JP2018041528A - Stage apparatus and charged particle beam apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stage apparatus which can improve accuracy of position control by suppressing a change in a temperature distribution of a stage caused by fluctuation of heat generation of a linear motor, and a charged particle beam apparatus using the same.SOLUTION: A heater is installed between a coil of a linear motor and a table. By supplementing decrease in a calorific value of a coil with the heater, it is possible to suppress a temperature change. Meanwhile, a temperature distribution formed on a stage is made to be the same regardless of when the heater generates heat or when the coil generates heat. By not changing a thermal deformation state of the stage determined by the temperature distribution, accuracy of position measurement of the stage is improved.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a stage apparatus and a charged particle beam apparatus using the stage apparatus, and more particularly to a stage apparatus and a charged particle beam apparatus suitable for suppressing an influence caused by a change in heat generated by driving a stage.

  With the recent miniaturization of semiconductor elements, not only manufacturing apparatuses but also inspection and evaluation apparatuses are required to have high precision corresponding thereto. As a tool for evaluating the performance of a semiconductor device, a scanning electron microscope (length measuring SEM) having a length measuring function is known.

  The length measurement SEM is a device that performs image processing on secondary electron signals obtained by irradiating an electron beam onto a wafer, determines the edge of the pattern from the change in brightness, and measures the dimension.

  The length measurement SEM is provided with an XY stage that moves the wafer in a direction orthogonal to the electron beam optical axis (XY direction) in order to enable measurement of a desired portion of the wafer. Yes. A laser interferometer is used as a means for specifying the irradiation position of the beam.

  Patent Document 1 discloses a laser interferometer that identifies a stage position (wafer position) by irradiating a mirror on a mirror bar with a laser. Patent Document 1 discloses a stage apparatus using a linear motor as a drive source, and further describes a method for controlling the drive amount of the stage based on the drive history of the stage.

  Further, in Patent Document 2, in order to suppress a change in the position of the stage due to a temperature drop of the driving motor when the stage is stopped, a current smaller than an excitation current necessary for driving is supplied to the driving motor. A technique for suppressing temperature drop is described.

  Further, Patent Document 3 describes a method of suppressing a positional variation based on a temperature difference between the sample and the sample stage by providing a heating element on the upper surface of the charged particle drawing apparatus facing the sample.

JP 2006-5137 A JP 2004-111684 A JP 2002-353116 A

  A linear motor is known as a kind of drive source for a stage apparatus used in a charged particle beam apparatus or the like. The linear motor is composed of, for example, a mover made of a coil and a stator made of a permanent magnet, and is a drive source that generates a drive force by supplying a current to the coil. On the other hand, since the mover and the stator are not in contact with each other due to the principle of the linear motor, the heat generated in the coil cannot be released via the stator and is transmitted to the table connected to the mover. In particular, in the case of a charged particle beam apparatus, heat cannot be released through air because the atmosphere in the sample chamber is kept in a vacuum. That is, the heat generated in the coil is transmitted to the stage connected to the mover, and the stage position may fluctuate due to the influence of the heat.

  On the other hand, a measuring device such as a length measuring SEM is controlled by a control program called a recipe, and an appropriate recipe is set according to the measurement purpose. However, when the recipe is changed, the heat transferred to the stage may change. For example, the heat transferred to the stage is different between a recipe with a large amount of stage movement and a recipe that does not move the stage. That is, changing the measurement conditions will change the temperature of the stage.

  As a result of investigations by the inventors, it has become clear that if such a temperature change is suppressed, measurement errors of the stage position using a laser interferometer or the like can be suppressed. Patent Documents 1 to 3 do not disclose means for suppressing the influence when the heat generated by the linear motor changes. In particular, with a stepping motor as described in Patent Document 2, it is desirable to take measures in accordance with a change in heat in view of a situation unique to a linear motor having a different heat transfer path.

  Hereinafter, a stage device and a charged particle beam device that are intended to perform high-precision stage control regardless of changes in heat generation of the linear motor movable element that may occur in accordance with changes in measurement or inspection conditions will be described.

  As one aspect for achieving the above object, a stage apparatus including a table on which a sample is placed and a linear motor that drives the table in a predetermined direction, wherein the linear motor has one of a coil or a permanent magnet. A stage device including a movable element having a stator and a stator having the other of a coil or a permanent magnet, a heater interposed between the movable element and the table, and a charged particle beam apparatus equipped with the stage device are proposed.

  According to the above configuration, it is possible to perform highly accurate stage control regardless of changes in the heat generation of the linear motor that may occur with changes in measurement or inspection conditions.

