JP2003045795A - Optical characteristics measurement method, adjustment and exposure method of projection optical system, and manufacturing method of aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure optical characteristics in a projection optical system. SOLUTION: The flatness of a wafer W arranged near the image surface of a projection optical system PL is measured. Then, taking into consideration the planarity, at least one of a position and incline regarding an optical axis AX direction of the projection optical system PL of the wafer W is adjusted, each pattern 67i ,j on a reticle RT is irradiated with an illumination light, and each pattern 67i ,j is transferred onto the substrate via an opening 70i ,j and projection optical system PL. In this case, adjustment in the position and posture of the substrate is made, so that a region on the substrate where the illumination light is applied coincides with the image surface as much as possible by considering the planarity of the substrate, thus setting the amount of misalignment from the reference position of the transfer position of each pattern to the amount of misalignment, that hardly contains misalignment constituents caused by the defocus of a substrate surface and reflects optical characteristics in the projection optical system, as they are. Hence accurate obtaining of the optical characteristics of the projection optical system can be made, based on the amount of misalignment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical characteristic measuring method, a projection optical system adjusting method and an exposure method, and an exposure apparatus manufacturing method, and more specifically, a pattern on a first surface on a second surface. Optical characteristic measuring method for measuring the optical characteristic of a projection optical system for projecting onto a projection, adjusting method for adjusting the projection optical system based on the result measured by the optical characteristic measuring method, and projection optical system adjusted by the adjusting method The present invention relates to an exposure method for transferring a mask pattern onto a substrate by using, and a method for manufacturing an exposure apparatus using the optical characteristic measuring method.

[0002]

2. Description of the Related Art Conventionally, semiconductor elements (CPU, DRA
M, etc.), image pickup devices (CCDs, etc.), liquid crystal display devices, thin film magnetic heads, etc. In the lithography process, various exposure apparatuses for forming a device pattern on a substrate are used. In recent years, with high integration of semiconductor elements and the like, a step-and-repeat type reduction projection exposure apparatus (so-called stepper) capable of accurately forming a fine pattern on a substrate such as a wafer or a glass plate with high throughput, A projection exposure apparatus such as a step-and-scan type scanning exposure apparatus (so-called scanning stepper), which is an improved version of this stepper, is mainly used.

By the way, when manufacturing a semiconductor device or the like, it is necessary to stack different layers of circuit patterns on a substrate, and therefore, the reticle (or mask) on which the circuit pattern is drawn and the substrate are formed. It is important to accurately superimpose the pattern already formed on each of the shot areas. This is because if the stacking is poor, the devices such as manufactured semiconductor devices will malfunction and the yield rate will increase.
This is because it causes a decrease in In order to perform superposition with high accuracy, it is necessary to accurately measure the optical characteristics of the projection optical system, adjust it to a desired state, and manage it.

Conventionally, as a method of measuring the optical characteristics of a projection optical system, exposure is performed using a measurement mask on which a predetermined measurement pattern is formed, and a substrate on which a projected image of the measurement pattern is transferred is developed. A method for calculating the optical characteristics based on the measurement result obtained by measuring the resist image obtained by
The “printing method”) is mainly used.
As this printing method, a method of measuring the amount of change in the relative position between the transfer images such as the resist image and calculating the aberration (aberration amount) of the projection optical system based on the amount of change in the relative position. There is.

For example, when a line-and-space pattern composed of three line patterns arranged with a predetermined line width and a predetermined pitch is used as a measurement pattern,
For example, assume that a resist image as shown in FIG. 9A is obtained as the resist image. In the case of FIG. 9A, the position of the resist image 82 of the central line pattern,
That is, using the center position of the line width as a reference, the amount of deviation (relative position change amount) Δ between the center positions of the outer sides of the line patterns 84 and 86 located on both sides with respect to the reference.
Can be measured, and the aberration of the projection optical system can be quantitatively evaluated based on the deviation amount Δ.

Also, for example, when a so-called box-and-box pattern is used as the measurement pattern, for example, when a pattern in which both the outer box and the inner box have the same center position is transferred, A resist image as shown in FIG. 9B is obtained. In the case of FIG. 9B, the shift amounts (relative position change amounts) Δx and Δy between the centers of the sides of the resist image 88 of the outer box pattern and the resist image 90 of the inner box pattern are measured. , These deviations Δ
It is possible to quantitatively evaluate the aberration of the projection optical system in the biaxial directions based on x and Δy.

Further, there is also known a method of calculating the wavefront aberration in which the aberration is expressed as a tilt amount (deviation amount) with respect to the ideal wavefront by converting the measured relative position change amount into each Zernike component. .

[0008]

However, in the above-mentioned conventional technique, the alignment of the wafer in the optical axis direction is adjusted so that the average surface of the entire wafer surface at the time of exposure matches the image plane of the projection optical system as much as possible. Since the exposure is performed with the tilt correction performed, there is an error in the position of the wafer surface in the optical axis direction when viewed from each point in the illumination area where the pattern is transferred, and this is the deviation of the pattern transfer position. It becomes a factor. Therefore, even if the above-mentioned shift amount is measured based on the pattern (resist image or the like) transferred onto the wafer, it does not depend on the aberration of the projection optical system or the defocus. It is difficult to distinguish. As a result, it is difficult to accurately calculate the aberration amount of the projection optical system based on the shift amount.

The present invention has been made under the above circumstances, and a first object thereof is to provide an optical characteristic measuring method capable of measuring the optical characteristic of a projection optical system with high accuracy.

A second object of the present invention is to provide a method for adjusting a projection optical system which can adjust the optical characteristics of the projection optical system with high precision.

A third object of the present invention is to provide an exposure method capable of accurately transferring a mask pattern onto a substrate.

A fourth object of the present invention is to provide a method of manufacturing an exposure apparatus capable of accurately transferring a mask pattern onto a substrate.

[0013]

The invention according to claim 1 is an optical characteristic measuring method for measuring the optical characteristic of a projection optical system (PL) for projecting a pattern on a first surface onto a second surface. The first step of measuring the flatness of the substrate (W) arranged on the second surface; and the optical axis direction of the projection optical system of the substrate in consideration of the measured flatness. The measurement pattern (67 _{i, j} ) arranged on the first surface is illuminated with illumination light in a state where at least one of the position and the inclination with respect to the plane orthogonal to the optical axis is adjusted, and the measurement pattern is displayed. A second step of transferring onto the substrate via the projection optical system; a third step of obtaining optical characteristics of the projection optical system based on a displacement amount of a transfer position of the measurement pattern from a reference position; It is an optical characteristic measuring method including.

According to this, the flatness of the substrate arranged on the second surface is measured (first step). Then, in consideration of the measured flatness of the substrate, the substrate is arranged on the first surface while adjusting at least one of the position of the substrate in the optical axis direction of the projection optical system and the inclination with respect to the plane orthogonal to the optical axis. The measured pattern thus obtained is illuminated with illumination light, and the measured pattern is transferred onto the substrate via the projection optical system (second step). In this case, the adjustment of at least one of the position of the substrate in the optical axis direction of the projection optical system and the inclination with respect to the plane orthogonal to the optical axis is performed in consideration of the measured flatness of the substrate. It is performed so that the region on the substrate to which the illumination light is applied sometimes coincides with the image plane as much as possible (being within the range of the depth of focus of the best imaging plane of the projection optical system). Therefore, the transfer image of the measurement pattern is formed on the substrate with a very small amount of positional deviation due to defocusing of the substrate surface. That is, the displacement amount of the transfer position of the measurement pattern from the reference position is a displacement amount that almost does not include the displacement component due to the defocus of the substrate surface and substantially reflects the optical characteristics of the projection optical system. .

Then, the optical characteristic of the projection optical system is accurately measured by obtaining the optical characteristic of the projection optical system based on the amount of displacement of the transfer position of the measurement pattern from the reference position (third step). It becomes possible to do.

Here, the "reference position" may be a design value, or may be a transfer position of a pattern which is least affected by the aberration of the projection optical system among a plurality of measurement patterns transferred at the same time, Alternatively, it may be the position of the reference pattern formed on the substrate in advance.

In this case, as in the optical characteristic measuring method according to the second aspect, the reference pattern (74 ₁ ) arranged on the first surface is illuminated by the illumination light, and the reference pattern is projected by the projection optical system. When the fourth step of transferring onto the substrate via the system is further included, the optical characteristic can be obtained in the third step with the transfer position of the reference pattern as the reference position.

Also in the transfer of the reference pattern in this case, in consideration of the measured flatness of the substrate, at least one of the position of the substrate in the optical axis direction of the projection optical system and the inclination with respect to the plane orthogonal to the optical axis is adjusted. It is desirable to be performed in the state.

In the optical characteristic measuring method according to the first aspect, as in the optical characteristic measuring method according to the third aspect, in the second step, the measuring pattern is formed on the first surface in a predetermined positional relationship. A plurality of measurement patterns (67 _{i, j} ) are illuminated with illumination light, and each of the illumination light generated from each of the plurality of measurement patterns is individually associated with each of the measurement patterns. Is projected onto the substrate through the pinhole-shaped opening (70 _{i, j} ) and the projection optical system, and the respective measurement patterns are transferred onto the substrate. In the third step, The wavefront aberration, which is one of the optical characteristics of the projection optical system, can be obtained based on the amount of displacement of the transfer position of each measurement pattern from the reference position.

In this case, a design value or the position of a reference pattern previously formed on the substrate can be adopted as the reference position. However, as in the optical characteristic measuring method according to claim 4, A plurality of reference patterns (76 _{i, j} ) are individually arranged on the first surface so as to correspond to the plurality of measurement patterns, and the plurality of reference patterns are illuminated by the illumination light. In the case where the method further includes a fourth step of transferring each onto the substrate via the projection optical system, in the third step, the displacement of the transfer position of each of the measurement patterns from the transfer position of the corresponding reference pattern is displaced. The wavefront aberration of the projection optical system can be obtained based on the quantity.

Also in the transfer of the reference pattern in this case, in consideration of the measured flatness of the substrate, at least one of the position of the substrate in the optical axis direction of the projection optical system and the inclination with respect to the plane orthogonal to the optical axis is adjusted. It is desirable to be performed in the state. In addition, the positional relationship of multiple reference patterns (such as intervals)
It is desirable to measure the above, and use the measurement result, for example, to obtain the above-mentioned positional deviation amount for each measurement pattern, or to correct the measurement result of the optical characteristics of the projection optical system.
As a result, it is possible to reduce the measurement error of the optical characteristics due to the position error of the plurality of reference patterns.

