JP4123558B2 - Exposure equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exposure apparatus used for transferring a mask pattern onto a photosensitive substrate in a lithography process for manufacturing, for example, a semiconductor element, a liquid crystal display element, or a thin film magnetic head.
[0002]
[Prior art]
Projection exposure apparatus for transferring an image of a reticle pattern as a mask to each shot region on a wafer (or glass plate or the like) coated with a resist as a substrate via a projection optical system when manufacturing a semiconductor element or the like Is used. Conventionally, as a projection exposure apparatus, a step-and-repeat type (batch exposure type) projection exposure apparatus (stepper) has been widely used. Recently, a reticle and a wafer are scanned synchronously with respect to a projection optical system. A scanning exposure type projection exposure apparatus (scanning type exposure apparatus) such as a step-and-scan system in which exposure is performed is also attracting attention.
[0003]
In a conventional exposure apparatus, a reticle stage that supports and conveys a reticle that is a pattern original and a wafer to which the pattern is transferred, and a drive unit of the wafer stage are fixed to a structure that supports a projection optical system, In addition, the vicinity of the center of gravity of the projection optical system is also fixed to the structure. Further, in order to position the wafer stage with high accuracy, the position of the wafer stage is measured by a laser interferometer, and a moving mirror for the laser interferometer is attached to the wafer stage.
[0004]
Further, in order to transfer the wafer to the wafer holder on the wafer stage, a wafer transfer arm for removing the wafer from the wafer cassette and transferring it to the wafer holder side and a wafer transfer arm for transferring the wafer from the wafer holder to the wafer cassette side are provided independently. When the wafer is carried in, the wafer carried by the wafer transfer arm is temporarily fixed and supported by a dedicated liftable support member provided in the wafer holder, and then the transfer arm is retracted. After that, the support member was lowered and the wafer was placed on the wafer holder. Thereafter, the wafer is vacuum-sucked on the wafer holder, and the reverse operation is performed when the wafer is unloaded from the exposure apparatus.
[0005]
[Problems to be solved by the invention]
As described above, in the conventional exposure apparatus, since the driving unit such as the wafer stage and the projection optical system are fixed to the same structure, the vibration generated by the driving reaction force of the stage is transmitted to the structure, and further the projection optical system. The vibration was also transmitted. Since all mechanical structures mechanically resonate with vibrations of a predetermined frequency, transmission of such vibrations to the structure causes deformation of the structure and resonance phenomenon, resulting in misalignment of the transferred pattern image. And there is a disadvantage that the contrast is lowered.
[0006]
Further, since the wafer stage moves a long distance from the wafer loading / unloading transfer arm to the exposure position, it is necessary to include a very long moving mirror for the laser interferometer. For this reason, the weight of the wafer stage is considerably heavy, and a heavy motor with a large driving force is required, so that the driving reaction force is also large. Further, when the moving speed or acceleration of the stage is increased in order to improve the throughput, the driving reaction force is further increased. As the mass and acceleration of the stage increase, the amount of heat generated by the motor also increases, resulting in inconvenience that the measurement stability of the laser interferometer decreases.
[0007]
Further, when the wafer is carried into and out of the exposure apparatus, the wafer is temporarily fixed and supported on a dedicated support member, so that it takes time to carry the wafer in and out, which causes a decrease in throughput. It was. Further, as an example, since transfer of wafers between transfer arms is performed, there is a high probability that the wafer will be contaminated with foreign matter, and there is a high probability that an operation error will occur when the wafer is transferred. In addition, since the number of transfer arms is a factor that determines the size of the transfer unit, if the transfer arms transfer wafers between transfer arms on the transfer path, the transfer path becomes longer and the floor required for installing the exposure apparatus is required. The area (footprint) was also large.
[0008]
  SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide an exposure apparatus that can perform high-precision exposure by reducing the influence of vibration generated when driving a wafer stage or the like on a projection optical system or the like. To do.
[0009]
[Means for Solving the Problems]
  The exposure apparatus of the present invention is an exposure apparatus for transferring an image of a pattern of a mask (1) onto a substrate (3) via a projection optical system (2).A mask stage (4) for moving the mask, a structure (6) for supporting the mask stage and the projection optical system, a substrate stage (5) for moving the substrate,A point on the optical axis of the projection optical system (hereinafter referred to as “reference point (17)”) that internally divides the distance between the object plane (15) and the image plane (16) of the projection optical system by the projection magnification ratio. Projection optical system support portions (19A to 19C) that support the projection optical system so that the projection optical system can rotate within a predetermined range.And the projection optical system support section includes at least three flexible structure support means extending from the structure, and each support line has its extension line intersecting at its reference point.It is.
[0010]
  The present inventionAccording to the above, even if the projection optical system (2) rotates within a predetermined range around the reference point (17), the positional relationship between the object plane (15) and the image plane (16) does not change. Accordingly, the projection optical system (2) is supported by the projection optical system support portions (19A to 19C), so that the projection optical system (2) is vibrated from the mask stage (4) and the substrate stage (5). Is transmitted, the positional relationship between the mask (1) and the substrate (3) does not shift, and thus the positional deviation of the pattern transferred onto the substrate (3) can be prevented.
[0011]
  Further, even if vibration is transmitted to the projection optical system (2), the projection optical system (2) is only slightly rotated around the reference point (17), so that the pattern transferred onto the substrate (3) Misalignment can be prevented, and the projection optical system support is flexible.Have meansTherefore, the minute vibration is attenuated with a simple configuration, and the deterioration of the contrast of the projected image can be prevented.
[0012]
  Further, in the present invention, a reference mirror having a substantial center on a plane passing through the reference point and perpendicular to the optical axis of the projection optical system, and a measurement beam is irradiated to the center of the reference mirror, and the reference A substrate-side laser interferometer that measures the position of the substrate stage with respect to a mirror.
[0013]
  Further, in the present invention, a reference mirror having a substantial center on a plane passing through the reference point and perpendicular to the optical axis of the projection optical system, and a measurement beam is irradiated to the center of the reference mirror, and the reference A mask-side laser interferometer that measures the position of the mask stage with reference to a mirror.
[0014]
  Further, the structure (6) can be supported via an anti-vibration mechanism (49) on the installation surface of the base member (7) on which the substrate stage (5) is placed. in this case,Since the structure (6) is separated from the substrate stage (5), the projection optical system (2) is hardly affected by the movement of the substrate stage (5).
