JP2009206274A - Optical characteristics adjusting method, exposure method, and manufacturing method of device - Google Patents

Abstract

An optical characteristic variation amount is accurately predicted under conditions actually used without obtaining and storing an accurate prediction model in advance.
A method for adjusting imaging characteristics when an image of a predetermined pattern is formed on a wafer using a projection optical system by using exposure light, and measuring a wavefront aberration of the projection optical system; Step 102 for adjusting the wavefront aberration, Step 104 for measuring predetermined imaging characteristics of the wavefront aberration after exposure on the wafer using the projection optical system, and exposure light in the projection optical system And step 105 for obtaining parameter information for predicting the fluctuation amount of the predetermined imaging characteristic with respect to the irradiation amount.
[Selection] Figure 7

Description

  The present invention relates to an optical characteristic adjustment technique for adjusting optical characteristics such as an imaging characteristic of an optical system, and an exposure technique and a device manufacturing technique using the optical characteristic adjustment technique.

  For example, in a lithography process for manufacturing a device (electronic device, microdevice) such as a semiconductor device or a liquid crystal display element, a wafer (with a resist applied to a pattern of a reticle (or photomask, etc.) via a projection optical system ( In addition, an exposure apparatus such as a batch exposure type projection exposure apparatus such as a stepper or a scanning exposure type projection exposure apparatus such as a scanning stepper is used for transfer onto a glass plate or the like. In these exposure apparatuses, the imaging characteristics (aberration characteristics) of the projection optical system gradually vary due to fluctuations in exposure light irradiation energy and atmospheric pressure.

Therefore, for example, an exposure apparatus having an imaging characteristic control mechanism that adjusts imaging characteristics by adjusting the position and tilt angle of an optical member constituting the projection optical system has been developed (see, for example, Patent Document 1). . In this exposure apparatus, for example, a prediction model for predicting the amount of exposure light irradiation and the amount of fluctuation in image formation characteristics associated with the change in atmospheric pressure is stored in advance. The amount of variation in imaging characteristics is predicted according to the amount of variation in atmospheric pressure. Then, the imaging characteristic control mechanism is driven so as to correct the predicted fluctuation amount of the imaging characteristic, so that the reticle pattern is always accurately applied to the wafer through the projection optical system with the predetermined imaging characteristic. I was able to transfer it.
JP-A-4-13481

  In the conventional exposure apparatus, prediction for predicting the amount of exposure light irradiation and the variation in imaging characteristics due to changes in atmospheric pressure using test prints under various exposure conditions (such as illumination conditions) in advance. I was looking for a model. However, recently, various conditions such as dipole illumination, quadrupole illumination, annular illumination, and small σ illumination with a small coherence factor have been set by various users of the exposure apparatus even with illumination conditions alone. Therefore, it is difficult to accurately obtain a prediction model for almost all exposure conditions that can be considered in advance.

In view of such circumstances, the present invention actually calculates and predicts an accurate prediction model of the variation amount of optical characteristics such as imaging characteristics of the optical system under test under various conditions in advance. An object of the present invention is to provide an optical characteristic adjustment technique capable of accurately predicting the fluctuation amount of the optical characteristic under the conditions used.
Another object of the present invention is to provide an exposure technique and a device manufacturing technique that can adjust the fluctuation amount of the optical characteristic with high accuracy using the optical characteristic adjustment technique.

  An optical property adjustment method according to the present invention is a method for adjusting an optical property of an optical system (PL) that forms an image of a predetermined pattern on an object using exposure light, and measures a plurality of optical properties of the optical system. The first measurement process (step 101), the first adjustment process (step 102) for adjusting the plurality of optical characteristics based on the measurement result of the first measurement process, and the plurality of optical characteristics are adjusted A second measurement step (step 104) for measuring a first set of optical characteristics among the plurality of optical characteristics after forming an image of the predetermined pattern on the object via the optical system; And a calculation step (step 105) for obtaining first parameter information for predicting the fluctuation amount of the first set of optical characteristics based on the information on the exposure light irradiation amount in the optical system. .

According to the present invention, in the first adjustment step, after adjusting a plurality of optical characteristics to a predetermined state, in the second measurement step, for example, a first set of optical characteristics having a large influence on the optical characteristics is measured, and a calculation step The first parameter information (prediction model) for predicting the fluctuation amount of the first set of optical characteristics is obtained.
Therefore, the amount of variation in optical characteristics under various conditions that are actually used can be obtained without obtaining and storing an accurate prediction model of the amount of variation in optical characteristics of the optical system in advance under various conditions. Can be accurately predicted.

Hereinafter, an example of a preferred embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows a schematic configuration of an exposure apparatus 100 according to the present embodiment. The exposure apparatus 100 is a so-called scanning stepper as a step-and-scan projection exposure apparatus (scanning exposure apparatus). In FIG. 1, an exposure apparatus 100 is emitted from an illumination system 10, a reticle stage RST that holds a reticle R (mask) illuminated by exposure light (exposure illumination light) IL from the illumination system 10, and a reticle R. Main controller 20 (FIG. 4) comprising a projection optical system PL for projecting exposure light IL onto wafer W (object), a stage apparatus having wafer stage WST and measurement stage MST, and a computer for overall control of the operation of the entire apparatus. Etc.). Wafer W is placed on wafer stage WST. In the following, the Z-axis is taken in parallel with the optical axis AX of the projection optical system PL, and the Y-axis is in the direction in which the reticle and wafer are relatively scanned in a plane perpendicular to the optical axis AX (the direction parallel to the paper surface of FIG. 1). X axis in the direction orthogonal to the Z axis and Y axis (direction perpendicular to the paper surface of FIG. 1), and the rotation (tilt) directions around the X axis, Y axis, and Z axis are respectively θx, θy, And the θz direction will be described.

  In FIG. 1, the illumination system 10 includes a light source and an illumination optical system as disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-313250 (corresponding US Patent Application Publication No. 2003/0025890). The illumination optical system includes an illuminance uniformizing optical system including an optical integrator (such as a fly-eye lens, a rod integrator (an internal reflection type integrator), or a diffractive optical element), a reticle blind, and the like (all not shown). The illumination system 10 illuminates the slit-shaped illumination area IAR on the reticle R defined by the reticle blind with the exposure light IL with a substantially uniform illuminance.

As the exposure light IL, for example, ArF excimer laser light (wavelength 193 nm), which is pulse light, is used. As exposure light, KrF excimer laser light (wavelength 248 nm), F ₂ laser light (wavelength 157 nm), harmonic of YAG laser, harmonic of solid-state laser (semiconductor laser, etc.), or emission line of mercury lamp (i-line) Etc.) can also be used.
Further, in the illumination optical system of the illumination system 10 of FIG. 1, an integrator sensor 4 comprising a beam splitter 3 for branching a part of the illumination light from the optical path of the exposure light IL and a photoelectric detector for receiving the branched illumination light. And the detection signal of the integrator sensor 4 is supplied to the exposure amount control system 36 of FIG. The exposure amount control system 36 is also supplied with a detection signal from an irradiation amount monitor 35 (see FIG. 2) comprising a photoelectric detector that measures the illuminance (product of pulse energy and frequency) of the exposure light IL on the measurement stage MST. ing. The exposure amount control system 36 stores in advance the value of the ratio between the detection signal of the integrator sensor 4 and the detection signal of the irradiation amount monitor 35 before exposure. During exposure, the value of the ratio and the value of the integrator sensor 4 are stored. The illuminance of the exposure light IL on the wafer W is indirectly measured using the detection signal. Based on this measured value and control information from the main controller 20 (pulse energy and oscillation frequency of the exposure light IL), the light emission operation of the light source of the exposure light IL is controlled.

