JP3218466B2 - Exposure method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method and an exposure apparatus suitable for application to, for example, a projection exposure apparatus having a leveling mechanism.

[0002]

2. Description of the Related Art When manufacturing a semiconductor device or a liquid crystal display device, a projection exposure apparatus for transferring an image of a pattern on a reticle to an exposure surface of a photosensitive substrate via a projection optical system is used. In this case, in order to transfer a clear image of the pattern on the exposure surface, the image forming plane (focal plane) of the projection optical system is used.
A leveling mechanism for setting the exposure surface of the photosensitive substrate to be parallel. This leveling mechanism is composed of a leveling optical system for measuring the state of inclination of the exposure surface of the photosensitive substrate from the imaging plane of the projection optical system, and a leveling stage for setting the state of inclination of the photosensitive substrate to a desired state. .

FIG. 7A shows a main part of a projection exposure apparatus provided with a conventional leveling mechanism. In FIG. 7A, reference numeral 1 denotes a reticle mounted on a reticle holder 2. The image of the pattern of the reticle 1 is transferred to the shot area of the wafer 4 via the projection optical system 3 under the exposure light L1. Reference numeral 5 denotes an upper stage on which the wafer 4 is placed, and 6 denotes a lower stage which supports the upper stage 5 with three fulcrums. As shown in FIG. 7C, three fulcrums 5a to 5c of the upper stage 5 are provided. The two fulcrums 5a and 5b can move up and down, and the other one fulcrum 5c
Is fixed. By adjusting the amount of movement of the two fulcrums 5a and 5b on the lower stage 6 side, the tilting state of the upper stage 5 can be set to a desired state. It is configured. The stage having the above configuration is disclosed in, for example, Japanese Patent Application Laid-Open No. 62-274201.

Reference numeral 7 denotes a wafer stage on which a lower stage 6 is mounted.
XY stage for two-dimensionally positioning the wafer 4 in a plane substantially perpendicular to the optical axis, a Z stage for positioning the wafer 4 in a direction parallel to the optical axis of the projection optical system 3, and the like. 8 is a laser interferometer, 9 is a driving means, and X
The coordinates of the Y stage are monitored by the laser interferometer 8, and the driving unit 9 positions the wafer stage 7.

[0005] Reference numeral 10 denotes a light source for a leveling optical system,
The detection light L2 from the light source 10 is converted into a parallel light beam by the projection objective lens 11, and this parallel light beam is
Is projected on the exposure surface (the surface of the resist layer) of the current shot area of the wafer 4 at an angle to the optical axis of the wafer 4. The detection light L2 composed of a parallel light flux reflected obliquely to the optical axis of the projection optical system 3 from the wafer 4
Is focused on the light receiving surface of the photoelectric sensor 13. Wafer 4
When the tilt state (tilt angle) of the exposure surface changes, the position of the center of gravity of the light quantity distribution on the light receiving surface of the photoelectric sensor 13 changes, so that the tilt state of the exposure surface of the wafer 4 can be detected. Japanese Unexamined Patent Publication No. 58-113706). Further, as shown in FIG.
It is composed of divided light receiving elements.

[0007] As shown in FIG. 7 (c), when the exposure surface of the wafer 4 having good flatness is parallel to the best imaging plane (best focus plane) of the projection optical system 3,
The detection light L2 reflected from the detection area 14 of the photoelectric sensor 13 is focused on the center of the light receiving surface of the photoelectric sensor 13.
Perform positioning of. After that, leveling is performed by adjusting the tilt state of the exposure surface of the wafer 4 via the leveling stages 5 and 6 so that the detection light L2 is focused on the center of the light receiving surface of the photoelectric sensor 13.

Although not shown in FIG. 7 (a), the height in a direction parallel to the optical axis of the projection optical system 3 at a predetermined measurement point on the exposure surface of the wafer 4 besides the leveling optical system. A focus detection optical system for measuring the distance is provided.
By driving the Z stage of the wafer stage 7 and adjusting the height detected by the focus detection optical system to the image forming surface of the projection optical system 3, the exposure surface of the wafer 4 is adjusted to the image forming surface of the projection optical system 3. It is set to be parallel and at the same height as this imaging plane.
That is, an autofocus mechanism is configured by the focus detection optical system and the Z stage.

