CrtSmile: a CAD tool for CMOS RF transistor substrate modeling incorporating layout effects

We present a new CAD tool CrtSmile, which automatically incorporates transistor layout effects for CMOS RF transistor modeling with an emphasis on substrate resistance extraction. The RF transistor layouts in the CIF/GDSII format are used to generate a layout dependent substrate model that can be included as a subcircuit with the BSIM3 device model. To support multifinger RF transistor layout/bulk recognition, a pattern based layout extraction method is presented. CrtSmile incorporates a scalable substrate model for multifinger transistors, which is dependent on transistor layout/bulk patterns and geometric layout information, such as the number of gate fingers, finger width, channel length, and bulk contact locations. This model is simple to extract and gives good agreement with the measured data for a 0.35 μm CMOS process. A low noise amplifier design is evaluated with the new layout dependent substrate model and the proposed tool, showing the importance of CMOS RF transistor layout on substrate resistance modeling.