JP3352280B2 - Projection exposure apparatus adjusting method and exposure method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting a projection exposure apparatus.
And a method of exposing a fine electronic circuit pattern such as an IC or LSI formed on a reticle (first object) surface onto a wafer (second object) surface by a projection lens system (projection optical system). In addition, when manufacturing a semiconductor device, the relative positional relationship between a reticle and a wafer is detected with high accuracy, and this is suitable for manufacturing a highly integrated semiconductor device.

[0002]

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

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

For example, light that does not expose a resist applied on a wafer (hereinafter referred to as “non-exposure light”), for example,
There is a method of detecting an alignment mark on a wafer using light having a wavelength of 633 nm from a He-Ne laser through a projection lens system (TTL), a so-called TTL off-axis method. In the TTL off-axis method, since a large amount of chromatic aberration occurs in the projection lens system, it is generally not possible to simultaneously observe the wafer and the reticle at the exposure position. For this reason, it is necessary to manage the fluctuation 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, a so-called TT for detecting an alignment mark on a wafer surface through a projection lens system using exposure light.
There is an L-on-axis system. A projection exposure apparatus using this TTL on-axis method is disclosed in, for example, Japanese Patent Application Laid-Open No. 58-256.
No. 38 and Japanese Patent Application Laid-Open No. 63-32303.

In these publications, a circuit pattern of a reticle is projected and exposed on a wafer by a projection lens system using light (exposure light) of g-line (436 nm), while a wavelength radiated from a He-Cd laser to an alignment system. Using 442 nm light (alignment light), each alignment mark on the reticle and the wafer is detected. Then, 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 advantage is that the principal 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 or reflected on the reticle surface remains unchanged. By utilizing this property, a highly accurate TTL on-axis system is configured. Note that the TTL on-axis system is to perform alignment between the reticle and the wafer in a state where exposure is performed via a projection optical system for exposure.

Japanese Patent Application Laid-Open No. 63-56917 has proposed a method of deflecting the angle of a principal ray of an illumination light beam of an observation device. In this publication, the relative position between the optical axis of the projection optical system and the observation position on the reticle side of the alignment optical system is detected, and the illumination light flux of the observation device is adjusted by the inclination angle of the principal ray of the projection lens obtained in advance according to the detected information. This deflects the chief ray angle.

[0009]

When observing an alignment mark on a wafer surface through a projection lens system, an alignment mark only at a specific position (image height) on the optical axis of the projection optical system is observed. For example, the principal 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 must be changed due to the reticle, etc.
There are times when it is necessary to change the observation image height to perform on-axis alignment or to arrange alignment marks and the like. At this time, if 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 perpendicular.

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

In FIG. 12, reference numeral 1 denotes a projection optical system in which the wafer 2 is telecentric, 2 denotes a wafer, 3 denotes a reticle pattern surface, and 10 denotes a stop in the projection optical system 1. If the pupil of the projection optical system 1 has spherical aberration, the image heights A, B, and C in FIG.
In order for the principal ray of the observation light to make the wafer surface 2 perpendicular to any image height on the wafer 2 side, the reticle 3 having the image height A
The angle of incidence of the principal ray on the reticle 3 must be inclined by + θ at the position corresponding to the reticle side of the image height B, and at -θ at the position corresponding to the reticle side at the image height C. Unless the angle of incidence on the reticle 3 is changed according to each image height, the angle of incidence of the observation light on the wafer 2 is
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 alignment mark position measurement value is shifted so as delta ₂ in focus. For this reason, the + side is Δ ₁ / D ₊ per ₁ μm defocus, and the Δ side is Δ ₂ / D ₋ per 1 μm defocus, and the measured value of the alignment mark depends on the defocus amount (hereinafter referred to as “defocus”). Called "characteristics").

