JP2006078984A - Lithographic optical member, projection optical system, projection exposure apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve imaging performance in a projection optical system of a projection exposure apparatus. <P>SOLUTION: The projection optical system forms an image of an object illuminated with illumination light at ≤400 nm wavelength, and it has wavefront aberration of a predetermined form. The wavefront aberration of a predetermined form is characterized in that when after the wavefront aberration of the predetermined form is subjected to fitting by a predetermined function, the form of the residual component remaining is within a given range. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a projection optical system for forming an image of an object, an optical member included in the projection optical system, a projection exposure apparatus including the projection optical system, and a projection exposure method using the projection optical system.

  In the projection optical system of the conventional projection exposure apparatus, the imaging performance is evaluated using the wavefront aberration. Typically, the wavefront aberration is fitted with a Zernike function, and each term of the Zernike function is The coefficient was used as the evaluation method.

  Further, in order to improve the imaging performance of the projection optical system, the optical member used in the projection optical system can reduce the surface shape error of the optical surface (refractive surface / reflective surface), There is a need for improved homogeneity. Here, when evaluating the surface shape error, the surface shape is fitted with a Zernike function, and the coefficient of each term of the Zernike function is used as the evaluation method. In evaluating the homogeneity inside the optical member, the shape of the transmitted wavefront of the optical member is fitted with a Zernike function, and the coefficient of each term of the Zernike function is used as an evaluation method.

  In the evaluation of the imaging performance as described above, the effect of the fitting residue component remaining after fitting the wavefront aberration, such as the Zernike function, on the imaging performance was unclear, so for this fitting residue component PK-PK The only aim was to reduce the value and the rms value. Therefore, there is a problem that it is difficult to feed back the evaluation of the imaging performance to the production of the projection optical system.

  Similarly, in the evaluation of surface shape error and the homogeneity inside the optical member, the effect of fitting residue components remaining after fitting the surface shape and the transmitted wavefront shape of the optical member on the imaging performance after fitting the Zernike function, etc. Since it was unclear, the aim was only to reduce the PK-PK value and the rms value for this fitting residue component. Therefore, there is a problem that it is difficult to feed back the evaluation of the surface shape error of the optical member and the evaluation of the homogeneity inside the optical member to the production of the optical member, and it is difficult to feed back to the production of the projection optical system. .

  Accordingly, an object of the present invention is to improve the imaging performance of a projection optical system.

  In order to achieve the above object, a projection optical system according to a first aspect of the present invention is a projection optical system that forms an image of an object illuminated with illumination light having a wavelength of 400 nm or less, and the projection optical system includes: The wavefront aberration having a predetermined shape is characterized in that the shape of the residual component remaining after fitting the wavefront aberration of the predetermined shape with a predetermined function is within a given range. .

  A projection exposure apparatus according to a second aspect of the present invention is a projection exposure apparatus that projects a predetermined pattern onto a photosensitive substrate, and includes the projection optical system according to the first aspect.

  A projection exposure method according to a third aspect of the present invention is a projection exposure method for projecting a predetermined pattern onto a photosensitive substrate, and the predetermined pattern using the projection optical system according to the first aspect. Is projected onto a photosensitive substrate.

An optical member according to a fourth aspect of the present invention is an optical member for lithography used with light having a wavelength of 400 nm or less, and the optical member includes one or more optical surfaces, The projection shape existing in the fitting residue shape remaining after fitting the error shape from the design value with a predetermined function is (25) [Σ {Tk × (Dk / 300) ² } ² ] ^1/2 <0. 00003λ
It is characterized by satisfying.

Where Tk is the height of the protrusion shape, Dk is the diameter of the circumscribed circle on the bottom surface of the protrusion shape, and λ is the wavelength of the light.
The protrusion shape has a ratio of base sizes of the protrusion shape as DVk in the vertical direction and DHk in the horizontal direction.
(26) 3 ≦ DVk ≦ 30
(27) 3 ≦ DHk ≦ 30, and (28) λ / 100 ≦ Tk
Satisfied.

An optical member according to a fifth aspect of the present invention is an optical member for lithography used with light having a wavelength of 400 nm or less, and the optical member includes one or more optical surfaces, The streak shape existing in the fitting residue shape remaining after fitting the error shape from the design value with a predetermined function is (29) [Σ {2 × Hl × Wl × Ll / 300 ² } ² ] ^1/2 < 0.00035λ
It is characterized by satisfying.