In each of the optical characteristic measuring methods described in claims 1 to 4, like the optical characteristic measuring method described in claim 5, in the third step, the measured flatness is further taken into consideration. The optical characteristics of the projection optical system can be obtained.

According to a sixth aspect of the present invention, there is provided an optical characteristic measuring method for measuring an optical characteristic of a projection optical system for projecting a pattern on a first surface onto a second surface, the method being arranged on the second surface. A first step of measuring the flatness of the formed substrate; illuminating a measurement pattern arranged on the first surface with illumination light, and transferring the measurement pattern onto the substrate via the projection optical system. And a third step of obtaining the optical characteristic of the projection optical system based on the amount of displacement of the transfer position of the measurement pattern from the reference position and the measured flatness. This is an optical characteristic measuring method.

According to this, the flatness of the substrate arranged on the second surface is measured (first step). Further, the measurement pattern arranged on the first surface is illuminated with illumination light, and the measurement pattern is transferred onto the substrate via the projection optical system (second step). Then, the optical characteristics of the projection optical system are obtained based on the amount of displacement of the transfer position of the measurement pattern from the reference position and the measured flatness of the substrate (third step).

Here, the amount of displacement of the transfer position of the measurement pattern from the reference position includes a displacement component reflecting the optical characteristics of the projection optical system and a displacement component due to defocus of the substrate at the time of transfer. It is almost always included.

However, in the present invention, since the optical characteristics of the projection optical system are obtained based on the above-mentioned amount of positional deviation and the measured flatness of the substrate, the influence of defocusing of the substrate surface during transfer is substantially exerted. It becomes possible to accurately obtain the optical characteristics of the projection optical system by eliminating

For example, based on the flatness of the substrate, the position shift component due to the defocus of the substrate surface at the time of transfer is obtained,
The positional deviation component reflecting the optical characteristics of the projection optical system is obtained by subtracting the positional deviation component due to defocus from the obtained positional deviation amount (measured value), and the optical characteristics of the projection optical system are calculated based on this. It is also possible to calculate the optical characteristics of the projection optical system based on the position shift amount (actual measurement value), correct the calculation result of this optical characteristic in consideration of the position shift component due to defocus, and then correct it. The optical characteristics of 1 may be used as the final optical characteristics. Further, instead of transferring the reference pattern, a reference in which a plurality of reference patterns are formed in the same positional relationship as a plurality of measurement points where measurement patterns are to be arranged in the visual field of the projection optical system (illumination light irradiation region) It is also possible to use a substrate and measure the amount of positional deviation of the measurement pattern using the reference pattern as the reference position at each measurement point. At this time, the positional relationship of the plurality of reference patterns on the reference substrate (interval, etc.)
It is desirable to measure the above, and use the measurement result, for example, to obtain the above-mentioned positional deviation amount for each measurement pattern, or to correct the measurement result of the optical characteristics of the projection optical system.
As a result, it is possible to reduce the measurement error of the optical characteristic due to the manufacturing error of the reference substrate (positional error of the reference pattern, etc.).

According to a seventh aspect of the present invention, there is provided the step of measuring the optical characteristic of the projection optical system by using the optical characteristic measuring method according to any one of the first to sixth aspects; And a step of adjusting the projection optical system based on the above.

According to this method, since the optical characteristics of the projection optical system are measured by using the optical characteristic measuring methods according to the first to sixth aspects, the optical characteristics of the projection optical system can be accurately measured.
Since the projection optical system is adjusted based on the measurement result of the optical characteristics measured with high accuracy, the optical characteristics of the projection optical system can be adjusted with high accuracy.

The invention described in claim 8 is an exposure method for transferring a pattern of a mask onto a substrate via a projection optical system, and the step of adjusting the projection optical system by the adjustment method according to claim 7. And; a step of transferring the pattern onto the substrate through the adjusted projection optical system.

According to this, since the projection optical system is adjusted by the adjusting method according to the seventh aspect, the optical characteristics of the projection optical system are adjusted with high accuracy. Then, since the mask pattern is transferred onto the substrate via the adjusted projection optical system, the pattern can be transferred onto the substrate with high accuracy.

A ninth aspect of the present invention is a method of manufacturing an exposure apparatus, which transfers a pattern of a mask (R) onto a substrate (W) via a projection optical system (PL). An exposure apparatus comprising: a step of measuring an optical characteristic of a projection optical system by using the optical characteristic measuring method according to any one of the above items; and a step of adjusting the projection optical system based on a measurement result of the optical characteristic. Is a manufacturing method.

According to this, the optical characteristics of the projection optical system are accurately measured by using each of the optical characteristic measuring methods described in claims 1 to 6, and the projection optical system is adjusted based on the measured optical characteristics. Therefore, the imaging characteristics of the projection optical system can be adjusted accurately. Therefore, an exposure apparatus is manufactured in which the imaging characteristics of the projection optical system are adjusted with high accuracy, and the pattern of the mask is accurately transferred onto the substrate through the projection optical system by performing exposure using the exposure apparatus. It will be possible.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION << First Embodiment >> A first embodiment of the present invention will be described below with reference to FIGS. 1 to 6B.

FIG. 1 shows a schematic structure of an exposure apparatus 10 according to the first embodiment. This exposure apparatus 10 is
This is a step-and-repeat reduction projection exposure apparatus using a pulse laser light source as an exposure light source (hereinafter referred to as “light source”), that is, a so-called stepper.

The exposure apparatus 10 serves as a mask stage for holding an illumination system including a light source 16 and an illumination optical system 12, and a reticle R as a mask illuminated by exposure illumination light EL as an energy beam from the illumination system. Reticle stage RST, a projection optical system PL for projecting the exposure illumination light EL emitted from the reticle R onto a wafer W (on the image plane) as a substrate, and a substrate on which a Z tilt stage 58 for holding the wafer W is mounted. A wafer stage WST as a stage and a control system for these are provided.

As the light source 16, here, ArF is used.
An excimer laser light source (output wavelength 193 nm) is used. As the light source 16, a light source that outputs pulsed light in the vacuum ultraviolet region such as an F ₂ laser light source (output wavelength 157 nm) or a KrF excimer laser light source (output wavelength 248 n
A light source that outputs pulsed light in the near-ultraviolet region such as m) may be used.

The light source 16 is actually the illumination optical system 1.
2 is installed in a low-clean service room different from the clean room in which the chamber 11 in which the exposure apparatus main body including the reticle stage RST, the projection optical system PL, the wafer stage WST, and the like is housed is installed. And is connected to the chamber 11 via a light-transmitting optical system (not shown) including an optical axis adjusting optical system at least partially called a beam matching unit. This light source 16
Is based on the control information TS from the main controller 50, the internal controller turns on / off the output of the laser beam LB.
Off, energy per pulse of the laser beam LB, oscillation frequency (repetition frequency), center wavelength, spectrum half width, etc. are controlled.

The illumination optical system 12 includes a cylinder lens,
Beam expander, zoom optical system (neither shown), and optical integrator (homogenizer)
Beam shaping / illuminance homogenizing optical system 20 including a fly-eye lens or an internal reflection type integrator (fly-eye lens in this embodiment) 22 as an illumination system aperture stop plate 2
4, first relay lens 28A, second relay lens 28
B, a reticle blind 30, a mirror M for bending the optical path, a condenser lens 32, and the like.

Beam shaping / illuminance uniforming optical system 20
Are connected to a light transmission optical system (not shown) through a light transmission window 17 provided in the chamber 11. This beam shaping
The illuminance homogenizing optical system 20 shapes the cross-sectional shape of the laser beam LB which is pulse-emitted by the light source 16 and is incident through the light transmission window 17 using, for example, a cylinder lens or a beam expander. Then, the fly-eye lens 22 positioned on the exit end side inside the beam shaping / illuminance uniformizing optical system 20.
In order to illuminate the reticle R with a uniform illuminance distribution, by the incidence of the laser beam whose cross-sectional shape is shaped, on the exit-side focal plane of the illumination optical system 12, which is arranged so as to substantially coincide with the pupil plane. A surface light source (secondary light source) including a large number of point light sources (light source images) is formed. The laser beam emitted from this secondary light source is hereinafter referred to as "illumination light EL".

An illumination system aperture stop plate 24 made of a disk-shaped member is arranged near the exit-side focal plane of the fly-eye lens 22. The illumination system aperture stop plate 24 has, for example, an aperture stop having a normal circular aperture (normal aperture) and an aperture stop having a small circular aperture (small aperture) for reducing a coherence factor σ value at substantially equal angular intervals. σ stop), a ring-shaped aperture stop for ring-shaped illumination (ring-shaped aperture stop), and a modified aperture stop formed by eccentrically arranging a plurality of apertures for the modified light source method (of which two types are shown in FIG. 1). Only the aperture stop is shown) and so on. The illumination system aperture stop plate 24 is adapted to be rotated by a drive device 40 such as a motor controlled by the main control device 50, whereby any aperture stop is selectively placed on the optical path of the illumination light EL. The light source surface shape in the Koehler illumination, which will be described later, is limited to an annular zone, a small circle, a large circle, a fourth circle, or the like. In this embodiment, the aperture stop plate 24
By using the light intensity distribution of the illumination light on the pupil plane of the illumination optical system (2
The shape and size of the next light source, that is, the illumination condition of the reticle R is changed, but instead of the aperture stop plate 24 or in combination with it, it is arranged by exchanging it on the optical path of the illumination optical system. An optical unit including at least one of a plurality of diffractive optical elements, at least one prism (such as a conical prism or a polyhedral prism) movable along an optical axis of an illumination optical system, and a zoom optical system is used as a light source 1.
6 and optical integrator (fly-eye lens)
22 and the variable intensity distribution of the illumination light on the incident surface of the optical integrator (fly-eye lens) 22 or the incident angle range of the illumination light to minimize the light amount loss due to the change of the illumination conditions. It is preferable to suppress it to the limit.

Illumination light EL emitted from the illumination system aperture stop plate 24
The reticle blind 30 on the optical path of the first
A relay optical system including a relay lens 28A and a second relay lens 28B is arranged. The reticle blind 30 is arranged on a conjugate plane with respect to the pattern surface of the reticle R, and has a rectangular opening that defines a rectangular illumination area IAR on the reticle R. Here, as the reticle blind 30, a movable blind whose opening shape is variable is used, and the opening is set by the main control device 50 based on blind setting information also called masking information.

A bending mirror M for reflecting the illumination light EL passing through the second relay lens 28B toward the reticle R is arranged on the optical path of the illumination light EL behind the second relay lens 28B constituting the relay optical system. And this mirror M
The condenser lens 32 is arranged on the optical path of the rear illumination light EL.

