# Patent

## Title
Movable body apparatus, pattern formation apparatus and exposure apparatus, and device manufacturing method

## Abstract

On the +X and −X sides of a projection unit, a plurality of Y heads are arranged in parallel to the X-axis by a predetermined distance half or less than half the effective width of the scale, so that two heads each constantly form a pair and face a pair of Y scales. Similarly, on the +Y and −Y sides of the projection unit, a plurality of X heads are arranged in parallel to the Y-axis by the predetermined distance described above, so that two heads each constantly form a pair and face a pair of X scales. Of the pair of heads consisting of two heads which simultaneously face the scale, measurement values of a priority head is used, and when abnormality occurs in the measurement values of the priority head due to malfunction of the head, measurement values of the other head is used. Then, by using the measurement values of the two pairs of Y heads and the pair of X heads, a position of a stage within a two-dimensional plane is measured in a stable manner and with high precision.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This non-provisional application claims the benefit of Provisional Application No. 60/996,209 filed Nov. 6, 2007, the disclosure of which is hereby incorporated herein by reference in its entirety.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to movable body apparatuses, pattern formation apparatus and exposure apparatus, and device manufacturing methods, and more particularly, to a movable body apparatus equipped with a movable body which substantially moves along a predetermined plane, a pattern formation apparatus which forms a pattern on an object mounted on a movable body, an exposure apparatus which forms a pattern on an object by irradiating an energy beam, and a device manufacturing method which uses the exposure apparatus.
2. Description of the Background Art
Conventionally, in a lithography process for manufacturing microdevices (electron devices) such as semiconductor devices, liquid crystal display devices and the like, exposure apparatuses such as a projection exposure apparatus by a step-and-repeat method (a so-called stepper) and a projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner) are mainly used.
With these types of projection exposure apparatus, the position of a stage holding a substrate subject to exposure, such as for example, a wafer, was generally measured using a laser interferometer. However, due to finer patterns which accompany higher integration of semiconductor devices, requirements in performance is becoming tighter, and for example, as for overlay error, the permissible value of the overall overlay error has become an order of several nm, while the permissible value of a position control error of the stage has also become equal to or less than a sub-nano order, and short-term variation of measurement values which is caused by air fluctuation which occurs due to the influence of temperature fluctuation and/or temperature gradient of the atmosphere on the beam path of the laser interferometer can no longer be ignored.
Therefore, recently, an encoder with a high resolution which is impervious to air fluctuation when compared with an interferometer has begun to gather attention, and an invention related to an exposure apparatus which uses the encoder in position measurement of a wafer stage and the like has been proposed (refer to, for example, the pamphlet of International Publication 2007/097379 and the like).
In the exposure apparatus and the like disclosed in the pamphlet of International Publication 2007/097379, position measurement of a wafer stage and the like is performed, using a plurality of encoder heads. However, when position measurement of a wafer stage and the like is performed using a plurality of encoder heads, malfunction of each encoder head, such as, for example, a mechanical failure and the like may cause an abnormality in the output of the encoder heads. Meanwhile, in order to achieve a highly precise exposure even in such a case, being able to measure the position of the wafer stage continuously with high precision is required.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a first movable body apparatus including a movable body which substantially moves along a predetermined plane, the apparatus comprising: a scale which is arranged at one of the movable body and the outside of the movable body, with a first direction within a plane parallel to the predetermined plane serving as a longitudinal direction, and having a grating section that has a predetermined width in a second direction orthogonal to the first direction; and a measurement device which measures positional information of the movable body in a periodic direction of the grating section at a plurality of measurement points placed on the scale, whereby the placement of the plurality of measurement points is decided so that of the plurality of measurement points, n points (wherein, n is an integer of two or more) or more are positioned within the predetermined width on the scale, and when the movable body is at a predetermined position, n+1 or more of the plurality of measurement points are positioned to be within the predetermined width on the scale.
According to this device, of the plurality of measurement points that the measurement device has, n points (wherein, n is an integer of two or more) or more are positioned within the predetermined width on the scale, and when the movable body is at a predetermined position, n+1 points or more are positioned within the predetermined width on the scale. Therefore, it becomes possible to measure positional information of the movable body in the periodic direction of the grating section which a scale has in at least one measurement point. Accordingly, even if abnormality occurs in a part of the measurement of n points positioned within the predetermined width on the scale or n+1 points when the movable body is at the predetermined position, it becomes possible to measure the positional information of the movable body in the periodic direction of the grating section which the scale has, unfailingly, with the remaining measurement points.
According to a second aspect of the present invention, there is provided a second movable body apparatus including a movable body which substantially moves along a predetermined plane, the apparatus comprising: a scale which is arranged at one of the movable body and the outside of the movable body, with a first direction within a plane parallel to the predetermined plane serving as a longitudinal direction, and having a grating section that has a predetermined width in a second direction orthogonal to the first direction; and a measurement device which measures positional information of the movable body in a periodic direction of the grating section at a plurality of measurement points placed on the scale, whereby the measurement device has a plurality of head sets including a first head which irradiates a measurement beam on a first measurement point and a second head which irradiates a measurement beam on the first measurement point or in its vicinity.
According to this device, the measurement device has a plurality of head sets including a first head which irradiates a measurement beam on a first measurement point of the plurality of measurement points that the measurement device has, and a second head which irradiates a measurement beam on the first measurement point or in its vicinity. Therefore, of the first head and the second head included in the head set, even it abnormality occurs in one of the heads, because the other head can be used, the head set stably irradiates measurement beams on the scale and measures the positional information of the movable body in the periodic direction of the grating section which the scale has. Accordingly, by using the measurement device which has the plurality of head sets, it becomes possible to unfailingly measure the positional information of the movable body in the periodic direction of the grating section which the scale has.
According to a third aspect of the present invention, there is provided a third movable body apparatus including a movable body which substantially moves along a predetermined plane, the apparatus comprising: a measurement device which measures positional information of the movable body a direction of one degree of freedom in the predetermined plane, at a plurality of measurement points placed in a movement range or the movable body, whereby the measurement device has a plurality of heads which generate measurement information by irradiating a measurement beam on at least one of the plurality of measurement points when the movable body is located at a predetermined position.
According to this device, the measurement device has a plurality of heads which generate measurement information by irradiating a measurement beam on at least one of the plurality of measurement points when the movable body is located at a predetermined position. Therefore, it becomes possible to measure the positional information of the movable body in a direction off one degree of freedom within the predetermined plane, using at least one head. Accordingly, even if abnormality occurs in a part of the plurality of heads, it becomes possible to measure the positional information of the movable body unfailingly in a direction of one degree of freedom within the predetermined plane, using another head in the remaining heads.
According to a fourth aspect of the present invention, there is provided a pattern formation apparatus that forms a pattern on an object, the apparatus comprising: a patterning device which forms a pattern on the object, and the movable body apparatus according to the present invention (to be precise, any one of the first, second, or, third movable body apparatus) in which the object is mounted on the movable body.
According to this apparatus, a pattern is generated by the patterning device on the object, which is on a movable body that configures a part of the movable body apparatus of the present invention and can unfailingly measure the positional information in the measurement direction. Accordingly, it becomes possible to form a pattern on the object with good precision.
According to a fifth aspect of the present invention, there is provided an exposure apparatus that forms a pattern on an object by irradiating an energy beam, the apparatus comprising: a patterning device that irradiates the energy beam on the object; the movable body apparatus according to the present invention in which the object is mounted on the movable body, and a drive device which drives the movable body to make the object relatively move with respect to the energy beam.
According to this apparatus, to make the object relatively move with respect to the energy beam irradiated on the object from the patterning device, the drive device drives the movable body on which the object is mounted with good precision. Accordingly, it becomes possible to form a pattern on the object with good precision by scanning exposure.
According to a sixth aspect of the present invention, there is provided a device manufacturing method which uses the exposure apparatus according to the present invention.



BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is a view schematically showing the configuration of an exposure apparatus related to an embodiment;
FIG. 2A is a planar view showing a wafer stage, and FIG. 2B is a planar view showing a measurement stage;
FIG. 3 is a view used to explain a placement of measurement axes of an interferometer system of the exposure apparatus in FIG. 1, and is a planar view of a stage device is, partially omitted;
FIG. 4 is a view showing a placement of various measurement systems which the exposure apparatus in FIG. 1 is equipped with;
FIG. 5 is a view showing a placement of an encoder head (an X head and a Y head) and an alignment system;
FIG. 6 is a view showing a placement of a Z head and a multipoint AF system;
FIG. 7 is a block diagram showing a main configuration of a control system of the exposure apparatus in FIG. 1;
FIGS. 8A and 8B are views used to describe position measurement of a wafer table within an XY plane by a plurality of encoders, and a switching of heads;
FIGS. 9A and 9B are views used to explain a baseline measurement operation of a secondary alignment system performed at the beginning of a lot;
FIGS. 10A and 10B are views used to explain a first and second modified example of the encoder system, respectively;
FIGS. 11A and 11B are views used to explain a third and fourth modified example of the encoder system, respectively; and
FIG. 12 is a view used to explain other modified examples of the encoder system.



