JP2006030057A - Calibration method for shearing interference measurement apparatus, shearing interference measurement method, shearing interference measurement apparatus, projection optical system manufacturing method, projection optical system, projection exposure apparatus manufacturing method, projection exposure apparatus, microdevice manufacturing method, and microdevice - Google Patents

Abstract

Data of shear direction of a shearing interference measuring apparatus is obtained with high accuracy.
A wavefront splitting means (41) capable of shearing a wavefront of a measurement light beam passing through a test optical system (0) in two directions whose relations are known, and shearing by the wavefront splitting means. A calibration method for a shearing interference measurement apparatus comprising an image pickup element (15) for detecting interference fringes formed on the predetermined plane by the wave fronts, wherein an arbitrary test optical system or reference optical system is included in the shearing interference measurement apparatus. The calibration measurement for obtaining the interference fringe data formed by the wavefronts sheared in one of the two directions and the interference fringe data formed by the wavefronts sheared in the other of the two directions. And a calculation procedure for acquiring shear direction data of the wavefront dividing means with reference to the imaging device based on the acquired two interference fringe data and the relationship.
[Selection] Figure 1

Description

The present invention relates to a calibration method of a shearing interference measurement apparatus, a shearing interference measurement method, and a shearing interference measurement apparatus applied to measurement of wavefront aberration of a projection optical system for EUVL (Extreme Ultra Violet Lithography).
The present invention also relates to a projection optical system manufacturing method, a projection optical system, a projection exposure apparatus manufacturing method, a projection exposure apparatus, a microdevice manufacturing method, and a microdevice to which a shearing interference measurement method is applied.

For measuring the wavefront aberration of the projection optical system for EUVL, a light source having the same wavelength as the wavelength used (EUV light (extreme ultraviolet)) is used. Therefore, a shearing interferometer that combines a mirror and a diffraction grating is effective. Possible (Patent Document 1, Patent Document 2, Patent Document 3, etc.).
This shearing interferometer includes a diffraction grating that shears (divides) the wavefront (transmitted wavefront) of a measurement light beam that has passed through a test optical system, and an image sensor that detects interference fringes formed by the sheared wavefronts. It is done. The data on the luminance distribution of the interference fringes detected by the image sensor is analyzed by a computer, and the transmitted wavefront of the test optical system is restored.

For the analysis, calibration data of the shearing interferometer is used. This is data such as the shear amount of the wavefront by the diffraction grating (shear amount expressed in the coordinate system on the image sensor) and the shear direction of the wavefront by the diffraction grating (shear direction expressed by the coordinate system on the image sensor).
Conventionally, shear direction data has been acquired by the following calibration method.
That is, an index is arranged in the measurement light beam before shear. In this state, the positions of the images formed individually by the one wavefront sheared by the diffraction grating and the other wavefront are detected by the image sensor. The direction of displacement of these images is regarded as the shear direction.
JP 2003-86501 A JP 2003-254725 A JP 2004-37429 A

However, with this method, since the resolution of the image sensor directly affects the detection accuracy in the shear direction, the data acquisition accuracy in the shear direction is low, and is not suitable for high-accuracy measurement such as a projection optical system for EUVL.
Therefore, an object of the present invention is to provide a calibration method for a shearing interferometer that can acquire shear direction data with high accuracy.

Another object of the present invention is to provide a shearing interference measurement method capable of measuring a transmitted wavefront of a test optical system with high accuracy.
It is another object of the present invention to provide a shearing interference measuring apparatus that can acquire shear direction data with high accuracy.
Another object of the present invention is to provide a projection optical system manufacturing method capable of manufacturing a high-performance projection optical system.

Another object of the present invention is to provide a high-performance projection optical system.
Another object of the present invention is to provide a method of manufacturing a projection exposure apparatus that can manufacture a high-performance projection exposure apparatus.
Another object of the present invention is to provide a high-performance projection exposure apparatus.
Another object of the present invention is to provide a microdevice manufacturing method capable of manufacturing a high-performance microdevice.

  Another object of the present invention is to provide a high-performance microdevice.

  A calibration method for a shearing interferometer according to claim 1, wherein the wavefront splitting means capable of shearing the wavefront of the measurement light beam passing through the test optical system in two directions whose relations are known, and the wavefront A shearing interference measuring apparatus calibration method comprising an imaging device for detecting interference fringes formed by wavefronts sheared by a dividing unit on a predetermined plane, wherein the shearing interference measuring apparatus includes an arbitrary optical system or reference Calibration to obtain data of interference fringes formed by wavefronts sheared in one of the two directions and data of interference fringes formed by wavefronts sheared in the other of the two directions with the optical system set. And a calculation procedure for acquiring shear direction data of the wavefront dividing means with reference to the image sensor based on the acquired two interference fringe data and the relationship. To.

The calibration method for the shearing interference measurement apparatus according to claim 2 is the calibration method for the shearing interference measurement apparatus according to claim 1, wherein in the calculation procedure, the wavefront aberration of the optical system to be measured is a phase distribution of the interference fringes. A predetermined arithmetic expression for removing the influence on the primary component is used.
The calibration method of the shearing interferometer according to claim 3 is the calibration method of the shearing interferometer according to claim 2, wherein the wavefront dividing means equalizes the wavefront in the X and Y directions orthogonal to each other. The predetermined arithmetic expression is obtained by calculating the Y direction component of the direction vector of the primary component of the phase distribution of the interference fringes formed by the wave fronts sheared in the X direction, and the Y direction. It is an arithmetic expression that takes the difference between the direction vector of the primary component of the phase distribution of the interference fringes formed by sheared wavefronts and the X direction component.

