Focus test mask, focus measurement method, exposure method and exposure apparatus

A focus test reticle for measuring focus information includes an outer pattern. The outer pattern has a line pattern composed of a light shielding film extending in the Y direction, a phase shift portion provided on a side in the +X direction of the line pattern and formed to have a line width narrower than the line pattern, a transmitting portion provided on a side in the −X direction of the line pattern and formed to have a line width narrower than the line pattern, a transmitting portion provided on a side in the +X direction of the phase shift portion, and a phase shift portion provided on a side in the −X direction of the transmitting portion. Focus information of a projection optical system is measured at a high measuring reproducibility and a high measuring efficiency.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a focus test mask formed with a pattern for measuring focus information (image plane information) of a projection optical system, a focus measuring method for measuring the focus information of the projection optical system by using the focus test mask, an exposure method, an exposure apparatus provided with the focus test mask, and a method for producing a device using the exposure apparatus.

2. Description of the Related Art

For example, the following procedure is performed in order to measure the focus information as the information about an image plane (best focus position) of a projection optical system in relation to an exposure apparatus used in the lithography step to produce an electronic device (microdevice) such as a semiconductor device or the like. That is, a test mask is arranged on an object plane of the projection optical system, and a substrate or the like is arranged on the image plane of the projection optical system. A predetermined evaluating pattern, which is provided on the test mask, is projected onto the substrate or the like via the projection optical system to measure, for example, a positional deviation amount or positional shift amount of an image of the evaluating pattern.

A method is known as a first conventional measuring method, wherein an evaluating pattern, which is provided with a phase changing portion for changing the phase of an illumination light (illumination light beam) at a space portion wider than the line width of each of line patterns between the line patterns each constructed of two light shielding films, is used, and a substrate coated with a photoresist is exposed with an image of the evaluating pattern formed by a projection optical system. See, for example, Japanese Patent Application Laid-open No. 6-204305. In this procedure, it is possible to determine the defocus amount of the surface of the substrate as well as the position of the image plane from the spacing distance between two line-shaped resist patterns formed on the substrate after the development.

A method is known as a second conventional measuring method, wherein a wafer is exposed in an overlay manner with an image of a diffraction grating-shaped evaluating pattern which includes a plurality of, for example, four or more light shielding lines such that phase distributions provided outside the respective light shielding lines are asymmetrical in the measuring direction and an image of a trim pattern, which is provided to extinguish or erase any image of any unnecessary light shielding line disposed on an outer side, of images of the plurality of light shielding lines. See, for example, Japanese Patent No. 3297423. Also in this case, it is possible to determine the defocus amount of the surface of the wafer from the shift amounts of the images of the plurality of remaining light shielding lines disposed at the center.

A method is known as a third conventional measuring method, wherein the lateral deviation amount is measured for a spatial image of an evaluating pattern which is provided in the vicinity of a plurality of line patterns and which has a phase shift portion wider than the line width of each of the line patterns. See, for example, International Publication No. 2005/004211. Also in this case, it is possible to determine the defocus amount of the light-receiving surface from the lateral deviation amount of images of the respective line patterns.

In the first and third measuring methods of the conventional measuring methods for measuring the focus information, the phase shift portion, which is disposed in contact with the line pattern (or in the vicinity thereof), has a width which is wider than the line width of the line pattern. In order to enhance the measuring sensitivity (lateral deviation amount of image/defocus amount), it is preferable that the line width of the line pattern is narrowed. However, if the line width of the line pattern is narrowed, it is feared that the reproducibility of measurement (measuring reproducibility) might be lowered. Further, in a case that the image of the resist pattern after the development is observed, it is feared that the falling (collapse) or the like of the resist pattern might be caused. Further, if the line width of the line pattern is narrow as described above, in a case that the numerical aperture of the projection optical system is high or large, it is feared that the measuring sensitivity might be lowered especially in a range in which a projection surface of the image of the line pattern is disposed near to the best focus position.

On the other hand, the second conventional measuring method involves such a problem that the efficiency of measurement (measuring efficiency) is low, because it is necessary to perform the exposure twice in order to extinguish the image of the unnecessary pattern.

SUMMARY OF THE INVENTION

Taking the foregoing circumstances into consideration, an object of the present invention is to measure the focus information of a projection optical system at a high reproducibility of measurement or with a high efficiency of measurement.

According to a first aspect, there is provided a focus test mask comprising a test pattern which is to be projected onto an object via a projection optical system;

wherein the test pattern includes: a first light shielding portion which extends in a line form in a first direction and which shields a light; a first phase shift portion which is provided on one side of the first light shielding portion in relation to a second direction perpendicular to the first direction, which extends in a line form in the first direction, which is formed to have a line width in relation to the second direction narrower than a line width of the first light shielding portion, and which changes a phase of the light transmitted therethrough; a first transmitting portion which is provided on the other side of the first light shielding portion in relation to the second direction, which extends in a line form in the first direction, which is formed to have a line width in relation to the second direction narrower than the line width of the first light shielding portion, and through which the light is transmitted; and a second phase shift portion which is provided on a side, of the first transmitting portion, opposite to the first light shielding portion in relation to the second direction, which is formed to have a line width in relation to the second direction wider than the first transmitting portion, and which changes the phase of the light transmitted therethrough.

According to a second aspect, there is provided a focus measuring method for measuring image plane information of a projection optical system, the focus measuring method comprising: a step of arranging the focus test mask according to the first aspect on a side of an object plane of the projection optical system; a step of projecting, onto a measuring surface, an image of the test pattern provided on the focus test mask, the image being formed by the projection optical system; and a step of measuring position information in a measuring direction of the image of the test pattern.

According to a third aspect, there is provided an exposure method comprising: arranging a mask for a device on a side of an object plane of a projection optical system; adjusting a focus position of an image of a pattern of the mask for the device based on the position information of the image of the test pattern measured by using the above-described focus measuring method, the image of the pattern of the mask for the device being formed by the projection optical system; and projecting onto a substrate the image, of the pattern of the mask for the device, of which focus position has been adjusted.

According to a fourth aspect, there is provided an exposure apparatus which illuminates a pattern of a mask with an exposure light and exposes a substrate with the exposure light via the pattern and a projection optical system, the exposure apparatus comprising: a mask stage which holds the focus test mask according to the first aspect; and a controller which causes the projection optical system to project an image of the test pattern of the focus test mask and which determines image plane information of the projection optical system based on position information in a measuring direction of the image of the test pattern.

According to a fifth aspect, there is provided a method for producing a device, the method comprising: transferring a pattern onto a substrate by using the exposure apparatus of the fourth aspect; and processing the substrate, onto which the pattern has been transferred, based on the pattern.

According to the above-described focus test mask and the respective aspects according thereto, the first phase shift portion is provided on one side in the second direction with respect to the first light shielding portion, and the first transmitting portion and the second phase shift portion are provided on the other side in the second direction with respect to the first light shielding portion. Therefore, it is possible to determine the defocus amount with respect to the image plane of the projection optical system as well as the focus information at a high measuring efficiency from the lateral deviation amount of the image of the first light shielding portion in the direction corresponding to the second direction. Further, since the width of the first light shielding portion is wider than the width of the first phase shift portion, it is possible to measure the focus information at a high measuring reproducibility.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

A first embodiment will be explained below with reference toFIGS. 1 to 8.

