A111Q3 Dfl713E NAFL INST OF STANDARDS & TECH R.I.C. A1 1103087132 QCIOO .U57 NO.400-, 20, 1975 C.2 NBS-PUB IX DO SPECIAL PUBLICATION 400-20 U.S. DEPARTMENT OF COMMERCE / National Bureau of Standards emiconductor Measurement Technology: Optical and Dimensional- Measurement Problems With Photomasking in Microelectronics NATIONAL BUREAU OF STANDARDS The National Bureau of Standards' was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Institute for Computer Sciences and Technology, and the Office for Information Programs. THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Meas- urement Services and the following divisions: Applied Mathematics — Electricity — Mechanics — Heat — Optical Physics — Nuclear Sciences - — Applied Radiation - — Quantum Electronics ' — Electromagnetics ' — Time and Frequency ^ — Laboratory Astrophysics " — Cryogenics THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to improved methods of measurement, standards, and data on the properties of well-characterized materials needed by industry, commerce, educational institutions, and Government; provides advisory and research services to other Government agencies; and develops, produces, and distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials and the following divisions: Analytical Chemistry — Polymers — Metallurgy — Inorganic Materials — Reactor Radiation — Physical Chemistry. THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to promote the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations leading to the development of technological standards (including mandatory safety standards), codes and methods of test; and provides technical advice and services to Government agencies upon request. The Institute consists of a Center for Building Technology and the following divisions and offices: Engineering and Product Standards — Weights and Measures — Invention and Innova- tion — Product Evaluation Technology — Electronic Technology — Technical Analysis — Measurement Engineering — Structures, Materials, and Life Safety* — Building Environment * — Technical Evaluation and Application * — Fire Technology. THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and provides technical services designed to aid Government agencies in improving cost effec- tiveness in the conduct of their programs through the selection, acquisition, and effective utilization of automatic data processing equipment; and serves as the principal focus within the executive branch for the development of Federal standards for automatic data processing equipment, techniques, and computer languages. The Institute consists of the following divisions: Computer Services — Systems and Software — Computer Systems Engineering — Informa- tion Technology. THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific information generated within NBS and other agencies of the Federal Government; promotes the development of the National Standard Reference Data System and a system of information analysis centers dealing with the broader aspects of the National Measurement System; provides appropriate services to ensure that the NBS staff has optimum accessibility to the scientific information of the world. The Office consists of the following organizational units: Office of Standard Reference Data — Office of Information Activities — Office of Technical Publications — Library — Office of International Relations. 1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234. » Part of the Center for Radiation Research. 3 Located at Boulder, Colorado 80302. Part of the Center for Building Technology. OP ST/> LIE": OCT 1 4 197S Semiconductor Measurement Technology: Optical and Dimensional-Measurement Problems With Fhotomaskingin Microelectronics ^ John M. Jerke Optical Physics Division Institute for Basic Standards National Bureau of Standards Washington, D.C. 20234 This activity was supported by The Defense Advanced Research Projects Agency 1400 Wilson Boulevard Arlington, Virginia 22209 under ARPA Order 2397, Program Code 4D10 U.S. DEPARTMENT OF COMMERCE, Rogers C.B. Morton, Secretary I James A. Baker, III, Under Secretary j Dr. |i Betsy Ancker-Johnson, Assistant Secretary for Science arid Technology IS .NATIONAL BUREAU OF STANDARDS, Emest Ambler. Acting Director Issued October 1975 Library of Congress Cataloging in Publication Data Jerke, John M. Optical and dimensional-measurement problems with photomask- ing in microelectrics. (Semiconductor Measurement Technology) (NBS Special Pub- lication; 400-20) Bibliography: p. Supt. of Docs. No.: C 13.10:400-20 1. Integrated circuits—Maska. 2. Photolithography. 3. Optical measurements. I. Title. II. Series. III. Series: United States. Na- tional Bureau of Standards. Special publication; 400-20. QC100.U57 No. 400-20 [TK7874] 389'.08s [621.38173] 75-619190 National Bureau of Standards Special Publication 400-20 Nat. Bur. Stand. (U.S.), Spec. Publ. 400-20, 42 pages (Oct. 1975) CODEN: XNBSAV U.S. GOVERNMENT PRINTING OFFICE WASHINGTON: 1975 For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 (Order by SD Catalog No. C13.10:400-20). Price $1,00 . (Add 25 percent additional for other than U.S. mailing). TABLE OF CONTENTS PAGE Preface iv 1. Introduction 1 2. Background 3 3. Approach 6 4. Results and Discuss'ion 7 4.1. Optics 7 4.2. Dimensional Measurements . 8 4.2.1. Measurement of Small Dimensions 10 4.2.2. Edge Definition 14 4.2.3. Registration 17 . 5. Conclusions 20 5.1. Optics 20 5.2. Dimensional Measurements • . • 20 6. Recommendations . / 22 6.1. Optics 22 6.2. Dimensional Measurements 22 7. References • 23 Appendix A. Comparison of Dimensional Measurements Made with Image-Shearing and Filar Eyepieces 27 Appendix B. Effects of Illumination Coherence on Apparent Edge Position in Optical -Imaging Systems ... 29 Appendix C. Selected Bibliography of Photomask Publications 31 i i i PREFACE This study was carried out in the Optical Physics Division as a part of the Semi- conductor Technology Program in the Electronic Technology Division at the National Bureau of Standards. The Semiconductor Technology Program serves to focus NBS efforts to enhance the performance, interchangeabil ity, and reliability of discrete semiconductor devices and integrated circuits through improvements in measurement technology for use. in specifying materials and devices in national and international commerce and for use by industry in controlling device fabrication processes. The Program receives direct financial support principally from three major sponsors: The Defense Advanced Research Projects Agency (ARPAja The Defense Nuclear Agency (DNA) and the National Bureau of Standards. The specific work reported herein was supported by ARPA.* During the conduct of this study, particularly strong statements were received from the integrated circuits industry emphasizing the critical need for the development of NBS line width standards in. the 1-ym range to assist the industry in meeting the micro- metrology requirements associated with high resolution photomasks. These statements in- cluded an emphasis both on the need for NBS traceability in this field by small mask making establishments in their marketplace interactioiis with larger organizations and Government and on internal needs of semiconductor device manufacturers in connection with productivity problems. In response to the needs disclosed and defined in this study, a two-year project, jointly funded by ARPA and NBS, was initiated to develop a 1-ym line width standard through implementation of the recommendations of this study. Special acknowledgement is gratefully made to Dr. Donald B. Novotny, Semiconductor Processing Section, Electronic Technology Division, NBS, for his considerable assistance in the study described in the present report. This assistance included, in part, participation in the visits to photomask and IC facilities, gathering and analyzing information from the open literature, participation in technical discussions with representatives from the IC industry, and helpful suggestions in the preparation of this report. — . Through ARPA Order 2397, Program Code 4D10. iv OPTICAL AND DIMENSIONAL-MEASUREMENT PROBLEMS WITH PHOTOMASKING IN MICROELECTRONICS BY JOHN M. JERKE Abstraot : Photomasks are the basic artifacts for transferring design