JP2003344219A - Method and instrument for measuring eccentricity, manufacturing method for projection optical system, and projection optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure various examined faces with sufficient precision, using the same eccentricity measuring instrument. <P>SOLUTION: An optical positional relation between the examined face and a fixed lens is set to make the examined face substantially consistent with a rear focal face of the fixed lens on the same space, using this eccentricity measuring instrument of the present invention provided with a focus lens system 112 comprising a movable lens 112a and the fixed lens 112b to conform a project position of an index 111a with a paraxial focus of the examined face 116, and detecting parts 113, 114, 117, 118 for generating a signals indicating the eccentricity of the examined face based on a beam emitted from the index and reflected on the examined face. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eccentricity measuring method, an eccentricity measuring apparatus, a projection optical system manufacturing method, and a projection optical system which are applied to manufacturing a projection optical system.

[0002]

2. Description of the Related Art FIG. 3 is a diagram for explaining the configuration of an eccentricity measuring device and a conventional eccentricity measuring method. In the eccentricity measuring device, light from a light source (not shown) collimator lens system 111
Is converted into a parallel light flux at. An index 111a is arranged in the collimator lens system 111, and the movable lens 112a and the fixed lens 1 arranged in order from the light source side.
The focus lens system 112 composed of 12b projects the index 111a onto the paraxial focal plane of the surface 116a to be tested.

At this time, the parallel light flux emitted from the index 111a is incident on the surface 116a to be inspected in an angled state by the action of the focus lens system 112, but after reflection, it becomes a parallel light flux and is reflected by the surface 116a to be inspected. PSD (Position Sensitive Device) after being condensed by a condenser lens 117 as a measurement light flux for generating a signal indicating eccentricity
It is incident on 118. The light receiving surface of the PSD 118 is an index 11
Since it has a conjugate relationship with 1a, the light receiving surface thereof has an index 111a.
Image (hereinafter, referred to as a circular spot) is formed.

Between the focus lens system 112 and the surface 116a to be inspected, in order to guide the measurement light beam reflected by 116a toward the condenser lens 117 and PSD 118,
Polarization beam splitter 113 and quarter wave plate 114
Has been inserted. In addition, the polarization beam splitter 113
A relay lens system 115 for projecting the test surface 116a near the fixed lens 112b of the focus lens system 112 is inserted between the test surface 116a and the test surface 116a.

Generally, the object to be measured is a convex surface 116a (FIG. 3A) or 116b (FIG. 3).
(B)), the concave fixed lens 112b is used in the focus lens system 112, and when the measurement target is the concave test surface 116c (FIG. 3C), the focus lens system 112 is convexly fixed. The lens 112b ″ is used. If the relay lens system 115 is inserted, the positions where the fixed lenses 112b and 112b ″ should be arranged can be made substantially the same, so that the arrangement of the optical elements in the eccentricity measuring device can be made. The above is convenient.

Incidentally, the conventional relay lens system 115 is
The surface 116 to be measured (in FIG. 3, the surface 116 to be measured)
The projection position of a) is designed to match the position of the fixed lens 112b. In the eccentricity measurement by the above eccentricity measuring device, the position of the movable lens 112a in the optical axis direction is adjusted and the focus lens system 112 is the surface to be measured 1 to be measured.
Index 1 on the paraxial focal plane of 16 (the surface 116a to be tested in FIG. 3)
11a is set to be projected, and in that state, the surface 116 to be inspected is rotated by 180 ° around a predetermined reference axis, and from the change in the output of the PSD 118 before and after the rotation, P
The deviation Δ of the spot (that is, the image of the index 111a) formed on the light receiving surface of the SD 118 is detected. Half of the deviation Δ of the spot is the surface to be measured 1 to be obtained.
16 eccentricity (eccentricity from the reference axis) θ.

[0007]

Various test surfaces 116 (for example, FIG. 3) can be obtained by the eccentricity measuring device described above.
As shown in FIG.
When trying to measure a, 116b, 116c), various problems occur.

