JP2005051147A - Exposure method and exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively correct a projection optical system for a variation (irradiation variation) in its image formation properties attendant on irradiation of a substrate with exposure light so as to realize exposure of high accuracy. <P>SOLUTION: This exposure method is a method of irradiating a substrate intermittently with exposure light for exposure through the intermediary of a projection optical system equipped with a mask where a pattern is formed and optical elements. In an exposure process, only a magnifying power variation generated in the projection optical system is successively corrected by driving the optical elements included in the projection optical system, and an aberration variation produced in the projection optical system is successively corrected by driving the optical elements while an exposure process is not carried out. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exposure method and an exposure apparatus used in a photolithography process provided as one of manufacturing processes of a semiconductor element, a liquid crystal display element, a thin film magnetic head, and other micro devices.

  Semiconductor integrated circuits, liquid crystal display elements, thin film magnetic heads, and other micro devices are generally manufactured using photolithography technology. Photolithographic technology irradiates a mask or reticle (hereinafter referred to as “mask” when these are collectively referred to as “mask”) on which a fine pattern is formed with exposure light, and the pattern is applied to a semiconductor wafer coated with a photosensitive agent such as a photoresist. This is a technique in which a resist pattern is formed on the surface of a substrate by transferring it onto a substrate such as a transparent glass substrate and developing a photosensitizer, and performing various processes such as etching on the substrate. The exposure apparatus is used when a mask pattern is transferred onto a substrate.

  Various types of exposure apparatuses have been realized. For example, when manufacturing a semiconductor element, a substrate is provided via a projection optical system having an image field capable of projecting the entire pattern formed on the mask at once. A step-and-scan method in which a projection exposure apparatus (so-called stepper) that exposes the substrate in a step-and-repeat mode and a pattern formed on the mask are sequentially scanned and exposed while the mask and the substrate are moved synchronously. Are often used.

  With the recent miniaturization of microdevices, high exposure accuracy is required for any of the above exposure apparatuses. In order to improve the exposure accuracy, the conjugate relationship between the surface on which the mask pattern is formed (hereinafter referred to as the pattern surface) and the substrate surface is accurately maintained, and the residual aberration is reduced as much as possible. It is necessary to adjust the projection optical system. As a technique for maintaining the conjugate relationship between the mask pattern surface and the substrate surface, a technique for correcting the positional deviation of the substrate with respect to the focal position in accordance with the fluctuation of the focal position of the projection optical system, and a fluctuation in the focal position of the projection optical system. There is a technique for correcting a focal position shift of the projection optical system by moving a part of the lens group included in the projection optical system in the optical axis direction.

Further, for example, in Patent Document 1 below, during non-exposure, the substrate is moved in the optical axis direction of the projection optical system to correct the positional deviation of the substrate with respect to the focal position of the projection optical system, and during exposure (during scanning exposure) ) Is a technique for correcting a focal position shift of the projection optical system by moving some lens groups included in the projection optical system in the optical axis direction without changing the position of the substrate in the optical axis direction of the projection optical system. Disclosure.
Japanese Patent Laid-Open No. 11-274070

  By the way, in a technique for correcting a focal position shift, aberration, magnification, etc. of a projection optical system by moving a part of a lens group included in the projection optical system, the heat and large amount generated by the projection optical system absorbing exposure light. Some lens groups are moved so as to obtain fluctuations in focus position deviation, aberration, magnification, and the like caused by fluctuations in atmospheric pressure and correct them.

  At this time, if a part of the lens group included in the projection optical system is moved in order to correct a focal position shift or the like, the imaging characteristics of the projection optical system (for example, the flatness of the image plane) ) May be deteriorated, a plurality of lens groups are moved when the lens group is moved, and the deterioration of the imaging characteristics due to the movement of one lens group is offset by the movement of the other lens group. .

  However, in recent years, in order to improve throughput (the number of substrates that can be exposed per unit time), the intensity of light (exposure light) used for exposure is set high, and exposure of exposure light to one shot area is performed. There is a tendency that time and non-irradiation time of exposure light for moving to the next shot area are shortened. For this reason, there is a problem that even if the lens group is driven to move to a target position in order to correct aberrations or the like, the actual position of the lens group may not sufficiently follow the target position.

  In particular, when moving a plurality of lens groups, even if one lens group sufficiently follows the target position, the other lens group must sufficiently follow the movement of one lens group. For example, the deterioration of the imaging characteristics of the projection optical system is inevitable.

  Such a problem is particularly serious in a projection optical system having an optical element (such as a lens) having a large variation in imaging characteristics (hereinafter sometimes referred to as irradiation variation) accompanying exposure light exposure.

  The present invention has been made in view of such problems of the prior art, and an object thereof is to effectively correct irradiation fluctuations of a projection optical system and realize high exposure accuracy.

  Hereinafter, in the description shown in this section, the present invention will be described in association with the member codes shown in the drawings representing the embodiments. However, each constituent element of the present invention is limited to the members shown in the drawings attached with these member codes. Is not to be done.

  In order to solve the above problems, according to a first aspect of the present invention, a projection optical system (PL) having a mask (R) on which a pattern is formed and optical elements (42b, 42d, 42e, 42f, 42g) is provided. In this exposure method, the substrate (W) is exposed by intermittently irradiating exposure light, and only the magnification fluctuation occurring in the projection optical system during driving is corrected by driving the optical element sequentially. There is provided an exposure method including a correction step (S12) and a second correction step (S15) for sequentially correcting aberration variations generated in the projection optical system by driving the optical element during non-exposure.

  To solve the above problems, according to a second aspect of the present invention, there is provided a projection optical system (PL) having a mask (R) on which a pattern is formed and optical elements (42b, 42d, 42e, 42f, 42g). An exposure apparatus that exposes the substrate (W) by intermittently irradiating exposure light via a driving device (45b, 45d, 45e, 45f, 45g) for driving the optical element, and the projection at the time of exposure The optical element is driven to sequentially correct only the magnification fluctuation occurring in the optical system, and the optical element is driven to sequentially correct aberration fluctuation generated in the projection optical system during non-exposure. An exposure apparatus comprising a control device (23, 27) for controlling the driving device is provided.

  In the present invention, during the exposure (period in which the exposure light is irradiated), only the magnification fluctuation, which has a smaller fluctuation amount than the aberration fluctuation, is driven to correct the optical element. Can sufficiently follow the target position. On the other hand, during non-exposure (period when exposure light irradiation is stopped), aberration fluctuations with a relatively large fluctuation amount are corrected by driving the optical element, and aberration fluctuations are corrected during exposure. Therefore, at the moment of shifting from exposure to non-exposure, the driving amount of the optical element increases, and it is highly possible that the actual position of the optical element cannot sufficiently follow the target position. In addition, since the aberration variation during non-exposure is smaller than that during exposure, the actual position of the optical element normally follows the target position until the next exposure starts. It is thought that it will be. Therefore, the actual position of the optical element sufficiently follows the target position immediately after the transition from the non-exposure time to the exposure time, and has occurred due to insufficient tracking. Deterioration of imaging characteristics (for example, deterioration of image plane) is prevented.

  In the exposure method according to the first aspect of the present invention and the exposure apparatus according to the second aspect, the actual position of the optical element is relative to the target position for driving the optical element for correcting the aberration variation. While not following, it is desirable not to start the next exposure. This is to prevent the next exposure process from being started in a state where the actual position of the optical element does not follow the target position.

