JP3316694B2 - Projection exposure apparatus and transfer method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus which can maintain the imaging characteristics of a projection optical system in a predetermined state even when the reflectance of a wafer changes, for example.

[0002]

2. Description of the Related Art When manufacturing a semiconductor element or a liquid crystal display element using a photolithography technique, a reduction projection exposure apparatus for transferring a reticle pattern onto a wafer via a projection optical system is used. One of the important performances of such a projection exposure apparatus is overlay accuracy, and a major factor affecting the overlay accuracy is the magnification error of the projection optical system. For example, the line width of a pattern used in an VLSI or the like has been miniaturized year by year, and a demand for improvement in overlay accuracy on a wafer has been increasing. Therefore, there is an increasing need to keep the projection magnification of the projection optical system within a predetermined range.

Incidentally, the projection magnification of the projection optical system is determined by a predetermined temperature change of the apparatus, a slight change in atmospheric pressure of the atmosphere in the clean room, a change in the temperature of the atmosphere, a history of irradiation of the projection optical system with exposure light, and the like. It has been found to fluctuate near the magnification. Therefore, some conventional projection exposure apparatuses have a magnification correcting mechanism for finely adjusting the magnification of the projection optical system to obtain a predetermined magnification. As such a magnification correcting mechanism, for example, a mechanism for changing a predetermined lens interval in the projection optical system or a mechanism for adjusting the pressure of a predetermined air chamber in the projection optical system is known.

Further, the position of the best imaging plane (focal plane) of the projection optical system, the state of distortion, and the like also change due to the same fluctuation factor as the magnification. For this reason, in addition to such a magnification correction mechanism, there is also a projection exposure apparatus including a focusing correction mechanism, a distortion correction mechanism, or the like. For example, by slightly tilting the reticle with respect to a plane perpendicular to the optical axis of the projection optical system, the state of distortion of the projection optical system can be adjusted to some extent.

In order to measure the irradiation amount of exposure light to the projection optical system among the above-mentioned fluctuation factors of the imaging characteristics of the projection optical system, a conventional projection exposure apparatus includes an integrator sensor and an irradiation amount. A sensor and a reflectance monitor are provided. The integrator sensor consists of a photoelectric conversion element that receives the light split by the beam splitter from the exposure light emitted from the illumination optical system toward the reticle, and thereby controls the amount of exposure light to the projection optical system. Can be monitored. An irradiation sensor is a photoelectric conversion element arranged on a stage on which a wafer is mounted. By moving the stage and disposing the irradiation sensor in an exposure area of a projection optical system, Of the exposure light can be monitored.

On the other hand, a reflectivity monitor refers to a secondary light source of exposure light with respect to a beam splitter disposed in an illumination optical system for exposure light as disclosed in, for example, Japanese Patent Application Laid-Open No. 62-183522. Is a photoelectric conversion element arranged at a position substantially symmetric with the aperture stop for setting the shape of the aperture stop. Since the aperture stop surface for setting the shape of the secondary light source of the exposure light is almost conjugate with the pupil plane of the projection optical system, it can be said that the reflectance monitor is arranged on a plane almost conjugate with the pupil plane of the projection optical system. be able to. The reflectance monitor photoelectrically converts the exposure light incident through the projection optical system and its beam splitter after being reflected by the wafer, thereby monitoring the reflectance of the wafer.

Conventionally, as a secondary light source of exposure light,
Generally, an ordinary secondary light source distributed in a circular shape in a region including the optical axis of the illumination optical system has been used. In this case, a circular secondary light source image is formed in the direction reflected by the beam splitter and also on a plane conjugate with the pupil plane of the projection optical system. A photoelectric conversion element having a light receiving surface equivalent to that of an image could be used.

