Bulletin of the American Physical Society
68th Annual Gaseous Electronics Conference/9th International Conference on Reactive Plasmas/33rd Symposium on Plasma Processing
Volume 60, Number 9
Monday–Friday, October 12–16, 2015; Honolulu, Hawaii
Session ET3: Diagnostic Probes |
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Chair: Edward Barnat, Sandia National Laboratories Room: 305 AB |
Tuesday, October 13, 2015 10:00AM - 10:15AM |
ET3.00001: Curling probe measurement of large-volume pulsed plasma confined by surface magnetic field Anil Pandey, Wataru Sakakibara, Hiroyuki Matsuoka, Keiji Nakamura, Hideo Sugai \textit{Curling probe} (CP) has recently been developed which enables the local electron density measurement even in plasma for non-conducting film CVD. The electron density is obtained from a shift of resonance frequency of spiral antenna in discharge ON and OFF monitored by a network analyzer (NWA). In case of a pulsed glow discharge, synchronization of discharge pulse with frequency sweep of NWA must be established. In this paper, we report time and space-resolved CP measurement of electron density in a large volume plasma (80 cm diameter, 110 cm length) confined by surface magnetic field (multipole cusp field $\sim$ 0.03 T). For plasma-aided modification of metal surface, the plasma is produced by 1 kV glow discharge at pulse frequency of 0.3 -- 25 kHz with various duty ratio in gas (Ar, N$_{2}$, C$_{2}$H$_{2})$ at pressure $\sim$ 1 Pa. A radially movable CP revealed a remarkable effect of surface magnetic confinement: detach of plasma from the vessel wall and a fairly uniform plasma in the central region. In afterglow phase, the electron density was observed to decrease much faster in C$_{2}$H$_{2}$ discharge than in Ar discharge. [Preview Abstract] |
Tuesday, October 13, 2015 10:15AM - 10:30AM |
ET3.00002: Electrostatic and Electromagnetic Resonances of the Curling probe Ali Arshadi, Leila Valadbeigi, Ralf Peter Brinkmann The term Active Plasma Resonance Spectroscopy denotes a class of plasma diagnostic techniques utilizing the natural ability of plasma to resonate on or near the electron plasma frequency: An electric signal in the GHz range is coupled into the plasma via a probe. The spectral response of the plasma is recorded and a mathematical model is used to find plasma parameters such as the electron density. The curling probe, recently invented by Liang et al., is a novel realization of this concept which has many practical advantages. In particular, it can be miniaturized, and flatly embedded into the chamber wall, enabling monitoring of plasma processes without perturbing them. Physically, the curling probe can be seen as a ``curled'' form of the hairpin probe. Assuming that the effect of the spiralization is negligible, this work investigates the features of a ``straightened'' curling probe by modeling it as a slot-type resonator which is in contact with the plasma. The diffraction of an incident plane wave at the slot is calculated by solving Maxwell's equations and the cold plasma model simultaneously. Electrostatic and Electromagnetic resonances are derived. Good agreement of the analytically computed resonance frequencies with the numerical results of the probe inventors is shown. [Preview Abstract] |
Tuesday, October 13, 2015 10:30AM - 10:45AM |
ET3.00003: Analyses of Different Techniques for the Plasma Probe Diagnostics Valery Godyak, Benjamin Alexandrovich The subject of this publication is comparison of the plasma parameters inferred from classical Langmuir probe procedure, from different theories of the ion current to the probe, and from measured EEDF using double differentiation of the probe characteristic We concluded that the plasma parameters inferred by the classical Langmuir procedure are subjected to significant inaccuracy due to non-Maxwellian EEDF, uncertainty of locating the plasma potential and arbitrariness in approximation of the ion current. The plasma density inferred from the ion part of the probe characteristic was found to diverge by as much as an order of magnitude from the density calculated as the EEDF integral, while the electron temperature is derived with significant uncertainty. Such inaccuracy is attributed to deficiencies in the ion current theories, i.e. unrealistic assumptions about Maxwellian-shaped EEDFs, underestimation of the ion collisions and the ion ambipolar drift, and some others. We concluded that for highly non-equilibrium gas discharge plasmas at low gas pressure the probe measurements based on EEDF diagnostics is single reliable tool of for the basic research and industrial applications. Examples of EEDF measurements reiterate significance of the instrument technical characteristics, such as high energy resolution and wide dynamic range and importance of displaying the probe current derivatives in real time. [Preview Abstract] |
Tuesday, October 13, 2015 10:45AM - 11:00AM |
