JP2000081320A - Face position detector and fabrication of device employing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a highly accurate system conveniently and efficiently by guiding a measuring luminous flux incident to and reflecting on the surface of an object to a photodetecting element through a light receiving optical system and guiding a reference luminous flux to the photodetecting element without reflecting on the surface of the object. SOLUTION: Light emitted from a light source LS illuminates a slit plate 50 having a face position measuring slit. A projection optical system PL projects the image of the slit onto a face to be detected, i.e., a wafer 4, through lenses 11, 12. An aperture stop 31 is arranged at the pupil face of the projection optical system PL and openings 31a, 31b are formed symmetrically to the optical axis PLa at the aperture stop 31. A luminous flux deflecting member, i.e., an optical wedge 41, is fixed to the opening 31b and a reference luminous flux passing through the lens 12 is deflected and delivered directly to a light receiving optical system DP without being projected to the wafer face 4. The luminous flux deflecting member 41 is not provided at the aperture stop 31a and the face measuring luminous flux is condensed toward the wafer face 4 and focused thereat.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface position detecting device and a method of manufacturing a device using the same, and more particularly, to a fine electronic circuit pattern such as an IC or LSI formed on a reticle (mask) surface, a CCD or the like. The reticle and the wafer are synchronously scanned by using a projection lens (projection optical system) or a projection mechanism (projection optical system) to project a pattern related to a device such as an image pickup device, a liquid crystal panel, and a magnetic head onto the wafer surface. By projecting while exposing, by detecting surface position information such as the surface position and inclination of the projection lens in the optical axis direction of the projection lens at the time of exposure, and positioning the wafer on the best imaging plane of the projection optical system This is suitable for manufacturing a highly integrated device.

[0002]

2. Description of the Related Art In recent years, semiconductor device manufacturing technology has been remarkably advanced, and fine processing technology has been remarkably advanced. In particular, the optical processing technology mainly uses a reduction projection exposure apparatus having a submicron resolution and a so-called stepper. To improve the resolution, the numerical aperture (NA) is increased and the exposure wavelength is shortened.

In order to further expand the exposure area, a reduction scanning projection exposure apparatus (scanning exposure apparatus) comprising a lens system or a lens system and a mirror system has been devised.
In the future, attention will be paid to the fact that projection exposure apparatuses will become the mainstream.

In this scanning type reduction projection exposure apparatus, both a stage on which a reticle having a circuit pattern is mounted and a stage on which a wafer for transferring a pattern is mounted are moved at a speed corresponding to a reduction magnification of a projection optical system. Exposure is performed while scanning relative to each other.

[0005] In these projection exposure apparatuses, the permissible depth (depth of focus) of the projection optical system decreases with the improvement of the resolving power, and strict accuracy is required for setting the wafer surface at the in-focus position of the projection optical system. Is required.

Conventionally, in a reduction projection type exposure apparatus for manufacturing a semiconductor device, a surface position of a reticle as a first object is projected and projected onto a wafer as a second object by a projection lens system. The position of the wafer surface in the optical axis direction is detected using a detection device (autofocus device, AF device), and the wafer surface is positioned at the best image forming surface of the projection lens.

[0007] Off-Axis (Off Axis) constituted by making a light beam obliquely incident on the wafer surface as one of the surface position detection mechanisms of the wafer surface used in the projection exposure apparatus.
There is a detection mechanism.

In this detection mechanism, a plurality of light beams are irradiated on a wafer surface as a surface to be inspected, a plurality of light beams reflected from the wafer surface are respectively received by a photoelectric conversion element, and the light beams on the photoelectric conversion element are received. From the incident position information, the Z
Comprehensive surface position information on the wafer surface is detected, such as detecting position information (focus) in the direction and detecting tilt information (tilt) on the wafer surface from the focus information of a plurality of measurement points.

The applicant of the present invention has previously disclosed a surface position detecting apparatus for irradiating a plurality of points on a surface to be scanned with light.
No. 11, JP-A-4-354320, and the like.

Japanese Patent Application Laid-Open No. Hei 3-246411 discloses a method in which a plurality of light beams are illuminated on a surface to be scanned from an oblique direction so that a projection image for measurement has the same shape at any measurement point on the surface to be inspected. Is disclosed. Also, Japanese Patent Application Laid-Open No.
No. 5,320,320 discloses an irradiation angle, an irradiation direction on a plane, and the like when a plurality of light beams are irradiated on a surface to be inspected from an oblique direction.

[0011]

A conventional projection exposure apparatus is housed in a clean chamber because dust or dust adheres to a reticle or a wafer surface, resulting in a defective device. The clean chamber is provided with an air-conditioning mechanism that keeps the internal temperature constant in order to prevent the influence of heat generated from a heat source such as a light source or an electric board attached to the projection exposure apparatus. This air-conditioning mechanism makes air at a certain temperature laminar or turbulent and flows from the upper part to the lower part of the projection exposure apparatus, or horizontally in the vicinity of a stage on which a wafer is mounted, so that the inside of the chamber is Is circulated, thereby suppressing the mechanical deformation of the projection exposure apparatus and maintaining the optical performance of the projection exposure in a good condition.

The vicinity of the surface position detecting mechanism for detecting the surface position information of the wafer is often located below the projection optical system.
Here, a laminar flow or a turbulent flow is also formed by the air conditioning mechanism.

In general, it is difficult to make the temperature of the circulating air inside the chamber completely constant, and a mass of air having a slight temperature difference flows in a layered or lump having a difference in refractive index. Due to this flow of air, the refractive index of the air is spatially disturbed. For this reason, the light beam for detecting the surface position of the wafer surface varies in the optical path due to layers or blocks having different refractive indexes, and a phenomenon occurs in which the incident position of the light beam on the detector differs. Therefore, there has been a problem that the detection accuracy of the wafer surface position is deteriorated.

In resolving these problems,
The present applicant utilizes a position detecting unit for detecting a position of a wafer surface in a projection optical axis direction of a projection exposure apparatus and a fluctuation detecting unit for detecting air fluctuation near the wafer surface in Japanese Patent Application Laid-Open No. 9-167737. A method for detecting the position of the wafer surface by using the method is disclosed.

