Six-degree-of-freedom workpiece carrying table

Abstract

The invention relates to a six-degree-of-freedom workpiece stage. The second carrying table is arranged on the first carrying table. The second platform deck provides six degrees of freedom. A chuck for holding a workpiece is disposed on the second stage. An actuator which enables movement in three directions is disposed on the second stage. The first stage and the second stage move independently of each other during inspection of the workpiece on the chuck.

Description

[0001] Information about divisional applications

[0002] This case is a divisional application. The parent case of the divisional application is an invention patent application with application date of June 19, 2020, application number 202080041644.9, and invention name “Six-degree-of-freedom workpiece carrier”.

[0003] CROSS REFERENCE TO RELATED APPLICATIONS

[0004] This application claims priority to provisional patent application No. 62 / 864,678 filed on June 21, 2019 and assigned U.S. application No. 62 / 879,011 filed on July 26, 2019 and assigned U.S. application No. 62 / 879,011, the disclosures of which are incorporated herein by reference. Technical Field

[0005] The present invention relates to positioning a workpiece on a stage, such as in a semiconductor inspection tool. Background Art

[0006] The semiconductor manufacturing industry uses complex techniques to manufacture integrated circuits from semiconductor materials that are layered and patterned onto wafers such as silicon wafers. Integrated circuits are typically made from multiple photomasks. The generation of photomasks and subsequent optical inspection of such photomasks have become standard steps in semiconductor production. The manufacture of semiconductor devices, such as logic and memory devices, typically involves processing semiconductor wafers using a large number of semiconductor manufacturing processes that employ multiple photomasks to form various features and multiple levels of semiconductor devices. Multiple semiconductor devices can be manufactured as an arrangement on a single semiconductor wafer and then separated into individual semiconductor devices. The position of the wafer relative to the photomask affects the manufacturing results.

[0007] After a wafer is manufactured, it can be inspected for defects or certain features of the wafer can be measured. Similarly, a mask can be inspected and mask features measured. Lithography and inspection systems require precise positioning and position detection systems.

[0008] Previous high vacuum systems had a coarse stage with position feedback for the chuck, which used a mirror plate mounted to the stage. Any small movement required moving the entire heavy stage, not just the wafer chuck. Moving the heavy mass stage for small movements creates vibrations, generates heat, requires overcoming ball bearing friction, and takes a lot of time to settle to the desired position. Moving the heavy mass stage also creates jitter from the ball bearings during a constant speed scan.

[0009] Therefore, there is a need for improved systems and methods of operation. Summary of the invention

[0010] In a first embodiment, a system is provided. The system includes: a first stage configured to move in at least an X direction and a perpendicular Y direction; a second stage disposed on the first stage, the second stage providing six degrees of freedom; and a chuck disposed on the second stage. The chuck is configured to hold a workpiece. At least one X-direction actuator is configured to move the second stage in the X direction. The X-direction actuator is disposed on the second stage. At least one Y-direction actuator is configured to move the second stage in the Y direction. The Y-direction actuator is disposed on the second stage. At least one Z-direction actuator is configured to move the second stage in the Z direction. The Z-direction actuator is disposed on the second stage. The Z direction is perpendicular to both the X direction and the Y direction. Two interferometer mirrors are disposed on the vertical edges of the second stage. At least one vertical position feedback sensor is disposed on the second stage. At least one balance spring is disposed between the first stage and the second stage.

[0011] The first stage may have a wider range of movement than the second stage.

[0012] The system may include four of the Z-direction actuators disposed on the second stage.

[0013] The system may include two of the Y-direction actuators disposed on the second stage.

[0014] The system may further include a base plate. The first stage is disposed on the base plate.

[0015] The system may further include two laser interferometers. Each of the laser interferometers directs laser light at one of the interferometer mirrors.

[0016] The workpiece may be a semiconductor wafer or a photomask.

[0017] The system may further include a semiconductor inspection system configured to direct a light beam at the chuck.

