Bulletin of the American Physical Society
71st Annual Gaseous Electronics Conference
Volume 63, Number 10
Monday–Friday, November 5–9, 2018; Portland, Oregon
Session DT4: Basic Plasma Physics Phenomena in Low-temperature Plasmas I |
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Chair: Qi Hua Fan, Michigan State University Room: Oregon Convention Center A107-A109 |
Tuesday, November 6, 2018 8:00AM - 8:30AM |
DT4.00001: The complex physics of pulsed and level-to-level discharges Invited Speaker: Matthew Goeckner While they are widely used, plasmas are not the ``perfect'' processing technology, particularly as critical device dimensions have shrunk. As long as two decades ago, it was understood that there were a number of mechanisms via which plasmas might induce damage on a device. For a multitude of reasons, pulsed and level-to-level plasmas have often been considered the most viable processing technology for overcoming the limitations of continuous wave processing. However, the combination of pulse rate, duty factor, power levels, gas species, flow rate and pressure, provides one with an almost endless free parameter space. This makes finding a set of ``ideal'' parameters difficult at best. For example, the plasma will `extinguish' under some fully pulsed conditions while under other very similar conditions it will not `extinguish'. This leads to very different restart during the plasma on portion of the pulse, `re-ignition' vs `re-energization'. In `re-energization', plasma sheaths will exist prior to the reapplication of power -- while in `re-ignition' the sheaths need to be reestablished. This subtle, yet significant, difference changes how power is initially deposited into the system. Such knowledge is critical in helping the general low-temperature plasma community establish guidelines for optimizing the use of pulsed and level-to-level discharges in industrially relevant processing conditions. In this talk, we will examine what is known about such systems and how that might impact the use of pulsed and level-to-level discharges. This work is supported by the National Science Foundation under Grant No. NSF IIP1338917. In addition, support from the industrial partners to the I/UCRC for Laser and Plasma Advanced Manufacturing, specifically Applied Materials and Lam Research. [Preview Abstract] |
Tuesday, November 6, 2018 8:30AM - 8:45AM |
DT4.00002: Standing Striations in Capacitively Coupled Argon Plasma Vladimir Kolobov, Valery Godyak Plasma stratifications are common in atomic and molecular gases. Moving striations are usually observed in DC discharges of noble gases, whereas standing striations are typically observed in molecular gases in both DC and RF plasmas. The nature of moving striations (ionization waves) is relatively well understood for DC discharges in noble gases [1]. Stratification of plasma in molecular gases is poorly understood. Although standing striations have been observed in capacitively coupled Argon plasma [2], their nature remained unclear. In this presentation we will report experimental observations and computer simulations of standing striations in Argon CCP. Experiments confirmed that standing striations do exists in pure Argon CCP in a long Pyrex tube with internal radius of 1.1 cm, the inter-electrode distance of 30 cm, at frequencies 3.6, 8.4 and 19.0 MHz, in a pressure range between 0.05 and 10 Torr, for a certain range of discharge currents (plasma densities). Comparison of computer simulations with experimental observations helped clarify the nature of these striations. [1] V I Kolobov, Striations in rare gas plasmas, J. Phys. D: Appl. Phys. \textbf{39}, R487 (2006) [2] H C J Mulders, W J M Brok and W Stoffels, Striations in a Low-Pressure RF-Driven Argon Plasma, IEEE Trans. Plasma Sci \textbf{36} 1380 (2008) [Preview Abstract] |
Tuesday, November 6, 2018 8:45AM - 9:00AM |
DT4.00003: Plasma modulation in a high-intensity acoustic standing wave field Bocong Zheng, Thomas Schuelke, Qi Hua Fan Modulating the spatiotemporal distributions of plasmas is scientifically interesting and practically attractive to promote the plasma-materials interactions. However, the long range electromagnetic forces generated by the motions of charged particles in a plasma restrict its response to the external influences. Subsequently the distributions of the excited species are little affected due to their short lifetimes outside the discharge region. This work presents a concept of using acoustic standing waves to modulate plasmas. The simulation results predict a strong coupling between acoustic waves and plasmas. The plasmas oscillate with the acoustic standing waves over a significant scale, which is difficult to achieve by other reported methods. The maximum/minimum ratio of the excited species fluxes reaches 200{\%}. This study initiates the effort to understand the mechanisms and characteristics of plasma discharges in a high-intensity acoustic standing wave field. Using acoustic waves to modulate plasmas has the potential to create many new applications and promote plasma-materials interactions. [Preview Abstract] |
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