EXPOSURE DEVICE HAVING A PLANAR MOTOR

Abstract: Disclosed is a planar motor device capable of effectively restraining thermal influence on the environment. When an electric current is supplied to armature coils (38) opposed to the magnet of a movable member (51), the movable member (51) is driven along a movement surface (21a) by electromagnetic force. When the movable member (51) is continued to be driven in a certain direction, electric current is supplied to the armature coils (38) opposed to the magnet for each movement position of the movable member (51), whereby the armature coils (38) supplied with electric current generate heat. The armature coils (38) are accommodated in a vacuum chamber (41) in a base (21), and are arranged so as to be in contact with a stator yoke (43), with a predetermined gap being defined between them and a ceramic plate (36) forming the vacuum chamber (41). Thus, the heat transmission from the armature coils (38) to the movement surface (21a) side is effected substantially by radiation alone, so that it is possible to effectively restrain thermal influence on the environment.

Description: EXPOSURE DEVICE HAVING A PLANAR MOTOR BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an exposure device having a planar motor and, more specifically, to a planar motor for driving a movable member including a magnet unit two-dimensionally by electromagnetic force and an exposure device using the planar motor to drive a substrate stage device. Description of the Related Art Conventionally, in lithography for producing semiconductor devices, liquid crystal display devices, etc, an exposure device has been used which transfers, by means of a projection optical system, a pattern formed in a mask or reticle (hereinafter generally referred to as "reticle") to a substrate such as a wafer or glass plate to which resist or the like is applied. In the exposure device, the wafer must be accurately positioned at the exposure position. Accordingly, the wafer is held on a wafer holder by vacuum attraction or the like, and the wafer holder is secured to a wafer table. To perform the positioning of the wafer more quickly without being affected by the accuracy of the mechanical guide surface, etc, and to avoid mechanical friction to attain a longer service life, a stage device has recently been developed in which a table on which the wafer is placed is driven two-dimensionally in a non-contact manner to position the wafer. As the drive source for such a non- contact drive stage device, a planar motor is known in which two axes of variable magnetic resistance drive type linear pulse motors are connected together. At present, the mainstream of variable magnetic resistance drive type planar motors is a construction in which two axes of variable magnetic resistance drive type linear pulse motors are connected together as in the case of the soyer motor. The variable magnetic resistance drive type linear pulse motor comprises a stator, formed, for example, by a plate-like magnetic body having teeth consisting of protrusions and recesses formed longitudinally at equal intervals, and a movable member in which a plurality of armature coils, having protrusions and recesses opposed to the teeth of the stator and having a different phase than that of the teeth, are connected through a permanent magnet. By utilizing a force generated to minimize the magnetic resistance between the stator and the movable member at each point in time, the movable member is driven. That is, by adjusting and controlling the current value and phase of the pulse current supplied to each armature coil, the movable member is operated stepwise. To use the above-described variable magnetic resistance drive type planar motor in precise positioning to realize high-speed positioning, it is necessary to obtain a large driving force. For this purpose, it is inevitably necessary to cause large current to flow through the armature coil, in this regard, the heat generation of the armature coil can create a great problem. Apart from this, there has been developed a Lorentz electromagnetic drive planar motor in which a linear motor is developed two-dimensionally (See, for example, USP No. 5196745). Such a Lorentz electromagnetic type planar motor is said to be valuable as a future stage drive source since it is superior in controllability, thrust linearity, and positioning performance. However, in this Lorentz electromagnetic drive planar motor also, it is necessary to cause a large current to flow through the armature coil to obtain a large thrust, and the armature coil is a heat generation source. Thus, taking into account the precision positioning device environment, a cooling design is indispensable to realize a planar motor in which the influence of heat is reduced. SUMMARY OF THE INVENTION The present invention has been made in view of the above problem. Accordingly, it is a first object of the present invention to provide a planar motor device capable of restraining thermal influence on the environment. A second object of the present invention is to provide an exposure device capable of high-accuracy exposure while maintaining high throughput. Between objects, heat is mainly transmitted by heat transfer, heat conduction and heat radiation, all of which vary by the difference in temperature between the objects. Heat transfer is transmission of heat due to molecular oscillation caused by heat or movement of electrons having energy, and heat conduction is transmission of heat due to convection between solid surface and fluid. In either of these, a medium for heat is necessary, and they can hardly occur in vacuum. In contrast, heat radiation is transmission of heat due to electromagnetic waves emitted from an object, so that it can occur in vacuum in which no medium for heat exists. However, the quantity of heat transmitted is relatively small as compared with heat transfer and heat conduction. In view of this, the present invention adopts the following construction. A first planar motor device according to the present invention comprises: a magnet unit (52, 53) having at least one magnet (54a to 54d) and adapted to move two- dimensionally along a predetermined movement surface (21a); a base (21 ) having the movement surface on the side opposite to the magnet unit and including a vacuum chamber (41 ) capable of maintaining a vacuum state in its interior; and a plurality of armature coils (38) arranged two-dimensionally in the vacuum chamber along the movement surface so as to define a predetermined gap between them and a first wall (36) on the side of the movement surface forming the vacuum chamber. In this construction, when electric current is supplied to the armature coils opposite to the magnet of the magnet unit, the magnet unit is driven along the movement surface by electromagnetic force. When the magnet unit is continued to be driven in a certain direction, electric current is supplied to the armature coils opposite to the magnet for each movement position of the magnet unit, whereby each armature coil supplied with electric current generates heat. In this case, the armature coils are accommodated in the vacuum chamber in the base, and arranged two-dimensionally along the movement surface in the vacuum chamber so as to define a predetermined gap between them and the first wall on the side of the movement surface forming the vacuum chamber. Thus, transmission of heat from