[0008]

However, recently,
The applicant has proposed a so-called multi-tilt illumination, which is an illumination method capable of further increasing the resolution of the projection optical system and maintaining the depth of focus relatively deep. With multiple tilt illumination, the secondary light source of the exposure light is decentered from the optical axis of the illumination optical system, respectively.
In addition, this is an illumination method formed by, for example, four modified secondary light sources separated from each other. Such multiple tilt illumination is used in accordance with the pattern of a reticle to be transferred, and for example, selects a desired aperture stop from a group of aperture stops arranged on a secondary light source forming surface. There has also been proposed a projection exposure apparatus which can be used by switching between a normal illumination method and a plurality of oblique illumination methods by a mechanism or the like. Further, a device that can use annular illumination or the like as needed is also conceivable.

In the case of using a plurality of oblique illuminations among these various illumination methods, a plurality of deformations are formed in a plane conjugate with the pupil plane of the projection optical system in a direction reflected by the beam splitter in a hollow state. The images of the secondary light sources are formed separately from each other. Therefore, the reflectance monitor prepared for the ordinary illumination method cannot receive the reflected light sufficiently, so that the reflectance of the wafer cannot be measured well. In this regard, if the light receiving area of the reflectance monitor is widened so as to completely cover the images of the plurality of deformed secondary light sources, the amount of received light increases, but as the light receiving area increases, the response speed of the photoelectric conversion element decreases. However, the measurement time becomes longer. In particular, when a pulse laser light source is used as the light source of the exposure light, it is desired that the response speed of the reflectance monitor be as high as possible. A similar inconvenience occurs when performing annular illumination.

In view of the foregoing, the present invention provides a wafer monitor having a relatively simple structure and a relatively small light receiving surface even when so-called multi-tilt illumination or annular illumination is performed. It can be monitored at a high response speed reflectance of the photosensitive substrate etc., a projection exposure apparatus capable of controlling the imaging properties of the projection optical system in accordance with the monitoring result, and the projection exposure apparatus
It is an object of the present invention to provide a transfer method using the same .

[0011]

According to a first projection exposure apparatus of the present invention, as shown in FIGS. 1 and 2, for example, a light source (1) for generating exposure light and a secondary light source are formed by the exposure light. Secondary light source forming means (5, 9), a condenser optical system (16) for condensing the exposure light IL1 from the secondary light source and illuminating the mask R, and converting the pattern of the mask R to the exposure light Substrate W on stage (20)
In the projection exposure apparatus having the projection optical system PL for transferring the light beam to the secondary light source, the secondary light source forming means (5, 9) has four deformations decentered and separated from the optical axis of the condenser optical system (16). A secondary light source (13a to 13d, 12) having a secondary light source or an annular modified secondary light source is formed, and
A beam splitter (15) arranged between the next light source forming means (5, 9) and the projection optical system PL, and the stage () separated via the projection optical system PL and the beam splitter (15) 20) Secondary light source image (image on plane P1) formed by reflected light IL2 from an object on top
Between the first plane P2 where the light rays IL3 heading from the innermost to the innermost point intersect with each other, and the second plane P3 where the light rays IL4 heading from the outermost to the innermost part of the secondary light source image intersect And an imaging characteristic control means (8, 20) for controlling the imaging characteristic of the projection optical system PL based on the photoelectric conversion signal from the photoelectric conversion element (25).
24). In addition, the second aspect of the present invention
Projection exposure apparatus comprises a light source (1) for generating the exposure light by the exposure light and the secondary light source forming means for forming a secondary light source (5,9), condensing the exposure light from the secondary light source And a condenser optical system (16) for illuminating the mask R, and the pattern of the mask is moved to the stage (2) under the exposure light.
0) In a projection exposure apparatus having a projection optical system PL for transferring to the upper photosensitive substrate W, a beam splitter (15) arranged in an optical path between the secondary light source forming means and the projection optical system; A photoelectric conversion element (25) arranged in an optical path separated through the beam splitter, and a diffusion plate (29) arranged in an optical path separated to the photoelectric conversion element through the beam splitter. It has. Further, the transfer method of the present invention is a transfer method using each projection exposure apparatus of the present invention, wherein the mask is illuminated with exposure light from the condenser optical system, and the mask is illuminated using the projection optical system. The pattern is transferred to the photosensitive substrate.

