JPH08262747A - Projection aligner and production of semiconductor device using the same - Google Patents

Abstract

PURPOSE: To provide a projection aligner with which the alignment of a reticle and wafer with high accuracy is possible and semiconductor devices of a high integration scale are obtainable and a process for producing the semiconductor devices by using the same. CONSTITUTION: This projection aligner has an ejection telecentric projecting lens system 1 which projects the patterns of the reticle 3 as a first object illuminated with the exposure light from an illumination system 4 for exposure onto the wafer 2 of the second object, an observation means which illuminates the alignment marks formed on a wafer surface with the observing light from an illumination system 35 for observation via this projecting lens system 1 and simultaneously detects the relative positional relation between the reticle 3 and the wafer 2 by the observation of the imaging position on the prescribed surface of these marks and a measuring means for the error of the measured value by this observing means based on the focus error on the wafer side of the projecting lens 1. The observing means has a moving mechanism 20 capable of arbitrarily changing the observation position of the wafer mark and a correction optical system 101 for adjusting the optical path of the main ray of the observing light for minimizing the measurement error.

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 and a semiconductor device manufacturing method using the same, and more particularly to a fine electronic circuit pattern such as an IC or LSI formed on a reticle (first object) surface. The projection lens system (projection optical system) projects and exposes the surface of the wafer (second object) to detect the relative positional relationship between the reticle and the wafer with high accuracy when manufacturing a semiconductor device. It is suitable for manufacturing semiconductor devices.

[0002]

2. Description of the Related Art In a projection exposure apparatus for manufacturing semiconductor devices, a circuit pattern of a reticle as a first object is projected onto a wafer as a second object by a projection lens system for exposure. At this time, an alignment mark (mark) on the wafer is detected by observing the wafer surface with an observing device prior to the projection exposure, and the position alignment (alignment) between the reticle and the wafer is performed based on the detection result. , So-called alignment is performed.

The alignment accuracy at this time largely depends on the optical performance of the observation apparatus. Therefore, the performance of the observation device is an important factor in the exposure device. Various methods have been conventionally proposed for those in which alignment is performed using such an observation device.

For example, light which does not expose the resist coated on the wafer (hereinafter referred to as "non-exposure light"), for example,
There is a so-called TTL off-axis method, which is a method for detecting an alignment mark on a wafer through a projection lens system (TTL) using light with a wavelength of 633 nm from a He-Ne laser. In the TTL off-axis method, since a large amount of chromatic aberration occurs in the projection lens system, it is generally impossible to simultaneously observe the wafer and reticle at the exposure position. Therefore, it is necessary to manage the variation of the baseline (the distance between the shot center at the alignment position and the shot center at the exposure position).

On the other hand, the so-called TT which detects the alignment mark on the wafer surface through the projection lens system using the exposure light.
There is an L-on-axis system. A projection exposure apparatus using this TTL on-axis system is disclosed in, for example, Japanese Patent Laid-Open No. 58-256.
No. 38, JP-A-63-32303, etc.

In these publications, the g-line (436 nm) light (exposure light) is used to project and expose a circuit pattern of a reticle onto a wafer by a projection lens system, while the alignment system is irradiated with a wavelength emitted from a He-Cd laser. Alignment marks of the reticle and the wafer are detected by using 442 nm light (alignment light). When observing the wafer surface from the reticle side by configuring a so-called bi-telecentric optical system so that the projection lens system is telecentric on both the reticle side and the wafer side,
The feature is that the chief ray of the alignment light is always perpendicular to the reticle surface.

As a result, even if the type of IC to be manufactured changes and the pattern size on the reticle surface changes to change the observation position of the alignment system, the angle of light incident on or reflected on the reticle surface remains unchanged. By utilizing this property, a highly accurate TTL on-axis system is constructed. The TTL on-axis system is to perform alignment between the reticle and the wafer in a state of being exposed through the projection optical system for exposure.

Further, Japanese Patent Laid-Open No. 63-56917 has been proposed as a method for deflecting the angle of the principal ray of the illumination light beam of the observation device. In this publication, the relative position between the optical axis of the projection optical system and the reticle side observation position of the alignment optical system is detected, and only the inclination angle of the chief ray of the projection lens obtained in advance according to the detection information is used to illuminate the observation device. The angle of the chief ray is deflected.

[0009]

When observing the alignment mark on the wafer surface through the projection lens system, it is necessary to observe the alignment mark only at a specific position (image height) on the optical axis of the projection optical system. For example, the chief ray of the illumination light may be set to be perpendicular to the wafer surface at the image height.

However, for example, when measuring a baseline for off-axis alignment, the measured image height has to be changed due to the reticle, and the TTL is required.
There are times when it is necessary to change the observation image height for on-axis alignment or for the arrangement of alignment marks and the like. At this time, if the spherical aberration of the pupil remains in the projection optical system, the angle between the wafer and the principal ray of the illumination light beam deviates from the vertical.

