JP2001059704A - Positioning stage device, semiconductor aligner and manufacture of device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the location of a stage highly accurately by a compact and lightweight location measuring mechanism by reflecting the plurality of measuring light of a first laser interferometer and second interferometer with parallel optical axes to each other at a reflecting mirror provided on a stage movable in first and second direction. SOLUTION: An XY stage 1 is movably supported in an XY plane and driven in XY directions and a direction of rotation (θ) in the plane. A Y interferometer 2a is used in combination with a reflecting mirror 3 provided on the XY stage 1 for measuring the Y-direction location of the XY stage 1. A Y interferometer 2b is provided at a predetermined distance from the Y interferometer 2a in such a way as to form an optical axis 4b in parallel with the measuring optical axis 4a of the Y interferometer 2a. Displacements in the θdirection are computed from the difference between the location measurement values of the Y interferometers 2a and 2b and the interval between their measuring optical axes 4a and 4b. An interferometer control system 7 outputs a stage displacement signal to be used in a stage control system 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stage device which is used in a semiconductor exposure apparatus, an inspection apparatus or the like, and positions an exposure master, an object to be exposed and an object to be inspected at predetermined positions.

[0002]

2. Description of the Related Art Conventionally, as an exposure apparatus used for manufacturing a semiconductor device, an apparatus called a stepper and an apparatus called a scanner are known. A stepper reduces and projects a pattern image formed on a reticle onto a wafer by a projection lens while step-moving a semiconductor wafer on a stage device under a projection lens, and sequentially exposes a plurality of locations on one wafer. It is something to do. The scanner moves (scans) the semiconductor wafer on the wafer stage and the reticle on the reticle stage relative to the projection lens,
During the scanning movement, the exposure light on the slit is irradiated to project a reticle pattern onto the wafer. Steppers and scanners are considered to be the mainstream of exposure apparatuses in terms of resolution and overlay accuracy.

FIG. 8 is a schematic top view of a wafer stage used in such an exposure apparatus. The wafer 102 to be exposed is mounted on the wafer stage 101 via a wafer chuck (not shown). Based on the exposure optical system,
In the figure, the position of the exposure optical axis 103 can be considered to be immobile. Therefore, the wafer stage 101 needs to move in the X and Y directions with respect to the exposure optical axis 103 in order to expose the entire surface of the wafer. Wafer 1 for adjusting the imaging focus
02 needs to move also in the Z direction and the tilt direction, but the description is omitted here. For the position measurement of the wafer stage 101 in the XY directions, a high-resolution laser interferometer is used to realize high-precision positioning. In order to use a laser interferometer, it is necessary to provide a reflection mirror 107 on the wafer stage 101 for reflecting laser light. However, this reflecting mirror 107 is
In order to reflect the laser light in the entire movement range of 01, a length equal to or longer than the movement distance of the wafer stage 101 is required. That is, assuming that the stage movement distance in the Y direction is Ly, the length of the reflecting mirror for X measurement is Ly.
The above is required.

In recent years, the wafer diameter tends to be large, for example, 300 mm in order to improve productivity. In order to expose the entire surface of the wafer, the moving stage is required to have a moving range at least equal to the diameter of the wafer. In addition, when the position where wafer alignment is performed is different from the exposure position, or when wafer exchange is taken into consideration, the movement range must be further increased. Inevitably, the reflector must be long.

[0005] For example, in FIG.
5 passes through the exposure optical axis center 103, and the Y interferometer optical axis 106 has the exposure optical axis center 103 and the alignment optical axis center 104.
And the stage movement distance in the Y direction (the distance between the position (solid line) at which the wafer stage 101 has moved the maximum in the Y + direction and the position (dashed line) the maximum movement in the Y- direction) is L.
y, exposure optical axis center 103 and alignment optical axis center 104
Is L2, the required minimum length Ly2 of the reflecting mirror 107 is Ly2 = Ly + L2.

However, making the reflecting mirror 107 longer requires
(1) It is difficult to make a long reflecting mirror having a high-precision mirror surface, (2) it is costly to make a long reflecting mirror surface, and (3) the weight of the reflecting mirror itself increases the entire stage. (4) heat generation of the stage driving device increases due to an increase in the stage weight, and (5) the natural frequency of the mechanical system of the stage decreases, thereby deteriorating the characteristics of the control system. Absent.

