JP4541481B2 - Position detection apparatus, exposure apparatus, and device manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present inventionobjectOn the bodyalignmentmarkPosition ofDetectRuPosition detection device.
[0002]
[Prior art]
Recent progress in the manufacturing technology of semiconductor devices is remarkable, and the progress of microfabrication technology accompanying it is also remarkable. In particular, optical processing technology is mainly reduced projection exposure equipment with submicron resolution, commonly known as steppers. To further improve resolution, the numerical aperture (NA) of the optical system is increased and the exposure wavelength is shortened. It has been.
Along with the shortening of the exposure wavelength, the exposure light source has also been changed from a g-line or i-line high-pressure mercury lamp to an KrF or ArF excimer laser.
[0003]
On the other hand, with the improvement of the resolution of the projection pattern, high precision is also required for the alignment for relative alignment of the wafer and the mask (reticle) in the projection exposure apparatus. A projection exposure apparatus is not only a high-resolution exposure apparatus but also a function as a highly accurate position detection apparatus.
[0004]
Furthermore, in recent years, the introduction of a wafer surface planarization technique called CMP (Chemical Mechanical Polishing) has been promoted as a semiconductor manufacturing process. As a background for promoting CMP, there is a reduction in the depth of focus of the exposure image plane as the wavelength of exposure light becomes shorter. Further, as the integration of the semiconductor chip itself increases, the vertical structure becomes thicker than before, and it becomes difficult to focus on the entire exposure region. Therefore, by flattening the step, there is an advantage that the entire area of all chips on the wafer can be focused within the depth of focus.
[0005]
Under such a background, an off-axis alignment detection system (hereinafter referred to as “Off-Axis AA”) is used as a wafer alignment method. This is arranged at a position different from the projection exposure optical system, detects the position of the alignment mark on the wafer without using the projection exposure optical system, and aligns the wafer based on the detection result.
[0006]
On the other hand, as a conventional alignment method, there is a method of detecting an alignment mark on a wafer using an alignment wavelength of non-exposure light via a projection light optical system called TTL-AA (Through the Lens Auto Alignment).
[0007]
The advantage of TTL-AA is that the optical axis of the projection exposure optical system and the optical axis of TTL-AA (so-called “baseline”) can be arranged very short, so that the amount of wafer stage drive during alignment measurement and exposure is small. . Accordingly, it is possible to suppress a measurement error caused by a change in the distance between the optical axis of the projection exposure optical system and the optical axis of TTL-AA due to the environmental change around the wafer stage. In other words, there is an advantage that the fluctuation of the baseline is small.
[0008]
However, when the exposure light shifts to short wavelength light such as KrF laser or ArF laser, the glass material used is limited, so that it becomes difficult to correct chromatic aberration with respect to the alignment wavelength of the projection exposure optical system. Therefore, an OA detection system that is not affected by the chromatic aberration of the projection exposure optical system has become important.
[0009]
Further, in the case of the OA detection system, there is an advantage that a light source having an arbitrary wavelength or a wide wavelength range can be used because no projection exposure optical system is used. As an advantage of using broadband wavelength light, it is possible to remove the influence of thin film interference on the photosensitive material (resist) coated on the wafer. Therefore, it can be said that an OA detection system capable of correcting aberrations with respect to broadband wavelength light is an important alignment detection system.
[0010]
A projection exposure optical system having a conventional OA detection system will be described with reference to a schematic diagram shown in FIG.
Light IL emitted from an exposure illumination optical system 1 including an exposure light source (a light source such as a mercury lamp, a KrF excimer laser, or an ArF excimer laser) illuminates a mask (reticle) 2 forming a pattern. At this time, the reticle 2 is placed in advance on the reticle holders 12 and 12 'so that the optical axis AX of the projection exposure optical system 3 and the center of the reticle pattern coincide with each other by the alignment detection system 11 disposed above (or below) the reticle 2. It is positioned.
[0011]
With the light passing through the reticle pattern, the projection exposure optical system 3 transfers the image onto the wafer 6 held on the wafer stage 8 at a predetermined magnification. Note that irradiating irradiation light from above the reticle and sequentially exposing the reticle pattern onto the wafer 6 at a fixed position via the projection exposure optical system is called a stepper, and the reticle and wafer are relatively driven (reticle of the reticle). An exposure apparatus that drives a drive amount multiplied by the projection magnification of the wafer drive amount is called a scanner (scanning exposure apparatus).
[0012]
On the other hand, the wafer 6 includes a type called a second wafer on which a pattern has already been formed. When the next pattern is formed on this wafer, the position of the wafer must be detected in advance. The position detection method includes the above-described TTL-AA method and OA detection method.
[0013]
Here, an alignment method including an OA detection system will be described with reference to FIG. As shown in FIG. 3, the OA detection system 4 is configured separately from the projection exposure optical system 3, and the wafer stage 8 is driven by a wafer drive system 10 based on an interferometer 9 capable of measuring a lateral distance. The wafer 6 is positioned in the observation area of the OA detection system 4. With respect to the wafer 6 positioned by the interferometer 9, the position of the alignment mark formed on the wafer 6 is detected by the OA detection system 4, and the arrangement information of the chips (elements) formed on the wafer 6 can be obtained. I can do it.