Next, with reference to FIG. 12, a description will be given of the case where the chief ray does not vertically enter the wafer surface and deviates when spherical aberration of the pupil remains in the projection optical system.

In FIG. 12, 1 is a projection optical system in which the wafer 2 side is telecentric, 2 is a wafer, 3 is a reticle pattern surface, and 10 is a diaphragm in the projection optical system 1. If the pupil of the projection optical system 1 has spherical aberration, the image heights A, B, C in FIG.
In order to make the principal ray of the observation light perpendicular to the wafer surface 2 at any image height on the wafer 2 side, the reticle 3 having an image height A is used.
The incident angle of the principal ray to the reticle 3 must be inclined by + θ where it corresponds to the side, 0 where it corresponds to the reticle side of the image height B, and −θ where it corresponds to the reticle side of the image height C. If the incident angle on the reticle 3 is not changed according to each image height, the incident angle of the observation light on the wafer 2 will be the projection optical system 1.
When the image forming magnification is −1 / β, the image height A is −βθ, the image height B is 0, and the image height C is + βθ.

[0013] Thus when the incident angle of the observation light to the wafer 2 had tilted, delta ₁ in D ₊ [mu] m defocused to + side as shown in FIG. 13 (A), - D on the side _- [mu] m de The alignment mark position measurement value deviates from the focus by Δ ₂ . For this reason, the + side has Δ ₁ / D ₊ per ₁ μm defocus, and the − side has Δ ₂ / D ₋ per 1 μm defocus, and the measured value of the alignment mark has a dependency on the defocus amount (hereinafter referred to as “defocus amount”). It is called "characteristic.").

In the above-mentioned Japanese Patent Laid-Open No. 63-32303, correction is performed by changing the posture of some optical elements of the alignment illumination system. Specifically, the angles of the mirrors and the like in the optical path are changed. Therefore, the angle changed for correction is half the angle required for the incident angle on the reticle side, which is a minute amount of angle, and it has been difficult to secure high correction accuracy.

In the above-mentioned Japanese Patent Laid-Open No. 63-56917, the relative position between the optical axis of the projection optical system and the observation position of the alignment optical system is detected, and the deviation of the telecentricity of the projection lens obtained in advance according to the detected information is detected. The angle of the chief ray of the illumination light flux of the observation device is deflected by an angle corresponding to the amount. Therefore, the correction accuracy includes the detection accuracy of the relative position between the optical axis of the projection lens and the observation position.

Further, when the correction table corresponding to the deviation amount of the telecentricity of the projection lens is provided in advance, if the deviation amount is obtained from the design value, the adjustment error due to the assembly remains and the correction error occurs.

Even when the shift amount is obtained by measurement, there is a problem that the correction accuracy is deteriorated due to a change with time due to replacement of the observation light source. Even when the correction table is regularly measured, the data at all image heights must be measured again, which causes a problem that it takes a lot of time.

Even when the correction table is regularly measured,
The data at all image heights must be remeasured, which requires a great deal of time.

Furthermore, the measurement error due to the focus error due to factors other than the shift amount of the telecentricity of the projection lens cannot be corrected. For example, when there is another component due to Z drive (when it moves diagonally), a measurement error due to a focus error occurs.

As described above, correction of a factor that cannot be done by the correction table is impossible in the conventional system, and highly accurate alignment cannot be expected at all.

According to the present invention, when the alignment mark on the wafer (second object) surface is observed through the projection optical system, the alignment mark is observed at various image heights even if some spherical aberration remains in the pupil of the projection optical system. A projection exposure apparatus that allows a principal ray of light to be incident perpendicularly on a wafer surface to perform relative alignment between a reticle (first object) and a wafer with high accuracy and to easily obtain a highly integrated semiconductor device. Another object of the present invention is to provide a method for manufacturing a semiconductor device using the same.

[0022]

A projection exposure apparatus according to the present invention comprises: (1-1) Ejection telecentric projection for projecting a pattern of a first object illuminated by exposure light from an exposure illumination system onto a second object. A lens system and a mark provided on the second object are illuminated with observation light from an observation illumination system through the projection lens system, and an image formation position of the mark on a predetermined surface through the projection lens system. By observing the first object and the second object to detect the relative positional relationship between the first object and the second object, and the measurement error of the measurement value by the observing device due to the focus error of the projection lens on the second object side. In the projection exposure apparatus having a measuring unit, the observing unit has a moving mechanism that can arbitrarily change the observing position of the mark of the second object, and a main beam of the observing light in order to minimize the measuring error. Adjust the optical path It is characterized by having a correction optical system.

In particular, (1-1-1) the observing means has a lens system that uses the observation light from the observation illumination system as afocal light, and the correction optical system is perpendicular to the optical axis and orthogonal to each other. Has a transparent parallel plane plate whose tilt can be adjusted about the axis, and the parallel plane plate is provided in the afocal optical path, and the tilt of the parallel plane plate is adjusted to adjust the optical path of the observation light. Being shifted parallel to the axis.

