JP5281024B2 - Sample stage and electron microscope apparatus using the same stage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that a plurality of braking mechanisms employed for positioning a sample stage each have different gaps, and if the same drive command is issued to respective braking mechanisms, braking forces produced by the respective braking mechanisms differ, resulting in a positional deviation of the sample stage. <P>SOLUTION: An actuator 301 of each of the plurality of braking mechanisms is driven by a predetermined drive command. While the actuator is being driven, a state difference Vba in the predetermined drive command among the braking mechanisms, when a brake pad 307 of each braking mechanism 125a contacts a braked surface 124u, is obtained based on a contact sensing output from a sensing mechanism for each braking mechanism 125a. Based on the obtained state difference Vba in the predetermined drive command, a final drive command Vat, ... corresponding to the drive state of the actuator 301 while a brake is in operation is decided for each braking mechanism. The actuator 301 of each braking mechanism 125a is driven by the decided final drive command of the corresponding braking mechanism. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention particularly relates to a sample stage and an electron microscope apparatus using the stage, which are suitable for use in semiconductor inspection and evaluation in the field of semiconductor manufacturing.

  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. Along with this, a scanning electron microscope having a length measuring function (hereinafter referred to as a length measuring SEM) is usually used to evaluate whether or not the shape dimension of the pattern formed on the semiconductor wafer is correct. ing.

  In the length measurement SEM, an electron beam is irradiated onto the wafer, the obtained secondary electron signal is subjected to image processing, and the edge of the pattern is discriminated from the change in brightness to derive the dimension. Therefore, in order to cope with the miniaturization of the semiconductor element as described above, it is important to obtain a secondary electron image with less noise at a high observation magnification. Therefore, in the length measurement SEM, it is necessary to improve the contrast by overlaying several secondary electron images, and the sample stage that holds and holds the wafer is required to suppress vibration and drift on the nanometer order. Is done.

  In order to suppress such vibration and drift, there is a technique (see Patent Document 1 and Patent Document 2) in which a sliding member (sliding brake) is attached to a sample stage to increase mechanical rigidity against vibration or the like. However, when a sliding member is used, the positioning of the sample stage is delayed because the frictional force of the sliding member prevents the movement of the sample stage when the sample stage is moved. Furthermore, the heat generated by the friction of the sliding member during the movement of the sample stage has also become a factor in causing drift due to thermal contraction of the member. As a technique for suppressing such drift due to frictional heat during movement, there is a technique (Patent Document 3) in which contact and release of a sliding member are controlled by an actuator.

USP 5314254 (FIGS. 5, 6, 10, and 11) JP 2002-184339 A (FIGS. 4 and 5) JP 2001-196021 A (FIGS. 2 and 3)

  By the way, when the brake mechanism for contacting / releasing such a sliding member is configured on the sample stage, the brake structure that presses and sandwiches one brake rail with two brake mechanisms or the moving axis of the sample stage A brake structure that presses two brake rails installed symmetrically with each brake mechanism can be configured.

  However, sliding between the sliding member contact surface of the brake mechanism (hereinafter referred to as the brake braking surface) and the brake rail due to a minute unevenness caused by processing accuracy on the sliding member contact surface of the brake rail. The distance between the member contact surface (hereinafter referred to as the brake brake surface), that is, the gap, varies by a minute amount depending on the brake movement position on the brake rail. As a result, if the same drive command is output to each brake mechanism, the magnitude of the force acting on the brake rail differs between the brake mechanisms, resulting in sample stage displacement and drift. There's a problem.

  In order to prevent such displacement and drift from occurring on the sample stage, it is necessary to measure the gap at each moving position on the brake rail for each brake mechanism and output a drive command for the brake mechanism that matches the gap. There is. However, it is difficult to accurately measure the gap between the brake braking surface and the braked surface during movement of the sample stage. In consideration of the effects of changes in the brake mechanism and brake rail over time, the drive command in accordance with the gap to the brake mechanism needs to be periodically adjusted in consideration of the influence of changes in the time.

  Therefore, according to the present invention, when positioning the sample stage, an optimal brake drive command with little sample stage position shift is applied to the brake mechanism according to the gap difference between each of the brake mechanisms and the brake target surface. It is an object of the present invention to provide a sample stage that can be given individually and does not require measurement of a brake gap or periodic adjustment of a drive command, and an electron microscope apparatus using the stage.

  The sample stage and the electron microscope apparatus according to the present invention include a movable table that is movably held along a guide mechanism, a moving mechanism that moves the movable table to an indicated position along the guide mechanism, and a braked surface. A sample stage having a brake pad that contacts or separates in response to the drive of the actuator and brakes the movable table, and is provided in each of the plurality of brake mechanisms. After the movable table is moved to the indicated position along the guide mechanism and stopped by the detecting means for detecting contact with the braking surface and immediately before stopping, the actuators of the plurality of brake mechanisms are driven. And a control device that operates a plurality of brake mechanisms, and the control device, when operating the plurality of brake mechanisms, The actuators of each of the brake mechanisms are driven by a predetermined drive command for bringing the brake pad into contact with the brake target surface, and a plurality of actuators are driven during driving of the actuators of the plurality of brake mechanisms based on the predetermined drive command Based on the detection output output from the detection means of each of the brake mechanisms, the state difference of the predetermined drive command between the plurality of brake mechanisms when the brake pads of each of the plurality of brake mechanisms contact the brake target surface is calculated. The final drive command corresponding to the drive state of the actuator at the time of the brake operation is determined for each of the plurality of brake mechanisms, and the actuators of the plurality of brake mechanisms are Drive according to the final drive command of the corresponding brake mechanism determined And features.

  According to the present invention, the sample stage can be positioned with high accuracy. Further, it is possible to provide a sample stage for realizing high-precision measurement with little vibration and drift when the sample is moved, and an electron microscope apparatus using the stage.

It is a block diagram of the stage mechanism of the sample stage which concerns on one Embodiment of this invention. It is the schematic which shows the attachment position of each brake mechanism each provided in X table and Y table. It is a block diagram of the brake mechanism shown in FIG.1 and FIG.2. It is a block diagram of the Example of the detection mechanism provided in the brake mechanism which detects contact with a brake pad and a brake rail. It is the graph which showed the relationship of the expansion | extension amount with respect to the magnitude | size of the drive voltage of a piezoelectric actuator. It is a graph which shows one Example of the predetermined drive command supplied to a piezo actuator. FIG. 7 is an explanatory diagram of the relationship between the drive voltage of each piezo actuator and the extended state when a predetermined drive command voltage shown in FIG. 6 is applied to each piezo actuator of each brake mechanism. It is a flowchart which shows the brake control process of the stage mechanism which concerns on a present Example. It is a position time response waveform schematically showing the relationship between the stage positioning state in the length measurement SEM and each process in the length measurement sequence. 1 is a diagram illustrating a schematic overall configuration of a length measurement SEM system according to an embodiment of the present invention. It is a flowchart which shows an example of the control processing of the length measurement SEM which consists of one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 11.

