JPH0358528B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical device having a means for switching the position of an optical element, and more particularly to an optical device that adjusts the position of an optical element by closed-loop control.

[Conventional technology]

As an example of this type of optical apparatus, FIG. 1 shows an example of an optical system for observing masks and wafers in a semiconductor printing apparatus. In FIG. 1, when trying to align the mask 1 and the wafer 2, the laser beam emitted from the laser light source 11 is passed through the scanning polygon mirror 10, the half mirror 9, the objective lens 8, and the mirror 5. and enters mask 1. This light passes through the projection lens 3, is reflected on the wafer 2, passes through the mirror 5, objective lens 8, and half mirror 9 again, and enters the photoelectric detector 12. wafer 2
There is also an alignment mark on the optical path of the laser beam L on the mask 1. The signal from this mark is detected by the photoelectric detector 12, the amount of deviation between the wafer 2 and the mask 1 is determined, and the moving stage 13 is moved by a driver (not shown) to align the mask 1 and the wafer 2. It is. Now, when the wafer 1 and the mask 2 are aligned in this manner, the shutter (not shown) of the exposure illumination device 4 is opened and exposure is performed. However, if the mirror 5 is at position a in FIG. 1 at this time, a shadow of the mirror 5 will be formed on the mask 1, resulting in unprinted areas or uneven illuminance on the mask 1. Therefore, before the exposure tip, move the mirror 5 to a position b where the printing light does not hit.
I need to move to. When the printing is completed, the mirror 5 is returned to position a for alignment for the next printing. The reproducibility of this position a is important; even a slight deviation in the inclination of the mirror 5 changes the incident path of the laser beam L, causing an error in measuring the amount of deviation between the mask 1 and the wafer 2.

Conventionally, such driving of the mirror 5 has been performed by position detection using a photo switch (not shown) or open loop control using a pulse motor 7 or the like.

[Problem to be solved by the invention]

However, this type of control has problems such as mechanical stability against vibrations and rattles, stability over time, photo switch accuracy, and the need for extremely precise assembly adjustments. .

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical device that eliminates the above-mentioned problems, improves mirror positioning accuracy, and allows stable position adjustment at all times.

[Means to solve the problem]

To achieve this objective, the optical device of the invention comprises a light source (laser light source 11) that generates a light beam for illuminating an object, and a light path between said object and said light source. a mirror 5 that is arranged and reflects the light beam from the light source and the reflected light from the object so as to deflect each of them;
A drive source (pulse motor 7, piezo element 30) for moving the mirror and photoelectric detection of a part of the reflected light from the object taken out from the optical path depending on the position of the object. a first photoelectric detector 12 that generates a signal, and a light-receiving surface on which another part of the reflected light from the object taken out from the optical path is incident; a second photoelectric detector 15 that generates a signal according to the position of a light spot formed on the light receiving surface by a second photoelectric detector 15; The mirror includes a control circuit (arithmetic circuit 16) that controls position adjustment of the mirror by the drive source based on a signal from the second photoelectric detector.

More preferably, the drive source moves the mirror between a first position and a second position, and the mirror irradiates the object with the light beam when it is in the second position. When the drive source moves the mirror from the first position to the second position, the control circuit moves the mirror between the first position and the second position.
After causing the drive source to move the mirror in an open loop to a predetermined position between the positions,
The control circuit controls the position adjustment of the mirror by the drive source based on the output signal from the second photoelectric detector, and further, the control circuit controls the position adjustment of the mirror by the drive source based on the output signal from the second photoelectric detector, and furthermore, the control circuit controls the position adjustment of the mirror by controlling the position adjustment of the mirror by the drive source. After the light is incident, the position adjustment of the mirror by the drive source is controlled based on the signal from the second photoelectric detector.

〔Example〕

The present invention will be explained below based on the illustrated embodiments.

FIG. 2 shows an embodiment of the present invention, in which one more half mirror 14 is added on the optical path of the laser beam L in FIG. 1. The light that is reflected by the mirror 5, passes through the mask 1, hits the wafer 2 by the projection lens 3, is reflected onto the wafer 2 surface, and then returns to the photoelectric detector 12 via the mirror 5, objective lens 8, and half mirror 9. . At this time, part of the optical path is changed by a half mirror 14 on the way and enters a newly created sensor 15. The sensor 15 is a split type sensor as shown in Fig. 3, and has two light receiving surfaces c and d.
and three electrodes e, f, and g. Here, electrode f is a common bias electrode, and an electric signal proportional to the amount of light incident on the light receiving surface is transmitted from electrode e.
Electric signals proportional to the amount of light incident on the light-receiving surface d from the electrode g can be extracted independently from each other. These electrodes e, f, and g are connected to an amplifier 18, and the amplifier 18 amplifies the signals of the electrodes e and g with equal gains, and sends the amplified signals to the arithmetic circuit 16 as signals h and i, respectively.

If mirror 5 is in the correct position, sensor 15
The reflected light R from the mirror 5 hits the central position as shown in FIG. At this time, the amounts of light received by the light receiving surfaces c and d are equal, and the outputs h and i of the amplifier 18 are equal.
are also equal in size. Next, if the mirror 5 deviates by a certain value from its normal position, the reflected light R from the mirror 5 that hits the light receiving surface of the sensor 15 will also deviate from the center as shown in FIG. Move to a different position. At this time, the outputs h and i of the amplifier 18 are no longer equal, and the difference corresponds to the amount of deviation of the mirror 5 from its normal position. The arithmetic circuit 16 calculates the mirror 5 from these two signals h and i.
Find the position of. Then, the pulse motor 7 is driven via the driver 17 so that the magnitudes of the signals h and i become equal, that is, so that the reflected light R is in a light receiving state as shown in FIG. That is, closed loop control is performed. Note that the pulse motor 7 meshes with the rotating shaft 6 of the mirror 5, and the rotation of the pulse motor 7 changes the angle of the mirror 5.