In JP-A-63-32303, correction is performed by changing the attitude of some optical elements of the alignment illumination system. Specifically, the angle of a mirror or the like in the optical path is changed. For this reason, the angle to be changed for correction is half of the angle required as the incident angle on the reticle side, which is a minute angle, and it has been difficult to ensure high correction accuracy.

In the above-mentioned Japanese Patent Application 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 determined in advance in accordance with the detected information. The angle of the principal ray of the illumination light beam of the observation device is deflected by an angle corresponding to the amount. For this reason, the correction accuracy includes the detection accuracy of the relative position between the projection lens optical axis and the observation position.

When a 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 a design value, an adjustment error due to assembling remains and becomes a correction error.

In the case where the amount of deviation is obtained by measurement, there is a problem that the correction accuracy is lowered due to a change over time due to replacement of the observation light source or the like. Even when the correction table is regularly measured, data at the entire image height must be re-measured, which takes a long time.

Even when the correction table is measured periodically,
A problem arises in that data at the entire image height must be re-measured, which takes a lot of time.

Further, a measurement error caused by a focus error due to a factor other than a shift amount of the telecentricity of the projection lens cannot be corrected. For example, when there is another component (when the component moves obliquely) due to the Z drive, a measurement error due to a focus error occurs.

As described above, correction of a factor which cannot be performed by the correction table cannot be performed by the conventional system, and high-precision alignment cannot be expected at all.

According to the present invention, when observing an alignment mark on a wafer (second object) surface via a projection optical system, exposure is performed at various image heights even if some spherical aberration remains in a pupil of the projection optical system. A projection exposure apparatus that enables high-precision relative alignment between a reticle (first object) and a wafer by allowing a chief ray of light to be perpendicularly incident on the wafer surface, thereby easily obtaining a highly integrated semiconductor device. Adjustment method and exposure method .

[0022]

According to the first aspect of the present invention, there is provided a projection exposure apparatus.
Adjustment method for an optical device, the pattern of the reticle onto the wafer
A projection optical system in which the light exit side to be projected is telecentric,
The mark on the wafer side is projected onto the projection light using the exposure light.
Illuminating through a system, and projecting light from the mark
Observation means for making the light incident on the image sensor via a scientific system
In the method of adjusting a projection exposure apparatus ,
The mark at the position defocused from the best focus plane
Measurement of the position of the mark
Measuring the defocus characteristic of the observation means,
Correction optical system to minimize the defocus characteristic
Adjusting the optical path of the principal ray of the exposure light.
It is characterized by:

The exposure method according to the second aspect of the present invention provides the exposure method according to the first aspect.
Retick the projection exposure apparatus adjusted by the adjustment method described
After supplying the wafer and the wafer and aligning them,
Exposing the wafer with the reticle pattern.
Features.

A method for manufacturing a semiconductor device according to a third aspect of the present invention.
The projection adjusted by the adjustment method according to claim 1.
Expose the wafer with the reticle pattern using the exposure tool
And developing the exposed wafer.
It is characterized by.

The invention of claim 4 is the invention according to claim 1.
The observation means uses the exposure light as afocal light
A lens system, wherein the correction optical system is perpendicular to the optical axis and
Transparent parallel plane whose inclination can be adjusted about an axis perpendicular to
A plate, wherein the plane-parallel plate is in the optical path of the afocal light.
And adjusting the inclination of the plane-parallel plate to adjust the exposure.
The feature is that the optical path of light is shifted in parallel.
You.

The invention of claim 5 is the invention according to claim 1.
The observation means uses the exposure light as afocal light.
A lens system for emitting light, and the correction optical systems are paired with each other.
The tilt can be adjusted with the optical axis as the center of rotation when facing
Has two transparent wedges that can change the distance between
A wedge member, and the two wedges are light beams of the afocal light.
It is provided in the road and adjusts the inclination and interval of the two wedges.
And the optical path of the exposure light is shifted in parallel.
And

[0027] The invention of claim 6 is the invention according to claim 1.
The correction optical system is a wedge composed of a plurality of wedges having different angles.
A member, and selecting one of the plurality of wedges to light
That the optical path of the exposure light is adjusted by arranging it in a path.
Features.

