JP5434498B2 - Optical element holding device, optical system, and exposure apparatus - Google Patents

Description

  The present invention relates to an optical element holding device, an optical system including the holding device, and an exposure apparatus including the optical system. The present invention further relates to a device manufacturing method using the exposure apparatus.

For example, in a lithography process, which is one of the manufacturing processes of a semiconductor device, a pattern formed on a reticle (or photomask or the like) is applied on a wafer (or glass plate or the like) coated with a resist via a projection optical system. In order to transfer the light, an exposure apparatus such as a batch exposure type such as a stepper or a scanning exposure type such as a scanning stepper is used.
The projection optical system mounted on these exposure apparatuses is assembled and adjusted so that various aberrations are within a predetermined allowable range. At this time, for example, even if rotational aberrations such as distortion and magnification error and low-order aberration components remain, these aberrations are caused by an imaging characteristic correction mechanism (for example, a predetermined value) mounted on the projection optical system. It can be corrected by a mechanism for controlling the position and tilt angle of the lens in the optical axis direction. On the other hand, when a non-rotationally symmetric aberration component such as astigmatism on the optical axis (hereinafter referred to as “center astigmatism”) remains, it is difficult to correct by the imaging characteristic correction mechanism. It is.

  Therefore, in order to correct such a non-rotationally symmetric aberration component, a correction mechanism has been proposed in which a non-rotationally symmetric stress is applied from the side surface to a predetermined lens in the projection optical system (for example, Patent Document 1). In addition, in order to correct a non-rotationally symmetric aberration component, a correction mechanism has also been proposed in which a convex portion on a side surface of an optical element such as a mirror is deformed by a minute amount with an actuator (see, for example, Patent Document 2). ).

Special Table 2002-519843 JP 2007-266511 A

The conventional non-rotationally symmetric aberration component correction mechanism directly mechanically deforms a part of a predetermined optical element in the projection optical system. Therefore, if the stress for deformation is increased, the optical element is damaged. There was a fear. Further, since the portion of the optical element through which the light beam passes is deformed by the deformation of the side surface of the optical element, it is difficult to accurately predict the aberration correction amount from the deformation amount of the side surface. Therefore, for example, it is necessary to actually measure and store the correction amounts of aberrations corresponding to combinations of various deformations in advance, and the method of using the correction mechanism is complicated.
In view of such problems, it is an object of the present invention to hold a deformable optical element in a state where there is no fear of damage to the optical element and the deformation state of the optical element can be accurately predicted.

According to the first aspect of the present invention, the support member that supports the optical element, the fluid holding member that holds the magnetic fluid that contacts at least a part of the surface of the optical element, and the fluid holding member holds the fluid. There is provided a holding device for an optical element, comprising: a pressure control device configured to control the pressure of the magnetic fluid and to deform the optical element.
According to the second aspect of the present invention, in an optical system including a plurality of optical elements, the optical element according to the first aspect of the present invention is used to support at least one optical element of the plurality of optical elements. There is provided an optical system that includes the holding device and controls the deformation amount of the optical system by the pressure control device according to the non-rotationally symmetric aberration of the optical system.

According to the third aspect of the present invention, the support member that supports the optical element, the fluid holding member that holds the magnetic fluid that contacts at least a part of the surface of the optical element, and the optical element There is provided an optical element holding device comprising: a temperature control device that adjusts a position of the magnetic fluid with respect to a surface to control a temperature distribution of the optical element.
According to the fourth aspect of the present invention, in an optical system including a plurality of optical elements, the optical element according to the third aspect of the present invention is used to support at least one optical element of the plurality of optical elements. An optical system including the holding device is provided.

According to the fifth aspect of the present invention, in an exposure apparatus that illuminates a pattern with exposure light and exposes the substrate with the exposure light through the pattern and the projection optical system, the exposure includes the optical system of the present invention. An apparatus is provided.
According to a sixth aspect of the present invention, the method includes forming a pattern of the photosensitive layer on the substrate using the exposure apparatus of the present invention, and processing the substrate on which the pattern is formed. A device manufacturing method is provided.

  According to the present invention, since the optical element is deformed by deforming the optical element via the magnetic fluid or controlling the temperature distribution of the optical element via the magnetic fluid, the optical element may be damaged. There is no. In addition, since the optical element is deformed mainly at the portion in contact with the magnetic fluid, the deformation state of the optical element can be accurately predicted from the distribution of the magnetic fluid.

It is the figure which a part showing the main-body part of the exposure apparatus of an example of embodiment is notched. It is sectional drawing which shows the holding | maintenance apparatus 50 holding the concave mirror 22 in FIG. (A), (B), (C), (D), (E), and (F) are figures which show various distribution of the magnetic fluid in the cross section which follows the AA line of FIG. (A) is sectional drawing which follows the BB line of FIG. 2, (B) is sectional drawing which follows the CC line of FIG. (A) is a figure which shows an example of the wavefront aberration of a projection optical system, (B) is a figure which shows the other example of the wavefront aberration of a projection optical system. (A) is an enlarged view showing an essential part of an example of a reticle pattern, and (B) is a diagram showing an example of the light intensity distribution of illumination light in the vicinity of the reflecting surface of the concave mirror 22. It is a flowchart which shows an example of the manufacturing process of a semiconductor device.

Hereinafter, an exemplary embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows an exposure main body of a scanning exposure type exposure apparatus EX composed of a scanning stepper according to the present embodiment. In FIG. 1, an exposure apparatus EX includes an exposure light source (not shown) that generates exposure illumination light IL (exposure light) and an illumination optical system ILS that illuminates a reticle R (mask) with the illumination light IL (in FIG. 1). And a projection optical system PL that forms an image of the pattern of the reticle R on the surface of the wafer W (substrate). Further, the exposure apparatus EX includes a main control system 5 including a reticle stage 15 that holds and moves the reticle R, a wafer stage 32 that holds and moves the wafer W, and a computer that controls the overall operation of the apparatus. (See FIG. 2).

