JPH0799148A - Measuring method of accuracy of stepping - Google Patents

Abstract

PURPOSE:To increase the efficiency of measurement of the accuracy of stepping of a wafer stage and also to analyze factors affecting the accuracy of stepping. CONSTITUTION:Marks (72XP1, 72YP1, etc.) for LIA measurement are formed by exposure as pattern images of a reticle sequentially in shot areas ES1 to ES16 on a wafer W. As a first measurement, the position of the mark for LIA measurement in each shot area is detected in the sequence of the shot areas ES13 to ES4, for instance, and the coordinates of a wafer stage whereon the wafer W is set is monitored by a laser interferometer. As a second measurement, thereafter, the position of the mark for LIA measurement in each shot area is detected in the sequence different from that in the first, for instance, and the coordinates of the wafer stage are monitored by the laser interferometer. An error in stepping is determined on the basis of a difference between the results of the measurements of two times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step-and-repeat method or a step-and-repeat method for manufacturing a semiconductor device or a liquid crystal display device by a photolithography process.
The present invention relates to a stepping accuracy measuring method suitable for measuring stepping accuracy of a wafer stage in a projection exposure apparatus that sequentially exposes a pattern image of a reticle to each shot area of a wafer by an AND-scan method.

[0002]

2. Description of the Related Art When a semiconductor device, a liquid crystal display device, or the like is manufactured by a photolithography process, a photosensitive material is applied with a pattern image of a photomask or reticle (hereinafter referred to as "reticle") through a projection optical system. A projection exposure apparatus for projecting each shot area on a wafer (or a glass plate or the like) is used. In recent years, as a projection exposure apparatus of this type, a wafer is placed on a wafer stage that is two-dimensionally movable, and the wafer stage is stepped by the wafer stage to form a reticle pattern image on the wafer. Repeat the operation of sequentially exposing the shot area,
So-called step-and-repeat type projection exposure apparatus,
In particular, a reduction projection type exposure apparatus (stepper) is often used.

In general, a semiconductor element or the like is formed by stacking multiple layers of circuit patterns on a wafer. Therefore, in a projection exposure apparatus, the circuit pattern already formed on the wafer and the pattern of the reticle to be exposed this time. An alignment system is provided for increasing the accuracy of superimposition with the image. The main factors that affect the overlay accuracy are
These are the positioning accuracy of the wafer stage when setting each shot area of the wafer to the exposure position, the accuracy of detecting the position of the alignment mark in the alignment system, and the environmental conditions such as room temperature. Below, the positioning accuracy of the wafer stage, the position detection accuracy in the alignment system, and the like are collectively considered as the stepping accuracy of the wafer stage.

Referring to FIG. 13, a shot centering method of the conventional stepping accuracy measuring methods will be described. In this measuring method, as shown in FIG. 13, first, as the first exposure for the wafer W, position measuring marks 81 ₁ , 81 ₂ , ... Are respectively formed at the centers of the shot areas ES1, ES2 ,. Expose. After that, as the second exposure for the wafer W, the shot area ES
Position measurement mark 8 repeatedly at the center of 1, ES2, ...
2 ₁ , 82 ₂ , ... Is exposed. At this time, due to the stepping error, the arrangement of the shot areas exposed for the second time is shifted like shot areas EQ1, EQ2, ....
Then, after developing the wafer W, the position measurement marks 81 ₁ , 81 ₂ , ... Formed by the first exposure and the position measurement marks 82 ₁ , 82 ₂ , formed by the second exposure,
By measuring the amount of positional deviation with respect to, the array accuracy when the shot areas are arrayed in a two-dimensional lattice can be checked.
This measuring method is close to the actual processing method of the wafer W.

Next, with reference to FIG. 14, description will be given of a shot peripheral alignment method of the conventional stepping accuracy measuring methods. In this measuring method, as shown in FIG. 14, shot areas ES1, ES2, ES3, ..., ES10, ES regularly arranged on the wafer W so that their peripheral portions overlap each other.
The position measurement marks are exposed around 11, ... After that, the wafer W is developed, and in the overlapping regions 83 ₁ , 83 ₂ , ... In the horizontal direction between the shot regions and in the overlapping regions 84 ₁ , 84 ₂ ,.
The amount of positional deviation of the position measuring marks exposed in the adjacent shot areas is measured. As a result, yawing of the wafer stage at the time of stepping, and stepping error to which a positioning error due to the moving direction of the wafer stage is further added can be obtained.

Here, referring to FIG. 15, for measuring the relative positional deviation amount between the position measuring mark formed by the first exposure and the position measuring mark formed by the second exposure. The conventional method will be described. In FIG. 15A, the position measurement mark 81 formed by hatching formed by the first exposure and the position measurement mark 82 formed by the second exposure are respectively in the X direction and the Y direction. It is a mark in which dot patterns are arranged at a predetermined pitch following a straight line pattern, and the relative positional deviation amount of the position measuring marks 81 and 82 is, for example, a TTL through a projection optical system.
(Through the lens) method and laser step
It is measured by an alignment (LSA) type alignment system.

That is, as shown in FIG. 15A, the wafer is scanned in the -X direction with respect to a slit-shaped light spot 85X which is formed by converging a laser beam and is long in the Y direction. The light spot 85X is the position measurement mark 8
When traversing the dot patterns 1 and 82, strong diffracted light is emitted in a predetermined direction. The diffraction intensity signal S (X) obtained by photoelectrically converting this diffracted light becomes a signal having two peaks as shown in FIG. 15B, and the position measurement mark 81 and the position measurement mark 81 are obtained from the difference between the two peak positions. The position shift amount of 82 in the X direction is detected.

Similarly, when the wafer is scanned in the -Y direction with respect to the slit-like light spot 85Y which is long in the X direction, when the light spot 85Y crosses the dot patterns of the position measuring marks 81 and 82, Strong diffracted light is emitted in a predetermined direction. The position shift amount of the position measurement marks 81 and 82 in the Y direction is detected from the diffraction intensity signal S (Y) shown in FIG. 15C obtained by photoelectrically converting this diffracted light. The amount of positional deviation between the two position measurement marks in the X and Y directions is the stepping error.

[0009]

In the conventional method of measuring the stepping accuracy as described above, the exposure is actually performed. Therefore, when the stepping accuracy of the projection exposure apparatus is evaluated after the assembly adjustment is completed, Is a suitable method. However, if the conventional measurement method is used, for example, in the step of adjusting the stepping accuracy of the wafer stage, it is necessary to repeat the steps of exposure → development → measurement of the positional deviation amount every time measurement is performed, which requires a long time for measurement. Therefore, there is an inconvenience that the throughput of the adjustment process is low. Further, in order to improve the reliability of measurement, it is necessary to repeat the stepping accuracy measurement for a plurality of wafers, which further reduces the throughput.

