WO2002025711A1

WO2002025711A1 - Method of measuring image characteristics and exposure method

Info

Publication number: WO2002025711A1
Application number: PCT/JP2001/008177
Authority: WO
Inventors: Hiroki Okuno; Masahiko Okumura
Original assignee: Nikon Corporation
Priority date: 2000-09-21
Filing date: 2001-09-20
Publication date: 2002-03-28
Also published as: AU2001288073A1; CN1462471A; JPWO2002025711A1; KR20030033067A

Abstract

A method of measuring image characteristics capable of high-precision measurement of the image characteristics of a projection optical system according to illuminating conditions at exposure and an atmospheric pressure surrounding the projection optical system, and an exposure method. With reference marks (34A, 34B) illuminated from the interior of a sample table (24) by illuminating light having the same wavelength as that of exposure light, positional deviations of reticle marks (37A, 37B) from images, via a projection optical system (PL), of the reference marks (34A, 34B) are measured by reticle alignment microscopes (38A, 38B), and a projection magnification β of the projection optical system (PL) is calculated from this measurement to determine an errorΔβ2 from its reference magnification β0. A correction value Δβ1 for a magnification error according to the illuminating conditions of a reticle (R) at exposure and an atmospheric pressure P surrounding the projection optical system (PL) is subtracted from the determined error Δβ2 to determine an actual residual magnification error Δβ(=Δβ2-Δβ1) at exposure.

Description

Description Measurement method of imaging characteristics and exposure method

The present invention relates to a method of transferring a photolithography-listed mask pattern onto a sensitive substrate for manufacturing a device such as a semiconductor device, an imaging device (such as a CCD), a liquid crystal display device, a plasma, or a thin-film magnetic head. The present invention relates to a method for measuring an imaging characteristic of a projection system of a projection exposure apparatus used, and an exposure method. Further, the present invention relates to a projection exposure apparatus using such a method for measuring an imaging characteristic. Background art

When manufacturing semiconductor devices, etc., the reticle pattern as a mask is transferred via a projection optical system to each shot area on a wafer (or glass plate, etc.) coated with a resist as a sensitive material or a photosensitive material. A projection exposure apparatus such as a stepper is used. For example, a semiconductor device is formed by stacking a dozen or more circuit patterns on a wafer in a predetermined positional relationship. Therefore, a projection exposure apparatus uses a reticle or alignment mark (reticle mark or wafer mark) on the wafer. It has been detected.

There are various methods. For example, an alignment sensor that detects a reticle mark illuminates the reticle mark with illumination light for exposure (exposure light), captures an image with a CCD camera or the like, and processes the obtained image data. A method using exposure light such as the VRA (Visual Reticle Alignment) method that measures the position of a reticle mark by image processing is used. Such a VRA type alignment sensor may be used when measuring imaging characteristics such as a projection magnification of a projection optical system.

Also, in a projection exposure apparatus, if the atmospheric pressure around the projection optical system changes, the refractive index of the entire projection optical system changes, and the projection magnification of the projection optical system changes. For example, a so-called lens controller (LC) is used to correct magnification fluctuations. This is because some lenses that make up the projection optical system The space between the windows is a closed space, and by adjusting the pressure of the gas in the closed space, the fluctuation of the projection magnification due to the atmospheric pressure change is corrected. Furthermore, in order to correct projection magnification errors caused by changes in atmospheric pressure and fluctuations in imaging characteristics such as various aberrations of the projection optical system, a driving member such as a piezo element is arranged on the lens support to adjust the lens interval. And an imaging characteristic control mechanism for controlling the exposure wavelength.

As described above, in the conventional projection exposure apparatus, in order to cope with fluctuations in the imaging characteristics due to a change in atmospheric pressure or the like, the imaging characteristics are controlled using an imaging characteristic control mechanism such as a lens controller. When such an imaging characteristic control mechanism is used, for example, at the start of the exposure sequence, and each time the exposure of a predetermined number of wafers is completed, the imaging characteristic using the VRA type alignment sensor is used. Is measured, and the measured imaging characteristics are set as an initial state, and thereafter, for example, using the amount of fluctuation of the imaging characteristics predicted by empirical rules, the imaging characteristics are set to fall within a predetermined target range. Had control. However, even when measuring the imaging characteristics, the atmospheric pressure around the projection optical system changes, and there is a possibility that an error may occur in the measured values of the imaging characteristics depending on the atmospheric pressure at the time of the measurement. is there. As described above, if an error occurs in the measured value (initial state) of the imaging characteristic itself, the residual error will remain even if the expected fluctuation amount of the imaging characteristic is corrected using the imaging characteristic control mechanism thereafter. Will happen. Such residual errors are considered to be small at present, but as circuit patterns become finer due to higher densities of integrated circuits, the yield of final manufactured devices will deteriorate. There is a fear of inviting.

Also, in a projection exposure apparatus, the illumination condition may be switched to so-called deformed illumination or illumination with a small coherence factor (small illumination) depending on the line width or pattern shape to be exposed. In some cases, the imaging characteristics such as the projection magnification of the projection optical system fluctuate slightly, and the image projected on the wafer may change slightly, resulting in a decrease in the overlay accuracy and the like.

The VRA alignment sensor, which detects the position of the reticle mark, illuminates the target mark with an illumination system separate from the exposure illumination optical system. If the projection magnification of the projection optical system is obtained from the projection optical system, the projection magnification at the time of exposure may be adjusted even if the projection magnification is adjusted based on the obtained projection magnification. There was a risk that an error would occur in the shadow magnification.

In view of the above, the present invention can adjust the imaging state with high accuracy even when the environmental conditions at the time of measuring (detecting) the imaging state (imaging characteristics) of the image of the pattern to be transferred are changed. The primary purpose is to do so.

In addition, the present invention provides a high-precision imaging state even when the illumination condition for measuring (detecting) the imaging state (imaging characteristic) is different from the illumination condition for actual exposure. The second purpose is to be able to adjust Disclosure of the invention

An exposure method according to the present invention illuminates a mask (R) with an exposure beam and transfers a pattern image of the mask onto a substrate (W) via a projection system (PL). The mark (34A, 34B) is detected, and the environmental condition at the time of detection is used when adjusting the image forming state of the pattern image based on the detection result.

