JP2007165845A - Exposure method and apparatus, and method of manufacturing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily adjust the formation state of a pattern image with accuracy when switching various illumination conditions and so on. <P>SOLUTION: The exposure method of illuminating a reticle R with exposure light IL and forming a pattern image of the reticle R on a wafer W through a projection optical system PL, comprises a calculation step of calculating moment information corresponding to an integral of the product of a distance from the reference position and an amount of exposure light IL on a plane conjugated to the pupil surface of the projection optical system PL, and an adjustment step of adjusting the formation state of the pattern image, based on the moment information calculated by the calculation step. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exposure technique for projecting an image of a predetermined pattern onto an object by a projection optical system, and a device manufacturing technique using this exposure technique.

  For example, in a lithography process for manufacturing a device such as a semiconductor integrated circuit, an imaging device (CCD, etc.), a liquid crystal display device, or a thin film magnetic head, a pattern of a reticle (or a photomask, etc.) is registered through a projection optical system. A batch exposure type projection exposure apparatus such as a stepper and a scanning exposure type projection exposure apparatus such as a scanning stepper are used to transfer to each shot area of a wafer (or glass plate or the like) coated with (photosensitive material). ing. In the projection exposure apparatus, in order to prevent the projection optical system from being gradually heated by the exposure light as the exposure beam and changing the imaging characteristics such as its magnification, a predetermined lens in the projection optical system is driven. An imaging characteristic correction mechanism that corrects imaging characteristics is provided (for example, see Patent Document 1).

The amount of variation in the imaging characteristics differs for each illumination condition related to the optical path of the exposure light in the projection optical system. Thus, conventionally, as an example, under all illumination conditions, for example, when the amount of exposure light irradiation reaches a predetermined amount, the amount of variation in imaging characteristics is obtained in advance by measurement, and when a certain illumination condition is selected. The imaging characteristic correction mechanism is driven so as to cancel out the stored variation corresponding to the illumination condition. As another example, the amount of variation in imaging characteristics is measured only for typical illumination conditions, and when other illumination conditions are used, the amount of variation obtained under illumination conditions close to that is interpolated. Thus, a method for obtaining the fluctuation amount of the imaging characteristic has been known.
JP-A-4-13481

  Recently, as illumination conditions, in addition to normal modified illumination in which the light amount distribution on the pupil plane of the normal illumination or illumination optical system is distributed at four locations centering on the optical axis, the light amount distribution on the pupil plane is Various illumination methods such as two-pole illumination and five-pole illumination distributed at two or five centers are being used. In addition, even when conditions other than illumination conditions such as the shape of the illumination area on the pattern to be transferred are switched, the light quantity distribution of the exposure light in the projection optical system changes and the imaging characteristics change. It is desirable to consider such conditions.

  However, as in the past, the method of measuring the fluctuation amount of the imaging characteristics in advance for all the illumination conditions is to measure the measurement time when the types of illumination conditions increase or when other conditions are considered. Is too long to apply. Further, the method of obtaining the fluctuation amount of the imaging characteristics for typical illumination conditions may cause a reduction in the correction accuracy of the imaging characteristics under conditions that are not measured.

  In view of this point, the present invention can easily and accurately adjust the formation state of a pattern image including the imaging characteristics of the projection optical system when the illumination conditions are changed variously. An object is to provide an exposure technique and a device manufacturing technique.

  In an exposure method according to the present invention, a pattern is illuminated with an exposure beam, and an image of the pattern is formed on an object by a projection optical system (PL). A distance from a reference position on a predetermined surface and the exposure beam A calculation step of calculating moment information corresponding to the integration of the product of the light quantity and an adjustment step of adjusting the image formation state of the pattern based on the moment information calculated in the calculation step.

  According to the present invention, the moment information is used as evaluation information when adjusting the image formation state of the pattern. The moment information can be used in common for various conditions such as lighting conditions and lighting areas, and can be easily calculated. Therefore, when the lighting conditions are switched variously by using the moment information, the pattern The image forming state can be easily adjusted with high accuracy.

The present invention can further include a preliminary step of obtaining a relationship between the moment information and the imaging characteristics of the projection optical system in advance. By using the relationship obtained in advance, the image formation state of the pattern can be adjusted with high accuracy.
Next, an exposure apparatus according to the present invention illuminates a pattern with an exposure beam and forms an image of the pattern on an object by a projection optical system (PL). Using the light amount distribution measuring device (29) to estimate or measure and the light amount distribution obtained by the light amount distribution measuring device, the product of the distance from the reference position and the light amount of the exposure beam on the predetermined plane is integrated. An arithmetic device (1) for calculating corresponding moment information and an adjusting device (39) for adjusting the image formation state of the pattern based on the moment information calculated by the arithmetic device are provided. With this exposure apparatus, the exposure method of the present invention can be implemented.

A device manufacturing method according to the present invention uses the exposure method or exposure apparatus of the present invention.
In addition, although the reference numerals in parentheses attached to the predetermined elements of the present invention correspond to members in the drawings showing an embodiment of the present invention, each reference numeral represents the present invention in order to make the present invention easier to understand. The elements are merely illustrative, and the present invention is not limited to the configuration of the embodiment.

[First Embodiment]
A preferred first embodiment of the present invention will be described below with reference to FIGS. In this example, the present invention is applied when exposure is performed by a scanning exposure type projection exposure apparatus (exposure apparatus) formed of a scanning stepper.
FIG. 1 shows a schematic configuration of the projection exposure apparatus of this example. In FIG. 1, an ArF excimer laser light source (wavelength 193 nm) is used as the exposure light source 6. As an exposure light source, an ultraviolet pulse laser light source such as a KrF excimer laser light source (wavelength 247 nm), an F ₂ laser light source (wavelength 157 nm), a harmonic generation light source of a YAG laser, or a harmonic generation of a solid-state laser (semiconductor laser, etc.) A device or a mercury lamp (i-line etc.) can also be used.

  The exposure light IL (exposure beam) pulsed from the exposure light source 6 during exposure passes through the mirror 7, a beam shaping optical system (not shown), the first lens 8A, the mirror 9, and the second lens 8B, and has a predetermined cross-sectional shape. And is incident on the fly-eye lens 10 as an optical integrator (a homogenizer or a homogenizer), and the illuminance distribution is made uniform. On the exit surface of the fly-eye lens 10 (pupil surface of the illumination optical system), an illumination system aperture stop member 11 around which various aperture stops (σ stop) are arranged is rotatably arranged by a drive motor 12. The illumination condition is set by rotating the illumination system aperture stop member 11 and setting a desired aperture stop on the optical path of the exposure light IL.

  As an example, the illumination system aperture stop member 11 has an aperture stop 13A (σ stop) for normal illumination that increases the light amount distribution of exposure light in a variable circular region, and the light amount distribution surrounds a region on the optical axis and 4 surrounding it. An aperture stop 13B for pentapole illumination that is enlarged in each region, an aperture stop 13C for annular illumination, and a first dipole illumination in which the light amount distribution is enlarged in two regions that are symmetrical in the first direction with respect to the optical axis. Aperture stop 13D, a second dipole illumination aperture stop (not shown) that enlarges the light quantity distribution in two regions that are symmetric in the second direction orthogonal to the first direction with respect to the optical axis, and light quantity distribution. An aperture stop (not shown) for modified illumination such as quadrupole illumination that is enlarged in four regions around the axis is disposed. Further, the aperture diameter of the aperture stop 13A for normal illumination is variable, and the coherence factor (σ value) of the exposure light IL can be controlled by controlling the aperture diameter.

