JPH0562871A - Scanning exposure device and object movement measuring apparatus - Google Patents

Abstract

PURPOSE:To perform an interference fringe type alignment without influence of scanning direction and speed substantially without interruption during scanning without using the position measured value of a scanning stage when reversely scanning to expose. CONSTITUTION:The scanning exposure device comprises frequency modulating means 502 for applying a predetermined frequency difference to two beams BL1, BL2 to irradiate from beam irradiating means 501 when an interference fringe alignment method is applied to an exposure device, and switching means 507 for so switching as to invert the polarity of the difference of the beams BL1, BL2 from the means 501 in response to whether the scanning direction of a mask R is a positive direction of a first direction or a negative direction. It is so constituted that the frequencies of first and second AC signals always become the difference or more of the two beams BL1, BL2 irrespective of the positive and negative of the scanning direction of the mark R. As a result, scanning speed and direction are not limited, and its throughput is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning exposure apparatus which simultaneously scans a mask and a photosensitive substrate with respect to a projection optical system when the pattern on the mask is projected and exposed on the photosensitive substrate. The present invention also relates to a device for measuring the speed, position, etc. of a moving object.

[0002]

2. Description of the Related Art (First Conventional Example of Scanning Exposure Apparatus) As a conventional scanning exposure apparatus, a mask stage for holding a mask and a substrate stage for holding a photosensitive substrate (wafer) are provided with a catoptric projection optical system of equal magnification. There is known a method in which scanning exposure is performed at the same speed by combining the scanning lines and a common moving column. This unit-magnification catoptric projection optical system has good chromatic aberration over a wide exposure wavelength range because it does not use a refraction element (lens).
The exposure intensity is increased by simultaneously using two or more (e.g., g-line and h-line) emission lines from the light source (mercury lamp) to enable high-speed scanning exposure. However, in the catoptric system, the point at which both the astigmatism of both the S (sagittal) image plane and the M (meridional) image plane becomes zero is limited to the vicinity of the image height position at a constant distance from the optical axis of the catoptric system. Therefore, the shape of the exposure light that illuminates the mask is a so-called arc slit shape, which is a part of the narrow annular zone. In such an equal-magnification scanning exposure apparatus (mirror projection aligner), if the pattern image of the mask projected on the wafer is prevented from having a mirror image relationship, the mask and the wafer will be aligned on an integral moving column. After the holding, the moving column performs one-dimensional scanning in the width direction of the arc-shaped slit illumination light to complete the exposure. As a matter of course, in a unity-magnification projection system in which the mask pattern image projected on the wafer has a mirror image relationship, it is necessary to move the mask stage and the wafer stage in opposite directions at the same speed.

(Second Prior Art of Scanning Exposure Apparatus) Further, as a conventional scanning exposure method, both the mask stage and the stage of the photosensitive substrate are magnified in a state in which a refraction element is incorporated to enlarge or reduce the projection magnification. It is also known to perform relative scanning at a speed ratio according to. In this case, as the projection optical system, a combination of a reflective element and a refraction element, or a combination of only a refraction element is used, and as an example of a reduction projection optical system in which a reflection element and a refraction element are combined, There is one disclosed in Japanese Laid-Open Patent Publication No. 63-163319. A scanning exposure apparatus using this projection optical system has been announced by Perkin Elmer as a step & scan aligner (trade name: Micrascan 1 system).

(Third Prior Art of Scanning Exposure Apparatus)
Using a reduction projection optical system capable of full-field projection,
One method of performing step & scan exposure is also disclosed in Japanese Patent Laid-Open No. 2-229423.

(Points of scanning exposure apparatus) Among the scanning type exposure apparatuses as described above, in an apparatus having a projection magnification other than 1 ×, the mask stage and the wafer stage are precisely moved by scanning at a speed ratio corresponding to the magnification. In addition to the above, it is necessary to keep the deviation from the alignment state between the mask pattern and the pattern on the wafer generated during the scanning within the allowable range. The allowable misalignment is roughly defined from the minimum pattern line width on the wafer, but for example 0.8 μ
When a pattern having a line width of about m is formed on the wafer, only a shift amount of 1/5 to 1/10 or less is allowed. Therefore, it is desirable to be able to constantly monitor the relative displacement between the mask and the wafer during scanning exposure.

(Conventional example of a scanning exposure apparatus with a positional deviation monitor during scanning) As one of the conventional examples, Japanese Patent Laid-Open No. 63-4
As disclosed in Japanese Patent No. 1023, a plurality of C-shaped reticle marks formed on a mask (reticle);
The relative positional relationship between the reticle and the wafer (including magnification error and rotation error) is detected by detecting a plurality of V-shaped wafer targets formed on the wafer immediately before or during scanning exposure. There is known a method of correcting the.

In the system disclosed in Japanese Patent Laid-Open No. 63-41023, a plurality of C-shaped mark groups RM1 formed around the reticle R, as shown in FIG.
RM2, RM3 and a plurality of C-shaped mark groups WM1, WM2 formed around the shot area SA on the wafer W.
WM3 and slit-shaped illumination luminous flux A arranged in a V shape
Relative scanning is performed one after another under the irradiation of IL. In FIG. 15, the projection optical system PL is shown at the same size for simplicity of explanation, and the reticle R and the wafer W scan and move in opposite directions as indicated by arrows. At this time, the change in the amount of specular reflection light or scattered light reflected from the reticle marks RM1, RM2, RM3 and the wafer marks WM1, WM2, WM3 by the irradiation of the illumination light flux AIL is as shown in FIG.
It is specified on the time axis.

FIG. 16A shows an example of a signal waveform obtained by photoelectrically detecting the reflected light from the reticle mark.
6B shows an example of a signal waveform obtained by photoelectrically detecting scattered light from the wafer mark. The alignment between the reticle R and the wafer W is such that the pulse P1 in the reticle signal waveform temporally aligns with the pair of pulses P2, P3 in the wafer signal waveform, and then the pulses P4, P7 in the reticle signal waveform.
Are a pair of pulses P5 and P6 in the wafer signal waveform, respectively.
, And the pulses P8 and P9 in time, by adjusting the scanning speed and relative position of the reticle R and the wafer W. However, if each mark is first detected during the actual scanning exposure, it means that precise alignment has not been achieved at the start of the scanning exposure.

Therefore, pre-scanning is performed as shown in FIG. 15 before the actual exposure is started, and the average position of each pulse P1, P4, P7 in the reticle signal waveform and each pulse in the wafer signal waveform. P2, P3, P5, P6, P8,
An average position of each position of P9 is obtained, and the alignment error ΔX in the scanning exposure direction can be known from the difference between the two average positions. When the following equation is calculated from the positions of the pulses P1 to P6, the alignment error ΔY in the direction orthogonal to the scanning direction can be found. ΔY = ((P5 + P6)-(P2 + P3))-(P4-P1)

[0010]

SUMMARY OF THE INVENTION In the above prior art,
Since each signal waveform is obtained only when the extremely thin slit-shaped illumination light flux AIL crosses each alignment mark, the positions of a plurality of marks are detected and the average value thereof is obtained in order to obtain high alignment accuracy. It becomes indispensable to process such as. Therefore, after the scanning for preliminary alignment is performed, the main scanning for exposure is performed. This inevitably suffers from a sacrifice in throughput. Further, in the above-mentioned conventional mark shape, even if the accuracy in detecting the mark at one place is sufficient, the size of the mark has an extremely narrow width dimension in the scanning direction, so that each pulse in the alignment signal waveform is Is intermittent in time, and substantially no alignment error is detected during the period in which no pulse is generated in the signal waveform. Therefore, in a portion between each of the plurality of marks arranged in the scanning direction, the measurement value of the laser interferometer that measures the position of the scanning stage that moves the reticle R or the wafer W is relied upon.

