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Title: Effects of in situ N{sub 2} plasma treatment on etch of HfO{sub 2} in inductively coupled Cl{sub 2}/N{sub 2} plasmas

Abstract

The etch selectivity of HfO{sub 2} to Si reported to date is poor. To improve the selectivity, one needs to either increase the etch rate of HfO{sub 2} or decrease the etch rate of Si. In this work, the authors investigate the etch selectivity of HfO{sub 2} in Cl{sub 2}/N{sub 2} plasmas. In particular, the effects of in situ N{sub 2} plasma treatment of HfO{sub 2} and Si were investigated. The silicon substrate was exposed to nitrogen plasma and was nitrided, which was confirmed by x-ray photoelectron spectroscopy. The nitrided Si etching was suppressed in Cl{sub 2}/N{sub 2} plasmas. The effectiveness of nitridation was studied with varying the plasma power, bias power, pressure, and N{sub 2} plasma exposure time. The results show that the etch resistance increased with increased power and decreased pressure. A minimum exposure time was required to obtain etch resistant property. The applied bias power increased the etch rate of Si substrate, so it should not be used during N{sub 2} plasma treatment. Fortunately, the etch rate of HfO{sub 2} was increased by the nitridation process. Therefore, HfO{sub 2}/Si selectivity can be improved by nitridation and became higher than 5 under proper exposure condition.

Authors:
; ; ; ; ; ;  [1];  [2]
  1. Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30043, Taiwan (China)
  2. (China)
Publication Date:
OSTI Identifier:
20979374
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films; Journal Volume: 25; Journal Issue: 3; Other Information: DOI: 10.1116/1.2731361; (c) 2007 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CHLORINE; DIELECTRIC MATERIALS; ETCHING; HAFNIUM OXIDES; NITRIDATION; NITROGEN; PLASMA; SEMICONDUCTOR MATERIALS; SILICON; SUBSTRATES; THIN FILMS; X-RAY PHOTOELECTRON SPECTROSCOPY