  The exposure light IL that has passed through one aperture stop in the illumination system aperture stop member 11 sequentially passes through the fixed blind 18A and the movable blind 18B through the beam splitter 14 and the relay lens 17A having a low reflectance. The movable blind 18B is disposed on a surface substantially conjugate with the pattern surface (reticle surface) of the reticle R (mask), and the fixed blind 18A is disposed on a surface slightly defocused from the surface conjugate with the reticle surface. Yes.

  The fixed blind 18A is used to define the illumination area 21R on the reticle surface as a slit-like area elongated in the non-scanning direction orthogonal to the scanning direction of the reticle R. The movable blind 18B is used to close the illumination region in the scanning direction so that unnecessary portions are not exposed at the start and end of the scanning exposure for each shot region to be exposed. The movable blind 18B is also used to define the center and width of the illumination area in the non-scanning direction. The exposure light IL that has passed through the blinds 18A and 18B illuminates the illumination region 21R of the pattern region of the reticle R with a uniform illuminance distribution through the sub-condenser lens 17B, the optical path bending mirror 19, and the main condenser lens 20.

  On the other hand, the exposure light reflected by the beam splitter 14 is received by the integrator sensor 16 formed of a photoelectric sensor via the condenser lens 15. The detection signal of the integrator sensor 16 is supplied to the exposure amount control system 3. The exposure amount control system 3 detects the detection signal and the optical system from the beam splitter 14 measured in advance to the wafer W as an object (photosensitive substrate). The exposure energy on the wafer W is indirectly calculated using the transmittance. The exposure amount control system 3 obtains an appropriate exposure amount on the wafer W based on the integrated value of the calculation result and control information from the main control system 1 (arithmetic unit) including a computer that controls the overall operation of the apparatus. The light emission operation of the exposure light source 6 is controlled as described above. Exposure light source 6, mirrors 7 and 9, lenses 8A and 8B, fly-eye lens 10, illumination system aperture stop member 11, beam splitter 14, relay lens 17A, blinds 18A and 18B, sub-condenser lens 17B, mirror 19 and main condenser The illumination optical system 5 includes the lens 20.

  Under the exposure light IL, the pattern in the illumination area 21R of the reticle R is projected at a projection magnification β (β is a reduction magnification of, for example, 1/4, 1/5, etc.) via the bilateral telecentric projection optical system PL. The image is projected onto a slit-like exposure area 21W elongated in the non-scanning direction on one shot area SA on the wafer W coated with the photoresist. The projection optical system PL is, for example, a refractive system, but a catadioptric system or the like can also be used. The pattern surface (reticle surface) of the reticle R and the surface (wafer surface) of the wafer W correspond to the object surface and the image surface of the projection optical system PL, respectively. Hereinafter, in FIG. 1, the Z-axis is taken in parallel to the optical axis AX of the projection optical system PL, and parallel to the non-scanning direction orthogonal to the scanning direction of the reticle R and wafer W during scanning exposure in a plane perpendicular to the Z-axis. In the following description, the X axis is taken and the Y axis is taken parallel to the scanning direction.

The projection optical system PL of this example is provided with an image formation characteristic correction device (adjustment device) for correcting (adjusting) the predetermined image formation characteristic.
FIG. 2 is a partially cutaway view showing the imaging characteristic correction device 39 of the projection optical system PL in FIG. 1. In FIG. 2, for convenience of explanation, the light is configured to constitute the projection optical system PL. lens 43 _1, 43 ₂ eight of a number of lens elements arranged along the axis AX, ..., shows only 43 _8. In this case, some of the lenses 43 ₁ to 43 ₈ , for example, the lenses 43 ₁ and 43 ₂ , are respectively directed to the optical axis AX direction (Z direction) and the XY plane by a plurality of drive elements (for example, piezo elements). It is configured so that it can be finely driven in an inclination direction around two orthogonal axes.

In this example, the drive voltage (drive amount of the drive element) applied to each drive element 37 is controlled by the imaging characteristic control system 36 in accordance with a command from the main control system 1. Furthermore, with respect to the projection optical system PL a predetermined lens 43 ₄ in the light for heating, for example near-infrared region is supplied from a light source (not shown) can be irradiated via the waveguides 38A and 38B, also the irradiation time It is controlled by the imaging characteristic control system 36. As described above, the imaging characteristic correction device 39 is configured including the drive element 37, the waveguides 38A and 38B, and the imaging characteristic control system 36. In this case, the drive element 37 corrects imaging characteristics such as magnification error and coma aberration of the projection optical system PL. Further, by irradiating light from the waveguides 38A and 38B, so-called center astigmatism that is astigmatism remaining on the optical axis, for example, can be corrected.

Note that the number of movable lenses may be arbitrary. However, for example, the number of movable lenses corresponds to the types capable of correcting the imaging characteristics of the projection optical system PL, excluding the focus, and the number of movable lenses depends on the type of imaging characteristics to be corrected. Alternatively, the degree of freedom of driving as a whole movable lens may be determined.
Returning to FIG. 1, the reticle R is sucked and held on the reticle stage 22, and the reticle stage 22 moves on the reticle base 23 in the Y direction at a constant speed and corrects the synchronization error in the X direction, the Y direction, and the Z direction. The reticle R is scanned by slightly moving in the direction of rotation around the axis. The position of the reticle stage 22 is measured by a movable mirror (not shown) and a laser interferometer (not shown) provided on the reticle stage 22, and based on the measured value and control information from the main control system 1, a stage drive system 2 controls the position and speed of the reticle stage 22 via a drive mechanism (not shown) such as a linear motor. A reticle stage system is configured by the reticle stage 22, the stage drive system 2, the drive mechanism, and the laser interferometer. A reticle alignment microscope (not shown) is arranged above the periphery of the reticle R.

On the other hand, wafer W is sucked and held on wafer stage WST via wafer holder 24, and wafer stage WST moves on wafer base 27 at a constant speed in the Y direction and moves in steps in the X and Y directions. 26 and a Z tilt stage 25.
As shown in FIG. 2, the Z tilt stage 25 is supported on the XY stage 26 at three points by three Z position driving units 34A, 34B, and 34C. These Z position driving units 34A to 34C have three actuators (for example, a voice coil motor) that independently drive the respective support points on the lower surface of the Z tilt stage 25 in the optical axis direction (Z direction) of the projection optical system PL. 32A, 32B, and 32C, and encoders 33A, 33B, and 33C that detect driving amounts in the Z direction of the respective support points by the Z position driving units 34A to 34C of the Z tilt stage 25.

  In this example, the Z position driving units 34A to 34C control the position of the Z tilt stage 25 (wafer W) in the optical axis AX direction, the rotation angle around the X axis, and the rotation angle around the Y axis. The stage drive system 2 in FIG. 1 drives the Z position drive units 34A to 34C of the Z tilt stage 25 so that the surface of the wafer W is focused on the image plane of the projection optical system PL during exposure. Further, as shown in FIG. 2, an oblique incidence type multi-point autofocus sensor (31a, 31b) including an irradiation system 31a and a light receiving system 31b is provided, and a test surface (for example, a wafer) is provided by the autofocus sensor. The defocus amount in the Z direction with respect to the image plane of the projection optical system PL on the surface of W) and the inclination angles around the X axis and the Y axis can be obtained. A detailed configuration of a multipoint focal position detection system similar to this autofocus sensor is disclosed in, for example, Japanese Patent Laid-Open No. Hei 6-283403.