First, when the object to be measured is, for example, a convex test surface 116b having a small radius of curvature as shown in FIG. 3 (B), its paraxial focus (mark X) is close to the test surface 116b. Therefore, when the movable lens 112a is arranged at the optimum position, the diameter db of the irradiation region (the region where the light flux emitted from the index 111a is incident) on the surface 116b to be measured becomes small. At this time, the diameter of the measurement light beam also decreases, and the diameter sb of the spot formed on the PSD 118 increases as shown in FIG. 3B, so that the detectable range of the spot deviation Δ decreases. At this time, the detectable range of the eccentricity θ, that is, the dynamic range of measurement is narrowed. Also, the spot diameter sb
Is too large to extend beyond the light receiving surface of the PSD 118, it becomes impossible to measure eccentricity.

On the other hand, when the object to be measured is a concave test surface 116c having a small radius of curvature as shown in FIG. 3C, the paraxial focus (marked with X) is on the side opposite to the convex surface. And the movable surface of the movable lens 1
When 12a is arranged at the optimum position, the diameter dc of the irradiation region on the surface 116c to be detected becomes large. At this time, although the diameter sc of the spot does not increase (FIG. 3C), the diameter dc of the irradiation region may extend beyond the diameter of the surface 116c to be inspected and the light quantity of the measurement light beam may be insufficient. in this case,
Since the light intensity of the spot formed on the PSD 118 is reduced, the S / N of the PSD 118, and thus the spot detection accuracy, and thus the eccentricity measurement accuracy, deteriorates.

Therefore, conventionally, the same eccentricity measuring device can be applied only to a test surface having a similar radius of curvature in a relatively narrow range, or depending on the test surface, the detection range of the eccentricity θ (measurement We had to tolerate a decrease in dynamic range) and a deterioration in measurement accuracy. Therefore, the present invention is an eccentricity measuring method capable of surely measuring various test surfaces while using the same eccentricity measuring apparatus, and an eccentricity measuring apparatus capable of reliably measuring various test surfaces. It is an object of the present invention to provide a high-performance or low-cost projection optical system manufacturing method and a high-performance or low-cost projection optical system.

[0011]

A method of measuring eccentricity according to claim 1, wherein a focus lens system comprising a movable lens and a fixed lens for matching the projection position of the index with the paraxial focal plane of the surface to be tested, An eccentricity measuring method using an eccentricity measuring device provided with a detection unit that generates a signal indicating the eccentricity of the surface to be inspected based on a light beam emitted from an index and reflected on the surface to be inspected, wherein the radii of curvature are mutually different. In eccentricity measurement of a plurality of different types of test surfaces, the optical positional relationship between the test surface and the fixed lens is such that the test surface and the rear focal plane of the fixed lens substantially match in the same space. It is characterized by setting as follows.

In the eccentricity measuring method according to a second aspect of the present invention, the focus lens system including a movable lens and a fixed lens for aligning the projection position of the index with the paraxial focal plane of the surface to be inspected, and the object to be emitted from the index, An eccentricity measuring method using an eccentricity measuring device provided with a detection unit that generates a signal indicating eccentricity of the surface to be inspected based on a light beam reflected on the surface to be inspected, and a plurality of types of inspecting objects having different radii of curvature In the eccentricity measurement of the surface, the optical positional relationship between the surface to be inspected and the fixed lens is set according to the radius of curvature of the surface to be inspected.

An eccentricity measuring apparatus according to a third aspect of the invention is a focus lens system including a movable lens and a fixed lens for aligning a projection position of an index with a paraxial focal plane of a surface to be inspected, and the object to be projected from the index. An eccentricity measuring device including a detection unit that generates a signal indicating the eccentricity of the surface to be inspected based on the light flux reflected on the surface to be inspected, wherein the optical positional relationship between the surface to be inspected and the fixed lens is It is characterized in that the surface to be inspected and the back focal plane of the fixed lens are set to substantially match in the same space.

A method of manufacturing a projection optical system according to a fourth aspect is a method of manufacturing a projection optical system including a step of measuring decentering of an optical element forming the projection optical system, wherein the decentering measurement includes the step of measuring the decentering. The eccentricity measuring method according to claim 1 or 2 is applied.