Citation Formats

Lin Chaung, Leou, K.-C., Fan, Y.-C., Li, T.-C., Chang, K.-H., Lee, L.-S., Tzeng, P.-J., and Electronic Research and Service Organization, Industrial Technology Research Institute, Hsinchu 30043, Taiwan. Effects of in situ N{sub 2} plasma treatment on etch of HfO{sub 2} in inductively coupled Cl{sub 2}/N{sub 2} plasmas. United States: N. p., 2007. Web. doi:10.1116/1.2731361.
Lin Chaung, Leou, K.-C., Fan, Y.-C., Li, T.-C., Chang, K.-H., Lee, L.-S., Tzeng, P.-J., & Electronic Research and Service Organization, Industrial Technology Research Institute, Hsinchu 30043, Taiwan. Effects of in situ N{sub 2} plasma treatment on etch of HfO{sub 2} in inductively coupled Cl{sub 2}/N{sub 2} plasmas. United States. doi:10.1116/1.2731361.
Lin Chaung, Leou, K.-C., Fan, Y.-C., Li, T.-C., Chang, K.-H., Lee, L.-S., Tzeng, P.-J., and Electronic Research and Service Organization, Industrial Technology Research Institute, Hsinchu 30043, Taiwan. Tue . "Effects of in situ N{sub 2} plasma treatment on etch of HfO{sub 2} in inductively coupled Cl{sub 2}/N{sub 2} plasmas". United States. doi:10.1116/1.2731361.
@article{osti_20979374,
title = {Effects of in situ N{sub 2} plasma treatment on etch of HfO{sub 2} in inductively coupled Cl{sub 2}/N{sub 2} plasmas},
author = {Lin Chaung and Leou, K.-C. and Fan, Y.-C. and Li, T.-C. and Chang, K.-H. and Lee, L.-S. and Tzeng, P.-J. and Electronic Research and Service Organization, Industrial Technology Research Institute, Hsinchu 30043, Taiwan},
abstractNote = {The etch selectivity of HfO{sub 2} to Si reported to date is poor. To improve the selectivity, one needs to either increase the etch rate of HfO{sub 2} or decrease the etch rate of Si. In this work, the authors investigate the etch selectivity of HfO{sub 2} in Cl{sub 2}/N{sub 2} plasmas. In particular, the effects of in situ N{sub 2} plasma treatment of HfO{sub 2} and Si were investigated. The silicon substrate was exposed to nitrogen plasma and was nitrided, which was confirmed by x-ray photoelectron spectroscopy. The nitrided Si etching was suppressed in Cl{sub 2}/N{sub 2} plasmas. The effectiveness of nitridation was studied with varying the plasma power, bias power, pressure, and N{sub 2} plasma exposure time. The results show that the etch resistance increased with increased power and decreased pressure. A minimum exposure time was required to obtain etch resistant property. The applied bias power increased the etch rate of Si substrate, so it should not be used during N{sub 2} plasma treatment. Fortunately, the etch rate of HfO{sub 2} was increased by the nitridation process. Therefore, HfO{sub 2}/Si selectivity can be improved by nitridation and became higher than 5 under proper exposure condition.},
doi = {10.1116/1.2731361},
journal = {Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films},
number = 3,
volume = 25,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • The etch rate of HfO{sub 2} etch processing has been feedback controlled in inductively coupled Cl{sub 2}/N{sub 2}/Ar plasmas. The ion current and the root mean square rf voltage on the wafer stage, which are measured using a commercial impedance meter connected to the wafer stage, are chosen as controlled variables because the positive-ion flux and ion energy incident upon the wafer surface are the key factors that determine the etch rate. Two 13.56 MHz rf generators are used to adjust the inductively coupled plasma power and bias power which control ion density and ion energy, respectively. The adopted HfO{submore » 2} etch processing used rather low rf voltage. The ion-current value obtained by the power/voltage method is underestimated, so the neural-network model was developed to assist estimating the correct ion-current value. The experimental results show that the etch-rate variation of the closed-loop control is smaller than that of the open-loop control. However, the first wafer effect cannot be eliminated using closed-loop control and thus to achieve a constant etch rate, the chamber-conditioning procedure is required in this etch processing.« less
  • The analysis of the ZrO{sub 2} thin film etch mechanism in the Cl{sub 2}/Ar, Cl{sub 2}/He, and Cl{sub 2}/N{sub 2} inductively coupled plasmas was carried out. It was found that an increase in additive gas fraction at fixed gas pressure and input power results in increasing ZrO{sub 2} etch rate, which changes from 1.2 nm/min for pure Cl{sub 2} plasma up to 3.15, 2.40, and 2.31 nm/min for 80% Ar, N{sub 2}, and He, respectively. Langmuir probe diagnostics and zero-dimensional plasma modeling indicated that both plasma parameters and active species kinetics are noticeably influenced by the initial composition of themore » gas mixture. From the model-based analysis of etch kinetics, it was shown that, similarly to the case of BCl{sub 3}-based plasmas, the behavior of the ZrO{sub 2} etch rate corresponds to the ion-flux-limited etch regime.« less
  • The etching properties of tantalum carbide (TaC) in inductively coupled Ar/HBr/Cl{sub 2} plasmas are investigated in this article. Both etching experiments on patterned and blanket wafers and an integrated plasma equipment-feature scale computational model are utilized in this investigation. Results show that TaC etching is adequately described by the classical reactive ion etching mechanism, whereby etching occurs due to the synergistic effect of Cl or Br atoms and energetic ions. TaC etches faster in the presence of Cl relative to Br. The TaC etch rate is small in gas mixtures containing 5% of Cl{sub 2} or HBr and 95% ofmore » Ar, and it increases considerably as Cl{sub 2} or HBr concentration is increased. Although this etch rate increase is partially due to the availability of more Cl or Br, the chemical nature of chlorine (Cl{sub 2}{sup +},Cl{sup +}) or bromine (Br{sup +}) ions also plays a strong role. The TaC etch rate increases little if Cl{sub 2} or HBr fraction in Ar/Cl{sub 2} or Ar/HBr gas mixture, respectively, is increased beyond 25%. The TaC etch rate increases with rf bias power under all conditions. Scanning electron micrographs of TaC films etched using a patterned mask show that TaC sidewalls are tapered at about 77 deg. {+-}3 deg. and the angle does not change appreciably with gas mixture or rf bias power. It is determined that an angle dependent ion etching yield captures well the observed trends in TaC sidewall slope.« less
  • GaN thin film etching is investigated and compared for mesa formation in inductively coupled plasma (ICP) of Cl{sub 2} with Ar and BCl{sub 3} gas additives using photoresist mask. Etch characteristics are studied as a function of ICP process parameters, viz., ICP power, radio frequency (RF) power, and chamber pressure at fixed total flow rate. The etch rate at each ICP/RF power is 0.1–0.2 μm/min higher for Cl{sub 2}/Ar mixture mainly due to higher Cl dissociation efficiency of Ar additive that readily provides Cl ion/radical for reaction in comparison to Cl{sub 2}/BCl{sub 3} mixture. Cl{sub 2}/Ar mixture also leads to bettermore » photoresist mask selectivity. The etch-induced roughness is investigated using atomic force microscopy. Cl{sub 2}/Ar etching has resulted in lower root-mean-square roughness of GaN etched surface in comparison to Cl{sub 2}/BCl{sub 3} etching due to increased Ar ion energy and flux with ICP/RF power that enhances the sputter removal of etch product. The GaN surface damage after etching is also evaluated using room temperature photoluminescence and found to be increasing with ICP/RF power for both the etch chemistries with higher degree of damage in Cl{sub 2}/BCl{sub 3} etching under same condition.« less
  • The mechanisms underlying selective etching of a SiO{sub 2} layer over a Si or Si{sub 3}N{sub 4} underlayer, a process of vital importance to modern integrated circuit fabrication technology, has been studied. Selective etching of SiO{sub 2}-to-Si{sub 3}N{sub 4} in various inductively coupled fluorocarbon plasmas (CHF{sub 3}, C{sub 2}F{sub 6}/C{sub 3}F{sub 6}, and C{sub 3}F{sub 6}/H{sub 2}) was performed, and the results compared to selective SiO{sub 2}-to-Si etching. A fluorocarbon film is present on the surfaces of all investigated substrate materials during steady state etching conditions. A general trend is that the substrate etch rate is inversely proportional to themore » thickness of this fluorocarbon film. Oxide substrates are covered with a thin fluorocarbon film ({lt}1.5 nm) during steady-state etching and at sufficiently high self-bias voltages, the oxide etch rates are found to be roughly independent of the feedgas chemistry. The fluorocarbon film thicknesses on silicon, on the other hand, are strongly dependent on the feedgas chemistry and range from {approximately}2 to {approximately}7 nm in the investigated process regime. The fluorocarbon film thickness on nitride is found to be intermediate between the oxide and silicon cases. The fluorocarbon film thicknesses on nitride range from {approximately}1 to {approximately}4 nm and the etch rates appear to be dependent on the feedgas chemistry only for specific conditions. The differences in etching behavior of SiO{sub 2}, Si{sub 3}N{sub 4}, and Si are suggested to be related to a substrate-specific ability to consume carbon during etching reactions. Carbon consumption affects the balance between fluorocarbon deposition and fluorocarbon etching, which controls the fluorocarbon steady-state thickness and ultimately the substrate etching. {copyright} {ital 1999 American Vacuum Society.}« less