According to the present invention, an image formation state (for example, projection magnification) of the pattern image is obtained from the detection result of the mark. In this case, the image formation state thus obtained changes according to the environmental conditions (for example, the atmospheric pressure around the projection system) at the time of detecting the mark. Therefore, for example, the relationship between the environmental condition and the imaging state obtained from the detection result of the mark is obtained and stored in advance, and correction according to the environmental condition is performed, thereby forming the image at the time of the detection. The image state can be measured with high accuracy. Then, using the measurement result, the imaging characteristic of the projection system is corrected so as to cancel the error of the imaging state from the target state, thereby forming the image of the projection image. The image state can be adjusted with high precision. On the other hand, if the adjustment of the imaging characteristics of the projection system is performed by using the value of the imaging state obtained from the detection result of the mark as it is, an adjustment error of the imaging state may remain during actual exposure. There is.

In this case, it is desirable to correct the adjustment amount of the imaging state obtained from the detection result based on the environmental condition. This makes it possible to easily adjust the imaging state with high accuracy.

In addition, the amount of adjustment of the image formation state is, for example, the condition for forming the pattern image and the amount of adjustment. It is determined to include an offset corresponding to the difference from the mark detection condition. For example, the illumination conditions at the time of detection of the mark as conditions for detecting the mark and the illumination conditions at the time of exposure during the actual lithography process as conditions for forming the pattern image include the numerical aperture of illumination light and the shape of the aperture stop. And other conditions may be different. Therefore, for example, the amount of change in the image formation state due to the difference in the illumination conditions is obtained in advance and tabulated, and the measured value of the image formation state obtained from the detection result of the mark is calculated according to the pattern image formation conditions. By performing the correction, the image formation state at the time of exposure can be adjusted with higher accuracy.

In addition, the offset differs as an example according to the pattern image forming conditions, and is corrected according to the environmental conditions. Illumination conditions as the formation conditions include a plurality of conditions such as normal illumination and annular illumination. By changing the offset of the adjustment amount for each of these conditions, the imaging state is enhanced under various conditions. The accuracy can be corrected. Note that the pattern image formation conditions are based on the above-described illumination conditions (ie, a predetermined plane (pupil plane of the illumination system) which has a substantially Fourier transform relationship with the pattern surface of the mask in the illumination system that illuminates the mask with the exposure beam. The intensity distribution of the exposure beam on the pupil plane of the projection system and the numerical aperture of the projection system. Further, the adjustment amount of the imaging state obtained from the detection result may be corrected based on the formation condition of the pattern image.

Next, the projection exposure apparatus according to the present invention comprises an illumination system (1, 3, 6 to 9, 13 to 19) for illuminating the mask (R) with an exposure beam, and a pattern image of the mask (W). ) A projection exposure apparatus having a projection system (PL) for projecting onto a mark, a mark detection system (38A, 38B) for detecting a mark via the projection system, and an environment for detecting the mark. An environment detection system (31) that detects conditions, and an image adjustment system (28, 42, 43) that uses the environmental conditions when adjusting the imaging state of the pattern image based on the detection results , 4 4). According to the present invention, the exposure method of the present invention can be performed.

In this case, it is desirable that the imaging state adjustment system corrects the adjustment amount of the imaging state obtained from the detection result based on the environmental condition.

Also, the imaging state adjustment system adjusts the adjustment amount to the pattern image forming conditions and the It is desirable that the determination be made to include an offset corresponding to a difference from the mark detection condition. Next, the method for measuring the imaging characteristics according to the present invention is a method for measuring the imaging characteristics of a projection system (PL) that projects an image of the object (R) on the first surface onto the second surface (W). A mark (34A) disposed on at least one of the first and second surfaces is detected through the projection system, and a first step (step) of calculating an imaging characteristic of the projection system from the detection result is performed.

10 1, 10 2) and a second step (steps 10 3, 10 3) for correcting the calculation result of the imaging characteristics obtained in the first step based on the environmental conditions at the time of executing the first step. 104).

According to the present invention, for example, the relationship between the environmental condition and the imaging characteristic (for example, projection magnification) of the projection system calculated in the first step is obtained in advance,

By correcting the imaging characteristics calculated in one step according to the environmental conditions, the imaging characteristics of the projection system can be corrected with high accuracy. 'In this case, it is desirable to change the correction amount of the calculation result according to the environmental conditions.

In addition, an offset corresponding to the difference between the mark detection condition and the image forming condition of the object is added to the calculation result to determine a correction amount of the imaging characteristic, and the offset is determined according to the environmental condition. It is desirable to change.

Next, the first and second device manufacturing methods according to the present invention each include a lithographic step of forming a device pattern on a substrate (W) using the exposure method or the projection exposure apparatus of the present invention. According to the present invention, since the exposure method or the projection exposure apparatus of the present invention is used, the image forming state of the pattern image can be adjusted with high accuracy, and a high-performance device can be manufactured. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a configuration diagram showing a projection exposure apparatus used in an example of an embodiment of the present invention. FIG. 2 is a diagram showing the aperture stop plate 9 of FIG. FIG. 3 is a perspective view showing a main part of a stage system and an alignment system of the projection exposure apparatus of FIG. FIG. 4 is an enlarged view showing an image in the observation field of view of the RA microscope 38A of FIG. Figure 5 shows the positional relationship between the reference mark image and the reticle mark during reticle alignment. FIG. FIG. 6 is a diagram showing an example of the relationship between the atmospheric pressure around the projection optical system and the corresponding correction value of the magnification error of the projection optical system. FIG. 7 is a flowchart showing an example of the calibration operation of the projection magnification of the projection optical system. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an example of a preferred embodiment of the present invention will be described with reference to the drawings. In this example, the present invention is applied to control the imaging characteristics of a projection exposure apparatus of a scanning exposure type using a step-and-scan method.

FIG. 1 shows a schematic configuration of a projection exposure apparatus used in the present embodiment. In FIG. 1, an ultraviolet pulse laser beam narrowed at a wavelength of 193 nm from an ArF excimer laser light source 1 is used. The exposure light IL passes through a beam matching unit (BMU) 3 including a movable mirror and the like, and enters a variable dimmer 6 via a light-shielding pipe 5. An exposure controller 29 for controlling the amount of exposure to the resist on the wafer controls the start and stop of light emission of the ArF excimer laser light source 1, the light emission intensity, the oscillation frequency, etc., and the variable light reduction. Adjust the extinction rate in the detector 6. The exposure controller 29 receives information such as the target exposure amount from the main control system 28 that supervises and controls the operation of the entire apparatus, and sends the information such as the actually measured exposure amount to the main control system 28 as described later. Output. As the exposure light (exposure beam), K r F excimer laser (wavelength 2 4 8 nm), K r 2 laser (wavelength 1 4 6 nm), or F ₂ other such laser (wavelength 1 5 7 nm) Laser light, i-line (wavelength 365 nm) of a mercury lamp, or soft X-ray can also be used.