  The calibration method of the shearing interferometer according to claim 4 is the calibration method of the shearing interferometer according to any one of claims 1 to 3, wherein the wavefront dividing means is related to the direction of the marking line. Has two known diffraction gratings, and the diffraction grating inserted into the measurement light beam can be switched between the two diffraction gratings while maintaining the relationship.

The calibration method of the shearing interference measurement apparatus according to claim 5 is the calibration method of the shearing interference measurement apparatus according to any one of claims 1 to 3, wherein the wavefront dividing unit includes a diffraction grating. In addition, the arrangement direction of the diffraction grating around the optical axis with respect to the measurement light beam can be switched to two known relations.
The calibration method for the shearing interference measurement apparatus according to claim 6 is the calibration method for the shearing interference measurement apparatus according to any one of claims 1 to 5, wherein the test optical system is a projection for EUVL. An optical system, wherein the measurement light beam is EUV light having a wavelength of 50 nm or less.

  The shearing interference measurement method according to claim 7 is a calibration procedure for acquiring the shear direction data of the shearing interference measurement device by the calibration method of the shearing interference measurement device according to any one of claims 1 to 6. A measurement procedure for setting the test optical system in the shearing interferometer and acquiring interference fringe data, and a measurement for restoring the transmitted wavefront of the test optical system based on the measurement data and the data in the shear direction Including a procedure.

  The shearing interference measuring apparatus according to claim 8 includes: a wavefront dividing unit capable of shearing a wavefront of a measurement light beam passing through a test optical system in two directions whose relations are known; and the wavefront dividing unit. An image sensor that detects interference fringes formed by sheared wavefronts on a predetermined plane, and an arbitrary test optical system or reference optical system set in the shearing interference measurement device, are sheared in one of the two directions. The interference fringe data formed by the wavefronts formed, the interference fringe data formed by the wavefronts sheared in the other of the two directions and the control means for acquiring the data, and the acquired two interference fringe data and the relationship And an arithmetic means for acquiring data in the shear direction of the wavefront dividing means with reference to the image sensor.

The shearing interferometer according to claim 9 is the shearing interferometer according to claim 8, wherein the calculation unit is configured to affect the wavefront aberration of the optical system to be measured on a primary component of the phase distribution of the interference fringes. It is characterized by using a predetermined arithmetic expression for removing.
The shearing interferometer according to claim 10 is the shearing interferometer according to claim 9, wherein the wavefront dividing means can shear the wavefront in equal amounts in the X and Y directions orthogonal to each other. The predetermined arithmetic expression is that the Y direction component of the direction vector of the primary component of the phase distribution of the interference fringes formed by the wave fronts sheared in the X direction and the wave fronts sheared in the Y direction are It is an arithmetic expression that takes the difference between the direction vector of the primary component of the phase distribution of the interference fringe formed and the X direction component.

The shearing interferometer according to claim 11 is the shearing interferometer according to any one of claims 8 to 10, wherein the wavefront splitting means includes two diffraction patterns whose relationship between the engraving directions is known. A diffraction grating having a grating and being inserted into the measurement light beam can be switched between the two diffraction gratings while maintaining the relationship.
The shearing interference measuring apparatus according to claim 12 is the shearing interference measuring apparatus according to any one of claims 8 to 10, wherein the wavefront dividing means includes a diffraction grating, and The arrangement direction of the measurement light beam around the optical axis can be switched to two known relations.

The shearing interference measuring apparatus according to claim 13 is the shearing interference measuring apparatus according to any one of claims 8 to 12, wherein the optical system to be measured is a projection optical system for EUVL, The measurement light beam is composed of EUV light having a wavelength of 50 nm or less.
According to a fourteenth aspect of the present invention, there is provided a projection optical system manufacturing method comprising: measuring a transmitted wavefront of the projection optical system by the shearing interference measurement method according to the seventh aspect; and adjusting the projection optical system based on the measurement result. It is characterized by.

According to a fifteenth aspect of the present invention, there is provided a projection optical system manufactured by the projection optical system manufacturing method according to the fourteenth aspect.
According to a sixteenth aspect of the present invention, there is provided a projection exposure apparatus manufacturing method including a procedure of manufacturing a projection optical system by the projection optical system manufacturing method according to the fourteenth aspect.
A projection exposure apparatus according to a seventeenth aspect is manufactured by the method for manufacturing a projection exposure apparatus according to the sixteenth aspect.

A projection exposure apparatus according to an eighteenth aspect includes the shearing interference measuring apparatus according to any one of the eighth to thirteenth aspects.
According to a nineteenth aspect of the present invention, there is provided a microdevice manufacturing method in which a microdevice is manufactured by the projection exposure apparatus according to the seventeenth or eighteenth aspect.
A microdevice according to claim 20 is manufactured by the method for manufacturing a microdevice according to claim 19.

ADVANTAGE OF THE INVENTION According to this invention, the calibration method of the shearing interference measuring apparatus which can acquire the data of a shear direction with high precision is implement | achieved.
Further, according to the present invention, a shearing interference measuring method capable of measuring the transmitted wavefront of the test optical system with high accuracy is realized.
In addition, according to the present invention, a shearing interference measuring apparatus capable of acquiring shear direction data with high accuracy is realized.

Further, according to the present invention, a method for manufacturing a projection optical system capable of manufacturing a high-performance projection optical system is realized.
Further, according to the present invention, a high-performance projection optical system is realized.
In addition, according to the present invention, a method of manufacturing a projection exposure apparatus that can manufacture a high-performance projection exposure apparatus is realized.

Moreover, according to the present invention, a high-performance projection exposure apparatus is realized.
In addition, according to the present invention, a method of manufacturing a microdevice that can manufacture a high-performance microdevice is realized.
Further, according to the present invention, a high-performance micro device is realized.