FIG. 1shows a schematic construction of an exposure apparatus EX of the scanning exposure type constructed of a scanning stepper (scanner) according to the embodiment. With reference toFIG. 1, the exposure apparatus EX includes an exposure light source (not shown), and an illumination optical system ILS which illuminates a reticle R (mask) with an illumination light or illumination light beam (exposure light or exposure light beam) IL radiated from the exposure light source. The exposure apparatus EX further includes a reticle stage RST which is movable while holding the reticle R, a projection optical system PL which projects the illumination light IL exiting from the reticle R onto a wafer W (substrate) coated with a photoresist (photosensitive material), a wafer stage WST which positions and moves the wafer W, a main control system2which is constructed of a computer integrally controlling the operation of the entire apparatus, other driving systems, etc.

The following description will be made assuming that the Z axis extends in parallel to an optical axis AX of the projection optical system PL, the X axis and the Y axis extend in two orthogonal directions in a plane (substantially a horizontal plane) perpendicular to the Z axis, and the directions of rotation (inclination) about the axes parallel to the X axis, the Y axis, and the Z axis are designated as θx, θy, and θz directions respectively. In this embodiment, the scanning direction for the reticle R and the wafer W during the scanning exposure is a direction (Y direction) parallel to the Y axis.

An ArF excimer laser (wavelength: 193 nm) is used as the exposure light source. Other than the above, those usable as the exposure light source include an ultraviolet pulsed laser light source such as a KrF excimer laser (wavelength: 248 nm) or the like, a high harmonic wave generating light source of a YAG laser, a high harmonic wave generator of a solid-state laser (a semiconductor laser, etc.), an electric discharge lamp such as a mercury lamp or the like, etc.

As disclosed, for example, in United States Patent Application Publication No. 2003/0025890, the illumination optical system ILS includes a light amount distribution setting optical system which includes a diffraction optical element, etc. and which sets the light amount distribution on a pupil plane in a circular, annular, or multipole area, etc.; an illuminance uniformalizing optical system which includes an optical integrator (for example, a fly's eye lens or a rod integrator), etc.; a reticle blind (variable field stop); a condenser optical system; and the like.

The illumination optical system ILS illuminates a rectangular illumination area10R, which is elongated or slender in the X direction (non-scanning direction), on a pattern area PA with the illumination light IL at a substantially uniform illuminance on a pattern surface (reticle surface) of the reticle R. With the illumination light IL, a circuit pattern, which is disposed in the illumination area10R of the reticle R, is projected onto an exposure area10W (area conjugate with the illumination area10R) disposed on one shot area SA on the wafer W at a predetermined projection magnification (for example, a reduction magnification of ¼, ⅕, etc.) via the projection optical system PL which is telecentric on the both sides (or telecentric on one side on the wafer side). The wafer W is prepared such that a surface of a disk-shaped base member having a diameter of about 200 to 450 mm constructed of, for example, a silicon semiconductor or SOI (silicon on insulator) is coated with a photoresist (photosensitive material). The projection optical system PL is, for example, of the dioptric system. However, it is also possible to use the catadioptric system, etc.

The reticle R is attracted and held on the reticle stage RST via a reticle holder (not shown). The reticle stage RST is placed on an upper surface of a reticle base RB parallel to the XY plane via an air bearing. The reticle stage RST is movable at a constant velocity in the Y direction on the upper surface, and the positions in the X direction and the Y direction and the angle of rotation in the θz direction are finely adjusted thereby. The two-dimensional position information of the reticle stage RST, which includes at least the positions in the X direction and the Y direction and the angle of rotation in the θz direction, is measured, as an example, by a reticle side interferometer including a laser interferometer8X for the X axis and two-axis laser interferometers8YA,8YB for the Y axis. Obtained measured values are supplied to a stage driving system4and the main control system2. The stage driving system4controls the velocity and the position of the reticle stage RST via an unillustrated driving mechanism (a linear motor, etc.) based on the position information and a control information from the main control system2.

On the other hand, the wafer W is attracted and held on an upper portion of the wafer stage WST via a wafer holder WH. The wafer stage WST includes an XY stage24, and a Z tilt stage22which is disposed thereon and which holds the wafer W. The XY stage24is placed on an upper surface of a wafer base26parallel to the XY plane via an air bearing. The XY stage24is movable on the upper surface in the X direction and the Y direction, and the angle of rotation in the θz direction is corrected, if necessary. The Z tilt stage22has, for example, Z driving sections (not shown) which are provided at three portions, which are displaceable in the Z direction, and which are driven individually to control the position (Z position) in the direction of the optical axis AX and the angles of inclination in the θx direction and the θy direction of the upper surface of the Z tilt stage22(wafer W).

With reference toFIG. 1, a multipoint autofocus sensor37, which is of the oblique incidence system, is provided on a side surface of the projection optical system PL. The autofocus sensor37is constructed in the same manner as that disclosed, for example, in U.S. Pat. No. 5,448,332, including a light-emitting system37aand a light-receiving system37bto measure the focus position at a plurality of points on the surface of the wafer W. The stage driving system4drives the Z tilt stage22in the autofocus manner so that the surface of the wafer W is coincident with the image plane of the projection optical system PL (image plane having been already determined by a test print, etc.) during the exposure based on the measurement result of the autofocus sensor37.

The two-dimensional position information of the wafer stage WST (Z tilt stage22), which includes at least the positions in the X direction and the Y direction and the angle of rotation in the θz direction, is measured, as an example, by a wafer side interferometer including two-axis laser interferometers36XP,36XF for the X axis and two-axis laser interferometers36YA,36YB for the Y axis. Obtained measured values are supplied to the stage driving system4and the main control system2. The position information is also supplied to an alignment control system6. The stage driving system4controls the two-dimensional position of the XY stage24of the wafer stage WST via an unillustrated driving mechanism (a linear motor, etc.) based on the position information and a control information from the main control system2.

The exposure apparatus EX is of the liquid immersion type which is provided with a local liquid immersion mechanism (not shown) wherein a liquid (pure or purified water, etc.), through which the illumination light IL is transmitted, is supplied to and recovered from a local space between the wafer W and an optical member disposed at an end portion of the projection optical system PL. A mechanism, which is disclosed, for example, in United States Patent Application Publication No. 2007/242247 or European Patent Application Publication No. 1420298, may be used as the local liquid immersion mechanism. The contents of United States Patent Application Publication No. 2007/242247 are incorporated herein by reference.

A wafer alignment system38of, for example, the image processing system, which is based on the off-axis system, is supported by an unillustrated frame on the side surface of the projection optical system PL in order to measure a position of an alignment mark on the wafer W. The detection result of the wafer alignment system38is supplied to the alignment control system6. The alignment can be performed for the wafer W in accordance with the detection result. Further, a reference member28is fixed in the vicinity of the wafer holder WH on the Z tilt stage22. Slit patterns30A,30B and a reference mark32are formed on the reference member28. A spatial image measuring system34, which receives a light flux passing through the slit patterns30A,30B, is accommodated in the bottom surface of the reference member28in the Z tilt stage22. The detection signal obtained by the spatial image measuring system34is supplied to the alignment control system6. The position of an image of an alignment mark (not shown) of the reticle R can be measured by the spatial image measuring system34. The alignment can be performed for the reticle R based on the measurement result. Further, the spatial image measuring system34is capable of measuring the position of an image of an evaluating pattern of a focus test reticle TR as described later on. The measurement result is supplied from the alignment control system6to the main control system2. Further, the positional relationship (baseline) between the center (exposure center) of the image of the pattern of the reticle R and the detection center of the wafer alignment system38can be measured via the reference mark32on the reference member28.