On the other hand, in recent years, various drive mechanisms have been mounted to achieve high-precision control. In particular, in the case of a scanning exposure apparatus, the wafer stage and the reticle stage are scanned at a considerable speed. As a result, vibration occurs in the entire exposure apparatus, and the surface position detecting apparatus also has a slight influence on the measured value due to vibration and slight twist.

The present invention further improves the surface position detecting device previously proposed by the present applicant, and totally corrects the disturbance factors such as the air fluctuation and the mechanical vibration, thereby making the system highly accurate and simple. It is an object of the present invention to provide a surface position detecting device realized with a good configuration and a method for manufacturing a device using the same.

[0017]

According to the present invention, there is provided a surface position detecting apparatus comprising: (1-1) an object surface provided near an imaging plane of a projection optical system, which is oblique to an optical axis of the projection optical system; A pattern is projected by a light projecting optical system, an image of the pattern formed on the object surface is formed on a light detecting element surface by a light receiving optical system, and a signal from the light detecting element is used to form an image of the object surface. In a surface position detection device that detects surface position information in the optical axis direction, a substantially pupil surface of the light projecting optical system and a substantially pupil surface of the light receiving optical system are respectively provided with a measurement light flux and a reference light pattern via a measurement pattern. A stop having a plurality of apertures for passing the reference light beam therethrough, and a light beam deflecting member for deflecting the reference light beam to at least one of the plurality of openings of the stop, The measurement light beam enters the object surface, is reflected by the object surface, and is reflected by the light receiving optical system. The reference light flux is guided to the photodetector by a light receiving optical system without being reflected by the object surface, and the light is guided to the photodetector by a signal obtained by the photodetector. This is characterized in that surface position information is obtained.

In particular, (1-1-1) the light beam deflecting members arranged on the substantially pupil plane of the light projecting optical system and the substantially pupil surface of the light receiving optical system are formed to have different shapes of light beam deflection angles. .

(1-1-2) In the optical path of the light projecting optical system,
Transmitted light amount varying means for adjusting the amount of transmitted light is provided in the optical path of the measurement light beam.

(1-1-3) The light projecting optical system has a plurality of light sources that emit light beams of different wavelength bands, and illuminates the same surface position measurement pattern with the light beams from the plurality of light sources. And one of the light paths in the measurement light path in the light path of the light projecting optical system.
An optical filter that passes only light beams of two wavelength bands must be provided.

(1-1-4) The projection optical system includes a measurement light illumination light source for emitting a measurement light beam, a measurement imaging lens for forming an image of a measurement mask illuminated with the measurement light beam on an object surface, and a reference light beam. And a reference imaging lens for imaging a reference mask illuminated with the reference light beam on a predetermined surface.

(1-1-5) The measurement imaging lens and a part of the reference imaging lens are shared.

(1-1-6) The light projection optical system forms an image of the measurement mask on an object plane, and the reference mask forms an aerial image between the projection optical system and the object plane. .

(1-1-7) The reference light beam is reflected by a final surface of the projection optical system.

(1-2) A pattern is projected from an oblique direction with respect to the optical axis of the projection optical system by an illumination optical system onto an object surface provided in the vicinity of the imaging plane of the projection optical system. An image of the formed pattern is detected by a photodetector by a light receiving optical system, and a signal from the photodetector is used to detect surface position information of the object surface in the optical axis direction. The light projecting optical system has a first mask, a second mask, a first light projecting optical system and a second light projecting optical system, and the first mask emits a light beam from the first mask. The projection optical system is projected on the object plane as a measurement light beam, limited by an aperture stop provided eccentrically near the pupil plane of the projection optical system, and the reflected light is captured by the light receiving optical system and is reflected on the photodetector. The second mask is re-imaged, and the light beam from the second mask is eccentrically provided near the pupil plane of the second projection optical system. The light is deflected by the upper light beam deflecting member, enters the light receiving optical system without being reflected by the object surface, and is re-imaged on the light detection element as a reference light beam for disturbance factor correction. Is used to determine surface position information of the object surface.

In particular, (1-2-1) the first light projecting optical system and a part of the second light projecting optical system are shared.

The exposure apparatus according to the present invention comprises the following steps: (2-1) The relative position between the first object and the second object is adjusted by using the surface position detecting device having the constitution (1-1) or (1-2). The method is characterized in that the pattern on the first object is transferred onto the second object after performing.

The method for manufacturing a device of the present invention comprises the steps of: (3-1) using the position detecting device of the constitution (1-1) or (1-2),
After detecting the relative position between the mask and the wafer,
The device is characterized in that a pattern on a mask surface is transferred onto a wafer surface, and then the wafer is subjected to a development process to produce a device.

(3-2) The pattern on the mask surface is transferred onto the wafer surface using the exposure apparatus of the constitution (2-1), and then the wafer is subjected to a developing process to produce a device. It is characterized by.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic principle of the surface position detection of the surface position detecting apparatus according to the present invention is as follows. A light beam is radiated obliquely onto a wafer surface as an object surface (object surface) and reflected on the object surface. A so-called oblique incidence method, in which the detected light flux is detected by a position detecting element, and position information (focus information) in the Z direction (optical axis direction) of the surface to be detected is detected from the amount of positional deviation of the light flux on the position detecting element surface. It was used.

Further, a plurality of light beams for surface measurement are projected at arbitrary positions in the surface to be inspected, and the amount of tilt of the surface to be inspected is calculated from focus information at each measurement point.

FIG. 1 is a schematic view of a principal part of a detection principle of a first embodiment of a surface position detecting device according to the present invention. The mechanism for detecting the position of the wafer surface 4 shown in FIG.
Only the means for detecting one measurement point on the four surfaces of the wafer is described.

In FIG. 1, LS is a light-emitting light source for detecting a surface position such as an LED.

In general, a resist as a photosensitive agent is applied in a thin film having a thickness of about 1 μm on the surface of a wafer as a test surface (object surface). In order to detect the surface position of the resist surface of the wafer with high accuracy, it is necessary to remove the influence of light interference by the resist thin film. for that purpose,
It is effective to increase the wavelength width of the light source for surface measurement.

