United States Patent [191
`Matsuura et al.
`I
`
`[11] Patent Number:
`[45] Date of Patent:
`
`4,465,368
`Aug. 14, 1984
`
`;
`.
`[54] EXPOSURE APPARATUS FOR
`PRODUCTION OF INTEGRATED CIRCUIT
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`[75] Inventors: Toshio Matsuura, Koshigaya;
`Kyoichi Suwa, Kawasaki; Hisayuki
`Shimizu, Tokyo; Akikazu Tanimoto,
`Kawasaki, all of Japan
`
`[73] Assignee: Nippon Kogaku K.K., Tokyo, Japan
`
`[21] Appl. No.: 335,733
`
`[22] Filed:
`
`Dec. 30, 1981
`
`[30]
`
`Foreign Application Priority Data
`
`_
`
`Jan. 14, 1981 [JP]
`
`Japan .................................. .. 56-4153
`
`[51] m. 01.3 .............................................. .. G01J 1/42
`[52] US. Cl. .................................... .. 356/218; 355/53;
`355/58; 355/72
`[58] Field Of Search ..................... .. 356/2l8,'223, 121;
`355/38, 53, 54,68, 77, 72
`
`4,205,918 6/1980 Kisanuki et al. ................ .. 355/38 X
`4,345,836 8/1982 Phillips ...................... .. 355/77X
`
`- Primary Examiner—Vincent P. McGraw
`Assistant Examiner-L. A. Dietert
`Attorney, Agent, or Firm—-Shapiro and Shapiro
`[57]
`ABSTRACT
`An exposure apparatus for production of ICs of the type
`that includes a stage on which is placed a semiconduc
`tor 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 illumina
`tion detection means on the stage in such a manner that
`the photo reception surface and the surface of the semi
`conductor wafer on the stage to be exposed are at sub
`stantially equal height relative to the stage.
`
`10 Claims, 6 Drawing Figures
`
`8
`S
`X-AXIS INTERFERENCE
`RANGE FINDER ‘
`
`Y—AX|S INTERFERENCE 8/9
`RANGE FINDER
`
`Nikon Exhibit 1021 Page 1
`
`

`

`U.S. Pat‘en‘t
`
`Aug. 14, 1984
`
`Sheet 1 of 2
`
`4,465,368
`
`FIG. I
`
`X-AXIS INTERFERENCE
`RANGE FINDER
`
`Y-AXIS INTERFERENCE f9
`RANGE FINDER
`
`Nikon Exhibit 1021 Page 2
`
`

`

`U.S-. Patent Aug. 14, 1984'
`
`Sheet 2 of2
`
`4,465,368
`
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`FIG. 4
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`//
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`+POSITION
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`7
`
`FIG. 5A
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`FIG. 5B
`
`5
`
`Y
`
`6
`
`6
`
`Nikon Exhibit 1021 Page 3
`
`

`

`l .
`
`EXPOSURE APPARATUS, FOR PRODUCTION OF
`INTEGRATED CIRCUIT
`
`4,465,368
`2
`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 judge's 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.
`
`5
`
`BACKGROUND OF THE INVENTION
`l. Field of the Invention
`The present invention relates to an exposure appara
`tus 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 havehigh
`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 pm. With the increase of the inte
`gration 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 illumina
`tion 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 dis
`posed ina space between the illumination light projec
`tion 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
`30
`intensity of illumination with the illuminometer, the
`illuminometer is mounted on a mounting table having a
`mechanism for moving the illuminometer one-dimen
`sionally or two-dimensionally. With this prior art ar
`rangement, the intensity of illumination or the distribu
`tion thereof actually measured is only that existing be
`tween 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 sur
`face of the wafer on which a pattern is to be printed.
`This is one of the disadvantages of the prior art expo
`sure 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 with
`out 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 il
`lumination system atthe time of manufacture of the
`apparatus to know the intensity of illumination or distri
`bution 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 carriedv out at a position
`deviated or completely different from the position of a
`wafer in the ‘?nally completed apparatus, the data of
`intensity of ‘illumination obtained therefrom are mere
`relative ones.'It is impossible to correctly know the real
`intensity of v illumination or distribution'thereof on the
`exposed surface of any wafer actually placed on the
`stage at any point in time. This constitutesa 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.
`
`10
`
`25
`
`40
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`50
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`55
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`60
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`65
`
`SUMMARY OF THE INVENTION
`Accordingly, it is an object of the invention to pro
`vide an exposure apparatus for production of ICs which
`enables measurements of the real intensity of illumina
`tion 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 illumina
`tion 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 showinganother
`embodiment of the invention; and
`FIG. 5B is a plan view of a stage showing a further
`embodiment of the invention.
`
`PREFERRED
`DETAILED DESCRIPTION
`>
`EMBODIMENTS
`Referring ?rst to FIG. 1 there is shown an embodi
`ment 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 illumi
`nation light passed through the condenser lens 1, a mini
`fled 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 illumi
`nometer 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 deter
`mined in the order of a unit of about 0.02 pm by an
`X-axis interference range ?nder 8 and a Y-axis interfer
`ence range finder 9. The information as to stage position
`
`Nikon Exhibit 1021 Page 4
`
`