It is an object of the present invention to perform interference fringe alignment without any interruption during scanning without using position measurement values of the scanning stage when scanning and exposing in mutually opposite directions and without being affected by the scanning direction. It is to provide a scanning exposure apparatus that enables the above. Another object of the present invention is to position the moving object,
An object of the present invention is to provide an apparatus capable of measuring speed and the like with high accuracy.

[0012]

The invention according to claim 1 will be described with reference to FIG. 1 (A) which is a diagram corresponding to claims. In the scanning exposure apparatus according to the present invention, a mask (R) is placed across a projection optical system (PL). ) And the photosensitive substrate (W) are arranged in an image forming relationship, and the mask stage (510) and the substrate stage (520) are simultaneously moved in the first direction (for example, the X direction) at a speed ratio according to the projection magnification. And applied to a device for scanning and exposing the original image pattern of the mask (R) onto the shot area on the photosensitive substrate (W).

Then, the scanning exposure apparatus according to the first aspect achieves the above-mentioned object by adopting the following configuration as shown in FIG. 1 (A). The mask (R) used in the present invention includes a mask grating (RM) including a plurality of grating elements arranged at a constant pitch in the first direction (X direction).
Are provided over the scanning range of the original image pattern.
Further, the photosensitive substrate (W) is also provided with a substrate grating (WM) corresponding to the mask grating (RM). Further, the two coherent beams (BL1, BL2), which are symmetrically inclined with respect to the first direction, irradiate the mask grating (RM) and the substrate grating (WM), respectively, so that the two beams (BL1, BL1, BL2) is directed to the photosensitive substrate (W) through the mask (R) and the projection optical system (PL), and the two beams (BL1 and BL2) emitted from the beam irradiation means 501 are constant. A frequency modulation means 502 for giving a frequency difference and two beams (B
The interference light formed by the two diffracted lights generated in the same direction from the mask grating (RM) by the irradiation of L1 and BL2) is photoelectrically detected, and the first of the frequencies corresponding to the frequency difference and the scanning speed of the mask (R) is detected. And a first photoelectric detector 503 which outputs an AC signal, and photoelectrically detects interference light formed by two diffracted lights generated in the same direction from the substrate grating (W) by irradiation of two beams (BL1, BL2). , A second photoelectric detector 504, which outputs a second AC signal having a frequency corresponding to the frequency difference and the scanning speed of the substrate (W), and the first AC signal and the second AC signal are compared, and the mask (R ) And substrate (W)
A positional deviation detecting unit 505 that detects a positional deviation during relative scanning with respect to the mask stage 510 and a driving unit 506 that controls the mask stage 510 and the substrate stage 520 according to the positional deviation detected by the positional deviation detecting unit 505; Depending on whether the scanning direction of (R) is the positive direction or the negative direction of the first direction, the polarity of the frequency difference between the two beams (BL1, BL2) from the beam irradiation means 501 is reversed. And a switching means 507 for switching, and the frequencies of the first AC signal and the second AC signal are always equal to or more than the frequency difference between the two beams (BL1, BL2) regardless of the positive / negative of the mask (R) in the scanning direction. To configure. As shown in FIG. 1B, an object movement measuring device according to a second aspect is arranged at a constant pitch along the first direction on an object 601 that reciprocates along the first direction. A diffraction grating 602 composed of a plurality of grating elements is provided, and two coherent beams 603 and 604 are simultaneously and obliquely irradiated to the same portion on the diffraction grating while being symmetrically inclined with respect to the first direction. It is applied to a device that measures the movement amount or the movement position of the object 601 based on the alternating current signal obtained by detecting the interference light formed by the two diffracted lights generated in 1) by the photoelectric detector 605. And the diffraction grating 602
And a switching means 607 for switching the polarity of the frequency difference between the two beams according to the directionality of the reciprocating movement of the object 601. The frequency of the signal obtained by the photoelectric detector 605 is always set to be equal to or more than the frequency difference regardless of the directionality of the reciprocating movement of the object 601.

[0014]

According to the first aspect of the invention, when the interference fringe alignment method is applied to the scanning exposure apparatus, it is incident on the mask grating (RM) and the substrate grating (WM) depending on the scanning direction of the mask (R). The polarities of the frequency differences of the beams (BL1, BL2) are switched. As a result, the frequencies of the first AC signal corresponding to the mask grating (RM) and the second AC signal corresponding to the substrate grating (WM) are always two regardless of whether the frequency is positive or negative in the scanning direction of the mask (R). It is equal to or more than the frequency difference between the beams (BL1, BL2). Therefore, the mask scanning direction and scanning speed are not limited, and the throughput is improved. In the invention of claim 2, the polarities of the frequency differences of the two beams 603 and 604 incident on the diffraction grating 602 are switched according to the moving direction of the object. As a result, the photoelectric detector 60
The frequency corresponding to each beam obtained in 5 is always the frequency difference or more regardless of the moving direction of the object. Therefore, the problem that the position and speed cannot be measured depending on the moving direction of the object and the accuracy thereof is reduced is solved.

In the description of the means and action for solving the above problems for explaining the structure of the present invention, the reference numerals of some embodiments are used to make the present invention easy to understand. It is not limited to the examples.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment (Overall Structure) FIG. 2 shows the structure of a step & scan exposure apparatus according to the first embodiment of the present invention, and FIG. 3 schematically shows the state during scan exposure. FIG. In FIG. 2, the projection optical system PL is, as an example, a full-field type ⅕ reduction projection lens composed of only conventional refracting elements, and both the reticle R side and the wafer W side are telecentric.

Illumination light from the exposure light source has a uniform illuminance distribution by a fly-eye lens or the like and illuminates a reticle blind 1 as an illumination field stop. Blind 1
Is provided with a slit opening for illuminating the reticle R on a slit. The longitudinal direction of this slit opening coincides with the scanning direction of the reticle R and the wafer W, for example, the Y direction orthogonal to the X direction. The illumination light that has passed through the slit opening of the blind 1 reaches the reticle R via the lens system 2, the mirror 3, the condenser lens 4, and the dichroic mirror (or beam splitter) 5. Here, the blind 1 is a lens system 2 and a condenser lens 4
With respect to the composite system of, the reticle R is arranged in a conjugate with the pattern surface (the surface facing the projection lens PL), and the image of the slit aperture is formed on the reticle R. Further, the center of the slit opening is the projection lens PL and the illumination optical system (lens system 2,
It is assumed that they coincide with the optical axis AX of the condenser lens 4 etc.).