[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS. 1, 2, 3, 4, and 5.
The present embodiment is an embodiment of a shearing interference measuring apparatus using a diffractive optical member as a wavefront dividing unit.
The test optical system of this measuring apparatus is a projection optical system mounted on a projection exposure apparatus for EUVL. The light used by this projection optical system is EUV light (light having a wavelength of 50 nm or less, for example, light having a wavelength of 13.4 nm).

FIG. 1 is a configuration diagram of the measurement apparatus.
First, the configuration of this measuring apparatus will be described.
In this measuring apparatus, an illumination optical system 11, a reflective pinhole plate 22, an optical system 0 to be tested, a diffractive optical member 41, a mask 42, and an image sensor 15 are arranged in this order. Further, the measurement apparatus includes a stage 16 for moving the diffractive optical member 41, a control circuit 17 for controlling each part, and a computer 18.

The reflection type pinhole plate 22 and the mask 42 are respectively disposed on the object plane and the image plane of the optical system 0 to be tested. The diffractive optical member 41 is disposed between the test optical system 0 and the image plane.
Next, the basic operation of this measuring apparatus will be described.
The illumination optical system 11 emits light having the same wavelength as the wavelength used by the test optical system 0 (here, EUV light) in accordance with an instruction from the control circuit 17. The light illuminates the reflective pinhole plate 22. An ideal spherical wave is generated in the pinhole H of the reflective pinhole plate 22.

The ideal spherical wave enters the test optical system 0 as a measurement light beam, and the wave front is deformed in accordance with the aberration of the test optical system 0 and is emitted from the test optical system 0.
The measurement light beam emitted from the test optical system 0 enters the diffractive optical member 41.
FIG. 2A shows an enlarged view of the periphery of the diffractive optical member 41. In FIG. 2A, the symbol W ₀ indicates the wavefront (transmitted wavefront) of the measurement light beam that has passed through the optical system 0 to be tested.

When the measurement light beam enters the diffractive optical member 41, it is sheared into + 1st order diffracted light and −1st order diffracted light.
These + 1st order diffracted light and −1st order diffracted light pass through the mask 42. On the other hand, other extraneous light (such as 0th-order diffracted light) generated by the diffractive optical member 41 is cut by the mask 42.
The + 1st order diffracted light and the −1st order diffracted light that have passed through the mask 42 are incident on the image pickup surface 15a of the image pickup device 15 with a predetermined amount of deviation, and cause interference fringes at the overlapping portions of both.

Note that the two diffracted lights to be contributed to interference can be a combination other than the + 1st order diffracted light and the −1st order diffracted light (such as the 0th order diffracted light and the + 1st order diffracted light) depending on the arrangement of the opening pattern of the mask 42. However, here, it is described as a combination of + 1st order diffracted light and −1st order diffracted light.
In this way, the interference fringes caused by the + 1st order diffracted light and the −1st order diffracted light are imaged by the image sensor 15 that has received an instruction from the control circuit 17.

Data acquired by the CDD image sensor 15 (interference fringe luminance distribution data) is taken into the computer 18 via the control circuit 17.
The computer 18 analyzes the luminance distribution data and obtains the phase distribution of the interference fringes.
This phase distribution represents the difference between the wavefront W ₁ of the + _{1st order} diffracted light and the wavefront W ₋₁ of the _{−1st order} diffracted light shown in FIG. 2A in a coordinate system (XY coordinate system) on the imaging surface 15a. It is.

Here, the direction of deviation between the + 1st order diffracted light and the −1st order diffracted light is referred to as “shear direction”, and the amount of deviation between the + 1st order diffracted light and −1st order diffracted light is referred to as “shear amount”.
Next, switching of the shear direction of this measuring apparatus will be described.
FIG. 2B is a diagram illustrating a state in which the diffractive optical member 41 is viewed from the optical axis direction.
As shown in FIG. 2B, the diffractive optical member 41 is formed with at least one pair of diffraction gratings 41X and 41Y that are perpendicular to each other in the engraving direction. 2B represents the approximate size of the cross section of the measurement light beam incident on the diffractive optical member 41. The dotted circle in FIG.

The diffractive member 41 is movable in a direction in which the diffraction grating inserted (set) in the optical path of the measurement light beam is switched between the diffraction grating 41X and the diffraction grating 41Y (arrow direction in FIG. 2B). The movement is performed by the stage 16 (see FIG. 1) that has received an instruction from the control circuit 17.
In addition, the engraving direction between the diffraction grating 41X and the diffraction grating 41Y is exactly orthogonal, and the engraving distance between the diffraction grating 41X and the diffraction grating 41Y is exactly the same.

At this time, when the diffraction grating 41X and the diffraction grating 41Y are switched, the shear amount does not change, and only the shear direction changes exactly 90 °.
Next, the relationship between the shear direction by the diffraction gratings 41X and 41Y and the XY coordinate system on the imaging surface 15a will be described with reference to FIG.
In FIG. 3, the shear direction by the diffraction grating 41X is D _X , and the shear direction by the diffraction grating 41Y is D _Y.

As shown in FIG. 3, the shear direction D _X and the shear direction D _Y are accurately shifted by 90 °.
However, since there is a slight misalignment (rotational deviation around the optical axis) between the diffractive optical member 41 and the image sensor 15, the X axis of the XY coordinate system on the imaging surface 15a and the shear direction D _X It is offset by a slight angle alpha, the Y-axis and the shear direction D _Y of the XY coordinate system on the image pickup surface 15a is offset by the same angle alpha.