FIG. 1 is a configuration diagram of a stage mechanism of a sample stage according to an embodiment of the present invention.
The stage mechanism 10 positions a sample holder 133 on which a semiconductor wafer (not shown) is mounted at an arbitrary coordinate position on the XY coordinate system shown in FIG. In the illustrated example, the stage mechanism 10 has the following configuration.

  A Y base 110 is fixed on the base 100, and a Y guide 111 is provided on the Y base 110 as a guide mechanism for moving and guiding the top table 130 including the sample holder 133 along the Y direction. . In the illustrated example, the Y guide 111 is fixedly arranged on the upper surface of the Y base 110, one at each of the central portion (not shown) in the X direction and the both ends thereof, for a total of three guide rails 111 ′. Consists of. Each guide rail 111 'is parallel to each other and extends along the Y direction. The Y table 112 is supported by the three guide rails 111 ′ so as to be movable on the Y base 110 in the Y direction. On the other hand, the Y table 112 is restrained from moving in the X direction on the Y base 110 by the Y guide 111.

  The Y base 110 is provided with a Y brake rail 114 for stopping and holding the Y table 112 movable in the Y direction with respect to the Y base 110. The Y brake rails 114 are fixed to both ends of the Y base 110 in the X direction and extend in the Y direction. On both ends of the Y table 112 in the X direction, a Y brake mechanism 115 that constitutes a brake mechanism in the Y direction together with the Y brake rail 114 is fixed with a brake pad to be described later facing the Y brake rail 114. .

  Further, the Y table 112 is moved to an arbitrary position in the Y direction with respect to the Y base 110 between the X direction end of the Y base 110 and the corresponding X direction end of the Y table 112. A Y linear motor 113 is provided. Each Y linear motor 113 has a configuration in which a movable element 113m is engaged with a shaft-shaped stator 113s supported by a support 113f. Each Y linear motor 113 is constituted by a shaft motor, for example, and its stator 113s is a shaft formed by connecting a plurality of permanent magnets having the same poles joined together, and the mover 113m is a shaft. The slider has an electromagnetic coil that fits loosely. Each Y linear motor 113 is fixed to the base 100 or the Y base 110 with the extending direction of the shaft whose support 113f is the stator 113s being the Y direction, and the movable element 113m is at the end of the Y table 112 in the X direction. It has a fixed configuration. Each Y linear motor 113 changes the magnetic pole of the electromagnetic coil of the mover 113m to apply thrust or braking force to the mover 113m with the permanent magnet of the stator 113s, and the mover 113m and thus the Y table 112. Can be moved to an arbitrary position in the Y direction. In FIG. 1, the Y linear motor 113 is provided at each of both ends in the X direction of the Y table 112, but these are provided only at one of the X direction ends if there is a necessary thrust or braking force. The provided structure may be sufficient.

  Further, on the upper surface of the Y table 112, an X sub guide 116 is provided as a guide mechanism in the X direction orthogonal to the Y direction of the top table 130 on which the sample holder 133 is provided. The X sub guide 116 has a configuration in which two guide rails 116 ′ are provided in parallel to each other and extend in the X direction, one at each end in the Y direction of the Y table 112.

  The X sub guide 116 is engaged with an X sub table (not shown in FIG. 1) provided on the lower surface of the top table 130. The X sub-table is integrally connected to the lower surface side of the top table 130. Accordingly, the X sub table and the top table 130 are restrained from moving in the Y direction relative to the Y table 112 by the X sub guide 116, and are allowed to move in the X direction along the X sub guide 116.

  Similarly, the X base 120 is fixedly provided on the base 100 so as to be positioned at both ends of the Y base 110 in the Y direction. Each X base 120 is provided with an X guide 121 as a guide mechanism for moving and guiding the top table 130 provided with the sample holder 133 along the X direction. In the illustrated example, the X guide 121 includes a guide rail 121 ′ that is fixedly disposed on the upper surface of the X base 120 and extends along the X direction.

  The X table 122 is supported by the guide rail 121 ′ of each X base 120 so as to be movable in the X direction on the X base 120. On the other hand, the X table 122 is restrained from moving in the Y direction on the X base 120 by the X guide 121.

  Each X base 120 is provided with an X brake rail 124 for stopping and holding the X table 122 movable in the X direction with respect to the X base 120. The X brake rail 124 extends in the X direction. An X brake mechanism 125 that constitutes a brake mechanism in the X direction together with the X brake rail 124 is fixed to both ends of the X table 122 in the Y direction so that a brake pad, which will be described later, faces the X brake rail 124. .

  Further, an X linear motor 123 for moving the X table 122 to an arbitrary position in the X direction with respect to the X base 120 is provided between each X base 120 and the corresponding Y direction end of the X table 122. Each is provided. Each X linear motor 123 is configured such that a movable element 123m is engaged with a shaft-shaped stator 123s supported by a support 123f. Each X linear motor 123 is constituted by, for example, a shaft motor, and its stator 123s is a shaft formed by connecting a plurality of permanent magnets having the same poles joined together, and the mover 123m is a shaft. The slider has an electromagnetic coil that fits loosely. Each X linear motor 123 is fixed to the base 100 or the X base 120 with the extending direction of the shaft whose support 123f is the stator 123s being the X direction, and the mover 123m is attached to the end of the X table 122 in the X direction. It is fixed. Each X linear motor 123 changes the magnetic pole of the electromagnetic coil of the mover 123m to apply a thrust or a braking force to the mover 123m with the permanent magnet of the stator 123s. Can be moved to an arbitrary position in the X direction. In FIG. 1, the X linear motor 123 is provided at each of both ends in the Y direction of the X table 122, but these are provided only at one end in the Y direction if there is a necessary thrust or braking force. The provided structure may be sufficient.

  Further, on the upper surface of the X table 122, a Y sub guide 126 is provided as a guide mechanism in the Y direction perpendicular to the X direction of the top table 130 on which the sample holder 133 is provided. The Y sub guide 126 has a configuration in which two guide rails 126 ′, one on each side in the X direction of the X table 122, extend in the Y direction in parallel with each other.

  The Y sub guide 116 is engaged with a Y sub table (not shown in FIG. 1) provided on the lower surface of the top table 130. The Y sub table is integrally connected to the lower surface side of the top table 130, and the Y sub table and the top table 130 are restrained from moving in the X direction with respect to the X table 122 by the Y sub guide 126. Linear movement in the Y direction along the Y sub guide 126 is allowed.

  Further, the X table 122 is formed with a long hole 127 extending in the Y direction through which the aforementioned X sub guide provided on the lower surface of the top table 130 passes. As a result, the X sub guide and the top table 130 can move in the long hole 127 along the longitudinal direction (Y direction) independently of the X table 122.

  In the stage mechanism 10, the X table 122 and the Y table 112 move along the corresponding X guide 121 and Y guide 111, respectively, so that the top table 130 can be two-dimensionally moved in the X direction and the Y direction. On the top table 130, a fixed mirror (X mirror 131, Y mirror 132) for measuring the two-dimensional movement position with a laser interferometer (not shown), and a sample holder 133 on which the sample is placed. Is provided.