Hereinafter, a plane that takes the Z axis parallel to the optical axis AX1 of the partial optical system on the reticle R side of the projection optical system PL (first imaging optical system G1 described later) and is perpendicular to the Z axis (in the present embodiment, substantially horizontal) ) In FIG.
A description will be given by taking the Y axis parallel to the paper surface of FIG. 1 and taking the X axis perpendicular to the paper surface of FIG. The scanning direction of reticle R and wafer W during scanning exposure is a direction (Y direction) parallel to the Y axis, and the pattern surface of reticle R and the surface of wafer W are substantially parallel to the XY plane. The rotation directions (inclination directions) around the axes parallel to the X axis, the Y axis, and the Z axis are also referred to as the θx direction, the θy direction, and the θz direction.

  First, the exposure main body including the projection optical system PL, the reticle stage 15 and the wafer stage 32 is supported by a frame mechanism. The frame mechanism includes a base member 1 made of a frame caster installed on the floor surface, for example, three (or four, etc.) first columns 2 installed on the upper surface of the base member 1, and the first of these. A second column 4 is provided on the upper surface of the column 2 via, for example, active vibration isolators 3A and 3B (actually three or four are disposed). The projection optical system PL is mounted on a U-shaped opening at the center of a flat support plate 4a provided at the bottom of the second column 4.

  An exposure light source (not shown) installed in the vicinity of the frame mechanism is an ArF excimer laser light source (oscillation wavelength 193 nm). In addition, a KrF excimer laser light source (wavelength 248 nm), or a solid-state laser (YAG laser or semiconductor laser) Etc.) can be used. The illumination light IL emitted from the exposure light source enters the illumination optical system ILS. The illumination optical system ILS illuminates a slit-like illumination area elongated in the X direction (non-scanning direction) of the pattern surface (lower surface) of the reticle R with illumination light IL with a substantially uniform illuminance distribution.

  The illumination optical system ILS disposed in the sub-chamber 14 includes a light amount distribution setting mechanism (not shown) including a diffractive optical element, an optical, as disclosed in, for example, US Patent Application Publication No. 2003/025890. Illumination uniformity optical system (not shown) including an integrator (such as a fly-eye lens or rod integrator), a variable field stop (not shown) such as a reticle blind, and a condenser optical system including lenses 11, 13 and a mirror 12 Contains. Further, according to the illumination conditions such as normal illumination, dipole illumination, quadrupole illumination, or annular illumination, the light amount distribution setting mechanism has a light amount of illumination light IL on a pupil plane (not shown) in the illumination optical system ILS. The distribution is switched to a distribution having a large light amount in a circular area centered on the optical axis, two areas sandwiching the optical axis, four areas sandwiching the optical axis, or a ring-shaped area.

  The illumination light IL that has passed through the reticle R is exposed through the projection optical system PL to be elongated in the X direction in one shot region on the surface of the wafer W, which is a disk-shaped substrate coated with a photoresist (photosensitive agent). An image obtained by reducing the pattern in the illumination area of the reticle R at a projection magnification β (for example, 1/4, 1/5, etc.) is formed in the area. The projection optical system PL is a catadioptric optical system. The projection optical system PL is placed on the support plate portion 4a by the flange portion 44a. The optical paths of the illumination light IL of the illumination optical system ILS and the projection optical system PL are almost hermetically sealed, and in these optical paths, a gas having a high transmittance with respect to light in a substantially vacuum ultraviolet region (hereinafter referred to as “purge gas”). The dry air, nitrogen, or rare gas (such as helium) is supplied through the supply pipe 20A and the exhaust pipes 21A and 21D.

  The reticle R is held on the upper surface of the reticle stage 15 via a reticle holder (not shown), and the reticle stage 15 is movable on the upper surface parallel to the XY plane of the reticle base 16 at a constant speed in the Y direction. And it is mounted in a state that can be displaced in the X direction, the Y direction, and the θz direction. The reticle base 16 is fixed to the upper end of the second column 4. At least the position of the reticle stage 15 in the X and Y directions and the rotation angle in the θz direction are measured by a laser interferometer 17, and based on this measured value and control information from the main control system 5, a drive including a linear motor and the like. An apparatus (not shown) drives the reticle stage 15.

On the other hand, the wafer W is held on the upper surface of the wafer table 31 via a wafer holder (not shown), and the wafer table 31 is fixed to the upper surface of the wafer stage 32. The wafer stage 32 is mounted on an upper surface parallel to the XY plane of the wafer base 33 so as to be movable at a constant speed in the Y direction and to be movable in steps in the X and Y directions. The wafer base 33 is placed on the base member 1 via active vibration isolators 38A and 38B. At least the position in the X direction and the Y direction of the wafer stage 32 and the rotation angle in the θz direction are measured by a laser interferometer 34, and a drive including a linear motor or the like is based on the measured value and control information from the main control system 5. An apparatus (not shown) drives the wafer stage 32.

  In addition, a focus / leveling mechanism for adjusting the Z-direction position (focus position) of the wafer table 31 (wafer W) and the inclination angles in the θx direction and the θy direction is incorporated in the wafer stage 32. Yes. A plurality of wafers W measured by an oblique incidence type multi-point focus position detection system (autofocus sensor) composed of a projection optical system 35A and a light receiving optical system 35B disposed on the lower side surface of the projection optical system PL. Based on the information of the focus position at the measurement point, the focus / leveling mechanism continuously focuses the surface of the wafer W on the image plane of the projection optical system PL during exposure. The projection optical system 35A and the light receiving optical system 35B are attached to a sensor column 36 attached to the bottom surface of the flange portion 44a of the projection optical system PL.

