Über das chemische Glänzen von Messing und Neusilber

Chemical Etching of Silicon

“…the steady-state condition can be achieved only after a concentration of HNO~ in excess of a threshold value has been built up in the vicinity of the silicon surface, either through the addition of a small amount of NaNO~ or as a consequence of the attainment by the etching reaction of a sufficient rate to accomplish this purpose. In this steady-state condition the mode of attack on the silicon is probably almost exclusively via HNO_~, and the site where the rate-determining processes play their roles has probably shifted from the silicon surface to the boundary layer surrounding the silicon specimen, in a mechanism similar to that suggested by Spahn and Schmid (9). It must be remembered that the formation of HNO_~ by the Abel and Schmid mechanism is autocatalytic, and that it requires the presence of HNO~ in order for the processes of Eq.…”

“…The net result as seen from the bulk solution is the diffusion of one molecule of HNO~ into the boundary layer, and one molecule of HNO., into the bulk solution. The ultimate form of the reduction product of nitric acid that is produced will depend only on the composition of the bulk solutions, as shown by Spahn and Schmid (9). In dilute HNO.~ solution the HNOo that enters the bulk solution will decompose rapidly to NO and HNO~ by the reversal of Eq.…”

“…[N~O~] : K [HNO~]~/P~o [9] Here the term K is the equilibrium constant for the reaction of Eq. [7], and P.~o is the partial pressure of nitric oxide.…”

On the Mechanism of Chemically Etching Germanium and Silicon

“…Therefore, if the rates of diffusion and convection of HNO~ and HF from the solution bulk to the Si surface are approximately equal, the maximum etching rate should occur when the mole ratio of HNO~ to HF is 1/3 [solution composition: 42% by wt (70%) HNO~ + 58% by wt (49%)HF]. Schmid and Spahn (21,23) found that HNO~ reduces beyond nitrous acid, HNO.~, to nitric oxide, NO, when copper is chemically etched in HNO~. For this mechanism, the over-all cathodic reduction of nitric acid is HNO~ + 3H+-> NO + 2H.~O + 3e § [5] Robbins and Schwartz (1,24) have assumed that HNO~ reduces to NO as in Eq.…”

Chemical Etching of Silicon

“…This mechanism is in accord with the observed autocatalytic behavior of the reaction. An additional possible interpretation of the mechanism is based on a paper by Schmid and Spahn (6) which considers the various equilibria involving nitrogen oxides and nitrous acid. The latter authors accept the basic ideas of Abel, et al (7)(8)(9) that the active oxidizing agent is HNO.. such that 2HNO.., + R ~ RO + 2NO + H~O (R = reducing agent) [4] and that the formation of HNO.., is rate determining.…”