Further, in the conventional stepping accuracy measuring method, since the correspondence between the measurement result and the factor that deteriorates the stepping accuracy is not clear, even if it is found that the stepping error is bad, which part of the wafer stage should be adjusted. I didn't know if it was good, and I had no choice but to make adjustments by trial and error. That is, even if the conventional method of measuring the stepping accuracy is used in the adjustment stage of the wafer stage, the drive unit and the mechanical unit of the wafer stage cannot be adjusted in the optimum procedure.

In view of the above problems, it is an object of the present invention to provide a stepping accuracy measuring method which has a high efficiency of measuring the stepping accuracy of a wafer stage and can analyze a factor affecting the stepping accuracy.

[0012]

A first stepping accuracy measuring method according to the present invention is, for example, as shown in FIGS. 1, 6 and 7, a photosensitive substrate on which a pattern on a mask (R) is exposed. A substrate stage (WS) that holds (W) and positions this substrate in a two-dimensional plane; and coordinate measuring means (15) that measures the positioning coordinates of this substrate stage,
In a method of measuring the stepping accuracy of a substrate stage (WS) of an exposure apparatus having an alignment system (17) for detecting the position of an alignment mark on a substrate (W),
A predetermined substrate on which a plurality of measurement patterns (ES1 to ES16) are formed in advance is placed on the substrate stage (WS),
The positions of the plurality of measurement patterns are respectively detected and stored by the alignment system (17) in a predetermined first order (FIG. 7A), and the positions of the plurality of measurement patterns are detected by the alignment system (17). Substrate stage (WS) measured by the coordinate measuring means (15) when the position is detected
Has a first step of storing the coordinate values of each.

The present invention further provides a predetermined second order (FIG. 7).
In (b)), the positions of the plurality of measurement patterns on the predetermined substrate are detected and stored by the alignment system (17), and the positions of the plurality of measurement patterns are detected by the alignment system (17). The second step of storing the coordinate values of the substrate stage (WS) measured by the coordinate measuring means (15) when the above is performed, and the first step of each of the plurality of measurement patterns on the predetermined substrate. And a third step of comparing the measurement result in step 2 with the measurement result in the second step.

A second stepping accuracy measuring method according to the present invention holds a photosensitive substrate (W) on which a pattern on a mask (R) is exposed, as shown in FIGS. 1 and 12, for example. The substrate stage (WS) for positioning the substrate in a two-dimensional plane, the coordinate measuring means (15) for measuring the positioning coordinates of the substrate stage (WS), and the position of the alignment mark on the substrate (W) are set. In a method of measuring the stepping accuracy of a substrate stage (WS) of an exposure apparatus having an alignment system (17) for detecting, a predetermined substrate on which a plurality of measurement patterns (ES1 to ES16) are formed in advance is used as a substrate stage (WS). The mask (R) is placed on the mask, and the pattern of the mask (R) is exposed in a predetermined order so as to correspond to each of the plurality of measurement patterns.
The positions of the plurality of measurement patterns when the pattern is exposed are detected and stored by the alignment system (17), respectively, and the coordinates are detected when the positions of the plurality of measurement patterns are detected by the alignment system (17). It has a first step of storing the coordinate values of the substrate stage (WS) measured by the measuring means (15).

Further, in the present invention, the alignment system (17) detects and stores the position of the pattern of the mask (R) exposed on the predetermined substrate in the first step, and the alignment system (17). The second step of storing the coordinate values of the substrate stage (WS) measured by the coordinate measuring means (15) when the exposure position of the pattern of the mask (R) is detected by the second step, and the measurement result in the first step And the measurement result of the second step, the substrate stage (WS)
And a third step of obtaining the stepping accuracy of.

[0016]

In general, the stepping error is caused by the combination of various error factors. The main error factors are the measurement error of the coordinate measuring means (15) of the substrate stage (WS), the detection error of the alignment system (17), the tracking error by the control system (responsiveness, set allowable range, etc.), exposure. The expansion of the substrate (W) due to, the twisting of the entire apparatus due to the driving of the substrate stage (WS), the yawing of the substrate stage (WS), and the like. When the coordinate measuring means (15) is a laser interferometer, the measurement error of the coordinate measuring means (15) includes quantization error due to measurement resolution, wavelength conversion error due to environmental temperature, atmospheric pressure, humidity, etc., and reference beam measurement. There are non-linear errors due to mixing with long beams, errors due to air fluctuations in the vicinity of the reference beam and measurement beam due to indoor air conditioning, and so on.

With respect to this, in the first stepping accuracy measuring method of the present invention, the substrate stage (WS) is actually stepped in the first step and the second step, and the positions of the plurality of measurement patterns on the substrate are determined. I am measuring. That is, coordinate values are measured by the coordinate measuring means (15) in synchronization with stepping drive of the substrate stage (WS), and in parallel, the position of the measurement pattern is detected by the alignment system (17). Therefore, it is possible to identify the factor that deteriorates the stepping accuracy, know where to adjust when adjusting the stage system, and improve the throughput of the adjustment process of the exposure apparatus.

In the first stepping accuracy measuring method, stepping and pseudo exposure are performed using a predetermined substrate on which a plurality of measurement patterns are formed by exposing and developing a predetermined mask pattern in advance. Because
The stepping error can be measured any number of times using the predetermined substrate. That is, unlike the conventional example, it is not necessary to perform exposure and development on the wafer for each measurement, the measurement time is shortened, and the reliability of the measurement result is improved.

On the other hand, according to the second stepping accuracy measuring method, the mask pattern is exposed while detecting the position of the measuring pattern already formed in the first step,
In the second step, the position of the exposed pattern is detected. Therefore, from the amount of positional deviation between the already formed measurement pattern and the newly exposed mask pattern,
It is possible to identify a factor that deteriorates the stepping accuracy and to know where to adjust when adjusting the stage system. Further, in the first step, the substrate stage (WS) is stepwise driven as in the case of actual exposure, the measurement value of the coordinate measuring means (15) is sampled at high speed during the stepping drive, and the alignment system is used at the time of measurement. (1
The detection result of 7) is sampled. Therefore, it is possible to obtain information not only on the amount of positional deviation (offset error) between shot areas as in the conventional measurement method but also on the deterioration of the projected image due to vibration or the like during actual exposure.

Further, it is possible to form a measurement pattern on the predetermined substrate with a stable pattern (SiO ₂ etc.) and handle the predetermined substrate like a reference wafer.
Then, for example, by repeating the first step and the second step for a plurality of exposure apparatuses, it is possible to detect not only the stepping accuracy of the exposure apparatus itself but also the matching state of the stepping accuracy between the plurality of exposure apparatuses.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a stepping accuracy measuring method according to the present invention will be described below with reference to FIGS. FIG. 1 shows a schematic configuration of a projection exposure apparatus suitable for applying the measuring method of the present embodiment. In FIG.
The illumination light IL generated from the ultra-high pressure mercury lamp 1 is an elliptical mirror 2
After being reflected by, and once condensed at the second focal point, it enters the illumination optical system 3 including a collimator lens, an interference filter, an optical integrator (fly eye lens), an aperture stop (σ stop), and the like. Although not shown, the fly-eye lens is arranged in the in-plane direction perpendicular to the optical axis AX so that the reticle-side focal plane of the fly-eye lens substantially coincides with the Fourier transform plane (pupil conjugate plane) of the reticle pattern.