  According to the present invention, there is an effect that it is possible to effectively correct fluctuations in imaging characteristics (irradiation fluctuations) associated with exposure light exposure in the projection optical system and to realize high exposure accuracy. In particular, the effect is great when applied to a projection optical system having an optical element with large irradiation fluctuation.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a view showing the schematic arrangement of an exposure apparatus according to an embodiment of the present invention. In the exposure apparatus shown in FIG. 1, a wafer W as a substrate is placed on a wafer stage 19 which can be moved two-dimensionally, and the wafer W is stepped (stepped) by the wafer stage 19 so that a reticle as a mask. This is a step-and-repeat type exposure apparatus (so-called stepper) that repeats the operation of sequentially exposing the R pattern image to each shot area on the wafer W.

  In this embodiment, “at the time of exposure” or “exposure period” mainly refers to a period from the start of exposure to one shot area to the end of exposure to the shot area. In addition, the “non-exposure” or “non-exposure period” mainly refers to a period from the end of exposure to one shot area to the start of exposure to the next shot area after stepping to the next shot area. Say. However, the “non-exposure time” or “non-exposure period” may include the interruption period when the exposure process is interrupted due to wafer replacement or other reasons.

  In the following description, the XYZ orthogonal coordinate system shown in FIG. 1 is set, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. The XYZ orthogonal coordinate system is set so that the X axis and the Z axis are parallel to the paper surface and the Y axis is perpendicular to the paper surface. 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.

  The exposure light EL generated from the ultra-high pressure mercury lamp 1 shown in FIG. 1 is reflected by the elliptical mirror 2 and once condensed at the second focal point, and then the first fly-eye lens 5 as an optical integrator via the shutter 3. Is incident on. The shutter 3 is disposed in the vicinity of the second focal point of the elliptical mirror 2, and the optical path of the exposure light EL is closed and opened by the motor 4. Actually, a collimator lens, an interference filter, and the like are arranged at the front stage or the rear stage (the front stage in this example) of the first fly-eye lens 5, and light of a predetermined wavelength (for example, i-line having a wavelength of 365 nm) is arranged by the interference filter. ) Pass through the first fly-eye lens 5.

  Exposure light EL from a plurality of light source images by the first fly-eye lens 5 is bent by the vibrating mirror 6 and enters the second fly-eye lens 7 as an optical integrator. A number of secondary light source images are formed on the exit surface of the second fly-eye lens 7. Although not shown, a plurality of types of illumination system aperture stops are arranged near the exit surface of the second fly-eye lens 7. The second fly's eye lens 7 is arranged so that its exit surface (exit-side focal plane) is substantially conjugate with the pupil plane of the projection optical system PL described later, that is, substantially coincides with the pupil plane of the illumination system. ing.

  The exposure light EL emitted from the second fly-eye lens 7 passes through a predetermined illumination system aperture stop, passes through the first relay lens 8, and then enters the beam splitter 9 having a transmittance of about 98%, for example. The exposure light EL transmitted through the beam splitter 9 reaches the reticle blind (illumination field stop) 10. The reticle blind 10 includes, for example, four movable blinds and a driving mechanism thereof, and each blind is in a direction orthogonal or parallel to each other in a plane orthogonal to the optical axis AX1 of the exposure light EL. Thus, it can be moved so as to advance or retreat with respect to the optical axis AX1.

  Each blind is provided with an optical linear scale (not shown) for position detection, and is detected by a position detection device (not shown) having an optical reading device provided facing the linear scale. The value is output to the main control system 23 described later. The main control system 23 sets the four blinds at appropriate positions, whereby the shape of the illumination area on the reticle R is defined by the rectangular opening formed by the leading edge of each blind. The arrangement plane of the reticle blind 10 is in the vicinity of the Fourier transform plane of the exit plane of the second fly-eye lens 7. That is, the arrangement surface of the reticle blind 10 is almost optically conjugate with the pattern formation surface of the reticle R.

  The exposure light EL that has passed through the reticle blind 10 passes through the second relay lens 11 and is reflected by the bending mirror 12, and then the illumination area on the reticle R as a mask is uniformly distributed through the condenser lens 13. Illuminate with.

  The reticle R can be finely moved by the motor 14 in a direction along the optical axis AX of the projection optical system PL, and is placed on a reticle stage 15 that can be two-dimensionally moved and rotated in a plane perpendicular to the optical axis AX. Has been. A movable mirror 16 that reflects the laser beam from the laser interferometer 17 is fixed to the end of the reticle stage 15, and the two-dimensional position of the reticle stage 15 is always detected by the laser interferometer 17 with a predetermined resolution. The detection result is output to the main control system 23.

  The pattern in the illumination area on the reticle R is, for example, a wafer as a substrate at a projection magnification α (α is, for example, 1/4 or 1/5) via a telecentric projection optical system PL. The image is projected onto the exposure field on W. By positioning each shot area on the wafer W with respect to the exposure field, irradiating the illumination area of the reticle R with the exposure light EL, and projecting an image of the pattern onto the exposure field via the projection optical system PL. A pattern is transferred to the shot area. In the present embodiment, the variable aperture stop AS is provided on the pupil plane of the projection optical system PL so that the numerical aperture NA of the projection optical system PL can be changed.

  In addition, the projection optical system PL is best subjected to aberration correction with respect to the wavelength of the exposure light EL under a predetermined air temperature (for example, 25 ° C.) and a predetermined atmospheric pressure (for example, 1 atmospheric pressure). R and the wafer W are conjugate with each other. Further, the exposure apparatus of this example employs Koehler illumination, and a secondary light source (a surface light source comprising a large number of light source images) formed on the pupil plane of the illumination system described above is connected to the pupil plane of the projection optical system PL. Imaged. The projection optical system PL has a plurality of optical elements such as lenses, and the glass material of the optical elements is selected from optical materials such as quartz and fluorite according to the wavelength of the exposure light EL.

  The wafer W is, for example, a silicon substrate, and a photosensitive agent such as a photoresist is applied on the surface thereof. The wafer W is placed on a wafer stage 19 as a substrate stage via a wafer holder 18. The wafer stage 19 is attached to the XY stage for two-dimensionally positioning the wafer W in a plane perpendicular to the optical axis AX of the projection optical system PL, and a mechanism for finely moving a table to which the wafer holder 18 is fixed. It is configured. This fine movement mechanism moves the wafer W in a direction (Z direction) parallel to the optical axis AX of the projection optical system PL and rotation directions (θx, θy, and θz directions) around the X axis, the Y axis, and the Z axis. Thereby, the relative position and inclination of the wafer W with respect to the imaging plane of the projection optical system PL can be adjusted. The fine movement mechanism may be capable of finely moving the wafer W in the X and Y directions in addition to the above four directions. In FIG. 1, an actuator of the wafer stage 19, which includes a linear motor that drives the XY stage and a voice coil motor or EI core that drives the table, is shown as a motor 22.

  An L-shaped movable mirror 20 is attached to one end of the upper surface of the wafer stage 19, and a laser interferometer 21 is disposed at a position facing the mirror surface of the movable mirror 20. Although shown in a simplified manner in FIG. 1, the movable mirror 20 includes a plane mirror having a reflecting surface perpendicular to the X axis and a plane mirror having a reflecting surface perpendicular to the Y axis. The laser interferometer 21 includes two X-axis laser interferometers that irradiate the moving mirror 20 with a laser beam along the X axis and a Y-axis that irradiates the movable mirror 20 with a laser beam along the Y axis. The X and Y coordinates of the wafer stage 19 are measured by one laser interferometer for the X axis and one laser interferometer for the Y axis. Further, the rotation angle (rotation amount in the θz direction) of the wafer stage 19 in the XY plane is measured by the difference between the measurement values of the two laser interferometers for the X axis. Instead of providing the movable mirror 20, for example, a reflection surface formed by mirror processing the end surface (side surface) of the wafer stage 19 may be used. Further, the laser interferometer 21 may be capable of measuring the rotation angle (rotation amount in the θx and θy directions) of the wafer stage 19 in the YZ and ZX planes.