The reticle R is adsorbed and held on the reticle stage 6 which is movable at least in the X direction. The reticle stage 6 scans and moves in the X direction on the column 7 by the motor 8. Of course, a fine movement mechanism in the Y direction and the θ direction is also necessary for alignment of the reticle R,
Here, illustration and description thereof are omitted. Reticle R
The image of the pattern existing in the slit illumination area of is image-projected on the wafer W by the projection lens PL. The wafer W is placed on a wafer stage 9 that moves largely in two dimensions (X and Y directions), and this stage 9 is driven by a motor 10. The laser interferometer 11 is the wafer stage 9
And the speed signal regarding the moving speed of the wafer stage 9 in the X direction and the Y direction is also output. The drive control unit 12 is the laser interferometer 1
The motor 10 based on the position information and speed signal from 1
Is controlled by an optimum drive pattern. In this embodiment, scanning exposure is performed by moving the wafer stage 9 in the X direction,
Although the movement in the Y direction is used for stepping, it goes without saying that the opposite may be used. Although not shown in FIG. 2, it is assumed that the reticle stage 6 has its coordinate position, rotation (yawing) error, and the like measured by a laser interferometer.

Next, an example of the arrangement of the alignment marks formed on the reticle R and the wafer W will be described with reference to FIG. As shown in FIG. 3, the reticle R and the wafer W are X
Since they are moved in the opposite directions along the direction,
In the street line area extending in the X direction around the pattern area PA on the reticle R, a plurality of grid elements R are arranged in the X direction at a constant pitch over the scanning range.
Ma and RMb are provided. Lattice mark RMa, RMb
Are provided so as to be separated from each other in the Y direction across the pattern area PA, but the positional relationship of the lattice pitch in the X direction is assumed to be the same.

On the other hand, a plurality of pattern (shot) areas SA are formed on the wafer W, and a similar grid is formed around each shot area SA at the position of the street line area corresponding to the grid mark RMa of the reticle R. The mark WMa is formed, and the similar lattice mark WMb is formed at the position of the street line area corresponding to the lattice mark RMb.

Lattice mark RMa of reticle R and wafer W
The relative positional deviation in the X direction with respect to the lattice mark WMa of is detected through an alignment optical system having an optical axis AXa,
The relative positional deviation in the X direction between the lattice mark RMb of the reticle R and the lattice mark WMb of the wafer W is detected via the alignment optical system having the optical axis AXb. Both of these optical axes AXa and AXb intersect the optical axis AX at the center of the pupil plane EP of the projection lens PL.

The alignment system and the control system will be described with reference to FIG. 2 again. In this embodiment, an interference fringe alignment method suitable for detecting the positional deviation of the lattice marks of the reticle R and the wafer W in the pitch direction is adopted. An example of this interference fringe alignment method is disclosed in, for example, JP-A-63-283129 and JP-A-2-227602.
Since it is disclosed in Japanese Laid-Open Publication No. Gazette, a brief description will be given here.

(General interference fringe alignment method) Ne-
Laser light source 2 for Ne, He-Cd, Ar ions, etc.
The coherent linearly polarized laser beam from 0 is incident on the dual beam frequency shifter unit 21 and two beams BL1 and BL2 having a frequency difference Δf are formed. The frequency difference Δf is
The upper limit is determined by the frequency response of the photoelectric detector that receives the light from the alignment mark, and for a semiconductor sensor, practically 100 kHz or less, for example, about 50 kHz is preferable. However, when using a photomultiplier tube (photomultiplier), a relatively high frequency can be used. Details of the dual-beam conversion frequency shifter unit 21 will be described later.

The two beams BL1 and BL2 are distributed to a plurality of alignment optical systems (having the above-mentioned optical axes AXa and AXb) via the light transmitting optical system 22. FIG. 2 shows the objective lens 23 and the tip mirror 24 that form one alignment optical system. The optical axis of the objective lens 23 corresponds to one of the optical axes AXa and AXb shown in FIG. The two beams BL1 and BL2 are symmetrically decentered from the optical axis of the objective lens 23 and enter the objective lens 23, and pass through the mirror 24 and the dichroic mirror 5 to the objective lens 23.
On the pattern surface of the reticle R existing at the focal point position of the reticle R. By this intersection, a one-dimensional interference fringe is formed on the grating mark RMa or RMb of the reticle R. Then, through the transparent part of the reticle R, 2
The beam of the book intersects on the grating mark WMa or WMb on the wafer W through the projection lens PL to form a one-dimensional interference fringe.

These interference fringes are Δf between the two transmitted beams.
Since there is a frequency difference of Δf, the interference fringes flow in the pitch direction at a speed proportional to Δf. The incident directions of the two light-transmitting beams are determined so that the pitch direction of each grating mark and the pitch direction of the interference fringes coincide with each other, and the pitch of the grating mark and the pitch of the interference fringes have a predetermined relationship (for example, an integer). When the crossing angle of the two light-transmitting beams is determined so that the ratio becomes, the interference light having the same beat frequency as the frequency difference Δf is generated in the vertical direction from each grating mark. This interference light constantly repeats bright and dark at the beat frequency Δf, and it is
Even if the relative position of the intersecting region of the transmitted light beam of the book is slightly deviated in the X direction, the beat frequency Δf does not change.

The interference light from these lattice marks is guided to the photoelectric detection unit 25 via the mirrors 5 and 24 and the objective lens 23, and the sinusoidal detection signals SR and SW are generated. The signal SR is obtained by photoelectrically detecting the interference light from the grating mark RMa or RMb of the reticle R, and the signal SW
Is obtained by photoelectrically detecting the interference light from the lattice mark WMa or WMb of the wafer W. When the reticle R and the wafer W are stationary, the frequency of both signals is Δ.
f. However, when the lattice mark of the reticle R and the lattice mark of the wafer W are deviated in the pitch direction,
A phase difference Δφ occurs between the two signals SR and SW. The phase difference Δφ is detected by the phase difference measuring unit 27, and the position shift amount corresponding to the detected phase difference is calculated. The detectable phase difference is usually in the range of ± 180 °, which is ± Pg / 2 (μm) or ± Pg / 4 (μ) when the pitch of the grating mark is Pg (μm).
It corresponds to m).