[0008]

As described above, when the flatness of the exposure surface of the wafer 4 is good, the exposure surface is made parallel to the image forming surface of the projection optical system 3 by a leveling mechanism. Can be. However, large irregularities with a large difference in elevation may occur on the exposed surface of the wafer through various processes, and the detection light L2 reflected from the wafer due to unevenness in application of the resist and the like may cause the tilted state of the exposed surface of the wafer. May not correspond to For this reason, even if the leveling mechanism is operated, the exposure surface of the wafer 4 is projected onto the projection optical system 3.
There is a disadvantage that it may not be possible to make the plane parallel to the imaging plane.

For example, FIG. 8A shows an example of a wafer 4A in which saw-toothed irregularities are formed on the exposure surface. In FIG. 8A, P1 is the best image forming surface of the projection optical system 3. I do. In this case, if leveling is performed by moving the upper stage 5 with the detection light L2 reflected from the wafer 4A, the average exposure surface of the wafer 4A and its best imaging plane P1 will not be parallel. Actually, as shown in FIG. 8B, it is desirable that the true average surface of the exposure surface of the wafer 4A coincides with the best imaging plane P1.

In the projection optical system 3, there is a case where the best image plane is not perpendicular to the optical axis AX due to the aberration of the lens. Has been adjusted so that the upper surface of the upper stage 5 on which is mounted is parallel. However, there was a case where there was a residual slope due to an adjustment error.

In view of the foregoing, the present invention provides an exposure method and an exposure method capable of setting an average surface of an exposed surface of an exposure surface of a photosensitive substrate in parallel with the best image forming surface of a projection optical system, even if the exposed surface has irregularities. An object of the present invention is to provide an exposure apparatus. Also, the present invention
It is an object of the present invention to provide an exposure method and an exposure apparatus which can always accurately set an exposure surface of a photosensitive substrate parallel to the best image formation surface even when the best image formation surface of the projection optical system is inclined.

[0012]

According to the exposure method of the present invention, as shown in FIGS. 2 to 4, for example, an image of a mask pattern (1) is transmitted through a projection optical system (3) to the optical axis of the projection optical system. In an exposure method for transferring an image onto an exposure surface of a substrate (4) mounted on a stage (7) movable in a plane substantially perpendicular to the plane, the projection optical system corresponds to a predetermined measurement point in an exposure area of the projection optical system. A focus detection optical system (21, 21) for detecting a deviation of the measurement point of the exposure surface of the substrate from the imaging plane of the projection optical system.
3, 17, 18, 25, 26, 27, 28) and by irradiating the exposure surface of the substrate with a light beam, the average surface of the exposure surface is tilted from the imaging plane of the projection optical system. Leveling optical system (10, 15, 17, 18,
13) and a leveling stage (5, 6) for setting the inclined state of the exposure surface of the substrate to a predetermined state.

The leveling optical system detects an inclined state of the exposure surface of the substrate having a good flatness in advance, so that the exposure surface of the substrate having the good flatness is projected through the leveling stage. A step (steps 108 and 109) of setting the stage parallel to the image forming plane of the optical system, and detecting the focus while moving the stage (7) in a plane substantially perpendicular to the optical axis of the projection optical system (3). Using the optical system, the amount of deviation from the imaging plane of the projection optical system at a plurality of measurement points on the exposure surface of the substrate with good flatness is detected, and the flatness of the flatness is detected from the plurality of detected deviations. Calculating and storing a good amount of tilt of the substrate (step 110), and setting a leveling stage of the average surface tilt state detected by the leveling optical system with respect to the exposure surface of the substrate to be processed. Through A step of setting the projection optical system in parallel with the imaging plane (step 115), and moving the stage in a plane perpendicular to the optical axis of the projection optical system while using the focus detection optical system to process the stage. Detecting deviation amounts of a plurality of measurement points on the exposure surface of the substrate from the imaging plane of the projection optical system, and calculating an inclination amount of the substrate to be processed from the detected plurality of deviation amounts (Step 11
6, 117), and the difference between the amount of inclination of the substrate having good flatness and the amount of inclination of the substrate to be processed is determined by the leveling optical system. Based on the tilt state obtained by adding the offset to the average plane tilt state, the exposure surface of the substrate to be processed is made parallel to the imaging plane of the projection optical system through the leveling stage. Step (Step 118,
119) and a step of transferring the image of the mask pattern to the exposed surface of the substrate to be processed via the projection optical system (Step 114).

