JP3701535B2 - Stage equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a stage drive mechanism such as a microscope stage that can move in the XY directions and can observe an integrated circuit pattern formed on, for example, a semiconductor wafer not only in a direction perpendicular to the wafer surface but also in an oblique direction. About.
[0002]
[Prior art]
13, FIG. 14, and FIG. 15 are explanatory diagrams of a conventional stage drive mechanism. In FIG. 13, the inclined frame 50 is supported by casing frames 52a and 52b by inclined central axes 51a and 51b provided at both ends thereof, and can be inclined with the inclined central axes 51a and 51b as fulcrums. A tilt motor 66 is fixed to the housing frame 52b, and an output shaft of the tilt motor 66 is integrated with the tilt center shaft 51b. By rotating this, the inclined frame 50 can be inclined. V-grooves 53a and 53b are provided at both ends of the inclined frame 50, and the V guides 55a and 55b of the X stage 54 are fitted into the V grooves 53a and 53b. The X stage 54 moves along the V grooves 53a and 53b. To do.
[0003]
Similarly, the Y stage 56 moves along V grooves 57 a and 57 b provided on the X stage 54. A semiconductor wafer 58 on which an integrated circuit pattern is formed as a sample is placed on the Y stage 56 and can freely move in both XY axial directions. The surface of the semiconductor wafer 58 is on a straight line connecting the centers of the inclined central axes 51 a and 51 b, and the focal point of the microscope 59 is also on the surface of the semiconductor wafer 58.
[0004]
The X stage 54 is moved by the following method. The X drive motor 60 is fixed to the housing frame 52a, and its rotation is transmitted to the universal joint 61a, the expansion / contraction spline 62, the universal joint 61b, and the bevel gears 63a to 63d to rotate the ball screw 64. Since the ball screw nut 65 is fixed to the X stage 54, the X stage 54 can be moved along the V grooves 53 a and 53 b of the inclined frame 50 by rotating the X drive motor 60. The Y stage 56 can also be moved along the V grooves 57a and 57b of the X stage 54 using a similar mechanism (not shown).
[0005]
FIG. 14 is a view showing a state in which the inclined frame 50 shown in FIG. When tilting, the distance between the universal joints 61a and 61b changes from moment to moment, so that an expansion / contraction spline 62 that can transmit rotation while expanding and contracting in the axial direction is required. Since the surface which is the observation surface of the semiconductor wafer 58 is on a straight line connecting the centers of the inclined central axes 51a and 51b, and the focal point of the microscope 59 is also on this straight line, the side surface of the pattern on the semiconductor wafer 58 is inclined. Can be observed. The entire surface of the semiconductor wafer 58 can be observed by moving the X stage 54 and the Y stage 56 in an inclined state.
[0006]
[Problems to be solved by the invention]
In the above prior art, the rotation of the stage drive motor is transmitted to the ball screw for moving the stage, and the universal joint, the expansion / contraction spline, the bevel gear, and many other members are involved, so the mechanism becomes complicated and a wide space is required. I needed it. In addition, the amount of each member is integrated, and the rotation of the drive motor is not faithfully transmitted to the ball screw, making it difficult to increase the accuracy. Further, when attaching the universal joints 61a and 61b, attention shown in FIG. 15 is necessary. That is, in order to rotate the input shaft 70 and the output shaft 71 at a constant speed, the input angle 72 (α1) and the output angle 73 (α2) must be set to be equal. Also, the claws 74a and 74b must be set exactly on the same plane. For this reason, there existed problems, such as requiring an advanced assembly technique, for the attachment of a universal joint.
An object of the present invention is to provide a stage driving mechanism that has a simple mechanism, does not take up space, and is highly accurate.
[0007]
[Means for Solving the Problems]
In the present invention, the object is achieved by adopting a configuration in which the rotation of the motor for driving the stage is taken in from the stage tilt center and transmitted to the stage moving ball screw using a belt, a bevel gear, a screw gear or the like. .
[0008]
In other words, the stage apparatus according to the present invention includes a stage that holds a sample on a sample mounting surface and is movable in two directions orthogonal to each other, and is tilted by rotating the stage around an inclination axis parallel to the sample mounting surface. And a stage driving means for driving the stage in the two directions orthogonal to each other. The stage driving means has a driving force transmission mechanism provided coaxially with the inclination axis, and transmits the driving force. A driving force is transmitted to the stage through a mechanism.
