Sensor for monitoring plasma parameters (original) (raw)
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Sensor for Monitoring Nanodevice-Fabrication Plasmas
2004
A spectrally tunable VCSEL (vertical cavity surface-emitting laser) was used as part of sensing hardware for measurements of the radial-integrated gas temperature inside an inductively coupled plasma reactor. The data were obtained by profiling the Doppler-broadened absorption of metastable Ar atoms at 763.51 nm in argon and argon/nitrogen plasmas (3, 45, and 90% N2 in Ar) at pressure 0.5-70 Pa and inductive power of 100 and 300 W. The results were compared to rotational temperature derived from the N2 emission at the (0,0) transition of the C - B system. The differences in integrated rotational and Doppler temperatures were attributed to non-uniform spatial distributions of both temperature and thermometric species (Ar* and N2*) that varied depending on conditions. A two-dimensional, two-temperature fluid plasma simulation was employed to explain these differences. This work should facilitate further development of a miniature sensor for non-intrusive acquisition of data (temperature and densities of multiple plasma species) during micro- and nano-fabrication plasma processing, thus enabling the diagnostic-assisted continuous optimization and advanced control over the processes. Such sensors would also enable tracking the origins and pathways of damaging contaminants, thereby providing real-time feedback for adjustment of processes. Our work serves as an example of how two line-of-sight integrated temperatures derived from different thermometric species make it possible to characterize the radial non-uniformity of the plasma.
A vertical cavity surface-emitting laser diode (VCSEL) was used as a spectrally tunable emission source for measurements of the radial-integrated gas temperature inside an inductively coupled plasma reactor. The data were obtained by profiling the Doppler-broadened absorption of metastable Ar atoms at 763.51 nm in argon and argon/nitrogen plasmas (3%, 45%, and 90% N2 in Ar) at pressures of 0.5–70 Pa and inductive powers of 100 and 300W. The results were compared to the rotational temperature derived from the N2 emission at the (0,0) vibrational transition of the C 3Πu–B 3Πg system. The differences in integrated rotational and Doppler temperatures were attributed to non-uniform spatial distributions of both temperature and thermometric species (Ar* and N2*) that varied depending on the conditions. A two-dimensional, three-temperature fluid plasma simulation was employed to explain these differences. This work should facilitate further development of a miniature sensor for non-intrusive acquisition of data (temperature and densities of multiple plasma species) during micro- and nano-fabrication plasma processing, thus enabling diagnostic-assisted continuous optimization and advanced control over the processes. Such sensors would also enable us to track the origins and pathways of damaging contaminants, thereby providing real-time feedback for adjustment of processes. Our work serves as an example of how two line-of-sight integrated temperatures derived from different thermometric species make it possible to characterize the radial non-uniformity of the plasma.
Diagnostics of the inductively coupled plasma by diode laser absorption spectroscopy
A vertical-cavity surface-emitting diode laser is used as a tunable emission source to measure the radius-integrated gas temperature in an inductively coupled plasma reactor. Relevant data are obtained by profiling the Doppler-broadened absorption of metastable Ar atoms at 763.51 nm in argon and argon–nitrogen (3, 45, and 90% N2 in Ar) plasmas in the pressure range 0.5–70.0 Pa and at an inductive power of 100 and 300 W. The results are compared with the rotational temperature of molecular nitrogen. The difference between the integrated rotational and Doppler temperatures is attributed to the nonuniform spatial distributions of the temperature and thermometric atomic and molecular species (Ar* and N2*). These distributions are computed in terms of the nonequilibrium hydrodynamic model of plasma. The objective of this work is to develop a contactless (nonintrusive) technique for measuring the temperature and concentration of different particles in the reactor with a microsensor.
Pure and Applied Chemistry, 1994
Although plasma techniques continue to emerge as one of the more efficient means for processing advanced materials, the technology transfer, including optimization and scaleup, of plasma systems (both thermal and non-equilibrium) is hindered by a lack of understanding of the basic mechanisms which govern the plasma process. Understanding the plasma chemical reactions that occur in these reactors depends on the ability to accurately determine the plasma gas temperature and species concentration distributions. Concentration gradient measurements in turn yield information on the homogenemwheterogeheous nature of the reactions, chemical kinetic constants, and mass transport coefficients. Detailed knowledge of the temperature and reaction rates is also essential to the success of any detailed modeling effort. Laser/optical diagnostic techniques have the capability to provide much of this crucial information. Many of these optical techniques are non-intrusive, species specific and yield excellent spatial and temporal resolution. Optical in-situ measurements, in contrast to measurements using conventional sampling probe techniques, provide valuable information on the presence of excited species (e.g., hydrogen atom concentration in the diamond deposition process) as well as the deviation from local thermodynamic equilibrium in the case of high temperature gas flows generated by plasma sources. This paper includes discussion of both opticaVlaser techniques and representative conventional probe techniques. Approximate temperature limitations, advantages, and disadvantages of representative temperature and species measurement techniques are summarized. A recent example of the complementary use of laser diagnostic techniques in plasma reactors for advanced material processing is presented.
Applied Spectroscopy, 2001
In order to investigate evaporation and desolvation capacities of the enclosed inductively coupled plasma discharge, rotational temperatures (which are com monly considered a good approximation of the heavy particle temperature or gas temperature) were determined as a function of their spatial distribution and their dependence on physical parameters such as gas ows (80-740 mL/min), moisture load, etc. The procedure utilizes the ne structure of the (A 2 S 1 ® X 2 P i ) O H band having its band head at 306.4 nm. The rotational temperatures were obtained from the slopes of their Boltzmann plots. Spatial resolution and simultaneous line detection was possible by using a charge-coupled device (CCD) cam era in the focal plane of the removed exit slit of a Czerny-Turner m onochromator. An interactive data language (ID L) program was developed to calculate the temperature distribution from the received CCD images. Results of the measurement show that the rotational temperatures are between 3750 and 4350 K . They further show the Mshaped spatial pro le of analyte intensities and temperature. In the examined gas ow range (80-740 mL/min) the dependence on absolute gas ows and moisture load (5 mg/L) is negligible.