In the above configuration, the fly-eye lens 2
The incident surface of No. 2, the arrangement surface of the reticle blind 30, and the pattern surface of the reticle R are optically set to be conjugate with each other, and are formed on the exit-side focal plane of the fly-eye lens 22 (the pupil of the illumination optical system). Surface) and the Fourier transform surface (exit pupil surface) of the projection optical system PL are optically set to be conjugate with each other to form a Koehler illumination system.

The illumination optical system 12 configured as described above
In brief, the laser beam LB pulse-emitted from the light source 16 is incident on the beam shaping / illuminance uniforming optical system and the cross-sectional shape is shaped, and then is incident on the fly-eye lens 22. As a result, the fly-eye lens 22
The secondary light source described above is formed at the exit end of the.

Illumination light EL emitted from the above-mentioned secondary light source
Passes through one of the aperture stops on the illumination system aperture stop plate 24, then passes through the first relay lens 28A, the rectangular aperture of the reticle blind 30, and then passes through the second relay lens 28B. After the optical path is bent vertically downward, the rectangular illumination area IAR on the reticle R held on the reticle stage RST is illuminated with a uniform illuminance distribution via the condenser lens 32.

The reticle R is mounted on the reticle stage RST and is held by suction via an electrostatic chuck (or vacuum chuck) or the like (not shown). The reticle stage RST is driven by a drive system (not shown) on a horizontal plane (XY
It is configured such that minute driving (including θz rotation (rotation around the Z axis)) is possible within a plane. Further, reticle stage RST is configured to be movable within a predetermined stroke range (about the length of reticle R) in the Y-axis direction. The position of the reticle stage RST is determined by a position detector (not shown) such as a reticle laser interferometer.
The measurement is performed with a predetermined resolution (for example, a resolution of about 0.5 to 1 nm), and the measurement result is supplied to the main controller 50.

As the projection optical system PL, for example, a bilateral telecentric reduction system is used. The projection magnification of this projection optical system PL is, for example, 1/4, 1/5 or 1/6.
Etc. Therefore, as described above, when the illumination area IAR on the reticle R is illuminated by the illumination light EL, the image formed by reducing the pattern formed on the reticle R by the projection optical system PL at the projection magnification is the surface. A rectangular exposure area IA on the wafer W coated with a resist (photosensitizer)
It is projected and transferred (usually coincident with the shot area).

As the projection optical system PL, as shown in FIG. 1, a refraction system consisting of a plurality of, for example, about 10 to 20 refraction optical elements (lenses) 13 is used. A plurality of lenses 13 forming this projection optical system PL
Among them, a plurality of lenses 13 on the object plane side (reticle R side) (here, four lenses for simplification of description)
₁ , 13, ₂ , 13 ₃ , and 13 ₄ are movable lenses that can be externally driven by the imaging characteristic correction controller 48. The lenses 13 ₁ , 13 ₂ and 13 ₄ are respectively held by lens holders (not shown), and these lens holders are supported at three points in the direction of gravity by drive elements (not shown) such as piezo elements. Then, by independently adjusting the voltage applied to these drive elements, the lens 1
3 ₁ , 13 ₂ , 13 ₄ are shift-driven in the Z-axis direction which is the optical axis direction of the projection optical system PL, and are driven in the tilt direction with respect to the XY plane (that is, the rotation direction around the X-axis and the rotation direction around the Y-axis). It is possible (tiltable). Further, the lens 13 ₃ is held by a lens holder (not shown) are driven element disposed such as a piezoelectric element at approximately 90 ° intervals, for example, in the outer peripheral portion of the lens holder, the two driving elements facing each other By adjusting the voltage applied to each drive element as a set, the lens 1
3 ₃ can be two-dimensionally shift-driven in the XY plane.

The reticle R and the optical elements (particularly lens elements) of the projection optical system PL are respectively illuminated by the illumination light E.
The glass material is appropriately selected according to the wavelength of L. For example,
When the wavelength of the illumination light EL is about 190 nm or more (the illumination light EL is ArF excimer laser light, KrF excimer laser light, or the like), synthetic quartz can be used. However, for example, when the wavelength of the illumination light EL is about 180 nm or less (the illumination light EL is F ₂ laser light or the like), it is difficult to use synthetic quartz in terms of transmittance and the like, so that fluoride crystals such as fluorite and impurities ( Synthetic quartz or the like doped with fluorine etc. is used.

The wafer stage WST can be freely driven in an XY two-dimensional plane by a driving device such as a linear motor (not shown). This wafer stage WS
The wafer W is held on the Z tilt stage 58 mounted on T by electrostatic attraction (or vacuum attraction) or the like via a wafer holder (not shown). Z tilt stage 5
Reference numeral 8 is finely driven in the Z-axis direction, the θx (rotation around the X-axis) and the θy (rotation around the Y-axis) directions by a drive system (not shown), and the position (focus position) of the wafer W in the Z-axis direction.
And a tilt angle of the wafer W with respect to the XY plane. As described above, the drive unit for wafer stage WST and the drive system for Z tilt stage 58 are provided separately, but in the following, wafer stage drive unit 56 shown in FIG. , Will be described as including a drive system.

Further, the X and Y positions of wafer stage WST, rotation (yawing (θz rotation), pitching (θx)
Rotation) and rolling (including θy rotation) are measured by an external wafer laser interferometer 54W via a movable mirror 52W fixed on the Z tilt stage 58, and the measured value of this wafer laser interferometer 54W is the main controller. It is designed to be supplied to 50.

On the Z-tilt stage 58, a reference mark plate FM having a first reference mark and other reference marks for so-called baseline measurement of a wafer alignment system (not shown) is formed on the surface of the wafer W. It is fixed so that it is flush with the surface of.

The exposure apparatus 10, as shown in FIG.
An irradiation system 80 that irradiates a large number of image forming light beams onto the surface of the wafer W from a direction inclined by a predetermined angle with respect to the optical axis of the projection optical system PL.
The focus sensor further includes a and a light receiving system 80b having a large number of light receiving elements that individually receive reflected light from the surface of the wafer W of the image-forming light beams. As the focus sensor (80a, 80b), for example, a multipoint focus position detection system disclosed in Japanese Patent Laid-Open No. 6-283403 is used. In this case, the irradiation points of the large number of imaging light fluxes are set, for example, in one shot area on the wafer W in a matrix arrangement of, for example, 7 × 7 at substantially equal intervals. Also,
The detection signal of the position in the optical axis direction of the surface of the wafer W at the irradiation point (each detection point) of each imaging light flux detected by each light receiving element in the light receiving system 80b, that is, the defocus signal at each detection point is mainly It is adapted to be supplied to the control device 50.

The control system is mainly constituted by the main controller 50 in FIG. The main controller 50 is composed of a so-called workstation (or microcomputer) including a CPU (central processing unit), a ROM (read only memory), a RAM (random access memory), etc. For example, the stepping between shots of the wafer stage WST, the exposure timing, etc. are centrally controlled so as to be performed accurately.

Next, the measurement reticle R _T as an optical characteristic measurement mask used when measuring the optical characteristics of the projection optical system PL of the exposure apparatus 10 of this embodiment will be described.

FIG. 2 shows this measuring reticle R._TOutline of
A perspective view is shown. Moreover, in FIG.
Reticle R loaded on the RST_TLight of
The schematic diagram of the XZ cross section near the axis AX is a model of the projection optical system PL.
It is shown with a schematic diagram. Further, in FIG. 4, the reticle is
Reticle R loaded on the stage RST _T
Is a schematic view of the XZ cross section near the −Y side end of the projection optical system P.
It is shown with a schematic diagram of L.

As is apparent from FIG. 2, the overall shape of this measurement reticle R _T is almost the same as that of a normal reticle with a pellicle. This measurement reticle R _T
Is a glass substrate 60 as a pattern forming member, and a lens mounting member 6 having a rectangular plate shape fixed to the central portion of the upper surface of the glass substrate 60 in FIG. 2 in the X-axis direction.
2. A spacer member 64 made of a frame-shaped member attached to the lower surface of the glass substrate 60 in FIG. 2 and having the same appearance as a normal pellicle frame, and the spacer member 6
4 is provided with an opening plate 66 and the like attached to the lower surface.

In the lens mounting member 62, n circular openings 63 _{i, j} (i = 1 to p, i = 1 to p, i = 1 to p, where n is a matrix) are arranged in almost the entire area except for some belt-shaped areas at both ends in the Y-axis direction.
j = 1 to q, pxq = n) are formed. Inside each circular opening 63 _{i, j,} a condenser lens 65 _{i, j} made of a convex lens having an optical axis in the Z-axis direction is provided (see FIG. 3).

Further, the glass substrate 60 and the spacer member 64
As shown in FIG. 3, reinforcing members 69 are provided at predetermined intervals inside the space surrounded by the opening plate 66.

Further, as shown in FIG. 3, measurement patterns 67 _{i, j} are formed on the lower surface of the glass substrate 60 so as to face the condenser lenses 65 _{i, j} . Further, as shown in FIG. 3, the opening plate 66 is formed with pinhole-shaped openings 70 _{i, j} facing the respective measurement patterns 67 _{i, j} . The pinhole-shaped opening 70 _{i, j} has a diameter of, for example, about 100 to 150 μm.

Returning to FIG. 2, the lens holding member 62 has a Y
The opening 7 is formed in the center of a part of the belt-shaped region at both ends in the axial direction.
2 ₁ and 72 ₂ are formed respectively. As shown in FIG. 4, a reference pattern 74 ₁ is formed on the lower surface (pattern surface) of the glass substrate 60 so as to face one opening 72 ₁ . Although not shown, the other opening 7
The lower surface of the glass substrate 60 (pattern surface) facing 2 ₂
In addition, a reference pattern similar to the reference pattern 74 ₁ (for convenience, described as “reference pattern 74 ₂ ”) is formed.

Further, as shown in FIG. 2, on the X axis passing through the center of the reticle of the glass substrate 60, a pair of reticle alignment marks RM1, which are symmetrically arranged with respect to the center of the reticle, are disposed on both outer sides of the lens holding member 62. RM2 is formed. Although these reticle alignment marks RM1 and RM2 are actually formed on the lower surface (pattern surface) of the glass substrate 60, they are shown on the upper surface side of the glass substrate 60 in FIG. 2 for convenience of illustration. .

Here, in the present embodiment, as the measurement pattern 67 _{i, j} , a mesh pattern (street line pattern) as shown in FIG. 5A is used.
Further, as shown in FIG. 5B, reference patterns 74 ₁ and 74 ₂ corresponding to the measurement pattern 67 _{i, j} are
A two-dimensional lattice pattern in which square patterns are arranged at the same pitch as the measurement patterns 67 _{i, j} is used.

