Bulletin of the American Physical Society
69th Annual Gaseous Electronics Conference
Volume 61, Number 9
Monday–Friday, October 10–14, 2016; Bochum, Germany
Session NW2: Plasma EtchingFocus
|
Hide Abstracts |
Chair: Pascal Chabert, Ecole Polytechnique Room: 2a |
Wednesday, October 12, 2016 3:00PM - 3:30PM |
NW2.00001: Layer by layer etching of LaAlSiO$_{\mathrm{x}}$ Invited Speaker: Hisataka Hayashi In order to fabricate a gate transistor with high-k oxide materials, removal of high-k oxide films after gate electrode etching is necessary for the formation of ohmic contacts on source and drain regions. It is crucial that the removal process of high-k oxide film by dry etching is highly selective to and low in damage to the Si substrate in order to avoid the degradation of device performances. Sasaki et al. have achieved a high LaAlSiO$_{\mathrm{x}}$-to-Si selectivity of 6.7 using C$_{\mathrm{4}}$F$_{\mathrm{8}}$/Ar/H$_{\mathrm{2}}$ plasma [1]. In the LaAlSiO$_{\mathrm{x}}$ etching process using C$_{\mathrm{4}}$F$_{\mathrm{8}}$/Ar/H$_{\mathrm{2}}$ plasma, H$_{\mathrm{2}}$ plays a role in breaking the metal-oxygen bond to enhance etching of LaAlSiO$_{\mathrm{x}}$ [1]. Based on this result, the process was decomposed into two steps: a surface modification step using H$_{\mathrm{2}}$ plasma to break the metal-oxygen bond, and a removal step using C$_{\mathrm{4}}$F$_{\mathrm{8}}$/Ar plasma. A sequential layer by layer etching could realize low damage etching, similar to atomic layer etching. Therefore, a sequential LaAlSiO$_{\mathrm{x}}$ etching process using a H$_{\mathrm{2}}$ surface modification step followed by a removal step using C$_{\mathrm{4}}$F$_{\mathrm{8}}$/Ar plasma is investigated. Experiments were carried out on 300 mm diameter wafers using the 100/13.56 MHz dual frequency superimposed capacitively coupled plasma reactor. The etching gases were H$_{\mathrm{2}}$ and C$_{\mathrm{4}}$F$_{\mathrm{8}}$/Ar for each step, respectively. Plasma process conditions were 100 MHz power of 1000 W (plasma generation), 13.56MHz power varied from 0 W to 300W (ion energy control). The substrate temperature was 40 °C. 15nm thick LaAlSiO$_{\mathrm{x}}$ blanket film was used for evaluation of the etched amount. Film thickness was measured by X-ray fluorescent analysis thickness meter before and after plasma exposure. The etched amount of LaAlSiO$_{\mathrm{x}}$ by the C$_{\mathrm{4}}$F$_{\mathrm{8}}$/Ar plasma step doubled with H$_{\mathrm{2}}$ modification. It is confirmed that when the C$_{\mathrm{4}}$F$_{\mathrm{8}}$/Ar plasma treatment time is sufficient to remove the surface modification layer, a self-limiting reaction is realized. Furthermore, it is confirmed that the etched amount per step can be controlled by control of the ion energy of H$_{\mathrm{2}}$ plasma. [1] T. Sasaki, K. Matsuda, M. Omura, I. Sakai, and H. Hayashi: Jpn. J. Appl. Phys. 54 (2015) 06GB03. [Preview Abstract] |
Wednesday, October 12, 2016 3:30PM - 3:45PM |
NW2.00002: Variation in photon-induced interface defects due to transient behavior of pulse modulated inductively coupled plasma Y. Miyoshi, M. Fukasawa, K. Nagahata, T. Tatsumi, Z. Liu, Y. Zhang, A. Ando, K. Takeda, K. Ishikawa, M. Sekine, M. Hori It is important to reduce photon-induced interface defects generated in the plasma process for electronic device performance. In this study, we investigated the effect of transient behavior of a pulse-modulated ICP on these defects. The C-V analysis revealed the pulse frequency (0.5 -- 20 KHz) dependence of the interface state density ($D_{it})$ in the SiN/Si interface whose variation was proportional to the UV fluence from discharge. By increasing the frequency, the $D_{it}$ increased, was a maximum at 10 kHz, and then decreased. The $D_{it}$ was lower than that in the CW at the lower frequencies, but was higher at the higher frequencies (\textgreater 10 KHz). The transient behavior of the pulse plasma is presumed to be the cause of this property. The time resolved OES revealed that the optical emission overshoot appeared after ignition due to the variation in the electron temperature and number density in the early ON phase. The number of overshoots increased with increasing frequency. Therefore, the UV fluence and the $D_{it}$ were increased. At the higher frequencies, the variation in the electron temperature and number density were suppressed due to the stepwise ionization via long-lived metastable species. Therefore the overshoot amplitude decreased. As a result, the UV fluence and the $D_{it}$ were decreased. The results revealed that control of the transient behavior of pulse-modulated plasma is important to reduce photon-induced defects in the plasma process. [Preview Abstract] |
Wednesday, October 12, 2016 3:45PM - 4:00PM |
