JP2003318083A - Optical characteristic measuring method, adjusting method of optical system, exposing method and device, and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate influence of a measurement error caused by a difference in an incident angle and to measure the characteristics of an optical system with high accuracy. <P>SOLUTION: In a state that incident angle (θ<SB>1</SB>, θ<SB>2</SB>and the like) of energy beams through the optical system are different, an object W having a photoresistive layer RL on the surface thereof is exposed, and images having a plurality of patterns are formed on the object. Next, the object formed with the images having a plurality of patterns are developed. Thus, transfer images (L1, L2 and the like) having the plurality of patterns are formed on the object. Next, each positional information of the transfer images having a plurality of patterns obtained after the development is measured. Taking into consideration a film thickness t of the photoresistive layer and the incident angle θ<SB>1</SB>, θ<SB>2</SB>or the like of the energy beams, the positional information is corrected in each transfer image, and the characteristics of the optical system are calculated by using the positional information of each of the corrected transfer image. Accordingly, it becomes possible to eliminate influences of the measurement error caused by a difference in the incident angle and to measure the characteristic of the optical system with high accuracy. <P>COPYRIGHT: (C)2004,JPO

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, an optical system adjusting method, an exposure method and apparatus, and a device manufacturing method, and more particularly, to exposing a photosensitive object by an energy beam through the optical system. Then, an optical characteristic measuring method for forming an image of a plurality of patterns on the photosensitive object and measuring the transferred image formed on the object after development to obtain the characteristic of the optical system, and the optical characteristic measuring method. The present invention relates to an adjusting method for adjusting an optical system based on a result, an exposure method and an exposure apparatus using a projection optical system adjusted by the adjusting method, and a device manufacturing method using the exposure 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. In order to perform such 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 for 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 the substrate on which the projected image of the measurement pattern is transferred is developed. A method of calculating optical characteristics based on a measurement result obtained by measuring the obtained resist image (hereinafter, referred to as “baking method”) is mainly used.

In the conventional exposure apparatus, low order aberrations such as so-called Seidel's 5 aberrations such as spherical aberration, coma aberration, astigmatism, field curvature, distortion (distortion) are measured by the above-mentioned printing method. It has been mainly performed to adjust and manage the above-mentioned various aberrations of the projection optical system based on the measurement result.

However, semiconductor devices are becoming highly integrated year by year,
Along with this, the exposure apparatus is required to have an exposure performance with higher accuracy, and in recent years, it has become insufficient to adjust only the above-mentioned low-order aberrations. Therefore,
The optical characteristics of the projection optical system including higher order aberrations can be measured by measuring the wavefront aberration of the projection optical system not only during assembly in the exposure equipment manufacturing plant but also after installation in the clean room of the semiconductor manufacturing plant. The need for maintenance has arisen.

As a technique for measuring the wavefront aberration using the above-mentioned printing method, a mask having a special structure is used, and a plurality of measurement patterns on the mask are individually provided with pinholes and projection optics. In addition to printing on the substrate sequentially through the system, the reference pattern on the mask is printed on the substrate via the projection optical system without passing through the condenser lens and pinhole, and multiple measurements are obtained as a result of each printing. U.S. Pat. No. 5,978,085 discloses an invention relating to a technique for calculating a wavefront aberration by measuring a positional deviation amount of each resist image of a work pattern with respect to a resist image of a reference pattern and performing a predetermined calculation.

In addition, as a method of measuring the defocus amount of the projection optical system, for example, in Japanese Patent Laid-Open No. 2002-55435, the diffraction efficiencies of the plus first-order diffracted light and the minus first-order diffracted light as test marks are different (for example, This test mark is used by using a test pattern including an asymmetrical diffraction grating pattern (where the diffraction efficiency is zero) and a reference pattern for obtaining a reference image when measuring the deviation of the image of this asymmetrical diffraction grating pattern. A method is disclosed in which the amount of defocus of the projection optical system is measured in one measurement by printing on a substrate via the projection optical system and measuring the resist image thereof. According to the method disclosed in this publication, the amount of lateral shift of the image of the asymmetric diffraction grating pattern in proportion to the defocus can be quantified, and the defocus amount with a sign can be easily and accurately measured.

[0009]

However, when the technique disclosed in the above-mentioned US patent is applied to an actual stepper or the like to measure the wavefront aberration of the projection optical system, it is different in the field of view of the projection optical system. Since each of the plurality of measurement patterns arranged at the position corresponding to the position on the mask is sequentially printed on the substrate through the individually provided pinhole and projection optical system, each measurement pattern is measured. Light fluxes originating from the pattern pass through different positions on the pupil plane. The difference in the passing position affects the shape of the transfer image (resist image) of each measurement pattern formed on the substrate, and as a result, causes a final measurement error of the wavefront aberration. As a result of such research, it was recently found.

That is, since the light beams originating from the respective measurement patterns that have passed through different positions on the pupil plane have different incident angles with respect to the substrate, the resist image formed on the substrate after development has its sectional shape. Becomes a parallelogram, and the inclination angle is different for each measurement pattern.
As a result, the line widths measured for the resist images of the respective measurement patterns formed under the same conditions are different from each other, and the difference in the line widths is the difference in the shift amount of the center position for each resist image of the measurement patterns. It becomes a factor. On the other hand, the reference pattern is placed near the optical axis of the projection optical system and is printed on the substrate while being fixed at that position and without passing through the pinhole, so that the light flux originating from the reference pattern is projected. The passing position on the pupil plane of the optical system is always the same position. Therefore, the resist image of the reference pattern has almost no shift of the center position, and even if there is any, the resist image of any reference pattern has the same shift amount.

However, until now, the difference in the shift amount of the center position for each resist image due to the difference in the inclination angle of the resist image has not been known, and therefore the position information for each resist image of the measurement pattern is known. It is clear that the wavefront aberration cannot be accurately obtained even if the measurement error differs (such as the amount of positional deviation from the reference pattern) and the position information including the measurement error is used.

Further, in the measuring method described in JP-A-2002-55435, as is clear from FIG. 5 of the publication, diffracted light (interference fringes) generated from the asymmetric diffraction grating pattern is formed on the substrate. It is incident at a predetermined incident angle other than 0 °. On the other hand, the diffracted light generated from the reference pattern is incident on the substrate at an incident angle different from the above incident angle. Therefore,
Even in the measuring method described in Japanese Patent Laid-Open No. 2002-55435, the same measurement error as described above may occur.

In addition, in the method of measuring the characteristics of the optical system using the printing method, when the resist images having a plurality of patterns are formed on the substrate with different incident angles, the difference in the inclination angle of the resist image is caused. The resulting measurement error can occur as well.

The present invention has been made under the above circumstances, and a first object thereof is to eliminate the influence of a measurement error due to the difference in the incident angle of the energy beam at the time of image formation and to improve the characteristics of the optical system. An object of the present invention is to provide an optical characteristic measuring method capable of measuring accurately.

A second object of the present invention is to provide an adjusting method of an optical system capable of adjusting its optical characteristics with high accuracy.

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

A fourth object of the present invention is to provide a device manufacturing method capable of improving device productivity.