A shutter (for example, a four-blade rotary shutter) 37 for closing and opening the optical path of the illumination light IL by a motor 38 is arranged near the second focal point of the elliptic mirror 2. As the illumination light for exposure, laser light such as an excimer laser (KrF excimer laser, ArF excimer laser) or a harmonic wave of a metal vapor laser or a YAG laser is used in addition to the bright line of the ultra-high pressure mercury lamp 1 or the like. It doesn't matter.

In FIG. 1, most of the illumination light (i-line etc.) IL in the wavelength range that exposes the photoresist layer emitted from the illumination optical system 3 is reflected by the beam splitter 4 and then the first relay. The light passes through the lens 5, the variable field diaphragm (reticle blind) 6 and the second relay lens 7 and reaches the mirror 8. Then, the illumination light IL reflected by the mirror 8 in a substantially vertically downward direction illuminates the pattern area PA of the reticle R with substantially uniform illuminance via the main condenser lens 9. The reticle blind 6 is placed on the reticle R
The reticle R is illuminated by changing the size and shape of the opening by opening and closing a plurality of movable blades that form the reticle blind 6 by the drive system 36 in a conjugate relationship (image forming relationship) with the pattern forming surface. The field of view can be set arbitrarily.

In the reticle R of this embodiment, alignment marks composed of two cross-shaped light-shielding marks are formed in the vicinity of the outer periphery of the reticle R so as to face each other. These two alignment marks are used for alignment of the reticle R (projection optical system 1
3 for alignment with the optical axis AX). The reticle R is driven by the motor 12 so that the optical axis A of the projection optical system 13 is
It is mounted on a reticle stage RS that can be finely moved in the X direction, and can be two-dimensionally moved and finely rotated in a horizontal plane perpendicular to its optical axis AX. At the end of the reticle stage RS, a moving mirror 11m that reflects a laser beam from a laser light wave interferometer (hereinafter referred to as "laser interferometer") 11 is provided.
Is fixed, and the two-dimensional position of the reticle stage RS is constantly detected by the laser interferometer 11 with a resolution of, for example, about 0.01 μm. Reticle alignment systems (RA systems) 10A and 10B are arranged above the reticle R, and these RA systems 10A and 10B are mounted on the reticle R.
Two cross-shaped alignment marks formed near the outer periphery of the are detected. By finely moving the reticle stage RS based on the measurement signals from the RA systems 10A and 10B, the reticle R is positioned so that the center point of the pattern area PA coincides with the optical axis AX of the projection optical system 13.

The illumination light IL which has passed through the pattern area PA of the reticle R is incident on the projection optical system 13 which is telecentric on both sides, and the projection optical system 13 projects the circuit pattern of the reticle R, which is reduced to, for example, 1/5. The image is projected (imaged) on the wafer W, which has a photoresist layer formed on the surface thereof and is held so that the surface thereof substantially coincides with the best imaging plane of the projection optical system 13.

The wafer W is vacuum-sucked by a finely rotatable wafer holder (not shown), and is held on the wafer stage WS via this wafer holder. The wafer stage WS is configured to be two-dimensionally movable by a step-and-repeat method by a motor 16, and a reticle R for one shot area on the wafer W is normally exposed.
When the transfer exposure of is completed, the wafer stage WS is stepped to the next shot position. A movable mirror 15m that reflects the laser beam from the laser interferometer 15 is fixed to the end of the wafer stage WS.
The two-dimensional coordinate of S is constantly detected by the laser interferometer 15 with a resolution of, for example, about 0.01 μm. The laser interferometer 15 is the projection optical system 1 of the wafer stage WS.
3 is for measuring coordinates in one direction perpendicular to the optical axis AX (referred to as the X direction) and in the Y direction perpendicular thereto, and the wafer stage WS
Stage coordinate system (stationary coordinate system) (X, Y) is defined. That is, the coordinate value of the wafer stage WS measured by the laser interferometer 15 is the coordinate value on the stage coordinate system (X, Y).

On the wafer stage WS, a reference member (glass substrate) 14 provided with a reference mark used when measuring a baseline amount (described later) or the like has almost the same height as the exposed surface of the wafer W. Is provided. The reference member 14 has, as a reference mark, a slit pattern composed of five light-transmitting L-shaped patterns and two sets of reference patterns formed of light-reflecting chrome (duty ratio is 1:
1) and are provided. One set of reference patterns is
A diffraction grating mark formed by arranging 7 dot marks arranged in the Y direction in three rows in the X direction, a diffraction grating mark formed by arranging three linear patterns in the X direction, and 12 extending in the Y direction. The bar marks of the book are arranged in the X direction. The other set of reference patterns is the one set of reference patterns rotated by 90 °.

Now, the slit pattern formed on the reference member 14 is illuminated from below (inside the wafer stage) by the illumination light (exposure light) transmitted below the reference member 14 using an optical fiber (not shown) or the like. Is configured to. The illumination light transmitted through the slit pattern of the reference member 14 forms a projected image of the slit pattern on the back surface (pattern surface) of the reticle R via the projection optical system 13. Further, the illumination light passing through any of the four reticle marks on the reticle R reaches the beam splitter 4 through the main condenser lens 9, the relay lenses 7 and 5, and the like.
The illumination light transmitted through the beam splitter 4 is received by a photoelectric detector 35 arranged near the pupil conjugate plane of the projection optical system 13. The photoelectric detector 35 outputs a photoelectric signal SS corresponding to the intensity of the illumination light to the main control system 18. In the following, an optical fiber (not shown), the reference member 14 and the photoelectric detector 3
5 is collectively called an ISS (Imaging Slit Sensor) system.

Further, in FIG. 2, an image formation characteristic correction unit 19 capable of adjusting the image formation characteristic of the projection optical system 13 is also provided.
The imaging characteristic correction unit 19 in this embodiment is the projection optical system 1
Some of the lens elements that make up part 3, especially reticle R
By independently driving (moving or tilting in a direction parallel to the optical axis AX) each of the plurality of lens elements close to each other by using a piezoelectric element such as a piezo element, For example, it corrects projection magnification and distortion.

Next, an off-axis type alignment sensor (hereinafter referred to as "Field Imag") is provided on the side of the projection optical system 13.
e Alignment system (FIA system) ”is provided. In this FIA system, the light generated by the halogen lamp 20 is converted into the condenser lens 21 and the optical fiber 22.
The light is guided to the interference filter 23 via the, and the light in the photosensitive wavelength region and the infrared wavelength region of the photoresist layer is cut off there.
The light transmitted through the interference filter 23 enters the telecentric objective lens 27 via the lens system 24, the beam splitter 25, the mirror 26 and the field stop BR.
The light emitted from the objective lens 27 is reflected by a prism (or mirror) 28 fixed around the lower part of the lens barrel of the projection optical system 13 so as not to block the illumination visual field of the projection optical system 13, and the wafer W is almost vertical. To irradiate.