In addition, a shearing interference type or point / diffraction / interference type (PDI type) wavefront aberration measuring device 39 disclosed in, for example, US Pat. No. 6,573,997 is provided above the wafer table 31. It has been. Information on the wavefront aberration of the projection optical system PL measured by the wavefront aberration measuring device 39 is processed by the imaging characteristic control system 6 of FIG.
At the time of exposure, after aligning the reticle R and the wafer W using an alignment system (not shown), the wafer stage 32 is stepped in the X direction and the Y direction so that the shot area to be exposed on the wafer W becomes the exposure area. Move to the front. Thereafter, the reticle R and the wafer W are projected in the Y direction via the reticle stage 15 and the wafer stage 32 while exposing the shot area of the wafer W with an image of the projection optical system PL of the pattern in the illumination area of the reticle R. Scanning exposure is performed in which the projection magnification of the optical system PL is synchronized with the speed ratio. By repeating the step movement and scanning exposure by the step-and-scan method, the image of the pattern of the reticle R is exposed on the entire shot area of the wafer W.

Next, the configuration of the projection optical system PL of the present embodiment will be described in detail.
In FIG. 1, a projection optical system PL composed of a catadioptric optical system includes a refractive first imaging optical system G1 that forms a first intermediate image of a pattern of a reticle R, a concave mirror 22, and two lenses having negative refractive power. L8, L9 and a second imaging optical system G2 that forms a second intermediate image that is approximately the same size as the first intermediate image, and the reticle R on the wafer W using light from the second intermediate image. A refraction-type third imaging optical system G3 that forms a final image of the pattern and a holding device 50 that holds the concave mirror 22 are provided. Further, the projection optical system PL has a reflection surface A that deflects the light from the first imaging optical system G1 toward the second imaging optical system G2, and the light from the second imaging optical system G2. An optical path bending mirror FM on which a reflecting surface B deflected toward the image optical system G3 is formed is provided. The first intermediate image and the second intermediate image are formed between the reflecting surface A and the second imaging optical system G2 and between the second imaging optical system G2 and the reflecting surface B, respectively.

The first imaging optical system G1 and the third imaging optical system G3 have an optical axis AX1 parallel to the Z axis, and the optical axis AX2 of the second imaging optical system G2 is orthogonal to the optical axis AX1. And parallel to the Y axis. Further, the optical axis AX1 and the optical axis AX2 intersect at an intersection line C (strictly speaking, an intersection line of the virtual extension surfaces) C of the two reflection surfaces A and B of the optical path bending mirror FM.
The first imaging optical system G1 includes a plane parallel plate L1, lenses L2, L3, L4, L5, L6, and L7 arranged in this order from the reticle R side. The second imaging optical system G2 is configured by disposing negative lenses L8 and L9 and a concave mirror 22 in order from the reticle side (that is, the incident side) along the light traveling path. The third imaging optical system G3 is configured by arranging lenses L10 and L11, an aperture stop AS, and lenses L12 and L13 in order from the reticle side along the light traveling direction. The arrangement surface of the aperture stop AS is the pupil plane of the projection optical system PL or a plane in the vicinity thereof, and the reflection surface 22b (see FIG. 2) of the concave mirror 22 is substantially conjugate with the pupil plane of the projection optical system PL. The configuration of the projection optical system PL is arbitrary.

In this embodiment, synthetic quartz or fluorite (CaF ₂ crystal) is used as the optical material of all refractive optical elements (lens components) constituting the projection optical system PL. The optical path bending mirror FM and the concave mirror 22 are formed by, for example, depositing a metal film such as aluminum or a dielectric multilayer film on the reflective surface of a composite material of silicon carbide (SiC) or SiC and silicon (Si). It is formed. At this time, it is preferable to coat the entire concave mirror 22 with silicon carbide or the like in order to prevent degassing. Further, as the material of the concave mirror 22, a low expansion material such as Corning's ULE (Ultra Low Expansion: trade name) or beryllium (Be) may be used. When beryllium is used, it is preferable to coat the entire concave mirror 22 with silicon carbide or the like.

  In addition, the plane parallel plate L1 and the lenses L2 to L7 of the first imaging optical system G1 are respectively divided into cylindrical divided lens barrels 41A through annular lens frames 42A, 42B, 42C, 42D, 42E, 42F, and 42G. , 41B, 41C, 41D, 41E, 41F, and 41G, and the divided lens barrels 41A to 41G have, for example, bolts (not shown) facing flange portions (not shown) in a state of maintaining airtightness along the optical axis AX1. Are fixedly connected to each other. The lens frames 42B to 42G and the like are formed with a plurality of openings for allowing the purge gas to flow (the same applies hereinafter).

  Similarly, the lenses L10, L11, L12, and L13 of the third imaging optical system G3 are respectively divided into cylindrical divided lens barrels 41H, 44, 41I, and 41J via annular lens frames 42H, 42K, 42I, and 42J. Is held in. The aperture stop AS is held in the divided lens barrel 41K sandwiched between the divided lens barrels 44 and 41I, and the divided lens barrels 41H, 44, 41K, 41I, and 41J are connected in a state of maintaining airtightness. The split lens barrel 44 is provided with a flange portion 44a. A cylindrical split lens barrel 43 having an opening in the + Y direction is connected between the split lens barrels 41G and 41H, and an optical path bending mirror FM is fixed to a protrusion in the split lens barrel 43 via a holding frame 43a. Yes. The first partial barrel 7 is constituted by the divided barrels 41A to 41K, 43, and 44.