DESCRIPTION OF THE EMBODIMENTS
An embodiment of the present invention will be described below, with reference to FIGS. 1 to 9B.
FIG. 1 shows a schematic configuration of an exposure apparatus 100 in the embodiment. Exposure apparatus 100 is a projection exposure apparatus by the step-and-scan method, or a so-called scanner. As discussed later on, in the embodiment, a projection optical system PL is arranged, and in the description below, a direction parallel to an optical axis AX of projection optical system PL will be described as the Z-axis direction, a direction within a plane orthogonal to the Z-axis direction in which a reticle and a wafer are relatively scanned will be described as the Y-axis direction, a direction orthogonal to the Z-axis and the Y-axis will be described as the X-axis direction, and rotational (inclination) directions around the X-axis, the Y-axis, and the Z-axis will be described as θx, θy, and θz directions, respectively.
Exposure apparatus 100 is equipped with an illumination system 10, a reticle stage RST, a projection unit PU, a stage device 50 having a wafer stage WST and a measurement stage MST, and a control system of these parts. Although a part of the configuration is different such as the configuration of the encoder system which will be described later on, as a whole, exposure apparatus 100 is configured similar to the exposure apparatus disclosed in the pamphlet of International Publication No 2007/097379 (and the corresponding U.S. Patent Application Publication No. 2008/0088843) previously described. Accordingly, in the description below, the explanation given for each component will be simplified, except when especially necessary. Incidentally, in FIG. 1, a wafer W is mounted on wafer stage WST.
Illumination system 10 includes a light source, an illuminance uniformity optical system, which includes an optical integrator and the like, an illumination optical system that has a reticle blind and the like (none of which are shown), as is disclosed in, for example, U.S. Patent Application Publication No. 2003/0025890 and the like. Illumination system 10 illuminates a slit-shaped illumination area IAR, which is set on reticle R with a reticle blind (a masking system), by an illumination light (exposure light) IL with a substantially uniform illuminance. In this case, as illumination light IL, for example, an ArF excimer laser beam (wavelength 193 nm) is used.
On reticle stage RST, reticle R on which a circuit pattern or the like is formed on its pattern surface (the lower surface in FIG. 1) is fixed, for example, by vacuum chucking. Reticle stage RST is finely drivable within an XY plane, for example, by a reticle stage drive section 11 (not shown in FIG. 1, refer to FIG. 7) that includes a linear motor or the like, and reticle stage RST is also drivable in a scanning direction (in this case, the Y-axis direction, which is the lateral direction of the page surface in FIG. 1) at a predetermined scanning speed.
The positional information (including rotation information in the θz direction) of reticle stage RST in the XY plane (movement plane) is constantly detected, for example, at a resolution of around 0.25 nm by a reticle laser interferometer (hereinafter referred to as a “reticle interferometer”) 116, via a movable mirror 15 (the mirrors actually arranged are a Y movable mirror (or a retro reflector) that has a reflection surface which is orthogonal to the Y-axis direction and an X movable mirror that has a reflection surface orthogonal to the X-axis direction). The measurement values of reticle interferometer 116 are sent to a main controller 20 (not shown in FIG. 1, refer to FIG. 7).
Projection unit PU is placed below reticle stage RST in FIG. 1. Projection unit PU includes a barrel 40, and projection optical system PL that has a plurality of optical elements which are held in a predetermined positional relation inside barrel 40. As projection optical system PL, for example, a dioptric system is used, consisting of a plurality of lenses (lens elements) that is disposed along an optical axis AX, which is parallel to the Z-axis direction. Projection optical system PL is, for example, a both-side telecentric dioptric system that has a predetermined projection magnification (such as one-quarter, one-fifth, or one-eighth times). Therefore, when illumination light IL from illumination system 10 illuminates illumination area IAR, illumination light IL that has passed through reticle R which is placed so that its pattern surface substantially coincides with a first plane (an object plane) of projection optical system PL forms a reduced image of the circuit pattern (a reduced image of a part of the circuit pattern) of reticle R formed within illumination area IAR, via projection optical system PL (projection unit PU), in an area (hereinafter, also referred to as an exposure area) IA conjugate to illumination area IAR on wafer W whose surface is coated with a resist (a sensitive agent) and is placed on a second plane (an image plane) side of projection optical system PL. And by reticle stage RST and wafer stage WST being synchronously driven, reticle R is relatively moved in the scanning direction (the Y-axis direction) with respect to illumination area IAR (illumination light IL) while wafer W is relatively moved in the scanning direction (the Y-axis direction) with respect to exposure area IA (illumination light IL), thus scanning exposure of a shot area (divided area) on wafer W is performed, and the pattern of reticle R is transferred onto the shot area. That is, in the embodiment, the pattern is generated on wafer W according to illumination system 10, reticle R, and projection optical system PL, and then by the exposure of the sensitive layer (resist layer) on wafer W with illumination light IL, the pattern is formed on wafer W.
In exposure apparatus 100 of the embodiment, a local liquid immersion device 8 is installed to perform exposure by a liquid immersion method. Local liquid immersion device 8 includes a liquid supply device 5, a liquid recovery device 6 (both of which are not shown in FIG. 1, refer to FIG. 7), a liquid supply pipe 31A, a liquid recovery pipe 31B, a nozzle unit 32 and the like. As shown in FIG. 1, nozzle unit 32 is supported in a suspended state by a mainframe (not shown) holding projection unit PU, so that the periphery of the lower end portion of barrel 40 that holds an optical element closest to the image plane side (the wafer W side) constituting projection optical system PL, in this case, a lens (hereinafter also referred to as a tip lens) 191, is enclosed. In the embodiment, as shown in FIG. 1, nozzle unit 32 is set so that its lower end surface is on a substantially flush surface with the lower end surface of tip lens 191. Further, nozzle unit 32 is equipped with a supply opening and a recovery opening of liquid Lq, a lower surface to which wafer W is placed facing and at which the recovery opening is arranged, and a supply flow channel and a recovery flow channel that are connected to a liquid supply pipe 31A and a liquid recovery pipe 31B respectively. Liquid supply pipe 31A and liquid recovery pipe 31B are slanted by around 45 degrees relative to an X-axis direction and Y-axis direction in a planar view (when viewed from above) as shown in FIG. 4, and are placed symmetric to a straight line (a reference axis) LV which passes through the center (optical axis AX of projection optical system PL, coinciding with the center of exposure area IA previously described in the embodiment) of projection unit PU and is also parallel to the Y-axis.
Liquid supply pipe 31A connects to liquid supply device 5 (not shown in FIG. 1, refer to FIG. 7), and liquid recovery pipe 31B connects to liquid recovery device 6 (not shown in FIG. 1, refer to FIG. 7). In this case, in liquid supply device 5, a tank to store the liquid, a compression pump, a temperature controller, a valve for controlling the flow amount of the liquid, and the like are equipped. In liquid recovery device 6, a tank to store the liquid which has been recovered, a suction pump, a valve for controlling the flow amount of the liquid, and the like are equipped.
Main controller 20 controls liquid supply device 5 (refer to FIG. 7), and supplies liquid between tip lens 191 and wafer W via liquid supply pipe 31A, as well as control liquid recovery device 6 (refer to FIG. 7), and recovers liquid from between tip lens 191 and wafer W via liquid recovery pipe 31B. During the operations, main controller 20 controls liquid supply device 5 and liquid recovery device 6 so that the quantity of liquid supplied constantly equals the quantity of water which has been recovered. Accordingly, in the space between tip lens 191 and wafer W, a constant quantity of liquid Lq (refer to FIG. 1) is held constantly replaced, and by this, a liquid immersion area 14 (for example, refer to FIG. 8A) is formed. Incidentally, in the case measurement stage MST which will be described later on is positioned below projection unit PU, liquid immersion area 14 can be formed similarly in the space between tip lens 191 and a measurement table described later on.
In the embodiment, as the liquid described above, pure water (hereinafter, it will simply be referred to as “water” besides the case when specifying is necessary) that transmits the ArF excimer laser light (light with a wavelength of 193 mm) is to be used. Incidentally, refractive index n of the water with respect to the ArF excimer laser light is around 1.44. In the water the wavelength of illumination light IL is 193 nm×1/n, shorted to around 134 nm.
As shown in FIG. 1, stage device 50 is equipped with a wafer stage WST and a measurement stage MST placed above a base board 12, a measurement system 200 (refer to FIG. 7) which measures positional information of the stages WST and MST, a stage drive system 124 (refer to FIG. 7) which drives stages WST and MST and the like. Measurement system 200 includes an interferometer system 118, an encoder system 150, and a surface position measurement system 190 as shown in FIG. 7. Incidentally, details on interferometer system 118, encoder system 150 and the like will be described later in the description.
Wafer stage WST and measurement stage MST are supported above base board 12, via a clearance of around several μm by a plurality of noncontact bearings (not shown) fixed to each of the bottom surfaces, such as, for example, air pads. Further, stages WST and MST are drivable independently within the XY plane, by stage drive system 124 (refer to FIG. 7) which includes a linear motor and the like.
Wafer stage WST includes a stage main section 91, and a wafer table WTB that is mounted on stage main section 91. Wafer table WTB and stage main section 91 are configured drivable in directions of six degrees of freedom (X, Y, Z, θx, θy, and θz) with respect to base board 12 by a drive system including a linear motor and a Z leveling mechanism (including a voice coil motor and the like).
In the center of the upper surface of wafer table WTB, a wafer holder (not shown) is arranged which holds wafer W by vacuum suction or the like. On the outer side of the wafer holder (mounting area of the wafer), as shown in FIG. 2A, a plate (a liquid repellent plate) 28 is arranged that has a circular opening one size larger than the wafer holder formed in the center, and also has a rectangular outer shape (contour). A liquid repellent treatment against liquid Lq is applied to the surface of plate 28 (a liquid repellent surface is formed). Incidentally, plate 28 is installed on the wafer table WTB upper surface, so that its entire surface or a part of the surface becomes flush with the surface of wafer W.
Plate 28 has a first liquid repellent area 28a having a rectangular outer shape (contour) with the circular opening described above formed in the center, and a second liquid repellent area 28b having a rectangular frame (loop) shape placed around the first liquid repellent area. Incidentally, in the embodiment, because water is used as liquid Lq as is previously described, hereinafter, the first liquid repellent area 28a and the second liquid repellent area 28b will also be referred to as a first water repellent plate 28a and a second water repellent plate 28b. 
On an end on the +Y side of the first water repellent plate 28a, a measurement plate 30 is arranged. On measurement plate 30, a fiducial mark FM is arranged in the center, and a pair of aerial image measurement slit patterns (slit-shaped measurement patterns) SL is arranged with the mark in between. And, in correspondence with each aerial image measurement slit pattern SL, a light-transmitting system (not shown) which guides illumination light IL passing through the slit patterns outside wafer stage WST (a photodetection system arranged in measurement stage MST which will be described later on) is arranged.
On second liquid repellent area 28b, scales for an encoder system (to be described later) are formed. More specifically, in areas on one side and the other side in the X-axis direction of the second water repellent plate 28b (both sides in the horizontal direction in FIG. 2A), Y scales 39Y1 and 39Y2 are formed, respectively. Y scales 39Y1 and 39Y2 are each composed of a reflective grating (for example, a diffraction grating) having a periodic direction in the Y-axis direction in which grid lines 38 having the longitudinal direction in the X-axis direction are formed in a predetermined pitch along a direction parallel to the Y-axis (the Y-axis direction). Similarly, in areas on one side and the other side in the Y-axis direction of the second water repellent plate 28b (both sides in the vertical direction in FIG. 2A), X scales 39X1 and 39X2 are formed, respectively, in a state where the scales are placed between Y scales 39Y1 and 39Y2. X scales 39X1 and 39X2 are each composed of a reflective grating (for example, a diffraction grating) having a periodic direction in the X-axis direction in which grid lines 37 having the longitudinal direction in the Y-axis direction are formed in a predetermined pitch along a direction parallel to the X-axis (the X-axis direction). The pitch of grid lines 37 and 38, for example, is set to 1 μm. Incidentally, in FIG. 2A, the pitch of the gratings is illustrated larger than the actual pitch for the sake of convenience. The same is true also in other drawings.
Incidentally, in order to protect the diffraction grating, it is also effective to cover the grating with a glass plate with low thermal expansion that has water repellency. In this case, as the glass plate, a plate whose thickness is the same level as the wafer, such as for example, a plate 1 mm thick, can be used, and the plate is set on the upper surface of wafer table WTB so that the surface of the glass plate becomes the same height (surface position) as the wafer surface.
Further, to the −Y end surface and the −X end surface of wafer table WTB, mirror-polishing is applied, respectively, and as shown in FIG. 2A, reflection surfaces 17a and 17b are formed for interferometer system 118 which will be described later in the description.