A projection optical system according to a fifth aspect is the projection optical system according to the fourth aspect.
It is manufactured by the method for manufacturing a projection optical system described in 1.

[0016]

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

[First Embodiment] A first embodiment of the present invention will be described with reference to FIG. The present embodiment corresponds to claim 1, claim 3 and claims in which they are cited.
In the present embodiment, eccentricity measurement is performed on various test surfaces. Hereinafter, in order to compare with the conventional one, the measurement target is shown in FIG.
A convex test surface 116a shown in FIG. 1A, a convex test surface 116b with a small radius of curvature shown in FIG. 1B, and a concave test surface 116c with a small radius of curvature shown in FIG. .

Some or all of the surfaces 116a, 116b and 116c to be inspected are surfaces of lenses in the projection optical system, for example. FIG. 1 is a diagram illustrating a configuration of an eccentricity measuring device used in the present embodiment and an eccentricity measuring method of the present embodiment. The optical elements used in the eccentricity measuring apparatus of this embodiment are basically the same as those shown in FIG. 3, and a light source (not shown), collimator lens system 111, focus lens system 112, and polarization beam splitter 113 are shown. , 1/4 wavelength plate 114, relay lens system 15, condensing lens 117, PS
For example, D118.

However, the relay lens system 15 of the present embodiment
Is different from the relay lens system 115 shown in FIG. The details will be described below. First, in the eccentricity measuring device,
Generally, when measuring a certain surface 116 to be inspected, the movable lens 112
The diameter d of the irradiation region on the surface 116 to be inspected after optimizing the position of a is represented by the following equation (1).

The optimization of the position of the movable lens 112a means that the movable lens 112a is arranged so that the projection position of the index 111a by the focus lens system 112 coincides with the paraxial focal plane of the surface 116 to be inspected, as in the conventional case. It means to do.

[Equation 1] Note that a is the diameter of the parallel light flux on the front side of the focus lens system 112, R is the radius of curvature of the surface 116 to be inspected, and D is the fixed lens 1.
12b is an optical interval between the surface 116 to be inspected (an interval in the same space), f _Fix is a focal length of the fixed lens 112b, and f _Fix is
_Move is the focal length of the movable lens 112a.

The eccentricity measuring apparatus of the present embodiment measures the various test surfaces 116a, 116b, 116c so that the diameter d of the irradiation region is constant regardless of the radius of curvature R of the test surface 116. Is set. For this purpose, it is sufficient to satisfy the equation (2).

[Equation 2] At this time, since d is represented by the equation (3), it is obvious that it does not depend on R.

[Equation 3] Now, in order to satisfy the equation (2), that is, the fixed lens 1
The optical distance D between the surface 12b and the surface 116 to be inspected is fixed to the fixed lens 1
In order to match the focal length f _{Fix of} 12b, the projection position (the position indicated by "I" in FIG. 1) of the surface 116 to be inspected by the relay lens system 15 should be matched with the rear focal position of the fixed lens 112b. Good. Incidentally, in the eccentricity measuring apparatus, the relay lens system 15 generally has a relatively high degree of freedom in design. Therefore, in the eccentricity measuring device according to the present embodiment, the relay lens system 15 includes the design data of the fixed lens 112b,
And the arrangement position of the surface to be inspected 116 (each surface to be inspected 116 a, 11
6b and 116c are common. ), And equation (2)
It may be designed according to.

Then, the eccentricity measurement of this embodiment may be carried out in the same manner as in the conventional case under the above settings. That is, first, the position of the movable lens 112a in the optical axis direction is optimized so that the projection position of the index 111a by the focus lens system 112 coincides with the paraxial focal plane of the surface 116 to be inspected arranged at a predetermined position.

Then, in this state, the test surface 116 (test surface 116a in FIG. 1) is rotated by 180 ° around a predetermined reference axis, and is formed on the light receiving surface of PSD 118 from the output change of PSD 118 before and after the rotation. The deviation Δ of the spot (image of the index 111a) to be calculated is calculated. The half of the spot deviation Δ is the eccentricity of the test surface 116 (test surface 116a in FIG. 1) to be obtained (eccentricity from the reference axis) θ.
(Note that it is general to obtain the eccentricity in more detail by referring to not only the spot deviation Δ but also the locus of the spot.)

