JPS63274143A - Alignment device - Google Patents

Abstract

PURPOSE:To make constant the illuminance of an illuminating light by a method wherein such a second object as a wafer is placed at a prescribed position to be lighted by an illumination optical system and the image is light-received by a detector to obtain a signal, the signal is compared with a reference value being stored in advance and the amount of light of the illuminating light is corrected. CONSTITUTION:The correction of the amount of a laser beam is performed by a method wherein an LED is lighted by an arithmetic system ARM and light is detected by a detector D. The output of the detector D is compared with the value of a reference output being stored in a memory MEM 1 by the system ARM. A wafer WF is installed at a prescribed position, a shutter being arranged in the interior of an illuminating system, which reaches to a lens EL from a light source LP2 through a fiber SF and so on, is opened and an illuminating light is lighted on the wafer WF. The reflected light reflected from the wafer surface or diffracted light is detected by the detector D through a projection lens PO and data are sent to the system ARM. The system ARM compares the measured data with a reference being stored in a memory MEM2, computes the correction amount of the illuminance on the side of the light source and commands to a driving unit KTU for correcting and controlling the amount of light. An element for adjusting the amount of light is rotated on the basis of the command to perform the correction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an alignment device, and more particularly to a device that observes an object having a transparent thin film on its surface, detects information thereof, and aligns the object. A typical example of this type of apparatus is an alignment apparatus that is applied to a projection exposure apparatus that exposes a pattern onto a wafer in sections.

[Prior Art and Problems to be Solved by the Invention] Two basic performances of an exposure apparatus to which this type of alignment apparatus is applied are resolution and overlay accuracy. Regarding resolution, handling is very simple. This is because there are only a few parameters that determine resolving power, and in devices called steppers, the resolving power of the optical system can be easily estimated by knowing the wavelength used and the numerical aperture (NA) of the projection lens. Further, even in the case of X-ray exposure, there are only limited parameters such as penumbra blur due to the size of the light source.

Since the realization of single-transistor memory cells, advances in lithography, that is, printing technology for fine line widths, and advances in process technologies such as etching have played a central role in increasing the degree of integration of semiconductors. In terms of resolution, optical systems have been steadily improving, as can be seen by tracing the history of stepper lenses. Optical systems have broken the 1 μm barrier, and lenses compatible with the submicron era are being announced one after another.

On the other hand, in the process, new ideas such as trenching methods and the combination of lower and higher height differences are being realized using three-dimensional IC concepts. The greatest point of contact between advances in resolution on the exposure equipment side and advances on the process side is the overlapping of patterns in each process. In this sense, it can be said that overlay accuracy is becoming increasingly important in exposure equipment.

It is difficult to express the accuracy of melon matching using simple parameters such as resolution. This reflects the diversity of wafer processes, but it can also be attributed to the wide variety of configurations of alignment systems used for overlaying. What makes wafer process factors even more complex is that this problem is not limited to just one substrate, but also needs to be considered in conjunction with the photoresist coated on the wafer. One of the obvious trends in current semiconductor technology is the trend toward three-dimensional IC configurations. Among these, it is unavoidable that the wafer surface has a high level difference, but this high level difference clearly has a negative effect on the coating state of the photoresist. Furthermore, wafers are becoming increasingly larger from 6 inches to 8 inches and even 10 inches. When applying photoresist to a large-diameter wafer using a spin method, it is obvious that the state of resist application differs between the center and the periphery, and this difference becomes more pronounced as the level difference on the wafer surface becomes larger. is also clear. In fact, it is well known that the alignment state changes under the influence of resist coating, and research is being conducted on how to achieve uniform coating.

Another thing to keep in mind when it comes to photoresists is the trend toward multilayering in the submicron era. Since means for improving resolution, such as a multilayer resist process and CEL, are inevitably employed in several processes, countermeasures for this are also necessary. It can be said that exposure equipment is being forced to deal with these new wafer processes in the field of stacking.

On the other hand, the diversity of alignment systems is a testament to the flexibility and difficulty of system configuration.

Currently, no two alignment systems that have been proposed and implemented are the same, and each system has its own advantages and disadvantages. For example, one example is the exposure apparatus 1 disclosed in Japanese Patent Application Laid-Open No. 58-25638r filed by the present applicant. This system uses a projection optical system that is telecentric to both the reticle and the wafer.
This is one of the excellent configuration examples that realize the concept of nAxis. Although the projection lens is aberration corrected for the g-line (436 nm), it is designed to exhibit similar performance at the He-Cd laser wavelength (442 nm). In one embodiment disclosed in this patent application, a laser beam scanning method using a He-Cd laser is adopted as an alignment signal detection method, and as a result, TTL on A
xis, that is, it is possible to start an immediate exposure operation in an aligned state. TTL on Axis
In the sense that the only error factor for an exposure apparatus is an alignment signal detection error, the S system has the configuration with the least systematic error factors, and is close to an ideal system. The only drawback to this system is that it is sensitive to processes that absorb wavelengths near the exposure wavelength, such as multilayer resists.

On the other hand, wavelengths other than the exposure wavelength, specifically e
line (546nm) or He-Ne laser (633nm)
), many system configuration examples using longer wavelengths have also been proposed. This system has the advantage of being robust against absorption-type processes such as multilayer resist because it uses a wavelength longer than the exposure wavelength. However, the image height for alignment is usually fixed with respect to the projection lens due to various chromatic aberrations of the projection lens, which introduces the error factor of moving the wafer to the exposure position after alignment is detected. Become. For this reason, alignment systems using light other than the exposure wavelength are inevitably TTL.
This results in an offAxis system.

However, in recent years, requirements for overlay accuracy have become increasingly strict, and even detection errors in alignment signals, which are the cause of errors in ideal systems, as shown in Japanese Patent Application Laid-open No. 58-25638, have even become a problem. ing.

According to the inventors' analysis of the detection error component of the alignment signal, it has been found that the majority of the error component is due to problems in coating the photoresist. There are various error factors caused by the photoresist, but the following two factors are thought to be the largest among them.

The first is the interference effect between light reflected from the surface of the resist and light that passes through the resist, hits the wafer substrate, and returns. In particular, as mentioned above, the photoresist is not always coated uniformly within the wafer, and the coating condition is often different between the center and the periphery. I have a problem with. Therefore, the structure of the alignment mark for each shot on the wafer differs depending on the location when considering the resist coating.
Therefore, the interference effects are also different. This interference seems to be the most significant cause of alignment errors due to the influence of resist coating.

The second factor is multiple reflection. The resist has the character of a leading wave path. Therefore, a portion of the light reflected by the wafer substrate is reflected at the resist-air interface, returns to the wafer, and is reflected again.

This effect becomes more pronounced as the reflectance of the substrate increases, and this multiple reflected light eventually causes interference and becomes a factor that deteriorates alignment accuracy.

Other resist factors can be considered, such as image deviation due to refraction, but these are only secondary factors, and alignment is achieved by eliminating the two factors mentioned above, especially the first interference effect. The analysis results confirmed that this greatly contributes to improving the accuracy of.

In order to solve the various problems mentioned above, the present applicant has already proposed an observation device j in Japanese Patent Application No. 134873/1987. In an apparatus that projects onto a second object such as a wafer via a projection optical system, an observation optical system that is coupled to the projection optical system and observes the second object is disposed, and the observation optical system is connected to a projection lens. This is a device that detects the position of a second object using illumination light applied from between the object and the second object without going through a projection lens. By applying the above invention to the alignment device, the influence of the resist can be reduced. We now have a prospect of achieving high-precision alignment.

On the other hand, it has been found that there are various practical problems when applying the above invention, and solutions have been desired.

For example, when aligning a first object and a second object with high precision, it is necessary to secure the signal output and S/N of the mark detection signal for alignment above a certain level. There is a problem in that it is necessary to take measures such as keeping the illuminance of the illumination light constant.

SUMMARY OF THE INVENTION In view of the problems of the conventional method described above, an object of the present invention is to provide a positioning apparatus and an exposure apparatus using the same, which achieve highly accurate positioning by keeping the illuminance of illumination light constant for mark detection. It is about providing.

[Means and operations for solving the problems] In order to achieve the above object, the present invention provides an apparatus for projecting a pattern drawn on a first object onto a second object via a projection optical system. In the apparatus for aligning the first object and the second object, the second object is illuminated by an illumination optical system, and an image of the second object caused by the illumination light is captured by a detector for alignment. Prior to receiving light, a second standard object is placed in a predetermined position and illuminated by the illumination optical system, and its image is received by the detector to obtain a signal, and the pre-stored reference value and the signal are The amount of illumination light from the illumination optical system is corrected based on the results of the comparison.

Thereby, the illuminance of the illumination light can be made constant.

Note that the illuminance may be corrected using a polarizing plate or an ND filter. Furthermore, it is convenient to correct the sensitivity of the detector before acquiring the signal from the second standard object, as this allows more accurate control of the illuminance of the illumination light. Furthermore, the second object is illuminated from between the projection optical system and the second object without going through the projection optical system, and an image of the second object resulting from the illumination is received through the projection optical system. For example, interference of reflected light can be suppressed and alignment can be performed with high precision.

[Explanation of Examples] The method of illuminating the wafer from outside the projection optical system and receiving light through the projection optical system as described above is adopted, and furthermore, the wavelength of the wafer illumination light is different from the exposure wavelength. The following methods of receiving light can be considered.

(1) A method of simply placing the light receiving system after passing through the reticle (2) A method of installing a chromatic aberration correction optical system between the reticle and the projection optical system and placing the light receiving system after passing through the reticle (3) Reticle and the projection optical system A method of placing a mirror between the systems and receiving light without going through a reticle (a chromatic aberration correction optical system is added). In some cases, due to chromatic aberration, a large window must be provided in the reticle or the image may become blurred.

Furthermore, according to method (2), since a small chromatic aberration correcting optical system has not been devised, there is a problem in that the exposure area is reduced or an escape mechanism is added to the chromatic aberration correcting optical system during exposure.