(Interference fringe alignment method adopted in the scanning exposure apparatus) The main control unit 30 inputs the value of this positional deviation amount, and inputs it to the drive control unit 12 of the wafer stage 9 or the drive control unit 28 of the reticle stage 6. Outputs the sequential correction value. In the conventional interference fringe alignment method described above, the main control system 30 simply drives the motor 8 or 10 until the phase difference reaches a predetermined value, and finely moves either the reticle stage 6 or the wafer stage 9. It was okay to let them do it. However, even during the scan exposure in which both the reticle R and the wafer W move at high speed as in the present embodiment, 2
Another problem arises when the phase difference between the two signals SR and SW is obtained. This is because the scanning mark causes the grating mark to continuously move in the pitch direction at a speed v (mm / s) with respect to the intersecting region of the two light-transmitting beams, so that the interference light from the grating mark to be photoelectrically detected causes the Doppler effect. Therefore, the frequencies of the detection signals SR and SW greatly vary from Δf. Frequency fs of signals SR and SW
(KHz) is the moving speed of the lattice mark (pitch Pg) by v
(Mm / s) is expressed by the following equation. fs = Δf + 2v / Pg (beat frequency Δf is 5
0 kHz) For example, if the speed v is -100 mm / s, the signals SR, S
If the frequency fs of W is Pg = 8 μm, it becomes 25 kHz, and if the speed v is +100 mm / s, the frequency f
s becomes 75 kHz.

Therefore, if such a system is adopted,
Generally, the scanning speed of the reticle stage 6 and the wafer stage 9 is accompanied by a certain limitation. For example, the scanning speed v may be set low so that a value that does not cause a problem in phase difference measurement can be secured as the frequency fs. It is necessary to avoid scanning direction (-X direction) where the frequency fs becomes low, and always perform scanning exposure only in + X direction.
Inevitable decrease in throughput. Therefore, in the scanning exposure apparatus according to the present invention, the polarities of the frequency difference Δf (equal to the beat frequency) between the two beams BL1 and BL2 are reversed according to the moving direction of the reticle R, and detection is performed regardless of the scanning direction of the reticle R. The frequencies of the signals SR and SW are set to be higher than the beat frequency, that is, the frequency difference Δf between the two beams.

(Two-beam conversion frequency shifter section 21 and switching section 3
2) A control unit for inverting the polarity of the frequency difference Δf according to the moving direction of the reticle R will be described with reference to FIG. In FIG. 4, the dual-beam conversion frequency shifter unit 21 includes a beam splitter 211 that splits the laser light from the alignment laser light source 20, and an acousto-optic element 212 on which one of the laser beams split by the beam splitter 211 is incident.
And the other laser beam split by the beam splitter 211 enters through the mirror 214.
3 and a frequency synthesizer 215 that outputs a high-frequency signal of frequency f1 and frequency f2 different from f1. The alignment light incident on each acousto-optic element 212, 213 is diffracted according to the high frequency signal sent from the frequency synthesizer 215 to each acousto-optic element 212, 213.

Here, when the frequency of the incident light on each of the acousto-optic elements 212 and 213 is f0 and the frequencies of the high frequency signals applied to the acousto-optic elements 212 and 214 are f1 and f2, respectively, the acousto-optic elements 212 diffract. Is ejected +
The frequency of the first-order diffracted light is f0 + f1, and the acousto-optic element 213
The frequency of the + 1st order diffracted light which is diffracted by and is emitted is f0 +
It becomes f21. Therefore, on the output side of each acousto-optic device,
Apertures 216 and 217 that extract only the 1st-order diffracted light are provided, and the alignment light that has passed through the aperture 217 is directly incident on the beam splitter 218.
The alignment light having passed through 16 is incident on the beam splitter 218 via the mirror 219. The beam splitter 218 defines the crossing angle of the alignment light beams that cross each other on the mask grating and the wafer grating.

A switch 220 is provided between the frequency synthesizer 215 and each of the acousto-optic elements 212 and 213.
The frequency synthesizer 215 is operated by operating the switch 220.
The signals of the frequency f1 and the signal of the frequency f2, which are output from, are selectively applied to one of the acousto-optic elements,
In this way, the polarities of the frequency differences of the alignment lights emitted from the acousto-optic elements 212 and 213 are reversed.
The switching of the switching unit 221 is switched by the switching driving unit 32 arranged outside the two-beam conversion frequency shifter unit 21. A scanning direction switching signal of the reticle R is input to the switching driving unit 32, and the switching driving unit 32 switches the switching unit 220 according to the scanning direction switching signal.

For example, it is assumed that the switch 220 is switched to the position shown in FIG. 4 when the reticle R is scanned in the positive X direction (the arrow direction in FIG. 3). At this time, the frequencies f1 and f of the two high frequency signals of the frequency synthesizer 215 are
When 2 is f1> f2, the difference between the frequency of the alignment light emitted from the acousto-optic element 212 and the frequency of the alignment light emitted from the acousto-optic element 213 is set to be smaller than the frequencies of the detection signals SR and SW. It is set. If the reticle scanning direction signal input to the switching drive unit 32 is switched to the negative direction, the switching device 2
20 is switched from the position shown in the figure, and a high-frequency signal with a low frequency is applied to the acousto-optic element 212, and a high-frequency signal with a high frequency is applied to the acousto-optic element 213. As a result, the frequency difference between the alignment lights emitted from the acousto-optic elements 212 and 213 is the same as that in the forward scanning, and the detection signals SR and S
It becomes smaller than the frequency of W. In this way, the reticle R
By reversing the polarity of the frequency difference between the beams BL1 and BL21 in accordance with the scanning direction of, the scanning speed and the scanning direction need not be limited, and the throughput can be improved.

(Main Control Section 30) Next, the main control section 30 for driving and controlling the stages 6 and 9 of the reticle R and the wafer W will be described. To realize a simpler alignment during scanning, the main control unit 30 of the present embodiment first controls the speed and position control unit 300 for driving the wafer stage 9 at a controlled constant speed and the reticle stage 6. It has a speed and position control unit 302 for driving at a constant speed and a tracking scan control unit 304.

In the case of normal positioning of the reticle alone, so-called reticle alignment, or alignment of the wafer alone, so-called wafer global alignment (or EGA), the controller units 300 and 302 are not related to each other and function as usual. To achieve. During scan exposure, the controller units 300 and 302 cooperate with each other to control the relative position and speed of the reticle stage 6 and the wafer stage 9. Regarding this coordinated control,
The same is done in the conventional device shown in FIG.

In this embodiment, a tracking scan control section 304 is further provided so that the normal cooperative control and the tracking control can be switched. In this tracking control, the drive control unit 28 of the reticle stage 6 is servo-controlled so that the positional deviation amount between the reticle R and the wafer W, which are successively output from the phase difference measuring unit 27, becomes a constant value. At the same time, the wafer stage 9 is simply controlled at a constant speed. Of course, the reticle stage 6 may be subjected to constant speed control and the wafer stage 9 may be subjected to tracking control.

That is, in the present embodiment, attention is paid to the fact that the signals SR and SW are continuously output during scanning exposure, that is, the change in the relative positional deviation amount between the reticle R and the wafer W is successively detected. Then, either one of the reticle and the wafer is scanned at a constant speed, and the other is controlled so as to follow the scanning movement.

In FIG. 2, the reference detection system 26 detects the beat frequency Δf of the two beams BL1 and BL2, and this detection signal is a sinusoidal reference signal SF of the frequency Δf, which is the phase difference measuring section 27. The phase difference measuring unit 27 obtains the deviation of the initial position of the reticle R from the phase difference between the reference signal SF and the detection signal SR, or the reference signal S.
The shift of the initial position of the wafer W can be obtained from the phase difference between F and the detection signal SW. Further, a circuit for detecting a frequency change is incorporated in the phase difference measuring unit 27, and by quantifying a frequency change of the detection signal SR or SW with respect to the reference signal SF, the speed of the reticle stage 6 or the wafer stage 9 is quantified. It is possible to detect the change directly from the movement of the lattice mark.

