JP2006073584A - Exposure apparatus and exposure method, and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure apparatus which can perform various operations such as exposure and measurement under a desired state of aberration having the non-rotational symmetry of a projection optical system. <P>SOLUTION: A main control system 20 calculates an aberration having a non-rotational symmetry of the projection optical system PL using a transfer function showing a relationship among the distribution of exposure light IL incident into the projection optical system PL, energy of the exposure light IL incident into the projection optical system PL, and a change in aberration having the non-rotational symmetry of the projection optical system PL. When the measured value exceeds a preliminarily set allowable value, exposure operation is suspended or switching-over of lighting conditions is delayed until the measured value becomes the allowable value or below. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exposure apparatus and method for transferring a mask pattern onto a substrate via a projection optical system, and a device manufacturing method for manufacturing a device using the exposure apparatus or method.

  When manufacturing a device such as a semiconductor element, a liquid crystal display element, an imaging device (CCD (Charge Coupled Device), etc.), a thin film magnetic head, etc., a wafer having a reticle pattern as a mask coated with a photoresist as a substrate (or In order to transfer to each shot area on a glass plate or the like, a projection exposure apparatus such as a stepper is used. In the projection exposure apparatus, the imaging characteristics of the projection optical system gradually change depending on the exposure light irradiation amount, ambient pressure change, and the like. For this reason, in order to always maintain the imaging characteristics in a desired state, the projection exposure apparatus can control the imaging characteristics by controlling the positions or postures of some optical members constituting the projection optical system, for example. An imaging characteristic correction mechanism for correction is provided. The imaging characteristics that can be corrected by a conventional imaging characteristic correction mechanism are low-order components having low rotational symmetry such as distortion and magnification.

  By the way, in recent exposure apparatuses, in order to increase the resolution for a specific pattern, so-called annular illumination or quadrupole illumination (an illumination method using four regions on the pupil plane of the illumination optical system as secondary light sources). There are increasing opportunities to use illumination conditions in which exposure light does not pass through a region including the optical axis on the pupil plane of the illumination optical system. When such an illumination condition is used, the exposure light is illuminated with the optical member in the vicinity of the pupil plane in the projection optical system being substantially hollow. Further, in order to increase the area of a pattern that can be transferred without increasing the size of the projection optical system, recently, a scanning exposure type projection exposure apparatus such as a scanning stepper is also frequently used. In the case of the scanning exposure type, the reticle is illuminated by a rectangular illumination area whose short side is the scanning direction. Therefore, the optical member close to the reticle and wafer in the projection optical system is mainly exposed to a non-rotationally symmetric area. It will be illuminated by light.

In such an exposure apparatus, there is a risk that high-order component fluctuations such as spherical aberration and non-rotationally symmetric fluctuations may occur. Accordingly, a projection exposure apparatus that suppresses these aberration fluctuations has been proposed in the following Patent Document 1, Patent Document 2, and the like. Further, a projection exposure apparatus in which the imaging characteristics of the projection optical system are strictly controlled even when the illumination condition is changed according to the reticle or reticle pattern is proposed in the following Patent Document 3 and the like.
Japanese Patent Laid-Open No. 10-64790 Japanese Patent Laid-Open No. 10-50585 JP-A-6-45217

  Recently, for example, when transferring a reticle pattern mainly including a predetermined line and space pattern, only two regions sandwiching the optical axis on the pupil plane of the illumination optical system are used as secondary light sources. Dipole illumination (bipolar illumination) may be used. Since this dipole illumination has a large light amount distribution and non-rotationally symmetric compared to quadrupole illumination, astigmatism on the optical axis (hereinafter referred to as “center ass”), which is a non-rotationally symmetric aberration component in the projected image. ) Occurs. Further, non-rotationally symmetric aberration fluctuations other than the center ass also occur due to the dipole illumination.

  Furthermore, when only one end of the rectangular illumination area on the reticle is illuminated with the exposure light, the exposure light quantity distribution is much larger and non-uniform on the reticle side and wafer side optical members of the projection optical system. Because of rotational symmetry, many non-rotationally symmetric aberration components are generated. Similarly, even when the reticle pattern density is particularly low in a specific area, the exposure light quantity distribution is large and non-rotationally symmetric on the reticle side and wafer side optical members of the projection optical system, so that it is non-rotationally symmetric. Aberration components are generated.

  Such non-rotationally symmetric aberration components cannot be corrected using the above-described imaging characteristic correction mechanism. Therefore, when the illumination condition is changed according to the reticle or reticle pattern, the projection optical system is not rotated even if the imaging characteristic of the projection optical system is controlled using the imaging characteristic correction mechanism under the new illumination condition. Symmetrical aberration components cannot be corrected. For this reason, the conventional technique cannot strictly control the imaging characteristics of the projection optical system in which an asymmetrical aberration component is generated.

  The present invention has been made in view of the above circumstances, and an exposure apparatus and method capable of executing various operations such as exposure and measurement while the imaging characteristics of the projection optical system are desired, and the exposure apparatus or method. It aims at providing the device manufacturing method which manufactures a device using. In particular, the present invention provides an exposure apparatus and method capable of performing various operations such as exposure and measurement in a state where the non-rotationally symmetric aberration of the projection optical system is desired, and a device is manufactured using the exposure apparatus or method. An object is to provide a device manufacturing method.

The present invention adopts the following configuration corresponding to each diagram shown in the embodiment. However, the reference numerals with parentheses attached to each element are merely examples of the element and do not limit each element.
In order to solve the above-described problems, an exposure apparatus of the present invention projects an image of a pattern on the substrate in the exposure apparatus that exposes the substrate by irradiating the substrate (W) with exposure light (IL). And a control system (20) for stopping the execution of the predetermined operation until the non-rotationally symmetric aberration of the projection optical system falls below a predetermined allowable value.
According to the present invention, the execution of the predetermined operation is stopped until the non-rotationally symmetric aberration of the projection optical system PL becomes a predetermined allowable value or less by the control system.
Here, the predetermined operation is an exposure operation on the substrate, or a distribution of the exposure light on a conjugate plane with respect to an image plane of the projection optical system, and the exposure light on the pupil plane or the conjugate plane of the projection optical system. It is characterized by including at least one change with the distribution.
Further, in the exposure apparatus of the present invention, the control system causes the distribution of light incident on at least part of the projection optical system, energy of light incident on at least part of the projection optical system, and non-projection of the projection optical system. A storage unit (37) for storing a transfer function indicating a relationship with a fluctuation amount of rotational symmetry aberration, and a measuring device for measuring the energy of light incident on at least a part of the projection optical system or an amount corresponding to the energy. A calculation unit (31) that calculates a non-rotationally symmetric aberration of the projection optical system based on a measurement result and the transfer function stored in the storage unit, and a non-rotation of the projection optical system calculated by the calculation unit And a determination unit (36) for determining whether or not the symmetric aberration is equal to or less than the predetermined allowable value.
In order to solve the above problems, an exposure method of the present invention irradiates a mask (R) with illumination light (IL), and transfers the mask pattern onto a substrate (W) via a projection optical system (PL). In the exposure method, the execution of the predetermined operation is stopped until the non-rotationally symmetric aberration of the projection optical system becomes a predetermined allowable value or less.
The device manufacturing method of the present invention includes a step (S46) of transferring a device pattern onto an object (W) using the above exposure apparatus or the above exposure method.

According to the present invention, it is possible to execute various operations in a state where the imaging characteristics of the projection optical system, in particular, non-rotationally symmetric aberration is desired.
Further, according to the present invention, a fine pattern can be faithfully transferred onto an object, and as a result, manufacturing defects can be reduced and devices can be manufactured with a high yield.

  Hereinafter, an exposure apparatus and method and a device manufacturing method according to an embodiment of the present invention will be described in detail with reference to the drawings.

[Exposure equipment]
FIG. 1 is a view showing the schematic arrangement of an exposure apparatus according to an embodiment of the present invention. The exposure apparatus shown in FIG. 1 moves the pattern formed on the reticle R onto the wafer W while moving the reticle R as a mask and the wafer W as a substrate relative to the projection optical system PL in FIG. This is a step-and-scan type scanning exposure type exposure apparatus that performs sequential transfer.

  In the following description, if necessary, an XYZ orthogonal coordinate system is set in the drawing, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. The XYZ orthogonal coordinate system shown in FIG. 1 is set so that the X axis and the Y axis are parallel to the wafer W, and the Z axis is set in a direction orthogonal to the wafer W. In the XYZ coordinate system in the figure, the XY plane is actually set to a plane parallel to the horizontal plane, and the Z-axis is set vertically upward. In this embodiment, the direction (scanning direction) in which the reticle R and the wafer W are moved synchronously is set to the Y direction.

The exposure apparatus shown in FIG. 1 includes an exposure light source 1, an illumination optical system ILS, a reticle stage RST, a projection optical system PL, a wafer stage WST, and a main control system 20 as a control system. The exposure light source 1 is, for example, a KrF excimer laser light source (wavelength 247 nm). As the exposure light source 1, an ultraviolet laser light source such as an ArF excimer laser light source (wavelength 193 nm), an F ₂ laser light source (wavelength 157 nm), a Kr ₂ laser light source (wavelength 146 nm), an Ar ₂ laser light source (wavelength 126 nm), Laser harmonic generation light sources, solid-state laser (semiconductor laser, etc.) harmonic generators, mercury lamps (i-line, etc.), etc. can also be used.

  The exposure light IL pulsed from the exposure light source 1 at the time of exposure is shaped into a predetermined shape through a beam shaping optical system (not shown), and the first fly eye as an optical integrator (a homogenizer or a homogenizer). The light is incident on the lens 2 and the illuminance distribution is made uniform. The exposure light IL emitted from the first fly-eye lens 2 is incident on a second fly-eye lens 4 as an optical integrator via a relay lens (not shown) and a vibrating mirror 3, and the illuminance distribution is further uniformized. . The vibrating mirror 3 is used for reducing speckles of the exposure light IL that is laser light and reducing interference fringes by a fly-eye lens. In place of the fly-eye lenses 2 and 4, a diffractive optical element (DOE: Diffractive Optical Element) or an internal reflection type integrator (rod lens or the like) can also be used.

