JPH09199573A - Positioning stage apparatus and aligner using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct an Abbe error in a wafer stage. SOLUTION: A wafer stage 4 for holding a wafer W1 has an XY stage 10, a leveling stage 11, and a wafer chuck 12, a tilt angle of the leveling stage 11 being adjusted based on an output of a wafer focus sensor 7. A laser beam M1 for measurement of positions of the wafer W1 in X and Y directions is partly separated as a monitor beam M2 by a half mirror 9a, and guided to a position sensor 9b to measure a positional displacement of the monitor beam M2 and to calculate an Abbe error on the basis of the measured displacement and the tilt angle of the leveling stage 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly accurate positioning stage device used in an exposure apparatus or the like for manufacturing a semiconductor integrated circuit, and an exposure apparatus using the same.

[0002]

2. Description of the Related Art An exposure apparatus for manufacturing a semiconductor integrated circuit is a step-and-repeat type exposure apparatus (stepper) in which a plurality of exposure regions of a substrate such as a wafer are sequentially moved to an image plane of a projection optical system for exposure. However, such an exposure apparatus requires a positioning stage device for positioning the substrate with respect to an original plate such as a reticle with high accuracy.

FIG. 4 illustrates a general stepper, which is the optical axis 0 of the exposure light generated from the light source 101.
A reticle stage 102, a projection optical system 103, and a wafer stage 104 are arranged along the wafer stage 104. The wafer stage 104 includes a well-known XY stage 110, a leveling stage 111 mounted on the XY stage 110, and the leveling stage 111. The held wafer chuck 112 is provided.

The bottom surface 110a of the XY stage 110 is finished with high surface accuracy (flatness and smoothness) and faces the guide surface 105a provided on the upper surface of the surface plate 105 of the exposure apparatus. The bottom surface 110a of the XY stage 110 and the bottom surface 110a of the XY stage 110 are kept in non-contact by a static pressure air bearing (not shown). The XY stage 110 is linearly driven by a linear motor or the like in the directions of two axes (X axis and Y axis) perpendicular to the optical axis 0 (Z axis) of the exposure light.
It consists of a stage and a Y stage, and the Y stage is a surface plate 1
Guide surface 106 on the side surface of the Y guide 106 that is erected on 05.
a through a static pressure air bearing (not shown) without contacting Y
It is guided in the axial direction, and the X stage is also in non-contact with the X guide installed upright on the Y stage via a static pressure air bearing.
Guided in the axial direction. The XY stage 104 is thus supported on the surface plate 105 in a non-contact manner, and is positioned with high accuracy at an arbitrary position in the XY plane by the linear motor or the like.

The leveling stage 111 mounted on the XY stage 110 is constructed so that its tilt angle can be finely adjusted. If the surface of the wafer W ₀ on the wafer chuck 112 has a waviness or an inclination, the image forming surface S ₀ of the projection optical system 103 will be described.
That is, the surface of the wafer W ₀ may deviate from the focus position and defocus may occur. Therefore, the wafer focus sensor 107 is used to detect the tilt of the surface of the wafer W ₀ for each exposure area, and the tilt angle of the leveling stage 111 is adjusted based on the detected value to avoid the defocus.

In recent years, the required line width of a semiconductor integrated circuit has been reduced to about submicron. For this reason, the projection optical system 10
3 has a large numerical aperture (NA) and a wide exposure field, and therefore tends to have a shallow depth of focus. So positioning step to zero the inclination of the surface of the wafer W ₀ for imaging surface S ₀ of the tilt angle adjusting to the projection optical system 103 of the leveling stage 111 for each exposure area of the wafer W ₀ is required.

The exposure light generated from the light source 101 projects a fine pattern of the reticle R ₀ held on the reticle stage 102 onto the wafer W ₀ via the projection optical system 103.
This is exposed. The position of the wafer W _{0 in} the XY directions before and during exposure is measured by an interferometer 109 which irradiates a mirror 108 integrated with the leveling stage 111 with a measurement laser beam M ₀ and obtains an interference fringe by the reflected light. To be done. The XY stage 110 is driven based on the output of the interferometer 109, and thus the wafer W ₀ and the reticle R ₀ are processed.
The alignment of is managed with high accuracy.

However, the leveling stage 111, which is integrated with the mirror 108, changes its tilt angle in accordance with the waviness and tilt of the surface of each exposure area of the wafer W ₀ , as described above, and therefore, the interferometer. An error due to a change in the tilt angle of the leveling stage 111, a so-called Abbe error occurs in the measured value of 109.

As shown in FIG. 5, the Abbe error ΔL is calculated by the following equation.

