Diagnostics of inductively coupled chlorine plasmas: Measurement of Cl2 and Cl number densities

Abstract

This article presents measurements of absolute Cl2 and Cl number densities in a chlorine transformer-coupled plasma. It is part of a series of reports on measurements of densities and energy distributions of all charged and neutral species in the same plasma system over an extensive range of pressure and power. Cl2 and Cl number densities were determined from optical emission spectroscopy and advanced actinometry. Number densities relative to the Xe actinometry gas are reported as a function of pressure (1–20 mTorr) and power (10–1000 W) during slow etching of SiO2-covered Si wafers. A detailed treatment of the effects of gas temperature on the conversion of these ratios into absolute number densities is also included. Cl2 is largely (∼90%) dissociated at the highest powers, with a somewhat higher degree of dissociation at low pressure. The Cl number density becomes nearly independent of power at high powers (especially at lower pressure) due to the combination of a higher degree of dissociation of Cl2 and an overall drop in number density due to heating of the gas. A zero-dimensional (global) model is used to compute Cl2 and Cl number densities. It gives a Cl wall recombination coefficient of 0.04 on the plasma-seasoned stainless steel walls.

Experimental and modeling study of O and Cl atoms surface recombination reactions in O2 and Cl2 plasmas

“…In addition, for comparable Cl-to-Cl 2 number density ratio, the absolute values of γ Cl are also in good agreement. These values are also comparable to the ones obtained by Malyshev et al [22] (γ Cl = 0.04 for n Cl /n Cl 2~ 30) and by Corr et al [63] (γ Cl = 0.02 for n Cl /n Cl 2~ 3) in highly and moderately dissociated Cl 2 ICP and by Richard and Sawin [64] (γ Cl = 0.007 for n Cl /n Cl 2~ 0.08) in a weakly dissociated capacitively coupled plasma.…”

“…As a result, the recombination coefficients determined from beam studies for a given atom on a given material often vary by orders of magnitude with respect to those obtained under dynamic plasma conditions. For example, Kota et al [19] found recombination coefficients for Cl atoms at 300 K of 0.2 for anodized Al and 0.7 for stainless steel (SS) in a molecular beam experiment while the values for these materials determined in high-density Cl 2 plasma reactors are usually in the 0.01-0.04 range [20][21][22]. An important factor influencing the surface recombination rates and thus the materials processing rates is the so-called "conditioning" or "seasoning" of the surface following exposure to reactive plasmas [23][24][25][26].…”

On the applicability of self-consistent global model for the characterization of Cl2/Ar inductively coupled plasma

“…These results are similar to those reported in Refs. [14,20] for both pure Cl 2 and Cl 2 /Ar ICP systems. Taking into account a weak sensitivity of T e to the variation of input power found by experiment and modeling, the effect of input power on n Cl and n Cl =n Cl 2 may be mainly related to the increasing Cl 2 dissociation rate through the increasing electron density.…”

“…The basic concepts of global model for low-pressure electronegative plasmas have already been described in several works [3][4][5][6][7]. The works of Ullal et al [8], Yonemura et al [9,10], Wainman et al [11], Gudmundsson [12] and Malyshev and Donnelly with co-authors [13][14][15][16] combined the experimental investigations and modeling for both Cl 2 and Ar inductively coupled plasmas (ICP) to obtain and verify the data on electron energy distribution function (EEDF), electron temperature and densities of active species. Also, the works of Efremov et al [17,18], Fuller et al [19,20] and Meeks et al [21] reported both experimental and modeling results for Cl 2 /Ar ICP with different gas mixing ratios.…”

Dry etching of zinc-oxide and indium-zinc-oxide in IBr and BI3 plasma chemistries

“…In general, an increase in ICP source power leads to an increase of both the reactive neutral density (through an increase of the dissociation degree of the reactive molecular species) and the positive ion density [47][48][49]. Moreover, Fig.…”