AVS 56th International Symposium & Exhibition
    Plasma Science and Technology Tuesday Sessions
       Session PS1-TuM

Paper PS1-TuM9
Effects of Hydrogen Bombardment during Polysilicon Gate Etching by HBr/O2 Plasmas

Tuesday, November 10, 2009, 10:40 am, Room A1

Session: Advanced FEOL and BEOL Etch
Presenter: T. Ito, Osaka University, Japan
Authors: T. Ito, Osaka University, Japan
K. Karahashi, Osaka University, Japan
M. Fukasawa, Sony Corporation
S. Kobayashi, Sony Corporation
N. Kuboi, Sony Corporation
T. Tatsumi, Sony Corporation
S. Hamaguchi, Osaka University, Japan
Correspondent: Click to Email
As the miniaturization of semiconductor devices continues, better control techniques of substrate surface damages as well as a better understanding of the mechanisms of surface modification during plasma processing are required for future semiconductor manufacturing. Especially during etching processes by HBr/O2 plasmas, which are widely used for etching of poly-silicon gate electrodes, it has been reported that the silicon substrate under a gate oxide film is seriously damaged during the gate electrode etching process. This phenomenon is known as a “Si recess”. The goal of the present study is to understand the cause of the Si recess and to propose a technique to minimize it. To understand the mechanism, we have used a multi-beam injection system, which can irradiate surfaces with independently controlled atoms, molecules and ions. In this way, the system enables us to simulate experimentally plasma-surface interactions that take place during plasma etching processes. The multi-beam system consists of three parts, i.e., a mass analyzed ion beam injector, a set of two independently controllable neutral radical/molecular beam injectors, and a reaction chamber in which a sample substrate can be placed. In this system, a monochromatic and mono-energetic ion beam as well as independently controlled radical/molecular beams can be simultaneously injected into a given substrate surface. The ion and radical sources are differentially pumped and therefore the chamber can be maintained at ultra-high vacuum. The change in chemical nature of the substrate surface can be observed in situ by X-ray photoelectron spectroscopy (XPS) that is installed in the reaction chamber. In this study, Si(100) surfaces were irradiated by H+, Ar+, or O+ ion beam at 500eV each as well as atomic oxygen (O) radical beams and are analyzed with (ex situ) High-Resolution Rutherford Backscattering (HRBS). The results have shown that a layer of structure alteration with 10 nm thickness is formed on the Si substrate surface only when H+ ions are injected into the surface. Furthermore it has been found that oxygen (O) diffusion is enhanced in the alteration layer due to amorphization of Si. Thus our multi-beam injection experiments corroborates the hypothesis that the Si recess during HBr/O2 plasma etching processes is caused by H+ ion injections from HBr plasmas and O radical diffusion. This also suggests the importance of precise control of incident ion energies for the minimization of Si recesses during the processes.