JP3013463B2 - Focus position detecting device and projection exposure device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus position detecting apparatus suitable for use in a so-called auto focus mechanism for automatically correcting a focus between a mask pattern and a wafer in a semiconductor projection exposure apparatus, and a focus position detecting apparatus suitable for the same. A projection exposure apparatus incorporating such a focus position detection device.

[0002]

2. Description of the Related Art A projection exposure technique in which a mask pattern and a stage are arranged with a projection optical system interposed therebetween, and the mask pattern is transferred to a sample on the stage using exposure light such as ultraviolet light,
It has been put to practical use in various precision processing fields such as the manufacture of semiconductor devices, and a wide variety of projection exposure apparatuses according to the respective applications in each field have been sold. In these projection exposure apparatuses, under the actual exposure light, the exposure surface of the sample is made to coincide with the conjugate position (height) of the mask pattern with respect to the projection optical system, that is, the mask pattern is focused on the exposure surface. This is a critical requirement. Therefore, a projection exposure apparatus for ordinary production purposes is equipped with a so-called auto-focus mechanism for automatically performing this focusing so as to achieve both the efficiency and reliability of projection exposure.

As such a focusing mechanism, for example, as shown in Japanese Patent Application Laid-Open No. 57-212406, a special mark formed on a mask pattern surface is directly projected onto an exposure surface of a sample. Although there has been reported a method of detecting a projected image via a projection optical system and a mark to directly determine a focal point, generally, a mask pattern on a reference surface provided on a stage is generally used. Combining means for directly detecting the focal point of the surface using exposure light, and means for measuring the stage-side height under the projection optical system, the origin of which is adjusted to the focal point height using the means, A method is employed in which the height of the exposure surface is indirectly detected using a measuring unit and the height is adjusted to the focal point height. As means for using the exposure light, for example, Japanese Patent Application Laid-Open No. 1-286418 discloses a method of projecting a special mark formed on a mask pattern surface onto a reference surface. In this method, a projected image of a mark formed on a reference plane is observed through a projection optical system and a mark, and a light amount peak of the projected image narrowed by the mark is detected to focus on the image. Is determined. As an example of the stage-side height measuring means, for example, Japanese Patent Laid-Open No. 41962/1994 discloses an exposure surface directly below the projection optical system using an optical system obliquely fixed outside the projection optical system. A method for measuring the height of the object is shown.

[0004]

At present, in the case of a semiconductor memory device having a particularly high processing accuracy, projection with a depth of focus of about 1 .mu.m is performed using an i-line having a wavelength of 365 nm, and even when the focusing accuracy is usually determined. In a special projection exposure utilizing an interference phenomenon of exposure light disclosed in Japanese Patent Publication No. Sho 62-50811, an extremely high precision of 0.05 μm or less is required. In order to satisfy such a high accuracy, the slight deflection and inclination of the mask itself can no longer be ignored, and the focal point of the mark provided at one corner of the mask pattern is detected to determine the focal point of the entire mask pattern. However, the conventional method cannot cope with such a problem, and it is required to adjust each portion of the exposure region on the sample side to the in-focus height with respect to each portion in the transfer region of the mask pattern. I have. Therefore, a method has been conceived in which the in-focus height is individually obtained at each portion in the transfer area of the mask pattern, and variations in the height are absorbed to the maximum by inclining the stage.

In this method, naturally, the focus height is individually obtained for each part of the actual mask pattern immediately before the exposure transfer, but this is done by directly using the conventional exposure light. It cannot be implemented by the detection method. For example, in order to carry out the method described in Japanese Patent Application Laid-Open No. 1-286418, it is necessary to arrange in-focus detection marks at respective portions in the transfer area of the mask pattern. This is unrealistic because it adversely affects the degree of integration of the mask pattern.

