Investigation of Pore Diameter Modulation in Depth in p-type Silicon

The possibility of local modulation of the macropore diameter has been investigated for macropores at different pore depths on pre-patterned low-doped p-type silicon (p-Si) substrates. Using electrolytes based on HF/organic solvents, it is relatively easier to vary the diameter of deep pores compared to shallow pores. Adding polyethylene glycol to the electrolyte helps to achieve pore diameter modulation even at shallow depths. Using Fast Fourier Transformation impedance spectroscopy (FFT-IS), the pore growth was analyzed in situ. A simple model was used to fit all the measured data, and some electrochemical parameters could be quantified. Comparing these parameters with the pore morphologies, it was observed that diffusion limitation is essential for achieving pore diameter modulation in p-Si by changing the applied current density.