ΔL = ν sin θ + (2Lc−Xm) {1-cos (θ + β)} (1) where ν: the height of the laser beam M ₀ and the image plane S ₀ of the projection optical system 103. Difference β: laser light M with respect to the image plane S ₀ of the projection optical system 103
Inclination angle of ₀ θ: Inclination angle of leveling stage 111 Lc: Distance from optical axis 0 of exposure light to interferometer 109 Xm: Distance from optical axis 0 of exposure light to reflection surface of mirror 108 In formula (1), Since the tilt angles β and θ are both very small, the laser beam M ₀ and the image plane S ₀ of the projection optical system 103 are not included.
Are the same and the laser light M ₀ is parallel to the image plane S ₀ of the projection optical system 103, ν = 0, β = 0, and therefore ΔL
Since ≈0, no countermeasure for Abbe error is required.

Therefore, when the stepper is installed, the height and tilt angle of the laser beam M ₀ are set to the image plane S ₀ of the projection optical system 103.
Or the laser light M for the image plane S ₀ of the projection optical system 103 is adjusted in advance as described above.
The height difference ₀ of ₀ and the inclination angle β are detected, and the Abbe error is calculated for each exposure cycle by the equation (1) to correct the measurement value of the interferometer 109. .

[0012]

However, according to the above-mentioned conventional technique, the method of adjusting the laser beam for measurement to the height and the tilt angle of the image plane of the projection optical system when the stepper is installed is the stepper periphery. There are inconveniences such as the impossibility of the space limitation of the equipment and the extremely complicated stepper assembly work. In addition, even if the laser light is aligned with the image plane of the projection optical system when the stepper is installed, the laser head that generates the laser light causes thermal distortion during measurement and its emission direction changes, or during exposure. In addition, if the height of the image plane of the projection optical system fluctuates due to thermal distortion of the stepper body, the Abbe error cannot be avoided.

In addition, a method in which the difference in height between the measuring laser beam and the image plane of the projection optical system and the tilt angle are measured in advance and the correction is performed by the formula (1) is also performed as the exposure cycle progresses. If the emission direction of the laser light changes due to the thermal strain of the head or the thermal strain of the stepper body, proper correction cannot be performed.

The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and the Abbe error included in the measurement value of the interferometer or the like is appropriately corrected to perform extremely highly accurate positioning. An object of the present invention is to provide a positioning stage device that can be used and an exposure apparatus that uses the positioning stage device.

[0015]

In order to achieve the above object, a positioning stage device of the present invention measures a holding plate movable along a predetermined reference plane and the position of the holding plate by measuring light. Position measuring means, tilt angle adjusting means for adjusting the tilt angle of the holding plate with respect to the reference plane, separating means for separating a part of the measuring light as monitor light, and displacement for detecting displacement of the monitor light. It is characterized by having detection means.

Correction means for correcting the output of the position measuring means based on the output of the displacement detecting means may be provided.

The separating means may include a half mirror.

The position measuring means, the separating means, and the displacement detecting means may be supported by a support made of a low thermal expansion material.

[0019]

The output of the position measuring means for measuring the position of the holding plate by the measuring light causes an Abbe error when the tilt angle of the holding plate changes with respect to the reference plane. Therefore, the Abbe error is calculated based on the tilt angle of the holding plate. Then, the output of the position measuring means is corrected. However, if the emission direction of the measurement light or the like changes, the Abbe error changes accordingly, and proper correction cannot be performed.

Therefore, a part of the measuring light is separated as monitor light, introduced into the displacement detecting means to detect the displacement, an accurate Abbe error is calculated based on the detected value, and the output of the position measuring means is outputted. To correct. In this way, the position of the holding plate can be accurately measured and the holding plate can be positioned with high accuracy.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an exposure apparatus according to one embodiment, which comprises a reticle stage 2 and a projection optical system 3 arranged along an optical axis 0 of the exposure light emitted from a light source 1.
A wafer stage 4 is provided with an exposure unit including the above, and the like. The wafer stage 4 includes a known XY stage 10 and a leveling stage 1 mounted on the XY stage 10 as an inclination angle adjusting unit.
1 and a wafer chuck 12 which is a holding plate held by the leveling stage 11.

The bottom surface 10a of the XY stage 10 is finished with high surface accuracy (flatness and smoothness) and faces the guide surface 5a provided on the upper surface of the surface plate 5 which is the support of the exposure apparatus. The guide surface 5a and the bottom surface 10 of the XY stage 10
The portion a is kept in non-contact with a static pressure air bearing (not shown). The XY stage 10 includes an X stage and a Y stage that are linearly driven by linear motors or the like in the directions of two axes (X axis and Y axis) perpendicular to the optical axis 0 (Z axis) of the exposure light. The stage is guided in the Y-axis direction in a non-contact manner through a static pressure air bearing (not shown) by a side guide surface of a Y guide 6 provided upright on the surface plate 5, and the X stage is also provided upright on the Y stage. The X guide is guided in the X axis direction in a non-contact manner via the hydrostatic air bearing. XY
The stage 4 is thus supported on the surface plate 5 in a non-contact manner,
The linear motor or the like allows highly accurate positioning at any position in the XY plane.

