Bulletin of the American Physical Society
72nd Annual Gaseous Electronics Conference
Volume 64, Number 10
Monday–Friday, October 28–November 1 2019; College Station, Texas
Session DT2: Plasma Materials I |
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Chair: Makoto Sekine Room: Century II |
Tuesday, October 29, 2019 10:00AM - 10:15AM |
DT2.00001: Multi-Fluid and PIC Simulation of Ion Energy Distributions through Different Aspect Ratio Holes in Capacitively Coupled Plasma Yao Du, Yuhua Xiao, Steven Shannon, Sang Ki Nam Ion energy distribution function (IEDF) plays a significant role in numerous plasma enhanced manufacturing processes in the semiconductor industry. A common objective in plasma etching is to form high aspect ratio (HAR) hole structures in a substrate. IEDF in both perpendicular and transverse directions contribute to the shape of these structures. Modelling ions travelling through HAR features helps in quantifying etching effect as a function of IEDF and optimizing etching processes. On the other hand, the IEDFs measured after different HAR features contain the information of ions velocities in both perpendicular and transverse directions at the sheath edge. Differentiation of the information with respect to different AR gives an estimate of ions angular distribution function (IADF) at the sheath edge. A low temperature plasma fluid code, Zapdos, is to be used for the global chamber simulation of a HAR process, matching the plasma conditions obtained using other diagnostic probes such as Hairpin probe and Langmuir probe and generating results to be incorporated in the input of a 2D particle-in-cell (PIC) code, XOOPIC. The PIC code is to be used for studying the evolution of the ion population through a HAR feature. [Preview Abstract] |
Tuesday, October 29, 2019 10:15AM - 10:30AM |
DT2.00002: Pattern Dependent Profile Distortion in High Aspect Ratio Plasma Etching of SiO$_{\mathrm{2}}$ and SiO$_{\mathrm{2}}$-Si$_{\mathrm{3}}$N$_{\mathrm{4}}$-SiO$_{\mathrm{2}}$ Stacks Shuo Huang, Sang Ki Nam, Seungbo Shim, Mark J. Kushner Transferring sub-10 nm microelectronics patterns using plasma etching into underlying materials is challenging due to feature distortions such as twisting, tilting and edge roughening. These distortions are attributed charging, polymer deposition and pattern dependencies. Randomness in distortions result from disparities in the fluxes of etching species into adjacent features, exacerbated in high aspect ratio (HAR) features due to conduction limits In this paper, we report on results from computational investigations of feature distortion during plasma etching of symmetric and asymmetric patterns in SiO$_{\mathrm{2}}$ and SiO$_{\mathrm{2}}$-Si$_{\mathrm{3}}$N$_{\mathrm{4}}$-SiO$_{\mathrm{2}}$ (ONO) stacks using the 3-dimensional Monte Carlo Feature Profile Model. Reactive fluxes to the substrate are produced by reactor scale modeling using the HPEM. Feature-to-feature variations mainly result from stochastic variations in energy, angle and sequence of incident species. With symmetric patterns, charging of the surfaces of HAR features results in tilting of features in random directions. With identical bounding features, electrical forces on ions inside features should cancel though statistical variations produce net forces. With asymmetric patterns, charging produces tilting pointing from dense to sparse areas of the pattern due to net horizontal electric fields which deviate ion trajectories. The tilting can be lessened by increasing bias power, which elevates ion energy and decreases etch time, resulting in less charging. [Preview Abstract] |
Tuesday, October 29, 2019 10:30AM - 11:00AM |