[0015]
  In addition, the support means of flexible structure (19A-19C) may have a rod.
[0016]
  Also, the support means of the flexible structure (19A ~19C) may suspend and support the outer periphery of the projection optical system (2).
[0017]
  In the present invention,As an example, the substrate stage (5) isA substrate table (20) for holding and moving the substrate (3) and a substrate stage (5) are supported.Base member(7) at least three supporting the substrate table (20) aboveTelescopic with respect to the support directionSupport legs (31A to 31C), Support legs (31A to 31C),Base memberBetween (7)ArrangedFluid bearing mechanism (32A-32C)WhenIt is what has.
[0018]
  This configurationAccording to the above, the tilt angle of the substrate table (20) or the position in the height direction is controlled by controlling the amount of expansion / contraction of the support legs (31A to 31C) that are extendable within a predetermined range with respect to the support direction. The surface of the substrate (3) can be matched with the image plane of the projection optical system (2) with a simple configuration.IncludedExposure can be performed.
[0019]
In addition, the mask (1) and the substrate (3) are moved synchronously during exposure, and the inclination angle in the scanning direction of the running surface of the substrate stage (5) of the structure (7) in the non-scanning direction. It is desirable to detect the tilt angle and height, and to control the extendable support legs (31A to 31C) based on the detection result. As a result, when performing scanning exposure as in the step-and-scan method, exposure can be performed with high accuracy while aligning the surface of the substrate (3) with the image plane.
[0020]
  Further, the rotation angle of the projection stage (5) around the optical axis of the projection optical system (2) and the amount of displacement are detected, and the mask stage (4) or the substrate stage is detected based on the detection result. It is desirable to control the position of (5). Thereby, the mask (1) and the substrate (3) can be superimposed with high accuracy.
  next,In the present invention,Supports the substrate stage (5)Base member(7) andBase memberA support portion (8) that supports (7) and drives in the height direction. The support portion (8) and the support portion (8)Base member(7) with viscoelastic bodyMay.
[0021]
  This configurationAccording toBase memberBy having the viscoelastic body between the support portion (8) that supports (7) and is driven in the height direction, vibration from the floor on which the exposure apparatus is installed can be reduced.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an exemplary embodiment of the present invention will be described with reference to the drawings. In this example, the present invention is applied to a step-and-scan type projection exposure apparatus.
FIG. 1 shows a projection exposure apparatus of the present example. In FIG. 1, a mercury lamp i-line from an illumination optical system (not shown) or KrF, ArF, F in FIG.₂ Exposure light such as excimer laser light or the like illuminates the illumination area of the pattern surface of the reticle 1. Then, the pattern image in the illumination area of the reticle 1 is projected onto the wafer 3 coated with the photoresist through the projection optical system 2 at a predetermined projection magnification β (β is usually 1/4, 1/5, etc.). Exposed. In the following description, the Z axis is taken parallel to the optical axis AX of the projection optical system 2 in the absence of vibration, and the orthogonal coordinate system in a plane perpendicular to the optical axis AX is taken as the X axis and Y axis.
[0025]
First, the reticle 1 is held on the reticle stage 4, and the reticle stage 4 continuously moves in the X direction (scanning direction) on the reticle base 9 in a linear motor system, and the position of the reticle 1 in the XY plane is fine. Make adjustments. The two-dimensional position of the reticle stage 4 (reticle 1) is measured by the movable mirrors 43X and 43Y on the reticle stage 4 and the laser interferometers 18X and 18Y, and this measurement value is from a computer that controls the overall operation of the apparatus. The main control system 50 controls the position and movement speed of the reticle stage 4 via the reticle stage control system 52 based on the measured value.
[0026]
On the other hand, the wafer 3 is held on the wafer stage 5 by vacuum suction, and the wafer stage 5 is placed on the wafer base 7 via three support legs 31A to 31C that are extendable within a predetermined range in the Z direction. ing. The expansion / contraction amount of the support legs 31A to 31C is controlled by the support leg control system 63 (see FIG. 16), and by making the expansion / contraction amount of the support legs 31A to 31C the same, the position of the wafer 3 in the Z direction (focus position) is adjusted. Control is performed, and the tilt angle of the surface of the wafer 3 is controlled (leveling) by independently controlling the amount of expansion / contraction of the support legs 31A to 31C.
[0027]
Further, the wafer stage 5 can be continuously moved on the wafer base 7 in the X direction and the Y direction by, for example, a linear motor method. Further, stepping can also be performed by the continuous movement. Further, in order to perform coordinate measurement of the wafer 3 (wafer stage 5), an X-axis movable mirror 44X (see FIG. 3) having a reflecting surface substantially perpendicular to the X-axis on the side surface of the wafer stage 5 and A Y-axis moving mirror 44Y (see FIG. 3) having a substantially vertical reflecting surface is fixed. Corresponding to these movable mirrors, an X-axis reference mirror 14 and a Y-axis reference mirror 13 are fixed to the side surface of the projection optical system 2.
[0028]
At the time of scanning exposure, the reticle stage 4 is moved at a constant speed in the X-axis direction, and the wafer stage 5 on which the wafer 3 is placed is moved at a speed obtained by reducing the movement speed of the reticle stage 4 by the projection magnification β times in synchronization therewith. Scanning exposure is performed by moving in the reverse direction. After the scanning exposure is completed, the wafer stage 5 is moved stepwise in the scanning direction or the Y-axis direction orthogonal to the scanning direction, and the reticle stage 4 and the wafer stage 5 are moved in synchronization with the opposite direction to the previous scanning exposure. . Thereafter, the pattern image of the reticle 1 is transferred to all shot areas on the wafer 3 by the same operation.
[0029]
Next, the reticle stage and reticle base of the exposure apparatus of this example will be described.
The reticle stage 4 is a guideless stage as disclosed in JP-A-8-63231, and can be driven in the X-axis direction, the Y-axis direction, and the rotation direction around the optical axis AX of the projection optical system 2. is there. Further, a pair of linear motors for driving the reticle stage 4 is constituted by a coil fixed to the side surface of the reticle stage 4 and a pair of motor magnets 11A and 11B fixed on the reticle base 9 so as to face each other. The reticle base 9 is supported on the upper surface 10 of the structure 6 via a fluid bearing (not shown) such as an air bearing. A pair of linear motors composed of the motor magnets 11A and 11B and the coil units 12A and 12B are inserted by inserting the ends of the coil units 12A and 12B installed on the structure 6 from the ends of the motor magnets 11A and 11B. Thus, the reticle base 9 is positioned in the X-axis direction with respect to the structure 6. And the structure 6 is supported on the floor by the anti-vibration pad 49 via the four leg parts 6a, and reduces the vibration from a floor.