[0018]

According to a first aspect of the present invention, an object having a photosensitive layer on its surface is exposed with different incident angles of energy beams through an optical system, and a plurality of patterns are formed on the object. The second step of developing the object on which the images of the plurality of patterns are formed; and the position information of each of the transfer images of the plurality of patterns obtained after the development is measured. Third step: taking into consideration the film thickness of the photosensitive layer and the incident angle of the energy beam, the position information is corrected for each transfer image, and the corrected position information of each transfer image is used. And a fourth step of calculating the characteristic of the optical system.

According to this, an object having a photosensitive layer on its surface is exposed in a state where the incident angles of the energy beams through the optical system are different, and a plurality of patterns of images are formed on the object. The object having the images of the plurality of patterns is then developed. As a result, a plurality of patterns of transferred images are formed on the object. Next, the position information of each of the transfer images of the plurality of patterns obtained after the development is measured. Then, the position information is corrected for each transfer image in consideration of the film thickness of the photosensitive layer and the incident angle of the energy beam, and the characteristic of the optical system is calculated using the corrected position information of each transfer image. . That is, the characteristic of the optical system is calculated using the position information in which the measurement error due to the difference in the incident angle of the energy beam that may be included in the measurement result of the position information of each pattern is corrected. Therefore, according to the present invention, it is possible to eliminate the influence of the measurement error caused by the difference in the incident angle of the energy beam at the time of image formation and to accurately measure the characteristics of the optical system.

In this case, as in the optical characteristic measuring method according to claim 2, in the fourth step, the positional information is corrected by further considering the image forming condition in the first step. can do.

In this case, as in the optical characteristic measuring method according to the third aspect, the considered image forming conditions are:
The integrated energy amount applied to the object in the first step may be included.

In each of the optical characteristic measuring methods described in claims 2 and 3, as in the optical characteristic measuring method described in claim 4, the considered image forming condition is that the photosensitive layer on the object is formed. It is also possible to include a distribution of the film thickness according to the position on the object. That is, as the image forming condition, only the distribution of the film thickness of the photosensitive layer on the object according to the position on the object may be considered, or the cumulative energy amount irradiated to the object may be considered together with this distribution. It may be done.

In each of the optical characteristic measuring methods described in claims 1 to 4, as in the optical characteristic measuring method described in claim 5, the image formation in the first step is performed by the optical system of the energy beam. It can be performed by using a mask in which a pattern that makes the passing position on the pupil plane different is formed.

In this case, as in the optical characteristic measuring method according to the sixth aspect, the mask has measurement patterns arranged at a plurality of evaluation points in the visual field of the optical system,
At each of the evaluation points, the energy beam can be incident on the optical system via the measurement pattern and the pinhole. Here, it suffices if there is at least one measurement pattern on the mask, and the measurement patterns may be simultaneously arranged at a plurality of measurement points in the field of view, or one measurement pattern may be sequentially evaluated. It may be placed at a point. Further, at least one pinhole pattern may be provided in the same manner as the measurement pattern, on the mask or separately from the mask and corresponding to the measurement pattern.

In the optical characteristic measuring method according to the fifth aspect, as in the optical characteristic measuring method according to the seventh aspect, the mask has a plurality of masks corresponding to a plurality of evaluation points in the visual field of the optical system. It may have a phase shift pattern. Alternatively, as in the optical characteristic measuring method according to the eighth aspect, the mask may have a plurality of measuring patterns whose forming conditions are different from each other. In the latter case, the measurement patterns need not be arranged at a plurality of evaluation points, and each measurement pattern may be a phase shift pattern or a normal pattern that is not a phase shift. In the case of this normal pattern, for example, the pitch may be different among a plurality of measurement patterns. However,
For example, it is necessary to cut unnecessary order diffracted light generated from the measurement pattern, or to irradiate each measurement pattern with energy beams having different incident angles. Moreover, it is not necessary to form a plurality of measurement patterns on the same mask.

In the optical characteristic measuring method according to any one of claims 1 to 5, as in the optical characteristic measuring method according to claim 9, the image formation in the first step is performed by the optical system. At least one of an illumination condition and an imaging condition of a pattern to be formed on the object via the optical system can be changed so that the passing position of the energy beam is different on the pupil plane. . Here, for example, the incident angle of the energy beam may be changed, or unnecessary diffracted light may be cut.
May be combined with the mask.

In each of the optical characteristic measuring methods described in claims 1 to 9, as in the optical characteristic measuring method described in claim 10, the position information is information on the relative position between each of the transferred images and the reference pattern. Can be

In this case, as in the optical characteristic measuring method according to claim 11, in the fourth step, the wavefront aberration of the optical system is calculated by using the corrected position information of each of the transferred images. Can be

In the optical characteristic measuring method according to any one of claims 1 to 9, as in the optical characteristic measuring method according to claim 12, the position information is relative position information between the transferred images. Can be

The invention according to claim 13 is the invention according to claims 1 to 1.
2. A method of adjusting an optical system, comprising: a step of measuring a characteristic of an optical system by the optical characteristic measuring method according to any one of 2); and a step of adjusting the optical system based on the measurement result.

According to this, by the optical characteristic measuring method according to any one of claims 1 to 12, the characteristic of the optical system is not affected by the measurement error caused by the difference in the incident angle of the energy beam at the time of image formation. The measurement is performed with high accuracy, and the optical system is adjusted based on the measurement result. Therefore, the optical characteristics of the optical system can be adjusted with high accuracy.

According to a fourteenth aspect of the present invention, there is provided an exposure method for transferring a device pattern formed on a mask onto an object having a photosensitive layer formed on the surface thereof via a projection optical system.
An exposure method comprising: a step of adjusting the projection optical system by the adjusting method according to claim 13; and a step of projecting an image of the device pattern onto the object by using the adjusted projection optical system. .

According to this, since the projection optical system is adjusted by the adjusting method according to the thirteenth aspect, the optical characteristics of the projection optical system are adjusted with high accuracy. Then, the image of the device pattern is projected onto the object by using the projection optical system whose optical characteristics are adjusted with high accuracy. Therefore, the device pattern can be accurately formed on the object.

According to a fifteenth aspect of the present invention, there is provided an exposure method for transferring a device pattern formed on a mask onto an object having a photosensitive layer formed on the surface thereof via a projection optical system.
The optical characteristic of the projection optical system is measured by the measuring method according to claim 1, and an image formation state of the device pattern on the object is measured based on the measured optical characteristic. The exposure method is characterized by adjusting.

According to this, the optical characteristic of the projection optical system is measured with high accuracy by the measuring method according to any one of claims 1 to 12, and the object is based on the optical characteristic measured with high accuracy. The imaging state of the device pattern above is adjusted. Therefore, the device pattern can be accurately formed on the object. Here, the adjustment of the imaging state is
An adjustment method according to the measured optical characteristics is adopted, for example, adjustment of the position of the object in the optical axis direction of the optical system, shift of the wavelength of the energy beam, or adjustment of the projection optical system,
Alternatively, an appropriate combination of at least two of these can be adopted.

A sixteenth aspect of the invention is a device manufacturing method including a lithographic step of transferring a device pattern onto the object using the exposure method according to the fourteenth or fifteenth aspect.

According to a seventeenth aspect of the present invention, there is provided an exposure apparatus which irradiates an energy beam on a mask and transfers the device pattern formed on the mask onto an object having a photosensitive layer formed on the surface thereof. An exposure apparatus comprising: a projection optical system adjusted by the adjusting method according to claim 10, which projects an energy beam emitted from the object onto the object.