The exposure light IL that has passed through the variable attenuator 6 is incident on an optical integrator (uniformizer or homogenizer) 8 such as a fly-eye lens through a beam shaping optical system including lens systems 7A and 7B. In the present embodiment, it is assumed that a fly-eye lens is used as the optical / integral lens 8 and the exit surface (the exit-side focal plane) of the optical / integral shutter 8 is substantially the same as the pupil plane (Fourier transform plane) of the illumination system. I do. Further, an aperture stop plate 9 of an illumination system is arranged on an emission surface of the optical integrator 8 so as to be rotatable by a drive motor 10. The internal reflection type 8 is referred to as the internal reflection type Or a diffractive optical element may be used. In particular, in the case of an internal reflection type laser, the exit surface is arranged almost conjugate with the pattern surface of the reticle R, and the aperture stop plate 9 is connected to the light source 1 and the optical integrator. Placed between evening 8

As shown in FIG. 2, the aperture stop plate 9 has a circular aperture stop 9a for normal illumination, and an annular aperture having an inner diameter of approximately 1/2 of an outer diameter for annular illumination as an example of deformed illumination. 1Z 2 annular aperture 9b, 2/3 annular aperture 9c with an inner diameter of almost 2Z3 annular aperture, and multiple as another example of modified illumination (in this example, An aperture stop 9 d for quadrupole illumination consisting of four (4) eccentric small apertures is arranged. Further, the aperture stop 9a for ordinary illumination is provided with an iris stop (not shown) for controlling the aperture shape in order to switch to illumination for a small coherence factor (low-value illumination). Returning to FIG. 1, the main control system 28 rotates the aperture stop plate 9 via the drive motor 10 in accordance with the illumination conditions, so that the predetermined aperture stop that defines the illumination conditions is optically integrated. Is set on the exit surface of

In addition, instead of or in combination with the aperture stop plate 9, for example, a plurality of diffractive optical elements that are exchanged and arranged in the illumination optical system, a prism (cone prism, polyhedron, etc.) movable along the optical axis of the illumination optical system An optical unit that includes at least one of a zoom optical system and a zoom optical system is placed between the light source 1 and the optical integrator 8, and when the optical integrator 8 is a fly-eye lens, the light enters. The intensity distribution of the exposure light IL on the surface, optical, when the integrator 8 is an internal reflection type integrator, the incident angle range of the exposure light IL with respect to the incident surface is variable, so that the Of the exposure light IL (size and shape of the secondary light source), that is, the illumination conditions can be changed, and the light amount loss due to the change of the illumination conditions is suppressed Is desirable.

Exposure light IL emitted from optical integrator 8 and passing through a predetermined aperture stop in aperture stop plate 9 is incident on beam splitter 11 having a high transmittance and a low reflectance. The exposure light reflected by the beam splitter 11 enters an integrator sensor 12 composed of a photoelectric detector, and a detection signal of the integrator sensor 12 is supplied to an exposure controller 29. The exposure controller 29 is an Integral

The illuminance (pulse) of the exposure light I 'L The energy), and the integrated value (exposure amount) are monitored.

The exposure light IL transmitted through the beam splitter 11 passes through a reflection mirror 13 and a condenser lens system 14 and enters a fixed field stop 15 in a reticle blind mechanism 16. When the projection exposure apparatus is of a scanning exposure type such as a step-and-scan method as in this example, in addition to a field stop 15 for defining an illumination area, unnecessary unnecessary light before and after scanning exposure is provided. A movable field stop is provided to prevent exposure of the area. The exposure light IL shaped by the field stop 15 of the reticle blind mechanism 16 is applied to the pattern area of the reticle R via the imaging lens system 17, the reflection mirror 18 and the main condenser lens system 19. Illuminate the rectangular illumination area 36 (see Fig. 3) with a uniform illuminance distribution. A r F excimer laser light source 1, B MU 3, variable dimmer 6, lens system 7A, 7B, optical integrator 8, aperture stop plate 9, mirror 13 An illumination optical system (illumination system) is configured.

Under the exposure light IL, the image of the circuit pattern in the illumination area of the reticle R is projected onto both sides (or one side on the wafer side) through a telecentric projection optical system PL to a predetermined projection magnification (eg, 1Z4, 1Z). 5), the light is projected onto the exposure area of the resist layer on the wafer W arranged on the image plane of the projection optical system PL. The exposure area is located on one of the plurality of shot areas on wafer W. The projection optical system PL corresponding to the projection system of the present invention is a dioptric system (refractive system). In order to reduce the absorption of short-wavelength exposure light, for example, International Publication (W （) 0 0 As disclosed in U.S. Pat. No. 3,996,23, a direct optical system is constructed by arranging a plurality of refractive lenses along one optical axis and two concave mirrors each having an opening near the optical axis. A cylindrical catadioptric system (catadioptric system) may be used. Alternatively, a catadioptric system or the like having an optical axis bent in a V-shape may be used as the projection optical system PL.

In this example, since the ArF excimer laser light (wavelength: 193 nm) in the vacuum ultraviolet region is used as the exposure light IL, it is necessary to prevent the absorption of the exposure light IL by a light absorbing substance such as oxygen. Therefore, a sub-champ 60 is provided to block the illumination optical path from the inside of the pipe 5 to the main condenser lens system 19 through the variable dimmer 6, the lens systems 7A and 7B, the optical integrator 8 and the like. ing. And the exposure light In order to avoid absorption by light-absorbing substances, the entire inside of the sub-chamber 60 and the entire space inside the lens barrel of the projection optical system PL (space between multiple lens elements) are dried through piping (not shown). A purge gas such as a nitrogen gas or a helium gas is supplied. In the following, the Z axis is taken parallel to the optical axis AX of the projection optical system PL, the X axis is taken perpendicular to the plane of Figure 1 in a plane perpendicular to the Z axis, and the Y axis is taken parallel to the plane of Figure 1 I do.

