Addition Of HF Research Articles

HI‐H2 vapor etch for low temperature silicon epitaxial manufacturing

AbstractEtching of semiconductor silicon slices at 998°C with HI‐H2 mixtures was developed to the level that practical etch rates (≥ 0.1 μm/min) and smoothness of surfaces were obtained in a manufacturing type reactor without the addition of HF or He. Such a low temperature etch is expected to lead to improved device characteristics, mainly because of more sharply defined junction surfaces.Using deposition at 998°C on very clean slices as a testing method, two sources of impurities that cause stacking faults in the deposition layers were identified and eliminated. These were the polypropylene vessel used in the slice cleanup procedure, and the hydrogen peroxide used in conjunction with sulfuric acid in the primary cleaning step.

Active surface sites and deactivation of chromosorb 102

A combined infrared spectroscopic and chromatographic study was undertaken in order to determine the adsorption properties of Chromosorb 102. This study shows that the unreacted vinyl groups in Chromosorb 102 are the active sites which give rise to extreme tailing of amine peaks when the material is used as a support material. A method was devised for removing these groups chemically by addition of HF to the double bond of the vinyl group. This method of deactivation is not dependent on the surface area of the support or on the amount of reagent used, as is the case in the deposition methods. The spectra obtained allow one to observe the interactions with the surface and enable one to predict which compounds give rise to extreme tailing in a chromatographic column. The predictions made were confirmed by running the test substances in a gas chromatograph containing support materials treated with HF, coated with Carbowax 20M, and untreated.

Rupture-Disk Ampoule for Anhydrous Addition of Hydrogen Fluoride.

The rapid increase in vapor pressure of liquid HF with temperature has been used in a rupture-disk-ampoule technique for mixing HF with materials under anhydrous conditions. At room temperature where HF has a vp near 1.4 atm, the disk with a rupture limit near 10 atm confines the acid. At higher temperatures, 100 and 150 °C, where the internal pressure of HF in the ampoule is 10 and 30 atm, respectively, the disk is ruptured and the acid is released. The construction of the ampoule from platinum and reuseable platinum-iridium parts; the details of the filling, sealing and weighing; and its use for anhydrous addition of HF to other materials in a closed vessel are described.

Experimental Investigation of Silicate Systems Containing Two Volatile Components; Part 2, the Effects of NH 3 and HF, in Addition to H 2 O on the Melting Temperatures of Albite and Granite

Addition of NH 3 to water-albite and water-granite mixtures at constant pressure raises the melting temperatures of albite and granite, whereas addition of HF to these mixtures causes marked lowering of melting temperatures. Results obtained at 2,750 bars pressure for charges containing 1:1 weight ratio of silicate to total volatiles are presented as perspective TX projections from within isobaric prisms onto the volatile faces of the prisms. In the presence of H 2 O alone at 2,750 bars pressure, albite melts between 795 degrees C. and 810 degrees C., and granite begins to melt at 670 degrees C.; in the presence of 8.2 weight percent NH 3 solution, the melting interval of albite is 805 degrees C. to 825 degrees C., and granite begins to melt at 690 degrees C.; in the presence of 8 weight percent HF solution, the melting interval of albite is 610 degrees C. to 685 degrees C., and granite begins to melt at 595 degrees C. No chemical reaction was detected in systems containing NH 3 , but considerable reaction occurs with HF. With increasing HF concentration in the system NaAlSi 3 O 8 -H 2 O-HF, quartz becomes a stable phase and the system is no longer ternary. In the presence of HF solutions, albite crystals grow much larger than in the presence of H 2 O alone.

Transformations of hexane, methylcyclopentane, and cyclohexane in presence of a rhenium-alumina catalyst and of hydrogen under pressure

1. A study was made of the catalytic properties of five rhenium-alumina catalysts of different rhenium contents (5, 15, and 20%) and with additions of ZnO and HF; they were used in the treatment of cyclohexane, hexane, and methylcyclopentane at 290–480° in presence of hydrogen at 5–30 atm at a space velocity of 1.0 hr−1 and a hydrogen to hydrocarbon ratio of 5. 2. Under the conditions investigated aromatic hydrocarbons (up to 78%) were formed only from cyclohexane. At temperatures above 400° and hydrogen pressures of 20 and 30 atm much hydrocracking of hydrocarbons was observed (about 60%). Hexane gave a particularly large amount of hydrocracking (up to 90%). 3. The most active catalyst found for the dehydrogenation of cyclohexane (380°,5 atm), the hydrogenolysis of hexane (300°, 5 atm), and the hydrogenolysis of methylcyclopentane (305°, 5 atm) was 20% Re-Al2O3. 4. The catalyzates of cyclohexane, hexane, and methylcyclopentane were subjected to detailed investigation by gas-liquid chromatography.