According to this, since the projection optical system adjusted by the adjusting method according to claim 13 is provided as the projection optical system for projecting the energy beam emitted from the mask onto the object, this projection optical system is provided. The optical characteristics of the system are adjusted with high precision. Then, at the time of exposure, the energy beam is applied to the mask on which the device pattern is formed, and the energy beam emitted from the mask is projected onto the object having the photosensitive layer formed on the surface by the projection optical system. The device pattern is transferred to the photosensitive layer on the object. Therefore, the device pattern can be accurately transferred onto the object.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG.
~ It demonstrates based on FIG.

FIG. 1 shows an exposure apparatus 10 according to one embodiment.
Is shown. This exposure apparatus 10 is a step-and-repeat type 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 the wafer W (on the image plane) as an object, and a substrate on which the Z tilt stage 58 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
For example, a light source that outputs pulsed light in the far 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 the present embodiment) 22 and the like, and 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 is used to change the light quantity distribution of illumination light (shape and size of the secondary light source) on the pupil plane of the illumination optical system, that is, the illumination condition of the reticle R. However, instead of or in combination with the aperture stop plate 24, it is possible to move along the optical axis of the illumination optical system and a plurality of diffractive optical elements that are arranged interchangeably on the optical path of the illumination optical system. An optical unit including at least one of at least one prism (a conical prism, a polyhedral prism, etc.) and the zoom optical system described above is arranged between the light source 16 and the optical integrator (fly-eye lens) 22, and the optical integrator (fly The intensity distribution of the illumination light on the incident surface of the (eye lens) 22 or the incident angle range of the illumination light can be changed to change the above-mentioned illumination conditions. It is preferable to suppress the Nau light loss to a minimum.

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 structure, 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 in this way
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 suction-held 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 rotation) 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 reticle stage RST is measured with a predetermined resolution (for example, a resolution of about 0.5 to 1 nm) by a position detector (not shown), for example, a reticle laser interferometer, and the measurement result is sent to main controller 50. It is being supplied.

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 lenses movable in the projection optical system PL are not limited to the above-mentioned four lenses, and the number thereof and the position in the projection optical system PL may be arbitrary. Further, the mechanism for adjusting the image forming characteristics of the projection optical system PL is not limited to the above-mentioned lens driving, but the wavelength of the illumination light EL is shifted, or the refractive index is changed in a part of the projection optical system PL. It does not matter which method is used.

The wafer stage WST can be freely driven in the XY two-dimensional plane by the wafer stage drive section 56. The wafer W is electrostatically attracted (or vacuum attracted) on the Z tilt stage 58 mounted on the wafer stage WST via a wafer holder (not shown).
And so on. The Z tilt stage 58 has the function of adjusting the position (focus position) of the wafer W in the Z direction and adjusting the tilt angle of the wafer W with respect to the XY plane. The X, Y position and rotation (including yawing, pitching, and rolling) of wafer stage WST are fixed to movable mirror 5 fixed on Z tilt stage 58.
An external wafer laser interferometer 54W measures through 2W, and the measured value of the wafer laser interferometer 54W is supplied to the main controller 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 almost flush with the surface.

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 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 measurement 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 entire 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 attachment member 62, n circular openings 63 _{i, j} (i = 1 to p, i = 1 to p, i = 1 to p
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, a first pattern 67 _{i, j} is formed on the lower surface of the glass substrate 60 so as to face each of the condenser lenses 65 _{i, j} .
The first pattern 67 _{i, j} is a pattern including a measurement pattern described later as a part thereof. In addition, the opening plate 66,
As shown in FIG. 3, pinhole-shaped openings 70 _{i, j} are formed to face the first patterns 67 _{i, j} , respectively. 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 second pattern 74 ₁ is formed on the lower surface (pattern surface) of the glass substrate 60 so as to face one opening 72 ₁ . Here, the second pattern is a pattern including a reference pattern described later as a part thereof. Although not shown, the second pattern 74 is formed on the lower surface (pattern surface) of the glass substrate 60 so as to face the other opening 72 _2.
The second pattern similar to ₁ (for convenience, "second pattern 7
4 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 are arranged on both outsides of the lens holding member 62 in a symmetrical arrangement with respect to the center of the reticle. RM2 is formed.

Here, in the present embodiment, the first pattern 6
7 _{i, j} are formed in a mesh-shaped (street line-shaped) light-shielding pattern 67a as shown in FIG. 5A, and in a central portion in each of the square divided regions divided by the light-shielding pattern 67a. A pattern including a square frame pattern, that is, a measurement pattern 67b composed of square frame patterns arranged in a matrix at a predetermined pitch is used. The first pattern 67 _{i, j} is a positive pattern (so-called unremoved pattern) formed by removing the chromium layer, which is the light-shielding portion, by patterning so that the light-shielding pattern 67a and the measurement pattern 67b remain.

Corresponding to the above first pattern 67 _{i, j} ,
As the second patterns 74 ₁ and 74 _2, as shown in FIG. 5B, the same pitch as the first pattern 67 _{i, j} (more accurately, the street line formed at the same pitch as the measurement pattern 67 b). -Shaped reference pattern 74a, and a square frame-shaped light-shielding pattern 74 formed in the central portion of each of the square divided areas divided by the reference pattern 74a
A pattern including b and is used. The second patterns 74 ₁ and 74 ₂ are positive patterns (so-called residual patterns) formed by removing the chromium layer, which is the light shielding portion, by patterning so that the reference pattern 74a and the light shielding pattern 74b remain.

Here, the first pattern 67 _{i, j} and the second pattern 67 _{i, j}
The relationship with the pattern 74 ₁ will be described based on FIGS. 6 (A) to 6 (C).

FIG. 6A shows an end view in which a part of the first pattern 67 _{i, j} is cross-sectioned, and FIG. 6B shows the first pattern 67 _{i, j} in a state of being aligned with the first pattern. An end view of a portion of two patterns is shown. From FIG. 6A and FIG. 6B, the relationship between the measurement pattern 67b and the light-shielding pattern 74b is that the measurement pattern 67b (more accurately, the measurement pattern 67b is formed in the light-shielding region of each light-shielding pattern 74b). It can be seen that there is a relationship in which each of the constituent square frame patterns) is completely included. Similarly, it can be seen that the reference pattern 74a and the light blocking pattern 67a have a relationship in which the reference pattern 74a is completely included in the light blocking region of the light blocking pattern 67a.

Therefore, the first pattern 67 _{i, j} is transferred to the resist layer on the wafer W, and the second pattern 74 ₁ (or 74 ₂ ) is superposed on the area where the latent image of the first pattern is formed. After the transfer, when the wafer W is developed, the wafer W
Assuming that the first pattern 67 _{i, j} and the second pattern 74 ₁ (or 74 ₂ ) are accurately superimposed on each other, a resist image as shown in FIG. 6C is formed. It will be. In FIG. 6C, reference numeral 67b '
Is a resist image of the measurement pattern 67b (more accurately, a square frame-shaped pattern that constitutes the measurement pattern 67b), and reference numeral 74a ′ is a resist image of a part of the reference pattern 74a.