  The two-dimensional coordinates of the wafer stage 19 are always detected with a predetermined resolution by the laser interferometer 21, and the stage coordinate system (stationary coordinate system) of the wafer stage 19 is determined by the coordinates in the X-axis direction and the Y-axis direction. Determined. That is, the coordinate value of the wafer stage 19 measured by the laser interferometer 21 is a coordinate value on the stage coordinate system. A position measurement signal indicating the X coordinate, the Y coordinate, and the rotation angle measured by the laser interferometer 21 is output to the main control system 23.

  The main control system 23 outputs a control signal for controlling the position of the wafer stage 19 to the motor 22 while monitoring the position measurement signal supplied from the laser interferometer 21. The main control system 23 performs various controls such as shutter 3 opening / closing control, reticle blind 10 drive control, exposure light EL intensity control, reticle stage 15 drive control, and imaging characteristic control of the projection optical system PL. . Details of the adjustment of the imaging characteristics of the projection optical system PL will be described later.

  Further, in the vicinity of the wafer W on the wafer stage 19, an irradiation amount sensor 24 composed of a photoelectric detector having a light receiving surface having the same height as the exposure surface of the wafer W is installed. The dose sensor 24 receives exposure light EL from a transmission portion provided on the light receiving surface and detects the dose in the exposure field. When measuring the dose, the wafer stage 19 is driven. Then, the dose sensor 24 is arranged at the center of the exposure field. The detection signal output from the dose sensor 24 is supplied to the main control system 23, and the main control system 23 controls the exposure dose control system (not shown) based on the detection signal to irradiate the wafer W. The intensity of the exposure light EL is controlled.

  Further, the light reflected by the beam splitter 9 having a transmittance of about 98% is condensed on the light receiving surface of the integrator sensor 25 including a photoelectric detector via a condenser lens (not shown). The light receiving surface of the integrator sensor 25 is, for example, substantially conjugate with the pattern forming surface of the reticle R and the exposure surface of the wafer W, and the detection signal (photoelectric conversion signal) of the integrator sensor 25 passes through an exposure amount control system (not shown). Are supplied to the power source system and the main control system 23 of the light source 1.

  An exposure amount control system (not shown) stores a conversion coefficient for obtaining an irradiation amount (exposure amount per unit time) on the wafer W from an output signal of the integrator sensor 25. Since the light receiving surface of the integrator sensor 25 is arranged at a position almost conjugate with the pattern surface of the reticle R, the illumination condition is changed by changing the shape of an illumination system aperture stop (not shown) arranged on the exit surface of the second fly-eye lens 7. Even when this is changed, an error does not occur in the detection signal of the integrator sensor 25. The light receiving surface of the integrator sensor 25 is arranged on an observation surface substantially conjugate with the Fourier transform surface (pupil surface) of the pattern of the reticle R in the projection optical system PL, and all light beams passing through this observation surface are received. You can make it possible.

  Furthermore, in this embodiment, a wafer reflectance sensor 26 made of a photoelectric detector is installed on the opposite side of the integrator sensor 25 with respect to the beam splitter 9 having a transmittance of about 98%, and the light receiving surface of the wafer reflectance sensor 26 is It is almost conjugate with the surface of the wafer W by a lens (not shown). In this case, of the exposure light EL that passes through the reticle R and is irradiated onto the wafer W through the projection optical system PL, the reflected light on the wafer W is reflected through the projection optical yarn PL, the reticle R, etc. Light is received by the reflectance sensor 26, and this detection signal (photoelectric conversion signal) is supplied to the main control system 23.

  The main control system 23 detects the light energy per unit time of the exposure light EL that is incident on the projection optical system PL via the reticle R, calculated from the detection signal of the dose sensor 24, and the detection by the wafer reflectance sensor 26. Based on the light energy per unit time of the reflected light from the wafer W calculated from the signal, the light energy per unit time of the exposure light EL passing through the projection optical system PL is obtained. Further, based on the thermal energy obtained by multiplying the thus obtained light energy by the exposure time, the main control system 23 predicts the thermal expansion amount of the projection optical system PL, and the projection based on the predicted thermal expansion amount. A change amount of each imaging characteristic of the optical system PL is obtained.

  An atmospheric pressure sensor 28 is provided in the vicinity of the lens barrel of the projection optical system PL, and the main control system 23 forms each image of the projection optical system PL due to fluctuations in atmospheric pressure based on the detection result of the atmospheric pressure sensor 28. Determine the amount of change in characteristics. The main control system 23 controls the imaging characteristic correction unit 29 provided in the projection optical system PL via the imaging characteristic control unit 27, so that each imaging characteristic of the projection optical system PL due to thermal expansion is controlled. Each imaging characteristic of the projection optical system PL due to the change and the change in atmospheric pressure is adjusted. The main control system 23 and the imaging characteristic control unit 27 correspond to a control device according to the present invention.

  Note that the atmospheric pressure sensor 28 is preferably provided at two locations, the inside of the lens barrel of the projection optical system PL and the outside of the lens barrel. As described above, the atmospheric pressure sensors 28 are provided at two locations inside and outside the projection optical system PL because the gas inside the projection optical system PL is different from the air outside the projection optical system PL (for example, nitrogen or This is because helium) may be filled or flowed. Nitrogen is used, for example, to suppress the generation of ozone in the projection optical system PL, and helium is used, for example, to reduce a change in imaging characteristics of the projection optical system PL because he has a smaller refractive index than air.

  In the present embodiment, the imaging light beam for forming a pinhole or slit-shaped image toward the imaging surface of the projection optical system PL is obliquely oriented with respect to the optical axis AX of the projection optical system PL. An oblique incidence type focal position detection system 30 is provided which includes an irradiation optical system 30a to be supplied and a light receiving optical system 30b that receives a reflected light beam of the imaging light beam on the surface of the wafer W. The focal position detection system 30 can detect the in-focus state between the wafer W and the projection optical system PL by detecting the position and tilt angle in the Z direction with respect to the imaging plane of the surface of the wafer W. .

  Further, on the back side of the reticle R, an irradiation optical system 31a for supplying an imaging light beam for forming a slit-shaped image from an oblique direction with respect to the optical axis AX of the projection optical system PL, and the imaging light beam An oblique incidence type focal position detection system 31 is provided which includes a light receiving optical system 31b for receiving a reflected light beam on the back surface of the reticle R. The focal position detection system 31 can detect the position in the Z direction and the tilt angle with respect to the imaging surface on the back surface of the reticle R to detect the conjugate relationship between the wafer W and the reticle R.

  Next, a schematic configuration and operation of the imaging characteristic correction unit 29 provided in the projection optical system PL will be described. FIG. 2 is a diagram showing a schematic configuration of the projection optical system PL provided in the exposure apparatus of the present embodiment, and FIG. 3 is a top view showing one of the divided lens barrels of the projection optical system. . 2 and 3, the XYZ orthogonal coordinate system similar to the XYZ orthogonal coordinate system shown in FIG. 1 is set and the positional relationship of each member will be described.