In the methods disclosed in JP-A-57-212406 and JP-A-1-286418, the light information from the projected image on the exposure surface is partially reflected on the optical path of the exposure light to the detector. Therefore, the reflected light of the exposure light in the optical path portion, for example, the exposure light reflected on each lens surface of the projection optical system, the back side of the mask pattern, and both sides of the mask returns to the detector as it is, In the detector, it is necessary to detect a peak of light information from the projected image by subtracting a huge background due to the reflected light of the exposure light. Therefore, the area of the mark occupying the illumination field (mask pattern) of the exposure light is small, the light shielding area occupying the mask pattern is large (the amount of reflection on the back side of the mask pattern is large), and the output of the light source fluctuates. In the case where the intensity of the exposure light changes every moment, peak detection becomes difficult, and there is a possibility that the in-focus point determination may not function normally.

[0007]

SUMMARY OF THE INVENTION According to the present invention, it is easy to individually determine the in-focus height for each part of an actual mask pattern immediately before exposure transfer, and a special mark is arranged in a transfer area of the mask pattern. It is an object of the present invention to provide a focus position detecting device and a projection exposure device that can reliably determine a focal point even when a light-shielding area occupying a mask pattern is large or an exposure light intensity changes every moment. And

According to a first aspect of the present invention, there is provided a focal position detecting apparatus for detecting a stage side conjugate position of a mask pattern surface with respect to a projection optical system. A reference surface on the formed stage, illumination means for guiding illumination light to the aperture pattern, and a projected image of the aperture pattern formed on the mask pattern surface by the projection optical system under the illumination light Detecting means for detecting the reflected light through the projection optical system and the aperture pattern again, and detecting a change in the amount of light of the projected image passing through the aperture pattern.

According to a second aspect of the present invention, there is provided the focal position detecting device according to the first aspect, wherein the focal amount detecting device is configured to reach a position at which a maximum or minimum of the light quantity change is obtained based on an output of the detecting means. A position adjusting means for moving the stage, and a measuring means for measuring a direction of a positional shift at an arbitrary position on the stage with reference to the position of the reference plane at the position.

According to a third aspect of the present invention, there is provided a focus position detecting apparatus according to the second aspect.
A scanning mechanism for scanning an arbitrary position on the projection surface under the field of view of the projection optical system, and a measuring device for measuring a position on the stage side with respect to the projection optical system with an optical path fixed to the projection optical system. Means.

According to a fourth aspect of the present invention, there is provided a focal position detecting device comprising:
4. The focus position detecting device according to claim 1, wherein the aperture pattern is formed in a plurality of parallel lines or a checkerboard pattern obliquely arranged with respect to a mask pattern. A projection exposure apparatus according to a fifth aspect of the present invention is a projection exposure apparatus that illuminates a mask with an exposure illumination system and transfers a mask pattern of the mask onto a sample by a projection optical system. The focus position detecting device of the item is provided. A projection exposure apparatus according to claim 6 of the present invention illuminates a mask with an exposure illumination system, and detects a focal point of the mask in a projection exposure apparatus that transfers a mask pattern of the mask onto a sample by a projection optical system. Means for detecting the inclination of the mask with respect to the projection optical system, leveling means for controlling the inclination of the sample, and an output from the detecting means,
And control means for controlling the leveling means so as to position the sample on the conjugate plane of the mask. In a projection exposure apparatus according to a seventh aspect of the present invention, in the projection exposure apparatus according to the sixth aspect, the means for detecting the inclination includes:
A reference surface on a stage on which an opening pattern having a predetermined shape is formed, an illuminating unit for guiding illumination light to the opening pattern, and a projection image of the opening pattern formed on the mask pattern surface by the projection optical system using the illumination light. Detecting means for detecting the reflected light via the projection optical system and the aperture pattern and detecting a change in the amount of light of the projected image of the aperture pattern. The projection exposure apparatus according to claim 8 of the present invention is provided on the stage in a projection exposure apparatus that illuminates a mask by an exposure illumination system and transfers a mask pattern of the mask to a sample on a stage by a projection optical system. A reference plane, and focus detection means for detecting a focal point between the mask pattern and the reference plane with respect to the projection optical system,
The stage is configured to be able to move an arbitrary position on the stage to a position immediately below the projection optical system, and the reference surface is such that the reference surface is directly below the projection optical system when the sample is exchanged. It is installed so that it becomes a position. According to a ninth aspect of the present invention, there is provided the projection exposure apparatus according to the eighth aspect.
5. The projection exposure apparatus according to claim 1, wherein the focus detecting unit includes a reference surface on a stage on which an opening pattern having a predetermined shape is formed, an illuminating unit for guiding illumination light to the opening pattern, and the mask using a projection optical system using the illumination light. Detecting means for detecting reflected light of the projected image of the opening pattern formed on the pattern surface via the projection optical system and the opening pattern, and detecting a change in the amount of light of the projected image of the opening pattern. .

