Silicon wafer, pits

In order to circumvent these shortcomings, a fabrication process based on macro PS as a sacrificial layer has been proposed [Le30]. The process sequence is shown in Fig. 10.25. First etch pits in the desired pore pattern are formed on the n-type silicon wafer surface by photolithography and subsequent alkaline etching. Then deep macropores are formed by electrochemical etching according to the... 

Use KOH solution to etch the part of the silicon wafer exposed through the square opening. The etch self-terminates at the Si(lll) planes, and a pyramidal pit is formed. 

Ill) face quite slowly. The difference in etch rates is 300 1. The wafer is immersed in the etch and, by carefully controlling the etch time or using an etch stop method, a deep pit is generated. Depending on the thickness of the wafer and the size of the etch window, a thin membrane of single-crystal silicon can be formed at the bottom. 

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