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 ET2: Modeling of Plasma Etching |
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Chair: Douglas Keil, Lam Research Room: State C |
Tuesday, November 4, 2014 1:30PM - 1:45PM |
ET2.00001: Profile Control Using Pulsed Power During Plasma Etching in Capacitively Coupled Plasmas Sang-Heon Song, Mark J. Kushner Profile control during plasma etching is becoming more challenging as feature sizes decrease. Pulse power in capacitively coupled plasmas (CCPs) is being developed as a means to provide more flexibility in reactive fluxes and ion energy and angular distributions (IEADs) to achieve this profile control. In this talk, we discuss results for profile control in etching of dielectrics from modeling studies of pulsed 2-frequency CCPs sustained in Ar/CF$_{\mathrm{4}}$/O$_{\mathrm{2}}$ mixtures. The simulators include a 2-d plasma hydrodynamics model to produce reactive fluxes and IEADs, and a 2-d Monte Carlo based profile model. IEADs are produced in three formats in pulsed CCPs -- when both the low frequency (LF) and high frequency (HF) are on, when only the LF or HF are on, and when both the LF and HF are off. The resulting IEADs are further modified by duty cycle and the size of the blocking capacitor. We found that the side-wall slope of high-aspect-ratio (HAR) features can be controlled by combinations of pulsing the LF and/or HF, and duty cycle. In addition to the feature receiving different IEADs, the ratio of polymerizing to ion fluxes which contributes to control of sidewall slope is also sensitive to these process variables. [Preview Abstract] |
Tuesday, November 4, 2014 1:45PM - 2:00PM |
ET2.00002: Insights into Plasma Etch Profile Evolution with 3D Profile Simulation Saravanapriyan Sriraman, Alex Paterson, Yiting Zhang, Mark Kushner Plasma etching is critical for pattern transfer in microelectronics fabrication. For planar devices, efforts in 2D etch profile simulations were sufficient to understand critical etch process mechanisms. In contrast, to understand the complex mechanisms in etching 3D structures of current technology nodes such as FinFETs, 2D profile simulators are inadequate. In this paper, we report on development of a 3D profile simulation platform, the Monte Carlo Feature Profile Model (MCFPM-3D). The MCFPM-3D builds upon the 2D MCFPM platform that includes aspects such as mixing, implantation, and photon assisted processes and addresses reaction mechanisms in surface etching, sputtering, and deposition to predict profile evolution. Model inputs include fluxes of species from plasma derived from the Hybrid Plasma Equipment Model (HPEM). Test cases of Si/SiO$_{\mathrm{2}}$ etching in Ar/Cl$_{\mathrm{2}}$ and Ar/CF$_{\mathrm{4}}$/O$_{\mathrm{2}}$ plasmas for representative 2D/3D feature topographies are considered and phenomena such as selectivity and aspect ratio dependent etching will be discussed. [Preview Abstract] |
Tuesday, November 4, 2014 2:00PM - 2:15PM |
ET2.00003: Multi Time-Step Feature Scale Simulations with FPS3D Paul Moroz, Daniel Moroz Most modern materials processing recipes include many time-steps, each one utilizing different chemistry and plasma parameters, resulting in different composition of fluxes coming to the wafer and different energy and angular distributions of incoming species. The FPS3D feature scale simulator [1-2] is capable of handling varied and complex cases due to its structure and numerical techniques. For this presentation, we selected a set of simulations for processes which are dramatically different from each other. One is the Bosch process, which is a high etch-rate (in the range of 1000 A/s or more) etching for features with dimensions in the range of 1 micron to 100s of microns. The other is the ALE (atomic layer etch), in which etching is done by a single atomic layer per cycle, allowing maximal processing accuracy but with etch rate in the range of one to a few A/min. Both of these processes involve multiple cycles through the etching and passivation (or deposition) steps. FPS3D is well suited for those tasks as it allows consideration of large fluxes and large dimensions of the Bosch process as well as the delicate ALE processing on an atomic level. Results of both 2D and 3D modeling will be presented and the details of the processes will be discussed.\\[4pt] [1] P. Moroz, IEEE Trans. on Plasma Science, \textbf{39} (11) 2804 (2011).\\[0pt] [2] P. Moroz, D. J. Moroz, ECS Transactions, \textbf{50} (46) 61 (2013). [Preview Abstract] |
Tuesday, November 4, 2014 2:15PM - 2:45PM |
