JP2000091219A - Position detecting device and aligner using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a position detecting device to detect an alignment mark with high accuracy by providing an objective lens containing a lens group which leads a luminous flux from a mirror that reflects and polarizes a luminous flux from a lens groups having positive refracting power, and a picture detecting element that performs photoelectric conversion on the image of the alignment mark formed through a third lens group to the detecting device. SOLUTION: A light beam IL transmitted through a second objective lens 4 is reflected by a reflecting mirror 5 and advances vertically downward toward a wafer 13. After being transmitted through a first convex lens (first lens group) 7, the light beam IL irradiates an alignment mark AM on the wafer 13 by Koehler illumination. Reflected, diffracted, and scattered light rays from the mark AM return to the first convex lens (positive lens) 7 and are led to the reflecting mirror 5 through a λ/4-plate 6. A detecting light beam ML transmitted through the λ/4-plate 6 is transformed into linearly polarized light polarized in the direction perpendicular to the plane of the figure from circularly polarized light. After being reflected by the reflecting mirror 5, the detecting light beam ML is transmitted through a second objective lens 4, led to a relay lens 10, and made to again form an image on the light receiving surface of a picture detecting element 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting apparatus and an exposure apparatus using the same, and more particularly, to a semiconductor IC, an LSI,
2. Description of the Related Art In a projection exposure apparatus for manufacturing various devices such as a CCD, a liquid crystal panel, and a magnetic head, positional information of an object such as a mask or a wafer is observed with high accuracy and stability by observing an image of the object without using a projection optical system. This is suitable for detecting an object and performing positioning of the object based on the detection information.

[0002]

2. Description of the Related Art Recent advances in semiconductor device manufacturing technology have been remarkable, and the accompanying fine processing technology has also advanced remarkably.
In particular, optical processing technology mainly uses a reduction projection exposure apparatus with a submicron resolution and a so-called stepper. To further improve the resolution, the numerical aperture (NA) of the optical system is increased and the exposure wavelength is shortened. Have been.

With the shortening of the exposure wavelength, the exposure light source has shifted from g-line and i-line high-pressure mercury lamps to KrF and ArF excimer lasers.

On the other hand, with the improvement of the resolution of a projection pattern, a wafer and a mask (reticle) in a projection exposure apparatus have been developed.
There is also a need for higher precision in alignment for relative positioning of. The projection exposure apparatus is required not only to be a high-resolution exposure apparatus but also to function as a highly accurate position detecting apparatus.

[0005] More recently, as a semiconductor manufacturing process, C
MP (Chemical Mechanical Po)
The introduction of a wafer surface flattening technique called “lancing” has been promoted. As a background of the promotion of CMP, there is a reduction in the depth of focus of an exposed image plane as the wavelength of exposure light is shortened. Further, as the integration density of the semiconductor chip itself increases, the vertical structure becomes thicker than before, and it becomes difficult to focus on the entire exposure area.
Therefore, there is an advantage that by flattening the steps on the wafer surface, it is possible to focus on all the chips on the wafer within the depth of focus.

Against this background, a system often used as a wafer alignment system includes an off-axis alignment detection system (Off-Axis AA;
A ". ).

The OA detection system is arranged at a different position from the projection exposure optical system (projection optical system), detects the position of the alignment mark on the wafer without passing through the projection exposure optical system, and based on the detection result. To align the wafer.

On the other hand, as a conventional alignment method, T
TL-AA (Through the Lens Au
There is a method of detecting an alignment mark on a wafer using light having an alignment wavelength of non-exposure light via a projection light optical system called “to alignment”.

An advantage of the TTL-AA is that the optical axis of the projection exposure optical system and the optical axis of the TTL-AA (so-called base line) can be arranged very short, so that the wafer stage is driven during alignment measurement and exposure. The amount is small. Therefore,
It is possible to reduce 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 the TTL-AA due to a change in environment around the wafer stage. That is, there is a merit that the fluctuation of the baseline is small.

However, when the exposure light is a KrF laser or Ar
When the wavelength shifts to short-wavelength light such as F laser, correction of chromatic aberration with respect to the alignment wavelength of the projection exposure optical system becomes difficult because the glass material used is limited. Therefore, an OA detection system which is not affected by the chromatic aberration of the projection exposure optical system has become important.

In the case of the OA detection system, there is also an advantage that a light source for an arbitrary wavelength or a wide wavelength range can be used because the OA detection system does not pass through a projection exposure optical system. The merit of using the broadband wavelength light is that the influence of the thin film interference on the photosensitive material (resist) applied on the wafer can be eliminated. Therefore, an OA detection system that can correct aberrations for light of a wide wavelength band can be said to be an important alignment detection system.

Here, the configuration of a conventional projection exposure optical system is as follows.
This will be described with reference to the schematic diagram shown in FIG. In FIG. 9, light 505 emitted from an exposure illumination optical system 500 including an exposure light source (a mercury lamp, a KrF excimer laser, an ArF excimer laser, or the like as a light source) illuminates a mask (reticle) 501 forming a pattern. I do. At this time, the reticle 501 is moved so that the optical axis 8a of the projection exposure optical system 8 and the center 501a of the reticle pattern coincide with each other by an alignment detection system (not shown) arranged above (or below) the reticle 501. 'Is pre-positioned.