NW2.00003: Computer modelling of cryogenic etching in SF6/O2/SiF4 and CxFy inductively coupled plasmas Quan-Zhi Zhang, Annemie Bogaerts Plasma etching plays a more and more important role in microchip fabrication, due to its anisotropy during surface processing. However, current state-of-the-art plasma processing faces significant challenges when going beyond 14 nm features, such as plasma induced damage. A novel process with limited plasma damage is cryogenic etching of low-k material with SF6/O2/SiF4 and CxFy plasmas. In this work, a hybrid Monte Carlo-fluid model is employed to describe the plasma behavior, including the species and temperature distributions and power deposition, for SF6/O2/SiF4 and CxFy gas mixtures, applied for cryogenic etching under various gas ratios and operating conditions, which can help to establish an optimal process window. [Preview Abstract] |
Wednesday, October 12, 2016 4:00PM - 4:15PM |
NW2.00004: Temporal evolution of as-developed line and space photoresist profiles during etch. Barton Lane, Peter Ventzek, Alok Ranjan, Vinayak Rastogi, Jun Yoshikawa We discuss here the etching of the as-developed photoresist pattern of lines and spaces. By examining time partition studies of the etching process, we show that the evolution of a photoresist profile has several distinct phases. These are caused by the material properties of the as-developed photoresist polymer, the change in these material properties due to the plasma interaction with the photoresist and to geometric effects caused by the interaction of faceting profiles and finite line widths. By exploiting sheath bending to direct ions into the sidewall of the lines we examine the etch characteristics of the photoresist side walls. Further by comparing wide to narrow lines, and nested to iso lines, we deconvolve the effects of line geometry and the material properties of the photoresist. For these studies pure argon and mixed argon/fluorocarbon chemistries are used. [Preview Abstract] |
Wednesday, October 12, 2016 4:15PM - 4:30PM |
NW2.00005: Origin of plasma-induced surface roughening and ripple formation during plasma etching Kouichi Ono, Nobuya Nakazaki, Hirotaka Tsuda, Yoshinori Takao, Koji Eriguchi Atomic- or nanometer-scale roughness on feature surfaces has become an important issue to be resolved in the fabrication of nanoscale devices. Control of the surface roughening during plasma etching might be possible, given a deeper understanding of plasma-surface interactions concerned with it. We have investigated the origin of plasma-induced surface roughening and ripple formation during plasma etching of silicon in chlorine, based on a comparison of experiments with Monte Carlo-based atomic-scale cellular model simulations for surface feature evolution and classical molecular dynamics simulations for etch fundamentals. The experiments showed two modes of surface roughening which occur depending on ion incident energy: one is the roughening mode, exhibiting an almost linear increase of roughness with time; the other is the smoothing mode, retaining a smooth surface during etching, and smoothing of initially rough surfaces. The experiments also demonstrated the ripple formation in response to ion incidence angle onto substrate surfaces. These results are interpreted in terms of effects of ion reflection from microscopically roughened surfaces on incidence, which depend on incident ion species. [Preview Abstract] |
Wednesday, October 12, 2016 4:30PM - 4:45PM |
NW2.00006: Tailored Voltage Waveforms in an SF6/O2 discharge: slope asymmetry and its effect on surface nanotexturing of silicon G. Fischer, E. Drahi, G. Poulain, B. Bruneau, E. V. Johnson The nanotexturing of the surface of a crystalline silicon (c-Si) wafer for improved photovoltaic performance can be achieved through the use of a SF6/O2 capacitively coupled reactive ion etching plasma. In this study, we attempt to modify the texturing conditions by taking advantage of slope asymmetries of Tailored Voltage Waveform (TVW) excitation. We show that TVW shapes resembling ``sawtooths'', presenting a large slope asymmetry, induce high ionization asymmetries in the discharge, and that the dominance of this effect strongly depends on both gas mixture and pressure. These asymmetries have been previously observed in other electronegative gas and are due to differing plasma sheath dynamics at powered and grounded electrode in a discharge operating in drift-ambipolar mode. The texturing of c-Si in SF6/O2 occurs through competing mechanisms, including etching by fluorine radicals and in-situ deposition of micro-masking species. The relative fluxes of etching and passivating species are expected to be strongly varied due to the plasma asymmetry. Morphological and optical characterization of textured c-Si surfaces will give more insight into both the plasma properties and the mechanisms involved in dry nanotexturing. [Preview Abstract] |
Wednesday, October 12, 2016 4:45PM - 5:00PM |
NW2.00007: WITHDRAWN 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