TMAH anisotropic etching is one of the basic technologies in bulk silicon micromachining. However, the etching rate of the wet anisotropic etching (e.g. TMAH) is crystal plane orientation dependent, the etching of convex corners often happened, due to the fact that some planes etch faster than others, resulting in a loss of the desired structure. The phenomena often leads to a serious problem in microsensor or microactuator applications. It is impossible to fabricate intact mesa structure without corner compensation structures.
This paper reports corner-compensation methods for fabricating the intact mesa structure in MEMS (Micro-Electro-Mechanical System). To investigate the undercutting problem in the mesa structure, over ten corner compensation patterns are designed by computing the relations among a series of parameters, e.g. etching rates in different crystal planes, etching depth, etching times, etc. The compensation patterns are then simulated by the simulation soft ware Anisotropic Crystalline Etch Simulation (ACES) beta 2, the 3D etching simulations were gotten. Various new compensation structures preventing the undercutting of convex corners of (100) silicon in THAH solution are redesigned and optimized based on the simulation results.
The difference of etching rates between crystal plane {100} and {311} in TMAH etching is carefully observed, which is the main reason of the undercutting. Experimental results and simulation results show a good agreement. Based on above, some nice patterns are obtained. The details will be presented at the conference.
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