In Situ Monitoring of Silicon Plasma Etching Using a Quantum Cascade Laser Arrangement

Stancu, Gabi-Daniel; Lang, N.; Röpcke, J.; Reinicke, M.; Steinbach, Annina M.; Wege, S.

doi:10.1002/cvde.200606584

Cited by 44 publications

(46 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore it has already been successfully applied to the study of plasma processes, e.g. of microwave and RF discharges [53,54]. Of special interest for all hydrocarbon-based processes is the capacity to detect transient molecules like the CH 3 radical, as the supposed key growth species, by means of QCLAS (figure 12).…”

Section: Plasma Diagnostics With High Time Resolutionmentioning

confidence: 99%

Kinetic and Diagnostic Studies of Molecular Plasmas Using Laser Absorption Techniques

Röpcke

Engeln

Schram

et al. 2010

Introduction to Complex Plasmas

View full text Add to dashboard Cite

Abstract. Within the last decade mid infrared absorption spectroscopy between 3 and 20 µm, known as Infrared Laser Absorption Spectroscopy (IRLAS) and based on tuneable semiconductor lasers, namely lead salt diode lasers, often called tuneable diode lasers (TDL), and quantum cascade lasers (QCL) has progressed considerably as a powerful diagnostic technique for in situ studies of the fundamental physics and chemistry of molecular plasmas. The increasing interest in processing plasmas containing hydrocarbons, fluorocarbons, organosilicon and boron compounds has lead to further applications of IRLAS because most of these compounds and their decomposition products are infrared active. IRLAS provides a means of determining the absolute concentrations of the ground states of stable and transient molecular species, which is of particular importance for the investigation of reaction kinetics. Information about gas temperature and population densities can also be derived from IRLAS measurements. A variety of free radicals and molecular ions have been detected, especially using TDLs. Since plasmas with molecular feed gases are used in many applications such as thin film deposition, semiconductor processing, surface activation and cleaning, and materials and waste treatment, this has stimulated the adaptation of infrared spectroscopic techniques to industrial requirements. The recent development of QCLs offers an attractive new option for the monitoring and control of industrial plasma processes as well as for highly time-resolved studies on the kinetics of plasma processes. The aim of the present article is threefold: (i) to review recent achievements in our understanding of molecular phenomena in plasmas, (ii) to report on selected studies of the spectroscopic properties and kinetic behaviour of radicals, and (iii) to describe the current status of advanced instrumentation for TDLAS in the mid infrared.

show abstract

Section: Plasma Diagnostics With High Time Resolutionmentioning

confidence: 99%

Kinetic and Diagnostic Studies of Molecular Plasmas Using Laser Absorption Techniques

Röpcke

Engeln

Schram

et al. 2010

Introduction to Complex Plasmas

View full text Add to dashboard Cite

show abstract

“…QCLAS in the gas phase is now applied in various fields covering environmental trace gas detection [1][2][3], detection of toxic species or explosives [4,5], isotope ratio measurements [6], breath gas analysis [7,8] as well as industrial process monitoring [9] and plasma diagnostics [10][11][12]. The first demonstration of a QCL in 1994 [13], based on the idea of Kazarinov and Suris [14], and further development enable now pulsed or continuous wave, thermoelectrically (TE) cooled, single-mode distributed feedback (DFB-)QCLs to be used in spectrometers.…”

Section: Introductionmentioning

confidence: 99%

“…However, at low pressure conditions the measured absorption features are affected by an obstacle known as the "rapid passage effect" accompanied by potential power saturation effects [16,17]. Nevertheless, if a sensible normalisation [12] or calibration [9,11] is performed quantitative results can be obtained. This also addresses the required high resolution spectra of molecules with a complex structure which are typically absent or difficult to measure in jet cooled experiments.…”