[0009]
The stage apparatus according to the present invention also includes an inclined frame that can be rotated about the inclination axis, an inclination means that rotates the inclination frame about the inclination axis, and an inclination frame that is parallel to the inclination axis. A first stage movable in one direction, a second stage movable on a first stage in a second direction orthogonal to the first direction, and the first and second stages are driven In the stage apparatus including the stage driving means, the stage driving means has a driving force transmission mechanism provided coaxially with the tilt axis, and transmits the driving force to the stage via the driving force transmission mechanism. To do.
[0010]
The stage driving means includes a rotating shaft provided coaxially with the tilt shaft and rotated by a driving source, a ball screw screwed to a nut fixed to the stage, a belt for transmitting rotation of the rotating shaft to the ball screw, and perforation. A belt, chain or toothed belt can be provided.
Alternatively, the stage driving means includes a rotating shaft that is provided coaxially with the inclined shaft and is rotated by a driving source, a ball screw that is screwed to a nut fixed to the stage, and a spur gear that transmits the rotation of the rotating shaft to the ball screw. Rows, bevel gears or screw gears can be provided.
[0011]
Furthermore, the stage apparatus of the present invention can be provided with a control system that controls the drive source so as to compensate for stage movement caused by rotation of the ball screw by planetary motion when the tilting means is operated. For example, a stepping motor is used as a drive source, and the control system sends a pulse in the reverse direction converted to the rotation angle of the ball screw rotated by planetary motion to the stepping motor when the stage (tilting frame) is tilted. This can be realized by controlling the ball screw so that it does not appear to rotate.
[0012]
Alternatively, the stage apparatus of the present invention compensates the stage movement measured by the measuring means for measuring the amount of movement of the stage moved by rotating the ball screw by planetary motion when the tilting means is operated. And a control system for controlling the drive source. For example, when the stage (tilt frame) is tilted, the moving amount of the stage moved by the planetary motion is measured by a measuring means such as a linear encoder, and the moving amount is corrected by closed loop control. be able to.
According to the present invention, space can be saved because the expansion / contraction spline used in the prior art is not used. In addition, since a universal joint can be used and the number of parts can be reduced, a stage with less backlash can be realized.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic perspective view showing an example of a stage driving mechanism according to the present invention. This figure shows a stage driving mechanism that can hold an X (Y) drive and tilt by holding a sample (for example, a semiconductor wafer) 13 observed by a microscope 14 such as a scanning electron microscope.
[0014]
The inclined frame 1 is supported by the housing frames 3a and 3b by inclined central axes 2a and 2b provided at both ends thereof, and can be inclined with the inclined central axes 2a and 2b as fulcrums. The tilt frame 1 is tilted by rotationally driving a tilt motor 31 fixed to the housing frame 3b. An X stage 5 is placed on the upper surface of the inclined frame 1 so as to be movable in a direction connecting the centers of the inclined central axes 2a and 2b. On the X stage 5, the Y stage 15 is mounted so as to be movable in a direction orthogonal to the direction connecting the inclined central axes 2a and 2b. A sample 13 such as a semiconductor wafer is held on the sample mounting surface of the Y stage 15. An X motor 9 for driving the X stage and a Y motor 20 for driving the Y stage are fixed to the housing frame 3b.
[0015]
FIG. 2 is a detailed cross-sectional view of a drive shaft portion that penetrates the housing frame 3a. The tilted central shaft 2a, which is integral with the tilted frame 1, is fitted in a through hole provided in the housing frame 3a so that it can freely rotate by contacting the inner surface of the through hole (the housing on the opposite side). The body frame 3b and the inclined central axis 2b have the same structure). The X drive shaft 30 of the X motor 9 with the X drive pulley 10 fixed at the tip is rotatable through the center of the inclined central shaft 2a. The Y drive shaft 23 driven by the belt from the Y motor 20 has a double shaft structure with the X drive shaft 30 of the X motor 9, contacts the inner surface of the inclined central shaft 2a and contacts the outer surface of the X drive shaft 30. The drive shaft 30 rotates about the central axis. A pulley 21b for transmitting power from the Y motor 20 and a Y drive pulley 24 for transmitting the power to the subsequent stage are integrally provided at both ends of the Y drive shaft 23. As described above, the X drive shaft 30 that transmits the driving force for driving the X stage 5 and the Y drive shaft 23 that transmits the driving force for driving the Y stage 15 are the tilt central axis of the tilt frame 1. It has a coaxial structure with 2a and is taken from the tilt center of the tilt frame 1.
