Production of Fluorine-Containing Molecular Species in Plasma-Generated Atomic F Flows

Abstract

The fluorine atomic radical reactions to form molecular fluorine and hydrogen fluoride are examined by time-of-flight mass spectroscopy (TOFMS) and kinetically modeled for various reaction orders. Fluorine radicals are generated from NF 3 or F 2 in microwave-generated and low-frequency (LF)-generated plasmas and are passed through flow tubes under various flow, pressure, and dilution conditions. In general, the concentrations of the mass spectroscopically measured products F, F 2 , and HF do not depend on the specific wall material (e.g., Teflon, stainless steel, Al, Ni, Al 2 O 3 , SiO 2 ); the only variations of [F]/[F 2 ]/[HF] ratios with wall material are found at pressures below 1 Torr. The most significant changes in these ratios are observed upon varying flow rates and pressures. Specifically, the F relative concentration decreases from ∼80% to ∼20%, and the F 2 relative concentration increases from ∼20% to ∼80%, as the pressure is varied over the range 0.5-10 Torr. In all cases, the HF concentration is found to decrease as the pressure increases. Data suggest that the composition of the tube surface material does not contribute significantly to the generation of F 2 ; however, since the wall surface carries adsorbed hydrogen sources such as H, H 2 O, H 2 , and OH, it becomes important in the generation of HF. A simple kinetic analysis of the experimental data suggests a combined two-reaction mechanism for F 2 and HF generation: (1) a pseudo-second-order volume reaction (k v ) to generate F 2 , and (2) a zero-or first-order wall reaction (k w ) to generate HF. Thus, both surface and volume reactions contribute to the overall F atom loss mechanism in the gas flow from the plasma source. The model fits our data best for a k v /k w ratio of about 75. The reaction order for the loss of F atom is found to be 1.68, while the reaction order for the formation of F 2 is found to be ∼2.

Production and transport chemistry of atomic fluorine in remote plasma source and cylindrical reaction chamber

“…The proposed model was further validated using experimental results obtained by earlier researchers [20] who studied the fluorine recombination process through a cylindrical reactor with dimensions of 3.4 cm inner diameter and 30.5 cm length. These dimensions are drastically different from those used at APCI facility.…”

Role of N2 during chemical dry etching of silicon oxide layers using NF3/N2/Ar remote plasmas

“…The remote plasma cleaning processes of the silicon dioxide and silicon nitride layers using PFCs such as C 2 F 6 , C 3 F 8 , C 4 F 8 , and NF 3 have been studied and used in the flat panel display (FPD) industry [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. The PFCs that are reemitted during chamber etching, however, are known to have a serious global warming effect in the atmosphere [10][11][12][13][14][15][20][21][22][23][24][25][26].…”

Downstream Plasma Delivery From a Remote VHF Source

“…A primary objective in any plasma application, remote or direct, is the ability to deliver a desired stream of energized particles (ions and neutrals) from the plasma to the surface being processed. The segregation of high energy species away from delicate layers is often a goal of remote plasma processing, but an unfavorable consequence can be the loss of potentially desirable species, resulting from wall and volumetric interaction associated with delivery through some distance to the processing chamber [13,14].…”