Section: Introductionmentioning

confidence: 99%

“…This also addresses the required high resolution spectra of molecules with a complex structure which are typically absent or difficult to measure in jet cooled experiments. In this case a calibrated effective absorption cross section determined for a distinct spectral micro-window is also sufficient: Stancu et al demonstrated this for SiF 4 where a temperature dependence was not observed, because the different contributions from several spectral lines tended to compensate each other [9]. In combination with TE cooled detectors QCL spectrometers became cryogen free and are hence particularly favourable for industrial applications and process monitoring.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Application of quantum cascade laser absorption spectroscopy to studies of fluorocarbon molecules

Welzel¹,

Степанов²,

Meichsner³

et al. 2009

J. Phys.: Conf. Ser.

View full text Add to dashboard Cite

Abstract. The recent advent of quantum cascade lasers (QCLs) enables room-temperature mid-infrared spectrometer operation which is particularly favourable for industrial process monitoring and control, i.e. the detection of transient and stable molecular species. Conversely, fluorocarbon containing radio-frequency discharges are of special interest for plasma etching and deposition as well as for fundamental studies on gas phase and plasma surface reactions. The application of QCL absorption spectroscopy to such low pressure plasmas is typically hampered by non-linear effects connected with the pulsed mode of the lasers. Nevertheless, adequate calibration can eliminate such effects, especially in the case of complex spectra where single line parameters are not available. In order to facilitate measurements in fluorocarbon plasmas, studies on complex spectra of CF 4 and C 3 F 8 at 7.86 µm (1269 -1275 cm -1 ) under low pressure conditions have been performed. The intra-pulse mode, i.e. pulses of up to 300 ns, was applied yielding highly resolved spectral scans of ~ 1 cm -1 coverage. Effective absorption cross sections were determined and their temperature dependence was studied in the relevant range up to 400 K and found to be non-negligible.

show abstract

“…Extensions originally developed for TDLAS, e.g., the sweep integration method [7,8], were adapted to pulsed QCL spectrometers [9] and enable a time-resolution of milliseconds. Employing this method is not only of interest for on-line trace gas measurements, on which most of the experiments carried out so far were focussing [5,6,[9][10][11][12][13][14][15][16][17], but also for monitoring species in plasma diagnostics [18][19][20]. Later, the inherent frequency-down chirp of the lasers was exploited by using long pulses to acquire absorption spectra during the pulse [21,22].…”

mentioning

confidence: 99%

Non-symmetrical line broadening effects using short-pulse QCL spectrometers as determined with sub-nanosecond time-resolution

Welzel

Röpcke

2010

Appl. Phys. B

Self Cite

View full text Add to dashboard Cite

Quantum cascade lasers (QCLs) have attracted considerable interest as an alternative tuneable narrow bandwidth light source in the mid-infrared spectral range for chemical sensing. Pulsed QCL spectrometers are often used with short laser pulses and a bias current ramp similar to diode laser spectroscopy. Artefacts in the recorded spectra such as disturbed line shapes or underestimated absorption coefficients have been reported. A detailed time-resolved high-bandwidth analysis of individual pulses during a laser sweep has been performed. Quantitative results for CH 4 absorption features around 1347 cm −1 (7.42 µm) fell short of the expected values for reasonable operating conditions of the QCL. The origin of the artefacts using short pulses was identified to be partly of the same nature as in the case of long laser pulses. A complex combination with the tuning principle was found, leading to an apparently increased instrumental broadening (effective line width) and underestimated concentrations at low-pressure conditions.

show abstract

In Situ Monitoring of Silicon Plasma Etching Using a Quantum Cascade Laser Arrangement

Cited by 44 publications

References 16 publications

Kinetic and Diagnostic Studies of Molecular Plasmas Using Laser Absorption Techniques

Kinetic and Diagnostic Studies of Molecular Plasmas Using Laser Absorption Techniques

Application of quantum cascade laser absorption spectroscopy to studies of fluorocarbon molecules

Non-symmetrical line broadening effects using short-pulse QCL spectrometers as determined with sub-nanosecond time-resolution

Contact Info

Product

Resources

About