On-wafer monitoring of electron and ion energy distribution at the bottom of contact hole

Abstract

In situ on-wafer monitoring of the electron and ion energies at the contact-hole bottom is primarily achieved in Ar ultrahigh-frequency plasma. The on-wafer probe reveals a lower electron density and higher electron temperature at the contact-hole bottom due to the electron-shading effect, as compared with that in the bulk plasma. The on-wafer probe also shows the ion energy distribution function (IEDF) at the contact-hole bottom. The peak energy of IEDF corresponded to the sheath potential. Accordingly, the authors found that the on-wafer probe is a very effective tool for investigating the electron and ion energies in real SiO2 contact structures.

On-wafer monitoring of charge accumulation and sidewall conductivity in high-aspect-ratio contact holes during SiO2 etching process

“…This accumulation is a result of "electron shading:" during plasma etching, electrons are retarded by the surface potential and cannot reach the bottom of the contact hole because of the ion sheath. 11 We also found that the amount of charge accumulated at the bottom of a contact hole depends on the conductivity, and thus on the chemical structure, of the deposited fluorocarbon polymer. 9 Their results indicated that when the aspect ratio reached a value greater than 7, the bottom surface would be charged to a potential high enough to prevent further etching by ions with an initial energy of 300 eV.…”

“…[10][11][12] As we proposed in the previous papers, ion bombardment increases the electrical conductivity of the fluorocarbon polymer deposited on the sidewall of SiO 2 contact holes. At the lower aspect ratio, although electric conductivity hardly increased after polymer deposition, the electric conductivity increased greatly after ion bombardment treatment ͓Fig.…”

Plasma chemical etching of high-aspect-ratio silicon micro- and nanostructures

“…A thin fluorocarbon film is conducting, and its charging should not occur. Experimental evidence for this suggestion was obtained on an example of high-aspectratio SiO 2 etching [50,51].…”

Feature Profile Evolution in Plasma Processing Using On-wafer Monitoring System

“…We have shown the electron temperature, electron density, ion energy, and sidewall resistance of a hole. [32][33][34][35][36] The electron temperature and density sensor revealed a lower electron density and a higher electron temperature at the bottom of contact holes due to the electron shading effect, than in bulk plasma. 32) The charge-up sensor showed that the electron shading effect could be clearly observed as the potential difference between the wafer surface and the bottom of contact holes.…”

“…[32][33][34][35][36] The electron temperature and density sensor revealed a lower electron density and a higher electron temperature at the bottom of contact holes due to the electron shading effect, than in bulk plasma. 32) The charge-up sensor showed that the electron shading effect could be clearly observed as the potential difference between the wafer surface and the bottom of contact holes. 33,34) It also revealed that a sidewall-deposited fluorocarbon film even in a high-aspect-ratio contact hole has a high electric conductivity, which may mitigate electric charge accumulation at the bottom of contact holes during SiO 2 etching processes.…”