On the other hand, various device patterns having different shapes and materials are formed on the wafer surface. Since the reflectivity of the surface measurement light is different in each manufacturing process of the semiconductor element or locally in the shot area, the light signal detected on the position detection element (light detection element) for detecting the incident position of the light flux is detected. The strength is also different.

In order to maintain high-accuracy surface position measurement, the intensity of incident light is adjusted at each step or at each measurement point in a shot to keep the signal intensity constant, and the S / S It is necessary to increase the N ratio.

In this embodiment, an LED is used as a light source that easily controls the light amount and emits a broad wavelength band.

In the present embodiment, the intensity of light emitted from the light emitting light source LS is arbitrarily controlled by changing the output from the light source or using a filter or the like.

The light emitted from the light source LS illuminates the slit plate 50. As shown in FIG.
As shown in (B), a slit (pattern) 50a for surface position measurement is provided.

In FIG. 1, the light projecting optical system PL has two lenses 1.
1 and 12. The slits 50a are projected onto the wafer 4 as the surface to be measured by the lenses 11 and 12. Due to the lenses 11 and 12, the surface of the slit plate 50 and the surface of the wafer 4 have an optically substantially conjugate relationship.

An aperture stop 31 is arranged on the pupil plane (Fourier transform plane) of the lens (light projection optical system) PL, and limits the NA (numerical aperture) of the projected light beam.

The aperture stop 31 has two openings 31a, 3
1b are formed symmetrically with respect to the optical axis PLa of the light projecting optical system PL, and a light deflecting member 41 such as an optical wedge is attached to one opening 31b to deflect a light beam (reference light beam). You are.

In this embodiment, the optical wedge 41 is provided on the reference light beam side, and the reference light beam emitted from the lens 12 is not projected onto the wafer surface 4 but directly received light optical system (re-imaging optical system). The light is allowed to enter the DP.

On the other hand, no light beam deflecting member is provided in the other opening 31a of the aperture stop 31 for the surface measurement light beam (measurement light beam), and the surface measurement light beam emitted from the second Fourier transform lens (lens) 12 is used. Are focused and imaged toward the wafer surface 4.

Next, referring to FIG. 1, the optical path of the light beam for surface measurement and the image forming relationship will be described in detail.

The light beam emitted from the slit plate 50 on which the mark (pattern) for surface measurement is formed is transmitted to the light projecting optical system P.
The light passes through the aperture stop 31 decentered from the optical axis PLa of L and is imaged on the wafer surface 4 by the second Fourier transform lens 12 as a light beam for surface measurement. The light beam for surface measurement specularly reflected on the wafer surface is guided to the aperture stop 32 by the third Fourier transform lens 21 which is one of the re-imaging optical systems DP for light reception. Like the aperture stop 31 in the light projection optical system PL, the light passes through the aperture 32a at a position decentered from the lens optical axis DPa,
The image is re-imaged on the position detecting element (light detecting element) D by the fourth Fourier transform lens 22.

Next, the optical path of the reference optical path and the imaging relationship will be described in detail.

The light beam emitted from the slit plate 50 on which the surface measurement mark common to the surface measurement light beam is formed is transmitted by the aperture stop 31 to the surface measurement light beam of the light projecting optical system PL. It passes through an opening 31b provided eccentrically at a position symmetrical to the optical axis PLa. Here, the reference light beam is deflected to a certain angle by a light deflecting member 41 such as an optical wedge. The deflected light beam travels as a reference light beam through the second Fourier transform lens 12 toward the opening of the light receiving optical system DP substantially parallel to the wafer surface without passing through the reflection on the wafer surface. The image forming point is formed as an aerial image substantially above the image forming point of the light beam for surface measurement on the wafer 4.

The light receiving optical system D directly without the intervention of the wafer 4
The light beam entering P is reflected on the position detecting element D by the optical wedge 42 provided in the opening 32b of the aperture stop 32 provided in the same manner as the light projecting optical system LP. Is imaged.

Next, the amounts of eccentricity of the apertures 31 and 32 of the light projecting optical system LP and the light receiving optical system DP and the light deflection angle of the optical wedge 41 provided in the reference optical path will be described quantitatively.

First, the eccentricity ΔL of the surface measurement light is
Oblique incidence angle θ for surface measurement and the second of projection optical system LP
It is determined by the focal length f2 of the Fourier transform lens 12.

When the aperture of the surface measurement light beam and the aperture of the reference light beam are arranged symmetrically with respect to the optical axis DPa of the imaging optical system DP, the following is obtained.

ΔL = f2 ^* tan (θ / 2) For example, if θ = 5 ° and f2 = 100 mm, ΔL = 4.4
mm.

Next, the deflection angle φ by the light beam deflecting member 41 provided in the reference optical path is determined by the reference optical axis height position H above the wafer and the second Fourier transform lens 12 of the light projection optical system LP.
Is related to the focal length f2.

The height of the reference optical path above the wafer is arbitrary at this deflection angle, and is given by the following relational expression.

H = f2 ^* tan φ or φ = atan (H / f2) When it is desired to pass a reference light beam to a height of 5 mm above the wafer, the focal length f2 of the second Fourier transform lens 12 is 100 = 100.
mm, the deflection angle of the light beam deflection member 41 is φ =
2.9 °. Therefore, it is understood that an optical wedge having an emission deviation angle of 2.9 ° may be used. If the refractive index is n = 1.5 and the incident angle is 0 °, the apex angle of the wedge is about 5.7 °.

On the other hand, the deflection angle of the light path deflecting member 42 disposed in the aperture stop 32 in the light receiving / imaging system for receiving the reference light is set differently from that of the light beam deflecting member 41 in the light projecting optical system LP. It is. This is because if the wedge angle in the light receiving optical system DP is the same as the wedge angle in the light projecting system, the surface measurement light flux and the reference light flux are formed at the same position on the position detection element D, and signal separation is not performed. The phenomenon that cannot be done is prevented.

By arbitrarily setting the angle of the optical path deflection wedge 42 in the light receiving optical system DP, it is possible to arbitrarily control the position of the reference light beam on the position detecting element D.