As described above, in the present embodiment, the resist image finally formed on the wafer W is only the resist image of the measurement pattern and the reference pattern, and the above-mentioned light-shielding pattern is the remaining pattern and the positive pattern. It is merely provided for convenience so that a desired pattern can be formed because the resist is used. Therefore, in the following description, the above-mentioned first pattern is referred to as a measurement pattern 67 _{i, j} ,
The second pattern will be referred to as the reference pattern 74 ₁ (or 74 ₂ ).

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, in main controller 50, a pair of reticle alignment marks RM1, on reticle R _T for measurement is used.
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 onto Z tilt stage 58 using a wafer loader (not shown).

Next, the main controller 50 includes all of the condenser lenses 65 _{i, j} of the measurement reticle R _T and does not include the openings 72 ₁ and 72 ₂ , and the lens holding member 62 in the X-axis direction. 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.

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. 7A 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 the 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 wafer stage WST is moved while monitoring the measurement value of the laser interferometer 54W so that the approximate center of the upper region substantially coincides with the optical axis 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 in an overlapping manner onto the region (referred to as 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, in the area S _1,1 on the wafer W, as shown in FIG. 7B, the latent image 67 ′ _1,1 of the measurement pattern 67 _{1,1 and} the latent image 74 of the reference pattern 74 ₁ are formed. ' ₁ is formed in the positional relationship shown in the same figure.

Next, in the main controller 50, the 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.

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. 7B are formed in the region S _{i, j} on the wafer W. A latent image is formed.

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 (C)
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.

In this way, for each area S _{i, j} ,
X, Y of the measurement pattern 67 _{i, j} with respect to the reference pattern
The positional deviation amount (Δξ _{i, j} , Δη _{i, j} ) in the two-dimensional direction is calculated.

Here, prior to the explanation of the calculation of the wavefront, the physical relationship between the positional deviation amount (Δξ _{i, j} , Δη _{i, j} ) and the wavefront will be briefly explained with reference to FIGS. 3 and 4. To do.

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_{k, l}
Of the projection optical system
The position passing through the pupil plane of PL is different. That is, of the pupil plane
The wavefront at each position is the measurement pattern corresponding to that position.
67_{i, j}(67_{k, l}) The wavefront of light through the position at
It corresponds to. Then, if the projection optical system PL has an aberration,
If there is no wavefront, their wavefronts are
In the pupil plane of L, the code F₁The ideal wavefront (see
It should be flat). However, there is no aberration
There is no projection optical system, so there is no projection optical system on the pupil plane.
Is, for example, a curved wavefront F as shown by a dotted line.₂
Becomes Therefore, the measurement pattern 67_{i , j}The statue of
Wave front F on W₂Shift according to the inclination of the ideal wavefront
The image is formed at the selected position.

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 _{i, j} , Δη _{i, j} )
Is 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 amount of positional deviation (Δξ _{i, j} , Δη _{i, j} ). As is clear from the physical relationship between the positional deviation amount (Δξ _{i, j} , Δη _{i, j} ) and the wavefront, the wavefront calculation principle in this embodiment is
This is the well-known Shack-Hartman principle of wavefront calculation.

Incidentally, in FIG. 3, for convenience of illustration, of the many diffracted lights generated in the respective measurement patterns 67 _{i, j} , a typical light among the lights passing through the corresponding pinhole-shaped openings 70 _{i, j.} Although only light is shown, each light passes through different positions on the pupil plane of the projection optical system PL, and the incident angle on the wafer W differs depending on the position. In this case, the incident angle of each light is determined by the measurement pattern 67.
Arrangement of _{i, j} in the visual field of the projection optical system PL, pitches, line widths, etc. of square frame patterns forming each measurement pattern, pinhole-shaped openings 70 _{i, j} and each measurement pattern 67 _{i. ,} determined by the positional relationship between the _j, the projection optical system PL
The position corresponds to the passing position on the pupil plane.

Here, when the incident angle of the light contributing to the image formation on the wafer W is not zero, the resist image obtained after developing the wafer W is at the reference position (reference pattern in the case of the present embodiment). (The position of the resist image as a reference) does not actually deviate from the position, the position is deviated and measured by an overlay measuring instrument or the like. This point will be described below.

FIG. 8A shows an end view in which a part of the resist image formed on the wafer W is sectioned. In FIG. 8A, reference characters L1 and L2 are part of the resist image of the measurement pattern, and reference characters L3, L4 and L5 are part of the resist image of the reference pattern. Resist image L
1 and L2 are formed by the lights respectively incident on the resist layer RL at the incident angles θ ₁ and θ ₂ shown in FIG. 8B. Here, the resist images L1 and L
2 will be explained. These resist images L1 and L
2 is measured by an overlay measuring device or other image processing device, and assuming that the designed line width is d and the resist layer RL has a uniform thickness t, the line widths of the resist images L1 and L2 are measured. The values L1 ′ and L2 ′ are expressed by the following equations (1) and (2).

L1 ′ = d + Δd ₁ (1) L2 ′ = d + Δd ₂ (2) Here, Δd ₁ and Δd ₂ represent the positional deviation amounts shown in FIG. 8A.

However, Δd ₁ and Δd ₂ are as shown in FIG.
As is clear from the geometrical relation of,
Display as in (4).

Δd ₁ = t · tan θ ₁ (3) Δd ₂ = t · tan θ ₂ (4) Therefore, the shift amounts δ ₁ and δ ₂ of the center positions of the resist images L 1 and L ₂ are respectively calculated by the following equations. It becomes like (5) and (6).

[0100] _{δ 1 = (d + Δd 1} ) / 2-d / 2 = Δd 1/2 = t · tanθ 1/2 ...... (5) δ 2 = (d + Δd 2) / 2-d / 2 = Δd 2 / _{2 = t · tanθ 2/2} ...... (6) However, in this case, resist image L1 is closer only [delta] ₁ to resist image L4 of the reference pattern of the left, resist image L2 is the resist image L4 to the right Go away by δ ₂ .

However, in general, the lines of the resist image of the same measurement pattern have the same incident angles θ ₁ and θ ₂ (see FIG. 9). That is, θ ₁ = θ ₂ = θ holds.

Therefore, in the following description, the corresponding reference pattern 74 ₁ (or 7) of the resist image 67 ′ _{i, j} of the measurement pattern 67 _{i, j} caused by the incident angle θy _{i, j} in the XZ plane will be described.
4 ₂ ) position error in the X-axis direction with respect to the resist image δx _{i, j}
Is-(t · tan θy _{i, j} ) / 2 or + (t · tan
θy _{i, j} ) / 2 (where θy _{i, j} ≧ 0).

Similarly, with respect to the resist image of the corresponding reference pattern 74 ₁ (or 74 ₂ ) of the resist image 67 ′ _{i, j} of the measurement pattern 67 _{i, j} due to the incident angle θx _{i, j} in the YZ plane. The position error δy _{i, j} in the Y-axis direction is − (t · tan
θx _{i, j} ) / 2, or + (t · tan θx _{i, j} ) / 2 (where θx _{i, j} ≧ 0).

Here, the incident angle θx _{i, j} and the incident angle θy _{i, j}
Is determined by the arrangement of each measurement pattern 67 _{i, j} in the visual field of the projection optical system PL and the positional relationship between the pinhole-shaped opening 70 _{i, j} and each measurement pattern 67 _{i, j.} It is determined according to the passing position on the pupil plane of the system PL. That is, it is calculated according to the design value without actually requiring measurement.