First, the projection optical system PL of the present example includes a plurality of optical members (typically, lenses LI and L2 are shown in FIG. 1) arranged along the optical axis AX, and a mirror that holds these. It consists of a tube and. Then, in order to control the projection magnification of the projection optical system PL and imaging characteristics such as predetermined aberrations (distortion, coma, astigmatism, curvature of field, etc.), the projection optical system PL includes The actuators 43, 44 are provided for driving the lenses L1, L2 in the Z direction at three independent positions at equal angular intervals, and the driving amount of the actuators 43, 44 is increased. It is controlled by the imaging characteristic controller 42. A piezoelectric element (piezo element, etc.) or an electric micro-mechanical element can be used for the actuators 43 and 44, and three actuators 43 (or 44) can be simultaneously expanded and contracted. Can drive the lens L 1 (or L 2) in the optical axis AX direction, and by changing the driving amount of the three actuators 43 (or 44), the lens L 1 (or L 2) can be driven. The tilt angles around the X and Y axes can be controlled. The imaging characteristics controller 42 and the actuators 43, 44 correspond to the imaging adjustment system of the present invention, and the imaging characteristics are controlled in accordance with a control command of the imaging characteristics from the main control system 28. The controller 42 drives the actuators 43, 44 so as to correct the specified imaging characteristics by the specified amount. The imaging adjustment system includes a lens controller (LC) that controls the pressure of a gas (purge gas) in an airtight chamber between predetermined lenses in the projection optical system PL, or a position in the optical axis direction of the reticle R. A mechanism for controlling at three points may be used. Also, for example, controlling the atmospheric pressure on the optical path of the exposure light IL is substantially equivalent to controlling the wavelength of the exposure light IL. Therefore, the image forming characteristic may be controlled by controlling the oscillation wavelength of the ArF excimer laser light source 1 by the exposure controller 29. In this case, the ArF excimer laser light source 1 and the exposure controller 29 form an image adjustment system.

The imaging characteristics depend on the pressure (atmospheric pressure) of the gas around the projection optical system PL. Even fluctuates. Therefore, a barometer 31 for measuring the atmospheric pressure is installed near the projection optical system PL, and the atmospheric pressure measured by the barometer 31 is supplied to the main control system 28. In this case, the relationship between the atmospheric pressure and the amount of change in the imaging characteristics is stored in advance as a table in the storage device in the main control system 28, and when the atmospheric pressure fluctuates, the imaging characteristics of the projection optical system PL are allowed. When it is predicted to fluctuate beyond the range, the main control system 28 adjusts the imaging characteristic via the imaging characteristic controller 42 so as to cancel the expected fluctuation amount of the imaging characteristic. to correct. In addition, since the imaging characteristics vary depending on the integrated energy of the exposure light IL passing through the projection optical system PL, for example, the main control system 2 is controlled in accordance with the integrated energy monitored by the integration sensor 12. 8 drives the imaging characteristic controller 42 so as to cancel the expected fluctuation amount of the imaging characteristic. As a result, the imaging characteristics are kept constant during the exposure. Note that the barometer 31 of the present example corresponds to the environment detection system of the present invention.

Further, since the image forming characteristics fluctuate in accordance with a change in the light amount distribution of the exposure light IL on the pupil plane of the projection optical system PL, for example, the image forming characteristic relates to the light amount distribution on the pupil plane of the projection optical system PL. According to the information, the main control system 28 adjusts the imaging characteristic via the imaging characteristic controller 42 so as to cancel out the expected fluctuation amount of the imaging characteristic. Here, the light quantity distribution on the pupil plane of the projection optical system PL is changed by changing the above-mentioned illumination conditions (light quantity distribution of the exposure light IL on the pupil plane (Fourier transform plane) of the illumination optical system) and the reticle. The main control system 28 calculates the amount of change or the amount of correction of the imaging characteristic according to the illumination conditions and the like, since the value changes according to the type of the pattern (line width or the like). At this time, instead of or in addition to moving at least one lens of the projection optical system PL via the imaging characteristic controller 42, the oscillation wavelength of the exposure light IL is changed via the exposure controller 29. Further, the fluctuation of the imaging characteristic may be corrected.

Next, the configuration of the stage system and the alignment system of the projection exposure apparatus of this embodiment will be described. First, reticle R is suction-held on reticle stage 20, and reticle stage 20 is mounted on reticle base 21 movably in the X, Y, and rotation directions.

FIG. 3 is a perspective view showing a main part of the stage system and the alignment system of FIG. 1. As shown in FIG. 3, the reticle stage 20 is substantially perpendicular to the X axis and the Y axis. A movable mirror 2 2a having two reflecting surfaces is fixed, and a two-axis laser beam LRX 1 and a two-axis parallel to the X axis are provided on the movable mirror 22 a by a laser interferometer in the drive control unit 22 shown in FIG. A laser beam LRY parallel to LRX2 and Y-axis is irradiated, and the X- and Y-coordinates and rotation angle of reticle stage 20 (reticle R) are measured in real time by the laser interferometer. Returning to FIG. 1, the drive control unit 22 based on the measurement results and the control information from the main control system 28, based on a drive module (not shown), a voice coil motor, etc. The positioning operation of reticle stage 20 is controlled via).

Next, the wafer W is suction-held on the sample table 24 via the wafer holder 23. The sample table 24 is placed on an XY plane (not shown) parallel to the image plane of the projection optical system PL. The sample stage 24 and the XY stage 25 are fixed on an XY stage 25 that moves two-dimensionally along the top surface, and a wafer stage 26 is configured. The sample stage 24 controls the focus position (position in the Z direction) and the tilt angle of the wafer W to adjust the surface of the wafer W to the image plane of the projection optical system PL by the autofocus method and the auto-repeller method. The XY stage 25 performs stepping of the wafer W in the X and Y directions. Further, an alignment sensor 35 for a wafer mark of an off-axis system and an image processing system is arranged on a side surface in the Y direction of the projection optical system PL.

Then, the side surface in the + X direction and the side surface in the + Y direction of the sample stage 24 are mirror-finished and used as a movable mirror. From the laser interferometer in the drive control unit 27, as shown in Fig. 3, the two-axis laser beams parallel to the X-axis are respectively applied to the + X side and + Y side of the sample stage 24. LWX 1, LWX 2, and a laser beam LWY parallel to the Y axis are emitted. In this case, the extension of the optical axis of the Y-axis laser beam LWY passes through the detection center of the alignment sensor 35 and the optical axis AX of the projection optical system PL, and the X-axis laser beams LWX 1 and LWX 2 The extension of the optical axis passes through the optical axis AX and the detection center of the alignment sensor 35, respectively. Therefore, the Y coordinate of the sample stage 24 is measured by the laser beam LWY, and the X coordinate of the sample stage 24 is measured by the laser beam LW X1 at the time of exposure in order to suppress the occurrence of Abbe error. At the time of alignment, it is measured by laser beam LWX2. Also, from the difference between the measured values of the two laser beams LWX 1 and LWX 2, The rotation angle of the sample stage 24 is measured.