The pattern of FIG. 5A is used as the reference patterns 74 ₁ and 74 ₂ and the pattern of FIG.
It is possible to use the pattern shown in (B).
Further, the measurement pattern 67 _{i, j} is not limited to this, and patterns of other shapes may be used. In that case,
As the reference pattern, a pattern having a predetermined positional relationship with the measurement pattern may be used. That is,
The reference pattern may be any pattern as long as it serves as a reference for the positional deviation of the measurement pattern, and its shape and the like are not limited, but in order to measure the optical characteristics (including the imaging characteristics) of the projection optical system PL, A pattern in which the pattern is distributed over the entire image field or exposure area of the optical system PL is desirable.

Next, the procedure for measuring the optical characteristics of the projection optical system PL using the measurement reticle R _T will be described.

First, main controller 50 loads measurement reticle R _T onto reticle stage RST via a reticle loader (not shown). Next, in main controller 50, while monitoring the output of laser interferometer 54W, wafer stage WST is moved via wafer stage drive unit 56, and a pair of reticle alignment reference marks (hereinafter, referred to as reference marks for reticle alignment on fiducial mark plate FM. A "second reference mark") is positioned at a predetermined reference position. Here, the reference position is, for example, the center of the pair of second reference marks,
It is set at a position corresponding to the origin on the stage coordinate system defined by the laser interferometer 54W.

Next, main controller 50 has a pair of reticle alignment marks RM1, on measurement reticle R _T.
The RM2 and the second reference marks corresponding thereto are simultaneously observed by a pair of reticle alignment microscopes (not shown), and projected images of the reticle alignment marks RM1 and RM2 on the reference plate FM and the corresponding second reference marks. The reticle stage RST is finely driven in the XY two-dimensional plane via a drive system (not shown) so that the positional deviation amounts of are both minimized. As a result, the reticle alignment is completed and the center of the reticle substantially coincides with the optical axis of the projection optical system PL.

Next, in main controller 50, a wafer W having a surface coated with a resist (photosensitive agent) is loaded on Z tilt stage 58 by using a wafer loader (not shown).

Next, main controller 50 measures the flatness within a predetermined region on wafer W onto which measurement pattern 67 _{i, j} on measurement reticle R _T is transferred later. This flatness is measured as follows.

That is, in the main controller 50, a large number of image forming light beams are emitted from the irradiation system 80a of the focus sensor to the wafer W.
The surface is irradiated and the position (Z position) in the optical axis direction of the surface of the wafer W at each detection point is calculated based on the defocus signal at each detection point, and the calculation result is used as the measurement value of the wafer laser interferometer 54W at that time. Correlate and store in memory. The position of wafer stage WST at this time is hereinafter referred to as an initial position.

Then, main controller 50 moves the wafer stage in the X-axis direction by a distance of, for example, half the interval (arrangement pitch) between the detection points of the focus sensor while monitoring the measurement value of wafer laser interferometer 54W. . Then
In the main controller 50, the irradiation system 80a of the focus sensor
A large number of imaging light fluxes are irradiated onto the surface of the wafer W, and the position (Z position) in the optical axis direction of the surface of the wafer W at each detection point is calculated based on the defocus signal at each detection point. It is stored in the memory in association with the measurement value of the wafer laser interferometer 54W.

Next, the main controller 50 monitors the measurement value of the wafer laser interferometer 54W and adjusts the position in the Y-axis direction from the initial position by a distance of, for example, half the arrangement pitch of the detection points of the focus sensor. Then, wafer stage WST is moved in the X and Y directions. Next, the main controller 50 irradiates the surface of the wafer W with a large number of imaging light beams from the irradiation system 80a of the focus sensor, and based on the defocus signal at each detection point, the position of the wafer W surface in the optical axis direction at each detection point. (Z position) is calculated, and the calculation result is stored in the memory in association with the measurement value of the wafer laser interferometer 54W at that time.

In the main controller 50, a 14 × 14 matrix arranged in the XY two-dimensional directions at intervals of half the arrangement pitch of the detection points of the focus sensor based on the information stored in the memory so far. The information of the Z position on the surface of the wafer W at the array point is calculated, the information is converted into table data corresponding to the XY coordinates of each array point, and the table data is stored again in the memory.

Then, main controller 50 returns wafer stage WST to the initial position while monitoring the measurement value of wafer laser interferometer 54W.

Next, main controller 50 includes all of condenser lenses 65 _{i, j} of measurement reticle R _T and does not include apertures 72 ₁ and 72 ₂ , so that lens holding member 62 in the X-axis direction is not included. In order to form a rectangular illumination area having a length within the maximum width in the X-axis direction, the opening of the reticle blind 30 is set via a drive system (not shown). At the same time,
The main controller 50 rotates the illumination system aperture stop plate 24 via the drive device 40 to set a predetermined aperture stop, for example, a small σ stop on the optical path of the illumination light EL. At this time, the luminous flux diameter (or incident angle range) of the illumination light incident on the optical integrator (fly-eye lens) 22 is reduced by using an optical unit (not shown) in the illumination optical system described above, for example, a zoom optical system. It is desirable to minimize light loss.

Next, main controller 50 reads the Z position data contained in the area on wafer W corresponding to the rectangular illumination area from the table data stored in the memory, and reads these data. Based on the above, an approximate plane (or an approximate curved surface) of the area portion on the surface of the wafer W is calculated by a predetermined calculation such as the least square method, and the approximate plane is made to match the image plane of the projection optical system PL as much as possible. Z of the Z tilt stage 58 via the wafer stage drive unit 56
At least one of the position and the inclination with respect to the XY plane is adjusted.

After such preparatory work, main controller 50
Then, the control information TS is given to the light source 16, the laser beam LB is emitted, and the reticle R _T is irradiated with the illumination light EL to perform exposure. As a result, as shown in FIG. 3, the respective measurement patterns 67 _{i, j} are simultaneously exposed to the wafer W via the corresponding pinhole-shaped openings 70 _{i, j} and the projection optical system PL.
Transferred to the upper resist (positive resist) layer. As a result, a reduced image (latent image) 6 of each measurement pattern 67 _{i, j} as shown in FIG. 6A is formed on the resist layer on the wafer W.
7 ′ _{i, j} are formed at predetermined intervals along the XY two-dimensional direction at predetermined intervals.

Next, in main controller 50, based on the measured value of a reticle laser interferometer (not shown) and the designed positional relationship between the reticle center and one of the reference patterns 74 ₁ ,
The reticle stage RS is arranged via a drive system (not shown) so that the center position of the reference pattern 74 ₁ coincides with the optical axis AX.
The T is moved in the Y-axis direction by a predetermined distance. Next, in the main controller 50, the illumination light EL is illuminated only on a rectangular area of a predetermined area (this area is not covered by any condenser lens) on the lens holding member 62 including the moved opening 72 _1. In order to define the area, the opening of the reticle blind 30 is set via a drive system (not shown).

Next, the main controller 50, the wafer W latent image 67 _'1,1 of the first measurement pattern 67 _1,1 are formed
The laser interferometer 5 is arranged so that the center of the upper region (referred to as the region S _1,1 ) substantially coincides with the optical axis of the projection optical system PL.
Wafer stage WST is moved while monitoring the measured value of 4 W. At this time, in the main controller 50, the latent image 67 '
_The Z tilt stage 58 is finely moved in the Z-axis direction based on the information of the Z position of the array point closest to the area on the wafer W in which _1,1 is formed, and the area S _1,1 of the projection optical system PL is moved. It is desirable to match the paraxial image plane.

Then, in the main controller 50, the control information T
S is given to the light source 16 to cause the laser beam LB to emit light, and the illumination light EL is irradiated to the reticle _RT to perform exposure.
As a result, the reference pattern 74 ₁ is transferred onto the region S _1,1 in which the latent image of the measurement pattern 67 _1,1 of the resist layer on the wafer W is already formed. As a result, the wafer W
The area S _1,1 of the upper, as shown in FIG. 6 (B), the latent image 67 of the measurement pattern 67 _{1, 1 ', 1} and the reference pattern 7
4 ₁ of the latent image 74 _'1 are formed in a positional relationship as in FIG.

Next, in main controller 50, reticle R
The design arrangement pitch p of the measurement patterns 67 _{i, j} on the wafer W is calculated based on the arrangement pitch of the measurement patterns 67 _{i, j} on _T and the projection magnification of the projection optical system PL, and the pitch is calculated. The wafer stage WST is moved in the X-axis direction by p, and the center of the area (called area S _1,2 ) on the wafer W where the latent image of the second measurement pattern 67 _1,2 is formed. Moves wafer stage WST so that it substantially coincides with the optical axis of projection optical system PL. Also at this time, in the main controller 50, in the same manner as described above, the area S on the wafer W is
It is desirable to match ₁ , ₂ with the paraxial image plane of the projection optical system PL.

Then, in the main controller 50, the control information T
S is given to the light source 16 to cause the laser beam LB to emit light, and the illumination light EL is irradiated to the reticle _RT to perform exposure.
As a result, the reference pattern 74 ₁ is transferred onto the area S _1,2 on the wafer W in an overlapping manner.

Thereafter, by repeating the inter-region stepping operation and the exposure operation similar to the above, the measurement pattern and the reference pattern similar to those in FIG. 6B are formed in the region S _{i, j} on the wafer W. A latent image is formed. Again, each region S _i, when the transfer of the reference pattern 74 ₁ for _j, it is desirable to match prior thereto each area S _{i, j} to the paraxial image plane of the projection optical system PL.

In this way, all exposure is completed.
In the main controller 50, a wafer loader (not shown) is used.
And unload the wafer W from the Z tilt stage 58.
Connected to the chamber 11 inline.
The illustrated coater / developer (abbreviated as "C / D" below)
Send) to. Then, the development of the wafer W is performed in the C / D.
And the matrix is formed on the wafer W after the development.
Areas S arranged in a line _{i, j}The same arrangement as in Fig. 6 (B)
A resist image of the measurement pattern and the reference pattern is formed by
To be done.

After that, the wafer W which has been developed is C /
Then, the overlay error is measured for each region S _{i, j} by using an external overlay measuring device (registration measuring device), and based on this result, each measurement pattern 67 _i, Positional error (positional shift amount) of the resist image of _j with respect to the resist image of the corresponding reference pattern 74 _1.
Is calculated. There are various possible methods for calculating the positional deviation amount, but in any case, it is preferable to perform statistical calculation based on the measured raw data from the viewpoint of improving accuracy.

In this way, for each area S _{i, j}
The positional shift amount (Δ′ξ, Δ′η) of the measurement pattern with respect to the reference pattern in the X and Y two-dimensional directions is obtained.