This angle α indicates the actual shear direction viewed in the XY coordinate system on the imaging surface 15a. Hereinafter, the angle α indicating the deviation between the coordinate axis and the shear direction is referred to as “shear direction deviation α”.
For the sake of explanation, in FIG. 3, the shear direction deviation α is shown to be larger than actual, but the actual deviation α is very small (the same applies to FIGS. 4 and 5 below).
Next, calibration of this measuring apparatus will be described.

In the calibration, the shear direction deviation α is acquired as calibration data.
In calibration, an arbitrary test optical system 0 (or an arbitrary reference optical system) is set in the present measurement apparatus. The pinhole H of the reflection type pinhole 22 is disposed at an arbitrary object point of the optical system 0 to be tested. That is, the incident position of the measurement light beam is arbitrary. In this state, two calibration measurements are performed.
In the first calibration measurement, the control circuit 17 sets the diffraction grating 41X via the stage 16.

The state on the imaging surface 15a at this time is as shown in FIG. 4 (aX), and the shear direction D _X is a direction close to the X direction (left-right direction in the figure) on the imaging surface 15a.
The interference fringes I _X generated at this time are substantially striped patterns extending in a direction close to the Y direction (vertical direction in the figure).
The control circuit 17 acquires the luminance distribution data of the interference fringes I _X via the image sensor 15 and sends it to the computer 18.

In the second calibration measurement, the control circuit 17 sets the diffraction grating 41Y via the stage 16.
The state on the imaging surface 15a at this time is as shown in FIG. 4A, and the shear direction D _Y is a direction close to the Y direction (vertical direction in the figure) on the imaging surface 15a.
The interference fringes I _Y generated at this time are substantially striped patterns extending in a direction close to the X direction (left and right direction in the figure).

The control circuit 17 acquires the luminance distribution data of the interference fringes I _Y via the image sensor 15 and sends it to the computer 18.
Next, the computer 18 obtains the phase distribution Ψ _X (X, Y) of the interference fringes I _X from the luminance distribution data acquired in the first calibration measurement (see the lower part of (aX)), and its primary component Ψ. A direction vector V _X of _X1 (X, Y) is extracted. FIG. 4 (bX) shows the extracted direction vector V _X.

Further, the computer 18 obtains the phase distribution Ψ _Y (X, Y) of the interference fringe I _Y from the luminance distribution data acquired in the second calibration measurement (see (aY) lower part), and its primary component Ψ _Y1. The direction vector V _Y of (X, Y) is extracted. FIG. 4 (bY) shows the extracted direction vector V _Y.
Here, if, as long as the optical system to be measured 0 no aberration, the direction vector V _X represents a shear direction D _X, the direction vector V _Y should show shear direction D _Y. In this case, the deviation between the direction vector V _X and the direction vector V _Y is exactly 90 °.

However, in reality, the test optical system 0 has an aberration, and the patterns of the interference fringes I _X and I _Y are affected by the aberration. Therefore, the direction vectors V _X and V _Y are also affected by the aberration. Therefore, the direction vectors V _X and V _Y indicate directions shifted from the shear directions D _X and D _Y.
Incidentally, since the influence of the direction vector V _{X and} the influence of the direction vector V _Y are different from each other, the deviation between the direction vector V _X and the direction vector V _Y deviates from 90 ° (FIG. 4 (bX), (See (bY)).

In order to remove these influences, the computer 18 of this measuring apparatus applies the direction vectors V _X and V _Y to the following equation (1) to obtain the shear direction deviation α.
α = (V _XY −V _YX ) / (2V _XX )
or
α = (V _XY −V _YX ) / (2V _YY ) (1)
However,
V _XX : X component of the direction vector V _X ,
V _XY : Y component of direction vector V _X ,
V _YY : Y component of direction vector V _Y ,
V _YX : X component of the direction vector V _Y.

Incidentally, since the calculation of the equation (1) does not require all the components of the direction vectors V _X and V _Y , the computer 18 uses the primary components Ψ _X1 (X, Y), Ψ _X1 (X, Y). Only three components (V _XY , V _YX , V _XX ) or (V _XY , V _YX , V _YY ) need be extracted from.
The meaning of this formula (1) will be described later. The computer 18 stores the obtained deviation α data as calibration data, and ends the calibration.

The computer 18 stores the data of “shear amount S” as calibration data together with the data of the shear direction deviation α.
The shear amount S is preferably measured separately, but may be obtained based on each optical design value in the measuring apparatus (the above is calibration).
Next, measurement performed after calibration (measurement of the optical system 0 to be tested) will be described.

  In the measurement of the test optical system 0, the test optical system 0 to be measured is set in the measurement apparatus. The pinhole H of the reflection type pinhole plate 22 is arranged at the measurement object point of the optical system 0 to be tested. That is, the incident position of the measurement light beam is adjusted to the measurement object point. In this state, the measurement of the optical system 0 to be tested is performed twice (note that it may be performed only once as required by the measurer, but here, the case of twice is described).

In the first measurement, the control circuit 17 sets the diffraction grating 41X via the stage 16, acquires the luminance distribution data of the interference fringes I _X generated at this time via the image sensor 15, and sends it to the computer 18. .
In the second measurement, the control circuit 17 sets the diffraction grating 41Y via the stage 16, acquires the luminance distribution data of the interference fringe I _Y generated at this time via the image sensor 15, and sends it to the computer 18. .

The computer 18 obtains the phase distribution Ψ _X (X, Y) of the interference fringes I _X from the luminance distribution data acquired in the first measurement, and the interference fringes I _Y from the luminance distribution data acquired in the second measurement. The phase distribution Ψ _Y (X, Y) is obtained.
Further, the computer 18 refers to the data of the shear direction deviation α stored in the calibration described above, and determines the obtained phase distributions Ψ _X (X, Y), Ψ _Y (X, Y) according to the value of α. The coordinates are transformed and expressed in the xy coordinate system on the diffractive optical member 41.