As an example, the aperture stop 32 of the light receiving optical system DP
The aperture angle of the light projecting optical system LP is determined by the deviation angle of the wedge 42.
If the angle of deviation is set to be 0.6 ° smaller than the deflection angle due to one wedge 41, the reference light beam is imaged on the position detecting element at a position about 1 mm away from the surface detection light beam (= f2 ^* tan Δφ = 100 ^* tan
0.6).

FIG. 3 shows an example of the output of the signal. The left signal is the surface measurement light signal, and the right signal is the reference light signal. As described above, the surface measurement optical signal and the reference light signal are set on the position detection element D so as to be spaced by a certain distance so as to sufficiently include the surface detection measurement range.

Since the reference light signal and the surface measurement light signal have an odd number of times of reflection in the optical path, they move in opposite directions against the influence of air fluctuations in the optical path.

The surface measurement light signal and the reference light signal are individually measured, and the measured values are subjected to arithmetic processing to remove disturbance components due to air fluctuations and vibrations.

When the light beam emitted from the same measurement mark is used in common as the measurement light and the reference light, if the light amount of the light source is controlled in accordance with the fluctuation of the light amount of the surface measurement light, the signal of the reference light also becomes Similarly, it fluctuates, saturates or becomes too low, and the accuracy of simultaneous measurement as the reference light under the same conditions decreases.

In FIGS. 1 and 4, a transmitted light amount variable member 52 is formed in the surface measurement light beam.

The member 52 is rotatable, the transmittance is continuously variable or stepwise variable, and a plurality of optical filters (ND filters and the like) are formed in a circular shape. Light amount adjustment.

FIG. 4 is a schematic view of a main part in which a surface position detecting device according to the present invention for correcting disturbance factors such as air fluctuation and vibration is mounted on a step-and-repeat type or step-and-scan type reduction projection exposure apparatus. is there. In FIG. 4, reference numeral 3 denotes exposure light, which is composed of a light beam from an i-line of DVU or an excimer laser of KrF or ArF and illuminates the reticle 1. The reticle 1 has a device pattern formed thereon. The reticle 1 is mounted on a reticle stage 5.

The wafer 4 as a photosensitive substrate is held by suction on a wafer chuck 6. The wafer chuck 6 is mounted on a wafer stage 7 and has a laser interferometer 9.
00 and the drive control means 1000 controls the drive in the XY directions.

Further, the position and inclination of the wafer stage 7 in the optical axis direction (Z direction) of the projection exposure system (projection optical system) 2 can be controlled. The reticle 1 and the wafer 4 are placed at optically conjugate positions via a projection exposure system 2, and an illumination light beam 3 from an illumination optical system (not shown) illuminates the reticle 1 as an exposure light beam. The exposure light beam 3 on the reticle forms an exposure light beam on the wafer 4 having a size compared to the projection magnification of the projection exposure system 2.
In the case of the reduction projection exposure of the batch exposure, a one-shot exposure is performed on a rectangular exposure area of about 22 mm.

In the case of the scanning type reduced projection exposure, the exposure light beam is formed in a slit shape, and both the reticle stage 5 and the wafer stage 7 are moved in accordance with the optical magnification of the projection optical system 2 with respect to the slit exposure light beam. The scanning is performed by moving the pattern transfer area on the reticle 1 and the pattern transfer area on the wafer 4 with respect to the fixed slit-shaped exposure light beam while moving in one direction at a given speed ratio.

In the projection exposure apparatus of this embodiment, the depth of focus on the wafer side is as small as about 1 μm or less, and the position of the wafer surface to be exposed is adjusted by the optimum exposure position of the projection optical system 2 in order to obtain the optimum resolution. Is set to In order to detect the surface position state (focus, tilt) of the wafer 4 placed on the wafer stage 7 in the Z direction, a surface position detection device using an oblique incidence method is set.

FIG. 5 shows an example of the relationship between the exposure area on the wafer 4 and the surface position measurement points when a scanning exposure apparatus is used as the projection exposure apparatus. In the case of scanning exposure, it is necessary to perform real-time focus, tilt measurement and correction, and it is necessary to cope with reciprocal scanning.

In order to properly use the measurement points according to the scanning exposure direction (B direction or F direction), a slit-shaped exposure area E is used.
The plane position measurement points A1, B1, and C1 and the plane position measurement points A3, B3, and C are located at positions symmetrical and separated by a distance L across F.
3 is set.

Similarly, three surface position measurement points A2, B2 and C2 are set in the exposure slit area EF for confirming the focus drive and the tilt drive.

In this embodiment, a total of nine measurement points are irradiated with a light beam for surface position measurement from an oblique direction. The measurement is
For example, in the case of scanning exposure in the F direction, surface positions are measured in advance at three measurement points A1, B1, and C1 before approaching the exposure position, and further, the focus values of these three points and a previously known measurement value are measured. The tilt amount around the Y axis is calculated from the point span amount.

Similarly, in the case of scanning exposure in the B direction, 3
The surface positions are measured in advance at A3, B3, and C3 at the measurement points, and the tilt amount around the Y axis is calculated from the focus of those three points and the previously measured measurement point span amount.

A driving mechanism command on the stage side is sent to drive a desired focus and tilt amount before approaching the exposure position.

On the other hand, the steps &
When a repeat type projection exposure apparatus is used, at least 5
Focus information of shot area by adopting point measurement points,
And tilt information are detected.

In the surface position detecting device for detecting the surface position information of the wafer surface 4 shown in FIG. 1, only the means for detecting one measurement point is described for simplification of the description. In addition, only the principal rays of the surface measurement light beam and the reference light beam are shown here for ease of explanation.

Next, the surface position detecting device according to the present embodiment will be described, although it partially overlaps with the description of FIG.

In FIG. 4, LS is a light source for detecting the surface position. The intensity of light emitted from the light source LS is arbitrarily controlled by the signal processing system 100. Light emitted from the light source LS illuminates the slit plate 50. As shown in FIG. 2, a plurality of slits 50a for surface position measurement are formed on the slit plate 50.

In FIG. 4, the light projecting lenses (lenses) 11 and 12 are shown.
Thereby projecting the slit plate 50 on the wafer 4 which is the surface to be inspected. The lenses 11 and 12 make the slit plate 50 and the surface of the wafer 4 optically substantially conjugate.