(Example 1) which shows an example of the charged particle beam apparatus provided with the stage apparatus which uses a linear motor as a drive source. The figure which shows an example of the stage apparatus which uses a linear motor as a drive source. Sectional drawing of a direction perpendicular | vertical to the rail for lower stages of a stage apparatus. Sectional drawing of a direction perpendicular | vertical to the rail for upper stages of a stage apparatus. The figure which shows an example of the temperature control system of a stage apparatus. The figure which shows the structure of the heater of a temperature control system. The figure which shows the principal part of a stage apparatus (Example 2). Sectional drawing of the direction perpendicular | vertical to the rail for upper stage of Example 2. FIG. The figure which shows the principal part of a stage apparatus (Example 3). Sectional drawing of a direction perpendicular | vertical to the upper stage rail for Example 3. FIG. FIG. 10 is a diagram illustrating an example of a heater control algorithm (Example 4). The figure which shows the outline | summary of a scanning electron microscope.

  There are two typical mechanisms for creating a linear motion of the XY stage: a mechanism using a rotary motor and a ball screw, and a mechanism using a linear motor. When a rotary motor such as a stepping motor is used, there is a mechanical contact point to change the rotary motion into a linear motion.

  On the other hand, since the linear motor does not require it, the mover and the stator in the drive mechanism are not in contact with each other. In a device that handles charged particle beams such as a length measurement SEM, a stage device must be disposed in a vacuum, and heat cannot be transferred through air at non-contact locations. For this reason, if a non-contact type linear motor is used, a heat dissipation path will be lost.

  In the case of a stepping motor, heat conduction occurs at a contact location for converting rotation to linear motion, and the heat generated by the motor can be released before the contact location. On the other hand, in the case of a linear motor, in a configuration in which a coil is used as a mover and a permanent magnet is used as a stator, Joule heat generated when a current is passed through the coil cannot be released to the stator side.

  For this reason, the temperature rise of the stage which moves integrally with the mover cannot be avoided. For this reason, if a linear motor is used for the XY stage of an apparatus that handles charged particle beams, it becomes more difficult to suppress temperature fluctuations.

  In a semiconductor inspection apparatus such as a length measuring SEM, an inspection menu is determined and wafers are inspected one after another by the same operation. Since the operation pattern per wafer is the same, the load applied to the linear motor is constant and the amount of heat generated by the coil is constant while the operation pattern is repeated. However, when the inspection menu is changed or when the inspection itself is paused, the amount of heat generated by the linear motor changes there.

  In general, the heat generated by the linear motor is radiated by some means. Therefore, if the amount of heat generated changes without changing the state of the heat radiating side, the temperature of the stage changes. When the temperature of the stage changes, the position of the stage changes due to the influence of thermal expansion, and deformation of the stage itself also occurs. When measuring the position of a stage using a mirror bar and a laser interferometer installed on the stage, if the angle of the reflecting surface of the mirror bar changes, an error occurs in the measurement result for that angle. The XY stage includes an upper stage and a lower stage so that the XY stage can move in two axial directions, and the upper stage moves on the lower stage. Therefore, when the lower stage is bent by thermal deformation, the flatness of the lower stage changes, and the horizontal angle of the upper stage that moves on the lower stage changes. As a result, the angle of the reflection surface of the mirror bar changes, and the position measurement result of the stage changes. Therefore, when the temperature distribution of the stage changes, the position measurement error increases in addition to the position change due to thermal expansion, and the position recognition information changes.

  Since such position measurement errors occur, in order to suppress thermal deformation caused by fluctuations in the amount of heat generated by the linear motor, not only keep the temperature of the location where the wafer is mounted, but also other types such as the lower stage. It is also required to suppress fluctuations in the thermal deformation of the part.

  In the following examples, in view of the above situation, by suppressing the heat change that occurs when the measurement conditions and inspection conditions are changed, the change in the heat transmitted to the stage is suppressed regardless of the measurement and inspection conditions. A stage apparatus that can be used will be described.

  More specifically, in a device that irradiates a sample placed in a vacuum with a charged particle beam, fixes the sample to a stage, and moves the stage to change the position of the sample to be irradiated with charged particles. The structure of the apparatus is that the slide unit is fixed to the table on which the sample is placed, the slide unit is constrained by the rail and moves, and the upper and lower stages are arranged in two stages. A linear motor is used to drive the upper stage and the lower stage, and the linear motor has a coil in the mover and a permanent magnet in the stator, and then the upper stage linear motor. A heater is provided between the position where the movable element of the linear motor is connected to the table of the upper stage, and the heater is heated when the heat generation of the movable element of the linear motor is reduced.

  By using the above configuration, even if the operating state of the stage changes, the change in the amount of heat generated by adding the heat generated by the mover and the heat generated by the heater can be reduced. This suppresses the time variation of the local temperature in the vicinity of the heater, transfers the heat from the heat source to the table, and transfers the heat to the rail through the slide unit, so that the temperature formed from the upper stage to the lower stage as a whole. The time change of the distribution can also be reduced. As a result, the state of thermal deformation of the stage determined by the temperature distribution of the entire stage does not change with time, and the measurement error for grasping the stage position is reduced.

