Bulletin of the American Physical Society
65th Annual Gaseous Electronics Conference
Volume 57, Number 8
Monday–Friday, October 22–26, 2012; Austin, Texas
Session SR2: Plasma Etching II |
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Chair: Ankur Agarwall, Applied Materials, Inc. Room: Classroom 203 |
Thursday, October 25, 2012 3:30PM - 4:00PM |
SR2.00001: Physics and chemistry of complex oxide etching and redeposition control Invited Speaker: Jo\"elle Margot Since its introduction in the 1970s, plasma etching has become the universal method for fine-line pattern transfer onto thin films and is anticipated to remain so in foreseeable future. Despite many success stories, plasma etching processes fail to meet the needs for several of the newest materials involved in advanced devices for photonic, electronic and RF applications like ferroelectrics, electro-optic materials, high-k dielectrics, giant magnetoresistance materials and unconventional conductors. In this context, the work achieved over the last decade on the etching of multicomponent oxides thin films such as barium strontium titanate (BST), strontium titanate (STO) and niobate of calcium and barium (CBN) will be reviewed. These materials present a low reactivity with usual etching gases such as fluorinated and chlorinated gases, their etching is mainly governed by ion sputtering and reactive gases sometimes interact with surface materials to form compounds that inhibit etching. The etching of platinum will also be presented as an example of unconventional conductor materials for which severe redeposition limits the achievable etching quality. Finally, it will be shown how simulation can help to understand the etching mechanisms and to define avenues for higher quality patterning. [Preview Abstract] |
Thursday, October 25, 2012 4:00PM - 4:15PM |
SR2.00002: A complete simulation of InP etching by Cl2/N2/Ar plasma mixture Romain Chanson, Ahmed Rhallabi, Marie Claude Fernandez, Christophe Cardinaud Deep anisotropic plasma etching of InP is an indispensable tool for the fabrication of a large variety of integrated optical devices. In this context, a 2D Monte Carlo etching model of InP by a Cl2/Ar/N2 plasma discharge coupled to a global kinetic plasma model and a sheath model have been developed. It allows the prediction of the geometrical and chemical profile of trenches etched through the mask versus the operating conditions. The plasma kinetic model is performed to quantify the reactive species densities and fluxes such as those of Cl, N and positive ions. The latter are introduced as the input parameters in the etching model. Under Cl2/Ar plasma mixture, the mechanism of the development of bowing defect is mainly attributed to the chemical etching of the adsorbed sites InClx. The impact of nitrogen addition into the Cl2/Ar gas mixture is studied. Both the simulations and the experiments show the role of the nitrogen on the disappearance of the bowing defect. This is attributed to the passivated layer due to the formation of InClxNy species. For a moderate nitrogen proportion, the passivated layer is mainly composed of InNCl2 and InNCl sites at the top of the InP etched trenches while at the bottom, the passivated layer is mainly composed by InN sites. [Preview Abstract] |
Thursday, October 25, 2012 4:15PM - 4:45PM |
SR2.00003: Plasma induced UV/VUV damage during Si and GaN device fabrication Invited Speaker: Tetsuya Tatsumi Plasma induced damages (PID) on semiconductor devices have been widely reported. Materials and the interface between stacked materials can be degraded by ions and photons during plasma processes. In this report, I focus on the effect of ultraviolet (UV) and vacuum ultraviolet (VUV) radiation on various devices. In the fabrication of Si-CMOS devices, high-density plasmas are used for dry etching. The light from plasma is absorbed by the materials when its energy is greater than the band gap (Eg). For example, the Eg of the gate SiO2 is about 8.8 eV; consequently the plasma emissions with wavelengths lower than 150 nm are absorbed by SiO2. These VUV lights degrade the surface structure of SiO2 and increase its wet etch rate [1]. SiOCH and ArF photo resist have been used to realize high-speed devices with low power consumption. These materials have a very weak bond, so there are sometimes problems such as increased dielectric constant in SiOCH or a roughening or wiggling of ArF resist caused by UV/VUV [2]. Plasma emission can also affect the electrical and/or optical properties of devices. I investigated the effect of radiation on the interface-trap density ($D_{it})$ of a SiN/Si structure [3]. When photons in the UV region (200--300 nm) were irradiated, the $D_{it}$ increased and a negative charge was generated in the interface. This indicates that VUV/UV radiation transmitting through the upper dielectrics causes the electrical characteristics of underlying devices to fluctuate. GaN-based semiconductors are used for optoelectronic device applications, so I also investigated the PID of a GaN/InGaN/GaN stacked structure. The samples were exposed to Cl2 plasma emission and analyzed by using photoluminescence (PL). PL intensity decreased when the plasma emission was irradiated. UV radiation ($<$360 nm) affects damage formation at the InGaN active layer [4]. Monitoring VUV/UV and understanding its effect on surface eactions, film damage, and electrical and/or optical performance are indispensable to fabricate advanced devices.\\[4pt] [1] T. Tatsumi \textit{et} \textit{al}., Jpn. J. Appl. Phys., 33 (1994) 2175. \\[0pt] [2] S. Uchida \textit{et} \textit{al}., J. Appl. Phys., 103 (2008) 073303. \\[0pt] [3] M. Fukasawa \textit{et} \textit{al}., Jpn. J. Appl. Phys., 51 (2012) 026201. \\[0pt] [4] M. Minami, \textit{et al}., Jpn. J. Appl. Phys 50 (2011) 08JE03 [Preview Abstract] |
