JP3440516B2 - Moving table position control method and its control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position control method for a moving table which moves in the XY and θ directions and a control device therefor.

[0002]

2. Description of the Related Art When observing an object using an optical microscope or the like, the object is placed on a table movable in the XY and θ directions so that the observation target position is below the optical axis of the optical microscope. Move the table. For example, when observing a pattern formed on a wafer with an optical microscope or an electron microscope, it is necessary to control the position of the table with high accuracy, and the moving mechanism 2 as shown in FIG. 3 is used.

That is, the moving mechanism 2 has a moving table 21 which can move in the XY directions, and X-axis drive units 2a and Y for moving the moving table 21 along the X-axis.
It is composed of a Y-axis drive unit 2b for moving along the axis and a θ-axis drive unit 2c for rotating in the θ direction (rotational direction) about the rotary shaft 20 at the substantially center of the moving table 21.

In order to observe an object such as a wafer using the moving mechanism 2, a wafer (not shown) is placed on the moving table 21, and the observation target position on the wafer is, for example, the optical axis of an optical microscope. The position of the moving table 21 is controlled so as to be below the reference shaft 10 (reference position). That is, this reference position is the center of the visual field of the optical microscope, and by arranging the target position to be observed at the reference position, observation with the optical microscope can be performed.

In order to control the moving table 21 so as to have such a positional relationship, the X-axis driving section 2a and the Y-axis driving section 2b are operated based on the coordinate data of the target position, and if necessary, the θ-axis. The drive unit 2c is also activated. By these operations, the moving table 21 moves in the XY plane by a predetermined moving amount, and the target position is located at the reference position.
Then, it becomes possible to observe the target position with the optical microscope.

[0006]

However, the position control of such a moving table has the following problems. That is, when the target position is arranged below the reference axis by using the X-axis driving unit and the Y-axis driving unit, when the θ-axis driving unit performs rotational movement in the θ direction, the rotation of the reference axis and the moving table is performed. If the axis is deviated, the target position will deviate from the reference position as the movable table rotates.

FIG. 4 is a schematic diagram for explaining movement of the target position due to rotation. That is, first, the moving object 3 is placed on the moving table 21, and the moving table 21 is moved to position the target position 31 below the reference axis 10.
When the movable table 21 is rotated about the rotary shaft 20 from this state, the target position 3 separated from the rotary shaft 20 is obtained.
1 is displaced from below the reference axis 10 by a predetermined amount based on the distance and the rotation angle.

If the target position 31 is displaced from the position below the reference axis 10 in this way, the object is out of the visual field of the optical microscope and observation becomes impossible. Therefore, it is necessary for the operator to perform an operation of rotating the moving table 21 and then moving the moving table 21 so that the object is within the field of view of the optical microscope to dispose the target position 31 below the reference axis 10.

However, in the case where a large number of similar shapes such as patterns on a wafer are lined up, it is very difficult to find out which pattern is the observation target after the subject has moved. Is. Further, when the observation magnification is high, the observation area serving as a visual field becomes narrow, and it is not easy to return the moved target position to the visual field. Therefore, an object of the present invention is to provide a position control method and a control device therefor in which the target position does not move even when the moving table is rotated.

[0010]

SUMMARY OF THE INVENTION The present invention is a moving table position control method and control device therefor, which have been made to solve such problems. That is, this position control method is a moving mechanism that includes a moving table that moves along orthogonal XY axes and a rotating unit that rotates the moving table around a fixed position on the moving table as a rotation center. A method of controlling the position of a moving table so that a target position on a moving object placed on the moving object is aligned with a reference position that is a constant coordinate with an origin of an XY plane constituted by XY axes as a reference. When the moving table is rotated by a predetermined angle with the center of rotation as a reference from the state where the target position on the object is at the reference position, the coordinate deviation of the target position in the rotation is calculated based on the distance between the target position and the rotation center and the predetermined angle. Then, the moving table is controlled so as to correct the coordinate shift based on the calculation result.

Further, while the moving table is rotated by a predetermined angle, the coordinate shift of the target position corresponding to the set angle is calculated for each set angle smaller than the predetermined angle, and the movable table is rotated by the set angle. It is also a method of controlling so as to correct the coordinate deviation for each.