[0012]

According to the present invention, when the secondary light source forming means (5, 9) forms a secondary light source decentered with respect to the optical axis of the condenser optical system (16), the stage (20)
The reflected light IL2 returning from the object above via the projection optical system PL and the beam splitter (15) forms an image of the decentered secondary light source on the plane P1, for example, as shown in FIG. However, since the decentered image of the secondary light source has a light amount distributed in a region distant from the optical axis, the light receiving area of the photoelectric conversion element (25) is required to receive the light amount of the entire image on the plane P1. And the response speed decreases.

Therefore, in the present invention, the first plane P2 where the light rays IL3 going from the innermost part (the part closest to the optical axis) of the secondary light source image on the plane P1 to the innermost part intersects, The second plane P where the light rays IL4 heading inward from the outermost (part farthest from the optical axis) of the secondary light source image
3, a photoelectric conversion element (25) is arranged. Thereby, even if the light receiving area of the photoelectric conversion element (25) is small, 光 量 of the light amount forming the secondary light source image on the plane P1 is obtained.
The degree can be received. Also, it is necessary to provide a diffusion plate.
So, even if the secondary light source image is in a hollow state,
Even a photoelectric conversion element with a small light receiving area can receive a certain amount of light
We can secure quantity.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the projection exposure apparatus according to the present invention will be described below with reference to the drawings. In this embodiment, the present invention is applied to a reduction projection exposure apparatus having an image forming characteristic control mechanism of a projection optical system. FIG. 1 is a simplified diagram showing the overall configuration of a reduction projection exposure apparatus according to this embodiment. In FIG. 1, reference numeral 1 denotes a mercury lamp. Exposure light IL from a mercury lamp 1 is focused by an elliptical mirror 2 and reflected by a mirror 3 before being converted into a substantially parallel light beam by an input lens 4.
A shutter 6 is arranged between the elliptical mirror 2 and the mirror 3,
By closing the shutter 6 by the drive motor 7, the supply of the exposure light IL to the input lens 4 can be stopped. Reference numeral 8 denotes a main control system for controlling the operation of the entire apparatus. The main control system 8 controls the operation of the drive motor 7. In addition to the mercury lamp 1, a pulsed laser light source such as a KrF excimer laser or other light sources can be used.

Exposure light IL emitted from the input lens 4 is incident on an optical integrator 5 composed of a fly-eye lens, and a number of secondary light sources are formed on a focal plane on the emission side (reticle R side) of the optical integrator 5. You. Further, a spatial filter plate 9 as a variable aperture stop is arranged on the surface on which the secondary light source is formed, and the spatial filter plate 9 can be set to a desired rotation angle by the rotation drive unit 10.

As shown in FIG. 2, four types of opening patterns 11 to 13 are provided around the rotation axis 9a of the spatial filter plate 9.
Are formed. First, the first opening pattern 11 is a circular opening pattern centered on a normal optical axis, and the second opening pattern 12 is a ring-shaped opening pattern. The third opening pattern 13 includes four relatively large opening patterns 13a to 13d eccentric from the optical axis, and the fourth opening pattern 14 includes four relatively small opening eccentric from the optical axis. It is composed of patterns 14a to 14d. The third opening pattern 13 and the fourth opening pattern 14 form a modified secondary light source for so-called multi-tilt illumination, and the second opening pattern 12 forms a secondary light source for annular illumination.

Returning to FIG. 1, a third aperture pattern 13 for a plurality of oblique illuminations of the spatial filter plate 9 is arranged on the secondary light source forming surface of the optical integrator 5. The opening pattern 13 can be regarded as a modified secondary light source decentered from the optical axis AX of the exposure light IL.
The exposure light IL1 emitted from the opening pattern 13 is
The light enters a main condenser lens 16 via a beam splitter 15 having a high transmittance and a low reflectance. The exposure light IL1 appropriately collected by the main condenser lens 16
Illuminates the reticle R with substantially uniform illuminance after being reflected by the mirror 17 and passing through a variable reticle blind 18 as an illumination field stop.

