JPS6042887B2 - alignment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an alignment device that aligns two objects using a diffraction grating.

BACKGROUND ART Recently, it is becoming practical to align two objects with high precision using a diffraction grating.

An example of this is shown in FIG. That is, while the diffraction grating 4 of the first object 3 placed on the table 2 via the vibrator 1 is provided, the second object 5 is supported on the support 6 above the first object 3. Install in parallel.
This second object 5 is provided with a second diffraction grating 7. Further, above the second object 5, a laser oscillator 8 is disposed so that the laser beam L, which is coherent light, is perpendicularly incident on the second diffraction grating 7, and the first and second diffraction gratings Detectors 9, 9 are arranged to receive the +nth order and -nth order diffracted lights by the gratings 4, 7. These data takers 9, 9 are connected to a drive source 1 that drives and controls the table 2 via a control device 10 that includes a differential amplifier, a smoothing circuit, an indicator, etc.
1 is electrically connected to. Then, the vibrator 1
The first object 3 is vibrated in the vertical direction, and the control device 10 compares the intensities of the n-th order diffracted lights detected by the pair of datatakers 9, 9, until the intensities match, that is, the pair of diffraction gratings By driving the table 2 by the drive source 11 until the striped patterns 4 and 7 match, the pair of objects 3 and 5 are aligned with high precision.

By the way, in such alignment, the diffraction grating 4
, 7 from a direction deviated by Δθ from the right angle, the alignment error ξ between the pair of objects 3 and 5 becomes ε■dsinΔθ.

Here, d is the interval between the pair of diffraction gratings 4 and 7. Therefore, the laser beam L must be incident on the diffraction gratings 4 and 7 at right angles, but in laser oscillators currently in practical use, the emission direction of the laser beam changes over time by approximately 10-' radians. Therefore, the alignment accuracy of the pair of objects 3, 5 depends on the fluctuation of the incident angle of the laser beam L and the first diffraction gratings 4, 7 provided on the pair of objects 3, 5.
A limit naturally arises depending on the interval. This invention was made based on the above circumstances, and its purpose is to insert a jig between a pair of objects, which is provided with a diffraction grating that faces the diffraction gratings provided on these objects. Accordingly, it is an object of the present invention to provide an alignment device that can reduce alignment errors caused by variations in the incident angle of laser light and accurately align a pair of objects. Hereinafter, one embodiment of the present invention will be described based on FIG. 2.

In the figure, 21 is the first object. This first object 21 is
Holder 2 attached to the rotating shaft 22a of the first drive source 22
It is held horizontally by 3. The first object 21
A second object 26 is held horizontally above the holder 25 attached to the rotating shaft 24a of the second drive source 24. Opposing surfaces of the first and second objects 21 and 26,
That is, first diffraction gratings 27 and 28 are provided on the upper surface of the first object 21 and the second object 26, respectively. Moreover, between a pair of objects 21 and 26 that are spaced apart and facing each other in parallel,
A flat plate-shaped jig 29 having a predetermined thickness is inserted horizontally. A vibrator 30 is provided on the lower surface of one end of the jig 29, and the vibrator 30 causes the jig 29 to vibrate in the vertical direction. On the upper and lower surfaces of this jig 29,
Second diffraction gratings 31 and 32 are provided opposite to first diffraction gratings 27 and 28 provided on the pair of objects 21 and 26, respectively. Above the second object 26 are a pair of opposing first and second diffraction gratings 27, 31 and 28, 3.
The first laser beam L is incident on each of the laser beams L from the vertical direction.
, second laser oscillators 33 and 34 are provided.

The angles are equiangular with respect to the optical axis of the laser beam L output from each laser oscillator 33, 34. The diffracted light reflected by the diffraction gratings 27, 31 and 28, 32 in the +n-th order direction and the -n-th order direction is received by each pair of arranged detakers 35, 35 and 36, 36, respectively. Reception by these data takers 35, 35 and 36, 36!
The optical signal is inputted to differential amplifiers 38, 38 after passing through a preamplifier 37, and the difference thereof is calculated. After unnecessary frequency components are removed from this differential output signal by filter circuits 39, 39, the signal is smoothed by sequentially passing through rectifier circuits 40, 40, smoothing circuits 41, 41, and then the indicator 42, It is displayed at 42. Further, the smoothed signal is fed back to the first and second drive sources 22 and 24 as alignment signals for the first and second objects 21 and 26. Next, the operation of the above configuration will be explained.