Where Hl is the height of the stripe shape, Wl is the width of the bottom surface of the stripe shape, Ll is the length of the bottom surface of the stripe shape, and λ is the wavelength of the light,
The streak shape is
(30) 3 ≦ Wl ≦ 30
(31) λ / 100 ≦ Hl is satisfied.

An optical member according to a sixth aspect of the present invention is an optical member for lithography used with light having a wavelength of 400 nm or less, and the optical member includes one or more optical surfaces, The protrusion shape and streak shape existing in the fitting residue shape remaining after fitting the error shape from the design value with a predetermined function is (32) [Σ {Tk × (Dk / 300) ² } ² ] ^1/2 + [Σ {2 × Hl × Wl × Ll / 300 ² } ² ] ^1/2 <0.00035λ
It is characterized by satisfying.
Where Tk is the height of the projection shape, Dk is the diameter of the circumscribed circle of the bottom surface of the projection shape, Hl is the height of the stripe shape, Wl is the width of the bottom surface of the stripe shape, and Ll is the length of the bottom surface of the stripe shape. , Λ is the wavelength of the light,
The protrusion shape has a ratio of base sizes of the protrusion shape as DVk in the vertical direction and DHk in the horizontal direction.
(26) 3 ≦ DVk ≦ 30
(27) 3 ≦ DHk ≦ 30, and (28) λ / 100 ≦ Tk
And the streak shape is
(30) 3 ≦ Wl ≦ 30, and (31) λ / 100 ≦ Hl
Satisfied.

An optical member according to a seventh aspect of the present invention is an optical member for lithography used with light having a wavelength of 400 nm or less, and an error shape with respect to a transmitted wavefront in a light transmitting material forming the optical member. The protrusion shape existing in the fitting residue shape remaining after fitting with a predetermined function is (33) [Σ {Tm × (Dm / 300) ² } ² ] ^1/2 <0.026
It is characterized by satisfying.
Where Tm is the height of the projection shape (nm), Dm is the diameter of the circumscribed circle on the bottom surface of the projection shape,
The protrusion shape is such that when the ratio of the size of the base of the protrusion shape is DVm in the vertical direction, DHm in the horizontal direction, and the wavelength of the light is λ,
(34) 3 ≦ DVm ≦ 30
(35) 3 ≦ DHm ≦ 30, and (36) λ / 100 ≦ Tm
Satisfied.

An optical member according to an eighth aspect of the present invention is an optical member for lithography used with light having a wavelength of 400 nm or less, and an error shape with respect to a transmitted wavefront in a light transmitting material forming the optical member. A streak shape existing in the fitting residue shape remaining after fitting with a predetermined function is (37) [Σ {2 × Hn × Wn × Ln / 300 ² } ² ] ^1/2 <0.026
It is characterized by satisfying.
However, Hn is the height (nm) of the stripe shape, Wn is the width of the bottom surface of the stripe shape, Ln is the length of the bottom surface of the stripe shape,
(38) 3 ≦ Wn ≦ 30
(39) λ / 100 ≤ Hn
Satisfied.

An optical member according to the ninth aspect of the present invention is an optical member for lithography used with light having a wavelength of 400 nm or less, and an error shape with respect to a transmitted wavefront in a light-transmitting material forming the optical member. The protrusion shape and streak shape existing in the fitting residue shape remaining after fitting with a predetermined function is (40) [Σ {Tm × (Dm / 300) ² } ² ] ^1/2 + [Σ {2 × Hn × Wn × Ln / 300 ² } ² ] ^1/2 <0.026
It is characterized by satisfying.
Where Tm is the height of the projection shape (nm), Dm is the diameter of the circumscribed circle on the bottom surface of the projection shape, Hn is the height of the stripe shape (nm), Wn is the width of the stripe shape bottom surface, and Ln is the stripe shape. The length of the bottom,
The protrusion shape is such that the ratio of the size of the base of the protrusion shape is DVm in the vertical direction and DHm in the horizontal direction.
(34) 3 ≦ DVm ≦ 30
(35) 3 ≦ DHm ≦ 30, and (36) λ / 100 ≦ Tm
And the streak shape is
(38) 3 ≦ Wn ≦ 30, and (39) λ / 100 ≦ Hn
Satisfied.

  As described above, according to the present invention, it is possible to evaluate the fitting residue component of the wavefront aberration of the projection optical system, and this can be easily fed back to the production of the projection optical system. Can be improved.