Further, the position control device for a moving table according to the present invention comprises a moving table for placing a moving object, an XY moving means for moving the moving table along mutually orthogonal XY axes, and a moving means. In a moving mechanism having a rotating means for rotating the moving table with a fixed position on the table as a rotation center, a target position on a moving object is fixed with reference to an origin of an XY plane constituted by XY axes. A device for controlling the position of the moving table so as to match the reference position which is the coordinate, and when the moving table is rotated by a predetermined angle with the rotation center as a reference from the state where the target position on the moving object is at the reference position, The coordinates of the rotation center are obtained from the moving mechanism, the coordinate deviation of the target position in the rotation is calculated, and the position information of the coordinate deviation is XY based on the calculation result. And coordinate deviation calculation means for outputting the motion means is a device that includes a computing management means for giving an instruction to calculate the coordinate offset relative coordinate deviation calculation means.

Moreover, the calculation management means stores a constant set angle, and causes the coordinate shift calculation means to calculate the coordinate shift of the target position for each set angle while rotating the moving table by a predetermined angle. It also gives instructions.

[0014]

The rotating shaft moves in the XY plane as the moving table moves, and the target position and the center of rotation may deviate when the target position is located at the reference position. When the moving table is rotated in this state, the target position is displaced by a predetermined amount. The control method of the present invention calculates this coordinate shift based on the distance between the target position and the center of rotation and the rotation angle, and controls the movement table to correct the coordinate shift based on the calculated result. After that, the target position can be maintained at the reference position.

Further, while rotating a predetermined angle, the coordinate shift is calculated for each set angle smaller than the predetermined angle, and the movement table is controlled so as to correct the coordinate shift each time the set angle is moved. The moving table will rotate around.

Further, in the control device of the present invention, when the moving table is rotated by a predetermined angle, the coordinate shift calculating means obtains the coordinates of the target position and the center of rotation from the moving mechanism and calculates the coordinate shift of the target position in the rotation. , And outputs position information of the coordinate shift to the XY moving means based on the calculation result. Further, the calculation managing means gives an instruction to calculate the coordinate shift to the coordinate shift calculating means, and controls the movement table to correct the coordinate shift.

Further, the calculation management means stores a fixed set angle, and by giving an instruction to the coordinate shift calculation means to calculate the coordinate shift for each set angle, the apparent target position is apparent. It becomes possible to perform control so that the moving table rotates around.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a moving table position control method and a control device therefor according to the present invention will be described below with reference to the drawings. 1A and 1B are views for explaining a position control method for a moving table according to the present invention. FIG. 1A is a coordinate system, and FIG. 1B is a diagram for explaining movement of a target position. Further, FIG. 2 is a diagram for explaining the position control device for the moving table according to the present invention.

As shown in FIG. 1A, the moving table 2
1 is movably provided along the X-axis and the Y-axis, and can be further rotated in the θ direction about the rotary shaft 20 at the substantially center of the moving table 21. When the target position 31 is observed using an optical microscope or the like with the moving object 3 made of, for example, a wafer placed on the moving table 21, the target position 31 is below the reference axis 10 serving as the optical axis. The moving table 21 is moved along the XY directions so as to be arranged.

Further, when it is desired to rotationally move the target position 31 under the reference shaft 10 in the θ direction, the moving table 21 is rotationally moved about the rotating shaft 20. Before the rotational movement, if the target position 31 is at the initial position (x ₁ , y ₁ ) with reference to the origin O shown in FIG. 1B, the rotational movement causes the position after the rotation (x ₂ , y ₂ ). Will be moved to. The position control method of the moving table 21 of the present invention calculates the coordinate shift (x _s , y _s ) between the initial position (x ₁ , y ₁ ) and the rotated position (x ₂ , y ₂ ), This is a method of controlling the moving table 21 so as to correct this.

Prior to explaining the position control method of the moving table 21, the position control device of the moving table 21 of the present invention will be described first. As shown in FIG. 2, the control device 1 includes a moving mechanism 21 in which the moving table 21 moves in the XY plane by the X-axis driving unit 2a, the Y-axis driving unit 2b, and the θ-axis driving unit 2c. It controls the position of.

The control device 1 obtains the X-axis coordinate data and the Y-axis coordinate data from the moving mechanism 2 and calculates the coordinate shift (x _s , y _s ) shown in FIG. Y
It is composed of a coordinate shift calculation unit 1a that outputs the coordinate data to the axis drive unit 2b, and a calculation management unit 1b that gives an instruction to the coordinate shift calculation unit 1a to perform the calculation based on the rotational movement of the moving table 21. There is.

To place the target position 31 below the reference axis 10 with the moving object 3 shown in FIG.
Then, predetermined coordinate data is given to actuate the X-axis drive unit 2a and the Y-axis drive unit 2b to move the moving table 21 by a predetermined amount.

