Projection exposure apparatus - Patent Review 4814829

Claims

What is claimed is:

1. A projection exposure apparatus for projecting a pattern formed on a first object upon a second object, having a mark and a radiation-sensitive layer, by use of a projection optical system to thereby expose the radiation-sensitive layer to the pattern of the first object, said apparatus comprising:

an illumination optical system adapted to illuminate, from between the projection optical system and the second object without use of the projection optical system, the surface of the second object on a side thereof on which the radiation-sensitive layer is provided; and

a detection optical system for detecting, by use of the projection optical system and by use of a light from said illumination optical system, the mark of the second member from the side thereof on which the radiation-sensitive layer is provided, wherein said detection optical system has an numerical aperture of sin A with respect to the second object, wherein said illumination optical system supplies an illuminating light to the second object at an angle B with respect to an optical axis of the projection optical system, and wherein A and B satisfy the following relation: B.gtoreq.A+10.degree..

2. An apparatus according to claim 1, wherein the illuminating light is projected upon the second object with a Brewster angle at respect to the radiation sensitive layer provided on the second object.

3. An apparatus according to claim 1, wherein the illuminating light is projected upon the second object in a direction perpendicular to an edge, to be detected, of the mark of the second object.

4. An apparatus according to claim 1, wherein said illumination optical system changes the angle over time, at which the illuminating light is incident upon the second member.

5. An apparatus according to claim 1, wherein said illumination optical system includes a stop provided therein to restrict the direction of the light impinging on the mark and the region on the second member to be irradiated with the illuminating light.

6. An apparatus according to claim 5, wherein said stop is inclined with respect to an optical axis of said illumination optical system.

7. An apparatus according to claim 1, wherein said detection optical system includes a spatial filter corresponding to the mark of the second object.

8. An apparatus according to claim 1, wherein said illumination optical system includes a light source comprising laser for producing the illuminating light.

9. An apparatus according to claim 8, wherein said illumination optical system produces illuminating light incident upon the second member in a P-polarized state.

10. An apparatus according to claim 8, wherein said illumination optical system includes a plurality of lasers producing lasers beams of different wavelengths and wherein said apparatus further comprises a plurality of detection optical system of a number corresponding to the number of said lasers.

11. An apparatus according to claim 8, wherein the laser beam is incident upon the second object with such angle of incidence that is effective to cause, when the mark is irradiated with the laser beam, a high-order diffraction light to be reflected from the mark and to advance substantially in parallel to the optical axis of the projection optical system.

12. A projection exposure apparatus for projecting a pattern formed on a first object upon a second object having a mark by use of a projection optical system, said apparatus comprising:

first illuminating means for illuminating the second object from between the projection optical system and the second object without use of the projection optical system;

second illumination means for illuminating a plate-like member having a reference mark formed therein;

detection means operable to detect the mark of the second object by use of an illuminating light supplied from said first illumination means and by use of the projection optical system, said detection means being also operable to detect the reference mark by use of an illuminating light supplied from said second illumination means and passing through said plate-like member, wherein said detection means has an numerical aperture of sin A with respect to the second object, wherein said first illumination means supplies an illuminating light to the second object at an angle B with respect to an optical axis of the projection optical system, and wherein A and B satisfy the following relation: B.gtoreq.A+10.degree.; and

control means for controlling the positional relation between the first and second objects in accordance with the detection by said detecting means.

13. An apparatus according to claim 12, wherein the reference mark is defined by an aperture formed in the plate-like member.

14. An apparatus for projecting a pattern formed on a first object upon a second object having a mark by use of a projection optical system, said apparatus comprising:

illumination means for illuminating the second object from between the projection optical system and the second object without use of the projection optical system;

imaging means for imaging, upon the second object, a reference mark formed on a plate-like member, by use of an illuminating light supplied from said illumination means and passing through the projection optical system;

detection means for detecting an image of the mark of the second object, which image is partially shaded by means of said reference mark, wherein said detection means has a numerical aperture of sin A with respect to the second object, wherein said illumination means supplies an illuminating light to the second object at an angle B with respect to an optical axis of the projection optical system, and wherein A and B satisfy the followimg relation: B.gtoreq.A+10.degree.; and

means for controlling the positional relation between the first and second objects in accordance with the detection by said detection means.

