Silicon (100) undercutting modelling and corner compensation structures design in wet anisotropic etching process

Abstract

Sharp right-angled corners are indispensable parts of many microstructures, such as microsensors and actuators, which are fabricated using well-known micromachining techniques in the microelectronics industry. The convex corner undercutting phenomenon prevents the production of sharp right-angled corners and leads to deformed round shaped right-angled corners which influence the functionality of the microstructure. This undesired phenomenon will be alleviated by the use of corner compensation structures. Knowing the undercutting rate is the first necessary step in the design process of these compensation structures. In this research, the undercutting rate of right-angled corners is simulated and the design of corner compensation structures based on the obtained undercutting rate is accomplished. In the presented model, the etch rate of basic and major planes such as (100), (110), (111), and (311), as well as the etch depth, are selected as the input variables. In addition, the undercutting rate diagram, dimensions of compensation structures and the required time in order to produce sharp right-angled corners constitute the output results. The results of the presented model and the experimental results are in good agreement.