the armature coils to the movement surface side is almost solely by heat radiation, so that it is possible to effectively restrain thermal influence on the environment. In this case, even when the interior of the vacuum chamber is in a vacuum state, air exists therein, so that it is impossible to completely exclude heat transfer and heat conduction, the degree of which depend on the vacuum degree. From this viewpoint, the higher the vacuum degree, the more desirable. However, when the vacuum degree is higher than a certain level, there is a danger that the base will be deformed by the difference in pressure between the atmospheric pressure and the pressure inside the vacuum chamber. To prevent such deformation, it is desirable to provide a deformation preventing member (39) for preventing deformation of the base due to the vacuum state between the first wall (36) forming the vacuum chamber (41 ) and a second wall (43) opposite to the first wall (36). However, in this case, the heat generated by the armature coils is transmitted through the second wall and the deformation preventing member to the first wall side, that is, the movement surface side. To restrain or prevent this heat conduction, it is desirable to form at least a part of the deformation preventing member of a heat insulating material, or to form the deformation preventing member in a configuration such that the surface area with which it is in contact with the second wall is smaller than the surface area of the other portion of the deformation preventing member. In the above case, it is more desirable that the base (21 ) further have on the side opposite to the movement surface of the vacuum chamber (41 ) a fluid passage (65a, 66, 42, 66, 65b) which is in contact with the vacuum chamber via the second wall (43). In this case, heat exchange is effected between the fluid in the fluid passage and the second wall, and the armature coils are cooled starting from the second wall side (the side opposite to the movement surface). In this case, it is possible to provide a temperature control device (79) for controlling the temperature of the fluid flowing through the fluid passage. It is only necessary for this temperature control device to control the temperature of the fluid to a temperature at least lower than the temperature of the second wall when the armature coils generate heat. However, the fluid may be controlled to a temperature lower than the ambient temperature of the base. In this case, it is possible to efficiently cool the armature coils starting from the side opposite to the movement surface. A second planar motor device according to the present invention comprises a magnet unit (52, 53) having at least one magnet (54a to 54d) and adapted to move two-dimensionally along a predetermined movement surface (21a); a base (21 ) having the movement surface on the side opposite to the magnet unit and including a vacuum chamber (41 ) capable of maintaining a vacuum state in its interior and a fluid passage situated on the movement surface side of the vacuum chamber; and a plurality of armature coils (38) arranged two- dimensionally in the vacuum chamber at predetermined intervals along the movement surface. In this construction, when electric current is supplied to the armature coils opposed to the magnet of the magnet unit, the magnet unit is driven along the movement surface by electromagnetic force. When the magnet unit is continued to be driven in a certain direction, electric current is supplied to the armature coils for each movement position of the magnet unit, whereby each armature coil supplied with electric current generates heat. In this case, the armature coils are arranged in the vacuum chamber in the base, and a fluid passage is provided on the side of the movement surface forming the vacuum chamber. Thus, in the vacuum portion in the vacuum chamber, transmission of heat from the armature coils is almost solely by heat radiation, and the heat transmitted to the movement surface side in the vacuum chamber is removed through heat exchange with the fluid in the fluid passage. Thus, it is possible to effectively restrain thermal influence on the environment. In this case, it is desirable that the temperature of the fluid in the fluid passage be lower than that of the base atmosphere. In accordance with the present invention, there is provided an exposure device for transferring a predetermined pattern to a substrate, characterized in that either the first or the second planar motor device of the present invention is used in the substrate stage device for driving the substrate. Since the planar motor device of the present invention is used in the substrate stage, it is possible to two-dimensionally drive the substrate in a non- contact state by electromagnetic force. Further, since it is possible to effectively reduce the influence of heat on the substrate due to the heat generation of the armature coils, it is possible to restrain air fluctuation, etc. of the interferometer beam for measuring the substrate position. Thus, it is possible to control the position of the substrate at high speed and with high accuracy, with the result that it is possible to effect exposure at high exposure accuracy while improving the throughput. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram showing the construction of an exposure device according to a first embodiment; Fig. 2 is a plan view showing the substrate stage device shown in Fig. 1 ; Fig. 3 is a sectional view taken along line A-A of Fig. 2; Fig. 4(A) is a perspective view showing the movable member of the planar motor constituting the substrate stage device of Fig. 1 ; Fig. 4(B) is an exploded perspective view of the movable member shown in Fig. 4(A); Fig. 5 is a base main body sectional view illustrating a modification of the column constituting the base main body; Fig. 6 is a base main body sectional view illustrating another modification of the column constituting the base main body; Fig. 7 is a base main body sectional view illustrating another modification of the base main body; Fig. 8(A) is a sectional view of the base main body of the second embodiment; and Fig. 8(B) is a diagram showing the flow of liquid refrigerant in a refrigerant passage on the vacuum chamber upper portion side. DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the present invention will be described with reference to Figs. 1 through 5. Fig. 1 is a schematic diagram showing the general construction of an exposure device according to an embodiment. This exposure device 100 is a scanning type exposure device of the so-called step- and-scan exposure system. The exposure device 100 comprises an illumination system 10, a reticle stage RST for holding a reticle (mask) R, a projection optical system PL, a substrate stage device 30 for driving a wafer W serving as the substrate two- dimensionally in the X- and Y-directions, and a control system for these components. As disclosed, for example, in Japanese Patent Laid-Open No. 9-320956, the illumination system 10 comprises a light source unit, a shutter, a secondary light source forming optical system, a beam splitter, a condenser lens, a reticle blind, and an image formation lens system (none of which is shown), and emits an exposure illumination light having a substantially uniform luminance distribution toward mirror M of Fig. 1. The optical path of the illumination light is bent by the mirror