15. An apparatus according to claim 14, wherein said detection means is arranged to scan the image of the mark of the second object, having been transmitted through said plate-like member, and also to photoelectrically convert the scanned image into an electrical signal.

16. An appartus for projecting a pattern formed on a first object upon a second object having a mark by use of projection optical system, said apparatus comprising illumination means for illuminating the second object from between the projection optical system and the second object without using the projection optical system;

means for scanning an image of the mark of the second object formed with the aid of the projection optical system and an image of reference mark provided on a plate-like member;

means for receiving the scanned images and converting the scanned images into electrical signals;

means for detecting the positional deviation of the second object from the reference mark, on the basis of the electrical signals; and

control means for controlling the positional relation between the first and second objects in accordance with the detection by said detecting means.

17. An apparatus according to claim 16, wherein said detecting means includes a plurality of light receiving means and wherein the image of the mark of the second object and the image of the reference mark are received separately by said plurality of light receiving means.

18. An apparatus according to claim 16, wherein said receiving means receives the image of the mark of the second object and the image of the reference mark with a predetermined time difference.

19. An apparatus according to claim 16, wherein each of the second object and the plate-like member has at least two marks provided with respect to X and Y directions, respectively, of an X-Y coordinate system and wherein said detecting means detects one of said at least two marks, associated with one of the X and Y directions, independently of the other associated with the other direction.

20. An apparatus according to claim 19, wherein said scanning means includes one movable polygonal mirror and wherein the images of the mark elements of the mark of the second object and the reference mark are scanned with the aid of movement of said polygonal mirror.

21. An apparatus for proejcting a pattern formed on a first object upon a second object having a mark by use of a projection optical system, said apparatus comprising:

an illumination optical system for illuminating the second object from between the projection optical system and the second object without using the projection optical system;

a detector for detecting, by use of the projection optical system, an image of the mark of the second object as illuminated by said illumination optical system;

means for monitoring a change in the sensitivity of said detector; by irradiating said detector with a light from a standard light source; and

means for controlling the positional relation between the first and second objects in accordance with an output of said detector when the image of the mark is detected thereby.

22. An apparatus according to claim 21, further comprising means for compensating for the change in the sensitivity of said detector, detected as a result of the monitoring, by controlling the intensity of light to be supplied form said illumination optical system.

23. An apparatus for projecting a pattern formed on a first object upon a second object having a mark by use of a projection optical system, said apparatus comprising:

an illumination optical system for illuminating the second object from between the projection optical system and the second object without using the projection optical system, said illumination optical system including a single-mode fiber for directing an illuminating light to the second object;

means for detecting, by use of the projection optical system, the mark of the second object by use of the illuminating light from said illumination optical system, wherein said detection means has an numerical aperture of sin A with respect to the second object, wherein said illumination optical system supplies an illuminating light to the second object at an angle B with respect to an optical axis of the projection optical system, and wherein A and B satisfy the following relation: B.gtoreq.A+10.degree.; and

control means for controlling the positional relation between the first and second objects in accordance with the detection by said detecting means.

24. An apparatus according to claim 23, wherein said illumination optical system includes a gradient index type lens system and an expander lens system provided adjacent to opposite ends of said single mode fibers.

25. An apparatus according to claim 23, wherein said illumination optical system comprises a plurality of illumination lights, and wherein said illumination optical system illuminates the second object by use of said plurality of illuminating light supplied along different optical path lengths.

26. An apparatus for projecting a pattern formed on a first object upon a second object having a mark by use of a projection optical system, said apparatus comprising:

an illumination optical system arranged to illuminate the second object from between the projection optical system and the second object and without using the projection optical system, said illumination optical system illuminating the scond object by use of lights projected in sequence and in a plurality of directions;

detection means for detecting, by use of the projection optical system, the mark of the second object by use of the lights projected in sequence from said illumination optical system, wherein said detection means has an numerical aperture of sin A with respect to the second object, wherein said illumination optical system supplies an illuminating light to the second object at an angle B with respect to an optical axis of the projection optical system, and wherein A and B satisfy the following relation: B.gtoreq.A+10.degree.; and

means for controlling the positional relation between the first and second objects in accordance with the detection by said detection means.