When the side surface of the sample stage 24 is used as a movable mirror as shown in Fig. 3, there is a displacement in the Z direction between the optical path of the laser beam and the surface of the wafer W. Abbe error may occur due to pitching or rolling of 24. To avoid this, the laser beams LWX 1, LWX 2, and LWY are each separated by a predetermined distance in the Z direction, and the laser beam is irradiated on the side surface of the sample table 24. Abbe error due to pitching of the sample stage 24 or the like may be corrected based on the measurement value by the laser beam. Similarly to the reticle stage 20, a movable mirror having an orthogonal reflection surface is installed on the sample stage 24, and the movable mirror is irradiated with a laser beam to measure the position of the sample stage 24. Is also good.

Referring back to FIG. 1, the two-dimensional position and rotation angle of the sample stage 24 (wafer W) measured by the laser interferometer in the drive control unit 27 are measured by the main control system 28 and the It is also supplied to the Lightment Contoller 30. The drive control unit 27 controls the positioning operation of the XY stage 25 via a drive motor (not shown) based on the measured values and the control information from the main control system 28. You. However, the rotation error of the wafer W is corrected, for example, by rotating the reticle stage 20 via the main control system 28 and the drive control unit 22.

At the time of exposure, the main control system 28 rotates the aperture stop plate 9 as necessary to set illumination conditions. Then, the reticle R is scanned through the reticle stage 20 in the + Y direction (or -Y direction), that is, in the scanning direction SD (see FIG. 3) at the speed Vr with respect to the illumination area of the exposure light IL. Synchronously, the speed of the wafer W in the -Y direction (or the + Y direction) with respect to the exposure area by the projection optical system PL via the XY stage 25 is 0-Vr (j3 is from the reticle R to the wafer W). Scanning magnification). The scanning directions of the reticle R and the wafer W are opposite because the projection optical system PL performs reverse projection.When the erect image is projected, the scanning directions of the reticle R and the wafer W are the same. Become. At this time, the exposure controller 29 controls the exposure amount for each shot area on the wafer W. Then, after the scanning exposure of the pattern image of the reticle R onto one shot area on the wafer W is completed, the next shot area on the wafer W is transferred to the exposure area by the projection optical system PL via the XY stage 25. Foreground After that, the operation of synchronously scanning the reticle R and the wafer W is repeated in a step-and-scan manner, and each shot area on the wafer W is scanned and exposed.

Before the exposure of each shot area on the wafer W as described above, it is necessary to preliminarily align the pattern of the reticle R with each shot area on the wafer W with high precision. Therefore, as shown in FIG. 3, a pair of reticle marks 37 A and 37 B are formed so as to sandwich the pattern area PA of the reticle R in the X direction (non-scanning direction), Image processing reticle alignment microscopes (hereinafter referred to as “RA microscopes”) 38 A and 38 B are arranged above the reticle marks 37 A and 37 B, respectively. The imaging signals of the RA microscopes 38A and 38B are supplied to the alignment controller 30. The alignment controller 30 converts the supplied imaging signals into the X and Y directions of two marks, respectively. The amount of displacement is calculated, and the obtained amount of displacement is supplied to the main control system 28 in FIG. The main control system 28 as an imaging adjustment system obtains a predetermined imaging characteristic from the supplied positional shift amount. In FIG. 3, a reference member 32 made of a glass substrate is fixed near the wafer holder 23 on the sample stage 24, and the upper surface of the reference member 32 is set at the same height as the surface (wafer surface) of the wafer W. ing. Two frame-like reference marks 34 A, 34 B arranged on the upper surface of the reference member 32 at predetermined intervals in the X direction, and a line-and-space pattern in the X direction and the Y direction A two-dimensional reference mark 33 is formed in combination with the line 'and' space pattern. The distance between the fiducial marks 34 A and 34 B in the X direction is set equal to the designed distance between the reticle marks 37 A and 37 B and the projected image on the wafer stage side. 4 The distance between the center of B and the center of fiducial mark 33 in the Y direction is the designed distance between the center of the pattern image of reticle R and the detection center of alignment sensor 35 (baseline amount) BL 1 Is set to.

Returning to FIG. 1, the alignment sensor 35 forms an epi-illumination system that illuminates the target mark with illumination light insensitive to the photoresist on the wafer W in a relatively wide band, and forms an image of the target mark. And a two-dimensional image sensor for imaging the image of the test mark and the index mark. The image signal of the image sensor is also provided. Alignment controller 30. The alignment controller 30 processes the imaging signal and detects the amount of displacement of the mark in the X and Y directions with respect to the center (detection center) of the index mark on the wafer stage 26 with respect to the wafer, and The detection result is supplied to the main control system 28. Further, inside the sample stage 24 on the bottom surface of the reference member 32, a tip of the transmission optical system 39, a lens 40 for condensing illumination light from the tip, and a reference mark for the condensed illumination light. A mirror 41 for bending is arranged on the 34A, 34B side. Leading to the side. Thus, the reference marks 34A and 34B of the present example are illuminated from the bottom side with illumination light having the same wavelength as the exposure light IL, and no chromatic aberration occurs in the projection optical system PL. Under the illumination light, the surface on which the reference marks 34A and 34B are formed and the surface on which the reticle marks 37A and 37B are formed (reticle surface) are conjugate with respect to the projection optical system PL. Therefore, without providing an optical system for correcting chromatic aberration, the RA microscope 38A (or 38B) above the reticle R allows the reference mark 34A (or 34B) to be projected onto the reticle surface by the projection optical system PL. The displacement of the reticle mark 37A (or 37B) can be detected with high accuracy. The reference marks 34A and 34B of this example correspond to the marks of the present invention, and the RA microscopes 38A and 38B correspond to the mark detection system. In this example, the illumination condition from the bottom of the reference marks 34A and 34B by the transmission optical system 39, the lens 40, and the mirror 41 is the illumination condition of the exposure light IL by the illumination optical system including the optical integral 8 Therefore, the measurement results of the imaging characteristics using the reference marks 34A and 34B are corrected in accordance with the actual lighting conditions at the time of exposure, as described later.