  Returning to FIG. 1, the Z tilt stage 25 performs focusing and leveling of the wafer W based on the measurement values of the autofocus sensors (31a, 31b) of FIG. The position of wafer stage WST in the XY plane and the rotation angles around the X, Y, and Z axes are measured by moving mirror 35W (see FIG. 2) and a laser interferometer (not shown). Based on control information from main control system 1, stage drive system 2 controls the operation of wafer stage WST via a drive mechanism (such as a linear motor) (not shown). The wafer stage system is constituted by the wafer holder 24, the wafer stage WST, the stage drive system 2, the drive mechanism, the laser interferometer, and the like described above.

Further, an off-axis alignment sensor ALG for wafer alignment is disposed on the side surface of the projection optical system PL, and the main control system 1 aligns the wafer W based on the detection result.
Further, in the vicinity of wafer holder 24 on wafer stage WST, the light quantity distribution of exposure light IL on the pupil plane of projection optical system PL as a predetermined plane or a conjugate plane thereof (for example, the pupil plane of illumination optical system 5) is measured. A wavefront measuring device 29 (light quantity distribution measuring device) is fixed. The wavefront measuring device 29 may be installed on the wafer stage WST as necessary as a detachable configuration.

  As shown in FIG. 2, the wavefront measuring device 29 is set to the same height as the surface of the wafer W and has a pinhole 30A, a slit 30X parallel to the X axis, and a slit 30Y parallel to the Y axis (see FIG. 1). 2D imaging such as a CCD substrate that detects information on the light quantity distribution of the illumination light IL that has passed through the lens 30B, a lens 30B that converts the exposure light IL that has passed through the pinhole 30A into a parallel light beam, and the lens 30B. It includes an element 30C, a lens 30D that condenses the exposure light EL that has passed through the slits 30X and 30Y, and a photoelectric sensor 30E such as a photodiode that photoelectrically converts the light collected by the lens 30D. For example, in an arrangement as shown in FIG. 2, in the state where the exposure light IL (imaging light beam) from the pattern RP of the reticle R is irradiated onto the wavefront measuring device 29 via the projection optical system PL, the imaging element 30C The imaging signal is supplied to an image processing unit in the main control system 1, and the image processing unit obtains a light amount distribution on the pupil plane PPL of the projection optical system PL from the imaging signal (details will be described later).

  Note that the predetermined surface can be regarded as an image surface of the projection optical system PL or a surface conjugate with the image surface (for example, a pattern surface of the reticle R). In this case, in order to measure the light amount distribution on the predetermined surface, a photoelectric sensor having a light receiving surface is arranged instead of the image sensor 30C, and the wafer stage WST is scanned while scanning in the X direction and the Y direction. A detection signal of the photoelectric sensor may be captured.

  For example, in order to measure imaging characteristics such as distortion of the projection optical system PL, in FIG. 2, a test reticle TR on which a measurement mark is formed is arranged instead of the reticle R, and the wafer stage WST is driven. Then, the image of the mark by the projection optical system PL is scanned by the slit 30X (or 30Y) of the wavefront measuring device 29, and the detection signal from the photoelectric sensor 30E is supplied to the signal processing unit in the main control system 1. The signal processing unit is also supplied with coordinate information of wafer stage WST. This signal processing unit processes the detection signal to obtain the coordinates and contrast of the image of the mark, and from these information, projection optical system PL The imaging characteristics of are obtained. For example, distortion, magnification, and the like can be obtained from the coordinates of a plurality of mark images, and the best focus position and astigmatism can be determined from the contrast at a plurality of Z-direction positions of a periodic mark image in the X and Y directions. (Including center ass).

Returning to FIG. 1, in the vicinity of wafer W on wafer stage WST, a dose monitor (not shown) having a light receiving surface larger than exposure area 21W and an illuminance sensor (not shown) having a pinhole-shaped light receiving surface. And the detection signals of these two sensors are supplied to the exposure amount control system 3.
At the time of exposure, the reticle stage 22 and wafer stage WST are driven, the reticle R and one shot area on the wafer W are synchronously scanned in the Y direction while the exposure light IL is irradiated, and the wafer stage WST is driven. Then, the step of moving the wafer W stepwise in the X and Y directions is repeated. Thereby, the pattern image of the reticle R is exposed to each shot area on the wafer W by the step-and-scan method.

Next, in the projection exposure apparatus of this example, an example of an operation for correcting the variation amount of the imaging characteristic of the projection optical system PL due to the irradiation heat of the exposure light IL when exposure is performed while switching the illumination conditions and the like will be described. .
In this example, in order to predict the fluctuation amount of the imaging characteristics of the projection optical system PL, the moment M of the light amount distribution of the exposure light IL on the predetermined surface is calculated. The moment M is the integration of the product of the distance from a predetermined reference position (in this example, predetermined first and second reference lines or reference points orthogonal to each other) on the predetermined plane and the amount of exposure light IL. Corresponding information. As the predetermined plane, here, the pupil plane of the illumination optical system 5 which is a conjugate plane with the pupil plane of the projection optical system PL is used. The pupil plane of the illumination optical system 5 is an arrangement surface of the aperture stops 13A to 13D and the like of the illumination system aperture stop member 11, and the illuminance unevenness of the exposure light IL incident on the illumination system aperture stop member 11 approximately can be ignored. In other words, the light amount distribution can be regarded as the distribution itself of the aperture area (light transmission area) of each aperture stop. The following operation will be described in a plurality of steps.

[Preliminary process]
In this step, three types of aperture stop shapes are set in advance before exposure, and the calculation unit in the main control system 1 calculates the moment M when using each aperture stop, and the imaging characteristics at that time are calculated. Is actually measured. Note that the number of aperture stops for calculating the moment M and measuring the imaging characteristics in advance may be two, or three or more. Information on aperture shapes such as aperture stops 13A to 13D of the illumination system aperture stop member 11 is stored in the storage unit in the main control system 1 in advance. Further, exposure data such as illumination conditions is stored in the storage device 1a such as a magnetic disk device connected to the main control system 1, and the control unit in the main control system 1 reads out from the storage device 1a. The aperture diameter of the aperture stop 13A is designated based on the exposure data.

  FIG. 3 shows the shapes of the aperture stops 13A1, 13A2, and 13D that are sequentially set on the pupil plane 5P of the illumination optical system 5. In FIG. 3, the aperture stops 13A1 and 13A2 are circular shapes having coherence factors of approximately minimum and maximum, respectively. Illumination is shown, and the aperture stop 13D shows dipole illumination. With the orthogonal coordinate system parallel to the X axis and the Y axis in FIG. 1 as the x axis and the y axis, with the optical axis IAX on the pupil plane 5P as the center, the light quantity distribution of the exposure light IL on the pupil plane 5P is I (x, y), a moment Mx in the x direction in which the y axis is regarded as a first reference line, a moment My in the y direction in which the x axis is regarded as a second reference line, and a radial moment in which the optical axis IAX is regarded as a reference point MR can be calculated from the following equations (1), (2), and (3). In this case, the aperture pattern itself of each aperture stop 13A1, 13A2, 13D of FIG. 3 may be used as the light quantity distribution I (x, y). At this time, the moment is calculated with the value of the position where the exposure light IL passes as 1 and the value of the position where the exposure light IL does not pass as 0.

  On the pupil plane 5P, the coordinate system obtained by shifting the origin of the orthogonal coordinate system (x, y) from the optical axis IAX and rotating it by a predetermined angle is defined as (x ′, y ′), and the y ′ axis and x ′. The axes may be considered as first and second reference lines, respectively. A point shifted from the optical axis IAX may be regarded as the reference point.