[0014]
Next, based on the arrangement information of the chips (elements), the wafer 6 is sequentially exposed by driving the wafer stage 8 to the exposure area (reticle transfer area) of the projection exposure optical system 3.
[0015]
Here, a focus detection system 5 for measuring the focus direction of the projection exposure optical system 3 is configured in the exposure area of the normal projection exposure optical system 3. In the configuration of the focus detection system 5, the light emitted from the illumination light source 501 illuminates the slit pattern 503 through the illumination lens 502. The slit pattern 503 is imaged on the wafer 6 by the illumination optical system 504 and the mirror 505 with the light transmitted through the slit pattern 503.
[0016]
The slit pattern projected on the wafer 6 is reflected on the wafer surface and enters a mirror 506 and a detection optical system 507 which are configured on the opposite side of the illumination system. The detection optical system 507 re-images the slit image formed on the wafer 6 on the photoelectric conversion element 508. As the wafer 6 moves up and down, the slit image on the photoelectric conversion element 508 moves, and the distance in the focus direction of the wafer 6 can be measured from the amount of movement. Usually, a plurality of slits (multiple points on the wafer 6) are prepared, and the respective focus positions are detected (multipoint measurement on the wafer 6), whereby the image plane of the reticle image of the projection exposure optical system 3 is obtained. It is also possible to measure the tilt of the wafer with respect to. The driving of the wafer stage 8 by the wafer driving system 10 is controlled by the control unit 14.
[0017]
On the other hand, the OA detection system 4 will be described with reference to the schematic diagram of FIG. In FIG. 4, the light guided from the illumination light source 401 (fiber or the like) is guided to the polarization beam splitter 403 by the illumination optical system 402. The S-polarized light perpendicular to the paper surface reflected by the polarizing beam splitter 403 passes through the relay lens 404 and the λ / 4 plate 409, is converted into circularly polarized light, and is formed on the wafer 6 through the objective lens 405. Marker AM is illuminated by Koehler.
[0018]
Reflected light, diffracted light, and scattered light generated from the alignment mark AM return to the objective lens 405 and the λ / 4 plate 409 again, and are converted into P-polarized light parallel to the paper surface, and pass through the polarization beam splitter 403 to be coupled. An image of the alignment mark AM is formed on the photoelectric conversion element 408 (for example, a CCD camera) by the image optical system 407. Based on the position of the alignment mark image subjected to photoelectric conversion, the position of the wafer 6 is detected.
[0019]
At this time, in order to accurately detect the alignment mark AM on the wafer 6, the image of the alignment mark AM must be clearly detected. That is, the focus of the OA detection system 4 must be aligned with the alignment mark AM.
[0020]
However, in the OA detection system as described above, the focus detection system 5 that is normally configured in the projection exposure optical system 3 cannot be configured due to the limitation of the surrounding space.
Therefore, when there is no separate focus detection system in the OA detection system 4, the focus value is once measured by the focus detection system 5 configured under the projection exposure optical system 3, and then the measurement area of the OA detection system is set. After driving, the position detection mark must be observed.
[0021]
In this way, for example, if a drive error occurs in the focus direction as another component due to the lateral drive of the wafer stage, or if the wafer is tilted, it is difficult for the OA detection system 4 to focus on the entire wafer. turn into. Therefore, each time a position is detected for a plurality of chips on the wafer 6, for example, a plurality of measurements are performed while moving the position in the focus direction, such as measuring the contrast of an image (hereinafter referred to as “driving AF measurement”). Measurement must be performed, resulting in a decrease in throughput.
[0022]
Therefore, it is considered that the OA detection system itself is configured with a focus detection system corresponding to the focus detection system 5.
A focus detection system (hereinafter referred to as “AF system”) configured in the conventional OA detection system 4 will be described based on the schematic diagram of FIG. In addition, about the part (part already mentioned above) which functions as a position detection system, the same code | symbol is described, description is abbreviate | omitted, and only a different part is demonstrated.
[0023]
The light emitted from the AF light source 413 illuminates the slit 416 (one or a plurality) on which the pattern is formed by the illumination lens 414. The effect of forming a plurality of slits is to improve the measurement accuracy (averaging effect) when detecting the position of the slit (described later). The light passing through the slit is further guided to the second relay lens 412 by the illumination lens 415 and the mirror 418. The mirror 418 is arranged substantially at a conjugate position with a Fourier transform plane (hereinafter referred to as “pupil plane”) of an observation object of an objective lens 405 described later. The light passing through the second relay lens 412 forms a slit image on the intermediate image plane IP, and then the slit image is formed on the observation object (on the wafer 6) by the first relay lens 411, the mirror 410, and the objective lens 405. Is imaged. The light source wavelength of the position detection system is different from the light source wavelength of the AF system. The mirror 410 is formed of a dichroic mirror so that the AF system light is reflected and the position detection system light is transmitted. be able to.