  Further, under the control of the imaging characteristic control system 6 in FIG. 2, for example, the lens frames 42A to 42E are driven to finely move the plane parallel plate L1 and the lenses L2 to L5 in the Z direction, θx direction, and θy direction. Accordingly, a rotationally symmetric imaging characteristic correction mechanism (not shown) for correcting relatively low-order aberrations with rotational symmetry such as distortion and coma aberration of the projection optical system PL is provided. As such a rotationally symmetrical imaging characteristic correction mechanism, for example, a mechanism disclosed in US Patent Application Publication No. 2006/244940 can be used.

  The lenses L8 and L9 of the second imaging optical system G2 are held in the cylindrical divided lens barrels 45 and 41L via holding frames 46A and 46B, respectively, and the concave mirror 22 is held by the holding device 50. The The holding device 50 is also a correction mechanism for correcting non-rotationally symmetric aberrations such as center ass and higher-order aberrations as the imaging characteristics of the projection optical system PL. The holding device 50 is connected to the divided lens barrel 41L and fixed to the end surface of the divided lens tube 47 so as to cover the cylindrical divided lens tube 47 in which the concave mirror 22 is housed and the + Y-direction opening of the divided lens tube 47. And a magnetic fluid Lm disposed on the back surface 22c of the concave mirror 22. The magnetic fluid Lm is, for example, a mixture of a predetermined amount of magnetic powder (for example, iron powder) in a Teflon (registered trademark) liquid.

As shown in FIG. 2, a cylindrical housing 49 whose end on the + Y direction side is closed is fixed to an end surface 47 b of the divided lens barrel 47 by bolts 40. Furthermore, the holding device 50 holds the magnetic fluid Lm on the back surface 22c side of the concave mirror 22 and the holding ring 48 that fixes the step 22a on the outer periphery of the concave mirror 22 between the stepped portion of the inner surface 47a of the split lens barrel 47. A fluid holding plate 51 arranged at a distance, a hinge member 52A elastically deformable in the Y direction connecting the fluid holding plate 51 to the inner surface of the housing 49, and a position in the Y direction of the fluid holding plate 51 with respect to the housing 49 are detected. The linear encoder 53A and a mounting member 55 that is fixed to the outer surface of the fluid holding plate 51 in the + Y direction and that is cylindrical and has an end in the + Y direction closed are provided. The hinge member 52A fixed to the housing 49 is fixed to the fluid holding plate 51 by a bolt 52Aa. The linear encoder 53A includes a scale portion 53Ab fixed to the fluid holding plate 51 and a detection portion 53Aa fixed to the housing 49.

On the side surface in the −Y direction of the convex portion 22 a of the concave mirror 22, hemispherical contact portions (not shown) are formed at three locations at substantially equal angular intervals, and the concave mirror 22 is stably held with respect to the divided lens barrel 47. Yes.
As shown in FIG. 4A, which is a cross-sectional view taken along line BB in FIG. 2, the fluid holding plate is formed by three identically configured hinge members 52A, 52B, and 52C arranged at equal angular intervals on the inner surface of the housing 49. 51 is supported. That is, the fluid holding plate 51 is stably held at three locations inside the housing 49. Further, linear encoders 53A, 53B, and 53C that detect the position of the fluid holding plate 51 in the Y direction with respect to the housing 49 are disposed in the vicinity of the hinge members 52A to 52C. The detection results of the linear encoders 53A to 53C are supplied to the pressure temperature control system 9 of FIG.

  In FIG. 2, the fluid holding plate 51 and the attachment member 55 are made of a paramagnetic metal having a high thermal conductivity, such as a titanium alloy or aluminum. The hinge member 52A and the housing 49 are made of, for example, metal. The distance between the back surface 22c of the concave mirror 22 and the fluid holding plate 51 is preferably about 1 to 3 mm, for example. In this embodiment, the interval is set to about 2 mm.

The holding device 50 is attached on the surface of the fluid holding plate 51 with an actuator 54A that displaces the fluid holding plate 51 in the Y direction with respect to the housing 49 via the hinge member 52A within the range of elastic deformation of the hinge member 52A. A plurality of permanent magnets 56A, 56B, and 56C (see FIG. 4B) and a plurality of electromagnets 57 disposed inside the member 55 are provided.
As shown in FIG. 4B, which is a sectional view taken along the line CC of FIG. 2, the housing 49 has the same configuration in which the fluid holding plate 51 is displaced in the Y direction via hinge members 52A, 52B, 52C. Actuators 54A, 54B and 54C are arranged. The actuators 54A to 54C are, for example, piezo elements (electrostrictive elements) or voice coil motors (VCM). Based on the detection results of the linear encoders 53A to 53C and the control information from the imaging characteristic control system 6, the pressure temperature control system 9 in FIG. 2 controls the drive amounts of the actuators 54A to 54C. By driving the actuators 54A to 54C, the Y-direction position of the fluid holding plate 51 with respect to the back surface 22c of the concave mirror 22, and the inclination angles in the θx direction and the θz direction can be controlled. The drive stroke in the Y direction of the actuators 54A to 54C is, for example, about several μm.