[0016]
Returning to FIG. 1, the surface of the sample 13 is on a straight line connecting the centers of the inclined central axes 2 a and 2 b of the inclined frame 1, and the focal point of the microscope 14 is also on the surface of the sample 13. Accordingly, the surface of the sample 13 can be tilted with respect to the microscope 14 by tilting the tilting frame 1 while keeping the focus of the microscope 14 on the sample surface, and the side surface of the pattern formed on the sample 13 can be seen on the microscope 14. It becomes possible to observe. Further, the entire surface of the sample 13 can be observed by moving the X stage 5 and / or the Y stage 15 with the tilt frame 1 tilted.
[0017]
Next, details of the X stage drive mechanism and the Y stage drive mechanism will be described. First, the X stage drive mechanism will be described with reference to FIG. FIG. 5 is a schematic diagram illustrating the mechanism shown in FIG. 1 with the portion related to the Y stage driving mechanism omitted, and a part of the tilt frame 1 being simplified to reveal the portion related to the X stage driving mechanism. It is.
[0018]
The inclined frame 1 has V grooves 4a and 4b on both sides, and V guides 6a and 6b provided on the lower surface of the X stage 5 are fitted into the V grooves 4a and 4b. The X stage 5 has a V groove 4a. , 4b. The X stage 5 is moved by the X ball screw 7. When the X ball screw 7 is rotated, the X nut 8 moves, and the X stage 5 integrated with the X nut 8 moves. The X ball screw 7 is rotated by an X motor 9. As described above, the X motor 9 is fixed to the housing frame 3a and rotates the X drive pulley 10 integrated with the motor shaft. The rotation of the X driving pulley 10 is transmitted to the X driven pulley 12 integrated with the X ball screw 7 through the X belt 11, and the X driven pulley 12 rotates to rotate the X ball screw 7, The X stage 5 is moved.
[0019]
FIG. 6 shows a state in which the tilting frame 1 is tilted by driving the tilting motor 31. Since the distance between the centers of the X driving pulley 10 and the X driven pulley 12 is constant regardless of the inclination angle, the rotation of the X motor 9 can be transmitted to the X ball screw 7 at an arbitrary inclination angle. Specifically, power is transmitted from the X drive pulley 10 to the X driven pulley 12, the X drive pulley 10 fixed to the X drive shaft tip of the X motor 9, the X ball screw 7 to which the X driven pulley 12 is fixed, and the X driven pulley 12. The X stage can be smoothly driven by the simple drive mechanism including the X belt 11 regardless of the tilt angle of the tilt stage 1.
[0020]
Next, the Y stage drive mechanism will be described with reference to FIG. 1 again. In FIG. 1, the rotation of the Y motor 20 is transmitted to the pulley 21 a, the motor belt 22, and the pulley 21 b of the Y drive shaft 23 to rotate the Y drive pulley 24 integrated with the Y drive shaft 23. The rotation of the Y drive pulley 24 is transmitted to the Y driven pulley 26 via the Y belt 25, and the spline shaft 27 integrated with the Y driven pulley 26 is rotated.
[0021]
The bevel gears 28 a and 28 b are used to convert the rotation of the spline shaft 27 into the rotation of a Y ball screw 29 disposed at a right angle to the spline shaft 27. That is, when the spline shaft 27 rotates, the rotation is converted into rotation of the Y ball screw 29 to which the bevel gear 28b is fixed by the bevel gears 28a and 28b. When the Y ball screw rotates, the Y stage 15 integrated with a Y nut (not shown) moves. The bevel gear 28a has an integral relationship with the spline shaft 27, and has a mechanism capable of transmitting rotation while simultaneously moving in the axial direction of the spline shaft 27. The structure will be described with reference to FIGS.
[0022]
3 is an enlarged view showing the relationship between the spline shaft 27 and the bevel gears 28a and 28b, and FIG. 4 is a cross-sectional view of the bevel gear 28a and the spline shaft 27 cut at right angles to the axial direction of the spline shaft 27. As shown in FIG. 3, a groove 32 is cut in the longitudinal direction on the surface of the spline shaft 27. As shown in FIG. 4, a protrusion 33 is provided inside the bevel gear 28 a (the surface of the through hole through which the spline shaft 27 passes). The protrusion 33 of the bevel gear 28 a is a groove 32 of the spline shaft 27. Is engaged. Therefore, the bevel gear 28 a having the projection 33 can rotate integrally with the spline shaft 27 while moving along the groove 32. The bevel gear 28a is restrained on the left and right by the guide plates 35a and 35b rising from the X stage 5 shown in FIG. 1, and moves following the movement of the X stage 5.