During the exposure, the liquid is supplied to the space between the projection optical system PL and the wafer W, and one shot area of the wafer W is exposed with the image of the pattern in the illumination area10R of the reticle R formed via the projection optical system PL and the liquid, while the reticle R and the wafer W are synchronously moved in the Y direction at a velocity ratio of the projection magnification. Accordingly, the above-described one shot area is subjected to the scanning exposure with the image of the pattern of the reticle R. After that, the operation in which the wafer W is step-moved in the X direction and the Y direction by driving the wafer stage WST and the scanning exposure operation are repeated. By doing so, the respective shot areas of the wafer W are exposed with the pattern image of the reticle R in the step-and-scan manner based on or using the liquid immersion method.

When the exposure is performed, if any portion, which is defocused while exceeding an allowable range from the image plane of the projection optical system PL, exists in each of the shot areas of the wafer W, then the imaging characteristic of the image with which the portion is exposed is deteriorated, and the yield is lowered, for example, for the semiconductor device to be finally produced. In view of the above, in this embodiment, in order to measure the focus information of the projection optical system PL which is the defocus amount (deviation amount of the Z position from the best focus position) at positions of a plurality of measuring points in a predetermined arrangement in the respective shot areas of the wafer (exposure field of the projection optical system PL) during the scanning exposure, a focus test reticle TR, which is formed with a plurality of evaluating patterns, is loaded on the reticle stage RST instead of the reticle R, and an evaluating wafer is exposed with an image of the pattern of the focus test reticle TR.

FIG. 2shows the pattern arrangement of the focus test reticle TR in a state that the focus test reticle TR is held on the reticle stage RST shown inFIG. 1. With reference toFIG. 2, measuring points P (i, j), which are disposed, as an example, in I rows in the X direction and J columns in the Y direction, are set in a rectangular pattern area PA provided on a pattern surface (lower surface) of the focus test reticle TR. I and J are integers of not less than 2, and i=1 to I and j=1 to J are given. An evaluating pattern12of the so-called bar-in-bar type, which is composed of an outer pattern14and an inner pattern13, is formed at each of the measuring points P (i, j). In this embodiment, the evaluating patterns12are arranged in 7 rows in the X direction and 9 columns in the Y direction (I=7, J=9). Further, alignment marks AM1, AM2are formed at positions which are close to the both sides in the X direction of the pattern area PA and which are included (within) in the width in the X direction of the illumination area10R.

FIG. 3Ashows one of the evaluating patterns12shown inFIG. 2. With reference toFIG. 3A, the outer pattern14(test pattern) of the evaluating pattern12has two line patterns, i.e., a line pattern14A (first light shielding portion) and a line pattern14B which have a same shape, which are formed with a predetermined spacing distance in the X direction (measuring direction), and each of which is formed of a rectangular light shielding film (chromium or the like) elongated in the Y direction. Further, the outer pattern14includes a phase shift portion15C (first phase shift portion) and a transmitting portion15D (second transmitting portion) which are arranged in order in the +X direction on a side of an edge portion in the +X direction of the line pattern14A as one of the line patterns, and a transmitting portion15B (first transmitting portion) and a phase shift portion15A (second phase shift portion) which are arranged in order in the −X direction on a side of an edge portion in the −X direction of the line pattern14A. The phase shift portion15C and the phase shift portion15A are formed so that the phase shift portions15C and15A have a same length in the longitudinal direction (Y direction). Note that it is also allowable to form the phase shift portion15C and the phase shift portion15A are formed so that the phase shift portions15C and15A have different lengths in the longitudinal direction. A line width a in the X direction of the line pattern14A is larger than a width b in the X direction of each of the phase shift portion15C and the transmitting portion15B which are in contact with the line pattern14A. For example, it is possible to make the line width a of the line pattern14A be not less than four times the width b of each of the phase shift portion15C and the transmitting portion15B as follows.
a≧4×b(1)

In the following description, the numerical values of the line width a and the width b are shown as numerical values obtained at the stage of the projected image. For example, in this case, it is preferable that the line width a is not less than 200 nm. As an example, the width b in the X direction of each of the phase shift portion15C and the transmitting portion15B is within a range to 50 to 200 nm. In this embodiment, it is preferable that the width b is within a range of 50 to 70 nm. In this range, the width b can be set, for example, to 60 nm. In this case, it is preferable that the line width a in the X direction of the line pattern14A is 2 to 3 μm. The length in the Y direction of each of the line pattern14A, the transmitting portion15B, and the phase shift portion15C is, as an example, 10 to 15 times the line width a of the line pattern14A. The spacing distance in the X direction between the line patterns14A,14B is set to be longer than the length of the line pattern14A.

The width a in the X direction of each of the phase shift portion15A and the transmitting portion15D is the same as the line width of the line pattern14A. However, it is sufficient or allowable that the width in the X direction of each of the phase shift portion15A and the transmitting portion15D is set to be wider than the width b of each of the transmitting portion15B and the phase shift portion15C which are in contact therewith. In other words, it is allowable that the width in the X direction of each of the transmitting portion15B and the phase shift portion15C is set to be narrower than the width b of each of the phase shift portion15A and the transmitting portion15D which are in contact therewith. As shown inFIG. 3Bwhich is a sectional view taken along a line BB shown inFIG. 3A, the transmitting portions15B,15B are portions of a surface (light-exiting surface) of a glass substrate of the focus test reticle TR; and the phase shift portions15A,15C are recesses each having a depth d formed, for example, by performing etching on the surface. Namely, the phase shift portions15A,15C are formed to be lower than the transmitting portions15B and15D with respect to the light-exiting surface. The line patterns14A,14B are formed to be higher than the transmitting portions15B,15D with respect to the light-exiting surface. In this case, the depth d is set so that a phase θAC of the illumination light IL transmitted through the phase shift portions15A,15C proceeds, for example, by 90° with respect to a phase θBD of the illumination light IL transmitted through the transmitting portions15B,15D. That is, it is preferable that a phase difference δθ between the phase θBD and the phase θAC is 90°. In a case that the range of the phase difference δθ is represented by 0°≦δθ<360°, it is preferable that the phase difference δθ has an arbitrary value other than 0° and 180°, for example, the phase difference δθ has an arbitrary value other than those of 0° to 30°, 150° to 210°, and 330° to 360°. The reason, why the phase difference δθ is made to have any value other than 180°, for example, the phase difference δθ is made to have any value other than those in the vicinity of 180° as described above, is, for example, that the boundary line between the phase shift portion15A and the transmitting portion15B is transferred as a dark line if the phase difference δθ is allowed to have the value of 180° or any value in the vicinity of 180°. Further, the reason, why the phase difference δθ is made to have any value other than those in the vicinity of 0° and 360°, is that the sensitivity is low in relation to the change of the spacing distance between the patterns13and14with respect to the defocus.

With reference toFIG. 3A, a phase shift portion15K, a transmitting portion15L, a phase shift portion15M, and a transmitting portion15N, which are constructed approximately in the same manner as the phase shift portion15A, the transmitting portion15B, the phase shift portion15C, and the transmitting portion15D provided on the both sides of the line pattern14A, are also provided on the both sides of the line pattern14B on the +X direction side of the outer pattern14. However, the phase shift portion15K has such a shape (L-letter shape in this embodiment) in which a portion having a width a in the X direction and a portion having a width a in the Y direction are connected to each other; and the transmitting portion15N is such a transmitting portion that the width in the X direction is not less than a.

Further, the outer pattern14has phase shift portions16A,15K, transmitting portions16B,16L, line patterns14C,14D, phase shift portions16C,16M, and transmitting portions16D,16N which are arranged in the Y direction and which are constructed such that the phase shift portions15A,15K, the transmitting portions15B,15L, the line patterns14A,14B, the phase shift portions15C,15M, and the transmitting portions15D,15N arranged in the X direction are integrally rotated by 90° with the center of the evaluating pattern12as the center of rotation.