The exposure apparatus according to the present invention, for example, as shown in FIG. 2, converts an image of a mask pattern (1) through a projection optical system (3) in a plane substantially perpendicular to the optical axis of the projection optical system. In an exposure apparatus for transferring an image onto an exposure surface of a substrate (4) mounted on a stage (7) movable by means of a projection optical system, the exposure surface of the substrate corresponding to a predetermined measurement point in the exposure area of the projection optical system is A focus detection optical system (21, 23, 24, 17, 17) for detecting the deviation of the measurement point from the image plane of the projection optical system.
18, 25, 26, 27, 28) and irradiating the exposure surface of the substrate with a light beam to detect an inclined state of the average surface of the exposure surface from the imaging surface of the projection optical system. An optical system (10, 15, 17, 18, 13);
A leveling stage (5, 6) for setting an inclined state of an exposure surface of the substrate to a predetermined state; and a focus detection optical system while moving the stage in a plane substantially perpendicular to an optical axis of the projection optical system. Control means (20, 29) for obtaining the deviation amounts of the plurality of measurement points on the exposure surface of the substrate from the imaging plane of the projection optical system via Calculating means (29) for calculating the amount of tilt of the exposure surface of the substrate; and offsetting the average tilt state of the exposure surface of the substrate detected by the leveling optical system based on the calculated amount of tilt. Offset means (29) to be added.

[0015]

In the present invention, a predetermined correction is made to the tilt state of the substrate detected by the leveling mechanism, and the correction amount is obtained by using the auto-focus mechanism. The principle of the present invention will be described with reference to FIG. FIG.
(A) to (f), 3 is the projection optical system, P1 is the best imaging plane of the projection optical system 3, 4B is a substrate having good flatness,
These substrates 4B or 4
C is placed on a leveling stage composed of an upper stage 5 and a lower stage. The leveling stage is moved along a plane P2 by an XY stage (not shown), and the plane P2 is not parallel to the best imaging plane P1.

First, as shown in FIG. 1A, a wafer 4B having good flatness is placed on a leveling stage, and a parallel detection light L2 of a leveling optical system is projected onto an exposure surface of the wafer 4B. Irradiation is performed obliquely to the optical axis No. 3 to detect the inclination of the exposure surface. After that, the leveling stage is driven to set the exposure surface of the wafer 4B in parallel with the best imaging plane P1. Since the flatness of the exposure surface of the wafer 4B is good, the inclination of the exposure surface can be accurately detected by the leveling optical system, and the exposure surface is set parallel to the best imaging plane P1.

Next, as shown in FIG. 1B, the leveling stage is moved leftward along the plane P2. Then, the focus position detecting optical system irradiates the detection light L3 obliquely to the optical axis of the projection optical system 3 and slits the measurement points on the exposure surface of the wafer 4B (for example, points intersecting with the optical axis of the projection optical system 3). An image of a probe pattern such as a pattern is formed. The reflected light from the probe pattern image is re-imaged on a predetermined light receiving surface by the focus position detecting optical system, and the height of the measurement point on the exposure surface of the wafer 4B is determined from the change in the position of the re-imaged probe pattern image. Detect In fact a deviation [delta] ₁₀ with, for example, heights of the best image plane P1 of the measurement point.

Thereafter, as shown in FIG. 1 (c), with the leveling stage moved rightward along the plane P2, the height of the current measurement point and the best image are formed using the focus position detecting optical system. a deviation [delta] ₂₀ between the height of the surface P1. In addition, by moving the leveling stage along the plane P2, deviations δ _j0 from the best imaging plane P1 at various measurement points on the exposure plane of the wafer 4B are _obtained . The average plane obtained from these deviations δ _j0 represents the plane P2 on which the leveling stage moves. Therefore, by measuring the height of each measurement point of the wafer 4B having good flatness by the focus position detecting optical system, the inclination of the plane P2 with respect to the best imaging plane P1 is obtained.