`

`4,465,368
`3
`4
`obtained by the range ?nders 8 and 9 may be used to
`distribution with time. In addition, by moving the stage
`program control the amount of movement of the stage
`5 in such a manner as to move the illuminometer 7 along
`5 employing a computer (not shown). In the embodi
`a diagonal line of the illuminated area 10, there can also
`ment shown, the maximum size of the area 10 to be
`be obtained data as to the uniformity of illumination
`illuminated is in the order of 10 mmX 10 mm.
`light on the area 10. Such data are obtainable simulta
`FIG. 3 is an enlarged sectional side view of the illumi
`neously with measuring the illumination distribution
`nometer 7, wafer 6 and stage 5. As seen in FIG. 3, a
`through a computer processing of the obtained illumi
`cap-shaped supporting and masking member 12 is em
`nation distribution.
`bedded in the stage 5. Within the supporting member
`The illuminometer may be used also to ascertain the
`12, the illuminometer 7 is ?xed on the inside of the
`real exposure area of the reticle. To this end, the illumi
`supporting member with its photo reception surface
`nometer 7 is moved to detect the rise and fall of the
`upward. Relative to the wafer supporting surface of the
`illumination distribution characteristic. Since the posi
`stage 5, the photo reception surface of the illuminome
`tion of the stage 5 at the rise and that at the fall can be
`ter 7 is maintained at a level substantially equal to the
`determined by the range ?nders 8 and 9, the real size of
`exposed surface of the wafer 6. The supporting and
`the illuminated area, that is, the size of the real pattern
`masking member 12 is formed of a material which inter
`printing area, can be measured in a simple manner. This
`cepts the illumination light. But, the supporting member
`measurement of the real pattern printing area size is of
`has a pin hole 12a in its top wall small (in order of 0.5
`signi?cance in particular when the effective area of the
`mm in diameter) relative to the area of the photo recep
`reticle is very small and the illuminated area on a wafer
`tion surface of the illuminometer 7 to allow only a lim
`becomes smaller than the square of 10 mmX 10 mm. In
`20
`ited very small area of the photo reception surface of
`this case, a mask is usually used to cover the surround
`the illuminometer 7 to be exposed to the illumination
`ing area of the reticle against light, leaving only the
`light as shown in FIG. 3. The illuminometer 7 converts
`pattern area of the reticle exposed. The above measure
`the light passed through the pin hole 120 into an electric
`ment of the real pattern area size is a very effective
`signal whereby the intensity of illumination is measured.
`method to ascertain whether or not the surrounding
`To measure the distribution of illumination, at ?rst
`area of the reticle is completely covered by an inter
`the stage Sis moved up to the position at which the pin
`cepting frame against the illumination light, the frame
`hole 12a falls within the area 10 to be illuminated.
`being designed in such a manner as to open only a pat
`Thereafter, the stage 5 is moved two-dimensionally in
`tern area of the reticle.
`such a manner as to scan the pin hole 12a in the illumi
`Obviously many modi?cations and variations of the
`nated area 10 while measuring the position of the stage
`present invention are possible in view of the above
`5 at any time by means of the range ?nders 8 and 9.
`teachings. The illuminometer shown in the above em
`Thus, the illumination distribution in the illuminated
`bodiment may be replaced by other illumination detect
`area 10 can be found from the illumination data ob
`ing means. FIGS. 5A and 5B show other forms of illum
`tained by the illuminometer 7 and the corresponding
`ination detecting means used in the invention. Illumina
`position data obtained by the range ?nders 8 and 9.
`tion detecting means shown in FIG. 5A is formed as a
`FIG. 4 shows, by Way of example, one-dimensional
`one-dimensional photo sensor 11. The photo sensor 11 is
`distribution of intensity of illumination as obtained
`composed of a number of elements such as photo diodes
`when the illuminometer 7 was one-dimensionally
`arranged in a row in a one-dimensional direction. With
`moved in the direction of the arrow within the illumi
`this one-dimensional photo sensor 11, the intensity of
`nated area 10. It is obvious that, similarly, two-dimen
`illumination can be measured by moving the stage 5
`sional distribution of illumination can be found by mov
`only in one direction intersecting, at a right angle, the
`ing the stage 5 two-dimensionally.
`length of the photo sensor 11.
`Instead of using interference range ?nders shown in
`Illumination detection means shown in FIG. 5B is
`the above embodiment, other measuring means for ob
`formed as a two-dimensional photo sensor 13 which is
`taining position data, such as linear scale, may be used.
`composed of a number of elements such as photo diodes
`Since the function of the pin hole 120 is to limit the
`arranged two-dimensionally. With this photo sensor 13,
`light receivable area of the illuminometer 7 to a very
`the characteristic of illumination distribution can be
`minute area, the resolving power for measuring the
`found merely by electrically scanning the photo sensor
`distribution of intensity of illumination, that is, the size
`13 after moving the stage 5 up to the position at which
`of the small opening 12a relative to the size of the illu
`the photo sensor 13 falls within the illuminated area 10.
`minated area 10 may be suitably selected as desired. The
`As for exposure, various types of rays may be used,
`form of the necessary small opening is not limited to a
`such as visible light, ultraviolet light and soft X-rays.
`pin hole as shown in the above embodiment. A small
`The illuminometer and the intercepting member in the
`opening in the form of a slit having a very small width
`present invention should be selected suitably according
`also may be used for this purpose.
`to the wavelength of the rays to be detected.
`In the above described type of exposure and printing
`We claim:
`apparatus it is a common practice in the art to control
`1. In an exposure apparatus for production of inte
`the respective operations of the apparatus by using a
`grated circuits including a stage on which a semicon
`computer. Therefore, it is recommended that a program
`ductor wafer is placed for exposure by illumination
`for measuring the illumination distribution be incorpo
`light projecting means and means for two-dimension
`rated into the sequential control program of the appara
`ally displacing said stage in a plane intersecting the
`tus. By doing so, it is possible to automatically measure
`illumination light at substantially right angles, an im
`the intensity of illumination and illumination distribu
`provement comprising:
`tion on an exposed surface during the operation of the
`illumination detecting means having a photo recep
`exposure and printing apparatus at a suitable operation
`tion surface; and
`step (for example at the step of wafer replacement).
`means for mounting said illumination detecting means
`Also, it is possible to know the change of illumination
`on said stage in such manner that said photo recep
`
`40
`
`45
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`65
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`Nikon Exhibit 1021 Page 5
`
`

