Role of contaminants in electron cyclotron resonance plasmas

Abstract

In this article, we examine the influence of contaminants on an electron cyclotron resonance discharge. For our discharge, the measured level of contaminant was highest just after startup, decreasing to a stable level after approximately 20 min.This is consistent with a limited source of gas trapped in the chamber walls. It is shown that the presence of these contaminants cause both the plasma and floating potentials vary by several volts. These potential variations are largest when the contamination is largest. Such variations were found in N2, CF4, and CHF3 discharges. The observed variation in the plasma potential should be of great concern in plasma-aided manufacturing environments. The larger variations represent approximately 10% of the potential that one would typically apply between a device and the plasma. Such large changes in the potential might result in substantial changes in both etch rate and anisotropy. This can have particularly adverse effects on those devices having fine structures. Thus, one should monitor these contaminants and not process devices while the contaminant level varies.

Chlorine plasma and polysilicon etch characterization in an inductively coupled plasma etch reactor

“…This tends to underestimate the ion density (n + i ∝ M eff i ) at low powers and high pressures where the density of Cl + 2 is expected to be larger due to a lower degree of dissociation [6,10,23]. All measurements were taken at a reactor wall temperature between 23˚C and 27˚C after a few minutes warm-up of the reactor to avoid any variations in the plasma properties due to contamination [24]. The probe tip was cleaned regularly by applying a positive bias slightly larger than the plasma potential (i.e.…”

Comparison endpoint study of process plasma and secondary electron beam exciter optical emission spectroscopy

“…Presence of these contaminants is further confirmed by reaction products such as SOF 2 and HF, which was measured through FTIR measurements. The walls of the mGEC chamber were not heated and contributions due to water desorbing from walls is well known, having been observed to minimize with time by Goeckner et al 25 In the e-beam difference spectra, Fig. 3(b), a prominent band around 300 nm was observed.…”