27. An apparatus for projecting a pattern formed on a first object upon a second object having a mark by use of a projection optical system, said apparatus comprising:

an illumination optical system arranged to illuminate the second object from between the projection optical system and the second object and without using the projection optical system, said illumination optical system illuminating the second object by use of lights projected in sequence and in a plurality of directions;

detection means for detecting, by use of the projection optical system, the mark of the second object by use of the lights projected in sequence from said illumination optical system; and

means for controlling the positional relation between the first and second objects in accordance with the detection by said detecting means, wherein said illumination optical system is adapted to project the lights toward the second object, in sequence and in four directions congruent with axes of an X-Y coordinate system defined on the second object.

28. An apparatus for projecting a pattern formed on a first object upon a second object having a mark by use of a projection optical system, said apparatus comprising:

an illumination optical system arranged to illuminate the second object from between the projection optical system and the second object without using the projection optical system, said illumination optical system illuminating the second object by use of lights projected in sequence and in a plurality of directions;

detection means for detecting, by use of the projection optical system, the mark of the second object by use of the lights produced in sequence from said illumination optical system; and

means for controlling the positional relation between the first and second objects in accordance with the detection by said detecting means, wherein said illumination optical system is adapted to sequentially project lights in two of four directions in an alternate fashion with the remaining two of the four directions.

29. An apparatus for projecting a pattern formed on a first object upon a second object having a mark by use of projection optical system, said apparatus comprising:

an illumination optical system for illuminating the second object from between the projection optical system and the second object without using the projection optical system;

image detecting means for receiving an image of the mark of the second object as illuminated by said illumination optical system, the image being formed with the aid of the projection optical system, wherein said image detecting means generates image data in response to the reception of the image by said image detecting means, wherein said image detecting means has an numerical aperture of sin A with respect to the second object, wherein said illumination optical system supplies an illuminating light to the second object at an angle B with respect to an optical axis of the projection optical system, and wherein A and B satisfy the following relation: B.gtoreq.A+10.degree.; and

control means for controlling the positional relation between the first and second objects in accordance with the image data.

30. An apparatus according to claim 29, wherein said illumination optical system is arranged to illuminate the second object by use of lights projected in sequence in a plurality of directions.

31. An apparatus for projecting a pattern formed on a first object upon a second object having a mark, by use of a projection optical system and with use of light of a first wavelength, said apparatus comprising:

an illumination optical system for illuminating the second object by use of a light of a second wavelength different from the first wavelength;

a detection optical system having a plurality of rear-surface reflection type mirrors each having parallel surfaces, said mirrors being disposed so as to be inclined with respect to an optical axis of said detection optical system;

detecting means for detecting, by use of the projection optical system and said detection optical system, the mark of the second object by use of the light from said illuminatiom optical system; and

means for controlling the positional relation between the first and second objects in accordance with the detection by said detecting means.

32. An apparatus according to claim 31, wherein said illumination optical system is arranged to illuminate the second object from between the projection optical system and the second object without using the projection optical system.

33. An apparatus for projecting a pattern, formed on a first object having an alignment mark upon a second object by use of a projection optical system, said apparatus comprising:

illumination means for illuminating with incoherent illuminating light, in a direction opposite to the directon of pattern projection, a reference mark formed on a plate-like member and the alignment mark of the first object, wherein said illumination means transmits the incoherent illuminating light through the reference mark of the plate-like member, and wherein the plate-like member is disposed between the projection optical system and the first object, wherein said illumination means illuminates the reference mark on the plate-like member and the alignment mark on the first oject from between the projection optical system and the plate-like member; and

means for receiving the light from said illumination means to obtain image data;

means for calculating the relative positional deviation between the reference mark and the alignment mark on the basis of the image data; and

means for aligning the first object on the basis of the positional deviation calculated by said calculating means.

