JP2000046517A - Length measuring instrument and exposing device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a length measuring instrument which can operate without returning a stage to the datum point of a moving device, even when measurement light or reference light is interrupted or instantaneously discontinued and the displacement data of a displacement interferometer becomes indistinct by allowing the stage to return to the datum point by itself. SOLUTION: A length measuring instrument is constituted by providing a position measuring means 30X which measures the absolute position of an object to be measured to an optical interference length measuring means. The measuring means 30X is constituted of the position detecting light source 31X which emits light to the mobile reflecting mirror 82X of the optical interference length measuring means at a prescribed angle θ, an optical position detector 33X which detects the position of the reflected light from the mirror 82X, and a processor 35X which calculates the position of the object from the signal of the detector 33X. When such a position detecting means is used, the position of the object can be measured when the position detecting light is restored even when measuring light or reference light is intercepted and the position of the object becomes indistinct at the optical interference length measuring means and, at the same time, the position detecting light is intercepted. In addition, the position of the object can be decided in detail from the position data of the position detecting means and the phase data of an optical interferometer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical interferometer for measuring the amount of movement of an object to be measured with high precision, and more particularly to a length measuring apparatus for an exposure apparatus for positioning and moving a stage with high precision.

[0002]

2. Description of the Related Art Since a length measuring apparatus utilizing light interference can measure with high accuracy in units of wavelength of light to be used, it has been conventionally used for checking the positioning accuracy of precision equipment and detecting the amount of movement of a precise stage. It's being used. As such a light source for a precision length measuring device, a laser is used because of the uniformity of the wavelength of light, the same phase, and the small divergence angle, and the dynamic range is expanded even in the light receiving element of the interferometer. As a result, it has become possible to measure the laser oscillation wavelength with an accuracy of a few tenths or less in the range of several meters. For this reason, in recent years, it has been used for stage movement control and the like of semiconductor manufacturing equipment.

A conventional laser interferometer used for measuring the amount of movement of a precision stage divides light from a light source into two parts, one to a movable reflecting mirror attached to the precision stage, and the other to a movable reflector. The amount of movement of the precision stage is measured by monitoring the change in interference fringes obtained by allowing the light from the movable reflecting mirror to interfere with the light from the fixed reflecting mirror by making the light incident on the fixed reflecting mirror.

Incidentally, the measurement of the position of the precision stage is performed as follows. First, the precision stage is first moved to a predetermined reference position, and measurement of the amount of movement by the optical interferometer is started. Then, the position of the precision stage is obtained by measuring a change in interference fringes detected by the optical interferometer on the precision stage and calculating the amount of movement of the precision stage from the reference position.

[0005]

However, in the displacement measurement of a moving object using such a displacement interferometer, the absolute position cannot be grasped. Position measurement of the moving precision stage
A relative position with respect to the position before the movement is calculated based on the number of passing interference fringes observed during movement from one arbitrary position to another arbitrary position and a change (relative displacement amount) of the interference fringes.

Therefore, in such an optical interference measuring device,
During the movement of the precision stage, the measuring light from the movable reflecting mirror and the reference light from the fixed reflecting mirror had to be constantly reflected. If the measurement light or reference light is interrupted during the measurement, if the measurement light source stops momentarily, or an error occurs in reading interference fringes due to high-speed movement, the measurement in that process and processing based on the measurement continue. There was a problem that it became impossible.

[0007] The present invention has been made in view of such a problem, and even when the measurement light or the reference light is blocked or momentarily interrupted, the displacement data of the displacement interferometer becomes unknown. An object of the present invention is to provide a length measuring device that operates by returning itself to a stage without returning a stage to a reference point of a moving device.

