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Extraction of Parameters for the PSP Model
Because of correlations, you should not derive all local parameters for a specific device simultaneously. The model developers outline a practical extraction sequence. This recommendation is the base for the default extraction flow programmed into the PSP Modeling Toolkit. The following describes the sequence of parameter extraction used in the toolkit.
For every device, the extraction of local parameters must be performed. However, not every local parameter for all devices must be extracted. Some parameters are extracted for only one device. Other parameters are extracted for a few devices and are fixed for other devices. A number of parameters can be kept fixed at default values and only optimized in fine tuning steps during extraction. Note, that for all extractions, the reference temperature TR must be set to the actual room temperature the devices are measured under.
Before extraction, switch parameters SWIGATE, SWIMPACT, SWGIDL, SWJUNCAP, and TYPE are set to appropriate values and QMC is set to 1 to include quantum mechanical corrections.
Some parameters influencing the DC behavior of a MOSFET are extracted accurately only from CV measurements (NP, for example).
In order to get good DC parameter values, you should start from the default parameter set and use a value of TOX as is known from technology. With this settings, extractions of VFB, NEFF, DPHIB, NP, and COX can be done using the measurement of CGG vs. VGS of the long, wide device.
The extraction process starts with local parameters for the Long/Wide device, followed by extraction of local parameters for the rest of the devices with max. length. Then there is a global parameter extraction/optimization step involving all devices of max. length. The next step uses the Short/Wide device (same width, but shortest length) to extract local parameters and so on. The following figure is a graphical representation of the extraction sequence. The numbers show the extraction order, the circles and squares with blue background (or shaded in a black and white representation) and blue numbers are local parameter extraction steps, the ones with a red frame and red numbers are global parameter extraction steps.
Figure 50 Flow of Extraction as programmed inside the PSP Toolkit
This procedure was enhanced since the one recommended by the model developers needs a totally regular arrangement of devices, a requirement usually not given in practice. Therefore, the PSP Modeling Package uses a somewhat different approach: local parameters that do not have, for example, a width dependency will be computed from global parameters and will not be extracted for the local model again.
The following table should clarify the extraction sequence as programmed for the standard extraction flow. This table shows, due to limited space, a reduced number of parameters only.
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