Measurement stage MST includes a stage main section 92 driven in the XY plane by a linear motor and the like (not shown), and a measurement table MTB mounted on stage main section 92, as shown in FIG. 1. Measurement stage MST is configured drivable in at least directions of three degrees of freedom (X, Y, and θz) with respect to base board 12 by a drive system (not shown).
Incidentally, in FIG. 7, the drive system of wafer stage WST and the drive system of measurement stage MST are included and are shown as stage drive system 124.
Various measurement members are arranged at measurement table MTB (and stage main section 92). As such measurement members, for example, as shown in FIG. 2B, members such as an uneven illuminance measuring sensor 94 that has a pinhole-shaped light-receiving section which receives illumination light IL on an image plane of projection optical system PL, an aerial image measuring instrument 96 that measures an aerial image (projected image) of a pattern projected by projection optical system PL, a wavefront aberration measuring instrument 98 by the Shack-Hartman method that is disclosed in, for example, the pamphlet of International Publication No. 2003/065428, an illuminance monitor (not shown) and the like are employed. Further, in stage main section 92, a pair of photodetection systems (not shown) is arranged in a placement facing the pair of light-transmitting systems (not shown) previously described. In the embodiment, in a state where wafer stage WST and measurement stage MST are in proximity within a predetermined distance in the Y-axis direction (including a contact state), illumination lights IL that has been transmitted through each aerial image measurement slit pattern SL of measurement plate 30 on wafer stage WST are guided by each light-transmitting system (not shown) and are received by light-receiving elements of each photodetection system (not shown) within measurement stage MST.
On the −Y side end surface of measurement table MTB, a fiducial bar (hereinafter, shortly referred to as an “FD bar”) 46 is arranged extending in the X-axis direction, as shown in FIG. 2B. In the vicinity of the end portions on one side and the other side in the longitudinal direction of FD bar 46, a reference grating (for example, a diffraction grating) 52 whose periodic direction is the Y-axis direction is respectively formed, placed symmetric to a center line CL. Further, on the upper surface of FD bar 46, a plurality of reference marks M is formed. As each of reference marks M, a two-dimensional mark having a size that can be detected by a primary alignment system and secondary alignment systems (to be described later) is used. Incidentally, the surface of FD bar 46 and the surface of measurement table MTB are also covered with a liquid repellent film (water repellent film).
On the +Y end surface and the −X end surface of measurement table MTB, reflection surfaces 19a and 19b are formed similar to wafer table WTB as is previously described (refer to FIG. 2B).
In exposure apparatus 100 of the embodiment, a primary alignment system AL1 having a detection center at a position spaced apart from optical axis AX of projection optical system PL at a predetermined distance on the −Y side is placed on reference axis LV previously described as shown in FIGS. 4 and 5. Primary alignment system AL1 is fixed by the lower surface of a (not shown) mainframe. On one side and the other side in the X-axis direction with primary alignment system AL1 in between, secondary alignment systems AL21 and AL22, and AL23 and AL24 whose detection centers are substantially symmetrically placed with respect to straight line LV are severally arranged. Secondary alignment systems AL21 to AL24 are fixed via a movable support member to the lower surface of the mainframe (not shown), and by drive mechanisms 601 to 604 (refer to FIG. 7), their detection areas (or detection center) can be driven independently in the X-axis direction. Accordingly, the relative positions of the detection areas of primary alignment system AL1 and secondary alignment systems AL21, AL22, AL23 and AL24 are adjustable in the X-axis direction. Incidentally, a straight line (a reference axis) LA which passes through the detection center of primary alignment system AL1 and is parallel to the X-axis shown in FIG. 4 and the like coincides with the optical axis of a measurement beam B6 from interferometer 127 previously described.
In the embodiment, as each of alignment systems AL1 and AL21 to AL24 for example, an FIA (Field Image Alignment) system by an image processing method is used. The imaging signals from each of alignment systems AL1 and AL21 to AL24 are supplied to main controller 20, via a signal processing system (not shown).
Incidentally, each of the alignment systems described above is not limited to the FIA system, and an alignment sensor, which irradiates a coherent detection light to a subject mark and detects a scattered light or a diffracted light generated from the subject mark or makes two diffracted lights (for example, diffracted lights of the same order or diffracted lights being diffracted in the same direction) generated from the subject mark interfere and detects an interference light, can naturally be used alone or in combination as needed.
Next, a configuration and the like of interferometer system 118 (refer to FIG. 7), which measures the positional information of wafer stage WST and measurement stage MST, will be described.
Interferometer system 118 includes a Y interferometer 16, X interferometers 126, 127, and 128, and Z interferometers 43A and 43B for position measurement of wafer stage WST, and a Y interferometer 18 and an X interferometer 130 for position measurement of measurement stage MST, as shown in FIG. 3. Y interferometer 16 and the three X interferometers 126, 127, and 128 each irradiate interferometer beams (measurement beams) B4 (B41, B42), B5 (B51, a B52), B6, and B7 on reflection surfaces 17a and 17b of wafer table WTB. And Y interferometer 16 and the three X interferometers 126, 127, and 128 each receive the reflected lights, and measure the positional information of wafer stage WST in the XY plane, and supply the positional information which has been measured to main controller 20.
Incidentally, for example, X interferometer 126 irradiates at least three measurement beams parallel to the X-axis including a pair of measurement beams B51 and B52 which passes through optical axis (in the embodiment, also coinciding with the center of exposure area IA previously described) AX of projection optical system PL and is symmetric about a straight line (reference axis LH (refer to FIGS. 4, 5 and the like)) parallel to the X-axis. Further, Y interferometer 16 irradiates at least three measurement beams parallel to the Y-axis including a pair of measurement beams B41 and B42 which is symmetric about reference axis LV previously described on reflection surface 17a and a movable mirror 41 (to be described later on). As described, in the embodiment, as each interferometer, a multiaxial interferometer which a plurality of measurement axis is used, with an exception for a part of the interferometers (for example, interferometer 128). Therefore, in addition to the X, Y positions of wafer table WTB (wafer stage WST), main controller 20 can also compute rotation information (that is, pitching amount) in the θx direction, rotation information (that is, rolling amount) in the θy direction, and rotation information (that is, yawing amount) in the θz direction, based on the measurement results of Y interferometer 16 and either X interferometers 126 or 127.
Further, as shown in FIG. 1, movable mirror 41 having a concave-shaped reflection surface is attached to the side surface on the −Y side of stage main section 91. As it can be seen from FIG. 2A, movable mirror 41 is designed so that the length in the X-axis direction is longer than reflection surface 17a of wafer table WTB.
A pair of Z interferometers 43A and 43B are arranged (refer to FIGS. 1 and 3), facing movable mirror 41. Z interferometers 43A and 43B irradiate two measurement beams B1 and B2, respectively, on fixed mirrors 47A and 47B, which are fixed, for example, on a frame (not shown) supporting projection unit PU, via movable mirror 41. And by receiving each reflected light, Z interferometers 43A and 43B measure the optical path length of measurement beams B1 and B2. And from the results, main controller 20 computes the position of wafer stage WST in four degrees of freedom (Y, Z, θy, and θz) directions.
In the embodiment, position information within the XY plane (including the rotation information in the θz direction) of wafer stage WST (wafer table WTB) is mainly measured by an encoder system (to be described later). Interferometer system 118 is used when wafer stage WST is positioned outside the measurement area (for example, near unloading position UP and loading position LP as shown in the drawings such as FIG. 4) of the encoder system. Further, interferometer system 118 is used secondarily when correcting (calibrating) a long-term variation (for example, temporal deformation of the scale) of the measurement results of the encoder system and the like. As a matter of course, all positional information of wafer stage WST (wafer table WTB) can be measured using both interferometer system 118 and the encoder system together.
Y interferometer 18 and X interferometer 130 of interferometer system 118 irradiate interferometer beams (measurement beams) on reflection surfaces 19a and 19b of measurement table MTB as shown in FIG. 3, and measure the positional information of measurement stage MST (including, for example, at least the positional information in the X-axis and the Y-axis directions and the rotation information in the θz direction) by receiving the respective reflected lights, and supply the measurement results to main controller 20.
Next, the structure and the like of encoder system 150 (refer to FIG. 7) which measures the positional information of wafer stage WST in the XY plane (including rotation information in the θz direction) will be described.
In exposure apparatus 100 of the embodiment, as shown in FIG. 4, four head units 62A to 62D are placed in a state extending from nozzle unit 32 in four directions. These head units 62A to 62D are fixed to the mainframe (not shown) holding projection unit UP in a suspended state, via a support member.
Head units 62A and 62C are equipped with a plurality of (nine, in this case) Y heads 651 to 659 and 641 to 649, as shown in FIG. 5, respectively. In detail, head units 62A and 62C are equipped with a plurality of (seven, in this case) Y heads 653 to 659 and 641 to 647 placed at a distance WD on reference axis LH previously described, respectively, and a plurality of (two, in this case) Y heads 651 and 652, and 648 and 649 placed at distance WD a predetermined distance away from reference axis LH in the −Y direction on the −Y side of nozzle unit 32 in parallel with reference axis LH, respectively. Incidentally, the distance between Y heads 652 and 653 and Y heads 647 and 648 in the X-axis direction is also set to WD. Hereinafter, Y heads 651 to 659 and 641 to 649 will also be described as Y heads 65 and 64, respectively, as necessary.
Head unit 62A constitutes a multiple-lens (nine-lens, in this case) Y linear encoder (hereinafter, shortly referred to as a “Y encoder” or an “encoder” as appropriate) 70A (refer to FIG. 7) that measures the position of wafer stage WST (wafer table WTB) in the Y-axis direction (Y position), using Y scale 39Y1 previously described. Similarly, head unit 62C constitutes a multiple-lens (nine-lens, in this case) Y linear encoder 70C (refer to FIG. 7) that measures the Y position of wafer stage WST (wafer table WTB) using Y scale 39Y2 described above. In this case, distance WD in the X-axis direction of the nine Y heads 64 and 65 (to be more accurate, the irradiation points of the measurement beams generated by Y heads 65 and 64 on the scale) that head units 62A and 62C are each equipped with, is set slightly narrower than the width (to be more precise, the length of grid line 38) of Y scales 39Y1 and 39Y2 in the X-axis direction. Accordingly, of each nine Y heads 65 and 64, at least two heads each constantly face the corresponding Y scales 39Y1 and 39Y2 at the time of the exposure. More specifically, of the measurement beams which each nine Y heads 65 and 64 generate, at least two measurement beams each can be irradiated on the corresponding Y scales 39Y1 and 39Y2.
As shown in FIG. 5, head unit 62B is placed on the +Y side of nozzle unit 32 (projection unit PU), and is equipped with a plurality of, in this case, seven X heads 668 to 6614 that are placed on reference axis LV previously described along Y-axis direction at distance WD. Further, head unit 62D is placed on the −Y side of primary alignment system AL1, on the opposite side of head unit 62B via nozzle unit 32 (projection unit PU), and is equipped with a plurality of, in this case, seven X heads 661 to 667 that are placed on reference axis LV at distance WD. Hereinafter, X heads 661 to 6614 will also be described as X heads 66, as necessary.
Head unit 62B constitutes a multiple-lens (seven-lens, in this case) X linear encoder (hereinafter, shortly referred to as an “X encoder” or an “encoder” as needed) 70B (refer to FIG. 7) that measures the position in the X-axis direction (the X-position) of wafer stage WST (wafer table WTB) using X scale 39X1 previously described. Further, head unit 62D constitutes a multiple-lens (seven-lens, in this case) X linear encoder 70D (refer to FIG. 7) that measures the X-position of wafer stage WST (wafer table WTB) using X scale 39X2 previously described.
Here, distance WD between adjacent X heads 66 (to be more accurate, the irradiation point of the measurement beam generated by X head 66 on the scale) in the Y-axis direction that are equipped in each of head units 62B and 62D is set shorter than half the width of X scales 39X1 and 39X2 (to be more accurate, the length of grid line 37) in the Y-axis direction. Accordingly, of the X heads 66 which head units 62B and 62D are equipped with, at least two heads face the corresponding X scales 39X1 and 39X2 at the time of the exposure and the like, except for times such as switching (linkage) which will be described later. More specifically, of the measurement beams which each seven X heads 66 generate, at least two measurement beams each can be irradiated on the corresponding X scales 39X1 and 39X2. Incidentally, the distance between X head 668 farthest to the −Y side of head unit 62B and X head 667 farthest to the +Y side of head unit 62D is set slightly narrower than the width of wafer table WTB in the Y-axis direction so that switching (linkage described below) becomes possible between the two X heads by the movement of wafer stage WST in the Y-axis direction.