[0024]
Further, as shown in FIG. 5, the light flux FIL of the illumination system is configured to pass through a position decentered from the optical axis on the pupil plane of the objective lens. For this reason, the light flux FIL of the slit is incident on the wafer 6 from an inclined angle and the light reflected on the wafer 6 (on the observation object) is relative to the position where the illumination light FIL on the pupil plane of the objective lens 405 has passed. Then, the light passes through a position symmetrical to the optical axis and travels toward the mirror 410 and the first relay lens 411. The slit image formed on the wafer 6 is formed again on the IP surface by the first relay lens 411, passes through the second relay lens 412, and then passes through the aperture stop 421 conjugated with the pupil plane of the objective lens. Then, a slit image is formed again on the photoelectric conversion element 419 by the imaging lens 420. An AF system is configured by such an optical arrangement, and the slit image on the photoelectric conversion element 419 moves with respect to the vertical driving of the wafer 6 (observation object). Can be detected.
[0025]
Conventionally, in such an AF system, a reference light is also configured in order to remove fluctuation components such as the photoelectric conversion element 419. In this figure, a half mirror 425 is formed between the second relay lens 412 and the imaging lens 420, and the reference light is guided onto the photoelectric conversion element 419 by the half mirror 425. .
[0026]
Light emitted from a light source 429 different from the light source 413 illuminates the reference light slit 427 uniformly by the AF reference light illumination lens 428.
[0027]
The light passing through the reference light slit 427 forms a reference light slit image on the photoelectric conversion element 419 by the AF reference light illumination optical system 426, the half mirror 425, and the imaging lens 420.
[0028]
The relationship between the reference light and the detection light will be explained a little more. The reference light and the detection light are different from each other. When the reference light is turned on, the detection light is turned off. Then, only the reference light is detected on the photoelectric conversion element 419, and a reference position is determined. Next, with the wafer 6 to be measured in the measurement region, the reference light side is turned off and the detection light side is turned on. The detection light passes through the optical path as described above, and forms a detection light slit image on the photoelectric conversion element 419. By detecting the position of the reference light detected previously and the relative position of the detection light, the position of the wafer 6 in the focus direction can be detected. By doing so, even if the position of the photoelectric conversion element 419 changes with time (from the reference light measurement to the detection light measurement is sufficiently stable), the relative position of the reference light and the detection light. Because this was detected, such fluctuation components could be removed.
[0029]
By configuring the AF system as described above as a position detection system, if the best focus position of the position detection system is measured with this chip with a chip on the wafer 6, when moving to the next chip, The focus value measured from the AF system can be used to always drive to the best focus position.
By doing so, it is not necessary to perform driving AF measurement on each chip, and thus throughput can be improved.
[0030]
[Problems to be solved by the invention]
However, the AF system as described above includes a factor that causes a measurement error. That is, when the detection light slit 416 itself moves in the measurement direction (the movement direction of the slit on the photoelectric conversion element), the measurement is performed with the focus shifted, although the focus has not changed.
[0031]
This phenomenon occurs when not only the detection light slit 416 but also the reference light slit 427 itself is changed, or the AF reference light illumination optical system 426, the imaging lens 420, and the second relay lens 412 that are configured in the middle. The same measurement error occurs even when the eccentricity of the mirrors 418 and 425 and the inclination eccentricity of the mirrors 418 and 425 formed in the middle occur.
Constructing another optical system for generating the reference light as in the prior art will cause an error factor in the reverse manner as described above.
[0032]
In general, such an AF system can be configured such that the incident angle of illumination light on the wafer 6 (observation object) is smaller than the NA of the objective lens itself. Therefore, the movement sensitivity of the slit on the photoelectric conversion element with respect to focus fluctuation is small. In other words, it is necessary to measure the focus fluctuation from the minute movement of the slit image on the photoelectric conversion element, which means that the influence on the measurement error due to the fluctuation of the slit itself and the like becomes large. .
[0033]
  The present invention has been made in view of the above problems., Advantageous in terms of accuracy of focusing on the alignment markProviding a position detection devicethingWith the goal.
[0034]
[Hands to solve problems]Steps]
  In order to achieve the above object, the present invention provides a position detection device for detecting the position of an alignment mark on an object.OhAnd
  An opening in which the first opening and the second opening are formed.MouthMaterialHaveTheIrradiate light that has passed through the first opening onto the object surface from an oblique direction.ShiAnd the first opening on the objectInAn illumination optical system for imaging,
  Having a photoelectric conversion element,Receiving the reflected light beam from the object surfaceOn the objectThe first openingofimageRe-imaged on the photoelectric conversion elementDetecting means for
  The illumination optical system includes theLight that has passed through the second openingTheThe objectInLight guideWithoutGuide to the detection meansHas a reflective member,
  Related to the re-imagingThe first openingofimageAnd formed through the reflecting memberThe second openingofimageWhenofOf the relative position on the photoelectric conversion elementinformationObtained by the detection means,Based on the information obtainedFocus on the alignment mark,thingCharacterized byIt is a position detection device.