The light from the objective lens 27 is applied to the partial area including the wafer mark (base mark) on the wafer W, and the light reflected from the area is the prism 28, the objective lens 27, the field stop BR, and the mirror 26. , Is guided to the index plate 30 via the beam splitter 25 and the lens system 29. Here, the index plate 30 is arranged in a plane conjugate with the wafer W with respect to the objective lens 27 and the lens system 29, and the image of the wafer mark on the wafer W is formed in the transparent window of the index plate 30. Further, the index plate 30 is formed with two linear marks extending in the Y direction at predetermined intervals in the X direction as index marks in the transparent window.
The light that has passed through the index plate 30 receives the first relay lens system 31,
The image of the wafer mark and the image of the index mark are formed on the light receiving surface of the image pickup device 34 by being guided to the image pickup device (CCD camera etc.) 34 via the mirror 32 and the second relay lens system 33. The image pickup signal SV from the image pickup device 34 is supplied to the main control system 1
8, the position (coordinate value) of the wafer mark in the X direction is calculated. The FIA system (X-axis FIA system) configured as described above is also provided with another set of FIA systems (Y-axis FIA system) for detecting the mark position in the Y direction.

Next, TT is provided on the upper side of the projection optical system 13.
An L (through the lens) type alignment sensor 17 is also arranged, and the position detection light from the alignment sensor 17 is transmitted through the mirrors M1 and M2 to the projection optical system 1.
It is led to 3. The light for detecting the position is the projection optical system 1
The wafer W on the wafer W is irradiated with the reflected light from the wafer W via the projection optical system 13, the mirror M2, and the mirror M1, and the alignment sensor 17
Returned to. The alignment sensor 17 obtains the position of the wafer mark on the wafer W from the signal obtained by photoelectrically converting the returned reflected light.

FIG. 2 shows a detailed structure of the TTL type alignment sensor 17 in FIG. 1. In FIG. 2, the alignment sensor 17 of this example is a two-beam interference type alignment system (hereinafter referred to as “LIA system”). ) And a laser step alignment type alignment system (hereinafter referred to as “LSA system”), and the optical members thereof are maximally shared. Although briefly described here, a more specific configuration is disclosed in Japanese Patent Laid-Open No. 2-272305.

In FIG. 2, a laser beam emitted from a light source (He-Ne laser light source, etc.) 40 is split by a beam splitter 41, and the laser beam reflected here is passed through a shutter 42 to a first beam shaping optical system. (LI
A optical system) 45. On the other hand, the laser beam transmitted through the beam splitter 41 enters the second beam shaping optical system (LSA optical system) 46 via the shutter 43 and the mirror 44. Therefore, the shutters 42 and 43
Can be used by switching between the LIA system and the LSA system by appropriately driving.

The LIA optical system 45 includes two sets of acousto-optic modulators and the like, and emits two laser beams having a predetermined frequency difference Δf substantially symmetrically with respect to the optical axis.
Further, the two laser beams emitted from the LIA optical system 45 reach the beam splitter 49 via the mirror 47 and the beam splitter 48, and the two laser beams transmitted therethrough are a lens system (inverse Fourier transform lens). 5
The light enters the reference diffraction grating 55, which is fixed on the apparatus, from two different directions at a predetermined crossing angle, and forms an image (crossing) through the mirror 3 and the mirror 54. The photoelectric detector 56 receives the interference light of the diffracted lights that are transmitted through the reference diffraction grating 55 and generated in substantially the same direction, and outputs a sinusoidal photoelectric signal SR corresponding to the intensity of the diffracted light to the main control system 18 (FIG. 2))
It is output to the A arithmetic unit 58.

On the other hand, the two laser beams reflected by the beam splitter 49 intersect once at the opening of the field stop 51 by the objective lens 50, and then the mirror M2 (see FIG. 1).
The inside mirror M1 is incident on the projection optical system 13 via a mirror (not shown). Further, the two laser beams incident on the projection optical system 13 become substantially symmetrical with respect to the optical axis AX on the pupil plane of the projection optical system 13 and once converged in a spot shape. The parallel luminous fluxes are inclined with respect to the direction (Y direction) with respect to each other with the optical axis AX in between, and become parallel luminous fluxes, which are incident on the wafer mark from two different directions at a predetermined crossing angle. A one-dimensional interference fringe that moves at a speed corresponding to the frequency difference Δf is formed on the wafer mark, and the ± first-order diffracted light (interference light) generated in the same direction from the mark, here, the optical axis direction, is projected by the projection optical system. The light is received by the photoelectric detector 52 via the system 13, the objective lens 50, etc., and the photoelectric detector 52 receives the sine-wave photoelectric signal S corresponding to the cycle of the change in brightness of the interference fringes.
Dw is output to the LIA operation unit 58. The LIA calculation unit 58 calculates the position deviation amount of the wafer mark from the phase difference on the waveforms of the two photoelectric signals SR and SDw, and uses the position signal PDs from the laser interferometer 15 to calculate the coordinate position of the wafer stage WS. And the information about the positional deviation amount and the coordinate position is obtained from the alignment data storage unit 6
1 (see FIG. 3).

On the other hand, the LSA optical system 46 includes a beam expander, a cylindrical lens and the like, and the laser beam emitted from the LSA optical system 46 enters the objective lens 50 via the beam splitters 48 and 49. Further, the laser beam emitted from the objective lens 50 once converges into a slit shape at the opening of the field stop 51, and then enters the projection optical system 13 via the mirror M2. The laser beam incident on the projection optical system 13 passes through almost the center of its pupil plane, then extends in the X direction within the image field of the projection optical system 13 and is directed to the optical axis AX as an elongated strip-shaped spot light on the wafer. Projected onto W.

When the spot light and the wafer mark (diffraction grating mark) on the wafer W are moved relative to each other in the Y direction, the light generated from the wafer mark passes through the projection optical system 13, the objective lens 50 and the like and is a photoelectric detector. The light is received at 52. The photoelectric detector 52 has ± 1st order of the light from the wafer mark.
Only the third-order diffracted light is photoelectrically converted, and the photoelectric signal SDi corresponding to the light intensity obtained by photoelectrically converting in this manner is used as the main control system 18
It is output to the LSA calculation unit 57 in the inside. The LSA arithmetic unit 57 has a position signal PDs from the laser interferometer 15.
Also, the LSA calculation unit 57 samples the photoelectric signal SDi in synchronization with the up / down pulse generated for each unit movement amount of the wafer stage WS. Furthermore, LS
The A calculation unit 57 converts each sampling value into a digital value and stores it in the memory in the order of addresses, and then calculates the position of the wafer mark in the Y direction by a predetermined calculation process, and stores this information in the alignment data storage of FIG. It is output to the unit 61.