  The embodiment described below relates to a stage apparatus mainly used for a charged particle beam apparatus or the like. For example, a length measurement SEM used for evaluating the circuit geometry and a SEM for reviewing defects based on defect coordinate information obtained by a higher-level defect inspection apparatus are representative examples of charged particle beam apparatuses. In addition, an apparatus that performs processing by irradiating a sample with an ion beam may be used. A device such as a length measuring SEM incorporates a stage device for aligning a fine circuit pattern or a defect portion formed on a large sample such as a semiconductor wafer. In particular, in the recent measurement SEM, the number of measurement points may reach several thousand points, and the heat generated by the linear motor that drives the stage tends to increase. For this reason, more effective countermeasures are required for problems caused by heat generated by the stage drive mechanism. As a means for solving this problem, embodiments will be described below with reference to the drawings.

  FIG. 12 is a diagram showing an outline of a scanning electron microscope (SEM). An electron beam 103 extracted from the electron source 101 by the extraction electrode 102 and accelerated by an accelerating electrode (not shown) is focused by a condenser lens 104 which is a form of a focusing lens, and then is scanned on a sample 109 by a scanning deflector 105. Are scanned one-dimensionally or two-dimensionally. The electron beam 103 is decelerated by the negative voltage applied to the electrode built in the sample stage 108 (stage device), and is focused by the lens action of the objective lens 106 and irradiated onto the sample 109. The inside of the sample chamber 107 is maintained at a predetermined degree of vacuum by a vacuum pump (not shown).

  When the sample 109 is irradiated with the electron beam 103, secondary electrons and electrons 110 such as backscattered electrons are emitted from the irradiated portion. The emitted electrons 110 are accelerated in the direction of the electron source by an acceleration action based on a negative voltage applied to the sample, and collide with the conversion electrode 112 to generate secondary electrons 111. The secondary electrons 111 emitted from the conversion electrode 112 are captured by the detector 113, and the output of the detector 113 changes depending on the amount of captured secondary electrons. In accordance with this output, the brightness of a display device (not shown) changes. For example, in the case of forming a two-dimensional image, an image of the scanning region is formed by synchronizing the deflection signal to the scanning deflector 105 and the output of the detector 113.

  In the example of FIG. 1, an example in which electrons emitted from a sample are converted by a conversion electrode and detected is explained. However, the present invention is not limited to such a configuration. It is possible to adopt a configuration in which the detection surface of the electron multiplier tube or the detector is arranged on the orbit.

  The control device 120 controls each component of the scanning electron microscope, and forms a pattern on the sample based on the function of forming an image based on detected electrons and the intensity distribution of detected electrons called a line profile. It has a function to measure the pattern width. The control device 120 has a built-in arithmetic device and executes control of a stage device and a heater described later.

  1 to 4 show the apparatus configuration in the first embodiment by various display methods and show one structure.

  FIG. 1 shows an external appearance so that the entire configuration can be seen, but is shown in a perspective view so that the inside of the apparatus can be seen. The sample chamber 1 is a vacuum vessel, and has a stage device in the vacuum space inside. A column 2 is attached to the central upper surface of the sample chamber 1. The column 2 generates a charged particle beam (= electron beam), irradiates the sample (= wafer), and measures the secondary electrons obtained thereby. The structure of the column is complicated, but here it is shown in a simplified shape to show only the position.

  A cooling plate 5 is attached to the bottom surface of the sample chamber 1 to cool the sample chamber 1 as a vacuum container from the outside. Heat transmitted from the sample chamber 1 can be removed by flowing cooling water through the cooling plate 5. Inside the sample chamber 1, a stage device including an upper stage and a lower stage is built in, and the upper stage is configured around the upper table 4. The lower stage is configured around the lower table 3. The linear motor that drives the upper stage includes a mover having a coil and a stator having a permanent magnet. By fixing the stator 12 to the lower table 3, the upper table can move relative to the lower table. The stator 15 of the linear motor for driving the lower stage has a permanent magnet and is fixed to the sample chamber 1.

  FIG. 2 is a perspective view seen from the same angle as FIG. 1, and the sample chamber 1, the column 2, the cooling plate 5, and the lower linear motor stator 15 are not shown, and the structure of the stage is easily understood. is there. A chuck 6 is fixed to the upper table 4, and the chuck 6 directly touches the sample (= wafer) and is fixed to the stage. The chuck 6 sucks the wafer with a force such as static electricity, and releases the sucking force when the wafer is replaced. Mirrors 7 and 8 are fixed to the upper table 4, and a distance from the reflecting surface is measured using a laser interferometer (not shown), and coordinates are calculated from the measurement result. Therefore, the coordinates of the wafer irradiated with the electron beam can be obtained from the positions of the mirrors 7 and 8. The upper stage is driven by a linear motor including a mover 10 having a coil and a stator 12 having a permanent magnet, and the mover 10 moves integrally with the table 4. In connecting the mover 10 to the table 4, the connection component 9 and the heater 11 are sandwiched between them. The heater 11 is for keeping the temperature of the stage constant by compensating for the heat generation of the mover 10. Since the heater 11 has a thin structure, it can be easily sandwiched between the component 9 and the mover 10, and the three members can be pressed and fixed with bolts (not shown). Thereby, the adhesion degree of the contact surface of the heater 11 is improved, heat transfer is improved, and uneven temperature can be reduced.