(1-1-2) The observing means has a lens system for emitting the observation light from the observing illumination system as afocal light, and the correcting optical systems rotate the optical axes in a state of facing each other. There is provided a wedge member having two transparent wedges whose center is adjustable in inclination and whose intervals can be arbitrarily changed, and the two wedges are provided in the afocal optical path, and the two wedges are provided. The optical path of the observation light is shifted parallel to the optical axis by adjusting the inclination and interval of the.

(1-1-3) The correction optical system has a wedge member composed of a plurality of wedges having different angles, and one of the plurality of wedges is selected and disposed in the optical path. The optical path of the observation light is adjusted.

(1-1-4) The correction optical system adjusts the optical path of the observation light in accordance with the change of the observation position of the mark on the second object surface by the moving mechanism.

(1-1-5) The optical path of the observation light of the observation means is adjusted based on the measurement result of the measurement means. The method of manufacturing a semiconductor device according to the present invention is characterized in that (1-2) after projecting a pattern on a reticle surface illuminated with exposure light onto a wafer surface by an emission telecentric projection lens system, When a semiconductor device is manufactured through a development process, a mark on the wafer surface is illuminated by observation means with observation light from an observation illumination system through the projection lens system, and the observation lens is illuminated through the projection lens system. When the image forming position of the mark on the predetermined surface is observed to detect the relative positional relationship between the reticle and the wafer, and when the observing position of the mark on the wafer surface is arbitrarily changed by the moving mechanism, the correction optical The system is characterized in that the optical path of the principal ray of the observation light is adjusted in order to minimize the measurement error by the system.

In particular, (1-2-1) the observing means has a lens system that uses the observation light from the observation illumination system as afocal light, and the correction optical system is perpendicular to the optical axis and orthogonal to each other. Has a transparent parallel plane plate whose tilt can be adjusted about the axis, and the parallel plane plate is provided in the afocal optical path, and the tilt of the parallel plane plate is adjusted to adjust the optical path of the observation light. Being shifted parallel to the axis.

(1-2-2) The observing means has a lens system for emitting the observation light from the observing illumination system as afocal light, and the correcting optical systems rotate the optical axes in a state of facing each other. There is provided a wedge member having two transparent wedges whose center is adjustable in inclination and whose intervals can be arbitrarily changed, and the two wedges are provided in the afocal optical path, and the two wedges are provided. The optical path of the observation light is shifted parallel to the optical axis by adjusting the inclination and interval of the.

(1-2-3) The correction optical system has a wedge member composed of a plurality of wedges having different angles, and one of the plurality of wedges is selected and disposed in the optical path. The optical path of the observation light is adjusted.

(1-2-4) The optical path of the observation light of the observation means is adjusted based on the measurement result of the measurement means. And so on.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of an essential part of an optical system of a first embodiment of a projection exposure apparatus for manufacturing a semiconductor device according to the present invention. In the figure, reference numeral 3 denotes a reticle as a first object, which is mounted on the reticle stage 3a and illuminated by the exposure light from the exposure illumination system 4. A wafer 2 is a second object, and an alignment mark (AA mark) is provided on its surface. A projection optical system (projection lens system) 1 is composed of an exit telecentric system and projects a circuit pattern or the like on the surface of the reticle 3 onto the surface of the wafer 2. Reference numeral 10 denotes a diaphragm of the projection lens system 1. Reference numeral 8 denotes a wafer chuck on which the wafer 2 is placed.

Reference numeral 7 denotes a θ-Z stage, on which a wafer chuck 8 is mounted, for performing θ rotation of the wafer 2 and focus adjustment, that is, adjustment in the Z direction. The θ-Z stage 7 is an XY for performing the tilt stage 6 and the step operation with high accuracy.
It is placed on the stage 5. An optical square (bar mirror) 11 serving as a reference for measuring the stage position is placed on the tilt stage 6, and the optical square 11 is monitored by a laser interferometer 12.

That is, the laser interferometer 12 includes the XY stage 5
The position is monitored and the position is controlled by the computer 41 through the line. In addition, a non-TTL on the tilt stage 6
-A fiducial mark 9 for alignment is provided.

In the present embodiment, the alignment between the reticle 3 and the wafer 2 is performed indirectly by aligning the reference marks whose positional relationship is determined in advance. Alternatively, the resist image pattern or the like is actually aligned and exposed, and the error (offset) is measured, and thereafter offset processing is performed in consideration of the value.