The computer 18 applies the phase distributions Ψ _X (x, y) and Ψ _X (x, y) that have undergone coordinate conversion to a known arithmetic expression that takes the shear amount S into account, and the measurement light beam that has passed through the optical system 0 to be measured. The phase distribution Ψ ₀ (x, y) of the wave front (transmitted wave front) W ₀ of the current is restored.
For example, the arithmetic expression is an integral expression that integrates Ψ _X (x, y) and Ψ _X (x, y) in the x direction and the y direction. Alternatively, it is an arithmetic expression for fitting Ψ _X (X, Y) and Ψ _X (X, Y) to a predetermined polynomial (measured above).

Next, the effect of this measuring apparatus will be described.
In the calibration of this measuring device, the phase distribution of the interference fringes generated in the measuring device is referred to when acquiring the data in the shear direction (here, the shift α in the shear direction).
Since this phase distribution is obtained by analyzing the luminance distribution data of the interference fringes, if the optical system 0 to be tested has no aberration, the shear direction can be detected with a resolution higher than the resolution of the image sensor 15. it can.

However, since there is an aberration in the actual optical system to be tested 0, in the calibration of this measuring apparatus, in order to remove the influence of the aberration, the shear direction is changed by exactly 90 °, and two kinds of interference fringes I are obtained. _X, the phase distribution [psi _X of _{I Y (X, Y),} Ψ Y (X, Y) acquired. Then, the direction vectors V _X and V _X of the primary components Ψ _X1 (X, Y) and Ψ _Y1 (X, Y) of the obtained phase distributions Ψ _X (X, Y) and Ψ _Y (X, Y) are Apply to equation (1).

Here, the meaning of the formula (1) will be described.
(V _XX and V _{XY in} formula (1))
First, the phase distribution Ψ ₀ of the transmitted wavefront W ₀ of the test optical system 0 includes the wavefront aberration component of the test optical system 0 in addition to the ideal spherical component. It is represented by the formula (2) depending on the system.

Ψ ₀ (X, Y)
= A _Z5 (X ² −Y ² ) + 2A _Z6 XY + b (X ² + Y ² ) + ΣA _Zi Z _i (X, Y) (2)
However, the first and second terms of the equation (2) are the astigmatic components of the wavefront aberration, the third term is the ideal spherical component, and the fourth term is a component other than the astigmatic component of the wavefront aberration (i = 0, 1,. .. 4,7,8, ...)

On the other hand, a coordinate conversion equation between the coordinates (X, Y) on the imaging surface 15a and the coordinates (x, y) on the diffractive optical member 41 is expressed by Equation (3) by the shear direction deviation α.
X = x−yα
Y = y + xα (3)
Here, as the xy coordinate system on the diffractive optical element 41, x-axis in the shear direction D _X, was employed xy coordinate system which arranged y-axis along shear direction D _Y.

Further, since α is very small, the approximation of cos α = 1 and sin α = α is applied to the coordinate conversion equation of Equation (3).
Using this equation (3), to represent the phase distribution [psi ₀ transmitted wavefront W ₀ in the xy coordinate system on the diffractive optical element 41, the equation (4).
Ψ ₀ (x, y)
= A _Z5 (x−yα) ² + 2A _Z6 (x−yα) (y + xα) −A _Z5 (y + xα) ²
+ B [(x−yα) ² + (y + xα) ² )] + ΣA _Zi Z _i (x, y) (4)
However, in the equation (4), Z _i (x, y) is a coordinate transformation of Z _i (X, Y).

Therefore, the phase distribution Ψ _X of the interference fringes I _{X formed} by shearing the transmitted wavefront W ₀ is expressed by the following equation (5) by the xy coordinate system on the diffractive optical member 41 when the shear amount is S.
Ψ _X (x, y)
= 2A _Z5 xS-2A _Z5 yαS + 2A _Z6 yS + 4A _Z6 xαS-2A _Z5 yαS
+ 2b (x−yα) S + 2b (y + xα) αS + ΣA _Zi ΔZ _i (x, y) (5)
In Expression (4), ΔZ _i (x, y) is obtained by shifting Z _i (x, y) by the shear amount S in the x direction.

Therefore, the first-order component Ψ _X1 of the phase distribution Ψ _X of the interference fringe I _X is expressed by Expression (6) by the xy coordinate system on the diffractive optical member 41.
Ψ _X1 (x, y)
= 2A _Z5 xS-2A _Z5 yαS + 2A _Z6 yS + 4A _Z6 xαS-2A _Z5 yαS
+ 2b (x−yα) S + 2b (y + xα) αS (6)
Note that the order of the final term ΣA _Zi ΔZ _i (x, y) in the equation (5) does not become “1”, and thus is eliminated from the primary component Ψ _X1 (x, y). That is, components other than the as-component of the wavefront aberration have no effect on the primary component Ψ _X1 (x, y).

Therefore, the direction vector V _X (direction vector V _X represented by XY coordinate system on the image pickup surface 15a) can be approximated as the following equation (7).
V _X = (V _XX , V _XY ) ≈ (2bS, 2bSα + 2A _Z6 S) (7)
Note that the approximation is based on the assumption that α is very small, and the ideal spherical component of the transmitted wavefront W ₀ of the optical system 0 to be tested is larger than the as-component of the wavefront aberration (b is sufficiently larger than A _Z5 and A _Z6. It was based on the premise that

What equation (7) shows will be described with reference to FIG.
The direction vector V _X is a vector indicating the shear direction D _X as shown in FIG. 5 (aX) if the astigmatism component of the wavefront aberration of the test optical system 0 is zero (A _Z6 = 0). 2bS, 2bSα).
However, since the as component is not actually zero (A _Z6 ≠ 0), the direction vector V _X has a direction (thick line) in which the magnitude of the Y component V _XY increases by 2A _Z6 S as shown in FIG. 5 (bX). It rotates in the direction of the arrow and becomes a vector (2bS, 2bSα + 2A _Z6 S).
(V _YY and V _{YX in} formula (1))
Similarly, the direction vector V _Y (direction vector V _Y expressed in XY coordinate system on the image pickup surface 15a) can be approximated as the following equation (8).