[0012]

According to the first aspect of the present invention, there is provided a focus position detecting device comprising:
The aperture pattern formed on the reference surface on the stage is projected on the mask pattern surface via the projection optical system in the direction opposite to the exposure light, and the reflected image of the projected image from the mask pattern surface is again reflected. The in-focus position is determined by detecting the change in the amount of light passing through the pattern. In other words, the mask pattern surface is regarded as the projection surface, and a projection image of the aperture pattern is formed by the projection optical system. Blurring of the projection image is minimized and light information from the projection image is maximized by the aperture pattern. Find the position (height) of the reference plane that can be captured by At this time, if the mask pattern surface is not illuminated by the exposure light by closing the shutter of the exposure light source or the like so that the exposure light does not directly enter the aperture pattern, the background of the light amount change detection is obtained. Is small and convenient. Also, the opening pattern
As the illumination light guided to the opening, the exposure light may be branched from the exposure light source and guided to the aperture pattern, or a dedicated light source having substantially the same output wavelength as the exposure light may be provided.

Here, as a means for guiding the illumination light to the aperture pattern, a combination of mirrors or a bundle of glass fibers can be employed, but the light information from the projected image is a part of the optical path of the illumination light. Unnecessary reflected light of the illumination light in this part also reaches the detection means and becomes the background when detecting the light amount change,
An obstacle to detection of a change in the light quantity of the projected image. However, the degree of the obstruction is much smaller than the conventional case where the entire mask pattern surface is exposed to the exposure light, because the illumination area is smaller. Therefore, in order to more reliably detect the change in the light amount of the projected image, the reflection ratio of the illumination light in the portion is reduced by devising the surface treatment of the optical element and the arrangement of the optical path.
It is convenient to take measures such as preventing reflection of the illumination light from reaching the detection means. If these measures are combined, the background of detection can be kept small even if the area of the aperture pattern is small, and peak detection with sufficiently high reliability can be performed.

On the other hand, the stage has a mechanism capable of moving an arbitrary position on the stage directly below the projection optical system, and scans the stage within the field of view of the projection optical system to form a mask pattern. The projected image of the aperture pattern can be moved to an arbitrary position above. Thus, the position (height) of the focal point can be detected at a number of places on the mask pattern, and the position and orientation of the exposure surface of the sample which is most convenient for the entire mask pattern can be known.

According to a second aspect of the present invention, there is provided a focus position detecting apparatus in addition to a means for directly determining a conjugate plane of a mask pattern with respect to a projection optical system using illumination light on a reference plane on a stage. Means for measuring the exposure surface position (height) corrected for the origin by the means. The position adjusting means adjusts the scale of the measuring means on the reference plane guided to the conjugate plane of the mask pattern (origin adjustment). ), And the direction of displacement (positive or negative) compared with the origin is determined at an arbitrary position on the stage by the measuring means.

According to a third aspect of the present invention, there is provided a focus position detecting device, comprising a combination of an optical measuring instrument fixed to a projection optical system and a stage scanning mechanism. Is determined. The optical measuring device is composed of, for example, a combination of a projector and a photosensor array in which an optical path is arranged by defining a reflection point substantially at the center of the field of view of the projection optical system. Measure the position (height) immediately below.

