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Browse Prior Art Database

An improved pattarn formation method for misalignment measurement in stepping exposure process

IP.com Disclosure Number: IPCOM000013670D
Original Publication Date: 2000-Mar-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 3 page(s) / 422K

Publishing Venue

IBM

Abstract

Disclosed is an improved pattern formation method for overlay measurements to accurately measure stitching overlay misalignment for photolithographic exposures on the same layer. In conventional misalignment measurements, first a larger square shape is formed on the initial layer, and a smaller square shape is formed on a subsequent layer as shown in Fig. 1. The difference in position of the subsequent pattern from the center of the first pattern indicates the overlay misalignment. The amount of vertical misalignment of the subsequent pattern to the first pattern is given by (Y1-Y2)/2, in Fig. 1. The amount of horizontal misalignment can be found in a similar manner. The conventional method does not work though for misalignment measurements between exposures on the same level because only the smaller square shape remains after both shapes are exposed and developed. Our previous disclosed pattern in the disclosure JA8-97-0616, which can be used to measure the misalignment between exposures on the same level, is shown in Fig. 2. The pattern shown in Fig. 2 is formed by exposing the two patterns, labeled "A" and "B" shown in Fig. 3 where pattern "A" is exposed prior to "B". The method of calculating the misalignment from exposure "A" to "B" is shown in Fig. 2. To understand the disclosed misalignment method, in Fig. 3 note that the inner square is defined by exposure "A" and the outer shape is defined by exposure "B". The pattern, indeed, can give us quick and accurate misalignment measurement, however, sometimes abnormal pattern shown in Fog. 4 is formed by high-viscosity-etchant. It is difficult for the high-viscosity-etchant to etch off the material between exposed pattern "A" and "B" due to a narrow gap. Making the dimension larger can solve the etching problem, however, the accurate measurement is achieved by using a high-powered optical microscope having a magnification of 1000 or more, Therefore the smaller the dimension is, the better the measurement accuracy become. Our disclosed pattern, which can improve the pattern formation easily, is shown in Fig. 5. The pattern shown in Fig. 5 is formed by exposing the two patterns, labeled "A" and "B" shown in Fig. 6 where pattern "A" is exposed prior to "B". The method of calculating the misalignment from exposure "A" to "B" is shown in Fig. 5. To understand the disclosed misalignment method, in Fig. 6 note that the inner square is defined by exposure "B" and the outer shape is defined by exposure "A". 1 2 3

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  An improved pattarn formation method for misalignment measurement in stepping exposure process

    Disclosed is an improved pattern formation method for overlay measurements to
accurately measure stitching overlay misalignment for photolithographic
exposures on the same layer. In conventional misalignment measurements, first a
larger square shape is formed on the initial layer, and a smaller square shape
is formed on a subsequent layer as shown in Fig. 1. The difference in position
of the subsequent pattern from the center of the first pattern indicates the
overlay misalignment. The amount of vertical misalignment of the subsequent
pattern to the first pattern is given by (Y1-Y2)/2, in Fig. 1. The amount of
horizontal misalignment can be found in a similar manner. The conventional
method does not work though for misalignment measurements between exposures on
the same level because only the smaller square shape remains after both shapes
are exposed and developed. Our previous disclosed pattern in the disclosure
JA8-97-0616, which can be used to measure the misalignment between exposures on
the same level, is shown in Fig. 2. The pattern shown in Fig. 2 is formed by
exposing the two patterns, labeled "A" and "B" shown in Fig. 3 where pattern "A"
is exposed prior to "B". The method of calculating the misalignment from
exposure "A" to "B" is shown in Fig. 2. To understand the disclosed misalignment
method, in Fig. 3 note that the inner square is defined by exposure "A" and the
outer shape is defined by exposure "B". The pattern, indeed, can give us quick
and accurate misalignment measurement, however, sometimes abnormal pattern shown
in Fog. 4 is formed by high-viscosity-etchant. It is difficult for the
high-viscosity-etchant to etch off the material between exposed pattern "A" and
"B" due to a narrow ga...