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Title: Spatial profile monitoring of etch products of silicon in HBr/Cl{sub 2}/O{sub 2}/Ar plasma

Abstract

The authors have developed a radical-distribution monitoring system for obtaining the spatial profiles of etching products. This system combines Abel inversion and actinometry to estimate the local densities of radicals. The profiles of Si, SiCl, and SiCl{sub 2} in HBr/Cl{sub 2}/O{sub 2}/Ar plasma are captured with this monitoring system. From the gradient analysis of silicon-containing etch products, they found that the source of SiCl{sub 2} is the wafer surface and Si and SiCl are produced in the plasma. In other words, SiCl{sub 2} is produced by the etching reactions on the wafer and diffuses into the plasma to be the source of Si or SiCl through dissociation. In the etcher used for this experiment, etching gases are supplied from a top plate inducing downward flows. At a pressure as low as 0.4 Pa, the effect of convection on etch products is also observed. Increasing total gas flow rate intensifies convection and changes the spatial profile of SiCl{sub 2}. However, on the wafer surface, the convective effect saturated at a total flow rate of 200 SCCM (SCCM denotes cubic centimeter per minute at STP). The ratio of the emission intensities of SiCl{sub 2} and supplied etching gases was found to bemore » a convenient index for visualizing the effect of gas flow. The shapes of the gas jet from both 170- and 50-mm-diameter gas inlets were drawn in contour plots. The jet from the narrow inlet swept away the etch products in the center of the wafer.« less

Authors:
;  [1]
  1. Central Research Laboratory, Hitachi, Ltd., 1-280 Higashi-koigakubo, Kokubunji, Tokyo 185-8601 (Japan)
Publication Date:
OSTI Identifier:
20979394
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: 2; Other Information: DOI: 10.1116/1.2539295; (c) 2007 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CHLORINE; ETCHING; FLOW RATE; GAS FLOW; HYDROBROMIC ACID; MONITORING; PLASMA; PLASMA DENSITY; PLASMA DIAGNOSTICS; PLASMA JETS; RADICALS; SEMICONDUCTOR MATERIALS; SILICON; SILICON CHLORIDES