Next, as shown in FIG. 1D, a wafer 4C to be processed having a large unevenness on the exposed surface is placed on a leveling stage. The detection light L2 from the leveling optical system is applied to the exposure surface of the wafer 4C to measure the tilt state, and the surface determined as an average surface is parallel to the best imaging plane P1 of the projection optical system 3. Set to. However, the true average plane P3 and the best imaging plane P1 of the wafer 4C are not set to be parallel due to the unevenness of the exposure surface.

Therefore, in the present invention, as shown in FIG. 1E, the leveling stage is moved leftward along the plane P2. Then, the projection optical system 3 is output from the focus position detection optical system.
Is irradiated with the detection light L3 obliquely to the optical axis of the wafer 4C.
The probe pattern image is formed on the measurement point on the exposure surface of (1). Then, by re-imaging the predetermined light receiving surface at the focus position detecting optical system the light reflected from the probe pattern image, a deviation [delta] ₁₁ between the height and the height of the best image plane P1 of the measurement point.

Next, as shown in FIG. 1 (f), with the leveling stage being moved rightward along the plane P2, the height of the current measurement point and the best result are determined using the focus position detecting optical system. a deviation [delta] ₂₁ between the height of the image plane P1. In addition, by moving the leveling stage along the plane P2, deviations δ _j1 from the best imaging plane P1 at various measurement points on the exposure surface of the wafer 4C are obtained, and an average is calculated by these deviations δ _j1. Seeking a positive aspect. Then, the wafer 4C
From the average inclination of the plane determined by the deviation δ _j1 of the wafer 4
By subtracting the average inclination of the surface obtained from the deviation δ _j0 of B, the inclination offset amount is calculated. This offset amount is added to the tilt amount of the exposure surface of the wafer 4C obtained by the leveling optical system, and based on the result, the leveling stage is driven to obtain the true average surface P3 of the uneven exposure surface of the wafer 4C. Is the best imaging plane P1 of the projection optical system 3.
Is set in parallel to

An exposure method according to the present invention clarifies the above procedure, and an apparatus for performing the exposure method is an exposure apparatus according to the present invention.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In this example, the present invention is applied to a projection exposure apparatus. In FIG. 2, the portions corresponding to FIG. 7 are denoted by the same reference numerals, and detailed description thereof will be omitted. FIG. 2 shows a main part of the projection exposure apparatus of this embodiment. In FIG. 2, an image of a pattern of the reticle 1 is projected on a wafer 4 as a photosensitive substrate through a projection optical system 3 under exposure light L1. Is transferred to the shot area. The wafer 4 is mounted on a leveling stage including an upper stage 5 and a lower stage 6, and the leveling stage is mounted on a wafer stage 7.

Reference numeral 10 denotes a light source for a leveling optical system.
The detection light L2 from the light source 10 is condensed on a pinhole formed in the aperture plate 15 by the condenser lens 11. The detection light L2 from this pinhole passes through the dichroic mirror 16 and then passes through the second projection objective 1
7, the parallel light beam is converted into a parallel light beam.
Irradiated on top. Then, the light beam reflected from the wafer 4 passes through the first converging objective lens 18 and passes through the dichroic mirror 19, and is then focused on the light receiving surface of the photoelectric sensor 13. As the photoelectric sensor 13, a sensor capable of detecting the two-dimensional coordinates of the center of the light amount distribution on the light receiving surface, for example, a light receiving element divided into four is used. The tilt information from the photoelectric sensor 13 is supplied to the signal processing circuit 20.

Reference numeral 21 denotes a light source for a focus position detecting optical system.
2 illuminates the upper part of the slit-shaped opening pattern (slit pattern) of the slit plate 23. The detection light L3 from the slit pattern is reflected by the dichroic mirror 16 via the first projection objective lens 24,
The projection objective lens 17 converges obliquely on the optical axis of the projection optical system 3 at a measurement point (for example, a point intersecting with the optical axis of the projection optical system 3) in the exposure area on the wafer 4, and the slit plate 23 Is formed. Also,
The reflected light from the image of the slit pattern is reflected by the dichroic mirror 19 through the first converging objective lens 18, and then is reflected by the second converging objective lens 25 and the vibrating mirror 26.
Are focused on the light receiving slit plate 27 through which the image of the slit pattern is re-imaged.