[0018] The system may further include a processor configured to send instructions for movement of the first stage and the second stage relative to each other. The processor is in electronic communication with the X-direction actuator, the Y-direction actuator, the Z-direction actuator, and the vertical position feedback sensor.

[0019] In a second embodiment, a method is provided. The method includes: providing a system including a first stage, a second stage disposed on the first stage, and a chuck disposed on the second stage. The first stage is configured to move in at least an X direction and a perpendicular Y direction. The second stage provides six degrees of freedom. A workpiece is disposed on the chuck. The workpiece is a semiconductor wafer or a photomask. The first stage and the second stage are moved independently of each other. The workpiece is inspected on the chuck.

[0020] Moving the second stage may include moving the second stage in the X-direction using at least one X-direction actuator disposed on the second stage.

[0021] Moving the second stage may include moving the second stage in the Y direction using at least one Y-direction actuator disposed on the second stage.

[0022] Moving the second stage may include moving the second stage in a Z direction using at least one Z-direction actuator disposed on the second stage. The Z direction is perpendicular to both the X direction and the Y direction.

[0023] The method may further include determining the position of the second stage in the X direction using a laser interferometer. A laser is directed to a reflective mirror disposed on the second stage.

[0024] The method further includes determining the position of the second stage in the Y direction using a laser interferometer. The laser is directed at a mirror disposed on the second stage.

[0025] The method may further include determining the position of the second stage in the Z direction using a vertical position feedback sensor disposed on the second stage.

[0026] The method may further include sending, using a processor, instructions for the movement. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] For a more complete understanding of the nature and objects of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which:

[0028] Figure 1 is a cross-sectional side view of a system according to the present invention;

[0029] Figure 2 is a bottom view of a second carrier according to the present invention;

[0030] Figure 3 is a perspective side view of a second stage according to the present invention;

[0031] Figure 4is a flow chart of a method according to the present invention; and

[0032] Figure 5 Contains various corresponding views of embodiments of the system according to the invention. DETAILED DESCRIPTION

[0033] Although the claimed subject matter will be described in terms of specific embodiments, other embodiments (including embodiments that do not provide all of the benefits and features set forth herein) are also within the scope of the invention. Various structural, logical, process step, and electronic changes may be made without departing from the scope of the invention. Accordingly, the scope of the present invention is defined solely by reference to the appended claims.

[0034] Semiconductor manufacturers need a stage with fine motion capabilities for X, Y, Z, pitch, roll, and rotation (i.e., yaw) movement. The embodiments disclosed herein provide this motion capability. The embodiments disclosed herein can also quickly settle into position and eliminate any residual vibrations. The stage with fine motion capability is placed on top of the coarse XY stage. This design can be used in high vacuum applications where laser interferometer feedback is operated.

[0035] A fine, short stroke stage can be used. The wafer or mask is placed on the fine, short stroke stage. The fine, short stroke stage can be guided by flexure, or can float without mechanical guidance. This fine, short stroke stage can have five or six degrees of freedom (DOF) with position sensor feedback and / or laser interferometer feedback to allow real-time position tracking or vibration cancellation. Due to the low moving mass and separation from the floor, this can provide greater throughput, fast settling time, or low jitter scanning. Lower jitter during constant speed can meet the sensitivity in high vacuum systems, which can enable the use of laser interferometers for chuck position feedback. The movement or feedback of the Z direction, pitch and roll actuators are not connected to the coarse XY stage.

[0036] Figure 1 1 is a cross-sectional side view of system 100. System 100 includes a first stage 101 configured to move in at least an X direction and a perpendicular Y direction. A second stage 102 is disposed on first stage 101. Second stage 102 provides six DOF and can move in the X direction, the Y direction, and the Z direction. Second stage 102 includes a base 103 and a frame 104. Frame 104 can support a chuck 105. Base 103 can be disposed on first stage 101 and can support some or all actuators for second stage 102. First stage 101 can be referred to as a coarse stage, and second stage 102 can be referred to as a fine stage.

[0037] The second stage 102 may be floated on an external frame using its actuators. It may not be rigidly carried by the first stage 101. The magnetic fields of the actuators and position sensors may maintain the relationship between the second stage 102 and the first stage 101 within a certain threshold or target.