In method (3), since the reticle serving as a reference cannot be observed simultaneously with the wafer, the problem is how to take the reference. However, setting a temporary reference also has the advantage that alignment can be performed by knowing the positional relationship between the reticle and the temporary reference.

Since the observation apparatus J of Japanese Patent Application No. 61-134873 filed by the present applicant uses dark field illumination of the wafer, the problem is how to illuminate and observe the temporary reference.

As a method that does not illuminate or observe a temporary reference, it is possible to use a detection detector (for example, a CCD screen) as a reference. Due to reasons such as installing a pupil filter to improve the S/N ratio for detecting wafer marks, various optical systems are installed in the standard detector, and their stability poses problems in measuring the relative position between the wafer and the standard. becomes.

Embodiments of the present invention that solve these problems will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of the overall configuration of a semiconductor projection exposure apparatus using an alignment apparatus according to an embodiment of the present invention. In the figure, a pattern drawn on a reticle LT is projected onto a wafer WF placed on an XY stage WS via a projection optical system PO using illumination light from an illumination system LP.

At this time, the wafer WF is aligned with the reticle LT in advance, and by moving the XY stage WS 8 times, the wafer WF is placed at a predetermined automatic alignment (hereinafter referred to as AA) end position, and is placed at an appropriate position. Projection will be performed.

The flow of light rays during AA will be explained below.

First, the wafer illumination system WL is connected to the projection optical system PO and the wafer W.
From between F, the wafer WF is illuminated with light having a wavelength different from the wavelength of the illumination light that exposes the wafer WF, without going through the projection optical system PO. Wafer W illuminated by wafer illumination system WL
The image of F is taken into the detection optical system after the mirror M1 via the projection optical system PO.

In the detection optical system, the image of the wafer WF is passed through the chromatic aberration correction optical system O3, which corrects chromatic aberration caused by light having a different exposure wavelength passing through the projection optical system Po, to a reference mask whose relative position with respect to the reticle LT is known. Image is formed on 8M. The optical system after the reference mask 8M is designed so that the mark on the reference mask 8M and the image of the wafer can be observed at the same time.

The image of the reference mark of the reference mask BM and the image of the wafer WF are divided into two by the roof prism DP via the objective lens L1 and the relay lens RL. Each of the further divided images is Erekta-EIX.

E I Y , through mirrors M5X and M5Y, pupil filter F1. ．． Leading to FIY. Mirrors M6x and M7 direct the image to a desired orientation for position detection in the X direction.
It reaches the image scanning mirror (polygon mirror here) PM via X, M8x and erector E2x. The same applies to the Y direction, but the configuration of the mirror that directs the image to the desired direction for position detection in the Y direction is different.

Then, the reference mark of the reference mask BM and the image of the wafer WF are scanned by the polygon mirror PM, and f
Slits SL, SLY through θ lenses L2x and L2y
, and the image forms again at 22. slit st, x,
A band-shaped aperture is provided at st and y, and the light transmitted through the band-shaped aperture is detected by detectors DX and DY. I
FM is an interferometer that detects the position of the stage, IM is an interferometer mirror, and MO is an XY stage drive system.

The operation of AA will be explained below.

FIG. 2 is a diagram showing the position of the mark MKI on the wafer WF and the illumination direction DR of the wafer illumination light. Same figure (b)
is an enlarged view of the sea urchin mark part in FIG. The direction is the wafer mark M K 1 x,
The four-tree incidence is perpendicular or parallel to M K 1 y. Note that the illumination light in the directions of DRI and DR2 is hardly reflected at the wafer mark MKIK, and the illumination light in the directions of DR3 and DR4 is hardly reflected at the wafer mark MK 1 y.
Therefore, the illumination light in the directions of DRI and DR2 is irradiated only around the wafer mark MKIY, and the illumination light in the directions DR3 and DR4 is irradiated only around the wafer mark MKIX. Further, each wafer illumination light is obliquely illuminated with respect to the wafer WF, and the incident angle is the first
The detection optical system shown in the figure for detecting reflected light from the wafer has the following relationship with respect to the maximum angle that it has on the wafer.

(Maximum angle +lO° that the detection optical system has on the wafer)≦(Incidence angle of illumination light onto the wafer) The wafer mark image illuminated in this manner is formed on the reference mask 8M in FIG. 1.

FIG. 3 is a diagram showing the arrangement of the illumination system of the reference mask BM and the arrangement of the reference mark MK and wafer mark image. In FIG. 5A, the wafer mark image passes through the window W of the reference mask BM and enters the objective lens L1. The reference mark portion of the reference mask BM is a transparent portion, for example, an opening made in the reference mask BM, and the reference mask illumination light is transmitted through the reference mark portion and becomes a reference mark image and enters the objective lens L1.

As a result, a reference mark signal with good S/H can be obtained.

The reference mark image and the wafer image are separated by the roof prism into images of the reference mark MK y and wafer mark MKIY and images of the reference mark MKX and wafer mark M K 1 x.

As shown in FIG. 1, the image extending in the X direction (for position detection in the Y direction) is mirror M5. ．． It is rotated by 90 degrees by May and M7y and enters the polygon PM. Also, Y
The image extending in the direction (for position detection in the X direction) is a mirror M5
x, M6x, M7, and M8x reach the polygon PM without rotating unlike the former, and the slits SLX and SL pass through fθ lenses L2X and L2Y, respectively.
Image is formed on Y. In these X-direction and Y-direction optical systems, the lenses Ll and RL are shared, and the erector E
lx and EIY%E2X and E2. are the same thing. These are optical systems that form images of each mark at a predetermined magnification.

As mentioned above, the marks in the X and Y directions arranged orthogonally to each other are separated by the roof prism DP, and one of the marks is further rotated by 90 degrees around the optical axis by the image rotation optical system to align the marks. It is now possible to scan with one polygon PM. It is clear that this is superior to the case where two polygons are prepared.

FIG. 4 is a diagram showing a reference mark image on a slit, a wafer mark image, a scanning direction, a slit shape, and an electric signal waveform detected from light transmitted through the slit. This is the first
The slits SLx and SL in the figure are used as fθ lenses.2. ,L2
It is a top view seen from the Y side.

The image formed on the slit SL is scanned by the polygon PM on the slit SL surface in the scanning direction indicated by the arrow in FIG. The slit SLY has a band-shaped transparent part, the slit SLye, SL? 2 is provided, and the slit S
A slit SLy+ is similarly provided in L. The light transmitted through these slits is detected by detectors Dx and Dy, and becomes an electric signal waveform S Y * S X. The relative position of the reference mark and wafer mark is measured using the obtained electrical signal waveform.

In addition, in Fig. 4, the detector D is connected to each slit SL□, 5L.
There are two in total, one behind Y2 and one behind 5Lxt.

Since the relative position of the reticle LT and the reference mask (reference mark) BM is known (for example, the reticle is aligned with the reference mask in advance), the wafer is removed from the reference mask by the positional deviation between the reticle and the reference mask. By shifting and aligning, the reticle and wafer can be aligned as a result.

Next, the slit light receiving method will be explained.

In FIG. 4, mark images M KY , M K 1
The slits corresponding to y are S LYI and S L, respectively.
It is Y2. The slits SLy+ and 5LY2 are offset by a predetermined amount 1 and formed on a single substrate. Behind the slits SLY l + S L Y2, one detector D is arranged which can receive both of the lights. The mark images MKy and MKIY are scanned in the direction of the arrow, and first the signal S1 of the reference mark image MKY is detected, and then the signal S2 of the wafer mark image MKIY is detected at an interval of offset 1.

Further, for mark images MK1x and MKx, one detector Dx is arranged behind the slit 5LXI. The mark images MKX and MKIX are scanned in the direction of the arrow,
First, the signal S3 of the reference mark image MKX is detected, and then the signal S4 of the wafer mark image MKIX is detected.

Then, relative position information between the two is calculated from the above signal.

FIG. 4(a) is information in the Y-axis direction in this example.

From the signals Sl and 32 in FIG. 4(a), mark images MKa and M
The relative position of KI is calculated based on a clock pulse (not shown), and the difference between this value and the known slit offset L corresponds to the amount of positional deviation. As the signal processing method, averaging and various other known methods can be used.

FIG. 4(b) is information in the X-axis direction in this example.

In FIG. 4(b), the arrangement relationship between the mark images MK I The position is calculated from the signals S3 and 34 using the same processing method as described above, and the difference between the value and the predetermined interval described above is equivalent to the positional deviation.

As described above, highly accurate position detection is possible by observing the reference marks and wafer marks placed apart on each of the X and Y axes with a simple configuration of one detector for each axis and one or two slits. Become.

Note that FIG. 5 shows another example of the slit light receiving method. In the figure, the detector includes each slit S LX3.
S LX4. 1 each behind S Lys+ S LY4
They are placed one by one. In the same figure (a), a reference mark image MKY and a wafer mark image MK for position detection in the Y direction are shown.
IY is scanned in the direction of the arrow, and slit SLY! and SL,4 and the detectors behind each,
Signals S5 and S6 are detected. Relative position information between the reference mark MKY and the wafer mark MKIY is calculated from the signals S5 and S6. The same is true for the X direction, and in FIG. 3B, the reference mark image M is scanned with an x and the wafer mark image MKIX is scanned in the direction of the arrow, and the slit SLX! and 5LX4 and the detectors behind each detect signals S7 and S8. Note that the slits 5LX3 and 5Lx4 are arranged at a predetermined interval, and the mark image M K x is
4, the mark images MKIX are detected by the slits 5LX3, and other signals are ignored.

The relative position information between the reference mark MKx and the wafer mark MKIX is calculated from the signals S7 and S8.

Compared to the light receiving method shown in FIG. 4, in FIG. 5, signals are taken in at the same time, and each mark is separately received by a separate detector. This makes it possible to minimize errors caused by uneven polygon rotation, and to appropriately arrange detectors for optical signals of different intensities (optimizing accuracy and cost).