The light receiving element 2 is provided on the back of the light receiving slit plate 27.
The detection signal from the light receiving element 28 is supplied to the signal processing circuit 20. When the wafer 4 moves in the direction of the optical axis of the projection optical system 3 in this state, the position of the image of the slit pattern on the wafer 4 shifts leftward or rightward. Is also shifted in a direction parallel to the light receiving slit plate 27. Further, the slit pattern image is vibrated at a predetermined period in the moving direction by the vibration mirror 26 at a predetermined amplitude. This is based on the detection principle of the photoelectric microscope. In the signal processing circuit 20, the detection signal of the light receiving element 28 is synchronously detected by the drive signal of the vibrating mirror 26, so that
When the measurement point of the wafer 4 matches the height of the image forming plane of the projection optical system 3, a so-called S-curve position detection signal which becomes zero cross is obtained. Based on the position detection signal, the deviation amount δ of the height of the measurement point of the wafer 4 from the best image plane of the projection optical system 3 is calculated.
Can be requested.

Reference numeral 29 denotes a main controller. The main controller 29 includes information on the inclination state of the exposure surface of the wafer 4 detected by the signal processing circuit 20 by the leveling optical system and the wafer 4 detected by the focus position detecting optical system. The information of the deviation amount δ of the predetermined measurement point from the best imaging plane is supplied. In response, main controller 29 controls the operation of wafer stage 7 via driving means 9 to position wafer 4 and controls leveling stages 5 and 6 to tilt the exposure surface of wafer 4. The state is set parallel to the best imaging plane of the projection optical system 3.

Next, the procedure of the leveling operation and the exposure operation of this embodiment will be described. First, a leveling operation and an exposure operation of a wafer to be processed will be described. In this case, the preliminary step shown in FIG. 3 is required to determine the image plane inclination of the projection optical system 3 and to check the parallelism between the best imaging plane of the projection optical system 3 and the moving surface of the leveling stage.

In the preliminary step shown in FIG. 3, as an initial step, a test reticle having a pattern formed only at predetermined lattice points is placed as reticle 1, and a test is performed on a leveling stage having good flatness and a resist applied. With the wafer for printing placed thereon, the Z stage in the wafer stage 7 is lowered, and the exposure surface of the wafer is arranged to be larger than the best imaging plane of the projection optical system 3. Next, in step 101, the first exposure is performed.
02 Z-coordinate of the Z stage checks whether reached the upper limit Z _{end The.} If the upper limit has not been reached, step 103
Then, the Z stage is moved in the direction of the projection optical system 3 by ΔZ, and the XY stage in the wafer stage 7 is driven to move the next shot area of the wafer to the exposure area of the projection optical system 3. After that, the process returns to step 101 to perform exposure. In setting the Z coordinate, the focus position detecting optical system is operated, so that the Z stage is set to ΔZ
To raise each time means, to be precise, to shorten the distance between the projection optical system 3 and the exposure surface of the wafer by ΔZ.

Then, after repeating steps 101 to 103 until the Z coordinate of the Z stage reaches the upper limit, the process proceeds to step 104 to develop the wafer and to expose the wafer in the exposure area (shot area) of the projection optical system 3. The Z coordinate at which the best image (best focus) is obtained at a plurality of points is obtained. Next, in step 105, when a plane formed by the Z coordinate of the best focus is obtained, this plane becomes the image forming plane of the projection optical system 3. If an image plane tilt exists, the image plane tilt is detected because the surface thus obtained is tilted with respect to a plane perpendicular to the optical axis of the projection optical system 3. The above is an example in which the image plane inclination of the projection optical system 3 is obtained by test printing. For example, a luminescent reference mark is provided on the wafer stage 7 and the image of this reference mark is transferred through the projection optical system 3 to the lower surface of the reticle. The image plane inclination can be obtained also by a system that forms an image on the (pattern surface) and that photoelectrically detects light from the pattern surface via a projection optical system and a reference mark. In this case, the best focus position at one point in the exposure area of the projection optical system is obtained based on a change in the photoelectric signal when the reference mark is moved in the optical axis direction (Z direction) of the projection optical system. By performing the measurement at a plurality of points in the exposure area, the image plane of the projection optical system 3 and thus the image plane inclination can be obtained.