The inner pattern13(auxiliary pattern) of the evaluating pattern12has two line patterns, i.e., a line pattern13A (second light shielding portion) and a line pattern13B which are arranged symmetrically between the two line patterns14A,14B of the outer pattern14and each of which is composed of a light shielding film having a short length in the Y direction with the same line width a in the X direction as that of each of the line patterns14A,14B. The inner pattern13further includes a transmitting portion15F (third transmitting portion) having a width b and a right-angled triangle-shaped phase shift portion15G (fourth phase shift portion) which are arranged in order in the +X direction on a side of an edge portion in the direction of the line pattern13A as one of the line patterns, and a phase shift portion15E (third phase shift portion) having a width b and a transmitting portion15D (fourth transmitting portion) having a width a which are arranged in order in the −X direction on a side of an edge portion in the −X direction of the line pattern13A. The average width in the X direction of the phase shift portion15G is wider than the width a. The transmitting portion15D (second transmitting portion and fourth transmitting portion) is commonly used for the inner pattern13and the outer pattern14. The condition of the width a and the width b is the same as that for the outer pattern14. The phase difference between the phase of the illumination light IL transmitted through the transmitting portions15D,15F and the phase of the illumination light IL transmitted through the phase shift portions15E,15G can have an arbitrary value other than 0° and 180° in the same manner as the phase difference δθ described above. However, the angle is more preferably 90°.

A transmitting portion15H, a phase shift portion15I, a transmitting portion15J, and a phase shift portion15K, which are constructed approximately in the same manner as the transmitting portion15D, the phase shift portion15E, the transmitting portion15F, and the phase shift portion15G provided on the both sides of the line pattern13A, are also provided on the both sides of the line pattern13B on the +X direction side of the inner pattern13. However, the transmitting portion15H is a right-angled triangle-shaped area, and the phase shift portion15K (fourth phase shift portion) is commonly used for the phase shift portion (second phase shift portion) of the line pattern14B.

Further, the inner pattern13has transmitting portions16D,15H, phase shift portions16E,16I, line patterns13C,13D, transmitting portions16F,16J, and phase shift portions15G,16I, which are arranged in the Y direction and which are constructed such that the transmitting portions15D,15H, the phase shift portions15E,15I, the line patterns13A,13B, the transmitting portions15F,15J, and the phase shift portions15G,15K are integrally rotated by 90° with the center of the evaluating pattern12as the center of rotation. A first pattern group is constructed to include the line patterns14A,13A, a second pattern group is constructed to include the line patterns14B,13B, a third pattern group is constructed to include the line patterns14C,13C, and a fourth pattern group is constructed to include the line patterns14D,13D.

That is, in the second pattern group, the transmitting portion15H and the phase shift portion15I, the line pattern138, the transmitting portion15J, the phase shift portion15K, the transmitting portion15L, the line pattern14B, the phase shift portion15M, and the transmitting portion15N extending in the Y direction respectively are arranged in the X direction. In the third pattern group, the phase shift portion16A, the transmitting portion16B, the line pattern14C, the phase shift portion16C, the transmitting portion16D, the phase shift portion16E, the line pattern13C, and the transmitting portion16F extending in the line form in the X direction respectively and the phase shift portion15G are arranged in the Y direction. In the fourth pattern group, the transmitting portion15H and the phase shift portion16I, the line pattern13D, the transmitting portion16J, the phase shift portion15K, the transmitting portion16L, the line pattern14D, the phase shift portion16M, and the transmitting portion16N extending in the X direction respectively are arranged in the Y direction.

Next, an explanation will be made with reference toFIGS. 4A and 4Babout the relationship between the defocus amount and the lateral deviation amount in relation to the image of the line pattern13A of the inner pattern13of the evaluating pattern12and the image of the line pattern14A of the outer pattern14of the evaluating pattern12. For the purpose of convenience of the explanation, it is assumed that the projection optical system PL forms an inverted image in the X direction.

As shown inFIG. 4Awhile being enlarged, a wavefront17A of the illumination light IL, which is transmitted through the transmitting portion15D and the phase shift portion15E disposed on the −X direction side of the line pattern13A, is inclined substantially clockwise in a ZX plane with respect to an incident light coming into the focus test reticle TR in the Z direction. Similarly, a wavefront17B of the illumination light IL, which is transmitted through the transmitting portion15F and the phase shift portion15G on the +X direction side of the line pattern13A, is also inclined clockwise in the ZX plane with respect to the incident light coming into the focus test reticle TR in the Z direction. Therefore, central light beams (central lights; hereinafter conveniently referred to as “main light beams (main lights”)17C,17D of the light fluxes passing through the both end portions of the line pattern13A are inclined clockwise with respect to the optical axis AX substantially in parallel. Therefore, main light beams17CP,17DP passing through both end portions in the X direction of an image13AP of the line pattern13A formed by the projection optical system PL are inclined counterclockwise with respect to the optical axis AX. Therefore, if the surface of the wafer W, which is arranged on the side of the image plane (image plane side) of the projection optical system PL, is defocused by FZ in the +Z direction with respect to the best focus position, the position of the image13AP is shifted by ΔX in the −X direction.

On the other hand, as shown inFIG. 4Bwhile being enlarged, wavefronts18A,18B of the illumination light IL, which are transmitted through the phase shift portion15A and the transmitting portion15B and the phase shift portion15C and the transmitting portion15D arranged on the both sides in the X direction of the line pattern14A, are inclined substantially counterclockwise. Therefore, main light beams18C,18D passing through the both end portions of the line pattern14A are inclined counterclockwise with respect to the optical axis AX substantially in parallel. Therefore, main light beams18CP,18DP passing through both end portions in the X direction of an image14AP of the line pattern14A formed by the projection optical system PL are inclined clockwise with respect to the optical axis AX. Therefore, if the surface of the wafer W is defocused by FZ in the +Z direction with respect to the best focus position on the image plane side of the projection optical system PL, the position of the image14AP is shifted by AX in the +X direction.

Therefore, if the surface of the wafer W is defocused on the image plane side of the projection optical system PL, the image of the line pattern14A arranged in the X direction of the outer pattern14shown inFIG. 3Aand the image of the line pattern13A of the inner pattern13are shifted in the opposite direction in relation to the X direction, and the image of the line pattern14B of the outer pattern14and the image of the line pattern13B of the inner pattern13are shifted in the opposite direction in relation to the X direction. Similarly, with respect to the defocus, the image of the line pattern14C arranged in the Y direction of the outer pattern14and the image of the line pattern13C of the inner pattern13are shifted in the opposite direction in relation to the Y direction, and the image of the line pattern14D of the outer pattern14and the image of the line pattern13D of the inner pattern13are shifted in the opposite direction in relation to the Y direction.

As a result, when the image of the evaluating pattern12formed by the projection optical system PL is projected onto the surface of the wafer and if the surface of the wafer is disposed at the best focus position (image plane), then a center14Q of an image14P of the outer pattern14of the evaluating pattern12(images14AP to14DP of the line patterns14A to14D) is disposed at the same position as that of a center13Q of an image13P of the inner pattern13(images13AP to13DP of the line patterns13A to13D) as shown inFIG. 5A. For the purpose of convenience of the explanation, it is assumed that an image formed by the projection optical system PL is an erecting image in the X direction and the Y direction, for example, inFIGS. 5A to 5CandFIGS. 6B and 6Cdescribed later on.

