3.8 Electrical Key-Parameter Extraction

To evaluate the electrical characteristics of a semiconductor device, the results of device simulation can be evaluated. Typical key parameters are the linear or saturation threshold $V_t$ [133], the transconductance $g_m$, or the saturation current $I_s$ of a CMOS transistor. For bipolar transistors the common emitter current gain $\beta$, the early voltage $V_{AF}$, or the collector resistance $R_C$ are examples for common key parameters.
Typically, TCAD vendors offer standard algorithms for extracting these parameters with post processing tools or scripts after the device simulation (e.g. Inspect [134] or Tonyplot [10] are such tools for showing electrical characteristics and extracting key parameters). The main basis for the definition of key electrical parameters are the SPICE models like BSIM3^3.3 [135],[136], however for manufacturing control these parameters are too cumbersome to obtain and the number of measurements is too high for gaining enough throughput in parameter test. Therefore fast extraction algorithms working with a few measurement points (e.g. threshold voltage is often extracted only with 5 current-voltage measurements) are thoroughly used. However, the algorithms may vary strongly between different semiconductor companies, since even a simple parameter like the CMOS threshold voltage may be measured in a lot of different ways. Therefore, a careful setup of these parameter extraction algorithms in simulation is very important to enable calibration of simulation against measurements and to benefit from the enormous database of electrical test data for calibration of simulation.
A method for setting up these algorithms in a very efficient way is shown in Chapter 4.

Footnotes

... BSIM3^3.3

The newer CMOS model BSIM4 has many advantages for modeling deep sub-micron devices, but the definition of key electrical parameters like threshold voltage gets more and more ambiguous, since the newer models tend to use the compact modeling and not the physical modeling approach.