Next, in step 106, an offset amount of the tilt amount of the leveling stage is calculated so that the image plane tilt becomes zero, and the offset amount for the leveling mechanism set in the storage section inside the main control device 29 is calculated. The offset amount is added to the target inclination amount. The main controller 29 controls the tilting state of the leveling stages 5 and 6 according to the target tilt amount to which the offset amount has been added, so that the exposure surface of the wafer on the leveling stage is best imaged by the projection optical system 3. Are set parallel to the plane (step 10
7).

Thereafter, the super flat wafer having extremely good flatness is placed on the leveling stage in step 108, the leveling mechanism is operated in step 109, and then the super flat wafer is used in step 110 by using the focus position detecting optical system. The unevenness of the surface of the flat wafer is measured. Specifically, with the leveling mechanism operating,
While moving the XY stage of the wafer stage 7, deviation amounts of a predetermined number of measurement points of the wafer from the best imaging plane of the projection optical system 3 are obtained, and an average surface is obtained from these deviation amounts. This average plane is calculated by, for example, a statistical calculation process (least square method or the like), a search method, or the like. Since the current wafer is a super flat wafer, the determined surface represents a leveling mating surface. The amount of inclination of the leveling mating surface from the best imaging plane of the projection optical system 3 is stored in the storage unit of the main controller 29 as the reference inclination amount. This completes the preliminary process.

Next, in step 111 of FIG. 4, the wafer 4 to be processed is placed on the leveling stage.
In step 112, it is determined whether or not the process is one in which a leveling abnormality occurs. The process in which the leveling abnormality occurs is a process in which the average surface of the wafer 4 detected by the leveling optical system is inclined with respect to the actual average surface of the wafer 4 (for example, the wafer 14A in FIG. 8 is formed). The existence of such a process is known empirically. In this case, if the process does not cause the leveling abnormality, the process proceeds to step 113 and the exposure is performed in step 114 with the leveling mechanism operated.

In the process in which a leveling abnormality occurs, the operation of the main controller 29 shifts to step 115, and the leveling mechanism is first operated. Thereafter, in step 116, main controller 29 moves the XY stage, thereby using the focus position detecting optical system to form the best number of projection optical systems 3 of the predetermined number of measurement points on the exposure surface of wafer 4 to be processed. The deviation from the image plane is measured. This means that the state of unevenness on the surface of the wafer 4 is measured. Then, main controller 29 obtains the average surface of the irregularities on the surface of wafer 4 from the shift amounts (step 117). However,
The average plane obtained in this way has a tilt of the plane on which the XY stage moves (that is, the plane including the rectangular coordinate system defined by the interferometer 8 and the imaging plane of the projection optical system with respect to this plane). Since the inclination of the surface caused by the XY stage has already been corrected, the leveling is performed by subtracting the inclination of the moving surface of the XY stage from the average inclination of the surface of the wafer 4 in step 118. The correction amount (new offset amount) of the tilt amount to the mechanism is calculated.

Thereafter, the main controller 29 adds the correction amount to the target tilt amount for the leveling mechanism set in the internal storage section, and according to the target tilt amount to which the correction amount has been added, the main controller 29. Controls the tilting state of the leveling stages 5 and 6, so that the true average surface of the exposure surface having the unevenness of the wafer 4 on the leveling stage is set in parallel with the imaging plane of the projection optical system 3 ( Step 11
9). Thereafter, the process proceeds to step 114 where the exposure is performed, whereby the pattern image of the reticle 1 is clearly transferred to the uneven exposure surface of the wafer 4.

It is to be noted that performing the above-described correction of the leveling mechanism for all the wafers of a predetermined lot processed in the process in which the leveling abnormality is presumed to occur causes a decrease in throughput. Furthermore, performing the correction for all shots of one wafer selected to perform the leveling mechanism correction also causes a decrease in throughput. Therefore, an example of a method of reducing the number of corrections of the leveling mechanism will be described with reference to FIGS.

First, in step 120 of FIG. 5, a shot (measurement shot) for measuring the unevenness of the surface using the focal position detecting optical system among all the shots is specified for the wafer for which the leveling mechanism is to be corrected. To specify the measurement point of the displacement in these measurement shots.
For the measurement shots, it is possible to specify shots or the like that are known to have severe irregularities empirically in the wafer, and as the measurement points in these shots, secure a sufficient number to define an average surface . Thereafter, in step 121, it is selected whether or not the leveling mechanism is to be corrected for every wafer in the lot to be processed.