M to become vertical, and the light illuminates a rectangular (or arcuate) illumination area IAR on the reticle R with a uniform luminance. The reticle R is secured to the reticle stage RST by, for example, vacuum attraction. The reticle stage RST can be driven on a reticle base (not shown) by a reticle drive section (not shown) formed by a linear motor or the like in a predetermined scanning direction (in this example, in the Y-axis direction) at a predetermined scanning speed. A movement mirror 15 reflecting a laser beam from a reticle laser interferometer (hereinafter referred to as "reticle interferometer") 16 is secured to the reticle stage RST, and the position of the reticle stage RST in the movement surface is constantly detected by the reticle interferometer 16 with a resolution, for example, of approximately 0.5 to 1 nm. Positional information of the reticle stage RST from the reticle interferometer 16 is transmitted to a stage control system 19 and to a main control device 20 through it. The stage control system 19 drives the reticle stage RST through a reticle drive section (not shown) in response to a command from the main control device 20 and on the basis of the positional information of the reticle stage RST. The projection optical system PL is arranged below the reticle stage RST in Fig. 1 , and its optical axis AX (which coincides with the optical axis IX of the illumination optical system) is in the Z-direction. Here, a refractive optical system is used which is composed of a plurality of lens elements arranged at predetermined intervals along the optical axis AX so as to realize a both-side telecentric optical arrangement. This projection optical system PL is a reduction optical system having a predetermined projection scaling of, for example, 1/5 (or 1/4). Thus, when the illumination area IAR of the reticle R is illuminated by the illumination light from the illumination system 10, a reduced image (partial inverted image) of the circuit pattern in the illumination area IAR of the reticle R is formed through the projection optical system PL in the exposure area IA conjugate with respect to the illumination area IAR on the wafer W to the surface of which photoresist is applied. The substrate stage device 30 comprises a base 21 , a substrate table 18 float-supported above the upper surface of the base via a clearance of approximately several μm by an air slider described below, and a driving device 50 for driving the substrate table 18 two-dimensionally in the XY-plane. As the driving device 50, a planar motor is used which comprises a stator 60 provided (embedded) in the upper portion of the base 21 and a movable member 51 secured to the bottom portion (the side opposite to the base). A planar motor device is formed by the movable member 51 , the base 21 , and the driving device 50. In the following description, the driving device will be referred to as the planar motor 50 for the sake of convenience. The wafer W is secured to the substrate table 18 by, for example, vacuum attraction. Further, a movement mirror 27 reflecting a laser beam from a wafer laser interferometer (hereinafter referred to as "wafer interferometer") 31 is secured to the substrate table 18, and the position of the substrate table 18 in the XY-plane is constantly detected with a resolution of, for example, approximately 0.5 to 1 nm by the wafer interferometer 31 arranged outside. In reality, as shown in Fig. 2, there are provided on the substrate table 18 a movement mirror 27Y having a reflection surface perpendicular to the Y-axis direction which is the scanning direction, and a movement mirror 27X having a reflection surface perpendicular to the X-axis direction which is the non-scanning direction, and the wafer interferometer 31 has one axis in the scanning direction and two axes in the non-scanning direction. In Fig. 1 , they are simply shown as the movement mirror 27 and the wafer interferometer 31. Positional information (or velocity information) of the substrate table 18 is transmitted to a stage control system 19, and, through this to a main control device 20. The stage control system 19 controls the movement of the substrate table 18 in the XY-plane through the planar motor 50 in response to a command from the main control device 20 and on the basis of the positional information (or velocity information). Here, the components of the substrate stage device 30 will be described in more detail with reference to Figs. 2 through 4, centering on the planar motor 50 and the components around it. Fig. 2 is a plan view of the substrate stage device 30, and Fig. 3 is a partially omitted enlarged sectional view taken along the line A-A of Fig. 2. As shown in Figs. 2 and 3, the substrate table 18 is supported by the upper surface (the surface on the opposite side of the surface opposed to the base 21 ) of the movable member 51 at three different points by support mechanisms 32a, 32b and 32c including a voice coil motor, making it possible to effect inclination with respect to the XY-surface and driving in the Z-axis direction. Though partially omitted in Fig. 1 , the support mechanisms 32a through 32c are actually independently driven and controlled by the stage control system 19 of Fig. 1 through a drive mechanism (not shown). As shown in the perspective view of Fig. 4(A) and the exploded perspective view of Fig. 4(B), the movable member 51 comprises an air slider 57 serving as a kind of air static pressure bearing device which is in the form of four squares in plan view, a flat magnetism generator 53 a part of which is engaged from above with the air slider 57 into an integral unit, and a magnetic member 52 engaged from above with the flat magnetism generator 53. The magnetic member 52 and the flat magnetism generator 53 constitute the magnet unit. The substrate table 18 is provided on the upper surface of the magnetic member 52 via the support mechanisms 32a through 32c. In the interior of the air slider 57, there are formed a supply passage for pressurized air, a passage for vacuum, etc. The supply passage for pressurized air is connected to an air pump 59 (See Fig. 1 ) through a tube 33, and the passage for vacuum is connected to a vacuum pump (not shown) through a tube 34. On the bottom surface of the air slider 57, there are provided an air pad connected to the passage for pressurized air and an air pocket connected to the passage for vacuum. Thus, in this embodiment, the thickness of the air layer, that is, the bearing gap, is maintained at a desired value by balancing between a downward force corresponding to the sum total of the weight of the movable member 51 , the substrate table 18, etc., the magnetic attraction force of the flat magnetism generator 53 and a stator yoke 43 described below forming the magnet unit, and the vacuum attraction force (pressurizing force) by the vacuum pump (not shown), and an upward force due to the pressure of the pressurized air supplied from the air pump 59 and blown upward toward the upper surface of the base 21 through the air pad, that is, the static pressure of the air layer between the bottom surface of the movable member 51 and the upper surface of the base 21 (that is, the in-gap pressure). In this way, the air slider 57 constitutes a kind of vacuum pressurizing type air static pressure bearing, and, by this air slider 57, the movable member 51 , the substrate table 18, etc. are float-supported above