Depth Homogeneity of Porous Silicon Multilayer

Porous silicon (PS) multilayer is not perfectly homogeneous with etch depth by analyzing reflectance spectra of PS multilayer samples. And, the dominant reason for this is decrease of HF concentration with etch depth. The decreasing HF concentration result in increasing porosity. However, as we all known, a low etch current density corresponds to a high porosity. For these reasons, we propose a method that a longer break time is introduced during formation of the individual PS layer at the same time etch current density reduced gradually with etch depth. As a result, the experimental reflectance spectra of PS multilayer formed in this way and the simulation result are consistent.