  Two guide rails 17 are fixed on the upper surface of the lower table 3 to restrain the movement of the upper table. Further, the lower table 3 moves while being restricted by the guide rail 18 fixed to the sample chamber 1. Therefore, the upper table 4 moves in the longitudinal direction of the guide rail 17 with respect to the lower table 3, and the amount of movement is grasped by measuring the distance of the reflecting surface of the mirror 7. Similarly, the lower table 3 moves in the longitudinal direction of the guide rail 18 with respect to the sample chamber 1, and the amount of movement is grasped by measuring the distance of the reflecting surface of the mirror 8. From these measurements, the XY coordinates of the table 4 are obtained, whereby the XY coordinates of the wafer are grasped.

  FIG. 3 is a cross-sectional view of the stage apparatus illustrated in FIG. 1. The cross-sectional direction is perpendicular to the longitudinal direction of the guide rail 18, and the cross-sectional position and direction are the BB cross-section shown in FIG. The column 2 arranged on the upper surface of the sample chamber 1 must be close to the wafer in order to photograph the wafer at high magnification. The chuck 6 on which the wafer is placed and the column 2 are close to each other. Since the upper table 4 moves along the guide rail 17, it moves in the lateral direction of the paper surface, and the vertical surface on the right side of the mirror 7 becomes the reflection surface to measure the movement distance.

  The upper table 4 has legs at four corners, and the legs are connected to the slide unit 20. Therefore, slide units 20 are installed at the four corners of the upper table 4. The slide unit has a large number of balls or roller rolling elements inside, and the rolling elements are in rolling contact with both the guide rail and the slide unit main body. Accordingly, the table can be moved in a state where friction is small and there is no play or play, and the table can be restrained so that it can move only in one direction. Since the guide rails 17 are fixed to the lower table 3, the upper table 4 can move only in the lateral direction of the paper with respect to the lower table 3, and all the movements in the direction perpendicular to the paper are in the lower stage. Will come to bear.

  The lower table 3 is connected to slide units 21 at four corners, and the four slide units 21 are restrained by two guide rails 18 so that the lower table 3 can move only in the direction perpendicular to the paper surface. The lower table 3 is driven by a linear motor including a mover 14 and a stator 15, and the mover 14 has a coil and the stator 15 has a permanent magnet. The mover 14 moves integrally with the lower table 3, and is connected via a connection component 13 and a thermal resistance component 16.

  Further, a slide unit 22 is fixed to the connection component 13, the slide unit 22 is in contact with the guide rail 19, and the guide rail 19 is fixed to the sample chamber 1. In this way, the heat generated by the mover 14 is more easily transmitted to the sample chamber 1 than to the table 3. That is, if a material having a low thermal conductivity such as resin or ceramic is used as the material of the heat resistance component 16, the heat conduction from the component 13 to the table 3 is hindered.

  On the other hand, since the heat generated in the movable element 14 does not disappear unless it is transmitted somewhere, it is transmitted from the component 13 to the slide unit 22 and is transmitted to the sample chamber 1 through the guide rail 19. By cooling the bottom surface of the sample chamber 1 with the cooling plate 15, the temperature rise as a whole can be reduced. That is, in the heat transfer path from the mover 14 serving as a heat source to the cooling plate 5 serving as a cooling source, an increase in temperature of the mover 14 can be suppressed by further reducing the overall thermal resistance. This means that the temperature difference between the mover 14 and the table 3 is reduced, and the temperature rise caused by the heat generated by the mover 14 being transmitted to the table 3 can be suppressed. Therefore, the temperature change of the table 3 accompanying the change in the heat generation amount of the mover 14 can be reduced.

  4 is a cross-sectional view of the stage apparatus illustrated in FIG. 1, as in FIG. 3. The cross-sectional direction is perpendicular to the longitudinal direction of the guide rail 20, and the cross-sectional position and orientation are the same as those shown in FIG. It is A cross section. Since the lower table 3 moves along the guide rail 18, it moves in the horizontal direction of the paper surface, and the vertical surface on the left side of the mirror 8 becomes a reflecting surface to measure the moving distance. Two slide units 22 are arranged in the longitudinal direction of the guide rail 19 to promote heat transfer. In addition, what was demonstrated in FIG. 3 is abbreviate | omitted by attaching | subjecting the same part number.

  The linear motor that drives the upper table 4 includes a mover 10 and a stator 12, and the stator 12 is fixed to the lower table 3. The stator 12 has a permanent magnet, and the mover 10 has a coil. When driving the linear motor, a current is passed through the coil, and the stage is moved using an electromagnetic force proportional to the current as a thrust. The coil is made of a material having a low electrical resistance such as a copper wire. However, since the electrical resistance cannot be made zero, Joule heat generation proportional to current × resistance voltage occurs. Since the resistance voltage is generated in proportion to the current × electric resistance, Joule heat is generated in proportion to the square of the current flowing through the coil.

