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Title: Plasma etching of HfO{sub 2} at elevated temperatures in chlorine-based chemistry

Abstract

Plasma etching of HfO{sub 2} at an elevated temperature is investigated in chlorine-based plasmas. Thermodynamic studies are performed in order to determine the most appropriate plasma chemistry. The theoretical calculations show that chlorocarbon gas chemistries (such as CCl{sub 4} or Cl{sub 2}-CO) can result in the chemical etching of HfO{sub 2} in the 425-625 K temperature range by forming volatile effluents such as HfCl{sub 4} and CO{sub 2}. The etching of HfO{sub 2} is first studied on blanket wafers in a high density Cl{sub 2}-CO plasma under low ion energy bombardment conditions (no bias power). Etch rates are presented and discussed with respect to the plasma parameters. The evolution of the etch rate as function of temperature follows an Arrhenius law indicating that the etching comes from chemical reactions. The etch rate of HfO{sub 2} is about 110 A /min at a temperature of 525 K with a selectivity towards SiO{sub 2} of 15. x-ray photoelectron spectroscopy analyses (XPS) reveal that neither carbon nor chlorine is detected on the HfO{sub 2} surface, whereas a chlorine-rich carbon layer is formed on top of the SiO{sub 2} surface leading to the selectivity between HfO{sub 2} and SiO{sub 2}. A drift of themore » HfO{sub 2} etch process is observed according to the chamber walls conditioning due to chlorine-rich carbon coatings formed on the chamber walls in a Cl{sub 2}-CO plasma. To get a very reproducible HfO{sub 2} etch process, the best conditioning strategy consists in cleaning the chamber walls with an O{sub 2} plasma between each wafer. The etching of HfO{sub 2} is also performed on patterned wafers using a conventional polysilicon gate. The first result show a slight HfO{sub 2} foot at the bottom of the gate and the presence of hafnium oxide-based residues in the active areas.« less

Authors:
; ; ; ; ; ; ;  [1];  [2];  [3];  [4]
  1. STMicroelectronics, 850 rue Jean Monnet, 38926 Crolles Cedex (France)
  2. (CEA-LETI), 38054 Grenoble Cedex 09 (France)
  3. (France)
  4. (United States)
Publication Date:
OSTI Identifier:
20776947
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: 24; Journal Issue: 1; Other Information: DOI: 10.1116/1.2134707; (c) 2006 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CARBON; CARBON DIOXIDE; CARBON TETRACHLORIDE; CHEMICAL REACTIONS; CHEMISTRY; CHLORINE; COATINGS; ETCHING; HAFNIUM CHLORIDES; HAFNIUM OXIDES; ION BEAMS; PLASMA; SILICA; SILICON OXIDES; SURFACES; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE 0400-1000 K; X-RAY PHOTOELECTRON SPECTROSCOPY

