U.S. patent number RE32,795 [Application Number 06/895,132] was granted by the patent office on 1988-12-06 for exposure apparatus for production of integrated circuit.
This patent grant is currently assigned to Nikon Corporation. Invention is credited to Toshio Matsuura, Hisayuki Shimizu, Kyoichi Suwa, Akikazu Tanimoto.
United States Patent |
RE32,795 |
Matsuura , et al. |
December 6, 1988 |
Exposure apparatus for production of integrated circuit
Abstract
An exposure apparatus for production of ICs of the type that
includes a stage on which is placed a semiconductor wafer to be
exposed by illumination light projecting means, and means for
two-dimensionally moving the stage within a plane intersecting the
illumination light at substantially right angles. The improvement
comprises illumination detection means provided with a photo
reception surface, and means for mounting the illumination
detection means on the stage in such a manner that the photo
reception surface and the surface of the semiconductor wafer on the
stage to be exposed are at substantially equal height relative to
the stage.
Inventors: |
Matsuura; Toshio (Koshigaya,
JP), Suwa; Kyoichi (Kawasaki, JP), Shimizu;
Hisayuki (Tokyo, JP), Tanimoto; Akikazu
(Kawasaki, JP) |
Assignee: |
Nikon Corporation (Tokyo,
JP)
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Family
ID: |
11576807 |
Appl.
No.: |
06/895,132 |
Filed: |
August 11, 1986 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
335733 |
Dec 30, 1981 |
04465368 |
Aug 14, 1984 |
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Foreign Application Priority Data
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Jan 14, 1981 [JP] |
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56-4153 |
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Current U.S.
Class: |
356/121; 355/53;
355/68; 355/72; 356/218; 356/225 |
Current CPC
Class: |
G03F
7/70058 (20130101); H01L 21/30 (20130101) |
Current International
Class: |
G03F
7/20 (20060101); H01L 21/30 (20060101); H01L
21/02 (20060101); G01J 001/42 (); G03B
027/42 () |
Field of
Search: |
;356/121,124,218,223,225,226,227,375 ;355/38,68 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Blum et al., "Beam Position and Intensity Analyzing Device", IBM
Tech. Disc. Bulletin, vol. 12, #10, 3/1970, pp. 1594-1595, copy
356/121..
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Primary Examiner: McGraw; Vincent P.
Attorney, Agent or Firm: Shapiro and Shapiro
Claims
We claim:
1. In an exposure apparatus for production of integrated circuits
including a stage on which a semiconductor wafer is placed for
exposure by illumination light projecting means and means for
two-dimensionally displacing said stage in a plane intersecting the
illumination light at substantially right angles, an improvement
comprising:
illumination detecting means having a photo reception surface;
and
means for .Iadd.fixedly .Iaddend.mounting said illumination
detecting means on said stage in such manner that said photo
reception surface lies substantially at the same level as the
exposed surface of said semiconductor wafer on said stage relative
to said stage.
2. The improvement as set forth in claim 1, wherein said
illumination light projecting means is so mounted as to illuminate
a selected area on said stage and wherein said illumination
detecting means is mounted out of said selected area on said
stage.
3. The improvement as set forth in claim 2 which further comprises
means for guiding said illumination detecting means into said
selected area.
4. The improvement as set forth in claim 3, wherein said displacing
means includes means for detecting the position of said
illumination detecting means and means for driving said stage in
response to said position detecting means.
5. The improvement as set forth in claim 1, wherein said mounting
means includes an intercepting member having an opening
therethrough that is very small in area parallel to said plane
relative to the area of the photo reception surface parallel to
said plane to limit the light receivable area on the photo
reception surface of said illumination detecting means.
6. The improvement as set forth in claim 1, wherein said
illumination detecting means comprises a one-dimensional photo
sensor.
7. The improvement as set forth in claim 1, wherein said
illumination detecting means comprises a two-dimensional photo
sensor.