Next, a mark (alignment) on the wafer 2 surface
A method of performing the position detection of 1 by using the observation means will be described. Reference numeral 35 is an illumination system for observation. The exposure light is introduced as observation light from the exposure illumination system 4 through the fiber 36 into the observation illumination system 35. Observation light from the observation illumination system 35 is reflected by the beam splitter 32 and is reflected by the relay lens 3
Incident on 1. The observation light from the relay lens 31 becomes parallel light (afocal), the optical path is displaced through the correction optical system 101 formed of a transparent plane parallel plate, passes through the diaphragm 23, and is incident on the objective lens 22. .

The objective lens 22 corrects aberrations for an object at infinity. The correction optical system 101 is arranged in the afocal position and at a position other than the pupil plane of the objective lens 22. The correction optical system 101 can be tilted about two axes perpendicular to the optical axis and orthogonal to each other by the driving means 100. The posture of the correction optical system 101 at this time is controlled by the computer 41 described later.

Observation light from the objective lens 22 is reflected by the mirror 21.
And illuminates the reticle 3. The diaphragm 23, the objective lens 22, and the mirror 21 can be moved in the optical axis direction (parallel to the reticle 3) by the moving mechanism 20. As a result, the height of the observed image on the surface of the wafer 2 is changed.
The moving mechanism 20 is controlled by the computer 41 through a line. Although the distance between the objective lens 22 and the relay lens 31 is changed by the moving mechanism 20, this optical path is an afocal so as not to affect the image formation state. A mechanism for correcting the optical path length in association with the movement of the objective lens may be provided in the afocal.

The observation light that has passed through the reticle 3 passes through the projection optical system 1 and the diaphragm 10 therein to illuminate an alignment mark (AA mark) on the surface of the wafer 2. At this time, as will be described later, even if the observation image height changes, the angle of the principal ray of the observation light is deflected by using the correction optical system 101 to correct the defocus characteristic. A on the surface of wafer 2
The reflected light from the A mark returns to the original optical path, and the projection lens system 1, the mirror 21, the objective lens 22, and the correction optical system 10 are sequentially arranged.
1, a relay lens 31, a beam splitter 32, and an erector lens 33 are incident on an image sensor (CCD camera) 34, and an image (AA mark image) on the wafer 2 surface and the reticle 3 surface is formed on the surface. It is a statue.

The AA mark image from the image pickup device 34 is arithmetically processed by the computer 41 through a line to obtain the relative positional relationship between the reticle 3 and the wafer 2. Then, the XY stage 5 is driven to align the reticle 3 and the wafer 2.

In the present embodiment, each element 21, 22, 2
3, 31, 32, 33, 34, and 35 constitute one element of the observation means.

As described above, the CCD 3 is used in this embodiment.
The positional relationship of the wafer 2 is obtained by observing (measuring) the positions of the mark images formed on the four surfaces. For example, the deviation of the mark image from the reference position (reference mark) on the CCD 34 surface is obtained.

In this embodiment, a plurality of observation means for detecting marks on the surface of the wafer 2 and means for aligning the reticle and the main body are provided symmetrically with respect to the optical axis of the projection lens system 1.

In this embodiment, the reticle 3 is used as described above.
And the wafer 2 are accurately aligned relative to each other, and then the pattern on the surface of the reticle 3 is projected and exposed on the surface of the wafer 2 by the projection lens system 1, and a semiconductor device is manufactured through a known developing process.

Next, the optical function of the correction optical system 101 in this embodiment will be described. Generally, in the projection optical system, the AA mark on the surface of the wafer 2 is the projection optical system 1 as described above.
When the projection optical system 1 has a spherical aberration of the pupil at this time, the incident angle of the principal ray exiting the projection optical system 1 onto the wafer 2 surface is changed. It deviates from the vertical.

In this embodiment, the correction optical system 101 corrects the defocus characteristic.

Measurement of defocus characteristics 1. Drive θ-Z in the Z direction by -a from the best focus surface. 2. The mark position is measured and the value is set to f (-a). 3. Drive θ-Z in the Z direction by + a from the best focus surface. 4. The mark position is measured and the value is defined as f (a). 5. The defocus characteristic Δ = (f (a) -f (-a)) / 2a is calculated.

Although two points have been described this time, more points may be measured. The orientation of the plane parallel plate of the microscope circle is changed so that the absolute value of Δ is minimized, and the inclination of the chief ray on the wafer surface is controlled.

FIG. 2 shows the correction optical system (parallel plane plate) 1 of FIG.
It is a principal part schematic which expanded the optical path of 01 vicinity. As shown in the figure, after the parallel light (observation light) from the relay lens 31 passes through the plane-parallel plate 101, it is parallelly decentered (shifted) with respect to the optical axis L and passes through the diaphragm 23, and then the objective lens 22 causes the reticle 3 to move. It is focused on the surface.