2010
A cross-flow atmospheric plasma jet with distilled water or analyte solution nebulization has been investigated. The plasma gas flows perpendicularly to the RF powered electrode (11.21 MHz) and a grounded electrode was added for plasma stabilization. The working parameters of the plasma generator can be controlled in order to maximize either the plasma power (75 W) or the voltage on the RF powered electrode (plasma power, 40 W). The plasma gas, pure argon (0.4 l min −1) or a mixture of argon (0.3-0.4 l min −1) and helium (0-0.2 l min −1), was also used for liquid nebulization. Optical emission of the plasma, collected in the normal viewing mode, was used for plasma diagnostics and for evaluating its excitation capabilities. The influence of helium content in the mixed-gas plasma on the plasma characteristics and on the emission axial profiles of the plasma gas constituents and of the analytes originate from the wet aerosol was studied. The addition of helium to the argon plasma, generally determines decreases in the emission of the plasma gas constituents (with the exception of molecular nitrogen), in the rotational temperature and in the electron number density and increases in the excitation temperatures and in the emission of easily excitable analytes. Based on the determined electron number densities, it was concluded that in the plasma zone which presents interest from analytical point of view the plasma is not very far from the partial thermodynamic equilibrium. In function of the helium content in the plasma gas and of the axial distance from the powered electrode the excitation temperatures are in the range of 2420-3340 K for argon, 2500-5450 K for oxygen and 900-2610 K for ionic calcium and the electron number densities are in the range of 1.2 10 12-1.25 10 13 cm −3. Some elements with excitation energy lower than 6 eV were excited in the plasma. The plasma excitation capability depends on the working conditions of the plasma generator (maximum power or maximum voltage on the RF powered electrode) and on the helium content in the mixed-gas plasma. The estimated detection limits for the studied elements (Na, Li, K, Ca, Cu, Ag, Cd, Hg and Zn) are in the range of 7 ng ml −1 to 28 μg ml −1 .
Feasibility of Laser Induced Plasma Spectroscopy for
2015
In this paper, experimental results obtained with Laser Induced Plasma Spectroscopy to retrieve local compositions are presented for an ambient pressure up to 5.0 MPa in a still cell. Well controlled mixtures of gases are introduced and plasma is obtained with the fundamental emission of a pulsed Nd:YAG laser. Simultaneously, plasma shape and spectrally resolved data are taken with a temporal resolution down to 2 ns. First, the temporal evolutions of a high-pressure nitrogen plasma are analyzed as function of spark energy. It is shown that plasma changes orientation from an elongated shape parallel to the laser line to a perpendicular one in a very short time. Results are reported for both spatial and spectral variations. Afterwards, the effects of increased carbon concentration are discussed in both shape and spectra. It is seen that strong intensity due to the atomic carbon emissions appear for the high-pressure case. From those experiments, calibration strategies are proposed to get equivalence ratio under high pressure conditions with a ratio of carbon versus nitrogen and oxygen. The delay between plasma and measurements is set to 2000 ns and the signal is integrated for 5000 ns, so as to yield a good signal to noise ratio and a good sensitivity of the technique to changes in mixture fraction. Calibration curves are reported for equivalence ratio up to 1.00 and for pressure from 1.0 to 5.0 MPa. It is shown that typical uncertainties are limited to 7.5% regardless the equivalence ratio in a single shot approach using a spectral fit procedure,whereas it accounts to two times more in a more classical peak ratio approach. Increasing the pressure tends to increase the precision as lower pressure had higher uncertainties.
Journal of Quantitative Spectroscopy and Radiative Transfer, 2001
Recent Fourier Transform Spectrometry measurements of a wide array of rovibrational lines of the first negative system of N 2 + were used to develop a quantitative line-by-line radiation code that can be used for accurate rotational temperature determinations in nitrogen and air plasmas. The model is applied to the interpretation of spectral measurements obtained in a nonequilibrium nitrogen/argon plasma produced by a 50 kW radio-frequency inductively coupled plasma torch. Two rotational temperature determination techniques are presented that consist either in performing a global fit of the spectral region 3700-3920 Å or in comparing the intensity of a single group of isolated lines at 3759.5 Å to the intensity of the (0-0) band head. Both techniques yield a rotational temperature of 4850 K with an accuracy of better than 2%.
Spectrochimica Acta Part B: Atomic Spectroscopy, 2017
In this work a new spectroscopic method, allowing gas temperature determination in argon non-thermal plasmas sustained at atmospheric pressure, is presented. The method is based on the measurements of selected pairs of argon atomic lines (Ar I 603.2 nm/Ar I 549.6 nm, Ar I 603.2 nm/Ar I 522.1 nm, Ar I 549.6 nm/Ar I 522.1 nm). For gas temperature determination using the proposed method, there is no need of knowing the electron density, neither making assumptions on the degree of thermodynamic equilibrium existing in the plasma. The values of the temperatures obtained using this method, have been compared with the rotational temperatures derived from the OH ro-vibrational bands, using both, the well-known Boltzmann-plot technique and the best fitting to simulated ro-vibrational bands. A very good agreement has been found.