8. In an exposure apparatus for production of integrated circuits
in which a pattern is illuminated to print an image of the pattern
through an optical system onto a surface to be exposed of a
semiconductor wafer having predetermined thickness, an improvement
comprising:
(a) a stage having a surface for supporting said semiconductor
wafer thereon at a predetermined location with said semiconductor
wafer surface to be exposed oriented substantially perpendicular to
the optical axis of said optical system, the stage being supported
to move on a two-dimensional plane substantially orthogonal to said
optical axis;
(b) limiting means providing a limited area through which light
passes, said limiting means being integral with said stage and
positioned at a location on said stage spaced laterally away from
said predetermined location;
(c) means detecting the light which passes through said limiting
means to convert it into an electric signal, said detecting means
.Iadd.being fixedly mounted on said stage and .Iaddend.having a
photo reception surface that is at substantially the same level
relative to said stage surface as the surface of the semiconductor
wafer to be exposed; and
(d) means for detecting the position of said stage on said
two-dimensional plane.
9. In an exposure apparatus for production of integrated circuits
in which a pattern is illuminated to print an image of the pattern
through an optical system onto a surface to be exposed of a
semiconductor wafer, an improvement comprising:
(a) a stage on which said semiconductor wafer is supported with
said semiconductor wafer surface to be exposed substantially
perpendicular to the optical axis of said optical system, the stage
being supported to move on a two-dimensional plane substantially
orthogonal to said optical axis;
(b) illumination detecting means having a photo reception surface
and being provided with an intercepting member having an opening
formed therethrough that is very small in area parallel to said
plane relative to the area of the photo reception surface parallel
to said plane to limit the light receivable area on the photo
reception surface, the illumination detecting means including means
to support said photo reception surface .Iadd.fixedly .Iaddend.on
said stage at a level substantially coincident with the level of
said semiconductor wafer surface to be exposed; and
(c) means detecting the position of said stage on said
two-dimensional plane.
10. The improvement as set forth in claim 9, wherein said
illumination detecting means includes a photoelectric element for
detecting the light which passes through said opening to convert it
into an electric signal. .Iadd.
11. The improvement as set forth in claim 1, wherein said
illumination detecting means is embedded in said stage. .Iaddend.
.Iadd.12. The improvement as set forth in claim 8, wherein said
detecting means is embedded in said stage. .Iaddend. .Iadd.13. The
improvement as set forth in claim 9, wherein said illumination
detecting means is embedded in said stage. .Iaddend. .Iadd.14. An
exposure apparatus for production of integrated circuits
comprising:
(a) illuminating means for illuminating a reticle;
(b) a stage provided with a supporting surface for supporting a
wafer on said supporting surface;
(c) moving means for moving said stage on a two-dimensional plane
which is parallel to a surface to be exposed of said wafer;
(d) position detecting means for detecting the position of said
stage on said two-dimensional plane;
(e) illumination light detecting means having a detection surface;
and
(f) mounting means for mounting said illumination light detecting
means fixedly on said stage so that said detection surface is
substantially at the same level as said surface of the wafer and
said illumination light detecting means is out of an area of said
stage where said wafer is disposed. .Iaddend. .Iadd.15. An
apparatus according to claim 14, wherein said light detecting means
is embedded in said stage. .Iaddend. .Iadd.16. An exposure
apparatus for production of integrated circuits comprising:
(a) illuminating means for illuminating a reticle, said
illuminating means having an optical system for forming a minified
image of the illuminated reticle on a predetermined plane so that
the size of said image of said reticle is smaller than the size of
said reticle;
(b) a stage provided with a supporting surface for supporting a
wafer on said supporting surface so that a surface to be exposed of
said wafer is substantially at the same level as said predetermined
plane;
(c) moving means for moving said stage on a two-dimensional plane
which is parallel to said predetermined plane;
(d) position detecting means for detecting the position of said
stage on said two-dimensional plane;
(e) light detecting means having a detection surface, said
detecting means detecting an intensity of light incident on said
detection surface to produce an electric signal conforming to the
detected intensity; and
(f) mounting means for mounting said light detecting means fixedly
on said stage so that said detection surface is substantially at
the same level as said predetermined plane and said detecting means
is out of an area of said stage where said wafer is disposed.
