Accurate rf Discharge Characterization and Influence of Reactor System Design on the Microscopic Plasma Parameters (original) (raw)
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The effect of radio frequency plasma processing reactor circuitry on plasma characteristics
Journal of Applied Physics, 1998
Past experiments have demonstrated that details of the external electrical circuitry can strongly influence the performance of radio frequency ͑rf͒ plasma processing reactors. Seemingly minor changes in the circuit, such as changing cable lengths, can lead to significantly different plasma characteristics. To investigate these couplings, a plasma equipment model has been developed which consists of a linked reactor simulation and a circuit model. In this hierarchy the results of the reactor simulation are periodically used in the circuit model to construct a simple representation of the plasma consisting of sheaths and resistors which are connected to the external circuit. Voltages ͑dc, fundamental and harmonics͒ and currents at all electrodes and reactor surfaces are computed, and are then employed as boundary conditions for the plasma reactor simulation. The models were used to investigate the effects of operating conditions, reactor geometry and stray coupling on the electrical characteristics of asymmetric capacitively coupled rf discharges. It was found that nonlinear sheaths lead to voltages and currents that have significant amplitudes at higher harmonics. As a consequence, external circuits that may appear identical to the plasma at the fundamental frequency may produce different plasma characteristics. Since plasmas are generally nonlinear and the combined plasma and circuit impedance is usually reactive, it was found that the voltage ͑or power͒ at the supply is not simply related to the voltages on electrode surfaces which generate the plasma.
Review of Scientific Instruments, 1994
A "reference cell" for generating radio-frequency (rf) glow discharges in gases at a frequency of 13.56 MHz is described. The reference cell provides an experimental platform for comparing plasma measurements carried out in a common reactor geometry by different experimental groups, thereby enhancing the transfer of knowledge and insight gained in rf discharge studies. The results of performing ostensibly identical measurements on six of these cells in five different laboratories are analyzed and discussed. Measurements were made of plasma voltage and current characteristics for discharges in pure argon at specified values of applied voltages, gas pressures, and gas flow rates. Data are presented on relevant electrical quantities derived from Fourier analysis of the voltage and current wave forms. Amplitudes, phase shifts, self-bias voltages, and power dissipation were measured. Each of the cells was characterized in terms of its measured internal reactive components. Comparing results from different cells provides an indication of the degree of precision needed to define the electrical configuration and operating parameters in order to achieve identical performance at various laboratories. The results show, for example, that the external circuit, including the reactive components of the rf power source, can significantly influence the discharge. Results obtained in reference cells with identical rf power sources demonstrate that considerable progress has been made in developing a phenomenological understanding of the conditions needed to obtain reproducible discharge conditions in independent reference cells.
Advanced Plasma Processing for Semiconductor Manufacturing
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Plasma modeling is a critical technology for the design of industrial plasma processing systems. Plasma processes are increasingly being extended to the sub-20 mTorr regime in the microelectronics industry, requiring accurate plasma models in the low pressure regime. Simultaneously, economic considerations are imposing stringent requirements on plasma uniformity over large substrates and plasma modeling is expected to address these uniformity challenges. These trends are necessitating good theoretical understanding in low temperature plasmas of (a) kinetic phenomena at low pressures and (b) the complex interplay between plasma, electromagnetic, chemical and fluid dynamics phenomena in three dimensions. Several fluid and particle-in-cell models are used in this paper to address issues of importance to the design and use of plasma etching and deposition systems.
Contributions to Plasma Physics, 2002
In the recent decade an RF driven, low-pressure plasma reactor with supersonic plasma jet was developed (RPJ). This reactor was successfully used for deposition of thin films of various materials. The deposition of thin films indicates that the properties of the deposited films are dependent on the sputtering or reactive sputtering processes appearing inside the nozzle (hollow cathode). The nozzle (hollow cathode) fabricated of different kinds of materials and alloys works both as a cathode of the radio frequency (RF) hollow cathode discharge and as a nozzle for plasma jet channel generation as well. The RF hollow cathode discharge is a secondary discharge, which is induced by the primary RF plasma generated in the reactor chamber. The present paper deals with the experimental study of this RF hollow cathode discharge. The stress is laid on the investigation of the axial distribution of discharge parameters and sputtering processes inside the nozzle. On the base of experiments, the simple model of the axial distribution of the investigated RF hollow cathode discharge has been developed.