On the other hand, if the surface of the wafer is defocused in the +Z direction, the center13Q of the image13P of the inner pattern13is shifted by DX in the −X direction and DY in the −Y direction with respect to the center14Q of the image14P of the outer pattern14as shown inFIG. 5B. Further, if the surface of the wafer is defocused in the −Z direction, the center13Q of the image13P of the inner pattern13is shifted by DX in the +X direction and DY in the +Y direction with respect to the center14Q of the image14P of the outer pattern14as shown inFIG. 5C. Therefore, it is appropriate that a following detection rate Rt, which is the ratio between the shift amounts (amounts of change of spacing distance) DX, DY in the X direction and the Y direction of the center13Q of the image13P with respect to the center14Q of the image14P in relation to the defocus amount FZ of the surface of the wafer, is previously determined, for example, by actual measurement or simulation.
Rt=DX/FZ(2A)
or
Rt=DY/FZ(2B)

The average value of the expressions (2A) and (2B) may be the detection rate Rt as follows.
Rt={(DX+DY)/2}/FZ(3)

It is also allowable that the detection rate Rt is not a constant. The detection rate Rt may be a 1st order, 2nd order or higher order function of the defocus amount FZ, or the detection rate Rt may be a function such as an exponential function or the like. If the expression (3) is used, it is possible to determine the defocus amount FZ at the measuring point at which the image is projected as well as the best focus position by projecting the image of the evaluating pattern12, measuring the shift amounts DX, DY of the image13P with respect to the image14P, and dividing the average value of the shift amounts by the detection rate Rt.

Next,FIG. 7Ashows result of a simulation of the relationship between the line width a (nm) of each of the line patterns13A to13D,14A to14D of the evaluating pattern12shown inFIG. 3Aand the detection rate Rt and a predicted maximum measurement error ZEr (nm) of the defocus amount. The condition of the simulation is as follows. That is, the numerical aperture NA of the projection optical system PL is 1, the coherence factor (σ value) of the illumination optical system ILS (illumination light IL) is 0.2, and the width b of, for example, each of the phase shift portions15C,15E is 60 nm. The measurement error ZEr is the sum of the error of the defocus amount resulting from the measurement error of the position of the image of the evaluating pattern12and the approximation error (nonlinear error) in relation to the expression (3).

With reference toFIG. 7A, a white bar graph B1, which is disposed at the position of each of the line widths a, represents the detection rate Rt when the defocus amount FZ is ±100 nm. A hatched bar graph B2represents the detection rate Rt when the defocus amount FZ is ±200 nm. A polygonal line C1of dotted line represents the measurement error ZEr when the defocus amount FZ is ±100 nm. A polygonal line C2of solid line represents the measurement error ZEr when the defocus amount FZ is ±200 nm. According toFIG. 7A, the values of the detection rate Rt (bar graphs B1, B2) and the measurement error ZEr (polygonal lines C1, C2) are constant when the line width a is not less than 600 nm. Therefore, it is possible to measure the focus information of the projection optical system FL highly accurately.

Further,FIG. 7Bshows an example of the result obtained when the measurement error ZEr of the defocus amount is evaluated while variously changing the numerical aperture NA of the projection optical system FL and the coherence factor (σ value) of the illumination light IL. In this case, the line width a of each of the line patterns13A to13D, etc. is 1000 nm, the width b of the phase shift portion15C, etc. is 60 nm, the measurement error of the image position of the evaluating pattern12is 0.5 nm, and the defocus amount FZ is ±100 nm. InFIG. 7B, the measurement error ZEr of an area D1surrounded by a curved line is 1 to 1.5 nm, the measurement error ZEr of an area D2is 1.5 to 2 nm, and the measurement errors ZEr of areas D3, D4, D5, . . . are respectively 2 to 2.5 nm, 2.5 to 3 nm, and 3 to 3.5 nm which are increased by 0.5 nm. According toFIG. 7B, it is appreciated that the measurement error ZEr is approximately not more than 2 nm in the areas D1and D2, wherein it is possible to measure the defocus amount highly accurately. The range of combination of the numerical aperture NA and the a value is considerably wide in the areas D1, D2. Therefore, it is appreciated that the defocus amount can be measured highly accurately even under various illumination conditions and numerical aperture conditions even in a case that the numerical aperture NA is large such that the numerical aperture arrives at 1.3.

Next, an explanation will be made with reference to a flow chart shown inFIG. 8about an example of the operation to measure the focus information of the projection optical system PL in the exposure apparatus EX of the embodiment. This operation is periodically executed, for example, during the exposure step under the control of the main control system2.

At first, in Step102shown inFIG. 8, the focus test reticle TR is loaded on the reticle stage RST shown inFIG. 1to perform the alignment therefor. Subsequently, in Step104, an unexposed evaluating wafer (referred to as “wafer W”), which is coated with the photoresist, is loaded on the wafer stage WST. Subsequently, in Step106, as shown inFIG. 6A, a large number of shot areas SAk (k=1 to K; K is an integer of not less than 2) of the wafer W is exposed with the image, formed by the projection optical system PL, of the large number of evaluating patterns12of the focus test reticle TR shown inFIG. 2in accordance with the scanning exposure method based on the liquid immersion method. During this process, whether the scanning direction with respect to the exposure area is a +Y direction DP or a −Y direction DM is stored for each of the shot areas SAk. As shown inFIG. 6Bwhile being enlarged, portions, which are disposed in the vicinity of respective measuring points Q (i, j) (i=1 to I; j=1 to J) arranged in the X direction and the Y direction in the respective shot areas SAk, are exposed with the image12P of the evaluating pattern12respectively. The image12P is composed of the image14P of the outer pattern14and the image13P of the inner pattern13as shown inFIG. 5A.

Subsequently, in Step108, the exposed wafer W is unloaded from the wafer stage WST, and the wafer W is developed by an unillustrated coater/developer. As a result, the image13P of the inner pattern13and the image14P of the outer pattern14, which constitute the image12P of the evaluating pattern12, are formed as resist patterns composed of protrusions and recesses as shown in an enlarged view ofFIG. 6Cin the vicinity of each of the measuring points Q (i, j) in one of the shot areas SAk of the wafer W shown inFIG. 6B.

Subsequently, in Step110, the wafer W after the development is transported to an overlay measuring apparatus (not shown) to measure shift amount (ΔXij, ΔYij) in the X direction and the Y direction (positional relationship between the images) of the center13Q of the image13P of the inner pattern13with respect to the center14Q of the image14P of the outer pattern14in relation to the image12P (FIG. 6C) of the evaluating pattern12at each of the measuring points Q (i, j) of one of the shot areas SAk (k=1 to K) of the wafer W by using the overlay measuring apparatus. The measurement results of the shift amounts are supplied to the main control system2shown inFIG. 1.

Subsequently, in Step112, the calculating section included in the main control system2divides the average value of the measured shift amounts (ΔXij, ΔYij) of the image12P of the evaluating pattern12by the known detection rate Rt of the expression (3) to determine a defocus amount FZij at the concerning measuring point Q (i, j). Further, in Step114, the calculating section included in the main control system2classifies the shot areas SAk of the wafer W into a first group and a second group distinctly based on the scanning directions DP, DM with respect to the exposure area so that a value, which is obtained by interpolating the average value <FZij> of the defocus amounts FZij at the respective measuring points Q (i, j) in the shot areas SAk of the first group, is stored as the correction value for the entire image plane in the exposure field in the scanning direction DP. Similarly, a value, which is obtained by interpolating the average value <FZij> of the defocus amounts FZij at the respective measuring points Q (i, j) in the shot areas SAk of the second group, is stored as the correction value for the entire image plane in the exposure field in the scanning direction DM.