34. An apparatus according to claim 33, whrein said illumination means comprises a Hg lamp for generating light comprising transmitting illumination light comprising g-line rays supplied from a Hg lamp.

35. An apparatus according to claim 33, wherein said apparatus further comprises means for producing light to be used for the projection of the pattern upon the second object and wherein the illuminating light is introduced from said producing means.

36. An apparatus for projecting a pattern, formed on a first object having a mark, upon a second object having a mark by use of a projection optical system, said apparatus comprising:

first mark supporting means for supporting a first reference mark operable as an index for the alignment of the first object;

second mark supporting means for supporting a second reference mark operable as an index for the alignment of the second object;

means for continuously monitoring the position of the mark of the first object with respect to the first reference mark;

detecting means for detecting, by use of the projection optical system, the positional relation between the mark provided on the second object and the second reference mark; and

control means for controlling the position of the second object in accordance with the detection by said detecting means.

37. An apparatus according to claim 36, wherein said monitoring means generates an output relating to data for moving the first object so that the first object is continuously held at a predetermined position.

38. An apparatus according to claim 36, wherein said monitoring means generates an output relating to data for controlling the movement of the second object to control the position of the second object.

39. An apparatus for projecting a pattern, formed on a first object having a mark, upon a second object by use of a projection optical system, said apparatus comprising:

mark supporting means for supporting a reference mark operable as an index for the alignment of the first object;

image pickup means for observing the reference mark and the mark provided on the first object;

means operable to cause said image pickup means to observe a grid-like distortion measuring reference mark, and for preparing correction data on the basis of the positions of intersections of the distortion measuring reference mark and the positions of the intersections as detected as a result of the observation by said image pickup menas; and

means for aligning the mark of the first object with the reference mark supported by said supporting means, on the basis of the observation of the reference mark and the mark of the first object by said image pickup means and in accordance with the correction data.

40. An apparatus for projecting a pattern formed on a first object upon a second object by use of a projection optical system, said apparatus comprising:

an illumination optical system for illuminating the second object from between the projection optical system and the second object without using the projection optical system;

a detector for receiving an image, formed through the projection optical system, of the second object as illuminated by said illumination optical system, said detector also receiving an image, formed through the projection optical system, of a second object, which is a standard, placed on a predetermined position and illuminated by said illumination optical system;

means for comparing a signal produced from said detector in response to the reception of the image of the standard, with a preparatorily stored reference value; and

means for correcting the intensity of the light from said illumination optical system in accordance with the comparison by said comparing means.

41. An apparatus according to claim 40, wherein said correcting means includes a polarizing member actable on the light from said illumination means.

42. An apparatus according to claim 40 wherein said correcting means includes a neutral density filter actable on the light from said illumination optical system.

43. An apparatus according to claim 40, wherein said detector has a sensitivity and wherein the sensitivity of the detector is adjusted prior to the reception of the signal from the standard.

FIELD OF THE INVENTION AND RELATED ART

This invention relates to a projection exposure apparatus and, more particularly, to a projection exposure apparatus having an optical system for detecting image information concerning an object having a surface transparent film. Typically, the invention is suitably applicable to projection exposure apparatuses (called "steppers") usable in the manufacture of semiconductor devices such as integrated circuits, for aligning a wafer coated with a photoresist material with respect to a reticle and, after alignment, for exposing the wafer to a pattern of the reticle with radiation.

In the projection exposure apparatus of the type described above, resolving power and superimposing accuracy are two basic performances required. As for the resolving power, it only needs very simple treatment because only a few parameters determine the resolving power. In the projection exposure apparatuses, called "steppers", used in the field of manufacture of semiconductor devices, it is easy to estimate the resolving power of a projection lens system once the numerical aperture (NA) and the wavelength to be used for the photoprinting through the projection lens system are determined. Also, in the case of X-ray exposure apparatuses, there are only a limited number of parameters such as "half shade" which is determined by the size of an X-ray source used.

