Production and destruction of CFx radicals in radio-frequency fluorocarbon plasmas

Abstract

Spacially resolved densities of CF, CF 2 , and CF 3 radicals in capacitively coupled 13.56 MHz radio-frequency ͑rf͒ discharges in CF 4 and CHF 3 were determined by means of infrared absorption spectroscopy employing a tunable diode laser spectrometer. It was established that the stationary CF 2 density and density profile in a CF 4 plasma depend strongly on the electrode material. This is attributed to different sticking coefficients of CF 2 on different surfaces. Furthermore, it was found that the densities of all CF x radicals increase near the electrodes at high gas pressures and rf powers in a CHF 3 plasma. This leads to the conclusion that production of CF x radicals takes place in the sheath region close to the electrodes. It is proposed that collisions between ions and source gas molecules are responsible for this production of CF x radicals. In the presence of a destruction process in the plasma glow ͑e.g., by three-body recombination with other radicals͒ and the absence of a fast surface loss process this results in the observed increase of CF x densities near the electrodes. In order to study the radical kinetics time dependent measurements were performed during power modulation of the plasma. It was found that the decay time of the CF 2 density in the afterglow of a CF 4 plasma is much shorter than the corresponding decay time in a CHF 3 discharge. This suggests that the surface loss is relatively less important in the latter case, in agreement with measurements of spatial density distributions. This is explained by the presence of a ͑CF x ) n layer, which is readily deposited on the electrodes in a CHF 3 discharge, and by low sticking probabilities of CF and CF 2 radicals on such a layer.

Difluorocarbene Studied with Threshold Photoelectron Spectroscopy (TPES): Measurement of the First Adiabatic Ionization Energy (AIE) of CF2

“…[5,6] Small reactive intermediates, such as CF 2 , play important roles in determining the etching rate, selectivity and anisotropy of plasma-etching processes. The mechanisms of CF 2 production and destruction in fluorocarbon reactive ionetching processes have been investigated using techniques such as laser induced fluorescence, [11] broad-band UV absorption spectroscopy, [12,13] infrared diode laser spectroscopy [14,15] and cavity-ring down spectroscopy. [16] It has been found that the primary mechanism for CF x production (where x = 1, 2 and 3) is neutralisation and fragmentation of CF x + (x = 1-4) ions incident on the powered electrode and not direct electron-impact induced fragmentation of the feedstock gas.…”

Production and loss of CF 2 and CF radicals at the polymerization in CF 4 plasma

“…On this reason we allowed dependences rcF2(TW) for one pressure but different discharge ourselves to discuss a little the possible loss currents. Solid lines are linear fits of data by using the expression mechanism of CF2 and CF on a fluorocarbon (11) (see text). surface by using the results of both our and other works.…”

“…It is reasonable that researches of CF4 plasma attract so particular interest [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. No wonder that many electrodynamic models of CF4 plasma with using different sets of electron scattering cross-sections on CF4 molecules exist now [15][16][17][18][19][20].…”

SiO2 etching using inductively coupled plasma

“…However, from this point of view, the seasoning procedure is also important. Here we report on wall heating and seasoning procedure as ways of controlling the chamber wall [11,12].…”