[0008]

In order to achieve the above object, a length measuring device according to the present invention further comprises a position measuring means for measuring a position of a stage which is an object to be measured, in addition to an optical interference measuring means, An arithmetic unit for outputting the position of the object to be measured from the measurement results obtained from the optical interference measuring unit and the position measuring unit is provided. With this configuration, even when the observation light of the optical interferometer is blocked and the stage position (relative position) is unknown by the optical interferometer,
Since the position of the stage is measured by the position measuring means, the stage position can be determined from the position information and the phase information of the interference fringes of the optical interference measuring means.

The position measuring means includes a position detecting light source for emitting light at a predetermined projection angle with respect to a movable reflecting mirror used in the optical interference measuring means, and receives the light reflected by the moving reflecting mirror. It is preferable to comprise a light position detector for detecting the light receiving position at predetermined intervals, and a processing device for calculating the position of the stage which is the measured object from the light receiving position and the projection angle. With this configuration, the position of the movable reflecting mirror, that is, the position of the stage, can be easily measured because the light receiving position on the light receiving element varies depending on the position of the moving reflecting mirror. Note that the above-mentioned interval refers to a fixed interval determined by the resolution and arrangement of the light receiving elements of the optical position detector. The predetermined interval means that this interval is equal to or less than the measurement visual field (for example, one fringe) of the optical interferometer. Say.

When the observation light of the optical interferometer is interrupted and the stage position in the optical interferometer becomes unknown, the data of the unknown stage position is measured as described above. It is preferable to replace the data with the stage position determined from the obtained position information and the phase information of the optical interference measuring means. With this configuration, the function of the stage can be restored without returning the stage to the reference point of the moving device.

In the displacement interferometer, the amount of movement measured is defined by the amount of movement of the movable reflecting mirror relative to the fixed reflecting mirror. Therefore, it is preferable that the fixed reflecting mirror is provided at a portion (reference fixing portion) serving as a reference for position measurement of the measured object.
When measuring the absolute movement amount of the stage, it is preferable that the reference fixing portion is disposed near the optical branching element or the optical interferometer of each axis. With such a configuration, it is possible to achieve improvement in measurement accuracy and downsizing of the device.

On the other hand, when measuring the relative position between the stage and another component, it is preferable to dispose the fixed reflecting mirror on the other component. By arranging the fixed reflecting mirror in this way, it is possible to realize relative position measurement that meets the purpose with high accuracy. For example, when such a length measuring apparatus is applied to a semiconductor exposure apparatus, a movable reflecting mirror is provided on a moving stage of a mask or a wafer, and a fixed reflecting mirror is provided on a lens barrel of the projection lens, thereby providing a projection lens. The relative position between the optical axis and the wafer can be controlled with high accuracy.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an example of the overall configuration of a length measuring device 1 according to the present invention. The length measuring device 1 includes a light source 10 of an optical interference measuring unit and a beam splitter 11 for splitting light from the light source 10 into two.
A branch measuring block 100X, 100Y including an optical interferometer and a position measuring means for measuring displacement using the light split by the beam splitter 11, and a stage 8
1 and light receiving sections 40X and 40Y for measuring interference fringes by a part of the optical interference length measuring means.
And the movable reflecting mirrors 82X and 82Y obtained by the optical interferometer.
And a controller 50 which is a calculating means for calculating the position of the stage 81 from the displacement data of the stage 81 and the position data obtained by the position measuring means.

Further, position measuring means 30X, 3 disposed in the branch measuring blocks indicated by 100X, 100Y in FIG.
0Y (see FIG. 2) and the components of the controller 50 that calculates the amount of movement of the stage 81 from the bright and dark outputs of the interference fringes observed by the light receiving units 40X and 40Y and that processes the position data measured by the position measuring means. Has a feature.

First, a position measuring means 30X according to a first preferred embodiment of the length measuring device according to the present invention will be described with reference to FIG. The position measuring means 30X is a measuring means for measuring the position of the stage 81 in the X-axis direction, and is disposed in the branch measuring block 100X together with the branch block 20X in the optical interference measuring means.