  In FIG. 1, on a reticle stage RST, a reticle R on which a circuit pattern or the like is formed on its pattern surface (lower surface) is held by, for example, vacuum suction, and a plurality of reticles R are positioned at positions shifted in the Y direction with respect to the reticle R. The measurement reference plate RFM on which the evaluation mark PM (see FIG. 3B) is formed is fixed. The reticle stage RST is formed with an opening through which the exposure light IL that has passed through the reticle R of the reticle stage RST and the measurement reference plate RFM is passed. The reticle stage RST can be finely driven in the XY plane by the reticle stage driving system 11 in FIG. 4 including, for example, a linear motor on the reticle base RBS in FIG. 2 and designated in the scanning direction (Y direction). It can be driven at the scanning speed.

  Position information (including position information in the X and Y directions and rotation information in the θz direction) within the moving surface of the reticle stage RST is transferred to the moving mirror 15 (the end surface of the stage) by a reticle interferometer 16R formed of a laser interferometer. For example, it may be always detected with a resolution of about 0.5 to 0.1 nm via a mirror-finished reflective surface. The measurement value of reticle interferometer 16R is sent to main controller 20 in FIG. Main controller 20 calculates positions of reticle stage RST in at least the X, Y, and θz directions based on the measurement values of reticle interferometer 16R, and controls reticle stage drive system 11 based on the calculation results. Thus, the position and speed of reticle stage RST are controlled.

  In FIG. 1, as the projection optical system PL disposed below the reticle stage RST, for example, a refractive optical system including a plurality of lens elements arranged along the optical axis AX is used. The projection optical system PL is, for example, telecentric on both sides and has a predetermined projection magnification β (for example, a reduction magnification of 1/4 times, 1/5 times, etc.). A variable aperture stop AS is disposed on the pupil plane PP (see FIG. 3A) of the projection optical system PL. When the illumination area IAR on the reticle R is illuminated by the exposure light IL from the illumination system 10, the circuit pattern of the reticle R in the illumination area IAR is passed through the projection optical system PL by the exposure light IL that has passed through the reticle R. An image is formed in an exposure area IA (an area conjugate to the illumination area IAR) on one shot area of the wafer W. In the wafer W of this example, for example, a resist (photoresist) that is a photosensitive agent (photosensitive layer) is applied to a surface of a disk-shaped semiconductor wafer having a diameter of about 200 mm to 300 mm with a predetermined thickness (for example, about 200 nm). Including things.

  The exposure apparatus 100 performs exposure using a liquid immersion method. In this case, in order to avoid an increase in the size of the projection optical system, a catadioptric system including a mirror and a lens may be used as the projection optical system PL. The exposure apparatus 100 performs exposure using a liquid immersion method, and therefore a lens barrel (not shown) that holds a tip lens 191 that is an optical element on the most image plane side (wafer W side) constituting the projection optical system PL. A nozzle unit 32 constituting a part of the liquid immersion device 8 is provided so as to surround the lower end portion.

  In FIG. 1, the nozzle unit 32 has a supply port that can supply an exposure liquid Lq (for example, pure water (water) or decalin) and a recovery port that can recover the liquid Lq. The supply port is connected to the liquid supply device 5 (see FIG. 4) via a supply flow path in the nozzle unit 32 and a supply pipe 31A. The recovery port is connected to the liquid recovery apparatus 6 (see FIG. 4) via a recovery flow path in the nozzle unit 32 and a recovery pipe 31B.

  The operations of the liquid supply device 5 and the liquid recovery device 6 in FIG. 4 are controlled by the main controller 20. The exposure liquid Lq delivered from the liquid supply device 5 of FIG. 4 flows through the supply flow path of the supply pipe 31A and the nozzle unit 32 of FIG. 1 and then is supplied from the supply port to the optical path space of the exposure light IL. The Further, the liquid Lq recovered from the recovery port of the nozzle unit 32 of FIG. 1 by driving the liquid recovery device 6 of FIG. 4 is recovered by the liquid recovery device 6 via the recovery pipe 31B. As a result, the liquid immersion region (immersion space) including the optical path space of the exposure light IL in the space between the tip lens 191 and the wafer W in FIG. 1 is locally filled with the liquid Lq.

  Assuming that the exposure liquid Lq is pure water (water), the refractive index n of water with respect to ArF excimer laser light is approximately 1.44. Therefore, the wavelength of the exposure light IL in the liquid Lq is shortened to 193 nm × 1 / n = about 134 nm, so that the resolution is improved. A part of the liquid immersion device 8, for example, at least the nozzle unit 32, may be supported by being suspended from a main frame (not shown) that holds the projection optical system PL, or may be provided on a frame member different from the main frame. Also good.

  Even when the measurement stage MST is positioned below the projection optical system PL in FIG. 1, it is possible to fill water between the measurement table MTB on the measurement stage MST and the tip lens 191 in the same manner as described above. As the liquid immersion device 8, a liquid immersion mechanism disclosed in International Publication No. 2004/053955 pamphlet or a liquid immersion mechanism disclosed in European Patent Application No. 1420298 may be applied. it can. Further, in the following FIG. 2 and FIG. 3A and the like, illustration of the liquid immersion device 8 is omitted for convenience of explanation.

  Returning to FIG. 1, the stage apparatus includes wafer stage WST and measurement stage MST arranged above base board 12, wafer interferometer 16W for measuring the position of wafer stage WST, and measurement stage interference for measuring the position of measurement stage MST. A total 18 and a stage drive system 43 (see FIG. 4) including a linear motor for driving wafer stage WST and measurement stage MST are provided. The bottom surfaces of the stages WST and MST are supported on the base board 12 by a non-illustrated air pad of an air bearing in a non-contact manner with a clearance of about several μm.

  Wafer stage WST also has a main body 91 including an XY stage and a Z leveling stage that move in the X and Y directions on base board 12, and is fixed on main body 91 to hold wafer W by vacuum suction or the like. And a wafer table WTB. On the wafer table WTB, a plate portion 28 subjected to liquid repellent processing is fixed so as to surround the wafer W. The measurement stage MST includes a main body 92 including an XY stage and a Z leveling stage that move in the X direction and the Y direction on the base board 12, and a measurement table MTB that is fixed on the main body 92 and has a slit, an opening, and the like. And.

  Wafer interferometer 16W and measurement stage interferometer 18 formed of a laser interferometer respectively apply laser beams to mirror surfaces (or movable mirrors) orthogonal to the side surfaces of wafer table WTB of wafer stage WST and measurement table MTB of measurement stage MST. By irradiating, the positions of those mirror surfaces are always detected with a resolution of about 0.5 to 0.1 nm, for example. The detection result is supplied to the main controller 20 in FIG. 4, and the main controller 20 measures the positions of the wafer table WTB (wafer W) and the measurement table MTB in at least the X direction, the Y direction, and the θz direction based on the detection result. To do. Based on this measurement value and the control information of main controller 20, stage drive system 43 in FIG. 4 controls the position and speed of wafer stage WST and measurement stage MST in the X, Y, and θz directions independently of each other.

