(2002). Reactive ion etching of quartz and pyrex for micro electronic applications. Journal of applied physics 92(7): 3624-3629 and may be found at https://doi.org/10.1063/1.1503167 Additional information: Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full DRO policy for further details. The reactive ion etching of quartz and Pyrex substrates was carried out using CF 4 /Ar and CF 4 /O 2 gas mixtures in a combined radio frequency rf/microwave w plasma. It was observed that the etch rate and the surface morphology of the etched regions depended on the gas mixture CF 4 /Ar or CF 4 /O 2), the relative concentration of CF 4 in the gas mixture, the rf power and the associated self-induced bias and microwave power. An etch rate of 95 nm/min for quartz was achieved. For samples covered with a thin metal layer, ex situ high resolution scanning electron microscopy and atomic force microscopy imaging indicated that, during etching, surface roughness is produced on the surface beneath the thin metallic mask. Near vertical sidewalls with a taper angle greater than 80° and smooth etched surfaces at the nanometric scale were fabricated by carefully controlling the etching parameters and the masking technique. A simulation of the electrostatic field distribution was carried out to understand the etching process using these masks for the fabrication of high definition features.

The description of optical fields in terms of their eigenmodes is an intuitive approach for beam characterization. However, there is a lack of unambiguous, pure experimental methods in contrast to numerical phase-retrieval routines, mainly because of the difficulty to characterize the phase structure properly, e.g. if it contains singularities. This paper presents novel results for the complete modal decomposition of optical fields by using computer-generated holographic filters. The suitability of this method is proven by reconstructing various fields emerging from a weakly multi-mode fiber (V approximately 5) with arbitrary mode contents. Advantages of this approach are its mathematical uniqueness and its experimental simplicity. The method constitutes a promising technique for real-time beam characterization, even for singular beam profiles.

The products of reaction and etch rates of Si and SiO2 in SF6-O2 plasmas have been studied as a function of feed composition in an alumina tube reactor at 27 mHz, 45 W, and 1 Torr. There is a broad chemical analogy with CF4-02 plasmas. As in CF4-02 mixtures, the rate of Si etching and 703.7-nm emission from electronically excited F atoms each exhibit distinct maxima as a function of feed gas composition; these data support a model in which fluorine atoms, the etching species, compete with oxygen atoms for chemisorption on the Si surface. Without oxygen in the feed or Si in the reactor, no stable products could be detected. With an SF6-O2 mixture in the absence of silicon, the final reaction products are F2, SOF4, and SO2F2. The product distribution was unaffected by small SiO2 substrates. When Si is etched, SiF4 is the only stable silicon-containing etch product and SOF2 is formed in oxygen-poor mixtures. Rapid etch rates (≳104 Å/min for Si) can be obtained with a high selectivity in favor of silicon (Si:SiO2≳40:1); thus SF6-O2 mixtures may represent an attractive alternative to CF4-O2 for the plasma etching of silicon and SiO2.

Fluorine atoms etch silicon with a rate, RF(Si) = 2.91±0.20×10−12T1/2nFe−0.108 eV/kT Å/min, where nF (cm−3) is the atom concentration. This etching is accompanied by a chemiluminescent continuum in the gas phase which exhibits the same activation energy. These phenomena are described by the kinetics: (1) F(g)+Sisurf→SiF2(g), (2) SiF2(g) +F(g) →SiF*3(g), (3) SiF2(g) +F2(g) →SiF*3(g) +F(g), (4) SiF*3(g) →SiF3(g) +hνcontinuum where formation of SiF2 is the rate-limiting step. A detailed model of silicon gasification is presented which accounts for the low atomic fluorine reaction probability (0.00168 at room temperature) and formation of SiF2 as a direct product. Previously reported etch rates of SiO2 by atomic fluorine are high by a constant factor. The etch rate of SiO2 is RF(SiO2) = (6.14±0.49)×10−13nF T1/2e−0.163/kT Å/min and the ratio of Si to SiO2 etching by F atoms is (4.74±0.49)e−0.055/kT.

No abstract