[0030]
When the reticle base 9 receives a driving reaction force applied by the motor magnets 11A and 11B when the reticle stage 4 moves during scanning exposure, the reticle base 9 is moved in a direction opposite to the moving direction of the reticle stage 4 by the linear motor having the coil units 12A and 12B. Move to save momentum. For example, when the reticle stage 4 and the reticle base 9 have masses of 20 kg and 1000 kg, respectively, and the reticle base 9 has a mass 50 times that of the reticle stage 4, the reticle stage 4 moves about 300 mm during scanning. The reticle base 9 is moved in the direction opposite to the moving direction of the reticle stage 4 by about 6 mm. By moving the reticle stage 4 and the reticle base 9 so as to preserve the momentum, transmission of the driving reaction force of the reticle stage 4 to the structure 6 is prevented, and generation of vibration that becomes a disturbance during positioning of the reticle stage 4 is generated. Can be prevented. Note that the displacement amount of the reticle base 9 is always measured by a linear encoder (not shown), and a current signal for driving the reticle stage 9 is generated based on the measured value.
[0031]
Further, in the projection exposure apparatus of this example, the center of gravity of the system above the reticle base 9 is not moved, so that the structure 6 that supports the reticle base 9 is not subjected to a variable load, and the reticle stage 4 and the projection optical system. The positions of the reference mirrors 13 and 14 used for measuring the relative position with respect to 2 do not fluctuate. If the reticle base 9 is mechanically interfered with other members when the reticle base 9 is displaced by a predetermined amount or more, coil units 12A and 12B, which are electromagnetic drive units provided between the reticle base 9 and the structure 6, are provided. What is necessary is to keep the reticle base 9 at a substantially constant position at all times while reducing vibrations to be controlled and transmitted to the structure 6. Thereby, it is possible to prevent the reticle base 9 from interfering with other members.
[0032]
Next, a method for supporting the projection optical system of the exposure apparatus of this example will be described.
FIG. 2 shows the projection optical system 2 of the exposure apparatus of the present example. In FIG. 2, the object plane 15 and the image plane 16 on the optical axis AX are set at a reduced projection magnification ratio β (= a / b). A point to be divided is set as a reference point 17 of the projection optical system 2. Even if the projection optical system 2 is slightly rotated with respect to an arbitrary axis in a plane orthogonal to the optical axis AX with the reference point 17 as the center, the positional relationship between the object plane 15 and the image plane 16 does not change. The centers of the reference mirrors 13 and 14 are set on a plane that passes through the reference point 17 and is perpendicular to the optical axis AX, and a laser beam is irradiated to these centers. Therefore, even when the projection optical system 2 is swung by disturbance vibration, the plane including the reference point 17 and orthogonal to the optical axis AX of the projection optical system 2 and the outer surface of the lens barrel enclosing the projection optical system 2 The relative displacement between the crossing point (reference mirrors 13 and 14), reticle stage 4 and wafer stage 5 is always measured by laser interferometers 18X and 18Y, and reticle stage 4 is set so that the measured value and the target value coincide with each other. By controlling the wafer stage 5, it is possible to prevent the positional deviation of the pattern formed on the wafer 3.
[0033]
Further, the lower portion of the projection optical system 2 is passed through an opening of a support plate 6b laid between the legs 6a with a gap, and the support portion of the projection optical system 2 includes three pieces extending from the structure 6. The rods 19 </ b> A to 19 </ b> C have a flexible structure, and the extension lines of the rods 19 </ b> A to 19 </ b> C intersect at one point, and the intersection points coincide with the reference point 17. Therefore, even when the projection optical system 2 is swung due to disturbance vibrations, the projection optical system 2 is slightly rotated around the reference point 17, so that the positions of the reference mirrors 13 and 14 in the X and Y directions are almost displaced. do not do. Further, since the rods 19A to 19C have a flexible structure, high-frequency vibrations are attenuated, and contrast deterioration during pattern transfer hardly occurs.
[0034]
Next, the wafer stage of the exposure apparatus of this example will be described.
As shown in FIG. 1, the wafer stage 5 is positioned on the wafer base 7, and the wafer base 7 is supported by an elevator driving unit 8 that can be displaced by several hundred μm in the vertical direction. In addition, a viscoelastic body (not shown) is provided between the wafer base 7 and the elevator drive unit 8 so that vibration from the floor can be reduced. In addition, the wafer base 7 is provided with five speed sensors (two of which are shown in FIG. 16), and the movement of the wafer stage 5 is measured. An acceleration sensor may be used instead of the speed sensor.
[0035]
3A to 3D are enlarged views of the wafer stage 5 of the exposure apparatus of this example, FIG. 3A is a plan view of the wafer table 20, and FIG. 3B is a BB line in FIG. 3A. 3 (c) is a front view of FIG. 3 (a) (however, the carrier 21 is not shown), and FIG. 3 (d) is a sectional view taken along the line DD of FIG. 3 (a). First, in FIG. 3D, the wafer stage 5 has a wafer table 20 on which the wafer 3 is placed and a carrier 21 that conveys a driving guide portion thereof. The carrier 21 is movable on the wafer base 7 and is driven in the X direction and the Y direction by a pulse motor type planar motor (for example, a soy motor). In this example, when the carrier 21 is driven, a pulse motor (not shown) is used for pulses according to the distance to the target position in an open loop system, and the pulses up to the target position are output to the motor controller. Therefore, it is not necessary to newly provide a position measuring device for the carrier 21. An ultrasonic motor can be used as the planar motor.
[0036]
On the other hand, as shown in FIG. 3A, a plurality of parallel shallow grooves 39 for vacuum-sucking the wafer 3 are provided on the upper surface of the wafer table 20, and many holes of the shallow grooves 39 are not shown. It communicates with the vacuum pump. Further, a deep groove 38 for inserting and removing a wafer transfer arm, which will be described later, is provided in the gap between the four shallow grooves 39 in the center without interfering with the shallow grooves 39, and the wafer 3 is fixed on the wafer table 20. At this time, the wafer transfer arm used for transferring the wafer 3 can be taken in and out without contacting the wafer table 20.