As a solution to this problem, Japanese Patent Laid-Open No. 7-253
No. 304 discloses a configuration as shown. This apparatus includes a laser interferometer, a moving mirror, an XY moving stage, and an arithmetic unit. The moving mirror is shorter than the stage moving distance in the Y direction, and a plurality of X interferometers are provided. The distance between the X interferometers is shorter than the length of the moving mirror, so that the measuring light of one of the X interferometers is irradiated on the moving mirror regardless of the position of the stage, and two measuring lights are simultaneously May be irradiated.
Which of the X interferometers can be measured is determined by the arithmetic unit from the value of the Y interferometer, and the length measurement result in the X direction is obtained. When the stage moves in the Y direction, the X interferometer, which can newly measure, performs a return operation at a predetermined position using the value of the interferometer that has been measured so far. The transfer of the value is sequentially used to measure the movement in the long range with the short movable mirror.

[0008]

Problems to be Solved by the Invention Japanese Patent Laid-Open No. 7-25330
According to the configuration disclosed in Japanese Patent Laid-Open No. 4 (Kokai) No. 4 (1999) -1995, the position measuring mechanism (reflector) mounted on the stage can be reduced in size and weight. However, the measurement accuracy is not always sufficient.

According to the findings of the present inventors, it is based on the following reasons. In other words, the XY stage needs to be positioned with high precision, and the positioning operation is performed by a control system using feedback of the measured value of the stage position. The stage control system is composed of a digital control system using high-frequency sampling, and uses high-gain feedback. The observation noise of the position measurement system is a disturbance to the control system, and if this influence is large, the closed loop characteristics of the control system cannot be improved.

The return operation of the interferometer requires a certain amount of time, and it is impossible to keep it within one sample time of the stage control system. Therefore, it is impossible to continuously transfer measured values to the control system even if the interferometer is reset as in the related art.

In addition, vibrational noise always appears in the measured value of the laser interferometer. This is due to electrical noise in the measurement system and mechanical vibration of the reflecting mirror and the laser interferometer itself. Therefore, when the values of the interferometer are transferred, the values on which the noise is superimposed are transferred. For example, when the stage is stationary positioned near the switching position of the laser interferometer, chattering in which the laser interferometer is switched and many values are exchanged in a short time due to slight stage vibration and noise of the switching position measurement system. Phenomenon may occur. If a value with noise is transferred many times, errors may be accumulated and the measurement error between the true position of the stage and the measured value may increase.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a configuration in which a position measuring mechanism mounted on a stage can be reduced in size and weight and high-precision stage position measurement can be performed even when the moving range of the stage is increased.

[0013]

To achieve the above object, a positioning stage apparatus according to the present invention measures a stage movable in a first direction and a second direction, and measures a displacement of the stage in the first direction. A first laser interferometer, a first reflecting mirror configured on the stage that reflects measurement light of the first laser interferometer, and a first mirror that measures displacement of the stage in the second direction; A plurality of second laser interferometers having parallel optical axes, and reflecting measurement light of the second laser interferometer;
A second reflecting mirror configured on the stage, and a displacement of the stage in the first direction based on a measurement value of the first laser interferometer, and selecting from the plurality of second laser interferometers And an interferometer controller for outputting the displacement of the stage in the second direction from the measured value of the second interferometer. The displacement of the stage in the first direction at the time of switching to the total is different depending on the moving direction of the stage in the first direction.

[0014]

According to the present invention, the length of the movable mirror can be increased by providing a plurality of second laser interferometers for measuring the stage position in the second axis direction orthogonal to the first axis direction in which the stage movement distance is relatively long. Therefore, the stage on which the movable mirror is mounted can be reduced in size and weight. Further, the measurement values of the plurality of second laser interferometers are switched in accordance with the measurement values of the first laser interferometer, and are changed depending on the moving direction in the first axial direction. This allows
A hysteresis characteristic can be provided at the switching position, chattering in which the measurement value is frequently switched can be prevented, and highly accurate stage position measurement can be performed.

[0015]

FIG. 1 shows the configuration of a positioning stage device according to one embodiment of the present invention. In the figure, XY
The stage 1 is movably supported on an XY plane on a surface plate (not shown) using a guide mechanism (not shown). Also, XY
The stage 1 is driven in an XY direction and a rotational direction (θ) in a plane by an actuator (not shown). A first Y interferometer 2a is provided integrally with a lens barrel base (not shown) for supporting a projection optical system (not shown) for measuring the position of the XY stage 1 in the Y direction, and a reflecting mirror provided on the XY stage 1 Used in combination with 3. The second Y interferometer 2b is integrated with a lens barrel base (not shown) so as to be separated from the first Y interferometer 2a by a predetermined distance and to have an optical axis 4b parallel to the measurement optical axis 4a of the first Y interferometer 2a. Is provided. First Y interferometer 2a
The displacement in the θ direction is calculated from the difference between the measured position of the second Y interferometer 2b and the distance between the measurement optical axes 4a and 4b.
In order to measure the displacement of the XY stage 1 in the X direction,
A first X interferometer 5a and a second X interferometer 5b are provided integrally with a lens barrel base (not shown). Reference numerals 6a and 6b denote measurement optical axes of the first X interferometer 5a and the second X interferometer 5b, respectively.