Incidentally, in the placement of X head 66 in the embodiment, on the switching (linkage) described above, only X head 668 farthest to the −Y side among X heads 66 belonging to head unit 62B faces the corresponding X scale 39X1, and only X head 667 farthest to the +Y side among X heads 66 belonging to head unit 62D faces the corresponding X scale 39X2. More specifically, only one each of the X heads 66 faces X scales 39X1 and 39X2. Therefore, the distance between head unit 62B and 62D can be narrower than distance WD, and at least one of X heads 666 and 669 can be made to face the corresponding X scales at the same time, as well as X head 668 and X head 667 which face the corresponding X scales also at the time of switching (linkage).
In the embodiment, furthermore, as shown in FIG. 4, head units 62E and 62F are respectively arranged a predetermined distance away on the −Y side of head units 62C and 62A. These head units 62E and 62F are fixed to the mainframe (not shown) holding projection unit UP in a suspended state, via a support member.
Head unit 62E is equipped with seven Y heads 671 to 677, as shown in FIG. 5. More particularly, head unit 62E is equipped with five Y heads 671 to 675 placed on the −X side of the secondary alignment system AL21 on reference axis LA at substantially the same distance as distance WD previously described, and two Y heads 676 and 677 placed on the +Y side of the secondary alignment system AL21 a predetermined distance away in the +Y direction from reference axis LA, at distance WD parallel to reference axis LA. Incidentally, the distance between Y heads 675 and 676 in the X-axis direction is also set to WD. Hereinafter, Y heads 671 to 677 will also be described, appropriately, as Y head 67.
Head unit 62F is symmetrical to head unit 62E with respect to reference axis LV previously described, and is equipped with seven Y heads 681 to 687 which are placed in symmetry to the seven Y heads 67 with respect to reference axis LV. Hereinafter, Y heads 681 to 687 will also be described, appropriately, as Y head 68.
On alignment operation and the like, at least two each of Y heads 67 and 68 face Y scales 39Y2 and 39Y1, respectively. More specifically, of the measurement beams which each seven Y heads 67 and 68 generate, at least two measurement beams each can be constantly irradiated on Y scales 39Y1 and 39X2 at the time of alignment and the like. The Y position (and θz rotation) of wafer stage WST is measured by these Y heads 67 and 68 (more specifically, Y encoders 70E and 70F configured by Y heads 67 and 68).
Further, in the embodiment, at the time of baseline measurement and the like of the secondary alignment system, Y head 675 and 683 which are adjacent to the secondary alignment systems AL21 and AL24 in the X-axis direction face the pair of reference gratings 52 of FD bar 46, respectively, and by Y heads 675 and 683 that face the pair of reference gratings 52, the Y position of FD bar 46 is measured at the position of each reference grating 52. In the description below, the encoders configured by Y heads 675 and 683 which face a pair of reference gratings 52, respectively, are referred to as Y linear encoders (also shortly referred to as a “Y encoder” or an “encoder” as needed) 70E2 and 70F2. Further, for identification, Y encoders 70E and 70F configured by Y heads 67 and 68 that face Y scales 39Y2 and 39Y1 described above, respectively, will be referred to as Y encoders 70E1 and 70F1.
The measurement values of linear encoders 70A to 70F described above is supplied to main controller 20, and main controller 20 controls the position within the XY plane of wafer stage WST based on three measurement values of linear encoders 70A to 70D or on three measurement values of encoders 70B, 70D, 70E1, and 70F1, and also controls the rotation in the θz direction of FD bar 46 based on the measurement values of linear encoders 70E2 and 70F2.
In exposure apparatus 100 of the embodiment, as shown in FIGS. 4 and 6, a multipoint focal position detecting system (hereinafter, shortly referred to as a “multipoint AF system”) by an oblique incident method is arranged, which is composed of an irradiation system 90a and a photodetection system 90b, having a configuration similar to the one disclosed in, for example, U.S. Pat. No. 5,448,332 and the like. In the embodiment, as an example, irradiation system 90a is placed on the +Y side of the −X end portion of head unit 62E previously described, and photodetection system 90b is placed on the +Y side of the +X end portion of head unit 62F previously described in a state of opposing irradiation system 90a. The multipoint AF system (90a, 90b) is fixed to the lower surface of the mainframe (not shown) holding projection unit PU previously described.
A plurality of detection points of the multipoint AF system (90a, 90b) are placed at a predetermined distance along the X-axis direction on the surface to be detected. In the embodiment, the plurality of detection points are placed, for example, in the arrangement of a matrix having one row and M columns (M is a total number of detection points) or having two rows and N columns (N=M/2). In FIGS. 4 and 6, the plurality of detection points to which a detection beam is severally irradiated are not individually shown, but are shown as an elongate detection area (beam area) AF that extends in the X-axis direction between irradiation system 90a and photodetection system 90b. Because the length of detection area AF in the X-axis direction is set to around the same as the diameter of wafer W, by only scanning wafer W in the Y-axis direction once, position information (surface position information) in the Z-axis direction across the entire surface of wafer W can be measured.
As shown in FIG. 6, in the vicinity of both end portions of beam area AF of the multipoint AF system (90a, 90b), heads 72a and 72b, and 72c and 72d of surface position sensors for Z position measurement (hereinafter, shortly referred to as “Z heads”) are arranged each in a pair, in symmetrical placement with respect to reference axis LV. Z heads 72a to 72d are fixed to the lower surface of a main frame (not shown).
As Z heads 72a to 72d, for example, a head of an optical displacement sensor similar to an optical pickup used in a CD drive device is used. Z heads 72a to 72d irradiate measurement beams to wafer table WTB from above, and by receiving the reflected lights, measure the positional information (surface position information) of the surface of wafer table WTB in the Z-axis direction orthogonal to the XY plane at the irradiation point. Incidentally, in the embodiment, a configuration is employed where the measurement beams of the Z heads are reflected by the reflection grating configuring the Y scales 39Y1 and 39Y2 previously described.
Furthermore, as shown in FIG. 6, head units 62A and 62C previously described are respectively equipped with Z heads 76j and 74i (i, j=1-9), which are nine heads each, at the same X position as Y heads 65j and 64i (i, j=1-9) that head units 62A and 62C are respectively equipped with, with the Y position shifted. In this case, Z heads 765 to 769 and 741 to 745, which are five heads each on the outer side belonging to head units 62A and 62C, respectively, are placed parallel to reference axis LH a predetermined distance away in the +Y direction from reference axis LH. Further, Z heads 761 and 762 and Z heads 748 and 749, which are two heads on the innermost side belonging to head units 62A and 62c, respectively, are placed on the +Y side of projection unit PU, and the remaining Z heads 763 and 764, and 746, and 747 are placed on the −Y side of Y heads 653 and 654, and 646 and 647, respectively. And Z heads 76j and 74i, which are nine heads each belonging to head units 62A and 62C, respectively, are placed symmetric to each other with respect to reference axis LV. Incidentally, as each of the Z heads 76j and 74i, an optical displacement sensor head similar to Z heads 72a to 72d described above is used.
The distance of the nine Z heads 76j and 74i (to be more accurate, the irradiation point of the measurement beam generated by the Z heads on the scale) in the X-axis direction that are equipped in each of head units 62A and 62C is set equal to distance WD of Y heads 65 and 64 in the X-axis direction. Accordingly, similar to Y heads 65 and 64, of each nine Z heads 76j and 74i, at least two heads each constantly face the corresponding Y scales 39Y1 and 39Y2 at the time of the exposure and the like. More specifically, of the measurement beams which each nine Z heads 76j and 74i generate, at least two measurement beams each can be irradiated on the corresponding Y scales 39Y1 and 39Y2.
Z heads 72a to 72d, 741 to 749, and 761 to 769 connect to main controller 20 via a signal processing/selection device 170 as shown in FIG. 7, and main controller 20 selects an arbitrary Z head from Z heads 72a to 72d, 741 to 749, and 761 to 769 via signal processing/selection device 170 and makes the head move into an operating state, and then receives the surface position information detected by the Z head which is in an operating state via signal processing/selection device 170. In the embodiment, a surface position measurement system 180 (a part of measurement system 200) that measures positional information of wafer stage WST in the Z-axis direction and the direction of inclination with respect to the XY plane is configured, including Z heads 72a to 72d, 741 to 749, and 761 to 769, and signal processing/selection device 170.
Furthermore, in exposure apparatus 100, above reticle stage RST, a pair of reticle alignment detection systems 13A and 13B (not shown in FIG. 1, refer to FIG. 7) consisting of TTR (Through The Reticle) alignment systems which use lights of the exposure wavelength is arranged. Detection signals of reticle alignment detection systems 13A and 13B are supplied to main controller 20 via an alignment signal processing system (not shown).
FIG. 7 shows the main configuration of the control system of exposure apparatus 100. The control system is mainly configured of main controller 20 composed of a microcomputer (or workstation) that performs overall control of the entire apparatus. Incidentally, in FIG. 7, various sensors such as uneven illuminance measuring sensor 94, aerial image measuring instrument 96 and wavefront aberration measuring instrument 98 that are arranged at measurement stage MST are collectively shown as a sensor group 99.
In exposure apparatus 100 of the embodiment, because the placement of the X scales and the Y scales on wafer table WTB previously described and the placement of the X heads and the Y heads previously described were employed, as shown in FIGS. 8A and 8B, in the effective stroke range (a range where the stage moves for alignment and exposure operation in the embodiment) of wafer stage WST, Y scales 39Y1 and 39Y2 face Y heads 65 and 64 (head units 62A and 62C) or Y heads 68 and 67 (head units 62F and 62E), while X head 66 (head unit 62B or 62D) also faces one of X scales 39X1 and 39X2 without fail. Incidentally, in FIGS. 8A and 8B, the heads which face the corresponding X scales and Y scales are shown circled by a solid line.
As previously described, at least two heads of each of the head units 62A to 62F constantly face the corresponding scale except for a part of the units (to be more precise, at least two measurement beams can be irradiated on the corresponding scale except for a part of the units). Therefore, main controller 20 pairs at least two heads facing the scale and uses the pairs for each of the head units 62A to 62F. Then, main controller 20 constantly monitors the measurement values of the two heads, and uses one of the measurement values as a representative of the pair of heads (or the head unit to which the two heads belong). Of the two heads, main controller 20, for example, uses the head which faces the scale first as a priority head, and the head which faces the scale later on as an auxiliary head. Or, main controller 20 can use the head near the center of the scale in a direction (the X-axis direction in the case of a Y scale) orthogonal to the longitudinal direction as a priority head, and the remaining head can be used as an auxiliary head. Main controller 20 can normally use the measurement values of the priority head as a representative, and in the case abnormality occurs in the output (measurement value) of the priority head, the measurement values of the auxiliary head can be used as the measurement values of the pair of heads (or head unit). Main controller 20 monitors the measurement values of the six head units according to this handling.
Main controller 20 monitors photoelectric conversion signals output by a light receiving element inside the head to inspect the correctness of the measurement result of the priority head, especially to inspect the output abnormality of the priority head due to malfunction (abnormality) of the head, and when there are no photoelectric conversion signals (when the signal intensity is zero) or when the signal intensity is at an extremely low level, main controller 20 judges that abnormality has occurred, and otherwise decides it is normal.
Therefore, in the effective stroke range of wafer stage WST previously described, by controlling each motor that configures stage drive system 124 based on three measurement values out of encoders 70A to 70D, or on three measurement values out of 70B, 70D, 70E1, and 70F1, positional information (including the rotation information in the θz direction) of wafer stage WST within the XY plane can be controlled with high precision.
Further, when main controller 20 drives wafer stage WST in the X-axis direction as shown by an outlined arrow in FIG. 8A, the pair of Y heads 65 and 64, which measures the position of wafer stage WST in the Y-axis direction, is sequentially switched to an adjacent pair of heads as shown by an arrow e1 in FIG. 8A. To enter the details, as for Y head 65, the pair of heads switched is from the pair 653 and 654 surrounded by the circle in a solid line to the pair 654 and 655 surrounded by the circle in a dotted line, and as for Y head 64, the pair of heads switched is from the pair 643 and 644 surrounded by the circle in a solid line to the pair 644 and 645 surrounded by the circle in a dotted line. In this case, one head (654, 644) is common in the pair of heads before the switching and the pair of heads after the switching.
In the embodiment, in order to perform the switching (linkage) of the Y heads 65 and 64 smoothly, as is previously described, of the Y heads 65 and 64 that head units 62A and 62C are equipped with, the distance (twice the distance WD of adjacent heads) between the two heads to be switched (for example, in the example in FIG. 8A, Y heads 653 and 655, and 643 and 645) is set smaller than the width of Y scales 39Y1 and 39Y2 in the X-axis direction. In other words, distance WD of adjacent Y heads is set it is narrower than half the width of Y scales 39Y1 and 39Y2 in the X-axis direction.