As can be seen from the above description, the incident angle of the light contributing to image formation is different for each measurement pattern 67 _{i, j} , that is _, for each region S _{i, j} on the wafer W. As an example, FIG. 9 shows that the incident angles of the light are different in three regions S _{a, b} , S _{k, l} , and S _{t, u} out of the p × q = n regions. ing.

Therefore, in the present embodiment, the main controller 50
However, prior to the calculation of the wavefront (wavefront aberration) described later, the above-mentioned positional displacement amounts (Δξ _{i, j} , Δη _{i, j} ) are calculated as δx _{i, j} and δ
Position information corrected using y _{i, j} (Δξ ′ _{i, j} , Δη ′
_{i, j} ) = (Δξ _{i, j} −δx _{i, j} , Δη _{i, j} −δy _{i, j} ) and calculates the wavefront aberration of the projection optical system PL based on the position information as described later. It is supposed to be calculated.

Next, a method for calculating the wavefront based on the above position information, that is, the corrected position shift amount (Δξ ′ _{i, j} , Δη ′ _{i, j} ) will be briefly described.

As described above, the positional deviation amount after correction (Δξ ′
_{i, j} , Δη ′ _{i, j} ) corresponds to the inclination of the wavefront, and the shape of the wavefront (strictly speaking, the deviation from the reference plane (ideal wavefront)) is obtained by integrating this. 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 following relational expressions (7) and (8) are established.

[0109]

[Equation 1]

Since it is not easy to directly integrate the slope of the wavefront, which is given only by the amount of displacement, it is assumed that the surface shape is developed into a series and fitted to it. 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 (9).

[0111]

[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 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, since the derivative is detected as the above-mentioned positional deviation amount, 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 (10) and (11).

[0114]

[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 (7) to (11) is 2
N (= about 162 to 800). From now on, for example, 2
Error for each coefficient to determine the coefficient of 7 much smaller (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, in this embodiment, as described above,
Each area S obtained by_{i, j}Against the reference pattern for
Amount of misalignment of measuring pattern in X, Y two-dimensional direction
(Δξ _{i, j}, Δη_{i, j}) Data is
Input to the main controller 50 via the input / output device 44 of FIG.
I will be forced. Note that the calculation was performed from an external overlay measuring instrument.
Each area S_{i, j}Amount of displacement (Δξ_{i, j}, Δ
η_{i, j}) Data to the main controller 50 online
It is also possible to enter.

In any case, in response to the above input,
In the CPU in the main controller 50, first, the following equation (12),
The calculation of (13) is performed.

Δξ ′ _{i, j} = Δξ _{i, j} −δx _{i, j} (12) Δη ′ _{i, j} = Δη _{i, j} −δy _{i, j} (13)

Next, the CPU corresponds to each area S _{i, j} based on the position information (Δξ ′ _{i, j} , Δη ′ _{i, j} ) using a predetermined arithmetic program according to the above-mentioned principle. ,
That is, the wavefront (wavefront aberration) corresponding to the first measurement point to the nth measurement point in the field of view of the projection optical system PL, here, the coefficient of each term of the Zernike polynomial, for example, the coefficient Z ₂ to the third term of the second term.
The coefficient Z _{36 of the} 6th term is calculated.

In the exposure apparatus 10 of the present embodiment, when manufacturing a semiconductor device, a reticle R for manufacturing a device is loaded on the reticle stage RST as a reticle, and then the 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 this exposure apparatus 10, maintenance is periodically performed, and at that time, the wavefront aberration is measured using the above-described measurement reticle R _{T according} to the procedure described above, and based on the measurement result. Thus, the projection optical system PL is adjusted. This adjustment is performed, for example, by the main control device 50 based on the measurement result of the wavefront aberration, astigmatism, coma aberration, distortion, field curvature (or focus), low-order aberration such as spherical aberration, that is, Seidel's 5 aberrations. Etc., and gives a command to the imaging characteristic correction controller 48 to correct these aberrations. As a result, the imaging characteristic correction controller 48 controls the applied voltage to a predetermined drive element that drives at least one predetermined movable lens of the movable lenses 13 _{1 to} 13 ₄ in at least one degree of freedom direction, and At least one of the position and the posture of the predetermined movable lens is adjusted, and the imaging characteristics of the projection optical system PL, such as distortion, field curvature, coma aberration, spherical aberration, and astigmatism, 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. At the same time, 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. 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, the above adjustment is performed using the 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 of the degrees of freedom is calculated according to the amount calculation program, and a command value of this adjustment amount 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 image forming characteristics of the projection optical system PL, such as distortion, field curvature, and coma aberration,
Spherical aberration, astigmatism, etc. are corrected. Regarding coma aberration, spherical aberration, and astigmatism, not only low-order aberrations but also high-order aberrations can be corrected.

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, in the optical adjustment of the projection optical system PL that is performed after being incorporated into the exposure apparatus main body, the measurement of the wavefront aberration of the projection optical system PL is performed using the measurement reticle R _T described above. I do. Then, based on this wavefront aberration result, Seidel aberration and the like are corrected in the same manner as during the above-mentioned maintenance. If necessary, the assembling of the lens or the like is readjusted based on the higher order aberrations. 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. The presence or the position of the element may be specified, and the re-machining 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.

By the way, as in this embodiment, the positional relationship between the image of the measurement pattern formed on the resist layer on the wafer and the image of the reference pattern is measured, and the positional relationship is measured when the measurement pattern is formed. When the optical characteristics of the projection optical system (wavefront aberration, etc.) are calculated based on the corrected position information after correction based on the incident angle of exposure light and the resist thickness, the thickness of the resist layer The above-mentioned correction amount is different. Therefore, if there is unevenness in the film thickness of the resist layer on the wafer surface and there is a film thickness distribution, an error will be included in the measurement result of the optical characteristics. Therefore, it is desirable that the thickness of the resist layer be substantially constant when measuring the optical characteristics of the projection optical system. However, as a practical matter, it is not easy to always make the thickness of the resist layer constant and uniform when the resist is applied onto the wafer using a spin coater or the like.

Therefore, when the optical characteristic of the projection optical system is measured using the same measurement reticle as the above-mentioned measurement reticle R _T , before the measurement is started, the optical method or the contact needle method is used. The thickness unevenness of the resist layer on the wafer used for measurement is measured and the measurement result is stored.
Then, in the same procedure as described above, the measurement pattern and the reference pattern are sequentially transferred onto the wafer, and the wafer is developed. Then, the positional relationship between the image of the measurement pattern formed on the wafer after the development and the image of the reference pattern is measured, and when the measured positional relationship is corrected as described above, it is stored in advance. It is desirable to further consider the uneven film thickness. By doing so, the optical characteristics (wavefront aberration, etc.) of the projection optical system PL can be accurately obtained without being affected by the unevenness of the resist film thickness.

When the integrated energy amount (exposure dose amount) of the illumination light EL irradiated on the wafer W via the measurement reticle R _T and the projection optical system is changed, the state of formation of the resist image after development is changed. (For example, including its film thickness) changes. This means that the formation state of the resist image after development can be controlled by changing the exposure dose amount. Therefore, by further considering the exposure dose amount, by correcting the positional relationship between the image of the measurement pattern and the image of the reference pattern formed on the wafer after the development described above,
More accurate position information (Δξ ' _{i, j} , Δη' _{i, j} )
Can be obtained.