ET2.00004: Modeling of plasma-induced damage during the etching of ultimately-scaled transistors in ULSI circuits---A model prediction of damage in three dimensional structures Invited Speaker: Koji Eriguchi An increasing demand for high performance field-effect transistors (FETs) leads to the aggressive critical dimension shrinkage and the currently-emerging three dimensional (3D) geometry [1]. Plasma processing is widely used also in the scaled- and 3D-FET (e.g. FinFET) manufacturing, where precise control of the reaction on the (sidewall) surfaces is a prime issue. In this study, damage creation mechanism during plasma etching---plasma-induced physical damage (PPD)---was investigated in such structures on the basis of the PPD range theory [2], atomistic simulations, and experiments. Compared to PPD in planar FETs (e.g. Si recess [2][3]), a stochastic modeling and atomistic simulations predicted that, during etching of ``fins'' in a 3D-FET, the following two mechanisms are responsible for damage creation in addition to an ion impact on the sidewall at an oblique incident angle: 1) incoming ions penetrate into the Si substrate and undergo scattering by Si atoms in the lateral direction even if the incident angle is normal to the surface [4] and 2) some of Si atoms and ions sputtered at the surface being etched impact on the sidewall with energies sufficient to break Si-Si bonds. These straggling and sputtering processes are stochastic and fundamental, thus, result in 3D structure damage (``fin-damage''). The ``fin-damage'' induced by straggling was modeled by the PPD range theory. Molecular dynamics simulations clarified the mechanisms under the various plasma conditions. Quantum mechanical calculations showed that created defect structures play the role of a carrier trap site, which was experimentally verified by an electrical measurement. Since they are intrinsic natures of etching, both straggling and sputtering noted here should be implemented to design a low-damage etching process. \\[4pt] [1] I. Ferain et al., Nature 479, 310 (2011).\\[0pt] [2] K. Eriguchi et al., Jpn. J. Appl. Phys. 49, 056203 (2010).\\[0pt] [3] S. A. Vitale and B. A. Smith, J. Vac. Sci. Technol. B21, 2205 (2003).\\[0pt] [4] K. Eriguchi et al., Jpn. J. Appl. Phys. 53, 03DE02 (2014). [Preview Abstract] |
Tuesday, November 4, 2014 2:45PM - 3:00PM |
ET2.00005: Molecular dynamics analysis of silicon chloride ion incidence during Si etching in Cl-based plasmas: Effects of ion incident energy, angle, and neutral radical-to-ion flux ratio Nobuya Nakazaki, Koji Eriguchi, Kouichi Ono Profile anomalies and surface roughness are critical issues to be resolved in plasma etching of nanometer-scale microelectronic devices, which in turn requires a better understanding of the effects of ion incident energy and angle on surface reaction kinetics. This paper presents a classical molecular dynamics (MD) simulation of Si(100) etching by energetic Cl$_{x}^{+}$ ($x=$ 1--2) and SiCl$_{x}^{+}$ ($x=$ 0--4) ion beams with different incident energies $E_{\mathrm{i}}=$ 20--500 eV and angles $\theta_{\mathrm{i}}=$ 0--85$^{\circ}$, with and without low-energy neutral Cl radicals (neutral-to-ion flux ratios $\Gamma _{\mathrm{n}}$/$\Gamma_{\mathrm{i}}=$ 0 and 100). An improved Stillinger-Weber interatomic potential was used for the Si/Cl system. Numerical results indicated that in Cl$^{+}$, Cl$_{2}^{+}$, SiCl$_{3}^{+}$, and SiCl$_{4}^{+}$ incidences for $\theta _{\mathrm{i}}=$ 0$^{\circ}$ and $\Gamma_{\mathrm{n}}$/$\Gamma _{\mathrm{i}}=$ 0, the etching occurs in the whole $E_{\mathrm{i}}$ range investigated; on the other hand, in SiCl$^{+}$ and SiCl$_{2}^{+}$ incidences, the deposition occurs at low $E_{\mathrm{i}}$\textless 300 and 150 eV, respectively, while the etching occurs at further increased $E_{\mathrm{i}}$ [1]. For SiCl$^{+}$ and SiCl$_{2}^{+}$, the transition energies from deposition and etching become lowered for $\Gamma_{\mathrm{n}}$/$\Gamma _{\mathrm{i}}=$ 100. Numerical results further indicated that in the SiCl$^{+}$ incidence for $\Gamma_{\mathrm{n}}$/$\Gamma _{\mathrm{i}}=$ 0, the etching occurs in the whole $\theta _{\mathrm{i}}$ range investigated for $E_{\mathrm{i}}\ge $ 300 eV; on the other hand, for $E_{\mathrm{i}}=$ 100 and 150 eV, the deposition occurs at low $\theta_{\mathrm{i}}$\textless 60$^{\circ}$ and 40$^{\circ}$, respectively, while the etching occurs at further increased $\theta_{\mathrm{i}}$; in addition, for $E_{\mathrm{i}}\le $ 50 eV, the deposition occurs in the whole $\theta_{\mathrm{i}}$ range investigated.\\[4pt] [1] N. Nakazaki \textit{et al}., Jpn. J. Appl. Phys. \textbf{53}, 056201 (2014). [Preview Abstract] |
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