Next, the wafer illumination optical system (WL in FIG. 1) will be explained.

The laser beam may be introduced onto the wafer by directly introducing the laser beam onto the wafer using a mirror or the like, or by routing the laser beam through an optical fiber OFF as shown in FIG. 6(C). However, using an optical system such as a mirror increases the size, restricts the degree of freedom in routing, and increases cost. Furthermore, when optical fibers are used, there is a problem in that the lights from each element are combined and cause interference, causing uneven illumination.

In this embodiment, the laser beam LSR is made to enter the sea urchin AWF through a single mode fiber SF as shown in FIG. 6(a). Single mode fiber SF is
Since there is no phase change or interference inside the
The emitted light has an ideal Gaussian distribution, making it possible to provide illumination without uneven illumination.

In FIG. 6(b), a gradient index lens SL and an expander lens EL are added to both ends of the single mode fiber SF. Gradient index lens S
L is designed to efficiently condense the incident light, introduce it into the fiber SF, and output it as parallel light. Thereafter, the light passes through an expander lens EL and becomes parallel light expanded to a desired size. By adding the gradient index lens SL and the expander EL, an illumination optical system with a high intensity and uniform illuminance distribution is realized. FIGS. 6(d) to 6(f) are conceptual diagrams of illuminance distribution in the wafer illumination light introduction method shown in FIGS. 6(a) to 6(C), respectively.

In addition, in such a single mode fiber SF, the second
The wafer is illuminated from each of the directions DRI to DR4 in FIG. 2B, and in this embodiment, the optical path lengths are determined so that the illumination in the opposing directions becomes non-interfering light with each other. That is, DRI and DR2 are made to have different optical path lengths for introducing illumination light by changing the length of the fiber SF, etc., so that the light beams do not interfere with each other. The same applies to DR3 and DR4. It is sufficient to make the illuminations in opposing directions become incoherent light, but the effect can be improved by making the optical path lengths different in all four directions so that each of the four illuminations becomes incoherent light. It's large.

Next, the chromatic aberration correction optical system will be explained.

When performing TTL alignment using light of a wavelength different from the exposure wavelength as in this embodiment, it is necessary to satisfactorily correct various chromatic aberrations caused by the projection optical system. At this time, if such a correction optical system is configured as a transmission type like O5 in FIG. 1, there is a drawback that the size becomes large. Therefore, we decided to arrange a plurality of back reflection mirrors so as to be inclined to each other with respect to the optical axis to form an optical system for correcting chromatic aberration.

FIG. 7 is a detailed diagram of the transmission type chromatic aberration correction optical system OS shown in FIG. Here, the chromatic aberration correction optical system O8 has a configuration in which three parallel plane plates GPI to GP3 are arranged tilted to each other with respect to the optical axis.

FIG. 8 shows a reflective type chromatic aberration correction optical system.

In the figure, reflected light from the wafer marks (M K 1 y, etc.) enters the mirror Mll in FIG. 8 via the projection optical system PO. Here, the mirror Mll is a plane-parallel back reflecting mirror and is inclined with respect to the meridional light beam of the projection optical system. After that, the light beam is transferred to mirror M12.
It enters M13. Here, mirror M12. M13 is M
Like ll, it is a back reflection type, but the tilt direction is mirror M.
It is orthogonal to ll. The light flux that has passed through the mirror M13 is reflected by the surface reflection type mirror M14 and is imaged on the reference mask 8M.

The necessity and operation of such a chromatic aberration correcting optical system will be explained below.

2. Description of the Related Art Observation devices that use an observation optical system to observe and detect the position of a projection surface projected by a projection optical system have been used in various optical instruments.

For example, in an exposure apparatus used in semiconductor manufacturing, a projection optical system projects a reticle surface as a first object onto a wafer surface as a second object, and an observation optical system observes the state on the wafer surface. This observation device is used to perform position matching between the reticle surface and the surface of the reticle, so-called alignment.

The alignment accuracy at this time largely depends on the optical performance of the observation device. Therefore, the performance of the observation device is an important factor in the exposure device.

Various types of alignment devices using such observation devices have been proposed in the past.

For example, the present applicant has also proposed an alignment system using an observation device in Japanese Unexamined Patent Publication No. 58-25638.

In this publication, G-line (436 nm) light is used in the projection optical system for projection exposure onto the surface of the sea urchin, and H-line is used in the alignment system.
Light with a wavelength (442 nm) emitted from an e-Cd laser is used. Since the two wavelengths used at this time are approximately equal, by configuring the projection optical system mainly,
Almost the same optical performance is obtained for both wavelengths of light. By constructing a so-called bi-telecentric optical system so that the projection optical system is telecentric on both the reticle side and the wafer side, when observing the wafer surface from the reticle side, the principal ray of the observation light is always aligned with the reticle surface. It takes advantage of the feature that it is perpendicular to . As a result, even if the type of IC to be manufactured changes, the pattern dimensions on the reticle surface change, and the observation position of the alignment system changes, the angle of the light incident on or reflected on the reticle surface remains unchanged.
By utilizing this property, highly accurate TTL on
It constitutes an Axis system.

Note that the TTL on Axis system aligns the reticle and the wafer in the exposed state via a projection optical system for exposure.

Generally, when performing alignment using the exposure wavelength or a wavelength equivalent thereto, the TTL on Axis system is a preferable method in terms of accuracy.

However, if the wavelengths for projection exposure and alignment are approximately the same, when a multilayer resist is used as the resist applied on the wafer surface, the multilayer resist absorbs the alignment light and reduces the light reflected from the alignment mark on the wafer surface. This causes a decrease in the S/N ratio and alignment accuracy. Therefore, it is necessary to make the alignment wavelength and the exposure wavelength different to improve the S/N ratio and improve the alignment accuracy.

When alignment is performed using the TTL method with different alignment wavelengths and exposure wavelengths, the projection optical system has various aberrations well corrected only for the exposure wavelength, so light other than the exposure wavelength causes various chromatic aberrations. In this case, axial chromatic aberration, lateral chromatic aberration, comatic aberration of other colors, astigmatism, spherical aberration, etc. occur, making it impossible to observe well and causing a decrease in alignment accuracy.

For this reason, various methods have been proposed in the past to properly observe the surface of a sea urchin through a projection optical system using light other than the exposure wavelength. Shifting the position of the reticle surface in the optical axis direction of the projection optical system by the amount of focus shift to establish a conjugate relationship between the reticle surface and the wafer surface, or providing auxiliary optical means between the reticle and the projection lens. A method has been adopted to do so.

However, in all of these methods, the correction of the chromatic aberration of the projection optical system was insufficient, so it was possible to form only a radial pattern image without asymmetric aberrations, such as coma aberration, lateral chromatic aberration, etc., that is, only in the sagittal direction. was used.

However, if only sagittal imaging is used, it becomes difficult to achieve high-precision alignment that accompanies high resolution in the submicron era. For example, a change in the imaging state of the projection optical system itself, such as a change in projection magnification due to a change in atmospheric pressure, or a partial distortion of the wafer can be regarded as equivalent to a change in magnification. Such a change that can be regarded as a change in magnification cannot be detected at all by using a radial pattern.

Furthermore, with only imaging in the sagittal direction, basically only one piece of information can be obtained by observing one point, and there is insufficient information to achieve two-dimensional alignment by observing only two points.

In the past, only sagittal imaging was used due to insufficient correction of chromatic aberration in the projection optical system, but in the future, sagittal imaging will be used to achieve higher resolution in the submicron era. Statues alone are no longer enough.

For this reason, there is a strong demand for an exposure apparatus for semiconductor manufacturing that is capable of highly accurate alignment and that satisfactorily corrects the chromatic aberration of the projection optical system at the observation wavelength.

Therefore, when observing the state of the projection surface using a projection optical system using a wavelength different from that used for projection, various chromatic aberrations caused by the projection optical system are corrected to improve observation. In order to make this possible, in particular, by using an observation optical system that has well corrected various chromatic aberrations caused by the projection optical system when performing TTL alignment at a wavelength different from the exposure wavelength in an exposure device used in semiconductor manufacturing. A chromatic aberration correction optical system is provided to enable precise alignment. In particular, it is compact if constructed using three parallel plane back reflection mirrors arranged as shown in FIG.

Of these, coma aberration with respect to the observation wavelength of the projection optical system is corrected by the back reflecting mirror Mll, which is tilted with respect to the meridional cross section of the projection optical system, that is, disposed obliquely and asymmetrically with respect to the imaging light beam of the meridional cross section. At this time, the tilt angle is determined depending on the amount of aberration generated by the projection optical system and the thickness of the back reflection mirror Mll. This single back reflection mirror M11 is effective against coma aberration, but on the other hand, it causes astigmatism. The sum of the astigmatism at this time and the astigmatism at the observation wavelength of the projection optical system becomes the astigmatism of the entire system. Therefore, in this embodiment, two back reflection mirrors M12. M13
The astigmatism of the entire system is corrected by arranging them at an angle to each other in a plane orthogonal to the plane on which the mirror Mll is inclined. In other words, two mirrors M1 are rotated in a plane with mirror Mll rotated by 90 degrees around the optical axis of the observation optical system.
2. M13 is installed.

Mirror M12. When the mirrors M13 have the same thickness, they can be arranged in a line-symmetrical relationship, and when the mirrors have different thicknesses, they can be arranged tilted at different angles.
2. The overall combination of M13 is designed to prevent coma aberration from occurring. However, mirror MI2. Since the astigmatism of M13 is exerted as a synergistic effect, astigmatism occurs, but by arranging it within a plane twisted by 90 degrees with mirror Mll, adjustment is made so that the occurrence of astigmatism cancels each other out. For example, if the aberration occurring at the observation wavelength of the projection optical system is only coma and no astigmatism, two mirrors M
If the thickness of 12°M13 is approximately % of the mirror Mll, and the angles made by the three mirrors Mll and M12 with respect to the optical axis of the observation optical system are all the same even though they are twisted, the coma aberration of the projection optical system can be reduced. Observation with astigmatism corrected becomes possible.