  In FIG. 4B, the central circular region inside the attachment member 55 is an effective region 62M corresponding to the effective region in which the concave mirror 22 in FIG. 2 is irradiated with the illumination light IL. In the effective area 62M, electromagnets 57 are respectively installed at a large number of driving points P (i, j) arranged at predetermined intervals in the X direction and the Z direction. The driving point P (i, j) is the i-th (i = 1 to I) in the + X direction and the j-th (j = 1 to J) driving in the + Z direction from the driving points in the −X direction and the −Z direction, respectively. Points (I and J are integers of 2 or more). The number of drive points P (i, j) and electromagnets 57 arranged in the X direction and the Y direction passing through substantially the center of the effective area 62 is, for example, about 10 to 20 (about 10 in FIG. 4B). By supplying a current to the coil of a certain electromagnet 57, a part of the magnetic fluid Lm on the back surface 22 c of the concave mirror 22 in FIG. 2 is moved to a region on the extension of the electromagnet 57 by the magnetic force generated by the electromagnet 57. be able to. The current (and hence the magnetic force) flowing through the coils of all the electromagnets 57 can be individually controlled by the pressure temperature control system 9 of FIG.

  3A to 3F are sectional views taken along line AA in FIG. 2, and FIGS. 3A to 3F are distributions of the magnetic fluid Lm on the back surface 22c of the concave mirror 22 in FIG. Is shown. Further, the effective area 62 on the back surface 22c in FIGS. 3A to 3F is an area facing the effective area 62M in FIG. 4B. By controlling the current flowing through the coils of all the electromagnets 57 in FIG. 2, the distribution of the magnetic fluid Lm in the effective region 62 of the back surface 22c is changed along the optical axis AX2 in FIG. 3A in the Z direction (on the reticle R). Two regions 63A and 63B sandwiched in the direction corresponding to the Y direction), one region 63C in FIG. 3C, two regions 63D and 63E sandwiching the optical axis in FIG. Various distributions such as a large number of regions 64F in FIG. 3E or an annular region 64G in FIG. 3F can be set. In the distribution of the magnetic fluid Lm as shown in FIG. By controlling the above, it is possible to slightly deform the reflecting surface 22b of the concave mirror 22 facing the back surface 22c where the magnetic fluid Lm exists. At this time, since the concave mirror 22 is placed horizontally, the reflecting surface 22b can be deformed with a slight force from the back surface 22c. This makes it possible to correct non-rotationally symmetric aberrations and higher-order aberrations (such as wavefront aberrations) of the projection optical system PL.

  4B, three arc-shaped retraction areas 64AM, 64BM, and 64CM are provided in the area outside the effective area 62M inside the attachment member 55 in FIG. 4B with the area in the vicinity of the hinge members 52A to 52C. A plurality of permanent magnets 56A, 56B, and 56C having the same configuration are installed in close proximity within the retreat areas 64AM, 64BM, and 64CM. The permanent magnets 56A to 56C hold the magnetic fluid Lm in the retreat areas 64A to 64C of the back surface 22c of the concave mirror 22 in FIG. 3B facing the retreat areas 64AM to 64CM in a state where all the electromagnets 57 are off. Used to do. A liquid repellent coating film (for example, a synthetic resin such as Teflon (registered trademark)) that repels the magnetic fluid Lm is formed on the back surface 22c of the concave mirror 22. Thus, the magnetic fluid Lm can be easily moved along the back surface 22c.

  In FIG. 2, a flow path 51a is provided inside the fluid holding plate 51, and one end and the other end of the flow path 51a are connected to the refrigerant supply device 59 via flexible pipes 60A and 60B, respectively. Yes. The refrigerant supply device 59 supplies the refrigerant Co whose temperature is controlled (cooled) to the flow path 51a through the pipe 60A, and collects the refrigerant Co that has flowed through the flow path 51a through the pipe 60B. A temperature sensor 61 is fixed to the fluid holding plate 51, and temperature information of the fluid holding plate 51 detected by the temperature sensor 61 is supplied to the pressure temperature control system 9. The pressure temperature control system 9 controls the temperature and flow rate of the refrigerant Co supplied to the flow path 51a via the refrigerant supply device 59 so that the temperature of the fluid holding plate 51 becomes a set value by the imaging characteristic control system 6. To do. As shown in FIG. 4A, the flow path 51a is formed so as to circulate almost the entire surface of the fluid holding plate 51 along the locus 69, so that the temperature distribution of the fluid holding plate 51 becomes substantially uniform. The holding device 50 includes a temperature sensor 61 and pipes 60A and 60B. In addition, as a refrigerant | coolant Co etc., a fluorine-type inert liquid etc. can be used, for example. As the fluorinated inert liquid, for example, Fluorinert (trade name of 3M, USA) can be used.

Next, an example of an operation for correcting non-rotationally symmetric aberration such as the center ass of the projection optical system PL using the holding device 50 that holds the concave mirror 22 will be described. In this case, as an example, the wavefront aberration of the projection optical system PL is measured using the wavefront aberration measuring device 39 of FIG. As a result of this measurement, the wavefront aberration on the pupil plane of the projection optical system PL, and consequently the wavefront aberration in the vicinity of the reflection surface 22b of the concave mirror 22, makes the optical axis AX2 substantially symmetric in the Z direction, as shown in FIG. Assume that the two sandwiched substantially circular regions 23A and 23B are negative. In this case, the imaging characteristic control system 6 in FIG. 2 supplies the pressure temperature control system 9 with information on the positions and sizes of the areas 23A and 23B, and information on the average wavefront aberration amount in these areas. To do.