(Relative Rotation Error between Reticle and Wafer) In this embodiment, as shown in FIG. 3, two sets of alignment systems (optical axes AXa and AXb) are used to form lattice marks RMa and RMb on both sides of the pattern area PA. Since the lattice marks WMa and WMb on both sides of the shot area SA are detected, the positional deviation amount ΔXa obtained from the alignment system unit having the optical axis AXa (hereinafter referred to as the alignment unit XA) and the optical axis AXb. If the difference between the positional deviation amount ΔXb obtained from the unit of the alignment system (hereinafter referred to as the alignment unit XB) having the above is sequentially calculated by, for example, a hardware digital subtraction circuit, the reticle R and the wafer W ( A change in relative rotation error with respect to one shot area SA) is immediately obtained during scanning exposure.

The relative rotation error also depends on the size of the pattern area PA or the shot area SA and the value of the minimum line width.
When a certain allowable amount is set and a rotation error exceeding the allowable amount may occur, the reticle stage 6 is rotated by a small amount Δθ.
It is desirable to feed back to the mechanism to correct the rotation error in real time during scanning exposure. In this case, Δ
The rotation center of the θ mechanism preferably coincides with the center of the slit aperture image of the blind 1 projected on the reticle R.

Here, a specific example of the light-sending optical system 22 and the photoelectric detection unit 25 in the apparatus shown in FIG. 2 will be described with reference to FIG. In FIG. 5, two transmitted light beams B
L1 and BL2 intersect each other on the illumination field stop 40 and are limited to an illumination region of a predetermined size. The limited two light-transmitting beams are transmitted through the lens system 41, the polarization beam splitter 42, and the quarter-wave plate 43 to the objective lens 2
It is incident on 3. As is clear from FIG. 5, the diaphragm 40
And the lattice mark RMa of the reticle R are arranged so as to be conjugate with each other with respect to the combined system of the lens system 41 and the objective lens 23. Then, the two transmitted beams BL1 and BL2 are converged as beam waists on the Fourier transform plane (the plane conjugate with the pupil EP of the projection lens PL) in the Fourier space between the lens system 41 and the objective lens 23. Along with
The chief rays of the transmitted beams BL1 and BL2 are parallel to and symmetrical with the optical axis AXa in Fourier space.

The two light-transmitting beams BL1 and BL2 are transmitted through the polarization beam splitter 42 almost 100%, and then are ¼.
It is converted into circularly polarized light that rotates in the same direction by the wave plate 43, and again becomes two parallel beams through the objective lens 23 and intersects at the position of the mark RMa. Although the arrangement of the mark RMa is shown in FIG. 4, the mark W on the wafer side is actually shown.
The relationship is set such that it is laterally offset with respect to Ma in the non-measurement direction (direction orthogonal to the grating pitch direction).

FIG. 6 is a lattice mark RM viewed from the reticle R side.
a and WMa, and the rectangular area ALx is the aperture 40
Is an aperture image of. Here, the lattice marks RMa and WMa have a line-and-space ratio of 1: 1 (duty 50%).
If the magnification of the projection lens PL is 1 / M, the pitch GPr of the mark RMa on the reticle R and the mark W
The pitch GPw of Ma on the wafer W is GPr = M ·
Determined by the GPw relationship. During scan exposure, the marks RMa and WMa move with respect to the area ALx on the reticle surface in the same direction (+ X direction in FIG. 6) at the same speed v. As shown in FIG. 6, when the alignment is achieved in the non-measurement direction (here, the Y direction), the lattice marks RMa and WMa are arranged laterally in advance so as to maintain a constant distance DS. This interval DS is determined depending on the alignment accuracy in the Y direction.

FIG. 7 shows a state in which the grating mark RMa or WMa moves in the pitch direction at a velocity + v or -v, and it is assumed that the interference fringes IF formed on each lattice mark are flowing at a velocity + Vf. To do. As shown in FIG. 7, when the grating mark moves at a velocity + v, the beat frequency of the interference light BT of ± 1st-order diffracted light vertically generated from the grating mark is 2 because it coincides with the flowing direction of the interference fringes IF. It becomes lower than the frequency difference Δf between the two beams BL1 and BL2, and when the grating mark moves at the speed −v, the direction is opposite to the direction in which the interference fringes IF flow, so the beat frequency becomes higher than Δf. In this example, regardless of the moving direction of the lattice mark, the beams BL1 and BL2 are set in accordance with the moving direction of the lattice mark so that the frequency of the detection signal is always higher than Δf.
Switching the frequency of.

Considering the lattice mark RMa, the incident angle θ of the two light-transmitting beams BL1 and BL2 is set symmetrically with respect to the optical axis AXa, and the relationship is set as follows. sin θ = λ / GPr With this, the ± first-order diffracted light from the grating mark RMa is generated in the vertical direction. Under these conditions, the interference fringe IF
Pitch Pif has a relationship of Pif = 1/2 · GPr.

From this fact, the transmitted beams BL1 and BL2 are
Frequency difference Δf (kHz) and lattice mark speed v (mm /
s) and the Doppler effect, the interference light BT
As described above, the frequency fs (kHz) of the light-dark change of is fs = Δf + 2v / GPr.

As shown in FIG. 5, the reticle lattice mark R
The interference light BTr from Ma and the lattice mark WMa of the wafer
The interference light BTw from the optical axis AXa passes through the objective lens 23, the quarter-wave plate 43, and the polarization beam splitter 42.
It returns above and enters the lens system 44. This lens system 44
Acts as an inverse Fourier transform lens, and the lattice mark RM
A plane conjugate with a or WMa is created. Lens system 44
The interference lights BTr and BTw from are split into two by the half mirror 45 and reach the light shielding plates 46R and 46W. The light shielding plate 46R is arranged at a position conjugate with the lattice mark RMa, and has an opening APR arranged so as to block other interference light BTw only through the interference light BTr from the mark RMa. Similarly, the light shielding plate 46W is arranged at a position conjugate with the lattice mark WMa, and has an opening APW arranged so as to shield other interference light BTr only through the interference light BTw from the mark WMa.

The photoelectric sensor (fetode diode, photomultiplier, etc.) 47R receives the interference light BTr from the aperture APR and outputs a signal SR, and the photoelectric sensor 47W is aperture AP.
The interference light BTw from W is received and the signal SW is output.
The processing of these signals SR and SW is as described in FIG.

As described above, in the present embodiment, the wafer stage 9 is controlled at a constant speed during the scanning exposure, because the fluctuation of the scanning speed causes the uneven exposure amount in the shot area SA. The blind 1 is not necessarily limited to the slit opening, and may be a regular hexagonal shape, a rectangular shape, a rhombus shape, an arc shape, or the like included in the circular image field of the projection lens PL.