[0038] The chuck 105 is placed on the second stage 102. Figure 1 104, but the chuck 105 may be positioned on an upper surface of the frame 104. A workpiece 106, such as a semiconductor wafer or a photomask, may be held by the chuck 105. The semiconductor inspection system 107 may be configured to direct a light beam at the chuck 105. The light beam may be a photon, ion, or electron beam.

[0039] like Figure 1 As shown in FIG. 1 , the first carrier 101 may be disposed on a base plate 108. The first carrier 101 may also be suspended on a bridge.

[0040] The first stage 101 may have a wider range of motion than the second stage 102. For example, the second stage 102 may have a range of motion that is less than 50%, less than 25%, less than 20%, less than 15%, or less than 10% of the range of motion of the first stage 101.

[0041] When the system 100 is operating, magnetic levitation may be activated so the second stage 102 does not contact the hard stop. Magnetic levitation may begin during initialization. In the case of magnetic levitation, the second stage 102 will be initialized first, and then the first stage 101 will be initialized.

[0042] In another embodiment, the system 100 is not a magnetically levitated stage.

[0043] The processor 109 may be in electronic communication with the first stage 101 and the second stage 102. The processor 109 may be configured to send instructions for movement of the first stage 101 and the second stage 102. The first stage 101 and the second stage 102 may be movable relative to each other. The processor 102 may be in electronic communication with one or more X-direction actuators, Y-direction actuators, Z-direction actuators, position feedback sensors, and / or laser interferometers in the second stage 102. The processor 109 may include a microprocessor, a microcontroller, or other device. The processor 109 may provide instructions to one or more amplifiers. The amplifiers may provide desired currents and voltages based on position errors.

[0044] The processor 109 may be coupled to the components of the system 100 in any suitable manner (e.g., via one or more transmission media, which may include wired and / or wireless transmission media) so that the processor 109 can receive the output. The processor 109 may be configured to perform a number of functions using the output. The system 100 may receive instructions or other information from the processor 109.

[0045] The processor 109, other systems, or other subsystems described herein may be part of a variety of systems, including a personal computer system, an image computer, a mainframe computer system, a workstation, a network appliance, an Internet appliance, or other devices. The subsystem or system may also include any suitable processor known in the art, such as a parallel processor. In addition, the subsystem or system may include a platform with high-speed processing and software as a stand-alone or networked tool.

[0046] Processor 109 may be disposed in or otherwise be part of system 100 or another device. In an example, processor 109 may be part of a stand-alone control unit, or in a centralized quality control unit. Multiple processors 109 may be used.

[0047] In practice, the processor 109 may be implemented by any combination of hardware, software, and firmware. In addition, its functions as described herein may be performed by one unit, or divided among different components, each of which may then be implemented by any combination of hardware, software, and firmware. Program codes or instructions for the processor 109 to implement various methods and functions may be stored in a readable storage medium.

[0048] The processor 109 may be configured to perform a number of functions using the output of the system 100 or other outputs. For example, the processor 109 may be configured to send the output to an electronic data storage unit or another storage medium. The processor 109 may be further configured as described herein.

[0049] The processor 109 may be configured according to any of the embodiments described herein.The processor 109 may also be configured to perform other functions or additional steps using the output of the system 100 or using images or data from other sources.

[0050] The processor 109 may be communicatively coupled to any of the various components or subsystems of the system 100 in any manner known in the art. In addition, the processor 109 may be configured to receive and / or obtain data or information from other systems via a transmission medium that may include wired and / or wireless portions. In this manner, the transmission medium may serve as a data link between the processor 109 and other subsystems of the system 100 or systems external to the system 100.