  In the configuration of the stage mechanism 10 described above, the linear motor is configured by a shaft motor in which a plurality of permanent magnets are connected to the stator and the mover is configured by an electromagnetic coil. A shaft motor in which a plurality of electromagnetic coils are connected in series and the mover is formed of a permanent magnet may be used. Further, the linear motor itself is not limited to the shaft motor, and any linear motor may be used as long as the linear motor is provided.

  FIG. 2 is a schematic diagram illustrating the mounting positions of the brake mechanisms provided on the X table and the Y table, respectively.

  The stage mechanism 10 engages with each of the X table 122 and the Y table 112 by moving and displacing the X table 122 and the Y table 112 with respect to the X direction and the Y direction as indicated by broken arrows in the figure. The top table 130 is positioned at an arbitrary coordinate position on the XY coordinates. The positioning is performed by thrust / brake control of each of the X linear motor 123 and Y linear motor 113 and operation control of each of the X brake mechanism 125 and Y brake mechanism 115.

  As described in FIG. 1, the stage mechanism 10 includes an X brake mechanism 125 corresponding to both ends 122 a and 122 b in the Y direction of the X table 122, and a Y brake mechanism 115 corresponding to both ends in the X direction of the Y table 112. Corresponding to each of 112a and 112b, a total of four brake mechanisms 125a, 125b, 115a and 115b are provided as shown in FIG. Each brake mechanism 125a, 125b, 115a, 115b pushes the brake rails 124a, 124b, 114a, 114b by moving the brake pads forward and backward with respect to the brake rails 124a, 124b, 114a, 114b in response to the displacement of the actuator. Thus, the braking force is generated or the generated braking force is released. A piezo actuator 301 is used as the actuator, and the braking force can be controlled by adjusting the magnitude of the voltage applied to the piezo element.

  3 is a configuration diagram of the brake mechanism shown in FIGS. 1 and 2, FIG. 3 (a) is a front view of the brake mechanism viewed in a direction orthogonal to the moving direction of the table, and FIG. FIG. 5 is a side view of the brake mechanism as viewed in the moving direction of the table. Here, the configuration of the brake mechanism 125a will be described in detail by way of example, but the configuration of the other brake mechanisms 125b, 115a, and 115b is the same as the configuration of the brake mechanism 125a, and thus the description thereof is omitted.

  In FIG. 3, a piezo actuator 301 has a stacked piezo element (not shown) mounted therein, and a tip 301t extends in the axial direction by applying a voltage to the piezo element. . The piezoelectric actuator 301 is integrally assembled to a mounting portion (not shown) formed on the holder 302 by a fixing bolt (not shown).

  The holder 302 is attached to the bottom surface of the X table 122. The holder 302 is attached with a link lever 303 for converting the axial displacement of the tip portion 301t of the piezo actuator 301 into the advance and retreat of a brake pad 307 described later. A shaft hole 302p is formed in the link lever 303, and one end side 305a of the shaft 305 is incorporated into the shaft hole 302p via a sleeve 304, and the link lever 303 and the shaft 305 are integrally engaged. . On the other hand, the other end 305b of the shaft 305 is engaged with a bearing 306 of a holder 302 that is incorporated in advance, and the link lever 303 and the shaft 305 can be integrally rotated by the bearing 306. It is supported by.

  The link lever 303 has a contact portion 303 a that contacts the tip portion 301 t of the piezo actuator 301 around the shaft 305, and an attachment portion 303 b to which the brake pad 307 is attached. A constant urging force (moment) is applied to the link lever 303 in the direction of arrow A by a spring (not shown) so that the contact portion 303a is always in contact with the tip portion 301t of the piezo actuator 301 and is not separated. It has become. As a result, the contact portion 303a of the link lever 303 and the tip portion 301t of the piezo actuator 301 are always in contact with each other, the drive voltage is not applied to the piezo actuator 301, and the tip portion 301t of the piezo actuator 301 retracts. However, the contact portion 303 a of the link lever 303 is in contact with the tip portion 301 t of the piezo actuator 301. In the link lever 303, the length L2 to the other end side where the attachment portion 303b is formed is longer than the length L1 to the one end side where the contact portion 303a is formed, with the shaft 305 as the center. The displacement of the tip 301t of the piezo actuator 301 can be amplified by the mounting portion 303b and taken out. In addition, a bracket 312 for attaching the brake pad 307 with the pad body 308 facing the brake rail 124 is fixed to the attachment portion 303b of the link lever 303.

  The brake pad 307 includes a pad main body 308 that abuts on the surface of the brake rail 124 to generate a braking force, and a pad holder 309 that is connected and fixed to the bracket 312 and integrally holds the pad main body 308. The pad main body 308 is made of, for example, SUS (stainless steel), and the surface shape (brake braking surface shape) has a curved shape with a central portion protruding from the peripheral portion. Further, a bolt hole for fastening a fixing bolt to the pad holder 309 is formed on the back surface.

  On the other hand, the pad holder 309 has a recessed structure on the mounting side surface of the pad main body 308, and a leaf spring 310 in which a fixing bolt insertion hole is formed is engaged with the periphery of the recessed portion. A compression spring 311 is interposed and supported in a space formed between the bottom surface of the recess.

  The brake pad 307 brings the back surface of the pad body 308 into contact with the leaf spring 310 of the pad holder 309 so that the support force of the pad body 308 by the leaf spring 310 and the compression spring 311, that is, the support force by the pad holder 309 becomes constant. Thus, it is connected to the pad holder 309 by the fixing bolt.

  The brake pad 307 configured by an integral structure of the pad main body 308 and the pad holder 309 is assembled and fixed to the bracket 312 on the attachment portion 303b side of the link lever 303 by a fixing bolt (not shown).

  In addition, the brake mechanism 125 a is attached to the X table 122 as shown in FIG. 3 using an attachment bolt hole (not shown) provided in the holder 30. At this time, the brake mechanism 125a has a minute gap between the brake braking surface (contact surface) of the pad main body 308 and the brake braked surface 124u of the X brake rail 124 in a state where no driving voltage is applied to the piezo actuator 301. The brake pad 307 is assembled and fixed to the bracket 312. Thus, when the brake mechanism 125a is braked off, there is a gap between the brake braking surface of the pad main body 308 and the braked surface 124u of the X brake rail 124, and the brake pad 307 is connected to the X brake rail 124. The pad main body 308 of the brake pad 307 is not dragged to the X brake rail 124 when the X table 122 moves in a non-contact state with respect to the brake target surface 124u.

  In each of the brake mechanisms configured as described above, the X-axis brake mechanisms 125a and 125b generate a braking force against the displacement of the X table 122 in the X direction, and the Y-axis brake mechanisms 115a and 115b are the Y table. A braking force is generated for the displacement of 112 in the Y direction. At that time, in both the X-axis and Y-axis brake mechanisms, the generation direction of thrust (details will be described later) generated in brake mechanisms 125a and 115a provided on one end side of the corresponding table, and the other The direction of thrust generation is as shown by the solid arrows in FIG. 2 so that the directions of thrust generation in the brake mechanisms 125b and 115b provided on the end sides of the two are opposite to each other. It is installed with the opposite.