[0038]
【Example】
(First embodiment)
First, the measurement principle regarding the AF system of the position detection apparatus or image detection apparatus according to the first embodiment will be described in detail with reference to FIG. Note that the components shown in FIG. 2 will be described by extracting only the components related to the AF system.
[0039]
First, the light emitted from the AF light source 413 uniformly illuminates the slit member 416 having a plurality of slits. The light that has passed through the slit 417 that is the opening of the slit member 416 passes through the AF illumination optical system 415 and is then guided to the objective lens 405 side by the mirror 418. The objective lens 405 and the AF illumination optical system 415 form a conjugate relationship (image formation relationship) between the wafer 6 surface and the slit member 416. Since the AF illumination light FIL is guided onto the wafer 6 through a position decentered with respect to the pupil plane of the objective lens 405, the AF illumination light FIL is incident on the wafer 6 from an inclined direction (angle θ), and a slit image is formed on the wafer 6. Imaged above. Further, it is assumed that the wafer is in the initial focus state (focus position) indicated by the solid line.
[0040]
The light (slit image) reflected by the wafer 6 is reflected at the same angle as the incident angle θ, passes through the objective lens 405, and passes through the detection system aperture stop 421. The light that has passed through the aperture stop 421 passes through the AF relay lens 420 and then forms a slit image on the photoelectric conversion element 419 that constitutes the detection means for detecting the focal position.
[0041]
Here, the size of the aperture stop 421 will be described. The size of the aperture stop 421 and the width of the slit member 416 may be determined so as to satisfy the following conditions.
[0042]
In this embodiment, the size of the aperture stop 421 and the size of the slit member 416 (slit width) are optimized so that the photoelectric change element 419 is perpendicular to the principal ray of the detection light FML. Can be placed. By arranging the photoelectric conversion element 419 vertically, it is possible to remove the influence of sensitivity unevenness depending on the incident angle of light of the photoelectric conversion element 419. For that purpose, the NA (in the figure: α) on the wafer 6 determined by the size of the aperture stop 421 with respect to the size of the slit (slit width) of the slit member 416 imaged on the wafer 6 (that is, α) It is sufficient to limit the focus range where the resolution is to be measured so that the influence of the contrast change of the slit image does not occur. (The depth of focus of the slit member 416 is made larger than the focus measurement range.) By doing so, the surface of the wafer 6 and the surface of the photoelectric change element 419 are in a so-called Scheinproof relationship with respect to the principal ray of the detection light FML. In other words, it can be arranged perpendicular to the principal ray of the detection light FML.
[0043]
By the way, it is assumed that the surface of the wafer 6 is shifted by ΔZ in the principal ray direction of the detection light FML. Then, the slit image projected on the wafer 6 is shifted by 2ΔZ × tan θ. Since the size of the aperture stop 421 is determined as described above, the contrast of the slit image projected on the wafer 6 hardly changes even if the ΔZ focus changes.
[0044]
Similarly to the above, FML ′ that has passed through the aperture stop 421 disposed on the pupil plane of the objective lens 405 (light indicated by a broken line) passes through the AF relay lens 420, and the slit image on the wafer 6 is the first. Is imaged on the photoelectric conversion element 419 at a position shifted by d. Here, when the imaging magnification from the wafer 6 to the photoelectric conversion element 419 determined by the objective lens 405 and the AF relay lens 420 is β, the following relationship is established between the defocus amount ΔZ and the incident angle θ. .
[0045]
d = 2 × β × ΔZ × tan θ
If we rewrite this for △ Z,
ΔZ = d / (2β tan θ)
Thus, defocus ΔZ is obtained from β and θ determined by design values and d obtained from the photoelectric conversion element 419.
The above is the basic principle of the AF system in this embodiment, and the AF system shown in FIG. 12 is a multi-type (multiple) AF slit.
[0046]
In FIG. 12, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and explanations of those components are omitted.
In FIG. 12, the AF slit member 416 includes a plurality of slits (three in this figure). The light that has passed through the slits ISa, ISb, and ISc of the AF slit member 416 passes through the AF illumination optical system 415 and then passes through the objective lens 405 as shown in FIG. The image is projected on the surface of the wafer 6.
[0047]
Thereafter, the light reflected on the surface of the wafer 6 passes through the objective lens 405 again, passes through the aperture stop 421 disposed on the pupil plane (or in the vicinity of the pupil plane) of the objective lens 405, and is reflected by the AF relay lens 420. A slit image is formed on the photoelectric conversion element 419.
[0048]
The slits ISa, ISb, and ISc are imaged on the photoelectric conversion element 419 as MSa, MSb, and MSc, respectively.
[0049]
Note that the size of the detection system aperture stop 421 satisfies the above-described conditions.