.Iaddend. .Iadd.17. An apparatus according to claim 16, wherein
said light detecting means has a photoelectric conversion element
and a light intercepting member provided with an opening, and said
photoelectric conversion element is attached to said light
intercepting member so that said photoelectric conversion element
detects light from said illuminating means through said opening.
.Iaddend. .Iadd.18. An apparatus according to claim 17, wherein
said stage has the shape of a rectangle and said light detecting
means is disposed adjacent to one of the corners of said rectangle.
.Iaddend. .Iadd.19. An apparatus according to claim 17, wherein
said position detecting means has two interference range finders
which measure a position of said stage in two directions which are
perpendicular to each other. .Iaddend. .Iadd.20. An apparatus
according to claim 16, wherein said light detecting means is
embedded in said stage. .Iaddend. .Iadd.21. An exposure apparatus
for production of integrated circuits comprising:
(a) illuminating means for illuminating a reticle, said
illuminating means having an optical system for forming a minified
image of the illuminated reticle on a predetermined plane so that
the size of said image of said reticle is smaller than the size of
said reticle;
(b) a stage for supporting a wafer thereon so that a surface to be
exposed of said wafer is substantially at the same level as said
predetermined plane;
(c) moving means for moving said stage on a two-dimensional plane
which is parallel to said predetermined plane; and
(d) measuring means for detecting positions of rise and fall of an
illumination distribution of the image of said illuminated reticle
on said predetermined plane to measure the size of an exposure area
corresponding to the image of the illuminated reticle, said
measuring means including light detecting means, mounting means for
mounting said light detecting means fixedly on said stage, and
position detecting means for detecting each of the positions of
said stage on said two-dimensional plane, said light detecting
means having a detection surface and detecting an intensity of
light incident on said detection surface to produce an electric
signal conforming to the detected intensity, said mounting means
mounting said light detecting means so that said detection surface
is substantially at the same level as said predetermined plane and
said detecting means is out of an area of said stage where said
wafer is
disposed. .Iaddend. .Iadd.22. An apparatus according to claim 21,
wherein said light detecting means has a photoelectric conversion
element and a light intercepting member provided with an opening,
and said photoelectric conversion element is attached to said light
intercepting member so that said photoelectric conversion element
detects light from said illuminating means through said opening.
.Iaddend. .Iadd.23. An apparatus according to claim 22, wherein
said stage has the shape of a rectangle and said light detecting
means is mounted adjacent to one of the corners of said rectangle.
.Iaddend. .Iadd.24. An apparatus according to claim 21, wherein
said light detecting means is embedded in said stage. .Iaddend.
