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Microplasma Optical Emission Spectrometer (MOES) on a chip. SFR Workshop November 8, 2000 Michiel Krüger, David Hsu, Scott Eitapence, K. Poolla, C. Spanos, D. Graves, O. Solgaard Berkeley, CA. - PowerPoint PPT Presentation
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11/8/2000
1
Microplasma Optical Emission Spectrometer (MOES) on a chip
SFR WorkshopNovember 8, 2000
Michiel Krüger, David Hsu, Scott Eitapence, K. Poolla, C. Spanos, D. Graves, O. Solgaard
Berkeley, CA
2001 GOAL: to build a microplasma generating system and test it with bulk optical components by 9/30/2001.
11/8/2000
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Motivation and background
• Motivation– Precise detection of compounds near substrate required
during semiconductor manufacturing
– Organic compounds, emitted during DUV, can coat optics of stepper
• Background– Small atmospheric pressure glow discharges can be used
for species excitation.
– Glow discharge optical emission spectroscopy has long history in analytical chemistry
11/8/2000
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Microplasma Optical Emission Spectrometer
• Basic idea: – OES from plasma reveals info about gas composition in
chamber
• Interdisciplinary:– plasma physics and chemistry
– MEMS processing
– optics and metrology
• Inter-departmental:– chemical engineering
– electrical engineering
– mechanical engineering
11/8/2000
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MOES (cont.)
• Generation of plasma with hollow cathode
• Generation of plasma possible if: 0.05<p.D<10Torr.cm
• Smaller diameter (75 m) allows plasma generation at atmospheric pressure!
• This results in smaller sensor• Many applications in (and outside!) IC processing
industry (for example in lithography)
D
cathode
dielectric
anode
plasma
mm
11/8/2000
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Schematic of initial MOES experimental configuration
detector array
grating
lens
• Combination of– Bulk optical optical
components
– Microplasma chamber,
fabricated in Si substrate
• Light emitted from
discharge is captured by
lens and collimated onto grating• Diffracted light from grating is
focused on detector array to record spectrum
11/8/2000
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Mica dielectric(drilled hole)
Silicon chip with 200m hole and aluminum cathode
Molybdenum anode
First experiments: plasma in 200m hole, 100Torr N2 ambient
vacuum chamber
chip
mica dielectric
molybdenum
11/8/2000
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200m
0.7m 1m
substrate
poly-SiSiO2
50-200m
Currently fabricated in UCB Microlab
• Relatively simple to make
• XeF2 etch to achieve required depth and undercut
• Very small diameters, i.e. high pressure, possible
cathode
anode
plasma
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Fabrication process and challenges
• Fabrication– OES cavity defined by deep reactive ion etching/XeF2 isotropic
etch
– anode/cathode defined on front and backside of wafer (metal or doped Silicon)
• Challenges– Microplasma stability and contamination
– Device sensitivity
– Packaging of device
– Exploration of pulsed operation to make autonomous power supply possible
– Integration of micro discharges onto chips for other applications
11/8/2000
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2002 and 2003 Goals
Build micro-optics for spectral analysis. Complete the preliminary designs for integrated MOES, by 9/30/2002.
Design and test integrated MOES. Calibration studies, sensor characterization, by 9/30/2003.