An image is transferred by a projection exposure optical system 8 to a wafer 13 held on a wafer stage 22 at a predetermined magnification by light passing through the reticle pattern. Hereafter, irradiation light is irradiated from above the reticle, and the projection exposure optical system 8
The stepper sequentially exposes the reticle pattern on the wafer 13 at a fixed position through the step is called a stepper, and the reticle and the wafer are relatively driven (the driving amount of the reticle is multiplied by the projection magnification of the wafer driving amount). The apparatus is called a scanner (scanning exposure apparatus).

On the other hand, there is a type of wafer 13 called a second wafer in which a pattern has already been formed. When a next pattern is formed on this wafer, the position of the wafer must be detected in advance. No. As the position detection method, there are the TTL-AA method and the OA detection method described above. FIG. 9 schematically shows the OA detection system. The OA detection system 504 is arranged at a position away from the projection exposure optical system 8 by a certain distance.

At this time, the length from the optical axis 8a of the projection exposure optical system 8 to the detection center 504a of the OA detection system 504 is set to the baseline B. L. I'm calling In actual alignment detection, the wafer stage 22 is driven by the amount corresponding to the baseline, and
After moving to the detection position of the OA detection system 504, the wafer 13
The position is detected by detecting the alignment mark formed thereon.

That is, the position is detected after the wafer stage is driven to the position 22 'in the X direction in the figure. For driving the wafer stage 22, a reflection mirror 503 is provided on the wafer stage 22.
3, the position is detected by the interferometer 23.

Accordingly, the actual alignment is calculated by the arithmetic processor 20 based on the position information of the alignment mark obtained from the OA detection system 504 and the position information of the wafer stage 22 obtained from the interferometer 23.

As described above, the OA detection system has a feature that alignment detection cannot be performed unless the wafer stage is driven by the amount of the baseline.

[0019]

The use of an OA detection system as described above in a position detection device for detecting the position of a wafer is difficult because the optical axis of the projection exposure optical system is separated from the detection area of the OA detection system. Therefore, the wafer stage must be driven during alignment measurement and exposure. Therefore, changes in the environment around the wafer stage affect the alignment accuracy, such as fluctuations in the baseline.

For example, if the length of the interferometer is different, the influence of air fluctuation changes, or the position of the interferometer, not shown in FIG.
An environmental change occurs that is different between the exposure and the alignment detection. Therefore, these factors cause a difference between the wafer driving grid at the time of exposure and the wafer driving grid at the time of alignment detection, resulting in a phenomenon that the alignment accuracy is deteriorated.

Therefore, by making the baseline as short as possible and making the environment of the wafer stage the same at the time of alignment and at the time of exposure, such deterioration of alignment accuracy can be eliminated. Therefore, it is necessary to arrange the OA detection system at such a position.

FIG. 10 is a schematic diagram of one type of OA detection system conventionally used. In FIG. 10, light (waveline: IL) emitted from the illumination light source 1 passes through the illumination optical system 2 and then enters the polarization beam splitter 3. In the polarization beam splitter 3, only the S-polarized light component is reflected and travels to the detection optical system (objective lens) 4 side. A λ / 4 plate 6 is arranged below the polarization beam splitter 3, and the λ / 4 plate 6 converts the S-polarized light component into circularly polarized light.

Thereafter, the wafer 13 is moved by the objective lens 4.
The upper alignment mark AM is Koehler-illuminated. Reflection, diffraction, and scattered light (collectively, “detection light: ML”) from the alignment mark AM return to the objective lens 4 and return to λ /
By passing through the four plates 6, the light becomes linearly polarized light rotated by 90 ° with respect to the irradiation.

The detection light now passes through the polarizing beam splitter 3 and travels to the relay lens 10. Relay lens 10
Forms an image plane conjugate with the alignment mark AM of the wafer 13. This image is formed again on the image detecting element 12 by the image forming optical system 11. In this manner, the image of the alignment mark AM is detected by the image detecting element 12, and the position of the alignment mark AM can be detected from the image.

The above is the outline of the conventional OA detection system. The length of the optical axis 8a of the projection exposure optical system 8 and the optical axis OLa of the OA detection system is B.B. L. And is called the baseline. Then, how short the baseline can be made leads to an improvement in the alignment performance of the OA detection system.

By the way, the shift to the low step structure called a CMP wafer as described above also causes the step structure of the alignment mark itself of the wafer to have a low step, which leads to a decrease in the detection rate of the alignment mark.

As a method of solving this low level alignment mark detection, there is a method of increasing the NA of the OA detection system.

