Diode laser spectroscopy of high density fluorocarbon plasmas for semiconductor material processing

Abstract

Inductively coupled, high-density plasma reactors are expected to play a key role in next generation 0.25 nm semiconductor manufacturing. This work focuses on diode laser diagnostics of two such reactors: a noncommercial research scale reactor known as the Gaseous Electronics Conference (GEC) inductively coupled plasma Reference Cell and a commercial reactor known as the AMAT 5300 HOP oxide etcher. Diode laser absorption spectroscopy provides a relatively simple and cost effective means of measuring radical species, in situ concentrations without perturbing the plasma. In this study, we employ diode lasers in the mid-IR regime (3-11 um) to detect radicals important to oxide etching. This work describes gas phase measurements of etchant species (CF and CF2) formed from dissociation of a C2F6 plasma, and etch-product species formed from plasma surface interactions. The technique is crucial to plasma model development since it is one of the few techniques that can reliably measure the absolute density of ground state radical species formed by electron impact dissociation in the discharge. A database of neutral radical species concentrations at various reactor power, bias and pressure settings is presented. This database is essential for theoretical plasma model calibration and validation.