Further, the surface 116 to be inspected having a different radius of curvature R.
When eccentricity is measured for each of a, 116b, and 116c,
The surfaces to be inspected 116a, 116b, 1 are respectively placed at the predetermined positions.
After arranging 16c, each of the above procedures including optimization of the position of the movable lens 112a may be executed. When measuring the test surface 116c which is a concave surface, a convex fixed lens 112b ″ may be arranged in the focus lens system 112 as in the conventional case. However, even when the fixed lens 112b ″ is replaced, the formula is changed. (2) is established.

As described above, in the eccentricity measurement of this embodiment in which the equation (2) is satisfied, the diameter da of the irradiation region at the time of measurement of the surface 116a to be tested (FIG. 1A) and the surface 116b to be tested.
(FIG. 1 (B)) the diameter db of the irradiation region at the time of measurement,
The diameter dc of the irradiation region at the time of measuring the surface 116c to be inspected (FIG. 1C) becomes the same. In this case, the surface 116b to be inspected
The spot diameter sb (FIG.
(B)) has an appropriate size, as does the diameter sa (FIG. 1A) of the spot on the surface 116a to be tested (FIG. 1A).

Further, the light intensity of the spot at the time of measuring the surface 116c to be tested (FIG. 1C) is as follows.
Similar to the light intensity of the spot at the time of (A)) measurement, the intensity is appropriate. Therefore, in the present embodiment, although the various test surfaces 116a, 116b, and 116c are measured using the same eccentricity measuring device, the dynamic range of the measurement becomes narrower and the measurement accuracy becomes lower than in the conventional case. It does not decrease.

Incidentally, in the conventional eccentricity measuring device, the equation (2) does not hold, and the relay lens is arranged so that the projection position of the surface 116 to be inspected becomes the position of the fixed lens 112b (the position indicated by "I" in FIG. 3). Since the system 115 was designed, the size of the spot diameter sb and the light intensity of the spot diameter sc were not appropriate, and the dynamic range of measurement was narrowed and the measurement accuracy was lowered.

In the eccentricity measuring apparatus of this embodiment, the relay lens system 15 is not limited to the configuration shown in FIG. 1, and if necessary, for example, a part of the lens surface of an optical system consisting of a plurality of lenses is relayed. May be configured to do so.
Although not mentioned in the above description, in the eccentricity measurement of the present embodiment, the diameter a of the parallel light flux is adjusted as follows.

First, when measuring a certain surface 116 to be inspected, the PSD
The diameter s of the spot formed on the light receiving surface of 118 is the surface to be inspected 1 when the focal length of the condenser lens 117 is f _focus.
It is represented by the formula (4) by the diameter d of the irradiation region on 16 (the letter “λ” in the formula is the light source wavelength).

[Equation 4] In the present embodiment, the above equation (2) is established, so this equation (4) is transformed into equation (5).

[Equation 5] Here, if the width of the light receiving surface of the PSD 118 in the lateral direction is A and the dynamic range required for measurement (the maximum value of the eccentricity θ to be measured) is θ _max , the spot diameter s is ( A-2θ _max ). Therefore, equation (6) must be satisfied.

[Equation 6] Therefore, the diameter a of the parallel light flux is adjusted so as to satisfy the expression (6). In the present embodiment, the parameter for satisfying the expression (2) is the relay lens system 15. However, if the expression (2) is satisfied, another parameter or a combination with another parameter is used. May be (however,
The relay lens system 15 is preferable because it can most easily satisfy the formula (2). ).

Further, in the present embodiment, the parameter for satisfying the equation (6) is the diameter a of the parallel light flux,
Other parameters and combinations with other parameters may be used as long as Expression (6) is satisfied (however, it is preferable to use the diameter a of the parallel light flux because Expression (6) can be satisfied most easily. ). [Second Embodiment] A second embodiment of the present invention will be described. The present embodiment corresponds to claim 2 and claims citing it.

