Photo-Assisted Etching in Halogen Containing Plasmas
type: CreativeWork
description: Plasma etching is indispensable in microelectronics manufacturing, due to its ability to precisely pattern feature with lateral dimensions of <10 nm. To advance this capability to etch layers with atomic fidelity, while also achieving ultra-high material selectivity, low ion energies (10s eV) are required. However, at low ion energies, an alternative etching pathway catalyzed by vacuum ultraviolet (VUV) photons generated in the plasma has been shown to be very important. In this thesis, photo-assisted etching (PAE) was studied in various halogen containing plasmas. Cl2, Br2, HBr, Br2/Cl2, and HBr/Cl2 feed gases diluted in Ar (50%–50% by volume) were used to study etching of p-type Si(100) in a radio frequency, inductively coupled, Faraday-shielded plasma. PAE was observed in all cases, with Br2/Ar and HBr/Cl2/Ar plasmas having the lowest and highest PAE rates, respectively. Etching rates measured under MgF2, quartz, and opaque windows showed that high energy VUV photons are more effective in inducing PAE compared to low energy photons. Characterization of etched surfaces using Scanning Electron and Atomic Force Microscopy (SEM and AFM) revealed that photo-etched surfaces were rough, quite likely due to the inability of the photo-assisted process to remove contaminants from the surface. PAE in Cl2/Ar plasmas resulted in the formation of 4-sided pyramidal features with bases that formed an angle of 45° with respect to <110> cleavage planes, suggesting that the PAE is sensitive to crystal orientation. Various mechanisms have been proposed to explain photo-assisted etching of Si, including photo-generated carrier-mediated etching, and photon-induced damage (breaking of Si-Si bonds) caused by VUV photons irradiating the substrate. Optical Emission Spectroscopy was used to gain an insight into possible in-plasma PAE mechanisms. Emissions from Cl, Si, SiCl, and Ar were recorded as a function of power while etching p-Si in a 50%Cl2/50%Ar plasma at a pressure of 60 mTorr wit…
abstract: Plasma etching is indispensable in microelectronics manufacturing, due to its ability to precisely pattern feature with lateral dimensions of <10 nm. To advance this capability to etch layers with atomic fidelity, while also achieving ultra-high material selectivity, low ion energies (10s eV) are required. However, at low ion energies, an alternative etching pathway catalyzed by vacuum ultraviolet (VUV) photons generated in the plasma has been shown to be very important. In this thesis, photo-assisted etching (PAE) was studied in various halogen containing plasmas. Cl2, Br2, HBr, Br2/Cl2, and HBr/Cl2 feed gases diluted in Ar (50%–50% by volume) were used to study etching of p-type Si(100) in a radio frequency, inductively coupled, Faraday-shielded plasma. PAE was observed in all cases, with Br2/Ar and HBr/Cl2/Ar plasmas having the lowest and highest PAE rates, respectively. Etching rates measured under MgF2, quartz, and opaque windows showed that high energy VUV photons are more effective in inducing PAE compared to low energy photons. Characterization of etched surfaces using Scanning Electron and Atomic Force Microscopy (SEM and AFM) revealed that photo-etched surfaces were rough, quite likely due to the inability of the photo-assisted process to remove contaminants from the surface. PAE in Cl2/Ar plasmas resulted in the formation of 4-sided pyramidal features with bases that formed an angle of 45° with respect to <110> cleavage planes, suggesting that the PAE is sensitive to crystal orientation. Various mechanisms have been proposed to explain photo-assisted etching of Si, including photo-generated carrier-mediated etching, and photon-induced damage (breaking of Si-Si bonds) caused by VUV photons irradiating the substrate. Optical Emission Spectroscopy was used to gain an insight into possible in-plasma PAE mechanisms. Emissions from Cl, Si, SiCl, and Ar were recorded as a function of power while etching p-Si in a 50%Cl2/50%Ar plasma at a pressure of 60 mTorr wit…
author: Sridhar, Shyam
language: eng
keywords: Photo-assisted etching, Plasma
date published: 2016-08
date modified: 2026-07-24T02:32:27Z
provider: University of Houston
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Houston

PropertyValue
property ID: Handle
value: http://hdl.handle.net/10657/3626