The invention of claim 7 is the invention according to claim 1.
The correction optical system is moved forward with the change of the mark position.
The optical path of the exposure light is adjusted.

[0029]

[0030]

[0031]

[0032]

FIG. 1 is a schematic view of a main part of an optical system of a projection exposure apparatus for manufacturing a semiconductor device according to a first embodiment of the present invention. In FIG. 1, reference numeral 3 denotes a reticle as a first object, which is mounted on a reticle stage 3a and illuminated by exposure light from an exposure illumination system 4. Reference numeral 2 denotes a wafer as a second object, on which an alignment mark (AA mark) is provided. Reference numeral 1 denotes a projection optical system (projection lens system) which is composed of an emission telecentric system and projects a circuit pattern or the like on the reticle 3 surface onto the wafer 2 surface. Reference numeral 10 denotes a stop 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, and performs θ rotation and focus adjustment of the wafer 2, 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 stage position measurement 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 is connected to the XY stage 5
Is monitored, and the position is controlled by the computer 41 through the line. Non-TTL on the tilt stage 6
A fiducial mark 9 for alignment is provided.

The alignment (alignment) between the reticle 3 and the wafer 2 in the present embodiment is performed indirectly by aligning each of the reference marks whose positional relationship is required in advance. Alternatively, exposure is performed by actually aligning a resist image pattern or the like, measuring an error (offset), and thereafter performing offset processing in consideration of the value.

Next, marks (alignment) on the two surfaces of the wafer
A method for detecting the position of the image using the observation means will be described. 35 is an illumination system for observation. Exposure light is introduced as observation light into the observation illumination system 35 from the exposure illumination system 4 through the fiber 36. The 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), displaces the optical path via the correction optical system 101 composed of a transparent plane-parallel plate, passes through the diaphragm 23, and enters the objective lens 22. .

The objective lens 22 corrects aberrations of an object at infinity. Further, the correction optical system 101 is disposed at a position other than the pupil plane of the objective lens 22 during the afocal period. The correction optical system 101 can be tilted about two axes perpendicular to the optical axis and perpendicular to each other by the driving unit 100. The attitude of the correction optical system 101 at this time is controlled by a computer 41 described later.

The observation light from the objective lens 22 is
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. This changes the observation image height on the wafer 2 surface.
The moving mechanism 20 is controlled by a computer 41 through a line. The distance between the objective lens 22 and the relay lens 31 is changed by the moving mechanism 20, but this optical path is afocal so as not to affect the imaging state. Note that a mechanism for correcting the optical path length in conjunction 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, passes through the aperture 10 therein, and illuminates an alignment mark (AA mark) on the surface of the wafer 2. At this time, as described later, the angle of the principal ray of the observation light is deflected by using the correction optical system 101 even when the observation image height changes, thereby correcting the defocus characteristic. A on wafer 2
The reflected light from the A mark returns to the original optical path, and sequentially returns to the projection lens system 1, the mirror 21, the objective lens 22, and the correction optical system 10.
1. The light enters the image pickup device (CCD camera) 34 via the relay lens 31, the beam splitter 32, and the erector lens 33, and forms an image (AA mark image) on the wafer 2 and the reticle 3 on the surface. I have an image.

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

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

As described above, in this embodiment, the CCD 3
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, a deviation of a mark image from a reference position (reference mark) on the surface of the CCD 34 is determined.

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

In this embodiment, the reticle 3
The relative positioning between the wafer and the wafer 2 is performed with high precision, and then the pattern on the reticle 3 surface is projected and exposed on the wafer 2 surface by the projection lens system 1, and a semiconductor device is manufactured through a known development process.

