Metal-assisted homogeneous etching of single crystal silicon: A novel approach to obtain an ultra-thin silicon wafer

Homogeneous etching of silicon is achieved through one-step metal-assisted chemical etching (MACE), which offers a simple route to obtain the ultra-thin silicon wafer with thickness below 50 μm. The surface of the ultra-thin silicon wafer obtained by this method is smooth at the nanometer scale, and its surface roughness is around 10 nm. The homogenous etching mechanism is discussed in terms of the hole injection principle. Itʹs found that the introduction of a high concentration of H2O2 facilitates the uniform distribution of the holes injected on the silicon surface, causing the homogeneous etching of the silicon. Meanwhile, the thinning is uniform across a large wafer area, and ultra thin silicon wafers up to 4 in. in diameter were obtained. Furthermore, any thickness of silicon wafer within 30–180 μm can be obtained by modulating the etching process accurately.