The light beam emitted from the slit plate 50 on which the measurement mark 50a is formed is transmitted to the aperture stop 3 eccentric from the optical axis 11a of the lens (first Fourier transform lens) 11.
The light passes through one opening 31a and is imaged on the wafer surface 4 by a lens (second Fourier transform lens) 12 as a surface measurement light beam (measurement light). The light beam for surface measurement specularly reflected on the wafer surface is guided to an aperture stop 32 by a light receiving lens (third Fourier transform lens) 21 which is one of light receiving optical systems. The image of the slit plate 50 on the wafer surface passes through the opening 32a eccentric from the lens optical axis similarly to the opening 31a of the aperture stop 31 in the lenses 11 and 12, and is positioned by the light receiving lens (fourth Fourier transform lens) 22. The image is re-imaged on the detection element (imaging means) D.

On the other hand, the light beam emitted from the slit plate 50 having the surface measurement mark formed in common with the surface measurement light beam is transmitted from the lens 11 by the aperture stop 31 to the surface measurement light beam. It passes through an opening 31b provided eccentrically at a position symmetric to the axis 11a. Here, the reference light beam that has passed through the opening 31b (reference light) is a light deflection member 4 such as an optical wedge.
Deflected to an angle by 1. The deflected light beam is passed through the second Fourier transform lens 12 as a reference light beam,
The light travels toward the opening of the light receiving lens 21 substantially in parallel with the wafer surface without being reflected by the wafer surface. The image forming point is formed substantially above the image forming point of the light beam for surface measurement on the wafer 4.

The light receiving lens 21 is not directly interposed through the wafer 4
Enters the aperture 32b of the aperture stop provided similarly to the lenses 11 and 12, and the light beam deflected by the optical wedge 42 in the direction in which the angle of the light beam is returned is detected by the light receiving lens 22. The light is incident on the element D, and the image of the slit plate 50 is re-imaged on the surface. Each element 1
1, 12, 31, and 41 constitute one element of the projection optical system,
Each of the elements 21, 22, 32, and 42 constitutes one element of the light receiving optical system.

In the present embodiment, with this configuration, the signals of the reference light and the measurement light are simultaneously taken into the position detecting element D, and the surface position signal processing system 100 reduces disturbance factors such as air fluctuation and vibration. Calculation is performed as follows.

Then, the calculated focus and tilt information of the wafer surface 4 is transferred to the CPU of the wafer stage 7.
Feedback to 1000.

Next, a second embodiment of the present invention will be described.

As described in the first embodiment, in order to maintain high-accuracy surface position measurement, the intensity of incident light is controlled for each process or for each measurement point in a shot, and the signal intensity is always controlled. S / N of the acquired signal
It is necessary to increase the ratio.

For this purpose, a light amount adjusting system having a good response and a wide dynamic range is required. If a semiconductor element such as a light emitting diode (LED) or a semiconductor laser (LD) is used as such a general light source, accurate light quantity control can be performed by controlling the current.

Further, if a light amount adjusting member or the like is provided in the light beam by mechanical rotation as in the first embodiment, the light amount adjusting member may further cause disturbance.

FIG. 6 is a schematic view of a main part of the second embodiment.
The figure shows two light sources LS1 and LS1, each of which has a different emission wavelength band, in order to illuminate a common mark 50 for surface measurement and reference measurement, and to perform light amount adjustment of only surface measurement light individually with high accuracy.
LS2.

The surface measurement light source LS1 is a light source that emits a light beam λ1 in a broad band for reducing thin-film interference. On the other hand, the reference light source LS2 is a light source having a wavelength λ2 different from the measurement wavelength λ1. Make up.

The surface measurement light source LS1 and the reference light illumination light source L
The light λ1, λ2 emitted from S2 is
And illuminates the measurement mark on the mask 50 by the common illumination optical system 70. Then, at the surface position of the aperture stop 31 of the light projecting optical system PL, the light beam of the wavelength band λ1 from the surface measurement light source LS1 is transmitted through the surface measurement light opening 31a, and the reference light source LS2 is Is provided with an optical filter 43 having such a characteristic as to cut off the luminous flux of the wavelength band λ2.

On the other hand, the reference wedge 41 is provided with an optical filter having such characteristics as to transmit the luminous flux in the wavelength band λ2 of the reference light source and cut the luminous flux in the wavelength band λ1 of the measurement light. Formed on the surface. The light receiving optical system DP has the same configuration as that of the first embodiment.

As described above, the surface measurement illumination light source LS1 and the reference light illumination light source LS2 are separately provided, and the light quantity can be individually controlled only by the surface measurement light by branching the light with the wavelength filter. On the other hand, since the reference light amount hardly changes, it may be controlled to a constant value.

Since the reference light is not affected by the thin-film interference on the wafer surface, a monochromatic laser light source (having a sharp wavelength band) with easy wavelength separation may be used as the reference light light source. This is, of course, different from the measurement wavelength. In this case, at the surface position of the aperture stop 31 of the projection optical system LP, light in the broad band λ1 is transmitted through the surface measurement light aperture 31a,
In addition, an optical filter having a characteristic of cutting the wavelength of the reference light is configured.

On the other hand, the reference light opening 31b is provided with an optical filter (bandpass filter) having a characteristic of transmitting light of a laser wavelength and cutting a wavelength band of measurement light.

Next, a third embodiment of the present invention will be described.

FIG. 7 is a schematic view of a main part of the third embodiment.
In the second embodiment, the optical wedge 41 is provided with an optical filter (bandpass filter).

In this embodiment, a similar effect is obtained without using a bandpass filter. In the present embodiment, FIG.
In the illumination optical system, as shown in FIG.
The aperture stop 76 is set at a position that is substantially the same as the surface of the aperture stop 31, and the reference light and the measurement light are guided by individual light sources by the light beam combining mirror 74.

In this configuration, since the reference light and the surface measurement light have the same wavelength characteristics, the amount of change in the reference light and the amount of change in the surface measurement light due to disturbance factors can be made close to the same. This constitutes a more accurate correction system. Incidentally, reference numerals 72 and 73 are lenses.