In the present embodiment, the resist image forming conditions are as follows: unevenness of the resist layer thickness on the wafer (thickness of the resist layer at the position where each resist image is formed on the wafer) and exposure dose amount. At least one of the above is taken into consideration, but instead of this or in addition thereto, other forming conditions such as uneven development of the wafer may be taken into consideration. The point is that the type and number of the forming conditions are arbitrary. I do not care.

Then, the optical characteristic of the projection optical system PL, for example, the wavefront aberration is obtained based on the position information. As a result, it is possible to measure the wavefront aberration with high accuracy, and by adjusting the projection optical system PL based on the measurement result, it is possible to accurately adjust the optical characteristics of the projection optical system, such as various aberrations. Is possible.

As described above, according to the present embodiment, when measuring the optical characteristics (wavefront aberration) of the projection optical system PL, a plurality of evaluation points provided in the visual field of the projection optical system PL are provided. for measurement pattern 67 _{i, j} and the measurement pattern 67 _i, a pinhole 70 i provided corresponding individually to _j, reticle for measurement and a _j R _T is the projection optical system P
It is arranged on the object plane of L. Therefore, the passing position of the illumination light EL on the pupil plane of the projection optical system PL via each measurement pattern 67 _{i, j} varies depending on the measurement pattern 67 _{i, j} . As a result, the wafer W having the resist layer on the surface is exposed in a state where the incident angle of the illumination light EL via the projection optical system PL is changed according to the position within the field of view for each measurement pattern, and the wafer W is exposed. Images of the plurality of measurement patterns 67 _{i, j} are formed on the upper surface.

Next, the reference pattern 74 ₁ (or 74 ₂ ) on the measurement reticle R _T is positioned on the optical axis of the projection optical system PL without using a pinhole and in a step-and-repeat system. Then, the measurement pattern 67 _{i, j} on the wafer W is transferred onto the area S _{i, j} where the latent image is formed.

Next, the plurality of measurement patterns 67
Image of _{i, j} and corresponding reference pattern 74 ₁ (or 74 ₂ )
The wafer W on which the image of is formed is developed. This allows
Images of the plurality of measurement patterns 67 _{i, j} and corresponding resist images of the reference pattern 74 ₁ (or 74 ₂ ) are formed on the wafer W. Next, the positional information of each of the resist images (transfer images) of the plurality of measurement patterns 67 _{i, j} obtained after the development, in this case, the positional deviation amount (Δξ _{i, j} , with respect to the resist image of the corresponding reference pattern, Δη _{i, j} ) is measured. Then, in consideration of the film thickness of the resist layer and the incident angle of the illumination light EL, the above-mentioned position information (Δξ is calculated for each resist image of the measurement pattern 67 _{i, j} by the calculation of the above equations (12) and (13). _{i, j} , Δη _{i, j} ) is corrected, and the position information (Δ) of the resist image of each corrected measurement pattern 67 _{i, j} is corrected.
ξ ′ _{i, j} , Δη ′ _{i, j} ), the characteristics of the projection optical system PL,
In this case, the wavefront aberration is calculated.

Therefore, according to the optical characteristic measuring method according to the present embodiment, the influence of the measurement error caused by the difference in the incident angle of the illumination light EL at the time of image formation is eliminated, and the characteristic (wavefront aberration) of the projection optical system is accurately measured. It is possible to measure well.

Further, according to the exposure apparatus 10 according to the present embodiment, maintenance is regularly performed, and at that time, the wavefront aberration of the projection optical system PL is measured, and the wavefront aberration of the projection optical system PL is measured. The measurement is performed accurately without the influence of the measurement error caused by the difference in the incident angle of the illumination light EL. Then, the projection optical system PL is adjusted based on this measurement result as described above. Therefore, the imaging characteristics, which are the optical characteristics of the projection optical system PL, such as distortion, field curvature, coma aberration, spherical aberration, and astigmatism, are corrected. At this time, regarding coma aberration, spherical aberration, and astigmatism, not only low-order aberrations but also high-order aberrations can be corrected.

Then, according to the exposure apparatus 10 and the exposure method thereof of the present embodiment, when the semiconductor device is manufactured, the image of the device pattern is formed on the wafer W by using the projection optical system PL in which the above-mentioned image forming characteristics are accurately adjusted. Projected on the top in a step-and-repeat manner. Therefore, the device pattern 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.

In the above embodiment, not only the measurement pattern but also the reference pattern is transferred onto the wafer W when the optical characteristic is measured, but the present invention is not limited to this. . That is, a reference wafer on which a reference pattern is formed in advance may be used as the object to which the measurement pattern is transferred. In this case,
When measuring the optical characteristics of the projection optical system PL, it is sufficient to transfer the measurement pattern. Therefore, the transfer of the reference pattern (normally this transfer is performed by the step-and-repeat method) becomes unnecessary, and The measurement time can be shortened, and the adjustment time of the projection optical system PL can be shortened.

In the above embodiment, the projection optical system PL
Although the case has been described where the wavefront aberration is obtained as the characteristic, the optical characteristic measuring method of the present invention is not limited to this. That is, in the present invention, when measuring the characteristics of an optical system, an object having a photosensitive layer on the surface is exposed by changing the incident angle of the energy beam through the optical system, and images of a plurality of patterns are formed on the object. It can be suitably applied if it forms For example, the above-mentioned Japanese Patent Laid-Open No. 2002
When measuring the field curvature of the projection optical system using the method for measuring the defocus amount of the projection optical system disclosed in Japanese Patent Application Laid-Open No. 55435, it corresponds to a plurality of evaluation regions within the field of view of the projection optical system. Then, a photomask (reticle) on which a plurality of the above-described test marks are arranged is used. This photomask is illuminated with illumination light to simultaneously print a plurality of test marks on the substrate via the projection optical system. At this time, diffracted light (interference fringe) from the asymmetric diffraction grating pattern (a type of phase shift pattern) that constitutes each test mark
Are incident on the wafer at an incident angle corresponding to the position in the visual field of the test mark, that is, the position in the pupil plane of the projection optical system through which the diffracted light that is the source of the interference fringes passes. Therefore, in the resist image of each test mark obtained by developing this wafer, the positional information of the image of the asymmetrical diffraction grating pattern, that is, the measurement result of the amount of displacement from the image of the reference pattern, is the same as in the above embodiment. The measurement error corresponding to the incident angle is also included. Therefore, also in this case, by correcting the position information of the image of the asymmetrical diffraction grating pattern for each test mark described above in consideration of the incident angle and the film thickness of the resist layer, the projection optical system at each evaluation point is corrected. The optical characteristics, for example, the defocus amount with a sign can be measured more accurately, and the defocus amount with a sign at each evaluation point is used to obtain an approximate curved surface by a statistical calculation such as the least squares method. It is possible to accurately obtain the surface curvature.

That is, the characteristic of the optical system targeted by the optical characteristic measuring method of the present invention is not limited to the wavefront aberration, but may be a part of the aberration, that is, the imaging characteristic such as field curvature.
Alternatively, it may be the focus position of the projection optical system. In the above embodiment, in order to adjust the image formation state of the pattern image projected on the wafer by the projection optical system PL,
Based on the optical characteristics measured as described above, the projection optical system PL
However, the method of adjusting the image formation state of the pattern image is not limited to this, and for example, the wavelength of the illumination light EL is slightly changed,
Alternatively, the wafer may be moved relative to the image plane of the projection optical system PL.