  As an example, assuming that the moments Mx in the x direction calculated corresponding to the respective aperture stops 13A1, 13A2, and 13D in FIG. 3 are Mx1, Mx3, and Mx2 on the horizontal axis in FIG. Thus, the imaging characteristics of the projection optical system PL are measured. Specifically, assuming that the imaging characteristic is a magnification error γ, for example, a test reticle for measuring an imaging characteristic in which a plurality of predetermined evaluation marks are formed on the reticle stage 22 in FIG. 1 instead of the reticle R. Is set to each aperture stop and the exposure light IL is irradiated for a predetermined time. After that, these evaluation marks are transferred onto an unexposed wafer coated with a resist via the projection optical system PL, and after development, the position of the image of these evaluation marks is measured using a coordinate measuring device or the like. As a result, the magnification errors γ1, γ2, and γ3 on the vertical axis in FIG. A characteristic curve 50 composed of a broken line connecting three points determined by the moments Mx1, Mx2, Mx3 and the corresponding magnification errors γ1, γ2, γ3 is stored in the storage unit in the main control system 1 with the moment Mx and the magnification error γ. Is stored as data indicating the relationship. Instead of the characteristic curve 50, for example, a high-order function curve of moment Mx optimized to pass through three points may be used.

  As shown in FIG. 4, the illumination area 21R on the reticle R (or test reticle) in FIG. 1 has a Y-direction (scanning direction) width of LY, but an X-direction (non-scanning direction) length. The length LX can be controlled by the movable blind 18B of FIG. Then, the light amount distribution on the pupil plane of the projection optical system PL changes depending on the shape of the illumination area 21R, and the amount of change in imaging characteristics due to irradiation heat also changes. Here, it is assumed that the length LX in the X direction of the illumination region 21R is set to the most frequently used width LX1. This preliminary step can be omitted.

[Calculation process]
In this process, in the actual exposure process, the illumination system aperture stop member 11 is driven to select an aperture stop (for example, an aperture stop 13C for annular illumination) that matches the reticle R to be exposed. Then, the calculation unit in the main control system 1 calculates the moment Mxm in the x direction from the shape data of the aperture stop 13C from the equation (1), and proceeds to the next adjustment step. The moments Mym and MRm may be calculated together with the formula (1) or using the formula (2) and / or the formula (3) instead of the formula (1).

[Adjustment process]
Here, the projection optical system PL is adjusted based on the moment Mxm calculated in the calculation process. For this purpose, the moment Mxm calculated in the calculation step is applied to the relationship (characteristic curve 50 in FIG. 5A) obtained in the preliminary step to obtain the corresponding magnification error γm. This corresponds to the step of estimating the imaging characteristics of the projection optical system PL by interpolating the result obtained in the preliminary step.

When the preliminary step is omitted, as an example, the magnification error may be calculated theoretically based on the calculated moment Mxm.
Next, the main control system 1 issues a command to correct the magnification error γm obtained for the imaging characteristic control system 36 of FIG. In response to this, the imaging characteristic control system 36 adjusts the magnification so as to cancel the magnification error γm by driving a predetermined lens in the projection optical system PL via the imaging characteristic correction device 39. . As a result, the magnification error γm due to the influence of the irradiation heat is removed, so that the projection magnification of the projection optical system PL easily becomes a target value, and the pattern of the reticle R can be transferred onto the wafer W with high accuracy. .

Similarly, when the illumination conditions are switched, the moment Mx is calculated from the aperture shape of the aperture stop used in the illumination system aperture stop member 11, and the magnification error γ is obtained from the characteristic curve 50 in FIG. Thus, the magnification of the projection optical system PL can be maintained at the target value easily and with high accuracy.
When calculating the moment Mx, the shape data of the illumination region 21R in FIG. 4, for example, the value of the ratio between the width LX in the X direction and the width LY in the Y direction (= LX / LY) may be taken into consideration. Good. For this purpose, as an example, the imaging characteristics may be measured when the width LX is set to the narrowest width LX2 and the widest width LX1 within the range used in the normal exposure process.

  FIG. 5B shows an example of the relationship between the moment Mx in the x direction and the magnification error γ when the shape of the illumination area 21R is considered in addition to the shape of the aperture stop. 1), the aperture stops of the illumination system aperture stop member 11 in FIG. 1 are sequentially set to the respective aperture stops 13A1, 13A2, and 13D in FIG. 3, and the moments Mx1, Mx3, and Mx2 in the x direction are calculated from the equation (1). calculate. Further, for example, the aperture stop 13A1 (moment Mx1) is set, and the test reticle for measuring the imaging characteristics is placed on the reticle stage 22 in FIG. 1, and the X direction of the illumination area 21R in FIG. By measuring the magnification error γ with the width set to LX2, the data of the point A1 in FIG. 5B is obtained. Next, the magnification error γ is measured in a state where the X-direction width of the illumination area 21R is set to LX1, thereby obtaining the data of the point A2 in FIG.

Similarly, in the moments Mx3 and Mx2, the magnification error γ is measured by sequentially setting the width in the X direction of the illumination region 21R to LX2 and LX1, and the magnification error γ is measured, and the shape and magnification of the illumination region 21R. As data representing the relationship with the error γ, a characteristic curve 51 corresponding to the width LX2 and a characteristic curve 52 corresponding to the width LX1 in FIG. 5B are obtained.
After that, when a certain aperture stop of the illumination system aperture stop member 11 in FIG. 1 is selected, the moment Mx in the x direction of the light quantity distribution calculated correspondingly is Mxm, and the X direction of the illumination region 21R is in the X direction. Assuming that the width is LX (LX2 ≦ LX ≦ LX1), in the main control system 1, first, in the characteristic curves 51 and 52 in FIG. 5B, the magnification error (points γm1 respectively) at points P1 and P2 where the moment is Mxm. And γm2). Next, a magnification error γm3 when the width of the illumination area 21R in the X direction is LX is obtained by the following interpolation calculation.

γm3 = γm1 + (γm2−γm1) (LX−LX2) / (LX1−LX2)
= {[Gamma] m1 (LX1-LX) + [gamma] m2 (LX-LX2)} / (LX1-LX2) (4)
Then, by correcting the magnification so as to cancel out the magnification error γm3 via the imaging characteristic correction device 39 of FIG. 2, even when the illumination conditions and the shape of the illumination area 21R are changed, the influence of irradiation heat is suppressed. Thus, the projection magnification of the projection optical system PL can be maintained at the target value.

  In the above embodiment, the magnification error is considered as the imaging characteristic of the projection optical system PL. However, as the imaging characteristic, the center as CA in FIG. 6A and the defocus in FIG. 6B are used. F and the spherical aberration SA in FIG. 6C can also be obtained from the moment M of the light amount distribution. That is, the center ass CA in FIG. 6A is obtained from the measurement data at two points regarding the difference (Mx−My) between the moment Mx in the x direction in the equation (1) and the moment My in the y direction in the equation (2). After determining the characteristic curve 53, the moment difference (Mx−My) calculated when an arbitrary aperture stop is selected can be obtained by fitting the characteristic curve 53.