Next, the optical operation of the correction optical system 101 in this embodiment will be described. Generally, in the projection optical system, the AA mark on the wafer 2 surface is
If the projection optical system 1 has a pupil spherical aberration, the incident angle of the principal ray exiting the projection optical system 1 on the wafer 2 surface is changed. Deviates from vertical.

In this embodiment, the defocus characteristic is corrected by the correction optical system 101.

Measurement of Defocus Characteristics Θ-Z is driven in the Z direction by −a from the best focus plane. 2. The mark position is measured and its value is set to f (−a). 3. Θ-Z is driven in the Z direction by + a from the best focus plane. 4. The mark position is measured and its value is set to f (a). 5. The defocus characteristic Δ = (f (a) −f (−a)) / 2a is calculated.

Although the above description has been made with reference to two points, more points may be measured. The attitude 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 principal ray on the wafer surface is controlled.

FIG. 2 shows the correction optical system (parallel plane plate) 1 of FIG.
It is the principal part schematic diagram which developed the optical path near 01. As shown in the drawing, the parallel light (observation light) from the relay lens 31 passes through the parallel flat plate 101, is decentered (shifted) parallel to the optical axis L, passes through the diaphragm 23, and is passed through the diaphragm 23. It is focused on the surface.

Now, the refractive index of the material of the parallel flat plate 101 is n, the incident angle of the observation light La to the parallel flat plate 101 is α, the thickness of the parallel flat plate 101 is d, and the parallel flat plate 1 of the observation light La is 1
Assuming that the shift amount after passing through 01 is S, S = (d / cos α) sin (α−θ) ‥‥‥ (1) Here, θ = sin ⁻¹ (sin α / n) ‥‥‥ (2). Therefore, the incident angle θ of the principal ray La1 on the reticle 3
_i is given by θ _i = tan ⁻¹ (S / f)） (3) Here, f is the focal length of the objective lens 22.
By inclining the plane-parallel plate 101 in this manner, the incident angle θ _i to the reticle 3 can be controlled.

When a specific numerical value is shown for the relationship between θ _i and α, if d = 10 mm and n = 1.5 f = 50 mm, α ≒ 14 ° is obtained in order to set θ _i = 1 °. According to the conventional example, α = 0.5 °. In the present invention, the driving angle for correction can be larger than that of the conventional example (Japanese Patent Laid-Open No. 63-30330), driving and detection are facilitated, and driving resolution is improved. The correction accuracy has been improved.

FIGS. 3A, 3B, and 3C are schematic diagrams of the optical path when the principal ray La1 that has passed through the correction optical system 101 enters the surface of the wafer 2 via the projection lens system 1. FIG. .

FIG. 3 shows a correction method for making the wafer surface 2 perpendicular to the principal ray La1 at each image height of the projection optical system 1 (hereinafter referred to as "wafer side telecentricity"). When spherical aberration of the pupil as shown in FIG. 12 remains in the projection optical system 1, the projection optical system 1 is used to make the wafer side telecentric at the image height of FIG.
It is necessary to generate the spherical aberration of the pupil of d ₁ at the position of the stop 10 of the inner. Therefore, the parallel flat plate 101 is set to the angle + θ.
Tilt _one . Whereby the principal ray La1 is shifted, the angle of incidence on the reticle 3 principal ray La1 is for generating a spherical aberration d ₁ of the pupil required to the wafer side telecentricity in aperture 10 of the projection optical system 1 Angle.
Therefore, at the image height A, the parallel flat plate 101 is inclined at an angle θ ₁ ,
Thereby, wafer side telecentricity is realized.

Similarly, at the image height B in FIG. 3B, the spherical aberration of the pupil necessary for achieving the telecentricity on the wafer side is zero. At the image height C in FIG. 3C, the required spherical aberration of the pupil is + d ₂ . Therefore the angle 0 plane-parallel plate 101, respectively, is inclined an angle - [theta] _1.