FIG. 11 shows a simulation of an alignment mark waveform obtained by changing the NA of an ideal lens in an alignment mark having a step structure when an ideal lens is used. FIG. 11C shows the step structure at this time.
FIG. 11A shows NA0.4, and FIG. 11B shows NA0.
2 is shown. As described above, the detected waveform is different by increasing the NA, and the clear detection of the waveform can improve the position detection accuracy of the alignment mark and the detection rate of the low step alignment mark. Connect.

As described above, the step d of the alignment mark
And the contrast of the detected waveform ((Max-Mi
FIG. 12 is a graph summarizing the relationship with n)) with NA.
Shown in

In FIG. 12, the horizontal axis indicates the step d of the alignment mark, and the vertical axis indicates the contrast with respect to the step of each alignment mark when NA 0.4 and NA 0.2. From this graph, it can be seen that increasing the NA for the same step d increases the contrast of the detected waveform. The higher the contrast, the higher the detection rate for the same step, and the higher the NA for a lower step, the easier it is to detect. That is, N of the detection system
As A is larger, a detection system that is more resistant to low steps can be achieved.

However, if the NA is to be increased and the baseline is to be shortened, a problem arises in the space in which it is arranged.

FIG. 13A is a schematic view of an arrangement for achieving a normal high NA. Here, the OA detection system 300 is arranged in parallel with the projection exposure optical system 400. By arranging in this manner, a high NA can be achieved. L. Does not shorten. In contrast, FIG.
(B), the reflection mirror 301 is arranged close to the projection exposure optical system 400, and L. Can be shortened, however, in this case, the working distance of the OA detection system 300 becomes long, and it is difficult to achieve a high NA detection system. The reason will be described in detail with reference to FIG.

FIG. 14 is a schematic view of the type shown in FIG. The illumination system and other detection systems will be omitted, and the explanation will be given in the vicinity of the wafer 13. Alignment mark AM on wafer 13
From the optical axis of the projection exposure optical system,
The light is reflected by the reflection mirror 5 and detected. Behind the mirror, an objective lens 4 composed of a convex lens 110 and a concave lens 111 is arranged.

When a high NA detection system is constructed with such a basic arrangement, the lens must have a large effective diameter in order for the convex lens 110 to capture all the effective light beams of the required NA. Therefore, the distance h between the convex lens 110 and the wafer 13 becomes very close, and the arrangement becomes difficult. For example, if d = 5 mm, NA 0.4 is h
= 1.6 mm and h = 4.5 mm at NA 0.2.

That is, in this phenomenon, the arrangement becomes severe as the NA of the OA detection system increases, and as a result
In addition, an OA detection system with a short baseline cannot be achieved. For this reason, there is a problem that it is impossible to provide a detection system capable of detecting alignment marks having a low level difference and suppressing fluctuation of a baseline.

The present invention has been made in view of the above-described problems, and it is an object of the present invention to easily achieve a high NA that shortens a baseline, suppresses a fluctuation component of the baseline as much as possible, and enables highly accurate detection of a low-level alignment mark. It is an object of the present invention to provide a position detecting device having an off-axis alignment detecting system capable of performing the above-mentioned steps and an exposure apparatus using the same.

[0037]

According to the position detecting apparatus of the present invention, (1-1) the first object and the second object are projected before the pattern on the first object is projected and exposed on the second object by the projection optical system. In a position detecting device for performing relative positioning with an object, the position detecting device includes an illumination system for illuminating an alignment mark on the second object surface, and an illumination system for illuminating an alignment mark on the second object surface without using the projection optical system. A position detection system for detecting position information of the alignment mark, the position detection system reflecting, in order from the second object side, a first lens group having a positive refractive power and a light beam from the first lens group. An objective lens including a mirror for deflecting, and a second lens group for guiding a light beam from the mirror, and an image detection element for photoelectrically converting the alignment mark image formed by the objective lens and a third lens group. It is characterized by having.

In particular, (1-1-1) position adjustment of each lens constituting the objective lens is performed using an evaluation value obtained by an image detection element for detecting position information of a mark provided on an adjustment wafer. It is characterized by having.

(1-1-2) Position adjustment of each lens constituting the objective lens can be obtained by an image detecting element for detecting position information of an adjustment mark provided on a stage on which the second object is placed. It is characterized in that evaluation is performed using evaluation values.

(1-1-3) A drive mechanism for eccentrically driving at least one of the first lens group and the second lens group, and an image detecting element for detecting position information of the adjustment mark. Calculating means for calculating the amount of eccentricity adjustment of the lens group based on the detection signal; driving the drive mechanism with a drive signal based on the amount of eccentricity adjustment;
It is characterized in that the relative position between the lens group and the second lens group is automatically adjusted.

(1-1-4) The position detecting system is the first type.
A correction optical member for correcting aberration caused by the eccentricity of the lens group and the second lens group, and based on a detection signal from an image detection element for detecting position information of the adjustment mark, the correction optical member; It is characterized by adjusting the system.