Citation Formats

Helot, M., Chevolleau, T., Vallier, L., Joubert, O., Blanquet, E., Pisch, A., Mangiagalli, P., Lill, T., Laboratoire des Technologies de la Microelectronique, CNRS, 17 rue des martyrs, LTPCM/INPG-CNRS-UJF, 1130 rue de la piscine, 38402 Saint-Martin-d'Heres, and Applied Materials, 974 E. Arques Ave. M/S 81334, Sunnyvale, California 94086. Plasma etching of HfO{sub 2} at elevated temperatures in chlorine-based chemistry. United States: N. p., 2006. Web. doi:10.1116/1.2134707.
Helot, M., Chevolleau, T., Vallier, L., Joubert, O., Blanquet, E., Pisch, A., Mangiagalli, P., Lill, T., Laboratoire des Technologies de la Microelectronique, CNRS, 17 rue des martyrs, LTPCM/INPG-CNRS-UJF, 1130 rue de la piscine, 38402 Saint-Martin-d'Heres, & Applied Materials, 974 E. Arques Ave. M/S 81334, Sunnyvale, California 94086. Plasma etching of HfO{sub 2} at elevated temperatures in chlorine-based chemistry. United States. doi:10.1116/1.2134707.
Helot, M., Chevolleau, T., Vallier, L., Joubert, O., Blanquet, E., Pisch, A., Mangiagalli, P., Lill, T., Laboratoire des Technologies de la Microelectronique, CNRS, 17 rue des martyrs, LTPCM/INPG-CNRS-UJF, 1130 rue de la piscine, 38402 Saint-Martin-d'Heres, and Applied Materials, 974 E. Arques Ave. M/S 81334, Sunnyvale, California 94086. Sun . "Plasma etching of HfO{sub 2} at elevated temperatures in chlorine-based chemistry". United States. doi:10.1116/1.2134707.
@article{osti_20776947,
title = {Plasma etching of HfO{sub 2} at elevated temperatures in chlorine-based chemistry},
author = {Helot, M. and Chevolleau, T. and Vallier, L. and Joubert, O. and Blanquet, E. and Pisch, A. and Mangiagalli, P. and Lill, T. and Laboratoire des Technologies de la Microelectronique, CNRS, 17 rue des martyrs and LTPCM/INPG-CNRS-UJF, 1130 rue de la piscine, 38402 Saint-Martin-d'Heres and Applied Materials, 974 E. Arques Ave. M/S 81334, Sunnyvale, California 94086},
abstractNote = {Plasma etching of HfO{sub 2} at an elevated temperature is investigated in chlorine-based plasmas. Thermodynamic studies are performed in order to determine the most appropriate plasma chemistry. The theoretical calculations show that chlorocarbon gas chemistries (such as CCl{sub 4} or Cl{sub 2}-CO) can result in the chemical etching of HfO{sub 2} in the 425-625 K temperature range by forming volatile effluents such as HfCl{sub 4} and CO{sub 2}. The etching of HfO{sub 2} is first studied on blanket wafers in a high density Cl{sub 2}-CO plasma under low ion energy bombardment conditions (no bias power). Etch rates are presented and discussed with respect to the plasma parameters. The evolution of the etch rate as function of temperature follows an Arrhenius law indicating that the etching comes from chemical reactions. The etch rate of HfO{sub 2} is about 110 A /min at a temperature of 525 K with a selectivity towards SiO{sub 2} of 15. x-ray photoelectron spectroscopy analyses (XPS) reveal that neither carbon nor chlorine is detected on the HfO{sub 2} surface, whereas a chlorine-rich carbon layer is formed on top of the SiO{sub 2} surface leading to the selectivity between HfO{sub 2} and SiO{sub 2}. A drift of the HfO{sub 2} etch process is observed according to the chamber walls conditioning due to chlorine-rich carbon coatings formed on the chamber walls in a Cl{sub 2}-CO plasma. To get a very reproducible HfO{sub 2} etch process, the best conditioning strategy consists in cleaning the chamber walls with an O{sub 2} plasma between each wafer. The etching of HfO{sub 2} is also performed on patterned wafers using a conventional polysilicon gate. The first result show a slight HfO{sub 2} foot at the bottom of the gate and the presence of hafnium oxide-based residues in the active areas.},
doi = {10.1116/1.2134707},
journal = {Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films},
number = 1,
volume = 24,
place = {United States},
year = {Sun Jan 15 00:00:00 EST 2006},
month = {Sun Jan 15 00:00:00 EST 2006}
}