the upper surface of the base 21 via a clearance of, for example, approximately 5 μm (See Figs. 1 and 3). As described above, in this embodiment, the air slider 57 is provided with a supply passage for pressurized air and a passage for vacuum, and an air pad and an air pocket respectively connected to them. However, it is not absolutely necessary to provide the passage for vacuum, etc. As shown in Fig. 4(B), the flat magnetism generator 53 are formed by four thrust generating magnets 54a, 54b, 54c and 54d arranged in a 2-row by 2- column matrix in order that the polarities of adjacent pole faces may be different, and interpolation magnets 55a, 55b, 55c and 55d arranged in the magnetic flux paths formed on the magnetic member 52 side by adjacent thrust generating magnets (54a, 54b), (54b, 54c), (54c, 54d), and (54d, 54a). The thrust generating magnets 54a through 54d consist of permanent magnets of the same thickness and the same configuration and have a square pole face. These thrust generating magnets 54a through 54d are arranged in the same plane in a 2-row by 2-column matrix such that the gaps between the thrust generating magnets adjacent in the X- and Y-directions are predetermined widths. In the thrust generating magnets 54a and 54b and the thrust generating magnets 54c and 54d, which are adjacent in the X-direction, the polarities of the adjacent pole faces are opposite to each other. In the thrust generating magnets 54a and 54d and the thrust generating magnets 54b and 54c, which are adjacent in the Y-direction, the polarities of the adjacent pole faces are opposite to each other. The interpolation magnets 55a through 55d consist of rectangular permanent magnets of the same thickness and are arranged such that, in plan view, they fill the gaps between the adjacent thrust generating magnets (54a, 54b), (54b, 54c), (54c, 54d) and (54d, 54a) and that, in side view, they are in the imaginary plane formed by the upper surfaces of the thrust generating magnets 54a through 54d. These interpolation magnets 55a through 55d have pole faces perpendicular to the pole faces of the thrust generating magnets 54a through 54d, and these pole faces have a polarity opposite to that of the pole faces of the thrust generating magnets 54a through 54d adjacent thereto in plan view. As shown in Figs. 2 and 3, the base 21 comprises a base main body 22 that is square in plan view and a pair of joint mounting members 23A and 23B mounted to the ends in the Y-direction of the base main body 22. The base main body 22 comprises a box-like thin, hollow container 35 whose upper side is open, a flat stator yoke 43 which is engaged from above with a first step portion 35a formed on the inner side of the peripheral wall of the container 35 and arranged parallel to the bottom wall of the container 35 with a predetermined gap (for example, approximately 2 mm) and which is formed of a magnetic material having a high heat conductivity (specifically, 30 [W/m-K] or more), and a ceramic plate 36 which is engaged from above with a second step portion 35b formed on the inner side of the upper end (open end) of the peripheral wall of the container 35 and which closes the opening. A movement surface 21a of the movable member 51 is formed on the surface of the ceramic plate 36 opposed to the movable member 51 (the upper surface). The inner space of the base 21 formed by the container 35 and the ceramic plate 36 is divided into upper and lower portions by the stator yoke 43. In the upper portion, a first chamber 41 serving as the vacuum chamber is formed, and, in the lower portion, a second chamber 42 is formed. The stator yoke 43 and the movement surface 21a are parallel to each other. As shown in Fig. 3, in the first chamber 41 , eighty-one armature coils 38 are arranged in 9-row/9-column matrix in the XY two-dimensional directions along the movement surface 21a via a predetermined gap (for example, approximately 2 mm) between them and the ceramic plate 36 and in contact with the stator yoke 43 (See Fig. 2). That is, in this embodiment, the first wall defining the first chamber 41 as the vacuum chamber accommodating a plurality of armature coils 38 is formed by the ceramic plate 36, and the second wall defining the second chamber 42 is formed by the stator yoke 43. As shown in Fig. 2, hollow square coils are used as the armature coils 38. In this embodiment, the stator 60 of the planar motor 50 is formed by the stator yoke 43, the armature coils 38, and the ceramic plate 36. As shown in Fig. 3, on the side of the ceramic plate 36 opposite to the movement surface 21a (the lower side), a large number of (145, in the example shown) protrusions 36a having a round cross-sectional configuration are formed at predetermined intervals. As shown in Fig. 2, when the ceramic plate 36 is engaged with the container 35, 9 x 9 = 81 protrusions 36a are at positions corresponding to the centers of the hollow portions of the armature coils 38, and 8 x 8 = 64 protrusions 36a are at positions corresponding to the spaces between the four adjacent armature coils 38. Further, between the protrusions 36a of the ceramic plate 36 forming the first chamber 41 and the stator yoke 43, there are provided columns 39 formed of a heat insulating material and serving as deformation preventing members. As shown in Fig. 5, the ceramic plate 36 may be formed as a completely flat plate, and it is possible to provide column-like deformation preventing members 39 partially including heat insulating material 40 between the flat plate 36 and the stator yoke 43. Referring again to Fig. 1 , the base 21 is connected to a vacuum pump 62 through a suction tube 61. The suction tube 61 is connected to a vacuum attraction port 63 provided on one side in the X-direction (+X side) of the base 21 shown in Fig. 2, and this vacuum attraction port 63 communicates with the first chamber 41. Here, the vacuum pump 62 consists of a turbo molecular pump. This turbo molecular pump has a vacuum creating capacity of creating a high vacuum state of, for example, 1 x 10-6 [Torr] or less in the firsts chamber 41. The above-mentioned pair of joint mounting members 23A and 23B are integrally mounted to the base main body 22 by welding or the like. These joint mounting members 23A and 23B have in their longitudinal centers screw holes 64a and 64b having a predetermined depth whose axial direction is in the Y- direction. As shown in Fig. 3, in the joint mounting member 23A, a groove 65a is formed whose one end communicates with the screw hole 64a, whose sectional configuration is a right-angled triangle, and whose size in the height direction (Z- direction) linearly diminishes from one side in the Y-direction to the other side. In the side wall on one side in the Y-direction of the container 35 constituting the base main body 22, a rectangular through-hole 66 is formed which has the same height and the same X-direction width as the second chamber 42 and whose section is thin and long, and the groove 65a communicates with the second chamber 42 through this through-hole 66. The container 35 is symmetrical, and another through-hole 66 (not shown) is formed in reality in the side wall on the other side in the Y-direction of the container 35. Further, as is apparent from the plan view of Fig. 2, the plan section of the groove 65a is an isosceles triangle whose width in the X-direction linearly increases from one side in the Y-direction to the other