RF sensing for real-time monitoring of plasma processing

Garvin, Craig; Grizzle, Jessy W.

doi:10.1063/1.56830

Cited by 2 publications

(1 citation statement)

References 6 publications

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“…The plasma reactor used for this study is equipped with a newly developed probe to monitor plasma density, called a broadband rf peak resonance absorption sensor [10][11][12]. Based on microwave resonance cavity perturbation theory, the broadband rf sensor monitors resonance peak frequencies as a function of plasma conditions, and from the relative shift in these peak absorption resonance positions determines the relative plasma density [13].…”

Section: Introductionmentioning

confidence: 99%

In situmeasurements of HCl during plasma etching of poly-silicon using a diode laser absorption sensor

Kim

Klimecky

Jeffries

et al. 2003

Meas. Sci. Technol.

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Tunable diode laser absorption spectroscopy is used to monitor hydrogen chloride (HCl) concentration in a commercial, high-density, low-pressure plasma reactor during plasma etching. A near-infrared diode laser is used to scan the P(4) transition in the first overtone of HCl near 1.79 µm to measure changes in HCl levels. A variety of HBr and Cl 2 feedstock recipes are investigated at a process pressure of 10 mTorr as a function of rf power transformer coupled plasma, bias power and the total flow rate. Using 50 ms averaging and a signal modulation technique, we estimate a minimum detectivity of 4 × 10 −6 in peak absorbance, which corresponds to an HCl number density of ∼2 × 10 11 cm −3. The diode-laser based HCl sensor is sufficiently sensitive to detect small concentration variations and HCl concentration correlates with poly-Si etch rate for the conditions studied. These measurements demonstrate the feasibility of a real-time diode laser-based sensor for etch rate monitoring and the potential for process control.

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Section: Introductionmentioning

confidence: 99%

In situmeasurements of HCl during plasma etching of poly-silicon using a diode laser absorption sensor

Kim

Klimecky

Jeffries

et al. 2003

Meas. Sci. Technol.

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Compensation for transient chamber wall condition using real-time plasma density feedback control in an inductively coupled plasma etcher

Klimecky

Grizzle

Terry

2003

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Articles you may be interested inSurface loss rates of H and Cl radicals in an inductively coupled plasma etcher derived from time-resolved electron density and optical emission measurements J. Vac. Sci. Technol. A 28, 360 (2010); 10.1116/1.3330766Feedback control of plasma electron density and ion energy in an inductively coupled plasma etcher Real-time control of ion density and ion energy in chlorine inductively coupled plasma etch processing Reactive ion etch processing is known to exhibit significant variability in final etch performance due to wall condition. Previous studies have shown that neutral species transients depend strongly upon chamber seasoning. In this article, we show simultaneous measurements of wall-state-induced changes in plasma density and poly-Si etch rate, and demonstrate a real-time feedback control system that corrects for the plasma density variation. We demonstrate that controlling the plasma density to constant value eliminates the classic ''first wafer effect'' in Cl 2 etching of poly-Si in a Lam 9400 transformer coupled plasma ͑TCP͒. Chamber conditions studied include fluorination/ cleaning by C 2 F 6 plasmas compared to chlorination/deposition from Cl 2 plasmas. Transient density changes due to wall condition were measured using a microwave resonance cavity technique called broadband rf. Following chamber fluorination, broadband data show a significant drop in electron density ͑ϳ39%͒ from nominal levels. This is followed by subsequent partial recovery of the nominal density during a 60 s Cl 2 etch. Independent measurements correlate strongly with the broadband signals; particularly real-time poly-Si etch rate and SiCl 4 etch product concentration. Observed real-time variations in all signals were then compensated using a single input/single output proportional-integral ͑PI͒ feedback control algorithm, in which the broadband peak frequency is the system output variable and TCP power is the system actuator. Such PI control not only stabilizes broadband peak frequencies, but also steadies poly-Si real-time etch rate and SiCl 4 etch product concentration. This compensation scheme is then applied over multiple runs to reduce etch depth variability due to chamber condition. Results of this control system are shown to attenuate first wafer effects by a factor of 3 and reduce overall etch depth variation from run to run by an additional 33% compared to standard manufacturing practice. When applied to patterned wafer etches, feedback control of plasma density with an oxide hardmask is found not to alter critical dimensions or profile in any observable way. Only total etch depth appears to be affected using density control, as the real-time etch rate is in general increased in comparison to open-loop etching.

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RF sensing for real-time monitoring of plasma processing

Cited by 2 publications

References 6 publications

In situmeasurements of HCl during plasma etching of poly-silicon using a diode laser absorption sensor

In situmeasurements of HCl during plasma etching of poly-silicon using a diode laser absorption sensor

Compensation for transient chamber wall condition using real-time plasma density feedback control in an inductively coupled plasma etcher

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