[0023]
When the tilt frame 1 is tilted, the distance between the axial centers of the Y drive pulley 24 and the Y driven pulley 26 is constant regardless of the tilt angle of the tilt frame 1, as described with respect to the X stage drive mechanism. The rotation of the Y motor 20 can be transmitted to the Y ball screw 29 at an inclination angle of. For the belts 11, 22, 25 connecting the pulleys, it is preferable to use a belt, a belt with a perforation driven by a sprocket, a chain, or a toothed belt.
[0024]
When the sample 13 is a semiconductor wafer, the surface that is the observation surface is on a straight line connecting the centers of the inclined central axes 2a and 2b of the inclined frame 1, and the focal point of the microscope 14 is also on this straight line. Thus, the side surface of the pattern on the semiconductor wafer can be observed. In the inclined state, the entire surface of the semiconductor wafer can be observed by driving the X motor 9 and the Y motor 20 to move the X stage 5 and the Y stage 15.
[0025]
In the tilting mechanism of the present invention, when the tilting frame 1 is tilted, as shown in FIG. 7, from the drive pulley 35 (corresponding to the X drive pulley 10 and the Y drive pulley 24 shown in FIG. 1) from the belt 37 The driven pulley 36 (corresponding to the X driven pulley 12 and the Y driven pulley 26 shown in FIG. 1) to which power is transmitted causes a planetary motion, and a ball screw (spline shaft) 38 rotates to move the stage. There is a problem of moving. When the pulley diameters of the driving pulley and the driven pulley are equal, the point A on the driven pulley 36 before the inclination is rotated by an angle equal to the inclination angle α ° after the inclination as shown in FIG. The stage moves to A 'and the stage moves by an amount corresponding to this rotation angle, so this needs to be corrected.
[0026]
Next, a method for correcting unintended stage movement associated with rotation of the driven pulley due to the inclination of the inclined frame 1 will be described. There are two correction methods: a correction method using an open loop control method and a correction method using a closed loop control method.
[0027]
FIG. 11 is an explanatory diagram of a correction method based on the open loop control method. As described above, this correction method uses the fact that the rotation angle of the ball screw is also known when the tilt angle of the tilt frame 1 is given, and is based on open loop control using a stepping motor as the X motor 9 or Y motor 20. This is a correction method. Assuming that the rotation angle of one step of the stepping motor is θ ° and the lead of the ball screw is p (μm) / 1 rotation, the movement amount S of the stage when the stage is inclined by α ° is expressed by the following equation (1 ).
S = (α ° / 360 °) × p (μm) (1)
[0028]
Further, the stage movement amount T by one step of the stepping motor is expressed by the following equation (2).
T = (θ ° / 360 °) × p (μm) (2)
Therefore, when the stage is inclined by α °, the number of pulses to be given to the stepping motor to correct the movement of the stage is expressed by the following equation (3) using equations (1) and (2).
N = S / T = α / θ (pulse) (3)
This is calculated by the control system 80 of FIG. 11 and given to the stepping motor 82 via the driver 81, and the ball screw 83 is rotated to correct the amount of movement of the stage 84.
[0029]
FIG. 12 is an explanatory diagram of a correction method using closed loop control. In this correction method, the position of the stage 84 is measured by the linear encoder 85 and fed back to the control system 87. A detector 86 of the linear encoder 85 is attached to the stage. When the stage 84 is tilted, the amount of movement of the stage due to the tilt is measured by the detector 86, the amount is fed back to the control system 87, given to the drive motor 89 via the driver 88, and the ball screw 83 is rotated to correct the position of the stage 84. With the correction means described above, it is possible to eliminate problems caused by tilting the stage.
[0030]
In the example shown in FIG. 1, a belt is used as means for connecting the X driving pulley 10 and the X driven pulley 12, and the Y driving pulley 24 and the Y driven pulley 26, but FIG. Even if a bevel gear train as shown in FIG. 9, a spur gear train as shown in FIG. 9, or a screw gear train as shown in FIG. 8, 9, and 10, reference numeral 40 denotes a drive shaft, and 41 denotes a driven shaft. In the bevel gear train shown in FIG. 8, the spur gear train shown in FIG. 9, and the screw gear train shown in FIG. 10, the rotation directions of the drive shaft 40 and the driven shaft 41 are not particularly limited. When gears are used instead of belts, a drive mechanism with higher rigidity can be manufactured.
[0031]
【The invention's effect】
According to the present invention, a compact drive mechanism with few components can be constructed, so that a highly accurate stage can be realized at low cost.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing an example of a stage driving mechanism according to the present invention.
