Bulletin of the American Physical Society
67th Annual Gaseous Electronics Conference
Volume 59, Number 16
Sunday–Friday, November 2–7, 2014; Raleigh, North Carolina
Session SF1: Plasma Sources |
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Chair: Julian Schulze, West Virginia University Room: State EF |
Friday, November 7, 2014 8:30AM - 9:00AM |
SF1.00001: EED$f$ and IED$f$ of the non-ambipolar e$^{-}$-beam plasma and their effects on etch Invited Speaker: Lee Chen The control of electron shading is crucial in achieving the super-high aspect ratio contact (HARC); precise ion-energy control is essential in the selective etching of lamella diblock copolymers to develop the nano-lines for Direct Self Assembly (DSA). The plasma EED$f$ not only determines the chemistry but also dictates the shading level of the features. The above processes are presented as examples to illustrate the effects of EED$f$ and the surgical surface-excitation by a controlled IED$f$. In addition to demonstrating the methods of achieving a prescribed IED$f$ through external bias, the properties of the non-ambipolar electron plasma (NEP) will be presented. NEP is heated by the non-ambipolar beam-current density in the range of 10s Acm$^{-2}$ through beam-plasma instabilities. Its EED$f$ has a Maxwellian bulk followed by a broad energy-continuum connecting to the most energetic group with energies above the beam-energy and such EED$f$ seems consistent with that required for deep-contact etching. The remnant of the injected electron-beam power terminates at the NEP end-boundary (i.e., wafer) could set up a controllable DC sheath potential resulting in mono-energetic surface excitation by the charge-neutral plasma beam without the application of external bias.\\[4pt] In collaboration with Zhiying Chen, Tokyo Electron America, Inc., Austin, TX 78741. [Preview Abstract] |
Friday, November 7, 2014 9:00AM - 9:15AM |
SF1.00002: ABSTRACT WITHDRAWN |
Friday, November 7, 2014 9:15AM - 9:30AM |
SF1.00003: Prevention of ion flux inhomogeneities in large area capacitively coupled discharges via the Electrical Asymmetry Effect Edmund Schuengel, Julian Schulze, Sebastian Mohr, Uwe Czarnetzki For large area processing applications of capacitively coupled radio frequency (CCRF) discharges, the lateral uniformity of the plasma surface interaction is crucially important. The benefit of an increase in the plasma density and, therefore, in the overall deposition rate by driving the discharge at higher frequencies is accompanied with inhomogeneities caused by the presence of electromagnetic effects. Here, we propose a method based on the Electrical Asymmetry Effect (EAE) to prevent such inhomogeneities. Spatially resolved measurements of the ion flux onto the grounded electrode of a CCRF discharge operated in hydrogen show a standing wave pattern in a 81.36 MHz single-frequency discharge, strongly reducing the ion flux uniformity. However, applying a dual-frequency voltage waveform consisting of 40.68 MHz + 81.36 MHz, the lateral distribution of the ion flux can be controlled via the phase angle between the two applied harmonics. Using the EAE, a phase angle dependent DC self-bias develops in the geometrically symmetric discharge. Tuning the phase angle allows for the compensation of ion flux inhomogeneities due to the standing wave effect. Thus, a high and laterally uniform ion flux can be generated in electrically asymmetric high frequency plasmas. [Preview Abstract] |
Friday, November 7, 2014 9:30AM - 9:45AM |
SF1.00004: Transient response of pulsed multi-source RF CCP discharges Theresa Kummerer, David Peterson, David Coumou, Steven Shannon The electrical response of a pulsed RF CCP discharge with a second CW power source is studied within the kHz timescale of a typical pulsed system. This response is compared to plasma parameters such as sheath thickness, electron density, electron temperature, and optical emission to elucidate trends with respect to operating condition. Several regions within the pulse cycle with characteristic decay constants and saturation points have been identified using voltage, current, and phase measurements from the CW powered electrode. These trends are compared to global plasma parameters measured using Langmuir probe, hairpin resonators, spectroscopy, and high time resolution in-line RF metrology. These observed transient regions have a dependence on pressure, relative power levels, pulse frequency, and gas composition. Data was taken using argon and argon-oxygen plasmas with pulsing plurality of frequency configurations where one generator is pulsed while the other maintains constant power output. The goal of this study is to parameterize conditions for active power delivery control in advanced multi-source RF systems that utilize pulsing on one or more of their power supplies. [Preview Abstract] |
Friday, November 7, 2014 9:45AM - 10:00AM |
SF1.00005: Etching of photoresist with an atmospheric pressure plasma jet Andrew West, Marc van der Schans, Cigang Xu, Timo Gans, Mike Cooke, Erik Wagenaars Low-pressure oxygen plasmas are commonly used in semiconductor industry for removing photoresist from the surface of processed wafers; a process known as plasma ashing or plasma stripping. The possible use of atmospheric-pressure plasmas instead of low-pressure ones for plasma ashing is attractive from the point of view of reduction in equipment costs and processing time. We present investigations of photoresist etching with an atmospheric-pressure plasma jet (APPJ) in helium gas with oxygen admixtures driven by radio-frequency power. In these experiments, the neutral, radical rich effluent of the APPJ is used for etching, avoiding direct contact between the active plasma and the sensitive wafer, while maintaining a high etch rate. Photoresist etch rates and etch quality are measured for a range of plasma operating parameters such as power input, driving frequency, flow rate and wafer temperature. Etch rates of up to 10 micron/min were achieved with modest input power (45 W) and gas flow rate (10 slm). Fourier Transform Infrared (FTIR) spectroscopy showed that the quality of the photoresist removal was comparable to traditional plasma ashing techniques. [Preview Abstract] |
Friday, November 7, 2014 10:00AM - 10:15AM |
SF1.00006: Development and characterization of a fast neutral beam source for damage-free etching Mark Bowden, Daniil Marinov, Adetokunbo Ayilaran, Nicholas Braithwaite, Ziad el Otell Etching with energetic neutral beams is a promising technology for next generation sub-10 nm device fabrication. In this study a fast neutral beam has been produced by accelerating, extracting and neutralizing positive and negative ions from different phases of a pulsed discharge. A cylindrical, inductively coupled plasma (ICP) was excited between two planar disk-electrodes in mixtures of SF$_{\mathrm{6}}$ and O$_{\mathrm{2\thinspace }}$at about 20 mTorr. The discharge was pulsed at 2 kHz and 50{\%} duty cycle. The extraction electrode was a 10 mm thick carbon plate (or a 0.8 mm steel plate) with an array of 1 mm holes, held at ground potential. Ions grazing the sides of the extraction holes incidence have a high probability (70-95{\%}) of neutralization. The other electrode was pulse-biased to extract negative or positive ions during the afterglow phase, after an ion-ion plasma had formed. The total flux and velocity distribution of extracted ions was measured using a retarding field analyser. Extraction of mono-energetic positive and negative ion beams with energies in the range 10 -- 300 eV was demonstrated. It was shown that the beam energy can be precisely controlled by the bias waveform tailoring and by positioning of the extraction electrodes. [Preview Abstract] |
Friday, November 7, 2014 10:15AM - 10:30AM |
SF1.00007: Hysteresis in Radio-Frequency Inductively Coupled Plasmas Hyo-Chang Lee, Chin-Wook Chung We present both experimental and theoretical studies of hysteresis in radio-frequency inductive discharges. It is found that the hysteresis is significantly affected by nonlinearity of the plasma with the modification of electron energy distribution (EED). This kind of hysteresis is also observed in various plasma discharges with powers, pressures, and magnetic field where EEDs are evolved. [Preview Abstract] |
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