  When moving the stage, thrust for acceleration is required when accelerating the stage for the first time, and it is necessary to pass a current through the coil in accordance with the required thrust. In order to maintain the moving speed of the stage at a constant speed, it is necessary to generate a thrust corresponding to the frictional resistance, and a current corresponding to the thrust is supplied to the coil. When the stage is decelerated and the stage is stopped at a predetermined position, a thrust in the opposite direction to that in acceleration is required, and a current in the opposite direction to that in acceleration is supplied to the coil in accordance with the required thrust.

  When the stage is moving, the coil crosses the magnetic field formed by the permanent magnet of the stator, so that an induced electromotive force is generated in the coil in proportion to the moving speed of the stage. Since the induced electromotive force works in the direction of decelerating the moving speed, the induced electromotive force generated in the coil can be used when the stage is decelerated. That is, when the stage is decelerated, it is possible to generate electric power with the coil of the mover, but as Joule heat generation, heat generation is generated in proportion to the square of the flowing current regardless of whether power is generated. Therefore, when the stage is decelerated, Joule heat is generated according to the thrust required for deceleration. In the case of an inspection apparatus such as a length measuring SEM, in order to perform inspection at one place, an operation of moving to that place is performed once, and acceleration, deceleration, and constant speed movement are performed within that one time.

  In addition, since the stage is stopped while imaging is performed by irradiating an electron beam, the linear motor is not energized during that period, and Joule heat is not generated. In this way, the Joule heat generated in the coil changes momentarily, but since the time interval is short, it is absorbed by the heat capacity of the motor mover and the temperature change as the motor mover is very small. This temperature change is not a problem. As the temperature change of the stage, the temperature fluctuation due to the fluctuation of the heat generation amount at the moment is not a problem, but when the average heat generation amount when repeating a series of operations changes due to the change of the operation pattern Arise. When the average calorific value of the linear motor changes due to the change of the operation pattern, the heater 11 is still used to reduce the temperature change. For example, the stage movement cycle is fast and the linear motor has a high average heat generation, and the inspection pattern has continued to be inspected. The stage movement cycle is slow and the linear motor has a low average heat generation. If you do nothing, the stage temperature will drop.

  Due to this temperature change, the thermal deformation state of the stage changes, and contraction corresponding to the temperature drop occurs. At this time, the position is changed by the amount of contraction, the state of deformation such that the stage is curved is also changed, and the angle of the reflecting surface of the mirror for measuring the position of the stage is also changed.

  In measuring the position of the stage, measurement is performed at a reference position in advance, and the true position is grasped while performing various corrections based on the measurement. Therefore, what is required for the reflecting surface of the mirror is not a perfect perpendicularity, and that the state does not change from when the measurement is performed at the reference position. For this reason, it is more important that the absolute value of the temperature does not change with time than the absolute value of the temperature is within a certain range.

  Therefore, a state where the temperature of the stage gradually decreases when the operation pattern of the stage is switched should be avoided. In the present embodiment, such a temperature change is suppressed using the heater 11. That is, if the heater 11 generates heat when the average heat generation amount of the mover 10 is reduced by switching the operation pattern, the total heat generation amount of the mover and the heater does not change before and after switching. . Moreover, since the mover 10 of the linear motor does not have any contact with the stator 12 and is disposed in the vacuum container, the mover 10 is moved from the mover 10 to the stator 12 via air. There is no heat transfer. Therefore, all the heat generated by the mover 10 is transmitted to the components 9 connected thereto. For this reason, when the heat generation of the mover 10 is reduced and the heat generation amount of the heater 11 is increased instead, if the total heat generation amount is the same, the heat amount transmitted to the component 9 is the same.

  If there is no connection member that connects the mover and the table, or if there is no connection member and the mover is directly attached to the table, the table is the only heat transfer path that substantially contacts the mover. In order to suppress the influence on the stage caused by the thermal change of the child, it is preferable to compensate the thermal change in the transmission path. By arranging the heater at the position illustrated in FIG. 4 and the like, the influence of the thermal change of the mover on the table can be made uniform regardless of the change in the operating condition of the stage. In addition, when there is a connecting member, the heater may be disposed between the connecting member and the mover, inside the connecting member, between the connecting member and the table, or the like.

  The amount of heat transferred to the component 9 is transferred to the components connected earlier, and the upper table 4, the slide unit 20, the guide rail 17, the lower table 3, the slide unit 21, the guide rail 18, the sample chamber 1, and the cooling plate 5. It will be transmitted in order. Since heat conduction always occurs from a higher temperature to a lower temperature, the temperature decreases in the order in which heat flows from the heat source side. The temperature difference is the temperature distribution of the entire stage, but even if the heat source is switched from the mover 10 to the heater 11, if the amount of heat generated from the heat source is the same, the temperature distribution formed on the entire stage is also the same. .