The position measuring means 30Y (branch measuring block 100Y) for measuring the stage position in the Y-axis direction also has a position measuring means 30X (branch measuring block 1) in the X-axis direction.
00X), and the description is redundant. Therefore, only the position measuring means 30X in the X-axis direction (branch measurement block 100X) will be described here, and the description in the Y-axis direction will be omitted.

The laser beam having the P-polarized light component and the S-polarized light component emitted from the length measuring light source 10 and split by the beam splitter 11 is incident on the branch block 20X in the branch measurement block 100X.

The branch block 20X includes an optical branch element 21X,
It is composed of wave plates 22X and 23X and a fixed reflecting mirror 24X. The light splitting element 21X is a polarization beam splitter, and has a property of transmitting P-polarized light and reflecting S-polarized light. The wave plates 22X and 23X are quarter-wave plates and rotate the polarization plane by 90 degrees by passing twice. That is, S-polarized light is converted to P-polarized light, and P-polarized light is converted to S-polarized light.

The S-polarized light of the laser light incident on the branching block 20X is reflected by the light branching element 21X, passes through the wave plate 22X, and travels to the stage 81 as measurement light. The stage 81 is provided with a moving reflecting mirror 82X, and the measurement light is reflected by the moving reflecting mirror 82X, passes through the wave plate 22X again, and returns to the light splitting element 21X. Here, the laser light incident as S-polarized light has passed through the wave plate 22X twice in this reciprocating optical path, so that the laser light returning to the light branching element 21X is P-polarized. Therefore, this time, it passes through the light branching element 21X and enters the light receiving section 40X.

On the other hand, the P-polarized light of the laser light incident on the branching block 20X passes through the light branching element 21X,
After passing through the wave plate 23X, the fixed reflecting mirror 2 is used as reference light.
Head to 4X. This reference light is reflected by the fixed reflecting mirror 24X, passes through the wave plate 23X again, and returns to the light branching element 21X. Here, the light incident as P-polarized light passes through the wave plate 23X twice in this reciprocating optical path, and returns to the light branching element 21X as S-polarized light. Therefore, this time, the light is superimposed on the measurement light reflected by the light branching element 21X and reflected by the movable reflecting mirror 82X and enters the light receiving unit 40X.

The light receiving section 40X is composed of a polarizer and a light receiving element, and the light receiving element outputs observation data of an interference image between the measurement light and the reference light observed on the polarizer to the controller 50X. The controller 50X converts the input observation data into a moving distance (displacement amount). In this optical interferometer, the displacement can be detected by the homodyne method or the heterodyne method.

Next, the position measuring means in the X-axis direction will be described. The position detection light source 31X is configured such that the position detection light emitted from the position detection light source
1 is arranged so as to be incident on the movable reflecting mirror 82X provided at 1 at a predetermined incident angle θ that satisfies the required measurement range and measurement accuracy. The position detection light reflected by the movable reflecting mirror 82X is received by a light position detector 33X that detects the position of the light such as a CCD light receiving element, for example, at each interval (for example, one pixel) corresponding to the light receiving position. Every)
The position output is output to the processing device 35.

For example, as shown in FIG. 2, the incident angle of the position detection light to the movable reflecting mirror 82X is θ, the distance on a perpendicular line lowered from the incident position of the reflecting mirror 82X is L, and this perpendicular line and position detection are performed. Assuming that the horizontal distance from the light source is a, a = Ltan θ, and the horizontal distance between the position detection light source 31X and the detection position of the light position detector 33X can be obtained by 2a. That is, the position of the stage 81 can be calculated from the relational expression based on the incident angle θ and the observation position of the position detection light measured by the optical position detector 33X.

As is apparent from the above equation, the change in the observation position by the position detector 33X is observed as a larger position change as the incident angle θ increases. Therefore, the predetermined incident angle θ is determined based on the resolution of the optical position detector with respect to the positional accuracy of the desired detection position, the measurement range, the size of the movable reflecting mirror to be used, and the like. The resolution of the optical position detector can be appropriately increased by, for example, disposing the light receiving element in an inclined manner, or configuring an optical lever using several reflecting mirrors.