Next, the structure of the main control system 18 of FIG. 1 will be described with reference to FIG. FIG. 3 shows the main control system 18 of this example and the members related thereto, and in FIG.
Arithmetic unit 57, LIA arithmetic unit 58, FIA arithmetic unit 59, alignment data storage unit 61, error arithmetic unit 62, storage unit 63, shot map data unit 64, system controller 65, wafer stage controller 66 and reticle stage controller 67.
The main control system 18 is configured by the above. Among these members, the LSA arithmetic unit 57 and the LIA arithmetic unit 58
The FIA calculation unit 59 obtains the positional shift amount of each wafer mark and the coordinate position (X, Y) of the wafer stage WS at the time of detecting the positional shift amount from the supplied photoelectric signal, and the obtained positional shift is detected. Information on the amount and the coordinate position (X, Y) is supplied to the alignment data storage unit 61. The information on the positional deviation amount and the coordinate position stored in the alignment data storage unit 61 is supplied to the EGA calculation unit 62.

The shot map data storage unit 64 stores the designed array coordinate values of the wafer marks belonging to each shot area on the wafer W in the coordinate system (x, y) on the wafer W. The array coordinate value of is supplied to the system controller 65. The system controller 65 is
Using the conversion coefficient from the coordinate system (x, y) on the wafer W to the stage coordinate system (X, Y), the array coordinate value of each wafer mark in the stage coordinate system (X, Y) is obtained. Then, the system controller 65 drives the wafer stage WS of FIG. 1 via the motor 16 while monitoring the measurement value of the laser interferometer 15 via the wafer stage controller 66 based on the array coordinate values, and drives the wafer W. Position each measurement area or exposure area above,
The exposure target area is exposed. Further, the system controller 65 drives the reticle stage RS of FIG. 1 via the motor 12 while monitoring the measurement value of the laser interferometer 11 via the reticle stage controller 67, and adjusts the position of the reticle R.

The error calculation unit 62 obtains a stepping error from the information of the positional deviation amount and the coordinate value (X, Y) of the wafer stage WS stored in the alignment data storage unit 61 as described later, and the stepping error is obtained. Is stored in the storage unit 63. In the description below, the LIA optical system 45 in the alignment sensor 17 is used as the alignment system. From the LIA optical system 45, when the wafer stage WS is at rest, two laser beams (heterodyne beam) having different frequencies with respect to a diffraction grating wafer mark on the wafer W are projected through the projection optical system 13. ) Is irradiated, and the + 1st-order diffracted light of the first laser beam and the −1st-order diffracted light of the second laser beam of the two laser beams are emitted from the wafer W substantially vertically in parallel. By photoelectrically converting the interference light composed of the ± 1st-order diffracted lights, a beat signal whose phase is modulated according to the position of the wafer mark is detected, and the beat signal is detected from the phase difference between the beat signal and the reference beat signal. The amount of displacement of the wafer mark from the reference position is detected.

FIG. 4 shows L in the alignment sensor 17.
The position detected by the IA optical system 45 and the positional relationship of the laser beam from the laser interferometer 15 of FIG. 1 with respect to the wafer stage WS are shown.
The movable mirror 15mX for the X direction of S is not shown in FIG.
Two laser beams L with an interval RL ₁ from one interferometer
B _X and LB _OF are irradiated parallel to the X axis, and the optical axis of the projection optical system 13 (the exposure field 13a of the projection optical system 13 is shown in FIG. 4) is present on the extension of the laser beam LB _X. On the extension of the beam LB _OF , there is an axis passing through the center of the observation field 27a by the objective lens 27 of the off-axis type FIA system of FIG. Similarly, a laser beam LB _Y is also irradiated to the Y-direction movable mirror 15mY of the wafer stage WS from an interferometric length measuring unit (not shown) in parallel with the Y-axis, and the projection optical system is extended on the extension of the laser beam LB _Y. Thirteen
There is an optical axis.

Then, the two-dimensional coordinates (X, Y) of the wafer stage WS on the optical axis of the projection optical system 13 are obtained from the measurement results of the laser beams LB _X and LB _Y. Since these laser beams LB _X and LB _Y intersect on the optical axis of the projection optical system 13, an Abbe error does not occur when measuring the coordinates of the wafer stage WS. Further, the two-dimensional coordinates of the wafer stage WS at a predetermined reference point in the observation field of the off-axis type FIA system are measured by the laser beams LB _OF and LB _Y without causing an Abbe error. Furthermore, the laser beam L
The yawing of the wafer stage WS is obtained from the difference between the measurement result by B _X and the measurement result by the laser beam LB _OF .

Further, in FIG. 4, a measurement point Mx in the Y direction in the exposure field 13a of the projection optical system 13 is irradiated with the heterodyne beam for position detection from the LIA optical system 45 of FIG. The heterodyne beam is irradiated from the LIA optical system for the Y axis to the measurement points My in the X direction on the inside. The measurement point Mx is spaced from the center of the exposure field 13a toward the observation field 27a by a distance RL _2.
The measurement point My is at the exposure field 1
It is located at a distance RL ₂ from the center of 3a toward the movable mirror 15mX.

Next, the reticle R used in this embodiment will be described with reference to FIG. FIG. 5A shows a pattern in the pattern area of the reticle R of this example.
In (a), a position measuring mark 71A is formed at the center of the reticle R, and a position measuring mark 71B is formed at a position having a distance a in the X direction and a distance b in the Y direction from the position measuring mark 71A. . The position measuring marks 71A and 71B are the same marks as the original image patterns of the position measuring marks 81 and 82 of FIG. 15 described in the conventional example. Therefore, the positions of the projected images of the position measurement marks 71A and 71B are determined by the method described with reference to FIG. 15, that is, the method using the LSA optical system 46 of FIG.
It can be detected by the alignment method).

Further, on a line extending in the Y direction of the dot pattern row extending in the Y direction of the position measuring marks 71B, grid-like position measuring marks (hereinafter referred to as "LIA measurement") arranged at a predetermined pitch in the X direction. 72X is formed, and grid-like LIA measurement marks 72Y arranged at a predetermined pitch in the Y direction are formed on the extension line in the X direction of the straight line portion extending in the X direction of the position measurement mark 71B. Has been formed. The pattern of the reticle R shown in FIG.
When the wafer W is exposed to light through 3 and developed, as shown in FIG.
As shown in (b), an image 71AP of the position measuring mark 71A is formed at the center of the exposure field 13a of the projection optical system 13. When the projection magnification of the projection optical system 13 is β, the position measuring mark 71AP is provided at the center of the exposure field 13a.
The wafer stage WS in the X direction from the state
5B in the Y direction, the image 71BP of the position measuring mark 71B moves to the center of the exposure field 13a, as shown in FIG.
The image 72XP of the LIA measurement mark 72X and the image 72YP of the LIA measurement mark 72Y move to the peripheral portion of a.
In the following, for the sake of simplicity, the position measurement mark image 71AP,
71BP is also referred to as "position measurement mark", and LIA measurement mark images 72XP and 72YP are also referred to as "LIA measurement mark".