  • Mercury cadmium telluride (MCT) CH{sub 4}-H{sub 2} based chemistry inductively coupled plasma (ICP) etching mechanisms are investigated. The effect of Ar and N{sub 2} addition in the mixture on plasma and MCT surface characteristics are studied by Langmuir probe, mass spectrometry, and x-ray photoelectron spectroscopy (XPS). In the authors' conditions, the HgTe faster removal than CdTe leads to the formation of a CdTe rich layer in the first 30 s of plasma exposure. Ion flux intensity and composition are only slightly influenced by N{sub 2} addition while a strong effect is shown on neutral species by the formation of NH{submore » 3}, HCN, and the increase in CH{sub 3} radical density. At the opposite, Ar addition to the gas mixture leads to a total ion flux increase and promote CH{sub 3}{sup +} formation while small changes are observed on neutral species. In our low pressure and high density conditions, same order of magnitude of ion and neutral CH{sub 3} flux on MCT surface is found, suggesting a chemical contribution of CH{sub 3}{sup +} ions in MCT etching. This is confirmed by a strong correlation of the MCT etching yield versus total (neutral and ionic) CH{sub 3} flux. These results suggest that the etching is limited by the supply of CH{sub 3} to the surface.« less
  • In this work, the authors investigated the etching characteristics of TaN and HfO{sub 2} layers for gate stack patterning in BCl{sub 3}/Ar and BCl{sub 3}/C{sub 4}F{sub 8}/Ar inductively coupled plasmas and the effects of C{sub 4}F{sub 8} addition on the etch selectivity of the TaN to the HfO{sub 2} layer. Addition of C{sub 4}F{sub 8} gas to the BCl{sub 3}/Ar chemistry improved the TaN/HfO{sub 2} etch selectivity because adding the C{sub 4}F{sub 8} gas enhances the formation of the CF{sub x}Cl{sub y} passivation layer on HfO{sub 2} surface and decreased the HfO{sub 2} etch rate more rapidly than the TaNmore » etch rate in a disproportionate way. Reduction in the etch time for HfO{sub 2} layer also increases the TaN/HfO{sub 2} etch selectivity because the etch time gets closer to the initiation time for HfO{sub 2} etching.« less
  • The authors have investigated the effects of elevated substrate temperature (T{sub s}) on cleaning of boron residues from silicon substrates in 1%H{sub 2}-Ar plasmas, following etching of HfO{sub 2} in BCl{sub 3} plasmas. Vacuum-transfer x-ray photoelectron spectroscopy (XPS) provided a measure of total B removal rates, as well as information on individual BCl{sub x}O{sub y} moities. B cleaning rates increased with T{sub s} in an Arrhenius manner, with an apparent activation energy of 1.7 kcal/mol. Conversely, the Si etching rate decreased with increasing substrate temperature with an apparent activation energy of -0.8 kcal/mol. Therefore, when considering selectivity with respect tomore » Si etching, it is advantageous to remove B at higher T{sub s}. For example, at T{sub s}=235 deg. C, {approx}90% of B is cleaned from Si in 10 s, while <1.5 nm of Si is removed. An apparent diffusion of H into the near-surface region of Si at higher temperatures, detected indirectly by a shift and broadening of the Si(2p) XPS peak, may limit the maximum optimum substrate temperature, however. It was also found that Si does not etch in 1%H{sub 2}/Ar plasmas if an oxide layer is present.« less
  • Equilibrium in HfO/sub 2/ reduction with carbon at 1200 to 2000 deg K and 70 to 1000 mm mercury pressure was studied. The oxycarbide formed has a practically constant composition and constant lattice values with nonstoichiometric HfC containing traces of oxygen. The reaction is expressed by the equation HfO/sub 2/ + 2.9 C in equilibrium HfC/sub 0.95/O/sub 0.05/ + 1/95 CO. The equilibrium is monovariant. The heat of formation and entropy of the oxycarbide are calculated for 298.1 deg K. (R.V.J.)
  • To minimize leakage currents resulting from the thinning of the insulator in the gate stack of field effect transistors, high-dielectric constant (high-k) metal oxides, and HfO{sub 2} in particular, are being implemented as a replacement for SiO{sub 2}. To speed the rate of processing, it is desirable to etch the gate stack (e.g., metal gate, antireflection layers, and dielectric) in a single process while having selectivity to the underlying Si. Plasma etching using Ar/BCl{sub 3}/Cl{sub 2} mixtures effectively etches HfO{sub 2} while having good selectivity to Si. In this article, results from integrated reactor and feature scale modeling of gate-stackmore » etching in Ar/BCl{sub 3}/Cl{sub 2} plasmas, preceded by photoresist trimming in Ar/O{sub 2} plasmas, are discussed. It was found that BCl{sub n} species react with HfO{sub 2}, which under ion impact, form volatile etch products such as B{sub m}OCl{sub n} and HfCl{sub n}. Selectivity to Si is achieved by creating Si-B bonding as a precursor to the deposition of a BCl{sub n} polymer which slows the etch rate relative to HfO{sub 2}. The low ion energies required to achieve this selectivity then challenge one to obtain highly anisotropic profiles in the metal gate portion of the stack. Validation was performed with data from literature. The effect of bias voltage and key reactant probabilities on etch rate, selectivity, and profile are discussed.« less