Further, as is apparent from the above description, a photomask (which can be used in the optical characteristic measuring method of the present invention, which makes the passing position of the energy beam via the pattern on the pupil plane of the optical system different ( The reticle may be a photomask having a plurality of phase shift patterns corresponding to a plurality of evaluation points in the visual field of the optical system.

Furthermore, in the present embodiment, the passing position of the illumination light EL on the pupil plane of the projection optical system, that is, the incident angle of the illumination light EL on the wafer is determined by using the mask of FIG. 2 or the phase shift mask. Although the pattern images are formed on the wafer by making them different, for example, a mask in which a plurality of measurement patterns having different formation conditions (pitch, etc.) from each other are formed is used, and an undesired order You may cut the diffracted light. Further, the method of forming the pattern image by changing the incident angle of the illumination light EL is not limited to the use of this type of mask, and the illumination condition and the imaging condition of the pattern to be transferred onto the wafer At least one of them may be changed, for example, the incident angle of the illumination light to the pattern may be made different, and unnecessary diffracted light of the diffracted light passing through the projection optical system may be shielded.

Of course, the mask used in the optical characteristic measuring method of the present invention is not limited to the above-mentioned measuring reticle or phase shift mask. At least one measurement pattern may be provided on the mask used in the present invention, and the measurement patterns may be simultaneously arranged at a plurality of measurement points in the visual field of the projection optical system, or one measurement pattern may be provided. The use patterns may be sequentially arranged at each evaluation point. Further, in the case of having a pinhole pattern together with the measurement pattern, at least one pinhole pattern is provided on the mask or on the exposure apparatus side corresponding to the measurement pattern separately from the mask, like the measurement pattern. I'm good.

By the way, also in the measurement of the field curvature using the above photomask, the test mark image forming conditions, for example, the integrated energy amount of the illumination light irradiated to the substrate,
Alternatively, it is desirable to further consider the distribution (film thickness unevenness) of the film thickness of the photosensitive layer on the substrate in accordance with the position on the substrate to correct the position information.

In the embodiment and the measurement of the field curvature described above, the positional relationship (relative position information) between the image of each measurement pattern (or asymmetrical diffraction grating pattern) and the corresponding image of the reference pattern is measured. In addition, the case where the measurement error used for the correction is calculated for each measurement pattern has been described, but the position information to be corrected and the method of obtaining the position error are not limited to these. For example, the measurement error (shift amount of the center position) of the image of any one measurement pattern is measured, and this measurement error is used as a reference,
The measurement error in each of the images of other measurement patterns may be calculated. Further, the position information to be corrected is not limited to the relative position information (positional deviation amount, etc.) between the image of the measurement pattern and the image of the reference pattern, but relative position information between the images of the measurement pattern. And so on,
Further, it is not limited to the relative position information, and may be the coordinate position of the actually measured image.

Besides, the optical characteristic measuring method of the present invention can be suitably applied not only to the projection optical system but also to the characteristic of the illumination optical system, for example, the measurement of the coherence factor σ value (illumination σ) of the illumination optical system. In this case, for example, the light source image is transferred onto the measurement wafer. At the time of such transfer, first, the measurement reticle on which the minute opening pattern is formed is loaded on the reticle stage RST, and the measurement wafer is loaded on the Z tilt stage 58. Then, the relationship between the arrangement position of the measurement reticle and the arrangement position of the measurement wafer is
It is set to a positional relationship (a positional relationship in which the pupil plane of the projection optical system PL and the surface of the measurement wafer are optically conjugate positions with respect to each other) shifted from the conjugate relationship with respect to the projection optical system PL by a predetermined amount.
The measurement reticle is illuminated by the Koehler illumination method. Then, the light that has passed through the minute aperture pattern of the measurement reticle passes through the projection optical system PL to expose the surface of the measurement wafer by the light, and the optical integrator, for example, a fly-eye lens is projected onto the measurement wafer. The light source image formed on the side focal plane is transferred. Then, the measurement wafer to which the light source image has been transferred is developed, and a predetermined calculation is performed based on the imaging result of the resist image formed on the wafer surface after the development to obtain the illumination σ.

As is clear from the description of the process of transferring the light source image onto the wafer, in this case as well, similar to the above embodiment, the minute aperture pattern of the measurement reticle causes the illumination light on the pupil plane of the projection optical system. Since the passing positions at are different, by using the optical characteristic measuring method of the present invention,
No further explanation will be needed on the possibility of improving the measurement accuracy.

In the above embodiment, the case where the resist image formed on the wafer is measured by using a dedicated measuring device such as an overlay measuring device outside the exposure apparatus has been described. Of course, it is not limited to. For example, a wafer alignment system (not shown) provided in the exposure apparatus may be used. In this case,
The wafer alignment system, for example, irradiates a target mark with a broadband detection light flux that does not expose the resist on the wafer, and reflects the light from the target mark to form an image of the target mark on the light receiving surface and an index (not shown). An image processing type image forming type alignment sensor (so-called FIA (Filed Image Alignment) system) for picking up an image with an image pickup device (CCD) and outputting the image pickup signals may be used, or coherent detection light. An alignment sensor for irradiating a target mark with light, detecting scattered light or diffracted light generated from the target mark, or interferingly detecting two diffracted light (for example, of the same order) generated from the target mark. Is also good.

In the above embodiment, 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 US Pat. No. 5,473,410 are synchronized. It can also be applied to a scanning type exposure apparatus that moves to transfer the pattern of the mask onto the 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 onto a rectangular glass plate, a plasma display, an organic EL, or the like. The present invention can be widely applied to the display device, the thin film magnetic head, the exposure machine for manufacturing the micromachine, the DNA chip 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.

In addition, 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. Furthermore, the exposure illumination light EL is not limited to ultraviolet light, but may be EUV light or charged particle beams such as electron beams and ion beams.

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 erbium (or both erbium and ytterbium), and a nonlinear It is also possible to use a harmonic wave whose wavelength is converted into ultraviolet light using an optical crystal. Further, the projection optical system may be not only a reduction system but also an equal magnification system or a magnification system, and may be a catadioptric system or a reflection system as well as a refraction system.

<< Device Manufacturing Method >> Next, an embodiment of a device manufacturing method in which the above-described exposure apparatus is used in a lithography process will be described.

FIG. 10 shows devices (semiconductor chips such as IC and LSI, liquid crystal panel, CCD, thin film magnetic head,
A flow chart of a manufacturing example of a micromachine etc. is shown. As shown in FIG. 10, first, step 20
In 1 (design step), a device function / performance design (for example, circuit design of a semiconductor device) is performed, and a pattern design for realizing the function is performed. Then, in step 202 (mask making step),
A mask on which the designed circuit pattern is formed is manufactured. On the other hand, in step 203 (wafer manufacturing step),
A wafer is manufactured using a material such as silicon.

Next, in step 204 (wafer processing step), the mask and wafer prepared in steps 201 to 203 are used to form an actual circuit or the like on the wafer by lithography or the like, as described later. . Next, in step 205 (device assembly step), device assembly is performed using the wafer processed in step 204. In this step 205,
Steps such as a dicing step, a bonding step, and a packaging step (chip encapsulation) are included as necessary.