According to a fourth aspect of the present invention, there is provided a focus position detecting apparatus comprising:
In the mask pattern plane described so far as a uniform projection plane, consideration is given to the possibility that the mask pattern interacts with the projected image of the aperture pattern and hinders detection of the maximum or minimum change in the amount of light. That is, since the local reflectance of the mask pattern surface differs depending on the presence / absence of the mask pattern, when the projected image of the aperture pattern exactly overlaps the mask pattern, the position where the maximum or minimum change in the amount of light is obtained is not necessarily the focal point. Will not always be. Therefore, it is necessary to select the shape of the aperture pattern so that the reflected light of the projected image does not exactly overlap the mask pattern. Since a mask pattern of a semiconductor integrated circuit is usually composed of a large number of vertical and horizontal parallel lines and a small number of diagonal lines at a specific angle, a plurality of parallel linear shapes that are not parallel to any of the lines as the opening pattern shape It is convenient to do. Here, the reason for selecting the shape of the parallel line is that the change in the amount of light due to the focal point is steep. Further, the parallel lines are made orthogonal to each other in order to avoid the influence of astigmatism of the projection optical system. A similar effect can be obtained by using a checkered lattice. The projection exposure apparatus of claim 5 of the present invention
Similar to the focus position detecting device of the first aspect, the projection image of the aperture pattern is formed by the projection optical system by regarding the mask pattern surface as the projection surface, and the blur of the projection image is minimized, and the projection image is shifted from the projection image by the aperture pattern. The position of the reference plane from which optical information can be captured to the maximum is determined, and the position and orientation of the most convenient exposure plane of the sample are determined. The projection exposure apparatus according to claim 6, wherein the sample is placed on a conjugate plane of the mask based on an output from a unit that detects a tilt of the mask with respect to the projection optical system by detecting a focal point of the mask. By controlling the leveling means so as to position the sample, the tilt of the sample is set in consideration of the tilt with the mask.
A projection exposure apparatus according to a seventh aspect of the present invention, like the focus position detection apparatus according to the first aspect, has a reference plane on which the blur of the projected image is minimized and the optical information from the projected image can be maximally captured by the aperture pattern. The posture of the sample is set by obtaining the position of. A projection exposure apparatus according to claim 8 of the present invention further includes a focus detection unit that detects a focal point between the mask pattern and the reference plane with respect to the projection optical system, wherein the reference plane is used when the wafer (sample) is replaced. In (2), the reference plane is located at a position immediately below the projection optical system, so that the position and orientation of the exposure surface of the wafer that is convenient for exposure are determined in parallel with the replacement of the wafer. According to the projection exposure apparatus of the ninth aspect of the present invention, similar to the focus position detecting apparatus of the first aspect, the reference plane on which the blur of the projected image is minimized and the optical information from the projected image can be captured to the maximum by the aperture pattern. Is obtained, and the most convenient position and orientation of the exposure surface of the wafer are obtained.

[0018]

An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view of an automatic focusing apparatus according to an embodiment of the present invention. This is an automatic focusing device mounted on a projection exposure apparatus for a semiconductor integrated circuit. Prior to projection exposure, the height of a conjugate plane is detected over the entire mask pattern and mounted on an XY stage. The height and inclination of the exposure surface on the placed wafer are adjusted so that the exposure surface coincides with the conjugate surface.

In FIG. 1, a mask 3 having a mask pattern on its lower surface is opposed to a stage 12 via a projection lens 2 and is illuminated by an exposure illumination system 4 during projection exposure. The stage 12 on which the wafer 11 is mounted can be moved to any position on the stage 12 directly below the projection optical system 2 by the XY drive system 15, and can be moved by the Zθ drive system 9.
The entire jig 12 can be adjusted to any height and inclination. On the stage 12, there is provided a fiducial surface 1 on which a predetermined opening pattern 1a is formed, and the opening pattern 1a includes an illumination light source 8, a glass fiber cable 13 and the like. The optical system is connected to a detection optical system including a glass fiber cable 13, a light amount detector 7, a half mirror 14, and the like. Incident focus sensors 5 and 6 for detecting a wafer surface are fixed to the projection optical system 2. Outputs of the sensor 6 and the detector 7 are input to a control system 10, and the drive system 9 is controlled by the control system 10.

In the automatic focusing apparatus thus configured, the illumination light output from the illumination light source 8 is transmitted through the cable 1.
3, the light is guided to the opening pattern 1a through the projection optical system 2, and is projected upward. A projection image of the opening pattern 1a is formed on the mask pattern surface via the projection optical system 2. The projected image is displayed on the drive system 15.
By scanning the fiducial surface 1 within the range of the field of view of the projection optical system 2 by using the above, it is possible to move to any place on the mask pattern, and it is possible to determine the focal point individually at each place. .