In this embodiment, an example will be described in which the position accuracy detected by the position detecting means is smaller than the position change corresponding to one fringe of the interference fringe observed by the light receiving section 40X.

The relational expression determined by the processing device 35X is stored in advance, and the position of the stage 81 in the X-axis direction is calculated from the observation position of the position detection light measured by the optical position detector 33X. Then, it outputs to the controller 50.

Further, the Y-axis of the length measuring device according to the present invention includes:
A branch measurement block 100 similar to the X axis described so far.
The controller 50 includes a stage 8
1, the calculation data of the Y-axis direction position is output similarly to the X-axis.

In the length measuring device according to the present invention configured as described above, for example, the measuring light or the reference light of the optical interference measuring means is blocked, or the measuring light source stops instantaneously.
Even when the stage position based on the movement distance measurement by the optical interference measurement unit is unknown, the controller 50 receives the position data of the stage 81 from the position detection units 30X and 30Y. The position data is transmitted to the light receiving units 40X, 4
Since it has a position accuracy of 1 fringe or less observed at 0Y, when the measurement light or the reference light of the optical interferometer returns and the interference fringes are observed again, the controller 50 The stage position at the time of return can be determined from the position data by the position detecting means and the phase data (detailed position data within one fringe) observed by the optical interference length measuring means.

When the stage position is determined in this way, the controller 50 is set to replace the unknown stage position data with the stage position data determined in this way. Therefore, the length measuring device according to the present invention is capable of self-returning at the measurement position of the optical interference measuring unit even when the measurement position of the optical interference measuring unit becomes unknown due to interruption of the measuring light or the reference light of the optical interference unit. .

Further, by configuring the length measuring device in this way, even if, for example, the position detecting light is interrupted or the position detecting light source is momentarily stopped, the stage position can be changed by the optical interference measuring means. It is not necessary to stop the length measuring device when the measurement is being performed. That is, according to such position detecting means 30X and 30Y, even if the position detecting light is interrupted, the stage position can be measured again with the return of the position detecting light, and the optical interference measuring means can be used. This is because the position does not become unknown.

In the first embodiment described above, an example has been described in which the position measuring light is directly applied to the movable reflecting mirror. However, as shown in FIG. 3, for example, a partial reflecting mirror 32X such as a half mirror or a prism is used. This can also be achieved by inputting the light to the movable reflecting mirror 82X as an optical path having the incident angle θ and substantially the same optical path as the measurement light.

With this configuration, it is possible to reduce the size of the moving reflector with higher precision than in the above-described embodiment, and it is also possible to reduce the size of the moving reflector by, for example, the flatness of the moving reflector or the difference between two measurement positions. Errors can be suppressed.

When the measurement light and the position detection light of the optical interference measuring means are projected on substantially the same optical path, each light becomes a disturbance factor of another measuring system, and the optical interference measuring means is disturbed. It is preferable to use appropriate means so that the position detector and the position detector do not cause erroneous detection. As a preferable means for this purpose, for example, a laser light source having a different oscillation wavelength is used for the length measuring light source and the position detecting light source of the optical interference measuring means, and a wavelength selective optical element is used for the partial reflecting mirror. , A detector that does not detect the wavelength of each other, or a method in which a narrow-band filter or the like is appropriately inserted and used.

For example, when the oscillation wavelength of the light source used is close, the polarization plane of the position detection light and the polarization plane of the measurement light are 9
A method in which a light source of the position detection light is disposed so as to have an angle of 0 degrees and a polarization beam splitter is used instead of the partial reflecting mirror 32X is also applicable.

Next, a second preferred embodiment of the length measuring device according to the present invention will be described with reference to FIG. In this embodiment, the configuration of the branch measurement block 110X (110Y) is the same as that of the branch measurement block 1 in the first embodiment.
It is different from the configuration of 00X (100Y).

