Scalable Modeling of MOSFET Source and Drain Resistances for MS/RF Circuit Simulation

Abstract

Large-width and short-length MOS transistors with multi-finger layouts are necessary for the mixed-signal and RF IC designs to achieve optimum gain and noise performances. As the total width (i.e., the product of the finger width and the number of fingers Nfg) increases, the parasitic source and drain resistances due to the contact and diffusion regions becomes comparable in magnitude to the MOSFET intrinsic channel resistances under many (bias and layout) scenarios and, hence, require accurate and scalable SPICE modeling. This paper presents a model for multi-finger MOSFET source /drain contacts and diffusion parasitic resistances, and a simple parameter extraction methodology to take into account the unwanted parasitic impacts from the wiring and measurement equipment; both can be readily applied to BSIM3v3 and BSIM4. Excellent accuracy and scalability have been achieved in comparison with measurement.

Modeling the Impact of Multi-Fingering Microwave MOSFETs on the Source and Drain Resistances

“…Thus, the term can be neglected when its exponent is greater than 2. and can then be rewritten as (8) and (9) where , is the number of vias per unit length, which is a constant, and . In this work, is equal to two vias per 1 m. In this way, and resistances can be determined by (10) (11) In our particular case, , which is equal to the product , is fixed to a given value, and thus, decreases when increases at the same rate. Similarly, and increase with the inverse of .…”

“…In this regard, some research on the geometry dependence of the substrate resistance has been carried out [9], [10]. Nonetheless, in spite of the fact that the geometry dependence of other extrinsic parameters, such as the drain and source series resistances and junction capacitances, is also becoming important for advanced devices [11], scalable models for these parameters still need to be developed. Among the reasons that make the development of geometry-dependent models for the extrinsic impedances important-in addition to -we highlight the corresponding impact on the MOSFET's input and output features [12], [13].…”

A Novel Nano-Scale Multi-Finger MOSFET DC Model Parameters Extraction Method

“…Meanwhile, with the increase of the finger numbers and effective channel width, channel resistance will decrease to a very small value. These two factors make probe resistance induced by measuring system ignored [2]. Besides, the parasitic Rds are no longer fixed with variable finger numbers.…”