  Therefore, even if the operation pattern changes, it is possible to keep the temperature of the lower table 3 constant by using the heater 11, and the curved state of the lower table 3 is not changed. Therefore, the inclination angle of the upper table 4 on the upper table 4 does not change, and the angles of the reflection surfaces of the mirrors 7 and 8 do not change. As a result, the measurement accuracy of the stage position is enhanced, and at the same time, the temperature of the chuck 6 becomes constant, and the temperature change of the wafer in contact therewith can be eliminated. Therefore, the position change due to expansion / contraction due to the temperature change of the wafer can be eliminated at the same time.

  FIG. 5 is a system configuration diagram in which a heater control system is added to the configuration of the stage in the first embodiment. Such a control system is built in the control device 120. The configuration shown here can be applied to the following second and third embodiments. A current is supplied to the heater 11 through the power wiring 30. In controlling the current, a temperature sensor 26 is disposed in the vicinity of the heater 11. More specifically, the measurement position of the temperature sensor 26 is a position where the temperature sensor 26 is similarly sandwiched when the heater 11 is sandwiched and fixed from both sides. By doing so, the temperature sensor 26 can detect the temperature of the component connected to the heater 11. The temperature sensor 26 is connected to a temperature controller 27, and the temperature device 27 grasps the temperature.

  Since the temperature controller 27 is an electric device, it is connected to a power source 29. In controlling the heater output by the temperature controller 27, a target temperature is determined in advance. When the temperature measured by the temperature sensor 26 falls below the target temperature, the heater 11 is operated. At the same time, the power supplied to the heater is determined according to the deviation from the target temperature. As a calculation method for determining the power, there is PID control or the like. In PID control, when determining an output value, an element that is proportional to a deviation from a target value, an element that depends on an integral value of the deviation, and an element that depends on a change in time of the deviation are combined.

  Furthermore, the coefficients related to these elements can be automatically tuned during the control operation, and can be calculated and controlled with more optimal coefficients. The power command value determined by the temperature controller 27 is sent to the amplifier 28 via the signal line 31. The amplifier 28 obtains power from the power supply 29 and outputs power proportional to the signal value of the signal line 31. In controlling the power of the heater, there is also a method of controlling ON / OFF time ratio by repeatedly turning on / off a constant voltage output.

  In the case of this method, since it is not necessary to change the output voltage, the equipment configuration is inexpensive. However, when electricity is supplied to the heater, a magnetic field is formed around the heating wire in proportion to the current, and the magnetic field slightly affects the trajectory of the electron beam of the electron microscope. Even if a magnetic field is given to the space through which the electron beam passes, there is no problem if it is a constant magnetic field that does not change, but if the magnetic field changes instantaneously, the deviation of the orbit of the electron beam will not be constant, It becomes noise for imaging. Therefore, in order to avoid a relatively large magnetic field change when the heater current is turned on / off, the power supply to the heater is not determined by the ON / OFF time ratio but by the voltage. It is better to control the power by changing.

  In this case, the current flowing through the heater changes gradually, and the change in the magnetic field generated by the current can be small. Thereby, noise that affects imaging is reduced. Therefore, the amplifier 28 is preferably one that changes the voltage or current when supplying power to the heater in proportion to the command value received through the signal line 31.

  In order to suppress the influence of the thermal change of the mover on the table, heater control based on the temperature setting and control of the total heat generation amount of the coil and the heater can be considered, but when performing the heater control based on the temperature setting, for example, By setting the temperature in the state where the stage is most heavily used as the target temperature, it is possible to realize stabilization of the stage temperature only by heating control.

  FIG. 6 is a diagram showing details of the heater 11 used in the first embodiment. The configuration shown here can be applied to the following second and third embodiments. The heater 11 is joined to the power wiring 30 at the terminal portion, and power is supplied. The power wiring 30 is composed of two wirings and is connected to both ends of one heating wire 32. Nichrome, SUS, titanium, or the like can be applied to the material of the heating wire 32. It is preferable to use a non-magnetic material for the heating wire 32 in order to make it less susceptible to the influence of a magnetic field.

  In designing the wiring shape of the heating wire 32, it is preferable to make a pair by bringing the wires that are in opposite directions close to each other. When a straight heating wire is present alone, a concentric magnetic field is formed around the wire, but when there are opposite wires in the immediate vicinity, each other's magnetic field interferes to cancel the magnetic field. Get up. For this reason, the heating wire 32 is folded back into two U-shapes on the left side of FIG. By using the folded wiring, the magnetic field can be canceled. In addition, the pair formed by turning back is opened. This is because when a pair is brought close to each other, the magnetic field cancels with the adjacent partner that comes close, and the magnetic field canceling effect with the paired partner weakens.

  In configuring the heater 11, not only a heating wire but also a configuration for electrical insulation is required. For this reason, the heating wire 32 is sandwiched between the insulating materials 33. Thus, when the heater and other parts are assembled, electrical insulation can be maintained. As a material of the insulating material 33, a resin material that can withstand a relatively high temperature, such as polyimide, may be used.