ET3.00004: Kinetic Damping in the Spectrum of the Spherical Impedance Probe Jens Oberrath, Ralf Peter Brinkmann Active plasma resonance spectroscopy is a widely used diagnostic method and several probes in different designs have been invented. One of them is the Spherical Impedance Probe. Its resonance behavior and the influence of kinetic effects on it can be described by a general kinetic model presented by the authors [1]. It was theoretically shown that kinetic effects are responsible for a broadening of the resonance peak in the spectrum. However, the broadening of the resonance peak in a kinetically determined spectrum in the geometry of an existing probe is not evaluated, yet. We present such a spectrum of the Spherical Impedance Probe. Therefore, the general solution of the model is expanded in an orthonormal system of basis-functions. This expansion is truncated to determine an approximated spectrum. Its resonance peak shows clearly a broadening compared to a peak in a spectrum, which is determined by a fluiddynamical model.\\[4pt] [1] J. Oberrath and R.P. Brinkmann, Plasma Sources Sci. Technol. 23, 045006 (2014) [Preview Abstract] |
Tuesday, October 13, 2015 11:00AM - 11:15AM |
ET3.00005: Using the Multipole Resonance Probe to Stabilize the Electron Density During a Reactive Sputter Process Moritz Oberberg, Tim Styrnoll, Stefan Ries, Stefan Bienholz, Peter Awakowicz Reactive sputter processes are used for the deposition of hard, wear-resistant and non-corrosive ceramic layers such as aluminum oxide (Al$_{\mathrm{2}}$O$_{\mathrm{3}})$. A well known problem is target poisoning at high reactive gas flows, which results from the reaction of the reactive gas with the metal target. Consequently, the sputter rate decreases and secondary electron emission increases. Both parameters show a non-linear hysteresis behavior as a function of the reactive gas flow and this leads to process instabilities. This work presents a new control method of Al$_{\mathrm{2}}$O$_{\mathrm{3}}$ deposition in a multiple frequency CCP (MFCCP) based on plasma parameters. Until today, process controls use parameters such as spectral line intensities of sputtered metal as an indicator for the sputter rate. A coupling between plasma and substrate is not considered. The control system in this work uses a new plasma diagnostic method: The multipole resonance probe (MRP) measures plasma parameters such as electron density by analyzing a typical resonance frequency of the system response. This concept combines target processes and plasma effects and directly controls the sputter source instead of the resulting target parameters. [Preview Abstract] |
Tuesday, October 13, 2015 11:15AM - 11:45AM |
ET3.00006: Wireless sensor technology for in-situ plasma process monitoring Invited Speaker: David Gahan There is an increasing demand for plasma measurement and control solutions to cope with the growing complexity of integrated circuit manufacture in the semiconductor industry. Standard plasma diagnostic instruments used in research, such as the Langmuir probe, are not suitable for use in the production environment for myriad reasons -- contamination of the process being one of the main concerns. Silicon wafer based wireless sensors, which measure temperature during the process, have gained the most traction with tool manufacturers and chip makers -- albeit during process development or the PM cycle rather than live production. In this presentation we will discuss two novel wireless technologies that have the potential for use in process tools. The first is an ion detector embedded in a silicon wafer. The sensor measures the average ion flux and the maximum ion energy during the process. This information is stored and is downloaded later for analysis. The second technology consists of a wireless sensor that sits inside the process and communicates data in real time to a detector installed on the rf power line. This platform is similar to RFID technology and can be combined with various sensor types to transmit data to the user during the process. [Preview Abstract] |
Tuesday, October 13, 2015 11:45AM - 12:00PM |
ET3.00007: Phase-resolved measurement of surface charge deposition in a laterally patterned barrier discharge system Lars Stollenwerk, Robert Wild In the present contribution a barrier discharge system with plane parallel electrodes is investigated. With appropriately chosen parameters, a patterned glow-like discharge arises. In the case of laterally inhomogeneous discharges (i.\,e. in the present patterned discharges or in the common filamentary discharges) also the surface charge distribution on the dielectric barriers is inhomogeneous. Due to its deformation of the electric field it provides a memory effect and thus contributes essentially to the stabilisation of the lateral structure. Therefor, the measurement of the surface charge has been come into focus in the last decade. In this contribution, spatially and temporally resolved electro-optical surface measurements are presented. The high temporal resolution allows for the first time the observation of the charge deposition during a single breakdown. The process starts in the center of a remnant surface charge spot, where the electrical field is highest. The maximum of the electrical field then moves radially outwards. A surface charge spot is hence replaced from the inside out by a charge spot of opposite polarity. These experimental findings verify previously unconfirmed predictions from earlier numerical calculations. [Preview Abstract] |
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