A step-and-scan type apparatus using a blind having a regular hexagonal opening is disclosed in Japanese Patent Laid-Open No. 2-229.
No. 423, the alignment control system of this embodiment may be incorporated into the apparatus disclosed therein.

-Second Embodiment- Next, a second embodiment of the present invention will be described. Here, the first embodiment is used as it is, and two-dimensional (X, Y directions) during scanning exposure. It enables the alignment of.

When the scanning exposure is in the X direction, the arrangement and structure of the lattice marks on the reticle R and the wafer W are slightly changed so that the same interference fringe alignment method can be used in the Y direction orthogonal to the X direction. In this embodiment, the TTR type alignment system shown in FIGS. 2 and 5 is used for the X direction and the Y direction.
Two axes are provided for each direction, and grid marks for the X direction and the Y direction are provided on each street line of the reticle and the wafer.

FIG. 8 shows the arrangement of each mark on the reticle R and the arrangement of the objective lens of the alignment system. In both sides of the pattern area PA of the reticle R, in the street line area extending in the X direction, that is, the scanning exposure direction, Lattice marks RMYa and RMYb for the Y direction and lattice marks RM for the X direction
Xa and RMXb are provided. These lattice marks are arranged as shown in an enlarged manner in FIG. 9, for example, and the lattice mark RMYa for the Y direction is formed by extending several line-and-space patterns in the X direction, and adjacent to the lattice mark for the X direction. A lattice mark RMXa is provided. Both sides of the lattice marks RMYa and RMXa on the reticle R are transparent portions, and the corresponding lattice marks WMY for the Y direction on the wafer W are formed.
a and the lattice mark WMXa for the X direction are located.

In this embodiment, among these lattice marks, X
Direction lattice marks RMXa (WMXa) and RMXb
(WMXb) is detected via the objective lenses 23Xa and 23Xb of the X-direction alignment system as in the first embodiment, and the Y-direction lattice mark RMYa (WMYa) and the mark RMYb (WMYb) are Y It is detected via the objective lenses 23Ya and 23Yb of the alignment system for directions.

The alignment system for the Y direction is basically the X system.
The configuration is the same as that of the alignment system for directions, except that the incident angles of the two beams BL1 and BL2 with respect to the reticle R (or wafer W) are inclined in the YZ plane. Further, the aperture stop (46R, 46W) inside the alignment system for the X direction is the grating mark RM for the Y direction.
It is set so as to also block interference light from Ya and WMYa (RMYb, WMYb), and the aperture stop inside the alignment system for the Y direction has grating marks RMXa, W for the X direction.
The interference light from MXa (RMXb, WMXb) is also set to be blocked.

Here, the reticle R and the wafer W are relatively moved to X.
When scanned in the direction, the interference light (beat light) from the Y direction grating mark RMYa on the reticle R and the interference light (beat light) from the Y direction grating mark WMYa on the wafer W are photoelectrically converted. The frequencies of the two signals obtained by detection are
It is almost constant (Δf) regardless of the scanning speed of the reticle R and the wafer W in the X direction. However, when the amount of alignment error in the Y direction changes abruptly with time, the frequency of progress may change accordingly, but this change is almost negligible. The amount of alignment error needs only to detect the phase difference between the two signals. Also in the case of this Y direction, the alignment error amount is successively output, so that the reticle stage 6 or the wafer stage 9 is finely moved in the Y direction so that the error amount always becomes a constant value. Alternatively, during scanning exposure, the drive system for the Y direction of reticle stage 6 or wafer stage 9 may be servo (feedback) controlled based on the Y direction alignment error signal.

In this embodiment, the X-direction alignment system and the Y-direction alignment system are juxtaposed in the scanning exposure direction, but it is possible to align the X-direction and the Y-direction with a single objective lens. You may make it the beam of a book enter simultaneously.

Although not shown in the apparatus shown in FIG. 2, a grating mark on the reticle R and a reference on the wafer stage 9 are provided above the reticle R under illumination light having the same wavelength as the exposure light. A TTR type alignment system for observing the marks is provided. This is because the alignment system shown in FIGS. 2 and 5 has a beam BL1 having a wavelength different from that of the exposure light.
, It is necessary for baseline management when using BL2.

Such a TT using the same wavelength as the exposure light
The R alignment system is arranged as shown in FIG. 10, for example. In FIG. 10, the objective lens 23 and the mirror 24 are the same as those in FIG. 2, and in addition to these, a TTR alignment system including an optical fiber 62, a beam splitter 61, an objective lens 60, an image pickup element 63 and the like is provided. Then, the fiducial mark plate FM is fixed on the wafer stage 9. The optical fiber 62 emits illumination light having the same wavelength as the exposure light, and the illumination light reflected by the beam splitter 61 illuminates the grating mark on the reticle R via the objective lens 60. The illumination light transmitted through the reticle R is projected by the projection lens P.
The grid mark on the reference mark plate FM is irradiated via L. On this fiducial mark plate FM, as shown in FIG. 10, grating marks are provided at positions that can be simultaneously detected via the objective lens 23.

The image pickup device 63 picks up images of the lattice mark of the reticle R and the lattice mark of the reference mark plate FM,
It is used to obtain the positional deviation amount (ΔXe, ΔYe) of both marks. At this time, the interference fringe type alignment system is simultaneously actuated via the objective lens 23 to obtain the relative positional deviation amount (ΔXa, ΔYa) between the lattice mark of the reticle R and the lattice mark of the reference mark plate FM. by this,
Baseline amount is (ΔXa-ΔXe, ΔYa-ΔYe)
Is sought after.

However, in this case, since the wafer stage 9 (reference mark plate FM) needs to be stationary, the wafer stage 9 is generally set so that the measurement value of the laser interferometer 11 becomes a constant value. Use feedback control.
However, since the laser optical path of the laser interferometer 11 is open to the atmosphere, the measurement value slightly changes due to slight air fluctuations. Therefore, in the above baseline measurement, even if the wafer stage 9 is stopped by the measurement value of the laser interferometer 11, drift due to air fluctuations will occur.

However, in the interference fringe type alignment system shown in FIGS. 2 and 5, between the reticle R and the projection lens PL,
Since the beam portion exposed in the air is small between the projection lens PL and the wafer W, even if the air fluctuation occurs, the measurement error due to the air fluctuation can be almost ignored. Therefore, the reticle stage 6 or the wafer stage 9 is feedback-controlled so that the reticle R and the fiducial mark plate FM are aligned by using an interference fringe type alignment system. This makes the reticle R
The relative displacement between the reference mark plate FM and the reference mark plate FM is driven to almost zero under the alignment system (objective lens 23) of another wavelength. Then, in this state, the image pickup element 63 is used to obtain the amount of positional deviation between the lattice mark of the reticle R and the lattice mark of the reference mark plate FM. The shift amount obtained by this is the baseline amount (ΔXB, ΔYB). This baseline amount (ΔXB, ΔYB) is the projection lens PL
Is an eigenvalue caused by the chromatic aberration of and is checked every time the detection position of the grating mark on the reticle R (image height point of the projection lens) changes.