  In that case, it is preferable to join the polyimide sheets by thermal welding rather than using an adhesive for joining the polyimide sheets covering from both surfaces of the heating wire 32. The electron microscope needs to be used in an environment in which a high degree of vacuum is maintained. When an adhesive is used, the degree of vacuum is deteriorated until the components thereof evaporate and the evaporation dies. In addition, ceramics such as alumina may be used as the insulating material 33.

  In that case, a heating wire may be formed on the surface of the ceramic plate by vapor deposition, and then sandwiched by another ceramic plate. The temperature sensor 26 installed in the vicinity of the heater 11 may be integrated with the heater 11 or may be a separate body. However, it is preferable to avoid the overlapping of the heating wire 32 and the temperature sensor 26. Since the heater 11 is sandwiched between the mover and the connecting part, it is preferable to fasten both of them with bolts, and it is preferable to make a hole in the heater 11 for the bolt to penetrate.

  7 and 8 show the apparatus configuration in the second embodiment, which shows one structure. The description of the same structure as in the first embodiment is omitted.

  FIG. 7 is a perspective view seen from the same angle as FIG. 2 of the first embodiment, in which parts similar to those in FIG. 2 are not shown, and the structure of the stage is easily understood. In addition, in FIG. 7, a part of the upper stage was cut to make the internal structure of the stage easier to understand. The difference between the second embodiment and the first embodiment is the structure between the heater 11 and the upper table 4. A thermal bypass component 23 exists as a component in contact with the upper side of the heater 11, and the thermal bypass component 23 and the upper table 4 are connected via a thermal resistance component 24. For this reason, the thermal bypass component 23 does not contact the upper table 4.

  FIG. 8 is a cross-sectional view at the same cross-sectional position as FIG. 4 of the first embodiment, and particularly shows the connection relationship of the thermal bypass component 23. The upper surface of the mover 10 of the linear motor for the upper stage is in contact with the heater 11, and the upper surface of the heater 11 is in contact with the thermal bypass component 23. A thermal resistance component 24 is in contact with the upper surface of the thermal bypass component 23, and this is connected to the upper table 4. The thermal bypass component 23 is in contact with the heater 11 and the thermal resistance component 24 and then connected to the thermal bypass slide unit 25.

  The thermal bypass slide unit 25 is in contact with the guide rail 17 installed on the lower table. Even if both or one of the linear motor movable element 10 and the heater 11 generate heat, all of the heat is transmitted to the thermal bypass component 23. From there, there are a path that is transmitted to the thermal resistance component 24 and a path that is transmitted to the thermal bypass slide unit 25 as the heat transfer path. The greater the thermal resistance of the thermal resistance component 24, the greater the proportion of heat flowing through the path of the thermal bypass slide unit 25. This means that the amount of heat transmitted to the upper stage 4 is reduced. When the amount of heat transmitted to the upper stage 4 is reduced, the temperature rise of the upper stage 4 caused by the heat generation of the mover 10 is reduced. If it becomes so, the temperature rise of the chuck | zipper 6 will also become small and the temperature change of the wafer which contacts this will also become small. Therefore, it is preferable to use a material having a low thermal conductivity such as resin or ceramic for the thermal resistance component 24 to increase the thermal resistance. On the other hand, the amount of heat transmitted to the thermal bypass slide unit 25 finally flows to the cooling plate 5 through the guide rail 17 and the lower table 3. By using the thermal bypass component 23, it is preferable to reduce the temperature change of the chuck 6 in terms of hardware because the control is easy even if the temperature is controlled by the heater 11.

  9 and 10 show an apparatus configuration in the third embodiment, which shows one structure. As in the previous case, the description of the same structure as in the first embodiment is omitted.

  FIG. 9 is a perspective view seen from the same angle as FIG. 2 of the first embodiment, in which parts similar to those in FIG. 2 are not shown, and the structure of the stage is easily understood. In this embodiment, the configuration of the linear motor for driving the upper table 4 ′ is different, the mover 34 has a permanent magnet, and the stator 35 has a coil. The mover 34 is connected to the upper table 4 'and moves together with the upper table 4'.

  FIG. 10 is a cross-sectional view at the same cross-sectional position as FIG. 4 of the first embodiment, and particularly shows the connection relationship around the linear motor for the upper stage. Since the mover 34 connected to the upper table 4 ′ is a part having a permanent magnet, it does not generate heat. For this reason, even if the upper stage is driven, the temperature of the upper table 4 ′ is not directly increased. If the temperature change of the upper table 4 'is small, the temperature change of the chuck 6 is also small, and this embodiment is effective as a hardware configuration for reducing the temperature change. However, since the stator 35 of the linear motor has a coil, the stator 35 generates heat as the upper stage moves. The stator 35 is connected to the lower table 3 'with the heater 11' interposed therebetween. Therefore, all the heat generated by the stator 35 is transmitted to the lower table 3 '. In order to suppress the temperature change of the lower table 3 'caused by this, the heater 11' is used. That is, when the operating amount of the upper stage decreases and the average heat generation amount of the stator 35 decreases, the heater 11 'compensates for the decrease, so that the total heat generation amount becomes constant and temperature changes can be prevented. become.

