Further Automation of Worst-Case SPICE Model Library Generation

The parametrized worst case model library generation is completely automated in UTMOST using "worst case" button in the SPICE library generation screen.

In the traditional method of generating Typical, Slow and Fast model libraries, users vary certain process related-test parameters such as TOX, VTO, RSH and create the corner libraries. This process requires repeating the non-varying parameters for each corner model. The result is a very large library text file and since it is done manually the process is very prone to typing errors.

The parameterization of the varying model parameters eliminates the repeating. The user can have a single parametrized model file and the corner models are specified using the ".PARAM" statement. (Figure 1.)



Figure 1. Parametrized model library.

 

To automatically generate a parametrized worst case model library in UTMOST, follow these steps:

  • Complete the modeling of the devices and make sure that final parameters are in the "opt" column of the parameters screen.
  • Select the Spice Library File option from the "Files"menu of UTMOST. This will open the Library Generation Screen.
  • Press the worst case button to open "Worst Case Library Generation Screen".

Enter the Number of parameters to be parametrized. Enter the Model Parameter Name, Parametrized Name (user can specify any name) and the Typical Slow and Fast values for each parameter. For the corner parameter values a percentage or the actual value can be used.

Enter the final output worse case library file name and press the execute button to generate the file.

To add the PMOS parameters to the library, repeat the previous steps and keep the same worst case library filename before executing. The PMOS parameters will be added to the ".PARAM" statement.

The Library generation screen creates four corner libraries in the worst case model library file: CORRELATION (extracted model parameters which were in the "opt" column of the parameters screen), TT (Typical Library), SS (Slow Library), FF (Fast Library)(Figure 1.).

Figure 2. Worst Case Library Generation Screen.