Next, a fourth embodiment of the present invention will be described.

In the first to third embodiments of the present invention in which a light beam is branched from a common measurement mark and a reference light path and a plane measurement light path are formed using a common projection optical system, the reference light and the plane measurement There is a slight difference in light path length between light and light due to the difference in light path near the wafer surface. As a result, there is a case where the focus is not exactly focused on the position detecting element. In order to accurately remove the influence of air fluctuations and other disturbances, it is necessary to adjust both focuses on the position detecting element.

FIG. 8 is a schematic view of a main part of the fourth embodiment. FIG. 9 shows an embodiment in which the problem of the individual light amount control of the surface measurement light and the problem of the above-described defocus are solved.

In the light projecting optical system for projecting a mark, different illumination lights are formed by setting the mark portions of the measurement light beam and the reference light beam to different paths.

First, by separately providing the surface measurement illumination system and the reference light illumination system, the light amount can be individually controlled. Furthermore, this configuration not only improves the light amount control, but also
There is an advantage that the focus adjustment of the measurement light and the reference light on the position detection element can be performed independently.

Next, a specific configuration will be described.

The optical path synthesizing mirror 15 provided in the light projecting optical system PL includes a surface measurement light flux from the light source LS1 and the light source LS2.
To synthesize the reference light beam from A high-reflection metal film is formed in a portion where the surface measurement light beam from the light source LS1 shines, and is reflected so as to enter the second Fourier transform lens 12, which is one of the light projection optical systems PL. The portion where the reference light beam from one light source LS <b> 2 hits is made of plain glass, passes through and enters the second Fourier transform lens 22.

50M is a first mask on which a mark for surface measurement is formed. The other 50R is a second mask on which a mark for reference measurement is formed.

A part of the lens 11M of the first projection optical system for projecting the first mask 50M and a part of the lens 11R of the second projection optical system for projecting the second mask 50R. Is a separate configuration, and each focus plane can be adjusted by adjusting the optical distance of the second Fourier transform lens 12 common to each of the first Fourier transform lenses 11M and 11R.

The marks 50M, 50R used for measurement are
As shown in FIG. 9, if the positions of the surface measurement mark (FIG. 9A) and the reference measurement mark (FIG. 9B) are shifted by a predetermined amount on the mask, as shown in FIG. Thus, it is easy to form two signals separated by a predetermined amount.

The aperture stop 31R in the light projecting optical system PL
The optical wedge 41 and the optical wedge 42 formed in the light receiving optical system DP may have the same apex angle.

The light receiving optical system DP comprises a common image forming optical system as in the first embodiment.

FIG. 10 is a schematic view of a main part of a projection exposure apparatus having the surface position detecting device of FIG. The basic configuration is the same as that of the first embodiment in FIG.

Next, a fifth embodiment of the present invention will be described.

In each of the embodiments described above, the surface position detecting system for measuring one point on the wafer surface has been described. However, the present invention is characterized by the fact that the pupil plane of the light projecting optical system is a feature of the present invention. By using a method that has a plurality of eccentric apertures and deflects one light beam, even in the configuration of multiple point projection for tilt measurement, reference light and surface measurement are performed on the same position detection element for each measurement point. Light can be formed simultaneously.

FIG. 11 is a schematic view of a main part of the fifth embodiment. FIG. 1 shows an example of a tilt detection optical system based on oblique multipoint projection. The figure shows only the chief ray for simplification.

In the figure, the splitting prisms 80M, 80
By R, a light projecting optical system having a different focus position is configured for each of a plurality of measurement points obliquely projected on the wafer (three points in the figure, but any number may be used). In the light receiving optical system, an enlarged re-imaging optical system is provided for each measurement point in order to improve the measurement resolution.

In the tilt detection optical system based on these oblique multipoint projections, a plurality of predetermined apertures and a light deflecting member are provided on the pupil plane of the projection optical system, and the reference light and the surface are located on the same position detecting element at each measurement point. It is possible to simultaneously form measurement light and correct disturbance factors such as air turbulence and vibration at each measurement point.

Light from the illumination systems 75 provided as many as the number of measurement points illuminates marks corresponding to each measurement point formed on the mask surface 51M.

The light beams emitted from the individual marks on the mask surface 51M are combined by the combining prism 80M.
The light is projected obliquely onto the wafer surface 4 by the projection optical systems 11M and 12 for surface measurement light. The imaging relationship of the plane measurement light at each measurement point is represented by a black circle on each principal ray.

The combining prism 80M spatially separates a plurality of luminous fluxes that are close to each other in a cross section perpendicular to the optical axis so that an individual illumination system 75 can be provided for each measurement point. This enables individual light quantity adjustment. Further, since the detection marks can be arranged in the same plane, it is only necessary to form marks for the number of measurement points on one mask member, so that the efficiency is high.

Similarly, on the light receiving side, it is necessary to guide a light beam onto the position detecting elements DA, DB, and DC for each measurement point. It branches to lead.

On the other hand, in the projection light optical system for the reference light, similarly, the light from the illumination systems 76 provided as many as the number of measurement points corresponds to each measurement point formed on the mask surface 51M. Light the mark.

The light beams emitted from the individual marks on the mask surface 51M are combined by the combining prism 81R, and are projected onto the space above the wafer 4 by the reference light projecting optical systems 11R and 12R. The imaging relationship of the reference light at each measurement point is represented by an arrow on each principal ray. According to the present invention, the reference light is collectively imaged above the wafer surface by a configuration in which the reference light is decentered at the aperture stop surface 31R of the projection optical system for reference light and only the reference light is changed in angle by the light beam deflecting member 41. .

Here, in the multi-point oblique projection system, if the reference light beam and the measurement light beam are branched from the same mark at each measurement point, the reference light beam and the measurement light beam are used at the measurement points A and C at different focus positions. The focus positions on the respective light receiving optical elements DA and DC do not match.