V _Y = (V _YX , V _YY ) ≈ (−2bSα + 2A _Z6 S, 2bS) (8)
What equation (8) shows is considered based on FIG.
The direction vector V _Y is a vector indicating the shear direction D _Y as shown in FIG. 5A if the as-component of the wavefront aberration of the test optical system 0 is zero (A _Z6 = 0). -2bSα, 2bS).

However, since the as component is not actually zero (A _Z6 ≠ 0), the direction vector V _Y has a direction (thick line) in which the magnitude of the X component V _YX decreases by 2A _Z6 S as shown in FIG. It rotates in the direction of the arrow, and becomes a vector (-2bSα + 2A _Z6 S, 2bS).
The rotation amount is the same as the rotation amount of the direction vector V _X , and the rotation direction is opposite to the rotation direction of the direction vector V _X. That is, the effect of vector V _X from the as component is opposite to the effect of vector V _Y from the as component.

Such direction vector V _X, expression for the V _Y (7), (8), equation (1) on the right side (in the direction of the vector V _X Y component V _XY and the direction vector V _Y of the X component V _YX Substituting into the difference equation), it can be seen that the influence of the as component on the direction vector V _X (2A _Z6 S) and the influence of the as component on the direction vector V _Y (2A _Z6 S) cancel each other.
Therefore, according to the equation (1), only the shear direction shift α is obtained without depending on the ass component (the explanation of the meaning of the equation (1)).

As described above, in the calibration of this measuring apparatus, the shear direction data can be obtained with high accuracy without being affected by the wavefront aberration of the optical system 0 to be tested.
In addition, since the data is used in the measurement of this measuring apparatus, the transmitted wavefront W ₀ of the optical system 0 to be measured can be restored with high accuracy.
In the measurement apparatus according to the present embodiment, the shear direction is accurately changed by 90 ° between the first calibration measurement and the second calibration measurement. It may deviate from °. However, the arithmetic expression used in that case is obtained by modifying Expression (1) according to a known deviation amount. Incidentally, if the change angle in the shear direction is precisely 90 °, the arithmetic expression can be simplified as shown in Expression (1).

  In the measurement apparatus of the present embodiment, the shear amount is not changed between the first calibration measurement and the second calibration measurement, but may be changed as long as it is a known change amount. However, the arithmetic expression used in that case is obtained by modifying Expression (1) in accordance with the known change amount of the shear amount. Incidentally, the calculation formula can be simplified as shown in the formula (1) when the shear amount is not changed.

Moreover, in the measuring apparatus of this embodiment, calibration and measurement are all automated, but part of the calibration and measurement described above may be performed manually.
[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIG.
The present embodiment is an embodiment of a shearing interference measuring apparatus using a diffractive optical member as a wavefront dividing unit. Here, only differences from the measurement apparatus of the first embodiment will be described.

FIG. 6 is a configuration diagram of the measurement apparatus.
The difference lies in how the shear direction is switched.
In the diffractive optical member 41 ′ of this measuring apparatus, it is not necessary to form the diffraction gratings 41X and 41Y perpendicular to each other in the engraving direction, and it is sufficient that at least one kind of diffraction grating 41X is formed. Instead, the diffractive optical member 41 ′ can rotate around the optical axis. The rotation is performed by a stage 16 ′ that receives an instruction from the control circuit 17.

When the shear direction is switched between the first calibration measurement and the second calibration measurement and between the first measurement and the second measurement, the control circuit 17 passes the stage 16 through the diffractive optics. The member 41 ′ is rotated exactly 90 °. At this time, the shear amount does not change, and only the shear direction changes by 90 °.
Also in the above measuring apparatus, the same effect as the measuring apparatus of the first embodiment can be obtained.

In the measurement apparatus of the present embodiment, the change angle in the shear direction may be slightly shifted from 90 ° as long as it is a known shift amount. However, the arithmetic expression used in that case is obtained by modifying Expression (1) according to a known deviation amount. Incidentally, if the change angle in the shear direction is precisely 90 °, the arithmetic expression can be simplified as shown in Expression (1).
Moreover, in the measuring apparatus of this embodiment, a part of calibration and measurement may be performed manually.

[Others]
In the above-described embodiment, the shearing interference measuring apparatus that measures the projection optical system mounted on the EUVL projection exposure apparatus has been described. However, other projection optical systems having different wavelengths to be used, and optical systems other than the projection optical system. A shearing interferometer for measuring the system may be configured similarly. Incidentally, when the wavelength used is longer than 50 nm, a transmissive pinhole plate can be used instead of the reflective pinhole plate 22.

[Third Embodiment]
The present embodiment is an embodiment of a projection exposure apparatus for EUVL equipped with the same function as the measurement apparatus of the first embodiment.
As shown in FIG. 7, the projection exposure apparatus includes an illumination optical system 101, a reflective reticle R, a reticle stage 102, a drive circuit 102c for the reticle stage 102, a reflective pinhole plate 22, a projection optical system PL, a wafer. W, wafer stage 106, drive circuit 106c for wafer stage 106, measurement unit 50, control unit 109, and the like are arranged.

