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The process of photoanodic etching of deep pores in lightly doped wafers was investigated. On a 6 in. wafer, more than 1 billion pores, regularly distributed over the wafer in a hexagonal array with a pitch of 3.5 μm, were obtained using an electrolytic back contact. The diameter of the pores was about 2 μm and depths up to 400 μm could be achieved. Kinetic experiments revealed that the etching process was diffusion controlled in a solution containing HF, , and ethanol. Electrochemical experiments showed that evolution took place at the back side of the Si wafer and that and evolved at the Pt cathode and anode, respectively. © 2000 The Electrochemical Society. All rights reserved.
Meerakker et al. (2000) studied this question.