A feature-based geometric modeling approach for surface micromachined micro-mechanical systems

Geometric modeling is an important aspect of MEMS design. Not only does geometric modeling create models for visual evaluation, but it also supplies input for device performance analysis. Lacking adequate geometric design capability is one of the main factors that impede MEMS development, especially for micro-mechanisms. MEMS developers are presently constrained with the cumbersome and unintuitive modeling methodologies in which the design of a new product begins with figuring out its fabrication mask layouts.;To remedy the above problem, this research concentrates on the development of a feature-based geometric modeling approach for surface micromachined microsystems. A microsystem feature model is proposed. A cellular geometry is adopted as the geometric kernel of the feature model. Along with the cellular geometric representation, a new feature management mechanism is developed to facilitate feature recording and maintenance. The geometries of surface micromachined MEMS are categorized as two sets of features: design features and fabrication features. The design features work as the interface between designers and the microfabrication process; they are the elements used to directly construct a device model. Fabrication features are connected with a specific fabrication process.;This bi-level feature structure leads to a kernel problem: bow to derive fabrication features from design features. The concept of Feature Mapping is introduced for this purpose. It is composed of a set of semantic rules that indicate the feature topology transformation and geometric reasoning algorithms that derive the geometric parameters of fabrication features from their design feature counterparts. Feature propagation operation is developed to distribute the shape modification on one layer to all other affected layers. The feature mapping and propagation are both built based on the underlying geometric dependency, which is intrinsic for SMM. The fabrication features recorded in MFM can be utilized to generate lithography masks. Compared with the conventional mask synthesis method, the method developed in this research is more accurate and efficient.;The research is the first attempt that uses the form features specified for SMM devices to construct feature models in a function-oriented mode, resulting in a generated model that is fabrication ready. During the modeling process, design intent and engineering information are explicitly recorded in terms of feature shapes and geometric constraints. This information is retained for design decision making and automatic model maintenance. The significance of this research is that it provides an intuitive and straightforward method for microsystem geometric modeling. Moreover, it establishes a useful intermediate step toward the development of function-oriented microsystem design methodology.