This baseline amount (ΔXB, ΔYB) is added as an offset to the relative positional deviation amount between the reticle R and the wafer W detected through the objective lens 23, and is used as a correction to the true overlay position. .. Since the position observed through the objective lens 60 is a position deviated from the irradiation region (slit shape) of the exposure illumination light on the reticle R, strictly speaking, the deviation may cause an inherent error. .. The error is mainly due to the distortion caused by the exposure wavelength of the projection lens PL. However, since the distortion amount at each point in the projection visual field of the projection lens PL can be obtained in advance, the distortion amount at the observation position of the objective lens 60 is stored as an offset amount peculiar to the apparatus, and the baseline is stored. It is advisable to further correct the measured value.

-Third Embodiment- FIG. 11 shows the arrangement of lattice marks according to the third embodiment of the present invention. In particular, the lattice marks formed in the street lines of the wafer W are two-dimensional lattices to save space. It is something that aims to change. In FIG. 11, on the reticle R, a lattice mark RMYa for the Y direction and a lattice mark RM for the X direction are provided.
Xa and the Xa are provided at a constant interval in the Y direction, and a two-dimensional lattice WMx on the wafer W is provided in this interval part (transparent part).
Set so that y is located. The two-dimensional lattice WMxy is an array of minute rectangular dot patterns arranged in both the X and Y directions at a predetermined pitch. At the time of actual alignment, it is better to separate the positions by the X-direction alignment system and the Y-direction alignment system as shown in FIG.

However, if the two beams for the X-direction alignment and the two beams for the Y-direction alignment are set to have polarization states complementary to each other, the interference light vertically generated from the two-dimensional grating WMxy is polarized. Since they can be separated according to their characteristics, it is possible to simultaneously irradiate four beams (two for the X direction and two for the Y direction) onto the lattice mark through the same objective lens 23.

By thus providing the two-dimensional lattice WMxy in the entire scanning direction along the shot area on the wafer, considerable space saving is achieved and two-dimensional alignment correction during scanning exposure becomes possible. .. By the way, the general street line area on the wafer is the width (Fig. 1
The dimension (1) in the Y direction) is about 70 μm. Two
When the dimensions of the rectangular dots of the three-dimensional lattice WMxy are 4 μm square (that is, the pitch is 8 μm), eight rectangular dots can be formed in the Y direction, and practically almost sufficient measurement accuracy can be expected. Also, the reticle side grating mark R in FIG.
MYa and RMXa can also have a two-dimensional lattice similar to that on the wafer side.

[Fourth Embodiment] FIG. 12 shows a lattice mark arrangement according to a fourth embodiment of the present invention, in which 1 is provided in the street line area extending in the scanning exposure direction outside the pattern area PA of the reticle R. -Dimensional or two-dimensional lattice marks RML1 to RML4, RMR1 to
RMR3s are provided at intervals in the X direction. On the wafer W, one-dimensional or two-dimensional lattice marks are provided discontinuously in the X direction at positions corresponding to them.

The marks RML1 to RML4 and the marks RMR1 to RMR3 are arranged in a nested state with each other, and the two objective lenses 23R and 23L of the alignment system are arranged.
Are arranged side by side in the Y direction, one of the objective lenses 23R and 23L is set so that interference light from the grating mark can always be incident upon the scanning exposure in the X direction. For example, when the reticle R is moved left and right from the position of FIG. 12, the lattice mark RML1 and the corresponding lattice mark on the wafer are aligned via the objective lens 23L, and two (or four) marks from the objective lens 23L are aligned. ) The irradiation area of the transmitted beam is the lattice mark RML1.
Immediately before it comes off, the grating mark RMR1 reaches the irradiation point of the light-transmitting beam from the objective lens 23R. Therefore, in the next cycle, the grating mark RMR1 and the corresponding grating mark on the wafer are aligned via the objective lens 23R. Similarly, the objective lenses 23R and 23L are alternately switched according to the scanning exposure signal to perform alignment. In this embodiment, the lattice mark RML is used.
When switching from 1 to RMR1, the interference beat light obtained through the objective lens 23L and the interference beat light obtained through the objective lens 23R are present at the same time for only a short time. Has been placed.

When the lattice marks are arranged as in this embodiment, another mark, for example, the global alignment (E) of the wafer is provided between the lattice marks in the X direction.
A mark for (GA) can be arranged.

-Fifth Embodiment- FIG. 13 shows the structure of a projection exposure apparatus according to the fifth embodiment of the present invention. The difference from the structure shown in FIG. 2 lies in the scanning direction of reticle R (and wafer W). This is because a plurality of objective lenses 23A, 23B, 23C and 23D of the alignment system are arranged. The reticle R and the lattice mark on the wafer W may be arranged by any of the methods shown in FIGS. 4, 8, 11 and 12.

In the case of FIG. 13, four objective lenses 23
A to 23D respectively enter interference beat light generated at different positions on the lattice mark to perform alignment during scanning movement of the reticle R and the wafer W. Depending on the scanning position, the objective lenses 23A and 23D on both sides may be aligned. Sometimes only one of them can be used. Then, as one alignment sequence, for example, when the reticle R is scanned from the left side to the right side in FIG. 13, the number of alignment systems used in the order of the objective lens 23A, the objective lens 23B, ... According to the scanning position of the reticle R. You can also change the position. Further, when a plurality of alignment systems can be used at the same time as shown in FIG. 13, the lattice marks RML1 ...
Even if the RML4 and the grating marks RMR1 to RMR3 are not in a nested relationship, the signal for alignment can be obtained almost continuously.

For that purpose, for example, the objective lenses 23A to
23D spacing in the scanning direction (X direction) and lattice mark RM
The distance between L1 and RML4 in the X direction may be different. The alignment method during scanning exposure according to the present invention can be directly applied to a conventional step & scan exposure apparatus.

FIG. 14 is a schematic overall configuration diagram of a catadioptric exposure apparatus to which the scanning exposure apparatus according to the present invention is applied.
The same parts as those in FIG. 2 are denoted by the same reference numerals, and only different points will be briefly described. 71 and 73 are reflection mirrors, 72 is an interferometer for measuring the position of the reticle stage 6, 74 is a lens, and 75 is A beam splitter, 76 is a concave mirror, and 77 is a refractometer. The alignment light emitted from the light transmitting optical system 22 is incident on the reticle gratings RMa and RMb of the reticle R via the mirror 71 and the objective lens 23, and at the same time, from the light transmitting portion of the reticle R to the mirror 73 and the lens 7.
4, through the beam splitter 75, the concave mirror 76, and the refraction lens system 77, the wafer gratings WMa and WMb on the wafer W.
(Not shown). The method of processing the interference light obtained by each grating and forming the interference light are the same as those described in the above-mentioned projection type exposure apparatus.

Although the interference fringe alignment method of the exposure apparatus has been described above, the diffraction grating is irradiated with light having a frequency difference to form a beat wave of interference light, and an object that moves based on the beat wave is formed. The present invention can also be applied to a device for measuring the position and speed of the.