[0051] The various steps, functions and / or operations of the system 100 and the methods disclosed herein are performed by one or more of the following: electronic circuits, logic gates, multiplexers, programmable logic devices, ASICs, analog or digital controls / switches, microcontrollers, or computing systems. Program instructions implementing methods (such as the methods described herein) may be transmitted or stored over or on a carrier medium. The carrier medium may include storage media such as read-only memory, random access memory, magnetic or optical disks, non-volatile memory, solid-state memory, magnetic tape, and the like. The carrier medium may include transmission media such as wires, cables, or wireless transmission links. For example, the various steps described throughout the present invention may be performed by a single processor 109 or alternatively by multiple processors 109. In addition, different subsystems of the system 100 may include one or more computing or logic systems. Therefore, the above description should not be interpreted as limiting the present invention, but only as an explanation.

[0052] An umbilical feed (not shown) may provide power to the second stage 102 .

[0053] Figure 2 1 is a bottom view of the second stage 102. The base 103 includes an actuator for moving the second stage 102. The base 103 includes at least one X-direction actuator 201, at least one Y-direction actuator 202, and / or at least one Z-direction actuator 203. The X-direction actuator 201, the Y-direction actuator 202, and the Z-direction actuator 203 are disposed on the second stage 102. The X-direction actuator 201 can move the second stage 102 in the X direction. The Y-direction actuator 202 can move the second stage 102 in the Y direction. The Z-direction actuator 203 can move the second stage 102 in the Z direction.

[0054] In an example, each of the Z-direction actuators 203 is disposed in a groove of the first stage 101 .

[0055] The X-direction actuator 201, the Y-direction actuator 202, and the Z-direction actuator 203 may be linear motors, rotationally driven ball screw linear motors, piezoelectric linear motors, electromagnetic actuators, voice coil actuators, arrays of magnet and coil arrangements, or other types of actuators or motors. The voice coil actuator may include a magnet assembly mounted to the second stage 102, a coil that pushes the magnet assembly away, concentrated to the top of the first stage 101, and a gap between the coil and the magnet assembly to allow fine movement. The linear motor may include a magnet assembly mounted to the top of the second stage 102 or the first stage 101, a coil that pushes away from the magnet assembly connected to the other of the tops of the second stage 102 or the first stage 101, and a gap between the coil and the magnet assembly to allow fine movement.

[0056] In an example, the Z-direction actuator 203 is a voice coil actuator, and the X-direction actuator 201 and the Y-direction actuator 202 are linear motors.

[0057] The X-direction actuator 201 and / or the Y-direction actuator 202 may provide a control force so as to maintain or obtain a desired position between the chuck 105 and the optical head of the semiconductor inspection system 107. The X-direction actuator 201 and / or the Y-direction actuator 202 may also provide a safety gap between the first stage 101 and the second stage 102. For example, the non-contact actuator may have a coil and a magnet with a gap therebetween, which may be the maximum travel of the second stage 102.

[0058] exist Figure 2 In the embodiment of FIG. 2 , there is one X-direction actuator 201, two Y-direction actuators 202, and four Z-direction actuators 203. Different numbers or combinations of actuators are possible.

[0059] There may be at least one balancing spring 204 disposed between the second stage 102 and the first stage 101 to compensate for the weight of the second stage 102. The balancing spring 204 is Figure 2 102. The balance spring 204 may be a magnetic spring, a compression spring, or a fixed force motor. One side of the balance spring 204 may be connected to the top surface of the first stage 101, and the other side of the balance spring 204 may be connected to the opposite bottom surface of the second stage 102.

[0060] The horizontal position feedback sensor 205 is disposed on the second stage 102. The horizontal position feedback sensor 205 may include a sensor and a target, one of which is mounted on the second stage 102 and the other of which is mounted on the first stage 101. The horizontal position feedback sensor 205 may control the safety gap between the second stage 102 and the first stage 101, and may also be used as a second control loop in the overall control of the second stage 102 relative to the optical head in the semiconductor inspection system 107.

[0061] The vertical position feedback sensor 206 is disposed on the second stage 102. In an example, the vertical position feedback sensor 206 is disposed on or in one or more of the Z-direction actuators 203. For example, the vertical position feedback sensor 206 may be disposed on or in all of the Z-direction actuators 203.