After that, in Step116, a reticle R for the device is loaded on the reticle stage RST shown inFIG. 1. In Step118, a wafer coated with the photoresist is loaded on the wafer stage WST. In Step120, each of the shot areas of the wafer is subjected to the scanning exposure with the image of the pattern of the reticle R, while correcting the S position measured by the autofocus sensor37by using the correction values for the image plane provided distinctly in relation to the scanning directions stored in Step114for the wafer. During this process, the measured value of the autofocus sensor37is corrected so that the measured defocus amount is corrected based on the image of each of the evaluating patterns12of the focus test reticle TR. Therefore, the focusing accuracy is improved for the surface of the wafer with respect to the image plane of the projection optical system PL. Therefore, the respective shot areas of the wafer are exposed with the image of the pattern of the reticle R highly accurately.

After that, the exposed wafer is unloaded in Step122. In Step124, it is judged whether or not the next exposure objective wafer is present. If any unexposed wafer is present, Steps118to122are repeated. If any unexposed wafer is absent in Step124, the exposure step comes to an end.

The effects, etc. of the embodiment are as follows.

(1) The exposure apparatus EX of the embodiment is provided with the focus test reticle TR for measuring the focus information of the projection optical system PL. The evaluating pattern12, which is formed on the focus test reticle TR, has the outer pattern14(test pattern). The outer pattern14is provided by arranging, in the X direction, the phase shift portion15A (second phase shift portion) having the width a in the X direction (second direction), the transmitting portion15B (first transmitting portion) having the width b narrower than the width a, the line pattern14A (first light shielding portion) having the line width a, the phase shift portion15C (first phase shift portion) having the width b, and the transmitting portion15D (second transmitting portion) having the width a which extend in the line form in the Y direction (first direction) respectively.

According to the focus test reticle TR, the main light beam of the illumination light IL passing through the phase shift portion15C and the transmitting portion15D disposed on the +X direction side of the line pattern14A and the main light beam of the illumination light IL passing through the phase shift portion15A and the transmitting portion15B disposed on the −X direction side of the line pattern14A are inclined in the same direction. Therefore, it is possible to determine, at the high measuring efficiency, the defocus amount of the formation surface of the image plane with respect to the image plane of the projection optical system PL, as well as the focus information, from the lateral deviation amount in the X direction of the image of the line pattern14A by merely performing the exposure with the image of the evaluating pattern12once. Further, since the line width a of the line pattern14A is wider than the widths b of the phase shift portion15C and the transmitting portion15B, it is possible to measure the focus information at the high measuring reproducibility.

(2) In this embodiment, the width b in the X direction of the transmitting portion15B is same as the width b in the X direction of the phase shift portion15C; and the lateral deviation amount is approximately same in relation to the both end portions of the image of the line pattern14A with respect to the defocus, and the line width of the image is approximately constant.

It is also allowable that the width in the X direction of the transmitting portion15B and the width in the X direction of the phase shift portion15C are different from each other.

It is not necessarily indispensable to provide the transmitting portion15D (second transmitting portion).

(3) The evaluating pattern12has the inner pattern13(auxiliary pattern) for measuring the positional deviation of the image of the outer pattern14. Therefore, it is possible to highly accurately measure the positional deviation amount of the image of the outer pattern14as well as the defocus amount.

It is also possible that the inner pattern13is regarded as the test pattern and the outer pattern14is regarded as the auxiliary pattern.

(4) The inner pattern13is provided by arranging, in the X direction, the transmitting portion15D (fourth transmitting portion) having the width a in the X direction, the phase shift portion15E (third phase shift portion) having the width b, the line pattern13A (second light shielding portion) having the line width a, and the transmitting portion15F (third transmitting portion) having the width b which extend in the line form in the Y direction respectively, and the phase shift portion15G (fourth phase shift portion) which has the average width of not less than the width a.

The phase distribution, which is provided on the both sides in the X direction of the line pattern13A of the inner pattern13, is symmetrical with the phase distribution which is provided on the both sides in the X direction of the line pattern14A of the outer pattern14. Therefore, the direction of the lateral deviation amount of the image of the line pattern13A, which is provided when the defocus is caused, is opposite to the direction of the lateral deviation amount of the image of the line pattern14A in relation to the X direction. Therefore, the defocus amount can be measured highly accurately with the two-fold sensitivity while compensating or counterbalancing the offset.

(5) The method for measuring the focus information of the projection optical system PL of the embodiment includes Step102of arranging the focus test reticle TR of this embodiment on the object plane of the projection optical system PL; Steps106,108of projecting the image, formed by the projection optical system PL, of the evaluating pattern12(outer pattern14and inner pattern13) of the focus test reticle TR onto the surface (measuring surface) of the wafer W; and Step110of measuring the spacing distance between the image of the outer pattern14and the image of the inner pattern13as the position information in the measuring direction of the image of the evaluating pattern12. Therefore, it is possible to measure the defocus amount with respect to the image plane of the projection optical system PL from the spacing distance (shift amount) between the images.

(6) The step of projecting the image includes Step108of developing the photoresist of the wafer W. Therefore, the spacing distance between the images can be measured highly accurately by using, for example, the overlay measuring apparatus.

(7) The exposure apparatus EX of the embodiment is the exposure apparatus which illuminates the pattern of the reticle R with the illumination light IL and exposes the wafer W (substrate) via the pattern and the projection optical system FL with the illumination light IL, the exposure apparatus including the reticle stage RST which holds the focus test reticle TR, and the main control system2(controller) which causes the projection optical system FL to project the image of the evaluating pattern12of the focus test reticle TR and which determines the correction value (image plane information) of the image plane of the projection optical system FL based on the position information in the measuring direction of the image of the evaluating pattern12.

Therefore, the focus information of the projection optical system PL can be measured efficiently and highly accurately merely by exchanging the reticle on the reticle stage RST with the focus test reticle TR and exposing the evaluating wafer with the image of the evaluating pattern12of the focus test reticle TR.

This embodiment is illustrative of the construction in which the outer pattern14is provided with the transmitting portions15D,16D. However, such a construction is also allowable that the inner pattern13is provided with the transmitting portions15D,16D. Similarly, this embodiment is illustrative of the construction in which the outer pattern14is provided with the phase shift portion15K. However, such a construction is also allowable that the inner pattern13is provided with the phase shift portion15K.

The following modifications are available in the embodiment.

(1) In this embodiment, the wafer is exposed with the image of the evaluating pattern12of the focus test reticle TR, and the positional relationship of the resist pattern formed after the development is measured by using the overlay measuring apparatus.

However, the exposure apparatus EX is provided with the spatial image measuring system34. Accordingly, it is also allowable that the image (spatial image) of the evaluating pattern12formed by the projection optical system PL is scanned in the X direction and the Y direction with the slit pattern30A of the spatial image measuring system34shown inFIG. 1, and the light intensity distribution of the spatial image is measured by the spatial image measuring system34. The spacing distance between the image of the outer pattern14and the image of the inner pattern13of the evaluating pattern12is determined from the measurement result, and the defocus amount is determined from the spacing distance. By doing so, it is possible to determine the focus information of the projection optical system PL.

(2) In this embodiment, the focus test reticle TR is exchanged with the reticle R, and the focus test reticle TR is loaded on the reticle stage RST. However, the plurality of evaluating patterns12, which are formed on the focus test reticle TR, may be formed on a reticle mark plate (not shown) which is fixed to an area disposed closely to the area of the reticle stage RST in which the reticle R is held. In this case, as necessary, by moving the reticle stage RST so as to move the reticle mark plate to the illumination area of the illumination light IL, it is possible to measure the focus information of the projection optical system PL.