  As shown in FIG. 2, the lens barrel 40 of the projection optical system PL includes a plurality of divided lens barrels 40 a to 40 l and is supported by a frame of an exposure apparatus (not shown) via a flange 41. The plurality of divided lens barrels 40a to 40l are stacked in the optical axis AX direction. In this embodiment, among the plurality of divided lens barrels 40a to 40l, the lenses 42b, 42d, 42e, 42f, and 42g supported by the divided lens barrels 40b, 40d, 40e, 40f, and 40g have the optical axis AX. The movable lens is movable in the direction (Z direction) and can be tilted (tilted) about the X direction or the Y direction. The configuration of the divided lens barrels 40b, 40d, 40e, 40f, and 40g holding the lenses 42b, 42d, 42e, 42f, and 42g will be described by taking the configuration of the divided lens barrel 40b as a representative. Note that the configuration of the other divided lens barrels 40d, 40e, 40f, and 40g is substantially the same as the configuration of the divided lens barrel 40b, and thus the description thereof is omitted here.

  The split barrel 40b includes an outer ring 43b connected to the split barrels 40a and 40c positioned above and below (Z direction) of the split barrel 40b, and a lens frame 44b that holds the lens 42b. This lens frame 44b can be moved in the optical axis direction (Z direction) with respect to the outer ring 43b, and can be tilted around an axis parallel to the X axis or an axis parallel to the Y axis. It is connected. Further, the split lens barrel 40b includes an actuator 45b attached to the outer ring 43b. As this actuator 45b, for example, a piezoelectric element can be applied. The actuator 45b drives the lens frame 44b through a link mechanism as a displacement magnifying mechanism composed of, for example, an elastic hinge under the control of the imaging characteristic control unit 27 shown in FIG. The actuator 45b is attached to three locations of the split lens barrel 40b, and thereby the three locations of the lens frame 44b are independently moved in the optical axis direction (Z direction). The lenses 42b, 42d, 42e, 42f, and 42g correspond to the optical elements referred to in the present invention, and the actuators 45b, 45d, 45e, 45f, and 45g correspond to the drive devices referred to in the present invention.

  This will be described in detail with reference to FIG. In the following description, when one of them is specified without distinguishing the divided lens barrels 40b, 40d, 40e, 40f, and 40g and the members constituting them, the symbol “ A description will be made with “a” to “g” omitted. In FIG. 3, three collar portions 51 a to 51 c are provided on the periphery of the lens 42 at every azimuth angle of 120 ° in the XY plane. The lens frame 44 includes clamp portions 52 a to 52 c, which hold the three flange portions 51 a to 51 c of the lens 42. The lens frame 44 is independently driven along the Z direction by three actuators (not shown) via link mechanisms at the positions of the driving points DP1 to DP3 at every azimuth angle of 120 ° in the XY plane.

  Here, when the driving amount in the Z direction by the three actuators is the same amount, the lens frame 44 moves in the Z direction (optical axis direction) with respect to the outer ring 43, and driving in the Z direction by the three actuators. When the amounts are different, the lens frame 44 is inclined with respect to the outer ring 43 around an axis parallel to the X axis or an axis parallel to the Y axis. When the driving amounts in the Z direction by the three actuators are different, the lens frame 44 may move in the Z direction (optical axis direction) with respect to the outer ring 43. The imaging characteristic correction unit 29 shown in FIG. 1 is realized by the above configuration.

  Now, referring back to FIG. 2, the split lens barrel 40b is provided with a drive amount measuring unit 46b which is attached to the outer ring 43b and is formed of, for example, an optical encoder (or a capacitance sensor or the like). The drive amount measuring unit 46b measures the amount of movement in the Z direction (optical axis direction) of the lens frame 44b with respect to the outer ring 43b at the positions of the three measurement points MP1 to MP3 at every azimuth 120 ° shown in FIG. . Therefore, the movement of the lens frame 44b, and hence the movement of the lens 42b, can be controlled in a closed loop by the actuator 45b and the drive amount measuring unit 46b.

  Among the divided lens barrels 40a to 40l shown in FIG. 2, the lenses 42a, 42c, 42h, 42i, 42j, 42k, and 42l supported by the divided lens barrels 40a, 40c, 40h, 40i, 40j, 40k, and 40l are as follows. , It is a fixed lens. The configuration of the split lens barrel 40c is representative of the configuration of the split lens barrels 40a, 40c, 40h, 40i, 40j, 40k, and 40l holding the fixed lenses 42a, 42c, 42h, 42i, 42j, 42k, and 42l. Let me explain. The configuration of the other divided lens barrels 40a, 40h, 40i, 40j, 40k, and 40l other than the divided lens barrel 40c is substantially the same as the configuration of the divided lens barrel 40c, and thus the description thereof is omitted here. The divided lens barrel 40c includes an outer ring 43c connected to the divided lens barrels 40b and 40d positioned above and below (Z direction) of the divided lens barrel 40c, and a lens frame 44c attached to the outer ring 43c and holding the lens 42c. And is configured.

  In the present embodiment, the actuator 45 is configured to use a high-precision, low-heat generation, high-rigidity, and high-cleanness piezoelectric element, and the driving force of the piezoelectric element is expanded by a link mechanism including an elastic hinge. There is an advantage that the piezoelectric element itself can be made compact. The actuator 45 may be composed of a magnetostrictive actuator or a fluid pressure actuator instead of a piezoelectric element. The lenses 42a to 42l may be composed of a single lens element, or may be composed of a lens group in which a plurality of lens elements are combined.

  In the projection optical system PL having the above configuration, the lenses 42a, 42c, 42h, 42i, 42j, 42k, and 42l do not change the posture (the position in the optical axis AX direction and the inclination with respect to the XY plane). , 42f, 42g can be varied. In this example, the imaging characteristic control unit 27 adjusts the posture of one of these lenses, or adjusts the postures of a plurality of lenses in association with each other, thereby generating 5 in the projection optical system PL. Two rotationally symmetric imaging characteristics (such as aberration) and five decentration aberrations can be individually corrected. Note that the five rotationally symmetric imaging characteristics mentioned here refer to magnification, distortion (distortion aberration), coma aberration, field curvature, and spherical aberration. The five decentering aberrations are decentering distortion (distortion aberration), decentering coma aberration, decentering astigmatism, and decentering spherical aberration.

  Next, a focus position adjusting method will be described. First, in order to match the reticle R and the wafer W to the conjugate state, the reference position of the wafer W in the Z direction is obtained by the following method. First, a reticle R on which a predetermined mark is drawn is mounted at a predetermined location on the reticle stage 15, and the predetermined mark on the reticle R is baked on the wafer W and developed while stepping the wafer stage 19 in the Z direction. To do. The position in the Z direction where the mark shape obtained by observing the wafer W with an optical microscope and having the best mark shape is set as the reference position, and the oblique incidence type focal position detection system 31 on the reticle R side and the oblique incidence on the wafer W side at that time. The output of the focus position detection system 30 is stored in a storage device (not shown) of the main control system 23 as a focus reference position. Subsequent corrections for changes in the focal position are performed based on the focal reference position. Instead of the printing, the best focus position may be obtained by detecting the projected image of the reticle mark on the image plane side of the projection optical system PL.

  Next, a focal position correction (adjustment) method using the wafer stage 19 in the present embodiment will be described. As described above, in the present embodiment, the reticle R and the wafer W are respectively connected to the reticle R and the wafer W by the oblique incidence focal position detection system 31 on the reticle R side and the oblique incidence focal position detection system 30 on the wafer W side. The displacement of the projection optical system PL in the optical axis AX direction can be detected. The main control system 23 performs focal position alignment using the detection results of the oblique incidence focal position detection systems 30 and 31 and the focal position fluctuation amount of the projection optical system PL itself.

