Fluorocarbon Plasma Etching Research Articles

Influence of reactor wall conditions on etch processes in inductively coupled fluorocarbon plasmas

The influence of reactor wall conditions on the characteristics of high density fluorocarbon plasma etch processes has been studied. Results obtained during the etching of oxide, nitride, and silicon in an inductively coupled plasma source fed with various feedgases, such as CHF3, C3F6, and C3F6/H2, indicate that the reactor wall temperature is an important parameter in the etch process. Adequate temperature control can increase oxide etch selectivity over nitride and silicon. The loss of fluorocarbon species from the plasma to the walls is reduced as the wall temperature increased. The fluorocarbon deposition on a cooled substrate surface increases concomitantly, resulting in a more efficient suppression of silicon and nitride etch rates, whereas oxide etch rates remain nearly constant.

Symmetric rate model for fluorocarbon plasma etching of SiO2

A symmetric rate model for plasma etching and plasma deposition in fluorocarbon plasmas is proposed. When there is no deposition, the symmetric rate model gives a plasma etch rate. When there is no etching, the model gives a plasma deposition rate. Electron cyclotron resonance and reactive ion etcher etch rates of SiO2 in CF4 plasma are found to be consistent with the model.

SiO2 to Si selectivity mechanisms in high density fluorocarbon plasma etching

This study examines the influence of plasma chemistry on SiO2 to Si etch selectivity in high density C2H2F4(1,1,1,2-tetrafluoroethane)/O 2 and CHF3/H2 discharges. Etch rate measurements of Si and SiO2 have been combined with chemical characterizations of the discharge using optical diagnostics and an in-line quadrupole mass spectrometer. The gas phase concentrations of CF2 and F as well as the mass spectrum of ions incident at the substrate have been measured for conditions producing SiO2/Si selectivities from 1 to over 30. For low density sources with high neutral to ion fluxes, the conventional theory is that selectivity is governed by the relative content of fluorine versus carbon in the fluorine and fluorocarbon radicals incident on the substrate. However, for the high density plasma discharges studied, the conventional theory may apply only when the contributions of both neutral radicals and fluorocarbon ions, CF+x, are considered. For the case of oxygen addition to C2H2F4 discharges, reactions between the fluorocarbon surface film and oxygen in the gas phase may also be important in controlling selectivity.

Substrate bias effects in high-aspect-ratio SiO2 contact etching using an inductively coupled plasma reactor

High-aspect-ratio sub-half-micron contacts were etched in SiO2 using a high-density C2F6 plasma generated by an inductively coupled, low-pressure reactor. As expected, oxide and resist etch rates increased with increasing bias. The aspect ratio (depth/width) dependence of the etch process was also shown to vary with bias power; at high bias power conditions, reactive ion etching (RIE) lag was observed, where high-aspect-ratio features etch slower than low-aspect-ratio features, and at low bias powers, inverse RIE lag was observed. Increasingly vertical sidewall angles and increasing microtrenching depth were also observed for higher rf bias conditions on contacts, trenches, and steps. Topography modeling shows that the microtrench profiles are consistent with specular ion reflection from sidewalls and the increase in their depths with rf bias is consistent with the energy-dependent etching yields in high-density, fluorocarbon plasma etch chemistries reported by Oehrlein et al. [J. Vac Sci. Technol. A 12, 323, 333 (1994)].

Effect of one monolayer of surface gold atoms on the epitaxial growth of InAs nanowhiskers

This letter shows that selective heteroepitaxy of nanometer-scale InAs whiskers on SiO2-patterned GaAs substrates [Yazawa, Koguchi, and Hiruma, Appl. Phys. Lett. 58, 1080 (1991)] is induced by surface contamination with Au resulting from the fluorocarbon plasma etching process used to etch the SiO2 mask. We demonstrate that high densities (≂1010/cm2) of InAs nanowhiskers 20–30 nm in diameter can be epitaxially grown on InAs(111)B substrates onto which 1 monolayer of Au atoms had been deposited. This wirelike growth appears to be induced by ultrafine alloy droplets generated by the reactions between Au-clusters and InAs substrates.