side. That is, the sectional area of the XZ section of the groove 65a is constant independently of the position in the Y-direction. In this case, one end of a refrigerant feeding joint (not shown) having a male screw in the outer periphery thereof is mounted to the screw hole 64a, and the other end of this refrigerant feeding joint is connected to a refrigerant feeder provided inside the cooling device 79 serving as the temperature control device through the refrigerant feeding tube 92 shown in Fig. 1. Thus, in this embodiment, a restricter having a constant sectional area is formed which squeezes liquid refrigerant as the fluid entering the inlet side (the screw hole 64a side) due to the groove 65a into a film-like shape and supplies it to the second chamber 42 through the through-hole 66. In this embodiment, the refrigerant inlet is formed by the screw hole 64a formed in the joint mounting member 23A (more precisely, the inner passage of the joint for feeding refrigerant (not shown)is threadedly engaged with the screw hole 64a). The other joint mounting member 23B has a groove 65b and a screw hole 64b so as to be symmetrical with the joint mounting member 23A, and the second chamber 42 communicates with the groove 65b through the through-hole formed in the side wall on the other side in the Y-direction of the container 35. Mounted to the screw hole 64b is one end of a refrigerant discharge joint (not shown) having a male screw in the outer periphery, and the other end of this refrigerant discharge joint is connected to a refrigerator provided in the cooling device 79 through the refrigerant discharge tube of Fig. 1. In this case, a refrigerant outlet is formed by the screw hole 64b formed in the joint mounting member 23B (more precisely, an inner passage of a refrigerant discharge joint (not shown) is threadedly engaged with the screw hole 64b). As is apparent from the above description, in this embodiment, liquid refrigerant, supplied to the base 21 (the second chamber 42) through the refrigerant feeding joint, cools the interior of the base 21 , and is then returned to the cooling device 79 through the refrigerant discharge joint, to be cooled and supplied to the base 21 again. In this way, the liquid refrigerant is used in circulation. The liquid refrigerant is, for example, water or fluorinert (manufactured by Sumitomo 3M Ltd., a fluorine-type inactive liquid). This liquid refrigerant is supplied to the base 21 in a state in which its temperature is controlled to be lower than the base ambient temperature. Further, the sectional area of the refrigerant passage (65a, 66, 42, 66, 65b) in the base 21 from the refrigerant feeding joint to the refrigerant discharge joint is constant throughout the entire passage. Further, in this embodiment, the wall surface (lower surface) on the second chamber 42 side of the stator yoke 43 is formed rough. This is for the purpose of positively disturbing the flow of the liquid refrigerant which flows along the lower surface of the stator yoke 43 to make the flow of the liquid refrigerant in the second chamber 42 (especially the boundary layer on the lower surface of the stator yoke 43) a turbulent flow whose Reynolds number is larger than critical Reynolds number. Next, the operational flow of the exposure operation in the exposure device 100 including the above-described stage device 30 will be briefly described. First, under the control of the main control device 20, reticle loading and wafer loading are effected by a reticle loader and wafer loader (not shown). Further, preparatory operations, such as reticle alignment and base line measurement are conducted according to predetermined procedures using a reticle microscope (not shown), a reference mark plate (not shown) on the substrate table 18, and an alignment detection system (not shown). After this, the main control device 20 performs alignment measurements such as EGA (enhanced global alignment) using an alignment detection system (not shown). In this operation, when movement of the wafer W is needed, the main control device 20 controls at least either the value or direction of the current supplied to the armature coils 38 opposed to the thrust generating magnets 54a through 54d through the stage control system 19, whereby the substrate table 18 holding the wafer W integrally with the movable member 51 is moved in a desired direction. After the completion of alignment measurement, a step-and-scan type exposure operation is performed as follows. In performing this exposure operation, first, the substrate table 18 is moved such that the XY position of the wafer W is the scanning start position for the exposure of the first shot area on the wafer W. At the same time, the reticle stage 18 is moved such that the XY position of the reticle R is the scanning start position. Then, on the basis of a command from the main control device 20, the stage control system 19 moves the reticle R and the wafer W in synchronism through a reticle drive section (not shown) and the planar motor 50 on the basis of information on the XY position of the reticle R measured by the reticle interferometer 16 and information on the XY position of the wafer W measured by the wafer interferometer 31 , whereby scanning exposure is effected. This movement of the wafer W is effected by controlling at least either the value or direction of the current supplied to the armature coils 38 opposed to the thrust generating magnets 54a through 54d through the stage control system by the main control device 20. When the transfer of a reticle pattern for one shot area has been thus completed, stepping of one shot area of the table 18 is effected, and the scanning exposure for the next shot area is performed. In this way, stepping and scanning exposure are sequentially repeated, and the requisite shot number of patterns are transferred onto the wafer W. During the above-mentioned alignment and scanning exposure, current is supplied as needed to each armature coil 38 constituting the stator 60 of the planar motor 50, so that the armature coils 38 generate heat. However, transmission of this heat to the movement surface 21 a side is effectively restrained (or prevented) as follows. First, the interior of the first chamber 41 in the base 21 accommodating a plurality of armature coils 38 is evacuated by a vacuum pump 62 to create a high vacuum state. Thus, a gap in a high vacuum state exists between the ceramic plate 36 on the movement surface 21a side forming the first chamber 41 and the armature coils 38 arranged on the stator yoke 43, so that the heat transmission from the armature coils 38 to the movement surface 21a side is effected practically by radiation alone. That is, the gap above the armature coils 38 functions as a kind of heat insulating layer to effectively restrain the heat transmission to the movement surface side. The higher the vacuum degree, the higher the heat insulating performance (heat transmission restraining effect) of the above vacuum layer as the heat insulating layer. In this embodiment, it is possible to realize a high vacuum state of 1 x 10-6 [Torr], so that there exists practically no air around the armature coils 38, and it is possible to restrain to a very small degree the heat transfer and heat conduction through air as heat transmission medium. The heat transmission restraining effect is very high. Since a number of columns 39 are arranged between the ceramic