DT2.00003: Modeling and controlling of defect generation in electronic devices during plasma etching processes---an optimization methodology of plasma-induced damage Invited Speaker: Koji Eriguchi Tremendous efforts have been devoted to the development of plasma etching processes in order to meet the increasing demand for higher performance of electronic devices. Plasma etching plays an important role in achieving fine patterns, where a plasma---device surface reaction should be atomically controlled. This study comprehensively addresses one of the negative aspects of plasma etching, i.e., ion bombardment damage---plasma-induced physical damage (PPD) [1][2]. Firstly, the typical defect structures and their impacts on the performance of etching process and device designs were briefly reviewed on the basis of experimental observations in combination with molecular dynamics and quantum mechanical calculations [3]. Not only the special profiles but also the energy states of created defects were principal parameters for controlling the PPD in plasma etching processes. An improved PPD range model was proposed, where the ion dose ($D_{\mathrm{ion}})$ dependence of the damaged layer formation was implemented in addition to the energy dependence. Then, the model prediction results were compared with the experimental data recently reported [4]. From the obtained evidences, it was concluded that PPD in plasma etching processes should be designed by taking into account the $D_{\mathrm{ion}}$ dependence. Finally, a methodology---how to control PPD by optimizing plasma etch parameters---was discussed on the basis of the present model prediction results as future perspectives. Since PPD is the intrinsic nature of plasma etching, the process design is defined as an optimization problem under the constraints imposed by plasma and device performance criteria. [1] G. S. Oehrlein, Mater. Sci. Eng. \textbf{B 4}, 441 (1989). [2] K. Eriguchi, J. Phys. D: Appl. Phys. \textbf{50}, 333001 (2017). [3] Y. Yoshikawa and K. Eriguchi, Jpn. J. Appl. Phys. \textbf{57}, 06JD04 (2018). [4] T. Hamano and K. Eriguchi, Jpn. J. Appl. Phys. \textbf{57}, 06JD02 (2018). [Preview Abstract] |
Tuesday, October 29, 2019 11:00AM - 11:15AM |
DT2.00004: Why does an SF$_{\mathrm{6}}$ plasma etch silicon much faster than any other fluorine atom generating plasma? Vincent M Donnelly, Priyanka Arora, Tam Nguyen It has long been known that F atoms are the reactive species responsible for etching of silicon in all fluorine containing plasma. Despite this, SF$_{\mathrm{6}}$ plasmas are widely found to etch silicon up to 100 times faster than the other fluorine-containing plasmas. We have found that this is due to the presence of adsorbed sulfur that catalyzes the fast reaction of F with Si. F atom reaction probabilities are \textasciitilde 30-fold higher in SF$_{\mathrm{6}}$ plasmas compared with values in NF$_{\mathrm{3}}$ plasmas. Addition of only 10{\%} SF$_{\mathrm{6}}$ to an NF$_{\mathrm{3}}$ plasma produced a much higher reaction probability (\textasciitilde 10-fold) than in a pure NF$_{\mathrm{3}}$ plasma. By allowing sulfur in isopropyl alcohol to evaporate on masked Si samples, sulfur could be preferentially deposited in relatively high concentrations in selected regions. When this sample is placed side by side with one not exposed to sulfur, the sulfur-dosed sample etched several times faster at the center of each bead, while sulfur-free surfaces exhibited the expected slower rate. Discrepancies among previous published studies will be resolved. Mechanisms for the catalytic behavior, such as enhanced chemisorption of F and electronic effects caused by S mid-bandgap states in Si, will be discussed. [Preview Abstract] |
Tuesday, October 29, 2019 11:15AM - 11:30AM |
DT2.00005: High-aspect-ratio organic-pattern formation with self-limiting manner by controlling plasma process based on substrate temperature measurement. Makoto Sekine, Yusuke Fukunaga, Takayoshi Tsutsumi, Kenji Ishikawa, Hiroki Kondo, Masaru Hori For further development in electric devices, it is necessary to reduce the pattern deformations, such as bowing, striation and line edge roughness. To solve them, the understanding of etch reactions on the sidewall of organic material patterns is required. We reported that the etch performance of organic materials greatly depends on the temperature. In this study, we