Further, in the case of Sec-BCHK (beginning of lot) described below, when main controller 20 drives wafer stage WST in the X-axis direction, main controller 20 sequentially switches the pair of heads in Y heads 67 and 68 measuring the position of wafer stage WST in the Y-axis direction to the adjacent heads similar to the description above.
Further, in the embodiment, as previously described, because distance WD of adjacent X heads 66 that head units 62B and 62D are equipped with is narrower than half the width of X scales 39X1 and 39X2 in the Y-axis direction, when main controller 20 drives wafer stage WST in the Y-axis direction as shown by an outlined arrow in FIG. 8B, the pair of X heads 66, which measures the position of wafer stage WST in the X-axis direction, is sequentially switched to an adjacent pair of heads as shown by an arrow e2 in FIG. 8B, similar to the description above. To enter the details, the pair of heads is switched from the pair 669 and 6610 surrounded by the circle in a solid line to the pair 668 and 669 surrounded by the circle in a dotted line. In this case, one head 669 is common in the pair of heads before the switching and the pair of heads after the switching.
In the embodiment, a method is employed where the encoder head used for measuring the position of wafer stage WST is switched from a pair of heads (for example, Eh1 and Eh2) to another pair of heads (Eh2 and Eh3) including one of the heads (Eh2), with the movement of wafer stage WST. However, as well as this method, a modified method of switching to another pair of heads (Eh3 and Eh4) which does not include a common head from a certain pair of heads (for example, Eh1 and Eh2) can be adopted. Also in this deformation method, similar to the method described above, the measurement values of the priority head should be used normally, and at the time of abnormality, the measurement values of the auxiliary head should be used representatively as the measurement values of the pair of heads (or the head unit to which these heads belong).
Incidentally, as the cause of abnormality being generated in the measurement values of the encoder, there is two major causes, that is, a cause coming from malfunction of the encoder head (head), and a cause coming from abnormality in the scale on which the measurement beam is irradiated. As an example of the former case, a mechanical failure of the head can be representatively given. To be concrete, a failure in the head itself, a failure in the measurement beam light source, a situation where water droplets adhere on the head and the like can be given. A situation where the intensity of the measurement beam becomes extremely low, if not the measurement beam light source fails to operate, can be said to be a cause coming from the head. Meanwhile, as an example of the latter case, the case can be given in which the liquid of the liquid immersion area remains or foreign materials such as dust and the like adheres on the scale surface, and the measurement beam scans the remaining liquid or the adhered foreign material.
The method in the embodiment in which a pair of heads configured by a priority head and an auxiliary head is made to constantly face at least one corresponding scale is effective to abnormality of the measurement values due to malfunction of the heads, and is also effective to abnormality of the measurement values due to abnormality in the scales.
Incidentally, because the optical path length of the two beams which are made to interfere is extremely short and substantially equal in encoders 70A to 70F used in the embodiment, the influence of air fluctuation can be almost ignored. The resolution of each encoder, for example, is around 0.1 nm.
Next, a baseline measurement (hereinafter, also appropriately referred to as Sec-BCHK (beginning of lot)) of the secondary alignment system AL2n (n=1-4) will be described, which is mainly performed just before (beginning of lot) starting the processing to the wafer of the lot. In this case, the base line of the secondary alignment system AL2n means the relative position of each (detection center of) secondary alignment system AL2n with (the detection center of) primary alignment system AL1 serving as a reference. Incidentally, the secondary alignment system AL2n (n=1-4) has the position in the X-axis direction set, for example, according to a shot map data of the wafer within the lot.
a. On Sec-BCHK (beginning of lot), first of all, main controller 20 detects a specific alignment mark on wafer W (a process wafer) at the beginning of the lot using primary alignment system AL1 as shown in FIG. 9A (refer to the star mark in FIG. 9A), makes a link between the detection results and the measurement values of encoders 70A, 70E1, and 70F1 at the time of the detection, and then stores them in memory. In the state shown in FIG. 9A, main controller 20 controls the position of wafer stage WST within the XY plane, based on two pairs of Y heads 683 and 684, and 674 and 675 (encoders 70E1 and 70F1) surrounded by a black line circle facing Y scales 39Y1 and 39Y2, respectively, and a pair of X heads 663 and 664 (encoder 70D) surrounded by a black line circle facing X scale 39X2.
b. Next, main controller 20 moves wafer stage WST in the −X direction by a predetermined distance, and detects (refer to the star mark in FIG. 9B) the specific alignment mark described above using the secondary alignment system AL21 as shown in FIG. 9B, makes a link between the detection results and the measurement values of encoders 70E1, 70F1, and 70D at the time of detection, and then stores them in memory. In the state shown in FIG. 9B, main controller 20 controls the position of wafer stage WST within the XY plane, based on two pairs of Y heads 681 and 682, and 671 and 672 (encoders 70E1 and 70F1) surrounded by a black line circle facing Y scales 39Y1 and 39Y2, respectively, and a pair of X heads 663 and 664 (encoder 70D) surrounded by a black line circle facing X scale 39X2.
c. Similarly, main controller 20 sequentially moves wafer stage WST in the +X direction, and sequentially detects the specific alignment mark described above using the remaining secondary alignment systems AL22, AL23, and AL24, makes a link between the detection results and the measurement values of encoders 70E1, 70F1, and 70D at the time of detection, and then stores them in memory.
d. Then, based on the processing results of paragraph a. above and the processing results of paragraph b. or c. above, main controller 20 respectively computes the base line of each secondary alignment system AL2n.
As described, by detecting the same alignment mark with primary alignment system AL1 and each secondary alignment system AL2n using wafer W (the process wafer) in the beginning of the lot, the baseline of each secondary alignment system AL2n is obtained, and by this processing, a difference of the detection offset between the alignment systems due to the process is also consequently corrected.
In the embodiment, because head units 62E and 62F are each equipped with seven Y heads 67 and 68 whose positions are different in the X-axis direction, when measuring the baseline of each secondary alignment system AL2n described above, in the case of detecting the specific alignment mark on the wafer using any one of the secondary alignment systems AL2n, as well as primary alignment system AL1, the Y position of wafer stage WST at the time of the detection and the θz rotation can be measured and controlled, based on the measurement values of the pair of Y heads 68 and 67 (encoders 70F1 and 70E1), facing Y scales 39Y1 and 39Y2. Further, at this point, the X position of wafer stage WST can be measured ad controlled, based on the measurement values of the pair of X heads 66 (encoder 70D) facing X scale 39X2.
Incidentally, instead of the alignment mark on the wafer, for example, fiducial mark FM of measurement plate 30 on wafer stage WST, or reference mark M of FD bar 46 on measurement stage MST can be used, to perform baseline measurement of the secondary alignment system AL2n.
In exposure apparatus 100 of the embodiment, a parallel processing operation using wafer stage WST and measurement stage MST is performed, basically in the same procedure as the exposure apparatus disclosed in the embodiment of the pamphlet of International Publication 2007/097379 previously described. Because this parallel processing operation is similar to the exposure apparatus disclosed in the embodiment of the pamphlet of International Publication 2007/097379 previously described except for the following two points, a detailed description will be omitted.
The first point is, when abnormality occurs in the output of one of the priority heads (the X head or the Y head) used for position measurement of the encoder system which measures the positional information of wafer stage WST in the case wafer stage WST is in the effective stroke area previously described, main controller 20 uses the measurement values of the auxiliary head which configures a pair of heads with the priority head as is previously described as the measurement values of the pair of heads (or the head unit to which the two heads belong).
The second point is, for example, at the time of stepping operation between shots of wafer stage WST on the exposure operation by the step-and-scan method, a switching of heads is performed by a switching method in which the encoder head used for measuring, for example, the X position of wafer stage WST is switched from a pair of heads (for example, Eh1 and Eh2) to another pair of heads (Eh2 and Eh3) which include one of the heads (Eh2).
As described above, according to exposure apparatus 100 of the embodiment, because two or more corresponding Y heads constantly face Y scales 39Y1 and 39Y2 arranged on wafer stage WST when wafer stage WST is in the effective stroke area previously described, main controller 20 can constantly measure the positional information of wafer stage WST in the periodic direction (Y-axis direction) of the grating section of Y scales 39Y1 and 39Y2 and rotation information in the θz direction, using at least one of the measurement results of the two Y heads. Further, when wafer stage WST is in the effective stroke area previously described, two or more corresponding X heads constantly face either one of X scales 39X1 and 39X2 arranged on wafer stage WST, except for some exceptional cases (in the case wafer stage WST is located at a position where X head 668 of head unit 62B and X head 667 of head unit 62D can be switched). Accordingly, main controller 20 can constantly measure the positional information of wafer state WST in the periodic direction (X-axis direction) of the grating section of Y scales 39Y1 and 39Y2, by using least one of the measurement results of the two X heads.
Further, in the case abnormality (or abnormality due to the abnormality of the scale) due to the abnormality of the head occurs in the measurement information of the priority head of at least the two heads located in the effective area (a grating section) on each scale, main controller 20 switches the measurement information used in position control of wafer stage WST from the measurement information obtained by the priority head to the measurement information from the auxiliary head. By this switching, it becomes possible to securely measure the positional information of wafer stage WST in the periodic direction of the grating section which each scale has.
Further, according to the exposure apparatus of the embodiment, encoder system 150 included in measurement system 200 has seven Y heads 67 and 68 whose positions are different in the X-axis direction and configure a part of head units 62E and 62F, respectively, placed on the outer sides of both the detection area of primary alignment system AL1 and the detection area of secondary alignment system AL21 to AL24. And, on alignment and the like, main controller 20 measures the positional information of wafer stage WST in the Y-axis direction (and positional information in the θz direction), based on measurement values of a pair of Y heads 68 and 67 (Y linear encoders 70F1 and 70E1) which face the pair of Y scales 39Y1 and 39Y2, respectively.
Therefore, for example, on Sec-BCHK (beginning of lot) previously described, also in the case when main controller 20 moves wafer stage WST in the X-axis direction in order to detect the specific alignment marks (or fiducial mark FM on wafer stage WST) on wafer W held by wafer stage WST using each of primary alignment system AL1 and the secondary alignment systems AL21 to AL24, in and the like, it becomes possible to measure at least the position of wafer stage WST in the Y-axis direction (and rotation in the θz direction) by Y linear encoders 70E1 and 70F1 whose short-term stability of measurement is good. Accordingly, based on detection results of alignment systems AL1, and AL21 to AL24 and the measurement values of Y linear encoder 70E1 and 70F1 at the time of the detection, main controller 20 can obtain the positional information of the mark (the specific alignment mark (or fiducial mark FM on wafer stage WST) in the Y-axis direction with good precision. Further, the position of wafer stage WST in the X-axis direction in case of Sec-BCHK (beginning of lot) is measured by the pair of X heads 66 (encoder 70D) which faces X scale 39X2. Accordingly, the base line (the X-axis direction and the Y-axis direction) of secondary alignment systems AL21 to AL24, can be obtained with high accuracy at the beginning of every lot.
Further, in the embodiment, the baseline of the secondary alignment systems AL21 to AL24 (the X-axis direction and the Y-axis direction) is measured (at each wafer exchange) at predetermined intervals.
And, by repeating a movement operation between shots in which wafer stage WST is moved to a scanning starting position (acceleration starting position) for exposure of each shot area on wafer W and a scanning exposure operation in which a pattern formed on reticle R is transferred onto each shot area by a scanning exposure method, based on the latest baseline obtained in such a manner and the results of wafer alignment (EGA), it becomes possible to transfer the pattern of reticle R on the plurality of shot areas on wafer W with good precision (overlay accuracy). Furthermore, in the embodiment, because a high-resolution exposure can be realized by liquid immersion exposure, a fine pattern can be transferred with good precision on wafer W also from this viewpoint.
Further, according to exposure apparatus 100 of the embodiment, of each of the seven Y heads 67 and 68 which are equipped in head units 62E and 62F, the two Y heads 676 and 677, and 681 and 682 located on the innermost side have positions different from the other Y heads in the Y-axis direction. This allows the two Y heads 676 and 677, and 681 and 682 located on the innermost side to be placed in an empty space in the periphery of alignment systems AL1, and AL21 to AL24, or more specifically, to be placed in accordance with the placement of alignment systems AL1, and AL21 to AL24.