  Further, according to the present invention, it becomes possible to evaluate the fitting residue component of the surface shape of the optical member and the shape of the transmitted wavefront of the optical member, and this is fed back to the manufacture of the optical member and thus the projection optical system. Thus, the imaging performance of the projection optical system can be improved.

  First, the inventors of the present application have identified what components remain in relation to the fitting residue components that remain after fitting up to 37 terms with the Fringe-Zernike function from the wavefront aberration generated by the optical system. investigated.

From this investigation, it was found that many shapes such as so-called protrusions and streaks were included as shown in FIG. 1 showing the wavefront aberration of the optical system three-dimensionally.
It has been clarified that the component (the coefficient of each term of the Zernike function) obtained by fitting the wavefront aberration of the optical system with the Zernike function has an effect on the imaging aberration.

  For example, numerical values allowed for the Zernike function fitting component are well known from the relationship between the Zernike function fitting component and the imaging aberration by various calculations such as Zernike linear combination.

  However, until now it has not been clarified how the shape of a so-called protrusion or the shape of a streak, which cannot be expressed by function fitting such as the Zernike function, affects the imaging performance.

  The inventors of the present application estimated the influence of the projection shape and streak shape generated on the wavefront aberration on the imaging performance, and found that the influence on the image magnification and the amount of distortion change due to the difference between the illumination conditions was most significant.

  Therefore, in one aspect of the present invention, by limiting the residual wavefront aberration shape with respect to the fitting residue shape remaining after fitting the wavefront aberration generated in the projection optical system with a predetermined function such as a Zernike function, Good imaging performance is obtained.

  In particular, when the shape of the fitting residue component has at least one of a protrusion shape and a streak shape, by restricting the protrusion shape and the streak shape, image magnification and distortion due to differences in illumination conditions can be reduced. The amount of change can be suppressed to an extremely small value.

  Note that wavefront aberrations such as protrusions and streaks are not caused by changes in the attitude of lenses, mirrors, etc. constituting the projection optical system, and surfaces of optical members constituting the projection optical system. It has been found that this is caused by errors occurring in each optical member such as shape processing errors and inhomogeneities (for example, refractive index unevenness) existing in the material of the optical member.

  Therefore, the surface shape processing error of the optical member causing the projection-shaped and streak-shaped wavefront aberrations, and the manufacturing error existing inside the optical member causing the projection-shaped and streak-shaped wavefront aberrations are within a predetermined range. By limiting to the inside, the imaging performance of the projection optical system can be improved.

With reference to FIG. 2, the protrusion shape in this embodiment is demonstrated. FIG. 2 is a schematic view showing the projection shape three-dimensionally. In the present embodiment, the size of the base of the projection shape is normalized by the magnitude of the NA (numerical aperture) of the wavefront aberration when the projection optical system has the maximum numerical aperture, and the projection shape with respect to the NA of the wavefront of the wavefront aberration When the ratio of the base size of the projection is DVi in the vertical direction and the ratio of the base size of the protrusion shape to the NA of the wavefront of the wavefront aberration is DHi in the horizontal direction,
(1) 1/100 ≦ DVi ≦ 1/10 and (2) 1/100 ≦ DHi ≦ 1/10
And the wavelength of the light used by the projection optical system is λ and the height of the protrusion shape is Ti,
(3) λ / 100 ≤ Ti
The shape satisfying the above is the projection shape.

Here, when the ratio of the diameter of the circumscribed circle of the bottom surface of the projection shape to the NA of the wavefront is Di,
(4) [Σ {Ti × Di ² } ² ] ^1/2 <0.00035λ
Is preferably satisfied.

  When the above condition (4) is not satisfied, the projection component in the wavefront aberration of the projection optical system becomes excessive, and the amount of change in image magnification and distortion caused by changing the illumination condition due to this projection component This is not preferable because the amount of change is not acceptable.

  Then, by limiting the surface shape processing error of the optical member constituting the projection optical system and the refractive index non-uniformity existing inside the optical member so as to satisfy the conditional expression (4), the illumination condition is set. The change amount of the image magnification and the change amount of the distortion at the time of the change can be suppressed extremely small.

Next, the streak shape in the present embodiment will be described with reference to FIG. FIG. 3 is a schematic view showing the stripe shape three-dimensionally. In the present embodiment, the size of the wavefront aberration at the maximum numerical aperture of the projection optical system is normalized by the size of the short side of the bottom of the streak shape, and the wavefront aberration wavefront is normalized. When the ratio of the length in the short direction of the bottom of the streak shape to the NA is Wj,
(5) 1/100 ≦ Wj ≦ 1/10
When the wavelength of light used by the projection optical system is λ and the height of the streak shape is Hj,
(6) λ / 100 ≤ Hj
The one that satisfies the above is a streak shape.