(1-1-5) The position detecting system is the first type.
A correction optical member for correcting aberration generated by eccentricity of the lens group and the second lens group, a driving mechanism for driving the correction optical member, and an image detecting element for detecting position information of the adjustment mark. Calculating means for calculating an adjustment amount of the correction optical member, based on the detection signal, and driving the drive mechanism by a drive signal based on the adjustment amount;
It is characterized in that the correction optical member is automatically driven.

The exposure apparatus of the present invention has the following structure (2-1).
-1) The position of the reticle and the wafer are aligned using the position detecting device described in any one of the above items 1), and the pattern on the reticle surface is projected and exposed on the wafer surface.

The method for manufacturing a device of the present invention comprises the steps of (3-
1) After aligning a reticle with a wafer by using the position detecting device according to any one of the constitutions (1-1), and projecting and exposing a pattern on the reticle surface onto the wafer surface, Is developed to produce a device.

[0045]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a main part of a first embodiment of the present invention. The figure mainly shows the OA detection system.
8, a projection optical system; and 9, a light beam passing through the projection optical system 8. Light IL emitted from the illumination light source 1 passes through the illumination optical system 2 and then enters the polarization beam splitter 3. The P-polarized component (parallel to the paper) is transmitted through the polarization beam splitter 3 and enters the second objective lens 4 side. still,
The polarizing beam splitter 3 is used to detect the detection light with high efficiency, and if there is no problem in the amount of light, there is no problem even if a normal half mirror is used.

The light IL transmitted through the second objective lens 4 is
The light is reflected by the reflection mirror 5 and directed downward in a direction perpendicular to the wafer 13. Below the reflection mirror 5, a λ / 4 plate 6 is arranged, and the light transmitted therethrough is converted into circularly polarized light. After that, after passing through the first convex lens (first lens group) 7, the alignment mark AM on the wafer 13 is subjected to Koehler illumination.

Each element from the illumination light source 1 to the alignment mark AM constitutes one element of the illumination system. The wafer 13 is held on a wafer stage 22 that can be driven in the X, Y, and Z directions and the rotation directions of those axes. still,
The wafer stage 22 can be driven by the drive mechanism 21 based on an instruction from the arithmetic processing unit 20. The reflected light, diffracted light, and scattered light (collectively, “detection light ML”) from the alignment mark AM are again converted into a first convex lens (positive lens).
7, the light is transmitted through the λ / 4 plate 6 and guided to the reflection mirror 5.

By arranging the first convex lens in this way,
The detection light ML enters the reflection mirror 5 with its divergence angle reduced. Therefore, the reflecting mirror 5 can be made small, and the effective diameter of the second objective lens 4 can be made small thereafter.

The detection light ML transmitted through the λ / 4 plate 6 is converted from circularly polarized light into linearly polarized light in the direction perpendicular to the paper surface (S-polarized light).
The detection light ML reflected by the reflection mirror 5 passes through the second objective lens 4, is guided to the polarization beam splitter 3, is reflected this time, and is guided to the relay lens 10. The objective lens OL includes the first convex lens 7, the λ / 4 plate 6, the reflection mirror 5, and the second objective lens 4.
Are configured so as to minimize occurrence of various aberrations.

However, regarding the aberration that cannot be completely corrected by the objective lens OL, the subsequent relay lens 10 and detection optical system 1
It may be corrected by 1. The relay lens 10 once forms an image of the alignment mark AM. Thereafter, the detection optical system 1
1 forms an image again on the light receiving surface of the image detecting element 12. Here, from the alignment mark AM, the image detecting element 1
Each element up to 2 constitutes one element of the position detection system.

The image detecting element 12 may be a two-dimensional image detecting element or a one-dimensional image detecting element. In the case of a two-dimensional image detecting element, one detecting system can be used to detect two X and Y directions on a wafer.
The direction can be detected. Therefore, in the case of a one-dimensional image detecting element, another image detecting element is required. However, since it is only necessary to arrange a detection system having the same configuration in a direction rotated by 90 °, the details thereof are omitted.

The processor 20 calculates the position of the wafer 13 based on the alignment mark signal detected by the image detecting element 12 and the position of the wafer stage 22. Based on the calculation result, the drive mechanism 21 of the wafer stage 22 is operated to position the wafer 13.

As described above, by dividing the plurality of lenses constituting the objective lens OL by the reflection mirror 5, the base line can be shortened and an OA detection system with a high NA is achieved.

The optical function of the objective lens OL will be described in detail with reference to FIG. This drawing shows the alignment mark A
Only the detection light from M is shown. The spread angle of the detection light is reduced by the first convex lens 7. afterwards,
The light passes through the λ / 4 plate 6 and enters the reflection mirror 5. Since the spread angle is reduced by the first convex lens 7, the size of the reflection mirror 5 can be reduced as much as possible. The light reflected by the reflection mirror 5 is incident on the second convex lens 401, and then passes through the concave lens 402.

The focal length of the objective lens OL is determined by the arrangement of the first convex lens 7, the second convex lens 401 and the concave lens 402, and the individual focal lengths, and is arranged to have a desired focal length. It is desirable that aberrations occurring in the entire objective lens OL be corrected by these lenses to such an extent that measurement accuracy is not affected.