[0037]
Further, as shown in FIG. 3B, a guide shaft 22B is installed on the carrier 21 via a support member 22C in the scanning direction (X direction), and the guide member straddles the guide shaft on the bottom surface of the wafer table 20. 22A is fixed. The wafer table 20 is restrained by a non-contact type guide shaft (for example, a fluid bearing or a magnetic bearing) including a guide member 22A and a guide shaft 22B for guiding the wafer table 20 in the X direction on the carrier 21. 3 (d), a pair of linear motors 23A, 24A, and 23B, which are composed of coil portions 23A and 23B fixed to the carrier 21 and magnet portions 24A and 24B fixed to the bottom surface of the wafer table 20. 24B is configured, and the linear motors 23A, 24A and 23B, 24B as non-contact type electromagnetic drive units drive the wafer table 20 in the Y direction and the rotation direction, and a linear encoder as a non-contact type position measuring device The displacement of the wafer table 20 relative to the carrier 21 is measured by (not shown). Further, the guide shaft 22B has a structure that can be rotated around the guide shaft by a rotating member 22D. When the linear motors 23A, 24A, and 23B, 24B generate driving force in the same direction, the wafer table 20 moves in the guide axis direction (X direction), and conversely, the linear motors 23A, 24A, 23B, When the driving force is generated in different directions, the wafer table 20 rotates around its center of gravity.
[0038]
Further, the centers of the thrusts of the linear motors 23A, 24A and 23B, 24B and the center of the guide member 22A are arranged so as to be located on a plane including the center of gravity of the wafer table 20 and parallel to the upper surface of the wafer base 7. Thus, an unnecessary tilt of the wafer table is prevented from occurring when the wafer table 20 is accelerated. Further, since the guide shaft 22B and the linear motors 23A, 24A, and 23B, 24B need only be long enough to move the wafer during scanning exposure, the carrier 21 is placed below the wafer table 20. It is configured to be small so that it can be accommodated, and the wafer can be moved at high speed and with high accuracy.
[0039]
Further, since the positioning accuracy required for transferring the wafer 3 is about several μm, there is no particular need for measurement by a laser interferometer in the region for transferring the wafer 3, and the resolution of the pulse motor or the position measurement of the carrier 21 is not required. The resolution of the vessel is sufficient. Accordingly, the moving mirrors 44X and 44Y provided on the wafer table 20 of FIG. 3 for the laser interferometers 18X and 18Y do not necessarily need to cover the entire moving area of the wafer table 20, but need to be precisely positioned in nm units. Only the length of the diameter of the wafer 3 is sufficient.
[0040]
Moving mirrors 44X and 44Y for the laser interferometer 18 are provided on the side surface of the wafer table 20 in this example, and the position of the wafer table 20 and the rotation angle around the Z axis are measured. Since the side surface of the wafer table 20 is used as the moving mirrors 44X and 44Y for the laser interferometers 18X and 18Y, the wafer table 20 is approximately the size that circumscribes the wafer 3, and is much larger than the conventional wafer table. It is small and lightweight. If the wafer table 20 is made of silicon carbide and has a thickness of about 3 mm and a rib structure on the bottom surface, the wafer table 20 weighs about 5 kg.
[0041]
FIG. 4 is a block diagram showing the configuration of a control system for controlling the wafer table 20 and the carrier 21. In FIG. 4, the main control system 50 supplies wafers to the subtracting units 54 and 57 in the wafer stage control system 25, respectively. The target positions of the table 20 and the carrier 21 are supplied. Then, the relative displacement amount of the wafer table 20 with respect to the carrier 21 is detected by a virtual subtraction unit 56 and a displacement sensor (linear encoder) 60, and the table control system 55 determines the output of the subtraction unit 54 or the displacement sensor 60. Based on this, the wafer table 20 is driven, and the carrier control system 58 drives the carrier 21 based on the output of the subtractor 57. The subtractor 54 outputs a value obtained by subtracting the measured values of the laser interferometers 18X and 18Y from the target value, and the subtractor 57 outputs a value obtained by subtracting the measured value of the virtual linear encoder 59 for the carrier 21 from the target value. To do.
[0042]
When the laser interferometers 18X and 18Y (see FIG. 1) are not used with the mode switch 26 turned off, that is, during rough positioning, the wafer stage control system 25 is based on the signal from the displacement sensor 60 as a linear encoder. The linear motors 23A, 24A and 23B, 24B in FIG. 3 are controlled so that the table 20 is always positioned at the midpoint of the movement range with respect to the carrier 21. When the drive unit of the carrier 21 has the encoder 59, the carrier control system 58 moves the carrier 21 to the target position while referring to the encoder 59, and when the encoder does not have an encoder as in the pulse motor of this example. In this case, pulses up to the target position are output to the motor controller to control the carrier 21. Therefore, the wafer table 20 is controlled to move while following the carrier 21 regardless of the presence or absence of the encoder.
[0043]
When the mode switch 26 of FIG. 4 is on and the wafer table 20 moves based on the measurement values of the laser interferometers 18X and 18Y, that is, during precise positioning, the table control system 55 is connected to the laser interferometers 18X and Based on the output of the subtracting unit 54 referring to the measured value of 18Y, thrust is generated in the linear motors 23A, 24A and 23B, 24B on the wafer table 20 to move the wafer table 20. The carrier 21 is controlled in the same manner as in the rough positioning.
[0044]
When the wafer table 20 moves at a constant speed while using the laser interferometers 18X and 18Y, that is, during scanning exposure, the table control system 55 outputs the output of the subtracting unit 54 that subtracts the measured values of the laser interferometers 18X and 18Y. Referring to FIG. 5, the thrust is generated in the linear motors 23A, 24A and 23B, 24B, and the wafer table 20 is moved. At this time, the carrier 21 remains stationary, and only the wafer table 20 moves at a constant speed. Accordingly, since only the lightweight wafer table 20 generates a driving reaction force on the wafer base 7 during scanning exposure, the generated disturbance force is extremely small, and scanning exposure can be performed at high speed and with high accuracy. .