  Similarly, the defocus F in FIG. 6B is obtained by converting the characteristic curve 54 from the measurement data at three points with respect to the average value (Mx + My) / 2 of the moment Mx in the equation (1) and the moment My in the equation (2). After the determination, the average value of moments (Mx + My) / 2 calculated when an arbitrary aperture stop is selected can be obtained by applying to the characteristic curve 54. Further, the spherical aberration SA in FIG. 6C is calculated when an arbitrary aperture stop is selected after determining the characteristic curve 55 from the measurement data at three points with respect to the radial moment MR in the equation (3). By applying the radial moment MR to the characteristic curve 55, it can be obtained.

  Among the imaging characteristics obtained from the moment M of the light quantity distribution in this way, the spherical aberration SA can be corrected by driving a predetermined lens by the imaging characteristics correction device 39 in FIG. On the other hand, the center ass CA can be corrected by, for example, irradiating light to a predetermined lens element from the waveguides 38A and 38B in FIG. 2, and the defocus F is, for example, the focusing operation of the wafer stage WST in FIG. It is possible to correct with.

  In the above embodiment, the moment M of the light quantity distribution is calculated by calculation on the pupil plane of the illumination optical system as the predetermined plane. In addition, the light quantity distribution on the pupil plane of the projection optical system PL of FIG. It is also possible to calculate the moment M from this result. For this purpose, as shown in FIG. 2, a wavefront measuring device is applied to an exposure region in a state where a reticle R on which an actual exposure pattern RP is formed is arranged on the object plane of the projection optical system PL and irradiated with exposure light IL. 29 is moved, and the light quantity distribution on the pupil plane PPL of the projection optical system PL may be actually measured using the image sensor 30C of FIG. As an example, it is assumed that the aperture stop 13A1 of FIG. 3 is set in the illumination optical system 5 of FIG.

  FIG. 7 shows an example of the light amount distribution on the pupil plane PPL centered on the optical axis AX of the projection optical system PL measured in this way. In FIG. 7, the zero-order light 13A1 of the aperture stop 13A1 in FIG. In addition to (0), diffracted light 13A1 (i, j) of i-th order in the X direction and j-th order (i, j is an integer other than 0) in the Y direction is measured as the light amount distribution. Therefore, in the main control system 1 of FIG. 1, the moment Mx in the x direction, the moment My in the y direction, and the radius are similar to the equations (1), (2), and (3) for the light quantity distribution in FIG. Calculate the directional moment MR. These moments Mx, My, MR can be used instead of the moments of the above-described embodiment.

In this case, since the moment M can be calculated based on the actual light amount distribution considering the influence of the pattern of the reticle R, the imaging characteristics of the projection optical system PL can be obtained with higher accuracy. As a result, The imaging characteristics can be controlled with higher accuracy.
In the above-described embodiment, the moment of the light quantity distribution is calculated on the pupil plane of the projection optical system PL or a conjugate plane thereof, but in addition, on the image plane of the projection optical system PL or a plane conjugate thereto. It is also possible to use the calculated moment of light distribution.

In the above-described embodiment, the imaging characteristics of the projection optical system PL are adjusted as the formation state of the pattern image formed on the wafer W. In addition, the spectral width of the exposure light EL, the exposure light EL It is also possible to adjust the exposure amount and the focus position (or tilt angle, etc.) of wafer stage WST (or reticle stage 22).
[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. In this example, the projection exposure apparatus shown in FIGS. 1 and 2 is also used. However, in order to correct the variation in the imaging characteristics of the projection optical system PL due to the irradiation of the exposure light EL, the information on the moment of the light quantity distribution is used. The image forming characteristic correction device 39 in FIG. 2 is different in that the irradiation coefficient for driving the lenses 43 ₁ and 43 ₂ to be driven is adjusted. The irradiation coefficient represents the driving amount of the lens with respect to the illuminance (or pulse energy, the same applies hereinafter) of the exposure light EL, and by driving the lens corresponding to the amount obtained by multiplying the irradiation coefficient by the illuminance of the exposure light EL, For example, the imaging characteristics that have been changed by the exposure light EL irradiation can be returned to the state before the change. The irradiation coefficient is actually a plurality of elements of a matrix in which the number corresponding to the degrees of freedom of the plurality of lenses driven by the imaging characteristic correction device 39 is the number of rows and columns, and the imaging characteristic control system 36 It is assumed that it is a single element for simplicity in the following.

  Hereinafter, with reference to the flowcharts of FIGS. 8 to 10, the pupil of the illumination optical system calculated in this example based on at least one of the above formulas (1), (2), and (3) FIG. 2 shows an example of an operation for correcting the imaging characteristics of the projection optical system PL shown in FIG. 2 that changes due to the irradiation of the exposure light EL by associating the moment M of the light amount distribution on the surface or the conjugate surface with the irradiation coefficient. explain. The following operations are controlled by the main control system 1 in FIG.

  First, after the projection exposure apparatus in FIG. 1 is installed in a device manufacturing factory or the like, or at the time of initial adjustment after the maintenance or the like is completed, the process proceeds from step 100 to step 110 as shown in FIG. An irradiation adjustment step for obtaining the relationship between the illumination condition and the irradiation coefficient by actual measurement is executed, and further, a moment calculation step for obtaining the relationship between the illumination condition and the moment M is executed at step 120. Thereafter, the process proceeds to step 140, where the initial adjustment is completed in step 150 by associating the moment M with the irradiation coefficient. An example of the irradiation adjustment process in step 110 is shown in FIG. 8B, and an example of the moment calculation process in step 120 is shown in FIG.

  In the irradiation adjustment step of FIG. 8B, first, a test reticle TR on which a plurality of marks for measuring imaging characteristics are formed is loaded on the reticle stage 22 of the projection exposure apparatus shown in FIG. Is set to drive the illumination condition (step 112). In the next step 113, irradiation of the exposure light EL is started, and as shown in FIG. 2, the wafer stage WST is driven, and images of the plurality of marks on the test reticle TR are projected by the projection optical system PL of the wavefront measuring device 29. By sequentially scanning with the slit 30X (or 30Y) and processing the detection signal of the photoelectric sensor 30E, the coordinates of the images of the plurality of marks are obtained, and predetermined aberrations such as distortion of the projection optical system PL based on these coordinates Measure (imaging characteristics).

  In the next step 114, the illuminance of the exposure light EL is set to a predetermined value, the exposure light EL is irradiated for a predetermined time, and the projection optical system PL is heated as in normal exposure (dummy heat). In the next step 115, it is determined whether or not the aberration fluctuation of the projection optical system PL due to the irradiation of the exposure light EL is almost saturated, that is, whether or not the measurement is finished. It should be noted that the execution order of step 113 and step 114 can be reversed. If the measurement is not completed, the aberration measurement in step 113 is performed again. If the measurement is completed in step 115, the process proceeds to step 116, where the lens to be driven of the imaging characteristic correction device 39 in FIG. An irradiation coefficient is calculated by dividing the driving amount by the illuminance of the exposure light EL. Next, the calculated irradiation coefficient is written in the table 1 in the storage device 1a of FIG. 2 in correspondence with the illumination condition (step 117), and the irradiation adjustment is completed. The operations in steps 112 to 117 are executed under a plurality of exposure conditions (conditions including illumination conditions, the numerical aperture of the projection optical system PL, the spectrum width of the exposure light EL, etc.). The irradiation coefficient may be written correspondingly.