Further, because the distance of each of the seven Y heads 67 and 68 which are equipped in head units 62E and 62F, respectively, in the X-axis direction is narrower than half the width (to be more precise, the length of grid line 38) of Y scales 39Y1 and 39Y2 in the X-axis direction, when wafer stage WST moves in the X-axis direction, the pair of Y heads used for measuring the positional information of wafer stage WST in the Y-axis direction is switched to an adjacent pair of Y heads (however, one of the heads of the pair of Y heads is in common with the preceding pair of heads) without any problems, and the measurement values are succeeded before and after the switching. Accordingly, on Sec-BCHK and the like described above, at least two each of Y heads 67 and 68 face Y scales 39Y2 and 39Y1, respectively, and by the pair of Y heads 67 and 68 (that is, Y encoders 70E1 and 70F1 configured by the pair of Y heads 67 and 68), the Y position (and θz rotation) of wafer stage WST is measured.
Further, at the time of detection of the alignment mark on wafer W by alignment systems AL1, and AL21 to AL24, main controller 20 selects two each of Y heads 67 and 68 which respectively face Y scales 39Y2 and 39Y1 from each of the seven Y heads 67 and 68 of head units 62E and 62F, as well as selects two X heads 66 which face the corresponding X scales 39X1 and 39X2 from a plurality of X heads 66 of head units 62B and 62D, and based on the measurement values of the two pair of Y heads that have been selected and the measurement values of the pair of X heads that have been selected, main controller 20 controls the position of wafer stage WST in the XY plane and rotation (θz rotation).
Modified Example
Incidentally, in the embodiment above, two encoder heads (heads) were constantly made to face a common scale to measure positional information of wafer stage WST in the XY movement plane in a stable manner and with high accuracy. And, of a pair of heads consisting of the two heads, measurement values of a priority head was used, and in the case abnormality was generated in the measurement value of the priority head due to malfunction of the head (or abnormality of the scale), measurement values of the other auxiliary head was to be used. However, as well as this, as a measurement method constantly using the two heads, which are the priority head and the auxiliary head, various modified examples can be considered.
Some representative examples will be shown below, which are modified examples, referring to FIGS. 10A to 12. Incidentally, in FIG. 10A to FIG. 12, scale SY (more specifically, the wafer stage) is to be moved in the −X direction. Further, scale SY is to be indicated as a Y scale, and the head is to be indicated as a Y head.
As a first modified example, two heads, which are a priority head and an auxiliary head, can be made into a set (to be referred to as a head set), and an example where at least one set is constantly made to face the scale can be given. In this first modified example, as shown in FIG. 10A, a head set Hs1 consisting of two heads Eh1 and Eh2 placed close to the longitudinal direction (the Y-axis direction) of scale SY, and another head set Hs2 consisting of two heads Eh3 and Eh4 placed close to the Y-axis direction face one scale, SY. In this first modified example, a plurality of head sets is prepared, configured of two heads in proximity to the Y-axis direction, and these head sets are placed in parallel with the X-axis direction at a distance smaller than the effective width of scale SY. Accordingly, one head set will constantly face scale SY.
When scale SY (more specifically, the wafer stage) moves in the −X direction from the state shown in FIG. 10A, head set Hs1 moves off of scale SY. To be more precise, irradiation points of measurement beams outgoing from the two heads Eh1 and Eh2 constituting head set Hs1, or more specifically, measurement points of heads Eh1 and Eh2 move off from an effective area of scale SY. Therefore, before head set Hs1 moves off from scale SY, main controller 20 switches the head set controlling the stage position from head set Hs1 to head set Hs2.
This first modified example is effective to abnormality of the measurement values due to malfunction of the heads previously described, and is also effective to abnormality of the measurement values due to abnormality in the scales.
A second modified example following the first modified example described above is shown in FIG. 10B. As it can be seen when comparing FIGS. 10B and 10A, in the first modified example, a configuration was employed where the two heads configuring the head set each scanned a different measurement point, whereas in the second modified example, a configuration is employed where the two heads configuring the head set scan the same measurement point. Accordingly, in the first modified example, the two heads show different measurement values, whereas in the second modified example, the two heads normally show measurement values equal to each other. By employing the configuration in the second modified example, even if abnormality occurs in the measurement values of a priority head due to mechanical failure and the like in the priority head, which is one of the two heads configuring the head set, the normal measurement values of the other head, or the auxiliary head, can be used as the measurement values of the head set. Accordingly, abnormality is not detected in the measurement results as the head set.
Incidentally, the difference in the second modified example and the first modified example is only whether the position of the measurement point of the two heads configuring the head set is the same or not. Accordingly, the placement of each head set and the individual heads configuring each head set in the second modified example should be set in a similar manner as the first modified example. By this arrangement, the procedure of the switching process also becomes the same.
In the first and second modified examples described above, the two heads configuring the head set is placed in parallel in the periodic direction (the Y-axis direction) of the scale. In correspondence with these examples, an example can also be considered where the placement is in parallel in a direction (the X-axis direction) orthogonal to the periodic direction of the scale.
FIG. 11A shows a third modified example, in correspondence with the first modified example in FIG. 10A. In the third modified example, similar to the first modified example, two heads, which are a priority head and a auxiliary head, are made into a set, and at least one set is constantly made to face the scale. However, in FIG. 11A, it is different from the first modified example, and a head set Hs1 consisting of two heads Eh1 and Eh2 placed close to the effective width direction (the X-axis direction) of scale SY, and another head set Hs2 consisting of two heads Eh3 and Eh4 placed close to the X-axis direction face one scale, SY. In this third modified example, a plurality of head sets is prepared, configured of two heads in proximity to the X-axis direction, and these head sets are placed in parallel with the X-axis direction so that one head set constantly faces scale SY. However, the distance of two adjacent head sets, is set to a distance so that the irradiation points (measurement points) of the measurement beams outgoing from (all four heads configuring) the two head sets are located within the effective area of scale SY, as shown in FIG. 11A.
When scale SY (more specifically, the wafer stage) moves in the −X direction from a state shown in FIG. 11A, the measurement point of head Eh1 moves off from the effective area of scale SY. If, supposing that head Eh1 was chosen as the priority head of head set Hs1, the main controller 20 switches the priority head to head Eh2 at a point in time when head EH1 moves off from scale SY. Furthermore, when scale SY moves in the −X direction, then the measurement point of head Eh2 moves off from scale SY. Therefore, by this point in time at the latest, or more specifically, before the measurement point of both heads Eh1 and Eh2 configuring head set Hs1 moves off from scale SY, the head set controlling the stage position is switched from head set Hs1 to head set Hs2.
This third modified example, similar to the first modified example, is effective not only to abnormality of the measurement values due to malfunction of the heads previously described, but is also effective to abnormality of the measurement values due to abnormality in the scales.
A fourth modified example following the third modified example described above is shown in FIG. 11B. As it can be seen when comparing FIGS. 11B and 11A, in the third modified example, a configuration was employed where the two heads configuring the head set each scanned a different measurement point, whereas in the fourth modified example, a configuration is employed where the same measurement point is scanned. Accordingly, in the third modified example, the two heads show different measurement values, whereas in the fourth modified example, the two heads normally show measurement values equal to each other. By the configuration in the fourth modified example, even if abnormality occurs in the measurement values of a priority head of the two heads configuring the head set due to mechanical failure and the like in the priority head, the normal measurement values of the other head, or the auxiliary head, can be used, therefore, abnormality is not detected in the measurement results as the head set.
Incidentally, the difference in the fourth modified example and the third modified example is only whether the position of the measurement point of the two heads configuring the head set is the same or not. Accordingly, the placement of each head set and the individual heads configuring each head set in the fourth modified example should be set in a similar manner as the third modified example. By this arrangement, the procedure of the switching process also becomes the same.
Further, as is obvious when comparing FIGS. 11B and 10B, since the fourth modified example and the second modified example are different merely regarding the proximity direction of the two heads which configure the head set, the effect that can be obtained is the same.
Further, in the third modified example in FIG. 11A, the distance of two adjacent head sets, was set to a distance so that the irradiation points (measurement points) of the measurement beams outgoing from (all four heads configuring) the two head sets were located within the effective area of scale SY. However, by reason of the switching process of the headset, the placement distance of the two adjacent headsets can be set to a placement distance in which the two heads (Eh3, Eh4) configuring one head set (Hs2) and one of the heads (Eh2) of the two heads (Eh1, Eh2) configuring the other head set (Hs1), or three heads (Eh2, Eh3, and Eh4), face scale SY, as shown in FIG. 12.
Incidentally, in the four modified examples, while a head set consisting of one priority head and one auxiliary head was used, the number of auxiliary heads is not limited to one, and a plurality of auxiliary heads can be arranged. In the case of employing such a configuration, reliability of the measurement results improves because more measurement data can be detected. Further, in the case the plurality of heads within the head set are observed to be at the same position in the transverse direction (the X-axis direction in the modified examples) of the scale as in the four modified examples, priority cannot be given according to the guidelines such as, “priority given to the head which becomes effective first,” or “priority given to the head closer to the scale center.” Accordingly, it is desirable to decide a fixed priority order in the headset in advance.
Incidentally, the configuration of each measurement device such as the encoder system described in the embodiment above is only an example, and it is a matter of course that the present invention is not limited to this. Further, in the embodiment above, an example has been described where the encoder system is employed that has a configuration where a grid section (a Y scale and an X scale) is arranged on a wafer table (a wafer stage), and X heads and Y heads facing the grid section are placed external to the wafer stage, however, the present invention is not limited to this, and as is disclosed in, for example, U.S. Patent Application Publication No. 2006/0227309, an encoder system which is configured having an encoder head arranged on the wafer stage and has a two-dimensional grid (or a linear grid section having a two-dimensional placement) facing the encoder heads placed external to the wafer stage can also be adopted. In this case, at least two encoder heads can be arranged on a plurality of places on the wafer stage, for example, on the four corners, and with one of the at least two encoder heads serving as a priority head and the remaining at least one encoder head serving as an auxiliary head, position control of the wafer stage can be performed similarly as in the embodiment and the modified examples above. Incidentally, the at least two encoder heads can be placed in proximity on the wafer stage, or can be placed a predetermined distance apart. Especially in the latter case, the heads can be placed along a radiation direction from the center of the wafer stage. Further, because the grating surface of the two-dimensional grid and the like arranged external to the wafer stage faces downward, it is considered that the liquid of the liquid immersion area will not remain and foreign materials such as dust and the like will not adhere on the surface. Accordingly, because abnormality of the encoder head output due to the abnormality of the scale does not have to be considered, the controller which performs the switching of the heads can decide to monitor only the output abnormality of the priority head due to the malfunction of the head.
Further, in the embodiment and the modified examples above, while the case has been described where the encoder head and the Z head were separately arranged, every encoder head can have a Z head, or each encoder head can be equipped with a Z head, or each encoder head can be a head (sensor) that can perform position detection in two directions, which are the X-axis or Y-axis direction, and the Z-axis direction. Especially in the former case, the encoder head and the Z head can be integrally arranged.
Further, in the embodiment and the modified examples above, malfunction (abnormality) of the encoder head includes gradient of the head or loss of telecentricity, besides mechanical failure. Further, in the case of the type of encoder system which has a head arranged on the stage and a scale arranged above the head, the case when foreign materials (including, for example, the liquid for liquid immersion) adhere on the head is included in the abnormality (malfunction) of the encoder head. Further, not only in the case when the position becomes unmeasurable, but the case when the measurement accuracy exceeds a permissible value (the output (intensity) of the encoder head results to be outside the permissible range) is also included in the abnormality of the encoder head.