Although the projection optical system 13 actually forms an inverted image of the reticle pattern on the wafer W, the projection optical system 13 forms an erect image on the wafer W for the sake of clarity. It is explained as a thing. And FIG.
The heterodyne beam from the LIA optical system 45 in the alignment sensor 17 is irradiated as a beam spot 73X on the LIA measurement mark 72XP of FIG. 5B, and the heterodyne beam from the YIA LIA optical system (not shown). Is radiated as a beam spot 73Y on the LIA measurement mark 72YP. As a result, the amount of misalignment of the LIA measurement mark 72XP in the X direction and the amount of misalignment of the LIA measurement mark 72YP in the Y direction are respectively L.
It is detected by the IA method (two-beam interference method). The LIA measurement marks 72XP and 72YP are sufficiently large lattice marks in consideration of the fact that the detection system including the LIA optical system 45 and the like have a certain installation error.

Using the reticle R of FIG. 5A, the following
As described above, the stepping accuracy is measured. That is, first of all
The wafer W coated with the photoresist by light is used as the wafer of FIG.
Placed on the Hastage WS and regularly on the wafer W
The pattern image of the reticle R shown in FIG.
The wafer W is developed. FIG. 6 shows a wafer on the wafer W after development.
FIG. 6 shows a hot arrangement, and in FIG.
16 shots at almost constant pitch in the X and Y directions
Area ES1, ES2, ..., ES16 are formed,
FIG. 5 is shown in each of the hot regions ESi (i = 1 to 16).
The pattern image of the reticle R in (a) is an uneven pattern.
Has been formed. For example, in the first shot area ES1
Is the position measurement mark 71AP₁And 71 BP₁And L
IA measurement mark 72XP₁And 72YP₁And formed
Has been. As described in FIG. 5B, the shot area
Position measurement mark 71AP during exposure to ES1₁Dew
It is located in the center of the light field, but
Shot area by stepping drive of Eha Stage WS
When detecting the position of ES1, the position measurement mark 71
BP₁Is set to the center of the exposure field and the LIA optical system
Heterodyne beam from LIA measurement mark 72X
P₁And 72YP ₁To irradiate.

Next, the wafer W exposed and developed as shown in FIG. 6 is placed on the wafer stage WS shown in FIG.
By driving the wafer stage WS by stepping drive, as shown in FIG.
…, ES16, ES9,…, ES12, ES5,…, E
LI of each shot area ESi by the LIA method in the order of S4
A The position of the measurement mark is detected. At this time, based on the array data of each shot area ESi (i = 1 to 16) on the wafer W of FIG. 6, the position measurement mark (71BP ₁ etc.) at the upper right corner of each shot area ESi is projected onto the projection optical system. The wafer stage WS is set stationary at the center of the exposure field 13 of FIG. Then, in this stationary state, coordinate measurement values X _Ai , Y _Ai , O by the laser beams LB _X , L B _Y , and L B _OF in FIG.
F _Ai , misalignment amount x _{Ai of} the X-axis LIA measurement mark (72XP _1, etc.) detected by the LIA method, Y-axis LIA measurement mark (72YP detected by the LIA method)
₁ ) and the like, the positional deviation amount y _Ai , the room temperature, the humidity, the atmospheric pressure, the interferometer correction value (the correction value of the wavelength of the laser beam due to the temperature, etc.), the torque value of the drive system of the wafer stage WS, etc. are sampled. The laser beams LB _X , LB _Y , L
The coordinate measurement value by B _OF and the detection result by the LIA method are sampled at 2 msec intervals and the measurement results are averaged. Other values are once for each shot area ESi and the exposure time at the time of actual exposure. Sampling is done for an equivalent time.

Next, the second measurement is performed on the wafer W of FIG. Also in this second measurement, by stepping the wafer stage WS, as shown in FIG. 7B, the shot areas ES13, ..., ES4 are arranged in the same order as in the first measurement by the LIA method. The position of the LIA measurement mark in each shot area ESi is detected. Even in this second measurement, each shot area ESi (i =
For 1-16), the laser beam LB _X in FIG. 4, LB _Y,
Coordinate measurement values by LB _OF X _Bi , Y _Bi , OF _Bi , LIA measurement mark for the X axis detected by the LIA method (72XP
₍₁ etc.) misalignment amount x _Bi , YIA LIA measurement mark (72YP ₁ etc.) position misalignment y _Bi detected by the LIA method, room temperature, humidity, atmospheric pressure, interferometer correction value (temperature The correction value of the wavelength of the laser beam, etc., and the torque value of the drive system of the wafer stage WS are sampled.

After that, the measurement results obtained by the two measurements as described above are analyzed to find the factor of the stepping error. First, the result of subtracting the measurement result of the first time (the value with the subscript A) from the measurement result of the second time (the value with the subscript B) is an error (stepping error) that occurs when the wafer stage WS is driven by stepping. Becomes Therefore, the stepping errors of the coordinate measurement values by the laser beams LB _X , LB _Y , and LB _OF are set as ΔX _i , ΔY _i , and ΔOF _i , and LI is set.
Supposing that the stepping error of the position deviation amount of the X-axis LIA measurement mark detected by the A method and the position deviation amount of the Y-axis LIA measurement mark detected by the LIA method is Δx _i and Δy _i , respectively. , These stepping errors are expressed as follows.

[0052]

[Number 1] _{ΔX i = X Bi -X A,} ΔY i = Y Bi -Y A, ΔOF
_i = OF _Bi −OF _A

[0053]

[Mathematical formula-see original document] In the same way as Δx _i = x _Bi −x _A and Δy _i = y _Bi −y _A , the stepping error is obtained by the difference calculation for the room temperature and the like. These stepping errors can be classified according to factors as follows. Offset error of measurement result of laser interferometer (ΔX _i , Δ
Y _i ): This is considered to be a stage control error of the wafer stage WS. (ΔOF _i −ΔX _i ) / (Interval RL ₁ between laser beams LB _X and LB _OF ) = YAW: This is considered to be a yawing error of wafer stage WS.

(Δx _i , Δy _i )-(ΔX _i , ΔY _i )-
(YAW RL ₂ , YAW RL ₂ ) (where YAW is the yawing error, RL ₂ is the LIA as shown in FIG. 4)
(The distance from the center of exposure of the measurement beam): This is considered to be an air fluctuation error and a laser interferometer error. Temperature, humidity, atmospheric pressure, stepping error of wavelength correction value of laser interferometer: These are considered to be correction errors of measurement result of laser interferometer. Stepping error of torque value of drive system of wafer stage WS: This is considered to be stage control accuracy of the wafer stage WS.