The interferometer control system 7 outputs a stage displacement signal used in the stage control system 8. Specifically, calculation and output of the Y direction and the above-described θ direction displacement, and output of the X direction stage displacement used for control calculation from the two X interferometers 5a and 5b are performed. In addition, initialization and return operations of all interferometers are also performed. The stage control system is based on the stage displacement signal output from the interferometer control system and the stage drive profile output from the main body controller (not shown),
It performs positioning control of the XY stage and outputs a control command to the actuator.

Referring to FIG. 2, a first X interferometer 5 for displacement in the X direction will be described.
The switching operation between the “a” and the second X interferometer 5b will be described. In the figure, A is the first X interferometer 5a and B is the second X interferometer 5a.
5 shows an interferometer 5b. Also, take the Y-direction displacement in the lateral direction,
The state of the measurement optical axes 6a and 6b of each of the X interferometers 5a and 5b and the position of the stage is indicated by a to b.

First, it is assumed that the situation of the XY stage 1 is a. At this time, the measurement optical axis of B is off the reflecting mirror, and B cannot be measured. A can be measured, and the measured value of A is used for measuring the displacement of the XY stage 1 in the X direction. XY
It is assumed that the stage has moved in the Y + direction (rightward on the paper surface) and the situation shown in FIG. The specific position of (b) is the time when the measurement optical axis of B is irradiated on the reflecting mirror, and the measurement of the displacement of the XY stage 1 in the X direction by B becomes possible. The interferometer measures the relative movement of the object to be measured based on a certain initial value of the counter of the interferometer measurement system. Will be possible. Therefore, it is necessary to perform a reset operation (reset) when the measuring light is again irradiated on the reflecting mirror. More specifically, error clearing or the like is performed in the interferometer measurement system, but is omitted here and only the counter is set to 0. In addition,
Instead of resetting the counter to zero during the return operation, A
May be given to B as an initial value. In FIG. 2, the upward arrow in the operation B of the interferometer control system indicates that this operation is performed only when the operation moves from the position A to the position B. Therefore, even if the XY stage moves from C to B, B reset is not performed. At this time, the displacement of the XY stage 1 in the X direction can be measured for both A and B, but the stage control system is A
The stage is controlled by using the measured values of.

Further, it is assumed that the XY stage moves in the Y + direction, passes through C, and enters the situation of d. At this point, the measured value of the displacement in the X direction used for controlling the XY stage is switched from the measured value of A to the measured value of B. Details of the method of transferring values in this switching will be described later. In FIG. 2, the upward arrow at d in the interferometer control system operation indicates that this operation is performed only for the movement from c to d and no switching operation is performed when the movement is from e to d. Is shown. Further, the XY stage moves in the Y + direction,
A of the measurement optical axis deviates from the reflecting mirror, and A cannot be measured. In summary, when the XY stage moves from A to F, the measured value of A from A to D and the measured value of B from D to D are used as the displacement in the X direction.

When the XY stage moves in the Y-direction from F to A, the same operation as above is performed. That is, A is reset when the situation of E is reached. The downward arrow in the operation e of the interferometer control system operation of FIG. 2 indicates that this operation is performed only when the operation is moved from the operation to the operation. At this point, A,
Both B can measure the displacement of the XY stage 1 in the X direction, but the stage control system controls the stage using the measured value of B.

The XY stage moves further in the Y-direction,
At the point of time C, the measurement of the displacement in the X direction is switched from the measured value of B to the measured value of A. The downward arrow of c in the operation of the interferometer control system in FIG. 2 indicates that this operation is performed only when moving from d to c. Therefore, when the XY stage moves from A to F, the measured value of B is used as the displacement in the X direction from F to C, and the measured value of A is used from H to A.

It is desirable to set the position interval between c and d as follows. In the transfer of measured values between the two interferometers (described in detail later), at least an error is added to the transferred value. If the transfer operation is performed a large number of times, the accumulation of errors will lower the reliability of the measured values and adversely affect the final exposure accuracy. Therefore,
The smaller the delivery, the better. Consider a situation in which the XY stage is stationary positioned between C and D. At this time, due to a servo error due to a disturbance to the XY stage or an observation noise in the measurement system, a vibration component of these errors overlaps the measurement value of the interferometer centering on the positioning command position. If the positions C and D are both within the range of the vibration, chattering in which a large number of transfers are performed at an extremely short time interval occurs, which is not preferable. Therefore, at least one of C and D is set at a position interval that deviates from this vibration region.