The objective lens is not limited to the above-described lens configuration. In particular, the second convex lens 401 and the concave lens 402 can have various lens configurations. They are,
They are arranged so as to satisfy the optimum conditions depending on the illumination wavelength, the detection area, and the like.

Therefore, it is important to form the first convex lens 7 above the wafer 13 so as to reduce the spread angle of the detection light, and satisfy the condition. As long as it can be arranged in a plurality of lenses, a plurality of lenses may be used. That is, there is an effect of the present invention in forming a lens having a positive focal length at the position of the first convex lens 7.

As described above, in order to achieve a high NA and a shortened base line, the position detecting device of the present embodiment projects at least the folded portion composed of the first convex lens (or lens group) and the reflection mirror to the projection exposure optical system. Place it close to.

Thereafter, a second lens group is formed, and the first convex lens, the reflection mirror, and the second lens group form an objective lens. A first convex lens disposed above the wafer;
By once reducing the spread angle of the detection light, the effective diameter of the optical system thereafter can be reduced, and the spatial arrangement of the objective lens can be facilitated.

Next, a second embodiment of the present invention will be described. FIG.
FIG. 1 is a schematic diagram of a main part of an OA detection system of the present embodiment. In the present embodiment, a method for adjusting the position of the first convex lens 7 or the second objective lens 4 is described. The basic configuration is the same as FIG. The first convex lens 7 and the second convex lens 4 are decentered (displaced in the direction parallel to the optical axis), and the positions 7a, 4a
In this case, the alignment mark image detected by the image detection element 12 is distorted.

If the alignment mark image is distorted, the alignment accuracy deteriorates. As described above, when the objective lens OL is divided into a plurality of lenses by a mirror,
Eccentricity is apt to occur, so that so-called eccentric coma and other aberrations are likely to occur.

FIG. 4 schematically shows a change in the detected waveform of the alignment mark image obtained by the image detecting element 12 when the first convex lens 7 is decentered with respect to the second objective lens 4. ing. FIG. 4A shows an alignment mark having a step structure, which has a step structure extending in the measurement direction. FIG. 4B shows a detection waveform when the first convex lens 7 is decentered by 0.01 mm in the positive direction of the X-axis.

As described above, an eccentric coma is generated by the eccentricity of the first convex lens 7, and the detected alignment mark waveform is distorted. On the other hand, FIG. 4C shows a waveform when the eccentricity is 0.01 mm in the negative direction of the X axis.

As shown here, the shape of the distorted waveform changes depending on the eccentric direction. Therefore, the distortion of the waveform is evaluated by an evaluation value E = c.
Defined by -d. FIG. 5 shows the evaluation value E on the vertical axis and the amount of eccentricity of the first convex lens 7 on the horizontal axis. As shown in FIG. 5, the evaluation value E changes in proportion to the amount of eccentricity of the first convex lens 7. In other words, the position of the first convex lens 7 is adjusted for eccentricity while monitoring the evaluation value E,
It is possible to adjust to the best position. Actually, by adjusting the eccentricity to a position where the evaluation value E becomes 0, O without eccentricity is adjusted.
A detection system can be configured.

The actual configuration will be described with reference to FIG. still,
Regarding the reference numerals in this figure, the same reference numerals as those in FIG. 1 described above have the same effect, and their explanation will be omitted, and different parts will be explained.

In FIG. 3, reference numeral 31 denotes a wafer stage 2 instead of the alignment mark AM of the wafer 13 shown in FIG.
2 means an adjustment mark formed on the second mark. The adjustment mark 31 is permanently provided on the wafer stage 22, and has a pattern in which the detected waveform changes significantly when there is an aberration such as an eccentric coma of the detection system.

The mark waveform of the adjustment mark is observed by the OA detection system shown in FIG. As shown in FIG. 4, when the first convex lens 7 and the second objective lens 4 are decentered, the detected waveform has a distortion in the alignment mark waveform.

Then, based on the detected waveform, the position of the first convex lens 7 or the second objective lens 4 is relatively adjusted so that the evaluation value E becomes zero. That is, when the first convex lens 7 is adjusted, it can be fixed at an optimum position by adjusting the position to the position 7b or the position 7a.

Although the case where the adjustment is performed in the X direction is described in this drawing, the adjustment can be similarly performed by adjusting the first convex lens 7 in the Y direction with respect to the Y direction perpendicular to the paper surface. .

When the position of the first convex lens 7 cannot be adjusted, the same effect can be obtained by adjusting the eccentricity of the second objective lens 4. That is, the second objective lens 4 is moved to the position 4
The object can be achieved by adjusting from b to the position 4a.

As described above, the adjustment mark 31 on the wafer stage is detected, and the first adjustment mark 31 is used to minimize the evaluation value E obtained by the image detecting element 12 using the adjustment mark 31.
By adjusting the eccentricity of the convex lens 7 or the eccentricity of the second objective lens 4, the relative positional relationship can be adjusted, and the accuracy deterioration of the detection system due to the eccentricity can be reduced.