In field of semiconductor devices, the progress in developing higher capacities and further miniaturization mainly owes to the advance of the photolithography technique (i.e. the technique of printing a pattern of a very narrow linewidth) and to the advance of the process technique such as the etching process technique. As regards the resolving power, the history of projection lens systems used in the steppers shows a steady advance of the resolving power. Recently, the minimum resolvable linewidth has become less than 1 micron which was a threshold in the past, and a variety of lens systems having resolution of an order of submicron linewidth have been developed.

On the side of the wafer process, there have recently been proposed various ideas such as a trenching process, a low-step structure, a high-step structure or the like. Briefly, these ideas relate to the development of developing three-dimensional integrated-circuits.

The advance of the resolving power having been achieved on the exposure apparatus side and the advance having been achieved on the process technique side come into intimate contact with each other, on the same stage of pattern superimposition. In this respect, the superimposing accuracy has become more and more important in the exposure apparatus.

It is difficult to treat the superimposing accuracy in terms of simple parameters with which the resolving power can be treated. This is just the implication of the variation of the wafer process. On the other hand, this is because of the multifariousness of the structures of alignment systems used for the superimposition. What makes the factors of the wafer process more complicated is the fact that the problem should be discussed not only in the phase of a wafer substrate but also in the phase of a photoresist coating applied to the wafer surface. One of the targets which are currently and apparently aimed at in field of semiconductor device is a three-dimensionally constructed integrated-circuit. In such a circuit the surface step (recess/protrusion) of the wafer must be made much deeper or higher. Clearly, this adversely affects the state of resist coating. Also, there is a tendency to further enlargement of the wafer size, i.e. from 6-inch wafers to 8-inch or 10-inch wafers. Where a large-diameter wafer is coated with a photoresist material in accordance with the drop-and-spin method, apparently the state of coating is uneven between a central portion and a peripheral portion of the wafer. Also, the unevenness grows with the increase in the depth/height of the surface recess/protrusion of the wafer. In fact, it is known that the state of alignment changes due to the influence of the application of the resist material to the wafer. The importance will be understood from the fact that studies have been made of how to uniformly apply the resist material.

Further, with regard to the photoresist, consideration has to be made of a tendency to using a multilayer resist in accordance with the "age" of submicron linewidth. Since, in a few manufacturing processes, some measures such as the aforementioned multilayer resist process or the contrast enhancement lithography (CEL) technique must be inevitably adopted in order to improve the resolving power, it is also necessary to arrange the exposure apparatus so as to meet them. It can be said that, in the phase of the pattern superimposition, it is required to provide the exposure apparatuses with effective measures for such newly proposed wafer processes as described above.

On the other hand, the multifariousness of alignment systems is evidence of the flexibility and difficulty in constructing the system. Every alignment system having been proposed or developed has a difference from the others, and each system has its own advantages and disadvantages. An example is found in an alignment system of a projection exposure apparatus of the type disclosed in Japanese Laid-Open Patent Application, Laid-Open No. 25638/1983. This is an example of excellent arrangement which practically embodies a so-called TTL (through the lens) on-axis alignment system with the aid of a projection lens optical system that is telecentric both on the reticle side and on the wafer side. While the projection lens system is arranged so that aberrations are corrected with respect to g-line rays (436 nm in wavelength), it shows substantially the same optical performance with respect to a He-Cd laser beam (442 nm in wavelength). The proposed alignment system uses the laser beam scanning method, using the He-Cd laser beam, for the detection of alignment signals. For this reason, the exposure operation can be initiated just in the state of completion of the alignment. Namely, the TTL on-axis alignment is practically embodied. The TTL on-axis alignment system is nearly ideal in a sense that the error in the detection of the alignment signals is the sole factor in the inaccurate operation of the exposure apparatus. Its only weak point is that the signal detection is not easy when the system is used with a resist material, such as the multilayer resist, having an absorbency with respect to wavelengths near that to be used for the photoprinting.