Now, the refractive index of the material of the plane-parallel plate 101 is n, the incident angle of the observation light La on the plane-parallel plate 101 is α, the thickness of the plane-parallel plate 101 is d, and the plane-parallel plate 1 of the observation light La.
If the shift amount after passing 01 is S, then S = (d / cos α) sin (α−θ) (1) However, θ = sin ⁻¹ (sin α / n) (2) Therefore, the incident angle θ of the principal ray La1 on the reticle 3
_i is θ _i = tan ⁻¹ (S / f) (3). However, f is the focal length of the objective lens 22.
By thus inclining the plane-parallel plate 101, the incident angle θ _i on the reticle 3 can be controlled.

Specific values of the relationship between θ _i and α are as follows: If d = 10 mm n = 1.5 f = 50 mm, then α≈14 ° for θ _i = 1 °. In the conventional example, α = 0.5 °, and in the present invention, the driving angle for correction can be made larger than in the conventional example (Japanese Patent Laid-Open No. 63-32303), driving and detection are easy, and the driving resolution is also high. Improved, and the correction accuracy is improved.

FIGS. 3A, 3B and 3C are schematic views of the optical path when the principal ray La1 passing through the correction optical system 101 is incident on the wafer 2 surface via the projection lens system 1. .

The drawing shows a correction method for making the wafer surface 2 and the principal ray La1 at each image height of the projection optical system 1 perpendicular (hereinafter referred to as "wafer side telecentricity"). When the spherical aberration of the pupil as shown in FIG. 12 remains in the projection optical system 1, in order to make the wafer side telecentric at the image height of FIG.
It is necessary to generate the spherical aberration of the pupil d ₁ at the position of the diaphragm 10 inside. Therefore, the plane parallel plate 101 is angled + θ
Tilt ₁ As a result, the principal ray La1 is shifted, and the incident angle of the principal ray La1 on the reticle 3 causes the spherical aberration d _{1 of the} pupil necessary for the wafer-side telecentricity at the diaphragm 10 in the projection optical system 1. Angle.
Therefore, at the image height A, the plane parallel plate 101 is tilted at an angle θ ₁
This realizes the telecentricity on the wafer side.

Similarly, at the image height B shown in FIG. 3B, the spherical aberration of the pupil required to obtain the telecentricity on the wafer side is zero. At the image height C in FIG. 3C, the necessary spherical aberration of the pupil is + d ₂ . For this reason, the plane parallel plates 101 are inclined at an angle of 0 and an angle of −θ ₁ respectively.

As described above, in this embodiment, the angle of the plane-parallel plate 101 is automatically corrected according to the image height to achieve the correction of the defocus characteristic. As a result, even if the focus is defocused during the alignment measurement for some reason, the position measurement value does not change as shown in FIG.

FIGS. 4, 5 and 6 are explanatory views of a drive mechanism for driving the plane parallel plate 101 for correcting the defocus characteristic in this embodiment. 4 is a plan view, FIG. 5 is a front view, and FIG. 6 is a perspective view. 4 to 6, 101 is a plane-parallel plate, 102 is a holder for fixing the plane-parallel plate, 103 is a motor for driving the plane-parallel plate 101 to rotate about the X axis, and 104 is holder 102 for fixing the motor shaft. Set screw 105, a photo switch 105 for detecting the origin position when driven by the motor 103, 106
Is a light blocking plate for blocking the photo switch 105, 107
Is a base for fixing the motor.

110 is a motor for driving the plane-parallel plate 101 to rotate about the Z-axis, 111 is a plate for fixing the motor,
112 is a base, 113 is a gear a for transmitting the rotation of the motor 110, 114 is a set screw for fixing the gear a113 to the motor shaft, 115 is a gear b for transmitting the rotation of the gear a113, 116 is a gear a113, A shaft for transmitting the rotation of the motor 110 via the gear b115, 117 is a set screw for fixing the gear b to the shaft 116, and 118 is a shaft 1
A bearing that supports 16; 119, a holder that holds the bearing; 120, a photo switch for detecting the origin position when rotationally driving around the Z axis; 121, a light shielding plate for shielding the photo switch.

Next, the operation will be described.

(B) Rotation around the X axis The plane parallel plate 101 is fixed to the holder 102, and the holder 1
02 is directly connected to the output shaft of the motor 103. The rotation of the motor 103 causes the plane-parallel plate 101 to rotate about the X axis. Light-shielding plate 10 fixed to holder 102
6 is the position where the photo switch 105 is shielded from the origin,
When the motor 103 rotates to the target position from there, the plane parallel plate 101 rotates about the X axis to the target position.

(B) Rotation around the Z-axis The rotation around the Z-axis is performed by rotating the shaft 116 arranged coaxially with the Z-axis center of the plane-parallel plate 101. The base 107 holds the drive system around the X axis and is fixed to the shaft 116. The rotation around the Z axis rotates the entire drive system around the X axis. Thereby, the X axis and the Z axis are driven independently. The rotation of the shaft 116 is performed by the motor 110 through a gear b115 and a gear a113 fixed to the shaft 116.
Driven by The detection of the origin is performed by blocking the photoswitch 120 with a light blocking plate 121 fixed to the base 107.