The exposure light IL1 that has passed through the pattern area of the reticle R is focused on a shot area on the wafer W by the projection optical system PL, so that the pattern of the reticle R is focused on the shot area of the wafer W at a predetermined reduction magnification. It is reduced and transferred. An aperture stop 19 is arranged on the Fourier transform plane (pupil plane) of the projection optical system PL, and the Fourier transform plane is conjugate with the secondary light source forming plane of the optical integrator 5. Further, the wafer W is held on a Z stage 20, and the Z stage 20 is mounted on an XY stage 21. The XY stage 21 can two-dimensionally position the wafer W in a plane perpendicular to the optical axis of the projection optical system PL, and the Z stage 20 moves the wafer W in a direction parallel to the optical axis of the projection optical system PL. Can be positioned.

In the vicinity of the wafer W on the Z stage 20, there is formed a reference mark plate 22 on which reference marks serving as references for various alignments and the like are formed. Also,
A light shielding plate 23 is provided near the opposite side of the wafer W, and the light shielding plate 23 protects a movable mirror (not shown) from exposure light. The moving mirror is XY by laser interferometer
It is used to measure the coordinates of the table 21. Also,
In this embodiment, the reference mark plate 22 and the light shielding plate 23 measure the reference reflectance when measuring the reflectance of the wafer W.

Reference numeral 24 denotes a pressure regulator, and the main control system 8 regulates the pressure of a predetermined air chamber inside the projection optical system PL via the pressure regulator 24. By adjusting the pressure in the air chamber, the imaging characteristics such as the projection magnification of the projection optical system PL can be adjusted within a predetermined range. Note that, instead of or in parallel with the pressure adjuster 24, the projection optical system PL
A mechanism may be provided for adjusting the distance between the lens groups constituting the lens unit, and a mechanism for slightly tilting the reticle R from a plane perpendicular to the optical axis of the projection optical system PL may be provided. The state such as distortion of the projection optical system PL can be adjusted by the inclination of the reticle R.

Further, although not shown, a device arranged around the projection optical system PL for measuring atmospheric pressure and temperature, an integrator sensor for receiving exposure light reflected by the beam splitter 15 on the outward path, and a Z stage 20 There is also provided an irradiation amount monitor which receives exposure light to be irradiated, and is provided with atmospheric pressure information, temperature information, integrated exposure amount information, irradiation amount information and the like from these devices to the main control system 8. Further, information such as the shape of the opening of the variable reticle blind 18 is also supplied to the main control system 8.

Next, the exposure light reflected from the wafer W is
The light returns to the beam splitter 15 via the projection optical system PL, the variable reticle blind 18, the mirror 17, and the main condenser lens 16. The image of the aperture pattern 13, that is, the image of the modified secondary light source is formed on the surface P1 by the exposure light IL2 reflected by the beam splitter 15. Therefore, the plane P
Reference numeral 1 denotes a conjugate with the secondary light source forming surface of the optical integrator 5 and the plane (pupil plane) of the projection optical system PL where the aperture stop 19 is arranged. Reference numeral 25 denotes a reflectance monitor composed of a photoelectric conversion element. In the present embodiment, the light receiving surface of the reflectance monitor 25 has a light receiving surface P2 separated from the surface P1 by a distance d _min and a light receiving surface P3 separated from the surface P1 by a distance d _max. And between them. As an example, the light receiving surface of the reflectance monitor 25 is disposed at the center between the plane P2 and the plane P3.

In this case, the plane P2 is a plane where the rays IL3 from the portion closest to the optical axis of the deformed secondary light source image on the plane P1 to the optical axis side intersect, and the plane P3 is on the plane P1. This is the plane where the light beams IL4 that go from the portion farthest from the optical axis of the modified secondary light source image to the optical axis side intersect with each other. The size of the light receiving surface of the reflectance monitor 25 is a circle having a diameter enough to receive the light beams IL3 and IL4, and supplies the photoelectric conversion signal S of the reflectance monitor 25 to the main control system 8.

Next, how to determine the planes P2 and P3 will be described with reference to FIG. FIG. 3 is a simplified optical system in which the mirror 17 and the beam splitter 15 are omitted from the optical system of FIG. 1, and FIG. 3 shows that the exposure light IL2 reflected from the wafer W is projected onto the projection optical system PL, the reticle R, and the main condenser. An optical path when the light enters a reflectance monitor (not shown) via a lens 16 is shown.