This is a problem that the number of reflections of the reference light and the measurement light is caused by the difference between the presence or absence of reflection on the wafer surface which is a non-inspection surface. Therefore, as shown in FIG. 11, in the light projecting optical system, the reference light and the surface
It is preferable to adopt a method in which the light is guided from M, combined by the optical path combining mirror 15 and projected onto the wafer surface 4. According to this method, since the direction of the mask 4 for the reference light is arbitrary, both the reference light and the surface measurement light can be focused on the position detection element D provided for each measurement point on the light receiving side.

In the embodiment described above, the reference light beam is guided directly to the light receiving optical system without being reflected on the non-inspection surface, and is guided on the same sensor as the inspection light beam reflected on the non-inspection surface. However, as shown in FIG. 12, the reference light beam is reflected on a reference surface, that is, the final surface of the projection lens or a reference reflection surface provided for exclusive use, and then guided to a light receiving optical system, where the reference light beam is on the same sensor as the inspection light beam. It is also effective to adopt a configuration in which the image is re-imaged on the image. In particular, in this case, since the number of reflections of the measurement light and the reference light is equal, the direction of change and the amount of change of the signal due to the fluctuation or vibration of the air can be made equal.

Further, since the measurement light and the reference light are guided on the same sensor, it is possible to eliminate a fluctuation factor due to thermal expansion of the sensor itself.

Here, what is characteristic of this embodiment is that the angle α between the optical axis of the projection optical system and the wafer surface is α = 0 °, and the optical axis of the wafer surface measurement light (the center of the light beam) ) And a reference optical axis to a reference surface (the last surface of the lens or a dedicated reference reflection surface, etc.) are symmetrically arranged with respect to the optical axis of the mark projection lens.

In FIG. 12, two apertures are provided at positions symmetrical with respect to the optical axis in an aperture stop in the projection optical system, and light flux deflecting members (optical wedges) 41M and 41M are provided in the apertures, respectively. 41R are provided.

Reference numeral 41M corresponds to the surface measurement light beam, and 41R corresponds to the reference light beam.

Hereinafter, the eccentricity of the aperture and the light deflection angle of the surface measurement light beam and the reference light beam of the aperture stop of the projection optical system and the light receiving optical system will be described quantitatively.

First, the amount of eccentricity ΔL of the surface measurement light and the reference light in the projection optical system with respect to the optical axis of the projection lens is determined by oblique incidence angle θ for surface measurement and the amount of the second Fourier transform lens 12 It is determined by the focal length f2.

When the aperture of the surface measurement light beam and the aperture of the reference light beam are arranged symmetrically with respect to the optical axis of the imaging optical system, the following is obtained.

ΔL = f2 ^* tan (θ / 2) As an example, the angle θ with respect to the surface of the wafer = 5 °, f2 = 100
mm, ΔL = 8.75 mm.

Next, the deflection angle φ by the light beam deflecting member 41 provided in the surface measurement light beam and the reference light beam of the aperture stop of the projection optical system will be estimated. These are related to the height H1 of the optical axis of the projection optical system with respect to the wafer surface, the height of the reference plane for reflecting the reference light beam, and the focal length f2 of the second Fourier transform lens 12 of the projection optical system.

Assuming that the optical axis of the projection optical system is set between the wafer surface and the reference surface, H = H1 = H2, and the following relational expression is obtained.

H = f2 ^* tanφ or φ = atan (H / f2) When the optical axis of the projection optical system is set to a height H1 = 10 mm above the wafer, the focal length f2 of the second Fourier transform lens 12 is If it is 100 mm, the deflection angle by the light beam deflecting member is φ = 5.7 °.

Accordingly, it can be seen that an optical wedge having an emission deflection angle of 5.7 ° may be used. It can be seen that if the refractive index is n = 1.5 and the incident angle is 0 °, the apex angle of the wedge should be about 11.2 °.

On the other hand, two apertures are similarly provided symmetrically with respect to the optical axis on the pupil plane in the light receiving and imaging system that receives the measurement light and the reference light, and an optical path deflecting member is disposed in each of the apertures. However, these deflection angles are set slightly different from those of the light beam deflecting member in the projection optical system. This is because if the wedge angle in the light receiving optical system is the same as the wedge angle in the light projecting system, the surface measurement light beam and the reference light beam are formed at the same position on the same position detection element, and the signals can be separated. It has been prevented from disappearing.

The two types of reference light reflected on the reference surface as described above, and the type of reference light transmitted through the air without passing through the reference surface as described in the first embodiment, are formed on the aperture stop. It is also possible to make selections under good conditions by making it possible to switch by.

[0143]

According to the present invention, by setting each element as described above, disturbance factors such as air turbulence and mechanical vibration are totally corrected, and the system can be easily and efficiently made highly accurate. And a method for manufacturing a device using the same.

As described above, according to the present invention, the light projecting optical system for projecting the surface measurement mark obliquely to the wafer surface and the light receiving optical system for receiving the specularly reflected light from the wafer surface are provided. Divides the light beam emitted from the surface measurement projection mark and projects one obliquely onto the surface to be inspected, such as a wafer, and one causes disturbance factors such as air fluctuation and vibration without reflecting the surface to be inspected. In the surface position detecting device which is directly incident on the light receiving optical system as the reference light for detecting the light and is condensed on the same position detecting element as the surface measurement light, the surface of the pupil plane of the light projecting optical system and the light receiving optical system Separating the aperture of the measurement light beam and the reference light beam, and having a light beam deflecting member on one side, splits the surface measurement light beam and the reference light beam, and the reference light beam is directly transmitted to the light receiving optical system without going through the wafer surface reflection. To be captured Ri, thereby reducing the influence of disturbance factors by air fluctuations or vibration in the vicinity of the wafer surface.

In particular, the optical system for correcting disturbance factors such as air fluctuations and vibrations near the wafer surface can be configured with higher accuracy only by a simple change from the conventional wafer surface position detection mechanism.

In the configuration of a plurality of projections for tilt measurement, the signal of the reference light beam and the signal of the surface measurement light beam are simultaneously formed on the same position detecting element for each measurement point without particularly complicated structure. This makes it possible to correct disturbance factors such as air fluctuation and device vibration for each measurement point.

In addition, with a small modification of the conventional surface position detecting device, disturbance factors such as air turbulence and vibration can be further reduced while suppressing a significant increase in cost, and the focus measurement accuracy is further improved. Improvement can be achieved.

