Self detachment of free-standing porous silicon membranes in moderately doped n-type silicon
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In this article we describe a reliable etching method to fabricate porous silicon free-standing membranes (FSMs) based on a self detachment of the porous layer in moderately doped n-type silicon substrates. We found that stable growth of smooth and straight pores is restricted to a narrow range of etching conditions and, unlike p-type substrates, the lift-off of the membrane is a self-limited process that does not require a large burst of current. The detachment of the porous membrane is independent of the structure of the already porosified layer, meaning that the average pore diameter can be tuned from nano to macro size within the same membrane. We also demonstrate that, despite their limited thickness, FSMs are quite robust and can sustained further processing. Thus, the etching receipt we are proposing here extends the range of sensors and filters that can be fabricated using porous silicon technology.
KeywordsPorous Silicon Applied Current Density Increase Annealing Time Transitional Layer Large Current Density
This work was supported by the European Commission through the project FP7-257401 POSITIVE. The authors acknowledge TNLabs network for the sharing of the experimental facilities. The authors are grateful for the manuscript review provided by Dr. M. Swann.
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