The above configuration achieves automatic correction of the defocus characteristic.

FIG. 7 is a schematic view of the essential portions of Embodiment 2 of the projection exposure apparatus of the present invention. This embodiment is different from Embodiment 1 in FIG. 1 in that the beam splitter 32 is provided between the relay lens 31 and the diaphragm 23 and the plane parallel plate 20 as a correction optical system is provided.
1 is provided between the observation illumination system 35 and the beam splitter 32, and is driven and controlled by the drive means 200, and the other configurations are the same.

In the figure, the observation light from the observation illumination system 35 is reflected by the beam splitter 32 via the plane-parallel plate 201, then passes through the diaphragm 23, and enters the objective lens 22. The subsequent optical path is the same as that of the first embodiment shown in FIG.

In this embodiment, the angle of the plane-parallel plate 201 is tilted according to the observation image height of the projection optical system 1 in the same manner as in Embodiment 1 of FIG. 1 to achieve the correction of the defocus characteristic at all image heights. are doing.

The present embodiment is characterized in that the inclination of the plane-parallel plate 201 does not affect the image forming performance of the AA mark image on the surface of the image pickup device 34.

FIG. 8 is a schematic view of the essential portions of a third embodiment of the projection exposure apparatus of the present invention. The present embodiment is different from the first embodiment in FIG. 1 in that a parallel plane plate 301 as a correction optical system is arranged between the diaphragm 23 and the objective lens 22 and the drive means 300 controls the drive. , And other configurations are the same.

In the figure, the observation light from the observation illumination system 35 is reflected by the beam splitter 32 and is reflected by the relay lens 3.
The light is incident on the beam No. 1 and is emitted as parallel light (afocal) from the relay lens 31. The observation light from the relay lens 31 passes through the diaphragm 23 and enters the objective lens 22 via the plane-parallel plate 301. The subsequent optical path is similar to that of the first embodiment shown in FIG.

In this embodiment, the plane parallel plate 301 is the diaphragm 23.
Since it is closer to the objective lens 22 side, the observation beam is
Pass through the center of. Therefore, the 0th-order diffracted light reflected by the wafer surface perpendicular to the observation light also passes through the center of the diaphragm 23. Therefore, the posture of the plane-parallel plate 301 is monitored by monitoring the shift amount between the center of the diaphragm 23 and the center of the 0th-order diffracted light with an optical system arranged on the relay lens 31 side with respect to the diaphragm 23. This ensures the correction of the defocus characteristic even at the entire image height.

FIG. 9 is a schematic view of the essential portions of Embodiment 4 of the projection exposure apparatus of the present invention. This embodiment uses a wedge member 401 having a plurality of transparent prisms (wedges) as a correction optical system as compared with the first embodiment shown in FIG. 1, and selects one of the wedge members 401 to select a beam splitter. 32 and relay lens 31
And a wedge having a target angle according to the observation image height is arranged in the optical path by the drive mechanism 400 based on a command from the computer 41. The difference is that the same effect as that of the first embodiment is obtained by changing the optical path of, and other configurations are the same.

In the figure, the observation light from the observation illumination system 35 is reflected by the beam splitter 32 and is reflected by the wedge member 401.
It is incident on the relay lens 31 via two wedges. The parallel light from the relay lens 31 passes through the diaphragm 23 and enters the objective lens 22. The subsequent optical path is similar to that of the first embodiment shown in FIG.

In this embodiment, the observation image height is limited, and it is most suitable when it is not necessary to correct the wafer side telecentricity for continuous image heights. When changing the image height, it is only necessary to replace the wedge, so there is no need to control the posture of the plane-parallel plate, and it has the advantage that it can be switched at high speed.

FIG. 10 shows a fifth embodiment of the projection exposure apparatus of the present invention.
FIG. In this embodiment, as compared with the first embodiment shown in FIG. 1, two transparent wedges 50 of the same quality and the same shape are used as a correction optical system.
A wedge member in which 1 and 502 are arranged to face each other is arranged between the relay lens 31 and the diaphragm 23, and based on a command from the computer 41, the drive mechanism 500 drives the two wedges 501 in accordance with the observed image height. The optical path of the observation light is displaced by changing the interval of 502 and rotating both with the optical axis as a rotation axis, which is different from that in which the same effect as in Example 1 is obtained. Have the same configuration.

In the figure, the observation light from the observation illumination system 35 is reflected by the beam splitter 32 and is reflected by the relay lens 31.
Becomes parallel light and passes through the wedges 501 and 502, and the diaphragm 23
Is incident on. The optical path of the observation light from the diaphragm 23 is the same as that in the first embodiment shown in FIG.

In this embodiment, since two transparent wedges 501 and 502 having the same shape and the same material and facing each other are used, the asymmetrical aberration generated by the wedges can be canceled and a good image is always obtained. Since it can be obtained, there is a feature that highly accurate alignment can be achieved.