Finally, step 206 (inspection step)
In step 1, inspections such as an operation confirmation test and a durability test of the device created in step 205 are performed. After these steps, the device is completed and shipped.

FIG. 11 shows a detailed flow example of step 204 in the semiconductor device. In FIG. 11, in step 211 (oxidation step), the surface of the wafer is oxidized. Step 212 (CV
In step D), an insulating film is formed on the wafer surface. In step 213 (electrode forming step), electrodes are formed on the wafer by vapor deposition. Step 214
In the (ion implantation step), ions are implanted in the wafer. Each of the above steps 211 to 214 constitutes a pretreatment process in each stage of wafer processing, and is selected and executed in accordance with a required process in each stage.

At each stage of the wafer process, after the above-mentioned pretreatment process is completed, the posttreatment process is executed as follows. In this post-treatment process, first, step 2
In 15 (resist formation step), a photosensitive agent is applied to the wafer. Subsequently, in step 216 (exposure step), the circuit pattern of the mask is transferred onto the wafer by the lithography system (exposure apparatus) and the exposure method described above. Next, in step 217 (developing step), the exposed wafer is developed, and in step 2
In 18 (etching step), the exposed member of the portion other than the portion where the resist remains is removed by etching. Then, in step 219 (resist removing step), the unnecessary resist after etching is removed.

By repeating these pre-processing step and post-processing step, multiple circuit patterns are formed on the wafer.

When the device manufacturing method of this embodiment described above is used, the exposure apparatus and the exposure method of the above embodiment are used in the exposure step (step 216), so that the device pattern on the mask is accurately formed on the wafer. Can be transcribed. As a result, it is possible to improve the productivity (including the yield) of highly integrated devices.

[0164]

As described above, according to the optical characteristic measuring method of the present invention, the influence of the measurement error caused by the difference in the incident angle of the energy beam at the time of image formation is eliminated, and the characteristic of the optical system is accurately measured. The effect is that it can be measured.

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

Further, according to the exposure method and apparatus of the present invention, there is an effect that the mask pattern can be accurately transferred onto the object.

Further, according to the device manufacturing method of the present invention, there is an effect that the productivity of the device can be improved.

[Brief description of drawings]

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

FIG. 5A is a diagram showing a measurement pattern formed on the measurement reticle according to the embodiment, and FIG.
FIG. 4A is a diagram showing a reference pattern formed on a measurement reticle according to an embodiment.

FIG. 6A is an end view in which a part of a first pattern (measurement pattern) 67 _{i, j} is shown in cross section, and FIG.
FIG. 9 is an end view in which a part of a second pattern (reference pattern) in a state of being aligned with the first pattern is sectioned.

7A 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. 7B is a diagram showing FIG. FIG. 4B is a diagram showing a positional relationship between the latent image of the measurement pattern of FIG.

8A is an end view in which a part of a resist image formed on a wafer W is sectioned, and FIG. 8B is a sectional view of FIG.
It is a figure which shows the incident angles (theta) ₁ , (theta) ₂ of the exposure light when forming the resist images L1 and L2 of (A).

FIG. 9 is a diagram illustrating a case where an image of a measurement pattern is formed on a plurality of regions S _{i, j} on a wafer, the incident angle of exposure light is different for each region, and the incident angles are almost the same for the same region. It is a figure which shows how it has become.

FIG. 10 is a flowchart showing an embodiment of a device manufacturing method of the present invention.

11 is a flowchart showing an example of a specific process of step 204 of FIG.

[Explanation of symbols]

10 ... Exposure device, 67 _{i, j} ... Measurement pattern, 74 ₁ , 7
4 ₂ ... Reference pattern, PL ... Projection optical system (optical system), E
L ... Exposure light (energy beam), W ... Wafer (object),
_RT ... Reticle for measurement (mask for measuring optical characteristics).

Claims (17)

[Claims] 1. A first step in which an object having a photosensitive layer on its surface is exposed with different incident angles of an energy beam through an optical system, and a plurality of patterns of images are formed on the object.
A second step of developing the object on which the images of the plurality of patterns are formed; a third step of measuring position information of each transfer image of the plurality of patterns obtained after the development;
In consideration of the film thickness of the photosensitive layer and the incident angle of the energy beam, the position information is corrected for each transfer image, and the characteristic of the optical system is used by using the corrected position information of each transfer image. And a fourth step of calculating. 2. The optical characteristic measuring method according to claim 1, wherein in the fourth step, the positional information is corrected by further considering the image forming condition in the first step. 3. The image forming conditions to be changed are:
The optical characteristic measuring method according to claim 2, further comprising an integrated energy amount applied to the object in the first step. 4. The conditions for forming the image to be changed are:
The optical characteristic measuring method according to claim 2, further comprising a distribution of a film thickness of the photosensitive layer on the object according to a position on the object. 5. The image formation in the first step is performed by using a mask on which a pattern is formed to make different passage positions of the energy beam on the pupil plane of the optical system. Item 5. The optical characteristic measuring method according to any one of Items 1 to 4. 6. The mask has a measurement pattern arranged at a plurality of evaluation points within a field of view of the optical system, and the energy beam is passed through the measurement pattern and a pinhole at each evaluation point. The optical characteristic measuring method according to claim 5, wherein the light is incident on the optical system. 7. The optical characteristic measuring method according to claim 5, wherein the mask has a plurality of phase shift patterns corresponding to a plurality of evaluation points in the visual field of the optical system. 8. The optical characteristic measuring method according to claim 5, wherein the mask has a plurality of measurement patterns whose forming conditions are different from each other. 9. The image formation in the first step is a pattern to be formed on the object via the optical system so that the passing position of the energy beam is different on the pupil plane of the optical system. At least 1 side of an illumination condition and an imaging condition is changed, The optical characteristic measuring method as described in any one of Claims 1-5 characterized by the above-mentioned. 10. The optical characteristic measuring method according to claim 1, wherein the position information is information on a relative position between each of the transferred images and a reference pattern. 11. The optical characteristic measuring method according to claim 10, wherein in the fourth step, the wavefront aberration of the optical system is calculated using the position information of each of the corrected transfer images. . 12. The optical characteristic measuring method according to claim 1, wherein the position information is relative position information between the transferred images. 13. A step of measuring a characteristic of an optical system by the optical characteristic measuring method according to claim 1, and a step of adjusting the optical system based on the measurement result. How to adjust the optical system. 14. An exposure method for transferring a device pattern formed on a mask onto an object having a photosensitive layer formed on the surface thereof via a projection optical system, wherein the projection optical method comprises the adjustment method according to claim 13. An exposure method comprising: adjusting a system; and projecting an image of the device pattern on the object using the adjusted projection optical system. 15. An exposure method for transferring a device pattern formed on a mask onto an object having a photosensitive layer formed on a surface thereof via a projection optical system, the method comprising: The exposure method is characterized by measuring the optical characteristic of the projection optical system by the measuring method and adjusting the image formation state of the device pattern on the object based on the measured optical characteristic. 16. A device manufacturing method including a lithography step of transferring a device pattern onto the object using the exposure method according to claim 14 or 15. 17. An exposure apparatus for irradiating a mask with an energy beam, and transferring the device pattern formed on the mask onto an object having a photosensitive layer formed on the surface thereof. An exposure apparatus, comprising: a projection optical system adjusted by the adjustment method according to claim 13, which projects onto the object.