In the first embodiment described above, the eccentricity measuring device satisfies the equation (2) (D = f _Fix ), but the measurement of the special surface to be _{examined in} which D = f _Fix cannot be satisfied will be described below. explain. Note that this special measurement of the surface to be inspected is characterized only by the setting contents of the eccentricity measuring device, and the method of measuring the eccentricity is the same as in the first embodiment, so only the items relating to the setting will be described below.

The special test surface referred to here is, for example, a test surface that cannot be arranged at the same position as other test surfaces due to a large arrangement restriction, or the radius of curvature is too small to shift the position. If not, part of the light beam is blocked. Therefore, in the present embodiment, the equation (2) (D = f _Fix )
Instead of allowing the failure of (1), each time the measurement is performed on each of the special surfaces to be inspected, the measurement is set again so that the measurement can be performed reliably.

This setting is for ensuring the dynamic range θ _max required for each measurement. That is, the diameter s of the spot is set to be smaller than (A-2θ _max ). First, in the eccentricity measuring device, generally, the diameter d of the irradiation region on the surface 116 to be inspected is expressed by the equation (1). The diameter s of the spot is generally represented by the equation (4).

Therefore, generally, the diameter s of the spot is expressed by the equation (7) with respect to the optical distance D between the fixed lens 112b and the surface 116 to be inspected.

[Equation 7] Therefore, the conditional expression for making the diameter s of this spot smaller than (A-2θ _max ) is Expression (8).

[Equation 8] Therefore, in the present embodiment, at least one of the optical interval D (that is, the position of the surface 116 to be inspected) and the diameter a of the parallel light flux so that the equation (8) is established for each measurement of the special surface to be inspected. To set. Incidentally, in equation (8), λ,
Each of f _Fix and f _Move is an amount (amount that cannot be adjusted) specific to the eccentricity measuring device. Therefore, in this embodiment,
The value of D or a is appropriately set according to the radius of curvature R of the surface 116 to be measured which is the measurement target.

In the measurement of such a special surface to be inspected, the diameter s of the spot is different from that in the measurement of other surfaces to be inspected.
The measurement accuracy and the dynamic range of the measurement may be different, but the accuracy and the dynamic range required for the measurement of the special surface to be measured are surely guaranteed as long as Expression (8) is satisfied. By the way, in the case of using the fixed lens 112b in which the special test surface to be measured is a convex surface and is concave, f _Fix R <0. Therefore, instead of Expression (8), Expression (9) is used.
Based on.

[Equation 9] As described above, the present embodiment ensures the measurement by actively performing the setting according to the radius of curvature R when measuring the special surface to be inspected. Therefore, although the procedure of setting the special test surface is increased, the measurement can be performed by the same eccentricity measuring device as that of the other test surfaces.

The eccentricity measuring device may be automated so that a part or all of the eccentricity measurement of this embodiment is automatically performed. Further, the eccentricity measuring device may be automated so that the eccentricity measurement of the first embodiment and the eccentricity measurement of the present embodiment are selectively performed according to the surface to be inspected. The eccentricity measurement of the present embodiment or the first embodiment can be applied to any surface to be inspected, which is a spherical surface or an aspherical surface (rotationally symmetric aspherical surface).

[Third Embodiment] A second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a schematic configuration diagram of the projection exposure apparatus of this embodiment. When manufacturing the projection optical system L mounted in this projection exposure apparatus, the eccentricity measurement of the first embodiment or the second embodiment is applied.

According to the first or second embodiment,
Since the same eccentricity measuring device can be used for eccentricity measurement of a plurality of surfaces among the lenses (or mirrors) L1 to Ln in the projection optical system L, the manufacturing cost of the projection optical system L can be suppressed. Alternatively, if the time remaining by applying the first embodiment or the second embodiment is applied to steps other than the eccentricity measurement,
It is also possible to further improve the precision of the projection optical system L.