  FIG. 11 is an algorithm diagram illustrating a method of controlling the heater power other than the system configuration using the temperature sensor 26 shown in FIG. For this reason, the combination of the hardware configurations of the stages can be combined with the configurations of the first to third embodiments.

  In the algorithm shown in FIG. 11, first, the usage state of an inspection apparatus such as a length measuring SEM is determined. The usage state is roughly divided into a case where the inspection apparatus is used and a case where the inspection device is not used. In this case, the heat generation amount of the target determined in advance is output as it is as the heat generation amount of the heater. While the inspection device waits for the next work, it does not work during that time, so it is a “stage pause”. By preheating with the heater during the stage pause, even if the operation of the stage starts and the heat generation of the linear motor starts, the temperature change of the stage can be eliminated by turning off the heat generation of the heater. . This preheating operation is also effective in the system of the temperature sensor of FIG. 5, and if the stage is already warmed before the stage operation, the subsequent temperature change can be reduced.

  Returning to the case where the temperature sensor is not used, it is in a state of doing some work other than "Stage Pause". In that case, what kind of inspection is performed is programmed. This determines the wafer inspection pattern. When the inspection pattern is determined, all inspection portions of one wafer are determined, and all operation paths of the stage for tracing the inspection portion can be calculated. When the operation amount and operation time of the upper stage are extracted with respect to the operation, the average heat generation amount of the upper stage linear motor can be calculated. By making the difference between the predicted heat generation amount and the target heat generation amount determined in advance as the heat generation amount of the heater, the output of the heater can be determined. While the wafer inspection pattern is the same, the heater continues to generate heat at the output determined by the calculation method. When this control algorithm is used, a calculation load is applied, but there is an advantage that a temperature sensor is unnecessary.

1 Sample chamber 2 Column 3 Lower table 4 Upper table 5 Cooling plate 6 Chuck 7 Mirror (for upper)
8 Mirror (for lower stage)
9 Upper-stage mover connecting part 10 Upper-stage linear motor mover 11 Preheating heater 12 Upper-stage linear motor stator 13 Lower-stage mover connecting part 14 Lower-stage linear motor mover 15 Lower-stage linear motor stator 16 Thermal resistance parts (For lower stage)
17 Upper stage guide rail 18 Lower stage guide rail 19 Heat radiation guide rail 20 Upper stage slide unit 21 Lower stage slide unit 22 Heat radiation slide unit 23 Thermal bypass component 24 Thermal resistance component (for upper stage)
25 Thermal bypass slide unit 26 Temperature sensor 27 Temperature controller 28 Amplifier 29 Power supply 30 Heater power wiring 31 Signal wiring 32 Heating wire 33 Insulating material 34 Upper linear motor movable element 35 Upper linear motor stator

Claims (9)

In a stage device including a table on which a sample is placed and a linear motor that drives the table in a predetermined direction,
The linear motor includes a mover having one of a coil or a permanent magnet and a stator having the other of the coil or the permanent magnet, and a heater is interposed between the mover and the table. apparatus. In claim 1,
A stage apparatus comprising: a slide unit that guides the table; a rail that contacts the slide unit and that regulates a moving direction of the table; and a cooling mechanism that contacts the rail. In claim 2,
A stage apparatus comprising: a temperature sensor installed between the heater and the slide unit; and a control device for controlling the heater based on temperature measurement by the temperature sensor. In claim 3,
The stage device is characterized in that the control device controls the heater so that a measurement result by the temperature sensor is constant or within a predetermined range. In claim 12,
A first table for moving the sample in a first direction; and a second table mounted on the first table for moving the sample in a second direction. A stage apparatus, wherein the stage apparatus is installed between a mover of a linear motor that drives a second table and the second table. In claim 5,
A slide unit that guides the second table, a mover that moves the second table, a thermal bypass member that is connected to the slide unit, the thermal bypass member, and the second table A stage apparatus comprising a heat resistance member installed between the two. In claim 1,
A stage apparatus comprising: a controller that estimates a heat generation amount of a linear motor from an operating state of a stage and controls a heat generation amount of a heater based on the estimation. In claim 1,
The heater is a heater using a heating wire, and the heating wire is a set of wirings in which the direction of the current is opposite to each other in close proximity, and the wirings in the opposite direction are separated from each other in the interval of the wirings in the opposite direction. A stage apparatus characterized by being further separated. A charged particle beam apparatus including a charged particle source, a table on which a sample irradiated with a beam emitted from the charged particle source is mounted, a stage mechanism for moving the table, and a vacuum chamber in which the stage mechanism is installed In
A linear motor including a mover having one of a coil or a permanent magnet, a stator having the other of a coil or a permanent magnet, and a heater installed between the mover and the table. A charged particle beam apparatus comprising: