Impact of metal etch residues on etch species density and uniformity

Abstract

Uniformity and wafer-to-wafer reproducibility of plasma etch processes are often related to the conditioning of the plasma etch chamber walls. For advanced complementary metal-oxide semiconductor fabrication, numerous metals are used which might deposit on the chamber walls during etch processes and as these metals are not always straightforward to remove, process instabilities can occur. This happens because recombination of atomic species on the chamber walls determines to a certain degree the plasma composition. Therefore, in this article, the impact of metal etch residues, especially titanium and tantalum residues, on plasma composition and uniformity is studied. The chamber walls are analyzed by x-ray photoelectron spectroscopy analysis of so-called floating samples and the densities of Cl, Br, O and F in Cl2, HBr, O2, and SF6 plasmas are monitored by optical emission spectroscopy. Plasma uniformity is checked by measuring etch rates across 300 mm silicon wafers. It is found that chlorine and bromine have similar recombination probabilities on the metals than on anodized aluminum. Fluorine and oxygen recombination, however, is strongly influenced by the presence of metal residues. Accordingly, for fluorine and oxygen based plasmas, metal residues showed to have an impact on the plasma uniformity.

Low temperature dry etching of chromium towards control at sub-5 nm dimensions

“…Note, etching in chlorine based chemistry is very sensitive to the chamber wall condition [23][24][25]. Chamber pre conditioning with the etch gas composition was performed for 5 min on a silicon wafer, prior to etching actual samples.…”

Effect of titanium contamination on oxygen atom recombination probability on plasma conditioned surfaces

“…3), an atomic concentration of Si:O:Ti ¼ 23:60:17 was obtained. Interestingly, Dictus et al 13 found that after etching of TiN to coat chamber walls with Ti, and then exposing the surface to an O 2 /5%Ar plasma, the optical emission from O atoms, normalized to Ar emission, decreased by 30% relative to that found when the reactor walls were coated with SiO 2 , suggesting an increase in O recombination. The pressure rises recorded for this "17% Ti" surface ( Fig.…”

Formation of AlFx Gaseous Phases during High Temperature Etching: A Reactive Force Field Based Molecular Dynamics Study

“…This feature makes AlF 3 an attractive inorganic resist for electron-beam nanopatterning techniques. , In addition to this, fluorine-rich cleaning discharges can transform chamber interior/mask components made from aluminum into aluminum fluoride, , and that enables application for fabrication of complementary metal oxide semiconductor devices. However, along with the significant study of the decomposition and formation of solid Al–F compounds, − formation of Al–F complex molecules is another common phenomenon, and very little information on this topic is available now . Metal fluorides are traditionally prepared by fluorination or other chemical synthesis, such as the plasma chemistry of dry etching method, which involves much more complicated processes exceeding the way that isolated atom or molecule diffuses over a metal surface.…”