By applying to a projection exposure apparatus,
As the depth of focus becomes extremely small in the future, it is possible to obtain high-precision printing performance.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of a mark used in the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a measurement signal obtained in the first embodiment of the present invention.

FIG. 4 is a schematic view of a main part when Embodiment 1 of the present invention is applied to a projection exposure apparatus.

FIG. 5 is a diagram illustrating a relationship between a measurement point on a wafer and an exposure area in the projection exposure apparatus according to the first embodiment of the present invention.

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

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

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

FIG. 9 is an explanatory diagram of a mark used in Embodiment 4 of the present invention.

FIG. 10 is a schematic diagram of a main part when Embodiment 4 of the present invention is applied to a projection exposure apparatus.

FIG. 11 is a schematic view of a main part when a fifth embodiment of the present invention is applied to a projection exposure apparatus.

FIG. 12 is a schematic view of a main part when still another embodiment of the present invention is applied to a projection exposure apparatus.

[Explanation of symbols]

 1: reticle 2: projection exposure lens 3: exposure illumination light beam 4: wafer 5: reticle stage 6: wafer stage 7: wafer stage 11, 12, 21, 22: imaging lens for surface position detection LS: light source 31: light projection Aperture stop 32: Reception aperture stop 41: Optical wedge 50: Projection mask D: Detection element 90: Marker for surface position detection 100: Surface position detection control means 900: Wafer stage laser interferometer 1000: Drive control means

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA02 AA03 AA37 AA54 CC20 DD03 DD04 DD10 DD14 EE06 FF10 FF51 GG07 GG12 HH12 LL10 LL21 LL28 LL30 MM03 PP12 5F046 BA05 CC01 CC05 DA05 DA14 DB05 DB08 DC10

Claims (13)

[Claims] 1. A pattern formed by projecting a pattern onto an object surface provided in the vicinity of an image forming surface of a projection optical system from an oblique direction with respect to the optical axis of the projection optical system by using a projection optical system. The image is formed on the surface of a photodetector by a light receiving optical system, and a signal from the photodetector is used to detect surface position information of the object surface in the optical axis direction. An aperture having a plurality of apertures for passing a measurement light beam through a measurement pattern and a reference light beam through a reference light pattern, respectively, on a substantially pupil surface of the optical optical system and a substantially pupil surface of the light receiving optical system,
A light beam deflecting member for deflecting the reference light beam with respect to at least one of the plurality of apertures of the stop, wherein the measurement light beam is incident on the object surface and reflected by the object surface. The light receiving optical system guides the light to the light detecting element, and the reference light flux is guided to the light detecting element by the light receiving optical system without being reflected by the object surface, and is obtained by the light detecting element. A surface position detecting device for obtaining surface position information of the object surface using a signal. 2. A light beam deflecting member disposed substantially on a pupil surface of the light projecting optical system and a substantially pupil surface of the light receiving optical system has a shape in which light beams are deflected at different angles from each other. Surface position detection device. 3. The surface position detecting device according to claim 1, further comprising a transmitted light amount varying means for adjusting a transmitted light amount in an optical path of a measurement light beam in an optical path of the light projecting optical system. . 4. The light projecting optical system has a plurality of light sources that emit light beams of different wavelength bands, and illuminates the same surface position measurement pattern with light beams from the plurality of light sources. 3. The surface position detecting device according to claim 1, further comprising an optical filter that passes only a light beam of one wavelength band in a measurement optical path in an optical path of the light projecting optical system. 5. The light projecting optical system includes a measurement light illumination light source that emits a measurement light beam, a measurement imaging lens that images a measurement mask illuminated with the measurement light beam on an object surface, and a reference light that emits a reference light beam. 5. The surface position detecting device according to claim 1, further comprising: an illumination light source; and a reference imaging lens for imaging a reference mask illuminated by the reference light beam on a predetermined surface. 6. The surface position detecting device according to claim 5, wherein a part of the measurement imaging lens and a part of the reference imaging lens are shared. 7. The projection optical system forms an image of the measurement mask on an object plane, and forms an aerial image of the reference mask between the projection optical system and the object plane. Item 7. The surface position detecting device according to any one of Items 1 to 6. 8. The surface position detecting device according to claim 1, wherein said reference light beam is reflected by a final surface of said projection optical system. 9. A pattern formed by projecting a pattern onto an object surface provided in the vicinity of an image forming plane of the projection optical system from an oblique direction with respect to the optical axis of the projection optical system by using a projection optical system. A light detecting element for detecting an image of the object by a light receiving optical system, and detecting surface position information of the object surface in the optical axis direction by using a signal from the light detecting element; The system has a first mask, a second mask, a first light projecting optical system, and a second light projecting optical system, and the first mask emits a light beam therefrom to a first light projecting optical system. Limited by an aperture stop provided eccentrically near the pupil plane of the optical system, it is projected on the object plane as a measurement light beam, the reflected light is captured by the light receiving optical system, and re-imaged on the photodetector The second mask causes a light beam from the second mask to shine on an aperture stop provided eccentrically near the pupil plane of the second projection optical system. Is deflected by the light beam deflecting member of
The light enters the light receiving optical system without being reflected by the object surface and is re-imaged on the light detection element as a reference light beam for disturbance factor correction, and the surface of the object surface is used by using a signal from the light detection element. A surface position detecting device for obtaining position information. 10. The system according to claim 9, wherein a part of the first light projecting optical system and a part of the second light projecting optical system are shared.
Surface position detection device. 11. The method according to claim 1, wherein after the relative position between the first object and the second object is adjusted using the surface position detecting device according to claim 1, the pattern on the first object is changed to the second object. 2
An exposure apparatus, wherein the image is transferred onto an object. 12. A pattern on a mask surface is transferred onto a wafer surface after a relative position between a mask and a wafer is detected by using the position detection device according to any one of claims 1 to 10. And then manufacturing the device through a development process of the wafer. 13. A device according to claim 11, wherein a pattern on the mask surface is transferred onto a wafer surface by using the exposure apparatus according to claim 11, and then the wafer is manufactured through a development process. Production method.