That is, in the first embodiment, the reference light of the optical interferometer is reflected by the fixed reflecting mirror 24X in the branching measurement block 100X, is superimposed on the measuring light by the light branching element 21X, and is superposed on the light receiving section 40X. The moving distance observed by the optical interferometer in this embodiment is a relative displacement between the fixed reflecting mirror 24X and the moving reflecting mirror 82X. However, since the fixed reflecting mirror 24 is disposed on the fixed portion of the optical interference length measuring means, the observed relative movement amount is regarded as the movement amount of the stage 81.

In the second embodiment according to the present invention,
The reference reflecting mirror 182X is disposed on a reference portion 181 serving as a reference for positioning the stage 81. The optical interferometer measures the relative displacement between the reference reflecting mirror 182X and the movable reflecting mirror 82X, that is, the reference portion 181 and the stage. The length of the relative movement 81 in the X-axis direction is measured. The position detecting means 130X is configured in the same manner as in the first embodiment and includes a stage position detecting system for detecting the position of the stage 81 in the X-axis direction and a reference position detecting system for detecting the position of the reference section in the X-axis direction. Have been.

The laser beam having the P-polarized component and the S-polarized component emitted from the length measuring light source 10 and split by the beam splitter 11 is incident on the branch block 120X in the branch measurement block 110X.

The branch block 120X includes the optical branch element 21
X, wavelength plates 22X and 23X, and a folding mirror 124X. The S-polarized light of the laser light incident on the branch block 120X is reflected by the light branching element 21X, passes through the wave plate 22X, is reflected toward the stage 81 as measurement light by the moving reflecting mirror 82X, and is again reflected by the wave plate. After passing through 22X, the light returns to the optical branching element 21X. Where S
The laser beam incident as polarized light is transmitted through the optical path of the
Since the laser beam has passed through X twice, the laser beam returning to the light branching element 21X is P-polarized light. Therefore, this time the optical branching element 2
The light passes through 1X and enters the light receiving unit 40X.

On the other hand, the P-polarized light of the laser light incident on the branch block 120X passes through the light branching element 21X and is turned back by the turning mirror 124X in parallel with the measurement light.
The light passes through the wave plate 23X and travels toward the reference reflecting mirror 182X as reference light. Then, the light is reflected by the reference reflecting mirror 182X, passes through the wave plate 23X again, and returns to the light splitting element 21X via the turning mirror. Here, the light incident as P-polarized light passes through the wave plate 23X twice in this reciprocating optical path, and returns to the light branching element 21X as S-polarized light. Therefore, this time, the light is superimposed on the measurement light reflected by the light branching element 21X and reflected by the movable reflecting mirror 82X and enters the light receiving unit 40X.

The controller 50X converts the input observation data from the light receiving unit 40X into a moving distance (amount of displacement).
Convert to The amount of displacement observed in this way is
This is a relative displacement amount between the stage 81 on which the movable reflecting mirror 82X is disposed and the reference section 181 on which the reference reflecting mirror 182X is disposed.

On the other hand, the position detecting means 130X is the position detecting means 30X shown in FIG.
In addition, a reference position detecting system for detecting the position of the reference reflecting mirror using the same method is added. That is,
The position detection light emitted from the position detection light source 31X is reflected by partial reflection mirrors 132X and 32X such as half mirrors so as to have substantially the same optical path as the reference light and the measurement light, respectively.
These return lights are made incident on the optical position detector 133X.

The light position detector 133X detects these two light positions and outputs them to the processor 135X. Processing unit 13
5X calculates the position of the stage 81 in the X-axis direction and the position of the reference unit 181 in the X-axis direction from a predetermined relational expression, and outputs these values to the controller 150.

Data from the similarly configured branch measurement block 110Y is also input to the controller 150, from which the controller 150 has data on the position of the stage 81, the position of the reference portion, and the relative positions of both. ing.