X-ray photoelectron spectroscopy studies of contamination and cleaning of surfaces exposed to a fluorocarbon plasma

A reactive ion etching (RIE) with a mixture of fluorocarbon gases is used to etch selectively SiO2 patterns on Si wafer. X-ray photoelectron spectroscopy (XPS) measurements were carried out to determine the walls contamination of the reactor with different cathode coatings like Al, Si, and photoresist. The contamination of different wafers (SiO2, Si with and without resist) following RIE processes was also studied in order to understand the mechanism of the selective etching. Then different cleaning processes, in particularly NF3 and O2 plasmas followed or not by a hydrophilic treatment, were also qualified by XPS. For every sample, the Al(2p) or Si(2p), C(1s), O(1s), and F(1s) photoelectron lines were monitored and concentrations determined as usual by integration of these lines. F(1s) and C(1s) were decomposed into several components corresponding to different chemical bonds. The results show that the contamination of the reactor walls by fluoropolymers is due to the presence of Si or of the photoresist on the cathode; there is no polymer formation with an Al cathode coating. The polymer contamination on the reactor walls is cleaned off by an O2 plasma and the residual fluorine forms a passivative layer with the Al of the reactor walls. During the plasma etching of a SiO2 film, there is formation of C–Si, C–C, O–Si–F, F–Si bonds but it is only when there is no oxygen left that CFx bonds are formed. These polymer layers stop the etching process on silicon. They are cleaned by O2 or NF3 plasma, but the latter removes the polymers without increasing the oxygen, fluorine or nitrogen contamination and appears to be most appropriate for improving the surface quality of silicon after fluorocarbon plasma etching.

Quantification of surface film formation effects in fluorocarbon plasma etching of polysilicon

A multibeam apparatus has been constructed which allows synthesis of the primary fluxes to a wafer surface during fluorocarbon plasma etching. These species include CF2 as a polymer forming precursor, F as the primary etchant, and Ar+ or CF+x for energetic ion bombardment. The individual fluxes can be adjusted to within an order of magnitude of those encountered in typical plasma etching processes, and can be manipulated independently to ascertain the effects of radical-to-ion flux ratio on fluorocarbon film formation and etching yields. Direct sticking of CF2 radicals on undoped polysilicon films can account for suppression of silicon MONITOR sputtering yields on the order of 70%, but cannot completely stop the net removal of silicon by Ar+ at energies above 150 eV. Studies of the competitive interaction between CF2 and F radicals on undoped silicon surfaces showed up to 30% suppression of Ar+/F etching yields under flux conditions representative of low pressure CF4 reactive ion etching (RIE).

Abstract: Some chemical aspects of the fluorocarbon plasma etching of silicon and its compounds

Abstract: Some chemical aspects of the fluorocarbon plasma etching of silicon and its compounds

Some chemical aspects of the fluorocarbon plasma etching of silicon and its compounds : J. W. Coburn and Eric Kay. Solid St. Technol. p. 117 (April 1979)

Some chemical aspects of the fluorocarbon plasma etching of silicon and its compounds : J. W. Coburn and Eric Kay. Solid St. Technol. p. 117 (April 1979)

Some chemical aspects of the fluorocarbon plasma etching of silicon and its compounds : J. W. Coburn and Eric Kay. IBM J. Res. Dev.23, (1) 33 (January 1979)

Some chemical aspects of the fluorocarbon plasma etching of silicon and its compounds : J. W. Coburn and Eric Kay. IBM J. Res. Dev.23, (1) 33 (January 1979)

Some Chemical Aspects of the Fluorocarbon Plasma Etching of Silicon and Its Compounds

Mass spectrometric sampling of fluorocarbon glow discharges and in situ measurements of the etch rate of Si and SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> with quartz crystal microbalances have been used to provide additional insight concerning the chemistry involved when additive gases such as O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O, and C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> F <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> are injected into a CF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> glow discharge. The results obtained in our low-pressure, long-residence-time system indicate that the etching behavior of the discharge is not significantly influenced by the molecular structure of the injected gas molecules but is determined primarily by the elemental composition of the glow discharge. This phenomenologically observed result can be used to predict qualitatively the relative etching behavior of a large class of gaseous etchant mixtures as well as the role of various electrode or wall materials in the plasma etching process. Although this oversimplified interpretation should not be extended to short-residence-time plasma systems, it is believed to be valid for some of the configurations used in plasma etching and reactive ion etching.