[0045]
Next, the guide member 22A and the guide shaft 22B of the wafer table 20 of the exposure apparatus of this example will be described.
FIG. 5 is an enlarged view of the guide member 22A and the guide shaft 22B shown in FIG. 3. In FIG. 5, springs 27A and 27B as elastic bodies are provided at both ends of the guide shaft 22B. When the wafer table 20 reciprocates with respect to the carrier 21, first, as shown in FIG. 5A, the kinetic energy of the wafer table 20 is converted into potential energy through the guide member 22A, and the spring 27A. Stored in. Next, as shown in FIG. 5B, the potential energy stored in the spring 27A is converted again into the kinetic energy of the wafer table 20, and the wafer stage control system 25 in FIG. 20 is controlled to move at a constant speed of −V. As shown in FIG. 5C, when the support member 22A hits the spring 27B, a repulsive force of + F is generated in the spring 27B, and the kinetic energy of the wafer table 20 is again converted into potential energy and stored in the spring 27B. . Accordingly, the mechanical energy consumed when reciprocating the wafer table 20 is mainly the viscous resistance to the air of the wafer table 20 and the heat generated when the elastic body is deformed, and the linear motors 23A, 24A and 23B. , 24B is extremely small.
[0046]
FIG. 6A shows a wafer table when the moving speed of the wafer table 20 is shifted to a constant speed (0.5 m / s) on the guide shaft 22B that is assumed to be a guide shaft not provided with an elastic body. FIG. 6A shows a time curve, and the horizontal axis represents time t (s), and the vertical axis represents the moving speed V (m / S) of the wafer table 20. FIG. 6B shows the thrusts of the linear motors 23A, 24A and 23B, 24B at that time. In FIG. 6B, the horizontal axis represents time t (s), and the vertical axis represents the linear motor. This is the thrust F (N). The used wafer table 20 has a weight of 5 kg. FIG. 7A shows a wafer table calculated on the assumption that an ideal wafer table 20 having no resonance is accelerated to a constant speed on a guide shaft having a predetermined spring corresponding to FIG. 6A. FIG. 7B shows linear motors 23A and 24A calculated on the assumption that the wafer table 20 that resonates is controlled using the speed curve of FIG. 7A as the speed command value. The thrust F (N) of 23B and 24B is shown. When FIG. 6 is compared with FIG. 7, the ratio of the calorific values of the linear motors 23A, 24A and 23B, 24B is 1: 0.94, which is substantially the same.
[0047]
FIG. 8A shows a speed curve when the wafer table 20 is accelerated to a constant speed using the guide shaft 22B provided with the springs 27A and 27B of FIG. 5 using the speed curve of FIG. 7A as a speed command value. FIG. 8B shows the thrust of the wafer table 20 at that time and the thrust generated by the linear motors 23A, 24A and 23B, 24B. In FIG. 8B, the horizontal axis represents time t (s The vertical axis represents the thrust F (N), the solid curve A represents the thrust applied to the wafer table 20, and the dashed line curve B represents the thrust of the linear motors 23A and 23B. The spring constants of the springs 27A and 27B are 1000 N / m, which is 40% of the ideal spring constant (2500 N / m). By using the springs 27A, 27B, the heat generation amount of the linear motors 23A, 24A and 23B, 24B can be reduced to about 35% of the heat generation amount when the elastic body is not used.
[0048]
FIG. 9A shows a speed curve when the wafer table 20 is accelerated to a constant speed by using the guide shaft 22B having the springs 27A and 27B having the optimum spring constant of 2500 N / m. (B) shows the thrust F of the wafer table 20 at that time. The amount of heat generated by the linear motors 23A, 24A and 23B, 24B is reduced to 1% or less when no elastic body is used. Thus, by providing the springs 27A and 27B at both ends of the guide shaft 22B, it is possible to reduce the amount of heat generated by the linear motors 23A and 24A and 23B and 24B when the wafer table 20 is moved at a constant speed.
[0049]
However, when the wafer table 20 is statically positioned at the end of the guide shaft 22B, the linear motors 23A, 24A, 23B, and 24B need to generate thrust that is balanced with the drag of the springs 27A and 27B. On the contrary, the heat generation amount of the motors 23A, 24A and 23B, 24B may increase.
FIG. 10 shows the drag of the springs 27A, 27B at the end of the guide shaft 22B with the springs 27A, 27B. In FIG. 10, the horizontal axis is the distance D (m) from the end of the guide shaft 22B, and the vertical The shaft is the drag F of the springs 27A and 27B_P (N). In order to statically position the wafer table 20 at the end of the guide shaft 22B, the linear motors 23A, 24A and 23B, 24B need to generate a large thrust (50 N) sufficient to balance the drag of the springs 27A, 27B. The calorific value increases. Therefore, in such a case, it is desirable to attach a magnetic member to the end portion of the guide shaft 22B and reduce the amount of heat generated when the wafer table 20 is stationaryly positioned using the attractive force.
[0050]
FIG. 11 shows a guide member 22A and a guide shaft 22B attached with magnetic members corresponding to FIG. 5. In FIG. 11, iron plates 29 are provided at both ends of the guide member 22A, and magnets 30 are provided at both ends of the guide shaft 22B. It is attached. As shown in FIG. 11A or 11C, when the wafer table 20 is stationaryly positioned via the guide member 22A at the end of the guide shaft 22B, the attractive force between the iron plate 29 and the magnet 30 is applied. The thrust generated by the linear motors 23A, 24A and 23B, 24B required to oppose the drag of the springs 27A, 27B can be reduced, and the amount of heat generated can be suppressed. Further, when the wafer table 20 is moved at a constant speed, as shown in FIG. 11B, the heat generated by the linear motors 23A, 24A and 23B, 24B is reduced using the drag of the springs 27A, 27B. In this case, the amount of heat generated by these linear motors is reduced to about one-sixth that when a spring or the like is not used for the guide shaft 22. In addition, when there is no restriction | limiting in the thrust of those linear motors, the potential energy in the both ends of the guide shaft 22B can also be set to zero. It should be noted that the installation relationship between the iron plate 29 and the magnet 30 may be reversed, and what is provided at the end of the guide shaft 22B generates an attractive force that can oppose the drag of the elastic members such as the springs 27A and 27B. I just need it.