The optical information from the projected image on the mask pattern surface forms an image on the conjugate plane of the mask pattern with respect to the projection optical system 2 by going back the optical path of the illumination light. At this time, if the height of the reference surface is in a conjugate positional relationship with respect to the mask pattern surface and the projection optical system 2, the projected image of the mask pattern surface becomes a clear one at the focused boundary, and the reflection of the projected image The second projected image of the light on the reference plane will also have a clear in-focus boundary. Here, the second projected image is
Naturally, since the aperture pattern 1a has the same shape, the same dimensions, and the same posture, the optical information from the projected image of the mask pattern surface is maximally incident on the aperture pattern 1a and proceeds through the detection optical system. The light reaches the detector 7 to give a peak of the amount of received light. on the other hand,
When the height of the reference plane is shifted from the conjugate plane of the mask pattern plane, the projected image of the mask pattern plane and the second projected image on the reference plane are out of focus and the boundary is blurred.
Therefore, the optical information is impaired by the amount of the second projected image that is protruded from the aperture pattern 1a and is incident on the aperture pattern, and the amount of received light reaching the detector 7 is reduced.

Accordingly, the stage 12 is moved by the drive system 15 to sequentially position the projection images at a plurality of locations defined on the mask pattern surface, and the control system 10 is located at each location.
The drive system 9 adjusts the height of the stage to a height at which the detector 7 detects a change in the amount of light, and accumulates the height information one after another. The optimum inclination angle of the stage is calculated from the height distribution information thus obtained, and the inclination of the stage 12 is corrected by the drive system 9 to this angle.

On the other hand, after the inclination is adjusted, the projected image is moved to the center of the mask pattern again, and the stage height is again adjusted by the drive system 9 until the fiducial surface 1 is at the focal point. Adjust the length. Thereafter, the origin adjustment of the incident focus sensors 5 and 6 is performed using the fiducial surface 1 adjusted to the focal point height. That is, the height of the reflected beam spot on the fiducial surface 1 is stored as the origin, and thereafter, when the field of view of the projection optical system is scanned at an arbitrary position on the stage, the incident light focus sensor is used. The height of the exposed surface of the sample is measured based on the height of the reflected beam spot at 5 and 6, and the control system 10 adjusts the stage height by the control system 9 so that the height becomes the height of the origin.

Next, detection of the focal plane in the present embodiment in various cases will be described in more detail.

FIG. 2 is a diagram of the detected light amount above and below the focal plane. In FIG. 1, the light emitted from the aperture pattern 1a is re-imaged and passed again through the aperture pattern 1a. 9 shows a relationship between focal positions. In this embodiment, the detection peak / background ratio can be made close to 50% by using a special light guide means described later, and more reliable detection can be performed.

[0027] In FIG. 2, the horizontal axis is stearyl - at the level of di-12, the closer the focus height Z ₀ to the projection optical system 2 in the center Z _-, farthest to the Z _+. The vertical axis is the detected light amount. Stearyl - but when the vertically di 12 amount is the height of the maximum, which is the focus height Z _0. To find this, the stage 12 is moved up and down along the optical axis of the projection optical system 2 based on the signals from the incident focus sensors 5 and 6. At the same time, if the light amount of the detector 7 is monitored, the diagram of FIG. 2 can be obtained. O Based on this - Tofo - the control unit 10 of the dregs to calculate the focus height Z _0, morphism incident follower hereinafter - keep the detected position of Kasusensa 5,6 it is matched therewith. When the stage 12 is moved by the XY drive system 15 and the wafer 11 is moved below the projection optical system 2, the incident focus sensors 5 and 6 apply the wafer to the focal plane of the projection optical system 2. 11 can be located. By the way, it is better for the signal as shown in FIG. 2 to have as large a slope as possible. For that purpose, the pattern of the opening pattern 1a projected on the fiducial plate 1 needs to have an appropriate line width. For example, consider a line and space as shown in FIG. 3 as the projection pattern. The pattern portion of the fiducial plate 1 is 1a, the pitch is P, the width of the opening is a, and the duty ratio (a / p) is 50%.
Then, the change of the detection light with respect to the focus position in FIG. 2 is approximately as follows.

| Z ₀ −Z ₋ | = | Z ₊ −Z ₀ | = a / 2 tan θ (1)

Here, θ is the angle of inclination of the light beam, and is an estimate when diffraction is ignored. For example, NA = 0.5, σ =
0.5, a = 2 μm, θ = 14.5 degrees, and |
Z ₀ −Z ₋ | is 3.9 μm.