The above adjustment has been described using the adjustment mark 31 having a step structure, but the present invention is not limited to this. That is, with respect to the eccentricity of the first convex lens 7,
The same adjustment can be made even by using an adjustment mark whose detected waveform changes, and the object of the present invention can be achieved.

Although the adjustment mark 31 is permanently provided on the wafer stage 22, it is not limited to this. In other words, it is also possible to arrange an adjustment wafer instead of a normal wafer in a state where adjustment is necessary (such as at the beginning of assembly), and to perform adjustment using a mark provided on the adjustment wafer.

As described above, in the present embodiment, the error factor caused by the eccentricity between the first convex lens group and the second lens group is adjusted to a state without eccentricity using the adjustment mark. The generated error can be minimized.
With the above configuration and adjustment method, highly accurate wafer position detection is performed.

Next, a third embodiment of the present invention will be described. The eccentricity adjustment of the OA detection system shown in the second embodiment is
It is assumed that the state at the time of assembly is always maintained. In other words, having an adjustment mechanism in consideration of the actual detection system may mean that the adjustment mechanism may change over time.

The present embodiment is directed to a detection system considering such a change with time. FIG. 6 is a schematic view of a main part of a third embodiment of the present invention. The basic configuration is the second embodiment.
The configuration is almost the same as that described above, and different points will be described. This embodiment is characterized in that the first convex lens 7 can be automatically adjusted.

The adjustment mark 31 described in the second embodiment is formed on the wafer stage 22. The first convex lens 7 is attached to the drive system 30 and is configured to be driven by receiving a drive signal. In this embodiment, an adjusting mechanism is added to the first convex lens 7, but the present invention is not limited to this.

That is, there is no problem even if a mechanism for driving the second objective lens 4 relative to the first convex lens 7 is added. Factors that determine these factors include the sensitivity of each lens to eccentricity and the spatial constraints of the drive mechanism.
Adjust the place that can be placed in consideration of these factors.

In the automatic adjustment sequence, the adjustment mark 31 on the wafer stage 22 is observed by the OA detection system according to the convenience of the operation of the apparatus (at the judgment of the apparatus operator or at a regular timing). After that, the evaluation value E is calculated from the detection waveform obtained by the OA detection system. The sign of the evaluation value E and the amount of adjustment of each lens (7 or 4) with respect to the amount of generation thereof are obtained in advance, and therefore the amount of adjustment is determined by the evaluation value E.

Actually, the evaluation value E is calculated by the arithmetic processing unit 20, and the eccentricity adjustment amount is calculated based on the calculation result.
A drive signal is sent to the adjustment drive mechanism 30 based on the adjustment amount, and the drive mechanism 30 adjusts the position of the lens 7 based on the signal.

After the adjustment, the image signal is fetched again by the image detecting element 12, and it is confirmed that there is no problem in the waveform.
Although the adjustment sequence of the closed loop has been described above, the adjustment sequence is not limited to this as long as the adjustment can be performed in the open loop.

As described above, even if eccentricity occurs with the passage of time due to the automatic adjustment, the eccentricity can be automatically adjusted on the apparatus, so that the occurrence of an alignment error due to the eccentricity can be suppressed.

Next, a fourth embodiment of the present invention will be described. Regarding the reflection mirror 5 shown in the first embodiment, the case where the reflection mirror 5 is arranged in a direction rotated by 45 ° about the Y axis has been described.

In the present embodiment, since the angle of the reflection mirror 5 may be arbitrary, a case where the angle has an angle other than 45 degrees will be described.

FIG. 7 is a schematic view of a main part of a fourth embodiment of the present invention. The basic configuration of the OA detection system is the same as that shown in FIG. 1, and only different points will be described. The difference is that the reflection mirror 5 sets the angle θ of the reflection surface to 4 with respect to the Y axis.
5 mm or more. By arranging like this,
Since the OA detection system can be arranged close to the projection optical system 8, the space for the device can be reduced.

In FIG. 7, the angle θ is expressed as a large value.
Another effect is expected. That is, even if the angle θ is inclined by several degrees, the value of the height h shown in FIG. 2 can be further increased, and therefore, there is an effect that the interference between the wafer surface 13 and the objective lens barrel can be further reduced.

Next, a fifth embodiment of the present invention will be described. In the third embodiment described above, an example in which aberration such as eccentric coma due to eccentricity in the objective lens group is corrected by eccentricity adjustment of the first lens group (first convex lens 7) and the second lens group. However, this aberration correction means is not limited to the eccentricity of these lenses.

In the fifth embodiment, a correction method other than the decentering of the first lens group and the second lens group will be described.

FIG. 8 is a schematic view of a main part of a fifth embodiment of the present invention. In the present embodiment, as a means for correcting aberration such as eccentric coma in the detection optical system, the parallel plate 24 is arranged at a position other than the image plane and the pupil plane (Fourier transform plane of the image plane). ing.