If the projection optical system has astigmatism at the observation wavelength, mirror Mll and two mirrors M12. If the angle formed by M13 is made different depending on the amount of astigmatism, observation with the aberration corrected becomes possible. That is, in the correction optical system shown in FIG. 8, the amount of correction can be arbitrarily controlled by adjusting the inclination of the parallel plane plate.

By properly correcting comatic aberration and astigmatism with the above configuration, aberrations can be corrected not only in the sagittal direction but also in all directions including the meridional direction, and both on the reticle surface and the wafer surface. This makes it possible to observe the alignment mark as a good image at the same time. This enables highly accurate alignment.

Furthermore, if it is configured as a reflective type as shown in Figure 8, since it is a back-reflection mirror, it requires only an abbreviation compared to a thicker transmissive type, and the correction optical system also serves as the optical path routing. , it has become possible to reduce the cost by being compact.

FIG. 9 shows a part of the previous embodiment constructed with a transmission type optical system.

Note that it is also possible to make the objective lens movable eight times, and to follow it, the chromatic aberration correction optical system can also be made to move. As a result, the objective can be moved in accordance with various shot sizes and chromatic aberration can be corrected accordingly, so that a flow of post-exposure after AA can be achieved, and throughput can be improved.

This concludes the explanation of the reflective chromatic aberration correcting optical system.

Next, the detector sensitivity correction will be explained.

Conventionally, there has been a problem that as the sensitivity of a light receiver such as a detector changes over time, accuracy deteriorates due to changes in signal strength, or in the worst case, detection becomes impossible. A possible solution to this problem would be to widen the dynamic range of the detection system gain, but this would result in high costs.

Therefore, in this embodiment, a standard light source is made incident on the detector and changes in sensitivity are monitored. This results in
The change in sensitivity can be used as a reference (software) and the gain can be changed, and the change in sensitivity can be dealt with by changing the intensity of the detection light source. The sensitivity monitor may be checked periodically at an appropriate timing, such as every carrier, every reticle exchange, or once a day.

By performing such detector sensitivity correction, there are effects such as (1) optimization of the design of the detection system (cost), (2) improvement in accuracy, (2) avoidance of failure to detect, and (2) improvement in reliability (self-diagnosis of troubles).

FIG. 1O shows the detector D (Dx) in FIG.

DY) is a detailed diagram of the portion. The LED is a light emitting diode that is a light source with approximately the same wavelength as the alignment wavelength. This is not limited to a light emitting diode, but any light source with a wavelength that is approximately the same as the alignment wavelength may be used.Here, the wavelength is 660 nm.
m red LED (manufactured by Stanley: F H1011
) is used. Lll is a condenser lens, and M21 is an optical path bending mirror. Although the optical path bending mirror M21 is arranged outside the effective optical path of the alignment position detection optical system,
It is arranged so that the light emitted from the LED via the condenser lens Lll is incident on the detector D.

FIG. 11 is a schematic block diagram of the detector sensitivity monitoring mechanism. The LED is turned on at an arbitrary time by the arithmetic control system ARM, and the detector D detects the light.

The output of the detector D is sent to the arithmetic and control system ARM, where it is compared with the reference output recorded in the memory MEM1, etc., and if the sensitivity of the detector D has changed, the arithmetic and control system ARM
controls and corrects a detector control circuit (not shown). - For example, controlling the voltage applied to the detector D.

Next, chopping and waveform processing will be explained.

In order to eliminate the influence of interference between the light reflected from the edge of the mark on the square and the light reflected from the resist surface, in this embodiment, the beam is incident on the mark from an oblique direction as shown in FIG. In this case, beams must be incident from four directions to obtain reflected light from each edge of the mark.

FIG. 12(a) shows the relationship between the mark and the incident beam in FIG. 1, and FIG. 12(b) shows the reflected light from the edge of beam 1 and beam 3. The reflected light from edge A by beam 1 is shown in FIG. A1, the reflected light from edge B is 81% beam 3
The reflected light from edge A is A3, and the reflected light from edge B is B! shall be. If beam 1 and beam 3 are incident on the mark at the same time, as shown in Fig. 12(b), at edge A, AI and As, and at edge B, B1 and B.
, interference occurs due to the reflected light. In order to eliminate the influence of this interference, it is sufficient to change the timing of the beam incidence to obtain the reflected light from each edge separately, and this method is called chopping.

Next, a method for obtaining the true position from reflected light that is not affected by interference obtained by chopping will be described.

By chopping, reflected light from each edge as shown in FIG. 13 is obtained. The waveform shown in the figure is the waveform obtained when the image of each edge is scanned with an ideal slit, that is, a slit with an infinitesimal width.

To explain chopping more clearly,
Assume that marks on the wafer and reticle are directly aligned. The marks on the wafer and reticle are shown in Figure 14 (a).
), the signal obtained by chopping from each edge will be as shown in FIG. 14(b). Note that the waveform representing the reflected light of beam 1 and the waveform representing the reflected light of beam 3 in FIG. As shown in FIG. 13, the peaks for each edge of each mark do not appear, but this is because the width of the slit is finite in the scan of the mark image actually performed in this embodiment. This is because the light emitted from the edge is the sum of the light from both edges. Therefore, the waveform in FIG. 14(b) is slightly distorted.

Next, the amplitude of the signal obtained from each edge is AI, A3
Then, as shown in FIG. 14(C), the amplitude of each signal is adjusted so that AI=A3, and a composite wave is obtained. A certain slice level K is determined for the amplitude A of the composite wave.

K = A X 307100 From this slice level K to the slice position PI.

P2 is determined, and the position of each mark is determined by setting the mark position on the wafer as a slice position to determine the amount of deviation from the true position.

Next, a second method for obtaining the true position from reflected light that is not affected by interference and is obtained by chopping will be described.

If light from each edge is received by an ideal infinitesimal or medium slit as described above, then reflected light from each edge as shown in FIG. 13 will be obtained by chopping. On the other hand, the marks on the wafer and reticle are
), and if the light from each edge is received by a slit of finite width, the signal obtained by chopping from each edge will be as shown in FIG. 15(b).

As shown in FIG. 15(C), the amplitude of the signal obtained from each edge is defined as A I * A 3. Then, for each signal, the slice level is + (K+ = AI
30/100), Ks (Ks dry A, X3
0/100). Slices are applied to each signal using these slice levels. As the slice position, as shown in FIG. 15, the steepest rising and falling sides of each signal are used as the slice positions. That is,
For example, focusing on the signal of amplitude AI, it is determined which position of Q+ or Q2 is steeper, and the steeper side is used as the slice position.

The slice position Q3 of the signal with the width A3. Similarly, the steep side is used for Q4. If Q and q are steep, the slice position PI.

If the midpoints Q2 and Q4 of P2 are steep, these midpoints are determined as the mark position. Note that for the sake of simplicity, Q+ and Q3 are used bare, and Q2 and Q4 are used bare. In this way, by determining the position of each mark, the amount of deviation from the true position is determined.

Furthermore, a third method of obtaining the true position from reflected light that is not affected by interference and is obtained by chopping will be described.

If light from each edge is received by an ideal infinitesimal or medium slit as described above, then reflected light from each edge as shown in FIG. 13 will be obtained by chopping. On the other hand, the marks on the wafer and reticle are
), and if the light from each edge is received by a finite slit, the signal obtained by chopping from each edge will be as shown in FIG. 16(b).

Next, as shown in FIG. 16(C), a differential signal of the signal obtained from each edge is obtained. For the signal obtained from beam 1, find the maximum peak position P, and for the signal obtained from beam 3, find the minimum peak position P3, P,...
By determining each mark position using the midpoint of P3, the amount of deviation from the true mark position is determined.

From these methods of obtaining the mark position by chopping, the most suitable method may be selected depending on the waveform of the mark on the wafer to be obtained.

This concludes the explanation of chopping and waveform processing.

Next, correction of the amount of laser light emitted from the wafer illumination system WL will be explained.

This is done to ensure a signal output and S/N ratio greater than -window in order to perform highly accurate positioning. To this end, changes and deterioration of the light source, all optical systems, and detectors are important issues, especially when obtaining alignment signals using multiple light sources, optical systems, and detectors as in this example. Become. Therefore, it is of great significance to detect and correct these changes and deteriorations.

FIG. 17 is a schematic diagram for explaining laser light amount correction. This figure is a schematic diagram of FIG. 1, and the same symbols indicate the same or common parts.

In FIG. 17, KTS is a light amount adjusting element and light source LP2.
If it is non-polarizing, it is an aperture stop or one in which various ND filters are arranged on the circumference. In addition, light source LP2
If is polarizing, a polarizing filter can also be used in addition to the above. KTU is a unit that controls and drives the light amount adjustment element KTS, and in this example, controls and drives the light amount adjustment element TS in the rotational direction. MEMI and MEM2 are memories. It is desirable that these be non-volatile.

In the figure, laser light amount correction is performed as follows. First, the aforementioned detector sensitivity correction is performed. That is, the arithmetic system ARM turns on the LED, and the detector D detects the light. The output of the detector D is compared with the reference output value stored in the memory MEM1 by the calculation system ARM, and if the sensitivity of the detector D has changed, the calculation system ARM controls the detector control circuit (not shown) to correct the sensitivity. do.

After such detector sensitivity correction, a reference wafer WF is mounted at a predetermined position.

Then, the lens E is connected from the light source LP2 through the fiber SF, etc.
A shutter (not shown) disposed inside the illumination system leading to L serves as an oven, and illumination light illuminates the wafer WF.

