82 IEEE TRANSACTIONS ON COMPUTER-AIDED DESIGN OF INTEGRATED CIRCUITS AND SYSTEMS, VOL. 13, NO. 1, JANUARY 1994 Semiconductor Wafer Representation for TCAD Martin D. Giles, Member, IEEE, Duane S. Boning, Member, IEEE, Goodwin R. Chin, Member, IEEE, Walter C. Dietrich, Jr., M. S. Karasick, Member, IEEE, Mark E. Law, Senior Member, IEEE, Purnendu K. Mozumder, Member, IEEE, Lee R. Nackman, Member, IEEE, V. T. Rajan, D. M. H. Walker, Member, IEEE, Robert H. Wang and, Alexander S. Wong Member, IEEE Abstract-This paper describes the Semiconductor Wafer Rep- resentation (SWR) for representing and manipulating wafer state during process and device simulation. The goal of the SWR is to provide an object-oriented interface to a collection of functions designed for developing and integrating Technology CAD (TCAD) applications. By providing functions which can be common across many applications, we aim to greatly reduce tool development and integration time. Corporate, vendor, and university TCAD developershave worked together under the aus- pices of the CAD Framework Initiative to create an architecture and C++ programming interface for an SWR 1.0 draft standard. Here we will describe this architecture and the results of creating and using a prototype implementation of the standard both to integrate existing TCAD tools and to develop simple new tools. I. INTRODUCTION I .I. Background and Motivation T is computer-aided design and engineering used in semi- conductor device design, fabrication process design, technol- ogy characterization for circuit design, manufacturing yield optimization and process centering, and computer-integrated manufacturing. It includes detailed numerical simulation of fabrication process steps, fast simulation of complete fab- rication processes, and detailed numerical simulation of the electrical performance of small (cell-level) circuits. TCAD is essential for the successful design of today’s devices and cir- cuits because of their increasing complexity and the increasing cost and delay of experimental design iteration. Practical TCAD problem solving usually requires the use of several different simulation programs. Since each program has its own, incompatible way of representing, reading, and writing design data, considerable time and effort can be wasted writing conversion routines between the various formats. Each program’s representations may not be complete, so auxiliary information must be saved elsewhere and merged into the design description again, when it is required if data fidelity Manuscript received December 12,1992; revised June 25,1993. This paper was recommendedby Associate Editor D. Scharfetter. M. D. Giles is with the University of Michigan, Ann Arbor, MI 48103. D. S. Boning and P. K. Mozumder are with Texas Instruments, Dallas, TX G. R. Chin is with Stanford University, Stanford, CA 94305. W. C. Dietrich, Jr., M. S. Karasick, L. R. Nackman, and V. T. Rajan are M. E. Law is with the University of Florida, Gainesville, FL 32611. D. M. H. Walker is with Camegie Mellon University, Pittsburgh, PA 15213. R. H. Wang is with the University of California, Berkeley, CA 94720. A. S. Wong is with Intel Corporation, Santa Clara, CA 95052. IEEE Log Number 9212340. ECHNOLOGY COMPUTER-AIDED DESIGN (TCAD) 75266. with IBM Corporation, Yorktown Heights, NY 10598. is to be preserved. Since the simulators have incompatible user interfaces, accessing designs must typically be done at a low level, making it hard to automatically control simulators for statistical studies and design optimization. These problems are not unique to the TCAD area, and frameworks have been found to help solve them. A framework is a set of interrelated services that provide infrastructure and support for computer-aided design system development and deployment [ 13. The functions or services provided by a framework can be divided into sets of domain- dependent and domain-independent functions. The domain- independent services, for example, database and intertool communication, are generic in that their value does not de- pend on the framework’s application (e.g., electrical CAD or mechanical CAD). Other services, such as design data repre- sentation, are domain-dependent. Development of framework standards is being promoted by the CAD Framework Initiative (CFI), a consortium dedicated to defining interface standards for design automation tools and design data that benefit end users and vendors worldwide. The physical wafer structure is only one part of the in- formation that must be available in a TCAD framework. In addition, users may wish to describe manufacturing process parameters and sequences, lithography mask information from circuit layouts, and device characteristics for circuit simulators. These requirements are being addressed by other technical committees within CFI. The Semiconductor Process Repre- sentation (SPR) working group is creating an information model and programmatic interface for describing process step modules or sequences and the details of unit process steps [2]. One highly desirable use of the SPR is to support “simulation management”utilities which use process sequence and process step class information to chain the invocation of different simulators or simulation modules. It is also valuable to be able to reference process sequences from inside wafer state descriptions to “tag” materials with information about the process that generated them, as suggested by recent material property modeling efforts [3]. The Device Modeling and Verification (DMV) working group is developing standards for device characterization information and an information model (IM) for device representation. The goal of the DMV work, which uses the EXPRESS and EXPRESS-G languages [4], is to develop an IM that not only encompasses the data representation needs of the SWR, but also fulfills the modeling requirements of the VISTA system [5] and BPIF [6]. The value of an IM for electronic CAD applications has been demonstrated by Lau and Kahn [71. 02784070/94$04.00 Q 1994 IEEE