  FIG. 2 shows a partial configuration of the projection optical system PL and the measurement stage MST of FIG. In FIG. 2, the oblique incidence of the same structure as that disclosed in, for example, Japanese Patent Laid-Open No. 6-283403 (corresponding US Pat. No. 5,448,332), which includes an irradiation system 19a and a light receiving system 19b. A multi-point focal position detection system (hereinafter abbreviated as AF system) 19 is provided. By processing the detection signal of the light receiving system 19b by the AF signal processing unit 19c of FIG. 4, the best focus position (position in the Z direction) at a plurality of measurement points in the test surface including the exposure area of the projection optical system PL. A deviation amount (defocus amount) from the focus position is obtained, and these defocus amounts are supplied to the main controller 20.

  When wafer stage WST in FIG. 1 is located on the lower surface of projection optical system PL, the surface of wafer W is focused on the image plane of projection optical system PL based on the measurement result of AF system 19. 4 drives the Z leveling stage of main body 91 of wafer stage WST to control the position of wafer table WTB in the Z, θx, and θy directions. On the other hand, as shown in FIG. 2, when the measurement stage MST is positioned below the projection optical system PL, for example, based on the measurement result of the AF system 19, for example, the upper surface of the measurement stage MST is placed on the projection optical system PL. The positional relationship with respect to the image plane (the image plane determined based on the measurement results so far) is set to a predetermined relationship (for example, a focused state or a state in which the defocus amount gradually changes by a predetermined value). As described above, the stage drive system 43 of FIG. 4 drives the Z leveling stage of the main body 92 (see FIG. 1) of the measurement stage MST.

  Further, as shown in FIG. 2, an alignment system ALG for irradiating the test mark with, for example, non-exposure light on the side surface of the projection optical system PL and capturing an image of the test mark is installed. The detection signal of the alignment system ALG is image-processed by the first signal processing unit 51 of FIG. 4 to determine the position of the test mark, and information on this position is supplied to the main controller 20. Further, a reference member (not shown) on which a reference mark and an index mark for alignment system ALG are formed is fixed on wafer table WTB of wafer stage WST in FIG. In order to detect the position of the reticle mark of the reticle R in the main body 91 on the bottom surface of the reference member and to align the reticle R, an image of the reticle mark through the projection optical system PL together with the index mark An aerial image measurement system for imaging is installed, and a detection signal of the aerial image measurement system is supplied to the first signal processing unit 51 in FIG. For example, a light transmission system that can be connected to and separated from wafer stage WSTWST and measurement stage MST may be provided, and an aerial image measurement system connected to the light transmission system may be provided in measurement stage MST. In this configuration, when reticle R is aligned, wafer stage WST and measurement stage MST may be connected so that the light transmission system is connected.

In addition, an imaging characteristic control mechanism is incorporated in the projection optical system PL of the present embodiment. That is, FIG. 2 representatively shows lens elements 13 _{1 to} 13 ₈ among a large number of lens elements in a lens barrel (not shown) of projection optical system PL. Note that the local liquid immersion device 8 of FIG. 1 is not shown. As an example, a plurality of lens elements 13 ₁ , 13 _2, etc. on the reticle R side are respectively connected to the Z direction, θx via drive elements 14 A, 14 B, etc., each composed of, for example, three piezo elements that can expand and contract in the Z direction. Is supported by the lens barrel so as to be displaceable in the direction θy. Similarly, for example, a plurality of lens elements 13 ₄ , 13 _6, etc. in the vicinity of the pupil plane of the projection optical system PL are supported on the lens barrel via a drive element (not shown) so as to be displaceable in the Z direction, θx direction, and θy direction. Has been.

Furthermore, for example, the lens elements 13 ₅ in the vicinity of the pupil plane of the projection optical system PL, the light guide 42A for irradiating non-exposure light LB which does not resist the wafer W is photosensitive, and 42B, the light guide 42A, the 42B And a light source unit 41 that supplies the non-exposure light LB. In practice, the light guide 42A, 42B is disposed on the optical axis of the lens element 13 ₅ at four positions such as to sandwich the X and Y directions. As the non-exposure light LB, for example, infrared light having a wavelength of 10.6 μm generated from a carbon dioxide (CO ₂ ) laser, infrared light generated from a light emitting diode, or the like can be used. By irradiating the non-exposure light LB from the light guides 42A and 42B, rotationally asymmetric aberration (for example, astigmatism generated during dipole illumination) of the projection optical system PL can be corrected. A more detailed configuration of the imaging characteristic control mechanism for irradiating the lens element of the projection optical system PL with non-exposure light is disclosed in, for example, International Publication No. 2005/022614. Further, when the projection optical system PL is, for example, a catadioptric system, the reflecting mirror near the pupil plane is made rotationally asymmetric instead of or together with the mechanism that irradiates the lens element near the pupil plane with non-exposure light. It is also possible to use a slightly deforming mechanism.

In the present embodiment, the image forming characteristic predicting unit 56 connected to the main controller 20 in FIG. 4 is controlled via the image forming characteristic control system 78 so as to suppress the fluctuation amount (aberration) of the image forming characteristic predicted. The second lens elements 13 ₁ , 13 ₂ , 13 ₄ , and 13 ₆ are driven and the non-exposure light LB is irradiated. Further, when defocus remains due to the operation of the imaging characteristic control system 78, the wafer table WTB or the Z leveling stage on the wafer stage WST or measurement stage MST side in FIG. 1 is corrected so as to correct the defocus. The positions in the Z direction, θx direction, and θy direction of the measurement table MTB are corrected. In order to correct the defocus, the Z position of the reticle R may be corrected on the reticle stage RST side.

As an example, imaging characteristics to be corrected of an image projected onto the wafer W by the projection optical system PL are represented by p (p is an integer of 3 or more) aberrations B1 to Bp. As an example, the aberration Bj (j = 1 to p) of this embodiment includes spherical aberration, coma aberration, distortion (including magnification), focus (shift amount of best focus position), and astigmatism. Further, the driving amount of the imaging characteristic control mechanism controlled by the imaging characteristic control system 78 of FIG. 2, that is, the driving amount of the lens elements 13 _{1 to} 13 ₆ , and the non-exposure light LB from the light guides 42A, 42B, etc. The amount of irradiation energy is represented by m driving amounts D1 to Dm (for example, the same integer as p). At this time, driving amounts D1 to Dm for correcting the aberrations B1 to Bp are as follows.

この式は、収差Ｂｊ（ｊ＝１〜ｐ）のベクトルをＢ、感度行列をＫ、駆動量Ｄｉ（ｉ＝１〜ｍ）のベクトルをＤとすると、次のようになる。
Ｂ＝Ｋ・Ｄ …（２）
従って、行列Ｋの逆行列をＫ^-1とすると、駆動量のベクトルＤは次のように求めることができる。なお、駆動量Ｄｉの個数ｍを収差Ｂｊの個数ｐよりも多くすることも可能であり、この場合には、逆行列Ｋ^-1は例えば最小自乗法によって求めることができる。

This equation is as follows, where B is a vector of aberrations Bj (j = 1 to p), K is a sensitivity matrix, and D is a vector of driving amounts Di (i = 1 to m).
B = K · D (2)
Therefore, if the inverse matrix of the matrix K is K ⁻¹ , the driving amount vector D can be obtained as follows. Note that the number m of the drive amounts Di can be made larger than the number p of the aberrations Bj. In this case, the inverse matrix K ⁻¹ can be obtained by, for example, the least square method.