(3) An evaluating pattern40of a first modification shown inFIG. 9Aor an evaluating pattern44of a second modification shown inFIG. 9Bmay be used in place of the evaluating pattern12shown inFIG. 3A.

With reference toFIG. 9A, the evaluating pattern40has a cross-shaped light shielding pattern41wherein a light shielding film which is elongated in the Y direction and which has a line width a in the X direction and a light shielding film which is elongated in the X direction and which has a line width a in the Y direction are made to intersect at the center. A transmitting portion42C having a width b and a square phase shift portion42D are provided in order on the +X direction side of a line portion41A (first light shielding portion of the test pattern) disposed in the +Y direction with respect to the center of the light shielding pattern41. A phase shift portion42B having the width b and a transmitting portion42A are provided in order on the −X direction side of the line portion41A. Further, a phase shift portion43C having the width b and a transmitting portion43D are provided in order on the +X direction side of a line portion41B (second light shielding portion of the auxiliary pattern) disposed in the −Y direction with respect to the center of the light shielding pattern41. A transmitting portion43B having the width b and a square phase shift portion43A are provided in order on the −X direction side of the line portion41B.

Further, a transmitting portion42C having the width b and a phase shift portion42D are provided in order on the +Y direction side of a line portion41C disposed in the +X direction with respect to the center of the light shielding pattern41. A phase shift portion43C having the width b and a transmitting portion43D are provided in order on the −Y direction side of the line portion41C. Further, a phase shift portion42B having the width b and a transmitting portion42A are provided in order on the +Y direction side of a line portion41D disposed in the −X direction with respect to the center of the light shielding pattern41. A transmitting portion43B having the width b and a phase shift portion43A are provided in order on the −Y direction side of the line portion41D. The relationship between the line width a and the width b is the same as or equivalent to that of the evaluating pattern12shown inFIG. 3A. The amounts of change of the phases of the phase shift portions42B,42D,43A,43C are the same as or equivalent to that of the phase shift portion15C shown inFIG. 3A.

An image40P of the evaluating pattern40of the first modification, which is formed by the projection optical system PL, is an image41P which is similar to the light shielding pattern41as shown inFIG. 10Aat the best focus position. On the other side, in a case that the measuring surface is defocused, as shown inFIG. 10B, the image40P of the evaluating pattern40is formed such that a shift amount DX in the X direction is generated between an image41AP of the line portion41A and an image41BP of the line portion41B, and that a shift amount DY in the Y direction is generated between an image41DP of the line portion41D and an image41CP of the line portion41C. Therefore, it is possible to determine the defocus amount on the measuring surface from the shift amounts DX, DY.

On the other hand, the evaluating pattern44of the second modification shown inFIG. 9Bhas an outer pattern46which is composed of a square frame-shaped light shielding film having the same line width as that of the line portion41A (seeFIG. 9A), and a square inner pattern45which is composed of a light shielding film formed at the inside of the outer pattern46. Further, a transmitting portion47D, which has the same width as that of the phase shift portion42B (seeFIG. 9A), is provided in the +X direction and the +Y direction of the inner pattern45(first light shielding portion); and a phase shift portion47E, which has a wide width, is provided at the outside of the transmitting portion47D. A transmitting portion47F, which has the same width as that of the transmitting portion47D, is provided between the phase shift portion47E and inner edge portions in the +X direction and the +Y direction of the outer pattern46. Further, a phase shift portion47C, which has the same width as that of the transmitting portion47D, is provided in the −X direction and the −Y direction of the inner pattern45; and a transmitting portion47B is provided at the outside of the phase shift portion47C. A phase shift portion47A, which has the same width as that of the phase shift portion47C, is provided between the transmitting portion47B and inner edge portions in the −X direction and the −Y direction of the outer pattern46.

The image44P of the evaluating pattern44of the second modification, which is formed by the projection optical system PL, is provided such that a center46PC of the inner edge portions of the image of the outer pattern46is coincident with a center45PC of the image45P of the inner pattern45as shown inFIG. 10Cat the best focus position. On the other hand, in a case that the measuring surface is defocused, as shown inFIG. 10D, the shift amounts DX, DY are generated in the X direction and the Y direction between the center46C of the inner edge portions of the image46P of the outer pattern46and the center45PC of the image45P of the inner pattern45in the image of the evaluating pattern44. Therefore, it is possible to determine the defocus amount on the measuring surface from the shift amounts DX, DY.

Second Embodiment

Next, a second embodiment will be explained with reference toFIGS. 11A and 11B. Also in this embodiment, the focus information of the projection optical system PL of the exposure apparatus EX shown inFIG. 1is measured. However, an evaluating pattern, which is formed on a focus test reticle TR, is differently constructed.

FIG. 11Ashows an enlarged plan view illustrating an evaluating pattern50of this embodiment. With reference toFIG. 11A, the evaluating pattern50is constructed by arranging, in the X direction, a first dummy pattern53A, a first main pattern51A, a subsidiary pattern52, a second main pattern51B, and a second dummy pattern53B. In this case, each of the dummy patterns53A,53B has two line patterns58A,58B each of which is composed of a light shielding film elongated in the Y direction and which are arranged in the X direction.

The first main pattern51A (test pattern) has line patterns54A,54B,54C each of which is composed of a light shielding film having a line width c in the X direction extending in the Y direction and which are arranged in the X direction at spacing distances d that are about three times the line width c, wherein substantially identical phase change portions are provided at the both end portions in the X direction of each of the line patterns54A to54C. Representatively, the phase change portion, which is provided for the line pattern54A (first light shielding portion), has a transmitting portion55C (first transmitting portion) having a width b and a phase shift portion55D (second phase shift portion) approximately having a width c which are arranged in order in the +X direction of the line pattern54A, and a phase shift portion55B (first phase shift portion) having the width b and a transmitting portion55A (second transmitting portion) having a width wider than the width b which are arranged in order in the −X direction of the line pattern54A. The second main pattern51B has line patterns54A to54C and phase change portion provided for each of the line patterns54A to54C in the same manner as the first main pattern51A. A phase shift portion55G, which is disposed at the end portion in the +X direction, is formed to have a narrow width.

The subsidiary pattern52(auxiliary pattern) has line patterns56A,56B,56C which have the same shapes as those of the line patterns54A to54C and which are arranged in the same manner as the line patterns54A to54C, and substantially identical phase change portions which are provided at the both end portions in the X direction of the line patterns56A to56C. Representatively, the phase change portion, which is provided for the line pattern56A (second light shielding portion), has a phase shift portion57B (third phase shift portion) having the width b and a transmitting portion57C (fourth transmitting portion) approximately having the width c which are arranged in order in the +X direction of the line pattern56A, and a transmitting portion57A (third transmitting portion) having the width b and a phase shift portion55F (fourth phase shift portion) having a width wider than the width b which are arranged in order in the −X direction of the line pattern56A. The phase shift portion55F is commonly used for the main pattern51A and the subsidiary pattern52.

In this embodiment, the line width c in the X direction of each of the line patterns54A to54C,56A to56C is set to be wider than the width b in the X direction of each of the transmitting portion55C and the phase shift portion55B. As an example, the line width c is 80 to 200 nm, and the width b is 50 to 70 nm at the stage of the projected image. Further, as an example, the line width c is 100 nm, and the width b is 60 nm in this case. Further, the phase difference between the phase of the illumination light passing through the phase shift portions55B,57B and the phase of the illumination light passing through the transmitting portions55A,57C, etc. is set to any value other than 0° and 180°. The phase difference is preferably 90°.