  As described above, the two brake mechanisms 125a and 125b (115a and 115b) provided on the both end sides of the table 122 (112) with respect to the moving direction of the table 122 (112) for the X axis and the Y axis, respectively. By making the thrusts in opposite directions along the moving direction of the table 122 (112), the magnitudes of the thrusts are balanced with each other, and the brake braking force is applied thereon, so that the stop position of the top table 130 does not shift. . The generation principle of the brake braking force and thrust will be described later.

  With the above structure, each brake mechanism 125a, 125b, 115a, 115b responds to the forward / backward displacement of the tip portion 301t based on ON / OFF of the drive voltage to the piezo actuator 301, and the link lever 303 is As shown by B, the shaft 305 is rotated and displaced in the counterclockwise / clockwise direction around the shaft 305. This rotational displacement of the link lever 303 is converted to a contact displacement or separation displacement of the pad body 308 of the brake pad 307 with respect to the braked surfaces 124u, 114 of the brake rails 124, 114 via the bracket 312. . Thus, if each brake mechanism 125a, 125b, 115a, 115b independently applies a drive voltage (ON) to the piezo actuator 301, the pad body 308 causes the brake braked surfaces 124u, When 114u is pressed and the drive voltage to the piezo actuator 301 is cut off (OFF), the pad body 308 is separated from the braked surfaces 124u, 114u of the corresponding brake rails 124, 114. Further, in this way, when the pad body 308 is brought into contact with or separated from the brake braking surfaces 124u and 114u of the brake rails 124 and 114, the displacement of the tip portion 301t generated by the piezo actuator 301 is changed to the link lever. The displacement is increased to the amount multiplied by the lever ratio (L2 / L1) by 303 and converted to the displacement of the pad body 308 of the brake pad 307 with respect to the brake rails 124 and 114.

  From such a structure of each brake mechanism 125a, 125b, 115a, 115b, as shown in FIG. 3, the brake rail 124 by the brake pad 307 when the brake mechanism 125a is operated (when a drive voltage is applied to the piezoelectric actuator 301). The pressing force 313 against the surface acts on the surface of the brake rail 124a, that is, the normal line P of the braked surface 124u with an inclination of a predetermined angle θ. Therefore, with respect to the pressing force 313 applied to the brake rail 124a by the brake pad 307, the vertical component force 314 in the normal direction of the braked surface 124u and the horizontal surface within the surface of the braked surface 124u according to the predetermined angle θ. It is decomposed into a component force 315. That is, by applying the vertical component force 314 in the normal direction to the X table 122 to which the brake mechanism 125a is attached, the table 122 to which the brake mechanism 125a is attached is braked with the brake rail 124a. Will be added. Here, the vertical component force 314 in the normal direction of the brake receiving surface 124u is also referred to as a braking force 314 for convenience. On the other hand, in the brake mechanism 125a, a motor thrust 316 is generated as a reaction so as to balance the horizontal component force 315 of the pressing force 313 against the brake-braking surface 124u. In response to the generation of the motor thrust 316, the X table 122 moves in the extending direction of the brake rail 124a, that is, in the X direction.

  That is, when a drive voltage is applied to the piezo actuator 301, the pressing force 313 applied to the brake rail 124a by the brake pad 307 acts as a load on the link lever 303, and the link lever 303 is deformed accordingly. Arise. However, since the brake pad 307 does not move with respect to the brake rail 124a, this deformation moves the X table 122 to which the brake mechanism 125a is attached along the extending direction (Y direction) of the brake rail 124a. It will end up.

  Therefore, the movement of the X table 122 in the X direction and the movement of the Y table 112 in the Y direction during the operation of the brake mechanisms 125a, 125b, 115a, and 115b are caused by the deformation amount of the link lever 303 based on the pressing force 313 of the brake pad 307. It will be done with the movement distance according to. The moving distance varies depending on the rigidity of the link lever 303.

  On the other hand, the pressing force 313 applied to the braked surfaces 124u and 114u by the brake pad 307 correlates with the drive voltage applied to the piezoelectric actuator 301 and the gap between the brake pad 307 and the brake rails 124 and 114. . Due to the characteristics of the piezo actuator 301, the pressing force 313 applied to the brake brake surfaces 124u and 114u by the brake pad 307 increases as the drive voltage (voltage applied to the piezo element described above) increases. When the drive voltage applied to the piezo actuator 301 is the same voltage, the pressing force 313 is maximized when the gap between the brake pad 307 and the brake rails 124 and 114 is zero, and the gap increases. At the same time, the pressing force 313 decreases.

  Therefore, the braking force 314 and the motor thrust 316 are determined by the pressing force 313 for each brake mechanism 125a, 125b, 115a, 115b. In other words, the motor generated as a reaction when each brake mechanism 125a, 125b, 115a, 115b is operated depending on the magnitude of the driving voltage of the piezoelectric actuator 301 and the size of the gap between the brake pad 307 and the brake rails 124, 114. The magnitude of the thrust 316 changes, and the amount of deformation of the link lever 303 and the actual movement distance of the tables 122 and 112 change.

  As described above, the brake mechanisms 125a, 125b, 115a, and 115b generate the braking force 314 and the motor thrust 315 with respect to the movement of the brake rails 124 and 114 in the extending direction when operating. Therefore, for each of the X table 122 and the Y table 112, the generation direction 315 of the motor thrust generated in one brake mechanism 125a, 115a and the generation direction of the thrust generated in the other brake mechanism 125b, 115b are opposite to each other. Each brake mechanism 125a, 125b, 115a, 115b is installed. In that case, it is important for the X table 122 and the Y table 112 to equalize the motor thrust 316 of the two brake mechanisms 125a and 125b and 115a and 115b.

  However, in order to equalize the braking force 314 of the two brake mechanisms 125a, 125b, 115a, 115b for each of the X table 122 and the Y table 112, a gap between the brake pad 307 and the brake rails 124, 114 is required. The problem is that the movement positions of the tables 122 and 112 on the brake rails 124 and 114 and the brake mechanisms 125a, 125b, 115a, and 115b are different.

  Therefore, if the gap between the brake pad 307 and the brake rails 124 and 114 is different, even when the same drive voltage is applied to the piezo actuators 301 of the brake mechanisms 125a, 125b, 115a, and 115b, the brake mechanisms 125a, 125b, The pressing forces generated on the brake rails 124 and 114 of the 115a and 115b are different. As a result, when the brake pressing force is different as described above, the amount of movement during the brake operation is also different, which causes a stage displacement.

  Therefore, each of the brake mechanisms 125a, 125b, 115a, and 115b described above includes a detection mechanism 400 for detecting contact between the brake pad 307 and the brake rails 124 and 114.

  FIG. 4 is a configuration diagram of an embodiment of a detection mechanism that is provided in the brake mechanism and detects contact between a brake pad and a brake rail.