In the case of a transparent mask 3 having no mask pattern, the glass surface on the lower surface of the mask 3 is a reflection surface, and its reflectance is about 4%. However, since the background is small, the detection sensitivity is low. Can be sufficiently detected by raising. In a normal case where there is a mask pattern, a reflectance of 10 to 70% of the chrome surface is secured, and the detection is sufficiently possible. Even if the chrome surface is coated with a low-reflection AR coating, there is no problem because it has a reflectance of several percent.

By the way, there is a step at the boundary between the chrome pattern and the glass surface, and there are two stages of the conjugate plane of the mask pattern surface. However, since the thickness of the chrome pattern is 100 nm or less, the projection optical When the system 2 has a reduction magnification, there is no practical problem. For example, if the chrome pattern thickness is 1
If the reduction projection magnification is 00 nm and the reduction projection magnification is 1/5, the error of the conjugate plane due to the step of chrome is 8 nm, which is a negligible level.

Next, Japanese Patent Publication No. Sho 62 by the same applicant as the present application.
Consider a case where a so-called phase shift film disclosed in Japanese Patent Publication No. 50811 is formed. The thickness of the phase shift film is d = λ / 2 (n−1), where n: refractive index,
λ: wavelength, and the reflected light on the surface of the phase shift film is twice the thickness of the phase shift film, ie, 2d
= Λ / (n−1), the optical path length is shorter than the reflected light on the glass surface of the mask. However, since n is selected to be about 1.5, this value is 2λ (an integer multiple of the wavelength), and the reflected light is apparently the same as when there is no phase shift film, and the influence is small.

As described above, since the mask pattern surface can be regarded as a normal reflecting surface in any case, highly accurate detection is possible.

Incidentally, in order to further reduce the influence of the chrome pattern of the mask 3 and to eliminate the influence of astigmatism when detecting the focal point around the visual field of the projection optical system 2, FIG. The projection pattern (the shape of the opening pattern 1a) shown in FIG. FIG. 4A shows a combination of vertical, horizontal and oblique patterns, and FIG. 4B shows a checker-flag (checkered) pattern.
These are on the fiducial surface 1 and each side is 100 μm to 100 μm.
It is formed in a square area of 500 μm. Also, in the case of the pattern shown in FIG. 3, it is effective to incline the side by about 10 to 45 degrees with the side of the mask pattern. this is,
Mask patterns used in semiconductor manufacturing are vertical and orthogonal.
This is because there are many horizontal patterns (0 degrees and 90 degrees).

FIG. 5 shows a special light guide means for preventing the reflected light from each element of the illumination optical system including the illumination 8 from being incident on the detector 7 and becoming a background of detection. Here is an example. In FIG. 5, a two-branch type fiber
The cable 13b has a fiber constituting the end face 13d and a fiber constituting the end face 13c randomly arranged on the end face 13e. The illumination light path and the detection light path are completely separated from each other, and the end faces 13c, 13e are separated. Does not reach the end face 13d. Therefore, the end face 13d is set to the detector 7, the end face c is set to the light source 8, and the end face 13e is set to the aperture pattern.
1a, the detection background can be smaller than when the transmission / reception system is separated using the half mirror 14 as shown in FIG.

As described above, according to this embodiment, the opening pattern 1 of the fiducial surface 1 provided on the stage 12 is provided.
is projected onto the mask pattern surface via the projection optical system 2,
Since the observation is performed again from the aperture pattern 1a of the fiducial surface 1, the TTL focus directly performed via the projection optical system 2 can be executed at an arbitrary position on the mask pattern surface, which has been difficult until now. Focus detection at the center of the screen is also easy. Further, if the end face of the fiber cable 13 is arranged conjugate with the exit pupil of the projection optical system 2 and the size of the end face is made equal to the size of the light source of the projection optical system,
It becomes possible to detect the in-focus state of the reflected light of the projected image with a σ value equivalent to the case where exposure transfer is actually performed,
High focusing accuracy can be expected.