  The focal position variation amount of the projection optical system PL itself is calculated based on the characteristics of the projection optical system PL, the amount of light incident on the projection optical system PL, and the atmospheric pressure. The focal position variation of the projection optical system PL itself is roughly divided into two factors. The first factor is a change in imaging characteristics based on a change in the environment around the projection optical system PL, that is, a change in atmospheric pressure, temperature, and humidity. The second factor is a change in imaging characteristics due to a change in the shape and refractive index of the lens constituting the projection optical system PL because the projection optical system PL itself absorbs the exposure light EL when the wafer W is exposed. . Since the exposure apparatus is usually installed in a chamber in which temperature and humidity are strictly controlled, changes in imaging characteristics due to changes in the temperature and humidity of the projection optical system PL are often negligible.

  For the focal position fluctuation of the projection optical system PL itself caused by the fluctuation of the atmospheric pressure, a relationship between the fluctuation rate of the atmospheric pressure and the change rate of the focal position of the projection optical system PL is obtained in advance, and this relationship and the atmospheric pressure sensor It calculates based on 28 detection results. The focal position variation of the projection optical system PL itself caused by the absorption of the exposure light EL is obtained by modeling the projection optical system PL in advance using a model function and obtaining the focal position variation rate due to the absorption of the exposure light EL. The calculation is performed based on the model function, the detection result of the integrator sensor 25, and the detection result of the wafer reflectance sensor 26. For details of the method for obtaining the focal position fluctuation amount of the projection optical system PL itself, see the above-mentioned Patent Document 1.

  Here, the displacement amount of the reticle R with respect to the focus reference position is Rz, the displacement amount of the wafer W with respect to the focus reference position is Wz, the projection magnification of the projection optical system PL is ML, and the focus position fluctuation amount of the projection optical system PL itself is FL. Then, the focal position displacement amount ΔF is expressed by the following equation (1).

ΔF = FL + Rz × ML ² −Wz (1)

  The conjugate relationship between the reticle R and the wafer W is maintained by adjusting the position of the wafer stage 19 in the Z direction so that the focal position displacement amount ΔF on the left side of the equation (1) becomes zero.

  Further, in the projection optical system PL, the imaging characteristics of the projection optical system PL change in addition to the above-described focal position fluctuation due to fluctuations in atmospheric pressure or absorption of the exposure light EL. That is, a change in magnification occurs due to a change in atmospheric pressure or the like, and astigmatism, distortion (distortion aberration), coma, curvature of field, and spherical aberration occur. In the present embodiment, in addition to the above-described fluctuation in the focal position of the projection optical system PL itself, the main control system 23 applies changes in the imaging characteristics of the projection optical system PL to the characteristics of the projection optical system PL and the projection optical system PL. Calculation is based on the amount of incident light and atmospheric pressure.

  The change in the imaging characteristics of the projection optical system PL caused by atmospheric pressure fluctuations is the relationship between the atmospheric pressure fluctuation rate and the field curvature change, magnification change, distortion change, coma aberration change, and spherical aberration change. Each is obtained in advance and calculated based on these relationships and the detection result of the atmospheric pressure sensor 28. Further, the imaging characteristics of the projection optical system PL caused by the absorption of the exposure light EL are modeled in advance for each aberration of the projection optical system PL using a model function in the same manner as in the case of obtaining the focal position variation. A change in aberration due to EL absorption is obtained and calculated based on these model functions, the detection result of the integrator sensor 25 and the detection result of the wafer reflectance sensor 26.

  An imaging characteristic change (field curvature change CU, magnification change M, distortion change D, coma aberration change CO, spherical aberration change SA) of the projection optical system PL is expressed by the following equation (2).

  However, each term in the above equation (2) represents the following change.

CU _PRESS : Field curvature change due to atmospheric pressure change M _PRESS : Magnification change due to atmospheric pressure change D _PRESS : Distortion change due to atmospheric pressure change CO _PRESS : Coma aberration change due to atmospheric pressure change SA _PRESS : Spherical aberration change due to atmospheric pressure change CU _HEAT : curvature of field change due to exposure light absorption M _HEAT : magnification change due to exposure light absorption D _HEAT : distortion change due to exposure light absorption CO _HEAT : coma aberration change due to exposure light absorption SA _HEAT : spherical aberration change due to exposure light absorption

In addition, the imaging characteristic change of the projection optical system PL with respect to the movement amounts G _{1 to} G ₅ of the lenses 42b, 42d, 42e, 42f, and 42g of the projection optical system PL shown in FIG. 2 is expressed by the following equation (3). Can do.

In the above equation (3), C _{11 to} C ₅₅ are coefficients, and these are movement amounts obtained by actually moving the lenses 42b, 42d, 42e, 42f, and 42g in the optical axis AX direction and changes in imaging characteristics. It is obtained from the relationship with quantity. Here, the case where the coefficients C _{11 to} C ₅₅ are obtained by experiments has been described, but they may be obtained by simulation from design data of the projection optical system PL.

The main control system 23 uses the above equation (2) to change the imaging characteristic (image) of the projection optical system PL from the detection result of the integrator sensor 25, the detection result of the wafer reflectance sensor 26, and the detection result of the atmospheric pressure sensor 28. Surface curvature change CU, magnification change M, distortion change D, coma aberration change CO, spherical aberration change SA) are obtained. For this reason, the movement amounts G _{1 to} G ₅ of the lenses 42b, 42d, 42e, 42f, and 42g for correcting the change in the imaging characteristics of the projection optical system PL are expressed by the following (4) from the relationship of the above expression (3). It can be expressed by a formula.

Therefore, the lenses 42b, 42d, 42e, and 42f are based on the movement amounts G _{1 to} G ₅ obtained by substituting the imaging characteristic change of the projection optical system PL obtained by the main control system 23 into the above equation (4). , 42g can be driven to correct a change in imaging characteristics of the projection optical system PL.

  The correction of the focal position using the wafer stage 19 and the correction of the imaging characteristic change due to the movement of the lens of the projection optical system PL have been described above. Next, the operation of the exposure apparatus of the present invention will be described. 4A and 4B are diagrams showing an example of a change in the position of a lens to be driven. FIG. 4A shows an example of a change in the position of a lens driven by a conventional method, and FIG. It is a figure which shows an example of the position change of the lens to drive.

  Note that FIG. 4 shows a change in the position of any two of the lenses 42b, 42d, 42e, 42f, and 42g included in the projection optical system PL. Here, the change in the position of the lenses 42b and 42d will be described. . In FIG. 4, a curve denoted by reference numeral Tr1 indicates a change in position of the lens 42b, and a curve indicated by reference sign Tr2 indicates a change in position of the lens 42d. Further, FIG. 4 illustrates changes in the positions of the lenses 42b and 42d with reference to the initial position of the lens 42a.

  In the conventional method shown in FIG. 4 (a), in order to correct this according to changes in the imaging characteristics due to changes in atmospheric pressure and absorption of exposure light of the projection optical system (variations in focus position and magnification), The lenses 42b and 42d are moved. At this time, the lens 42d is driven so as to cancel out the deterioration of the imaging characteristics of the projection optical system PL caused by the movement of the lens 42b, for example. Referring to FIG. 4A, the exposure light EL is absorbed in the projection optical system PL during exposure, and the change in the imaging characteristics of the projection optical system PL is large, so that the positions of the lenses 42b and 42d change greatly. . Further, as the irradiation time of the exposure light EL becomes longer (that is, the amount of heat accumulated in the projection optical system PL increases due to the absorption of the exposure light EL), the position change of the lenses 42a and 42d gradually increases.

