Certify- A Characterization and Validation Tool for Behavioral Models Weifeng Li University of Arkansas wxl002@uark.edu Omair Abbasi University of Arkansas omair.abbasi@gmail.com Naveed S. Hingora University of Arkansas nhingor@uark.edu Yongfeng Feng University of Arkansas yfeng@uark.edu H. A. Mantooth University of Arkansas mantooth@uark.edu ABSTRACT Device modeling plays an important role in VLSI circuit design because computer-aided circuit analysis results are only as accurate as the models used. This indicates a need for robust tools that can facilitate the testing, validation and characterization procedure of semiconductor device models. Certify, the graphical tool for model characterization and validation, is a step in this direction [1]. The software architecture and different modules of Certify have been described in this paper. 1. INTRODUCTION As semiconductor devices scale into the nanometer range, the fabrication process of these device structures becomes more time consuming and expensive. As a result, modeling is having an increasingly important role, as one can perform simulations much faster with much less cost, and different device geometries can be investigated before their actual fabrication. Writing a model which can accurately depict the characteristics of a real device is a challenging task. An efficient model should not only include the device characteristics in normal conditions of operation but should also be able to accurately depict the device behavior under worst case conditions such as high temperature ranges, extreme conditions etc. There are various programming languages in which such models can be written. They can be written in popular programming languages such as C and C++. Models for most popular circuit simulator SPICE (and its variants), are written in C. A second choice is writing these models in Hardware Description Languages (HDLs). The syntax of HDLs is easier to understand as they deal specifically with the problems of describing hardware. Various HDLs are available today for different purposes. VHDL and Verilog were invented to describe digital systems. Then came MAST [2], VHDL-AMS [3] and Verilog-AMS [4] which are used to describe analog and mixed–signal systems. Though HDLs simplified the model creation process significantly, the modeler still had no escape from customs and practices of coding and debugging [1]. Writing a model solves just half of the problem. The other half is testing, characterizing and validating the model. The process of extracting the optimum values of model parameters is called model characterization. Once the model is characterized it has to be validated by simulating it under various test conditions and then comparing the results with the results of actual device. Modelers greatly feel the need for a tool which can facilitate the whole characterization and validation process. This paper describes a software tool called Certify that is specifically designed to fulfill this need. Certify reads semiconductor device models written in the Common Model eXchange (CMX) language in order to test and characterize them [5][6]. The modeling tool Paragon was developed as a graphical editor for this format [7]. In addition, different hardware description languages such as Verilog-A, Verilog-AMS, VHDL-AMS, or MAST can be converted to CMX using the commercial version of Paragon, ModLyng tool of Lynguent, Inc [8]. Using Certify, a user can work in a virtual test bench environment. Virtual test benches can be added and deleted in a highly user friendly Graphical User Interface (GUI). Experiments for each test bench can be defined and whole recipes can be saved. Certify has an in-built optimizer that can be used to optimize the model parameters and thus, characterize the model. 2. CERTIFY Certify UI consists of a test-bench editor, an experiment editor, analyses dialogs, and an optimizer dialog. It is fully integrated with Saber Simulator [9] and partially integrated with Virtual Test Bed (VTB) simulator [10]. Certify makes calls to ModLyng to extract the model information in CMX format. The elaborator module of Certify calls the appropriate simulator in order to test and characterize the desired model. Figure 1 shows a brief overview of how the different components of Certify interact with ModLyng and the simulators. The following sections describe each component in further detail. 978-1-4244-1567-0/07/$25.00 © 2007 IEEE 40