In FIG. 8, the parallel plate 24 is connected to the relay lens 1.
The eccentric coma component is corrected by tilting the parallel plate 24 with respect to the optical axis.

As described in the first embodiment, the alignment mark AM on the wafer is illuminated by the illumination optical system, and the detection light ML from the alignment mark AM is applied to the objective lens OL.
The light is guided to the relay lens 10 by the mirror 3. Behind the relay lens 10, a parallel plate 24 is arranged, and the parallel plate 24 is held by a driving member (not shown). The parallel plate 24 can be inclined with respect to the optical axis of the detection light ML by a driving member.

For example, assume that an eccentric coma has occurred in the X direction in FIG. In this case, by rotating the parallel plate 24 around the Y axis as the rotation axis, the eccentric coma generated in the X direction can be corrected. Since the amount of inclination differs depending on the amount of generated eccentric coma, the arrangement position of the parallel plate 24, and the like, the optimum angle is calculated by calculating the evaluation value E.

The method of calculating and detecting the evaluation value E is the same as that described in the second embodiment, and thus the detailed description is omitted.

The eccentricity adjustment may be performed so as to be optimal at the time of assembling the apparatus, or may be automatically performed on the apparatus using the adjustment marks in the same manner as described in the third embodiment. Is also good.

In the case of automatic correction, an adjustment mark 31 is arranged on the observation surface of the detection system instead of the alignment mark AM, and the waveform is captured by the image detection element 12.
The arithmetic processing unit 20 calculates the evaluation value E from the captured waveform and obtains the optimum tilt amount of the parallel plate 24. A command corresponding to the tilt amount is sent to the parallel plate adjusting drive mechanism 32 to drive the parallel plate 24.

As described above, the position detection system can always be set to the optimum state on the main body. In order to correct the eccentric coma in the X and Y directions by the parallel plate 24, it is necessary to incline the Y axis and the X axis as rotation axes. Therefore,
Thus, it is desirable to configure a driving member that can rotate the parallel plate 24 in two directions.

However, the provision of such a mechanism for rotating about two axes may complicate the driving mechanism. In such a case, the parallel plate 24 is arranged in two places (not shown in FIG. 8), one of which has a mechanism for tilting around the X axis and the other has a mechanism for tilting around the Y axis. Thus, complication of the driving member can be reduced, and the effect of the present embodiment can be exhibited.

In the above embodiment, the parallel plate 24 as a correction optical member is disposed behind the relay lens 10 and is inclined with respect to the optical axis of the detection light, so that the first lens group 7 and the second lens group 4 Although the case of reducing the eccentric coma caused by the eccentricity has been described, the present invention is not limited to this.

In other words, the correction optical member may be arranged at any place, and the correction optical system is made to have an optimum shape according to the arrangement position, and the position adjustment, angle adjustment and rotation adjustment of the correction optical system are performed. It suffices if it has a configuration capable of correcting the aberration generated by the eccentricity of the lens group and the second lens group, and can adjust these correction optical systems based on the evaluation value E.

Next, an embodiment of a method of manufacturing a semiconductor device using the above-described projection exposure apparatus will be described.

FIG. 15 shows a flow of manufacturing a semiconductor device (a semiconductor chip such as an IC or an LSI, or a liquid crystal panel or a CCD).

In step 1 (circuit design), a circuit of a semiconductor device is designed. Step 2 is a process for making a mask on the basis of the circuit pattern design.

On the other hand, in step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4
The (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 called a post-process, and is a process of forming a semiconductor chip using the wafer produced in step 4, and includes an assembly process (dicing and bonding) and a packaging process (chip encapsulation). And the like.

In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 16 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface.

In step 13 (electrode formation), electrodes are formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 15
In (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the above-described exposure apparatus to print and expose the circuit pattern of the mask onto the wafer.

In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist are removed. In step 19 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the manufacturing method of this embodiment, it is possible to easily manufacture a highly integrated semiconductor device which has been conventionally difficult to manufacture.

[0110]

According to the present invention, by setting each element as described above, the baseline can be shortened, the fluctuation component of the baseline can be suppressed as much as possible, and the alignment mark with a low step can be detected with high accuracy. , A position detecting device having an off-axis alignment detecting system capable of easily achieving a high NA, and an exposure apparatus using the same.

In particular, according to the present invention, a part of the objective lens is formed as a convex lens, and the divergence angle of the detection light is reduced by the convex lens, whereby the objective lens can be made compact and the baseline can be shortened. A stable position detection system for the baseline can be created. Further, by increasing the NA, it is possible to increase the detection rate of alignment marks having a low step, and to provide a highly accurate alignment detection system. In addition, since the adjustment of the objective lens or the correction optical system is performed using the adjustment marks, it is possible to eliminate factors that cause deterioration of alignment accuracy such as eccentric coma.

With the above configuration and adjustment method, a highly accurate position detection system can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a main part of a first embodiment of the present invention.

FIG. 2 is an explanatory view of a part of FIG.