  On the focal plane on the exit side of the second fly-eye lens 4 (pupil plane of the illumination optical system ILS), the exposure light quantity distribution (secondary light source) has a small circle (small σ illumination), a normal circle, and a plurality of eccentricity. An illumination system aperture stop member 5 for determining an illumination condition by setting it to any one of a region (dipole and quadrupole illumination), an annular shape, and the like is rotatably arranged by a drive motor 5c. The main control system 20 comprising a computer that controls the overall operation of the apparatus controls the rotation angle of the illumination system aperture stop member 5 via the drive motor 5c to set the illumination conditions.

  In the state shown in FIG. 1, among the plurality of aperture stops (σ stops) of the illumination system aperture stop member 5, first dipole illumination (bipolar illumination) in which two circular apertures are formed symmetrically about the optical axis. ), And a second dipole illumination aperture stop 5b having a shape obtained by rotating the aperture stop 5a by 90 °. A first aperture stop 5 a for dipole illumination is installed on the focal plane on the exit side of the second fly-eye lens 4. In this example, the light quantity distribution on the pupil plane of the illumination optical system ILS is adjusted using the illumination system aperture stop member 5a. However, as disclosed in US Pat. No. 6,563,567. The light quantity distribution on the pupil plane of the illumination optical system ILS may be adjusted using the optical member.

  The exposure light IL that has passed through the aperture stop 5a in the illumination system aperture stop member 5 enters the beam splitter 6 having a low reflectance, and the exposure light reflected by the beam splitter 6 passes through a condenser lens (not shown). The integrator sensor 7 receives the light. The detection signal of the integrator sensor 7 is supplied to the main control system 20, and based on this detection signal, the main control system 20 controls the output of the exposure light source 1, and uses a dimming mechanism (not shown) as necessary. The pulse energy of the exposure light IL is controlled stepwise.

  The exposure light IL transmitted through the beam splitter 6 is incident on the opening of the field stop 9 through a relay lens (not shown). The field stop 9 is actually composed of a fixed field stop (fixed blind) and a movable field stop (movable blind). The latter movable field stop is disposed on a surface substantially conjugate with the pattern surface (reticle surface) of the reticle R, and the former fixed field stop is disposed on a surface slightly defocused from the conjugate surface with the reticle surface. Yes. The fixed field stop is used to define the shape of the illumination area on the reticle R. Here, the case where the fixed field stop is slightly defocused from the conjugate plane with the reticle plane will be described as an example, but the fixed field stop may be arranged on the conjugate plane. The movable field stop moves in synchronization with the reticle R (or wafer) so that unnecessary portions are not exposed at the start and end of scanning exposure to each shot region to be exposed, and the illumination region thereof Used to block. Further, although the fixed field stop does not move during scanning exposure, it is also used to define the center and width of the illumination area in the scanning direction and non-scanning direction as necessary.

  The exposure light IL that has passed through the aperture of the field stop 9 illuminates the illumination area of the reticle surface of the reticle R with a uniform illuminance distribution through a condenser lens (not shown), a mirror 10 for bending an optical path, and a condenser lens 11. The normal shape of the aperture of the field stop 9 (fixed field stop) is a rectangle having an aspect ratio of about 1: 3 to 1: 4. Therefore, the normal shape of the illumination area on the reticle R substantially conjugate with the aperture of the field stop 9 is also rectangular.

  Under the exposure light IL, the pattern in the illumination area of the reticle R is coated with a photoresist at a projection magnification β (β is 1/4, 1/5, etc.) via a telecentric projection optical system PL. And projected onto an exposure area on one shot area on the wafer W. The exposure area is a rectangular area conjugate with the illumination area on the reticle R with respect to the projection optical system PL. The wafer W is a disk-shaped substrate having a diameter of about 200 to 300 mm, such as a semiconductor (silicon or the like) or SOI (silicon on insulator).

  A part of the exposure light IL is reflected by the wafer W, and the reflected light returns to the beam splitter 6 through the projection optical system PL, the reticle R, the condenser lens 11, the mirror 10 and the field stop 9 in this order, and further by the beam splitter 6. The reflected light is received by a reflection amount sensor (reflectance monitor) 8 through a condenser lens (not shown). The detection signal of the reflection amount sensor 8 is supplied to the main control system 20. In addition, environmental sensors 12 for measuring atmospheric pressure and temperature are arranged outside the projection optical system PL (for example, a total of four locations on the ± X side and ± Y side of the projection optical system PL). Measurement data measured by the sensor 12 is also supplied to the main control system 20.

  The illumination optical system ILS is composed of the exposure light source 1, the fly-eye lenses 2 and 4, the mirrors 3 and 9, the illumination system aperture stop member 5, the field stop 9, the condenser lens 11, and the like. The illumination optical system ILS is further covered with a sub-chamber (not shown) as an airtight chamber. In order to maintain a high transmittance with respect to the exposure light IL, dry air from which impurities are highly removed (nitrogen gas when the exposure light is an ArF excimer laser) is placed in the subchamber and in the lens barrel of the projection optical system PL. , Helium gas, etc. are also used).

  Further, the projection optical system PL of the present embodiment is a refractive system, and a plurality of optical members constituting the projection optical system PL are quartz that is rotationally symmetric about the optical axis AX (in the case where the exposure light is an ArF excimer laser). A plurality of lenses made of fluorite or the like, and a plate-like aberration correction plate made of quartz. An aperture stop 13 is disposed on the pupil plane PP of the projection optical system PL (a plane conjugate with the pupil plane of the illumination optical system ILS), and a lens L as a predetermined optical member is disposed in the vicinity of the pupil plane PP. ing. The lens L is irradiated with illumination light for non-rotationally symmetric aberration correction in a wavelength region different from that of the exposure light IL (details will be described later). The projection optical system PL incorporates an imaging characteristic correction mechanism 14 for correcting rotationally symmetric aberration, and the main control system 20 operates the imaging characteristic correction mechanism 14 via the control unit 15. To control.

  FIG. 2 is a diagram illustrating an example of the imaging characteristic correction mechanism 14. In FIG. 2, for example, five lenses L1, L2, L3, L4, and L5 selected from a plurality of optical members can be independently expanded and contracted in the three optical axis directions in the lens barrel of the projection optical system PL. The drive elements 14a, 14b, 14c, 14d, and 14e are held. Fixed lenses (not shown) and aberration correction plates are also arranged before and after the lenses L1 to L5. In this case, the three drive elements 14a (only two are shown in FIG. 2) are arranged in a positional relationship that is substantially the apex of a regular triangle, and each of the other three drive elements is similarly provided. Each of 14b to 14e is also arranged in a positional relationship that is substantially a vertex of an equilateral triangle. As the extendable drive elements 14a to 14e, for example, piezoelectric elements such as piezo elements, magnetostrictive elements, or electric micrometers can be used. The control unit 15 independently controls the expansion / contraction amount of each of the three drive elements 14a to 14e based on the control information from the main control system 20, whereby each of the five lenses L1 to L5 in the optical axis direction. The position and the tilt angle about two orthogonal axes perpendicular to the optical axis can be controlled independently. Thereby, a predetermined rotationally symmetric aberration in the imaging characteristics of the projection optical system PL can be corrected.

  For example, distortion aberration (including magnification error) and the like can be corrected by controlling the position and tilt angle of the lenses L1 and L5 near the reticle or wafer in the optical axis direction. Further, for example, spherical aberration or the like can be corrected by controlling the position in the optical axis direction of the lens L3 near the pupil plane of the projection optical system PL. 2 may be the same as the lens L irradiated with the aberration correction illumination light in the projection optical system PL of FIG. Such a mechanism for driving the lens and the like in the projection optical system PL is also disclosed in, for example, Japanese Patent Laid-Open No. 4-134814. Further, instead of or together with the optical member in the projection optical system PL, the position in the optical axis direction of the reticle R in FIG. 1 may be controlled to correct a predetermined rotationally symmetric aberration. Further, as the imaging characteristic correction mechanism 14 of FIG. 1, as disclosed in, for example, Japanese Patent Laid-Open No. 60-78454, the image forming characteristic correction mechanism 14 is arranged in a sealed space between two predetermined lenses in the projection optical system PL. A mechanism for controlling the gas pressure may be used.

  Returning to FIG. 1, the reticle R is sucked and held on the reticle stage RST, and the reticle stage RST moves on the reticle base (not shown) at a constant speed in the Y direction and corrects the synchronization error in the X and Y directions. The reticle R is scanned by slightly moving in the rotation direction. The position and rotation angle of the reticle stage RST in the X and Y directions are measured by a movable mirror (not shown) and a laser interferometer (not shown) provided thereon, and the measured values are supplied to the main control system 20. Has been.

  On the upper side surface of the projection optical system PL, a slit image is obliquely projected onto the pattern surface (reticle surface) of the reticle R, the reflected light from the reticle surface is received, and the slit image is re-imaged. An oblique-incidence autofocus sensor (hereinafter referred to as “reticle-side AF sensor”) 16 that detects displacement in the Z direction of the reticle surface from the amount of lateral shift of the image is disposed. Information detected by the reticle side AF sensor 16 is supplied to the main control system 20. A reticle alignment microscope (not shown) for reticle alignment is disposed above the periphery of the reticle R.

  On the other hand, wafer W is sucked and held on Z tilt stage 17 via a wafer holder (not shown), Z tilt stage 17 is fixed on wafer stage WST, and wafer stage WST is in the Y direction on a wafer base (not shown). At a constant speed, and move stepwise in the X and Y directions. The Z tilt stage 17 controls the position of the wafer W in the Z direction and the tilt angles around the X and Y axes. The position and rotation angle in the X and Y directions of wafer stage WST are measured by a laser interferometer (not shown), and the measured values are supplied to main control system 20. Main control system 20 controls the position and speed of wafer stage WST based on the measurement values and various control information.

  On the lower side surface of the projection optical system PL, a plurality of slit images are projected obliquely onto the surface of the wafer W (wafer surface), the reflected light from the wafer surface is received, and the slit images are re-imaged. An oblique focus type autofocus sensor (hereinafter referred to as “wafer side AF sensor”) 18 for detecting displacement (defocus amount) and tilt angle of the wafer surface in the Z direction from the lateral displacement amount of the slit images is disposed. ing. Information detected by the wafer side AF sensor 18 is supplied to the main control system 20, and the main control system 20 always projects the wafer surface based on the detection information of the reticle side AF sensor 16 and the wafer side AF sensor 18. The Z tilt stage 17 is driven by an autofocus method so that it is focused on the image plane of the system PL.