In this case, the following configuration is adopted. First
A diffraction grating composed of a plurality of grating elements arranged at a constant pitch along the first direction is provided on an object that reciprocates along the direction, and two coherent elements are provided in the same portion on the diffraction grating. The beams are irradiated at the same time while being symmetrically inclined with respect to the first direction. A photoelectric detector detects interference light formed by two diffracted lights generated in the same direction from this diffraction grating. The moving amount or moving position of the object is measured based on the AC signal obtained by the photoelectric detector. Further, there are provided frequency modulation means for applying a predetermined frequency difference to the two beams irradiating the diffraction grating, and switching means for switching the polarity of the frequency difference between the two beams depending on the directionality of the reciprocating movement of the object. The frequency of the AC signal obtained by the photoelectric detector is always set to be equal to or more than the frequency difference between the two beams regardless of the directionality of the reciprocal movement of the object.

[0075]

As described above, according to the first aspect of the invention, when the interference fringe alignment method is applied to the scanning exposure apparatus, the polarities of the frequency differences of the beams respectively incident on the mask grating and the substrate grating are Since the switching is made according to the scanning direction of the mask, each frequency of the first AC signal from the first photoelectric detector corresponding to the mask grating and the second AC signal from the second photoelectric detector corresponding to the substrate grating is changed. Is always equal to or more than the frequency difference between the two beams regardless of whether the scanning direction of the mask is positive or negative.
Throughput is improved. According to the invention of claim 2, the polarities of the frequency differences of the two beams incident on the diffraction grating are switched according to the moving direction of the object, so that the frequencies corresponding to the respective beams obtained by the photoelectric detector are changed. However, the frequency difference is always greater than or equal to the moving direction of the object, and the position of the object or the like can be accurately measured regardless of the moving direction of the object.

[Brief description of drawings]

[Fig. 1] Claim correspondence diagram

FIG. 2 is a diagram showing a configuration of a projection type scanning exposure apparatus according to an embodiment of the present invention,

FIG. 3 is a perspective view illustrating an alignment method by the apparatus of FIG.

FIG. 4 is a block diagram illustrating details of a dual-beam conversion frequency shifter unit.

5 is a diagram showing a configuration of an alignment system of the apparatus shown in FIG.

6 is a diagram showing the arrangement of reticle and wafer lattice marks used in the apparatus of FIG. 2;

FIG. 7 is a diagram for explaining the operation principle of the alignment system of FIG.

FIG. 8 is a plan view of a reticle having a mark arrangement according to the second embodiment,

9 is a plan view showing the mark arrangement of FIG. 8 in a partially enlarged manner;

FIG. 10 is a diagram for explaining a baseline measurement method;

FIG. 11 is a diagram for explaining mark arrangement according to the third embodiment;

FIG. 12 is a diagram for explaining mark arrangement according to the fourth embodiment;

FIG. 13 is a diagram illustrating a device configuration according to a fifth embodiment.

FIG. 14 is a perspective view showing an example of a catadioptric exposure apparatus to which the present invention can be applied.

FIG. 15 is a perspective view illustrating an alignment method in a conventional step & scan exposure apparatus.

16 is a waveform diagram showing a signal waveform for alignment obtained by the alignment method of FIG.

[Explanation of symbols]

R reticle, RMa, RMb, RMXa, RMYa, RMXb, RM
Yb reticle grating mark, WMa, WMb, WMYa, WMXa, WMxy wafer grating mark, W wafer PL projection optical system 1 reticle blind 6 reticle stage 8 reticle stage drive motor 9 wafer stage 10 wafer stage drive motor 11 laser interferometer 12 wafer stage Drive control unit 20 Laser light source 21 2 Luminous flux conversion frequency shifter unit 22 Transmitting optical system 23 Alignment objective lens 25 Photoelectric detection unit 27 Positional deviation amount detection unit 32 Switching drive unit 212, 213 Acousto-optical element 215 Frequency synthesizer 216, 217 Aperture 220 switch

Claims (2)

[Claims] 1. A mask stage capable of reciprocating in a first direction along a surface of the original pattern while holding a mask having the original pattern formed thereon, and the original pattern or a part thereof at a predetermined magnification. A projection optical system for projecting; and a substrate stage capable of reciprocating in the first direction while holding the photosensitive substrate so that the photosensitive substrate is positioned on an image plane of the projection optical system, the mask stage; An apparatus for scanning and exposing a projection image of the original image pattern onto the photosensitive substrate by simultaneously moving the substrate stage at a speed ratio according to the magnification, wherein the mask has a constant pitch in the first direction. A mask grid composed of a plurality of grid elements arranged in a line is provided over the range of the scanning exposure of the original image pattern, and the photosensitive substrate is fixed along the first direction. A substrate grating composed of a plurality of grating elements arranged in an array over the range of the scanning exposure of the original image pattern, and two coherent beams symmetrically inclined with respect to the first direction are the mask grating. A beam irradiating means for directing the two beams to the photosensitive substrate through the mask and the projection optical system so as to irradiate each of the substrate grating and the substrate grating; Frequency modulation means for imparting a constant frequency difference to the beam, and photoelectrically detecting interference light formed by two diffracted lights generated in the same direction from the mask grating by irradiation of the two beams to detect the frequency difference and the mask. A first photoelectric detector that outputs a first AC signal having a frequency according to the scanning speed of the same, and the same from the substrate grating by the irradiation of the two beams. A second photoelectric detector that photoelectrically detects interference light formed by two diffracted lights generated in the opposite direction and outputs a second AC signal having a frequency corresponding to the frequency difference and the scanning speed of the substrate; Positional deviation detecting means for comparing the first AC signal and the second AC signal to detect positional deviation during relative scanning between the mask and the substrate, and the mask according to the positional deviation detected by the positional deviation detecting means. A driving unit for driving and controlling the stage and the substrate stage; and 2 from the beam irradiating unit depending on whether the scanning direction of the mask is the positive direction or the negative direction of the first direction.
Switching means for switching so as to invert the polarity of the beam frequency difference of the two beams, and the frequencies of the first AC signal and the second AC signal are always the two beams regardless of whether the frequencies are positive or negative in the scanning direction of the mask. A scanning exposure apparatus characterized in that it is configured to have a frequency difference equal to or more than. 2. A diffraction grating composed of a plurality of grating elements arranged at a constant pitch along the first direction is provided on an object that reciprocates along the first direction. The two coherent beams are symmetrically tilted with respect to the first direction and irradiated at the same time, and interference light formed by two diffracted lights generated in the same direction from the diffraction grating is detected by a photoelectric detector. An apparatus for measuring the amount of movement or the position of movement of the object based on the generated AC signal, a frequency modulation means for giving a predetermined frequency difference to the two beams irradiating the diffraction grating, and a reciprocating movement of the object. Switching means for switching the polarity of the frequency difference between the two beams depending on the directionality, and the frequency of the AC signal obtained by the photoelectric detector is independent of the directionality of the reciprocating movement of the object. Always moving measuring device on the object, characterized by being configured such that the above said frequency difference.