If correction is to be performed for each wafer, step 12
After moving to step 2, the leveling mechanism is operated, and then the measurement shot specified in step 120 is moved to (step 123), and the state of unevenness on the surface of each measurement shot is measured using the focus position detection optical system. (Step 12
4). Steps 123 to 125 are repeated until the measurement is completed for all the measurement shots.
In step 6, a correction amount of the target tilt amount to the leveling mechanism is calculated. This correction amount is different for each shot. Then, the leveling mechanism corrected by the correction amount is operated (step 127), and exposure is performed on all shots (step 128).

If the correction is not performed for each wafer in step 121, the operation proceeds to step 129 in FIG. 6, and it is determined whether or not the leveling mechanism is to be corrected for the first wafer in the lot. When the correction is performed on the first wafer, the process moves from step 130 to step 131 for the first wafer, and in this step 131, the same processes as steps 122 to 127 in FIG. A correction value of the target tilt amount to the target is calculated. Thereafter, in step 132, the first wafer is exposed.

Then, for the second and subsequent wafers,
The process proceeds from step 130 to step 132 to perform exposure with the leveling mechanism corrected based on the correction amount obtained from the leading wafer. On the other hand, step 129
If the correction is not performed for the first wafer in step S <b> 132, the process directly proceeds to step 132, and the exposure is performed without correcting the leveling mechanism. Note that, for example, exposure may be performed while performing correction on a predetermined number of wafers from the top, and correction may be performed on subsequent wafers based on the average value of correction amounts up to that time.

As described above, according to the present embodiment, the state of the irregularities on the surface of the wafer is measured using the focus position detecting optical system. Therefore, the average of the exposure surface of the wafer detected by the leveling optical system is used. Even when the target surface intersects the true average surface, the correction value of the amount of tilt for the leveling mechanism can be set. Therefore, accurate leveling can be performed even when there are irregularities on the surface of the wafer. Further, even if the best image forming plane of the projection optical system is inclined, the exposure surface of the wafer can always be set accurately and parallel to the best image forming plane.

Note that a sensor capable of multipoint measurement may be used as the focal position detecting optical system. A sensor capable of multi-point measurement means projecting two elongated slit images along a diagonal line where an exposure area (shot area) of a projection optical system intersects, or, for example, three elongated slits parallel to the exposure area. An image that is re-formed by reflected light, such as by projecting an image, is divided into a plurality of parts by a one-dimensional or two-dimensional image sensor and received, and the height of a plurality of portions of an exposure area can be measured at once. It is. According to this, the measurement time can be significantly reduced. It should be noted that the present invention is not limited to the above-described embodiments, but can take various configurations without departing from the gist of the present invention.

[0043]

According to the present invention, the measurement result of the leveling optical system is corrected by using the focus detection optical system. Therefore, even if the exposure surface of the photosensitive substrate has irregularities or the like, the exposure surface can be corrected. There is an advantage that a true average plane can be set parallel to the best imaging plane of the projection optical system. Further, there is an advantage that the exposure surface of the photosensitive substrate can always be set accurately and parallel to the best imaging plane even if the best imaging plane of the projection optical system is inclined.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of an exposure method and an exposure apparatus according to the present invention.

FIG. 2 is a configuration diagram showing a main part of a projection exposure apparatus according to one embodiment of the present invention.

FIG. 3 is a flowchart showing a preliminary step of a correcting operation of the leveling mechanism of the embodiment.

FIG. 4 is a flowchart showing a correction operation of the leveling mechanism.

FIG. 5 is a flowchart showing a part of an operation when selectively correcting a leveling mechanism for a wafer to be processed in the embodiment.

FIG. 6 is a flowchart showing the remaining operation of the operation in FIG. 5;

7A is a configuration diagram showing a main part of a conventional projection exposure apparatus, FIG. 7B is a front view of the photoelectric sensor of FIG. 7A, and FIG.
FIG. 8 is a perspective view showing the leveling optical system of FIG.