[0051]
FIG. 12A shows a speed curve calculated on the assumption that an ideal wafer table 20 having no resonance is accelerated to a constant speed on a guide shaft 22B having a spring, an iron plate, and a magnet. 12 (a), the horizontal axis represents time t (s), and the vertical axis represents the moving speed V (m / s) of the wafer table 20. FIG. 12B shows the thrusts of the linear motors 23A, 24A and 23B, 24B calculated on the assumption that the wafer table 20 that resonates is controlled using the speed curve of FIG. 12A as a speed command value. In FIG. 12B, the horizontal axis represents time t (s), and the vertical axis represents the linear motor thrust F (N). FIG. 13A shows a speed curve when the wafer table 20 is accelerated to a constant speed on the guide shaft 22 provided with the iron plate 29 and the magnet 30 using the speed curve of FIG. 12A as a speed command value. FIG. 13B shows the thrust F (solid curve A) applied to the wafer table 20 at that time, and the thrust F (dotted line curve B) of the linear motors 23A, 24A and 23B, 24B. The spring constants of the springs 27A and 27B are 2000 N / m, which is an optimal spring constant. In this case, the amount of heat generated by the linear motors 23A, 24A and 23B, 24B is 1% or less when the spring, the magnet, and the iron plate are not used. Further, as compared with the case where no magnet or the like is provided, the thrust required at the start of movement is small, and the wafer table 20 is gradually accelerated. Therefore, there is an advantage that the mechanical resonance of the wafer table 20 can be reduced.
[0052]
14 shows a resultant force F of the attractive force of the iron plate 29 and the magnet 30 and the drag force of the springs 27A and 27B at the end of the guide shaft 22B to which the iron plate 29 and the magnet 30 are attached in correspondence with FIG._P In FIG. 14, the horizontal axis is the distance D (m) from the end of the guide shaft 22B. By attaching the magnet 30 to the end of the guide shaft 22B and the iron plate 29 to the guide member 22A, the thrust of the linear motors 23A, 24A and 23B, 24B required for stationary positioning of the wafer table 20 at the end of the guide shaft 22B Is reduced and the amount of heat generation is suppressed.
[0053]
Next, the structure of the support legs 31A to 31C for supporting the wafer table 20 of the exposure apparatus of this example with respect to the wafer base 7 will be described.
15A is an enlarged view showing the support legs 31A and the like of the wafer table 20, and FIG. 15B is a side view thereof. In FIG. 15, the support legs 31A have bottom portions of the slit portions 31Aa and 31Ab. Is the displacement portion 34. A fluid bearing 32A is attached to the bottom of the displacement portion 34 via a spherical bearing 35 so as to be rotatable. The fluid bearing 32A is attached so that it can rotate. Similarly, as shown in FIG. 3, fluid bearings 32B and 32C are attached to the other support legs 31B and 31C. The fluid bearing 32A is placed on the wafer base 7 in FIG. 3 by a static pressure gas bearing system. 3C, the piezo actuator 33 is attached to the support legs 31A to 31C, and the piezo actuator 33 is fixed to the wafer table 20 via the attachment member 53. As shown in FIG.
[0054]
Returning to FIG. 15, a displacement enlarging mechanism that can expand and contract with respect to the support direction includes a piezo actuator 33 and a displacement portion 34. The fluid bearing 32A includes a magnet for pressurization or a vacuum suction unit. In general, the displacement by the piezo actuator is only about 60 μm, so a displacement magnifying mechanism is required. The displacement magnifying mechanism of this example uses Scott Russell's parallel motion link structure. When the expansion / contraction part of the piezo actuator 33 presses the input point A of the slit part 31Aa of the support leg 31A, the input point A is linearly displaced in the horizontal direction in the minute displacement region. Then, the point B of the link mechanism part of the displacement part 34 of the displacement magnifying mechanism rotates around the point C. As a result, the point D is displaced in the vertical direction. In the displacement portion 34 of the displacement magnifying mechanism of this example, the inclination of the link is 26.6 degrees, the displacement magnification rate is doubled, and the displacement can be displaced by a maximum of 120 μm. Then, the displacement of the displacement portion 34 of the support legs 31 </ b> A to 31 </ b> C is adjusted to correct the tilt angle of the wafer table 20 (leveling) and to correct the position in the vertical direction with respect to the wafer base 7 (focus adjustment).
[0055]
If focus adjustment or leveling cannot be performed properly even if the support legs 31A to 31C are displaced by 120 μm which is the maximum displacement width, the surface position of the wafer 3 is measured in advance before the exposure is started. 1 is driven to position the wafer base 7 so that the position of the surface 3 is at a predetermined position (image plane of the projection optical system 2), and then the support legs 31A to 31C are adjusted. Focus adjustment or leveling may be performed.
[0056]
FIG. 16 is a block diagram showing the configuration of a control system for controlling the reticle stage 4 and the wafer stage 5. In FIG. 16, the main control system 50 is for the X and Y directions of the wafer table 20 of the wafer stage 5. The target position and the target value of the displacement amount in the Z direction of the support legs 31A to 31C are supplied to the subtracting units 61 and 62, respectively. The wafer stage control system 25 drives the wafer stage 5 based on a value obtained by subtracting a value obtained by subtracting a value obtained by multiplying the measurement values of the laser interferometers 18X and 18Y by the conversion unit 65 from the target position by the subtraction unit 61. . The subtracting unit 62 adds a value obtained by integrating the speed in the Z direction of the wafer base 7 measured by the speed sensor 36B to the target value, and further defocusing the wafer stage 5 measured by an autofocus sensor (not shown). A value obtained by subtracting the amount is supplied to the support leg control system 63, and the support leg control system 63 controls the amount of expansion / contraction of the support legs 31A to 31C that support the wafer stage 5 based on the supplied value. , Focus adjustment or leveling. Further, from the detection result of the displacement in the direction orthogonal to the scanning direction of the wafer base 7 detected by the speed sensor 36 </ b> A and the vibration component (yawing) in the rotation direction around the optical axis of the projection optical system 2 and the output of the conversion unit 65. The reticle stage control system 52 controls the reticle stage 4 based on the value obtained by subtracting the measured values of the laser interferometers 18X and 18Y, thereby reducing the influence of horizontal vibration of the wafer base 7. Then, the vibration in the Z direction of the wafer base 7 is reduced by the viscoelastic body 64.