D = K ⁻¹ · B (3)
In the imaging characteristic control system 78, information of the inverse matrix K ⁻¹ is stored in advance, and this is multiplied by the aberration vector B supplied from the imaging characteristic prediction unit 56, thereby forming an imaging characteristic control mechanism. Each driving amount Di (vector D) can be obtained. By driving the imaging characteristic control mechanism in this way, even if the imaging characteristics (aberrations B1 to Bp) of the projection optical system PL vary due to variations in the irradiation amount of the exposure light IL and atmospheric pressure, the variation amount Are offset, and the pattern image of the reticle R can be exposed on the wafer W with high accuracy.

  In order to drive the imaging characteristic control system 78 in this way, for example, the imaging characteristics including the aberrations B1 to Bp to be corrected in the projection optical system PL are periodically measured with high accuracy, and those imaging characteristics are also measured. It is necessary to obtain an irradiation parameter that is a parameter for predicting the irradiation amount (product of illuminance and time) of the exposure light IL and the variation amount associated with the variation in atmospheric pressure. It should be noted that fluctuations in imaging characteristics due to changes in atmospheric pressure can be handled in the same manner as fluctuations associated with the exposure dose of the exposure light IL, and therefore will not be described in the following embodiments. As a measuring device for the imaging characteristics, the wavefront aberration measuring device 21 and the aerial image measuring system 45 of FIG. 2 are provided in the measuring stage MST of the present embodiment.

First, since the aberration Bj such as the spherical aberration and distortion can be uniformly expressed by wavefront aberration, in this embodiment, for example, when a plurality of lots of wafers are exposed under new exposure conditions, or for example, periodically During typical maintenance, the wavefront aberration measuring device 21 of FIG. 2 is used to measure the wavefront aberration of the image of the projection optical system PL.
FIG. 2 shows a state in which a reticle 27 for aberration measurement is loaded on the reticle stage RST in order to measure the wavefront aberration of the projection optical system PL. In FIG. 2, the incident surface of the wavefront aberration measuring device 21 of the measurement stage MST has moved to the exposure area of the projection optical system PL. The reticle 27 has a plurality of circular openings (pinholes) 27a for measuring aberration in the light-shielding film along the X direction and the Y direction (in FIG. 2, only one of them is shown at the center) in a matrix shape. Is formed. The central opening 27a is positioned substantially on the optical axis AX of the projection optical system PL. The reticle 27 is also formed with alignment marks for positioning in a predetermined relationship with the opening 27a. The opening 27a of the reticle 27 can be formed in the measurement reference plate RFM.

  Further, the wavefront aberration measuring apparatus 21 includes a sign plate 22 made of a glass substrate provided on the measurement stage MST. At the time of wavefront aberration measurement, the sign plate 22 is positioned at almost the same height position (Z position) as the image plane of the projection optical system PL (the image plane measured so far). The sign plate 22 is used in common with a later-described aerial image measurement system 45. The reflective film 26 on the surface of the marking plate 22 is formed with a calibration opening (light transmitting portion) 26a. An alignment mark (not shown) is also formed in a predetermined positional relationship with the opening 26a. The opening 26a is set larger than the image of the opening 27a of the reticle 27 formed via the projection optical system PL.

  Further, in the wavefront aberration measuring apparatus 21, light from the image (primary image) of the opening 27a of the reticle 27 formed on the image plane via the projection optical system PL passes through the opening 26a and the collimating lens 23. , Enters the micro fly's eye 24. The micro fly's eye 24 is an optical element composed of a large number of microlenses having a square positive refracting power that are densely arranged in the X direction and the Y direction, respectively.

  Therefore, the light beam incident on the micro fly's eye 24 (wavefront dividing element) is two-dimensionally divided by a large number of microlenses, and an image (two images) of one opening 27a is provided in the vicinity of the rear focal plane of each microlens. Next image) is formed. A large number of secondary images formed in this way are detected by a CCD-type or CMOS-type two-dimensional image sensor 25. Detection signals read from a large number of pixels of the image sensor 25 are supplied to the second signal processing unit 52 of FIG. In the second signal processing unit 52, the detection signal is converted into digital data, and the wavefront aberration of the projection optical system PL is obtained by obtaining the amount of positional deviation of the many secondary images by a predetermined calculation process. The obtained wavefront aberration is supplied to the main controller 20. Such a wavefront aberration detection principle is disclosed in detail in, for example, Japanese Patent Application Laid-Open No. 2002-71514.

At this time, since the reticle 27 is provided with a plurality of openings 27a, the measurement stage MST is driven in the X direction and the Y direction to sequentially open the plurality of openings 26a of the wavefront aberration measuring device 21. The wavefront aberration can also be measured by moving to the position of the image of the opening 27a.
In the present embodiment, the wavefront aberration measuring device 21 is configured to include the marking plate 22, the collimating lens 23, the micro fly's eye 24, and the image pickup device 25, and the wavefront aberration measuring device 21 is disposed in the housing 21a and the measurement stage MST. It is installed in the main body 92 (see FIG. 1). The wavefront aberration measuring device 21 may be a detachable method. As disclosed in JP-A-2002-71514, a relay optical system is disposed between the collimating lens 23 and the micro fly's eye 24 in FIG. A plurality of mirrors may be arranged.

  Further, as shown in FIG. 2, in order to illuminate the opening 27a with a numerical aperture greater than or equal to the object-side numerical aperture NAp of the projection optical system PL (incoherent illumination), the space between the illumination system 10 and the reticle 27 in FIG. A diffusing plate 38 such as rubbed glass for diffusing a light beam is provided in the optical path so as to be detachable. Instead of the diffusing plate 38, a diffractive optical element that diffracts incident light in various directions or a lemon skin plate may be used.

  In this embodiment, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2006-279028, an aberration function indicating wavefront aberration is series-expanded by a Zernike's polynomial from the first order to the 37th order, and k The aberration is represented by a coefficient Zk of the next Zernike polynomial (k = 1 to 37). Assuming that the aberration represented by the coefficient Zk is Zk, the 37 aberrations Zk measured by the wavefront aberration measuring device 21 are p (p) which are all imaging characteristics corrected by the imaging characteristic control mechanism. <37) aberration Bj is included.

  Specifically, focus (defocus amount) is aberration Z4, low-order and middle-order spherical aberration is Z9, Z16, low-order and middle-order coma aberration is aberrations Z7, Z8, Z14, Z15, distortion (here magnification) Are represented by aberrations Z2 and Z3, and low-order astigmatism is represented by aberrations Z5 and Z6. In this way, when only the low-order and middle-order aberrations are a problem, the wavefront aberration may be expressed by a coefficient Zk from the first order to the 16th order.

  Next, in order to measure the wavefront aberration with high accuracy using the wavefront aberration measuring apparatus 21 described above, a process such as setting a diffusion plate 38 on the reticle stage RST as shown in FIG. Cost. Therefore, in order to measure a specific imaging characteristic in the above-mentioned p aberrations Bj in a short time, for example, during wafer exchange during exposure of one lot of wafers, as shown in FIG. An aerial image measurement system 45 is housed in the MST.