Next, a method of transferring measured values between interferometers will be described. First, as a simple case, it is assumed that the stage moves only in the Y direction, the displacement in the θ direction is always zero, and the reflecting mirror is truly flat. In this case, the transfer of the measured value may be performed by transferring the value of the first X interferometer to the second X interferometer or vice versa. However, even when the stage is stationary in the X direction as described above, the difference value between the two interferometers actually has an oscillating error component in the signal whose center value is 0 bit as shown in FIG. Interferometer measurement resolution). In this case, if only one sample value is used, there is a possibility that an error of 10 bits or more is delivered (for example, if the 76th sample is delivered, an error of 14 bits occurs).

In order to avoid this situation, the following processing is performed by the interferometer control system. In FIG. 3, the sample time 10
Suppose that delivery is performed at 0. At this time, an average value is obtained using a plurality of sample values before the sample 100. As an example, when the average of the samples 91 to 100 is taken, it becomes −1, and the transfer value can be obtained with sufficient accuracy in practical use. The averaging technique is the simplest,
In addition, a smoothing process may be performed using various filters used for general data processing, and a noise component may be removed from the difference value. That is, by using a plurality of sample values before the transfer, the reliability of the transferred value is increased, and the error is reduced.

Now, it is assumed that the value is transferred from the first X interferometer that measures the stage position from the stage origin to the second X interferometer after performing the return operation. The first X interferometer measures the displacement of the stage in the X direction, while the second X interferometer sets the counter to 0 in the return operation. Therefore, a difference is generated between the two measured values by a value corresponding to the displacement in the X direction. The interferometer control system outputs a value obtained by adding the smoothed difference value α as an offset to the measurement value of the second X interferometer as an X-direction interferometer position signal.

FIG. 4 shows the concept of delivery. Similarly, when the stage moves in the Y direction, the first X interferometer once comes out of the measurement area, returns to the measurement area and completes the return operation, and then passes the measured value from the second X interferometer to the first X interferometer. Do. At this time, the measurement value (offset α) of the second X interferometer
) And the offset obtained by smoothing the difference value of the first X interferometer as β, and the interferometer control system outputs a value obtained by adding β to the measurement value of the first X interferometer as an X-direction measurement value. The same operation is performed each time the interferometer is switched.

Consider a case where the XY stage is displaced in the θ direction. As shown in FIG. 5, since the optical axis 6a of the first X interferometer and the optical axis of the second X interferometer 6b are separated by d, a difference occurs in each X direction measurement value by δ = dθ due to displacement in the θ direction. Therefore, it is necessary to correct the value of δ in the calculation of the offsets α and β described above.

Further, the reflecting mirror is not a perfect plane but has a geometrical shape error (FIG. 6). Therefore, the correction is performed using the functions f1 (y) and f2 (y) of the deformation values of the reflecting mirror calculated separately. The functions f1 and f2 are respectively the first
Using the Y-direction stage positions y of the X interferometer and the second X interferometer as arguments, the deviation of the reflecting mirror from the ideal plane is output. f
There is a relationship between f1 (y) = f2 (y + d) between 1 and f2. Similarly, for the first Y interferometer and the second Y interferometer, the geometric error of the reflecting mirror is corrected by the correction function fy1.
Correction is made using (x) and fy2 (x).

FIG. 7 shows the operation of calculating the offset value at the time of transfer when all the corrections are used. In this example,
The calculation method of the offset α at the time of transfer from the first X interferometer to the second X interferometer is shown. The displacement in the X direction is the sum of the value of the first interferometer and the value of the offset β. The geometric error of the reflecting mirror is corrected by the above-described correction function using the X-direction displacement and the Y-direction displacement. The θ-direction displacement of the XY stage is determined from the first Y interferometer, the second Y interferometer, and the distance between the optical axes of the two. Correction of δ calculated from the displacement in the θ direction and the distance d between the optical axes of the first and second X interferometers is performed to calculate a difference value, and the difference value is smoothed to obtain an offset value α.
Is calculated. When transferring from the second X interferometer to the first X interferometer, the offset value β is calculated by the same procedure.