The tilting angle of the leveling stage 11 mounted on the XY stage 10 is finely adjustable. When the surface of the wafer W ₁ on the wafer chuck 12 has a waviness or an inclination, the image forming plane S of the projection optical system 3 which is the reference plane is formed.
₁ That is likely to generate a defocus offset surface of the wafer W ₁ from the focal position. Therefore, the wafer focus sensor 7 is used to detect the tilt of the surface of the wafer W ₁ for each exposure area, and the tilt angle of the leveling stage 11 is adjusted based on the detected value to avoid the defocus.

In recent years, the required line width of a semiconductor integrated circuit has been reduced to about submicron, and for this reason, the projection optical system 3 has a large numerical aperture (NA) and a wide exposure field, and thus has a shallow depth of focus. Tend to be used. Therefore, the leveling stage 11 is provided for each exposure area of the wafer W _1.
The step of adjusting the tilt angle of the wafer W ₁ to zero with respect to the image plane S ₁ of the projection optical system 3 is required.

The exposure light generated from the light source 1 projects a fine pattern of the reticle R ₁ held on the reticle stage 2 onto the wafer W ₁ through the projection optical system 2 and exposes it. The position of the wafer W _{1 in} the XY directions before and during exposure is
Irradiating a laser beam M ₁ is the measurement light to the mirror 8a is integral with the leveling stage 11, is measured by the interferometer 8b is a position measuring means for obtaining an interference fringe by the reflected light. The XY stage 10 is driven based on the output of the interferometer 8b, and thus the wafer W ₁ and the reticle R _{1 are}
The alignment of is managed with high accuracy.

The interferometer 8b and the laser head 8c for generating the laser beam M ₁ are supported by a supporting member which is integral with the surface plate 5.

As described above, the leveling stage 11 which is integrated with the mirror 8 changes its inclination angle in accordance with the waviness and inclination of the surface of each exposure region of the wafer W _1. Therefore, the measurement of the interferometer 8b is performed. An error due to a change in the tilt angle of the leveling stage 11, that is, an Abbe error occurs in the value.

Since the Abbe error is calculated by the equation (1), the height difference ν and the tilt angle β of the laser beam M ₁ with respect to the image plane S ₁ of the projection optical system 3 should be detected in advance. For example, each time the tilt angle θ of the leveling stage 11 changes, the Abbe error ΔL can be calculated by the equation (1) to correct the measurement value of the interferometer 8b.

However, when the relative position of the laser beam M _{1 to} the image plane S ₁ of the projection optical system 3 changes due to thermal strain of the laser head 8c which generates the laser beam M ₁ or thermal strain of the stepper body during exposure. , The values of ν and β in the equation (1) change, and an accurate Abbe error ΔL cannot be calculated. Therefore, a half mirror 9a as a separating means is provided in the optical path of the measurement laser beam M _1.
By this, a part of the laser light M ₁ is separated as monitor light M ₂ and introduced into a position sensor 9b which is a photoelectric sensor (displacement detecting means) on the surface plate 5, and as shown in FIG. A shift amount τ which is a displacement of the monitor light M _{2 on} the detection surface 9b is detected. Projection optical system 3
The relationship between the height difference ν of the laser light M ₁ with respect to the image forming surface S ₁ and the inclination angle β and the shift amount τ of the monitor light M ₂ of the laser light M _{1 on} the detection surface of the position sensor 9b is as follows. To establish.

Τ = (Lh + Ls + Lp) Tanβ (2) Here, Lh: Distance from interferometer 8b to laser head 8c Ls: Distance from interferometer 8b to half mirror 9a Lp: From half mirror 9a Distance to Position Sensor 9b Further, if the distance from the interferometer 8b to the mirror 8a is Ld, then ν = (Lh + Ld) Tanβ (3) Since equation (2) and equation (3) ν = (Lh + Ld) / (Lh + Ls + Lp) × τ (4) Further, since β≈0 in the equation (2), it can be approximated as follows.

Β = 1 / (Lh + Ls + Lp) × τ (5) That is, before or during the exposure of each exposure region of the wafer W ₁ , using the detection value τ of the position sensor 9b, the expression ( 4) and (5), ν and β are calculated, the Abbe error ΔL is calculated by the equation (1), and a correction means for automatically correcting the measurement value of the interferometer 8b is provided.
Therefore, the positioning accuracy of the wafer W ₁ can be greatly improved, and the alignment with respect to the reticle R ₁ can be stably controlled with high accuracy.