plate 36 and the stator yoke 43 at substantial equal intervals over the entire area of the base main body, the ceramic plate 36, etc. are not deformed by the external air pressure if the above-mentioned high-vacuum state is established in the base main body 22, and it is possible to maintain the movement surface 21a on the upper surface of the ceramic plate 36 flat. When, as described above, a large number of columns 39 are provided between the ceramic plate 36 and the stator yoke 43, there is a danger of the heat generated by the armature coils 38 being transmitted through the stator yoke 43 and the columns 39 to the ceramic plate 36 side, that is, the movement surface 21a side. However, in this embodiment, at least part of each column 39 is formed of a heat insulating material, so that it is possible to substantially prevent heat conduction through the columns 39. Further, since the stator yoke 43 in contact with the armature coils 38 is formed of a magnetic material having a high heat conductivity, the stator yoke 43 not only functions as a magnetic circuit forming member but efficiently transmits the heat generated by the armature coils 38 to the surface of the base main body 22 on the opposite side movement surface 21a. Further, on the side of the stator yoke 43 in the base 21 opposite to the movement surface 21a, there is provided a second chamber 42 in contact with the vacuum chamber 41 through the intermediation of the stator yoke 43, and the interior of this second chamber 42 communicates with a refrigerant supply joint connected to one side in the Y-direction of the base 21 and a refrigerant discharge joint connected to the other side in the Y-direction of the base 21 , a liquid refrigerant (fluid) whose temperature is controlled to be lower than that of the base atmosphere being supplied to the second chamber 42 through the refrigerant supply joint by the cooling device 79. Thus, heat exchange is effected between the stator yoke 43 and the liquid refrigerant, and it is possible to efficiently cool the armature coils 38 from the lower side, whereby it is possible to restrain the temperature rise of each armature coil 38. Further, in this embodiment, there is provided in the base 21 a refrigerant passage of a fixed cross-sectional area for discharging liquid refrigerant supplied from one side in the Y-direction through the refrigerant supply joint through the refrigerant discharge joint on the other side in the Y-axis direction, so that the liquid refrigerant entering the base through the refrigerant supply joint is spread in a film-like state to uniformly find its way below the armature coils, with the result that the plurality of armature coils developed in a plane uniformly undergo heat removal. Further, the wall surface (lower surface) of the stator yoke 43 on the second chamber 42 side is formed as a rough surface and has surface irregularities, so that the Reynolds number of the flow of the liquid refrigerant flowing along the lower surface of the stator yoke 43 is larger than critical Reynolds number, and the flow becomes a turbulent flow. When the flow in the flow passage is a turbulent flow, the solid-liquid heat transfer coefficient is (ten to several tens of times) larger than that in the case of a laminar flow. Further, it is a flow grown fast both fluidally and thermally, so that the heat removal of the armature coils 38 is effected quickly and uniformly. From this viewpoint, protrusions may be provided at predetermined intervals on the lower surface of the stator yoke 43. Due to the above arrangement, it is possible to effectively restrain the transmission of the heat emitted from the entire surface of the armature coils 38 to the movement surface side, and it is possible to restrain as much as possible the thermal influence on the environment. Further, in this embodiment, liquid refrigerant is supplied from the cooling device 79 to the base 21 through the refrigerant supply tube 90 and the refrigerant supply joint, and this liquid refrigerant passes through the refrigerant passage in the base 21 to cool the armature coils 38 from the down surface side. The liquid refrigerant, the temperature of which has risen as a result of this cooling, returns to the cooling device 79 through the refrigerant discharge joint and the refrigerant discharge tube 93, and it is cooled there before it is supplied to the base 21 again to cool the armature coils 38. Since the liquid refrigerant is used in circulation in this way, it is possible to always cool the armature coils 38 by using a substantially fixed amount of liquid refrigerant, which is advantageous from the economical point of view. As described above, in this embodiment, it is possible to restrain as much as possible the thermal influence on the device environment, so that the air fluctuation, etc. of the interferometer beam of the interferometer 31 for measuring the position of the wafer table 18 substantially involves no problem, and the positioning and the positional control of the wafer can be effected accurately. Thus, in the exposure device 100 of this embodiment, the positional control of the wafer W can be effected accurately and quickly by the substrate stage device 30 equipped with the planar motor 50 of electromagnetic drive type, and it is possible to effect exposure with high exposure accuracy while improving throughput. The construction of the base 21 in the above-described embodiment is only represented as an example, and the present invention is not restricted thereto. For example, while in the above-described embodiment columns 39 entirely or partially formed of a heat insulating material are provided between the ceramic plate 43 and the stator yoke 43, it is also possible, as shown in Fig. 6, to provide as deformation preventing members columns 80 whose ends on the stator yoke 43 side (lower ends) are tapered so that the area with which they are in contact with the stator yoke 43 is smaller than the cross-sectional area of the other portion thereof. Since the configuration of the columns 80 is such that heat is not easily transmitted from the stator yoke 43 side, it is not necessary to form them of a heat insulating material. Further, while in the above-described embodiment nothing is arranged in the gap between the armature coils 38 and the ceramic plate 43, a small amount of air exists although the gap is in a vacuum state. Thus, heat transfer and heat conduction can occur using the air as the heat transmission medium. To further restrain such phenomenon, it is possible, as shown in Fig. 7, to provide a heat insulating material 81 in the gap between the armature coils 38 and the ceramic plate 43. Further, while in the above-described embodiment the first wall forming the first chamber 41 is formed by the ceramic plate 36 having the movement surface 21 a on the surface thereof facing the movable member 51 , the first wall and the movement surface forming member may be separate members. In this case, it is necessary to form both the first wall and the movement surface forming member of a non-magnetic material such as ceramic. Further, while in the above-described embodiment the second chamber 42 constituting the refrigerant passage as the fluid passage is provided below the stator yoke 43, this should not be construed restrictively. That is, it is only necessary for a predetermined gap to exist between the armature coils 38 and the ceramic plate 36, the