FIG. 11 is a sixth embodiment of the projection exposure apparatus of the present invention.
FIG. In this embodiment, as compared with the first embodiment of FIG. 1, each element 21, 22, 23, 31, 32, 33, 34 of the observation means for observing the AA mark on the surface of the wafer 2 is provided with the reticle 3 and the projection lens system 1. Between them and not through the reticle 3, a luminous flux (non-exposure light) having a different wavelength from the exposure light is used as the observation light from the observation illumination system 610, and the exposure light is used as the observation light. In order to correct various aberrations such as coma and astigmatism generated from the projection lens system 1 due to the use of lights having different wavelengths, the aberration correction lens 24 is provided between the mirror 21 and the projection lens 1. They are different in that they are arranged between them, and other configurations are the same.

In this embodiment, the aberration correction lens 24 and the diaphragm 2
3, the objective lens 22, the mirror 21 and the like are moved by the moving mechanism 60 in a direction parallel to the surface of the reticle 3 to change the observation image height.

In the present embodiment, the observation light from the observation illumination system 610 is changed in order by the beam splitter 32 and the relay lens 3.
1, the correction optical system 601, the diaphragm 23, the objective lens 22, and the optical path to the mirror 21 are the same as in the first embodiment of FIG.

As compared with the first embodiment, the observation light from the mirror 21 is incident on the projection lens system 1 via the aberration correction lens 24, and the reflected light from the AA mark on the wafer surface 2 is the projection lens 1. The difference is that the light passes through and is reflected by the mirror 21 via the aberration correction lens 24.
Other configurations are the same.

In each of the above embodiments, the case where the AA mark on the surface of the reticle 3 or the surface of the wafer 2 is observed to align the reticle 3 and the wafer 2 has been described, but the correction optical system according to the present invention is used. If used, it is possible to detect the sharpness of the mark on the surface of the wafer 2, that is, the focus state, and drive and control the θ-Z stage 7 so that the wafer 2 is positioned on the best image plane of the projection optical system 1. That is, the correction optical system can be similarly applied as an automatic focus detection system.

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

FIG. 14 shows a flow of manufacturing a semiconductor device (semiconductor chip such as IC or LSI, or liquid crystal panel, CCD or the like). In step 1 (circuit design), the circuit of the semiconductor device is designed. In step 2 (mask manufacturing), a mask having the designed circuit pattern is manufactured.

On the other hand, in step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4
The (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by a lithography technique using the mask and the wafer prepared above.

The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip by using the wafer manufactured in step 4, an assembly process (dicing, bonding), a packaging process (chip encapsulation). Etc. are included. In step 6 (inspection), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and a durability test. Through these steps, the semiconductor device is completed and shipped (step 7).

FIG. 15 shows a detailed flow of the wafer process. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed on the wafer surface. In step 13 (electrode formation), electrodes are formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted in the wafer. Step 1
In 5 (resist processing), a photosensitive agent is applied to the wafer.

In step 16 (exposure), the circuit pattern of the mask is printed and exposed on the wafer by the exposure apparatus described above. In step 17 (development), the exposed wafer is developed. In step 18 (etching), parts other than the developed resist image are removed. In step 19 (resist peeling), the resist that has become unnecessary due to etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

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

[0087]

As described above, according to the present invention, when the alignment mark on the wafer (second object) surface is observed through the projection optical system, some spherical aberration remains in the pupil of the projection optical system. And a projection exposure apparatus which can easily obtain a highly integrated semiconductor device by correcting the defocus characteristics at various image heights to perform the relative alignment between the reticle (first object) and the wafer with high accuracy. A semiconductor device manufacturing method using the same can be achieved.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram when a part of the optical path of FIG. 1 is expanded.

FIG. 3 is an explanatory diagram when an optical path of a part of FIG. 1 is expanded.

FIG. 4 is a schematic view of a main part of a driving mechanism of a correction optical system according to the present invention.

FIG. 5 is a schematic view of a main part of a driving mechanism of a correction optical system according to the present invention.

FIG. 6 is a schematic view of a main part of a driving mechanism of a correction optical system according to the present invention.

FIG. 7 is a schematic view of the essential portions of Embodiment 2 of the projection exposure apparatus of the present invention.

FIG. 8 is a schematic view of the essential portions of Embodiment 3 of the projection exposure apparatus of the present invention.

FIG. 9 is a schematic view of the essential portions of Embodiment 4 of the projection exposure apparatus of the present invention.

FIG. 10 is a schematic view of the essential portions of Embodiment 5 of the projection exposure apparatus of the present invention.

FIG. 11 is a schematic view of the essential portions of Embodiment 6 of the projection exposure apparatus of the present invention.

FIG. 12 is an explanatory diagram of spherical aberration of the pupil of the projection optical system.

FIG. 13 is an explanatory diagram of defocus characteristics of the projection optical system.