  FIG. 4A is a configuration diagram of an embodiment of a detection mechanism that detects contact between a brake pad and a brake rail.

  In this embodiment, the detection mechanism 400 pays attention to the fact that the pad body 308 of the brake pad 307 is formed of a conductive material such as SUS (stainless steel), and the pad body 308 from the current detection circuit 401. The contact between the brake pad 307 and the brake rails 124 and 114 is detected by detecting a change in the potential when the pad main body 308 is in contact with the brake rail 124 that is also made of a conductive material. It is configured to do.

  However, in this case, for example, a weak current flowing from the current detection circuit 401 to the pad main body 308 flows to another part other than the brake rails 124 and 114 through another path, so as not to cause erroneous detection and erroneous measurement, for example, The pad holder 309 of the brake pad 307 that holds the pad main body 308 or the bracket 312 for attaching the brake pad 307 to the link lever 303 is formed of a non-conductive material such as ceramic. The brake rails 124 and 114 have at least a braked surface 124u formed of a conductive material and connected to a ground potential.

  According to the present embodiment, the current detection circuit 401 detects contact / separation between the brake pad 307 and the brake rails 124 and 114 as a voltage change based on conduction / cutoff of a weak current, and the detection signal is illustrated. To the brake control device (in the length measurement SEM system described later, it is included in the stage control device 1012).

  FIG. 4B is a configuration diagram of another embodiment of a detection mechanism that detects contact between a brake pad and a brake rail.

  In the case of the present embodiment, the detection mechanism 400 pays attention to the fact that the pressing force 313 applied to the brake rails 124 and 114 by the brake pad 307 acts as a load on the link lever 303, and a strain gauge 411 attached to the link lever 303. The contact between the brake pad 307 and the brake rails 124 and 114 is detected by detecting distortion generated in the link lever 303 when the brake rails 124 and 114 are pressed by the brake pad 307. The strain gauge 411 is connected to the strain gauge 413 via the bridge box 412.

  According to this embodiment, the strain gauge 413 detects the contact / separation between the brake pad 307 and the brake rails 124 and 114 as a voltage change based on the impedance change via the bridge box 412. The detection signal is supplied to a brake control device (not shown).

  FIG. 4C is a configuration diagram of still another embodiment of a detection mechanism that detects contact between a brake pad and a brake rail.

  In the case of the present embodiment, the detection mechanism 400 operates the brake mechanism 125a, and when the brake pad 307 comes into contact with the brake rails 124 and 114, the leaf spring 310, which is one of the components of the brake pad 307, slightly increases. Note that δ is displaced by δ as shown in FIG. 4C, and the capacitance changes in accordance with the distance between the bottom surface of the recess of the pad holder 309 and the opposing surface of the leaf spring 310. A sensor 421 is provided on the brake pad 307 to detect contact between the brake pad 307 and the brake rails 124 and 114. The capacitance sensor 421 is connected to the capacitance measurement circuit 422.

  According to the present embodiment, the capacitance measuring circuit 422 detects the contact / separation between the brake pad 307 and the brake rails 124 and 114 by a voltage change based on the capacitance change of the capacitance sensor 421. The detection signal is supplied to a brake control device (not shown).

  As a detection mechanism for detecting contact between the brake pad 307 and the brake rails 124 and 114, a configuration using an optical sensor, a magnetic sensor, or the like is possible in addition to these embodiments.

  Next, the piezo actuator 301 as an actuator of each brake mechanism 125a, 125b, 115a, 115b will be described in detail.

  FIG. 5 is a graph showing the relationship between the amount of expansion and the magnitude of the driving voltage of the piezo actuator.

  As shown in FIG. 5, in the piezo actuator 301, the magnitude of the drive voltage and the expansion amount are in a proportional relationship. Therefore, if the magnitude of the drive voltage applied to the piezo actuator 301 is increased, the extension amount of the piezo actuator 301 increases and the protrusion amount on the tip portion 301t side also increases.

  FIG. 6 is a graph showing an example of a predetermined drive command supplied to the piezo actuator.

  The piezo actuators 301 of the brake mechanisms 125a, 125b, 115a, and 115b each include a predetermined voltage composed of a drive voltage applied to the piezo actuator 301 from a brake control device (not shown) individually for each brake mechanism 125a, 125b, 115a, and 115b. Each drive command is supplied.

  In the present embodiment, the brake control device, in the brake control processing of the X brake mechanism 125a, 125b or the Y brake mechanism 115a, 115b, has its drive voltage at a constant rate of change from a low voltage to a target voltage as shown in FIG. Is supplied individually to the piezoelectric actuators 301 of the X brake mechanisms 125a and 125b or the Y brake mechanisms 115a and 115b. In the case of the present embodiment, for example, within a time range of 30 milliseconds, for example, a drive command for gradually increasing the drive voltage of the piezoelectric actuator 301 from a low voltage to a target voltage as shown in FIG.

  Here, the target voltage is a piezoelectric actuator for each of the brake mechanisms 125a, 125b, 115a, and 115b, which is sufficient to generate the prescribed braking force 314 targeted by each of the brake mechanisms 125a, 125b, 115a, and 115b. The driving voltage 301 is indicated. The target specified braking force 314 corresponds to a target specified pressing force 313 for generating the target specified braking force 314. That is, the target voltage is the magnitude of the driving voltage of the piezo actuator 301 for obtaining a sufficient extension amount of the piezo actuator 301 to generate the target pressing force 313.

  FIG. 7 is an explanatory diagram of the relationship between the drive voltage of each piezo actuator and the extended state when the predetermined drive command voltage shown in FIG. 6 is applied to the piezo actuator of each brake mechanism. The characteristic between the driving voltage and the extension amount of the piezo actuator shown in the figure is related to the movement of the X table 122 and also when the piezo actuator 301 of each of the X brake mechanisms 125a and 125b is driven. This is the same when the piezo actuators 301 of the Y brake mechanisms 115a and 115b are driven in accordance with the movement of the X brake mechanism 115a and 115b. Therefore, here, when the piezo actuators 301 of the X brake mechanisms 125a and 125b are driven in accordance with the movement of the X table 122. Explained as an example.

  A predetermined drive command for gradually increasing the drive voltage of the piezo actuator 301 from a low voltage to a target voltage as shown in FIG. 6 is individually provided by the brake control device for each of the piezo actuators 301 of the X brake mechanisms 125a and 125b. When output, the piezoelectric actuator 301 of each of the X brake mechanisms 125a and 125b increases in accordance with the increase in drive voltage based on the drive command, and the respective extension amounts increase in accordance with the relationship shown in FIG. The amount of protrusion on the part 301t side also increases. It is assumed that at least one brake pad 307 in the brake mechanisms 125a and 125b is brought into contact with the brake rail 124 from the separated state at a drive voltage V of a certain drive command. The brake control device can detect the contact of the brake pad 307 based on a detection signal supplied from the detection mechanism 400 shown in FIG. 4 provided in each of the brake mechanisms 125a and 125b.