As mentioned above, the reflected or diffracted light from the eight surfaces of the wafer is detected by the detector D via the projection lens Po, and the data is sent to the calculation system ARM.The calculation system ARM collects the measurement data and the reference stored in the memory MEM2. A correction amount for the illuminance on the light source side is calculated, and a command is given to the light amount correction control drive unit KTU. Based on the command, the light amount adjustment element rotates in this example to perform correction. Repeat the correction operation again if necessary.

In the above example, the sensitivity of the detector and the illuminance of the light source are each corrected to constant values as a correction method, but it is also possible to correct one of them relative to the other. The light source is preferably a laser, but other light sources may be used. Further, the light amount adjusting element and the control driving method may be other methods.

In conventional methods, this kind of light intensity correction simply detects and corrects changes in illuminance on the light source side, but it is possible to perform more accurate correction than that, and it also reduces the cost of signal processing circuits, etc., and reduces the processing software. It has become possible to simplify and speed up processing time.

Next, various modifications of wafer mark position detection will be described.

First, the position where the wafer mark is observed is not limited to one location. That is, it is not limited to a single-eye objective; therefore, if you have two or more eyes, you can measure the θ direction and magnification of the wafer at the same time as the XY directions.

Furthermore, instead of observing only the wafer mark of one shot, it is also possible to simultaneously observe the wafer mark of the next shot. Therefore, even with one eye, it is possible to measure the θ direction and magnification of the lens without reducing the throughput.

FIG. 18 shows an example in which the wafer marks of the next shot are observed at the same time. In the figure, the B shot wafer mark 101 and the wafer mark 102 of the next shot, the C shot, are alternately arranged and observed simultaneously. In the same figure (b), wafer mark MK1ya and wafer mark MK
1 xa is B shot mark, wafer mark MK
1 vc and wafer mark M K 1 xc are C shot marks.

Figure 19 shows the signals obtained by arranging the marks in this way and scanning the images of these marks over the slits placed at predetermined positions.The correspondence between each signal, marks, and slits is as follows. It becomes like this.

■Signal S9...Detection signal at slit 5LYs of image of reference mark MK ■Signal Sll...Wafer mark M K I Yc
Based on the detection signals S9 and Sll at the slit 5LY7, the amount of positional deviation of the C shot in the Y direction can be detected.

■Signal SIG...Detection signal at slit 5LY6 of image of reference mark MKY■Signal S12...Wafer mark MK 1 ya
Slit SLY? Based on the detection signals SIO and 312, the amount of positional deviation of the B shot in the Y direction can be detected.

■Signal S13...Detection signal at slit SLx@ of image of reference mark MKX■Signal SIS...Detection signal at slit 5Lxs of wafer mark MKI□Based on these signals S13 and S15, B shot The amount of positional deviation in the X direction can be detected.

■Signal S14...Slit SLX of image of reference mark MKX? Detection signal ■ Signal S16...Wafer mark M K 1 xc
Based on the detection signals S14 and S16 at the slit SLo, the amount of positional deviation of the C shot in the X direction can be detected.

As described above, the relative positions of the B shot and C shot with respect to the reference mark can be measured.

Therefore, while measuring the right mark of shot A in Fig. 18, the left mark of shot B is measured at the same time, and furthermore, by measuring the right mark of shot B and the left mark of shot C at the same time, the shot (B shot in this case) can be measured in the θ direction and magnification error without reducing throughput.

Next, a modification of the reference mask shown in FIGS. 1 and 3 will be described with reference to FIG. 20. This is an example in which the reference mask and the sea urchin are aligned relative to each other without the illumination optical system BML of the reference mask.

FIG. 20(a) shows the appearance of a reference mask BM that can eliminate the illumination optical system BML.
is provided with a window W through which the image of the wafer mark can pass through, and the window W is provided with members 5DWI and 5DW2 that can cast a shadow on the wafer mark. As a result, a shadow can be created on the wafer mark as shown in FIG. 1(b), and an image as shown in FIG. 1(C) can be obtained on the slit surface (SLx and 5LY in FIG. 1).

SDW in FIG. 3(C) shows a portion shaded by members 5DWl and 5DW2 of the reference mask BM.

The image shown in FIG. 4C is scanned by a polygon in the direction shown in FIG. 2D, and the light transmitted through the slit is detected to obtain a signal S21. There are parts of this signal 521 where the signal strength drops corresponding to the shadowed parts.
By obtaining such a signal, the relative position of the wafer and the reference mask can be measured. In this case, the wafer mark attached to the wafer is the mark MKI for position detection in the X direction.
X is a shape extending in the X direction, mark M for position detection in the Y direction
For K 1 y, one extending in the Y direction will be used.

Next, the chopping operation in this embodiment will be explained with reference to FIG. 21.

FIG. 21 is a schematic configuration diagram of this embodiment, which is a simplified version of FIG. 1. Prior to position detection on the sea urchin, the position of the alignment mark on the reticle is first converted into an electrical signal by the M-system photoelectric detection system DM.

On the other hand, the chopping circuit C also applies to marks on the wafer.
) Chopping is performed in the IP, a laser beam is irradiated from the wafer illumination system WL, and is converted into an electric signal by the W-based photoelectric detection system DW via the projection lens Po.

The reflected light signal from the edge of the mark is converted into an electrical signal by the M-system photoelectric detector DM and the W-system photoelectric detector DW.
After the signal section is detected by the signal component detection circuit SL which is synchronized with the chopping circuit CHP, it is converted into a digital quantity by the A/D converter ADC and stored in the wave memory WBM. After the signals from all edges are measured, the digital signal processor DSP
The signal processing to determine the mark position is performed at high speed by the CPU, the amount of deviation is determined by the CPU, and the motor MO is controlled.
Positioning is performed by driving Y stage WS.

FIG. 22 shows a flowchart during alignment of the system of this embodiment. When alignment is started in step 101, chopping is first performed in step 102. Step 1
In step 03, set the signal gain from the edge so that the A/D converter does not overflow, and then proceed to step 1.
04 converts it into a digital amount and stores it in the storage. In step 105, it is checked whether signals of all edges are obtained or not.
If so, perform rough chopping and repeat the processing up to now. If "Y", perform waveform processing on the waveform signal stored in the memory to find the mark position, and in step 107, perform waveform processing on the waveform signal stored in memory. The amount of deviation is measured, and based on the amount of deviation, a tolerance determination is made in step 108, and if it is outside the tolerance, the stage is driven in step 109. On the other hand, if it is within the tolerance, step 1
The alignment ends at 10.

Next, AA using He-Ne laser and image processing
I will explain about it.

Conventionally, in a reduction projection exposure apparatus, He
- Possible methods include using a Cd laser or image processing. In this case, due to limitations of the projection lens, it is necessary to use a wavelength close to the exposure wavelength in order to observe/measure the reticle/urchin. As a result, the resist near the alignment mark is burnt, and the reflected light of the illumination light and the diffracted or reflected light used for measurement interfere with each other, resulting in signal distortion or interference fringes and alignment errors.

In this embodiment, as described above, since the illumination light for detecting the position of the wafer is applied from between the projection lens and the square, there is particularly little interference due to the influence of the resist. Further, the mark shape is a linear mark as shown in FIGS. 2 and 3.

FIG. 23 shows an example of performing AA in image processing. Second
FIG. 4 shows a block circuit diagram of the image processing section. The image illuminated by the wafer illumination system WL is converted into an electrical signal by an ITV camera, solid-state image sensor (CCD in this example), etc.
The image is digitized by the /D converter ADC and stored in the frame memory FMH as image digital data. Focusing on this image digital data in the direction of each linear mark, data is obtained by projecting and integrating only the required length in the X or Y direction using the projection integration window TSW shown in FIG. By determining the center of gravity of the projection data TDA thus obtained, the amount of relative deviation between the mark on the reference mask and the wafer mark is calculated. In this embodiment, since there are no interference fringes in the obtained image, sufficient accuracy can be obtained because the center of gravity of the integrated data is determined. Therefore, as shown in FIG. 24, the amount of deviation can be measured at high speed and with high precision without requiring any special hardware except for the part where XY projection integration is performed. In addition, if even higher-precision displacement measurement is required, After calculating the difference before and after and removing noise components from this difference signal, calculate the moment at each of the above points of the difference signal, and determine the mark position by finding the point where the moment crosses zero among the above points. or ■ Setting multiple windows of a predetermined size, integrating image signals in one direction of two-dimensional coordinates within the windows, and calculating the center of each mark window based on the integrated signal for each window. The method of calculating the value and determining the position of the mark based on the center value of each window, etc. may also be applied.

In addition, even when performing such image processing, when beam 1 and beam 3 shown in FIG. Therefore, the intensities of beam 1 and beam 3 and A,
, A, B+, and Bs, A1+As versus Br+B3 may not be balanced.

In order to solve this problem, a configuration as shown in FIG. 26 can be used. In this figure, the circuit diagram of FIG. 24 has two frame memories, and four wafer illumination system WL light projection control blocks TC
This is the one with O added.

With this configuration, first, the projection of beam 1 in Fig. 12 is turned on and the beam 3 is turned off, and the image data is loaded into the frame memory FME 1, and then the projection of beam 1 is turned off and the beam 3 is turned on. , the image data is taken into another frame memory FME 2, and the center of gravity is separately determined for each frame memory using the method explained in FIGS. 23 to 25 above, and the amount of deviation is determined. Furthermore, the above-mentioned problem can be solved by calculating the average of data when beam 1 is turned on and when beam 3 is turned on. Also, change the data when beam L is turned on and the data when beam 3 is turned on so that the peaks are the same, and calculate the data when beam 1 is turned on and beam 3. The same effect can be obtained by applying the above method to the data obtained by adding the data when the switch is turned on.

Next, reticle positioning will be explained.

There are two main methods for aligning the pattern on the reticle and the pattern on the wafer. One is a method that directly captures the reticle and wafer pattern simultaneously and performs relative alignment (hereinafter referred to as the direct method). ).

