We demonstrate to the acceleration of the moistureless etching reaction between the silicon native oxide and the anhydrous hydrogen fluoride (AHF) gas, using remote-plasma-excited Ar gas at room temperature.
The etching reaction is significantly enhanced by the remote-plasma-excitation for both the chemically grown native oxide films and the dehydrated oxide films. Then, we attempt to improve the selectivity
of the oxide etching with respect to silicon by introducing hydrogen into this system, and to realize the highly selective etching
of native oxide with respect to silicon. With the increase of the hydrogen partial pressure, the etch rate of silicon rapidly decreases due to the suppression of the density of fluorine radicals in the gas phase.
We have confirmed the value of the etch rate selectivity to be at least 4.
The time slot interchanger (TSI) is employed widely in practice as the switch fabric of digital cross‐connect systems or exchange systems in the digital synchronized network. With the increasing need for ISDN with the fundamental rate of 64 kbit/s as the background, it is desired to realize a large‐capacity TSI. This paper discusses the optimum design of the pipelined TSI which has been proposed in the past, aiming at the realization of a large‐capacity TSI.
First, the TSI configuration is proposed which realizes the time slot integrity in multislot connection, which has been a problem in the traditional pipelined TSI. The proposed method corresponds to the traditional TSI using RAM, where the time slot sequence integrity is realized by employing the double‐buffer structure.
Then the optimum design method for the proposed pipelined TSI is presented, where the evaluation measure is the performance index, defined as the product of memory capacity and the operation speed. For comparison based on the defined performance index, the pipelined TSI optimized by the proposed method has several tens to several hundred times better performance than the conventional TSI using RAM or shift registers. Thus, it is demonstrated that the proposed construction is effective in realizing a large‐capacity TSI.
The adsorption of anhydrous hydrogen fluoride (AHF) on the surfaces of silicon native oxide was investigated by in situ X-ray photoelectron spectroscopy (XPS) in order to understand the reaction between HF and the oxide films at room temperature. A significant amount of the component is located at 670.0 eV binding energy in the observed XPS spectra, and is most likely derived from HF molecules. Moreover, the surface density of F-Si bonds slowly increases with the AHF exposure. We also attempted to accelerate the etching of the native oxide without moisture, supplying the AHF gas with remote-plasma-excited Ar, and obtained the enhanced etch rate.
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