Deep Etching of Single- and Polycrystalline Silicon with High Speed, High Aspect Ratio, High Uniformity, and 3D Complexity by Electric Bias-Attenuated Metal-Assisted Chemical Etching (EMaCE)

In this work, a novel wet silicon (Si) etching method, electric bias-attenuated metal-assisted chemical etching (EMaCE), is demonstrated to be readily available for three-dimensional (3D) electronic integration, microelectromechinal systems, and a broad range of 3D electronic components with low cost. On the basis of the traditional metal-assisted chemical etching process, an electric bias was applied to the Si substrate in EMaCE. The 3D geometry of the etching profile was effectively controlled by the bias in a real-time manner. The reported method successfully fabricated an array of over 10 000 vertical holes with diameters of 28 μm on 1 cm(2) silicon chips at a rate of up to 11 μm/min. The sidewall roughness was kept below 50 nm, and a high aspect ratio of over 10:1 was achieved. The 3D geometry could be attenuated by the variable applied bias in real time. Vertical deep etching was realized on (100)-, (111)-Si, and polycrystalline Si substrates. Complex features with lateral dimensions of 0.8-500 μm were also fabricated with submicron accuracy.