Further, in this state, the operator moves the moving mechanism 2
When a rotational movement instruction is given to, the θ-axis driving unit 2c operates and the moving table 21 rotates about the rotating shaft 20 by a predetermined amount. When this movement instruction is given and the movement table 21 rotates, the calculation management unit 1b gives an instruction to the coordinate shift calculation unit 1a to calculate the coordinate shift based on this rotation. The coordinate shift calculator 1a calculates the coordinate shift based on this instruction, and outputs the calculation result as X.
It is given to the axis drive unit 2a and the Y-axis drive unit 2b, and thereby the position of the moving table 21 is corrected.

Next, a method of controlling the position of the moving table 21 using the control device 1 will be described. First, Fig. 1
The target position 31 on the moving object 3 shown in FIG.
It is located below 0, and from this state θ shown in FIG.
The operator gives an instruction to the moving mechanism 2 to rotationally move the shaft driving unit 2c at a predetermined angle (θ ₂ shown in FIG. 1B).

According to this rotational movement instruction, the θ-axis drive unit 2c
Is activated to start the rotational movement of the moving table 21. With the rotation of the moving table 21, the calculation managing unit 1b gives an instruction to the coordinate shift calculating unit 1a, and the coordinate shift calculating unit 1a follows the instruction and the first position (x ₁ , y shown in FIG. 1B).
Calculate the coordinate shift (x _s , y _s ) when rotated by θ ₂ from ₁ ).

To calculate the coordinate shift (x _s , y _s )
The angle θ ₁ formed by the line connecting the center of rotation (x ₀ , y ₀ ) and the initial position (x ₁ , y ₁ ) with the X axis is calculated by the formula shown in Formula 1.

[Equation 1]

Next, the distance a between the center of rotation (x ₀ , y ₀ ) and the initial position (x ₁ , y ₁ ) is calculated by Equation 2.

[Equation 2]

Next, the position (x ₂ , y ₂ ) after the rotation of the target position 31 by θ ₂ is calculated by the above equation, and θ ₁ and a and the value of the rotation center (x ₀ , y ₀ ) are calculated. It is obtained by using Equations 3 and 4.

[Equation 3]

[Equation 4]

Then, the coordinate shift (x _s , y _s ) which is the difference in the coordinate value between the initial position (x ₁ , y ₁ ) and the position after rotation (x ₂ , y ₂ ) is expressed by equations (5) and (6). Calculate using.

[Equation 5]

[Equation 6]

The above-described calculation is performed by the coordinate shift calculation unit 1a, and the coordinate shift calculation unit 1a uses the respective values of the coordinate shift data (x _s , y _s ) as the X-axis drive unit 2a and the Y-axis drive unit 2b, respectively. Give to. The X-axis drive unit 2a and the Y-axis drive unit 2b are moved so as to correct the position of the movement table 21 by the given value of the coordinate shift (x _s , y _s ). As a result, the target position 31 that should move due to the rotation of the moving table 21 remains in a state of being arranged below the reference shaft 10.

Next, another embodiment of the position control method for the moving table and the control apparatus therefor according to the present invention will be described. That is,
This position control method is a method for correcting the position of the moving table 21 by calculating a coordinate deviation for each set angle smaller than the angle θ ₂ while moving the moving table 21 by θ ₂ rotation. When performing this control method, the setting angle is stored in the calculation management unit 1b of the control device 1.

For example, the setting angle of 1 ° is stored in the calculation management unit 1b, and in this state, when an operator gives a rotational movement instruction to the moving mechanism 2, first the θ-axis driving unit 2 is moved.
The movement table 21 is rotated by the operation of c, and when the rotation reaches the set angle of 1 °, the calculation management unit 1b sends a coordinate shift calculation instruction to the coordinate shift calculation unit 1a.

According to this instruction, the coordinate shift calculation section 1a
Calculates the coordinate shift of the target position 31 when the moving table 21 rotates by a set angle of 1 °. Then, the calculation result is given to the X-axis drive unit 2a and the Y-axis drive unit 2b, and the position is corrected when the moving table 21 rotates by the set angle of 1 °. By this position correction, the target position 31 becomes the reference axis 10
Will be placed below.

Further, when the operator gives a rotational movement instruction, the calculation management section 1b outputs the calculation instruction again at the stage of rotating the set angle by 1 ° from that position,
The coordinate shift calculation unit 1a calculates the coordinate shift when the set angle is moved by 1 °. Then, position correction is performed based on the coordinate shift, and the target position 31 is moved below the reference axis 10.