[0050]
Next, assuming that the wafer 6 is disposed at a position shifted by ΔZ, the light beam passes as shown by a broken line, and the whole is shifted by d on the photoelectric conversion element 419, as described for the apparatus shown in FIG. A slit image is formed at the positions (MSa ′, MSb ′, MSc ′).
[0051]
Each of the three slits is detected at a position shifted by d. Here, by obtaining three average positions, the accuracy is improved by the averaging effect.
[0052]
Generally, the accuracy is improved by using a plurality of detection marks in this way, and the detection accuracy is expected to be improved by multi-marking (plurality) in the AF system.
[0053]
As described above, the focal position of the wafer 6 can be detected with higher accuracy by making the slit multi-marked and obtaining the average position change d of the mark.
[0054]
Next, the first embodiment of the present invention will be described in detail with reference to FIG.
The alignment detection system is the same as that shown in FIG.
The light emitted from the AF illumination light source 413 uniformly illuminates the slit member 416 by the illumination lens 414. The slit member 416 has a plurality of (two or more) slits (three in the figure), and is attached to the light that has passed through the detection light slit 450 that is the first opening. I will explain.
[0055]
The light FIL (solid line) that has passed through the slit 450 forms a slit image on the intermediate image plane IP by the AF illumination optical system 415, the mirror 418, and the second relay lens 412. A partial reflection member 422 that partially reflects is formed on the intermediate image plane IP. The light that has passed through the detection light slit 450 passes through the transmission part of the partial reflection member 422 and is directly guided to the first relay lens 411 side. After passing through the first relay lens 411, it is reflected by the dichroic mirror 410 (described above), and passes through the position decentered by the objective lens pupil plane 406. Since the light that has passed through the objective lens 405 is decentered on the pupil plane, it is irradiated on the wafer 6 surface from an oblique direction to become detection light FIL, and an image of the slit portion 450 is formed on the wafer 6. The reflected light FML from the wafer 6 passes through the opposite side of the optical axis from the incident light at the pupil plane 406 of the objective lens 405, and again passes through the dichroic mirror 410, the first relay lens 411, and the partial reflection member 422. , Passing through the aperture stop 421. The partial reflection member 422 needs to have a size that does not block the detection light within the range of the focus detection position of the wafer 6.
[0056]
As described above, the aperture stop 421 is disposed at a position conjugate or substantially conjugate with the pupil plane 406 of the objective lens 405, and is disposed at a position eccentric from the optical axis center of the objective lens 405. It is the same. Further, as described above, the size of the aperture stop 421 is set to a size that allows the change in the contrast of the slit image to be allowed within the focus detection range of the wafer 6. The light FML that has passed through the aperture stop 421 forms an image of the detection light slit 450 imaged on the wafer 6 on the photoelectric conversion element 419 by the imaging lens 420. Therefore, the change in position of the wafer 6 in the focus direction can be detected as the slit position on the photoelectric conversion element 419 as described in the principle.
[0057]
On the other hand, the reference light will be explained. The light that has passed through the reference light slit 417 as the second opening on the slit member 416 passes through the AF illumination optical system 415, the mirror 418, and the second relay lens 412 in the same manner as the detection light FIL. The image is formed on the intermediate image plane IP. However, the reflection surface of the partial reflection member 422 is formed at the image formation position of the reference light slit portion 417, and the light of the reference light slit portion 417 directly passes without passing through the first relay lens side. The light is guided to the second relay lens 412 and the aperture stop 421 side. Thereafter, the image is formed on the photoelectric conversion element 419 by the imaging lens 420 in the same manner as the detection light. However, the image is formed at a position different from the detection light. The basic positional relationship is that the imaging magnification from the slit member 416 to the photoelectric conversion element 419 (determined by the AF illumination optical system 415 and the imaging lens 420) and the distance from the reference light slit 417 to the detection light slit 450. It is determined by.
[0058]
The reference light slit portion 417 and the detection light slit portion 450 are configured in the same slit member 416, and the relative position of the reference light and the detection light on the photoelectric conversion element 419 is detected at the same time, thereby detecting the focal position of the wafer 6. I can do it.
[0059]
By adopting the above configuration, it is not necessary to configure a separate optical system called a reference light illumination system as in the prior art, a simple configuration as a detection system is possible, and components that cause an error can be reduced. In addition, it is possible to correct for variations in the slit member 416 itself, variations in many components such as the mirror 418, the AF illumination optical system 415, the second relay lens 412, the imaging optical system 420, the photoelectric conversion element 419, and the like. It becomes possible to detect the focal position with higher accuracy on the surface of the wafer 6.
[0060]
Here, the relationship between the reference light and the detection light will be described in detail with reference to FIG.
First, FIG. 6A shows a slit portion on the slit member 416. RSa and RSb both indicate slits through which the reference light passes, and are guided directly to the photoelectric conversion element 419 side by the partial reflection member 422 without passing through the objective lens 405 side.