The projection optical system PL is a projection optical system for EUVL, and the illumination optical system 101 emits EUV light as illumination light for exposure. This illumination light beam is also used as a measurement light beam when measuring the projection optical system PL.
The reflective pinhole plate 22 is inserted into the object plane of the projection optical system PL instead of the reticle R only when measuring the projection optical system PL.

FIG. 7 shows a state in which the reticle R and the reflective pinhole plate 22 are both supported by the reticle stage 102. By movement of the reticle stage 102, the reticle R and the reflective pinhole plate 22 are interchanged.
In the measurement unit 50, the diffractive optical member 41, the stage 16, the mask 42, and the image sensor 15 of the measurement apparatus of the first embodiment are arranged in a predetermined positional relationship.

The measurement unit 50 is set in the optical path on the image side of the test optical system PL instead of the wafer W only when measuring the projection optical system PL.
FIG. 6 shows a state in which the wafer W and the measurement unit 50 are both supported by the wafer stage 106. By moving the wafer stage 106, the wafer W and the measurement unit 50 are interchanged, and the optical system 10 to be tested can be inserted into the optical path.

The control unit 109 uses such a measurement unit 50 to execute calibration and measurement as in the first embodiment.
According to the operation of the control unit 109, the transmitted wavefront of the projection optical system PL can be measured with high accuracy.
Therefore, the projection exposure apparatus is a high-performance projection exposure apparatus that can perform self-measurement of the projection optical system PL with high accuracy.

In the present embodiment, the EUVL projection exposure apparatus having the same function as that of the measurement apparatus of the first embodiment has been described. However, other projection exposure apparatuses having different operating wavelengths and the measurement apparatus of the second embodiment are described. A projection exposure apparatus equipped with the same function can be configured.
[Fourth Embodiment]
A fourth embodiment of the present invention will be described with reference to FIG.

The present embodiment is an embodiment of a method for manufacturing a projection optical system. This projection optical system may be a projection optical system for EUVL or other projection optical system.
FIG. 8 is a flowchart showing the procedure of the method for manufacturing the projection optical system.
The optical design of the projection optical system is performed (step S101). In step S101, each surface shape of each optical member in the projection optical system is determined.

Each optical member is processed (step S102).
While measuring the surface shape of each processed optical member, the processing is repeated until the surface accuracy error is reduced (steps S102, S103, S104).
After that, when the surface accuracy errors of all the optical members are within the allowable range (Step S104 OK), the optical members are completed, and the projection optical system is assembled with these optical members (Step S105).

After assembling, the transmission wavefront of the projection optical system is measured by any of the measurement apparatuses of the above-described embodiments (step S106), and the distance between the optical members is adjusted and the eccentricity is adjusted (step S108). When the wavefront aberration of the system falls within the allowable range (step S107OK), the projection optical system PL is completed (the procedure of the manufacturing method).
Next, the effect of this manufacturing method will be described.

In the present manufacturing method, any of the measurement apparatuses of the above-described embodiments is used for measurement of the projection optical system. According to this measuring apparatus, the projection optical system can be measured with high accuracy. Therefore, according to this manufacturing method, a high-performance projection optical system can be manufactured.
Furthermore, by using this manufacturing method, a high-performance projection exposure apparatus that can transfer a reticle pattern onto a wafer with high accuracy can be manufactured.

[Fifth Embodiment]
A fifth embodiment of the present invention will be described with reference to FIG.
The present embodiment is an embodiment of a manufacturing method for manufacturing a micro device (a semiconductor element, an image sensor, a liquid crystal display element, a thin film magnetic head, etc.) by any of the projection exposure apparatuses of the above-described embodiments.

This manufacturing method consists of the procedure shown in FIG.
A metal film is deposited on one lot of wafers (step S301).
A photoresist is applied on the metal film on the wafer of one lot (step S302).
Using the projection exposure apparatus of any of the above-described embodiments, the pattern image on the mask is sequentially exposed and transferred to each shot area on the wafer of one lot (step S303).

  After developing the photoresist on the one lot of wafers (step S304), in step 305, etching is performed on the one lot of wafers using the resist pattern as a mask. Thereby, a circuit pattern corresponding to the pattern on the mask is formed in each shot area on each wafer. Thereafter, the upper layer circuit pattern is formed and the microdevice is completed.

  As described above, in this manufacturing method, since any one of the projection exposure apparatuses of the above-described embodiments is used in Step 303, a high-performance microdevice can be manufactured.

It is a block diagram of the shearing interference measuring apparatus of 1st Embodiment. (A) is a figure which shows the mode of the periphery of the diffractive optical member 41. FIG. (B) is a figure which shows a mode that the diffractive optical member 41 was seen from the optical axis direction. It is a figure explaining the relationship between the shear direction by diffraction gratings 41X and 41Y, and the XY coordinate system on the imaging surface 15a. It is a figure explaining the procedure of calibration of a 1st embodiment. It is a figure explaining Formula (1). It is a block diagram of the shearing interference measuring apparatus of 2nd Embodiment. It is a block diagram of the projection exposure apparatus of 3rd Embodiment. It is a flowchart which shows the procedure of the manufacturing method of the projection optical system of 4th Embodiment. It is a flowchart which shows the procedure of the manufacturing method of the microdevice of 5th Embodiment.