Citation Formats

Tanaka, Junichi, and Miya, Go. Spatial profile monitoring of etch products of silicon in HBr/Cl{sub 2}/O{sub 2}/Ar plasma. United States: N. p., 2007. Web. doi:10.1116/1.2539295.
Tanaka, Junichi, & Miya, Go. Spatial profile monitoring of etch products of silicon in HBr/Cl{sub 2}/O{sub 2}/Ar plasma. United States. doi:10.1116/1.2539295.
Tanaka, Junichi, and Miya, Go. Thu . "Spatial profile monitoring of etch products of silicon in HBr/Cl{sub 2}/O{sub 2}/Ar plasma". United States. doi:10.1116/1.2539295.
@article{osti_20979394,
title = {Spatial profile monitoring of etch products of silicon in HBr/Cl{sub 2}/O{sub 2}/Ar plasma},
author = {Tanaka, Junichi and Miya, Go},
abstractNote = {The authors have developed a radical-distribution monitoring system for obtaining the spatial profiles of etching products. This system combines Abel inversion and actinometry to estimate the local densities of radicals. The profiles of Si, SiCl, and SiCl{sub 2} in HBr/Cl{sub 2}/O{sub 2}/Ar plasma are captured with this monitoring system. From the gradient analysis of silicon-containing etch products, they found that the source of SiCl{sub 2} is the wafer surface and Si and SiCl are produced in the plasma. In other words, SiCl{sub 2} is produced by the etching reactions on the wafer and diffuses into the plasma to be the source of Si or SiCl through dissociation. In the etcher used for this experiment, etching gases are supplied from a top plate inducing downward flows. At a pressure as low as 0.4 Pa, the effect of convection on etch products is also observed. Increasing total gas flow rate intensifies convection and changes the spatial profile of SiCl{sub 2}. However, on the wafer surface, the convective effect saturated at a total flow rate of 200 SCCM (SCCM denotes cubic centimeter per minute at STP). The ratio of the emission intensities of SiCl{sub 2} and supplied etching gases was found to be a convenient index for visualizing the effect of gas flow. The shapes of the gas jet from both 170- and 50-mm-diameter gas inlets were drawn in contour plots. The jet from the narrow inlet swept away the etch products in the center of the wafer.},
doi = {10.1116/1.2539295},
journal = {Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films},
number = 2,
volume = 25,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • SiCl{sub X} (X=0-2) radicals' concentrations have been measured by broadband ultraviolet absorption spectroscopy during the etching of 200 mm diameter silicon wafers in HBr/Cl{sub 2}/O{sub 2} plasmas. We report the variations of the concentrations of these radicals as a function of the radio frequency (rf) source power and rf-bias power. The silicon wafer etch rate is measured simultaneously. From the measured radicals densities and using electron impact ionization cross sections found in the literature, the densities of SiCl{sub X}{sup +} ions are calculated and are found to be in good agreement with ion densities measured by mass spectrometry. The uppermore » limit for the SiCl{sub 2} radical concentration is calculated from the wafer etch rate. By comparison with the measured SiCl{sub 2} radical concentration it is concluded that SiCl{sub 2} radicals should also be produced by the reactor walls due to the etching of silicon containing species adsorbed on the reactor walls. Finally, using electron impact dissociation cross sections, the densities of SiCl and Si are calculated from the measured densities of SiCl{sub 2} and SiCl, respectively. The comparison between the calculated and measured values of SiCl{sub X} densities allowed us to conclude that SiCl (and Si) are produced both in the gas phase by electron impact dissociation of SiCl{sub 2} (SiCl) radicals and at the reactor wall surfaces by the neutralization and reflection of {approx_equal}50% of the flux of SiCl{sup +} (Si{sup +}) ions impinging on these surfaces. At the same time SiCl and Si are estimated to be lost (adsorption and abstraction reactions) on the reactor walls with a probability ranging between 0.2 and 1.« 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
  • We have investigated the etching of high aspect ratio holes ({approx}4 {mu}m deep, {approx}0.2 {mu}m diameter) in silicon using plasmas maintained in mixtures of SF{sub 6}, O{sub 2}, and HBr or Cl{sub 2} gases. The etching experiments were conducted in a low pressure (25 mTorr), high density, inductively coupled plasma etching reactor with a planar coil. Visualization of the profiles with scanning electron microscopy is used in conjunction with plasma diagnostics such as optical emission and mass spectroscopies to understand the key factors that control the feature profile shape and etch rate. HBr addition to SF{sub 6}/O{sub 2} mixture reducesmore » the F-to-O ratio, increases sidewall passivation and reduces mask undercut. Addition of Cl{sub 2} to SF{sub 6}/O{sub 2} discharge also decreases the F-to-O ratio, but Cl-enhanced F chemical etching of silicon significantly increases the mask undercut and lateral etching. In both SF{sub 6}/O{sub 2}/HBr and SF{sub 6}/O{sub 2}/Cl{sub 2} mixtures, reduction of O{sub 2} flow rate and subsequent increase of the halogen-to-O ratio eventually results in significant lateral etching because of the lack of oxygen required to form a siliconoxyhalide passivating film on the sidewalls.« less
  • Comments are made on a recent article by Kim, Chang, and Kim [J. Vac. Sci. Technol. A 21, 426 (2003)], which describes the preparation and the x-ray photoemission spectroscopy study of the etching effects produced by Ar-based plasmas of different composition on the surface chemistry of a CeO{sub 2} film grown on Si. We discuss some chemical interactions taking place between Ce, Si, and the ambient humidity during the early stages of film deposition, and demonstrate that the many-body effects involved in Ce 3d spectra provide a key for better understanding of the etching mechanisms exerted by the plasma treatments.
  • 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