Performance Evaluation of RF Generators with In-Situ Plasma Process Monitoring Sensors
Journal of Nanoscience and Nanotechnology, 2019
Plasma-processing equipment consists of numerous components, and RF power delivery system is one of the most critical for maintaining the requisite wafer quality. In this research, we investigate the use of in-situ plasma process monitoring sensors to evaluate the performance of the RF generator used in plasma enhanced chemical vapor deposition (PECVD) equipment. We employ three kinds of in-situ plasma process monitoring sensors, optical emission spectroscopy (OES), an optical plasmamonitoring sensor (OPMS), and a voltage-current (VI) probe, to monitor the plasma conditions produced by three different RF generators (RFGs). We found no significant differences among the test wafers. Thus, we conclude that the three RFGs each perform similarly in the PECVD system. We also found the OES is useful for analyzing the plasma chemistry and the degree of dissociation and ionization, the OPMS to be useful for monitoring the long-term stability in plasma processing, and the VI probe to be helpful for detecting instantaneous faults in semiconductor manufacturing.
Volumetric plasma source development and characterization
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The development of plasma sources with densities and temperatures in the 10 15 -10 17 cm -3 and 1-10eV ranges which are slowly varying over several hundreds of nanoseconds within several cubic centimeter volumes is of interest for applications such as intense electron beam focusing as part of the x-ray radiography program. In particular, theoretical work suggests that replacing neutral gas in electron beam focusing cells with highly conductive, pre-ionized plasma increases the time-averaged e-beam intensity on target, resulting in brighter x-ray sources. This LDRD project was an attempt to generate such a plasma source from fine metal wires. A high voltage (20-60kV), high current (12-45kA) capacitive discharge was sent through a 100μm diameter aluminum wire forming a plasma. The plasma's expansion was measured in time and space using spectroscopic techniques. Lineshapes and intensities from various plasma species were used to determine electron and ion densities and temperatures. Electron densities from the mid-10 15 to mid-10 16 cm -3 were generated with corresponding electron temperatures of between 1 and 10eV. These parameters were measured at distances of up to 1.85 cm from the wire surface at times in excess of 1μs from the initial wire breakdown event. In addition, a hydrocarbon plasma from surface contaminants on the wire was also measured. Control of these contaminants by judicious choice of wire material, size, and/or surface coating allows for the ability to generate plasmas with similar density and temperature to those given above, but with lower atomic masses.
In this research, the electrical characteristics of glow discharge plasma were studied. Glow discharge plasma generated in a home-made DC magnetron sputtering system, and a DC-power supply of high voltage as input to the discharge electrodes were both utilized. The distance between two electrodes is 4cm. The gas used to produce plasma is argon gas which flows inside the chamber at a rate of 40 sccm. The influence of work function for different target materials (gold, copper, and silver),-5cm in diameter and around 1mm thickness-different working pressures, and different applied voltages on electrical characteristics (discharge current, discharge potential, and Paschen's curve) were studied. The results showed that the discharge current and potential increase by increasing the applied voltage ranging between 300-700 V. Discharge current increased as working pressure increased in the beginning, and then semi-stabilized (slight increase) starting from 1×10 0 mbar, while discharge potential decreased at the beginning as working pressure increased and then semi-stabilized at the same point at which discharge current stabilized. The Paschen's curves were compared with each other. It was concluded that the lower breakdown voltage was associated with lower work function of the (Au, Cu, and Ag) cathode material. Breakdown voltages were (395, 398, and 420) for Ag, Cu and Au respectively.
2007 Plasma Source Science and Technology
An atmospheric argon plasma jet generated by an original dc double anode plasma torch has been investigated through its electrical and spectroscopic diagnostics. The arc instabilities and dynamic behavior of the argon plasma are analyzed using classical tools such as the statistical method, fast Fourier transform (FFT) and correlation function. The takeover mode is identified as the fluctuation characteristic of the double arc argon plasma jet in our experiment. The FFT and correlation analysis of electrical signals exhibit the only characteristic frequency of 150 Hz, which originates from the torch power and is independent of any change in the operating parameters. No high frequency fluctuations (1-15 kHz) are observed. This indicates that the nature of fluctuations in an argon plasma jet is induced mainly by the undulation of the tri-phase rectified power supply. It is found that each arc root attachment is diffused rather than located at a fixed position on the anode wall. Moreover, the emission spectroscopic technique is performed to determine the electron temperature and number density of the plasma jet inside and outside the arc chamber. Along the torch axis, the measured electron temperature and number density of the double arc argon plasma drop from 12 300 K and 7.6 × 10 22 m −3 at the divergent part of the first anode nozzle, to 10 500 K and 3.1 × 10 22 m −3 at the torch exit. In addition, the validity criteria of the local thermodynamic equilibrium (LTE) state in the plasma arc are examined. The results show that the measured electron densities are in good agreement with those calculated from the LTE model, which indicates that the double arc argon plasma at atmospheric pressure is close to the LTE state under our experimental conditions.