In this case, it is sufficient that the relative positions of the pattern on the reticle and the pattern on the wafer match regardless of the position of the reticle as long as the accuracy is within the guaranteed range. Therefore, there is no need for highly accurate alignment of the reticle.

The second method of alignment means is to first align the reticle accurately with the alignment reference on the device, and then align the wafer pattern with the alignment reference on the device whose positional relationship is guaranteed in advance. In this method, the reticle and wafer pattern are aligned by aligning them (hereinafter referred to as indirect method).

In this case, the alignment error of the reticle with respect to the reference on the apparatus is directly added as an alignment error between the reticle and the wafer. That is, the reticle must be aligned with high precision with respect to the reference.

Conventionally, reticle alignment (hereinafter referred to as RA) for setting a reticle on a main body has been performed using a laser scanning method. The laser scanning method scans a laser beam at a constant speed to create an auto alignment mark (hereinafter referred to as A).
In this method, the reflected and diffracted light from the edge portion of the AA mark (referred to as the A mark) is received by the Fourier transform surface of the AA mark, and relative positional deviation is detected and corrected with high precision from there.

When performing the direct method, after such RA, the reticle and wafer are viewed through one optical system and the two objects are directly aligned.

On the other hand, when performing alignment in which alignment standards on the main body intervene during this time, in other words, when implementing an indirect method using a laser scanning method for RA, the following problems are factors that hinder realization. (See Figure 27).

■Generation of noise due to speckles of the laser (coherent light) ■Since the signal is the reflected and diffracted light of the reticle pattern, the signal output will drop if the pattern is drawn on a material with low reflection. This makes it difficult to detect the signal.

■Currently, alignment is performed while maintaining a certain amount of gap between the mark on the reticle side and the AA mark on the main body. As this gap changes, the optical path length of the signal light changes and interference occurs (waveform distortion occurs), so the signal output changes.

Among these methods, since laser light is particularly used, the influence of interference cannot be avoided, making it difficult to achieve even more precise reticle alignment.

RA that takes the above points into consideration will be described below with reference to the drawings.

FIG. 28 is an example of a reticle alignment detection system to which the indirect method is applied. This detection system is guaranteed to have a relative positional relationship with the reference mark BM shown in FIG. An illumination system LP3 illuminates an alignment mark (not shown) for reticle alignment via a half mirror HM. Objective lens L31 is imaging lens L32
cooperate to form an image of the alignment mark on the detector D1. The detector D1 is an image detector such as a CCD or an image pickup tube, and serves as a positional reference for reticle alignment. Since the relative positional relationship between the reference mark BM and COD is guaranteed in advance, the reticle LT is aligned with the CCD, and the wafer WF is aligned with the reference mark BM. However, even with this configuration, there are problems such as poor contrast.

Next, referring to FIG. 29, we will explain the RA adopted in this example.
Explain the method.

In the figure, a mercury lamp 1 is used as a light source. G-line is selected from the light generated from the mercury lamp 1 and guided to the main body via the optical fiber 3. The fiber 3 is installed so that the light enters an optical system that illuminates the main body side reticle alignment mark (hereinafter referred to as the main body side RA mark) from below. This light transmits and illuminates the RA mark on the main body side and the RA mark on the reticle side, which is present with a certain gap therebetween, and images each RA mark on the CCD or image pickup tube 9. The detected images are sent to the computer 13 and subjected to image processing to detect the relative displacement of each RA mark. The data is transferred to a reticle stage drive system (not shown) to correct the deviation and align the reticle and the main body.

FIG. 30 is a sectional view showing how the mark portion is illuminated through transmission, and FIG. 31 is an example of an alignment mark.

This method has several advantages in that it can achieve high accuracy in reticle alignment.

■Even if the gap between the RA mark on the main body side and the RA mark on the reticle side changes, no interference will occur because the illumination light is incoherent light. Therefore, stable signal output can be obtained.

■Since it is transmitted illumination, images with good mark contrast can be obtained. Furthermore, if the material used to draw the pattern on the reticle does not transmit light, it will not affect the contrast, so there will be almost no change in signal output when changing the reticle.

Since the positional shift is detected by zero image processing, the shape of the RA mark can have flexibility such as increasing the amount of information compared to conventional marks.

As described above, a higher precision than that which can be obtained with conventional reticle alignment can be obtained. Therefore, it is possible to align the reticle with higher precision than in the past, which means that it is possible to align the reticle and wafer with higher precision.

Next, RA using the above-mentioned transmission type illumination will be explained in more detail.

FIG. 32 shows the hardware configuration of the position detection device according to the RA method shown in FIG. 29.

In the figure, 20 is an analog-to-digital converter (hereinafter referred to as an A/D converter), which converts a video signal (video signal) that is an analog signal sent from a video signal control unit (not shown) into 256 gradations. into a digital signal. 21 is a two-dimensional grayscale image memory (hereinafter referred to as
An input image for position detection captured by an imaging device (referred to as a gradation memory) is stored in this gradation memory 21 after A/D conversion.

First, the coarse detection section will be explained. Block H in the figure is a histogram processor.

In block H, 22 is a converter that adds data from the density memory 21, 23 is a density histogram memory (hereinafter referred to as histogram memory) that stores the addition output, and 24 is a divider that divides the density memory 21 into a plurality of partial areas. death,
This is a memory division control circuit that controls the address of the histogram memory 23 in order to extract a density histogram for each. The density memory 21 is divided into 16 areas in the X direction and 16 areas in the Y direction, for example, as shown in FIG. Hereinafter, such division is divided into r division number 113X
It is expressed as 16J. In the histogram processor H, the memory division control circuit 24 divides the density memory 21 according to the division number mxn from the microprocessor 25, and a density histogram is extracted for each partial area. and stored in the histogram memory 23.

In the binarization threshold calculation unit (microprocessor 25), each of the density histogram data for each of the plurality of partial regions extracted by the histogram processor H is processed using a discriminant analysis method (bisection method using the maximum variance of a bimodal histogram) or Calculate the binarization threshold using the P-tile method, etc. (The discriminant analysis method or the P-tile method is detailed in Coronasha's "Image Recognition Theory" by Makoto Nagao, "4-1 Binarization and Thresholding"). ing).

Block B is a binarization processor. In block B, 26 is a binarization comparator for binarizing the data from the gray scale memory 21, and 27 is a binarization slice level register that stores the slice level (binarization threshold) of the binarization comparator 26. be. The binarization threshold for each partial region calculated by the binarization threshold calculation unit is stored in this binarization slice level register 27. A memory division control circuit 28 controls the binarization slice level register 27 in order to divide the grayscale memory 21 and perform binarization for each divided area. This memory division control circuit 28
share the division control circuit 24 of the histogram processor H. The data binarized by the binarization processor B is stored in a two-dimensional binarization memory (hereinafter referred to as binary memory) 29.

By using the above-described histogram processor H, the binarization threshold calculation unit of the microprocessor 25, and the binarization processor B, by performing binarization processing for each partial region,
Adaptive binarization that is not affected by the size of marks or the brightness of lighting becomes possible.

Block S is a reduced smoothing processor. In the block S, 30 is a reduction smoother that extracts an area of nxn pixels (for example, 4x4 pixels) from the binary image data stored in the binary memory 29 and compresses it into one pixel, and 31 is a reduction threshold of the reduction smoother 30. This is a reduced slice level register that stores (described later).

The reduction smoothing function in the reduction smoothing processor S will be explained. FIG. 34 is a diagram showing a case where 4×4 pixels are compressed into one pixel. This kind of reduction will be expressed as "shrinking Sogetsu." In the case of the reduced Sogetsu, among the 4x4-16 pixels in the input crab value image data from the binary memory 29,
Count the number W of pixels whose data is 1, compare this W with the reduction threshold t, and if it is wet, compress the target 16 pixels to 1 pixel with data 1. If W≦t, convert the target 16 pixels to data. Compress to 1 pixel of 0. With this operation, for example, 512
x 51212 pixel value image data is 128 x 12
The image data is reduced to 828 pixel value image data. By appropriately selecting the reduction threshold t, noise can be removed and the shape of the object can be adjusted. Such reduction smoothing processing is effective as a preprocessing for template matching processing in the following respects. That is, when performing template matching processing on a binary image after reduction and smoothing, (1) a small template with a small number of pixels can be used;
Since the range of template matching processing is small,
It does not require a large memory capacity, the hardware scale can be reduced, and processing time can also be shortened.

(2) Since noise in the target image data is removed and the shape of the target object is adjusted, the detection rate and accuracy of template matching processing are increased.

There is an advantage.

The reduction ratio and reduction threshold t can be specified by the microprocessor 25 depending on the size of the object and the situation of the input image. The binary image data after reduction and smoothing is stored in 32 reduced two-dimensional binary image memories (hereinafter referred to as reduction memories).

Block T is a template matching processor. In the block T, 33 is a 32×32 pixel correlator, and 34 is a template register that stores a reference template group. The template data specified by the microprocessor 25 and the data in the reduced memory 32 are compared and verified in the correlator 33, and when the degree of correlation output from the correlator 33 is the largest, that degree of correlation and the address on the reduced memory 32 are compared. is stored in the 35 maximum correlation registers. By multiplying this address by the reciprocal of the reduction rate (4 times for reduced Sogetsu), the position coordinates of the object in the input image can be determined with an error of ±4 pixels. This position is defined as the rough detection position.

-a light memory 21. Binary memory 29 and reduced memory 3
Image memory block M consisting of 2 and blocks H1B, S
, T are connected to the microprocessor 25 by an image address bus 36 and an image data bus 37, and blocks M, H, B, S, and T are connected to the microprocessor 25 by a data bus 38. The image memory and the registers of each processor can be read and written by the microprocessor 25.

39 is a read address counter that generates an address when displaying image memory data on a monitor TV or reading image memory data while each processor is operating (image processing operation); 40 is an A/D A at converter 20
This is a write address counter that generates an address when writing /D-converted digital image data to the gray scale memory 21 or when writing image data to the image memory during image processing operation.