In the length measuring device according to the present invention configured as described above, for example, the measuring light or the reference light of the optical interferometer is interrupted, or a momentary stop of the measuring light source occurs.
Even when the stage position with respect to the reference unit 181 by the optical interference measurement unit becomes unknown, the position data of the stage 81 and the position data of the reference unit 181 are input to the controller 150 from the position detection units 130X and 130Y, and the calculation is performed from these. Data of the relative position to be set.

Since the position data and the relative position data have a position accuracy of one fringe or less of the light receiving sections 40X and 40Y, the measuring light or the reference light of the optical interferometer returns and the interference occurs. When the fringe is observed again, the controller 150 returns the stage 81 at the time of restoration from the position data by the position detecting means and the phase data (detailed position data within one fringe) observed by the optical interference measuring means. And the relative position (and also the absolute position) of the reference unit 181 can be determined.

When the relative position between the stage 81 and the reference section 181 is determined in this way, the controller 50 replaces the unknown relative position data with the relative position data thus determined. Is set. Therefore, the length measuring device according to the present invention, even when the measurement position of the optical interferometer is unknown due to interruption of the measurement light or reference light of the optical interferometer,
Self-return is possible at that position.

Further, by configuring the length measuring device in this manner, even if, for example, the position detection light is interrupted or the position detection light source is momentarily stopped, the stage position and the stage position can be determined by the optical interference measurement unit. When the reference position is being measured, there is no need to stop the length measuring device. That is, according to such position detection means 130X and 130Y, even if the position detection light is interrupted, the stage position and the reference position can be measured again with the return of the position detection light, and the optical interferometer can be used. This is because the position does not become unknown unlike the means.

In this embodiment, the position detecting means 130X
Has been described using a pair of position detection light sources 31X and a light position detector 133X, but the present invention is not limited to such a condition. For example, two position detection It is also possible to use a pair of position detection light sources and an optical position detector to individually detect the position of the stage and the reference unit.

Further, as a specific embodiment of the present apparatus, for example, when the present invention is applied to a semiconductor exposure apparatus, the stage is a moving stage of a wafer, and a lens barrel of a projection objective is selected and referred to in the reference section 181. Reflecting mirror (fixed reflecting mirror 1
82) is preferably provided. With this configuration, it is possible to maintain and control the relative position between the optical axis of the projection objective lens and the object to be exposed, which is required as a movement measuring device or a positioning device of the exposure device, with high accuracy. Become.

Next, a third preferred embodiment of the length measuring device according to the present invention will be described with reference to FIG. In the present embodiment, as an example, an example is shown in which the measurement axis in the X-axis direction of the stage 81 in the first or second embodiment is further added to two axes, and the description is given of the first embodiment. An example will be described in which the number of measurement axes is two.

In order to increase the number of measurement axes, the embodiment shown in FIG. 5 shows an example in which the light transmitted through the beam splitter 11 is further divided by the beam splitter 12. This splitting method may be a method of splitting the light reflected by the beam splitter 11. Further, for example, when increasing the number of measurement axes on both the X-axis and the Y-axis, it is preferable to further split the beam by inserting a beam splitter into both the light transmitted through the beam splitter 11 and the reflected light.

As shown in the figure, by making the light incident on the movable reflecting mirror 82X provided on the stage 81 into two horizontal axes, the rotation of the stage 81 around the Z axis can be detected. Further, when the light incident on the movable reflecting mirror 82X is configured as two axes in the vertical direction, the rotation of the stage 81 around the Y axis can be detected. When the light incident on the movable reflecting mirror is provided in both the horizontal and vertical directions and a measurement axis in the vertical direction with respect to the Y-axis direction is added, the rotation amounts of all the axial directions of the stage 81 are detected. can do.

With such a configuration, it is possible to provide a highly accurate length measuring device capable of self-returning in all axial directions even when the length measuring light and the reference light of the optical interference length measuring means are cut off. .