FIG. 14 is a flowchart of a method for manufacturing a semiconductor device of the present invention.

FIG. 15 is a flowchart of a method for manufacturing a semiconductor device of the present invention.

[Explanation of symbols]

1 Projection Lens 2 Wafer 3 Reticle 4,35 Illumination Optical System 5 XY Stage 6 Tilt Stage 7 θ-Z Stage 8 Wafer Chuck 9 Fiducial Mark 10 Aperture 11 Bar Mirror 12 Laser Interferometer 21 Mirror 22 Objective Lens 23 Aperture 24 Correction optical system 31 Relay lens 32 Beam splitter 33 Erector 34 CCD camera 36 Light guide 41 Computer 100,200,300,400,500,600
Drive mechanism 101, 201, 301, 601 Parallel plane plate 102, 119 Holder 103, 110 Motor 104, 114, 117 Set screw 105, 120 Photo switch 106, 121 Light-shielding plate 107, 112 Base 111 Plate for fixing motor 113 Gear a 115 gear b 116 shaft 118 bearing 401, 402, 501, 502 wedge

Claims (9)

[Claims] 1. An exit telecentric projection lens system for projecting a pattern of a first object illuminated by exposure light from an exposure illumination system onto a second object, and an illumination system for observing marks provided on the second object. By observing the image formation position on the predetermined surface of the mark through the projection lens system while illuminating it with the observation light from, the relative distance between the first object and the second object can be increased. In the projection exposure apparatus, the observing means includes the observing means for detecting the positional relationship and the means for measuring the measurement error of the measurement value by the observing means due to the focus error on the second object side of the projection lens.
It has a moving mechanism capable of arbitrarily changing the observation position of the mark of the object and a correction optical system for adjusting the optical path of the principal ray of the observation light in order to minimize the measurement error. Projection exposure system. 2. The observing means has a lens system that uses the observation light from the observing illumination system as afocal light, and the correction optical system adjusts the inclination about axes perpendicular to the optical axis and orthogonal to each other. It has a possible transparent plane-parallel plate, the plane-parallel plate is provided in the afocal optical path, and the tilt of the plane-parallel plate is adjusted to shift the optical path of the observation light parallel to the optical axis. The projection exposure apparatus according to claim 1, wherein: 3. The observing means has a lens system for emitting observation light from the observing illumination system as afocal light, and the correction optical system is tilted with the optical axis as a rotation center in a state of facing each other. A wedge member having two transparent wedges which are capable of changing the distance between the two.
Two wedges are provided in the afocal optical path, and
The optical path of the observation light is shifted in parallel to the optical axis by adjusting the inclination and interval of the two wedges.
Projection exposure equipment. 4. The correction optical system has a wedge member composed of a plurality of wedges having different angles, and one of the plurality of wedges is selected and placed in the optical path to set the optical path of the observation light. The projection exposure apparatus according to claim 1, wherein the projection exposure apparatus is adjusted. 5. The correction optical system adjusts the optical path of the observation light according to the change of the observation position of the mark on the second object plane by the moving mechanism.
Or the projection exposure apparatus of 4. 6. After observing a pattern on a reticle surface illuminated with exposure light onto a wafer surface by a projection telecentric projection lens system, the wafer is observed by a observing means when a semiconductor device is manufactured through a developing process. The mark on the wafer surface is illuminated with the observation light from the observation illumination system through the projection lens system, and the image formation position of the mark on the predetermined surface is observed through the projection lens system to obtain the reticle. The relative position between the wafer and the wafer is detected, and when the observation position of the mark on the wafer surface is arbitrarily changed by the movement mechanism, the measurement error is minimized by the correction optical system, A method of manufacturing a semiconductor device, characterized in that an optical path of a light beam is adjusted. 7. The observing means has a lens system that uses the observation light from the observing illumination system as afocal light, and the correction optical system adjusts inclination around axes perpendicular to the optical axis and orthogonal to each other. It has a possible transparent plane-parallel plate, the plane-parallel plate is provided in the afocal optical path, and the tilt of the plane-parallel plate is adjusted to shift the optical path of the observation light parallel to the optical axis. The method for manufacturing a semiconductor device according to claim 6, wherein 8. The observing means has a lens system for emitting the observation light from the observing illumination system as afocal light, and the correction optical system is tilted with the optical axis as a rotation center in a state of facing each other. A wedge member having two transparent wedges, which are possible and whose intervals can be arbitrarily changed.
Two wedges are provided in the afocal optical path, and
7. The optical path of the observation light is shifted parallel to the optical axis by adjusting the inclination and spacing of the two wedges.
Of manufacturing a semiconductor device. 9. The correction optical system has a wedge member composed of a plurality of wedges having different angles, and one of the plurality of wedges is selected and placed in the optical path to set the optical path of the observation light. 7. The method for manufacturing a semiconductor device according to claim 6, wherein the adjustment is performed.