[0061]
On the other hand, the detection light that has passed through the slits (MSa, MSb, MSc: three in this figure) reaches the wafer 6 side as described above, and an image is formed on the photoelectric conversion element 419. Thus, there is an advantage in arranging the detection light so as to sandwich the reference light. This is because the detection system as described above has a magnification error and an optical error factor such as distortion. If the arrangement is such that the reference light and the detection light are not sandwiched, the above-mentioned optical error factor is greatly received and an offset occurs.
[0062]
Therefore, by sandwiching the detection light with respect to the reference light, there is an advantage that magnification and distortion are distributed, and the influence of such an optical error factor is eliminated.
[0063]
Here, FIG. 6B schematically shows signal waveforms obtained from the photoelectric conversion element 419 of the reference light and the detection light when the wafer 6 is at the basic focus position (best focus position). . Thus, at the best focus position, the detection light is arranged at the center with respect to the reference light signal. However, as shown in FIG. 6C, when the wafer 6 is driven in the focus direction, only the detection light signal moves in the lateral direction. The focal position of the wafer 6 can be detected by detecting this movement amount e (the center position of RSa and Rsb and the center position shift from MSa to MSc). As for the detection light, an average position is calculated from the positions of the three slit images, and the focal position is detected based on this information, whereby a multimark effect (average effect) can be obtained.
[0064]
On the other hand, for example, consider the case where the photoelectric conversion element 419 has moved in the measurement direction without changing the focal position of the wafer 6. In this case (FIG. 6D), if the reference light is not constituted, the position of the detection light changes. However, in this embodiment, the reference light itself changes by the same amount, and as a result, the reference light is changed. The relative position of the light and the detection light does not change, and therefore AF measurement is not fooled.
[0065]
In the AF measurement, it is necessary to adjust the light amount according to the reflectance of the wafer 6 (measurement object).
For example, the amount of light returning to the photoelectric conversion element 419 of AF detection light differs between a Si wafer substrate and a wafer substrate coated with a resist. Of course, it can be said that the reflectance change is larger when various processes in the semiconductor manufacturing process are taken into consideration.
[0066]
In the present embodiment, both the reference light and the detection light are configured in the same slit and illuminated by the same light source. Therefore, for example, when the reflectance of the wafer 6 is low with respect to the AF light source wavelength, it is necessary to increase the light amount of the light source in order to obtain the optimum light amount so as to increase the detection accuracy. However, since the light amount of the light source is increased in accordance with the light amount of the detection light, the light amount of the reference light that is simultaneously illuminated becomes very large.
[0067]
In this case, the light from the reference light may cause leakage light such as flare, which may hinder the detection light. For this, the light quantity of the reference light may be reduced in advance.
[0068]
That is, when measuring the reference light, the area of the reference light slit is made smaller than the area of the detection light slit so that the signal intensity can be obtained only when the light quantity of the AF light source is maximized.
[0069]
Alternatively, the reflectance of the reference light reflecting surface of the partial reflection member 422 may be reduced in advance. In any method, it suffices that the light amount of the reference light can be made smaller than the light amount of the detection light.
[0070]
The measurement procedure in the case of the configuration described above will be described with reference to FIG.
FIG. 7A shows a slit in which the area of the reference light slit is smaller than that of the detection light slit. The measurement signal intensity is configured to increase or decrease in proportion to the area of the slit (for example, integration in the non-measurement direction). In this way, the reference light slit signal intensity and the detection light slit signal intensity are compared in advance so that the signal intensity of the reference light is reduced, and AF measurement is performed without the wafer 6. At that time, as shown in FIG. 7B, since there is no reflecting object on the surface of the wafer 6, only the signal of the reference light is generated, and only the position of the reference light is detected and stored. Next, FIG. 7C shows a schematic diagram of the reference light and the detection light signal when the reflectance is relatively high on the surface of the wafer 6 (the AF light source is darkened). As described above, in the case of the wafer 6 having a relatively high reflectance, the reference light is detected outside the detection light signal with a low signal intensity. Therefore, a phenomenon such as leakage light to the detection light does not occur. Next, a signal when the reflectance of the wafer 6 is the worst (the AF light source is the brightest) is shown in FIG. Thus, since the signal of the reference light is optimized only when the AF light source is maximized, the influence of the leaked light of the reference light does not occur even in this case.
[0071]
As described above, the reference light slit part 417 is provided on the same member as the detection light slit part 450, and the reference light is directly passed through the photoelectric conversion element without passing through the wafer 6 by the partial reflection member 422 disposed on the intermediate image plane. Since the light is guided to 419, the relative position to the detection light is detected, and the focal position of the wafer 6 is detected, an optical system dedicated to the reference light is not required, and a large number of fluctuation factors can be eliminated, and high-precision AF Measurement is possible. In addition, expansion of the apparatus can be prevented.
[0072]
Incidentally, the arrangement of the slits and the lens and mirror as shown in the present embodiment are not limited to these. That is, if the reference light slit and the detection light slit are configured on the same member and only the reference light is guided to the photoelectric conversion element 419 side by the reflection member configured in the detection system, Various modifications can be made without departing from the scope of the invention.