By the way, when loading the wafer 11 with the place where the fiducial surface 1 is set, the projection optical system 2 is used.
In this case, focusing can be performed in parallel with loading, so that time loss is eliminated. In this case, the TTL focus can be achieved for about one minute each time the wafer is exchanged, so that it is possible to easily cope with the temporal change of the focal point position of the projection optical system 2.

The projection pattern of the fiducial surface 1 is
(Aperture pattern 1a) and incident focus sensor 5,
6 is preferable, but when the detection range of the incident focus sensors 5 and 6 is small, a portion other than the aperture pattern 1a on the fiducial surface 1 is incident.
The focus height can also be detected by detecting with the scum sensors 5 and 6. In this case, the fiducial surface 1
Must be sufficiently good, but some errors can be corrected later as offset values.

When the mask 3 is mounted obliquely as shown in FIG. 6, the conjugate surface 20 on the wafer side has a tilting relationship. The inclination of the wafer surface can be calculated from the above, and the leveling device 21 on the stage can be driven through the leveling control system 22 to position the wafer on the conjugate plane with the mask.

If a highly reflective surface is provided outside the circuit pattern of the mask 3, the quantity of light returning from the reflected light of the projected image of the mask pattern surface to the detector 7 can be increased, and high accuracy can be achieved. Can be expected.

Incidentally, the aperture pattern 1a of the fiducial plate 1 is not limited to the lattice having the slit-like openings as described above, but also the fiducial plate 101 having the phase grating as shown in the plan view of FIG. It is also possible. That is, in the pattern section 101a, 101b
And 101c are both transparent regions, but have different thicknesses and are formed so as to have a phase difference with respect to light passing therethrough. Specifically, a phase difference is provided on a glass plate by etching or vapor deposition of a transparent material.
When such a phase grating is used, the amount of detection light can be increased because light is not shielded as compared with the fiducial plate 1 shown in FIG. 3, and the back surface reflection at the aperture pattern can be reduced. Since it can be eliminated, detection accuracy can be improved, which is advantageous. By appropriately selecting the phase difference of the phase grating, an output signal as shown in FIG. 8 can be obtained unlike FIG. In this case, the position where the signal intensity becomes minimum is detected as the in-focus position, and the other processing is the same as in the above-described embodiment.

[0042]

According to the focal position detecting apparatus of the present invention, it is easy to individually determine the focal point for each part of the actual mask pattern immediately before the exposure transfer, and a special mask is provided in the transfer area of the mask pattern. It is not necessary to dispose the laser beam, and even if the light shielding area occupying the mask pattern is large or the intensity of the exposure light changes every moment, the focus can be determined with high reliability.

In the focal position detecting apparatus according to the second aspect of the present invention, it is possible to adjust the exposure surface to an in-focus position at an arbitrary position on the stage using the measuring means.

The focal position detecting device according to the third aspect of the present invention can be adjusted so that the exposure surface coincides with the focal point at an arbitrary position on the stage using a measuring instrument.

The focus position detecting device according to claim 4 of the present invention is
The focal point can be determined without being affected by the mask pattern. According to the projection exposure apparatus of the fifth aspect of the present invention, it is easy to individually obtain the focal height of the actual mask pattern immediately before the exposure transfer, and the focal point can be determined with high reliability. According to the projection exposure apparatus of the sixth aspect of the present invention, it is possible to set the posture of the sample corresponding to the inclination with respect to the mask. In the projection exposure apparatus according to the seventh aspect of the present invention, it is easy to individually obtain the focal point height of the actual mask pattern immediately before the exposure transfer, and the focal point can be determined with high reliability. The projection exposure apparatus according to claim 8 of the present invention can perform precise exposure transfer with less time loss by performing highly reliable focus determination in parallel with wafer replacement. According to the projection exposure apparatus of the ninth aspect of the present invention, it is easy to individually obtain the focal point height of the actual mask pattern immediately before the exposure transfer, and the focal point can be determined with high reliability.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a focus adjustment mechanism according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining light amount change detection in an embodiment of the present invention.