In the present embodiment, the amount of positional deviation (Δ′ξ, Δ′η) in the X and Y two-dimensional directions of the measurement pattern with respect to the reference pattern for each area S _{i, j} obtained as described above. ) Data is
It is input to the main controller 50 via the input / output device 44 of FIG. It is also possible to input the data of the calculated positional deviation amount (Δ′ξ, Δ′η) for each region S _{i, j} from the external overlay measuring device to the main controller 50 online. is there.

In any case, in response to the above input,
The main controller 50 uses the table data stored in the memory (information on the Z position on the surface of the wafer W at the 14 × 14 matrix array points) to determine the amount of positional deviation (Δ′ξ, Δ′η). ), The true positional deviation amount (Δξ, Δη) that directly reflects the wavefront aberration of the projection optical system PL, in which the positional deviation component caused by the defocus remaining at the time of transferring each measurement pattern 67 _{i, j} described above is corrected. ) Is calculated.

More specifically, at the time of transfer of each of the measurement patterns 67 _{i, j} described above, the wafer W is adjusted so that the calculated approximate plane (or approximate curved surface) matches the image plane of the projection optical system PL as much as possible. Since the Z position and the inclination with respect to the XY plane are adjusted, the alignment of the wafer in the optical axis direction and the alignment of the average surface (approximate surface) of the entire wafer surface to the image plane of the projection optical system are aligned and adjusted. The position shift component due to the defocus at this time is extremely small as compared with the conventional technique in which exposure is performed in a state in which the tilt is corrected. However, the above array points and each measurement pattern 6
Since it does not match the projection position of 7 _{i, j,} the image formation point of each measurement pattern 67 _{i, j} does not always match the image plane of the projection optical system PL.

Therefore, the main controller 50 calculates the true defocus amount at the time of transfer for each measurement pattern 67 _{i, j} , for example, as follows. That is, for example, a bicubic bi-spline curved surface is calculated using the data at the array points of 4 × 4 matrix-shaped arrangement around the projected position of each measurement pattern 67 _{i, j and} the projected position on the curved surface is calculated. Estimate Z position information. Then, the estimated Z position information and the previously calculated approximate plane (or approximate curved surface)
The difference from the Z position information at the projection position above is taken as the residual defocus amount at the time of transfer of each measurement pattern. Then, the position shift component corresponding to this defocus amount is obtained for each measurement pattern, and the position shift component is subtracted from the position shift amount (Δ′ξ, Δ′η) to obtain the wavefront aberration of the projection optical system PL. Then, the true positional deviation amount (Δξ, Δη) that reflects the above is calculated.

Here, the wavefront of the projection optical system PL is calculated by calculation based on this position shift amount. As a premise of this, the physical relationship between the position shift amount (Δξ, Δη) and the wavefront is A brief description will be given with reference to FIGS. 3 and 4.

FIG. 3 shows a measurement pattern 67._{k, l}About
Then, as representatively shown, the measurement pattern 67_{i, j}
(67_{k, l}) Of the diffracted light generated by
Opening 70 _{i, j} The light that has passed through the_{i, j}
(67_{k, l}) Depending on where the light comes from
Thus, the position passing through the pupil plane of the projection optical system PL is different. Sanawa
The wavefront at each position on the pupil plane corresponds to that position
Measurement pattern 67_{i, j}(67_{k, l}) Position
Corresponds to the wavefront of the light passing through. And if projection optics
Assuming that the system PL has no aberrations, their wavefronts
Is a symbol F on the pupil plane of the projection optical system PL.₁Is indicated by
It should be an ideal wavefront (here, a plane). Only
However, there is actually no projection optical system that has no aberration.
Therefore, in the pupil plane, for example, as shown by the dotted line
Curved wavefront F₂Becomes Therefore, the measurement pattern 67
_{i, j}(67_{k, l}) Image is a wavefront F on the wafer W.₂The ideal wave
An image is formed at a position displaced according to the inclination with respect to the surface.

On the other hand, the reference pattern 74 ₁ (or 7
4 ₂ ) generates diffracted light, as shown in FIG.
Without being restricted by the pinhole-shaped opening, the light directly enters the projection optical system PL and is imaged on the wafer W through the projection optical system PL. Furthermore, this reference pattern 74
_Since exposure using ₁ is performed with the center of the reference pattern 74 ₁ being positioned on the optical axis of the projection optical system PL, most of the imaging light flux generated from the reference pattern 74 ₁ is an aberration of the projection optical system PL. The image is formed on the minute area including the optical axis without any positional deviation without being affected by.

Therefore, the positional deviation amount (Δξ, Δη) becomes a value that directly reflects the inclination of the wavefront with respect to the ideal wavefront, and conversely the wavefront can be restored based on the positional deviation amount (Δξ, Δη). In addition, the amount of positional deviation (Δξ,
As is clear from the physical relationship between Δη) and the wavefront, the wavefront calculation principle in this embodiment is based on the well-known Shack-Hart method.
It is the wavefront calculation principle of man itself.

Next, a method of calculating the wavefront based on the above-mentioned positional deviation amount will be briefly described.

As described above, the positional deviation amount (Δξ, Δη) corresponds to the inclination of the wavefront, and by integrating this, the shape of the wavefront (strictly speaking, deviation from the reference surface (ideal wavefront)).
Is required. If the equation of the wavefront (deviation of the wavefront from the reference plane) is W (x, y) and the proportional coefficient is k, the relational expressions such as the following equations (1) and (2) are established.

[0098]

[Equation 1]

Since it is not easy to directly integrate the wavefront inclination given only by the amount of positional deviation, the surface shape is developed into a series and fitted to this. In this case, the series should be orthogonal. The Zernike polynomial is a series suitable for expanding an axisymmetric surface, and expands into a trigonometric series in the circumferential direction. That is, when the wavefront W is represented by the polar coordinate system (ρ, θ), the Zernike polynomial can be expanded as R _n ^m (ρ) as shown in the following expression (3).

[0100]

[Equation 2]

Since the specific form of R _n ^m (ρ) is well known (for example, it is described in a general textbook of optics), detailed description thereof will be omitted. Since it is an orthogonal system, the coefficients of each term, A _n ^m and B _n ^m, can be independently determined.
Cutting with a finite term corresponds to performing some sort of filtering.

In practice, the differential is detected as the above-mentioned amount of positional deviation, so the fitting needs to be performed on the differential coefficient. Polar coordinate system (x = ρcos θ, y = ρs
in θ) is expressed by the following equations (4) and (5).

[0103]

[Equation 3]

Since the differential form of the Zernike polynomial is not an orthogonal system, the fitting must be performed by the least square method. The information (the amount of deviation) from one measurement pattern is X
And the number of measurement patterns is N (N is, for example, about 81 to 400),
The number of observation equations given by the above equations (1) to (5) is 2N.
(= About 162 to 800). From now on, for example, 27
Much smaller the error of each coefficient to determine the coefficients (the variation coefficients except A _{¹ 1,} B _{1 1} representing the tilt of the surface is accommodated in several nm).

Each term in the Zernike polynomial corresponds to an optical aberration. Moreover, the low-order terms almost correspond to Seidel aberrations. Therefore, the wavefront aberration of the projection optical system PL can be obtained by using the Zernike polynomial.

Therefore, main controller 50 uses a predetermined calculation program to correspond to each region S _{i, j} based on the positional deviation amount (Δξ, Δη) according to the above-mentioned principle, that is, the projection optical system. The wavefront (wavefront aberration) corresponding to the first measurement point to the nth measurement point in the field of view of PL, here, the coefficient of each term of the Zernike polynomial, for example, the coefficient Z _{2 of} the second term.
The coefficient Z ₃₆ of the 36th term is calculated.

By the way, in the exposure apparatus 10 of the present embodiment, maintenance is regularly performed. At that time, the measurement reticle R _T is used to measure the wavefront aberration in the procedure described above, and the projection optical system PL is adjusted based on the measurement result. This adjustment is performed by, for example, the main controller 50 based on the measurement result of the wavefront aberration, based on the low-order aberrations such as astigmatism, coma, distortion, field curvature (or focus), and spherical aberration, that is, Seidel's 5
Aberrations and the like are obtained, and a command to correct these aberrations is given to the imaging characteristic correction controller 48. As a result, the image formation characteristic correction controller 48 causes the movable lens 13 ₁
To 13 at least one predetermined movable lens of the _four, the voltage applied to the predetermined drive device for driving at least one degree of freedom direction is controlled, at least one of the position and attitude of the predetermined movable lens is adjusted, Imaging characteristics of the projection optical system PL, such as distortion, field curvature,
Coma aberration, spherical aberration, astigmatism, etc. are corrected.

In this case, the relationship between the unit drive amount of each movable lens in the direction of each degree of freedom and the change amount of the wavefront aberration (the coefficient of each term of the Zernike polynomial) is obtained in advance and stored in a memory as a database. Remember
An adjustment amount calculation program for calculating the adjustment amount of the imaging characteristic based on this database and the coefficient of each term of the Zernike polynomial may be prepared. In this way, in the main controller 50, when the measurement result of the wavefront aberration (calculated value of the coefficient of each term of the Zernike polynomial) is obtained,
Using the above database and the obtained measurement result of the wavefront aberration, an adjustment amount for driving the movable lenses 13 _{1 to} 13 ₄ in each degree of freedom is calculated according to the above adjustment amount calculation program, and this adjustment amount is calculated. Is given to the imaging characteristic correction controller 48. As a result, the imaging characteristic correction controller 48 controls the applied voltage to each drive element that drives the movable lenses 13 _{1 to} 13 ₄ in the respective degrees of freedom, and at least the positions and orientations of the movable lenses 13 _{1 to} 13 ₄ are controlled. One of them is adjusted almost at the same time, and the imaging characteristics of the projection optical system PL, such as distortion, curvature of field, coma, spherical aberration, and astigmatism, are corrected. Regarding coma aberration, spherical aberration, and astigmatism, not only low-order aberrations but also high-order aberrations can be corrected.

In the exposure apparatus 10 of the present embodiment, when manufacturing a semiconductor device, a reticle R for device manufacturing is loaded as a reticle on the reticle stage RST, and thereafter, reticle alignment and a so-called baseline of a wafer alignment system not shown. Measurement and EGA
Preparation work such as wafer alignment such as (enhanced global alignment) is performed. After that, the same step-and-repeat exposure is performed as in the measurement of the optical characteristics described above. However, in this case, stepping is performed in units of shots based on the wafer alignment result. Since the operation during exposure does not differ from that of a normal stepper, detailed description thereof will be omitted.

