Geometrical instruments – Miscellaneous – Light direction
Reexamination Certificate
2002-02-01
2003-11-18
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Miscellaneous
Light direction
C033S613000, C033S645000, C414S935000, C414S936000, C356S003090
Reexamination Certificate
active
06647632
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a position measuring apparatus adapted to detect a lateral variation of a stage during straight motion of the stage.
2. Related Art
A plurality of thin film magnetic heads are formed on a semiconductor wafer with the use of a thin film process, and thereafter the heads are cut off from the semiconductor wafer on which the magnetic heads are formed, for being separated from one another. Accordingly, if the accuracy of alignment of the heads formed in a row on the wafer is low, individual shapes and dimensions of magnetic poles become non-uniform (uneven) so that available characteristics of the magnetic heads are non-uniform. Thus, it is required to measure the alignment of an array of heads (which will be hereinbelow referred to “head array”) formed on the semiconductor wafer with a high degree of accuracy.
Heretofore, there has been used an apparatus for measuring an alignment of the above-mentioned head array, in which a semiconductor wafer is mounted and fixed on an X-stage guided by a direct-operated static air bearing, the direction of the head array to be measured on the semiconductor wafer being set to be coincident with the direction of movement of the X-stage, the wafer is moved by the X-stage, pitch by pitch for measurement while the alignment of the head array to be measured are measured by a TV microscope, in order to precisely measure an alignment of the array.
Although this apparatus can precisely measure the alignment of the head array on the basis of a degree of accuracy as to the straight guide of the direct-operated static air bearing, it can hardly avoid affection by vibration of air in the air bearing unit including a ball screw, a linear motor and the like for driving the X-stage, and accordingly, it is difficult to obtain a reproducibility of measurement within 0.02 &mgr;m.
Further, there has been used another apparatus in which an X-Y stage
41
carrying thereon a wafer
46
is provided with an orthogonal plain reflector
42
in parallel with the X-axis and Y-axis, respectively, as shown in
FIG. 5
of the accompanying drawings, illustrating an exposure apparatus used in the field of semiconductors, and displacements of the X-Y stage
41
in the X- and Y-axial directions are measured by laser interferometers
23
,
24
for measuring relative displacements between themselves and the orthogonal plane reflectors
42
.
However, in the above-mentioned conventional apparatus, although an alignment of a head array to be measured (that is, electronic devices formed on the wafer
46
) is measured on the basis of the orthogonal plane reflector
42
, it is required to position the X-Y stage
41
and the orthogonal plane reflector
42
over an entire measuring area in order to measure the alignment of the array over the entire measuring area on the wafer. Accordingly, the distances between the orthogonal plane reflector
42
and the laser interferometers
43
,
44
should be set so as to include the above-mentioned entire measuring area in the extent of movement of the X-stage. For example, if the measuring area has 200 mm diameter, the distances between the orthogonal plane reflector
42
and the laser reflectors
43
,
44
should be set to be greater than at least 200 mm diameter. In this configuration, if the temperature varies by 0.05 deg. C., thus measured distances vary by 200 mm×0.5 deg. C.×1×10
−6
/deg. C.=1×10
−4
mm=0.1 &mgr;m, and accordingly, it has been raised such a problem that this variation directly causes measuring errors.
Meanwhile, in order to measure an alignment of an array of electronic devices such as the above-mentioned thin film magnetic heads, the measuring errors should be settled within 0.01 &mgr;m, and accordingly, a temperature difference should be held within 0.05 deg. C. during measurement. Further, in the above-mentioned conventional measuring apparatus, in addition to the temperature variation, a variation in the atmospheric pressure should be limited to a small value, and further, other mechanical deformation including thermal expansion should be limited to small values. However, it is difficult to economically materialize such an apparatus.
Further, in a process of manufacturing liquid crystal substrates or liquid crystal display elements, it is required to measures dimensions of a precise pattern such as a mask formed on the surface thereof. Heretofore, as to an apparatus for measuring such a precise pattern, there has, in general, been well-known such an apparatus that a substrate to be measured is shifted by an X-Y stage while an image of the precise pattern on the surface thereof is picked up by a TV microscope in order to measure the pattern.
By the way, these years, there has been raised such a demand that display units using the above-mentioned liquid crystal substrate or liquid crystal display elements, are required to be large-sized and highly accurate. In order to satisfy the above-mentioned demands even a two-dimensional liquid display apparatus for measuring dimensions of a precise pattern on the liquid crystal substrate or the liquid crystal display element, is required to high-precisely measure the precise pattern which is formed with a high degree of accuracy on such a large-sized substrate or element. Specifically, a reproducibility (measuring accuracy) of less than 0.1 &mgr;m is required over a range of several hundreds to several thousands millimeters (several 100 to several 1,000 mm).
Conventionally, there has been used a two-dimensional measuring apparatus as shown in
FIG. 6
of the accompanying drawings. That is, as shown in the figure, an X-stage
2
and a Y-stage
22
provided on a portal frame
21
extending across the X-stage
2
thereover are provided on a base
1
, and a Z-stage
27
is assembled to the Y-stage
21
while a TV microscope
29
is mounted on the Z-stage
27
. With this arrangement, the TV microscope
29
is positioned above the above-mentioned substrate while the X-stage
2
, the Y-stage
22
and the Z-stage
27
are moved. It is noted that displacements of the X-stage
2
and the Y-stage
22
are precisely measured by means of laser interferometers
8
a,
8
b,
8
c
and plane reflectors
7
a,
7
b,
37
. Thus, two-dimensional dimensions (in X- and Y-axial directions) of the point to be measured on the above-mentioned object to be measured can be obtained from the position of the point to be measured within the field of vision of the microscope, which is measured by the TV microscope
29
and the image processing device (which is not shown), and from the displacements of the X-stage
2
and the Y-stage
22
which are measured by the laser interferometers
8
a,
8
b,
8
c.
By the way, in the above-mentioned conventional two-dimensional measuring apparatus and the method therefor, reproducible measuring errors during measurement of, for example, dimensions, are added with errors caused by lateral motions of the stage during movement in X- and Y-axial directions. That is, when the stage is moved in, for example, the X-axial direction, lateral or sidewise motions are caused in the Y-axial direction (a direction orthogonal to the advancing direction of the stage) due to affection by yawing, rolling or the like during movement of the stage, and these lateral motions cause the errors. Thus, it is required to maximumly enhance the reproducibility of straightness during movement in X- and Y-axial directions, and accordingly, static air bearings
53
a,
53
b
and
63
and linear drive motors
54
,
64
are used in combination for guiding the stage in the X- and Y-axial directions.
However, with the above-mentioned technologies, since the accuracy of reproducible measurements falls in a range from about 0.1 to 0.2 &mgr;m, the obtained straight guide reproducibility has become about 0.2 &mgr;m. However, as mentioned above, since objects to be measured have become larger and larger, the static air bearings capable of moving the stage over a distance in a range fro
Hirokawa Satoshi
Tominaga Tamotsu
Antonelli Terry Stout & Kraus LLP
Gutierrez Diego
Hitachi Kokusai Electric Inc.
Hoolahan Amanda J
LandOfFree
Position measuring apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Position measuring apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Position measuring apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3159270