In FIG. 3, the projection magnification (reciprocal of the normal reduction magnification) of the projection optical system PL from the wafer W to the reticle R is β, the numerical aperture of the projection optical system PL is NA, and the square exposure area 26 on the wafer W is Is 2L, and the focal length of the main condenser lens 16 is f. In this case, the radius of the circumference circumscribing the exposure area 26 on the wafer W is r1,
Assuming that the radius of the circumference circumscribing the pattern area on the reticle R conjugate to the exposure area 26 is r2, the following relationship is established. r1 = 2 ^1/2 · L (1) r2 = 2 ^1/2 · L · β (2)

The secondary light source image 2 formed on the plane P1
The radius of the circle (minimum inscribed circle) inscribed inside 7 is σ _min ,
A circle circumscribing the outside of the secondary light source image 27 (maximum circumscribed circle)
_Is assumed to be σ _max . However, the radius of the minimum inscribed circle and the radius of the maximum inscribed circle are values normalized by the numerical aperture of the projection optical system PL, respectively, and are equal to the radius of the aperture stop of the projection optical system PL in consideration of magnification. The radius is 1.

Next, for generalization, in the state shown in FIG. 3, the radius r3 of the secondary light source 27 on the surface P1 is set to the projection optical system P.
Normalized by the numerical aperture of L and represented by radius σ. The half angle of the opening of the exposure light IL2 reflected from the wafer W is θ1, the half angle of the opening of the exposure light IL2 passing through the reticle R is θ2, and the plane P
The opening half angle of the exposure light IL2 in the secondary light source image 27 of No. 1 is θ3. In this case, the opening half angles θ1 and θ2 can be respectively expressed as follows. sin θ1 = NA · σ (3) sin θ2 = NA · σ / β (4)

Further, assuming that the focal length of the main condenser lens 16 is f and the main condenser lens 16 satisfies the sine condition, the focal length of the main condenser lens 16 on the plane P1 is calculated by using the equation (4).
The actual value of the radius r3 of the next light source image 27 is as follows. r3 = f · sin θ2 = f · NA · σ / β (5) Further, the half opening angle θ3 of the exposure light IL2 in the secondary light source image 27 on the plane P1 can be expressed as follows using the equation (2). it can. f · tan θ3 = r2 = 2 ^1/2 · L · β (6) From this equation (6), the opening half angle θ3 can be expressed as follows. θ3 = arctan (2 ^1/2 · L · β / f) (7)

Assuming that the normalized value of the radius r3 of the secondary light source image 27 on the plane P1 is σ _min , the ray I passing through the portion of the radius r3 toward the optical axis AX at the incident angle θ3
A plane P2 is located at a position where L3 intersects the optical axis AX, and a distance d _min between the plane P2 and the plane P1 can be expressed as follows. d _min · tan θ3 = r3 (8) By substituting the equations (5) and (6) into the equation (8), the following equation is obtained. d _min · 2 ^1/2 · L · β / f = f · NA · σ / β (9) Accordingly, the interval d _min is as follows. d _min = (f / β) ² NA · σ _min / (2 ^1/2 · L) (10)

Similarly, assuming that the normalized value of the radius r3 of the secondary light source image 27 on the plane P1 is σ _max , the ray I passing through the portion of the radius r3 to the optical axis AX at the incident angle θ3
A plane P3 (see FIG. 1) is located at a position where L4 intersects the optical axis AX, and a distance d _max between the plane P3 and the plane P1 can be expressed as follows. d _max = (f / β) ² NA · σ _max / (2 ^1/2 · L) (11)

Therefore, in FIG.
Assuming that the distance between the surface 5 and the plane P1 is d, the distance d in Expression (10)
The interval d may satisfy the following condition using _min and the interval d _max in the equation (11). d _min <d <d _max (12)

