Effect of current density on silicon surface in electrochemical etching

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.