[0062] The horizontal position feedback sensor 205 or the vertical position feedback sensor 206 may each be a capacitive sensor or an eddy current sensor. The capacitive sensor may include a sensor head mounted to the first stage 101 or the second stage 102, and a target mounted to the other of the first stage 101 or the second stage 102. The sensor head may include a shield, a sensing area, and a body. The capacitive sensor may provide a resolution up to nanometers.

[0063] The eddy current sensor may include a sensor head mounted to the first stage 101 or the second stage 102, and a target mounted to the other of the first stage 101 or the second stage 102. The sensor head includes a transmitting coil and a receiving coil. In the case of using an eddy current sensor, sub-micron resolution is possible.

[0064] In an embodiment, the system 100 includes four vertical position feedback sensors 206. During operation, the system 100 may use six sensors. This includes three sensors for Z-direction movement, tip, and tilt. This may also include three sensors for X-direction movement, Y-direction movement, and rotation.

[0065] Using the designs disclosed herein, the second stage 102 can provide fast fine X, Y, Z, pitch, roll, and rotation movements that can cancel and compensate for noise from the system and / or the first stage 101. The system 100 can be deployed in high vacuum tools such as e-beam and reticle inspection tools.

[0066] The processor 109 may monitor two feedback systems: a coarse sensor and at least one laser interferometer relative to a fine stage of an optical head of a semiconductor inspection system 107. The processor 109 may command movement of a first stage 101, which may be at high speed and may include a long travel distance, and movement of a second stage 102 with its more limited travel. The second stage 102 may provide a last fast setup position when stopped, or may maintain a desired jitter during a constant speed scan. The processor 109 may have nested servo loops, where the inner loop is the coarse feedback, and the outer loop is a position error loop of the optical head of the semiconductor inspection system 107 relative to the chuck 105. These servo loops may both be six DOF.

[0067] The proposed six-DOF second stage 102 can operate without any guide bearing system and can contain nested frames driven by actuators and feedback devices to generate X-direction, Y-direction and yaw motion. The nested frames of the second stage can be placed on the first stage 101. The second stage 102 can be driven by three or more actuators with feedback devices.

[0068] In the example, the Z center hub is mounted on the first stage 101 and the drive actuator and the second loop feedback sensor are mounted on the main external static plate. The Z direction actuator 203 can bear the weight of the second stage 101.

[0069] The second stage 102 can operate without any guide bearings or flexures. Various actuators can push the payload (e.g., chuck 105) while holding the position using feedback sensors. The second stage 102 can perform Z-direction, tilt and pitch movements up to short strokes, and can perform X-direction, Y-direction, and yaw movements.

[0070] In an example, the second stage 102 may be positioned on an X, Y bridge.

[0071] Figure 3 30 is a perspective side view of the second stage 102. The first interferometer mirror 301 and the second interferometer mirror 302 are disposed on the edge of the frame 104 of the second stage 102. The first interferometer mirror 301 and the second interferometer mirror 302 are disposed on the vertical edge of the frame 104 of the second stage 102.

[0072] At least two laser interferometers 303 direct laser light (indicated by dashed lines) at one of the first interferometer mirror 301 or the second interferometer mirror 302. For example, three laser interferometers 303 may be used.

[0073] At least one laser interferometer beam may be used to measure movement in the Z direction. At least two laser interferometer beams may be used to measure movement in the X direction, Y direction, tip, tilt, pitch, and yaw. These may be differential beam arrangements to provide accurate feedback of the chuck 105 relative to the optical head in the semiconductor inspection system 107 for all six DOF in real time. The optical head itself may have some movement from vibrations that may be followed.

[0074] A short-stroke, high-bandwidth, unguided second stage 102 with six DOF and laser interferometers may allow for real-time vibration cancellation and improved settling time.

[0075] Although a laser interferometer is specifically disclosed, an external grid encoder plate feedback sensor may also be used.

