Measurement of Radial and Axial Neutral Gas Temperature in a Semi-Conductor Plasma Reactor

Abstract

Plasma‐etching and plasma deposition processes are used in the fabrication of ultra large scale integration (ULSI) semi‐conductor circuits. Plasma based processing systems have evolved from capacitive coupled plasma sources to high density inductively coupled and magnetically enhanced plasma sources. As processing evolves from 200‐mm to 300‐mm wafers and as critical dimensions continue to shrink continued improvement in a number of process variables, including process uniformity, are required. Process uniformity is governed by a number of factors including plasma density uniformity, reactive neutral uniformity, wafer temperature, and incident ion energy uniformity. The mechanisms leading to neutral radical non‐uniformity, including gas heating and plasma pumping have been given less attention, therefore plasma diagnostics and modeling of neutral gas density, temperature, and dissociation in the reactor are needed to improve the understanding of how neutral gas conditions influence process uniformity. Radial and axial rotational temperature profiles in a large‐area high‐density plasma reactor (inductively coupled plasma discharge) have been obtained using the electron beam fluorescence technique (EBF) and optical emission spectroscopy (OES). These two diagnostics can provide the temperature measurements over the entire range of gas pressure (1–50mTorr) and input power (0‐3000W). These two diagnostic techniques for temperature measurement are compared with a simple analytic model of gas heating and gas depletion.