  Further, near the wafer W on the Z tilt stage 17, an irradiation amount sensor 19 including a photoelectric sensor having a light receiving surface covering the entire exposure area of the exposure light IL is fixed, and a detection signal of the irradiation amount sensor 19 is received. It is supplied to the main control system 20. Before the exposure is started or periodically, the exposure light IL is irradiated with the light receiving surface of the irradiation sensor 19 moved to the exposure area of the projection optical system PL, and the detection signal of the irradiation sensor 19 is used as the detection signal of the integrator sensor 7. The main control system 20 calculates and stores the transmittance of the optical system from the beam splitter 6 to the dose sensor 19 (wafer W). On the Z tilt stage 17, an aberration measuring device 21 for measuring the aberration of the projection optical system PL is provided. As the aberration measuring device 21, for example, an aerial image sensor as disclosed in Japanese Patent Application Laid-Open No. 2002-14005 (corresponding US Patent Publication No. 2002/0041377) can be used. The measurement result of the aberration measuring device 21 is supplied to the main control system 20.

  Further, an off-axis alignment sensor (not shown) for wafer alignment is disposed above wafer stage WST, and the main control system is based on the above-described reticle alignment microscope and the detection result of the alignment sensor. 20 performs alignment of the reticle R and alignment of the wafer W. At the time of exposure, the reticle stage RST and wafer stage WST are driven in a state where the illumination area on the reticle R is irradiated with the exposure light IL, and the reticle R and one shot area on the wafer W are synchronously scanned in the Y direction. The operation and the operation of moving wafer W stepwise in the X direction and the Y direction by driving wafer stage WST are repeated. By this operation, the pattern image of the reticle R is exposed to each shot area on the wafer W by the step-and-scan method.

[Internal configuration of main control system]
FIG. 3 is a block diagram showing an internal configuration of the main control system 20 and an apparatus for exchanging various signals with the main control system 20. As shown in FIG. 3, the main control system 20 includes an imaging characteristic calculation unit 31, an imaging characteristic control unit 32, an exposure amount control unit 33, a stage control unit 34, a Z tilt stage control unit 35, a controller 36, and a memory 37. Consists of including.

  The imaging characteristic calculation unit 31 uses the detection signals of the integrator sensor 7 and the reflection amount sensor 8 to reflect the integrated energy of the exposure light IL incident on the projection optical system PL from the reticle R and the projection optical system reflected by the wafer W. The integrated energy of the exposure light IL returning to PL is calculated. Information about illumination conditions during exposure is also supplied from the controller 36 to the imaging characteristic calculation unit 31. In addition, the imaging characteristic calculation unit 31 uses information such as illumination conditions, accumulated energy of the exposure light IL, and ambient atmospheric pressure and temperature supplied from the environment sensor 12 in the imaging characteristics of the projection optical system PL. A fluctuation amount of the rotationally symmetric aberration component and the non-rotationally symmetric aberration component is calculated.

  Here, when the imaging characteristic calculation unit 31 calculates the fluctuation amount of the non-rotationally symmetric aberration component in the imaging characteristic of the projection optical system PL, the transfer function (details) read out from the memory 37 by the controller 36. Is calculated using the following. Further, when a measurement result is output from the aberration measuring device 21, the amount of fluctuation of the rotationally symmetric aberration component and the non-rotationally symmetric aberration component in the imaging characteristics of the projection optical system PL is calculated from the measurement result.

  The imaging characteristic control unit 32 controls the operation of the imaging characteristic correction mechanism 14 via the control unit 15 based on the fluctuation amount of the aberration component of the projection optical system PL calculated by the imaging characteristic calculation unit 31. Alternatively, the operation of the non-exposure light irradiation mechanism 40, which will be described later, is controlled to suppress the fluctuation amount of the imaging characteristics of the projection optical system PL so that the desired imaging characteristics are always obtained. When the imaging characteristic correction mechanism 14 corrects the imaging characteristic of the projection optical system PL, three control units 15 are provided on the basis of control information from the imaging characteristic control unit 32 in the main control system 20. By independently controlling the amount of expansion / contraction of the drive elements 14a to 14e, the position in the optical axis direction of each of the five lenses L1 to L5 and the inclination angle about two axes perpendicular to the optical axis are independently determined. And thereby a predetermined rotationally symmetric aberration in the imaging characteristics of the projection optical system PL is corrected. Details of the method for correcting the imaging characteristics of the projection optical system PL by the non-exposure light irradiation mechanism 40 will be described later.

  The exposure amount control unit 33 indirectly calculates the exposure energy on the wafer W using the detection signal of the integrator sensor 7 and the transmittance of the optical system from the beam splitter 6 to the wafer W measured in advance. Here, the transmittance of the optical system from the beam splitter 6 to the wafer W is determined based on the exposure light IL in a state where the light receiving surface of the dose sensor 19 is moved to the exposure area of the projection optical system PL before the exposure starts or periodically. Irradiation is performed by dividing the detection signal of the dose sensor 19 by the detection signal of the integrator sensor 7. The exposure amount control unit 33 controls the output of the exposure light source 1 so that the integrated exposure energy on the wafer W is within the target range, and exposure is performed using a dimming mechanism (not shown) as necessary. The pulse energy of the light IL is controlled stepwise.

  The stage control unit 34 controls the position and speed of the reticle stage RST based on measurement values of a laser interferometer (not shown) provided on the reticle stage RST and various control information. Further, the position and speed of wafer stage WST are controlled based on the measurement values of a laser interferometer (not shown) provided on wafer stage WST and various control information. Further, the Z tilt stage control unit 35 is configured to automatically focus the wafer surface on the image plane of the projection optical system PL based on the detection information of the reticle side AF sensor 16 and the wafer side AF sensor 18. To drive the Z tilt stage 17.

  The controller 36 controls the overall operation of the exposure apparatus by controlling the imaging characteristic calculation unit 31, the imaging characteristic control unit 32, the exposure amount control unit 33, the stage control unit 34, and the Z tilt stage control unit 35. Control. Although details will be described later, the controller 36 performs control to stop execution of the predetermined operation until the non-rotationally symmetric aberration of the projection optical system PL calculated by the imaging characteristic calculation unit 31 is equal to or less than a preset allowable value. I do.

  For example, the exposure operation on the wafer W is interrupted until the non-rotationally symmetric aberration of the projection optical system PL becomes equal to or less than a preset allowable value, or the non-rotationally symmetric aberration of the projection optical system PL is equal to or less than a preset allowable value. Control is performed to delay the change of the illumination conditions until The change of the illumination condition or the like here means a change of the distribution of the exposure light IL on the conjugate plane (the surface on which the field stop 9 is disposed or the reticle surface) with respect to the image plane of the projection optical system PL, and the projection optical system. This includes changing the distribution of the exposure light IL on the pupil plane PP of PL or its conjugate plane (such as the position where the illumination system aperture stop member 5 is disposed).

  The memory 37 shows the relationship between the distribution of light incident on at least a part of the projection optical system PL, the energy of light incident on at least a part of the projection optical system PL, and the amount of fluctuation of the non-rotationally symmetric aberration of the projection optical system PL. Store the transfer function shown. Further, the memory 37 stores an allowable value for determining whether or not to interrupt the exposure operation on the wafer W or whether to switch illumination conditions or the like. Although the transfer function related to the non-rotationally symmetric aberration of the projection optical system PL will be mainly described here, the transfer function related to the rotationally symmetric aberration of the projection optical system PL may also be stored in the memory 37.

但し、
Ｆ ：露光光吸収によるフォーカス変化量
Δｔ：露光光吸収によるフォーカス変化量の計算間隔
Ｔ_ｋ ：露光光吸収によるフォーカス変化時定数
Ｆ_ｋ ：露光光吸収による時刻Δｔ前のフォーカス変化時定数
Ｃ_ｋ ：露光光吸収に対するフォーカス変化率の時定数
Ｒ_ｗ ：ウェハ反射率
α ：ウェハ反射率依存性
Ｑ ：露光光の入射エネルギー A general expression of the transfer function stored in the memory 37 is expressed by, for example, the following expression (1).

However,
F: focus change amount due to exposure light absorption Δt: calculation interval of focus change amount due to exposure light absorption T _k : focus change time constant due to exposure light absorption F _k : focus change time constant before time Δt due to exposure light absorption C _k : Time constant of focus change rate with respect to exposure light absorption _Rw : Wafer reflectivity α: Wafer reflectivity dependence Q: Incident energy of exposure light

  The transfer function shown in (1) is a transfer function indicating the amount of focus fluctuation when the projection optical system PL is irradiated with the exposure light IL. By changing the variable Q in the above equation (1) according to the illumination condition (incident condition of the exposure light IL with respect to the projection optical system PL), it is possible to obtain the amount of fluctuation of the non-rotationally symmetric aberration of the projection optical system PL. Although details will be described later, when dipole illumination is performed, the exposure light IL is intensively illuminated at two places in the X direction or two places in the Y direction on the pupil plane of the projection optical system PL. The curvature in the X direction and the curvature in the Y direction of the lens L provided near the pupil plane of the system PL change. Therefore, the center ass is obtained by obtaining the focus fluctuation amount in the X direction and the focus fluctuation amount in the Y direction according to the illumination condition.

[Description of non-rotationally symmetric aberration components]
The schematic configuration of the exposure apparatus of the present invention has been described above. Next, non-rotationally symmetric aberration components generated in the projection optical system when dipole illumination is performed will be described. 4 and 5 are diagrams for explaining a change in the shape of the lens that occurs when dipole illumination is performed. First, when the aperture stop 5a having two apertures separated in the direction corresponding to the X direction is arranged on the focal plane on the exit side of the second fly-eye lens 4, the main transfer formed on the reticle R As an example, as shown in FIG. 4A, the pattern for use is formed by arranging a line pattern elongated in the Y direction in the X direction (non-scanning direction) at a pitch substantially close to the resolution limit of the projection optical system PL. X-direction line and space pattern (hereinafter referred to as “L & S pattern”) PV. At this time, another plurality of L & S patterns having an arrangement direction larger than the L & S pattern PV and having an arrangement direction in the X direction and the Y direction (scanning direction) are usually formed on the reticle R.