  In response to this, the pressure-temperature control system 9 first controls the currents of all the electromagnets 57 so that the distribution of the magnetic fluid Lm on the back surface 22c of the concave mirror 22 is a region facing the regions 23A and 23B in FIG. Set to 63A, 63B. Further, the pressure temperature control system 9 drives the actuators 54A to 54C, and the displacement in the regions 23A and 23B of the reflecting surface 22b is approximately ½ of the wavefront aberration amount in a state where the fluid holding plate 51 is parallel to the back surface 22c. Then, the fluid holding plate 51 is displaced in the Y direction. As a result, the pressure of the magnetic fluid Lm between the back surface 22c of the concave mirror 22 and the fluid holding plate 51 changes. This change in the pressure of the magnetic fluid Lm gives a biasing force to the regions 23A and 23b in the back surface 22c of the concave mirror 22, and the non-rotationally symmetric aberration is reduced (corrected). The relationship between the magnetic force of the electromagnet 57, the amount of movement of the fluid holding plate 51 in the Y direction (the distance between the back surface 22c and the fluid holding plate 51), and the displacement of the reflecting surface 22b is obtained and stored in advance by calculation or measurement. You may keep it. If the wavefront aberration amount differs between the two regions 23A and 23B, the inclination angle of the fluid holding plate 51 in the θx direction may be adjusted accordingly.

  Further, as shown in FIG. 5B, when the measured wavefront aberration becomes a negative value in the two regions 23D and 23E that sandwich the optical axis AX2 obliquely almost symmetrically, the back surface 22c of the concave mirror 22 is used. The distribution of the magnetic fluid Lm is set in the two regions 63D and 63E in FIG. 3D, and the drive amounts of the actuators 54A to 54C may be adjusted. Similarly, the wavefront aberration can be reduced by controlling the distribution of the magnetic fluid Lm and the urging force by the fluid holding plate 51 in accordance with various wavefront aberrations to be measured. When the wavefront aberration becomes positive in the two regions 23A and 23B, for example, if the magnetic fluid Lm is distributed in the region surrounding the corresponding two regions 63A and 63B in FIG. Good.

  Further, when the currents of all the electromagnets 57 are adjusted in order to control the distribution of the magnetic fluid Lm in this way, the temperature of the fluid holding plate 51 rises and the temperature of the concave mirror 22 also rises via the magnetic fluid Lm. Therefore, when the temperature of the fluid holding plate 51 exceeds the allowable value, the refrigerant Co is supplied from the refrigerant supply device 59 to the flow path 51a of the fluid holding plate 51 to cool the fluid holding plate 51. Thereby, the temperature rise of the concave mirror 22 can be suppressed.

  Next, another example of the operation for correcting the non-rotationally symmetric aberration of the projection optical system PL will be described. In this case, the temperature distribution of the concave mirror 22 is predicted in advance from the pattern of the reticle R and the illumination conditions. That is, the main pattern formed on the reticle R is, for example, an enlarged line and space pattern (hereinafter referred to as “the pattern of the resolution limit” in the Y direction as shown in FIG. 6A). In the case of 71H (referred to as an L & S pattern), dipole illumination is used as the illumination condition of the illumination optical system ILS. As a result, as shown in FIG. 6B, the amount of illumination light IL in the pupil plane of the projection optical system PL and eventually the reflecting surface of the concave mirror 22 is two areas 72 that sandwich the optical axis AX2 substantially symmetrically in the Z direction. Becomes higher, and the temperature of the region 72 rises.

  2 is supplied from the imaging characteristic control system 6 of FIG. 2 to the pressure temperature control system 9, the pressure temperature control system 9 is connected to the back surface 22 c of the concave mirror 22 by the electromagnet 57. The distribution of the magnetic fluid Lm is set in the two regions 23A and 23B in FIG. However, the drive amount of the actuators 54A to 54C is set to approximately zero. That is, the urging force by the magnetic fluid Lm and the fluid holding plate 51 is not generated on the back surface 22 c of the concave mirror 22. In this case, the pressure / temperature control system 9 functions as a control system for moving the magnetic fluid because the pressure of the magnetic fluid Lm between the back surface 22c of the concave mirror 22 and the liquid holding plate 51 is not adjusted. In addition, the cooled refrigerant Co is supplied to the flow path 51 a of the fluid holding plate 51 through the refrigerant supply device 59. As a result, the temperatures of the regions 23A and 23B are lowered, and the temperature distribution of the concave mirror 22 approaches a rotationally symmetric distribution, so that non-rotationally symmetric aberration is reduced.

  For example, when annular illumination is used, the amount of light in the portion corresponding to the annular region 23G increases on the reflecting surface of the concave mirror 22 in FIG. 3F, and the temperature of the portion corresponding to the region 23G is increased. Rises. Therefore, the pressure-temperature control system 9 distributes the magnetic fluid Lm in the ring-shaped region 64G of the back surface 22c and supplies the refrigerant Co to the flow path 51a of the fluid holding plate 51. Can be reduced. Similarly, when the temperature of the reflecting surface rises in other various regions, the distribution of the magnetic fluid Lm is set in accordance with the region, and the refrigerant Co is supplied to the fluid holding plate 51. / Or higher order aberrations can be reduced.

The effects and the like of this embodiment are as follows.
(1) The projection optical system PL of the present embodiment includes a holding device 50 that holds the concave mirror 22. The holding device 50 holds the magnetic fluid Lm that is in contact with at least a partial region of the split lens barrel 47 (support member) that supports the concave mirror 22 (optical element) and the back surface 22c (part of the front surface) of the concave mirror 22. A fluid holding plate 51 (fluid holding member) and actuators 54A to 54C (pressure control devices) that deform the concave mirror 22 by controlling the pressure of the magnetic fluid Lm held by the fluid holding plate 51 are provided.