Further, in the embodiment above, while the case has been described where head units 62E and 62F each are equipped with seven Y heads, the number is not an issue as long as there are Y heads arranged on both sides of a plurality of mark detection systems (in the embodiment above, alignment systems AL1, and AL21 to AL24). The important thing is that in each of the plurality of mark detection systems, at least two or more each of Y heads 68 and 67 are to face a pair of Y scales 39Y1 and 39Y2 when detecting the specific alignment mark on wafer W. Further, in the embodiment above, while the case has been described where the Y position of the two Y heads which were located innermost among the plurality of Y heads arranged on both of the outer sides of the plurality of mark detection systems were different from the other Y heads, the Y position of any other Y heads can also be different. The important thing is, the Y position of an arbitrary Y head should be different from the Y position of other Y heads, in correspondence with the empty space. Or, in the case there is enough empty space on both of the outer sides of the plurality of mark detection systems, all the Y heads can be placed at the same Y position.
Further, the number of mark detection systems (alignment systems) is not limited to five, and while it is desirable that two or more mark detection systems whose position of the detection area is different in a second direction (the X-axis direction in the embodiment above), the number is not an issue in particular.
Incidentally, in the embodiment above, while the lower surface of nozzle unit 32 and the lower end surface of the tip optical element of projection optical system PL were substantially flush, as well as this, for example, the lower surface of nozzle unit 32 can be placed nearer to the image plane (more specifically, to the wafer) of projection optical system PL than the outgoing surface of the tip optical element. That is, the configuration of local liquid immersion device 8 is not limited to the configuration described above, and the configurations which are described in, for example, EP Patent Application Publication No. 1420298, U.S. Patent Application Publication 2006/0231206, U.S. Patent Application Publication 2005/0280791, and U.S. Pat. No. 6,952,253 and the like can also be used. Further, as disclosed in, for example, U.S. Patent Application Publication No. 2005/0248856, the optical path on the object plane side of the tip optical element can also be filled with liquid, in addition to the optical path on the image plane side of the tip optical element. Furthermore, a thin film that is lyophilic and/or has dissolution preventing function may also be formed on the partial surface (including at least a contact surface with liquid) or the entire surface of the tip optical element. Incidentally, quartz has a high affinity for liquid, and also needs no dissolution preventing film, while in the case of fluorite, at least a dissolution preventing film is preferably formed.
Incidentally, in the embodiment above, pure water (water) was used as the liquid, however, it is a matter of course that the present invention is not limited to this. As the liquid, a chemically stable liquid that has high transmittance to illumination light IL and is safe to use, such as a fluorine-containing inert liquid can be used. As the fluorine-containing inert liquid, for example, Fluorinert (the brand name of 3M United States) can be used. The fluorine-containing inert liquid is also excellent from the point of cooling effect. Further, as the liquid, liquid which has a refractive index higher than pure water (a refractive index is around 1.44), for example, liquid having a refractive index equal to or higher than 1.5 can be used. As this type of liquid, for example, a predetermined liquid having C—H binding or O—H binding such as isopropanol having a refractive index of about 1.50, glycerol (glycerin) having a refractive index of about 1.61, a predetermined liquid (organic solvent) such as hexane, heptane or decane, or decalin (decahydronaphthalene) having a refractive index of about 1.60, or the like can be cited. Alternatively, a liquid obtained by mixing arbitrary two or more of these liquids may be used, or a liquid obtained by adding (mixing) at least one of these liquids to (with) pure water may be used. Alternatively, as the liquid, a liquid obtained by adding (mixing) base or acid such as H+, Cs+, K+, Cl−, SO42−, or PO42− to (with) pure water can be used. Moreover, a liquid obtained by adding (mixing) particles of Al oxide or the like to (with) pure water can be used. These liquids can transmit ArF excimer laser light. Further, as the liquid, liquid, which has a small absorption coefficient of light, is less temperature-dependent, and is stable to a projection optical system (tip optical member) and/or a photosensitive agent (or a protection film (top coat film), an antireflection film, or the like) coated on the surface of a wafer, is preferable. Further, in the case an F2 laser is used as the light source, fomblin oil can be selected. Further, as the liquid, a liquid having a higher refractive index to illumination light IL than that of pure water, for example, a refractive index of around 1.6 to 1.8 may be used. As the liquid, supercritical fluid can also be used. Further, the tip optical element of projection optical system PL may be formed by quartz (silica), or single-crystal materials of fluoride compound such as calcium fluoride (fluorite), barium fluoride, strontium fluoride, lithium fluoride, and sodium fluoride, or may be formed by materials having a higher refractive index than that of quartz or fluorite (for example, equal to or higher than 1.6). As the materials having a refractive index equal to or higher than 1.6, for example, sapphire, germanium dioxide, or the like disclosed in the pamphlet of International Publication No. 2005/059617, or kalium chloride (having a refractive index of about 1.75) or the like disclosed in the pamphlet of International Publication No. 2005/059618 can be used.
Further, in the embodiment above, the recovered liquid may be reused, and in this case, a filter that removes impurities from the recovered liquid is preferably arranged in a liquid recovery unit, a recovery pipe or the like.
Further, in the embodiment above, the case has been described where the exposure apparatus is a liquid immersion type exposure apparatus. However, the present invention is not limited to this, but can also be employed in a dry type exposure apparatus that performs exposure of wafer W without liquid (water).
Further, in the embodiment above, the case has been described where the present invention is applied to a scanning exposure apparatus by a step-and-scan method or the like. However, the present invention is not limited to this, but may also be applied to a static exposure apparatus such as a stepper. Even in the case of a stepper, because the position of the stage on which the object subject to exposure is mounted can be measured using an encoder as in the embodiment described above, a similar effect can be obtained. Further, the present invention can also be applied to a reduction projection exposure apparatus by a step-and-stitch method that synthesizes a shot area and a shot area, an exposure apparatus by a proximity methods a mirror projection aligner, or the like. Moreover, the present invention can also be applied to a multistage type exposure apparatus equipped with a plurality of wafer stages, as is disclosed in, for example, the U.S. Pat. No. 6,590,634, the U.S. Pat. No. 5,969,441, the U.S. Pat. No. 6,208,407 and the like.
Further, the magnification of the projection optical system in the exposure apparatus of the embodiment above is not only a reduction system, but also may be either an equal magnifying system or a magnifying system, and projection optical system PL is not only a dioptric system, but also may be either a catoptric system or a catodioptric system, and in addition, the projected image may be either an inverted image or an upright image. Further, the illumination area and exposure area described above are to have a rectangular shape. However, the shape is not limited to rectangular, and can also be circular arc, trapezoidal, parallelogram or the like.
Incidentally, a light source of the exposure apparatus in the embodiment above is not limited to the ArF excimer laser, but a pulse laser light source such as a KrF excimer laser (output wavelength: 248 nm), an F2 laser (output wavelength: 157 nm), an Ar2 laser (output wavelength: 126 nm) or a Kr2 laser (output wavelength: 146 nm), or an extra-high pressure mercury lamp that generates an emission line such as a g-line (wavelength: 436 nm), an i-line (wavelength: 365 nm) and the like can also be used. Further, a harmonic wave generating unit of a YAG laser or the like can also be used. Besides the sources above, as is disclosed in, for example, U.S. Pat. No. 7,023,610, a harmonic wave, which is obtained by amplifying a single-wavelength laser beam in the infrared or visible range emitted by a DFB semiconductor laser or fiber laser as vacuum ultraviolet light, with a fiber amplifier doped with, for example, erbium (or both erbium and ytterbium), and by converting the wavelength into ultraviolet light using a nonlinear optical crystal, can also be used.
Further, in the embodiment above, illumination light IL of the exposure apparatus is not limited to the light having a wavelength equal to or more than 100 nm, and it is needless to say that the light having a wavelength less than 100 nm can be used. For example, in recent years, in order to expose a pattern equal to or less than 70 nm, an EUV exposure apparatus that makes an SOR or a plasma laser as a light source generate an EUV (Extreme Ultraviolet) light in a soft X-ray range (e.g. a wavelength range from 5 to 15 nm), and uses a total reflection reduction optical system designed under the exposure wavelength (for example, 13.5 nm) and the reflective mask has been developed. In the EUV exposure apparatus, the arrangement in which scanning exposure is performed by synchronously scanning a mask and a wafer using a circular arc illumination can be considered, and therefore, the present invention can also be suitably applied to such an exposure apparatus. Besides such an apparatus, the present invention can also be applied to an exposure apparatus that uses charged particle beans such as an electron beam or an ion beam.
Further, in the embodiment above, a transmissive type mask (reticle) is used, which is a transmissive substrate on which a predetermined light shielding pattern (or a phase pattern or a light attenuation pattern) is formed. Instead of this reticle, however, as is disclosed in, for example, U.S. Pat. No. 6,778,257, an electron mask (which is also called a variable shaped mask, an active mask or an image generator, and includes, for example, a DMD (Digital Micromirror Device) that is a type of a non-emission type image display device (spatial light modulator) or the like) on which a light-transmitting pattern, a reflection pattern, or an emission pattern is formed according to electronic data of the pattern that is to be exposed can also be used.
Further, for example, the present invention can also be applied to an exposure apparatus (lithography system) that forms line-and-space patterns on a wafer by forming interference fringes on the wafer.
Moreover, as disclosed in, for example, U.S. Pat. No. 6,611,316, the present invention can also be applied to an exposure apparatus that synthesizes two reticle patterns via a projection optical system and almost simultaneously performs double exposure of one shot area by one scanning exposure.
Further, an apparatus that forms a pattern on an object is not limited to the exposure apparatus (lithography system) described above, and for example, the present invention can also be applied to an apparatus that forms a pattern on an object by an ink-jet method.
Incidentally, an object on which a pattern is to be formed (an object subject to exposure to which an energy beam is irradiated) in the embodiment above is not limited to a wafer, but may be other objects such as a glass plate, a ceramic substrate, a film member, or a mask blank.
The use of the exposure apparatus is not limited only to the exposure apparatus for manufacturing semiconductor devices, but the present invention can also be widely applied, for example, to an exposure apparatus for transferring a liquid crystal display device pattern onto a rectangular glass plate, and an exposure apparatus for producing organic ELs, thin-film magnetic heads, imaging devices (such as CCDs), micromachines, DNA chips, and the like. Further, the present invention can be applied not only to an exposure apparatus for producing microdevices such as semiconductor devices, but can also be applied to an exposure apparatus that transfers a circuit pattern onto a glass plate or silicon wafer to produce a mask or reticle used in a light exposure apparatus, an EUV exposure apparatus, an X-ray exposure apparatus, an electron-beam exposure apparatus, and the like.
Electronic devices such as semiconductor devices are manufactured through the steps of; a step where the function/performance design of the device is performed, a step where a reticle based on the design step is manufactured, a step where a wafer is manufactured from silicon materials, a lithography step where the pattern of a reticle is transferred onto the wafer by the exposure apparatus (pattern formation apparatus) in the embodiment previously described, a development step where the wafer that has been exposed is developed, an etching step where an exposed member of an area other than the area where the resist remains is removed by etching, a resist removing step where the resist that is no longer necessary when etching has been completed is removed, a device assembly step (including a dicing process, a bonding process, the package process), inspection steps and the like. In this case, in the lithography step, because the device pattern is formed on the wafer by executing the exposure method previously described using the exposure apparatus of the embodiment, a highly integrated device can be produced with good productivity.
While the above-described embodiments of the present invention are the presently preferred embodiments thereof, those skilled in the art of lithography systems will readily recognize that numerous additions, modifications, and substitutions may be made to the above-described embodiments without departing from the spirit and scope thereof. It is intended that all such modifications, additions, and substitutions fall within the scope of the present invention, which is best defined by the claims appended below.