However, in the exposure apparatus 10, the image forming characteristics of the projection optical system PL described above are corrected (adjusted) before the exposure at the time of the above-mentioned maintenance or at other necessary timings. Projection optical system P after correction
Using L, the step-and-repeat exposure is performed.

Next, a method of manufacturing the exposure apparatus 10 will be described.

In manufacturing the exposure apparatus 10, first, an illumination optical system 12 including optical elements such as a plurality of lenses and mirrors, a projection optical system PL, a reticle stage system including a large number of mechanical parts, a wafer stage system, and the like. , Assembling each as a unit, and performing optical adjustments so that each unit exhibits the desired performance as a unit,
Make mechanical and electrical adjustments.

Next, the illumination optical system 12, the projection optical system PL, etc. are assembled in the exposure apparatus main body, and the reticle stage system, wafer stage system, etc. are attached to the exposure apparatus main body to connect wiring and piping.

Next, the illumination optical system 12 and the projection optical system PL
With respect to, the optical adjustment is further performed. This is because the optical characteristics of those optical systems, in particular, the projection optical system PL slightly change before and after assembling to the exposure apparatus main body. In the present embodiment, when the optical adjustment of the projection optical system PL is carried out after being incorporated in the exposure apparatus main body, the wavefront aberration of the projection optical system PL is measured by the procedure described above using the measurement reticle R _T described above. To do. And
Based on this wavefront aberration result, Seidel aberration and the like are corrected in the same manner as during the above-mentioned maintenance. Also,
If necessary, readjust the assembling of the lens or the like based on the higher-order aberration. If the desired performance cannot be obtained by the readjustment, it is necessary to reprocess some lenses. In order to easily reprocess the optical elements of the projection optical system PL, the above-mentioned wavefront aberration is measured before the projection optical system PL is incorporated into the exposure apparatus main body, and the optical processing that requires reprocessing is performed based on this measurement result. Identify the presence or absence of elements and their positions,
The reprocessing of the optical element and the readjustment of other optical elements may be performed in parallel.

Thereafter, further comprehensive adjustment (electrical adjustment, operation confirmation, etc.) is performed. This makes it possible to manufacture the exposure apparatus 10 of the present embodiment, which can accurately transfer the pattern of the reticle R onto the wafer W by using the projection optical system PL whose optical characteristics are adjusted with high accuracy. . It is desirable that the exposure apparatus be manufactured in a clean room where the temperature and cleanliness are controlled.

As described above, according to the present embodiment, the flatness of the surface of the wafer W placed on the wafer stage WST is controlled by the main controller 50 before the measurement of the wavefront aberration of the projection optical system PL. Sensor (80a,
80b). Then, information on the flatness of the surface of the wafer W, for example, information on the Z position on the surface of the wafer W at the above-mentioned 14 × 14 matrix array points is stored in the memory as table data.

When measuring the wavefront aberration of the projection optical system PL, the measuring reticle R _T is mounted on the reticle stage RST, and the measuring patterns 67 _{i, j} on the measuring reticle R _T are measured. Prior to transfer, each measurement pattern 67
_{In order that} the rectangular area of _{i, j} to be transferred may coincide with the image plane of the projection optical system PL as much as possible, the main controller 50 considers the information on the flatness of the surface of the wafer W and the projection optical system of the wafer W. At least one of the position of the system PL in the optical axis direction and the inclination with respect to the plane orthogonal to the optical axis is adjusted.

Next, each measurement pattern 67 _{i, j} on the measurement reticle R _T is illuminated with the illumination light, and each measurement pattern 67 _{i, j} is provided corresponding to each measurement pattern individually. It is transferred to the rectangular area on the wafer W through the pinhole-shaped opening 70 _{i, j} and the projection optical system PL.

Next, the reference pattern 74 ₁ (74 ₂ ) on the measurement reticle R _T is transferred so as to be superimposed on the transfer image (latent image) of each measurement pattern transferred on the wafer W.

After that, the wafer W is developed, and the amount of positional deviation of the transfer image (resist image) of each measurement pattern formed on the wafer W after the development with respect to the resist image of the corresponding reference pattern is obtained.

Then, the main controller 50 corrects the positional deviation component, which is included in the positional deviation amount and is caused by the defocus remaining at the time of transferring the measurement pattern, and corrects it based on the corrected true positional deviation amount. Then, the wavefront aberration of the projection optical system PL is calculated by a predetermined calculation. in this case,
As described above, the positional deviation amount is an amount that accurately reflects the optical characteristics (wavefront aberration) of the projection optical system PL, and based on this amount, the wavefront aberration of the projection optical system PL is very accurately determined. It is possible.

Further, according to the present embodiment, the wavefront aberration of the projection optical system PL is measured with high accuracy at the time of maintenance and the like, and the projection optical system PL is adjusted based on the measurement result of the wavefront aberration measured with high accuracy. Since it is adjusted, the optical characteristics of the projection optical system PL can be adjusted with high accuracy.

Then, according to the exposure apparatus of this embodiment, the pattern of the reticle R is transferred onto the wafer W using the projection optical system PL whose optical characteristics are adjusted as described above, prior to exposure. Therefore, the pattern of the reticle R can be accurately transferred onto the wafer W.

Furthermore, according to the present embodiment, the exposure apparatus 1
Even when 0 is manufactured, after the projection optical system PL is incorporated in the exposure apparatus main body, as described above,
Is measured, and the projection optical system PL is adjusted based on the measured wavefront aberration, so that the imaging characteristics of the projection optical system are adjusted with high accuracy. Therefore, the exposure apparatus 10 in which the image forming characteristics of the projection optical system are adjusted with high accuracy is manufactured, and exposure is performed using the exposure apparatus 10, whereby the reticle pattern is accurately transferred onto the wafer via the projection optical system PL. It becomes possible to transfer.

<< Second Embodiment >> Next, a second embodiment of the present invention will be described with reference to FIGS. here,
Constituent parts that are the same as or equivalent to those of the first embodiment described above will be denoted by the same reference numerals, and the description thereof will be simplified or omitted.

In the second embodiment, when measuring the optical characteristics of the projection optical system PL, specifically, the wavefront aberration, the measuring reticle R ′ shown in FIG. 7 is used instead of the above-described measuring reticle R _{T. T} and the measurement reticle R ″ _T shown in FIG.
And are used.

[0127] The measurement reticle R _'T, as shown in FIG. 7, is configured similarly to the fundamentally reticle R _T for measurement as described above, the lower surface of the glass substrate 60 (pattern surface) The difference is that the reference pattern is not formed at all, and correspondingly, the lens holding member 62 is not provided with an opening forming a passage of illumination light with respect to the reference pattern. The other parts are configured similarly to the measurement reticle R _T.

On the other hand, the measurement reticle R ″ _T is a normal reticle with a pellicle as shown in FIG. 8. That is, the measurement reticle R ″ _T is on the pattern surface (lower surface) of the glass substrate 60. , The condenser lens 63 _{i, j of} the measurement reticle R ′ _T , that is, the measurement pattern 67 _{i, j} (see FIG.
(See (A)) The reference pattern
_{The i and j} are formed, and the reticle alignment marks RM1 and RM2 are formed in the same arrangement as the measurement reticle R ′ _T. In this case, each reference pattern 7
As 6 _{i, j} , the same pattern as the reference pattern 74 ₁ described above is used.

In the measurement reticle R ″ _T , as shown in FIG. 8, the pattern surface of the glass substrate 60 is placed at a predetermined distance from the pattern surface via the pellicle frame 73, for example, 6 m.
A pellicle 71 is provided parallel to the pattern surface on a surface separated by about m.

Next, a method of measuring the wavefront aberration of the projection optical system according to the second embodiment will be described. In the second embodiment as well, the wavefront aberration of the projection optical system PL of the exposure apparatus 10 is measured. As a premise, it is assumed that the measurement reticles R ′ _T and R ″ _T are stored in a reticle storage unit (not shown).

[0131] First, the main controller 50 loads the measurement reticle R _'T on the reticle stage RST via a reticle loader (not shown). Then, the main controller 50
Then, reticle alignment is performed on the measurement reticle R ′ _{T in the same} manner as in the case of the measurement reticle R _T described above. As a result, the reticle alignment is completed and the center of the reticle substantially coincides with the optical axis of the projection optical system PL.

Next, main controller 50 uses wafer loader (not shown) to load wafer W, the surface of which is coated with a resist (photosensitive agent), onto Z tilt stage 58.

Next, in the main controller 50, the flatness within a predetermined region on the wafer W onto which the measurement pattern 67 _{i, j} on the measurement reticle R ′ _T is transferred later is determined by the above-described first embodiment. And the Z position on the surface of the wafer W at 14 × 14 matrix-shaped arrangement points arranged in the XY two-dimensional direction at intervals of half the arrangement pitch of the detection points of the focus sensor obtained as a result. Store table data for information in memory. Then, main controller 50 returns wafer stage WST to the initial position which is the start position of the flatness measurement, while monitoring the measurement value of wafer laser interferometer 54W.

Next, main controller 50 includes all of condenser lenses 65 _{i, j} of measurement reticle R ′ _T and has a length in the X-axis direction within the maximum width of lens holding member 62 in the X-axis direction. The opening of the reticle blind 30 is set via a drive system (not shown) in order to form a rectangular illumination area having a.
At the same time, main controller 50 sets the illumination conditions in the same manner as in the case of the first embodiment described above.

Next, main controller 50 reads the Z position data included in the area on wafer W corresponding to the rectangular illumination area from the table data stored in the memory, and reads these data. Based on the above, an approximate plane (or an approximate curved surface) of the area portion on the surface of the wafer W is calculated by a predetermined calculation such as the least square method, and the approximate plane is made to match the image plane of the projection optical system PL as much as possible. Z of the Z tilt stage 58 via the wafer stage drive unit 56
At least one of the position and the inclination with respect to the XY plane is adjusted.

After such preparatory work, main controller 50
Then, the control information TS is given to the light source 16, the laser beam LB is emitted, and the reticle R ′ _T is irradiated with the illumination light EL to perform exposure. As a result, in the resist layer on the wafer W, each measurement pattern 67 _{i, j} is formed in the same manner as in FIG.
Reduced images (latent images) 67 ′ _{i, j} are formed at predetermined intervals along the XY two-dimensional direction at predetermined intervals.

[0137] Next, loading the main controller 50, as well as unload the measurement reticle R _'T via a reticle loader (not shown) from the reticle stage RST, a measurement reticle R _"T on the reticle stage RST Next, main controller 50 performs reticle alignment for measurement reticle R ″ _T , as in the case of measurement reticle R _T described above. This completes the reticle alignment of the measurement reticle R ″ _T , and the reticle center substantially coincides with the optical axis of the projection optical system PL.