As described above, in this embodiment, the correction of the defocus characteristic is achieved by automatically correcting the angle of the parallel flat plate 101 according to the image height. This prevents a change in the position measurement value as shown in FIG. 13 even if defocusing occurs during alignment measurement for some reason.

FIGS. 4, 5, and 6 are explanatory views of a driving mechanism for driving the parallel flat plate 101 for correcting the defocus characteristic in the present embodiment. 4 is a plan view, FIG. 5 is a front view, and FIG. 6 is a perspective view. 4 to 6, reference numeral 101 denotes a parallel flat plate, 102 denotes a holder for fixing the parallel flat plate, 103 denotes a motor for driving the parallel flat plate 101 to rotate around the X axis, and 104 denotes a holder for fixing the holder 102 to the motor shaft. Screw 105 for detecting the origin position when driven by the motor 103, 106
Denotes a light shielding plate for shielding the photo switch 105 from light;
Is a base for fixing the motor.

Reference numeral 110 denotes a motor for rotating the parallel flat plate 101 around the Z axis, 111 denotes 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 b 115, 117 is a set screw for fixing the gear b to the shaft 116, and 118 is a shaft 1
Reference numeral 119 denotes a bearing for holding the bearing, reference numeral 119 denotes a holder for holding the bearing, reference numeral 120 denotes a photo switch for detecting the origin position when rotating around the Z axis, and reference numeral 121 denotes a light shielding plate for shielding the photo switch from light.

Next, the operation will be described.

(A) Rotation about the X-axis The parallel flat plate 101 is fixed to the holder 102 and the holder 1
Reference numeral 02 is directly connected to the output shaft of the motor 103. When the motor 103 rotates, the parallel flat plate 101 rotates around the X axis. Light shield plate 10 fixed to holder 102
6, the position where the photo switch 105 is shielded from light is set as the origin,
When the motor 103 rotates to the target position, the parallel flat plate 101 rotates around the X axis to the target position.

(B) Rotation around Z-axis Rotation around the Z-axis is performed by rotating a shaft 116 coaxially arranged 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 about the Z axis rotates the entire drive system about the X axis. Thus, driving is independently performed on each of the X axis and the Z axis. The rotation of the shaft 116 is performed by a motor 110 via a gear b 115 and a gear 113 fixed to the shaft 116.
Driven by The origin is detected by the light shielding plate 121 fixed to the base 107 shielding the photo switch 120 from light.

The above configuration achieves automatic correction of the defocus characteristic.

FIG. 7 is a schematic view of a main part of a projection exposure apparatus according to a second embodiment of the present invention. In this embodiment, a beam splitter 32 is provided between the relay lens 31 and the stop 23 and the parallel plane plate 20 as a correction optical system is different from the first embodiment of FIG.
1 is provided between the observation illumination system 35 and the beam splitter 32 and is driven and controlled by the driving means 200, and the other configuration is the same.

In the drawing, the observation light from the observation illumination system 35 is reflected by the beam splitter 32 via the parallel plane plate 201, passes through the stop 23, and enters the objective lens 22. Subsequent optical paths are the same as in the first embodiment of FIG.

In this embodiment, the angle of the plane parallel plate 201 is inclined in accordance with the observation image height of the projection optical system 1 in the same manner as in the embodiment 1 of FIG. are doing.

This embodiment is characterized in that the inclination of the plane parallel plate 201 does not affect the imaging performance of the AA mark image on the surface of the image sensor 34.

FIG. 8 is a schematic view of a main part of a third embodiment of the projection exposure apparatus according to the present invention. This embodiment is different from the first embodiment shown in FIG. 1 in that a parallel plane plate 301 as a correction optical system is disposed between the diaphragm 23 and the objective lens 22 and the driving unit 300 controls the driving. The other configuration is the same.