  Next, in the moment calculation process of FIG. 9, after starting the operation in step 121, when calculating the moment based on the actual value of the light amount distribution, the process proceeds to step 122, and the moment is calculated based on the prediction of the light amount distribution. Sometimes step 126 is entered. In the former step 122, the reticle R for actual exposure on which the original pattern of the pattern formed in each shot area of the wafer W is loaded on the reticle stage 22 of FIG. Driving conditions are set by driving. In the next step 123, irradiation of the exposure light EL is started, and as shown in FIG. 2, the wafer stage WST is driven to move the pinhole 30A of the wavefront measuring device 29 onto the optical axis AX of the projection optical system PL. Then, the light quantity distribution on the pupil plane PPL of the projection optical system PL is measured by processing the image pickup signal of the image pickup element 30C by the image processing unit in the main control system 1. Next, using the measured value of the light quantity distribution, the moment M is calculated using the above equation (1) or the like (step 124), and then the calculated moment M is associated with the illumination condition in the storage device 1a. (Step 125), the moment calculation is completed (step 132). Also in this case, the moment may be calculated corresponding to a plurality of exposure conditions and written in the table 2.

  On the other hand, in step 126, an illumination condition is set in the main control system 1, and in the next step 127, it is determined whether or not it is a special illumination condition. When the illumination condition is a commonly used illumination condition such as normal illumination, annular illumination, or dipole illumination, the operation proceeds to step 128, and the calculation unit in the main control system 1 Using the light amount distribution (predicted distribution) of the exposure light EL on the pupil plane of the illumination optical system corresponding to the illumination condition (or approximately the aperture shape of the aperture stop), the above equation (1) and the like can be obtained. To calculate the moment M. Thereafter, the calculated moment M is written in the table 2 in the storage device 1a in correspondence with the illumination condition (step 129), and the calculation of the moment is completed (step 132). Also in this case, the moment may be calculated corresponding to a plurality of exposure conditions.

  In step 127, if the illumination condition is a special illumination condition that is not generally used (for example, predetermined modified illumination), the operation proceeds to step 130 and the calculation in the main control system 1 is performed. The unit uses the set value (or aperture shape of the aperture stop) of the exposure light EL on the pupil plane of the illumination optical system corresponding to the illumination condition to calculate the moment M using the above equation (1) and the like. calculate. Thereafter, the calculated moment M is written in the table 2 in the storage device 1a in correspondence with the illumination condition (step 131), and the moment calculation is completed (step 132). Also in this case, the moment may be calculated corresponding to a plurality of exposure conditions. Further, the moment may be calculated under both general illumination conditions and special illumination conditions, and the result may be written in the table 2.

  Next, in step 140 of FIG. 8A, the calculation unit in the main control system 1 of FIG. 2 performs the table 1 created by the irradiation adjustment operation of FIG. 8B and the moment calculation operation of FIG. By comparing the created table 2 with the moment M and the irradiation coefficient in the same illumination condition (or exposure condition), the moment (pair) irradiation coefficient table 3 is created, and the table 3 is stored in the storage device. Store in 1a.

  Next, when an irradiation coefficient is set in the imaging characteristic control system 36 of the imaging characteristic correction device 39 in FIG. 2 during the actual exposure process, in step 162 in FIG. 10, the contents in the storage device 1a in FIG. Determine whether or not to use exposure-adjusted exposure data (data indicating the sequence of the exposure operation in which the irradiation coefficient determined in the operation of FIG. 8B according to the illumination condition, reticle pattern, etc.) is recorded When the exposure data is used, in step 163, the irradiation coefficient corresponding to the illumination condition to be used is read from the exposure data, and in step 164, the irradiation coefficient is read by the imaging characteristic correction device 39 in FIG. By setting the image characteristic control system 36, the calculation of the irradiation coefficient is completed (step 169). On the other hand, when the exposure data that has been subjected to irradiation adjustment in step 162 is not used, the process proceeds to step 165, and the illumination condition (irradiation adjusted) that was used when creating table 1 in step 117 of FIG. Determine whether lighting conditions are used. In the case of using the illumination condition that has been adjusted for irradiation, in step 166, the irradiation coefficient corresponding to the illumination condition is read from the table 1 in the storage device 1a, and in step 164, the irradiation coefficient is corrected for the imaging characteristics in FIG. By setting the imaging characteristic control system 36 of the apparatus 39, the determination of the irradiation coefficient is completed.

  If the illumination condition that has been adjusted for irradiation is not used in step 165, the process proceeds to step 167, and the moment M of the light amount distribution is read from the exposure data. This may be obtained in advance or at the time of exposure by calculation similar to step 124, 128, or 130 in FIG. In the next step 168, the moment M read in step 167 is applied to the moment (pair) irradiation coefficient table 3 created in step 140 of FIG. 8A, and the irradiation coefficient is calculated by, for example, interpolation calculation. Thereafter, in step 164, the irradiation coefficient is set in the imaging characteristic control system 36 of the imaging characteristic correction apparatus 39 in FIG. By driving the imaging characteristic correction device 39 based on the irradiation coefficient, the imaging characteristic of the projection optical system PL can be maintained in a predetermined state even when the illumination condition or the exposure condition is switched. Thus, according to this example, since the irradiation coefficient can be determined directly from the moment of the light amount distribution, the imaging characteristics of the projection optical system PL can be maintained in a predetermined state quickly and with high accuracy.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS. This example basically uses the projection exposure apparatus shown in FIGS. 1 and 2 except that a detachable wavefront sensor 90 shown in FIG. 11 is used instead of the wavefront measuring apparatus 29 shown in FIG. That is, the light quantity distribution is measured on the pupil plane of the projection optical system PL of the projection exposure apparatus shown in FIG. 1 (the conjugate plane of the pupil plane of the illumination optical system), or the wavefront aberration is measured as the imaging characteristic of the projection optical system PL. In this case, the wavefront sensor 90 in FIG. 11 is mounted in the vicinity of the wafer holder 24 on the wafer stage WST in FIG. 2, and the wavefront sensor 90 is removed from the wafer stage WST in other cases. From the light quantity distribution on the pupil plane of the projection optical system PL, the moment can be calculated with high accuracy based on the above equation (1). Hereinafter, the configuration and operation of the wavefront sensor 90 of this example will be described.

  FIG. 11 shows a wavefront sensor 90. As the wavefront sensor 90, a Shack-Hartmann type wavefront sensor using a microlens array in a light receiving optical system is used. As shown in FIG. 11, the wavefront sensor 90 includes a casing 97 having an internal space whose YZ cross section is substantially L-shaped, and a plurality of optical elements arranged in a predetermined positional relationship inside the casing 97. A light receiving optical system and a detector 95 arranged at the + Y side end inside the housing 97 are provided. The casing 97 is formed of a member having an L-shaped YZ cross section, a space formed therein, and an uppermost portion (+ Z side end face) opened. An opening 97 a having a circular shape in plan view at the top of the housing 97 is covered with a sign plate 91.

  The marking plate 91 is made of, for example, a glass substrate as a base material, and is orthogonal to the optical axis AX1 of the wavefront sensor 90 at the same height position (Z direction position) as the surface of the wafer W fixed to the wafer holder 24 of FIG. Has been placed. As shown in FIG. 12, a circular opening 91a is formed on the surface of the marking plate 91 at the center of the reflective film made of a metal such as chromium. Around the opening 91a, there are formed three or more sets (four sets in FIG. 12) of two-dimensional position detection marks 91b whose positional relationship with the opening 91a is known by design. In this example, a combination of a line and space mark 91c periodically formed in the X direction and a line and space mark 91d periodically formed in the X direction is employed as the mark 91b. The line and space marks 91c and 91d can be detected by the alignment sensor ALG in FIG. 2, and the position of the opening 91a can be aligned based on the detection result.