Next, a fourth preferred embodiment of the length measuring device according to the present invention will be described. In this embodiment, the stage for measuring the position by the length measuring device described so far is provided so that it can be appropriately replaced with another stage according to the progress of the length measurement and the processing. This will be described below with reference to FIG.

The length measuring device shown in FIG. 6 is, for example, a length measuring device having any of the functions of the first to fourth embodiments described above, and a plurality of stages having a movable reflecting mirror are prepared. These are sequentially loaded into a length measuring device and unloaded after a series of measurement or processing is completed.

For example, in FIG. 6, a stage 81A as a first stage includes movable reflecting mirrors 82AX and Y in the X-axis direction.
The length measuring device is provided with, for example, branch measuring blocks 100X and 100Y shown in FIG. When the measurement or the processing of the stage 81A is completed, the stage 81A is unloaded, and the stage 81B as the second stage is loaded instead.

At this time, since there is no return light of the measuring light in the length measuring device, a state occurs in which subsequent length measuring cannot be performed. On the other hand, the newly loaded stage 81B includes a movable reflecting mirror 82BX in the X-axis direction and a movable reflecting mirror 8BX in the Y-axis direction.
2BY is provided, and the measurement light and the position detection light are detected when set in the length measuring device. Here, the value detected by the position detecting means returns to the measured value again with a measuring accuracy of one fringe or less of the optical interference measuring means.

Here, the controller 151 determines the value of the stage 81B from the position data of the stage 81B outputted from the position detecting means and the more detailed phase data of one fringe or less outputted from the optical interference measuring means. .

When the position of the stage 81B is determined in this way, the controller 151 sets the second stage position data that cannot be measured to be replaced with the stage position data thus determined. Have been. Therefore, the length measuring device according to the present invention can be used even when the measurement of the optical interferometer becomes impossible as a result of the interruption of the measurement light or the reference light of the optical interferometer in the step of exchanging a plurality of stages. Length measurement or processing can be performed continuously without returning to the origin.

In a conventional semiconductor exposure apparatus, for example, after positioning and exposing a wafer on a stage, the exposed wafer is taken out, and the exposure apparatus performs exposure while the next wafer is positioned on the stage. Could not do. Further, after positioning on the stage, the stage is again moved to the reference position of the optical interferometer, and the exposure cannot be positioned unless the reference position data of the optical interferometer is input.

However, according to the above embodiment,
The exposure apparatus positions the wafer with respect to the first stage, the wafer can be positioned on the second stage during the exposure, and the second stage is simultaneously unloaded and the second stage is unloaded. Exposure positioning operation can be performed.

[0063]

As described above, the length measuring apparatus according to the present invention is provided with the position measuring means for measuring the position of the stage to be measured in addition to the optical interference measuring means. For this reason, even when the optical path of the optical interferometer is interrupted and the stage position (relative position) is unknown by the optical interferometer, the position of the stage is measured by the position measuring unit. The stage position can be determined from the information and the phase information of the optical interferometer.

The position measuring means comprises: a position detecting light source for emitting light at a predetermined projection angle with respect to a moving reflecting mirror used in the optical interference measuring means; and a light reflected by the moving reflecting mirror. The optical encoder includes a light position detector that receives light and detects the light receiving position at predetermined intervals, and a processing device that calculates the position of the stage, which is the object to be measured, from the light receiving position and the projection angle. Compared with the case where a magnescale or the like is used, the above-described length measuring device can be easily configured without requiring a special configuration separately for the measured object and without complicating the device.

Further, by using an optical element such as a half mirror so that the light from the position detecting light source and the measuring light have substantially the same optical path, the area of the movable reflecting mirror can be effectively utilized.

The fixed reflecting mirror for reference light of the optical interference measuring means is
Depending on the configuration of the device, it can be provided in the reference fixing part of the length measuring device or the stage moving device. Therefore, even when the positional accuracy of the relative positional relationship is required, this can be easily achieved.