Instead of illuminating the reference marks 34 A and 34 B from the bottom using the transmission optical system 39, for example, illuminating the RA microscopes 38 A and 38 B with illumination light of the same wavelength as the exposure light A mechanism may be provided. In this case, RA microscope

The reticle marks 37A, 37B are illuminated from above by the illumination light from 38A, 38B, and the reference marks 34A, 37A, 37B are illuminated through the projection optical system PL with the illumination light transmitted around the reticle marks 37A, 37B. Illuminate 34 B. And fiducial mark 34A, 3

4 R due to reflected light from B and reflected light from reticle marks 37 A and 37 B By detecting the images of both marks formed inside the A microscopes 38A and 38B, it is possible to detect the amount of displacement between the two marks.

Also, reference marks are provided on the reticle stage 20 corresponding to the reference marks 34A and 34B on the reference member 32 in FIG. 3, and the reference marks on the reticle stage 20 are used instead of the reticle marks 37A and 37B. The amount of displacement between the reference marks 32A and 34B on the reference member 32 may be detected by the RA microscopes 38A and 38B. At this time, the reference marks on the reticle stage 20 are arranged, for example, at the positions of the respective vertices of a rectangle, and the reference marks are provided in a frame-like arrangement on the reference member 32 so as to correspond to the reference marks. The distortion of the optical system PL can also be measured. When the fiducial marks are provided on the reticle stage 20 as described above, the degree of freedom of the arrangement increases.

The reference marks 34A and 34B, the reticle marks 37A and 37B, and the RA microscopes 38A and 38B are used when performing reticle alignment.In this example, these mechanisms and the imaging characteristic controller 42 and the like are used. The measurement and correction of the predetermined imaging characteristics of the projection optical system PL are performed by using this. In the following, an example of the measurement operation and the correction operation (calibration operation of the projection magnification) of the projection magnification will be described with reference to the flowchart of FIG. 7, using the imaging characteristic of the measurement target as the projection magnification of the projection optical system PL. .

First, in step 101 of FIG. 7, as shown in FIG. 3, the amount of displacement of the reticle marks 37A, 37B with respect to the projected image of the reference marks 34A, 34B on the reticle surface is determined by the RA microscopes 38A, 38B. measure. Therefore, the main control system 28 in FIG. 1 drives the XY stage 25 to move the reference marks 34A, 34B of the reference member 32 to a position substantially conjugate with the reticle marks 37A, 37B. Next, in this state, the reference marks 34A and 34B are illuminated from the bottom surface of the reference member 32 with the illumination light having the same wavelength as the exposure light I by using the transmission optical system 39, the lens 40, and the mirror 41 of FIG.

FIG. 4 shows the observation field of view 38 Aa on the reticle surface of one RA microscope 38 A. In FIG. 4, the image 34 AR of one reference mark 34 A and the image of the reticle mark 37 A are RA An image was taken with a microscope 38 A, and the image signal was compared with the alignment control shown in Fig. 1. Processing by the controller 30 detects the amount of displacement (ΔΧ1, ΔΥ1) of the center RA of the reticle mark 37A in the X and Y directions with respect to the center 8 of the image 3481 of the reference mark. . In parallel with this, via the other RA microscope 38 B, the center RB of the reticle mark 37 B with respect to the center FB (see FIG. 5) of the image of the other reference mark 34 B in the X and Y directions. The deviation (Δ 量 2, ΔY2) is detected.

Here, in this example, the reticle alignment is performed based on the detected positional deviation amounts of the reticle marks 37A and 37B. First, as shown in FIG. 5 (A), the main control system 28 determines the center 1 ^ 8, RB of the reticle mark 37A, 373 with respect to the straight line connecting the image centers FA, FB of the reference marks 34A, 34B. , Ie, the rotation angle の of the reticle R with respect to the reference member 32. Next, the reticle stage 20 is rotated by −0 through the drive control unit 22, and the position of the reticle stage 20 in the に direction is adjusted so that the displacement amounts ΔΥ1 and ΔΥ2 in the Y direction become 0, respectively. . As a result, the center 18, RB of the reticle mark 37 37, 378 is located on a straight line connecting the center 8, FB of the image of the reference mark 34Α, 348. Then, as shown in Fig. 5 (Β), the main control system 28 distributes the amount of displacement of the center RA and RB with respect to the center FA and FB in the X direction symmetrically, that is, the two center RA and RB The reticle stage 20 is moved in the X direction so that the amount of displacement in the X direction is symmetrically set by ΔD. This completes the reticle alignment. At this time, the displacement AD in the X direction may be measured again through the RA microscopes 38A and 38B. In this case, assuming that the displacement of the center RA in the X and Y directions with respect to the center FA is (△ D, 0), the displacement of the other is (−AD, 0).

Next, proceeding to step 102, based on the amount of displacement of the detected reticle marks 37A, 37B with respect to the images of the reference marks 34A, 34B, the projection magnification of the projection optical system ΡL / 3 (reticle surface From the standard magnification (design value) βο. In this case, the projection magnification] 3 is obtained by dividing the distance DW between the centers of the reference marks 34Α and 34Β on the wafer stage side by the distance between the reference marks 34Α and 34: 6 at the center of the image 8 and FB on the reticle surface. When the distance between the center RA and RB of the reticle mark 37 A, 37 mm is DR, the projection magnification] 3 Is represented by the following equation.

β = Ό / (DR + 2-ΔΌ)… (1)

In Fig. 5 (5), the center of the image of fiducial mark 34Α, 34: 8? 8) If the distance between FBs is shorter than the distance DR between the centers RA and RB of the reticle marks 37A and 37 符号, the sign of the displacement AD in equation (1) becomes one (minus). You. Here, the distance DW between the centers of the reference marks 34A and 34B on the wafer stage side and the distance DR between the centers RA and RB of the reticle marks 37A and 37B are measured in advance with high precision and stored in the main control system 28. This is stored as a known exposure parameter in the apparatus. The main control system 28 calculates the projection magnification] 3 from equation (1), and then calculates the projection magnification as follows: the reference magnification of 6/3. From the error Δ / 32. .