As described above, since the stepping errors classified as to form the stepping error as a whole, the stepping error is adjusted efficiently by adjusting the factors worse than the predetermined reference value among these numerical values. The accuracy can be improved. In the example of FIG. 7, the stepping order is the same in the first and second steps, but even if the stepping direction is changed in the first and second steps as shown in FIGS. 8A and 8B. good. That is, in FIG. 8A, the shot areas ESi are measured in the same order as in FIG. 7A, but in FIG.
…, ES8, ES12,…, ES9, ES8,…, ES
5, ES4, ..., ES1 are measured in this order. In this way, by changing the stepping direction between the first and second times, it is possible to check the difference in stepping accuracy depending on the stepping direction. It is also possible to check the influence of the expansion of the wafer W by the exposure by performing the measurement while actually exposing each shot area ESi in the first time and performing the measurement in the second time without performing the exposure. . In addition, it is possible to investigate the influence of the case where the auto leveling for correcting the inclination of the wafer is performed and the case where it is not performed.

Next, an example of a method of displaying the measurement result will be described. First, considering the case of individually displaying the above-mentioned results (1) to (3), the vector display as shown in FIG. 9 is preferable.
FIG. 9 shows each shot area ES1, ES2, E on the wafer W.
For each S3, ..., Shown is an offset obtained by subtracting the coordinate (X _Ai , Y _Ai ) measured for the first time from the coordinate (X _Bi , Y _Bi ) measured for the second time by a laser interferometer, for example. Vectors (ΔX ₁ , ΔY ₁ ), (ΔX ₂ , ΔY ₂ ), (ΔX ₃ ,
ΔY ₃ ), ... Are enlarged and plotted. If the error factor of the offset can be further divided into a linear error, a non-linear error, and the like to be displayed, the characteristics of each row of the shot area on the wafer W and the characteristics of the shot area in the peripheral area can be checked for the stepping error. It can be identified at a glance.

The coordinates measured by the laser interferometer
(X, Y) and coordinates (x, y) measured by the LIA method
And for the offset in each shot area ESi
(ΔX _i, ΔY_i) And (Δx_i, Δy_i) And 2msec
A value that is three times the standard deviation (3
σ) may be displayed. Figure 10 (a) shows
X-coordinate offset Δ in the measurement result by the laser interferometer
X_iIs displayed for each shot area ESi.
10 (b) shows 3σ of the sampling value of the X coordinate.
It is displayed for each dot area ESi. The value of 3σ
How much vibration is occurring during actual exposure
It is possible to check the
It is also possible to prevent the deterioration of the image.

Further, as shown in FIG. 11, the measurement data for each shot area may be Fourier transformed and the intensity may be displayed on the vertical axis with the frequency f as the horizontal axis. As a result, it is possible to accurately check which vibration of the driving unit in the exposure apparatus affects the stepping error. In this regard, it is also possible to examine the average vibration of the exposure apparatus by Fourier-transforming the measurement data for each shot area and averaging the results. Alternatively, the measurement may be performed several times for each shot area, the measurement data may be Fourier-transformed, and the Fourier-transformed results may be averaged to examine the difference between the shot areas. In addition, in the method of performing the Fourier transform as described above, the measurement accuracy particularly when the position detection is performed by the LIA method occurs as a new error factor, but by performing the measurement a plurality of times and averaging the Fourier transform results, the new Such error factors are errors that can be ignored.

Next, a second embodiment of the present invention will be described with reference to FIG. Also in this embodiment, the projection exposure apparatus shown in FIGS. 1 to 3 is used. Further, as the reticle, the reticle R on which the pattern of FIG. 5A is formed is used, and as the wafer, as shown in FIG. 6, shot areas ES arranged in the X direction and the Y direction at substantially constant pitches.
It is assumed that a wafer W on which the pattern of the reticle R shown in FIG.

FIG. 12 shows a wafer W used in this embodiment.
However, in the first stage, the shot areas ES1, ES2, ...,
Each ES16 has a position measurement mark 71 shown in FIG.
Images of A, 71B and LIA measurement marks 72X, 72Y
Are formed as an uneven pattern. From this state,
Predetermined order for each shot area ESi (i = 1 to 16)
(For example, in the order of FIG. 7A), each shot area ES
LIA measurement mark in i (72XP₁, 72YP₁etc)
Position is detected using the LIA optical system 45 of FIG.
In this state, the pattern of the reticle R is exposed. And dew
Laser beam LB of FIG. 4 in a stationary state in the light_X, LB_Y, L
B_OFCoordinate measurement value X_Ai, Y_Ai, OF _Ai, LIA method
LIA measurement mark (72XP) for X axis detected by₁
Misalignment amount x)_Ai, For Y-axis detected by LIA method
LIA measurement mark (72YP ₁Misalignment amount y)
_Ai, Room temperature, humidity, atmospheric pressure, interferometer correction value (temperature etc.
Laser beam wavelength correction value) and wafer stay
The torque value of the drive system of the WS is sampled.

[0061] Thus, for example, with respect to the shot area ES1, the pattern image of the reticle R is exposed on the shot area EQ1 around the position measurement mark 71 bp _1, in the vicinity of the position measurement marks 71 bp ₁ is 5
Image 71AQ ₁ of position measuring mark 71A at the center of (a)
Is exposed. Similarly, each shot area ES2, E
The pattern images of the reticle R are exposed on shot areas EQ2, EQ3, ..., EQ16 which are laterally displaced with respect to S3 ,. Then, by developing the wafer W, the pattern image on the shot regions EQ1 to EQ16 becomes an uneven pattern.

Next, the shot areas EQ1 to EQ1 on the wafer W are formed.
The position of the LIA measurement mark in each shot area EQi is detected using the LIA optical system 45 of FIG. 2 in a predetermined order with respect to the EQ 16 (for example, in the order of FIG. 7B). Then, the positional deviation of the coordinate measurement values XQ _Bi , YQ _Bi , OFQ _Bi by the laser beams LB _X , LB _Y , LB _OF in FIG. 4 and the LIA measurement mark for the X axis (72XP _1, etc.) detected by the LIA method. Quantity xQ _Bi , L for Y axis detected by LIA method
IA measurement mark (72YP ₁ etc.) displacement amount y
Q _Bi , room temperature, humidity, atmospheric pressure, interferometer correction value (correction value of laser beam wavelength due to temperature, etc.), and torque value of drive system of wafer stage WS are sampled.

After that, the measurement results obtained by the two measurements as described above are analyzed to find the factor of the stepping error. In this case, as an example, the difference between the first time and the second time is obtained by the method described in the first embodiment, and the stepping error is classified by each factor. In addition, since the second measurement result is the actual exposure result in this embodiment, by comparing the stepping error obtained in this embodiment with the stepping error obtained in the method of the first embodiment, The presence of errors other than the stepping error obtained by the method of the first embodiment (errors due to the twist of the exposure apparatus, the drift of the reticle R, etc.) can be predicted. Further, the method of the second embodiment is
It may be used for checking the state of stepping accuracy not only when adjusting the exposure apparatus but also at the actual use place during maintenance or the like.