According to this embodiment, since the concave mirror 22 is deformed via the magnetic fluid Lm, there is no fear of the concave mirror 22 being damaged. In addition, since the concave mirror 22 is deformed at the portion in contact with the magnetic fluid Lm and the portion of the reflecting surface of the concave mirror 22 facing the portion, the concave mirror 22 can be used in a state where the deformation state of the concave mirror 22 can be accurately predicted. It can be transformed into a desired shape.
(2) The holding device 50 also includes a plurality of electromagnets 57 (distribution setting devices) for controlling the distribution of the magnetic fluid Lm on the back surface 22c of the concave mirror 22. Therefore, by controlling the current of the electromagnet 57 individually, the distribution of the magnetic fluid Lm can be easily set to various distributions.

(3) Further, each of the actuators 54A to 54C displaces the fluid holding plate 51 in the direction perpendicular to the back surface 22c (Y direction) with respect to the housing 49 (base member). Accordingly, the fluid holding plate 51 can be displaced with three degrees of freedom, and the pressure of the magnetic fluid Lm on the back surface 22c can be changed depending on the position.
The holding device 50 may include only one actuator, and the actuator may only displace the fluid holding plate 51 in the Y direction with respect to the housing 49 using this actuator. In this case, when the magnetic forces of the electromagnets 57 are equal to each other, the pressure of the magnetic fluid Lm on the back surface 22c is substantially equal regardless of the position. On the other hand, by changing the magnetic force for each electromagnet 57, it is possible to increase the pressure of the magnetic fluid Lm in the portion where the magnetic force is strong.

(4) The holding device 50 includes a temperature control device that controls the temperature distribution of the concave mirror 22 by adjusting the position (distribution) of the magnetic fluid Lm with respect to the back surface 22 c of the concave mirror 22. This temperature control device includes a pipe 60A that is provided on the fluid holding plate 51 and is supplied with a temperature-controlled refrigerant Co, and a plurality of electromagnets 57 that attract the magnetic fluid Lm.
Therefore, when it can be predicted in advance that the temperature distribution of the concave mirror 22 becomes non-rotationally symmetric, for example, when using dipole illumination, the magnetic fluid Lm is controlled so as to suppress the non-rotationally symmetric temperature distribution. By controlling the distribution and its temperature, non-rotationally symmetric aberration can be reduced. In addition, rotationally symmetric high-order aberrations can be reduced.

Thus, when adjusting only the temperature distribution of the concave mirror 22 through the magnetic fluid Lm, the actuators 54A to 54C may be omitted.
In addition, the back surface 22c of the concave mirror 22 is divided into a plurality of regions by a lattice-shaped partition member, and the plurality of regions are filled with the magnetic fluid Lm, and the magnetic fluid Lm is divided into a plurality of regions by a Peltier element (temperature control device). The temperature may be controlled. Even with this configuration, the temperature distribution of the concave mirror 22 can be corrected.

(5) Further, the magnetic fluid Lm can be retracted by the permanent magnets 56A to 56C in the retreat areas 64A to 64C outside the effective area 62 effective for controlling the temperature distribution of the back surface 22c of the concave mirror 22. Therefore, for example, even if the current of all the electromagnets 57 is turned off, the magnetic fluid Lm does not leak out of the back surface 22c.
(6) Moreover, the magnetic fluid Lm is hold | maintained so that at least one part area | region of the back surface 22c of the reflective surface 22b of the concave mirror 22 (mirror) may be contacted. Therefore, the distribution of the displacement or the temperature distribution of the reflecting surface 22b facing the magnetic fluid Lm on the back surface 22c can be accurately controlled.

  Note that a holding device using the magnetic fluid Lm similar to the holding device 50 may be applied to, for example, the lens L11 in the projection optical system PL. In this case, the magnetic fluid may be held so as to be in contact with at least a part of the region of the surface of the lens L11 where the light beam of the illumination light IL does not pass. In this configuration, the magnetic fluid is distributed in a region where the wavefront aberration is generated or a region close to the region where the temperature is rising, and by controlling the pressure and / or temperature, the non-rotationally symmetric aberration and / Or higher order aberrations can be corrected.

  (7) In addition, the projection optical system PL includes a holding device 50 for supporting the concave mirror 22 among the optical elements in an optical system including the lenses L8 and L9 and the concave mirror 22 (a plurality of optical elements). The deformation amount of the concave mirror 22 is controlled via the magnetic fluid Lm by the actuators 54A to 54C (pressure control device) according to the non-rotationally symmetric aberration of the projection optical system PL. Therefore, the non-rotationally symmetric aberration of the projection optical system PL can be reduced.

It should be noted that a holding device similar to the holding device 50 can be provided for each of the plurality of optical elements in the projection optical system PL.
(8) Further, the exposure apparatus EX of the present embodiment illuminates the pattern of the reticle R with the illumination light IL (exposure light), and the wafer W (substrate) through the pattern and the projection optical system PL with the illumination light IL. In the exposure apparatus that performs exposure, the projection optical system PL includes a holding device 50.

Therefore, since the non-rotationally symmetric aberration of the projection optical system PL can be reduced, the pattern image of the reticle R can be exposed to each shot area of the wafer W with high accuracy.
Note that a holding device similar to the holding device 50 (however, the magnetic fluid Lm is a region around a portion where the luminous flux of the lens passes) is applied to an optical element (for example, a lens near the pupil plane) in the illumination optical system ILS of the exposure apparatus EX. Distributed). In this case, the illumination conditions can be set with high accuracy.

  Next, when a semiconductor device (electronic device) is manufactured using the exposure apparatus EX of the above-described embodiment, as shown in FIG. Step 222 for producing a mask (reticle) based on the steps, Step 223 for producing a substrate (wafer) as a base material of the device, and exposure of the reticle pattern onto the resist-coated substrate (photosensitive substrate) by the exposure apparatus EX A process of developing the exposed substrate to form a resist pattern, a substrate processing step 224 including heating (curing) and etching of the developed substrate, a device assembly step (dicing process, bonding process, packaging process, etc.) (Including machining process) 225, inspection step 226, etc. It is produced.