[0030]

Next, an embodiment of a method of manufacturing a semiconductor device using the above-described exposure apparatus will be described. FIG. 9 shows a manufacturing flow of a semiconductor device (a semiconductor chip such as an IC or an LSI, or a liquid crystal panel or a CCD). In step 1 (circuit design), the circuit of the semiconductor device is designed. Step 2 is a process for making a mask on the basis of the circuit pattern design. In step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. Step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer produced in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). . In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 10 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 1
In 5 (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the above-described exposure apparatus to print and expose the circuit pattern of the mask onto the wafer. Step 17 (development) develops the exposed wafer. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer. By using the manufacturing method of this embodiment, it is possible to manufacture a highly integrated semiconductor device, which has been conventionally difficult to manufacture.

In this embodiment, the number of interferometers for measuring the displacement of the stage in the X direction is two, but the present invention is not limited to this, and two or more interferometers may be provided. In this case, it goes without saying that the distance between the optical axes of adjacent interferometers is smaller than the length of the reflecting mirror.

[0033]

According to the positioning stage apparatus of the present invention, the size of the reflecting mirror can be reduced, the size and weight of the stage can be reduced, and chattering can be prevented to achieve a high-precision stage position. Measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a top view of an XY stage according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an interferometer switching operation and a stage position in the apparatus of FIG.

FIG. 3 is a diagram illustrating an example of interferometer measurement values in the apparatus of FIG. 1;

FIG. 4 is a conceptual diagram of the transfer of measured values in the apparatus of FIG.

FIG. 5 is a conceptual diagram of an error in displacement in the X direction due to displacement in the θ direction in the apparatus of FIG. 1;

FIG. 6 is a conceptual diagram of a geometric error of a reflecting mirror in the apparatus of FIG.

FIG. 7 is a diagram showing an operation of transferring measured values using all corrections in the apparatus of FIG. 1;

FIG. 8 is a top view of a conventional XY stage.

FIG. 9 is a diagram showing a flow of manufacturing a micro device.

FIG. 10 is a diagram showing a detailed flow of a wafer process in FIG. 9;

[Explanation of symbols]

1: XY stage, 2a, 2b: Y interferometer, 3: reflective mirror, 4a, 4b, 6a, 6b: measurement optical axis, 5a, 5b:
X interferometer, 7: interferometer control system, 8: stage control system.

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Claims (8)

[Claims] 1. A stage movable in a first direction and a second direction, a first laser interferometer for measuring a displacement of the stage in the first direction, and a measuring light of the first laser interferometer. A first reflecting mirror configured on the stage to reflect; a plurality of second laser interferometers having optical axes substantially parallel to each other for measuring the displacement of the stage in the second direction; A second reflecting mirror configured on the stage, which reflects measurement light of the laser interferometer, and a first reflecting mirror of the stage based on a measurement value of the first laser interferometer.
And an interferometer controller for outputting a displacement in the direction and outputting the displacement of the stage in the second direction from the measurement value of the second interferometer selected from the plurality of second laser interferometers. Wherein the displacement of the stage in the first direction when the selected second laser interferometer is switched to another adjacent second laser interferometer is different depending on the moving direction of the stage in the first direction. Positioning stage device. 2. The method according to claim 1, wherein when switching the second laser interferometer selected by the interferometer controller, the measured value after switching is corrected based on a plurality of measured values before switching. The positioning stage device according to the above. 3. When switching the second laser interferometer selected by the interferometer controller, the measured value after the switching is corrected based on the difference between the measured values of the laser interferometer before the switching. 3. The positioning stage device according to claim 1, wherein 4. When switching the second laser interferometer selected by the interferometer controller, a correction value is calculated by smoothing a difference value of a measurement value of the laser interferometer before the switching. The positioning stage device according to claim 1. 5. A third laser interferometer having an optical axis parallel to an optical axis of the first laser interferometer, and the third laser interferometer and the third laser interferometer are used to determine Means for calculating a rotational direction displacement in a horizontal plane of the positioning stage, wherein when switching the second laser interferometer selected by the interferometer controller, the laser interference after switching based on the rotational direction displacement The positioning stage device according to any one of claims 1 to 4, wherein the measurement value of the meter is corrected. 6. When switching the second laser interferometer selected by the interferometer controller, correcting a measurement value of the laser interferometer based on a geometrical shape error of the second reflecting mirror. The positioning stage device according to claim 1, wherein: 7. A semiconductor exposure apparatus comprising the positioning stage device according to claim 1. 8. A device comprising: a step of applying a photosensitive agent to a wafer; a step of exposing the wafer using the semiconductor exposure apparatus according to claim 7; and a step of developing the exposed wafer. Production method.