In an image50P (assumed as an erecting image) of the evaluating pattern50formed by the projection optical system PL, as shown inFIG. 11B, an image51AP of the first main pattern51A, an image52P of the subsidiary pattern52, and an image51BP of the second main pattern51B are arranged between images53AP,53BP of the dummy patterns (images58AP,58BP of the line patterns58A,58B). The images51AP,51BP are composed of the images54AP to54CP of the line patterns54A to54C respectively. The image52P is composed of the images56AP to56CP of the line patterns56A to56C. In this case, the phase distribution provided at the both end portions in the X direction of the line patterns54A to54C and the phase distribution provided at the both end portions in the X direction of the line patterns56A to56C are symmetrical with each other in the X direction. Therefore, if the images51AP,51BP of the main patterns are moved in the −X direction as depicted by images El of dotted lines with respect to the defocus of the measuring surface, the image52P of the subsidiary pattern is moved in the +X direction (opposite direction) as depicted by an image E2of dotted lines.

Therefore, the defocus amount of the measuring surface can be determined by measuring, as an example, the shift amount DX between the central position (average position of the respective centers) in the X direction of the images54AP to54CP of the six line patterns of the images51AP,51BP of the main patterns and the central position in the X direction of the images56AP to56CP of the three line patterns of the image52P of the subsidiary pattern. Further, in this embodiment, the positions of the images of the dummy patterns53A,53B are usable, for example, when the positional deviation amounts of the images of the main patterns51A,51B and the positional deviation amount of the image of the subsidiary pattern52are individually evaluated.

In this embodiment, the numbers of the line patterns54A to54C constructing the main patterns51A,51B and the number of the line patterns56A to56C constructing the subsidiary pattern52may be at least one. It is not necessarily indispensable to provide the dummy patterns53A,53B. It is also possible to omit, for example, the second main pattern51B.

Next,FIG. 12Ashows an evaluating pattern60of a modification of the second embodiment. With reference toFIG. 12Ain which the same reference numerals are affixed to the portions corresponding to those shown inFIG. 11A, the evaluating pattern60has dummy patterns53A,53B which are arranged at the both end portions in the X direction. Line patterns54A,56A,54B,56B,54C,56C,54D,56D, which have identical shapes, are arranged in the X direction between the dummy patterns53A,53B at spacing distances which are approximately two times to three times the line width.

A transmitting portion55C (first transmitting portion) and a phase shift portion61A (second phase shift portion) having a wide width are arranged on the +X direction side of the line patterns54A to54D (first light shielding portion), and a phase shift portion55B (first phase shift portion) and a transmitting portion61B (second transmitting portion) having a wide width are arranged on the −X direction side of the line patterns54A to54D. A phase shift portion57B (third phase shift portion) and a transmitting portion61B (fourth transmitting portion) having a wide width are arranged on the +X direction side of the line patterns56A to56D (second light shielding portion), and a transmitting portion57A (third transmitting portion) and the phase shift portion61A (fourth phase shift portion) are arranged on the −X direction side of the line patterns56A to56D. The phase shift portion61A is commonly used for the test pattern including the line patterns54A to54D and the auxiliary pattern including the line patterns56A to56D.

In an image60P (assumed as an erecting image) of the evaluating pattern60formed by the projection optical system PL, as shown inFIG. 12B, images54AP to54DP of the line patterns54A to54D and images56AP to56DP of the line patterns56A to56D are alternately formed in the X direction between the images53AP,53BP of the dummy patterns. In this case, the phase distribution at the both end portions in the X direction of the line patterns54A to54D and the phase distribution at the both end portions in the X direction of the line patterns56A to56D are symmetrical with each other. Therefore, if the images54AP to54DP are moved in the −X direction as depicted by images El of dotted lines with respect to the defocus of the measuring surface, the images56AP to56DP are moved in the +X direction (opposite direction) as depicted by images E2of dotted lines.

Therefore, the defocus amount of the measuring surface can be determined by measuring, as an example, the shift amount DX between the central position (average position of the respective centers) in the X direction of the images54AP to54DP of the four line patterns and the central position in the X direction of the images56AP to56DP of the four line patterns.

In this embodiment, the numbers of the line patterns54A to54D and56A to56D may be at least one respectively. It is not necessarily indispensable to provide the dummy patterns53A,53B.

Although the foregoing explanation has been made as exemplified by the local liquid immersion exposure apparatus provided with a local liquid immersion mechanism, it is possible to apply the present invention also to an exposure apparatus of such a liquid immersion type that immerses an object entirely in the liquid, in addition to a local liquid immersion exposure apparatus in which the liquid is intervened only in a local liquid immersion space between the projection optical system and an object (a part of the object). Further, it is also possible to apply the present invention to an exposure apparatus of such a liquid immersion type that maintains the liquid immersion area between the projection optical system and the substrate with an air curtain around the liquid immersion area. The present invention is applicable to not only a case of performing the exposure by using the exposure apparatus of the liquid immersion type but also a case for measuring the focus information for a projection optical system of an exposure apparatus of the dry exposure type which does not allow any liquid to intervene. The present invention is also applicable to a case that the focus information is measured for a projection optical system in an exposure apparatus of the full field exposure type such as a stepper or the like other than the exposure apparatus of the scanning exposure type.

The present invention may be also applicable to a case of using a multi-stage type exposure apparatus or exposure method provided with a plurality of substrate stages as disclosed, for example, in U.S. Pat. Nos. 6,590,634, 5,969,441 and 6,208,407 or to a case of using an exposure apparatus or exposure method provided with a measuring stage provided with a measuring member (for example, reference member and/or sensor, etc.) as disclosed, for example, in International Publication No. 1999/23692 and U.S. Pat. No. 6,897,963.

In a case that an electronic device such as a semiconductor device is produced by using the exposure apparatus EX of the respective embodiments described above (or by an exposure method with the exposure apparatus EX), as shown inFIG. 13, the electronic device is produced by performing a step221of designing the function and the performance of the electronic device; a step222of manufacturing a mask (reticle) based on the designing step; a step223of producing a substrate (wafer) as a base material for the device and coating a resist on the substrate (wafer); a substrate-processing step224including a step of exposing the substrate (photosensitive substrate) with a pattern of the mask by the exposure apparatus or exposure method of the embodiment described above, a step of developing the exposed substrate, a step of heating (curing) and etching the developed substrate, etc.; a step225of assembling the device (including processing processes such as a dicing step, a bonding step, and a packaging step); an inspection step226; and the like.

Accordingly, the substrate-processing step224of the method for producing the device includes the exposure step of forming a predetermined pattern onto the substrate by using the exposure apparatus or exposure method of the embodiment described above, and the processing step of processing the substrate onto which the pattern has been formed. According to the exposure apparatus or exposure method, it is possible to efficiently measure the focus information of the projection optical system at a high reproducibility of measurement. Therefore, it is possible to produce the electronic device highly precisely by controlling the auto focus, etc. based on the measurement results.

The present invention is not limited to the application of the exposure apparatus for producing the semiconductor device. The present invention is also widely applicable to an exposure apparatus for a display apparatus or device including a plasma display, a liquid crystal display element formed on the square or rectangular glass plate, etc. and to an exposure apparatus for producing various devices including an image pickup element (CCD or the like), a micromachine, a thin film magnetic head, MEMS (Microelectomechanical Systems), a DNA chip, etc. Further, the present invention is also applicable to an exposure step when a mask (photomask, reticle, etc.), which is formed with mask patterns of various devices, is produced by using the photolithography step.

The present invention is not limited to the embodiments described above, which may be embodied in other various forms within a scope without deviating from the gist or essential characteristics of the present invention.