Here, the mirror 5 is moved from position b to position a in FIG.
We will explain the case of moving to . While the mirror 5 moves from position b to position a, the arithmetic circuit 16 coarsely moves the pulse motor 7 by a predetermined number of pulses via the driver 17 in an open loop. Then, by this driving, the mirror 5 is moved within a predetermined range near the position a, that is, within a range where the reflected light R from the mirror 5 can be detected by the sensor 15. after that,
The signals h and i from the sensor 15 are checked, and precise position control as shown in FIG. 3 is performed to stabilize the mirror 5 at the normal position a. In this case, instead of applying a predetermined pulse to the pulse motor 7, the sensor 15 itself detects that the reflected light R from the mirror 5 is within the detection range of the sensor 15. It is also possible to stop the pulses applied to the pulse motor 7. Furthermore, a sensor for detecting the approximate position of the mirror 5 may be provided separately. That is, it is only necessary to coarsely move the mirror 5 in an open loop to a position where the mirror 5 can be precisely controlled in a closed loop using the sensor 15.

In this embodiment, the position b of the mirror 5 does not require particular precision, so it is sufficient to detect the position b using a general photo switch (not shown) or the like. Even if both a and b require precision, it goes without saying that they can be similarly detected and controlled using the sensor 15 or the like described above.

In the above embodiment, the means for moving the mirror 5 is not limited to a pulse motor, but any means capable of controlling the rotation angle and position, such as a CD motor with an encoder, may be used.

Further, the sensor is not limited to the two-split type sensor 20 as shown in FIG. 3, but if a four-split type sensor 20 as shown in FIG. 4 is used, control in one more axial direction can be performed. Furthermore, sensors are not limited to split types;
A one-dimensional or two-dimensional position sensor, image sensor, etc. may also be used.

Furthermore, although FIG. 2 shows the case where the pulse motor 7 is pulse-driven as a means for positioning the mirror 5, a piezo element 30 can also be used as shown in FIG. That is, in the figure, the movable part 32 is minutely moved in the direction of the arrow by driving the stacked piezo elements 30 via the piezo drive circuit 31 based on the signal from the arithmetic circuit 16 of FIG. be. Here, the movable part 32 comes into contact with the mirror 5, acts as a stopper for positioning the mirror 5, and enables minute and accurate position control.

Further, in FIG. 2, part of the laser light for aligning the mask 1 and the wafer 2 is used as a light source, but a separate light source may be newly provided and used.

Although the above-described embodiments have been described with respect to a semiconductor printing apparatus, the present invention can be applied to any optical apparatus having a means for switching the position of an optical element.

〔Effect of the invention〕

As described above, according to the present invention, the mirror is arranged in relation to the optical path between the object and the light source and reflects the light beam from the light source and the reflected light from the object so as to deflect each of them. It becomes possible to accurately adjust the position of the optical device, and it becomes possible to provide an optical device that is stable over time. Further, according to the present invention, there is no need for particularly precise adjustment during assembly and maintenance of the device.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an optical system for observing masks and wafers in a conventional semiconductor printing apparatus, Fig. 2 is a schematic diagram showing an embodiment of the present invention, and Fig. 3 is a split-type sensor used in the present invention. FIG. 3 is a perspective view showing an example of the split-type sensor; FIG. 4 is a plan view of another example of the split-type sensor; FIG. 5 is a position adjustment means according to the present invention. It is a schematic diagram showing another example of. 5... Mirror, 6... Rotating shaft, 7... Pulse motor, 11... Laser light source, 14... Half mirror, 15... Split type sensor, 16... Arithmetic circuit, 17... Driver, 18... ...Amplifier, 20...
...4-split sensor, 30...piezo element, 3
1...Piezo drive circuit, 32...Movable part.

Claims (1)

[Scope of Claims] 1. A light source that generates a light beam for illuminating a target object, and a light source that is arranged to be associated with an optical path between the target object and the light source, and a light source that generates a light beam from the light source and the target object. a mirror that deflects each reflected light from the object; a driving source for moving the mirror; and photoelectric detection of a portion of the reflected light from the object taken out from within the optical path. a first photoelectric detector that generates a signal according to the position of the object; a light receiving surface on which another part of the reflected light from the object taken out from the optical path is incident; a second photoelectric detector that generates a signal according to the position of a light spot formed on the light receiving surface by another part of the light; An optical device comprising: a control circuit that controls position adjustment of the mirror by the drive source based on a signal from the second photoelectric detector so that the mirror is irradiated with the following relationship. 2. The drive source moves the mirror between a first position and a second position, the mirror irradiates the object with the light beam when it is in the second position, and the drive source moves the mirror between a first position and a second position. When moving the mirror from the first position to the second position, the control circuit causes the drive source to move the mirror in an open loop until it reaches a predetermined position between the first position and the second position. 2. The optical device according to claim 1, further comprising controlling the position adjustment of the mirror by the drive source based on the output signal from the second photoelectric detector. 3. The control circuit controls position adjustment of the mirror by the drive source based on a signal from the second photoelectric detector after another part of the reflected light is incident on the light receiving surface. An optical device according to claim 2 characterized by: