Comparison of Erosion Behavior and Particle Contamination in Mass-Production CF₄/O₂ Plasma Chambers Using Y₂O₃ and YF₃ Protective Coatings

Yttrium fluoride (YF₃) and yttrium oxide (Y₂O₃) protective coatings prepared using an atmospheric plasma spraying technique were used to investigate the relationship between surface erosion behaviors and their nanoparticle generation under high-density plasma (10¹²–10¹³ cm⁻³) etching. As examined by transmission electron microscopy, the Y₂O₃ and YF₃ coatings become oxyfluorinated after exposure to the plasma, wherein the yttrium oxyfluoride film formation was observed on the surface with a thickness of 5.2 and 6.8 nm, respectively. The difference in the oxyfluorination of Y₂O₃ and YF₃ coatings could be attributed to Y–F and Y–O bonding energies. X-ray photoelectron spectroscopy analyses revealed that a strongly fluorinated bonding (Y–F bond) was obtained on the etched surface of the YF₃ coating. Scanning electron microscopy and energy dispersive X-ray diffraction analysis revealed that the nanoparticles on the 12-inch wafer are composed of etchant gases and Y₂O₃. These results indicate that the YF₃ coating is a more erosion-resistant material, resulting in fewer contamination particles compared with the Y₂O₃ coating.

Extensive theoretical study on various low-lying electronic states of silicon monochloride cation including spin-orbit coupling

The potential energy curves of the 23 Omega states generated from the 12 valence Lambda-S states of silicon monochloride cation are calculated for the first time using the internally contracted multireference configuration interaction method with the Davidson correction and entirely uncontracted cc-pV5Z basis set. Spin-orbit coupling is taken into account by the state interaction approach with the full Breit-Pauli Hamiltonian. Very good agreement is achieved between our computed spectroscopic properties and the available experimental data. In particular, the adiabatic excitation energies of the a3Pi(0+) and a3Pi(1) states computed by us are 31,708 and 31,830 cm(-1), respectively, in excellent agreement with the respective experimental values of 31,721 +/- 2 and 31,836 +/- 3 cm(-1). The curve crossings and the predissociation mechanism are investigated. The transition dipole moments are analyzed and the transition properties of the a3Pi(0+)-X1Sigma(0+)+ and a3Pi(1)-X1Sigma(0+)+ transitions are predicted, including the Franck-Condon factors and the radiative lifetimes.

Plasma-surface reactions at a spinning wall

We report a new method for studying surface reactions and kinetics at moderately high pressures (<10 Torr) in near real time. A cylindrical substrate in a reactor wall is rotated at up to 200,000 rpm, allowing the surface to be periodically exposed to a reactive environment and then analyzed by a triple-differentially pumped mass spectrometer in as little as 150 micros thereafter. We used this method to study oxygen plasma reactions on anodized aluminum. When the substrate is spun with the plasma on, a large increase in O2 signal at m/e = 32 is observed with increasing rotation frequency, due to O atoms that impinge and stick on the surface when it is in the plasma, and then recombine over the approximately 0.7 to 40 ms period probed by changing the rotation frequency. Simulations of O2 signal versus rotation frequency indicate a wide range of recombination rate constants, ascribed to a range of O-binding energies.

Recombination Reactions of Oxygen Atoms on an Anodized Aluminum Plasma Reactor Wall, Studied by a Spinning Wall Method

We have studied the recombination of O atoms on an anodized Al surface in an oxygen plasma, using a new "spinning wall" technique. With this method, a cylindrical section of the wall of the plasma reactor is rotated and the surface is periodically exposed to an oxygen plasma and then to a differentially pumped mass spectrometer (MS). By varying the substrate rotation frequency (r), we vary the reaction time (t(r)), that is, the time between exposure of the surface to O atoms in the plasma and MS detection of desorbing O(2) (t(r) = 1/2r). As t(r) is increased from 0.7 to 40 ms, the O(2) desorption signal decreases by a factor of 2 for an O-atom flux of 1 x 10(16) cm(-2) s(-1) and by a factor of 6 when the O flux is 1 x 10(17) cm(-2) s(-1). The O(2) signal decay is highly nonexponential, slowing at longer times and reaching zero signal as r --> 0. A model of O-atom recombination is compared with these time-dependent results. The model assumes adsorption occurs at surface sites with a range of binding energies. O can detach from these sites, become mobile, and diffuse along the surface. This leads to desorption of O, reattachment at free adsorption sites, and recombination to form O(2) that promptly desorbs. With several adjustable parameters, the model reproduces the observed shapes of the O(2) desorption decay curves and the lack of detectable desorption of O and predicts a high O-atom recombination coefficient on anodized aluminum.