Self-etching conditions

The achievements of making controllable self-organized columnar porous alumina, porous Si and porous InP [27-32] raise the question whether we can obtain a similar porous structure in SiC by controlling the etching conditions. This section focuses on the fabrication of columnar porous SiC. The necessary etching conditions and formation mechanisms are also discussed. 

Although some of the presented acidic methacrylates are promising candidates to enter dental materials, they also suffer a major drawback. Indeed, the methacrylate group is not stable in acidic aqueous conditions and tends to hydrolyze. As a consequence, acidic methacrylates are not stable when stored in water. They should therefore preferably be used in materials which do not contain water, such as self-etch cements. SEAs comprising such monomers need to be stored in the refrigerator and have a limited shelf life. In order to circumvent this problem, new monomers exhibiting improved stability towards hydrolysis were synthesized. 

These authors constructed Pourbaix diagrams for the MnTe, ZnTe, Cdi , Mn i Te, and Cdi cZn cTe systems and argued that the related analysis is an effective approach to determine conditions for selective etching, chemical polishing, passivation, and self-metallization of ZnTe, MnTe, and their solid solutions. 

Initial processing experiments showed however, that under typical O2 RIE conditions (power 0.1 to 0.2 W/cm self-bias — —250 to —350 V, pressure — 5 to 20 mTorr O2), these resists are not very resistant, particularly under prolonged etching. Effective pattern transfer may require etch times of 15 to 30 min (11,12). which are sufficient to cause extensive degradation of the resist. Such behavior is reminiscent of poly (olefin sulfone)s such as the well-known PBS e-beam resist, which is etched 5-7 times faster than polystyrene in an oxygen plasma (5). 

SEM images in Fig. 1 illustrate dependence of a relief of the ciystal surface self-formed near the vertex of the mask right comer on the etchant composition. The analysis of all data set of such images observed for samples etched under the experimental conditions enables us to conclude that the surfaces emerging under the mask convex comer are not perfect low-index planes. The evidences of their imperfection are the bend within their borders the nonparallelism of upper surface border (which intersected the mask) to lower one a quite complicated and various relief which has stepped character in a number of experiments (see Fig. 1). 

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