  On the other hand, during non-exposure, the exposure of the exposure light EL is stopped by the shutter 3 and the exposure light EL is not absorbed by the projection optical system PL. Therefore, the absorbed heat is radiated and the projection optical system PL is connected. The image characteristics gradually return to the initial state. In accordance with this, the lenses 42b and 42d are controlled to gradually move toward the initial position. When exposure is started again, the exposure light EL is absorbed by the projection optical system PL, so that the positions of the lenses 42b and 42d change greatly. Thereafter, such an operation is repeated.

  From the viewpoint of improving the throughput, the intensity of the exposure light EL is set high. For this reason, when exposure is started after the non-exposure period ends, the amount of light energy incident on the projection optical system PL changes abruptly, and the amount of exposure light EL absorbed also increases abruptly. The imaging characteristics of the system PL change greatly. Even if the lenses 42b and 42d are driven to correct the change in the imaging characteristics, the response characteristics of the imaging characteristics correction unit 29 are slow, and the lenses 42b and 42d may not follow the target position to be moved.

  As described with reference to FIGS. 2 and 3, the lenses 42b and 42d are driven at three points by the actuators 45b and 45d, respectively. If the drive amount in the Z direction by each of the actuator 45b and each of the actuator 45d is made equal, the lenses 42b and 42d should move in parallel along the optical axis AX direction (Z direction). However, due to variations in the characteristics of each of the actuators 45b and each of the actuators 45d, the lenses 42b and 42d may be tilted even when trying to translate them. This inclination becomes prominent when the amount of movement of the lenses 42b and 42d per unit time is increased by increasing the driving amount.

  Therefore, when the lenses 42b, 42d, 42e, 42f, and 42g are driven by the conventional driving method, the lenses 42b, 42d, 42e, 42f, and 42g do not follow the target position, or the lenses 42b, 42d, 42e, 42f, There has been a problem that 42 g of inclination occurs and the change in the imaging characteristics of the projection optical system PL cannot be corrected, and the imaging characteristics of the projection optical system PL are deteriorated. Further, when the driving amount of the lenses 42b, 42d, 42e, 42f, and 42g during exposure increases, vibration may occur due to the driving of the lenses 42b, 42d, 42e, 42f, and 42g.

  In order to solve such a problem, in this embodiment, the lenses 42b, 42d, 42e, 42f, and 42g are not driven as much as possible during exposure, and the lenses 42b, 42d, 42e, 42f, and 42g are driven and projected during non-exposure. The imaging characteristics of the optical system PL are corrected. Specifically, only the change in magnification of the projection optical system PL is corrected during exposure, and other imaging characteristics changes (field curvature change, distortion change, coma change, spherical aberration change) are corrected during non-exposure. ing.

  Here, the reason for correcting only the magnification change at the time of exposure is that the amount of change is small compared to other aberrations, and correction can be made with a small amount of movement of the lenses 42b, 42d, 42e, 42f, and 42g. Further, the fluctuation of the focal position of the projection optical system PL during exposure is corrected by driving the wafer stage 19 to control the position of the wafer W in the optical axis AX direction (Z direction). In order to clarify the difference from the conventional method shown in FIG. 4A, in the description of this embodiment, the case where the lenses 42b and 42d are driven to correct the imaging characteristics of the projection optical system PL is also described. An example will be described.

  In FIG. 4B, a curve indicated by a broken line denoted by reference symbol OP1 indicates the target position of the lens 42b, and a curve indicated by a broken line denoted by reference symbol OP2 indicates the target position of the lens 42d. Referring to FIG. 4B, the curve OP1 indicating the target position of the lens 42b and the curve Tr1 indicating the position change of the lens 42b substantially coincide with each other except for a predetermined time after the end of exposure. It can be seen that the curve OP2 indicating the target position of the lens 42d and the curve Tr2 indicating the change in position of the lens 42d are substantially the same. Further, the lens 42d has a position change substantially opposite to that of the lens 42b. In this embodiment, the lens 42d moves so as to cancel out the deterioration of the imaging characteristics of the projection optical system PL caused by the movement of the lens 42b. You can see that

  For the target positions of the lenses 42b and 42d, the main control system 23 calculates the imaging characteristic change of the projection optical system PL from the detection result of the integrator sensor 25, the detection result of the wafer reflectance sensor 26, and the detection result of the atmospheric pressure sensor 28. Then, this calculation result is obtained by substituting it into the above-mentioned equation (4). As described above, only the change in magnification of the projection optical system PL is corrected during exposure. For this reason, during exposure, the values of field curvature change CU, distortion change D, coma aberration change CO, and spherical aberration change SA other than the magnification change M in equation (4) are set to zero, so that the magnification A lens movement amount capable of correcting only the change M is obtained.

  Referring to FIG. 4B, the curves OP1 and OP2 indicating the target positions of the lenses 42b and 42d do not change so much during the exposure, but change rapidly at the end of the exposure until the next exposure ends. It is changing slowly. The change in the target position of the lenses 42b and 42d during exposure is small because only the magnification of the projection optical system PL is corrected, and the change in the target position of the lenses 42b and 42d increases rapidly at the end of exposure. This is because correction of field curvature change, distortion change, coma aberration change, and spherical aberration change that has not been performed during exposure is started.

  As described above, the target positions of the lenses 42b and 42d change abruptly at the end of exposure, but the lenses 42b and 42d cannot actually follow such a sudden change in the target position. For this reason, the change in position of the lenses 42b and 42d at the end of exposure indicates a change deviated from the curves OP1 and OP2 indicating the target positions, as indicated by the curves denoted by symbols Tr1 and Tr2.

  Next, the flow of the correction operation of the imaging characteristics of the projection optical system PL according to the present embodiment will be described. FIG. 5 is a flowchart showing the flow of the correction operation of the imaging characteristics of the projection optical system PL in the present embodiment. When the exposure process is started, first, the main control system 23 reads various information (recipe) necessary for the exposure operation stored in a storage device (not shown), and performs initial processes necessary for performing the exposure process. Do. The initial processing here refers to, for example, the introduction of the reticle R, the loading of the wafer W, the setting of the illumination area on the reticle R, the reticle R for the wafer stage 19 with respect to the projection optical system PL (that is, the stage coordinate system described above). Alignment (alignment), processing for aligning the shot area to be exposed first to the position where the pattern image of the reticle R is projected, and the like.

  Assume that the above initial processing is completed, the exposure light EL is irradiated onto the irradiation area on the reticle R, and the pattern image of the reticle R is projected onto the substrate W via the projection optical system PL. The main control system 23 first determines whether or not exposure is currently being performed (step S10). Since the exposure is being performed here, the determination result in step S10 is “YES”, and the main control system 23 determines from the detection result of the integrator sensor 25, the detection result of the wafer reflectance sensor 26, and the detection result of the atmospheric pressure sensor 28. Changes in imaging characteristics of the projection optical system PL (field curvature change CU, magnification change M, distortion change D, coma aberration change CO, spherical aberration change SA) are calculated (step S11).