  In FIG. 3A, the aerial image measurement system 45 uses the exposure light IL transmitted through a slit 26b elongated in the X direction and a slit (not shown) elongated in the Y direction formed in the reflective film 26 on the marking plate 22. A condensing lens 46 for condensing light and a photoelectric detector 47 such as a photodiode or a photomultiplier tube for receiving the condensed exposure light IL are configured. The housing 45a of the aerial image measurement system 45 is housed in the main body 92 of the measurement stage MST. The detection signal of the photoelectric detector 47 (aerial image measurement system 45) is supplied to the third signal processing unit 53 in FIG. 4, and the third signal processing unit 53, for example, the evaluation mark PM formed on the measurement reference plate RFM. The position of the image of the evaluation mark PM is processed by processing a detection signal obtained when the image by the projection optical system PL is scanned in the Y direction by the slit 26b (or when scanned in the X direction by a slit elongated in the Y direction). And the contrast and the like.

  On the measurement reference plate RFM, as shown in FIG. 3B, positions P (i, j) at predetermined intervals in the X and Y directions within an area having the same size as the illumination area IAR of the exposure light IL. (I = −I to + I, j = −J to + J: In FIG. 3B, I and J are integers of 2 or more), respectively, and evaluation marks PM are formed. For example, as shown in FIG. 3C, the evaluation mark PM includes a line and space pattern (hereinafter referred to as an L & S pattern) 33X having a predetermined pitch in the X direction and an L & S pattern 33Y having a predetermined pitch in the Y direction. Yes. The average value of the best focus positions of the images of the L & S patterns 33X and 33Y becomes the best focus position of the projection optical system PL, and the difference between the best focus positions becomes astigmatism. In practice, the evaluation mark PM includes a plurality of X and Y direction L & S patterns having line widths and / or pitches different from those of the L & S patterns 33X and 33Y.

  In this case, the position P (i) is changed while changing the position of the upper surface of the measurement stage MST in the Z direction in a state where the center position P (0, 0) of the measurement reference plate RFM is aligned with the optical axis of the projection optical system PL. , J), from the contrast of the detection signal obtained when the image of the evaluation mark PM is scanned by the slit 26b of the aerial image measurement system 45, the best focus position (image plane) of the projection optical system PL at that position, Astigmatism and spherical aberration can be measured. Further, coma aberration, distortion (including magnification), and the like can be measured from the positions in the X direction and Y direction of the image of the evaluation mark PM at a plurality of positions P (i, j) measured by the aerial image measurement system 45. .

Next, distortion Di (aberration Z ₂ , Z ₃ ) is used as an imaging characteristic for the irradiation parameters for predicting the amount of fluctuation of the imaging characteristics (aberrations B1 to Bp) to be corrected from the irradiation amount of the exposure light IL. Is described as an example.
When the irradiation amount of the exposure light IL incident on the projection optical system PL via the reticle R in FIG. 1 is E, the illuminance on the upper surface (wafer surface) of the exposure light IL during exposure is generally constant. Therefore, it is possible to treat the irradiation amount E as being substantially proportional to the time t from the start of exposure. In this case, assuming that the saturation distortion per unit illuminance of the exposure light IL incident on the projection optical system PL is Sdiuni, the illuminance is P, and the distortion time constant is Tdi, a dotted curve 60 in FIG. Thus, the distortion Di at time t changes as follows. Note that Sdiuni × P = Sdi.

Di = Sdiuni × P × [1-exp (−t / Tdi)] (4)
In this case, the irradiation parameters (initial values) for predicting the fluctuation amount of the distortion Di from the irradiation amount E (illuminance P and elapsed time t) are the saturation distortion Sdiuni and the time constant Tdi. However, the initial values (Sdiuni, Tdi) of these irradiation parameters are obtained when, for example, a reticle having a predetermined transmittance on which a predetermined standard pattern is formed is used as the reticle R and a predetermined illumination condition is used. Is a value calculated theoretically.

  However, in practice, the transmittance and the light amount distribution vary depending on the pattern of the reticle R, and the exposure conditions including the illumination conditions are set variously by the user. Therefore, the distortion Di actually changes as shown by a solid curve 60R in FIG. 5A, and the saturation distortion Sdmuni (= Sdm / P) and the time constant Tdm, which are irradiation parameters, are different from the initial values. ing.

  Further, in reality, since the exposure light IL is not irradiated during the exchange of the wafer (time ΔT), the distortion Di changes as the curve 60F in FIG. . On the horizontal axis (time t) in FIG. 5B, the time points when the exposure of one wafer is completed are indicated by t1, t2, t3,. A calculation formula corresponding to the formula (4) in consideration of such a relaxation effect is disclosed in, for example, International Publication No. 2005/022614.

  For all the aberrations Bi (i = 1 to p) to be corrected, initial values of corresponding irradiation parameters are obtained in advance and stored in the irradiation parameter storage unit 54 of FIG. Further, in the present embodiment, the irradiation parameter calculation unit 55 in FIG. 4 calculates the actual irradiation parameter value in accordance with the curve 60R indicating the actual fluctuation in FIG. 5A during the exposure, for example. When the calculated irradiation parameter value changes beyond the allowable range compared to the previous value (such as an initial value), the previous value is updated with the calculated irradiation parameter value. Thus, each irradiation parameter is gradually updated during the process of exposing the reticle pattern for the actual device under the respective exposure conditions. Using the information about the irradiation parameters and the dose E stored in the irradiation parameter storage unit 54, the imaging characteristic prediction unit 56 in FIG. Calculate Correspondingly, the imaging characteristic control system 78 drives the imaging characteristic control mechanism of FIG. 2 with the driving amount Di (i = 1 to m) obtained by the equation (3), so that the aberration Bi is 0 respectively. It is corrected to become.

  Therefore, in the state where the imaging characteristic control mechanism of FIG. 2 is operating during the exposure process, the aberration Bi measured by the wavefront aberration measuring device 21 or the aerial image measuring system 45 is, for example, as shown in FIG. As indicated by a solid line 61F taking the distortion Di as an example, a residual ΔDi is obtained by subtracting the variation corrected by the imaging characteristic control mechanism from the distortion Di in the variation of FIG. Further, by updating the irradiation parameter in accordance with the actual amount of aberration variation during exposure, the residual ΔDi decreases as shown by the dotted curve 61M in FIG. 5C.

  For example, when the pattern of the reticle R includes the L & S pattern 63X having a fine pitch in the X direction shown in FIG. 6A, the illumination condition is set to bipolar illumination in the X direction as an example, and the projection optical system PL As shown in FIG. 6B, the light amount distribution on the pupil plane PP is a large distribution in the regions 64A and 64B sandwiching the optical axis AX in the X direction. As a result, the best focus position of the image of the L & S pattern in the X direction and the Y direction changes as shown by the curves 65V and 65H in FIG. The best focus position changes as indicated by the dotted curve 65A.

  In other words, in such a case, the focus (best focus position) has a large influence among the aberration Bi to be corrected. In this case, with particular emphasis on focus measurement, by adjusting the imaging characteristics of irradiating the lens element with non-exposure light from the light guides 42A and 42B in FIG. 2, the dotted line in FIG. As indicated by a curve 66A, the focus residual ΔF can be reduced.