First, while operating the vibrator 30 and vibrating the jig 29 in the vertical direction, the laser beam L is emitted from the first laser oscillator 33.
is made incident on the first diffraction grating 27 provided on the upper surface of the opposing first object 21 and the second diffraction grating 31 provided on the lower surface of the jig 29. At this time, if the position of the first diffraction grating 27 of the first object 21 with respect to the second diffraction grating 31 of the jig 29, that is, the striped pattern of each diffraction grating 27, 31, matches, the pair of data takers 35, 35
The intensities of the +n-order and -n-order diffracted lights received by the detector are equal, and this fact is displayed on the display 42. However, if there is a misalignment between the pair of diffraction gratings 27 and 31, the intensity of the diffracted light received by the pair of daytakers 35 and 35 will differ depending on the amount of misalignment. Then, the difference is calculated by the differential amplifier 38, which is displayed on the display 42, and a signal corresponding to the difference is output from the smoothing circuit 41 to the first drive source 22. The first drive source 22 is activated to drive the first object 21 in the direction of the arrow in the figure (referred to as the X direction). The first drive source 22 drives the first object 21, and the first drive source 22 drives the first object 21.
If the striped patterns of the second diffraction gratings 27 and 31 match, the intensities of the diffracted lights received by the pair of datatakers 35 and 35 become equal, so the first drive source 22 stops. That is, the first object 21 is aligned with the jig 29 at a predetermined position. In this way, the first object 2
1, the second object 26, which is the same as the first object 21, is aligned with the jig 29 by activating the second laser oscillator 34. The first object 21 and the second object 26 are aligned via 29. By the way, in such alignment, since the emission direction of the laser beam L output from the laser oscillators 33 and 34 changes with time, when the angle of incidence on the diffraction grating deviates from the vertical by Δθ, the 1. As described above, an error of ε=DsjnΔθ occurs in the positioning accuracy of the second objects 21 and 26.

Here, since d is the distance between the upper and lower surfaces of the first and second objects 21 and 26, the first and second objects 21 and 26
The greater the distance between them, the lower the alignment accuracy will be. However, in this invention, a jig 29 is inserted between the pair of objects 21 and 26, and the upper and lower surfaces of the jig 29 are connected to the upper surface of the first object 21 and the second object.
The first diffraction grating 27, 2 provided on the lower surface of the object 26
8, and second diffraction gratings 31 and 32 facing each other are provided.

Therefore, the first and second objects 21,
The error caused by the variation in the emission direction of the laser beam L in the alignment accuracy of 26 is E1=ΔDsinΔθ.
Here, Δd is the distance between the upper and lower surfaces of the jig 29 and the upper and lower surfaces of the opposing first and second objects 21 and 26, respectively.
This Δd is smaller than the distance d between the pair of objects 21, 26, and can be made extremely small by increasing the thickness of the jig 29, so it is caused by fluctuations in the emission direction of the laser beam L. A jig 29 is used to align the pair of objects 21 and 26.
This can be done with high precision through Note that the present invention is not limited to the above-mentioned embodiment, and for example, the jig 29 is generally composed of a pair of legs 43, 44 having different lengths inserted between a pair of objects 21, 26, as shown in FIG. A second diffraction grating 31 is formed on each leg 43, 44.
32 may be provided, and with such a configuration, the interval between the first diffraction gratings 21, 28 and the second diffraction gratings 31, 32, depending on the distance between the pair of objects 21, 26,
In other words, Δd can be reduced.

Further, in the above embodiment, the reflected diffraction light is received by the data taker, but even if the transmitted diffraction light is received, the same alignment as in the above embodiment can be performed.

In this case, the pair of objects must be provided with a transparent portion through which the laser beam passes, but with such a configuration, there is no need to vibrate the jig. Alternatively, instead of using two laser oscillators, one laser oscillator may be used and the laser beam output from this laser oscillator may be divided.
Furthermore, although the above embodiment described aligning a pair of objects in only one direction, it is possible to align them in the X, Y, Z, and θ directions by using multiple sets of devices. Of course. As described above, in the present invention, a jig provided with a second diffraction grating facing the first diffraction grating is inserted between a pair of objects provided with a first diffraction grating, and The above-mentioned pair of objects are aligned via a jig by inputting a laser beam into a pair of first and second diffraction gratings and detecting the intensities of the +n-th and -n-th order diffracted lights. Therefore, alignment errors due to variations in the incident angle of the laser beam can be made extremely small.

In other words, conventionally, when the distance between a pair of objects is large, the error increases in proportion to the distance, but according to the present invention, the objects can be aligned with high precision regardless of the distance between the objects. This has a great practical effect.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing a conventional device, FIG. 2 is a schematic block diagram showing one embodiment of the present invention, and FIG. 3 is a side view of a jig showing another embodiment of the present invention. be. 21,26...object, 22,24...
Drive source, 27, 28...First diffraction grating, 29
...Jig, 31, 32... Second diffraction grating, 33, 34... Laser oscillator, 35, 36...
...Detaketor, 38...Differential amplifier.

Claims (1)

[Claims] 1. A first diffraction grating provided on each of the opposing surfaces of two objects arranged in parallel and facing each other to be aligned, a jig inserted between these objects, and a jig with the above-mentioned a pair of second diffraction gratings provided to face the pair of first diffraction gratings, and a laser oscillator that makes laser light incident on the pair of opposing first and second diffraction gratings from a perpendicular direction, respectively; , ± from each diffraction grating above
An alignment device comprising means for detecting the intensity of n-th order diffracted light and aligning the two objects based on this intensity.