* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download FileNewTemplate
Survey
Document related concepts
Electrical ballast wikipedia , lookup
History of electric power transmission wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Opto-isolator wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Current source wikipedia , lookup
Voltage optimisation wikipedia , lookup
Surge protector wikipedia , lookup
Buck converter wikipedia , lookup
Power MOSFET wikipedia , lookup
Rectiverter wikipedia , lookup
Stray voltage wikipedia , lookup
Transcript
Plato Probe “ Deposition Tolerant Langmuir Probe Talk Outline Standard Langmuir probe • • • • Issues in deposition systems RF biased probe techniques Sobolewski Method Booth / Braithwaite Probe Impedans diagnostic technique • Calibration • RF current and voltage waveforms • IV characteristic generation The Plato probe overview Summary Standard Langmuir Probe Standard Langmuir probes biased at low frequency (DC) Conductive probe tip – often tungsten DC Voltages applied – DC currents recorded Plasma A Current drawn from the plasma by probe – returned to the plasma through conductive chamber wall Probe Voltage biased from negative potential up to 5 or 10V past the plasma potential Tip is positively biased to clean (energetic electron bombardment heats ‘white’ hot) V Langmuir Probes: Issues in deposition systems • Probe tip becomes coated during plasma process • Insulating coatings prevent DC current flow – probe fails • Standard cleaning method does not work • Even if probe is clean, insulated reactor walls problematic • Conductive layer increase tip area – analysis complicated • Langmuir probe immune to coatings highly desirable Ceramic Probe Tip Layer deposited RF biased techniques: Sobolewski Method • ICP sustains plasma, RF bias controls ion energy • RF bias is capacitively coupled through blocking capacitor • Capacitive probe measures Voltage (with dc component) • Inductive pickup measures Current (no DC component) Note: Blocking capacitor behaves in a similar way to insulating layer RF biased techniques: Sobolewski Method • Current through RF biased sheath • At turning points of RF waveform dV/dt=0 • At most negative point Ie=0 also • RF bias is capacitively coupled (no net current) • Constant ion current (DC current) recovered RF biased techniques: Booth / Braithwaite • RF biased planar probe with guard-ring • Planar sheath ensured • Pulse modulated RF bias charges/discharges external capacitance • By monitoring voltage and current the probe IV characteristic is determined RF biased techniques: Booth / Braithwaite Plato Probe The Impedans RF biased probe technique for for use in systems depositing insulating layers Calibration • RF biased electrode in ICP plasma • Measured IV waveforms using oscilloscope • Stray impedance calibrated using 2 port network theory • Short and open circuit terminations of the electrode surface • Frequency domain calibration as stray impedance is a function of frequency • Langmuir probe used to validate results RF Current and Voltage waveforms RF Current and Voltage waveforms RF Current and Voltage waveforms RF Current and Voltage waveforms • Black – Total current to the electrode • Blue – Conduction current IV characteristic generation Plato Probe Overview • Capacitively coupled rf bias applied to tip • 200 micron recess around the tip circumference • Probe front end fully replaceable when coated layer exceeds 50 micron • 2 frequencies used to check / compensate for deposited layer Plato Probe Overview 3 Micron Layer No Layer Solid Line 200kHz; Dashed Line 400kHz Solid Line 200kHz; Dashed Line 400kHz 0.00016 0.00016 0.00014 0.00014 0.00012 0.00012 0.0001 0.0001 0.00008 0.00008 0.00006 0.00004 0.00006 0.00002 0.00004 -40 0.00002 -30 -20 -30 -20 -10 0 -0.00002 10 -0.00004 0 -40 0 -10 -0.00002 0 10 10 Micron Layer -0.00004 Solid Line 200kHz; Dashed Line 400kHz 0.00016 0.00014 0.00012 • CCP • Argon / 2Pa 0.00008 • Ne= 1.2x1015 m-3, 0.00006 • Te= 2.3eV, • As layer capacitance decreases, RF Voltage drop increases 0.0001 0.00004 0.00002 -40 -30 -20 0 -10 0 -0.00002 -0.00004 10 20 Plato Probe Overview Blocking capacitor I probe Layer Capacitance V probe Sheath Impedance V sheath Summary RF Biased probes can be used to measure plasma parameters in deposition environments Technique developed by Impedans allows much of IV characteristic to be recovered Plato probe allows operation even with layer thicknesses of up to 50 microns present 2 frequencies used to check / compensate for deposited layers