On the other hand, many proposals have been made for alignment systems using a wavelength other than the photoprinting wavelength, more particularly using a longer wavelength such as that of e-line rays (546 nm) or that of a He-Ne laser beam (633 nm). Because of the use of a wavelength longer than the photoprinting wavelength, these alignment systems are reliable, for the wafer process using absorptive resist materials such as the multilaser resist. However, due to various aberrations of the projection lens system caused in relation to the "chromaticity", the position that allows detection of a wafer alignment mark by way of the projection lens system (in other words, the position in the image height direction related to the projection lens system) is usually fixed. Therefore, while it depends on the positional relation of the alignment mark with an associated shot area of the wafer, it is necessary to move the wafer after the mark is detected, so as to move the associated shot area to the exposure position. Such movement leads to a factor of inaccuracy.

However, recent demands for the superimposing accuracy are very strict. Even the above-described signal detection error which is the sole factor of inaccuracy in the idealistic alignment system of the type described in the aforementioned Japanese Patent Application, Laid-Open No. 25638/1983, has to be treated as a problem.

The inventors of the subject application have made an analysis of components of the error in the detection of the alignment signal and, from the results, it has been found that almost all the error components result chiefly from the application of the photoresist to the wafer surface. While there are many factors of inaccuracy related to the resist coating, it is considered that the most important factors are the following two:

The first is the effect of interference between the light reflected by the surface of the resist layer and the light passing through the resist layer and reflected backwardly from the substrate of the wafer. Particularly, as described hereinbefore, the application of the photoresist material to the wafer is not always uniform. In many cases, the resist coating is uneven between the central portion and the peripheral portion. Also, the wafer substrate itself is involved in unevenness in the working processes such as the etching, the sputtering, etc. As a consequence, the structures of respective alignment marks associated with different shot areas on the wafer, when they are considered in the condition that the resist coating exists on the wafer, are different from each other (the variation occurring with the difference in the location on the wafer). Accordingly, the effect of interference varies with the location on the wafer. It appears that the interference described above is the most striking one of the effects of the resist coating that causes the alignment error.

The second factor is that of multiple reflection. One function of the resist layer is to act as an optical waveguide. For this reason, a portion of the light reflected by the wafer substrate is reflected a interface between the resist layer and the air. This portion of light goes back to the wafer substrate and is reflected thereby again. The higher the reflection factor of the wafer substrate, the more noticeable is the effect of multi-reflection. Moreover, the multiple reflection finally causes interference which results in further deterioration of the alignment accuracy.

As another factor of inaccuracy resulting from the photoresist, there is the shift of an image due to the refraction by the resist material. However, such factor is merely a secondary factor. It has been confirmed as a result of the above analysis that the exclusion of the above-discusses two factors, particularly the effect of interference, is contributive to the improvement of the alignment accuracy, to a great extent.

SUMMARY OF THE INVENTION

It is accordingly a primary object of the present invention to provide a systematic arrangement which alleviates the effect of interference to thereby ensure higher alignment detection accuracy. Also, it is an object of the present invention to provide a projection exposure apparatus having such a systematic arrangement.

According to one aspect of the present invention, to achieve these objects, there is provided a projection exposure apparatus for transferring a pattern of a first member onto a second member by way of an imaging projection optical system, wherein a detection optical system is provided so as to detect the second member by way of the projection optical system. The detection optical system is arranged to detect light from an illumination optical system which is adapted to project an illumination light from between the projection optical system and the second member and without irradiating the projection optical system.

Problems which are encountered in practically embodying the above-described systematic arrangement, have already been considered by the inventors of the subject application.

For the position detection, for example, there is proposed a method wherein the first member is used as a reference and the position of the second member with respect to the reference is directly detected. Also, there is a method wherein the first member is preparatorily aligned with respect to a stationary portion of the apparatus while, on the other hand, the position of the second member is detected while using, as a reference, a mark provided on the stationary portion of the apparatus. In a case, such as the latter case, where it is desired to detect the position with respect to a reference mark thereby to indirectly detect the relative position of the first and second members, the problem to be considered is how to detect such reference mark, more particularly how to obtain signals of a good signal-to-noise ratio (S/N ratio) from the reference mark.