[0076] The feedback loop can be a combination of internal position feedback (e.g., capacitive sensors, encoders, etc.) for fine and precise position feedback and an external laser interferometer beam directed to the second stage 102. The laser beam can be referenced to the scanning optics and provide differential feedback between the second stage 102 and the inspection optics. The position feedback control loop of the second stage 102 can maintain the true chuck position relative to the optical inspection head in the semiconductor inspection system 107.

[0077] Two laser beams positioned perpendicular or parallel to each other (eg, using the first interferometer mirror 301) can determine the pitch, yaw, or roll by calculating the difference between the two laser beams.

[0078] For example, an optional laser beam aimed at the chuck 105 can be used to determine the Z-direction movement or position. The chuck 105 can include an optional third interferometer mirror 304 to provide these measurements.

[0079] The sensors disclosed herein can be used to determine how far the center of the second stage 102 is from the center of the first stage 101. Measuring this relative position can avoid the use of hard stops.

[0080] Moving the second stage 102 (which includes the chuck 105) without any bearing mechanism may generate less vibration, less heat, and may settle into position faster. The second stage 102 may receive position feedback in all degrees of freedom from a laser interferometer or encoder grid plate pointed at the chuck mirror. The second stage 102 may also have a position sensor to be located in the second control loop.

[0081] Higher throughput and lower vibration are possible using the embodiments disclosed herein. The embodiments disclosed herein can also provide sensitivity in high vacuum systems where a laser interferometer can be used as chuck position feedback. It can also be used in atmospheric applications if an external six-DOF encoder system (not mounted on the stage) can be used as feedback.

[0082] Figure 5 Various corresponding views of embodiments of systems, such as system 100, are included. Laser interferometer (I / F) beams and other sensors can provide measurements of X, Y, Z, pitch, roll, and yaw. Figure 5 X, Y1, Y2, Z1, Z2, Z3, and Z4 in FIG. 8 represent actuators that move in the directions indicated by their abbreviated names. Figure 5 Xs, Ys1, Ys2, Zs1, Zs2, Zs3, and Zs4 in FIG. 1 are position sensors for measuring in the directions indicated by their abbreviated names. Thus, X is an actuator that moves in the X direction, Y2 is an actuator that moves in the Y direction, and Zs2 is a position sensor that measures movement in the Z direction.

[0083] Figure 4 4 is a flow chart of method 400. At 401, a system is provided. The system includes: a first stage, a second stage disposed on the first stage, and a chuck disposed on the second stage. The first stage is configured to move in at least an X direction and a perpendicular Y direction. The second stage provides six degrees of freedom. For example, system 100 can be provided.

[0084] At 402, a workpiece is placed on a chuck. The workpiece may be a semiconductor wafer or a photomask. At 403, the first stage and the second stage are moved independently of each other. The movement of the first stage and the second stage may be coordinated so that the workpiece is positioned, maintained, or scanned to a desired inspection position relative to a semiconductor inspection system. A processor may send instructions to move the first stage and / or the second stage. At 404, the workpiece on the chuck is inspected.

[0085] Moving the second stage may include: moving the second stage in the X direction using at least one X-direction actuator disposed on the second stage; moving the second stage in the Y direction using at least one Y-direction actuator disposed on the second stage; and / or moving the second stage in the Z direction using at least one Z-direction actuator disposed on the second stage.

[0086] The position of the second stage can be determined in the X direction and / or the Y direction using a laser interferometer. The laser is directed to a reflector mounted on the second stage. The position of the second stage in the Z direction can be determined using a vertical position feedback sensor mounted on the second stage.

[0087] As disclosed herein, additional embodiments relate to a non-transitory computer-readable medium storing program instructions executable on a processor to perform a computer-implemented method for moving a first stage and / or a second stage. An electronic data storage unit or other storage medium may contain a non-transitory computer-readable medium including program instructions executable on the processor 109. The computer-implemented method may include any of the steps of any of the methods described herein.

[0088] Program instructions for implementing methods such as those described herein may be stored on a computer-readable medium. The computer-readable medium may be a storage medium such as a magnetic or optical disk, a tape, or any other suitable non-transitory computer-readable medium known in the art.