report organic pattern etching and trimming by H2/N2 plasma using a precise wafer-temperature control system. A CCP reactor with H2/N2 (75/25 sccm) gas flow was kept at 2.0 Pa. A 100-MHz power for plasma generation and 2-MHz power for wafer biasing were supplied to the upper and the lower electrode, respectively. The bias power was off during the trimming. Wafer temperature was measured every 50 ms by auto correlation type frequency domain low coherence interferometer. Our system controlled the intervals of ON-OFF of the power supplies to maintain the wafer temperature with a range of 3ºC from 100ºC during the process. The organic films were etched off in the first 40 s etching by ion-induced reactions. After the 10 s of over-etching, the trimming process was applied for 300 s. We found that the etching of sidewalls stopped and about 10-nm width patterns were formed with a self-limited manner. This self-limitation possibly confirms that the formation of protective layer against etch species i.e. H atoms. We also investigate this phenomenon by in-situ XPS of blanket films exposed to N and H atoms. [Preview Abstract] |
Tuesday, October 29, 2019 11:30AM - 11:45AM |
DT2.00006: On finding low Global Warming Potential (GWP) precursor for SiO$_{\mathrm{2}}$ etching through plasma radical measurement Chul Hee Cho, SiJun Kim, JangJae Lee, YeongSeok Lee, SangHo Lee, InHo Seong, ShinJae You C$_{\mathrm{4}}$F$_{\mathrm{8}}$, and CF$_{\mathrm{4}}$ are precursor for etching SiO$_{\mathrm{2}}$, but they have high Global Warming Potential (GWP), so many researches to find low GWP precursors were investigated. However, the problem is that if the low GWP precursors were found, SiO$_{\mathrm{2}}$ etching characteristics with those precursors should be researched by SiO$_{\mathrm{2}}$ etching process, so it takes too much time. In this research, we proposed a new mechanism to forecast SiO$_{\mathrm{2}}$ etch rate, and Si/SiO$_{\mathrm{2}}$ selectivity by diagnostics of plasma radical density. The radical diagnostics data shows that C$_{\mathrm{4}}$F$_{\mathrm{9}}$I has similar selectivity and SiO$_{\mathrm{2}}$ etch rate with C$_{\mathrm{4}}$F$_{\mathrm{8}}$, and C$_{\mathrm{6}}$F$_{\mathrm{12}}$O has better selectivity and SiO$_{\mathrm{2}}$ etch rate than C$_{\mathrm{4}}$F$_{\mathrm{8}}$. To verify this mechanism, SiO$_{\mathrm{2}}$ etch data were analyzed by Scanning Electron Microscope (SEM) and it confirmed well with this mechanism. This research contributes plasma diagnostics in etching process. [Preview Abstract] |
Tuesday, October 29, 2019 11:45AM - 12:00PM |
DT2.00007: Student Excellence Award Finalist: Computational study on the formation of Nickel hexafluoroacetylacetonate complexes Ni(hfac)$_{\mathrm{2}}$ on a rough NiO surface during thermal atomic layer etching (ALE) Processes Abdulrahman Basher, Marjan Krstic, Michiro Isobe, Tomoko Ito, Karin Fink, Masato Kiuchi, Kazuhiro Karahashi, Takae Takeuchi, Wolfgang Wenzel, Satoshi Hamaguchi Thermal ALE by the formation of volatile organic metal complexes is expected to establish damageless and atomically controlled metal etching processes for nano-scale devices. For example, hexafluoroacetylacetone (hfacH) as an organic gas has proved its efficiency in etching magnetic metals at an elevated surface temperature. In a previous work, we demonstrated using first-principles quantum mechanical (QM) simulations how hfacH molecules are adsorbed and decomposed on a metallic nickel (Ni) surface while they can be adsorbed without decomposition on an oxidized nickel (NiO) surface. The goal of this study is to show how nickel hexafluoroacetylacetonate Ni(hfac)$_{\mathrm{2}}$ is formed after hfacH molecues are adsorbed on a NiO surface. We have used Gaussian 09 and Turbomole codes to evaluate the interaction of hfacH molecules with flat and non-flat NiO surfaces to understand the conditions on which Ni atoms are removed from the surface by the formation of Ni(hfac)$_{\mathrm{2}}$. [Preview Abstract] |
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