Effect of current density on silicon surface in electrochemical etching

Abstract

A simple and reliable fabrication technique for producing nanoporous filters is presented. The nanoporous filter plays an important role in biomedical microelectromechanical systems applications, especially in filtering out waste and solute from inside human blood. Nanosized components in the biological fluid are filtered using silicon membranes that are controlled by nanosized pores. The technique explored was the electrochemical etching (ECE) process of silicon. This approach starts with thinning the bulk silicon until only several micrometres thick using the KOH process and then carry out ECE to produce pores. The yield of the process was a 3 µm thick nanoporous silicon membrane with pore sizes of less than 100 nm. This physical characteristic enables the membrane to filter all the waste and solute particles of less than 100 nm. Owing to this simple and reliable method, the development of nanoporous silicon membrane can be used in nanofiltration applications especially in an artificial kidney.

Self-Adjusting Electrochemical Etching Technique for Producing Nanoporous Silicon Membrane

“…This equation is also used by some researchers [31][32][33][34]. But other equations have been proposed in the process of liquidation in accordance with the method of surface oxidation of silicon, exchange hole and electrons that become a source of divalent silicon on the oxidation level [35].…”

“…Ion dissolution process is dependent on the current density during the electrochemical etching process. The current density also affects the pore structure like spongy or columnar structure [33]. The current density is also among the parameters that can be manipulated to produce the perfect pore structure.…”

“…Besides that, n-type silicon substrate is more efficient to collect the charge carrier with the assistance of photoluminescence to promote columnar pore structure due to the depletion of holes during pore passivity against dissolution [41]. P-type silicon substrate is suggested to use high current density to get the columnar and well-ordered pore structure [33].…”

Electrochemically etched nanoporous silicon membrane for separation of biological molecules in mixture

“…For our application, the pore holes has to be columnar, with pore sizes of less than 50 nm. Our previous work has shown that pore sizes and uniformity are reproducible given the specific set of parameters [33,40,41].…”

“…A high current density is needed to get columnar pore structure [22,40]. For this work, current density of 600 mA cm −2 was used with ethanol:HF at 1:1 ratio as the electrolyte.…”