  Here, the brake control device uses Va as the drive voltage V of the drive command when the brake pad 307 and the brake rail 124a are in contact with each other with respect to the brake mechanism 125a (represented by a circle symbol indicated by an arrow 501 in FIG. 7). Is obtained. Similarly, for the brake mechanism 125b, the brake control device determines Vb (at 502 in FIG. 7) as the drive voltage V of the drive command at the time of contact with the brake rail 124a in the same manner as the brake mechanism 125a. It is assumed that (represented by an x symbol indicated by an arrow) is acquired.

  By the way, in order for each of the brake mechanisms 125a and 125b to generate a braking force 314 having a predetermined magnitude on each of the brake rails 124a and 124b, each of the brake mechanisms 125a and 125b applies a pressing force 313 having a predetermined magnitude. It must be generated for each of the rails 124a and 124b. Further, the magnitude of the pressing force 313 generated by each of the brake mechanisms 125a and 125b on the brake rails 124a and 124b is the same as that of the brake pad 307 when the rigidity of the link lever 303 is known as described above. Corresponds to the magnitude of the load applied to the link lever 303 from the piezo actuator 301 from when it becomes stationary with respect to the brake rail 124a. Further, the magnitude of the load applied to the link lever 303 from the piezo actuator 301 at that time is such that the piezo actuator 301 further extends after the tip portion 301t of the piezo actuator 301 contacts the contact portion 303a of the link lever 303. If the extension amount of the piezo actuator 301 increases corresponding to the amount, the load acting on the link lever 303 also increases.

  Therefore, in FIG. 7, the piezo actuators of the X brake mechanisms 125 a and 125 b when the X brake mechanisms 125 a and 125 b respectively generate a braking force 314 of the same magnitude on the X brake rails 124 a and 124 b, respectively. The drive voltage V of the drive command for each 301 is represented by Vat (represented by a Δ symbol indicated by an arrow 503 in the figure) and Vbt (represented by an inverted Δ symbol indicated by an arrow 504 in the figure). ing.

  Here, the drive voltages Vat, Vbt for generating a braking force 314 having the same predetermined magnitude are different between the X brake mechanisms 125a, 125b, and the extension amounts of the respective piezoelectric actuators 301 are different. As described above, the pressing force 313 has the magnitude of the load applied from the piezo actuator 301 to the link lever 303 after each brake pad 307 is stationary with respect to the brake rail 124a. This is to respond.

  In the example shown in FIG. 7, the driving voltages Va and Vb when the tip portion 301t of each piezoelectric actuator 301 contacts the contact portion 303a of the link lever 303 are different between the X brake mechanisms 125a and 125b. Vb−Va can be replaced with the difference in the amount of extension until the piezo actuators 301 come into contact with the brake rails 124a and 124b (indicated by arrows 505 in the figure). The difference 505 in the extension amount is the gap between the initial brake pad 307 and the brake rail 124a of the X brake mechanism 125a and the gap between the initial brake pad 307 and the brake rail 124b of the X brake mechanism 125b. It corresponds to the gap difference.

  Here, the actual gap between the brake pad 307 and the brake rail 124 is not the same amount as the extension amount of the piezoelectric actuator 301 because the displacement of the piezoelectric actuator 301 is enlarged by the link lever 303. However, since the link lever 303 as the displacement magnifying mechanism used in each of the X brake rails 124a and 124b is the same, the displacement magnification rate is the same, and adjusting the extension amount difference 505 of the piezo actuator 301 is not possible. This is the same as adjusting the gap difference between each brake pad 307 and each X brake rail 124a, 124b. Therefore, if the difference 505 in the extension amount of each piezo actuator 301 between the X brake mechanism 125a and the X brake mechanism 125b is known, the movement position of the X table 122 and the brakes on both ends of the X table 122 are different. The difference in gap between the brake pad 307 and the brake rail 124 can be adjusted.

  In the example shown in FIG. 7, a voltage for obtaining an extension amount (indicated by 506 in the figure) equivalent to the difference 505 in the extension amount with respect to the X brake mechanism 125a is defined for the X brake mechanism 125b. Is added to the drive voltage Vt (in the case of FIG. 7, Vt = Vat), and the drive voltage Vbt of the final drive command is used to adjust the amount of extension that is insufficient for the X brake mechanism 125b. It means that can be done. At this time, the voltage for obtaining the expansion amount 506 equivalent to the expansion amount difference 505 can be obtained from the relationship between the expansion amount and the drive voltage of the piezo actuator 301 shown in FIG.

  FIG. 8 is a flowchart showing a brake control process of the stage mechanism according to the present embodiment.

  When the movement along the X guide 121 and the Y guide 111 by the operation of the X linear motor 123 and the Y linear motor 113 is performed for each of the X table 122 and the Y table 112, the brake control device corresponds to the corresponding brake mechanism. A brake control process as shown in FIG. 8 is performed on each of 125a, 125b, 115a, and 115b. Note that this brake control processing differs only in the target brake mechanisms 125 and 115 when the X table 122 is moved and when the Y table 112 is moved, so here the X table 122 is moved. In addition, since the individual brake control processing for the brake mechanisms 125a and 125b is the same for the brake mechanism 125a and the brake mechanism 125b, the brake control processing for the brake mechanism 125a will be described as an example. To do.

  When the X table 122 is moved to the X-direction position xi on the X guide 121 by stopping the driving of the X linear motor 123 by the drive control of the X linear motor 123 by a movement control device (not shown). Or immediately before the driving of the X linear motor 123 is stopped and moved to the X direction position xi, the piezoelectric actuator 301 of each of the X brake mechanisms 125a and 125b of the X table 122 is as shown in FIG. Start the brake control process. When starting the brake control process, the X brake mechanisms 125a and 125b are in a state (non-contact state) in which the brake pads 307 are separated from the braked surfaces 124u of the brake rails 124a and 124b. Yes. This is because when the brake control device starts moving the X table 122 toward the X direction position xi by driving the X linear motor 123, the brake pad 307 is not dragged against the brake rails 124a and 124b during the movement. This is because a drive command for turning off the drive voltage has already been supplied to the piezoelectric actuators 301 of the X brake mechanisms 125a and 125b. Hereinafter, as described above, the X brake mechanism 125a will be described as an example.

  In the state described above, when the brake control device starts the brake control process for the brake mechanism 125a of the X table 122, the brake control device gives a predetermined drive command for increasing the drive voltage at a constant rate of change as shown in FIG. In order to apply to the piezoelectric actuator 301 of 125a, as shown in FIG. 8, after the drive voltage of the drive command is set to the initial low voltage (step S801), the drive voltage V of this drive command is set to the X brake mechanism 125a (125b). ) Is applied to the piezoelectric actuator 301 (step S802).

  Then, the brake control device determines whether or not the brake pad 307 of the brake mechanism 125a is in contact with the brake rail 124a based on the detection signal supplied from the detection mechanism 400 shown in FIG. 4 provided in the brake mechanism 125a. Based on the determination (step S803), if not yet contacted, the drive voltage of the drive command is changed to a drive voltage next to a predetermined drive command in which the drive voltage increases at a constant rate of change as shown in FIG. V is updated (step S804), and this time, the drive voltage V of this drive command is applied to the piezo actuator 301 of the X brake mechanism 125a (125b) (step S802).