Here, when the streak shape is Lj, the ratio of the length in the longitudinal direction of the bottom of the streak shape to the NA of the wavefront of the wavefront aberration is
(7) [Σ {2 × Hj × Wj × Lj} ² ] ^1/2 <0.00035λ
Is preferably satisfied.

  If the above condition (7) is not satisfied, the streak component in the wavefront aberration of the projection optical system becomes excessive, and the amount of change in image magnification and distortion caused by changing the illumination condition due to this streak component This is not preferable because the amount of change is not acceptable.

  Then, by limiting the surface shape processing error of the optical member constituting the projection optical system and the refractive index non-uniformity existing inside the optical member so as to satisfy the conditional expression (7), the illumination condition is set. The change amount of the image magnification and the change amount of the distortion at the time of the change can be suppressed extremely small.

In addition, when both the projection shape and the streak shape are included in the wavefront aberration of the projection optical system,
(8) [Σ {Ti × Di ² } ² ] ^1/2 + [Σ {2 × Hj × Wj × Lj} ² ] ^1/2 <0.00035λ
Is preferably satisfied.

  When the above condition (8) is not satisfied, the projection component and the streak component in the wavefront aberration of the projection optical system become excessive, and the illumination condition is changed due to the projection component and the streak component. This is not preferable because the amount of change in image magnification and the amount of change in distortion become unacceptable.

  Then, by limiting the surface shape processing error of the optical member constituting the projection optical system and the refractive index non-uniformity existing inside the optical member so as to satisfy the conditional expression (8), the illumination condition is set. The change amount of the image magnification and the change amount of the distortion at the time of the change can be suppressed extremely small.

  FIG. 4 is a graph showing the relationship between the volume of the projection component and the streak component in the wavefront aberration and the difference between the illumination conditions of the distortion. From this graph, the projection component and the streak component in the wavefront aberration It is understood that by suppressing the volume to a small value, the difference between the illumination conditions of the distortion can be set to a value having no practical problem. By satisfying the above condition (4), (7) or (8), the projection component in the fitting residue shape remaining after fitting the wavefront aberration generated in the projection optical system with a predetermined function such as a Zernike function, and In addition, the volume of the streak component can be reduced, and thereby, the difference between the illumination conditions of the distortion can be reduced.

FIG. 5 is a diagram showing a schematic configuration of a projection exposure apparatus provided with the projection optical system 40 of the present embodiment. In FIG. 5, a predetermined wavelength λ (typically 193 nm for ArF excimer laser, 248 nm for KrF excimer laser, i-line (365 nm) for mercury lamp, 157 nm for F ₂ laser, 13 nm for EUV, etc. The illumination optical system 20 illuminates a mask (reticle) 30 on which a predetermined pattern such as a circuit pattern is formed. At this time, the illumination optical system 20 has a light intensity distribution (for example, two poles, three poles) in illumination conditions for the mask 30, typically, an illumination pupil of the illumination optical system (a position optically conjugate with the aperture stop of the projection lens). 4 poles, 5 poles, 6 poles, 8 poles, or other multipoles or ring zones).

  The projection optical system 40 disposed in the optical path between the mask 30 as the object and the wafer 50 as the photosensitive substrate forms an image of a predetermined pattern on the mask 30 on the wafer 50 on the wafer stage 60. At this time, the magnification of the projection optical system 40 may be a reduction magnification, an enlargement magnification, or an equal magnification. The projection optical system 40 includes lenses 41 to 47 as a plurality of optical members arranged along the optical axis Ax. Although FIG. 5 shows the projection optical system 40 having seven lenses for simplification of the drawing, the number of lenses may be larger. In this embodiment, the refractive projection optical system is used. However, the projection optical system may be a catadioptric projection optical system including a lens and a mirror, or a reflective projection optical system including only a mirror. .

In the present embodiment, the plurality of lenses 41 to 47 are included in the fitting residue shapes remaining after fitting an error shape from a design value for each of one or more optical surfaces (lens surfaces) with a predetermined function. The existing projection shape is (9) [Σ {Tk × (Dk / PS) ² } ² ] ^1/2 <0.00035λ
Is preferably satisfied.