  In the dipole illumination in the X direction using the aperture stop 5a, assuming that there is no reticle, as shown in FIG. 4B, the pupil plane PP of the projection optical system PL is 2 symmetrical in the X direction across the optical axis AX. The exposure light IL illuminates two circular regions IRx. Even when various reticle patterns are arranged on the optical path of the exposure light IL, the light amount of the 0th order light is usually much larger than the light amount of the diffracted light and the diffraction angle is small. Most of the image light flux) passes through the circular region IRx or its vicinity. Therefore, when the exposure is continued, the temperature distribution of the lens L in the vicinity of the pupil plane PP becomes the highest in the two circular regions IRx sandwiching the optical axis in the X direction, and gradually decreases toward the peripheral region. The lens L is thermally expanded (thermally deformed) according to this temperature distribution.

  In this case, side views in which the change is exaggerated when the lens L is viewed in the Y direction and the X direction are as shown in FIGS. 4C and 4D, respectively. In these drawings, if the surface shape of the lens L before absorption of exposure light is a surface A, the thermally expanded surface B after absorption of exposure light has a wide range in the direction along the X axis (FIG. 4C). Since the two convex portions sandwiching the optical axis are formed, the refractive power is reduced, and in the direction along the Y axis (FIG. 4 (d)), one convex portion is locally formed in the central portion, and thus the refractive power. Will increase. Thus, if there is a difference in the refractive power between the X direction and the Y direction, center ass is generated. FIG. 6 is a diagram showing a center ass caused by dipole illumination. As shown in FIG. 6, the image plane of the projection optical system PL becomes a lower (−Z direction) image plane IV because the refractive power decreases with respect to the light beam opened in the X direction, and the light beam opened in the Y direction. Since the refractive power increases, the upper (+ Z direction) image plane IH is obtained. Therefore, a center assigma ΔZ that is astigmatism on the optical axis is generated. The center ass ΔZ can be calculated using the transfer function shown in the above equation (1).

  In the state where the center ass has occurred, in addition to the L & S pattern PV in the X direction on the reticle R, the Y direction arranged at a predetermined pitch in the Y direction (this pitch is usually larger than the pitch of the L & S pattern PV). If the L & S pattern (not shown) is formed, the exposure light that has passed through the L & S pattern PV in the X direction spreads in the X direction, and the exposure light that has passed through the L & S pattern in the Y direction spreads in the Y direction. Therefore, since the image of the L & S pattern PV in the X direction is formed on the lower image plane IV in FIG. 6 and the image of the L & S pattern in the Y direction is formed on the upper image plane IH in FIG. When aligned with the surface IV, the image of the L & S pattern PV in the X direction is transferred with high resolution, but the image of the L & S pattern in the Y direction is blurred due to defocusing.

  On the other hand, as shown in an enlarged view in FIG. 5A, on the reticle R, line patterns elongated mainly in the X direction are arranged in the Y direction (scanning direction) at a pitch substantially close to the resolution limit of the projection optical system PL. It is assumed that a Y-direction L & S pattern PH is formed. In this case, an aperture stop 5b having a shape obtained by rotating the aperture stop 5a by 90 ° is set on the pupil plane of the illumination optical system ILS in FIG. In the dipole illumination in the Y direction using the aperture stop 5b, assuming that there is no reticle, as shown in FIG. 5B, the pupil plane PP of the projection optical system PL is symmetrical in the Y direction with the optical axis AX in between. The exposure light IL illuminates the two circular regions IRy. At this time, even if various reticle patterns are arranged in the optical path of the exposure light IL, usually most of the exposure light IL (imaging light beam) passes through the circular region IRy and the vicinity thereof. When the reticle R shown in FIG. 5A is arranged in the optical path of the exposure light IL, ± first-order diffracted light from the L & S pattern PH having a pitch close to the resolution limit also passes through the circular region IRy or the vicinity thereof. Therefore, the image of the L & S pattern PH is projected onto the wafer W with high resolution.

  In this case, the light amount distribution of the exposure light IL incident on the lens L in the vicinity of the pupil plane PP of the projection optical system PL of FIG. 1 is also substantially the light amount distribution of FIG. Therefore, when the exposure is continued, the temperature distribution of the lens L in the vicinity of the pupil plane PP becomes the highest in the two circular regions IRy sandwiching the optical axis in the Y direction, and gradually decreases toward the peripheral region. The lens L is thermally expanded according to the distribution. Therefore, the image plane of the projection optical system PL is almost opposite to the case of FIG. 4, and the refractive power increases with respect to the light beam opened in the X direction, so that it is in the vicinity of the upper image plane IH and in the Y direction. Since the refractive power of the opened light beam decreases, it becomes near the lower image plane IV, and a center ass having the same size as that of FIG. Since the reticle R is illuminated by a rectangular illumination area whose longitudinal direction is the X direction (non-scanning direction), the center ass resulting from the illumination area is always slightly generated with the same sign as the center ass in FIG. is doing. On the other hand, the center spot generated by the dipole illumination of FIG. 5B is opposite in sign to the center spot due to the rectangular illumination area, and the center spot as a whole is shown in FIG. Slightly smaller than when dipole illumination is used.

  These center astigmatisms are non-rotationally symmetric aberrations, and other non-rotationally symmetric aberrations (such as a difference in projection magnification between the X direction and the Y direction) are also generated by dipole illumination. Cannot be substantially corrected by the imaging characteristic correction mechanism 14 of FIG. Further, when other non-rotationally symmetric illumination conditions are used, non-rotationally symmetric aberration occurs. Further, as in the case of performing small σ illumination in which the value of illumination σ representing the ratio of the numerical aperture of projection optical system PL and the numerical aperture of illumination optical system ILS is, for example, 0.4 or less, the pupil of illumination optical system When the light quantity distribution of the exposure light IL on the surface (the pupil plane of the projection optical system PL) changes greatly in the radial direction, high-order spherical aberration or the like that cannot be corrected satisfactorily by the imaging characteristic correction mechanism 14 The following rotationally symmetric aberration may occur. Therefore, in the exposure apparatus of the present embodiment, in order to correct the non-rotationally symmetric aberration or higher-order rotationally symmetric aberration, the exposure light IL is applied to the lens L near the pupil plane PP of the projection optical system PL in FIG. A non-exposure light irradiation mechanism 40 for irradiating illumination light for correcting aberrations (hereinafter referred to as “non-exposure light”) LB in a wavelength region different from that of FIG. Hereinafter, the configuration of the non-exposure light irradiation mechanism 40 for irradiating the lens L with the non-exposure light LB and the aberration correction operation will be described in detail.

[Non-exposure light irradiation mechanism]
In the present embodiment, light in a wavelength range that hardly exposes the photoresist applied to the wafer W is used as the non-exposure light LB. For this reason, as the non-exposure light LB, for example, infrared light having a wavelength of 10.6 μm that is pulsed from a carbon dioxide laser (CO ₂ laser) is used. Note that continuous light may be used as the CO ₂ laser. This infrared light having a wavelength of 10.6 μm has high absorption of quartz, and almost all (preferably 90% or more) is absorbed by one lens in the projection optical system PL. There is an advantage that it is easy to use to control the aberration without giving any. Further, the non-exposure light LB irradiated to the lens L of the present embodiment is set so that 90% or more is absorbed. As the non-exposure light LB, in addition to the above infrared light, near infrared light having a wavelength of about 1 μm emitted from solid laser light such as a YAG laser, or infrared having a wavelength of about several μm emitted from a semiconductor laser. Light or the like can also be used. That is, as the light source that generates the non-exposure light LB, an optimum light source can be adopted according to the material of the optical member (lens or the like) irradiated with the non-exposure light LB. In FIG. 1 and the like, the lens L is drawn like a convex lens, but may be a concave lens.

  In the non-exposure light irradiation mechanism 40 of FIG. 1, the non-exposure light LB emitted from the light source system 41 passes through a plurality of optical paths (eight in this embodiment) and one optical path toward the photoelectric sensor 43 by the mirror optical system 42. Branch off. A detection signal corresponding to the light amount of the non-exposure light LB detected by the photoelectric sensor 43 is fed back to the light source system 41. In addition, the non-exposure light LB of two optical paths among the plurality of optical paths is respectively exposed to the non-exposure light LBa and LBb via two irradiation mechanisms 44a and 44b arranged so as to sandwich the projection optical system PL in the X direction. As shown in FIG.

  FIG. 7 is a top view showing a detailed configuration example of the non-exposure light irradiation mechanism 40. In FIG. 7, the light source system 41 in FIG. 1 includes a light source 41a and a control unit 41b. The non-exposure light LB emitted from the light source 41a is high speed in either a state where the optical path of the non-exposure light LB is bent by 90 ° (closed state) or a state where the non-exposure light LB is allowed to pass through as it is (open state). The galvanometer mirrors 45g, 45c, 45e, 45a, 45h, 45d, 45f, and 45b as movable mirrors that can be switched to are incident on the photoelectric sensor 43, and the detection signal of the photoelectric sensor 43 is supplied to the control unit 41b. . Galvano mirrors 45a to 45h correspond to the mirror optical system 42 of FIG. The control unit 41b controls the light emission timing and output of the light source 41a and the opening and closing of the galvano mirrors 45a to 45h according to control information from the main control system 20.

  Further, the non-exposure light LB whose optical path is sequentially bent by the eight galvanometer mirrors 45a to 45h is guided to the irradiation mechanisms 44a to 44h via the optical fiber bundles 46a to 46h (or a metal tube or the like can be used), respectively. Yes. The eight irradiation mechanisms 44a to 44h have the same configuration, and the irradiation mechanisms 44a and 44b include a condenser lens 47, a beam splitter 48 having a predetermined low reflectance, an optical fiber bundle or a relay lens system, and the like. A light guide portion 49, a condensing lens 51, and a holding frame 50 for fixing the condensing lens 47 and the light guide portion 49 to the beam splitter 48.