In the figure, the observation light from the observation illumination system 35 is reflected by the beam splitter 32 and
1 and exits from the relay lens 31 as parallel light (afocal). Observation light from the relay lens 31 passes through the stop 23 and enters the objective lens 22 via the parallel plane plate 301. Subsequent optical paths are the same as in the first embodiment of FIG.

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

FIG. 9 is a schematic view of a main part of a projection exposure apparatus according to a fourth embodiment 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 in FIG. 1, and selects one of the wedge members 401 to form a beam splitter. 32 and relay lens 31
And a wedge having an angle of interest corresponding to the observation image height is arranged in the optical path by the drive mechanism 400 based on a command from the computer 41, whereby the observation light Are different from each other in that the same effect as that of the first embodiment is obtained by changing the optical path of the first embodiment, and the other configuration is the same.

In the figure, the observation light from the observation illumination system 35 is reflected by the beam splitter 32 and
The light enters the relay lens 31 via two wedges. The parallel light from the relay lens 31 passes through the stop 23 and enters the objective lens 22. Subsequent optical paths are the same as in the first embodiment of FIG.

In the present embodiment, the observation image height is limited, and is optimal when it is not necessary to correct the wafer side telecentricity for a continuous image height. When changing the image height, it is only necessary to change the wedge, so that there is no need to control the attitude of the plane-parallel plate, and it is possible to switch at a high speed.

FIG. 10 shows a projection exposure apparatus according to a fifth embodiment of the present invention.
FIG. In the present embodiment, two transparent wedges 50 of the same quality and the same shape are used as a correction optical system as compared with the first embodiment of FIG.
The wedge member having the first and second wedges 501 and 502 disposed between the relay lens 31 and the diaphragm 23, and the two wedges 501 and 501 according to the observation image height by the driving mechanism 500 based on a command from the computer 41. The optical path of the observation light is displaced by changing the interval of 502 and rotating both of them with the optical axis as the rotation axis, thereby obtaining the same effect as in the first embodiment. Is the same.

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

In this embodiment, since two transparent wedges 501 and 502 of the same shape and the same material which are opposed to each other are used, it is possible to cancel the asymmetrical aberration generated by the wedges and always obtain a good image. Therefore, there is a feature that highly accurate alignment can be achieved.

FIG. 11 shows a sixth embodiment of the projection exposure apparatus according to the present invention.
FIG. In this embodiment, 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 different from that of the first embodiment of FIG. And that no reticle 3 is interposed therebetween, that 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 that 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 light of different wavelengths, the aberration correction lens 24 is connected between the mirror 21 and the projection lens 1. The difference lies in the arrangement between them, and the other configuration is 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 the direction parallel to the reticle 3 surface to change the observation image height.

In this embodiment, the observation light from the observation illumination system 610 is sequentially transmitted to the beam splitter 32 and the relay lens 3.
1. The optical path to the correction optical system 601, the diaphragm 23, the objective lens 22, and the mirror 21 is the same as that of the first embodiment in FIG.

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

In each of the above embodiments, the description has been given of the case where the AA mark on the reticle 3 surface or the wafer 2 surface is observed and the reticle 3 and the wafer 2 are aligned with each other. If it is used, the sharpness of the mark on the surface of the wafer 2, that is, the focus state can be detected, and the drive of the θ-Z stage 7 can be controlled 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 embodiment of a device manufacturing method using the above-described exposure apparatus will be described.

FIG. 14 shows a flow of manufacturing a semiconductor device (a semiconductor chip such as an IC or an LSI, or a liquid crystal panel or a CCD). In step 1 (circuit design), the circuit of the semiconductor device is designed. Step 2 is a process for making a mask on the basis of the circuit pattern design.

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 lithography using the prepared mask and wafer.

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

FIG. 15 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into 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 above-described exposure apparatus. Step 17 (development) develops the exposed wafer. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), the resist that has become unnecessary after the 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 conventionally been difficult to manufacture.