In the following, in the exposure apparatus 100 of FIG. 1 of the present embodiment, for example, using a reticle R that has not been used so far, the corresponding exposure conditions (illumination conditions, numerical aperture of the projection optical system PL, irradiation dose) are several. An example of the operation when exposure is performed on a lot of wafers will be described with reference to the flowchart of FIG.
First, in step 101 of FIG. 7A, a measurement reticle 27 is loaded on the reticle stage RST as shown in FIG. 2, and a diffusion plate 38 is installed above the reticle 27 to measure the wavefront aberration of the measurement stage MST. The apparatus 21 is used to measure the wavefront aberrations represented by the aberrations (Zernike polynomial coefficients) Z1 to Z37 of the image of the projection optical system PL, and the measurement results are shown in the main controller 20 and the imaging characteristic prediction unit 56 in FIG. To the imaging characteristic control system 78. During this measurement, wafer stage WST in FIG. 1 moves to the loading position, and in step 111 in FIG. 7A, wafer W (here, the first wafer) is loaded onto wafer stage WST. A resist is applied to the wafer W by a resist coater / developer (not shown) (step 121).

  In step 102 following step 101, the imaging characteristic control system 78 uses the imaging characteristic control mechanism shown in FIG. 2 to determine all imaging characteristics of the correction target in the wavefront aberration of the projection optical system PL, that is, the expression (1). Are corrected so that all the aberrations Bj (j = 1 to p) are zero. At substantially the same time, the reticle R is loaded on the reticle stage RST, the diffusing plate 38 is retracted, and then the reticle R is aligned. In step 103 following step 102 and step 111, as shown in FIG. 1, wafer stage WST moves below projection optical system PL, and alignment of wafer W is performed using alignment system ALG in FIG. Is called. Next, one wafer is exposed while measuring the irradiation amount of the exposure light IL by the integrator sensor 4 of FIG. Specifically, the wafer stage WST of FIG. 1 is driven in the X direction and the Y direction, and the wafer W is stepped to the scanning start position. Subsequently, supply of the liquid Lq between the projection optical system PL and the wafer W is started, irradiation of the exposure light IL is started, and the reticle R is scanned in the Y direction via the reticle stage RST. Then, scanning exposure is performed through the wafer stage WST to scan one shot area on the wafer W in the direction corresponding to the exposure area of the projection optical system PL using the projection magnification as the speed ratio. An image of the pattern of the reticle R is transferred to each shot area on the wafer W by a step-and-scan operation that repeats the step movement and scanning exposure.

  Further, using the irradiation parameter stored in the irradiation parameter storage unit 54 of FIG. 4 using, for example, the equation (4) using the irradiation amount of the exposure light IL measured by the integrator sensor 4 during the exposure of the single wafer W. ) And the like, the imaging characteristic prediction unit 56 predicts the fluctuation amount of the aberration Bj (j = 1 to p) in a predetermined calculation cycle. Then, the imaging characteristic control mechanism 78 is driven by the imaging characteristic control system 78 so that the predicted variation amount of the aberration Bj is set to 0 (corrected).

  Thereafter, the operation of wafer stage WST proceeds to step 112, and after wafer unloading D is performed, the operation proceeds to step 108. On the other hand, measurement stage MST moves below projection optical system PL in step 104 following step 103. Then, as shown in FIG. 3A, after the reticle stage RST is driven and the measurement reference plate RFM is moved to the illumination area of the exposure light IL, measurement is performed using the aerial image measurement system 45 of the measurement stage MST. An image of a predetermined evaluation mark PM at a predetermined position on the reference plate RFM is measured. Then, imaging characteristics of spherical aberration, distortion, focus, and magnification (part of distortion) of the projection optical system PL, which are a part of the above-described aberration Bj, are measured, and information on the measurement result and dose is shown in FIG. To the irradiation parameter calculation unit 55. The irradiation parameter calculation unit 55 is also supplied with information on the predicted value of the current aberration Bj (that is, the correction amount by the imaging characteristic control mechanism) from the imaging characteristic prediction unit 56. Note that the imaging characteristics measured in step 104 vary depending on the reticle R and exposure conditions. Specifically, the imaging characteristics that are expected to have a great influence on the pattern image of the reticle R are measured. Further, the operations in steps 104 to 108 may be performed each time a predetermined number of wafers are exposed, for example.

  In the next step 105, the irradiation parameter calculator 55 calculates the corresponding spherical aberration, distortion, focus, and magnification irradiation parameter values so as to match the imaging characteristics measured by the aerial image measurement system 45. In the case of distortion Di, the measured value is the residual ΔDi of the dotted curve 61M in FIG. 5, and the calculated irradiation parameters are the saturation distortion (Sdm / illuminance) and the solid curve 60R in FIG. Time constant Tdm. Note that the calculation of the irradiation parameter in step 105 may be performed based on, for example, the average value of the measurement results every time the imaging characteristic measurement in step 104 is performed a plurality of times.

  In the next step 106, the irradiation parameter calculation unit 55 compares the calculated irradiation parameter value with the irradiation parameter value stored in the irradiation parameter storage unit 54, and the calculated irradiation parameter change amount is calculated. Determine if the tolerance is exceeded. If there is an irradiation parameter whose change amount exceeds the allowable range, the process proceeds to step 107, and the irradiation parameter whose change amount exceeds the allowable range is stored in the irradiation parameter storage unit 54. The value is updated, and the irradiation parameter whose change amount does not exceed the allowable range is not updated. Next, the routine proceeds to step 108. On the other hand, if there is no irradiation parameter whose change amount exceeds the allowable range in step 106, the process proceeds to step 108 as it is.

  If a wafer to be exposed remains, wafer stage WST moves to step 111 to load the next wafer. Further, the measurement stage MST moves to step 103 and retreats from below the projection optical system PL. Thereafter, exposure of the wafer in steps 103 to 108 (correction of the predicted aberration is performed using the updated irradiation parameter), measurement of the irradiation parameter of a predetermined imaging characteristic, and updating as necessary are repeated.

  For example, after the completion of one lot of wafers, instead of step 104, in step 104A of FIG. 7B, the imaging characteristics of the measurement target are further reduced, and the aerial image measurement of FIG. Only the focus and magnification may be measured using the system 45. In this case, in the subsequent step 105, the irradiation parameter values of only the focus and magnification measured in step 104A are calculated. This is because it is considered that the irradiation parameters are obtained almost accurately for other imaging characteristics (here, spherical aberration, distortion (excluding magnification)) by measurement during exposure of one lot. Therefore, depending on the pattern of the reticle R and / or the exposure conditions, spherical aberration or the like may be measured also in step 104A.

  In step 108, the exposure process ends when the wafer to be exposed is exhausted. The exposed wafer W unloaded in step 112 is transferred from the exposure apparatus 100 to a coater / developer (not shown), and in step 122, the resist on the wafer is developed. In the next step 123, substrate processing including heating (curing) of the developed wafer and etching process is performed. In the next step 124, the lithography process and the substrate processing process are repeated as necessary, and then the semiconductor is subjected to a device assembly step (including processing processes such as a dicing process, a bonding process, and a packaging process), an inspection step, and the like. Devices such as devices are manufactured. At this time, since exposure is performed on the wafer according to the present embodiment while maintaining necessary imaging characteristics within the required accuracy, values of various irradiation parameters are stored in the irradiation parameter storage unit 54 in FIG. 4 in advance. Devices can be manufactured with high accuracy without storing them.

  The value of the irradiation parameter calculated at the end of the exposure process is stored as exposure data corresponding to the pattern of the reticle R and the exposure conditions. Next, when the same reticle R is exposed under the same exposure conditions, the stored value is used as an irradiation parameter. Then, in step 104 of FIG. 7A, as in step 104A of FIG. 7B from the beginning, by reducing the imaging characteristics of the measurement target to the necessary minimum, without reducing the exposure accuracy, Throughput of the exposure process can be improved.