  The non-exposure light LB is irradiated to the lens L in the projection optical system PL as non-exposure light LBa and LBb from the irradiation mechanisms 44a and 44b, respectively. In this case, the first pair of irradiation mechanisms 44a and 44b and the second pair of irradiation mechanisms 44c and 44d are arranged to face each other so as to sandwich the projection optical system PL in the X direction and the Y direction, respectively. . The third pair of irradiation mechanisms 44e and 44f and the fourth pair of irradiation mechanisms 44g and 44h are respectively arranged such that the irradiation mechanisms 44a and 44b and the irradiation mechanisms 44c and 44d are centered on the optical axis of the projection optical system PL. Are arranged at an angle rotated 45 ° clockwise. And the non-exposure light LB is irradiated to the lens L in the projection optical system PL as non-exposure light LBc-LBh from the irradiation mechanisms 44c-44h, respectively.

  The region irradiated with the pair of non-exposure light LBa and LBb onto the lens L is a symmetric circular region IRx that sandwiches the optical axis AX in FIG. 4B in the X direction, and the pair of non-exposure light LBc and LBd. The region irradiated on the lens L is a symmetrical circular region IRy that sandwiches the optical axis AX in FIG. 5B in the Y direction. In addition, the regions irradiated with the non-exposure light LBe and LBf and the non-exposure light LBg and LGh on the lens L are the symmetric circular region IRx in FIG. 4B and the symmetric circle in FIG. 5B, respectively. This is a region obtained by rotating the region IRy by 45 ° clockwise around the optical axis AX. The optical member irradiated with the non-exposure light LBa to LBh, and the shape and size of the irradiation region of the non-exposure light LBa to LBh on the optical member, non-rotationally symmetric aberration is reduced as much as possible through experiments and simulations. To be determined.

  In addition, photoelectric sensors 52a to 52h that respectively receive part of the non-exposure light reflected by the beam splitters 48 of the irradiation mechanisms 44a to 44h are provided, and the detection signals of the eight photoelectric sensors 52a to 52h are also controlled. It is supplied to the part 41b. The control unit 41b can accurately monitor the light amounts of the non-exposure lights LBa to LBh immediately before being irradiated from the irradiation mechanisms 44a to 44h to the lens L in the projection optical system PL by the detection signals of the photoelectric sensors 52a to 52h. On the basis of this monitoring result, each of the irradiation amounts of the non-exposure lights LBa to LBh is set to a value instructed by the main control system 20, for example. Even if the lengths (optical path lengths) of the optical fiber bundles 46a to 46h are various by measuring the irradiation amount of the non-exposure light LB by the photoelectric sensors 52a to 52h immediately before the projection optical system PL, the optical system or the like The amount of irradiation of the non-exposure light LBa to LBh irradiated to the lens L can be accurately monitored without being affected by the change with time.

  FIG. 8 is a front view with a section of a part of the projection optical system PL. As shown in FIG. 8A, the irradiation mechanisms 44a and 44b are slightly inclined downward toward the lens L in the openings Fa and Fb provided in the flange portion F of the lens barrel of the projection optical system PL, respectively. It is arranged to incline. The non-exposure lights LBa and LBb emitted from the irradiation mechanisms 44a and 44b enter the lens L in a direction that obliquely intersects the optical path of the exposure light IL. Similarly, the other irradiation mechanisms 44c to 44h in FIG. 7 are arranged at the same inclination angle in the opening in the flange portion F of FIG. The light enters the lens L in a direction that obliquely intersects the optical path. As a result, the optical path of the non-exposure light LBa to LBh in the lens L is lengthened, and most of the non-exposure light LBa to LBh is absorbed in the lens L and hardly emitted from the projection optical system PL. Incidentally, the lens surface of a part of the optical member (lens L) of the projection optical system PL, that is, the region where the exposure light IL can enter (or exit) is not exposed without passing through other optical members of the projection optical system PL. Since the light LB is irradiated, it is possible to more effectively adjust the temperature distribution of the lens L and further the imaging characteristics (non-rotationally symmetric aberration) of the projection optical system PL.

  FIG. 8B is a modification of FIG. 8A. As shown in FIG. 8B, the irradiation mechanisms 44a and 44b (the same applies to the other irradiation mechanisms 44c to 44h) are respectively used for the projection optics. In the openings Fc and Fd provided in the flange portion F of the lens barrel of the system PL, the lens PL is arranged so as to be slightly inclined upward toward the lens L, and the bottom surface of the lens L with the non-exposure light LBa and LBb. The side may be illuminated. In this case, it is possible to further reduce the amount of the non-exposure light LBa to LBh that leaks from the wafer W side of the projection optical system PL.

  Returning to FIG. 7, the light source system 41a, the controller 41b, the galvano mirrors 45a to 45h, the optical fiber bundles 46a to 46h, the irradiation mechanisms 44a to 44h, and the photoelectric sensors 52a to 52h constitute the non-exposure light irradiation mechanism 40. For example, when the lens L is irradiated with only two non-exposure lights LBa and LBb in the X direction, the galvano mirror 45a is opened from a state where all the galvano mirrors 45a to 45h are opened (a state where the non-exposure light LB is passed). May be alternately repeated for the predetermined time (state in which the non-exposure light LB is reflected) and for closing the galvano mirror 45b for the predetermined time. By switching the galvanometer mirror in a sufficiently short time (for example, 1 msec) that does not affect the aberration, it is possible to eliminate the influence on the aberration. Further, since the non-exposure light LB is pulsed light, the opening / closing operation of the galvanometer mirrors 45a to 45h may be performed in units of a predetermined number of pulses. Similarly, when the lens L is irradiated with only two non-exposure lights LBc and LBd in the Y direction, an operation of closing the galvano mirror 45c for a predetermined time and an operation of closing the galvano mirror 45d for a predetermined time are alternately repeated. Good. As described above, by using the galvanometer mirrors 45a to 45h, the lens L can be efficiently irradiated with almost no light loss of the non-exposure light LB.

  In the configuration example of FIG. 7, eight regions on the lens L can be illuminated with the non-exposure light LB. For example, only four regions on the lens L in the X direction and the Y direction are not exposed. Even if it can be illuminated with the light LB, most aberrations that occur in normal applications can be corrected. Instead of using the galvanometer mirrors 45a to 45h, for example, a fixed mirror and a beam splitter may be combined to branch the non-exposure light LB into eight light beams, and these light beams may be opened and closed using a shutter. In this configuration, a plurality of places can be irradiated with the non-exposure light LB simultaneously. Further, when a carbon dioxide laser or a semiconductor laser is used as the light source, as many light sources as the number of necessary irradiation regions on the lens L (eight in FIG. 7) are prepared, and light emission of these light sources is turned on / off or The irradiation area on the lens L may be directly controlled by the shutter.

  Next, a method for correcting the non-rotationally symmetric aberration of the projection optical system using the non-exposure light irradiation mechanism 40 having the above configuration will be described. Here, a description will be given by taking as an example a case of correcting the center ass caused in the case of dipole illumination. FIG. 9 is a diagram for explaining an example of a correction method for non-rotationally symmetric aberration of the projection optical system using the non-exposure light irradiation mechanism. As shown in FIG. 4B, when the exposure light IL is irradiated onto two circular regions IRx that sandwich the optical axis AX symmetrically in the X direction on the pupil plane PP of the projection optical system PL, The exposure light IL is irradiated to the region IRx that sandwiches the optical axis AX symmetrically in the X direction and a region in the vicinity thereof. As shown in FIG. 9A, in the present embodiment, a circular region that is substantially the region IRx rotated by 90 ° around the optical axis AX and that is sandwiched approximately symmetrically with the optical axis AX in the Y direction on the lens L. The non-exposure lights LBc and LBd shown in FIG. 7 are respectively irradiated on LRc and LRd. The shape and size of the irradiation area of the non-exposure light LBc, LBd (the same applies to the other non-exposure light), for example, the position of the lens 51 in the irradiation mechanisms 44c, 44d in FIG. It is also possible to change it.

  By irradiating a region obtained by rotating the irradiation region of the exposure light IL by 90 ° with the non-exposure light LBc and LBd, the temperature distribution of the lens L is increased in the region IRx and the regions LRc and LRd, and gradually decreases as the distance from the region increases. Become. In FIG. 9, when the origin of the X axis and the Y axis is the optical axis AX, a cross-sectional view along the non-scanning direction in the plane including the optical axis AX and the X axis of the lens L, and the optical axes AX and Y axes are included. Both cross-sectional views along the in-plane scanning direction are exaggerated in FIG. 9B. As shown in FIG. 9B, the thermal expansion of the lens L is almost the same as the cross-sectional shape in the non-scanning direction and the scanning direction, and the shape expanded in the left and right, and the refractive index distribution is also in the central portion. It changes more greatly than the other areas on the left and right. As a result, the deformation state of the lens L irradiated with the exposure light IL and the non-exposure light LBc, LBd is non-scanning compared to the deformation of FIGS. 4C and 4D when only the exposure light IL is illuminated. Since the states are similar in the direction and the scanning direction, the focus positions for the light beams opened in the X direction and the Y direction are substantially equal to each other, and the center ass hardly occurs. That is, the non-rotationally symmetric aberration is changed to the rotation-symmetric aberration. Since the rotationally symmetric aberration can be corrected by the imaging characteristic correction mechanism 14 shown in FIG. 2, the imaging characteristic of the projection optical system PL can be strictly controlled.

  If the lens that irradiates the non-exposure light is a lens in the vicinity of the pupil plane of the projection optical system PL that is conjugate with the pupil plane of the illumination optical system ILS, such as the lens L, the effect of correcting the center ass is increased. At this time, a plurality of lenses near the pupil plane may be irradiated with non-exposure light. Furthermore, it is more effective that the irradiation region where the exposure light and the non-exposure light are combined is as close to rotational symmetry as possible on the optical member to be irradiated. However, regardless of the position of the optical member (lens or the like) in the projection optical system PL that is irradiated with non-exposure light, it is possible to obtain a center astigmatism correction effect in a substantially desired range by controlling the irradiation amount. it can. In addition, by irradiating non-exposure light together with exposure light, non-rotationally symmetric aberrations other than center ass are also reduced.