By performing such position correction for each set angle until there is no instruction of rotational movement from the operator,
Apparently, the state is such that the target position 31 is rotating. That is, even if the moving table 21 rotates by a minute set angle, the target position 31 does not largely shift, and by continuously correcting minute coordinate shifts, the field of view of an optical microscope or the like can be maintained. The target position 31 will rotate.

If the set angle is too small, the processing time becomes long. Therefore, the set angle may be changed depending on the range of the visual field, that is, the magnification of the optical microscope or the like. Further, even if the magnification is the same, if the distance a between the target position 31 and the rotation center is large, the coordinate shift becomes large,
For example, the set angle corresponding to the relationship between the distance a and the magnification may be stored in the calculation management unit 1b as matrix data. That is, the set angle according to the distance a between the target position 31 and the center position when rotating the moving table 21 and the magnification of the optical microscope is read from the matrix data,
The position of the moving table 21 is controlled based on the set angle.

In the above embodiments, the observation of the moving object 3 using the optical microscope has been described as an example, but the present invention is not limited to this. That is, the moving table 2
Any control method and control device that requires the control of disposing the target position 31 of the moving object 3 below the reference axis 10 by moving 1 can be applied.

[0039]

As described above, the position control method for a moving table and the control apparatus therefor according to the present invention have the following effects. That is, even if the moving table is rotated, the target position does not deviate from the reference position, so that the target position does not deviate from the visual field of the optical microscope, for example. Therefore, the operator does not need to perform a troublesome operation of returning the target position to the visual field, and the operability of rotating the stage is significantly improved.

Further, by performing the position correction for each small set angle, it is possible to apparently perform the rotational movement around the target position. INDUSTRIAL APPLICABILITY The present invention is a particularly effective method and apparatus when observing a minute subject such as a pattern on a wafer.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the present invention, in which (a) is a coordinate system,
(B) shows the movement of the target position.

FIG. 2 is a diagram illustrating a control device of the present invention.

FIG. 3 is a diagram illustrating a conventional example.

FIG. 4 is a schematic diagram illustrating movement of a target position due to rotation.

[Explanation of symbols]

1 control device 1a Coordinate shift calculation section 1b Calculation management unit 2 moving mechanism 2a X-axis drive unit 2b Y-axis drive unit 2c θ-axis drive unit 3 Moving object 10 Reference axis 20 rotation axis 21 Moving table 31 target position

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/68 G05D 3/00 H01L 21/027 B23Q 15/013

Claims (4)

(57) [Claims] 1. A moving mechanism comprising: a moving table that moves along orthogonal XY axes; and a rotating unit that rotates the moving table around a fixed position on the moving table as a rotation center. A method of controlling the position of the moving table so that a target position on the moving object placed on the moving object is aligned with a reference position that is a constant coordinate with reference to an origin of an XY plane constituted by the XY axes. When the moving table is rotated by a predetermined angle with the rotation center as a reference from the state where the target position on the moving object is at the reference position, the coordinate deviation of the target position in the rotation is calculated as follows. A movement that is calculated based on the distance and the predetermined angle, and the movement table is controlled so as to correct the coordinate deviation based on the calculation result. Table position control method. 2. While rotating the predetermined angle, a coordinate shift of the target position is calculated according to the set angle for each set angle set smaller than the predetermined angle, and the movement table rotates the set angle. 2. The position control method for a moving table according to claim 1, wherein the control is performed so as to correct the coordinate shift each time the movement is performed. 3. A moving table on which a moving object is placed, XY moving means for moving the moving table along mutually orthogonal XY axes, and a fixed position on the moving table as a rotation center. A moving mechanism having a rotating means for rotating the moving table, wherein the target position on the moving object is adjusted to a reference position which is a constant coordinate with an origin of an XY plane constituted by the XY axes as a reference. A device for controlling the position of a moving table, wherein when the moving table is rotated by a predetermined angle with the rotation center as a reference from a state where the target position on the moving object is at the reference position, the target position and the rotation The coordinate of the center is obtained from the moving mechanism, the coordinate shift of the target position in the rotation is calculated, and the position information of the coordinate shift is calculated based on the calculation result. And coordinate deviation calculation means for outputting the motion means, the position control device of the moving table, characterized in that it comprises a calculation management means for giving an instruction for calculating the coordinate displacement to the coordinate deviation calculation means. 4. The calculation management means stores a fixed set angle, and coordinates of the target position for each set angle with respect to the coordinate shift calculation means while rotating the moving table by the predetermined angle. A position control device for a moving table, which gives an instruction to calculate a shift.