41 is a digital-to-analog converter that converts the digital image data stored in the image memory block M into an analog video signal for display on a monitor TV; 42 is a reference clock generation circuit; and 43 is a reference for the reference clock generation circuit 42. This is a TV synchronization signal generation circuit that generates a TV horizontal synchronization signal, vertical synchronization signal, blanking signal, etc. based on a clock.

The above is the configuration of the rough detection section and the hardware according to an embodiment of the present invention.

Next, the precision detection section will be explained.

In the re-binarization threshold calculation unit (microprocessor 25),
From the partial areas divided in the rough detection process, partial areas near the coarse detection position are extracted based on the rough detection position, and these areas are divided by interpolation from the binarization threshold of those areas calculated during the rough detection process. The microprocessor 25 approximately calculates the binarization threshold value of the sub-divided partial area when the area is further divided. The size of the range to be extracted from the vicinity of the rough detection position at this time is determined by the size of the target object (mark, etc.).

FIG. 35 shows how the re-binarization threshold is calculated using such an interpolation method. The figure shows a case where a 4×4 area is extracted as the vicinity of the rough detection position, and the 4×4 area E surrounded by the solid line is one of the partial areas divided by the rough detection process. . Furthermore, an area e surrounded by a broken line and a solid line, which is obtained by further dividing the area E into four, is one of the finely divided partial areas in the precise detection process. In the same figure, t+
, tz, t3. t4 is a binarization threshold for each area in the rough detection process. These are the binarization thresholds at the center of each area, and from these, the binarization thresholds a, b, c, and d of each area in precise detection processing are approximately calculated by interpolation.
is an approximate calculation of 0 or more expressed by the following formula,
Binarization thresholds are calculated for all the divided partial regions in the precise detection process, and each divided part is binarized even more finely than in the coarse detection process, thereby improving the position measurement accuracy in the precise detection process. The binarization process is performed by a binarization processor in the same way as the rough detection.

FIG. 36 shows how one of the position detection marks used in this embodiment is binarized by precision detection processing. For example, the mark part is represented by 1, and the other parts are represented by 0.

In the centroid calculation section, the microprocessor 25 calculates the centroid of each component of the object. In this example,
For example, the center of gravity of a line segment element of a mark as shown in the same figure is calculated. First, based on the rough detection position, areas a, b, and c that include the line components of the mark can be set. Find the center of gravity of the line component within each region (ax, ay).

(bx, by) and (cx, cy). Then, the X coordinate 7m of the center of the mark is given by the following equation.

YIIl=-(ay+2by+cy) The X coordinate of the center of the mark is determined by setting the area in the X direction, as in the case of the X coordinate.

The above is the processing of the center of gravity calculation section. The precision detection processing unit, which performs re-binarization near the coarse detection position and centroid calculation processing, improves the position detection accuracy to a thousand pixels, supplementing the detection accuracy by the coarse detection processing unit.

FIG. 37 shows a flowchart of processing operations in one embodiment of the present invention described above.

In addition, by using the center of gravity of the data projected and integrated in the mark direction as shown in FIG. 25 using the XY projection integration unit shown in FIG. If the center of gravity is calculated for the data in the grayscale memory, re-binarization processing is not necessary, and the center of gravity is also calculated in three-dimensional directions including the brightness direction (density), which improves position measurement accuracy. will improve.

Next, correction of geometric distortion in the image input system will be explained.

In the human image system used for RA as described above, factors such as lens distortion in the optical system, graphical distortion of the imaging device such as a CCD camera, and sampling error during A/D conversion of the video signal cause errors in the input image. Geometric distortions occur.

Therefore, in order to obtain accurate measurement results, it is necessary to correct these distortions.

First, a method for correcting geometric distortion of the imaging system will be explained.

FIG. 38 shows an absolute grating drawn on a reticle using EB, and its drawing accuracy is sufficiently high.

Correction is performed by determining a transformation (-order transformation formula) between the grid image obtained by imaging this grid and the actual grid.

The transformation from an actual lattice (hereinafter referred to as a real lattice) to a lattice image is approximated by local linear transformation. The intersection of the grids or the center point of the area surrounded by the grids is measured on the grid image by calculating the center of gravity, and the position is determined as (x', y')
, and the corresponding position on the real grid is (x, y).

If we express it as X' = AX+E becomes. Therefore X' = A-' (X'-E) It is.

FIG. 39 shows a real lattice and a lattice image captured from the real lattice.

By measuring XI', X2', x, and #, and solving the simultaneous equations, El and the temporary transformation A are found. Hereafter, the area surrounded by points XI', X2', x, and J (X+',
The position X' measured within X2', Xs') is A I +
By E I, X' = A, -'(X' -E) ...-.
-Correct as 0-order, measure X4' and x, ', x2'
.

X4' to A2. Find ES.

After that, in the gold area in the image, X1',...,X
By measuring 0', A, , E, corresponding to each local area can be found as shown in FIG. This is called an imaging system distortion correction map (hereinafter referred to as a correction MAP).

By correcting the measured position within the image using the 0 formula using the correction map, highly accurate position measurement is possible. The correction map need only be created once as a characteristic of the imaging system, but if it changes over time, it must be created again periodically in accordance with the period.

In addition, if even higher precision is required, approximation is performed using a higher-order transformation, and conversely, if so much precision is not required,
The measurement points of X,', . . . , xn' may be thinned out. FIG. 41 shows the flow of correction map creation.

By the way, the X1' value measured as above is not necessarily the correct value due to defects in the absolute grid drawn by EB on the reticle, scratches on the reticle, dust on the reticle, etc. Therefore, after measuring XI', first The abnormal value check for X1' will be described later. If the number m of abnormal values exceeds the preset upper limit M of the number of abnormal values, change the field of view and remeasure xI' in a part with fewer abnormal values. Change the field of view and measure The method to redo the correction map and obtain an accurate correction map is as described below.
The value of is determined, for example, to be 10% of the total number of measurements of XI'.

If X,′ is determined to be abnormal, the value of
Interpolate from xI' in the direction. FIG. 42 shows the method of interpolating the abnormal values.

If xj′ is abnormal and the immediately surrounding X,′ to X6′ are proper, then d” I X4′−XJ l −I XJ −Xs
'l+ I Xz'-XjI -I XJ -X7'1
+ l X3'-XJ l -I XJ -Xa'
I+ I XI'-XJ I-l XJ-Xa'
Xj' is determined so that I...■ is minimized. Roughly speaking, not all the surroundings of x,' are correct. In such a case, calculate d using the closest proper X,'' in each direction and its positional relationship. For example, if xs' is also abnormal, If X a', which is one grid away from
'l+kslXc'-X''l- to 41X'-Xd'
51Xe'-Xj'1-kalX,'-Xr'l to l+
+kylXg'-Xj'l-1calX''-X+'l
So, X-', Xb'..."X+" is X J' (
7) 8 Direction Te closest appropriate value, kl * k2 *
. . . kA is a coefficient representing their positional relationship on the real lattice.

After abnormal value interpolation, A, , E are calculated and a correction map is created.

Next, abnormal value checking will be explained.

A,,E obtained from measured values including the abnormal value Xj'.

If correction is performed based on , there is a risk that the measurement accuracy will be adversely affected, so abnormal value checking is to find such an abnormal value xj'. This check is done globally, not locally.

The real lattice points X+, X2, . . . The overall linear transformation is given by:

θ: slope β: Magnification x and y are in each direction S: Shift amount Here, the measured value X1' of the grid point on the grid image.

x2′,...Xn′ is Ll, V=”Σl H
+ l'(H+=di'-xi)σ= ・n
n-1) Determine an abnormal value using σ. In other words, the lattice d′ which is closest to the measurement value L1 among the conversion lattices that uniformly linearly transform the whole
is calculated using the least squares method, and then Id+'-JZI 1
It is determined whether JZI is an abnormal value based on the variation in .

If there is one abnormal value, that is, if one J2° is abnormal, it can be determined as follows.

In other words, as shown in Figure 43 (both the amount of deviation and the position of grid intersection points are expressed in one dimension for convenience of explanation), only one grid female point among the measured values of n grid intersection points had a deviation that was significantly different from the others. In this case, the method for finding this is r/σ>K (r, σ are the values shown in FIG. 43, and K is a constant value).

At this time, σ was obtained using the data including the abnormal value candidates in Figure 43(a) (not 7n, but σ excluding the abnormal value candidates in Figure 43(b). It is better to use -1. itself can be prevented from deteriorating due to abnormal values, and abnormal values can be clearly identified.This is because the abnormal measured values X, ', X2',
...xn' is the distribution N (m, σ.

This is a judgment based on the assumption that the value does not comply with -1). Therefore, the abnormal value is determined using the following formula.

Abnormal value determination method> When r/σ>K, the i-th measurement is considered abnormal. However, K=constant value (currently 3.0) β8. β2. θ8. θ,,S,,S,,V are obtained by excluding the i-th grid intersection dl * P l is the position of the i-th grid intersection...
・■ This determination method ■ predicts the size of the random error of the process using σ, and determines abnormal values based on that value, so it can be expected to determine abnormal values regardless of the process.

In order to find one abnormal lattice intersection among n lattice intersections, it is necessary to perform the determination of equation 0 n times, but (iw
l-n), this requires a large amount of calculation and is not practical. Therefore, in reality, among the n grid intersections, one lattice female point that is more likely to be abnormal is found, and that lattice intersection is determined to be abnormal using formula 0. , we will remove it as an outlier.

The lattice intersection that is a candidate for an abnormal value is the lattice intersection that is farthest from the lattice when all ntg child intersections are corrected.

On the other hand, if there are a plurality of abnormal values, that is, if there are two or more abnormal value grid intersections, rl/σ cannot be determined because i in equation 0 is not one.

Furthermore, even if it is determined by some method that a certain set of m lattice intersections among the n lattice intersections is an abnormal value, there will be nC1 combinations, and the amount of calculation will be too large.