[0073]
However, in this embodiment, since the slit member 416, the partial reflection member 422, and the photoelectric conversion element 419 are all arranged in a conjugate relationship, the inclination eccentricity of the partial reflection member 422 (of course, because of the mirror, the parallel eccentricity is There is also an advantage that the position of the reference light does not change even if it does not work.
[0074]
(Second embodiment)
FIG. 8 shows the slit illumination unit shown in the first embodiment. As described above, when the reference light and the detection light are illuminated and detected by the same light source, the measurement timings of the reference light and the detection light are made different as in the first embodiment, and the reference light and the detection light are serially generated. Must be measured. That is, basically, the reference light and the detection light cannot be measured at the same time with respect to various wafers 6 (reflectance), and there may be a fluctuation component between them.
[0075]
Therefore, in the second embodiment, a description will be given of a configuration in which the reference light and the detection light can be simultaneously measured with respect to the illumination system of the AF slit portion.
[0076]
FIG. 9 shows an illumination system using a bundle fiber for the light source 413.
This bundle fiber is characterized in that there is one at the exit and two on the incident side. One incident-side fiber includes a light source 431a on the reference light side and an illumination optical system 430a that guides the light to the fiber, and guides light serving as reference light to the fiber 413a side.
[0077]
On the other hand, the detection system side is similarly guided to the fiber 413b by the light source 431b on the detection system side and the illumination optical system 430b that guides the light to the fiber. The light sources 431a and 431b are configured such that the light amount can be adjusted independently.
[0078]
The fibers 413a and 413b are bundled as a single fiber at 413. When the cross section is viewed, the fiber 413b is filled inside, and the fiber 413a is disposed at the periphery thereof. The exit end face of the fiber 413 forms an image on the slit member 416 by the illumination lenses 432 and 414. As shown in the drawing, the relationship between the image of the end face and the slit is such that the reference light slit portion 417 enters the fiber 413a portion and the detection light slit portion 450 enters the fiber 413b. In this way, by configuring the illumination system, the reference light and the detection light can be dimmed independently. Therefore, the light amount of the reference light can be optimized without depending on the reflectance of the wafer 6, and only the light amount of the detection light can be adjusted according to the wafer 6. Therefore, it is possible to measure the reference light and the detection light at the same time for the wafer 6 having any reflectivity, and to improve the accuracy of the focal position detection.
[0079]
The present invention is not limited to the form of the fiber shown in the present embodiment. In other words, if a fiber with two incident light sides and one outgoing light side is used and the fiber exit end face and the slit are configured in an imaging relationship, the cross-sectional shape of the fiber and the optical arrangement Is not limited to this embodiment.
[0080]
(Third embodiment)
Similar to the second embodiment, the AF illumination system according to the third embodiment will be described with reference to FIG.
[0081]
In this figure, the slit member 416 to the illumination lens 432 shown in FIG. The difference is that a partial reflection mirror 433 is arranged on the surface conjugate with the slit member 416 instead of the fiber. The reflection region of the partial reflection mirror 433 and the detection light slit portion on the slit member 416 are arranged to coincide with each other. The light emitted from the light source 435a illuminates the partial reflection mirror 433 by the illumination optical system 434a. The light reflected by the partial reflection mirror 433 illuminates the detection light slit by the illumination lenses 432 and 414. On the other hand, light emitted from a light source 435b different from the light source 435a illuminates the reference light slit through the illumination lenses 432 and 414 via the illumination lens 434b. That is, the light of the light source 435a is guided to the detection light slit portion by the partial reflection mirror 433, and the light of the light source 435b not shielded by the partial reflection mirror 433 is illuminated on the reference light slit portion.
[0082]
By configuring as described above, the reference light and the detection light can be dimmed separately, and the reference light and the detection light can be emitted and measured simultaneously as in the second embodiment.
[0083]
(Fourth embodiment)
In the configuration shown in the above example, the illumination lens 432 has to be configured. However, FIG. 11 is used in connection with a fourth embodiment in which the same effect can be obtained without configuring this lens. Explain.
[0084]
The light source 436a that illuminates the detection light slit portion emits light having a certain spread. Similarly, the light source 436b emits light having a spread. A partial reflection mirror 433 is formed between each of the light sources 436 a and 436 b and the illumination lens 414. The light sources 436a and 436b and the slit have a Fourier transform relationship, and the light emitted from the light source 436b is shielded depending on the angle. In this way, the configuration can be simplified, and the reference light and the detection light can be dimmed independently, so that the reference light and the detection light can be emitted and measured simultaneously. Accordingly, it is possible to detect the focal position of the wafer 6 with higher accuracy.
[0085]
[Example of device production method]
Next, an embodiment of a device production method using the exposure apparatus or the exposure method provided with the detection apparatus described above will be described.