  In other words, the device manufacturing method forms the pattern of the photosensitive layer on the substrate (wafer) using the exposure apparatus of the above embodiment, and processes the substrate on which the pattern is formed (step 224). ). According to this manufacturing method, since the exposure apparatus can reduce various aberrations including non-rotationally symmetric aberration, a device having a fine pattern can be manufactured with high accuracy.

In the present invention, for example, the aberration correction of the projection optical system of the immersion type exposure apparatus disclosed in US Patent Application Publication No. 2007/242247 or European Patent Application Publication No. 1420298 is performed. It can also be applied to. The present invention can be applied not only to a scanning type exposure apparatus but also to a batch exposure type exposure apparatus (such as a stepper).
The present invention can also be applied to the case where aberration correction of a projection optical system of a projection exposure apparatus using extreme ultraviolet light (EUV light) having a wavelength of about several nm to 100 nm as exposure light is performed. When EUV light is used as the exposure light, the projection optical system is composed of a plurality of mirrors (concave mirrors, convex mirrors, plane mirrors, etc.) excluding a specific filter and the like. It can be used to hold at least one of the plurality of mirrors.

  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 apparatus when manufacturing a mask (photomask, reticle, etc.) on which a mask pattern of various devices is formed using a photolithography process.

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

  EX ... exposure apparatus, R ... reticle, W ... wafer, Lm ... magnetic fluid, ILS ... illumination optical system, PL ... projection optical system, 9 ... pressure temperature control system, 22 ... concave mirror, 39 ... wavefront aberration measuring device, 47 ... Split barrel, 49 ... housing, 50 ... holding device, 51 ... fluid holding plate, 52A-52C ... hinge member, 53A-53C ... linear encoder, 54A-54C ... actuator, 56A-56C ... permanent magnet, 57 ... electromagnet, 59. Refrigerant supply device

Claims (21)

A holding device for an optical element,
A support member for supporting the optical element;
A fluid holding member that holds a magnetic fluid in contact with at least a partial region of the surface of the optical element;
A pressure control device for controlling the pressure of the magnetic fluid held by the fluid holding member to deform the optical element;
A holding device for an optical element, comprising: 2. The optical element holding device according to claim 1, wherein the pressure control device includes at least one actuator that displaces the fluid holding member with respect to a base member.   The optical element holding device according to claim 1, further comprising a temperature control device that adjusts a position of the magnetic fluid with respect to a surface of the optical element to control a temperature distribution of the optical element. .   The optical element holding device according to claim 3, further comprising a piping member provided in the fluid holding member and supplied with a temperature-controlled refrigerant.   5. The optical element holding device according to claim 3, wherein the temperature control device includes a plurality of electromagnets for attracting the magnetic fluid.   The holding of the optical element according to any one of claims 3 to 5, wherein the magnetic fluid can be retracted outside a region effective for controlling the temperature distribution on the surface of the optical element. apparatus.   The said optical element is a mirror, The said magnetic fluid is hold | maintained so that at least one area | region of the back surface of the reflective surface of the said mirror may be contacted. The holding device for an optical element according to 1.   7. The optical element according to claim 1, wherein the optical element is a lens, and the magnetic fluid is held so as to be in contact with at least a part of a region of the lens surface where a light beam does not pass. The optical element holding device according to claim 1. In an optical system including a plurality of optical elements,
In order to support at least one optical element of the plurality of optical elements, the optical element holding device according to any one of claims 1 to 8, comprising:
An optical system characterized in that a deformation amount of the optical system is controlled by the pressure control device according to a non-rotationally symmetric aberration of the optical system. In an exposure apparatus that illuminates a pattern with exposure light and exposes the substrate through the pattern and the projection optical system with the exposure light,
An exposure apparatus comprising the optical system according to claim 9.   The exposure apparatus according to claim 10, wherein the optical system is the projection optical system. A holding device for an optical element,
A support member for supporting the optical element;
A fluid holding member that holds a magnetic fluid in contact with at least a partial region of the surface of the optical element;
A temperature control device that controls the temperature distribution of the optical element by adjusting the position of the magnetic fluid relative to the surface of the optical element;
A holding device for an optical element, comprising:   The optical element holding device according to claim 12, further comprising a piping member that is provided in the fluid holding member and is supplied with a temperature-controlled refrigerant.   14. The optical element holding device according to claim 12, wherein the temperature control device includes a plurality of electromagnets for attracting the magnetic fluid.   15. The optical element holding device according to claim 14, wherein the magnetic fluid can be retracted outside an area effective for controlling the temperature distribution on the surface of the optical element.   The said optical element is a mirror, The said magnetic fluid is hold | maintained so that it may contact at least one area | region of the back surface of the reflective surface of the said mirror. The holding device for an optical element according to 1.   16. The optical element according to claim 12, wherein the optical element is a lens, and the magnetic fluid is held so as to be in contact with at least a part of a region of the lens surface through which a light beam does not pass. The optical element holding device according to claim 1. In an optical system including a plurality of optical elements,
An optical system comprising the optical element holding device according to any one of claims 12 to 17, in order to support at least one optical element of the plurality of optical elements. In an exposure apparatus that illuminates a pattern with exposure light and exposes the substrate through the pattern and the projection optical system with the exposure light,
An exposure apparatus comprising the optical system according to claim 18.   The exposure apparatus according to claim 19, wherein the optical system is the projection optical system. Forming a pattern of a photosensitive layer on a substrate using the exposure apparatus according to claim 10, claim 11, claim 19, or claim 20;
Processing the substrate on which the pattern is formed.

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