[0057]
Next, the wafer transfer mechanism of the exposure apparatus of this example will be described. In FIG. 1, a transfer base 45 is installed on the front side of the wafer base 7 via an anti-vibration table 51, and wafer transfer mechanisms such as wafer transfer arms 40 </ b> A and 40 </ b> B and a wafer cassette 48 are placed on the transfer base 45. Has been.
FIG. 17A is a plan view showing a part of the wafer transport mechanism of the exposure apparatus of this example, and FIG. 17B is a side view thereof. In FIG. The mounted wafer stage 5 moves from the exposure end position A to the wafer carry-out position B, and the wafer 3A moves to the position P1. At this time, the three arms of the wafer transfer arm 40 </ b> A enter the space surrounded by the deep groove 38 of the wafer table 20 and the wafer 3 </ b> A and do not come into contact with the wafer table 20. The wafer transfer arm 40A is placed on the support portion 67A via a rotation upper and lower portion 69A that can rotate and expand and contract in the Z direction, and the support portion 67A moves on the transfer base 45 by the drive portion 68A. The other wafer transfer arm 40B is also provided with a support part 67B, a rotating upper and lower part 69B, and a driving part (not shown). When the wafer stage 5 is stationary, the wafer table 20 releases the fixation of the wafer 3A by vacuum suction, and the wafer transfer arm 40A vacuum-sucks the wafer 3A and is raised by the rotating upper and lower portions 69A. Then, the exposed wafer 3A is collected in the wafer cassette 48 shown in FIG.
[0058]
At the same time as the wafer transfer arm 40A is raised, the wafer stage 5 is moved to a position below the wafer transfer arm 40B (wafer transfer position C) holding the unexposed wafer 3B at high speed. When the wafer table 20 of the wafer stage is stationary, the wafer transfer arm 40B is lowered by the rotating upper and lower portions 69B, and the unexposed wafer 3B is placed on the wafer table 20 and vacuum-sucked. Also at this time, since the wafer transfer arm 40B enters between the deep grooves 38, it does not come into contact with the wafer table 20. Thereafter, the wafer stage 5 moves from the wafer carry-in position C to the exposure start position D at high speed, and the wafer 3B moves to the position P2 to start exposure. At the same time, the wafer transfer arm 40B takes out a new wafer from the wafer cassette 48 of FIG.
[0059]
When performing overlay exposure, the rotation angle of the wafer to be exposed is measured in advance, and the wafer table 20 is rotated when the wafer stage 5 is positioned at the wafer loading position C so as to cancel the angle. Thus, when the orientation of the wafer table 20 is adjusted to the scanning direction, the pattern formed on the shot area already arranged in a lattice pattern on the wafer and the pattern image of the reticle 1 have a predetermined positional relationship. Can be.
[0060]
18A is a plan view showing the peripheral portion of the wafer cassette 48 when the wafer is unloaded, and FIG. 18B is a side view of FIG. 18A. In FIG. 18, the wafer transfer arms 40A and 40B are shown. Can be driven in three directions: a rotation direction around the Z axis, a scanning direction (X direction), and a vertical direction (Z direction), and a wafer cassette support 47 that supports the wafer cassette 48 on the transfer base 45 is in the vertical direction. It can be driven freely. When the exposed wafer 3A is collected in the wafer cassette 48, first, the wafer transfer arm 40A holding the wafer 3A is rotated by the rotating upper and lower portions 69A. As soon as the wafer 3A reaches the front surface of the wafer cassette 48 via the position P4, the support portion 67A of the wafer transfer arm 40A linearly moves to the position P3 in the X-axis direction so that the wafer 3A moves linearly in the Y-axis direction. The wafer transfer arm 40A rotates. Next, when the wafer 3A reaches a predetermined position in the wafer cassette 48, the vacuum suction by the wafer transfer arm 40A is released, the wafer cassette support 47 is raised, and the wafer 3A is lifted. Then, wafer transfer arm 40A is retracted by performing the reverse operation.
[0061]
19A is a plan view showing the peripheral portion of the wafer cassette 48 when the wafer is carried in, and FIG. 19B is a side view of FIG. 19A. In FIG. 19, the unexposed wafer 3B is shown. Move to the bottom. When unloading from the wafer cassette 48, the wafer transfer arm 40B first moves to the lower part of the unexposed wafer 3B. When the wafer transfer arm 40B is stationary, the wafer cassette support 47 is lowered, and the wafer 3B is placed on the wafer transfer arm 40B. Then, after the wafer transfer arm 40B vacuum-sucks the wafer 3, the support portion 67B of the wafer transfer arm 40B moves linearly in the X-axis direction, and the wafer transfer arm 40B pivots by the rotating upper and lower portions 69B. Is removed from the wafer cassette 48. And it waits until the wafer stage 5 arrives. Since the wafer transfer arm 40B can move linearly in parallel with the front surface of the apparatus, it can also be configured in-line with a peripheral apparatus such as a coater developer.
[0062]
As described above, by moving the wafer stage 5 of FIG. 17 to the wafer carry-out position or the carry-in position, it becomes unnecessary to temporarily fix and support the wafer as in the conventional exposure apparatus, and between the wafer transfer arms. Therefore, it is not necessary to transfer the wafer, so that the probability of foreign matter adhering to the wafer and the probability of a transfer error are reduced. In addition, the wafer transfer arm is less susceptible to the vibration of the wafer transfer arm due to the weight of the wafer than the wafer transfer arm to the exposure position. can do.
[0063]
In addition, this invention is not limited to the above-mentioned embodiment, Of course, a various structure can be taken in the range which does not deviate from the summary of this invention.
[0064]
【The invention's effect】
  The present inventionAccording to the above, by providing the projection optical system support unit that supports the projection optical system so that the projection optical system rotates within a predetermined range around the reference point, vibration from the mask stage and the substrate stage is caused in the projection optical system. Even if it is transmitted, the positional relationship between the object plane (mask) and the image plane (substrate) does not shift, so that the position of the transferred pattern can be prevented from being shifted and high-precision exposure can be performed.
[0065]
  The apparatus further includes a mask stage that moves the mask, a structure that supports the mask stage and the projection optical system, and a substrate stage that moves the substrate, and the projection optical system support section extends from the structure. Support for one flexible structuremeansWith each supportmeansConfigured so that the extension lines ofIsEven if vibration is transmitted to the projection optical system, the projection optical system rotates slightly around the reference point, so that it is possible to prevent the displacement of the pattern transferred onto the substrate.TheAlso supportmeansSince this is a flexible structure, minute vibrations are attenuated and deterioration of the contrast of the formed pattern can be prevented.