Furthermore, it is difficult to judge what the value of m is, so if there are many abnormal lattice intersections, the above abnormal value is 1
Extract one lattice intersection using the method when
From the grid intersection point, m grid intersection points are removed in the same manner as the next 1#r child intersection point.

At this time, if there are abnormal values at two lattice intersections as shown in FIG. 45, even if the first lattice intersection is removed, the σ of the remaining lattice intersections is still large, so r/a does not become large.

If one more lattice intersection is removed, there are no abnormal values, so σ becomes smaller and r/σ becomes larger.

Such a change in the value of r/σ takes the form shown in Figure 46. If there is an abnormal value at the intersection of two lattice points as shown in Figure 45, the two lattice intersections are removed as shown in Figure 46 (C). r when
/a now indicates a peak. Therefore, record the value of r/σ while removing each grid intersection, and if the maximum value of r/σ exceeds K, discard the grid intersections up to that point as abnormal values, and if the maximum value does not exceed K. This means that there is no abnormality.

In fact, when abnormality candidates are removed one after another, σ tends to a smaller value, and when there are three remaining lattice intersections, σ=0 and r/σ=■. Furthermore, since it is meaningless to remove too many grid intersections compared to the original number of grid intersections, an upper limit M is set for the number of grid intersections that can be removed.

The algorithm that ultimately finds the outlier is that the outlier is 1.
Regardless of whether it is a lattice intersection or multiple lattice intersections, the flowchart shown in FIG. 47 is obtained.

Next, a method for obtaining an accurate correction map by changing the field of view and performing measurements will be explained.

FIG. 48(a) shows an area (■) where data that is not an abnormal value is continuous based on the measured correction map and the abnormal value check.
Each point in the figure, indicated by (1) and (2), indicates each grid intersection of the absolute grid on the imaged reticle.

In this state, the reticle is moved relative to the imaging means. In this embodiment, the objective optical system is driven in the X and Y directions by a motor (not shown) to move the target image relative to the field of view, and the reticle is moved relative to the imaging means. Process in the same manner to obtain a correction map. In Figure (b), after obtaining the correction map shown in Figure (a), by shifting the field of view by two grids to the right and re-measuring, normal correction map information for ■~■ and ■'~■' can be obtained. It shows that you are getting it. By repeating this process until there are no abnormal values in the correction data or the range does not exceed the upper limit M, an accurate correction map that is not affected by mark defects, scratches, dust, etc. can be obtained.

Next, monitoring of the reticle position will be explained.

In the AA method of this embodiment, the reticle and wafer are not observed at the same position, so it is assumed that the relative positions of the respective detection systems do not deviate. Furthermore, it is meaningless if the reticle shifts after alignment and during the wafer alignment operation. Therefore, in order to achieve high alignment accuracy, it is of great significance to constantly detect (monitor) the position of the reticle.

In FIG. 49, LTS is a stage that can move the reticle LT in the XYθ directions, WS is a stage that can move the wafer WF in the XYθ directions, Ml, BM, and D are the aforementioned wafer position detection systems, and OBI and OR3 are the 29th stage. This is a detection system for aligning the reticle shown in the figure. Note that these detection systems are shown schematically and various members shown in FIGS. 1 and 29 are omitted. Also, MO and MOL are each X
The drive system that drives and positions the Yθ stages WS and LTS, and the ARM, is an arithmetic control system that calculates each position error based on signals from the wafer position detection system and the reticle position detection system and controls the operation of each drive system. . Although the wafer stage WS includes the interferometric length measuring meter IFM shown in FIG. 1, it is omitted here. Position information of the interferometric length measuring needle IFM is also input to the arithmetic control system.

In conventional position detection devices, the reticle is assumed to be fixed after alignment, but for some reason it may move.According to this embodiment, the reticle may move during the wafer alignment operation. At the same time, the reticle position is detected by OBI and OB.
2, and the arithmetic control system ART provides feedback to the drive system MOL so as to always maintain a predetermined position.

That is, the reticle position is monitored and the reticle is driven when it deviates from a predetermined position. This ensures the reticle position at all times.

Note that instead of driving the reticle, the amount of positional deviation of the reticle may be reflected on the wafer side. In other words, as described above, the reticle position is constantly monitored and if it deviates from the predetermined position, the arithmetic control system adjusts the wafer position. It may also be fed back to the command value.

Furthermore, it is also possible to drive both the reticle and the wafer so that the relative positional relationship is at a predetermined position.

Furthermore, it is of course possible to perform monitoring and correction at any timing as necessary.

[Effect of the invention] As explained above, according to the present invention, the standard second
Since the illuminance of the illumination light is corrected by measuring with the object, the signal output of the mark detection signal and the S/
Since N can be kept constant, highly accurate positioning can be achieved.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an alignment apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing the position of marks on a wafer and the illumination direction of wafer illumination light, and FIG. 3 is a diagram showing a reference mask. Figures 4 and 5 are conceptual diagrams for explaining the slit light reception method. Figure 6 is a diagram showing the wafer illumination light introduction method and illuminance distribution. 7 to 9 are block diagrams of the chromatic aberration correction optical system, Figures 10 and 11 are block diagrams and schematic block diagrams of the detector sensitivity monitoring mechanism, and Figures 12 to 16 are is a conceptual diagram for explaining chopping and waveform processing, FIG. 17 is a schematic diagram for explaining laser light intensity correction, FIG. 18 is a diagram showing an example of simultaneously observing wafer marks of the next shot, Fig. 19 is a diagram showing the slit light reception method in the case of Fig. 18, Fig. 20 is a diagram showing a reference mask using a shadow mark as a reference mark, and Fig. 21 is a schematic configuration of the device shown in Figs. 22 is a flowchart of the alignment operation of the system of this embodiment, FIGS. 23 and 24 are a configuration diagram and a block circuit diagram when performing AA in image processing, and FIG. 25 is a FIG. 26 is a diagram showing another example of performing AA in image processing. FIG. 27 is a schematic diagram showing conventional reticle alignment. FIG. 28 is a diagram showing the indirect method. 29 is a diagram showing the applied reticle alignment detection system; FIG. 29 is a diagram illustrating the reticle alignment detection system of this embodiment; FIG. 30 is a cross-sectional view showing how the mark portion is illuminated; FIG. 31 Figure 32 shows an example of alignment marks.
33 is a diagram showing an example of a plurality of partial regions in binarization, FIG. 34 is a diagram illustrating reduction and smoothing processing, and FIG. 35 is a diagram showing the hardware configuration of the alignment device.
Figure 36 is a diagram explaining the interpolation method of the binarization threshold, Figure 36 is a diagram explaining the center of gravity calculation, Figure 37 is a processing flow diagram, and Figure 38 is a diagram showing the absolute grid drawn on the reticle. Figures 39 and 40 are a diagram showing a real grid and a grid image taken from the real grid, and a diagram showing a corrected map, and Figure 41 is
A flowchart for creating a corrected map, FIG. 42 is a schematic diagram showing a method of abnormal value interpolation, FIGS. 43 to 47 are graphs and flowcharts for explaining an abnormal value determination method, and FIG. FIG. 49 is a schematic diagram showing the field of view when changing and remeasuring to create a corrected map. FIG. 49 is a configuration diagram of a mechanism for monitoring the reticle. LP: illumination system, LT: L, chicle, Po: projection optical system,
WL: Wafer illumination system, WS + wafer stage, O8 dichroic aberration correction optical system, BM two-reference mask, DP: Roof prism, PM: Polygon mirror/Dx/DY: Detector. Patent Applicant Canon Co., Ltd. Representative Patent Attorney Tetsuya Ito Representative Patent Attorney Tatsuo Ito Figure 6 A Word Cause U Figure 10 Figure 11 (b) Figure 12 Beam 3 Etsuzuka 1 by Beam 1 anti-n=1t'' of beam 3 -' Fig. 13 (a) (b) Fig. 14 (CI) (b) Fig. 15 (a) (b) Fig. 16 Fig. 17 Fig. 22 Fig. 4/ 'A78M (a) IY I through r7 wafer mark M 1-20 Fig. 23 Fig. 24 Fig. 25 Fig. M27 Fig. 30 Fig. 31 tXI Fig. 33 Fig. 34 Fig. 35-l Fig. 36 Fig. 37 Fig. 39 Fig. 40 Fig. 41 (7n-+Yama-1 Rishiko Tang, abnormal A directness ≠ Rita law @ 44 multiple books) Hand exchange, grudge abnormal I directness. Fig. 45 la) (b )(c)
(d) Multi-lattice woman's abnormal operation 11 times Figure 46 Arrangement of stomach normal hand exchange commands Figure 47 (a) (b) Figure 48 Figure 49

Claims (1)

[Claims] 1. Alignment of the first object and the second object in a device that projects a pattern drawn on the first object onto the second object via a projection optical system The apparatus includes an illumination optical system that illuminates the second object, a detector that receives an image of the second object by illumination light from the illumination optical system for alignment, and a standard second object. means for placing an object at a predetermined position and illuminating it with the illumination optical system and receiving the image with the detector to obtain a signal; and means for comparing the signal with a pre-stored reference value; An alignment device comprising means for correcting the amount of illumination light from the illumination optical system based on the comparison result. 2. The alignment device according to claim 1, wherein the correction means corrects the illumination light from the illumination optical system using a polarizing plate. 3. The correction means adjusts the illumination light from the illumination optical system to N
The alignment device according to claim 1, wherein the alignment device performs the correction using a D filter. 4. The alignment device according to claim 1, 2, or 3, wherein the sensitivity of the detector is corrected prior to acquiring the signal from the second object serving as the standard. 5. Illumination light from the illumination optical system illuminates the second object from between the projection optical system and the second object without going through the projection optical system, and the detector illuminates the second object. The alignment apparatus according to claim 1, 2, 3, or 4, which receives an image of 1 through the projection optical system.