Tuning the pore diameter of porous silicon (PS) is essential for some applications such as biosensing, where the pore size can filter the entrance of some analytes or increase its sensitivity. However, macropore (>50 nm) formation on p-type silicon is still poorly known due to the strong dependence on resistivity. Electrochemically etching heavily doped p-type silicon usually forms micropores (<5 nm), but it has been found that bigger sizes can be achieved by adding an organic solvent to the electrolyte. In this work, we present the results of using dimethylformamide (DMF), dimethylsulfoxide (DMSO), potassium hydroxide (KOH) and sodium hydroxide (NaOH) for macropore formation in p-type silicon with a resistivity between 0.001 and 0.02 Ω∙cm, achieving pore sizes from 5 to 100 nm.
Macropore formation in p-type silicon: toward the modeling of morphology