Effects and the like of this embodiment are as follows.
(1) The image formation characteristic (optical characteristic) adjustment method of the exposure apparatus 100 of the above-described embodiment uses an exposure light to generate an image of a pattern (predetermined pattern) on the reticle R via the projection optical system PL (optical system). This is a method of adjusting the imaging characteristics (optical characteristics) of the projection optical system PL when forming on the wafer W, and includes a plurality of imagings including a plurality of aberrations Bj (j = 1 to p) of the projection optical system PL. Step 101 (first measurement step) for measuring characteristics (wavefront aberrations represented by aberrations Z1 to Z37) and step 102 (first adjustment step) for adjusting a plurality of aberrations Bj based on the measurement result of step 101 And have. Further, in the adjustment method, an image of the pattern of the reticle R is formed on the wafer W via the projection optical system PL in which the plurality of aberrations Bj are adjusted, and then spherical aberration and distortion among the plurality of aberrations Bj. Step 104 (second measurement step) for measuring (including magnification) and focus (first set of imaging characteristics), information on the amount of exposure light IL by the projection optical system PL, and measurement at step 104 Step 105 (calculation step) for obtaining an irradiation parameter (first parameter information) for predicting the variation amount of the first set of imaging characteristics using the result.

Therefore, the projection optical system PL can be used under the conditions actually used without obtaining and storing in advance an accurate prediction model of the variation amount of the imaging characteristics of the projection optical system PL under various conditions. It is possible to accurately predict the fluctuation amount of the imaging characteristics. Further, by first correcting the plurality of aberrations Bj, the influence of the imaging characteristics other than the measurement target on the image can be reduced.
(2) After step 102, the initial value or the value before update (second parameter information) of the irradiation parameter for predicting the variation amount of the plurality of aberrations Bj in consideration of the irradiation amount of the exposure light IL And a step 103 (second adjustment step) for adjusting a plurality of aberrations Bj based on the measurement information of the irradiation amount of the exposure light IL. Therefore, it is possible to correct imaging characteristics that vary according to the dose during exposure.

  (3) In step 105, the adjustment amount of the imaging characteristic predicted from the measured value of the irradiation amount of the exposure light IL and the initial value (or the value before update) of the irradiation parameter used in step 103 is measured. The irradiation parameter is obtained by subtracting from the imaging characteristics. Accordingly, it is possible to obtain the irradiation parameters of the changed imaging characteristics with high accuracy while correcting the imaging characteristics by the imaging characteristics control mechanism.

  (4) Further, after forming an image of the pattern of the reticle R on the wafer W via the projection optical system PL in which the first set of imaging characteristics is adjusted in Step 103, the first set of imaging characteristics Of these, step 104A (third measurement step) for measuring the focus and magnification (second set of imaging characteristics) is included, and in step 105, based on the measured value of the exposure light IL in the projection optical system PL. Then, an irradiation parameter (third parameter information) for predicting the variation amount of the second set of imaging characteristics is obtained. As a result, with respect to the imaging characteristics for which the irradiation parameters are required with high accuracy, the measurement can be omitted and the throughput can be improved.

(5) Further, as an example, the first set of imaging characteristics measured in step 104 has a variation amount due to exposure light exposure that is greater than a variation amount of other imaging properties in the plurality of aberrations Bj. Is preferably large.
(6) Further, as another example, the imaging characteristics of the first set of the first set of imaging characteristics are affected by the variation in the pattern of the reticle R caused by the exposure light irradiation. It is preferable that the influence is greater than the influence of the imaging characteristics.

This makes it possible to perform exposure with high accuracy while reducing the imaging characteristics of the measurement target.
(7) In step 101 of FIG. 7A, the wavefront aberration of the projection optical system PL represented by the aberrations Z1 to Z37 of the projection optical system PL is measured. The first set of imaging characteristics measured in step 104 preferably includes at least two of spherical aberration, coma aberration, distortion, magnification error, and focus (defocus) in the wavefront aberration. . Thereby, measurement efficiency can be improved.

(8) Since the wavefront aberration to be measured is represented by the aberrations Z1 to Z37, for example, higher-order aberrations can be corrected. For example, when only low-order and medium-order aberrations are corrected, only the wavefront aberrations represented by the aberrations Z1 to Z16 may be measured. Further, only the aberration corresponding to the p aberrations Bj (j = 1 to p) actually corrected in the wavefront aberration may be measured.
(9) Further, the imaging characteristic control mechanism in FIG. 2 controls the posture of the lens element of the projection optical system PL and heats a predetermined lens element. However, the image formation characteristic control mechanism, for example, when adjusting a plurality of aberrations Bj of the projection optical system PL in step 102, controls the attitude of the optical member constituting the projection optical system PL, and the optical axis direction of the projection optical system PL. Even at least one of position control of the wafer W or reticle R, heating of the reticle R, heating of the optical member constituting the projection optical system PL, and deformation of the optical member constituting the projection optical system PL is executed. Good. Note that the degree of freedom of driving by the imaging characteristic control mechanism is preferably set to be equal to or greater than the number of imaging characteristics to be corrected.

  (10) The exposure method using the exposure apparatus 100 of the above embodiment is an exposure method in which an image of the pattern of the reticle R is formed on the wafer W through the projection optical system PL using the exposure light IL. While adjusting the first set of imaging characteristics of the projection optical system PL based on the irradiation parameter information obtained using the imaging characteristics adjustment method and the irradiation amount of the exposure light IL on the wafer W, Step 103 (formation process) for forming an image of the pattern of the reticle R on the wafer W is included.

Therefore, the first set of imaging characteristics can be driven within a predetermined allowable range with high accuracy, and the pattern of the reticle R can be exposed onto the wafer W with high accuracy.
(11) In the device manufacturing method of the above embodiment, the exposure method is used to expose the wafer W (substrate) placed on the image plane of the projection optical system PL (step 103), and the exposure is performed. Processing the wafer W (steps 122 and 123). As a result, various patterns can be exposed on the substrate with high accuracy, and thus a device in which various patterns are formed in a plurality of layers can be manufactured with high accuracy.

In the above embodiment, the projection optical system PL is regarded as an optical system. However, as shown in FIG. 8 (A), it is also possible to regard the one optical system of the projection optical system PL the reticle R and the transmittance eta _PL transmittance eta _R as a whole. The transmittance η _R of the reticle _R can be obtained, for example, by measuring the illuminance of the exposure light IL with the dose monitor 35 of FIG. 2 depending on whether the reticle R is not present or not, and is transmitted through the projection optical system PL. The rate η _PL can be obtained from, for example, the measured value of the integrator sensor 4 in FIG. 1 when there is no reticle R, the measured value of the dose monitor 35, and the known transmittance of the illumination optical system.

In this case, for example, when the distortion Di is taken as an example, the distortion Di can be calculated from, for example, the following equation instead of the equation (4).
Di = Sdiuni × P _PL × [1-exp (−t / Tdi)]
+ SdRuni × P _R × [1-exp (−t / TdR)] (5)
In this formula, P _PL and P _R are the illuminance on the image plane (wafer plane) and the bottom surface of the reticle R in the projection optical system PL in FIG. 8 (A), SdRuni saturated distortion per unit illuminance on the reticle R , TdR is a time constant in the reticle R. There are four irradiation parameters: Sdiuni, SdRuni, Tdi, and TdR.