FIG. 13 shows a flow of manufacturing a microdevice (a semiconductor chip such as an IC or LSI, a liquid crystal panel, a CCD, a thin film magnetic head, a micromachine, etc.). In step 1 (circuit design), a device pattern is designed. In step 2 (mask or reticle fabrication), a mask (reticle) on which the designed pattern is formed is fabricated. On the other hand, in step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon or glass. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. The next step 5 (assembly) is referred to as a post-process, and is a process for forming a semiconductor chip using the wafer produced in step 4, such as an assembly process (dicing, bonding), a packaging process (chip encapsulation), and the like. including. In step 6 (inspection), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and a durability test. Through these steps, the semiconductor device is completed and shipped (step 7).
[0086]
FIG. 14 shows a detailed flow of the wafer process. In step 11 (oxidation), the wafer surface is oxidized. In step 12 (CVD), an insulating film is formed on the wafer surface. In step 13 (electrode formation), an electrode is formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. In step 15 (resist process), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern of the mask is printed onto the wafer by exposure using the exposure apparatus having the position or image detection apparatus described above. In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist after etching is removed. By repeatedly performing these steps, multiple circuit patterns are formed on the wafer.
[0087]
In the present embodiment, in each of the repeated processes, the alignment electron beam acceleration voltage is optimally set as described above, thereby enabling accurate alignment without being affected by the process.
By using the production method of this embodiment, a highly integrated device that has been difficult to manufacture can be manufactured at low cost.
[0088]
【The invention's effect】
  As described above, according to the present invention,It is possible to provide a position detection device that is advantageous in terms of accuracy of focusing on the alignment mark..
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a position or image detection apparatus according to a first embodiment of the present invention.
FIG. 2 is a principle diagram of a focus detection (AF) system according to the first embodiment of the present invention.
FIG. 3 is a schematic view of a projection exposure optical system provided with a position detection system.
FIG. 4 is a schematic diagram of a position detection system.
FIG. 5 is a detailed view showing an example of a conventional position detection device.
FIG. 6 is a schematic diagram of a reference light and a detection light signal.
FIG. 7 is a schematic diagram showing a relationship between reference light and detection light quantity.
FIG. 8 is a schematic diagram showing an AF illumination system according to a first embodiment of the present invention.
FIG. 9 is a schematic view showing an AF illumination system according to a second embodiment of the present invention.
FIG. 10 is a schematic view showing an AF illumination system according to a third embodiment of the present invention.
FIG. 11 is a schematic diagram showing an AF illumination system according to a fourth embodiment of the present invention.
FIG. 12 is a principle diagram of a multi-mark AF system.
FIG. 13 is a diagram showing a flow of manufacturing a microdevice.
FIG. 14 is a diagram showing a detailed flow of the wafer process in FIG. 13;
[Explanation of symbols]
1: exposure illumination optical system, 2: reticle (mask), 3: projection exposure optical system, 4: position detection system, 5: focus detection system, 6: wafer, 8: wafer stage, 10: wafer drive system, 13: Alignment reference mark, 14: control unit, 405: objective lens, 413: AF light source, 415: AF illumination optical system, 416: AF slit member, 417: slit (second opening), 419: photoelectric conversion element, 420: AF relay lens, 421: aperture stop, 422: partial reflection member, 450: slit (first opening).

Claims (9)

And have you in the position detecting device for detecting the position of the alignment mark on the object,
Has an open mouth member first opening and the second opening is formed, said object a and first opening by irradiating light that has passed through the first opening from an oblique direction on the object plane An illumination optical system that forms an image on the top;
A photoelectric conversion element, and detecting means for re-imaging on the photoelectric conversion element the image of said first opening on a reflection light beam by the light receiving said object from the該物body surface,
The illumination optical system includes a reflecting member for guiding the detecting means without guiding the light passing through the second opening to said object,
Obtained by the detection means information relative position on the photoelectric conversion elements of the image of the second opening formed through an image and the reflection member of the first opening of the該再imaging, A position detecting device , wherein the alignment mark is focused based on the obtained information . The position detection device according to claim 1 , further comprising a light source for illuminating the first opening and the second opening. Compared to the intensity of the first signal corresponding to the image of the first opening portion obtained by the photoelectric conversion element, the intensity of the second signal is smaller corresponding to the image of the second opening portion obtained by the photoelectric conversion element The position detection device according to claim 1, wherein the position detection device is configured as described above. Said opening member, the position detecting device according to claim 1 in which two of said second openings sandwiching the first opening is formed, it is characterized. Wherein the detection range of the detection means is retracted to said object, said position of the image of the second opening portion obtained by the detecting means, the position detecting device according to claim 1, characterized in that. The light source position detecting device according to claim 2, wherein the first light source for illuminating an opening and a light source for illuminating the second opening, it is characterized. The reflecting member, the position detecting device according to claim 1, wherein the second is disposed in the opening a conjugate position, it is characterized. An exposure apparatus comprising the position detection device according to claim 1 , wherein an object whose alignment mark position is detected by the position detection device is exposed . A device manufacturing method comprising: exposing an object using the exposure apparatus according to claim 8 ; and developing the object exposed in the step .

Images