Thursday, October 25, 2012 4:45PM - 5:00PM |
SR2.00004: Role of Photons, Ion Implantation and Mixing in Sub-threshold Selective Etching of Si Juline Shoeb, Saravanapriyan Sriraman, Tom Kamp, Alex Paterson As device sizes shrink, control of selectivity and damage during plasma etching becomes important. Recent literature reports the role of photons in the cleaving of surface and sub-surface Si-Si bonds which may initiate Si etching by radicals, even below the threshold energies needed for ion-assisted etch.\footnote{H. Shin, W. Zhu, V. M. Donnelly, and D. J. Economou, J. Vac. Sci. Technol. A \textbf{30(2)}, 021306 (2012).} Simultaneous effects of photons and ion~penetration can degrade the selectivity. Photon assisted Si etching in below-threshold ion energies in Cl$_{2}$ plasmas reported 4-10 nm/Min. etch rate.\footnote{Ibid.} We investigated the effects of photons in sub-threshold etching of Si in HBr/He/O$_{2}$ plasmas. As photons with wavelengths $<$170 nm have enough energy to cleave Si-Si bonds, we concentrated on 58.4 nm photons emitting from He(2 $^{1}$p) and 130nm photons emitted by O(3s) which can penetrate $\sim $10nm intoe Si.\footnote{J. R. Woodworth, M. E. Riley, V. A. Amatucci, T. W. Hamilton, and B. P. Aragon, J. Vac. Sci. Technol. A \textbf{19}, 45 (2001).} This paper will discuss the role of photons and mixing in silicon-dioxide/silicon etching using modeling {\&} simulation, experiments and diagnostics. [Preview Abstract] |
Thursday, October 25, 2012 5:00PM - 5:15PM |
SR2.00005: Plasma damage and restoration of a spin-on organic ultra low-k material (k=2.3) Mikolaj Lukaszewicz, Jean-Francois de Marneffe, Christopher J. Wilson, Liping Zhang, Hsin-Ying Peng, Patrick Verdonck, Mikhail Baklanov As interconnect dielectrics, spin-on polymers might offer some advantages over OSG materials. In particular, a lower k-value is possible with less porosity, smaller pore size. They also have greater resistance to plasma damage due to their mono-component nature. However, some chemical modifications during the plasma exposure cannot be avoided. In this work, we study the changes caused by a N$_{2}$-H$_{2}$-C$_{2}$H$_{4}$ CCP discharge used for damascene patterning, on a spin-on k=2.3 organic low-k material. It is shown that this plasma forms amine and ester groups, leading to hydrophilization and k-value degradation. Several restoration treatments are studied on blanket wafers, trying to restore the chemical composition, minimize the k-value and hydrophilization. Those treatments include exposure to in-situ He-H$_{2}$ discharge, high temperature He-H$_{2}$ afterglow and combinations thereof, low- and high-temperature VUV treatments. It is found that the best k-value gain is around 50{\%}, and the most promising repair treatment results from the short exposure to a combination of low temperature in-situ He-H$_{2}$ discharge and high temperature He-H$_{2}$ afterglow. Applying such restoration process to an array of 30nm trenches, the integrated k-value showed a gain of 13{\%} in RC constant, indicating efficient restoration to pristine k-value, although the chemical composition was not completely restored in all evaluated conditions. [Preview Abstract] |
Thursday, October 25, 2012 5:15PM - 5:30PM |
SR2.00006: Controlling Ion and UV/VUV Photon Fluxes in Pulsed Low Pressure Plasmas for Materials Processing Peng Tian, Mark J. Kushner UV/VUV photon fluxes in plasma materials processing have a variety of effects ranging from damaging to synergistic. To optimize these processes, it is desirable to have separate control over the fluxes of ions and photons, or at least be able to control their relative fluxes or overlap in time. Pulsed plasmas may provide such control as the rates at which ion and photon fluxes respond to the pulse power deposition are different. Results from a computational investigation of pulsed plasmas will be discussed to determine methods to control the ratio of ion to photon fluxes. Simulations were performed using a 2-dimensional plasma hydrodynamics model which addresses radiation transport using a Monte Carlo Simulation. Radiation transport is frequency resolved using partial-frequency-redistribution algorithms. Results for low pressure (10s of mTorr) inductively and capacitively coupled plasmas in Ar/Cl$_{2}$ mixtures will be discussed while varying duty cycle, reactor geometry, gas mixture and pressure. We found that the time averaged ratio of VUV photon-to-ion fluxes in ICPs can be controlled with duty cycle of the pulsed power. Even with radiation trapping, photon fluxes tend to follow the power pulse whereas due to their finite response times, fluxes of ions tend to average the power pulse. Due to the overshoot in electron temperature that occurs at the start of low-duty-cycle pulses, disproportionately large photon fluxes (compared to ion fluxes) can be generated. [Preview Abstract] |
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