8A is a diagram showing a state in which an average surface detected by a leveling optical system of a wafer is set in parallel with a best image forming surface, and FIG. 8B is a diagram showing a true average surface of the wafer; FIG. 3 is a diagram showing a state in which is set parallel to the best imaging plane.

[Explanation of symbols]

 Reference Signs List 1 reticle 3 projection optical system 4 wafer 5 upper stage 6 lower stage 13 photoelectric sensor 15 aperture plate 16, 19 dichroic mirror 17 second projection objective lens 18 first converging objective lens 20 signal processing circuit 23 slit plate 24 first projection objective Lens 25 Second focusing objective lens 26 Vibration mirror 27 Light receiving slit plate 28 Light receiving element 29 Main controller

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-102518 (JP, A) JP-A-2-207522 (JP, A) JP-A-2-271516 (JP, A) JP-A 64-64 13723 (JP, A) JP-A-58-122541 (JP, A) JP-A-62-94809 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027

Claims (2)

(57) [Claims] 1. An exposure method for transferring an image of a mask pattern via a projection optical system to an exposure surface of a substrate mounted on a stage movable in a plane substantially perpendicular to the optical axis of the projection optical system. A focus detection optical system that detects a deviation of a measurement point on an exposure surface of the substrate corresponding to a predetermined measurement point in an exposure area of the projection optical system from an imaging surface of the projection optical system; A leveling optical system that detects a tilt state of an average surface of the exposure surface from an image forming surface of the projection optical system by irradiating a light beam onto a surface, and a tilting state of the exposure surface of the substrate in a predetermined state. By using a leveling stage to be set in advance, by detecting in advance the inclined state with respect to the exposure surface of the substrate having good flatness by the leveling optical system, the exposure surface of the substrate having good flatness is set to the leveling stage. Through the A step of setting the plane parallel to the imaging plane of the optical system; and moving the stage in a plane substantially perpendicular to the optical axis of the projection optical system while using the focus detection optical system to improve the flatness of the substrate. Of the projection optical system at a plurality of measurement points of the exposure surface are detected from the imaging surface of the projection optical system, and the inclination amount of the substrate having good flatness is calculated and stored from the detected plurality of deviation amounts. Setting an average surface inclination state detected by the leveling optical system with respect to an exposure surface of a substrate to be processed in parallel with an imaging plane of the projection optical system via the leveling stage. While moving the stage in a plane perpendicular to the optical axis of the projection optical system, the projection optical system at a plurality of measurement points of the exposure surface of the substrate to be processed using the focus detection optical system The amount of deviation from the image plane is detected and the detection is performed. Calculating the tilt amount of the substrate to be processed from the plurality of shift amounts obtained, and the tilt amount of the difference between the tilt amount of the substrate to be processed with good flatness and the tilt amount of the substrate to be processed. Based on the tilt state obtained by adding as an offset to the average tilt state of the exposure surface of the processing target substrate detected by the leveling optical system, the substrate to be processed through the leveling stage Making the exposure plane parallel to the imaging plane of the projection optical system, and transferring the image of the mask pattern to the exposure surface of the substrate to be processed via the projection optical system. Characteristic exposure method. 2. An exposure apparatus for transferring, via a projection optical system, an image of a mask pattern onto an exposure surface of a substrate mounted on a stage movable in a plane substantially perpendicular to the optical axis of the projection optical system. A focus detection optical system that detects a deviation of a measurement point on an exposure surface of the substrate corresponding to a predetermined measurement point in an exposure area of the projection optical system from an imaging surface of the projection optical system; A leveling optical system that detects a tilt state of an average surface of the exposure surface from an image forming surface of the projection optical system by irradiating a light beam onto a surface, and a tilting state of the exposure surface of the substrate in a predetermined state. A leveling stage to be set to the projection optical system at a plurality of measurement points on the exposure surface of the substrate via the focus detection optical system while moving the stage in a plane substantially perpendicular to the optical axis of the projection optical system. System deviation from image plane Control means for calculating; calculating means for calculating a tilt amount of the exposure surface of the substrate from the obtained shift amounts at the plurality of measurement points; and the leveling optical system detected by the leveling optical system based on the calculated tilt amount. An exposure apparatus, comprising: offset means for offsetting an average inclination state of an exposure surface of a substrate.