  The light receiving optical system of the wavefront sensor 90 is sequentially disposed on the + Y side of the folding mirror 96 and the collimator lens 92 (objective lens) and the folding mirror 96 which are sequentially disposed below the marking plate 91 inside the casing 97. The relay lens system 93 includes lenses 93a and 93b and a microlens array 94 as a wavefront splitting optical element. The optical path of the light incident on the collimator lens 92 vertically downward through the opening 91 a of the index plate 91 is bent by the bending mirror 96 toward the relay lens system 93 at a substantially right angle. The light incident on the collimator lens 92 is converted into parallel light, and then enters the microlens array 94 via the bending mirror 96 and the relay lens system 93.

  As shown in FIG. 13A, the microlens array 94 is held by a square frame-shaped holding member 82, and the wavefront dividing unit 84 is configured by the microlens array 94 and the holding member 82 (see FIG. 11). ). FIG. 13B is a cross-sectional view taken along line BB in FIG. 13A, and as can be seen from FIGS. 13A and 13B, the holding member 82 has an L-shaped cross section. The square opening 82a is formed by the end surface of the inner peripheral side. One end of the piston rod 86 is fixed to the upper end (+ Z side end) of the holding member 82. A piston (not shown) is provided at the other end of the piston rod 86, and the piston is accommodated in an air cylinder 88 shown in FIG.

  In FIG. 11, one end of air pipes 72 and 74 is connected to the air cylinder 88 in the vicinity of one end (upper end) and the other end (lower end), respectively. The air passages in the air pipes 72 and 74 communicate with the space inside the air cylinder 88, respectively. The other ends of the air pipes 72 and 74 are respectively connected to ports A and B of a flow path switching valve 76 formed of a four-way valve. One end of each of the air piping 72 and 74 is connected to the vacuum pump 78. The other end of the connected pipe 62 and the other end of the pipe 64 connected at one end to an air supply mechanism 66 incorporating a compressor are connected. The flow path switching valve 76 is controlled by the main control system 1 in FIG. 2, and the first state in which the port A and the port C are connected and the port B and the port D are connected, and the port A and the port D are connected. And the second state in which the port B and the port C are connected are switched. The main control system 1 also controls on / off of the vacuum pump 78 and the air supply mechanism 66.

  For example, when the main control system 1 switches the flow path switching valve 76 to the second state and turns on both the vacuum pump 78 and the air supply mechanism 66, the piston (and the piston rod 86) inside the air cylinder 88 is turned on. Thus, the wavefront dividing unit 84 is moved from the first position (for example, the upper movement limit position) retracted from the optical path to the second position (lower movement limit position) shown in FIG. This second position is set in advance as a position where the center of the microlens array 94 constituting the wavefront dividing unit 84 substantially coincides with the optical axis AX1.

  On the other hand, when the wavefront dividing unit 84 is in the second position shown in FIG. 11, the main control system 1 switches the flow path switching valve 76 to the first state, and further turns on the vacuum pump 78 and the air supply mechanism 66. As a result, the piston (and piston rod 86) inside the air cylinder 88 is pushed up, and the wavefront splitting unit 84 moves from the second position to the first position (upper movement limit position) and retracts from the optical path.

As described above, in this embodiment, the air cylinder 88, the flow path switching valve 76, the vacuum pump 78, and the air supply mechanism 66 are used to insert the microlens array 94 as the wavefront splitting optical element into and out of the optical path. A removal mechanism is configured. The microlens array 94 is configured by arranging a plurality of small lenses (microlenses) in an array in a plane orthogonal to the optical path. More specifically, as shown in FIGS. 13A and 13B, the microlens array 94 includes a microlens 98 having a large number of square positive refractive powers each having a side length D _1. Are densely arranged in a matrix. Here, the optical axes of the microlenses 98 are substantially parallel to each other. FIG. 13A shows an example in which microlenses 98 are arranged in a matrix of 7 rows × 7 columns. Such a microlens array 94 is formed by performing an etching process on a parallel flat glass plate. In the microlens array 94, an image forming light beam of an image is emitted for each microlens 98 through the opening 91 a of the marking plate 91.

  The detector 95 of the wavefront sensor 90 includes a light receiving element (hereinafter referred to as a CCD) 95a composed of a two-dimensional CCD, and an electric circuit 95b such as a charge transfer control circuit. The CCD 95a has an area sufficient to receive all of the light beams incident on the collimator lens 92 and emitted from the microlens array 94. The CCD 95a is an imaging plane on which an image of a pin pole pattern, which will be described later, formed in the opening 91a is re-imaged by each microlens 98 of the microlens array 94, and is an optical conjugate of the surface on which the opening 91a is formed. The surface has a light receiving surface. In addition, this light receiving surface is located on a surface slightly deviated from the conjugate surface with the pupil plane of the projection optical system PL when the microlens array 94 is retracted from the optical path.

  In the detector 95, when the microlens array 94 is in the second position described above, the imaging result of the pinhole pattern image re-imaged by each microlens 98 is input to the main control system 1 as imaging data IMD1. Send. Further, when the micro lens array 94 is in the first position, the detector 95 transmits the imaging result of the image formed on the light receiving surface to the main control system 1 as imaging data IMD2. The outer shape of the casing 97 is fitted to the sensor mounting portion of wafer stage WST in FIG. 2 and is detachable from wafer stage WST.

  When measuring the wavefront aberration of the projection optical system PL with the wavefront sensor 90 of this example mounted on the wafer stage WST of FIG. 2, a predetermined pinhole pattern is formed instead of the reticle R of FIG. The test stage is loaded, and wafer stage WST is driven so that an image of the pinhole pattern by projection optical system PL is positioned within opening 91a of sign plate 91 in FIG. Next, the microlens array 94 is installed between the relay lens system 93 and the detector 95 via the insertion / removal mechanism of FIG. 11, and the imaging signal of the CCD 95a of the detector 95 is processed to By determining the position of the light beam collected by each microlens, the wavefront aberration of the projection optical system PL can be determined. The operation for obtaining the wavefront aberration can be performed in place of the aberration measurement operation in FIG. That is, various aberrations such as distortion of the projection optical system PL, spherical aberration, and astigmatism can be obtained from the wavefront aberration.

  Next, when measuring the light amount distribution of the exposure light EL on the pupil plane PPL of the projection optical system PL of FIG. 2, the actual exposure reticle is loaded as the reticle R of FIG. Wafer stage WST is driven so that opening 91a of sign plate 91 in FIG. 12 substantially matches optical axis AX. Then, the light quantity distribution on the pupil plane PPL can be obtained by processing the imaging signal of the CCD 95a of the detector 95 in a state where the microlens array 94 is retracted from the optical path via the insertion / removal mechanism of FIG. This step can be executed in place of the pupil light amount distribution measurement in step 123 of FIG. 9, and the moment can be calculated from the light amount distribution thus obtained by the above equation (1) or the like.

As described above, according to this example, by using the detachable wavefront sensor 90, the information on the moment of the light amount distribution can be easily and accurately associated with the wavefront aberration (imaging characteristic) of the projection optical system PL. It can be performed.
In the projection exposure apparatus of the above embodiment, an illumination optical system composed of a plurality of lenses and a projection optical system are incorporated in the exposure apparatus main body and optical adjustment is performed, so that a reticle stage or wafer stage composed of a large number of mechanical parts is provided. It can be manufactured by attaching to the exposure apparatus main body, connecting wiring and piping, and further performing general adjustment (electrical adjustment, operation check, etc.). The exposure apparatus is preferably manufactured in a clean room where the temperature, cleanliness, etc. are controlled.