Next, in the main controller 50, the illumination light EL is turned on.
Reticle R "_TTo irradiate and expose. This makes
Each measurement pattern 67 of the resist layer on the roof W has already been measured._{i, j}
Reduced image (latent image) 67 '_{i, j}Each area S where the
_{i, j}, The corresponding reference pattern 76 _{i, j}Overlap each other
Transcribed. In the case of this embodiment, the reference pattern 76_{i, j}
When transferring the wafer, the illumination area, the Z position of the wafer W and the X position
The inclination with respect to the Y plane is first measured 67_{i, j}Turn over
Since it is set to the optimum state when copying it, those
It is not necessary to make adjustments or settings.

In this way, all exposure is completed.
In the main controller 50, a wafer loader (not shown) is used.
And unload the wafer W from the Z tilt stage 58.
Connected to the chamber 11 inline.
The illustrated coater / developer (abbreviated as "C / D" below)
Send) to. Then, the development of the wafer W is performed in the C / D.
And the matrix is formed on the wafer W after the development.
Areas S arranged in a line _{i, j}The same arrangement as in Fig. 6 (B)
A resist image of the measurement pattern and the reference pattern is formed by
To be done.

After that, the wafer W which has been developed is
Then, the overlay error is measured for each region S _{i, j} by using an external overlay measuring device (registration measuring device), and based on this result, each measurement pattern 67 _{i, The} positional error (positional shift amount) of the resist image of _j with respect to the resist image of the corresponding reference pattern 76 _{i, j} is calculated.

In this way, for each area S _{i, j}
The positional shift amount (Δ′ξ, Δ′η) of the measurement pattern with respect to the reference pattern in the X and Y two-dimensional directions is obtained.

In the present embodiment, the amount of positional deviation (Δ′ξ, Δ′η) in the X and Y two-dimensional directions of the measurement pattern with respect to the reference pattern for each area S _{i, j} obtained as described above. ) Data is
It is input to the main controller 50 via the input / output device 44 of FIG. It is also possible to input the data of the calculated positional deviation amount (Δ′ξ, Δ′η) for each region S _{i, j} from the external overlay measuring device to the main controller 50 online. is there.

In any case, in response to the above input,
The main controller 50 uses the table data stored in the memory (information on the Z position on the surface of the wafer W at the 14 × 14 matrix array points) to determine the amount of positional deviation (Δ′ξ, Δ′η). ), The true positional deviation amount (Δξ, Δη) that directly reflects the wavefront aberration of the projection optical system PL, in which the positional deviation component caused by the defocus remaining at the time of transferring each measurement pattern 67 _{i, j} described above is corrected. )
Is calculated in the same procedure as in the first embodiment described above, and the wavefront aberration of the projection optical system PL is calculated based on the calculated positional deviation amount (Δξ, Δη).

Also in the second embodiment, the maintenance of the exposure apparatus is periodically performed, and the measurement reticle R ′ _T , R ″ _T described above is used to measure the wavefront aberration in the procedure described above. Based on the measurement result, the projection optical system PL is adjusted in the same manner as in the first embodiment. Further, also in the manufacturing process of the exposure apparatus, the projection optical system PL is attached to the exposure apparatus main body. After that, the measurement of the wavefront aberration and the adjustment of the projection optical system PL based on the measurement are performed in the same manner as in the first embodiment.

According to the second embodiment described above,
It is possible to obtain the same effect as that of the first embodiment described above. In addition to this, in this embodiment, when measuring the optical characteristics (wavefront aberration) of the projection optical system PL, the measurement reticle R ′ is used.
_T, by exchanging the measurement reticle R _"T, since the transfer of the reference pattern can be performed in one exposure,
It is possible to reduce the exposure time, and hence the time required to measure the optical characteristics of the projection optical system, as compared with the case where the transfer of the reference pattern is performed by the step-and-repeat method. Further, since the positioning error of the stage at the time of transferring each reference pattern is not included in the error factor of the positional deviation amount, the improvement of the measurement accuracy can be expected.

In each of the above-described embodiments, the wafer stage WST is used when acquiring the information on the flatness of the surface of the wafer W.
(Wafer W) is moved in the X-axis direction and the Y-axis direction from the initial position by a distance half the arrangement pitch of the detection points of the focus sensor, and as a result, an interval of half the arrangement pitch of the detection points of the focus sensor. Although the information on the Z position on the surface of the wafer W at the matrix-shaped arrangement points arranged in the XY two-dimensional direction is obtained in the above, the present invention is not limited to this. That is, when acquiring the information on the flatness of the surface of the wafer W described above, the wafer stage WST is stepwise moved in the X-axis direction and the Y-axis direction within the range of the arrangement pitch of the detection points of the focus sensor with reference to the initial position. Then, the Z position information on the surface of the wafer W at the detection point of the focus sensor may be acquired for each moving position. In this case, the distance between the steps does not have to be constant. Further, the movement distance between steps in the X-axis direction and the Y-axis direction may not be the same. If the distance between the detection points of the focus sensor is wide to some extent and only the Z position information of the wafer surface at each detection point obtained at one time from the focus sensor is used, the Z position information of the wafer surface between the detection points is detected when the wafer surface has irregularities. This is because the measurement accuracy of the flatness of the wafer surface is deteriorated due to the lack of the measurement value, and the measurement accuracy can be improved by the amount of information that can supplement the measurement accuracy. From this meaning, the shorter the above step distance is, the better, but if it is too short, the number of times of measurement increases and the measurement time increases accordingly. Considering the balance between the required measurement accuracy and the measurement time, It is desirable to determine the distance between the above steps. Alternatively, the wafer stage WST is moved stepwise in the X-axis direction and the Y-axis direction at a predetermined step pitch within the range of the arrangement pitch of the detection points of the focus sensor with respect to the initial position, and the focus sensor is detected at each movement position. The Z position information of the surface of the wafer W at the point is acquired. Then, based on the obtained Z position information, an interpolation calculation for calculating an approximate curved surface or the like may be performed using an appropriate interpolation function, for example, a three-dimensional bi-spline function or other function. In the case of such interpolation calculation, it is possible to accurately obtain the information on the flatness of the surface of the wafer W without making the predetermined step pitch so short.

Further, the wafer W is placed on the wafer stage WST.
If the flatness of the surface of the wafer W can be measured after loading, the flatness of the wafer W may be measured using a measuring device other than the focus sensor described above. Further, before loading the wafer W on the wafer stage WST, or before loading the wafer W into the exposure apparatus, the flatness may be measured using, for example, an optical sensor or an atomic force microscope.

In each of the above embodiments, the measurement pattern 67 is obtained based on the obtained information on the flatness of the wafer W.
_At the time of transferring _{i, j} (and the reference pattern), at least one of the Z position of the wafer W and the inclination with respect to the XY plane is adjusted, and the position deviation amount obtained by actual measurement is corrected. The invention is not limited to this.

That is, at least one of the Z position of the wafer W and the inclination with respect to the XY plane is adjusted when the measurement pattern 67 _{i, j} is transferred (and the reference pattern) based on the information on the flatness of the wafer W. It's just good. In such a case, adjustment of at least one of the Z position of the projection optical system PL of the wafer W and the inclination with respect to the XY plane is performed in consideration of the measured flatness of the wafer. Is performed so that the region on the wafer irradiated with is coincident with the image plane as much as possible (within the range of the depth of focus of the best imaging plane of the projection optical system). Therefore, the transfer image of the measurement pattern is formed on the wafer with a very small amount of positional deviation due to defocusing of the wafer surface. That is, the amount of positional deviation of the transfer position of the measurement pattern from the reference position (the position of the resist image of the reference pattern in the above embodiment) hardly includes the positional deviation component caused by defocusing of the wafer surface. The positional deviation amount reflects the optical characteristics of PL almost as it is. Then, by obtaining the optical characteristic of the projection optical system PL (wavefront aberration in the above embodiment) based on the amount of positional deviation, the optical characteristic of the projection optical system PL can be accurately measured.

Alternatively, the obtained information on the flatness of the wafer W is not particularly considered when transferring the measurement pattern 67 _{i, j} (and the reference pattern), and the transfer is finally performed. The obtained amount of positional deviation of the transfer position of the measurement pattern 67 _{i, j} from the reference position (the position of the resist image of the reference pattern in the above embodiment) is corrected based on the information on the flatness of the wafer W. You may only do it.
In this case, when the measurement patterns 67 _{i, j} are transferred, as in the conventional case, the wafer is moved in the optical axis direction of the wafer so that the average surface of the entire wafer surface coincides with the image plane of the projection optical system as closely as possible. Positioning and tilt correction will be performed. Therefore, the above correction of the positional deviation amount uses the information of the wafer flatness and the average surface to measure the residual defocus amount at the time of transfer of the measurement pattern, for each projection position of each measurement pattern, It is performed in the same manner as in the above-described embodiment, and is performed by correcting the position shift component due to the defocus. However, the corrected positional deviation amount obtained in this case is also the positional deviation amount that directly reflects the wavefront aberration of the projection optical system PL. Therefore, by calculating the wavefront aberration of the projection optical system in the same manner as described above based on the corrected position shift amount, the wavefront aberration can be accurately obtained.

In the above description, when obtaining the wavefront aberration of the projection optical system, the information on the obtained flatness of the wafer W is taken into consideration to correct the positional deviation amount which is the premise of the calculation of the wavefront aberration. However, the wavefront aberration of the projection optical system is calculated based on the positional deviation amount (actually measured value), and the calculated wavefront aberration is corrected in consideration of the flatness information of the wafer W. However, the corrected wavefront aberration may be used as the final wavefront aberration. The point is that the final wavefront aberration may be obtained by a predetermined calculation based on the information on the flatness of the wafer W and the amount of positional deviation.

In each of the above embodiments, after the measurement pattern (and the reference pattern) is transferred onto the wafer W,
Although the wavefront aberration of the projection optical system PL is calculated based on the measurement result of the resist image obtained by developing the wafer, the invention is not limited to this, and the measurement pattern and the reference pattern of the measurement pattern formed on the resist layer are not limited to this. The latent image or the image obtained by etching the wafer may be measured. Even in such a case, the amount of displacement from the reference position of the latent image or etching image of the measurement pattern (for example, the projected position of the designing measurement pattern or the position of the latent image or etching image of the reference pattern) is measured. If so, it is possible to obtain the wavefront aberration of the projection optical system based on the measurement result in the same procedure as in the above-described embodiments. Further, in the above-described embodiment, the amount of positional deviation described above is measured using the overlay measuring device, but other than that, for example, an alignment sensor or the like provided in the exposure apparatus may be used.