.Iadd.25. An exposure apparatus for production of integrated
circuits comprising:
(a) illuminating means for illuminating a reticle, said
illuminating means having an optical system for forming a minified
image of the illuminated reticle on a predetermined plane so that
the size of said image of said reticle is smaller than the size of
said reticle;
(b) a stage provided with a supporting surface for supporting a
wafer on said supporting surface so that a surface to be exposed of
said wafer is substantially at the same level as said predetermined
plane;
(c) moving means for moving said stage on a two-dimensional plane
which is parallel to said predetermined plane;
(d) position detecting means for detecting the position of said
stage on said two-dimensional plane;
(e) light detecting means having a detection surface, said
detecting means detecting an intensity of light incident on said
detection surface to produce an electric signal conforming to the
detected intensity; and
(f) mounting means for mounting said light detecting means fixedly
on said stage so that said detection surface is substantially at
the same level as
said predetermined plane. .Iaddend. .Iadd.26. An apparatus
according to claim 25, wherein said light detecting means is
embedded in said stage. .Iaddend. .Iadd.27. An exposure apparatus
for production of integrated circuits comprising:
(a) illuminating means for illuminating a reticle, said
illuminating means having an optical system for forming a minified
image of the illuminated reticle on a predetermined plane so that
the size of said image of said reticle is smaller than the size of
said reticle;
(b) a stage for supporting a wafer thereon so that a surface to be
exposed of said wafer is substantially at the same level as said
predetermined plane;
(c) moving means for moving said stage on a two-dimensional plane
which is parallel to said prerdetermined plane; and
(d) measuring means for detecting positions of rise and fall of an
illumination distribution image of the illuminated reticle on said
predetermined plane to measure the size of an exposure area
corresponding to the image of said illuminated reticle, said
measuring means including light detecting means, mounting means for
mounting said light detecting means fixedly on said stage, and
position detecting means for detecting each of the positions of
said stage on said two-dimensional plane, said light detecting
means having a detection surface and detecting an intensity of
light incident on said detection surface to produce an electric
signal conforming to the detected intensity, said mounting means
mounting said light detecting means so that said detection surface
is substantially at the same level as said predetermined plane.
.Iaddend.
.Iadd.28. An apparatus according to claim 27, wherein said light
detecting means is embedded in said stage. .Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exposure apparatus for
production of integrated circuits (ICs) with an illuminometer for
measuring intensity of illumination and/or distribution thereof on
the water surface to be exposed by a light source.
2. Description of the Prior Art
The exposure apparatus for production of ICs of the type mentioned
above is usually required to have high uniformity of illumination
by which the wafer surface is to be exposed. In recent years, the
degree of integration of ICs has become higher and higher up to the
pattern line width of about 1 .mu.m. With the increase of the
integration degree of ICs, the requirement for uniformity of
illumination has become more and more severe. The control on the
pattern line width is directly affected by irregularity of the
illumination. Irregularity of illumination results in irregularity
of line width.
Conventionally, the intensity of illumination of the exposure
apparatus is measured by an illuminometer. According to the prior
art, the illuminometer is disposed in a space between the
illumination light projection part (for example, the light
projection part of a projection lens system) and the sample stage
on which a wafer is placed. Also, to measure the distribution of
intensity of illumination with the illuminometer, the illuminometer
is mounted on a mounting table having a mechanism for moving the
illuminometer one-dimensionally or two-dimensionally. With this
prior art arrangement, the intensity of illumination or the
distribution thereof actually measured is only that existing
between the illumination light projection part and the stage, not
the intensity of illumination directly on the part to be actually
illuminated, that is, the exposed surface of the wafer on which a
pattern is to be printed. This is one of the disadvantages of the
prior art exposure apparatus.
To meet the increasing integration degree of ICs, the exposure
apparatus recently developed are generally complicated in
structure. Because of the complicated structure, some of these
known apparatus have no space available for mounting the
illuminometer with or without the above mentioned moving mechanism
between the light projection part and the stage. In such cases, a
characteristic test is carried out beforehand on the illumination
system at the time of manufacture of the apparatus to know the
intensity of illumination of distribution thereof on the portion to
be illuminated by the illumination system. After the preliminary
test, all of the components are assembled together into an exposure
apparatus for production of ICs. However, since such a preliminary
measurement is carried out at a position deviated or completely
different from the position of a wafer in the finally completed
apparatus, the data of intensity of illumination obtained therefrom
are mere relative ones. It is impossible to correctly know the real
intensity of illumination or distribution thereof on the exposed
surface of any wafer actually placed on the stage at any point in
time. This constitutes a second disadvantage of the prior art
apparatus.
Furthermore, there is another problem in the prior art apparatus.
The output of the lamp at the illumination light projection part
decreases gradually with time. Conventionally, the deterioration of
the lamp has been judged on the basis of only the lit time thereof.