A β 2 = β- β ο… (2)

Next, in step 103, a correction value Δ / 31 of the magnification error according to the atmospheric pressure 周囲 around the projection optical system PL and the illumination conditions at the next exposure is calculated. As the illumination conditions, the numerical aperture NA! LL of the illumination system and the shape of the illumination system aperture stop (which one of the apertures 9a to 9d in FIG. 2 is used) are used. Further, in this example, the numerical aperture NA _PL of the projection optical system PL is also considered as the illumination condition. Note that a σ value (= NA _ILL / NAPL) may be used instead of the numerical aperture NA _ILL of the illumination system.

Figure 6 shows an example of the relationship between the atmospheric pressure P around the projection optical system PL when measuring the projection magnification and the magnification error measured accordingly (hereinafter referred to as the “magnification error correction value Δj31”). In FIG. 6, the horizontal axis represents the atmospheric pressure P (hPa), and the vertical axis represents the magnification error correction value 1 (ppm). As shown in FIG. 6, the magnification error of the projection optical system PL changes almost linearly with respect to the atmospheric pressure P at the time of measuring the projection magnification, and the correction value Δ1 of the magnification error is expressed by the following equation. Can be approximated.

Δ / 31 = a · P + b… (3)

Here, the coefficients a (ppm / hPa) and b (ppm) are the slope and offset of the magnification error with respect to the atmospheric pressure P, respectively, and the values of these coefficients a and b differ depending on the lighting conditions. Table 1 shows examples of measured values of coefficients a and b under various lighting conditions. In Table 1, NA _PL and NA _ILL are the numerical apertures of the projection optical system PL and the illumination optical system, respectively. For the normal illumination in the illumination method, use the aperture stop 9a shown in FIG. Ring illumination uses a 1/2 annular aperture 9b, and 2Z3 annular illumination uses a 2/3 annular aperture 9c. Further, the numerical aperture NA _{I LL} of the illumination optical system at the time of annular illumination means the numerical aperture of the outer diameter of the annular zone. The coefficient a _SIM (ppm Pa) indicates the slope of the magnification error under each lighting condition obtained by simulation. Table 1 shows that the simulation results agree well with the measured data.

【table 1】

In this example, the values of the slope a of the magnification error and the offset b of the magnification error corresponding to each lighting condition are recorded as a table in a storage device inside the main control system 28 or an external host computer in FIG. The main control system 28 obtains, from the table, values of the gradient a of the magnification error and the offset b of the magnification error corresponding to the illumination condition at the time of exposure. Then, the main control system 28 obtains a correction value Δ; 31 of the magnification error from the equation (3) based on the measured value of the atmospheric pressure P by the barometer 31.

Next, proceeding to step 104, the main control system 28 sets the reference magnification of the projection magnification] 3 obtained in step 102 to [3]. 32, the actual residual magnification error (3 (= Δ / 32−Δ / 31) during exposure is subtracted from the magnification error correction value Δ / 31 found in step 103 from the error Δ | 32 Ask.

Then, in step 105, the main control system 28 adjusts the state of the lenses L 1 and L 2 of the projection optical system PL by driving the actuators 43 and 44 via the imaging characteristic controller 42. Then, the projection magnification 0 of the projection optical system PL is corrected so as to cancel the residual magnification error Δ / 3, that is, the projection magnification becomes (β-room β). Thus, based on the illumination conditions at the time of exposure and the measured value of the atmospheric pressure P around the projection optical system PL, the projection magnification measured by the RA microscopes 38A and 38B;

By correcting (2), the projection magnification can be determined with high accuracy according to the illumination conditions at the time of exposure and the atmospheric pressure P around the projection optical system PL.Based on this result, the projection magnification can be determined with high accuracy. Can be calibrated. Further, according to the present example, since the images of the reference marks 34 A and 34 B and the detection results of the reticle marks 37 A and 37 B by the RA microscope 38 A and 38 B are used, the reticle alignment There is an advantage that the projection magnification can be adjusted at the same time.

After the projection magnification i3 is adjusted as described above, an exposure step (step 106) is performed. After the exposed wafer is subjected to the development step, the resist pattern left after the development is masked. Through a processing step of performing etching, ion implantation, etc., and a resist removing step of removing unnecessary resist after the processing step. Then, the steps of exposure, image development, processing, and resist removal are repeated, thereby completing the process. When the wafer process is completed, in the actual assembly process, a dicing process of cutting wafers into chips for each burned circuit, a bonding process of wiring each chip, and a packaging process of packaging each chip Finally, semiconductor devices such as LSIs are manufactured through processes.

In addition, an illumination optical system composed of multiple lenses and a projection optical system are incorporated into the main body of the projection exposure apparatus to perform optical adjustment, and a reticle stage and a wafer stage composed of many mechanical parts are attached to the main body of the exposure apparatus and wired. The projection exposure apparatus according to the present embodiment can be manufactured by connecting the pipes and pipes and performing the overall adjustment (electrical adjustment, operation check, etc.). It is desirable to manufacture the projection exposure apparatus in a clean room where the temperature and cleanliness are controlled. ―

In the above embodiment, the lenses LI and L2 are driven to control the imaging characteristics. However, instead of or in combination with this, the exposure light from the ArF excimer laser light source 1 is used. The oscillation wavelength λ of the IL may be controlled.

Further, in the above embodiment, the projection magnification of the projection optical system PL is used as the imaging state or the imaging characteristic. In addition, the distortion, coma, and non- Measurement and control of point aberration and the like may be performed. When measuring distortion, for example, three or more fiducial marks 34A and 34B may be arranged, and the displacement of each projected image may be measured. When measuring coma, For example, a box-in-box mark may be used in place of the fiducial marks 34A and 34B to measure the amount of displacement between the outer poxmark image and the inner poxmark image.

In the above embodiment, the illumination system for the RA microscopes 38 A and 38 B is provided separately from the illumination optical system, but at least a part of the illumination optical system is provided for the RA microscopes 38 A and 38 B. May be used as an illumination system. For example, at least a part of the exposure light IL emitted from the aperture stop plate 9 is guided to the RA microscopes 38A and 38B, and the exposure light IL is irradiated on the reticle mark and the reference mark. Good. Alternatively, a beam splitter is disposed above the reticle marks 37A and 37B so as to be retractable, and at the time of mark measurement, the beam splitter is set in the optical path of the exposure light IL to expose the light from the illumination optical system. The reticle marks 37 A and 37 B and the reference marks 34 A and 34 B are illuminated with light IL, and the reflected light from those marks is passed through the beam splitter to the RA microscopes 38 A and 38 B. You may make it detect.

