Geometrical instruments – Straight-line light ray type – Reticle
Reexamination Certificate
2002-03-11
2004-06-08
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Straight-line light ray type
Reticle
C033S613000, C356S401000
Reexamination Certificate
active
06745484
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims priority of Japanese Patent Application No. 2001-272291, filed on Sep. 7, 2001, the contents being incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reticle, and a pattern positional accuracy measurement device and method and, more particularly, to a reticle required to have high positional accuracy in, e.g., an edge portion of a device pattern, and a device and method of measuring the pattern positional accuracy of the reticle.
2. Description of the Related Art
In the fabrication processes of devices such as semiconductor devices (including LSIs), magnetic devices, liquid crystal devices, and printed circuit boards, a reticle having device patterns to be transferred is used to transfer the device patterns onto (to expose) a semiconductor wafer (to be also simply referred to as a “wafer” hereinafter).
FIG. 5A
is a view showing a reticle having device patterns formed on it.
Referring to
FIG. 5A
, a reticle
50
has, e.g., a glass plate as its substrate, and a plurality of device patterns
52
to be transferred are repeatedly formed at intervals in a device region
51
of this substrate. These device patterns
52
are formed by, e.g., chromium which functions as a light-shielding film during exposure.
A method of fabricating this reticle
50
will be explained below. First, a chromium layer is formed on a glass substrate. In the fabrication of the reticle
50
described above, a resist portion of the substrate coated with the resist is irradiated with an electron beam (EB) or a laser in accordance with the shape of the device patterns
52
. After that, an unnecessary resist is removed by development. In addition, the residual resist is used as a mask to perform etching, thereby forming the device patterns
52
by chromium on the substrate.
FIG. 5B
is a view showing device patterns
55
transferred onto a semiconductor wafer
53
by using the reticle
50
shown in FIG.
5
A. As shown in
FIG. 5B
, the device patterns
55
having the same shape as the device patterns
52
formed at intervals in the device region
51
of the reticle
50
are transferred onto the wafer
53
.
FIGS. 5C and 5D
are enlarged views of a portion
54
having a plurality of transferred device patterns shown in FIG.
5
B.
That is,
FIG. 5C
shows the device patterns
55
transferred onto the wafer
53
by using the reticle
50
in which no deviation occurs in the arrangement in the row direction of the device patterns
52
. As shown in
FIG. 5C
, no deviation from a dotted line Y
51
occurs in the arrangement in the row direction of the device patterns
55
transferred onto the wafer
53
.
On the other hand,
FIG. 5D
shows the device patterns
55
transferred onto the wafer
53
by using the reticle
50
in which deviation occurs in the arrangement in the row direction of the device patterns
52
. In this case, as shown in
FIG. 5D
, deviation having a distance L
51
from the dotted line Y
51
occurs in the arrangement in the row direction of the device patterns
55
transferred onto the wafer
53
.
This deviation occurring in the arrangement of the device patterns
55
transferred onto the wafer
53
by the deviation in the arrangement of the device patterns
52
of the reticle
50
causes variations in the performance of the fabricated devices. In the fabrication of a reticle, therefore, the positional accuracy of the device patterns
52
on the reticle is measured to check whether the required positional accuracy is met, i.e., whether deviation has occurred in the arrangement of the device patterns
52
.
A method of measuring the positional accuracy of device patterns on a conventional reticle will be explained with reference to
FIGS. 6 and 7
.
FIG. 6
is a view showing a method of arranging positional accuracy measurement patterns for measuring the positional accuracy of device patterns on a conventional reticle. As shown in
FIG. 6
, cross-shaped positional accuracy measurement patterns
61
are evenly arranged in positions fixed regardless of layers in the perimeter outside a device region
51
of a reticle
50
. “Layers” mean the layers of each device formed on a wafer.
To measure the positional accuracy of device patterns on the reticle, as shown in
FIG. 7
, each of the cross-shaped positional accuracy measurement patterns
61
arranged as above is scanned in an X direction
71
and a Y direction
72
, thereby acquiring X-coordinates X
71
and X
72
and Y-coordinates Y
71
and Y
72
. In addition, the position of a pattern center CP
2
is calculated on the basis of the X-coordinates X
71
and X
72
and the Y-coordinates Y
71
and Y
72
. More specifically, the X-coordinate of the pattern center CP
2
is calculated by (X
71
+X
72
)/2, and the Y-coordinate of the pattern center CP
2
is calculated by (Y
71
+Y
72
)/2.
The position of the pattern center CP
2
calculated as above is compared with the central position of a positional accuracy measurement pattern based on the design value of the reticle. In this manner, the positional accuracy of device patterns on the reticle is measured and evaluated.
In the above method of measuring the positional accuracy of device patterns on a reticle, however, the positional accuracy of device patterns is measured and evaluated on the basis of the position of the pattern center of each positional accuracy measurement pattern formed. Therefore, even if the formed positional accuracy measurement pattern evenly becomes thick or thin, it does not change the center position of the positional accuracy measurement pattern, and the measurement result of the positional accuracy of device patterns is thus to be ±0. That is, it is determined that no deviation has occurred in the arrangement of device patterns.
Assume, for example, that a cross-shaped positional accuracy measurement pattern
81
having a design value Ld
81
as a width as shown in
FIG. 8A
is to be formed. If, as shown in
FIG. 8B
, the pattern dimensions increase (the pattern becomes thick) symmetrically with respect to central lines in the X and Y directions of this positional accuracy measurement pattern
81
, and if a positional accuracy measurement pattern
82
having a width Ly
81
is formed, pattern centers CP
3
and CP
4
of these positional accuracy measurement patterns
81
and
82
are in the same position because the pattern dimensions increase symmetrically with respect to the central lines in the X and Y directions.
Analogously, as shown in
FIG. 8C
, if the pattern dimensions decrease (the pattern becomes thin) symmetrically with respect to the central lines in the X and Y directions of this positional accuracy measurement pattern
81
, and if a positional accuracy measurement pattern
83
having a width Ly
82
is formed, pattern centers CP
3
and CP
5
of these positional accuracy measurement patterns
81
and
83
are in the same position because the pattern dimensions decrease symmetrically with respect to the central lines in the X and Y directions.
Also, in the recent reticle fabrication, reticles are beginning to be required to have high device pattern positional accuracy, high pattern size accuracy, and the like, with the advancing downsizing and increasing storage capacity of devices, Accordingly, the positional accuracy and the like must be measured more accurately to guarantee the quality of reticles.
Additionally, the positional accuracy of device patterns on the conventional reticle is ensured on the basis of the pattern center of a measured positional accuracy measurement pattern. In a device such as a magnetic device, for example, high positional accuracy is sometimes required in an edge portion of a device pattern which is different from the pattern central position of a positional accuracy measurement pattern.
FIG. 9
is a view for explaining the relationship between the positional accuracy of a positional accuracy measurement pattern on the conventional reticle and the positional accuracy of device patterns
Horie Tsutomu
Ohta Kazutoshi
Cohen Amy R.
Gutierrez Diego
Staas & Halsey , LLP
LandOfFree
Reticle, and pattern positional accuracy measurement device... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reticle, and pattern positional accuracy measurement device..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reticle, and pattern positional accuracy measurement device... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3365129