  When the imaging characteristic change of the projection optical system PL is calculated, the main control system 23 uses the above-described equation (4) to correct the magnification change M from the calculated imaging characteristic change of the projection optical system PL. The drive amounts (target positions) of 42d, 42e, 42f, and 42g are calculated, and the drive amounts are output to the imaging characteristic control unit 27. The imaging characteristic control unit 27 drives at least one of the lenses 42b, 42d, 42e, 42f, and 42g based on the drive amount output from the main control system 23 to follow the target position (step S12).

  Further, the main control system 23 calculates the focal position fluctuation amount FL of the projection optical system PL itself from the detection result of the integrator sensor 25, the detection result of the wafer reflectance sensor 26, and the detection result of the atmospheric pressure sensor 28, and this calculation. The focal position displacement amount ΔF is obtained from the above-described equation (1) using the results and the detection results of the oblique incidence focal position detection systems 30 and 31. Then, the wafer stage 19 is driven so that the focal position displacement amount ΔF becomes zero, and the position of the wafer W in the optical axis AX direction (Z direction) (the interval of the wafer W with respect to the projection optical system PL) is adjusted (step). S13). When this process ends, the process returns to step S10 again to determine whether or not exposure is in progress.

  Since the processes of steps S11 to S13 are repeatedly performed during the exposure process, the magnification change of the projection optical system PL is sequentially obtained, and the lenses 42b, 42d, 42e, 42f, and 42g are driven, and the projection optical system PL Are sequentially corrected, the positional deviation of the wafer W with respect to the focal position of the projection optical system PL is sequentially obtained, the wafer stage 19 is driven, and the positional deviation of the wafer W with respect to the focal position of the projection optical system PL is sequentially incremented. It is corrected.

  On the other hand, when the exposure process is finished and the non-exposure state is reached, the determination result in step S10 is “NO”. When the determination result is “NO”, due to the change in imaging characteristics of the projection optical system PL caused by the heat stored in each lens of the projection optical system PL due to the heat dissipation characteristics of the projection optical system PL and the change in atmospheric pressure. A change in imaging characteristics of the projection optical system PL is calculated (step S14).

  When calculating the imaging characteristic change of the projection optical system PL, the main control system 23 uses the above-described equation (4), and various aberrations occurring in the projection optical system PL from the calculated imaging characteristic change of the projection optical system PL. The drive amounts (target positions) of the lenses 42b, 42d, 42e, 42f, and 42g that can correct (field curvature, distortion, coma aberration, spherical aberration) are calculated, and the drive amounts are output to the imaging characteristic control unit 27. (Step S15). Since the magnification of the projection optical system PL is corrected at the time of exposure, the case where the magnification is not corrected at the time of non-exposure will be described here. Of course, it is desirable to also correct the magnification at the time of non-exposure. The change amount of the imaging characteristics of the projection optical system PL is always calculated by the main control system 23 without distinguishing between the exposure period and the non-exposure period. The main control system 23 calculates the calculation result at the end of the exposure period. The above correction is performed. At this time, the main control system 23 may calculate not only the change amount of the imaging characteristics but also the drive amount of each lens without distinction of the above-mentioned period.

  Next, the main control system 23 determines whether or not to stop a series of exposure processing (step 16). This determination is provided because, for example, there is no wafer W to be processed next, or the exposure apparatus may be stopped due to maintenance or the like. If the determination result in step S16 is “YES”, the series of processing ends. On the other hand, if the determination result in step S16 is “NO”, the main control system 23 determines whether or not the exposure start time has come (step S17).

  If the determination result of step S17 is “NO”, the process returns to step S10. At the time of non-exposure, the determination results in steps S10, S16, and S17 are all “NO”. For this reason, the processes of steps S14 and S15 are repeated, and the lenses 42b, 42d, 42e, 42f, and 42g are driven to sequentially correct various aberrations of the projection optical system PL.

  On the other hand, in step S17, when the exposure start time is reached (when the determination result is “YES”), whether or not the lenses 42b, 42d, 42e, 42f, and 42g being driven follow the target position. Is determined (step S18). If this determination is “YES”, the flow returns to step S10. Here, since it is the exposure start time, the determination result in step S10 is “YES”, and the processes in steps S11 to S13 described above are repeated.

  If the determination result in step S18 is “NO”, the main control system 23 performs a process of extending the non-exposure period (step S19). FIG. 6 is a diagram illustrating an example of the tracking characteristics of the lenses 42b, 42d, 42e, 42f, and 42g with respect to the target position. As shown in FIG. 6, for example, the lens 42b changes its position indicated by the reference symbol Tr1 with respect to the curve OP1 indicating the target position, and the lens 42d changes the position indicated by the reference symbol Tr2 with respect to the curve OP2 indicating the target position. Suppose that

  When the lenses 42b and 42d change in position as described above, even when the non-exposure period ends and the exposure start time is reached, the curve Tr1 and the curve OP1 do not coincide with each other, and the curve Tr2 and the curve OP2 are different. The lenses 42b and 42d do not follow the target position. When exposure is started in this state, the correction of the imaging characteristic change of the projection optical system PL is not completed. In particular, in the present embodiment, as described above, only the variation in magnification is corrected during exposure, and other aberrations are corrected. Since (field curvature, distortion, coma aberration, spherical aberration) are not corrected, exposure is performed in a state where the imaging characteristics of the projection optical system PL are deteriorated.

  In order to prevent this problem, in this embodiment, when the exposure start time is reached, it is determined whether or not the lenses 42b, 42d, 42e, 42f, and 42g are following the target position. The non-exposure period is extended. The non-exposure period may be extended by a predetermined time or may be extended until the lenses 42b, 42d, 42e, 42f, and 42g follow the target position. In the imaging characteristic control unit 27, the driving amount of each lens 42b, 42d, 42e, 42f, 42g can be obtained from the measurement result of the driving amount measuring unit 46b shown in FIG. By comparing the drive amount (target position) output from the system 23, information indicating whether or not each lens is following can be output to the main control system 23.

  As described above, in the present embodiment, only the magnification change of the projection optical system PL that can be corrected with a small amount of lens movement is corrected during exposure, and other aberrations are corrected during non-exposure. When the exposure starts, the lens included in the projection optical system cannot follow the target position, and the exposure process is not started in a state where the imaging characteristics of the projection optical system PL are deteriorated. In addition, since the amount of lens fluctuation during exposure may be such that the change in magnification can be corrected, the deterioration of the imaging performance of the projection optical system PL caused by the adverse effects of each other when driving a plurality of lenses is minimized. Can be reduced.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention. For example, in the above embodiment, the curvature of field, distortion, coma aberration, and spherical aberration are corrected during the non-exposure period, but the types and number of imaging characteristics to be corrected during the non-exposure period are limited to this. It is not what is done. In the above embodiment, it is sufficient that at least one imaging characteristic other than the magnification is included, but all imaging characteristics that can be corrected by the exposure apparatus may be used. At this time, for example, the above-described change in the focal position may be corrected by the wafer stage 19.

  In the above-described embodiment, only the position of the wafer W in the Z direction is adjusted in the above-described step S13. However, considering the curvature of field, for example, the wafer W (one wafer W within the irradiation area of the exposure light EL) The tilt angle (rotation amount in the θx and θy directions) of the wafer W may be adjusted so that the surface of the shot region is set within the depth of focus of the projection optical system PL.

  Further, in the above embodiment, the magnification and various aberrations are adjusted only by moving the imaging characteristic correction unit 29, that is, the lens of the projection optical system PL. However, at least one other correction mechanism, for example, the Z direction of the reticle R is used. The imaging characteristics of the projection optical system PL may be adjusted by combining a mechanism for moving and tilting the lens, a mechanism for shifting the wavelength of the exposure light EL, and the like. At this time, the correction mechanism other than the imaging characteristic correction unit 29 may correct the imaging characteristic to be corrected only during the non-exposure period.