interior of the first chamber 41 being evacuated by the vacuum pump 62. It is not absolutely necessary to provide the base 21 with a joint mounting member, etc. for supplying refrigerant to the second chamber 42. In this case, the second wall of the container 35 (base 21 ) with which the armature coils 38 are contact in contact and on which they are arranged is formed of a magnetic material such as iron, whereby the second wall functions as a magnetic circuit forming member, and heat exchange is effected between the second wall and the external air to thereby cool the lower surface of the armature coils 38. In this case, it is desirable for the second wall to be formed of a magnetic material having high heat conductivity. Second Embodiment Next, the second embodiment of the present invention will be described with reference to Fig. 8(a). The second embodiment slightly differs from the first embodiment in the internal construction of the base main body 22. Apart from this, its construction is the same as that of the first embodiment, so a description of the components which are common to these embodiments will be abridged or omitted, and the same or equivalent components are indicated by the same reference numerals. Fig. 8(A) is a partially omitted sectional view of the base main body 22 of the second embodiment. In the second embodiment, the armature coils 38 are arranged in the vacuum chamber 41 of the base main body 22 two-dimensionally at predetermined intervals along the movement surface 21a and in contact with the stator yoke 43, as in the above-described first embodiment. However, the movement surface 21a side of the vacuum chamber 41 is defined by a thin plate 82 formed of a non-magnetic material and arranged so as to be in contact with the movement surface side of the armature coils 38, and a refrigerant passage 99 as a fluid passage is provided on the movement surface 21a side of the vacuum chamber 41. Liquid refrigerant from the cooling device 79 of Fig. 1 is supplied in circulation to this refrigerant passage 99. Apart from this, the construction of the embodiment is the same as that of the first embodiment. In the second embodiment, constructed as described above, the same effect as that of the above-described first embodiment can be obtained. That is, since the armature coils 38 are arranged in the vacuum chamber 41 in the base, and the refrigerant passage 99 is provided on the side of the movement 21a forming the vacuum chamber 41 , the heat transmission from the armature coils 38 is effected practically by radiation alone in the vacuum portion in the vacuum chamber (more specifically, between the hollow portions of the armature coils 38 and the columns 80, and between the central gap between adjacent armature coils 38 and the columns 80), and the heat transmitted to the movement surface 21a side in the vacuum chamber 41 is removed by heat exchange with the liquid refrigerant flowing through the refrigerant passage 99 and controlled to be at a temperature lower than the base ambient temperature. Thus, it is possible to effectively restrain the thermal influence on the environment. Fig. 8B is a cross-sectional diagram illustrating the properties of coolant flow through the refrigerant passage 99. In convective heat transfer, a cool fluid flowing in a direction from left to right through the refrigerant channel 99 between a warm surface, in this case thin plate 82, and a cool surface, ceramic plate 36, creates a thermal boundary as seen in Fig. 8B. The thin plate 82 is heated due to the armature coils 38 of Fig. 8A. The thermal boundary layer extends from the thin plate 82 into the passage 99 toward the ceramic plate 36. The boundary layer thickness gradually increases with distance along the flow direction from the entrance of the passage, from left to right in the illustrated figure. If the boundary layer were to continue to grow until fully developed, it would extend completely across passage 99. However, if at the outlet end of the passage, the boundary layer has not completely extended across the passage 99, minimal heat is transferred across the passage 99, and the temperature of the ceramic plate 36 remains near its original upstream temperature, which is significantly lower than the temperature of the thin plate 82. In this fashion, the heat transferred from the thin plate 82 into the passage 99 to create the thermal boundary layer is removed at the outlet end (not shown) of the passage 99 by the coolant flowing through the passage. In order to create the above described flow and boundary layer, it is desirable that the surface of the thin plate 82 be finished with satisfactory flatness so that the boundary layer of the flow of the liquid refrigerant flowing along the thin plate 82 may be a laminar flow (not more than critical Reynolds number). This prevents mass transfer of warm fluid from the armature coils 38 into the flow through the refrigerant passage 99 and the corresponding fast boundary layer growth of turbulent flows. Accordingly, this makes the flow between the thin plate 82 and the ceramic plate 36 a flow having a boundary between high temperature and low temperature portions as described above and shown in Fig. 8(B), whereby it is possible to reliably prevent the heat of the armature coils 38 from being transmitted to the ceramic plate 36. While in the above-described first and second embodiments the liquid refrigerant as the fluid is used in circulation, this should not be construed restrictively. That is, instead of a liquid, a gas may be used as the fluid. When, for example, air or the like is used as the fluid, it is not absolutely necessary to use it in circulation. While in the above embodiments the stage device of the present invention is applied to a substrate stage device, the stage device is also naturally applicable to a reticle stage, RST. As described with reference to the above embodiments, in the exposure device of the present invention, the positional control of the substrate can be effected accurately and quickly, and the components of the device are connected and assembled electrically, mechanically or optically so that exposure can be effected with high exposure accuracy while improving throughput. While in the above embodiments the planar motor device of the present invention is applied to the substrate stage device of a scanning type DUV exposure device, this should not be construed restrictively. It is also naturally applicable to static exposure devices such as steppers. Further, it is also applicable to charged particle beam exposure devices such as electron beam exposure devices and EUVL exposure devices using light having a wavelength in a soft X-rays range of 5 to 15 nm as the exposure light, and to devices other than exposure devices, such as inspection devices and substrate conveying devices. Further, the technical idea of the present invention, according to which armature coils are arranged in a vacuum chamber, is also applicable to a linear motor. Having thus described the invention in considerable detail with reference to certain preferred embodiments thereof, it will be appreciated that other embodiments are possible. It will be understood by those skilled in the art that many changes in construction of the invention will suggest themselves without departing from the spirit and scope of the invention. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiments contained therein.

