Using Models from Process Foundries

Summary

This article describes how to use models obtained from process foundries.

The article does not cover the installation of models for discrete devices. See Installing Models for information on that subject.

Hspice Models

Many foundries supply models in many different formats for various simulators. Usually you should use models designed for Hspice. SIMetrix is compatible with the basic Hspice syntax used for defining models such as the .LIB/.ENDL syntax and the method used for model binning.

Installing Models

The library search mechanism designed for discrete devices doesn't work with models that use the Hspice style .LIB syntax. So you don't need to install the models, but instead you must place a reference to the model files in your circuit. This is usually placed in the F11 window.

If you are not familiar with the F11 window, open a schematic and press F11. You will see an edit box appear at the bottom of the sheet. Anything placed in here will be appended to the netlist when it is created prior to simulation.

To specify an Hspice model you need to provide the file path and a symbol name within the file that specifies the process corner. The process corner name is something you can only find from the model file itself or its accompanying documentation. We will use an example of a TSMC 0.18u process which uses the name 'TT', 'SS' and 'FF'.

When you have this information, you must add a .LIB line to the F11 window. This must be of the form:

.LIB 'filepath' symbol

E.g.

.LIB 'E:\TSMC\T-018-MM-SP-002\fp1\hspice\mm018.l' TT

If you wish to change the process corner, just change TT to SS or whatever.

Creating Schematic Symbols for MOS Devices

SIMetrix is supplied with 4 symbols for CMOS design. These are NMOS and PMOS devices with 3 and 4 terminals. The symbols supplied are explained in the User's Manual Chapter 4, "Using Schematic Editor for CMOS IC Design"

Procedure for Creating MOS Symbols (Version 4.2 and later)

This is the complete procedure for creating you own MOS symbols and assigning them to toolbar buttons.

1. Create your new symbol using the graphical symbol editor. You might like to base the symbols on the existing symbols. If you are using version 5.0, you can instead use some newer symbols that will be introduced with version 5.1 but which are compatible with version 5.0. See XXX for more details. Note the internal name for each symbol you create; you will need this in order to define a tool bar button for the symbol.
2. Select command shell menu "File | Scripts | Edit Startup...".
3. Enter a DefButton command for each toolbar button you wish to redefine. For the MOS symbols the commands will be one or more combinations of the following:
   
   DefButton NMOS4 "inst /ne your_nmos4_symbol"
   DefButton PMOS4 "inst /ne your_pmos4_symbol"
   DefButton NMOS3IC "inst /ne your_nmos3_symbol"
   DefButton PMOS3IC "inst /ne your_pmos3_symbol"
   
   Replace your_nmos4_symbol, your_pmos4_symbol etc with the internal names of your new symbols.