Книги2 / 1993 P._Lloyd,__C._C._McAndrew,__M._J._McLennan,__S._N

Preface

We would like to present the proceedings of the first "Workshop on Technology CAD Systems" (TCS) which was held at the Technical University of Vienna, Austria, on September 6th , 1993, in conjunction with the "Fifth International Conference on Simulation of Semiconductor Devices and Processes" (SISDEP 93).

This workshop is a first attempt to account for the increasing interest of the semiconductor industry, universities and vendors in the design, development and application of Technology CAD Systems. The continuously growing demands on numerical process and device simulation result in large computer programs with hundred thousands lines of code, becoming more difficult to manage and maintain by the programmer, and uncomfortable and complicated to use by the process and device engineer. The recently emerging Technology CAD Systems try to manage this increasing complexity both from the programmers' and users' point of view. The TCS Workshop brings together TCAD system developers and users from all over the world, ranging from industrial in-house developers over university researchers to professional TCAD vendors.

The organizers of the TCS Workshop have prepared a program with fourteen outstanding invited papers for oral presentation. Their respective origins reflect the international nature of the conference: 8 from the USA, 4 from Europe and 2 from Japan. The TCS Workshop is organized in five paper sessions covering the following topics: the US industrial perspective, the US university perspective, the European perspective, the Japanese perspective and the vendor perspective.

The proceedings are printed from direct lithographs of the authors' manuscripts. The editors are not responsible for any inaccuracies,· comments or opinions expressed in the papers.

We would like to express our sincere appreciation to the authors for their high quality contributions and for their cooperation and effort.

Franz Fasching

Stefan Halama

Siegfried Selberherr

Institute for Microelectronics

Vienna, September 1993

viii Table of Contents

The STORM Technology CAD System. . . . . . . . . . . . . . . . . . . .. 163

J.Lorenz, C. Hillt, H. Jaouent, C. Lombardi·, C. Lyden+, K. De Meyer#, J. Pelka§, A. Poncet$, M. Rudan%, and S. Solmi&

Fraunhofer-Institut fiir Integrierte Schaltungen, GERMANY tGEC Marconi Material Technology, UNITED KINGDOM

tSGS Thomson, FRANCE 'SGS Thomson, ITALY +NMRC, IRELAND #IMEC, BELGIUM

§FhG-ISiT, GERMANY $CNET, FRANCE

%DEIS, University of Bologna, ITALY &CNR-LAMEL, ITALY

S.Halama, F. Fasching, C. Fischer, Ch. Pichler, H. Pimingstorfer, H. Puchner, G. Rieger, G. Schrom, T. Simlinger, H. Stippel, E. Strasser, W. Thppa, K. Wimmer, and S. Selberherr

Institute for Microelectronics, TU Vienna, AUSTRIA

Edited by F. Fasching, S. Halama, S. Selberherr - September 1993

Technology CAD at AT&T

P. Lloyd, C.C. McAndrew, M.J. McLennan, S. Nassif, K. Singhal, Ku. Singhal, P.M. Zeitzoff, M.N. Darwish, K. Haruta, J.L. Lentz, H. Vuong, M.R. Pintot, C.S. Rafferty t, and I.C. Kizilyalli+

AT&T Bell Laboratories,

1247 South Cedar Crest Boulevard, Allentown, PA 18103, USA

t AT&T Bell Laboratories, 600 Mountain Avenue, Murray Hill, NJ 07974, USA +AT&T Bell Laboratories, 555 Union Boulevard, Allentown, PA 18103, USA

Abstract

Technology computer-aided design (TCAD) is essential to the design of modem integrated circuit fabrication processes. TCAD tools must not only model real processes accuratdy, to allow predictive simulation during technology research and development, but must work together as an integrated system to allow efficient exploration of technology options. Sensitivity and statistical analyses using an integrated TCAD system provide rapid technology characterization, including the examination of process extremes, before fabrication. This predictive capability reduces the technology design interval, and enables the design of optimized, manufacturable designs. This paper describes the integrated TCAD system in use at AT&T.

1.Introduction

Efforts to reduce the dimensions and increase the performance of integrated circuits (lCs) are becoming more challenging than in the past. Small structures are more difficult to manufacture than the large structures of past technologies, and are more sensitive to process variations. Their electrical characteristics are often distorted by new physical effects, making it more difficult to use them as conventional devices. Small oxide thicknesses, channel lengths and junction depths require small supply voltages, forcing digital circuits to operate in more of an analog regime. At the same time, circuits of greater complexity must be produced in shorter development cycles, forcing designers to rely more on computer-aided design (CAD) tools to develop and verify their designs.

Tools supporting this Technology CAD (TCAD) at AT&T cover a wide range of disciplines that includes process and device simulation, compact model parameter extraction, interconnect simulation, and circuit simulation. As the demand for these tools has grown, the tools themselves have matured into a system providing an end-to-end simulation capability for process to cell level design [1]. This system is always in a state of continuous improvement.

Accuracy of the physical models within the tools is paramount to the predictive capability of the overall system. Simulated results must be carefully verified against experimental data, and models must be improved when discrepancies arise. When individual tools produce accurate results, the entire system of tools can be used to study high level design issues. Examples include optimization of transistor characteristics and of manufacturability, and studies of the effects of statistical process variations on yield and circuit performance. A tight link to manufacturing data allows on-going verification of our TCAD tools. Figure 1 gives a high level block diagram of our system, showing how our individual tool set fits into our overall TCAD process.

In recent years, the UNIX® environment has provided the glue needed to bind our tools into an integrated system [1]. Task threads were described in shell scripts, and programs (written, for example, in awk [2]) were used to filter and translate data being passed from one tool to another. As software systems have continued to grow, new software technologies have emerged to help us manage the increased complexity. Object oriented programming, for instance, has provided us with a new way to organize data and the procedures that operate on them, in contrast to earlier systems, that had different file formats for individual tools and a network of conversion programs to link one tool to another. For example, in process simulation, object oriented programming has significantly simplified tool development, by providing a simple and unified access mechanism to objects that represent a device structure. Increased complexity in the control of the tools is managed by using an extension language in place of the input deck parsers of earlier tools. Finally, the actions among groups of tools are coordinated by messages passed via intertool communication facilities.

Besides point tools and software systems for integrating them, people and communications amongst them are essential to define tasks. More important, people are necessary to detect weaknesses in tools and method.

The organization of this paper is as follows. In section 2, we describe the capabilities of our point tools. These tools have been used in an end-to-end system for some time. The integration within this system is being improved using several emerging software technologies, as described in section 3. In section 4, we present several applications of the system, each one emphasizing a different aspect of TCAD simulation. In the last section we present concluding remarks and some directions for the future.

2.TCAD Point Tool Capabilities

TCAD activities at AT&T involve tools for process and device simulation, interconnect simulation, measurements, compact modeling, parameter extraction, and circuit simulation, and an optimizer that can work with all these tools. In this section we describe the tools used for each of these tasks, and the capabilities of each point tool.

2.1Process Simulation

Process simulation is used during technology development to refine a process recipe, and during technology characterization to model the input structure for device simulation.