  In this way, the brake control device applies a predetermined drive command for increasing the drive voltage at a constant rate of change as shown in FIG. 6 to the piezo actuator 301 of the brake mechanism 125a (steps S802 to S804). When it is determined that the brake pad 307 of the brake mechanism 125a has contacted the brake rail 124a with the drive voltage Va of the drive command (step S803), the brake pad 307 is applied to the brake rail before the brake mechanism 125b as another brake mechanism. Whether or not the contact with the brake 124 is determined in relation to the brake mechanism 125b in which similar brake control processing is performed individually (step S805).

  As a result, when detected earlier, the brake control device sets the drive voltage Vat of the final drive command for the brake mechanism 125a to the voltage Vt of the final drive command defined from the beginning (where Vt> Va). (Step S806) Whether or not the brake pad 307 of the brake mechanism 125b as another brake mechanism has contacted the brake rail 124b is determined in relation to the brake mechanism 125b in which similar brake control processing is performed individually. (Step S807). As a result, when detected earlier, the drive voltage of the drive command for the brake mechanism 125a is applied until the brake pad 307 of the brake mechanism 125b as another brake mechanism is in contact with the brake rail 124b. The pressing force 313, the braking force 314, and the horizontal component force 315 against the brake rail 124a are not generated while the driving voltage of the driving command when the pad 307 contacts the brake rail 124 is maintained.

  On the other hand, when it is detected later, the brake control device similarly applies the drive voltage Vb of the drive command when the brake pad of the brake mechanism 125b with which the brake pad 307 is in contact with the brake rail 124b first is in contact. Acquired in association with the brake mechanism 125b for which the brake control processing is performed individually, and the extension corresponding to the difference voltage Vba (= Vb−Va) from the drive voltage Vt of the final drive command defined from the beginning An additional drive voltage for further extension is calculated, and the drive voltage Vat of the final drive command for the brake mechanism 125a is set to a drive voltage obtained by adding this additional drive voltage to the drive voltage Vt of the final drive command defined from the beginning. (Step S806). In this case, the differential voltage Vba corresponds to a difference in gap between the brake pad 307 and the brake rail 124 between the brake mechanism 125a and the other brake mechanism 125b. Further, when calculating the additional drive voltage, the brake control device can use the relationship of the expansion amount with respect to the drive voltage of the piezo actuator 301 shown in FIG. 4 stored in advance as a table.

If the brake mechanism 125a and the other brake mechanism 125b are in a state where the brake pad 307 is in contact with the brake rail 124, the brake control device performs the process of step S806 or step S808 for the brake mechanism 125a. The voltage Vt of the final drive command obtained in the above is applied to the piezo actuator 301 of the brake mechanism 125a (step S809). In this case, the final drive command voltage Vat is applied in the same way as the final drive command voltage Vbt applied by the other brake mechanism 125b, for example , from the current drive command voltage Va to the final drive command voltage Vat. Until the voltage Vat of the drive command is reached, the applied voltage of the drive command may be applied while further increasing the voltage of the drive command at the constant rate of change shown in FIG. 6, or the current drive command The voltage Vaat of the final drive command may be applied suddenly from the voltage Va.

  Note that the brake control device performs the brake control process including the processes of steps S801 to S809 described above on the brake mechanism 125a for each of the other brake mechanisms 125b as well, so that the brake mechanisms 125a and 125b respectively press the brake control process. The pressure 313 and the braking force 314 and the motor thrust 315 based on the pressing force 313 can be generated while balancing each other between the X brake mechanism 125a and the X brake mechanism 125b of the X table 122.

  Further, depending on the difference in the gap between the brake mechanisms 125a and 125b, the piezo actuator is more in contact with the brake rail 124 of one of the brake pads 307 than the brake rail 124 of the other brake pad 307. Even when the extension amount of 301 is delayed due to shortage, it is possible to suppress a difference in braking force between the two.

  As a result, there is no difference in the braking force of each brake mechanism 125a, 125b due to the gap difference between the brake pad 307 and the brake rail 124, and the position displacement of the stage due to the brake operation can be reduced.

  In the brake control processing by the brake control device described above, the brake control device generates a predetermined magnitude of braking force 314 for each of the brake rails 124a and 124b. Instead of the configuration having the drive voltage Vt, it may be configured to have a predetermined extension amount of the piezo actuator 301 from when the brake pad 307 contacts the brake rail 124. In this case, in steps S806 and S808, the brake control device further increases the piezoelectric actuator 301 by this predetermined extension amount from the drive voltages Va and Vb of the drive command when the brake pad 307 of the brake mechanism 125a contacts the brake rail 124a. The drive voltage of the drive command when it is extended can be calculated as the drive voltages Vat and Vbt of the final drive command.

  In addition, the brake control device stores the drive voltages Vat and Vbt of the final drive commands of the brake mechanisms 125a and 125b acquired by the processes of steps S801 to S809 described above, and stores the current drive voltage Vat and Vbt by operating the X linear motor 12 therein. Is stored in correspondence with the movement position xi on the X axis of the X table 122, so that the drive voltage of the final drive command of each of the brake mechanisms 125a and 125b corresponding to the movement position xi on the X axis of the X table 122 is stored. If a final drive command table relating to Vat and Vbt is created, the movement position x on the X axis of the X table 122 at the time of another specimen observation is stored in this final drive command table in the drive voltage Vat, If Vbt is the movement position xi on the X axis stored, this storage Driving voltage Vat final drive command being the Vbt, brake mechanism 125a, it is possible to operate by applying 125b suddenly stepwise to each of the piezoelectric actuator 301.

  Next, the length measurement SEM including the sample stage provided with the stage mechanism 10 described above will be described.

  FIG. 9 is a position time response waveform schematically showing the relationship between the stage positioning state in the length measurement SEM and each process in the length measurement sequence.

  The stage positioning state in the length measurement SEM includes the stage movement state T1 (time zone indicated by arrow 901 in the figure) according to the conditions for performing each length measurement process, and the measurement point from a nearby reference pattern. A state T2 in which addressing can be specified from the relative position information (time zone indicated by an arrow 902 in the figure), and a state T3 in which auto-focusing is possible in which the measurement point is imaged at a high magnification and focused. , 903), and a state T4 (time zone indicated by 904 in the drawing) in which a high-magnification pattern for length measurement can be detected. In the length measurement sequence, in order to perform the length measurement process, the state T2 in which addressing is possible from the stage movement state T1, the state T3 in which autofocus is possible from the addressable state T2, and the stage positioning state are measured. Each process in the long sequence needs to be within an allowable range of vibration amplitude and drift amount.

  FIG. 10 is a diagram showing a schematic overall configuration of a length measurement SEM system according to an embodiment of the present invention.

