Anisotropic Wet Etching Of Silicon And Its Application In The Micro-nano Structures

Anisotropic wet etching of silicon is one of the most important techniques in silicon micromachining, which has been extensively employed to fabricate a wide variety of micro-structures including membranes, grooves, suspended beams, etc, and also utilized as one of the effective approachs in the fabrication of nano-structures in recent years.In this dissertation, anisotropic wet etching of {110}, {111} and {100} silicon are studied systematically, including the etched structures and their changing laws, etching rates, etching morphology and surface roughness. The corresponding micro-structure and nanopore cavity arrays have been made. The research results are shown as follows:1. The crystal structure and anisotropic wet etching technology of the monocrystalline silicon are introduced. According to the properties of different etchants, TMAH is selected as the main etchant in this work. By three typical etching models, the mechanism of anisotropic wet etching of silicon is analyzed. On the basis of the mechanism and the crystallographic properties, the experimental process and program are designed.2. By comparative experiments under etching mask windows of different shapes in TMAH solutions, the changing laws of etched structures are obtained respectively by experimental results and theoretical analysis, which lay a foundation for the fabrication of nanopore cavity arrays. The etching characteristics in TMAH solution with different surfactants (ammonium persulfate, IPA, etc.) are also discussed in detail, and it is found that ammonium persulfate and IPA can improve the quality of the etched surface remarkably while etching rates decrease to a certian extent. Then the pre-etching techniques are briefly discussed, which provide a way to make more special etched cavities.3. Based on available tilted structures with the inclining angle of 70.5°and vertical walls by anisotropic wet etching of {110} silicon, a novel micromachined tuning fork gyroscope is preliminarily studied, and after analyzing the structural error, a correction scheme is proposed. And based on the available octahedral cavity by etching of {111} silicon and the inverted pyramidal cavity by {100} silicon, two corresponding nanopore cavity arrays are fabricated separately, which provide effective templates for the fabrication of metallic nanostructure arrays.