Explanation of symbols

11 Illumination Optical System 22 Reflective Pinhole Plate 41 Diffractive Optical Member 42 Mask 15 Imaging Element 16 Stage 17 Control Circuit 18 Computer 41X Diffraction Grating 41Y Diffraction Grating 15a Imaging Surface

Claims (20)

Wavefront dividing means capable of shearing the wavefront of the measurement light beam passing through the optical system to be measured in two directions whose relations are known;
An image sensor for detecting interference fringes formed by wavefronts sheared by the wavefront dividing means on a predetermined plane, and a calibration method for a shearing interference measuring apparatus comprising:
In the state where any test optical system or reference optical system is set in the shearing interference measuring apparatus, data of interference fringes formed by wavefronts sheared in one of the two directions and sheared in the other of the two directions. A calibration measurement procedure for acquiring data of interference fringes formed by wavefronts;
A shearing interference measuring apparatus, comprising: a calculation procedure for acquiring data in the shear direction of the wavefront dividing means based on the image sensor based on the acquired two interference fringe data and the relationship. Calibration method. In the calibration method of the shearing interference measuring apparatus according to claim 1,
In the calculation procedure,
A method for calibrating a shearing interferometer, wherein a predetermined arithmetic expression is used to remove the influence of the wavefront aberration of the optical system to be measured on the primary component of the phase distribution of the interference fringes. In the calibration method of the shearing interference measuring apparatus according to claim 2,
The wavefront dividing means is
It is possible to shear the wavefront in equal amounts in the X and Y directions orthogonal to each other,
The predetermined arithmetic expression is
The Y direction component of the direction vector of the primary component of the phase distribution of the interference fringe formed by the wavefronts sheared in the X direction and the primary component of the phase distribution of the interference fringe formed by the wavefronts sheared in the Y direction. A calibration method for a shearing interference measuring apparatus, characterized in that an arithmetic expression for calculating a difference between the directional vector and the X direction component is used. In the calibration method of the shearing interference measuring apparatus according to any one of claims 1 to 3,
The wavefront dividing means is
It has two diffraction gratings whose relationship between the engraving directions is known, and the diffraction grating inserted into the measurement light beam can be switched between the two diffraction gratings while maintaining the relationship. Calibration method of shearing interference measuring apparatus. In the calibration method of the shearing interference measuring apparatus according to any one of claims 1 to 3,
The wavefront dividing means is
A method for calibrating a shearing interferometer, comprising a diffraction grating and capable of switching the direction of arrangement of the diffraction grating around the optical axis with respect to the measurement light beam to two directions having a known relationship. In the calibration method of the shearing interference measuring apparatus according to any one of claims 1 to 5,
The test optical system is:
A projection optical system for EUVL;
The measurement luminous flux is
A calibration method for a shearing interference measuring apparatus, comprising EUV light having a wavelength of 50 nm or less. A calibration procedure for acquiring the shear direction data of the shearing interference measurement device by the calibration method of the shearing interference measurement device according to any one of claims 1 to 6,
A measurement procedure for obtaining interference fringe data by setting a test optical system in the shearing interference measurement device;
A shearing interference measurement method comprising: a measurement procedure for restoring a transmitted wavefront of a test optical system based on the measurement data and the shear direction data. Wavefront dividing means capable of shearing the wavefront of the measurement light beam passing through the optical system to be measured in two directions whose relations are known;
An image sensor for detecting interference fringes formed on the predetermined plane by wavefronts sheared by the wavefront dividing means;
With any test optical system or reference optical system set in the shearing interference measuring apparatus, interference fringe data formed by wavefronts sheared in one of the two directions and sheared in the other of the two directions. Control means for acquiring the interference fringe data formed by the wave fronts, respectively,
Shearing interference measurement, comprising: arithmetic means for acquiring data in the shear direction of the wavefront dividing means based on the image sensor based on the acquired two interference fringe data and the relationship apparatus. The shearing interference measurement apparatus according to claim 8,
The computing means is
A shearing interference measuring apparatus using a predetermined arithmetic expression that removes the influence of the wavefront aberration of the optical system to be measured on the primary component of the phase distribution of the interference fringes. In the shearing interference measuring apparatus according to claim 9,
The wavefront dividing means is
It is possible to shear the wavefront in equal amounts in the X and Y directions orthogonal to each other,
The predetermined arithmetic expression is
The Y direction component of the direction vector of the primary component of the phase distribution of the interference fringe formed by the wavefronts sheared in the X direction and the primary component of the phase distribution of the interference fringe formed by the wavefronts sheared in the Y direction. A shearing interference measuring apparatus, characterized by being an arithmetic expression that takes a difference between the direction vector of the X direction component and the X direction component. In the shearing interference measuring device according to any one of claims 8 to 10,
The wavefront dividing means is
It has two diffraction gratings whose relationship between the engraving directions is known, and the diffraction grating inserted into the measurement light beam can be switched between the two diffraction gratings while maintaining the relationship. Shearing interference measuring device. In the shearing interference measuring device according to any one of claims 8 to 10,
The wavefront dividing means is
A shearing interference measuring apparatus having a diffraction grating and capable of switching the arrangement direction of the diffraction grating around the optical axis with respect to the measurement light beam to two known relations. In the shearing interference measuring device according to any one of claims 8 to 12,
The test optical system is:
A projection optical system for EUVL;
The measurement luminous flux is
A shearing interference measuring device comprising EUV light having a wavelength of 50 nm or less. A transmitted wavefront of the projection optical system is measured by the shearing interference measuring method according to claim 7,
The projection optical system is adjusted based on a result of the measurement. A projection optical system manufactured by the method for manufacturing a projection optical system according to claim 14. A method for manufacturing a projection exposure apparatus, comprising a step of manufacturing a projection optical system by the method for manufacturing a projection optical system according to claim 14. A projection exposure apparatus manufactured by the method for manufacturing a projection exposure apparatus according to claim 16. A projection exposure apparatus comprising the shearing interference measuring apparatus according to any one of claims 8 to 13. A microdevice is manufactured by the projection exposure apparatus according to claim 17 or 18. A microdevice manufactured by the method for manufacturing a microdevice according to claim 19.

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