  In addition, for microdevices such as semiconductor devices, the step of designing the function / performance of the microdevice, the step of manufacturing a mask (reticle) based on this design step, the step of manufacturing the substrate that is the base material of the device, as described above Substrate processing steps including a step of exposing a reticle pattern onto a substrate (wafer or the like) by the projection exposure apparatus of the embodiment, a step of developing the exposed substrate, a heating (curing) and etching step of the developed substrate, and a device assembly step (Including a dicing process, a bonding process, and a packaging process) and an inspection step.

  The present invention can be applied not only to a scanning exposure type projection exposure apparatus (such as a scanning stepper) but also to a batch exposure type projection exposure apparatus (such as a stepper). The present invention is also applicable to the case where the imaging characteristics of the projection optical system are corrected by an immersion type exposure apparatus disclosed in, for example, the pamphlet of International Publication No. 99/49504, the pamphlet of International Publication No. 2004/019128, etc. can do.

In the above-described embodiment, a reticle (mask) on which a transfer pattern is formed is used. Instead of this reticle, for example, as disclosed in US Pat. No. 6,778,257. In addition, an electronic mask that forms a transmission pattern or a reflection pattern based on electronic data of a pattern to be exposed may be used.
In addition, the present invention is not limited to application to an exposure apparatus for manufacturing a semiconductor device, for example, an exposure apparatus for a display device such as a liquid crystal display element formed on a square glass plate or a plasma display, It can also be widely applied to an exposure apparatus for manufacturing various devices such as an imaging device (CCD or the like), a micromachine, a thin film magnetic head, a MEMS (Microelectromechanical Systems), and a DNA chip. Furthermore, the present invention can also be applied to an exposure process (exposure apparatus) when manufacturing a mask (photomask, reticle, etc.) on which mask patterns of various devices are formed using a photolithography process. As described above, the present invention is not limited to the above-described embodiment, and can have various configurations without departing from the gist of the present invention.

  By using the present invention, it is possible to easily and accurately adjust the formation state of the pattern image when the illumination conditions and the like are switched in various ways in the exposure apparatus. It becomes possible to manufacture with high accuracy.

1 is a perspective view showing a projection exposure apparatus according to a first embodiment of the present invention. FIG. 2 is a partially cutaway view showing an imaging characteristic correction device 39 and a wavefront measuring device 29 in FIG. 1. It is a figure which shows three types of aperture stops. It is a top view which shows the shape of the illumination area | region on a reticle. (A) is a diagram showing an example of the relationship between the moment of the light amount distribution and the magnification error γ, and (B) further shows an example of the relationship between the moment of the light amount distribution and the magnification error γ when the shape of the illumination area is taken into consideration. FIG. (A) is a diagram showing an example of the relationship between the moment of the light amount distribution and the center ass, (B) is a diagram showing an example of the relationship between the moment and the defocus amount, and (C) is a diagram showing the relationship between the moment and the spherical aberration. It is a figure which shows an example. It is a figure which shows an example of light quantity distribution in the pupil plane of projection optical system PL. (A) is a flowchart showing an example of the operation of associating the moment and the irradiation coefficient in the second embodiment of the present invention, (B) is a flowchart showing an example of the irradiation adjustment operation of step 110 of FIG. 8 (A). It is. It is a flowchart which shows an example of the moment calculation operation | movement of step 120 of FIG. 8 (A). It is a figure which shows an example of the operation | movement which sets an irradiation coefficient using the table calculated | required by step 140 of FIG. 8 (A). It is sectional drawing which shows the wavefront sensor 90 used in the 3rd Embodiment of this invention. It is an enlarged plan view which shows the pattern of the marking board 91 of FIG. (A) is a top view which shows the micro lens array 94 of FIG. 11, (B) is sectional drawing which follows the BB line of FIG. 13 (A).

Explanation of symbols

  R ... reticle, PL ... projection optical system, W ... wafer, 1 ... main control system, 5 ... illumination optical system, 22 ... reticle stage, WST ... wafer stage, 29 ... wavefront measuring device, 36 ... imaging characteristic control system, 39 ... Imaging characteristic correction device, 90 ... Wavefront sensor

Claims (15)

In an exposure method of illuminating a pattern with an exposure beam and forming an image of the pattern on an object by a projection optical system,
A calculation step for calculating moment information corresponding to an integral of a product of a distance from a reference position on the predetermined surface and the light amount of the exposure beam;
And an adjusting step of adjusting an image formation state of the pattern based on the moment information calculated in the calculating step.   The exposure method according to claim 1, wherein the predetermined plane is a pupil plane of the projection optical system or a plane conjugate with the pupil plane.   The exposure method according to claim 1, wherein the adjusting step includes a step of correcting an imaging characteristic of the projection optical system.   4. The exposure method according to claim 3, further comprising a preliminary step of obtaining a relationship between the moment information and the imaging characteristics of the projection optical system in advance.   5. The relationship between the moment information and the imaging characteristics of the projection optical system is obtained in advance in the preliminary step in correspondence with exposure conditions including illumination conditions of the exposure beam. Exposure method.   In the preliminary step, the illumination conditions of the exposure beam are set to two conditions and dipole illuminations having different coherence factors, and the relationship between the moment information and the imaging characteristics of the projection optical system is obtained. The exposure method according to claim 5. The adjusting step includes estimating the imaging characteristics of the projection optical system by interpolation using the relationship obtained in the preliminary step and the moment information calculated in the calculation step;
The exposure method according to claim 4, further comprising a step of adjusting the projection optical system so as to correct the estimated imaging characteristics.   The moment information calculated in the calculating step is orthogonal to the first moment information corresponding to the integral of the product of the distance from the first reference line at each position and the light amount of the exposure beam, and the first reference line. The second moment information corresponding to the integration of the product of the distance from the second reference line and the light amount of the exposure beam, and the integration of the product of the distance from the predetermined reference point and the light amount of the exposure beam The exposure method according to claim 1, further comprising at least one of the third moment information. In an exposure apparatus that illuminates a pattern with an exposure beam and projects an image of the pattern onto an object by a projection optical system,
A light amount distribution measuring device for estimating or measuring the light amount distribution of the exposure beam on a predetermined surface;
An arithmetic unit that calculates moment information corresponding to an integral of a product of a distance from a reference position and a light amount of the exposure beam on the predetermined surface, using a light amount distribution obtained by the light amount distribution measuring device;
An exposure apparatus comprising: an adjustment device that adjusts an image formation state of the pattern based on moment information calculated by the arithmetic device.   The exposure apparatus according to claim 9, wherein the predetermined plane is a pupil plane of the projection optical system or a plane conjugate with the pupil plane.   11. The exposure apparatus according to claim 9, wherein the arithmetic unit stores a relationship between the moment information obtained in advance and an imaging characteristic of the projection optical system.   The arithmetic unit stores a relationship between the moment information and an imaging characteristic of the projection optical system in correspondence with a plurality of exposure conditions including an illumination condition of the exposure beam. The exposure apparatus according to any one of 11 to 11.   13. The exposure apparatus according to claim 12, further comprising an illumination optical system capable of switching the illumination condition of the exposure beam to two conditions having different coherence factors and a plurality of illumination conditions including dipole illumination.   14. The adjusting device includes a member that adjusts at least one of a position in the optical axis direction and a tilt angle of a predetermined optical member constituting the projection optical system. The exposure apparatus described in 1.   A device manufacturing method using the exposure apparatus according to claim 9.

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