  As shown in FIG. 10, in the length measurement SEM system, the stage mechanism 10 described above is mounted in a sample chamber 1002 that can be evacuated by a vacuum pump 1001. In addition, an electron microscope 1003 for measuring the length is mounted on the upper part of the sample chamber 1002, and the electron microscope 1003 is controlled by the system control device 1010. The operation of each unit and the display of images are performed using a computer 1011. The stage mechanism 10 is controlled by the stage control device 1012 under control based on an operation from the system control device 1010, and the stage states T1 to T4 described above are transmitted to the system control device 1010. Are synchronized. The stage control device 1012 also has a function as the brake control device described above in connection with the movement of the X table 122 and the Y table 112 of the stage mechanism 10.

  FIG. 11 is a flowchart showing an example of the control process of the length measurement SEM according to the embodiment of the present invention.

  In FIG. 11, the stage control apparatus 1012 first moves the sample stage (the above-described top table 130 on which the sample is mounted on the sample holder 133) to the target position (step S1101), and then the sample stage. Of the X table 122 and the Y table 112 is determined based on the completion of the movement and positioning of the X table 122 and the Y table 112 to the designated position corresponding to the target position (step S1102). When the movement positioning is completed, the brakes shown in FIG. 8 are used for the plurality of X brake mechanisms 125 provided on the X table 122, and when the movement positioning of the Y table 112 is completed for the plurality of Y brake mechanisms 115 provided on the Y table 112. Each control process is executed (step S1103).

  Thereafter, the stage control apparatus 1012 waits until the addressable state T2 is reached from the state T1 corresponding to step S1101 to step S1103 described above (step S1104), and the sample stage vibration amplitude and drift amount allowance for performing addressing. If the range condition C1 is satisfied, the system control apparatus 1010 is notified that the addressable state T2 has been reached (step S1105). Further, the stage controller 1012 continues from the addressable state T2 and similarly waits until the autofocus is enabled (step S1106), and the vibration amplitude and the drift amount are within an allowable range for performing autofocus. The system control apparatus 1010 is notified that the autofocus enabled state T3 has been reached by satisfying the condition C2 (stricter than the condition C1) (step S1107). Further, the stage controller 1012 continues from the auto-focusable state T3, and similarly waits until the high-magnification pattern can be detected (step S1108), and the vibration amplitude and the drift amount are for performing the high-magnification pattern detection. The system control apparatus 1010 is notified that the high-magnification pattern detectable state T4 has been reached by satisfying the allowable range condition C3 (stricter than the condition C2) (step S1109). Then, when the stage control device 1012 receives a notification from the system control device 1010 that the high-magnification pattern detection processing has ended (step S1110), the stage control device 1012 is in a brake operation state by executing the above-described step S1103. Each of the X brake mechanism 125 and the Y brake mechanism 115 of the X table 122 and the Y table 112 is turned off to be in an inoperative state (step S1111).

  The stage control apparatus 1012 repeats the processes of steps S1101 to S1111 each time the side long point on the sample changes.

  In the above-described embodiment, the brake control process shown in FIG. 8 is performed for each length measurement point in the brake control process shown in step S1103, and the brake pads 307 and the brakes of the X brake mechanism 125 and the Y brake mechanism 115 respectively. The contact with the rails 124 and 114 is detected and the brake gap is adjusted. However, the optimum drive command (that is, the final drive command) obtained once is stored in association with the measuring point, and the next and subsequent times. The embodiment can be configured to realize high-speed and high-accuracy positioning by using the drive command after positioning.

10 stage mechanism, 100 base, 110 Y base, 111 Y guide,
112 Y table, 113 Y linear motor, 114 Y brake rail,
115 Y brake mechanism, 116 X sub guide, 120 X base,
121 X guide, 122 X table, 123 X linear motor,
124 X brake rail, 125 X brake mechanism, 126 Y sub guide,
127 long hole, 130 top table, 131 X mirror,
132 Y mirror, 133 Sample holder, 301 Piezo actuator,
302 holder, 303 link lever, 304 sleeve,
305 shaft, 306 bearing, 307 brake pad,
308 pad body, 309 pad holder, 310 leaf spring,
311 compression spring, 312 bracket, 313 pressing force,
314 Normal component force (braking force), 315 horizontal component force, 316 motor thrust,
400 detection mechanism, 401 current detection circuit, 411 strain gauge,
412 bridge box, 413 strain gauge, 421 capacitance sensor,
422 capacitance measurement circuit, 1001 vacuum pump, 1002 sample chamber,
1003 electron microscope, 1010 system controller,
1011 computer, 1012 stage control device,

Claims (7)

A movable table held movably along the guide mechanism;
A moving mechanism for moving the movable table to an indicated position along the guide mechanism;
A sample stage having a brake pad that contacts or separates in response to driving of an actuator with respect to a brake surface to be braked, and a plurality of brake mechanisms that brake the movable table,
A detecting means provided in each of the plurality of brake mechanisms for detecting contact of a brake pad with a braked surface;
After the movable table is moved to the indicated position along the guide mechanism by the moving mechanism and stopped, or immediately before stopping, the actuators of the plurality of brake mechanisms are driven to operate the plurality of brake mechanisms. A control device,
When the control device operates the plurality of brake mechanisms,
Driving the actuators of each of the plurality of brake mechanisms according to a predetermined drive command for bringing a brake pad into contact with a braked surface;
The brake pads of each of the plurality of brake mechanisms are braked based on the detection output output from the detection means of each of the plurality of brake mechanisms during driving of the actuators of the plurality of brake mechanisms based on the predetermined drive command. Obtaining a state difference of the predetermined drive command between the plurality of brake mechanisms when contacting the braked surface;
Based on the state difference of the acquired default drive command, a final drive command corresponding to the drive state of the actuator at the time of brake operation is determined for each of the plurality of brake mechanisms,
A sample stage, wherein the actuator of each of the plurality of brake mechanisms is driven by the determined final drive command of the corresponding brake mechanism. The state difference of the predetermined drive command corresponds to a difference between gaps between the brake pad and the braked surface between the plurality of brake mechanisms,
Of the plurality of brake mechanisms, a final drive command for a brake mechanism having a large gap is obtained by adding an actuator drive command corresponding to a difference between the gaps to a predetermined final drive command for a brake mechanism having a small gap. The sample stage according to claim 1.   The sample stage according to claim 2, wherein the actuator of each of the plurality of brake mechanisms is a piezo actuator. The detection means includes
A weak current is passed through a brake pad that is insulated from the other part of the brake mechanism, and the contact of the brake pad with the braked surface is detected from the potential change of the brake pad based on the contact with the braked surface. The sample stage according to claim 1. The detection means includes
A strain gauge provided in the brake mechanism;
2. The sample stage according to claim 1, wherein the contact of the brake pad with the brake receiving surface is detected from a change in the output of the strain gauge. The detection means includes
It is a capacitance sensor provided on the brake pad,
2. The sample stage according to claim 1, wherein the contact of the brake pad with the brake surface to be braked is detected from a change in the output of the capacitance sensor. The electron microscope apparatus provided with the sample stage as described in any one of Claims 1-6.

Images