The projection exposure apparatus includes at least the wafer stage 108 and a light source section 101 for supplying light.
And a projection optical system L. Here, the wafer stage 1
The reference numeral 08 indicates the surface 10 of the substrate (wafer) W coated with the photosensitizer.
It can be placed on 8a. In addition, the stage control system 10
Reference numeral 7 controls the position of the wafer stage 108. The projection optical system L is a high-precision projection lens manufactured using the interferometers according to the above-described embodiments. Further, the projection optical system L is arranged between the object plane P1 on which the reticle (mask) R is arranged and the image plane P2 matched with the surface of the wafer W. Further, the projection optical system L has an alignment optical system applied to a scan type projection exposure apparatus. Further, the illumination optical system 102 includes an alignment optical system 103 for adjusting the relative position between the reticle R and the wafer W. The reticle R is for projecting an image of the pattern of the reticle R onto the wafer W, and is arranged on the reticle stage 105 that can move in parallel with the surface 108a of the wafer stage 108. Then, the reticle exchange system 104 exchanges and carries the reticle R set on the reticle stage 105.
The reticle exchange system 104 also includes a stage driver (not shown) for translating the reticle stage 105 with respect to the surface 108a of the wafer stage 108.
In addition, the main control unit 109 controls the series of processes from alignment to exposure.

[0040]

As described above, according to the present invention,
An eccentricity measurement method that enables reliable measurement of various test surfaces while using the same eccentricity measurement device, and an eccentricity measurement device that can reliably measure various test surfaces. A costly manufacturing method of a projection optical system and a high-performance or low-cost projection optical system are realized.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of an eccentricity measuring device and an eccentricity measuring method of the present embodiment.

FIG. 2 is a diagram illustrating a schematic configuration of a projection exposure apparatus according to a third embodiment and a conventional eccentricity measuring method.

FIG. 3 is a diagram illustrating a configuration of an eccentricity measuring device and a conventional eccentricity measuring method.

[Explanation of symbols]

15,115 Relay lens system L projection optical system W wafer (wafer surface) R reticle (reticle surface) 101 light source 102 Illumination optical system 103 Alignment optical system 104 Reticle exchange system 105 reticle stage 107 Stage control system 108 wafer stage 109 Main control unit 111 Collimator lens system 112 Focus lens system 112a movable lens 112b Fixed lens 113 Polarizing beam splitter 114 1/4 wave plate 116 test surface 117 Condensing lens 118 PSD

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Claims (5)

[Claims] 1. A focus lens system including a movable lens and a fixed lens for matching a projection position of an index with a paraxial focal plane of a surface to be inspected, and a light flux emitted from the index and reflected by the surface to be inspected. An eccentricity measuring method using an eccentricity measuring device having a detection unit that generates a signal indicating the eccentricity of the surface to be inspected, wherein the eccentricity is measured for a plurality of types of surfaces to be inspected having different radii of curvature, An eccentricity measuring method, characterized in that an optical positional relationship between an inspection surface and the fixed lens is set such that the surface to be inspected and a rear focal plane of the fixed lens substantially match in the same space. 2. A focus lens system composed of a movable lens and a fixed lens for aligning a projection position of an index with a paraxial focal plane of the surface to be inspected, and a light beam emitted from the index and reflected by the surface to be inspected. An eccentricity measuring method using an eccentricity measuring device having a detection unit that generates a signal indicating the eccentricity of the surface to be inspected, wherein the eccentricity is measured for a plurality of types of surfaces to be inspected having different radii of curvature, An eccentricity measuring method, characterized in that an optical positional relationship between an inspection surface and the fixed lens is set according to a radius of curvature of the inspection surface. 3. A focus lens system comprising a movable lens and a fixed lens for matching a projection position of an index with a paraxial focal plane of the surface to be inspected, and a light flux emitted from the index and reflected by the surface to be inspected. An eccentricity measuring device including a detection unit that generates a signal indicating the eccentricity of the surface to be inspected, wherein the optical positional relationship between the surface to be inspected and the fixed lens is one of the surface to be inspected and the fixed lens. An eccentricity measuring device, characterized in that the eccentricity is set so as to substantially coincide with the rear focal plane in the same space. 4. A method of manufacturing a projection optical system including a step of measuring eccentricity of an optical element that constitutes the projection optical system, wherein the eccentricity measurement method according to claim 1 or 2 is used for the eccentricity measurement. A method for manufacturing a projection optical system, wherein: 5. A projection optical system manufactured by the method for manufacturing a projection optical system according to claim 4.