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Proceedings Paper

Evaluation of a new photomask CD metrology tool
Author(s): Leonard F. Dubuque; Nicholas G. Doe; Patrick St. Cin
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Paper Abstract

In the integrated circuit (IC) photomask industry today, dense IC patterns, sub-micron critical dimensions (CD), and narrow tolerances for 64 M technologies and beyond are driving increased demands to minimize and characterize all components of photomask CD variation. This places strict requirements on photomask CD metrology in order to accurately characterize the mask CD error distribution. According to the gauge-maker's rule, measurement error must not exceed 30% of the tolerance on the product dimension measured or the gauge is not considered capable. The traditional single point repeatability tests are a poor measure of overall measurement system error in a dynamic, leading-edge technology environment. In such an environment, measurements may be taken at different points in the field- of-view due to stage in-accuracy, pattern recognition requirements, and throughput considerations. With this in mind, a set of experiments were designed to characterize thoroughly the metrology tool's repeatability and systematic error. Original experiments provided inconclusive results and had to be extended to obtain a full characterization of the system. Tests demonstrated a performance of better than 15 nm total CD error. Using this test as a tool for further development, the authors were able to determine the effects of various system components and measure the improvement with changes in optics, electronics, and software. Optimization of the optical path, electronics, and system software has yielded a new instrument with a total system error of better than 8 nm. Good collaboration between the photomask manufacturer and the equipment supplier has led to a realistic test of system performance and an improved CD measurement instrument.

Paper Details

Date Published: 27 December 1996
PDF: 10 pages
Proc. SPIE 2884, 16th Annual BACUS Symposium on Photomask Technology and Management, (27 December 1996); doi: 10.1117/12.262804
Show Author Affiliations
Leonard F. Dubuque, IBM Microelectronics Div. (United States)
Nicholas G. Doe, Technical Instruments Co. (United States)
Patrick St. Cin, Technical Instruments Co. (United States)

Published in SPIE Proceedings Vol. 2884:
16th Annual BACUS Symposium on Photomask Technology and Management
Gilbert V. Shelden; James A. Reynolds, Editor(s)

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