When the measuring light or the reference light of the length measuring device is interrupted and the stage position becomes unknown by the optical interference measuring means, the positional information measured by the above-described position measuring means and the optical interference measuring length are used. It is desirable to replace the stage position data determined from the phase information of the means with the unknown position data.

With this configuration, it is not necessary to return the stage to the origin of the length measuring device, input the origin data again, and move the stage again to the vicinity of the unknown position. Can be restored. Therefore, the processing in the same process can be continued without deteriorating the productivity of the apparatus, so that the defect rate can be reduced and the yield can be improved.

Further, such a length measuring device can be constituted by providing a plurality of stages. Therefore, the operation rate of the device can be dramatically increased as compared with the conventional length measuring device.

The above length measuring device is preferably used as a length measuring device or a positioning device for an exposure device. A highly productive exposure apparatus that satisfies the positional accuracy required by the exposure apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a length measuring device according to the present invention.

FIG. 2 is a configuration diagram showing an example of a branch length measurement block in the first embodiment of the length measurement device according to the present invention.

FIG. 3 is a configuration diagram showing another example of the branch length measurement block in the first embodiment of the length measurement device according to the present invention.

FIG. 4 is a configuration diagram showing a configuration of a branch length measurement block in a second embodiment of the length measurement device according to the present invention.

FIG. 5 is a configuration diagram showing a third embodiment of the length measuring device according to the present invention.

FIG. 6 is a configuration diagram showing a fourth embodiment of the length measuring device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Length measuring device 10 Light source for length measurement (identical light source) 20X, 20Y Branch block (reference fixed part) 21X, 21Y Optical branching element 24X, 24Y Fixed reflecting mirror 30X (30Y) Position measuring means 31X (31Y) Position detecting light source 32X (32Y) Optical element (partial reflection mirror) 33X (33Y) Optical position detector 35X (35Y) Processing device 50X (50Y) Operation means (controller) 81 Object to be measured (stage) 82X, 82Y Moving reflection mirror 100X, 100Y , 110X, 110Y Branch measurement block 130X (130Y) Position measurement means 132X (132Y) Optical element (partial reflection mirror) 133X (133Y) Optical position detector 135X (135Y) Processing unit 150X (150Y) Operation means (controller) 181 Reference Fixed part (reference part) 182X, 182Y Fixed reflector (reference reflector)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA03 AA06 AA09 CC17 DD11 DD19 EE05 FF09 FF49 FF55 GG04 GG23 HH04 HH08 JJ05 JJ16 JJ18 JJ25 LL12 LL36 LL37 PP12 PP22 QQ28 QQ51

Claims (5)

[Claims] 1. A fixed reflecting mirror and a movable reflecting mirror provided on an object to be measured, wherein light emitted from the same light source and reflected by the fixed reflecting mirror and light reflected by the moving reflecting mirror are respectively provided. Optical interference measuring means for causing interference and measuring the displacement of the position of the object to be measured, position measuring means for measuring the position of the object to be measured, measurement results obtained from the optical interference measuring means and the position measurement And a calculating means for outputting the position of the object to be measured from a measurement result obtained from the means. 2. The position measuring means comprises: a position detecting light source for emitting light at a predetermined angle to the movable reflecting mirror; and a light for detecting a position of the light reflected by the moving reflecting mirror at predetermined intervals. 2. The apparatus according to claim 1, further comprising: a position detector; and a processing device that calculates a position of the object to be measured from a signal of the optical position detector.
Length measuring device described in 3. The measuring device according to claim 2, wherein said position measuring means has an optical element for guiding light emitted from said position detecting light source to substantially the same optical path as said measuring light. Long equipment. 4. The length measuring apparatus according to claim 1, wherein the fixed reflecting mirror is provided at a portion serving as a reference for position measurement of the measured object. 5. An exposure apparatus, wherein the length measuring apparatus according to claim 1 is used as a wafer or mask positioning apparatus in a projection exposure apparatus.