[0066]
  When measuring the position of the substrate stage or the mask stage with reference to a reference mirror having a substantial center on a plane perpendicular to the optical axis of the projection optical system through the reference point, a pattern formed on the substrate Can be reduced.
[0067]
  Furthermore, the structure is separated from the substrate stage.in case of,The projection optical system is affected by the movement of the substrate stage.furtherThe pattern can be projected without receiving it.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a schematic configuration of a projection exposure apparatus used in an example of an embodiment of the present invention.
2 is a cross-sectional view with a part cut away showing a method of supporting the projection optical system 2 of FIG. 1. FIG.
3A is a plan view showing the wafer stage 5 in FIG. 1, FIG. 3B is a cross-sectional view taken along the line BB in FIG. 3A, and FIG. 3C is a part of FIG. The front view and (d) which were made are sectional drawings which follow the DD line of Fig.3 (a).
4 is a block diagram showing a configuration of a control system that controls the wafer table 20 and the carrier 21. FIG.
5 is a schematic view for explaining the operation of the guide member 22A and the guide shaft 22B of the wafer table 20 of FIG. 3;
6A is a view showing the speed of the wafer table 20 when the movement speed of the wafer table 20 is shifted to a constant speed on a guide shaft not provided with an elastic body, and FIG. It is a figure which shows the thrust of a linear motor at the time.
7A is a diagram showing a velocity curve of a wafer table calculated on the assumption that an ideal wafer table having no resonance is accelerated to a constant speed on a guide shaft provided with a spring, and FIG. It is a figure which shows the thrust of the linear motor calculated supposing the case where the wafer table with resonance was controlled by using the speed curve of 7 (a) as a speed command value.
8A is a diagram showing a speed when the wafer table 20 is accelerated to a constant speed using a guide shaft having a spring with the speed curve of FIG. 7A as a speed command value; FIG. These are figures which show the thrust of the wafer table 20 at that time, and the thrust which the linear motor generate | occur | produced.
FIG. 9A is a diagram showing a speed curve when the wafer table 20 is accelerated to a constant speed using a guide shaft having a spring having an optimum spring constant, and FIG. 9B is a wafer at that time. It is a figure which shows the thrust of the table.
FIG. 10 is a view showing a drag force of a spring at an end portion of a guide shaft provided with a spring.
11 is a schematic view for explaining the operation of the guide member 22A and the guide shaft 22B in the case where a magnetic member is further provided in FIG.
FIG. 12A is a view showing a speed calculated on the assumption that an ideal wafer table 20 having no resonance on a guide shaft including a spring, an iron plate, and a magnet is accelerated to a constant speed; ) Is a diagram showing the thrust of the linear motor calculated on the assumption that the wafer table 20 having resonance is controlled using the speed curve of FIG. 12A as a speed command value.
13A is a diagram showing a speed curve when the wafer table 20 is accelerated to a constant speed on a guide shaft provided with an iron plate and a magnet using the speed curve of FIG. 12A as a speed command value; b) is a diagram showing the thrust of the wafer table 20 and the thrust of the linear motor at that time.
FIG. 14 is a diagram showing the resultant force of the attractive force of the iron plate and the magnet and the drag force of the spring at the end of the guide shaft to which the iron plate and the magnet are attached.
FIG. 15A is a schematic diagram showing an enlarged view of a support leg 31A for supporting the wafer table 20 and its periphery, and FIG. 15B is a side view of FIG. 15A.
16 is a block diagram showing a configuration of a control system that controls reticle stage 4, wafer stage 5, and wafer base 7. FIG.
FIG. 17 is a view for explaining the operation of the wafer stage 5 when a wafer is carried into or out of the exposure apparatus.
FIG. 18 is a view for explaining the operation of the wafer transfer arm 40A when the exposed wafer 3A is carried out of the exposure apparatus.
FIG. 19 is a view for explaining the operation of the wafer transfer arm 40B when an unexposed wafer 3B is carried into the exposure apparatus.
[Explanation of symbols]
1 Reticle
2 Projection optical system
3 Wafer
4 Reticle stage
5 Wafer stage
6 Structure
7 Wafer base
8 Elevator drive
9 Reticle base
15 Object plane
16 Image plane
17 Reference point
19A ~ C Rod
20 Wafer table
22A Guide member
22B Guide shaft
23A, 23B Linear motor coil
24A, 24B Linear motor magnet
25 Wafer stage control system
27A, 27B Spring
29 Iron plate
30 magnets
31A-31C Support leg
32A-32C Fluid bearing
38 Deep Groove
40A, 40B Wafer transfer arm
47 Wafer cassette support
48 Wafer cassette
52 Reticle stage control system

Claims (5)

In an exposure apparatus for transferring an image of a pattern of a mask onto a substrate via a projection optical system,
A mask stage for moving the mask;
A structure that supports the mask stage and the projection optical system;
A substrate stage for moving the substrate;
The projection optical system can be rotated within a predetermined range around a reference point on the optical axis of the projection optical system that internally divides the distance between the object plane and the image plane of the projection optical system by a projection magnification ratio. A projection optical system support that supports the projection optical system,
The projection optical system support unit comprises a support means of at least three flexible structure extending from said structure, said support means, an exposure apparatus, each of the extension is characterized in that intersect at the reference point. A reference mirror having a substantial center on a plane passing through the reference point and perpendicular to the optical axis of the projection optical system;
  The exposure apparatus according to claim 1, further comprising: a substrate-side laser interferometer that irradiates the center of the reference mirror with a measurement beam and measures the position of the substrate stage based on the reference mirror. . A reference mirror having a substantial center on a plane passing through the reference point and perpendicular to the optical axis of the projection optical system;
  The mask-side laser interferometer that irradiates the measurement beam to the center of the reference mirror and measures the position of the mask stage with reference to the reference mirror. Exposure device. The exposure apparatus according to claim 1, wherein the flexible structure supporting means includes a rod. 5. The exposure apparatus according to claim 1, wherein the structure is supported via an anti-vibration mechanism on an installation surface of a base member on which the substrate stage is placed. .

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