  In the above embodiment, the focal position detection system 31 for detecting the position information of the pattern surface of the reticle R is provided on the object plane side of the projection optical system PL. The focal position detection system 30 may be used.

For example, in the above embodiment, the case where the present invention is applied to a stepper has been described as an example, but the present invention can also be applied to a step-and-scan type exposure apparatus. In the above embodiment, i-line (wavelength 365 nm) is used as the exposure light EL, but it is emitted from a KrF excimer laser (wavelength 248 nm), ArF excimer laser (wavelength 193 nm), or F ₂ excimer laser (157 nm). Laser light or a harmonic of a metal vapor laser or a YAG laser may be used.

  Furthermore, as disclosed in, for example, International Publication (WO) 99/46835, a single wavelength laser in the infrared or visible range oscillated from a DFB semiconductor laser or fiber laser is used, for example, erbium (or erbium and yttrium). Both of them may be amplified with a doped fiber amplifier and a harmonic converted into ultraviolet light using a nonlinear optical crystal may be used.

  Alternatively, a soft X-ray region generated from a laser plasma light source or SOR, for example, EUV (Extreme Ultra Violet) light having a wavelength of 13.4 nm or 11.5 nm may be used. Furthermore, you may use charged particle beams, such as an electron beam or an ion beam. The projection optical system may be any one of a reflection optical system, a refractive optical system, and a catadioptric optical system, and may be any one of a reduction system, an equal magnification system, and an enlargement system.

  Furthermore, not only an exposure apparatus for transferring a device pattern used for manufacturing a semiconductor element onto a wafer, but also an exposure apparatus for transferring a device pattern used for manufacturing a display including a liquid crystal display element onto a glass plate, a thin film magnetic head. The present invention can also be applied to an exposure apparatus for transferring a device pattern used for manufacturing a ceramic wafer onto an ceramic wafer, an exposure device used for manufacturing an imaging device (CCD or the like), a micromachine, a DNA chip, and the like. The present invention can also be applied to an exposure apparatus used for manufacturing a mask (reticle) used in the exposure apparatus. Furthermore, the present invention can be applied to an immersion type exposure apparatus disclosed in, for example, International Publication (WO) 99/49504. Further, as disclosed in, for example, International Publications (WO) 98/24115 and 98/40791, an exposure apparatus including two wafer stages capable of performing an exposure operation and an alignment operation (mark detection operation) substantially in parallel. The present invention can also be applied to.

  An illumination optical system and projection optical system composed of multiple lenses are incorporated into the exposure apparatus body for optical adjustment, and a reticle stage and substrate stage consisting of numerous mechanical parts are attached to the exposure apparatus body to connect wiring and piping. Further, the exposure apparatus of the present embodiment can be manufactured by further comprehensive adjustment (electrical adjustment, operation check, etc.). The exposure apparatus is preferably manufactured in a clean room in which the temperature, cleanliness, etc. are controlled.

  A semiconductor element includes a step of designing a function / performance of a device, a step of manufacturing a reticle based on the design step, a step of manufacturing a wafer from a silicon material, and a reticle pattern by the exposure apparatus of the above-described embodiment. It is manufactured through an exposure transfer step, a device assembly step (including a dicing process, a bonding process, and a packaging process), an inspection step, and the like.

It is a figure which shows schematic structure of the exposure apparatus which concerns on embodiment of this invention. It is a figure which shows schematic structure of the projection optical system with which the exposure apparatus which concerns on embodiment of this invention is provided. It is a top view which shows one division lens tube of the division lens barrels of a projection optical system. It is a figure which shows an example of the position change of the lens driven, Comprising: (a) shows an example of the position change of the lens driven by the conventional method, (b) is the lens driven by the method of this embodiment An example of a change in the position is shown. It is a flowchart which shows the flow of the correction | amendment operation | movement of the image formation characteristic of the projection optical system of embodiment of this invention. It is a figure which shows an example of the tracking characteristic of the lens with respect to a target position.

Explanation of symbols

19 ... Wafer stage (substrate stage)
23 ... Main control system (control device)
27. Imaging characteristic control unit (control device)
42b, 42d, 42e, 42f, 42g ... lens (optical element)
45b, 45d, 45e, 45f, 45g ... Actuator (drive device)
PL ... Projection optical system R ... Reticle (mask)
W ... Wafer (substrate)

Claims (12)

An exposure method for exposing a substrate by intermittently irradiating exposure light through a projection optical system having a mask on which a pattern is formed and an optical element,
A first correction step of sequentially correcting only the magnification fluctuation occurring in the projection optical system during exposure by driving the optical element;
And a second correction step of sequentially correcting aberration fluctuations occurring in the projection optical system by driving the optical element during non-exposure.   2. The exposure method according to claim 1, further comprising an adjustment step of adjusting a position of the substrate in a direction along the optical axis of the projection optical system in accordance with a change in a focal position of the projection optical system during exposure. A calculation step of calculating the magnification variation, the aberration variation, and the focal position variation based on the amount of light incident on the projection optical system, atmospheric pressure, and characteristics of the projection optical system,
The exposure according to claim 2, wherein the correction of the magnification variation, the correction of the aberration variation, and the adjustment of the position of the substrate in accordance with the focal position variation are performed based on a calculation result of the calculation step. Method.   The exposure method according to any one of claims 1 to 3, wherein a driving amount of the optical element at the time of non-exposure is larger than a driving amount of the optical element at the time of exposure.   5. The next exposure is not started while the actual position of the optical element does not follow the target position of driving the optical element for correcting the aberration variation. The exposure method according to one item.   The projection optical system includes a plurality of optical elements, and driving of the optical elements cancels a change in optical characteristics of the projection optical system caused by driving any one of the optical elements by driving other optical elements. The exposure method according to claim 1, wherein the exposure method is performed as described above. An exposure apparatus that exposes a substrate by intermittently irradiating exposure light via a projection optical system having a pattern-formed mask and an optical element,
A driving device for driving the optical element;
The optical element is driven to sequentially correct only the magnification fluctuation occurring in the projection optical system during exposure, and the optical element is sequentially corrected to correct aberration fluctuation generated in the projection optical system during non-exposure. An exposure apparatus comprising: a control device that controls the drive device so as to drive. A substrate stage capable of adjusting the position in the direction along the optical axis of the projection optical system while holding the substrate;
The exposure apparatus according to claim 7, wherein the control apparatus controls the substrate stage during exposure to adjust the position of the substrate in accordance with a focal position variation of the projection optical system.   The control device calculates the magnification variation, the aberration variation, and the focal position variation based on the amount of light incident on the projection optical system, atmospheric pressure, and characteristics of the projection optical system, and based on the calculation result 9. The exposure apparatus according to claim 8, wherein the driving device and the substrate stage are controlled.   The exposure apparatus according to claim 7, wherein a driving amount of the optical element at the time of non-exposure is larger than a driving amount of the optical element at the time of exposure.   The control device performs control so that the next exposure is not started while the actual position of the optical element does not follow the target position of driving the optical element for correcting the aberration variation. The exposure apparatus according to any one of claims 7 to 10.   The projection optical system includes a plurality of optical elements, and driving of the optical elements cancels a change in optical characteristics of the projection optical system caused by driving any one of the optical elements by driving other optical elements. The exposure apparatus according to claim 7, wherein the exposure apparatus is performed as described above.

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