[0089] The program instructions may be implemented in any of a variety of ways, including program-based technology, component-based technology, and / or object-oriented technology, etc. For example, the program instructions may be implemented using ActiveX controls, C++ objects, JavaBeans, Microsoft Foundation Classes (MFC), Streaming SIMD Extensions (SSE), or other technologies or methods as needed.

[0090] Each step of the method may be performed as described herein. The method may also include any other steps that may be performed by a processor and / or computer subsystem or system described herein. The steps may be performed by one or more computer systems, which may be configured according to any embodiment described herein. In addition, the method described above may be performed by any system embodiment described herein.

[0091] Although the present invention has been described with respect to one or more specific embodiments, it should be understood that other embodiments of the present invention can be made without departing from the scope of the present invention. Therefore, the present invention is deemed to be limited only by the appended claims and reasonable interpretations thereof.

Claims

1. A system comprising: A first stage configured to move in at least an X direction and a perpendicular Y direction; A second stage, which is disposed on the first stage, wherein the second stage provides six degrees of freedom; a chuck disposed on the second stage, wherein the chuck is configured to hold a workpiece; at least one X-direction actuator configured to move the second stage in the X-direction, wherein the X-direction actuator is disposed on the second stage; at least one Y-direction actuator configured to move the second stage in the Y-direction, wherein the Y-direction actuator is disposed on the second stage; at least one Z-direction actuator configured to move the second stage in a Z-direction, wherein the Z-direction actuator is disposed on the second stage, and wherein the Z-direction is perpendicular to both the X-direction and the Y-direction; two interferometer mirrors disposed on vertical edges of the second stage; at least one vertical position feedback sensor disposed on the second stage; and At least one balance spring is disposed between the first platform and the second platform.

2. The system of claim 1, wherein the first stage has a wider range of motion than the second stage.

3. The system of claim 1, wherein the system comprises four of the Z-direction actuators disposed on the second stage.

4. The system of claim 1, wherein the system comprises two of the Y-direction actuators disposed on the second stage.

5. The system of claim 1, further comprising a base plate, wherein the first stage is disposed on the base plate.

6. The system of claim 1, further comprising two laser interferometers, wherein each of the laser interferometers directs laser light at one of the interferometer mirrors.

7. The system of claim 1, wherein the workpiece is a semiconductor wafer or a photomask.

8. The system of claim 1, further comprising a semiconductor inspection system configured to direct an optical beam at the chuck.

9. The system of claim 1 , further comprising a processor configured to send instructions for movement of the first stage and the second stage relative to each other, wherein the processor is in electronic communication with the X-direction actuator, the Y-direction actuator, the Z-direction actuator, and the vertical position feedback sensor.

10. A method comprising: Providing a system comprising a first stage, a second stage disposed on the first stage, and a chuck disposed on the second stage, wherein the first stage is configured to move in at least an X direction and a perpendicular Y direction, and wherein the second stage provides six degrees of freedom; placing a workpiece on the chuck, wherein the workpiece is a semiconductor wafer or a photomask; moving the first stage and the second stage independently of each other, wherein moving the second stage comprises moving the second stage in the X direction using at least one X-direction actuator disposed on the second stage; and The workpiece on the chuck is inspected. 11 . The method of claim 10 , wherein moving the second stage further comprises moving the second stage in the Y direction using at least one Y-direction actuator disposed on the second stage.

12. The method of claim 10, wherein moving the second stage further comprises moving the second stage in a Z direction using at least one Z-direction actuator disposed on the second stage, and wherein the Z direction is perpendicular to both the X direction and the Y direction.

13. The method of claim 10, further comprising determining the position of the second stage in the X direction using a laser interferometer, wherein a laser is directed at a mirror disposed on the second stage.

14. The method of claim 10, further comprising determining the position of the second stage in the Y direction using a laser interferometer, wherein the laser is directed at a mirror disposed on the second stage.

15. The method of claim 10, further comprising determining the position of the second stage in the Z direction using a vertical position feedback sensor disposed on the second stage.

16. The method of claim 10, further comprising using a processor to send instructions for the movement.

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