Optical plasma emission spectroscopy of etching plasmas used in Si-based semiconductor processing

Abstract

Previously published applications of optical emission spectroscopy as a quantitative plasma diagnostic technique are reviewed. By adding traces of rare gases to the plasma, electron temperatures (T e) and relative electron and ion densities can be determined from electron impact-induced optical emission. Excitation from both the ground state and metastable states of the rare gases must be considered. At higher rare gas partial pressures, UV radiation trapping and optical cascading must also be taken into account. Absolute species concentrations (e.g. Cl 2 , Cl, O, and F) can be derived from their optical emissions, combined with T e measurements determined from rare gas optical emission. Examples are given of neutral and ion species density measurements in chlorine, oxygen, and fluorocarbon-containing low-pressure, high charge-density plasmas. Typical results of T e measurements are also presented and compared with Langmuir probe measurements.

Low temperature–low hydrogen content silicon nitrides thin films deposited by PECVD using dichlorosilane and ammonia mixtures

“…4 shows the spectra of films deposited at 20, 30, 60 and 80 W. As can be seen from this figure, the emission spectrum for the lowest value of RF power (20 W) shows predominantly a continuum band extending from 250 to 425 nm, and other lines in 20 the region from 410 to 500 nm. The continuous band can be identified as the superposition of two well-known continuums; one due to emission from H 2 molecules and another due to SiCl 2 molecules and SiH x Cl y species [31,32]. The other intense lines are identified with species such as SiH (414 nm), Cl (425 nm), Cl 2 (450 nm), and atomic H (434, 486 nm).…”

Optical Diagnostics for Thin Film Processing

“…Optical emission spectroscopy (OES) is a convenient tool for semiquantitative analysis of processing plasmas and is widely used to assess trends in plasma etching (6) and deposition, including sputter deposition, and for process control (7). It provides information about the densities of a given excited state being probed and becomes a powerful quantitative tool of ground state density (which usually ≈ total density) when emission intensities of species of interest are compared to those from a stable rare gas reference, as in actinometry.…”

Controllable optical emission spectroscopy diagnostic system for analysis of process chemistries

“…OES also plays an important role in providing an optical process parameter to the now widely applied statistical method known as principal component analysis ͑PCA͒. They are signal attenuation due to optical window contamination, 8,9 and short and long term drifts in the optical signal intensities. 3 As feature sizes have decreased, newer processing systems have begun to employ upstream plasma where there is very little optical emission 4 above the active etch reaction region.…”