Bulletin of the American Physical Society
65th Annual Gaseous Electronics Conference
Volume 57, Number 8
Monday–Friday, October 22–26, 2012; Austin, Texas
Session ET4: Ion Distribution Functions |
Hide Abstracts |
Chair: Svetlana Radovanov, Varian Semiconductor Equipment Associates, Inc Room: Salon DE |
Tuesday, October 23, 2012 1:30PM - 1:45PM |
ET4.00001: 2D ion velocity distribution function measurements by laser-induced fluorescence above a radio-frequency biased silicon wafer Nathaniel Moore, Walter Gekelman, Patrick Pribyl, Yiting Zhang, Mark Kushner Ion dynamics have been measured in the sheath above a 30 cm diameter, 2.2 MHz-biased silicon wafer in a plasma processing etch tool using laser-induced fluorescence (LIF). The velocity distribution function of argon ions was measured at thousands of positions above and radially along the edge of the wafer by sending a planar laser sheet from a pulsed, tunable dye laser into the tool. The RF sheath is clearly resolved. The laser sheet entered the machine both parallel and perpendicular to the wafer in order to measure the distribution function for both parallel and perpendicular velocities/energies (0.4 eV $< E_{max} <$ 600 eV). The resulting fluorescence was recorded using a fast CCD camera, which provided spatial (0.4 mm) and temporal (30 ns) resolution. Data was taken at eight different phases of the 2.2 MHz cycle. The distribution functions were found to be spatially non-uniform near the edge of the wafer and the distribution of energies extremely phase-dependent. Several cm above the wafer the distribution is Maxwellian and independent of phase. Results are compared with simulations; for example, the experimental time-averaged ion energy distribution function compares favorably with a computer model carefully constructed to emulate the device. [Preview Abstract] |
Tuesday, October 23, 2012 1:45PM - 2:00PM |
ET4.00002: Space and Phase Resolved Modeling of Ion Energy Angular-Distributions from the Bulk Plasma to the Wafer in Dual Frequency Capacitively Coupled Plasmas Yiting Zhang, Nathaniel Moore, Patrick Pribyl, Walter Gekelman, Mark J. Kushner The control of ion energy and angular distributions (IEADs) is of critical importance for anisotropic etching or conformal deposition in microelectronics fabrication. Dual-frequency capacitively coupled plasmas (CCPs) are being investigated with the goal of having flexible control where the high frequency (HF) controls the plasma density, while the ion energy is mainly determined by the low frequency (LF). However, over select ranges of LF and HF, the IEAD has characteristics of both the LF and HF. To understand this coupling, we report on results of a numerical investigation of phase and spatially resolved transport of ions through the sheath. These results were generated using a two-dimensional plasma hydrodynamics model having an ion Monte Carlo simulation. Inductively coupled plasmas sustained in Ar/O$_{2}$ with a multi-frequency bias on the substrate were modeled. The IEADs are tracked as a function of height above the substrate and phase within the rf cycle. The computed results are compared to laser-induced fluorescence (LIF) experiments. We found that the ratios of HF/LF voltage and driving frequency are critical parameters in determining the shape of the IEADs, with evidence of the HF component occurring up to 30 MHz. This tunability may provide additional control for the width and maximum energy of the IEADs. [Preview Abstract] |
Tuesday, October 23, 2012 2:00PM - 2:15PM |
ET4.00003: Ion energy distributions at the electrodes of high pressure capacitive dual-frequency hydrogen discharges Edmund Sch\"ungel, Sebastian Mohr, Julian Schulze, Uwe Czarnetzki Capacitively coupled radio frequency (CCRF) discharges are widely used for surface processing applications, such as thin film solar cell manufacturing. In order to optimize the plasma surface interactions, the fluxes and energy distributions of radicals and ions at the substrate need to be controlled. In particular, the ion energy distribution function (IEDF) plays a crucial role. Previous investigations have shown that the mean ion energy can be changed in low pressure argon discharges via the Electrical Asymmetry Effect (EAE). Here, two consecutive harmonics are applied to the powered electrode. The main control parameter is the phase angle between the frequencies, which allows to adjust the symmetry of the discharge, the DC self bias, and the sheath voltages. In this work, the EAE is investigated in a parallel plate CCRF discharge operated in pure hydrogen at pressures of several hundred Pa. The axial component of the IEDF of the dominant ion species, H$_{3}^{+}$, is measured at the grounded electrode using a plasma process monitor. The results focus on the question how the shape of the IEDF, the mean ion energy, and the total ion flux change as a function of the phase angle. Funded by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (0325210B). [Preview Abstract] |
Tuesday, October 23, 2012 2:15PM - 2:45PM |
ET4.00004: High Energy IED measurements with MEMs based Si grid technology inside a 300mm Si wafer Invited Speaker: Merritt Funk The measurement of ion energy at the wafer surface for commercial equipment and process development without extensive modification of the reactor geometry has been an industry challenge. High energy, wide frequency range, process gases tolerant, contamination free and accurate ion energy measurements are the base requirements. In this work we will report on the complete system developed to achieve the base requirements. The system includes: a reusable silicon ion energy analyzer (IEA) wafer, signal feed through, RF confinement, and high voltage measurement and control. The IEA wafer design required carful understanding of the relationships between the plasma Debye length, the number of grids, intergrid charge exchange (spacing), capacitive coupling, materials, and dielectric flash over constraints. RF confinement with measurement transparency was addressed so as not to disturb the chamber plasma, wafer sheath and DC self-bias as well as to achieve spectral accuracy The experimental results were collected using a commercial parallel plate etcher powered by a dual frequency (VHF + LF). Modeling and Simulations also confirmed the details captured in the IED. [Preview Abstract] |
Tuesday, October 23, 2012 2:45PM - 3:00PM |
ET4.00005: Single and multi-point ion energy distributions in a VHF+RF commercial plasma reactor measured by novel in-wafer ion energy analyzer Barton Lane, Merritt Funk, Lee Chen, Radha Sundararajan, Jianping Zhao A novel, all silicon, minimally perturbing, non-contaminating, in-wafer, 2 and 3 layer ion energy analyzer described elsewhere in this conference is used to measure ion energy distributions for a variety of realistic processing conditions in a commercial VHF + 13.56 MHZ RF reactor with no modifications to its basic geometry or RF delivery system. Spectra with energies as high 1 keV are measured with resolution on the order of 1{\%}. We show data and discuss the splitting of the high energy peaks due to finite ion sheath crossing time effects and how this splitting scales with frequency, power and pressure. We discuss the origin of the charge exchange peaks. We use the identification of atomic and molecular oxygen ion peaks to estimate the resolution of the diagnostic. The effect of VHF in narrowing ion energy distributions and yielding moderate ion energies will be highlighted. Spectra using a multi-point, 2 layer variant of the ion energy analyzer design were obtained at 4 radial locations for a variety of conditions in argon and oxygen plasmas. These spectra quantify center to edge variations and reveal unique spectral features due to pre-existing modifications to the test reactor's upper counter electrode surface. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700