ABSTRACT
Analytical transistor analysis inevitably involves approximations and assumptions in order to obtain closed-form solutions. Numerical analysis based on the fundamental differential equations governing semiconductors has become necessary in integrated circuit technology development, and is often referred to as “device simulation.” * Commercial device simulators (e.g., Sentaurus from Synopsys) are for many the go-to choice for device-level simulation. They are typically part of a technology computer-aided-design (TCAD) package, which includes process simulation, device simulation, and parameter extraction programs. The use of a device simulator, or TCAD tools in general, requires substantially more knowledge of the internal workings of the simulator than the use of, say, a circuit simulator such as SPICE. For instance, users must choose which mobility model to use, which statistics (Fermi–Dirac or Boltzmann) to use, and whether or not to account for incomplete ionization of dopants. The default physical models are usually the simplest ones, and often give inaccurate results, particularly for advanced device technologies such as SiGe. Users are also responsible for the “meshing” of the device structure, which can affect the simulation results significantly. This chapter describes the differential equations and physics implemented in commercial device simulators, as well as the practical aspects of using these simulators for device analysis and optimization. †