According to this embodiment, the leveling stage 1
Since the Abbe error ΔL due to the change in the tilt angle of 1 can be accurately corrected and the alignment between the wafer W ₁ and the reticle R ₁ can be managed with high accuracy, transfer deviation occurs even if the fine pattern becomes finer. It is possible to realize an extremely high-performance exposure apparatus that is free from the risk of

Interferometer 8b and position sensor 9b
In the calibration between and, the pre-marked test wafer is placed on the wafer stage 4 and the leveling stage 11 is tilted to detect the positional deviation of the test wafer mark by an alignment detection system (not shown). It is done by In addition, since the values of θ and β in expression (1) are minute, the following approximate expression (6) obtained by Taylor expansion may be used instead of expression (1).

ΔL = {ν + (2Lc−Xm) β} θ (6) A part of the monitor light M ₂ of the laser light M ₁ is located between the half mirror 9a and the position sensor 9b.
It may be reflected by the light receiving surface of b and cause a ghost in the interferometer 8b. Therefore, a window 9c is provided between the half mirror 9a and the position sensor 9b to prevent the occurrence of the ghost. Additionally, or is slightly inclined from a position perpendicular to the monitor light M ₂ of the laser beam M ₁ the light receiving surface of the position sensor 9b, also be provided an antireflection film on the light receiving surface of the position sensor 9b, preventing the ghost Has a great effect on

When the support member that supports the interferometer 8b, the laser head 8c, the position sensor 9b, and the surface plate 5 undergoes significant thermal expansion during measurement with the laser beam M _{1, the} Abbe error is corrected as described above. I can't do it properly. Therefore, it is desirable to use a low thermal expansion material such as ceramic for the surface plate 5 and the like.

FIG. 3 shows a modification, which is an interferometer 8b.
In the interferometer 28b similar to the above, the measurement laser beam M ₁
Separating the portion as the reference beam M _3, which is the one which reflected by a plane mirror 23 mounted on the barrel of the projection optical system 3, the reference light M ₃ of the half mirror part 2
9a, the monitor light M ₄ is separated and introduced into the position sensor 29b.

As described above, it is also possible to detect ν and β in the formula (1) or the formula (6) using the reference light of the interferometer.

[0039]

Since the present invention is configured as described above, it has the following effects.

An Abbe error included in a measurement value of an interferometer or the like for measuring the position of the wafer stage can always be properly corrected to perform extremely highly accurate positioning. By using such a positioning stage device for a wafer stage or the like of an exposure device, extremely highly accurate transfer and printing can be realized. Further, since the Abbe error can be corrected online, there is no need to interrupt the semiconductor manufacturing process or the like for measurement.

[Brief description of drawings]

FIG. 1 is a schematic elevational view showing an exposure apparatus according to an embodiment.

FIG. 2 is a diagram illustrating an expression for obtaining a height and a tilt angle of a laser beam for measurement from an output of a position sensor of the apparatus shown in FIG.

FIG. 3 is a schematic elevational view showing a modified example.

FIG. 4 is a schematic elevation view showing one conventional example.

FIG. 5 is a diagram illustrating an expression for calculating an Abbe error.

[Explanation of symbols]

 1 Light Source 2 Reticle Stage 3 Projection Optical System 4 Wafer Stage 5 Surface Plate 7 Wafer Focus Sensor 8a Mirror 8b, 28b Interferometer 8c Laser Head 9a, 29a Half Mirror 9b, 29b Position Sensor 11 Leveling Stage 12 Wafer Chuck

Claims (7)

[Claims] 1. A holding plate movable along a predetermined reference plane, position measuring means for measuring the position of the holding plate by measuring light, and adjusting a tilt angle of the holding plate with respect to the reference plane. 2. A positioning stage device having: the tilt angle adjusting means, the separating means for separating a part of the measurement light as monitor light, and the displacement detecting means for detecting the displacement of the monitor light. 2. The positioning stage apparatus according to claim 1, further comprising a correcting unit that corrects the output of the position measuring unit based on the output of the displacement detecting unit. 3. The positioning stage device according to claim 1, wherein the separating means has a half mirror. 4. The positioning stage apparatus according to claim 1, wherein the position measuring means, the separating means, and the displacement detecting means are supported by a support body made of a low thermal expansion material. . 5. The positioning stage apparatus according to claim 4, wherein the low thermal expansion material is ceramic. 6. The positioning stage device according to claim 1, wherein the displacement detecting means is a photoelectric sensor. 7. An exposure apparatus having the positioning stage apparatus according to claim 1 and an exposure unit that exposes a substrate positioned by the positioning stage apparatus.