FIG. 3 is a schematic diagram of a main part of a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of a detection waveform obtained by the image detection element according to the second embodiment of the present invention

FIG. 5 is an explanatory diagram of an eccentric amount and an evaluation value according to a second embodiment of the present invention.

FIG. 6 is a schematic diagram of a main part of a third embodiment of the present invention.

FIG. 7 is a schematic diagram of a main part of a fourth embodiment of the present invention.

FIG. 8 is a schematic diagram of a main part of a fifth embodiment of the present invention.

FIG. 9 is a schematic view of a main part of a conventional projection exposure apparatus.

FIG. 10 is a schematic diagram of a position detection device in a conventional projection exposure apparatus.

FIG. 11 is an explanatory diagram of a detection signal obtained by a position detection device in a conventional projection exposure apparatus.

FIG. 12 is an explanatory diagram of a detection signal obtained by a position detection device in a conventional projection exposure apparatus.

FIG. 13 is an explanatory diagram of a position detection device in a conventional projection exposure apparatus.

FIG. 14 is an explanatory diagram of a position detection device in a conventional projection exposure apparatus.

FIG. 15 is a flowchart of a device manufacturing method according to the present invention.

FIG. 16 is a flowchart of a device manufacturing method according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 illumination light source 2 illumination optical system 3 polarizing beam splitter 4 second lens group 5 reflection mirror 6 λ / 4 plate 7 first convex lens 8 projection exposure optical system barrel 9 projection exposure light beam 10 relay lens 11 detection optical system 12 image detection element DESCRIPTION OF SYMBOLS 13 Wafer 20 Arithmetic processor 21 Drive mechanism 22 Wafer stage 23 Interferometer 24 Parallel plate 30 Lens adjustment drive mechanism 31 Adjustment mark 32 Parallel plate adjustment drive mechanism 110 Convex lens 111 Concave lens 300 Off-axis detection system 301 Reflective mirror 401 Convex lens 402 Concave lens 500 Exposure light source 501 Reticle (mask) 502 Reticle holding member 503 Reflecting mirror 504 OA detection system 505 Exposure light

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA03 AA20 BB02 BB27 CC18 CC19 CC20 EE08 FF01 FF04 HH10 JJ02 JJ03 JJ19 JJ25 JJ26 LL36 LL37 NN20 PP12 5F046 BA04 BA05 CA04 CC01 CC16 EB01 FB11 FB02 FB03 FB04

Claims (8)

[Claims] 1. A position detecting device for performing relative positioning between a first object and a second object before projecting and exposing a pattern on the first object onto a second object by a projection optical system. The detection device has an illumination system that illuminates the alignment mark on the second object surface, and a position detection system that detects position information of the alignment mark on the second object surface without passing through the projection optical system, The position detection system includes, in order from the second object side, a first lens group having a positive refractive power, a mirror for reflecting and deflecting a light beam from the first lens group, and a second lens for guiding the light beam from the mirror. A position detecting device comprising: an objective lens including a group; and an image detecting element that photoelectrically converts the alignment mark image formed by light passing through the objective lens. 2. The method according to claim 1, wherein the position of each lens constituting the objective lens is adjusted using an evaluation value obtained by an image detecting element for detecting position information of a mark provided on an adjustment wafer. The position detecting device according to claim 1. 3. The position adjustment of each lens constituting the objective lens using an evaluation value obtained by an image detecting element for detecting position information of an adjustment mark provided on a stage on which the second object is placed. 2. The position detection device according to claim 1, wherein the position detection is performed. 4. A driving mechanism for eccentrically driving at least one of the first lens group and the second lens group, and a detection signal from an image detection element for detecting position information of the adjustment mark. Calculating means for calculating an eccentricity adjustment amount of the lens group, driving the drive mechanism with a drive signal based on the eccentricity adjustment amount, and automatically adjusting a relative position between the first lens group and the second lens group. The position detecting device according to claim 3, wherein: 5. An image for detecting position information of the adjustment mark, wherein the position detection system has a correction optical member for correcting an aberration generated by eccentricity of the first lens group and the second lens group. The position detecting device according to claim 3, wherein the correction optical system is adjusted based on a detection signal from a detection element. 6. A correction optical member for correcting an aberration generated by eccentricity of the first lens group and the second lens group, a driving mechanism for driving the correction optical member, Calculating means for calculating an adjustment amount of the correction optical member based on a detection signal from an image detection element for detecting position information of the adjustment mark, and the drive mechanism is controlled by a drive signal based on the adjustment amount. 6. A position detecting device comprising the position detecting device according to claim 5, wherein the position detecting device is driven to automatically drive the correction optical member. 7. A reticle and a wafer are aligned using the position detecting device according to claim 1, and a pattern on the reticle surface is projected and exposed on the wafer surface. Exposure apparatus characterized by the above-mentioned. 8. After aligning a reticle with a wafer using the position detecting device according to claim 1, after projecting a pattern on the reticle surface onto the wafer surface, A device manufacturing method, wherein the device is manufactured by developing the wafer.