  The method for correcting the non-rotationally symmetric aberration that occurs when dipole illumination is performed has been described above. However, the present invention is not limited to dipole illumination, and the illumination system aperture stop member 5a and the field stop 9 can be changed to change the illumination. Non-rotationally symmetric aberrations may also occur when the reticle R is illuminated under certain conditions or when the reticle R with a deviated pattern distribution is used. Non-rotationally symmetric aberrations are not limited to center astigmatism, and non-rotationally symmetric aberrations such as projection magnification differences in the X and Y directions and image shifts can occur depending on illumination conditions and pattern characteristics of the reticle R. There is also sex. In the above description, the non-exposure light irradiation mechanism 40 applies the non-exposure light to the lens L in the vicinity of the pupil plane of the projection optical system PL so as to correct the center spot in the imaging characteristics of the projection optical system PL. Although the LB is irradiated, the optical member that irradiates the non-exposure light LB, and the irradiation position, shape, and size of the non-exposure light LB on the optical member depend on the illumination condition and the type of aberration. It can be changed as appropriate.

[Exposure method]
Next, the exposure method of the present invention will be described. The main control system 20 can select a mode in which the above-mentioned non-exposure light irradiation mechanism 40 is used and a mode in which the main exposure system 40 is not used. First, here, exposure when the aberration correction by the non-exposure light irradiation mechanism 40 is not performed is performed. A method will be described. FIG. 10 is a flowchart showing an example of the exposure method of the present invention. The flowchart shown in FIG. 10 shows the exposure process for one wafer W. When the exposure process is continued for a plurality of wafers W, the process shown in FIG. Is called.

  When the exposure operation is started, first, the exposure amount control unit 33 (see FIG. 3) in the main control system 20 controls the exposure area of the projection optical system PL so that the light receiving surface of the irradiation amount sensor 19 is controlled by the controller 36. The control signal is output to the exposure light source 1 to emit the exposure light IL, and the detection signal of the dose sensor 19 and the detection signal of the integrator sensor 7 are obtained, and the beam splitter 6 is obtained from these detection signals. To the transmittance of the optical system from the wafer W to the wafer W. Next, a predetermined reticle R is transferred and held on reticle stage RST, and wafer W is transferred and held on wafer stage WST.

  Next, the stage control unit 34 in the main control system 20 outputs a control signal to each of the reticle stage RST and the wafer stage WST under the control of the controller 36 to place the reticle R at the movement start position, and to move the wafer. The shot area to be exposed at the beginning of W is moved to the movement start position. Here, an aperture stop 5a having two apertures separated in a direction corresponding to the X direction is disposed on the focal plane on the exit side of the second fly-eye lens 4, and in the pupil plane PP of the projection optical system PL. It is assumed that the exposure light IL is illuminated on two circular regions IRx symmetrical in the X direction across the optical axis AX.

  When the above initial processing is completed, stage control unit 34 outputs a control signal to each of reticle stage RST and wafer stage WST, for example, starts acceleration of reticle stage RST in the + Y direction, and −Y of wafer stage WST. Start accelerating in the direction. When a predetermined time elapses after the acceleration of the reticle stage RST and the wafer stage WST starts, and each of these stages reaches a constant speed, the controller 36 controls the exposure amount controller 33 to generate the exposure light IL from the exposure light source 1. Let it fire.

  The exposure light emitted from the exposure light source 1 sequentially passes through the first fly-eye lens 2, the vibrating mirror 3, the second fly-eye lens 4 and the like, and then passes through the aperture stop 5a formed in the illumination system aperture stop member 5. To Penetrate. The exposure light IL transmitted through the aperture stop 5 a is shaped into a slit shape by the field stop 9 via the beam splitter 6, deflected in the −Z direction by the mirror 10, and then irradiated onto the reticle R via the condenser lens 11. Is done. The exposure light IL is shaped by the aperture stop 5a, and the irradiation area on the reticle R has a long slit shape in the X direction.

  The exposure light transmitted through the reticle R is irradiated onto the first shot area to be exposed on the wafer W via the projection optical system PL, whereby a part of the pattern formed on the reticle R is exposed at the beginning of the wafer W. Transferred to a part of the shot area to be processed. While the exposure light IL is being irradiated, detection signals are output from the integrator sensor 7 and the reflection amount sensor 8, and the imaging characteristic calculation unit 31 uses the detection signals of the integrator sensor 7 and the reflection amount sensor 8. Thus, the integrated energy of the exposure light IL incident on the projection optical system PL from the reticle R and the integrated energy of the exposure light IL reflected by the wafer W and returning to the projection optical system PL are calculated.

  The imaging characteristic calculation unit 31 is supplied with information on illumination conditions during exposure (setting state of the illumination system aperture stop member 5 and the field stop 9) from the controller 36 and stored in the memory 37. The transfer function is read and supplied, and the imaging characteristic calculation unit 31 includes information such as illumination conditions, accumulated energy of the exposure light IL, ambient atmospheric pressure and temperature supplied from the environment sensor 12, and the transfer function. Is used to calculate the fluctuation amount of the rotationally symmetric aberration component and the non-rotationally symmetric aberration component in the imaging characteristics of the projection optical system PL. Note that the fluctuation amount of the non-rotationally symmetric aberration component in the imaging characteristics of the projection optical system PL is calculated using the above-described equation (1) (step S10). The calculated calculation result is output from the imaging characteristic calculation unit 31 to the controller 36.

  Next, the controller 36 reads the allowable value stored in the memory 37, and whether the fluctuation amount of the non-rotationally symmetric aberration component in the imaging characteristics of the projection optical system PL calculated in step S10 exceeds the allowable value. It is determined whether or not (step S11). This allowable value is determined by the illumination conditions, the pattern characteristics of the reticle R, the required pattern transfer accuracy, and the like. When the variation amount of the non-rotationally symmetric aberration component does not exceed the allowable value (when the determination result is “NO”), the exposure process for the shot area is continued while scanning the reticle stage RST and wafer stage WST. (Step S12). Next, the controller 36 determines whether or not the exposure process for one shot area (here, the shot area to be exposed first) has been completed (step S13). If the determination result is “NO”, the process returns to step S10, and the exposure process for the shot area is continued.

  If the determination result in step S13 is “YES”, the controller 36 determines whether there is another shot area to be exposed. When the determination result is “YES”, the controller 36 controls the stage control unit 34 to move the wafer stage WST, moves the shot area to be exposed next to the exposure start position, and performs the process of step S10. Return to. That is, when the determination result in step S11 is “NO”, that is, when the fluctuation amount of the non-rotationally symmetric aberration component in the imaging characteristics of the projection optical system PL calculated in step S10 does not exceed the allowable value. The processes in steps S10 to S13 or steps S10 to S14 are repeated until the exposure process for a plurality of shot areas set on the wafer W is completed.

  On the other hand, when the fluctuation amount of the non-rotationally symmetric aberration component in the imaging characteristics of the projection optical system PL calculated in step S10 exceeds the allowable value and the determination result in step S11 becomes “YES”, the controller 36 It is determined whether or not the exposure processing for the area has been completed (step S15). If this determination is “NO”, the process proceeds to step S 12 to continue the exposure process for that shot area. That is, even when the fluctuation amount of the non-rotationally symmetric aberration component in the imaging characteristics of the projection optical system PL exceeds the allowable value, the exposure light IL is irradiated onto the reticle R and the wafer W to transfer the pattern. While the process is being performed, the exposure process is continued.

  When the exposure process for the shot area is completed and the determination result in step S15 is “YES”, the controller 36 interrupts the exposure operation (step S16). Since the exposure light IL is not irradiated onto the projection optical system PL while the exposure operation is interrupted, the non-rotationally symmetric aberration in the imaging characteristics of the projection optical system PL that has fluctuated due to the exposure light IL is naturally present. It will return to. While the controller 36 interrupts the exposure operation, the imaging characteristic calculation unit 31 calculates the non-rotationally symmetric aberration of the projection optical system PL at a constant calculation interval using the above-described equation (1) (step S17). ), The controller 36 determines whether or not the calculation result is equal to or less than the allowable value read from the memory 37 (step S18). Note that the calculation interval may be set in consideration of the temporal change (decrease rate) of non-rotationally symmetric aberration based on experiments and simulations, and may be changed according to illumination conditions and the like.

  If this determination is “NO”, the processing returns to step S17. On the other hand, if the determination result in step S18 is “YES”, the controller 36 outputs a control signal to the stage control unit 34, the exposure amount control unit 33, etc., and resumes the exposure operation (step S19). When the exposure operation is resumed, the controller 36 first determines whether there is another shot area to be exposed (step S14). If the result of this determination is “YES”, the process returns to step S10. If the determination result is “NO”, the exposure process is completed for all the shot areas set on the wafer W, and the process ends.

  FIG. 11 is a diagram showing a variation example of the non-rotationally symmetric aberration of the projection optical system when the exposure process is performed according to the flowchart shown in FIG. In FIG. 11, a curve denoted by reference symbol AV0 shows an example of variation in non-rotationally symmetric aberration when the conventional exposure method is performed, and a curve denoted by reference symbol AV1 is subjected to exposure processing according to the flowchart shown in FIG. 6 shows an example of fluctuations in non-rotationally symmetric aberration of the projection optical system.

  As shown in FIG. 11, it is determined whether or not the non-rotationally symmetric aberration of the projection optical system PL exceeds the allowable value Th using the transfer function, and when the exposure operation is not interrupted, the projection optical system PL is increased over time. It can be seen that the non-rotationally symmetric aberration increases as shown by the curve AV0. On the other hand, when the exposure process is performed according to the flowchart shown in FIG. 10, the non-rotationally symmetric aberration of the projection optical system PL becomes a value in the vicinity of the allowable value Th as shown by the curve AV1, and varies greatly from the allowable value Th. There is nothing. Therefore, the non-rotationally symmetric aberration component generated in the projection optical system PL can be efficiently controlled, and the exposure operation can be performed in a desired state in which the non-rotationally symmetric aberration is smaller than a predetermined allowable value.

  In the above description, the case where the dipole illumination shown in FIG. 4B is performed using the aperture stop 5a formed in the illumination system aperture stop member 5 has been described. However, the projection is performed under other illumination conditions. Non-rotationally symmetric aberration components generated in the optical system PL can also be controlled by the same method. The main control system 20 can also select a mode using the non-exposure light irradiation mechanism 40 shown in FIG. When the non-exposure light irradiation mechanism 40 is used, it is possible to eliminate the non-rotationally symmetric aberration variation of the projection optical system PL or to reduce the aberration variation.

