Analysis of the chemical composition and deposition mechanism of the SiOx–Cly layer on the plasma chamber walls during silicon gate etching

Abstract

Articles you may be interested inInfluence of the reactor wall composition on radicals' densities and total pressure in Cl 2 inductively coupled plasmas: II. During silicon etching Influence of ion mixing on the energy dependence of the ion-assisted chemical etch rate in reactive plasmas During silicon gate etching in low pressure high density HBr/Cl 2 /O 2 plasma, SiOCl x layers are deposited on the reactor walls. These layers are at the origin of process drifts. However their chemical composition, deposition mechanism and their influence on the plasma chemistry remains poorly understood. In this study, the chemical composition of this layer has been investigated by a ''plasma etching-sputtering'' technique: the silicon oxychloride layer deposited on the reactor walls during the etching of a 200 mm diam silicon wafer has been subsequently submitted to an Ar plasma with the addition of a few % SF 6 . During the slow etch process of this layer, time-resolved optical emission spectroscopy and mass spectrometry have been used to follow the time evolution of the gas phase concentration of different atoms and radicals, the etch products of the SiOCl x layer. The results give insight into the chemical nature of the deposited layer and of its variation as a function of the depth. In particular, it will be shown that these layers are chlorine-rich and not oxidelike. Also, their composition is not homogeneous through their depth. In a second set of experiments, the SiOCl x layer has been exposed to an Ar/O 2 plasma providing information on the oxidation mechanism of the Si-Cl bonds and thus on the SiOCl x film deposition mechanism in HBr/Cl 2 /O 2 plasmas. This oxidation mechanism is acting through the entire volume of the 10 nm thick layers and proceeds by substitution of Cl atoms of SiCl bonds by O atoms, resulting in desorption of a large amount of Cl atoms from the chamber walls during the layer oxidation. Finally, the layer on the chamber walls has been exposed to an Ar/Cl 2 plasma, demonstrating that SiOCl x layers are not etched significantly by Cl atoms.

Sub-50-nm self-assembled nanotextures for enhanced broadband antireflection in silicon solar cells

“…In addition to stripping the alumina caps, the etch narrows the texture radius by several nm, consistent with removal of a silicon oxide layer that has been previously observed during studies of similar etch chemistries ( Supplementary Fig. 5) 30,31 . These results are consistent with transmission electron microscopy images showing the etched silicon nanotextures coated with an amorphous material ( Supplementary Fig.…”

“…9) 28 . The chlorine, bromine and oxygen etch chemistries we use to generate the nanotextures are known to modify the silicon within B5-10 nm of the surface 28,29 , including redeposition of silicon oxychloride 30,31 , creating a surface layer with substantially different optical properties 32 and providing an additional mechanism for grading n i between air and silicon. In nanotextures with larger dimensions, this surface layer is an inconsequential fraction of the total volume.…”

Correlation and Interaction between Sidewall Passivation and Chamber Walls Deposition During Silicon Gate Etching

“…5 shows the time evolution of signals related to halogen, oxygen and silicon containing species during the layer etching in an Ar/5% SF 6 plasma. As described elsewhere [16] the layer etch rate is non-uniform in the chamber: the layer is removed faster on the quartz roof of the chamber because the ion flux (and energy) is higher at this position than on the chamber walls. The layer is totally removed from the quartz roof after 20 seconds, while it takes more than 40 seconds to restore the Al 2 O 3 chamber walls.…”

“…So, the Cl 2 signal of the MS was converted to equivalent Cl 2 gas flow desorbing from the chamber walls [16]. We can then deduce that the typical SiO y Cl x layer deposited on the chamber walls by the main etch process contains about 10 20 Cl atoms.…”

Chemical analysis of deposits formed on the reactor walls during silicon and metal gate etching processes

“…This transition from a SiOCl coating after the SL step to a SiOBr coating after the OE step can be explained by the substitution of Cl atoms by Br atoms in the SiOCl layer coated on the chamber walls, in a similar way that F atoms can substitute to Cl during the removal of the SiOCl layer in a SF 6 plasma. 9 The substitution may either be direct or proceed through a heteronuclear abstraction reaction ͑formation and desorption of BrCl ͑Ref. 18͒ followed by bromination of the dangling bonds͒.…”