## Claims

1. A movable body apparatus including a movable body which substantially moves along a predetermined plane and is movable to a predetermined position within the predetermined plane, the apparatus comprising:
a scale which is arranged at one of the movable body and an outside of the movable body, with a first direction within a plane parallel to the predetermined plane serving as a longitudinal direction, the scale having a predetermined width in a second direction orthogonal to the first direction within the plane parallel to the predetermined plane, the scale having a length extending in the first direction and having a width extending in the second direction, the length being substantially longer than the width;
a measurement device having a plurality of sensors each of which measures positional information of the movable body in a periodic direction of the scale at a plurality of measurement points placed on the scale within the width of the scale so that of the plurality of measurement points, n (wherein, n is an integer of two or more) or more points are positioned within the predetermined width of the scale, and when the movable body is at the predetermined position, n+1 or more of the plurality of measurement points are positioned within the predetermined width of the scale; and
a controller which performs position control of the movable body, using, as primary information, a first measurement information including measurement information at a first measurement point out of the n or more measurement points positioned within the predetermined width of the scale or the n+1 or more measurement points positioned within the predetermined width of the scale when the movable body is located at the predetermined position, wherein
the controller switches measurement information to use as the primary information in position control of the movable body to a second measurement information including measurement information at a second measurement point different from the first measurement point, when abnormality occurs, due to malfunction of one of the sensors, in the first measurement information at the first measurement point positioned within the predetermined width of the scale.

2. The movable body apparatus according to claim 1 wherein
the scale is arranged on a surface substantially parallel to the predetermined plane of the movable body.

3. The movable body apparatus according to claim 2 wherein
on the movable body, the scale is arranged in a pair separated from each other in the second direction, and
the measurement points are placed so that n or more measurement points are constantly positioned in at least one of the pair of scales when the movable body is in a predetermined range within the predetermined plane.

4. The movable body apparatus according to claim 2 wherein
on the movable body, another pair of scales is further arranged with each of the longitudinal directions being the second direction, the another pair of scales being separated from each other in the first direction, wherein
the measurement points are placed so that n or more measurement points are constantly positioned in at least one of the another pair of scales when the movable body is in a predetermined range within the predetermined plane.

5. The movable body apparatus according to claim 1 wherein
each of the first measurement information and the second measurement information includes measurement information at a plurality of measurement points.

6. The movable body apparatus according to claim 1 wherein
each of the first measurement information and the second measurement information is measurement information at a single measurement point.

7. The movable body apparatus according to claim 1 wherein
each of the plurality of sensors has a head which irradiates a measurement beam on a measurement point, and
the controller performs the switching when the abnormality in measurement information occurs due to malfunction of one of the heads.

8. The movable body apparatus according to claim 1 wherein
each of the plurality of sensors has a head which irradiates a measurement beam on a measurement point, and a plurality of the heads irradiate the measurement beams on different measurement points, respectively.

9. The movable body apparatus according to claim 1 wherein
the measurement points are substantially equally spaced from each other in a direction orthogonal to the longitudinal direction of the scale by half or less than half of the predetermined width of the scale.

10. The movable body apparatus according to claim 1 wherein
the measurement device has a first head and a second head which irradiate measurement beams on a same measurement point, and
an irradiation area of the measurement beam irradiated from the first head is in proximity with an irradiation area of the measurement beam irradiated by the second head, without overlapping.

11. A pattern formation apparatus that forms a pattern on an object, the apparatus comprising:
a patterning device which forms a pattern on the object, and
the movable body apparatus according to claim 1 in which the object is mounted on the movable body.

12. The pattern formation apparatus according to claim 11 wherein
the object has a sensitive layer, and the patterning device forms a pattern on the object by exposing the sensitive layer.

13. An exposure apparatus that forms a pattern on an object by irradiating an energy beam, the apparatus comprising:
a patterning device that irradiates the energy beam on the object;
the movable body apparatus according to claim 1 in which the object is mounted on the movable body, and
a drive device which drives the movable body to make the object relatively move with respect to the energy beam.

14. A device manufacturing method comprising:
exposing an object with the exposure apparatus according to claim 13; and
developing the exposed object.

15. A movable body apparatus including a movable body which substantially moves along a predetermined plane, the apparatus comprising:
a scale which is arranged at one of the movable body and an outside of the movable body, with a first direction within a plane parallel to the predetermined plane serving as a longitudinal direction, the scale having a predetermined width in a second direction orthogonal to the first direction within the plane parallel to the predetermined plane;
a measurement device which measures positional information of the movable body in a periodic direction of the scale at a plurality of measurement points placed on the scale, the measurement device having a plurality of head sets each of which includes a first head that receives a first positional information of a first measurement point and a second head that receives a second positional information of a second measurement point within a predetermined distance of the first measurement point, the predetermined distance being less than one-half the predetermined width of the scale; and
a controller which controls a position of the movable body using, as primary information, measurement information generated by the first head, and switches the measurement information used as the primary information from the measurement information generated by the first head to measurement information generated by the second head when abnormality occurs in the measurement information generated by the first head due to malfunction of the measurement device.

16. The movable body apparatus according to claim 15 wherein
the scale is arranged on a surface substantially parallel to the predetermined plane of the movable body.

17. The movable body apparatus according to claim 15 wherein
the first measurement points, or the first and second measurement points, on which the measurement beams are respectively irradiated by the first heads and the second heads included in the plurality of head sets, respectively, are substantially equally spaced by the predetermined width.

18. The movable body apparatus according to claim 15 wherein
in the measurement device, at least a part of a measurement area where the measurement beam of the first head irradiates overlaps a part of a measurement area where the measurement beam of the second head irradiates in parallel.

19. The movable body apparatus according to claim 15 wherein
the controller performs the switching when the abnormality in measurement information occurs due to malfunction of the first head.

20. A pattern formation apparatus that forms a pattern on an object, the apparatus comprising:
a patterning device which forms a pattern on the object, and
the movable body apparatus according to claim 15 in which the object is mounted on the movable body.

21. The pattern formation apparatus according to claim 20 wherein
the object has a sensitive layer, and the patterning device forms a pattern on the object by exposing the sensitive layer.

22. An exposure apparatus that forms a pattern on an object by irradiating an energy beam, the apparatus comprising:
a patterning device that irradiates the energy beam on the object;
the movable body apparatus according to claim 15 in which the object is mounted on the movable body, and
a drive device which drives the movable body to make the object relatively move with respect to the energy beam.

23. A device manufacturing method comprising:
exposing an object with the exposure apparatus according to claim 22; and
developing the exposed object.

24. A movable body apparatus including a movable body which substantially moves along a predetermined plane, the apparatus comprising:
a measurement device which measures positional information of the movable body in a direction of a single degree of freedom which is along the predetermined plane, at a plurality of measurement points of the movable body placed in a movement range of the movable body, wherein
the measurement device has a plurality of heads which simultaneously generate respective measurement information on at least a same single measurement point of the plurality of measurement points when the movable body is located at a predetermined position.

25. The movable body apparatus according to claim 24 wherein
the plurality of heads are placed at the movable body.

26. The movable body apparatus according to claim 24 wherein
the movable body has a scale which reflects the measurement beams irradiated from the plurality of heads.

27. The movable body apparatus according to claim 24 wherein
the plurality of heads include a first head and a second head which respectively irradiate measurement beams on the same single measurement point of the plurality of measurement points when the movable body is at the predetermined position, and
at the same single measurement point, at least a part of an irradiation area of the measurement beam irradiated from the first head overlaps at least a part of an irradiation area of the measurement beam simultaneously irradiated from the second head.

28. The movable body apparatus according to claim 24 wherein
the plurality of heads include a first head and a second head which respectively irradiate measurement beams on the same single measurement point of the plurality of measurement points when the movable body is at the predetermined position, and the apparatus further comprises:
a controller which controls a position of the movable body using, as primary information, measurement information generated by the first head of the plurality of heads irradiating measurement beams on the same single measurement point, and switches the measurement information used as the primary information from the measurement information generated by the first head to measurement information generated by the second head when abnormality occurs in the measurement information generated by the first head.

29. The movable body apparatus according to claim 28 wherein
the controller performs the switching when the abnormality in measurement information occurs due to malfunction of the first head.

30. A pattern formation apparatus that forms a pattern on an object, the apparatus comprising:
a patterning device which forms a pattern on the object, and
the movable body apparatus according to claim 24 in which the object is mounted on the movable body.

31. The pattern formation apparatus according to claim 30 wherein
the object has a sensitive layer, and the patterning device forms a pattern on the object by exposing the sensitive layer.

32. An exposure apparatus that forms a pattern on an object by irradiating an energy beam, the apparatus comprising:
a patterning device that irradiates the energy beam on the object;
the movable body apparatus according to claim 24 in which the object is mounted on the movable body, and
a drive device which drives the movable body to make the object relatively move with respect to the energy beam.

33. A device manufacturing method comprising:
exposing an object with the exposure apparatus according to claim 32; and
developing the exposed object.