Returning to FIG. 1, an example of a method for measuring the reflectance of the wafer W using the reflectance monitor 25 will be described. In this case, assuming that the reticle R is set, the main control system 8 sets the shape of the opening of the variable reticle blind 18 to a predetermined state, and then opens the shutter 6 via the drive motor 7. Thereafter, the main control system 8 moves the XY stage 21 via a driving device (not shown) to sequentially dispose the reference mark plate 22 and the light shielding plate 23 in the exposure area of the projection optical system PL. The photoelectric conversion signal S of the reflectance monitor 25 is detected. The photoelectric conversion signals S corresponding to the reference mark plate 22 and the light shielding plate 23 are denoted by S1 and S2, respectively. Further, an accurate reflectance R1 of the reference mark plate 22 with respect to the exposure light IL1.
And the correct reflectance R of the light shielding plate 23 for the exposure light IL1
2 is stored in the memory of the main control system 8 in advance.

Next, the main control system 8 moves the XY stage 21 to arrange the wafer W in the exposure area of the projection optical system PL, and detects the photoelectric conversion signal S of the reflectance monitor 25 at this time. . Then, the main control system 8 calculates the reflectance R of the wafer W with respect to the exposure light IL1 by the following interpolation formula. R = R1 + {(S-S1) / (S2-S1)} (R2-R1) (13) Thereafter, the main control system 8 sets the reflectance R of the obtained wafer W and the environmental conditions around the projection optical system PL. In accordance with the exposure amount of the exposure light IL1 to the projection optical system PL and the like, the imaging magnification of the projection optical system PL is set to a predetermined state via the pressure adjuster 24.

In this case, since a plurality of oblique illuminations are used, the deformed secondary light source image formed on the plane P1 is in a hollow state and the circumcircle is a considerably large circle. However, in this embodiment, the light receiving surface of the reflectance monitor 25 is not disposed on the surface P1, but the surface P2 is separated from the surface P1 by the interval d _min and the surface P3 is separated from the surface P1 by the interval d _max.
The light receiving surface of the reflectance monitor 25 is disposed between the two.
Therefore, a light receiving surface of a size about a circle inscribed in the deformed secondary light source image on the surface P1 can receive a light amount of about １ ／ of the entire deformed secondary light source image. The area of the inscribed circle is, for example, about 1/4 of the area of the circumscribed circle. Only needs to be done. That is, the response speed can be increased by reducing the light receiving area of the reflectance monitor 25, and the SN of the photoelectric conversion signal is good.

Further, even when other aperture patterns 11, 12, and 14 (see FIG. 2) are arranged on the secondary light source forming surface of the optical integrator 5 by changing the rotation angle of the spatial filter plate 9, the reflectance monitor thereof is provided. 25 allows the reflected light from the wafer W to be received with a sufficient amount of light.

Next, another embodiment of the present invention will be described with reference to FIG. In FIG. 4 in which portions corresponding to those in FIG. 1 are assigned the same reference numerals, of the exposure light IL2 reflected by the beam splitter 15, of the exposure light reflected from the wafer W, An image is formed. In this example, the field lens 28 is arranged near the plane P1. Then, assuming that the focal length of the field lens 28 is f1, the light receiving surface of the reflectance monitor 25 is disposed on a plane P4 separated from the field lens 28 by the distance f1, that is, on the Fourier transform plane on the rear side of the field lens 28. The plane P4 is also conjugate with the exposure plane of the wafer W in FIG. Other configurations are the same as those in FIG.

In the example of FIG. 4, a Fourier transform image of the secondary light source image formed on the plane P1 is received by the reflectance monitor 25. Since the Fourier transform image of the secondary light source image has the strongest distribution on the optical axis, a sufficient amount of light can be received even if the light receiving area of the reflectance monitor 25 is small. Further, FIG.
No matter which one of the aperture patterns 11 to 14 is used, the intensity distribution of the Fourier transform image is substantially similar. Therefore, even if any of the aperture patterns 11 to 14 is used in the example of FIG. The reflected light from the wafer W can be received by the amount of light.