In the above embodiment, the TTL alignment sensor 17 is used to detect the position of each shot area. However, the off-axis alignment system (20 to 34) of FIG. 1 is used. Projection optical system 13
The position of each shot area may be detected by using an alignment system that does not intervene. In this case, although the measurement position is slightly different from the actual exposure position, the same stepping error can be detected. There Further, even when using a an off-axis alignment system, by performing coordinate measurement using a laser beam LB _Y and LB _OF 4, an advantage that the occurrence of Abbe errors can be suppressed . Furthermore, the position of each shot area may be detected by using a TTR (through the reticle) type alignment system capable of simultaneously measuring the reticle R and the wafer W.

Further, although the above-described embodiment is one in which the present invention is applied to a step-and-repeat type projection exposure apparatus (stepper or the like), the present invention is applied to a slit-shaped illumination area for each shot area. It can also be applied to a so-called step-and-scan type exposure apparatus that scans and exposes a reticle and a wafer. In this case, a laser interferometer that monitors the relative position of the reticle and the wafer, a homodyne LIA alignment system that can continuously monitor the position of the wafer in the scanning direction, and a continuous non-scanning direction that is perpendicular to the scanning direction. By using the heterodyne type LIA alignment system capable of monitoring the position by using the stepping error, it is possible to measure the stepping error as in the above-described embodiment.

Further, in the above-mentioned embodiment, the position of each mark is detected after the wafer W is developed. However, the position of each mark may be detected at the latent image stage without developing after the exposure. Good. As described above, the present invention is not limited to the above-described embodiments, and various configurations can be taken without departing from the gist of the present invention.

[0067]

According to the first stepping accuracy measuring method of the present invention, since it is only necessary to compare the measurement results of two times without actually performing the exposure, there is an advantage that the stepping accuracy of the wafer stage is measured with high efficiency. There is. Further, since the measurement result by the coordinate measuring unit and the measurement result by the alignment system are individually stored, there is an advantage that a factor affecting the stepping accuracy can be analyzed. Therefore, when it is used particularly in the adjustment process of the exposure apparatus, the factor of the stepping error can be specified, and the adjustment time can be shortened.

Further, according to the second stepping accuracy measuring method, since the measurement is carried out during the exposure, there is an advantage that the stepping accuracy measuring efficiency of the wafer stage is high. Further, since the measurement result by the coordinate measuring unit and the measurement result by the alignment system are individually stored, there is an advantage that a factor affecting the stepping accuracy can be analyzed.
Further, since the actual exposure result is used, the factor of deterioration of the exposed image can also be analyzed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a projection exposure apparatus to which a stepping accuracy measuring method according to an embodiment is applied.

FIG. 2 is a TTL alignment sensor 1 shown in FIG.
7 is a block diagram showing a detailed configuration of No. 7.

3 is a block diagram showing a detailed configuration of a main control system 18 and the like in FIG.

FIG. 4 Measurement beam of laser interferometer and wafer stage W
FIG. 6 is a plan view showing a positional relationship with S and the like.

5A is a plan view showing a pattern of a reticle R used in the embodiment, and FIG. 5B is a partially cutaway view showing a projected view of the pattern of the reticle R. FIG.

FIG. 6 is a plan view showing a shot array on a wafer W to be measured in an example.

FIG. 7 is a diagram showing an example of a first measurement procedure and a second measurement procedure in the first embodiment.

FIG. 8 is a diagram showing another example of the first measurement procedure and the second measurement procedure in the first embodiment.

FIG. 9 is a diagram showing an example in which a stepping error is shown in a vector display.

10A is a diagram showing an offset of a stepping error, and FIG. 10B is a diagram showing three times the standard deviation of measurement results.

FIG. 11 is a diagram showing an example of the result of Fourier transform of the measurement result.

FIG. 12 is a plan view showing a shot array obtained by performing position measurement and exposure of each shot area on the wafer in the second embodiment.

FIG. 13 is a plan view showing a shot array on a wafer in an example of a conventional method of measuring stepping accuracy.

FIG. 14 is a plan view showing a shot array on a wafer in another example of the conventional method of measuring the stepping accuracy.

FIG. 15 is a diagram for explaining a conventional method for measuring a position measuring mark.

[Explanation of symbols]

 1 Mercury Lamp 3 Illumination Optical System 9 Main Condenser Lens R Reticle 13 Projection Optical System W Wafer WS Wafer Stage 15 Laser Interferometer 17 TTL Method Alignment Sensor 18 Main Control System ES1 to ES16 Shot Area 71AP, 71BP Position Measurement Mark 72XP, 72YP LIA measurement mark

Claims (2)

[Claims] 1. A substrate stage for holding a photosensitive substrate on which a pattern on a mask is exposed and positioning the substrate in a two-dimensional plane, and coordinate measuring means for measuring the positioning coordinates of the substrate stage, In a method of measuring the stepping accuracy of the substrate stage of an exposure apparatus having an alignment system for detecting the position of a mark for alignment on a substrate, a predetermined substrate on which a plurality of measurement patterns are formed in advance is placed on the substrate stage. And when the positions of the plurality of measurement patterns are detected and stored by the alignment system in a predetermined first order, and the positions of the plurality of measurement patterns are detected by the alignment system. A first step of storing coordinate values of the substrate stage measured by the coordinate measuring means, and a predetermined base in a predetermined second order. The substrate which is detected by the alignment system and stores the positions of the plurality of measurement patterns above, and which is measured by the coordinate measuring unit when the positions of the plurality of measurement patterns are detected by the alignment system. A second step of storing the coordinate values of the stage and a measurement result of the first step and a measurement result of the second step are compared for each of the plurality of measurement patterns on the predetermined substrate. A stepping accuracy measuring method comprising: a third step. 2. A substrate stage for holding a photosensitive substrate on which a pattern on a mask is exposed and positioning the substrate in a two-dimensional plane, and coordinate measuring means for measuring the positioning coordinates of the substrate stage, In a method of measuring the stepping accuracy of the substrate stage of an exposure apparatus having an alignment system for detecting the position of a mark for alignment on a substrate, a predetermined substrate on which a plurality of measurement patterns are formed in advance is placed on the substrate stage. And exposing the mask pattern in correspondence with each of the plurality of measurement patterns in a predetermined order, and aligning the positions of the plurality of measurement patterns when the mask pattern is exposed. The coordinate system detects and stores the coordinate system when the positions of the plurality of measurement patterns are detected by the alignment system. A first step of storing coordinate values of the substrate stage measured by means, and a position of the pattern of the mask exposed on the predetermined substrate in the first step is detected and stored by the alignment system. And a second step of storing coordinate values of the substrate stage measured by the coordinate measuring means when the exposure position of the pattern of the mask is detected by the alignment system, and a measurement result in the first step And a third step of obtaining the stepping accuracy of the substrate stage using the measurement result of the second step, the stepping accuracy measuring method.