[0087]

As described above, according to the present invention, when observing the alignment mark on the wafer (second object) surface via the projection optical system, some spherical aberration remains in the pupil of the projection optical system. However, in a projection exposure apparatus, the defocus characteristic is corrected at various image heights, the relative positioning between the reticle (first object) and the wafer is performed with high accuracy, and a highly integrated semiconductor device can be easily obtained. An adjustment method and an exposure method can be achieved.

[Brief description of the drawings]

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

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

FIG. 3 is an explanatory diagram when a part of the optical path in FIG. 1 is developed.

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

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

FIG. 6 is a schematic diagram 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 a main part of a projection exposure apparatus according to a second embodiment of the present invention.

FIG. 8 is a schematic diagram of a main part of a third embodiment of the projection exposure apparatus of the present invention.

FIG. 9 is a schematic view of a main part of a projection exposure apparatus according to a fourth embodiment of the present invention.

FIG. 10 is a schematic view of a main part of a projection exposure apparatus according to a fifth embodiment of the present invention.

FIG. 11 is a schematic view of a main part of a projection exposure apparatus according to a sixth embodiment of the present invention.

FIG. 12 is a diagram illustrating spherical aberration of a pupil of a projection optical system.

FIG. 13 is an explanatory diagram of a defocus characteristic of a projection optical system.

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

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

[Explanation of symbols]

Reference Signs List 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 Elector 34 CCD camera 36 Light guide 41 Computer 100, 200, 300, 400, 500, 600
Driving 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 shield plate 107, 112 Base 111 Plate for fixing motor 113 Gear a 115 gear b 116 shaft 118 bearing 401, 402, 501, 502 wedge

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

Claims (7)

(57) [Claims] 1. A reticle pattern is projected onto a wafer.
The projection optical system with a telecentric light emission side and the exposure light
The mark on the wafer side through the projection optical system.
And illuminate the light from the mark through the projection optical system.
And an observation means for causing the light to enter the image sensor.
In the adjusting method of the optical device, defocusing is performed from a best focus plane of the projection optical system.
By measuring the position of the mark at the position,
The defocus characteristic of the observation means for measuring the position of the
Measuring and minimizing the defocus characteristic.
The optical path of the principal ray of the exposure light is adjusted by the correction optical system
Adjusting the projection exposure apparatus.
Adjustment method. 2. The method according to claim 1, wherein
The reticle and wafer are supplied to the projection exposure apparatus
After the alignment, the reticle pattern
An exposure method comprising exposing a wafer. 3. The adjustment method according to claim 1, wherein
Wafers in a reticle pattern using a projection
An exposure step and a step of developing the exposed wafer.
A method of manufacturing a semiconductor device. 4. The observing means has a lens system that uses the exposure light as afocal light, and the correction optical system is a transparent parallel flat lens whose inclination can be adjusted about axes perpendicular to and perpendicular to the optical axis. It has a face plate, the parallel flat plate of the afocal light
2. The method according to claim 1, wherein the light path of the exposure light is shifted in parallel by adjusting a tilt of the plane-parallel plate and provided in an optical path. 5. The observing means has a lens system for emitting the exposure light as afocal light, and the correction optical systems are capable of adjusting an inclination about an optical axis as a rotation center in a state where the correction optical systems are opposed to each other so that the distance between the two can be adjusted. A wedge member having two transparent wedges that can be changed arbitrarily, the two wedges being provided in the optical path of the afocal light, and adjusting the inclination and the interval of the two wedges to expose the light. 2. The method for adjusting a projection exposure apparatus according to claim 1, wherein an optical path of light is shifted in parallel.
Law . 6. 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 arranged in an optical path to change the optical path of the exposure light. 2. The adjustment of the projection exposure apparatus according to claim 1 , wherein the adjustment is performed.
How . 7. A method of adjusting a projection exposure apparatus according to claim 1, wherein the correcting optical system with a change of the mark position is characterized in that to adjust the optical path of the exposure light.