Browse Prior Art Database

Automatically Sensible Measurement for Overlay Accuracy

IP.com Disclosure Number: IPCOM000122795D
Original Publication Date: 1998-Jan-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Okajima, K: AUTHOR [+2]

Abstract

Disclosed is a pattern for overlay measurement that is used to accurately measure overlay misalignment for photolithography processes. The overlay of the photolithography includes both that of stitching on the same layer and layer-to-layer overlay.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Automatically Sensible Measurement for Overlay Accuracy

      Disclosed is a pattern for overlay measurement that is used to
accurately measure overlay misalignment for photolithography
processes.  The overlay of the photolithography includes both that of
stitching on the same layer and layer-to-layer overlay.

      In the conventional method, a smaller square pattern is formed
on the upper layer, and a larger square pattern is formed on the
lower layer, as shown in Fig. 1.  The difference in position of the
upper pattern from the center of the lower pattern indicates the
overlay misalignment.  In this method, however, the pattern detection
sometimes fails in an automatic overlay measurement because low
contrast does not permit successful pattern recognition.  In fact,
the failure rate of  automatic pattern recognition using this method
is more than 70%. Back  lighting cannot be used because the upper
pattern cannot be then separated from the lower pattern.  Our
disclosed pattern, as shown in Fig. 2, can be used with back lighting
which improves the contrast. With  this pattern, the pattern
recognition does not fail.  The success rate  was 100%.  The vertical
misalignment amount of upper pattern to lower pattern is given by
(A-B)/2.