In each of the above embodiments, the case where the wavefront aberration is obtained as the optical characteristic of the projection optical system has been described, but the present invention is not limited to this. That is, the optical characteristic is not limited to the wavefront aberration, and may be any optical characteristic that is obtained based on the amount of displacement of the projection position of the measurement pattern on the mask from the predetermined reference position, such as coma aberration, astigmatism, It may be various aberrations such as spherical aberration, field curvature, and distortion.

In each of the above embodiments and the above description, a reference pattern, which is a reference for the amount of misalignment of each measurement pattern, is transferred onto a wafer, and the transferred image (a resist image, an etching image, a latent image, etc.) is transferred. (Including the above) is used as a reference to measure the amount of positional deviation of each measurement pattern, but the present invention is not limited to this, and a design value may be used as the reference position, or the visual field (illumination) of the projection optical system. Within a light irradiation area), prepare a reference wafer on which a plurality of reference patterns are formed in the same positional relationship as the plurality of measurement points where measurement patterns should be arranged, and apply resist to the reference wafer for measurement. When the patterns are transferred in an overlapping manner, the position shift amount of the measurement pattern may be measured using the position of the reference pattern on the reference wafer as the reference position at each measurement point. At this time, the positional relationship (interval, etc.) of the plurality of reference patterns on the reference wafer is measured, and the above-mentioned positional deviation amount is obtained for each measurement pattern using this measurement result, or It is desirable to correct the measurement result of the optical characteristics. As a result, it is possible to reduce the measurement error of the optical characteristic due to the manufacturing error of the reference substrate (positional error of the reference pattern, etc.).

Further, at least one measurement pattern may be formed on the reticle without forming a plurality of measurement patterns on the reticle corresponding to the projection visual field (illumination light irradiation area) of the projection optical system PL. In this case, the reticle is moved within the object plane (first plane) of the projection optical system. At this time, a positioning error that may occur when the reticle stage RST is moved is measured, for example, for each position where the measurement pattern is to be arranged, and the above-mentioned positional deviation amount is obtained for each measurement pattern using this measurement result. Alternatively, it is desirable to correct the measurement result of the optical characteristics of the projection optical system. Further, although the measurement reticle is used in the above embodiment, for example, at least one measurement pattern is formed on the reticle stage RST, and
A plate on which a pinhole is formed when measuring the optical characteristics of the projection optical system may be arranged close to the pattern surface of the reticle, or a pinhole plate may be provided on the lower surface of the reticle stage close to the measurement pattern. . That is, the pattern forming member on which the measurement pattern is formed is not limited to the mask or the reticle, and is a concept including a pattern plate provided on the reticle stage, for example. Further, when forming a plurality of measurement patterns on the pattern forming member, the positional relationship (interval, etc.) is measured in the same manner as the reference pattern described above, and the measurement result is used to obtain the amount of positional deviation described above. Alternatively, it is preferable to correct the measurement result of the optical characteristics.

In each of the above embodiments, the case where the present invention is applied to the stepper has been described. However, the present invention is not limited to this, and the mask and the substrate disclosed in, for example, US Pat. No. 5,473,410 may be used. The present invention can also be applied to a scanning type exposure apparatus that moves in synchronism to transfer a mask pattern onto a substrate.

The application of the exposure apparatus is not limited to the exposure apparatus for semiconductor manufacturing, and for example, an exposure apparatus for liquid crystal for transferring a liquid crystal display element pattern to a rectangular glass plate, a thin film magnetic head, a micromachine. And DNA
It can be widely applied to exposure apparatuses for manufacturing chips and the like. Further, not only microdevices such as semiconductor elements, but also glass substrates or silicon wafers for manufacturing reticles or masks used in light exposure apparatuses, EUV exposure apparatuses, X-ray exposure apparatuses, electron beam exposure apparatuses, etc. The present invention can also be applied to an exposure apparatus that transfers a circuit pattern onto a substrate.

The light source of the exposure apparatus of the above embodiment is
Not only UV pulse light sources such as F ₂ laser light source, ArF excimer laser light source, KrF excimer laser light source, but also ultra-high pressure mercury lamps that emit g-line (wavelength 436 nm), i-line (wavelength 365 nm) and other bright lines can be used. Is.

Further, a single-wavelength laser light in the infrared region or visible region emitted from a DFB semiconductor laser or a fiber laser is amplified by a fiber amplifier doped with, for example, erbium (or both erbium and ytterbium) to obtain a nonlinear It is also possible to use a harmonic wave whose wavelength is converted into ultraviolet light using an optical crystal. Further, the magnification of the projection optical system is not limited to a reduction system, and may be a unity magnification system or a magnification system.

For semiconductor devices, the step of designing the function / performance of the device, the step of producing a reticle based on this design step, the step of producing a wafer from a silicon material, and the reticle of the reticle by the exposure apparatus of the above-described embodiment. Transferring the pattern to the wafer,
It is manufactured through a device assembly step (including a dicing process, a bonding process, a packaging process), an inspection step, and the like.

[0161]

As described above, according to the optical characteristic measuring method of the present invention, the optical characteristic of the projection optical system can be measured with high accuracy.

Further, the adjusting method of the projection optical system according to the present invention has an effect that the optical characteristics of the projection optical system can be adjusted with high accuracy.

Further, according to the exposure method of the present invention, there is an effect that the mask pattern can be accurately transferred onto the substrate. Further, according to the method for manufacturing an exposure apparatus according to the present invention, such an exposure apparatus can be manufactured.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an exposure apparatus according to a first embodiment.

FIG. 2 is a schematic perspective view showing a measurement reticle.

FIG. 3 is a diagram showing a schematic view of an XZ section in the vicinity of the optical axis of a measurement reticle in a state of being mounted on a reticle stage together with a schematic diagram of a projection optical system.

FIG. 4 is a diagram showing, together with a schematic diagram of a projection optical system, a schematic diagram of an XZ cross section in the vicinity of the −Y side end portion of a measurement reticle in a state of being loaded on a reticle stage.

5A is a diagram showing a measurement pattern formed on the measurement reticle of the first embodiment, and FIG.
FIG. 6B is a diagram showing a reference pattern formed on the measurement reticle of the first embodiment.

6A is a diagram showing a reduced image (latent image) of a measurement pattern formed at a predetermined interval on a resist layer on a wafer, and FIG. 6B is a diagram showing FIG. FIG. 7A is a diagram showing a positional relationship between the latent image of the measurement pattern and the latent image of the reference pattern.

FIG. 7 is a schematic perspective view showing one measurement reticle used in the optical characteristic measuring method according to the second embodiment.

FIG. 8 is a schematic perspective view showing another measuring reticle used in the optical characteristic measuring method according to the second embodiment.

9A and 9B are views for explaining a conventional technique.

[Explanation of symbols]

10 ... Exposure device, 67 _{i, j} ... Measurement pattern, 70 _{i, j} ...
Pinhole-shaped opening, 74 ₁ , 74 ₂ ... Reference pattern, E
L ... Illumination light, PL ... Projection optical system, R ... Reticle (mask), W ... Wafer (substrate).

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03F 9/00 H01L 21/30 516A F term (reference) 2F065 AA02 AA03 AA04 AA20 BB02 BB27 CC00 EE00 FF10 FF41 FF51 HH12 JJ01 JJ03 JJ08 NN20 PP12 PP13 QQ17 QQ18 QQ23 QQ25 QQ41 2G086 HH06 5F046 BA04 BA05 CB17 CB25 DA13 DB05

Claims (9)

[Claims] 1. An optical characteristic measuring method for measuring an optical characteristic of a projection optical system for projecting a pattern on a first surface onto a second surface, wherein flatness of a substrate arranged on the second surface is measured. First to measure
In the state where at least one of a position of the substrate in the optical axis direction of the projection optical system and an inclination with respect to a plane orthogonal to the optical axis is adjusted in consideration of the measured flatness, the first step A second step of illuminating the measurement pattern arranged on the surface with illumination light and transferring the measurement pattern onto the substrate through the projection optical system; and from a reference position of a transfer position of the measurement pattern. And a third step of obtaining the optical characteristic of the projection optical system based on the positional deviation of the optical characteristic measuring method. 2. The method further comprises a fourth step of illuminating a reference pattern arranged on the first surface with the illumination light, and transferring the reference pattern onto the substrate via the projection optical system. The optical characteristic measuring method according to claim 1, wherein in the three steps, the optical characteristic is obtained by using the transfer position of the reference pattern as the reference position. 3. In the second step, a plurality of the measurement patterns are arranged on the first surface in a predetermined positional relationship, and
The plurality of measurement patterns are illuminated with illumination light, and each of the plurality of measurement patterns is provided on the substrate through a pinhole and the projection optical system that are individually provided for the respective measurement patterns. The wavefront aberration, which is one of the optical characteristics of the projection optical system, is obtained based on the positional deviation of the transfer position of each of the measurement patterns from the reference position in the third step. 1. The optical characteristic measuring method described in 1. 4. A plurality of reference patterns are arranged on the first surface so as to correspond to the plurality of measurement patterns, respectively, and the plurality of reference patterns are illuminated by the illumination light. The method further includes a fourth step of transferring each onto the substrate via the projection optical system, and in the third step, based on a positional deviation of a transfer position of each of the measurement patterns from a transfer position of a corresponding reference pattern. The optical characteristic measuring method according to claim 3, wherein a wavefront aberration of the projection optical system is obtained. 5. The optical characteristic of the projection optical system is determined in the third step, further considering the measured flatness. Optical characteristic measurement method. 6. An optical characteristic measuring method for measuring an optical characteristic of a projection optical system for projecting a pattern on a first surface onto a second surface, the flatness of a substrate arranged on the second surface being measured. First to measure
A second step of illuminating the measurement pattern arranged on the first surface with illumination light and transferring the measurement pattern onto the substrate through the projection optical system; And a third step of obtaining an optical characteristic of the projection optical system based on a displacement amount of a transfer position from a reference position and the measured flatness. 7. A step of measuring an optical characteristic of a projection optical system by using the optical characteristic measuring method according to claim 1, and the projection optical system based on a measurement result of the optical characteristic. Adjusting the projection optical system. 8. An exposure method for transferring a pattern of a mask onto a substrate via a projection optical system, the step of adjusting the projection optical system by the adjusting method according to claim 7, and the adjusted projection. A step of transferring the pattern onto the substrate via an optical system; 9. A method for manufacturing an exposure apparatus, which transfers a mask pattern onto a substrate via a projection optical system, wherein the exposure method uses the optical characteristic measuring method according to any one of claims 1 to 6. A method of manufacturing an exposure apparatus, comprising: measuring an optical characteristic of an optical system; and adjusting the projection optical system based on a measurement result of the optical characteristic.