`

`4,465,368
`5 .
`tion surface lies substantially at the same level as
`the exposed surface of said semiconductor'wafer
`on said stage relative to said stage.
`i
`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 detect
`ing 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
`20
`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 25
`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-di
`mensional photo sensor.
`~
`8. In an exposure apparatus for production of inte
`grated 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 hav
`ing predetermined thickness, an improvement compris
`
`6
`(b) limiting means providing a limited area through
`which light passes, said limiting means being inte
`gral with said stage and positioned at a location on
`said stage spaced laterally'away from said predeter
`mined location;
`(c) means detecting the light which passes through
`said limiting means to convert it into an electric
`signal, said detecting means having a photo recep
`tion 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 inte
`grated 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 re
`ception surface and being provided with an inter
`cepting member having an opening formed there
`through 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 re
`ceivable area on the photo reception surface, the
`illumination detecting means including means to
`support said photo reception surface on said stage
`at a level substantially coincident with the level of
`said semiconductor wafer surface to be exposed;
`and
`(0) 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 photoelec
`tric element for detecting the light which passes
`through said opening to convert it into an electric sig
`nal.
`
`* l * it
`
`it
`
`(It
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`30
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`35
`
`mg:
`'
`(a) a stage having a surface for supporting said semi
`conductor wafer thereon at a predetermined loca
`tion with said semiconductor wafer surface to be 40
`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;
`
`45
`
`50
`
`55
`
`65
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`Nikon Exhibit 1021 Page 6
`
`