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Proceedings Paper

Compensating measured intra-wafer ring oscillator stage delay with intra-wafer exposure dose corrections
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Paper Abstract

The purpose of this paper is to use measurements on real working devices to derive more information than typically measured by the classic line-width measurement techniques. The first part of the paper will discuss the principle of the measurements with a ring oscillator, a circuit used to measure the speed of elementary logic gates. These measurements contribute to the understanding of the exact timing dependencies in circuits, which is of utmost importance for the design and simulation of these circuits. When connecting an odd number of digital inverting stages in a ring, the circuit has no stable digital state but acts as an analog oscillator with the oscillation frequency dependent on the analog propagation delay of the signals through the stages. By varying some conditions during a litho step, the delay change caused by the process condition change can be measured very accurately. The response of the ring oscillator delay to exposure dose is measured and presented in this paper together with a comparison of measured line-width values of the poly gate lines. The second part of the paper will focus on improving the intra-wafer variation of the stage delay. A number of ring oscillators are put in a design at different slit and scan locations. 200mm wafers are processed with 48 full dies present. From the intra-wafer delay fingerprint and the dose sensitivity of the delay an intra-wafer dose correction, also called a dose recipe, is calculated. This dose recipe is used on the scanner to compensate for effects that are the root cause for the delay profile; including reticle and processing such as track, etch and annealing.

Paper Details

Date Published: 24 March 2006
PDF: 9 pages
Proc. SPIE 6152, Metrology, Inspection, and Process Control for Microlithography XX, 61521Y (24 March 2006); doi: 10.1117/12.659320
Show Author Affiliations
Staf Verhaegen, IMEC (Belgium)
Axel Nackaerts, IMEC (Belgium)
Mircea Dusa, ASML US Inc. (United States)
Rene Carpaij, ASML Netherlands B.V. (Netherlands)
Geert Vandenberghe, IMEC (Belgium)
Jo Finders, ASML Netherlands B.V. (Netherlands)

Published in SPIE Proceedings Vol. 6152:
Metrology, Inspection, and Process Control for Microlithography XX
Chas N. Archie, Editor(s)

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