Next, still another embodiment of the present invention will be described with reference to FIG. In FIG. 5, in which portions corresponding to those in FIG. 1 are assigned the same reference numerals, of the exposure light IL2 reflected by the beam splitter 15, of the exposure light reflected from the wafer W, a secondary light source is formed on the surface P1. An image is formed. In this example, the diffusion plate 29 is arranged near the plane P1,
The reflectance monitor 25 is arranged at a position separated by a predetermined distance from the diffusion plate 29. Ground glass,
A Fresnel lens type phase diffraction grating, a normal diffraction grating, a random pinhole plate, or the like can be used. Other configurations are the same as those in FIG.

In the example of FIG. 5, light from the secondary light source image formed on the plane P1 is diffused by the diffusion plate 29 and enters the light receiving surface of the reflectance monitor 25. Accordingly, even if the light receiving area of the reflectance monitor 25 is small, a certain amount of light enters the light receiving surface, and the response speed of the reflectance monitor 25 is good. 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.

[0040]

According to the present invention, the amount of light in a state where the secondary light source image formed by the reflected light from the object on the stage is defocused is detected by the photoelectric conversion element. Therefore, even when so-called multi-tilt illumination or annular illumination is performed, the reflectance of the photosensitive substrate can be reduced by using a photoelectric conversion element (reflectance sensor) having a relatively simple configuration and a relatively small light receiving surface. Monitor with high response speed. Further, the imaging characteristics of the projection optical system can be controlled by the imaging characteristics control means according to the monitoring result.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram including a partial cross-sectional view showing an overall configuration of an embodiment of a projection exposure apparatus according to the present invention.

FIG. 2 is a diagram showing an opening pattern of a spatial filter plate 9 of FIG.

FIG. 3 is a diagram for explaining a method of _obtaining an interval d _min and an interval d _{max in} FIG. 1;

FIG. 4 is a configuration diagram showing a main part of another embodiment of the present invention.

FIG. 5 is a configuration diagram showing a main part of still another embodiment of the present invention.

[Explanation of symbols]

 R Reticle PL Projection optical system W Wafer 1 Mercury lamp 4 Input lens 5 Optical integrator 8 Main control system 9 Spatial filter plate 11 First opening pattern 13 Third opening pattern 15 Beam splitter 16 Main condenser lens 20 Z stage 21 XY stage 22 fiducial mark plate 23 light shielding plate 24 pressure regulator 25 reflectance monitor

Claims (3)

(57) [Claims] 1. A light source for generating exposure light, secondary light source forming means for forming a secondary light source from the exposure light, and condenser optics for condensing the exposure light from the secondary light source to illuminate a mask. A projection optical system having a system and a projection optical system for transferring the pattern of the mask onto a photosensitive substrate on a stage under the exposure light, wherein the secondary light source forming means is disposed on an optical axis of the condenser optical system. Forming a secondary light source having four modified secondary light sources or annular modified secondary light sources decentered and separated from each other, and disposed in an optical path between the secondary light source forming means and the projection optical system; The beam splitter thus intersected and the light rays going from the innermost part to the innermost part of the secondary light source image formed by the reflected light from the object on the stage separated via the projection optical system and the beam splitter intersect each other. A photoelectric conversion element disposed between a first surface to be inserted and a second surface at which light rays from the outermost to the innermost of the secondary light source image intersect; and photoelectric conversion from the photoelectric conversion element. A projection exposure apparatus comprising: an imaging characteristic control unit configured to control an imaging characteristic of the projection optical system based on the conversion signal. 2. A light source for generating exposure light, secondary light source forming means for forming a secondary light source from the exposure light, and condenser optics for condensing the exposure light from the secondary light source to illuminate a mask. A projection optical system for transferring a pattern of the mask onto a photosensitive substrate on a stage under the exposure light, wherein the projection optical system is disposed between the secondary light source forming means and the projection optical system. A beam splitter, a photoelectric conversion element disposed in an optical path separated via the beam splitter, and a diffusion plate separated in the optical path to the photoelectric conversion element separated via the beam splitter, A projection exposure apparatus comprising: 3. A transfer method using the projection exposure apparatus according to claim 1 or 2 , wherein the mask is illuminated with exposure light from the condenser optical system, and the mask is illuminated using the projection optical system. A transfer method comprising transferring a pattern to the photosensitive substrate.