When the lamp has been used for illumination for a certain
predetermined time, one judges this to be the end of the life of
the lamp. In other words, replacement of the old lamp has
conventionally been done based on a mere rough estimate of the
useful life of the lamp. Obviously, this method is subject to
errors.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide an
exposure apparatus for production of ICs which enables measurements
of the real intensity of illumination and distribution thereof on
the exposed surface of a wafer in a very simple manner and at any
desired points in time.
It is another object of the invention to provide an exposure
apparatus for production of ICs which enables correct judgment of
the deterioration of the lamp of the illumination light projection
part at any time.
To attain the above and other objects according to the invention
there is provided such exposure apparatus for production of ICs
which is provided with illumination detecting means mounted on the
stage.
Other and further objects, features and advantages of the invention
will appear more fully from the following description taken in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of an embodiment of the present
invention;
FIG. 2 is a plan view of the stage of the apparatus shown in FIG.
1;
FIG. 3 is an enlarged sectional view of the essential part of the
apparatus shown in FIG. 1;
FIG. 4 is a graph showing the distribution of intensity of
illumination attained by the apparatus;
FIG. 5A is a plan view of a stage showing another embodiment of the
invention; and
FIG. 5B is a plan view of a stage showing a further embodiment of
the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring first to FIG. 1 there is shown an embodiment of the
invention formed as a minifying projection exposure apparatus for
production of ICs.
Designated by 1 is a condenser lens 1. An IC pattern is on a
reticle 2. 3 is a minifying projection lens whose pupil is
designated by 4. A stage 5 on which a wafer 6 is placed is movable
two-dimensionally. By the illumination light passed through the
condenser lens 1, a minified image of an IC pattern on the reticle
2 is projected on the wafer 6 positioned on the stage 5. Thus, the
wafer 6 is exposed to the IC pattern on the reticle 2. An
illuminometer 7 is embedded in the stage 5. This illuminometer 7 is
composed of a photoelectric transducer element such as photo
diode.
FIG. 2 is a plan view of the stage 5 as seen from above. The stage
5 can be moved in two-dimensional directions in a plane including
the stage surface by means of an X-Y moving mechanism not shown.
The two-dimensional position of the stage 5 can be determined in
the order of a unit of about 0.02 .mu.m by an X-axis interference
range finder 8 and a Y-axis interference range finder 9. The
information as to stage position obtained by the range finders 8
and 9 may be used to program control the amount of movement of the
stage 5 employing a computer (not shown). In the embodiment shown,
the maximum size of the area 10 to be illuminated is in the order
of 10 mm.times.10 mm.
FIG. 3 is an enlarged sectional side view of the illuminometer 7,
wafer 6 and stage 5. As seen in FIG. 3, a cap-shaped supporting and
masking member 12 is embedded in the stage 5. Within the supporting
member 12, the illuminometer 7 is fixed on the inside of the
supporting member with its photo reception surface upward. Relative
to the wafer supporting surface of the stage 5, the photo reception
surface of the illuminometer 7 is maintained at a level
substantially equal to the exposed surface of the wafer 6. The
supporting and masking member 12 is formed of a material which
intercepts the illumination light. But, the supporting member has a
pin hole 12a in its top wall small (in order of 0.5 mm in diameter)
relative to the area of the photo reception surface of the
illuminometer 7 to allow only a limited very small area of the
photo reception surface of the illuminometer 7 to be exposed to the
illumination light as shown in FIG. 3. The illuminometer 7 converts
the light passed through the pin hole 12a into an electric signal
whereby the intensity of illumination is measured.
To measure the distribution of illumination, at first the stage 5
is moved up to the position at which the pin hole 12a falls within
the area 10 to be illuminated. Thereafter, the stage 5 is moved
two-dimensionally in such a manner as to scan the pin hole 12a in
the illuminated area 10 while measuring the position of the stage 5
at any time by means of the range finders 8 and 9. Thus, the
illumination distribution in the illuminated area 10 can be found
from the illumination data obtained by the illuminometer 7 and the
corresponding position data obtained by the range finders 8 and
9.