Further, in the above embodiment, RA microscopes 38A and 38B were used as the mark detection system of the present invention, but the mark detection system is not limited to the RA microscope, and the configuration may be arbitrary. Absent. For example, as the mark detection system, a space image measurement system or the like that detects a spatial image of a mark projected through the projection optical system PL through a predetermined opening on the wafer stage 26 side may be used. In this case, for example, an opening wider than the line width of the image of each mark constituting the test mark is used as the opening, and an image signal obtained by imaging the image of the test mark is differentiated. The position of the image of the test mark may be detected from the obtained signal. As a mark detection system, the slit is illuminated from the wafer stage 26 side with illumination light having the same wavelength as the exposure light, transmitted through this slit, and further reflected by the reticle R via the projection optical system PL. A focus position detection sensor that detects the best focus position of the projection optical system PL by receiving light through the slit may be used.

Further, in the above-described embodiment, the adjustment of the imaging state or the imaging characteristics is performed simultaneously with the reticle alignment, but both need not be performed at the same time. Only the detection may be performed without adjusting the state or the imaging characteristics. Further, in the above-described embodiment, atmospheric pressure (pressure in an installation environment such as a projection optical system) is used as an environmental condition, but temperature or the like may be used instead or in combination therewith.

The present invention is not limited to an exposure apparatus for manufacturing a semiconductor device as in the above-described embodiment. For example, an exposure apparatus for a liquid crystal for exposing a liquid crystal display element pattern on a square glass plate, and a plasma It can be widely applied to exposure devices for manufacturing devices such as display elements, micromachines, thin-film magnetic heads, and DNA chips. Further, the magnification of the projection optical system is not limited to a reduction system, and may be any one of an equal magnification and an enlargement system.

Note that the present invention is not limited to the above-described embodiment, and can take various configurations without departing from the spirit of the present invention. In addition, all disclosures of Japanese Patent Application No. 2000-2806515, filed on September 21, 2000, including the specification, claims, drawings, and abstract are as follows: , And are incorporated in the present application as they are. Industrial applicability

According to the exposure method of the present invention, even when environmental conditions at the time of detecting a mark are variously changed, for example, by correcting the detection result of the mark using the environmental condition at the time of the detection, the detection result can be obtained. It can be used to adjust the imaging state of the pattern image with high precision.

When determining the adjustment amount of the imaging state including an offset corresponding to a difference between the pattern image forming condition and the mark detection condition, for example, the imaging state is detected (measured). Even when the illumination condition at the time of exposure differs from the illumination condition at the time of actual exposure, the imaging state can be adjusted with high accuracy.

Next, according to the projection exposure apparatus of the present invention, the exposure method of the present invention can be performed. Further, according to the imaging characteristic measuring method of the present invention, the imaging characteristic of the projection system can be adjusted with high accuracy in accordance with the environmental conditions at the time of the measurement.

Further, according to the first and second device manufacturing methods of the present invention, the image forming state of the pattern image can be adjusted with high accuracy, and a highly functional device can be manufactured.

Claims

The scope of the claims

1. An exposure method for illuminating a mask with an exposure beam and transferring a pattern image of the mask onto a substrate via a projection system,

An exposure method comprising: detecting a mark via the projection system; and using the environmental condition at the time of the detection when adjusting an image forming state of the pattern image based on the detection result.

2. The exposure method according to claim 1, wherein an adjustment amount of the imaging state obtained from the detection result is corrected based on the environmental condition.

3. The exposure method according to claim 2, wherein the adjustment amount is determined including an offset corresponding to a difference between a condition for forming the pattern image and a condition for detecting the mark.

4. The exposure method according to claim 3, wherein the offset varies depending on a condition for forming the pattern image and is corrected according to the environmental condition.

5. The exposure method according to any one of claims 1 to 4, wherein the adjustment amount of the imaging state obtained from the detection result is corrected based on a condition for forming the pattern image.

6. The imaging characteristic of the projection system is calculated based on the detection result, and the imaging state is adjusted based on the calculated imaging characteristic and the environmental condition. 5. The exposure method according to claim 1.

7. A projection exposure apparatus comprising: an illumination system for illuminating a mask with an exposure beam; and a projection system for projecting a pattern image of the mask onto a substrate.

A mark detection system for detecting a mark via the projection system,

An environment detection system for detecting an environmental condition at the time of detecting the mark,

An imaging state adjustment system that uses the environmental condition when adjusting the imaging state of the power image based on the detection result;

A projection exposure apparatus comprising:

8. The projection according to claim 7, wherein the imaging state adjustment system corrects the adjustment amount of the imaging state obtained from the detection result based on the environmental condition.

9. The image forming state adjusting system according to claim 8, wherein the adjustment amount is determined to include an offset corresponding to a difference between a condition for forming the pattern image and a condition for detecting the mark. The projection exposure apparatus according to claim 1.

10. The imaging state adjustment system according to claim 7, 8, or 9, wherein the imaging state adjustment system corrects the adjustment amount of the imaging state obtained from the detection result based on a condition for forming the pattern image. 3. The projection exposure apparatus according to claim 1.

11. An imaging characteristic of the projection system is calculated based on the detection result, and the imaging state is adjusted based on the imaging characteristic and the environmental condition. 10. The projection exposure apparatus according to claim 9.

1 2. In the method of measuring the imaging characteristics of the projection system that projects the image of the object on the first surface onto the second surface,

A first step of detecting, via the projection system, a mark arranged on at least one of the first and second surfaces, and calculating an imaging characteristic of the projection system from the detection result; and executing the first step A second step of correcting the calculation result of the imaging characteristic obtained in the first step based on the environmental conditions at the time.

A method for measuring imaging characteristics, comprising:

13. The method according to claim 12, wherein a correction amount of the calculation result is changed according to the environmental condition.

14. An offset corresponding to a difference between the mark detection condition and the image forming condition of the object is added to the calculation result to determine a correction amount of the imaging characteristic,

13. The method according to claim 12, wherein the offset is changed according to the environmental condition.

15. The method for measuring imaging characteristics according to claim 14, wherein the offset and the correction amount thereof are made different according to the image forming conditions of the object.

16. The method for measuring imaging characteristics according to any one of claims 12 to 15, wherein the calculation result is corrected using the image forming conditions of the object.

17. A device manufacturing method including a lithographic step of forming a device pattern on a substrate by using the exposure method according to any one of claims 1 to 4. Method.

18. A device manufacturing method including a lithographic process of forming a device pattern on a substrate using the projection exposure apparatus according to any one of claims 7 to 9.