Where Tk is the height of the projection shape, Dk is the diameter of the circumscribed circle of the bottom surface of the projection shape, PS is the size of the region where the light beam from a predetermined point on the object reaches the optical member, and λ is This is the wavelength of the illumination light. And when the ratio of the size of the base of the protrusion shape is DVk in the vertical direction and DHk in the horizontal direction,
(10) PS / 100 ≦ DVk ≦ PS / 10
(11) PS / 100 ≦ DHk ≦ PS / 10, and (12) λ / 100 ≦ Tk
A shape that satisfies the above is a projection shape.

  Here, a projection shape existing in a fitting residue shape remaining after fitting an error shape from a design value for one or more optical surfaces (lens surfaces) with a predetermined function is to satisfy the above condition (9). When the fitting residue shape is cut out in the region having the size of the PS, it indicates a case where the above condition (9) is satisfied regardless of the cutting method.

  If the above condition (9) is not satisfied, the projection component in the wavefront aberration of the projection optical system becomes excessive due to the projection component in the lens surface shape error of the lenses 41 to 47 as the optical member, As shown in FIG. 4, the amount of change in image magnification and the amount of change in distortion when the illumination conditions are changed are not preferable.

  When the projection optical system has a reflecting surface, the projection shape existing in the fitting residue shape remaining after fitting the error shape from the design value for the reflecting surface with a predetermined function is the above condition. It is preferable that (9) is satisfied.

In the present embodiment, the plurality of lenses 41 to 47 are included in the fitting residue shapes remaining after fitting an error shape from a design value for each of one or more optical surfaces (lens surfaces) with a predetermined function. The existing stripe shape is (13) [Σ {2 × Hl × Wl × Ll / PS ² } ² ] ^1/2 <0.00035λ
Is preferably satisfied.

Where Hl is the height of the stripe shape, Wl is the width of the bottom surface of the stripe shape, Ll is the length of the bottom surface of the stripe shape, and PS is when the light beam from a predetermined point on the object reaches the optical member. Λ is the wavelength of the illumination light. And
(14) PS / 100 ≦ Wl ≦ PS / 10, and (15) λ / 100 ≦ Hl
The one that satisfies the above is a streak shape.

  Here, a streak shape existing in a fitting residue shape remaining after fitting an error shape from a design value for one or more optical surfaces (lens surfaces) with a predetermined function satisfies the above condition (13). When the fitting residue shape is cut out in the region having the size of the PS, it indicates a case where the above condition (13) is satisfied regardless of the cutting method.

  When the above condition (13) is not satisfied, the streak component in the wavefront aberration of the projection optical system becomes excessive due to the streak component in the lens surface shape error of the lenses 41 to 47 as the optical member, As shown in FIG. 4, the amount of change in image magnification and the amount of change in distortion when the illumination conditions are changed are not preferable.

  When the projection optical system has a reflecting surface, the protrusion shape existing in the fitting residue shape remaining after fitting the error shape from the design value for the reflecting surface with a predetermined function is the above condition. It is preferable that (13) is satisfied.

In the present embodiment, the plurality of lenses 41 to 47 are included in the fitting residue shapes remaining after fitting an error shape from a design value for each of one or more optical surfaces (lens surfaces) with a predetermined function. The existing protrusion shape and stripe shape are (16) [Σ {Tk × (Dk / PS) ² } ² ] ^1/2 + [Σ {2 × Hl × Wl × Ll / PS ² } ² ] ^1/2 <0.00035 λ
Is preferably satisfied.

  Where Tk is the height of the protrusion shape, Dk is the diameter of the circumscribed circle on the bottom surface of the protrusion shape, and PS is the size of the region when the light beam from a predetermined point on the object reaches the optical member. , Hl is the height of the stripe shape, Wl is the width of the bottom surface of the stripe shape, Ll is the length of the bottom surface of the stripe shape, and PS is the light flux from a predetermined point on the object when reaching the optical member. The size of the region, λ, is the wavelength of the illumination light.

Here, those satisfying the above conditions (10) to (12) are defined as protrusions, and those satisfying the above conditions (14) and (15) are defined as stripes.
Here, the protrusion shape and the streak shape existing in the fitting residue shape remaining after fitting the error shape from the design value for one or more optical surfaces (lens surfaces) with a predetermined function satisfy the above condition (16). Satisfied refers to a case where, when the fitting residue shape is cut out in the region having the PS size, the above condition (16) is satisfied regardless of the cut-out method.

  If the above condition (16) is not satisfied, the projection component and streak in the wavefront aberration of the projection optical system due to the projection component and streak component in the lens surface shape error of the lenses 41 to 47 as the optical members. This is not preferable because there are too many components, and the amount of change in image magnification and the amount of change in distortion when the illumination conditions are changed as shown in FIG.

