owing to buildup of hard-to-dissolve oxidation products at the etching surface.The three prototype systems studied [en-HC1-K3Fe (CN) 6, NH3-NH4CI-I~Fe (CN) 6, and KOH-KH2PO4-K3Fe (CN)6] are all capable of excellent etching of high resolution tungsten device circuits as long as the selected composition meets the criterion of H + absorbing capacity. We tend to favor KOH-KH2PO4-K3Fe (CN)6 (even though it furnishes the lowest etching rates) for general work owing to its long shelf life and relative independence of component concentrations. Where speed is required or thick tungsten samples (> 5000A) mus~ be etched, then the en-HC1-KsFe (CN)6 system is recommended, provided the user is aware of the short shelf life of the etchant.The gentle nature of KsFe(CN)6 coupled with the near-neutral pH of etchant operation makes these systems completely compatible with all presently available photoresists.
AcknowledgmentWe wish to thank J. L. Bartelt for suggesting the advantages of strong acids for buffering amines.
ABSTRACTIn order to illustrate the effect of metal vapors on chemical reactions carried out at high temperatures, the example has been taken of propane cracking in an argon plasma, yielding acetylene. The reaction takes place in the homogeneous phase, in the presence of iron vapor. Molar ratios propane/ argon of 1.5 and 6.0% have been used, associated with 0.25, 0.75, and 1.00% iron/argon molar ratios. It is observed that the reaction temperatures required for obtaining the maximum conversion of propane into acetylene are considerably lowered in the presence of iron vapor, attaining then 3200 ~ 4200~ while, all other conditions being equal, except for the presence of iron vapor, these temperatures are of the order of 5000~176The latter conditions also lead to maximum conversions of propane into acetylene which are of the order of 40 % while these conversions attain 100 % when iron vapor is present. Possible mechanisms are suggested, relating the results observed either to a catalytic effect generated by condensing iron particles, or to a photosensitization process by which excited iron vapor emissions around 30,00.7 and 5328.5A contribute to the stabilization of acetylene and C2H precursor during the quenching stage, thus avoiding the decomposition of these species into solid carbon and hydrogen. * Electrochemical Society Active Member.
ABSTRACTActivities and activity coefficients of indium and tin in their amalgams were determined by means of potentiometric measurements in the temperature region 150~176The equilibrium potential of indium amalgam was