It is accordingly another object of the present invention to provide a systematic arrangement and a projection exposure apparatus using the same, wherein mark detection signals of a high signal-to-noise ratio are obtainable, with a simple structure, from a reference mark usable as a reference upon the position detection.

According to another aspect of the present invntion, to achieve this object, there is provided a position detecting device, usable with a first member such as a reticle and a second member such as a wafer, for detecting the position of the second member relative to the first member, wherein a reference mark is provided in a predetermined positional relation with the first member and wherein the relative position of the second member is detected by detecting the position of the second member with respect to the reference mark.

In one preferred form, the reference mark is defined by a light-transmitting window formed in a light-blocking member. An illumination system for illuminating the reference mark is disposed on one side of the light-blocking member, and a photodetector is disposed on the other side of the light-blocking member. Thus, a transmitted illumination system is defined with the result that the alignment mark (light-transmitting window) is detected on the basis of detection of light transmitted through the mark.

The position of the second member is detected by detecting the relative position of the reference mark and a mark provided on the second member. Since the eeference mark signal is obtained by illuminating the reference mark from the back thereof, a mark signal of good S/N ratio is obtainable.

Also, to achieve the same object, the present invention in one aspect thereof provides an alignment system, usable in an apparatus for projecting a pattern of a first member upon a second member by use of a projection exposure apparatus, for aligning the first member with the second member, wherein a reference mark is used as a reference upon alignment of the second member and wherein the reference mark is formed by a light-transmitting portion effective to transmit a portion of an image of the second member, and by a member effective to block another portion of the image of the second member as it passes through the light-transmitting portion. The second member is aligned in accordance with the detection of the relative position of the reference mark and a mark provided on the second member. At the final stage, the reference mark is used in the form of a shadow mark which blocks a portion of the image of the mark of the second member. By this, signals of a good signal-to-noise ratio are obtainable.

Further, for the alignment, a mark provided on a member such as a wafer is optically detected to obtain an optical signal the optical signal is converted into an electrical signal. On the basis of the electrical signal, the alignment is executed. In order to accomplish high-accuracy alignment of the member such as the wafer, it is necessary to obtain a mark signal of high resolution and good S/N ratio.

Accordingly, it is a further object of the present invention to provide a systematic arrangement and a projection exposure apparatus using the same, by which arrangement a mark signal of high resolution and good S/N ratio is obtainable with a simple structure, and whereby high-accuracy alignment is attainable.

In accordance with one aspect of the invention, to achieve this object, a projection optical system is provided to project a pattern of a first member upon a second member having a mark, and the mark of the second member is illuminated by use of a light projected thereupon from between the projection optical system and the second member and without use of the projection optical system. By the light illuminating the mark of the second member and by use of the projection optical system, an image of the mark is formed. The image of the mark of the second member and an image of a reference mark are scanned with slit means, and the thus scanned images are converted into electrical signals, on the basis of which any positional deviation of the second member from the reference mark is detected.

This allows detection of the relative position of the second member with respect to the reference mark as well as the alignment of the second member, only by a simple structure which comprises a few photoreceptors and slit means. The reception of the image of the reference mark and the image of the mark provided on the second member, is attainable in various ways. For example, these images may be received by separate light-receiving means. Alternatively, they may be received time-sequentially, i.e. at different times. The mark of the second member and the reference mark may be formed so as to allow detection of positional components in two orthogonal X and Y directions. Conveniently, these mark images may be scanned with the slit means with the aid of a common polygonal mirror.

Another problem is encountered in a case where a light of a wavelength different from the photoprinting wavelength is used as an illumination light for the position detection. In such case, it is necessary to correct chromatic aberrations, and it is desirable to achieve this by use of a correcting optical system which is simple and compact in structure and which can be manufactured at a low cost.

It is accordingly a still further object of the present invention to provide a systematic arrangement and a projection exposure apparatus using the same, by which various aberrations of a projection optical system caused in relation to the "chromaticity" can be corrected with a simple and compact and low-cost structure, and whereby clear detection and, therefore, high-accuracy position detection are ensured.

To achieve this object, the present invention in one aspect thereof provides a position detecting device which uses a light of a wavelength, different from a photopri