gov/eao/gcr03-844/append-a.htm Cleaning Deposition Lithography Etching

5. 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 500-750 GHz (Amplifiers) Component Diagram Phase Shifter (FM) ~40 kHz

6. 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

7. Transceiver

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

9. Applied Materials Reactor

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

11. 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)

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

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

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

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

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

17. Flow Ratio

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

19. 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

20. 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:1836.126)