In this case, the ratio between the exposure light IL absorption amount ΔER of the reticle R and the exposure light IL absorption amount ΔEPL of the projection optical system PL is as follows.
ΔER: ΔEPL = (1-η _R ): η _R (1-η _PL ) (6)
Accordingly, the ratio of the influence EFR of the reticle R on the fluctuation of the imaging characteristics is as follows.
EFR = ΔER / (ΔER + ΔEPL) (7)
This effect EFR changes in inverse proportion to the transmittance η _R of the reticle R as shown in FIG. Therefore, when the transmittance η _R of the reticle _R is small, the influence EFR of the reticle R becomes large, so that it is particularly effective to consider the contribution of the reticle R as shown in equation (5).

  The present invention can also be applied to the case where the above-described wavefront aberration measurement device 21 and / or aerial image measurement system 45 is exposed by an exposure apparatus mounted in wafer stage WST. The present invention is also applicable to exposure using a step-and-repeat type projection exposure apparatus (stepper or the like) in addition to the above-described step-and-scan type scanning exposure type projection exposure apparatus (scanner). it can. Furthermore, the present invention can be similarly applied to exposure using a dry exposure type exposure apparatus other than an immersion type exposure apparatus.

  In addition, the present invention is not limited to application to an exposure apparatus for manufacturing a semiconductor device, for example, an exposure apparatus for a display device such as a liquid crystal display element formed on a square glass plate or a plasma display, It can also be widely applied to an exposure apparatus for manufacturing various devices such as an image sensor (CCD or the like), a micromachine, a thin film magnetic head, and a DNA chip. Furthermore, the present invention can also be applied to an exposure process (exposure apparatus) when manufacturing a mask (photomask, reticle, etc.) on which mask patterns of various devices are formed using a photolithography process.

  In addition, this invention is not limited to the above-mentioned embodiment, A various structure can be taken in the range which does not deviate from the summary of this invention.

It is a figure which shows schematic structure of the exposure apparatus used in an example of embodiment of this invention. FIG. 2 is a partially cutaway view showing a device configuration for wavefront aberration measurement for the projection optical system PL in FIG. 1. 1A is a partially cutaway view showing a state in which an image of an evaluation mark is measured using the aerial image measurement system 45 in FIG. 1, and FIG. 3B is a measurement reference plate RFM in FIG. FIG. 6C is an enlarged view showing the evaluation mark PM of FIG. 3B. It is a figure which shows the structure of the control system etc. of the exposure apparatus 100 of FIG. (A) is a figure which shows an example of the change of the distortion according to time or irradiation amount, (B) is a figure which shows an example of the change of the distortion when irradiation of exposure light is interrupted, (C) is an imaging characteristic It is a figure which shows an example of the change of the distortion at the time of performing correction | amendment. FIG. 6A is an enlarged view showing an example of a reticle pattern, FIG. 6B is a view showing an example of a light amount distribution of exposure light when the pattern of FIG. 6A is exposed, and FIG. FIG. 6D is a diagram showing an example of a change in focus corresponding to the light amount distribution of the exposure light, and FIG. 6D is a diagram showing an example of a change in focus when an operation for performing focus correction is used in the case of FIG. is there. (A) is a flowchart showing an example of an exposure operation of the exposure apparatus 100 in FIG. 1, and (B) is a diagram showing an operation in place of step 104 in FIG. 7 (A). (A) is a diagram showing a state in which the pattern of the reticle R is exposed on the wafer W via the projection optical system PL, and (B) is a diagram showing an example of the ratio of the influence of the reticle R on the imaging characteristics.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Illumination system, R ... Reticle, RFM ... Measurement reference plate, PL ... Projection optical system, W ... Wafer, WST ... Wafer stage, MST ... Measurement stage, 14A, 14B ... Drive element, 19 ... AF system, 20 ... Main controller, 21 ... wavefront aberration measuring device, 22 ... sign plate, 42A, 42B ... light guide, 45 ... aerial image measuring system, 78 ... imaging characteristic control system

Claims (11)

A method for adjusting the optical characteristics of an optical system that forms an image of a predetermined pattern on an object using exposure light,
A first measurement step of measuring a plurality of optical characteristics of the optical system;
A first adjustment step of adjusting the plurality of optical characteristics based on a measurement result of the first measurement step;
A second set of measuring a first set of optical characteristics among the plurality of optical characteristics after forming an image of the predetermined pattern on the object via the optical system in which the plurality of optical characteristics are adjusted; Measuring process;
A calculation step of obtaining first parameter information for predicting a fluctuation amount of the first set of optical characteristics based on information on the exposure light dose in the optical system;
A method for adjusting optical characteristics, comprising:   After the first adjustment step, based on second parameter information for predicting the variation amounts of the plurality of optical characteristics in consideration of the exposure light dose, and measurement information on the exposure light dose. The method for adjusting an optical characteristic according to claim 1, further comprising a second adjustment step of adjusting the plurality of optical characteristics.   The calculation step is characterized in that the first parameter information is obtained on the basis of information on the exposure light dose and the second parameter information used in the second adjustment step. 3. The optical property adjusting method according to 2. After forming the image of the predetermined pattern on the object through the optical system in which the first set of optical characteristics is adjusted, the second set of optical characteristics is measured among the first set of optical characteristics. A third measuring step to
The calculation step is characterized in that third parameter information for predicting a variation amount of the second set of optical characteristics is obtained based on information related to an irradiation amount of the exposure light in the optical system. 2. The optical property adjusting method according to 1.   5. The first set of optical characteristics according to claim 1, wherein a variation amount of the first set of optical characteristics due to the exposure light irradiation is larger than a variation amount of other optical characteristics in the plurality of optical characteristics. The optical property adjusting method according to any one of the above.   The first set of optical characteristics has a larger influence on an image formation error of the pattern due to a variation caused by irradiation of the exposure light than an influence of other optical characteristics of the plurality of optical characteristics. The optical property adjusting method according to any one of claims 1 to 4. The plurality of optical characteristics measured in the first measurement step include a wavefront aberration of the optical system,
The first set of optical characteristics measured in the second measurement step includes at least two of spherical aberration, coma aberration, distortion, magnification error, and defocus of the optical system. The optical characteristic adjustment method according to any one of claims 1 to 6.   The optical characteristic adjusting method according to claim 7, wherein the wavefront aberration is expressed by a coefficient of a Zernike polynomial of a first order to a 37th order or a first order to a 16th order.   When adjusting the plurality of optical characteristics in the first adjustment step, the posture control of the optical member constituting the optical system, the position control of the object or the pattern in the optical axis direction of the optical system, the pattern is formed 9. The method according to claim 1, wherein at least one of heating of a member, heating of an optical member constituting the optical system, and deformation of an optical member constituting the optical system is performed. The imaging characteristic adjusting method according to any one of the above. In an exposure method for forming an image of a predetermined pattern on an object via an optical system using exposure light,
Based on the first parameter information obtained by using the optical characteristic adjustment method according to any one of claims 1 to 9, and the exposure light irradiation amount on the object, the optical An exposure method comprising: forming an image of the predetermined pattern on the object while adjusting the first set of optical characteristics of the system. Exposing a substrate placed on the image plane of the projection optical system using the exposure method according to claim 10;
Processing the exposed substrate. A device manufacturing method comprising:

Images