FIG. 4 shows, by way of example, one-dimensional distribution of
intensity of illumination as obtained when the illuminometer 7 was
one-dimensionally moved in the direction of the arrow within the
illuminated area 10. It is obvious that, similarly, two-dimensional
distribution of illumination can be found by moving the stage 5
two-dimensionally.
Instead of using interference range finders shown in the above
embodiment, other measuring means for obtaining position data, such
as linear scale, may be used.
Since the function of the pin hole 12a is to limit the light
receivable area of the illuminometer 7 to a very minute area, the
resolving power for measuring the distribution of intensity of
illumination, that is, the size of the small opening 12a relative
to the size of the illuminated area 10 may be suitably selected as
desired. The form of the necessary small opening is not limited to
a pin hole as shown in the above embodiment. A small opening in the
form of a slit having a very small width also may be used for this
purpose.
In the above described type of exposure and printing apparatus it
is a common practice in the art to control the respective
operations of the apparatus by using a computer. Therefore, it is
recommended that a program for measuring the illumination
distribution be incorporated into the sequential control program of
the apparatus. By doing so, it is possible to automatically measure
the intensity of illumination and illumination distribution on an
exposed surface during the operation of the exposure and printing
apparatus at a suitable operation step (for example at the step of
wafer replacement). Also, it is possible to know the change of
illumination distribution with time. In addition, by moving the
stage 5 in such a manner as to move the illuminometer 7 along a
diagonal line of the illuminated area 10, there can also be
obtained data as to the uniformity of illumination light on the
area 10. Such data are obtainable simultaneously with measuring the
illumination distribution through a computer processing of the
obtained illumination distribution.
The illuminometer may be used also to ascertain the real exposure
area of the reticle. To this end, the illuminometer 7 is moved to
detect the rise and fall of the illumination distribution
characteristic. Since the position of the stage 5 at the rise and
that at the fall can be determined by the range finders 8 and 9,
the real size of the illuminated area, that is, the size of the
real pattern printing area, can be measured in a simple manner.
This measurement of the real pattern printing area size is of
significance in particular when the effective area of the reticle
is very small and the illuminated area on a wafer becomes smaller
than the square of 10 mm.times.10 mm. In this case, a mask is
usually used to cover the surrounding area of the reticle against
light, leaving only the pattern area of the reticle exposed. The
above measurement of the real pattern area size is a very effective
method to ascertain whether or not the surrounding area of the
reticle is completely covered by an intercepting frame against the
illumination light, the frame being designed in such a manner as to
open only a pattern area of the reticle.
Obviously many modifications and variations of the present
invention are possible in view of the above teachings. The
illuminometer shown in the above embodiment may be replaced by
other illumination detecting means. FIGS. 5A and 5B show other
forms of illumination detecting means used in the invention.
Illumination detecting means shown in FIG. 5A is formed as a
one-dimensional photo sensor 11. The photo sensor 11 is composed of
a number of elements such as photo diodes arranged in a row in a
one-dimensional direction. With this one-dimensional photo sensor
11, the intensity of illumination can be measured by moving the
stage 5 only in one direction intersecting, at a right angle, the,
length of the photo sensor 11.
Illumination detection means shown in FIG. 5B is formed as a
two-dimensional photo sensor 13 which is composed of a number of
elements such as photo diodes arranged two-dimensionally. With this
photo sensor 13, the characteristic of illumination distribution
can be found merely by electrically scanning the photo sensor 13
after moving the stage 5 up to the position at which the photo
sensor 13 falls within the illuminated area 10.
As for exposure, various types of rays may be used, such as visible
light, ultraviolet light and soft X-rays. The illuminometer and the
intercepting member in the present invention should be selected
suitably according to the wavelength of the rays to be
detected.
* * * * *