FIG. 3 is a plan view of a fiducial plate according to the embodiment of the present invention.

FIGS. 4 (a) and 4 (b) are plan views of another example of the opening pattern.

FIG. 5 is a schematic view of another example of the light guide means.

FIG. 6 is a schematic diagram of an example of a leveling mechanism.

FIG. 7 is a plan view of a fiducial plate according to another embodiment of the present invention.

FIG. 8 is a diagram for explaining light amount change detection by the fiducial plate shown in FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fiducial board 2 Projection optical system 3 Mask 4 Exposure light source system 5 Projection focus sensor 6 Projection focus sensor 7 Detector 8 Light source 9 Zθ drive system 10 Control system 11 Wafer 12 Stage 13 Fiber cage Bull 14 Half mirror 15 XY drive system 1a Opening pattern

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 7/20 G03F 9/02

Claims (9)

(57) [Claims] 1. A focus position detecting apparatus for detecting a stage side conjugate position of a mask pattern surface with respect to a projection optical system, comprising: a reference surface on a stage on which an opening pattern having a predetermined shape is formed; and illumination for guiding illumination light to the opening pattern. Means for detecting, via the projection optical system and the opening pattern, reflected light of the projection image of the opening pattern formed on the mask pattern surface by the projection optical system under the illumination light, and the projection image passing through the opening pattern And a detecting means for detecting a change in the amount of light. 2. The focus position detecting device according to claim 1, wherein
Position adjustment means for moving the stage to a position at which the maximum or minimum change in the light amount is obtained based on the output of the detection means; and a position shift at an arbitrary position on the stage with reference to the position of the reference surface at the position. A focus position detecting device, comprising: a measuring unit for measuring a direction. 3. The focus position detecting device according to claim 2,
A scanning mechanism for scanning an arbitrary position on the stage under the field of view of the projection optical system, and a measuring device for measuring a position on the stage side with respect to the projection optical system with an optical path fixed to the projection optical system, A focus position detecting device comprising: 4. The focus position detecting device according to claim 1, wherein the opening pattern is formed in a plurality of parallel lines or checkered patterns obliquely arranged with respect to a mask pattern. Focus position detecting device. 5. A projection exposure apparatus which illuminates a mask by an exposure illumination system and transfers a mask pattern of the mask onto a sample by a projection optical system, wherein the focus position detection apparatus according to claim 1 is provided. A projection exposure apparatus, comprising: 6. A projection exposure apparatus which illuminates a mask by an exposure illumination system and transfers a mask pattern of the mask onto a sample by a projection optical system, wherein the projection optical system of the mask is detected by detecting a focal point of the mask. Means for detecting a tilt with respect to a system; leveling means for controlling the tilt of the sample; and controlling the leveling means so as to position the sample on a conjugate plane of the mask based on an output from the detecting means. A projection exposure apparatus, comprising: 7. A means for detecting the inclination includes: a reference surface on a stage on which an opening pattern of a predetermined shape is formed; an illuminating means for guiding illumination light to the opening pattern; and the mask using a projection optical system with the illumination light. Detecting means for detecting reflected light of the projected image of the opening pattern formed on the pattern surface via the projection optical system and the opening pattern, and detecting a change in the amount of light of the projected image of the opening pattern. The projection exposure apparatus according to claim 6, wherein 8. A projection exposure apparatus which illuminates a mask with an exposure illumination system and transfers a mask pattern of the mask to a sample on a stage by a projection optical system, wherein: a reference surface provided on the stage; Focus detection means for detecting a focal point between the mask pattern and the reference plane with respect to the system, wherein the stage is configured to be able to move an arbitrary position on the stage to a position immediately below the projection optical system. The projection exposure apparatus, wherein the reference plane is set so that the reference plane is located immediately below the projection optical system when the sample is replaced. 9. The focus detecting means includes: a reference surface on a stage on which an opening pattern of a predetermined shape is formed; an illuminating means for guiding illumination light to the opening pattern; Detecting means for detecting reflected light of the projected image of the aperture pattern formed on the aperture pattern through the projection optical system and the aperture pattern, and detecting a change in the amount of light of the projected image of the aperture pattern. A projection exposure apparatus according to claim 8.