  In the above-described embodiment, the interruption of the exposure operation is determined based on the non-rotationally symmetric aberration, but determination based on the rotationally symmetric aberration may be used in combination. In such a case, an allowable value for the rotationally symmetric aberration is set, and the calculation of the rotationally symmetric aberration of the projection optical system PL using a predetermined transfer function and the correction operation of the imaging characteristic correction mechanism 14 based on the calculation are repeated. It is desirable to interrupt the exposure operation when the rotationally symmetric aberration cannot be reduced to a predetermined allowable value or less even when the correction operation of the imaging characteristic correction mechanism 14 is executed. In particular, when the non-exposure light irradiation mechanism 40 is used, the non-rotationally symmetric aberration is changed to the rotation-symmetric aberration, and the fluctuation of the rotation-symmetric aberration may increase. It is desirable to consider symmetric aberration variations together. In this way, the exposure operation can be performed with the imaging characteristics of the projection optical system PL in a desired state.

  Further, when the exposure operation is interrupted, the non-exposure light LB from the non-exposure light irradiation mechanism 40 may or may not be irradiated. For example, when the exposure operation is interrupted because the non-rotationally symmetric aberration exceeds a predetermined allowable value, the non-exposure light irradiation mechanism 40 sends the non-exposure light LB to reduce the non-rotationally symmetric aberration in a shorter time. Can be irradiated to some optical members (for example, the lens L) of the projection optical system PL. Alternatively, when the exposure operation is interrupted because the rotationally symmetric aberration exceeds a predetermined allowable value, the irradiation of the non-exposure light LB from the non-exposure light irradiation mechanism 40 is not performed and the optical member of the projection optical system PL is not irradiated. It is possible to wait until the temperature decreases and the rotationally symmetric aberration is below a predetermined tolerance.

  In the above embodiment, the case where the exposure operation is interrupted after the exposure process for one shot area set on the wafer W is finished and the exposure process for the next shot area is started has been described. However, the exposure process may be interrupted after the exposure process for one wafer W is completed until the exposure process for the next wafer W is started. In short, the timing of interrupting the exposure operation may be determined based on the relationship between the aberration tolerance described above, the aberration that results in exposure failure (transfer failure), and the time required for exposure of each shot. For example, if the difference between the above-described aberration tolerance and the aberration that causes exposure failure is large and the exposure time of each shot is short, as described above, the exposure operation is performed after the exposure processing for one wafer W is completed. And the start of the exposure process for the next wafer W can be delayed.

[Other exposure methods]
FIG. 12 is a flowchart showing another example of the present invention. The flowchart in FIG. 12 explains the operation when the exposure condition is switched after the exposure of one lot is completed and the wafer of the next lot is exposed. Similar to the case described with reference to FIG. 10, the transmittance of the optical system from the beam splitter 6 to the wafer W is obtained, and the reticle R and the wafer W are transported and held on the reticle stage RST and the wafer stage WST, respectively. For example, an aperture stop 5 a for dipole illumination is arranged on the focal plane on the exit side of the second fly-eye lens 4. When the above initial processing is completed, the reticle stage RST and the wafer stage WST are scanned, and the pattern formed on the reticle R is transferred to each shot area on the wafer W at the head of the lot via the projection optical system PL. Is done.

  When the exposure process for one wafer W is completed (step S20), the controller 36 determines whether or not the exposure process has been completed for all the wafers W included in the lot (step S21). If the determination result is “NO”, the process returns to step S20. The processes in steps S20 and S21 are repeated until the exposure process for all the wafers W included in the lot currently undergoing the exposure process is completed. Even during this processing, the non-rotationally symmetric aberration of the projection optical system PL is calculated using the transfer function shown in the above-described equation (1), and the exposure operation is interrupted for each shot region or for each wafer W. You may do it.

  If the determination result in step S21 is “YES”, then the main control system 20 determines whether there is a next lot (step S22). If the determination result in step S22 is “NO”, the series of exposure processing ends. When the determination in step S22 is “YES”, the main control system 20 determines whether or not the illumination condition needs to be switched in order to expose the wafer of the next lot (step S23). If the determination result in step S23 is “NO”, the process returns to step S20, and exposure processing for the next lot is started. When the determination result in step S23 is “YES”, the main control system 20 calculates a non-rotationally symmetric aberration component (and, if necessary, a rotation symmetric aberration component) in the imaging characteristics of the projection optical system PL. (Step S24).

  Next, the controller 36 reads the switching allowable value for switching illumination conditions stored in the memory 37, and the non-rotationally symmetric aberration in the imaging characteristics of the projection optical system PL calculated in step S24 is the switching allowable value. It is judged whether it is larger than (step S25). If the determination result in step S25 is “NO”, switching of the illumination conditions for exposing the wafer of the next lot is executed (step S26), and then the process returns to step S20 to perform the exposure processing of the next lot. Start. If the determination result in step S25 is “YES”, the lighting condition switching operation is not performed and a predetermined time is awaited (step 27). When the predetermined time has elapsed, the process returns to step S24, and the calculation of the non-rotationally symmetric aberration is repeated at a constant calculation interval until the fluctuation amount of the non-rotationally symmetric aberration component becomes smaller than the switching allowable value. The calculation interval may be set in consideration of the temporal change (decrease rate) of non-rotationally symmetric aberration based on experiments and simulations as in the previous embodiment. You may change according to lighting conditions.

  FIG. 13 is a diagram showing a variation example of the non-rotationally symmetric aberration of the projection optical system when processing is performed according to the flowchart shown in FIG. In FIG. 13, a curve denoted by reference numeral AV <b> 10 shows a variation example of the non-rotationally symmetric aberration of the projection optical system when the exposure process is performed according to the flowchart shown in FIG. 13. First, for example, the aperture stop 5a is arranged on the focal plane on the exit side of the second fly-eye lens 4, the illumination condition is set to dipole illumination (first illumination condition), and the exposure process is started from time t0.

  During the exposure process at times t0 to t1, the non-rotationally symmetric aberration of the projection optical system PL gradually increases as shown by the curve AV10, but at the time t1 when the exposure process for one lot is completed, the projection optical system PL Is stopped, the non-rotationally symmetric aberration of the projection optical system PL gradually decreases as shown by the curve AV10. However, since the non-rotationally symmetric aberration of the projection optical system PL is larger than the switching threshold Th1 at time t1, the illumination condition is switched from the first illumination condition to the second illumination condition immediately after the exposure processing for the lot is completed. Instead, the switching of the illumination condition is delayed until the non-rotationally symmetric aberration of the projection optical system PL becomes equal to or less than the switching threshold Th1 (until time t3). By performing such control, since the illumination condition is switched after the non-rotationally symmetric aberration of the projection optical system PL becomes smaller than a predetermined allowable value, the wafer of the next lot under the new illumination condition The exposure process for can be started immediately. Moreover, it can control strictly for every illumination condition, As a result, a lot defect can be suppressed.

  Note that the above-described switching allowable value (threshold value) is set so that the exposure process can be started immediately after the switching operation of the illumination condition, regardless of how the next illumination condition (second illumination condition) is set. . The allowable value of the aberration (particularly non-rotationally symmetric aberration) of the projection optical system PL may vary depending on the illumination conditions. For example, the illumination conditions set when a pattern composed mainly of the L & S pattern PV shown in FIG. 4A is transferred with high resolution, the L & S pattern PV shown in FIG. 4A, and the L & S shown in FIG. 5A. The permissible value is different from the illumination condition set when a pattern in which the pattern PH is mixed is transferred with high resolution.

  However, in this embodiment, since the illumination condition switching allowable value is set smaller than any allowable value, the exposure processing for the next lot can be started immediately after the illumination condition switching operation. Of course, the switching allowable value can be set in accordance with the allowable value of the aberration of the projection optical system PL under the second illumination condition. In this case, the waiting time for the switching operation can be shortened when the allowable aberration value under the second illumination condition is larger (slower) than the allowable aberration value under the first illumination condition.

  In the flowchart of FIG. 12, the illumination condition switching operation (setting switching of the illumination system aperture stop member 5 and the field stop 9) is not performed until the non-rotationally symmetric aberration becomes smaller than a predetermined allowable value. However, only the illumination condition is switched first, and the exposure operation under the switched illumination condition (second illumination condition) is not performed until the non-rotationally symmetric aberration becomes smaller than a predetermined switching allowable value. That is, you may make it cancel.

  12 and 13, the non-rotationally symmetric aberration of the projection optical system PL can be efficiently corrected using the non-exposure light irradiation mechanism 40 shown in FIG. In the flowchart of FIG. 12, when it is determined that the non-rotationally symmetric aberration calculated in step S24 is larger than the switching allowable value, the non-exposure light irradiation mechanism 40 is set so that the non-rotationally symmetric aberration is reduced. The non-exposure light LB may be applied to some optical members of the projection optical system PL. In the embodiment described with reference to FIGS. 12 and 13, an illumination condition switching allowable value related to rotationally symmetric aberration may be set.

  In the embodiment described above, the case of calculating the non-rotationally symmetric aberration of the projection optical system PL using the transfer function has been described. However, the non-rotation symmetry of the projection optical system using the aberration measuring device 21 shown in FIG. You may make it measure rotationally symmetric aberration. When the exposure operation is interrupted using the measurement result of the aberration measuring device 21, the PL aberration (non-rotationally symmetric aberration) of the projection optical system is measured every time the wafer W is replaced or every predetermined time. .

  The exposure apparatus and method according to the embodiment of the present invention have been described above. However, the present invention is not limited to the above embodiment, and can be freely changed within the scope of the present invention. For example, in the above embodiment, the aberration of the projection optical system PL is obtained from the transfer function, or the aberration of the projection optical system PL is measured using the aberration measuring device 21, and an allowable value is provided for these aberrations. . However, an allowable value may be set for the temperature. In this case, the temperature (temperature distribution) of at least some optical members of the projection optical system PL can be measured using a temperature sensor, an infrared center, or the like.