FIG. 2 is a detailed cross-sectional view of a drive shaft portion that penetrates a housing frame.
FIG. 3 is an enlarged view showing a relationship between a spline shaft and a bevel gear.
FIG. 4 is a cross-sectional view of a bevel gear and a spline shaft cut at right angles to the axial direction of the spline shaft.
5 is a schematic view showing a part related to an X stage driving mechanism in the mechanism shown in FIG. 1;
FIG. 6 is a schematic view showing a state in which an inclined frame is inclined.
FIG. 7 is a conceptual diagram illustrating planetary motion that occurs when tilting a tilted frame.
FIG. 8 is a diagram for explaining an example in which a bevel gear train is used as a connecting means between a drive shaft and a driven shaft.
FIG. 9 is a diagram for explaining an example in which a spur gear train is used as a connecting means between a drive shaft and a driven shaft.
FIG. 10 is a diagram for explaining an example in which a screw gear train is used as a connecting means between a drive shaft and a driven shaft.
FIG. 11 is a block diagram illustrating a planetary motion correction method using an open loop control method.
FIG. 12 is a block diagram showing a planetary motion correction method using a closed loop control method.
FIG. 13 is an explanatory diagram of a conventional stage driving mechanism.
FIG. 14 is a view showing a state in which a conventional stage drive mechanism is tilted.
FIG. 15 is a detailed view of a universal joint.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Inclination frame, 2a, 2b ... Inclination center axis, 3a, 3b ... Housing frame, 4a, 4b ... V groove, 5 ... X stage, 6a, 6b ... V guide, 7 ... X ball screw, 8 ... X nut , 9 ... X motor, 10 ... X drive pulley, 11 ... X belt, 12 ... X driven pulley, 13 ... sample, 14 ... microscope, 15 ... Y stage, 20 ... Y motor, 22 ... motor belt, 23 ... Y Drive shaft, 24 ... Y drive pulley, 25 ... Y belt, 26 ... Y driven pulley, 27 ... Spline shaft, 28a, 28b ... Bevel gear, 29 ... Y ball screw, 30 ... X drive shaft, 31 ... Tilt motor 32 ... Groove, 33 ... Projection, 35 ... Drive pulley, 36 ... Driven pulley, 37 ... Belt, 38 ... Ball screw (spline shaft), 40 ... Drive shaft, 41 ... Driven shaft, 50 ... Inclined frame, 51a , 51b ... inclined central axis, 2a, 52b ... housing frame, 53a, 53b ... V groove, 54 ... X stage, 55a, 55b ... V guide, 56 ... Y stage, 57a, 57b ... V groove, 58 ... semiconductor wafer, 59 ... microscope, 60 ... X drive motor, 61a, 61b ... universal joint, 62 ... telescopic spline, 63a-63d ... bevel gear, 64 ... ball screw, 65 ... ball screw nut, 66 ... tilt motor, 70 ... input shaft, 71 ... output shaft, 72 ... Input angle, 73 ... Output angle, 80 ... Control system, 81 ... Driver, 82 ... Stepping motor, 83 ... Ball screw, 84 ... Stage, 85 ... Linear encoder, 86 ... Detector, 87 ... Control system, 88 ... Driver, 89 ... Drive motor

Claims (2)

A stage that holds the sample on the sample mounting surface and is movable in two directions orthogonal to each other;
Tilting means for tilting the stage by rotating it around an tilt axis parallel to the sample mounting surface;
A rotation shaft provided coaxially with the inclined shaft and rotated by a drive source; a ball screw screw-coupled to a nut fixed to the stage; and a rotation transmission means for transmitting rotation of the rotation shaft to the ball screw; And a stage driving means for driving the stage in two directions orthogonal to each other, and the driving source so as to compensate for the stage movement caused by the ball screw rotating by planetary motion when the tilting means is operated. A control system to control,
A stage apparatus comprising: An inclined frame rotatable around an inclination axis;
Tilting means for tilting the tilting frame by turning the tilting frame around the tilting axis;
A first stage movable on the tilt frame in a first direction parallel to the tilt axis;
A second stage movable on the first stage in a second direction perpendicular to the first direction;
A rotation shaft provided coaxially with the inclined shaft and rotated by a drive source; a ball screw screw-coupled to a nut fixed to the stage; and a rotation transmission means for transmitting rotation of the rotation shaft to the ball screw; Stage driving means for driving the first and second stages;
A control system for controlling the drive source so as to compensate for stage movement due to rotation of the ball screw by planetary motion when the tilting means is operated;
A stage apparatus comprising:

Images