Claims: WHAT IS CLAIMED IS: 1. A planar motor device comprising: a magnet unit having at least one magnet and adapted to move two- dimensionally along a predetermined movement surface; a base having said movement surface on the side opposing said magnet unit and having a vacuum chamber capable of maintaining a vacuum state in the interior thereof; and a plurality of armature coils arranged in said vacuum chamber two- dimensionally along said movement surface so as to define a predetermined gap between them and a first wall on the side of said movement surface forming said vacuum chamber. 2. The planar motor device according to Claim 1 , wherein a deformation preventing member for preventing deformation of said base by said vacuum state is provided between said first wall forming said vacuum chamber and a second wall opposed to the first wall. 3. The planar motor device according to Claim 2, wherein at least a part of said deformation preventing member is formed of a heat insulating material. 4. The planar motor device according to Claim 2, wherein a surface area of a portion of said deformation preventing member which is in contact with said second wall is smaller than a surface area of other portions of said deformation preventing member. 5. The planar motor device according to Claim 4, wherein said base further comprises a fluid passage, through which fluid is passed, in contact with said vacuum chamber through said second wall on a side of said vacuum chamber opposite to said movement surface. 6. The planar motor device according to Claim 5, further comprising a temperature controlling device for controlling the temperature of said fluid passing through said fluid passage. 7. The planar motor device according to Claim 6, wherein said temperature controlling device controls said fluid to a temperature lower than the ambient temperature of said base. 8. The planar motor device according to Claim 7, wherein the fluid passage is configured such that the flow of said fluid flowing at least along said second wall of the fluid passage is a turbulent flow. 9. The planar motor device according to Claim 8, wherein the fluid passage has a cross-sectional area which is substantially fixed throughout the entire length thereof. 10. The planar motor device according to Claim 9, further comprising a coolant passage having a first side in contact with the movement surface side of the vacuum chamber and a second side in contact with the first wall, wherein the fluid is flowed through the coolant passage. 11. The planar motor device according to Claim 10, wherein the coolant passage is configured such that the flow of fluid through the coolant passage along the side in contact with the vacuum chamber is a laminar flow. 12. The planar motor device according to Claim 11 , wherein the fluid flowing through the coolant passage has a thermal boundary layer having a thickness over the length of the coolant passage less than a distance between the first side and the second side of the coolant passage. 13. The planar motor device according to Claim 1 , wherein a heat insulating material is provided between said first wall forming said vacuum chamber and said armature coils. 14. A planar motor device comprising: a magnet unit having at least one magnet and adapted to move two- dimensionally along a predetermined movement surface; a base having said movement surface on a side opposed to said magnet unit and including a vacuum chamber capable of maintaining a vacuum state in its interior and situated on the movement surface side of said vacuum chamber; and a plurality of armature coils arranged in said vacuum chamber two- dimensionally at predetermined intervals along said movement surface. 15. A substrate stage device to position a substrate for an exposure operation, including the planar motor device as claimed in any one of Claims 1 through 14. 16. An exposure device for transferring a predetermined pattern to a substrate, using the planar motor device as claimed in any one of Claims 1 through 14 to drive said substrate on a substrate stage. 17. An exposure apparatus for transferring a pattern onto an object, comprising: an exposure device that transfers the pattern onto the object; a stage device associated with the exposure device, the stage device having a movable stage and a drive to drive the movable stage; a vacuum chamber that surrounds at least part of said stage device in a vacuum state; and a cooling device connected to said stage device to cool said stage device. 18. The exposure apparatus according to Claim 17, wherein said stage device holds the object. 19. The exposure apparatus according to Claim 17, wherein said vacuum chamber surrounds at least part of the drive. 20. The exposure apparatus according to Claim 17, wherein said cooling device cools said stage device by a fluid. 21. The exposure apparatus according to Claim 17, wherein said cooling device is located outside of said vacuum chamber. 22. The exposure apparatus according to Claim 17, wherein said drive is a planar motor. 23. The exposure apparatus according to Claim 17, wherein said pattern is formed on a mask. 24. The exposure apparatus according to Claim 23, wherein said stage device holds the mask. 25. The exposure apparatus according to Claim 16, wherein said exposure device transfers said pattern by an electron beam.

Inventors: EATON JOHN K, HAZELTON ANDREW J, TANAKA KEIICHI, EATON, JOHN, K., HAZELTON, ANDREW, J., TANAKA, KEIICHI
Applicants: EATON JOHN K, HAZELTON ANDREW J, NIPPON KOGAKU KK, TANAKA KEIICHI, EATON, JOHN, K., HAZELTON, ANDREW, J., NIKON CORPORATION, TANAKA, KEIICHI
Application year: 1999
Main classification: G03F
IPC codes: G03F7, H01J37, H01L21, H02K41