  In the above-described embodiment, the interruption of the exposure operation and the standby of the switching operation of the illumination condition are mainly described. However, the interruption and the standby of the operation based on the non-rotationally symmetric aberration are not limited to these, for example, projection optics Various measurement operations performed using the system PL may be interrupted and waited based on non-rotationally symmetric aberration. In the above-described embodiment, the non-exposure light LB is irradiated to some optical members of the projection optical system PL to adjust the non-rotationally symmetric aberration of the projection optical system PL. However, the method disclosed in JP-A-8-8178 can be selected as appropriate or applied in appropriate combination. In addition, the projection optical system PL can be configured to include a refractive element and a reflective element, or can be configured to include only a reflective element.

  In the above-described embodiment, the case where the present invention is applied to a step-and-scan type exposure apparatus has been described as an example. However, a step-and-repeat type exposure apparatus that collectively transfers a reticle pattern. The present invention can also be applied to a so-called stepper. The present invention can also be applied to an exposure apparatus using a liquid immersion method as disclosed in International Publication No. 99/49504. The exposure apparatus of the present invention is an exposure apparatus that is used for manufacturing a semiconductor element to transfer a device pattern onto a semiconductor substrate, an exposure apparatus that is used for manufacturing a liquid crystal display element to transfer a circuit pattern onto a glass plate, The present invention can also be applied to an exposure apparatus that is used for manufacturing a thin film magnetic head and transfers a device pattern onto a ceramic wafer, and an exposure apparatus that is used to manufacture an image sensor such as a CCD.

[Device manufacturing method]
Next, a method for manufacturing a semiconductor element using the exposure apparatus will be described in which the exposure apparatus according to the embodiment of the present invention is applied to an exposure apparatus for manufacturing a semiconductor element. FIG. 14 is a flowchart showing a part of a manufacturing process for manufacturing a semiconductor element as a microdevice. As shown in FIG. 14, first, in step S30 (design step), the function / performance design of the semiconductor element is performed, and the pattern design for realizing the function is performed. Subsequently, in step S31 (mask manufacturing step), a mask (reticle) on which the designed pattern is formed is manufactured. On the other hand, in step S32 (wafer manufacturing step), a wafer is manufactured using a material such as silicon.

  Next, in step S33 (wafer processing step), using the mask and wafer prepared in step S30 to step S32, an actual circuit or the like is formed on the wafer by lithography or the like, as will be described later. Next, in step S34 (device assembly step), device assembly is performed using the wafer processed in step S33. Step S34 includes processes such as a dicing process, a bonding process, and a packaging process (chip encapsulation) as necessary. Finally, in step S35 (inspection step), inspections such as an operation confirmation test and a durability test of the microdevice manufactured in step S34 are performed. After these steps, the microdevice is completed and shipped.

  FIG. 15 is a diagram showing an example of a detailed flow of step S33 of FIG. In FIG. 15, in step S41 (oxidation step), the surface of the wafer is oxidized. In step S42 (CVD step), an insulating film is formed on the wafer surface. In step S43 (electrode formation step), an electrode is formed on the wafer by vapor deposition. In step S44 (ion implantation step), ions are implanted into the wafer. Each of the above steps S41 to S44 constitutes a pre-processing process at each stage of the wafer processing, and is selected and executed according to a necessary process at each stage.

  At each stage of the wafer process, when the above-described pre-processing step is completed, the post-processing step is executed as follows. In this post-processing step, first, in step S45 (resist formation step), a photosensitive agent is applied to the wafer. Subsequently, in step S46 (exposure process), the mask pattern is transferred to the wafer by the lithography system (exposure apparatus) and the exposure method described above. Next, in step S47 (development process), the exposed wafer is developed, and in step S48 (etching step), the exposed members other than the portion where the resist remains are removed by etching. In step S49 (resist removal step), the resist that has become unnecessary after the etching is removed. By repeatedly performing these pre-processing steps and post-processing steps, multiple patterns are formed on the wafer.

  If the device manufacturing method of the present embodiment described above is used, the pattern formed on the reticle is controlled while the non-rotationally symmetric aberration of the projection optical system PL provided in the exposure apparatus is controlled in the exposure step (step S46). Transferred onto the wafer W. For this reason, since non-rotation symmetric aberration or rotation symmetric aberration is controlled according to illumination conditions, a fine pattern can be faithfully transferred onto the wafer, resulting in reduced manufacturing defects and high yield. Can be manufactured.

  The present invention relates to an immersion exposure apparatus that locally fills the space between the projection optical system PL and the wafer W with a liquid, and a stage that holds a substrate to be exposed as disclosed in JP-A-6-124873. An immersion exposure apparatus for moving a liquid in a liquid tank, a liquid tank having a predetermined depth formed on a stage as disclosed in Japanese Patent Application Laid-Open No. 10-303114, and an immersion exposure for holding a substrate therein The present invention can be applied to any exposure apparatus.

It is a figure which shows schematic structure of the exposure apparatus by one Embodiment of this invention. 3 is a diagram illustrating an example of an imaging characteristic correction mechanism 14. FIG. FIG. 2 is a block diagram showing an internal configuration of the main control system 20 and a device that exchanges various signals with the main control system 20. It is a figure for demonstrating the shape change of the lens which arises when performing dipole illumination. It is a figure for demonstrating the shape change of the lens which arises when performing dipole illumination. It is a figure which shows the center ass which arises by dipole illumination. 4 is a top view showing a detailed configuration example of a non-exposure light irradiation mechanism 40. FIG. It is the front view which made a part of projection optical system PL the cross section. It is a figure for demonstrating an example of the correction method of the non-rotationally symmetric aberration of the projection optical system using a non-exposure light irradiation mechanism. It is a flowchart which shows an example of the exposure method of this invention. It is a figure which shows the example of a fluctuation | variation of the non-rotationally symmetric aberration of the projection optical system at the time of performing an exposure process according to the flowchart shown in FIG. It is a flowchart which shows the other example of this invention. It is a figure which shows the example of a fluctuation | variation of the non-rotationally symmetric aberration of the projection optical system at the time of performing an exposure process according to the flowchart shown in FIG. It is a flowchart which shows a part of manufacturing process which manufactures the semiconductor element as a microdevice. It is a figure which shows an example of the detailed flow of step S33 of FIG.

Explanation of symbols

5 Lighting system aperture stop member (change member)
9 Field stop (change member)
14 Imaging characteristic correction mechanism (imaging characteristic control means, correction mechanism)
20 Main control system (control system)
21 Aberration Measuring Device 31 Imaging Characteristic Calculation Unit (Calculation Unit)
36 Controller (Judgment part)
37 Memory (storage unit)
40 Non-exposure light irradiation mechanism (imaging characteristic control means)
IL exposure light (illumination light)
ILS Illumination optical system (illumination system)
PL projection optical system W wafer (substrate, object)

Claims (14)

In an exposure apparatus that exposes the substrate by irradiating exposure light onto the substrate,
A projection optical system for projecting a pattern image on the substrate;
An exposure apparatus comprising: a control system that suspends execution of a predetermined operation until a non-rotationally symmetric aberration of the projection optical system becomes a predetermined allowable value or less.   The exposure apparatus according to claim 1, wherein the predetermined operation includes an exposure operation for the substrate. The control system includes a relationship between a distribution of light incident on at least a part of the projection optical system, a light energy incident on at least a part of the projection optical system, and a fluctuation amount of non-rotationally symmetric aberration of the projection optical system. A storage unit for storing a transfer function indicating
Based on the measurement result of a measuring device that measures the energy of light incident on at least a part of the projection optical system or the amount corresponding to the energy, and the transfer function stored in the storage unit, the non-projection of the projection optical system A calculation unit for calculating rotationally symmetric aberration;
The determination unit according to claim 1, further comprising: a determination unit configured to determine whether or not the non-rotationally symmetric aberration of the projection optical system calculated by the calculation unit is equal to or less than the predetermined allowable value. Exposure device.   When the non-rotationally symmetric aberration of the projection optical system is larger than the predetermined allowable value, the control system ends the exposure process for each of the plurality of partitioned regions set on the substrate and when the substrate is replaced. 4. The exposure apparatus according to claim 1, wherein the predetermined operation is interrupted at at least one time point.   The predetermined operation includes changing at least one of the distribution of the exposure light on the conjugate plane with respect to the image plane of the projection optical system and the distribution of the exposure light on the pupil plane of the projection optical system or its conjugate plane. The exposure apparatus according to any one of claims 1 to 4, wherein the exposure apparatus is characterized. An illumination system for illuminating the pattern;
The illumination system includes a changing member that changes at least one of a distribution of exposure light on a plane conjugate with the pupil plane of the projection optical system and a distribution of exposure light on a plane conjugate with the image plane of the projection optical system. An exposure apparatus according to claim 5. An aberration measuring device for measuring the aberration of the projection optical system,
The control system includes a determination unit configured to determine whether or not a non-rotationally symmetric aberration of the projection optical system is equal to or less than the predetermined allowable value based on a measurement result of the aberration measuring device. The exposure apparatus according to any one of claims 1 to 6.   The exposure apparatus according to claim 1, further comprising an imaging characteristic control unit that controls imaging characteristics of the projection optical system.   The imaging characteristic control means controls the imaging characteristic of the projection optical system by irradiating at least a part of the projection optical system with a light beam having a wavelength different from the wavelength of the exposure light. The exposure apparatus according to claim 8. The imaging characteristic control means has a correction mechanism for correcting rotational symmetry aberration of the projection optical system,
10. The exposure according to claim 9, wherein a light beam having a wavelength different from the wavelength of the exposure light is irradiated to change a non-rotationally symmetric aberration of the projection optical system into a rotationally symmetric aberration and corrected by the correction mechanism. apparatus. In an exposure method of irradiating a mask with illumination light and transferring a pattern of the mask onto a substrate via a projection optical system,
An exposure method characterized in that execution of a predetermined operation is stopped until a non-rotationally symmetric aberration of the projection optical system becomes a predetermined allowable value or less.   12. The exposure apparatus according to claim 11, wherein the predetermined operation includes an exposure operation for the substrate.   The predetermined operation includes changing at least one of the distribution of the exposure light on the conjugate plane with respect to the image plane of the projection optical system and the distribution of the exposure light on the pupil plane of the projection optical system or its conjugate plane. The exposure method according to claim 11 or 12, characterized in that: A step of transferring a device pattern onto an object using the exposure apparatus according to any one of claims 1 to 10 or the exposure method according to any one of claims 11 to 13. A device manufacturing method comprising:

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