  When the projection optical system has a reflecting surface, the projection shape existing in the fitting residue shape remaining after fitting the error shape from the design value for the reflecting surface with a predetermined function is the above condition. It is preferable that (16) is satisfied.

Further, in the present embodiment, the plurality of lenses 41 to 47 are error shapes with respect to the transmitted wavefront of a light transmitting material (for example, a crystal material such as quartz glass or fluorite, or an ultraviolet transmitting glass) forming each lens. The protrusion shape existing in the fitting residue shape remaining after fitting with a predetermined function is (17) [Σ {Tm × (Dm / PD) ² } ² ] ^1/2 <0.026
Is preferably satisfied.

  Where Tm is the height of the projection shape (nm), Dm is the diameter of the circumscribed circle on the bottom surface of the projection shape, and PD is the size of the region when the light beam from a predetermined point on the object reaches the optical member. It is the size of the smaller one. In the case of an optical member such as a lens or a plane-parallel plate, when considering the size of a region when a light beam from a predetermined point on the object reaches the optical member, the incident-side optical surface (lens surface) Although it is necessary to consider both the optical surface (lens surface) on the exit side, in the case of the condition (17), attention is paid to the smaller of the size of the area in both.

And when the ratio of the size of the base of the protrusion shape is DVm in the vertical direction, DHm in the horizontal direction, and the wavelength of the illumination light is λ,
(18) PD / 100 ≦ DVm ≦ PD / 10
(19) PD / 100 ≦ DH m ≦ PD / 10, and (20) λ / 100 ≦ Tm
Projection shape that satisfies the above.

  Here, the protrusion shape existing in the fitting residue shape remaining after fitting the error shape with respect to the transmission wavefront of the light transmitting material forming each lens (optical member) with a predetermined function is the above condition (17 ) Is satisfied, the transmitted wavefront of the light transmissive material is measured using a known interferometer or the like, and the difference shape (error wavefront) between the measured transmitted wavefront and the ideal transmitted wavefront is, for example, a Zernike function Fitting is performed using a predetermined function of the above, and when the residue component (residue shape) that has not been fitted is cut out in the region having the PD size, the above condition (17) is satisfied regardless of the cutting method. If you want to.

  If the condition (17) is not satisfied, the projection component in the wavefront aberration of the projection optical system increases due to internal inhomogeneities such as the refractive index of the lenses 41 to 47 as the optical members. This is not preferable because the change amount of the image magnification and the change amount of the distortion when the illumination condition is changed as shown in FIG.

Further, in the present embodiment, the plurality of lenses 41 to 47 are error shapes with respect to the transmitted wavefront of a light transmitting material (for example, a crystal material such as quartz glass or fluorite, or an ultraviolet transmitting glass) forming each lens. The streak shape existing in the fitting residue shape remaining after fitting with a predetermined function is (21) [Σ {2 × Hn × Wn × Ln / PD ² } ² ] ^1/2 <0.026
Is preferably satisfied.

  Where Hn is the height of the stripe shape (nm), Wn is the width of the bottom surface of the stripe shape, Ln is the length of the bottom surface of the stripe shape, and PD is the light beam from a predetermined point on the object to the optical member. It is the smaller of the size of the area when reaching. In the case of an optical member such as a lens or a plane-parallel plate, when considering the size of a region when a light beam from a predetermined point on the object reaches the optical member, the incident-side optical surface (lens surface) Although it is necessary to consider both the optical surface (lens surface) on the exit side, in the case of the condition (21), attention is focused on the smaller of the size of the area in both.

And
(22) PD / 100 ≦ Wn ≦ PD / 10
(23) λ / 100 ≦ Hn
The one that satisfies the above is a streak shape.

  Here, the streak shape existing in the fitting residue shape remaining after fitting the error shape of the transmitted wavefront of the light transmissive material forming each lens (optical member) with a predetermined function is the above condition (21 ) Is satisfied, the transmitted wavefront of the light transmissive material is measured using a known interferometer or the like, and the difference shape (error wavefront) between the measured transmitted wavefront and the ideal transmitted wavefront is, for example, a Zernike function The above-mentioned condition (21) is satisfied, regardless of how to cut out the residual component (residue shape) that has not been fitted in the region having the PD size. If you want to.

  When the above condition (21) is not satisfied, streak components in the wavefront aberration of the projection optical system increase due to internal inhomogeneities such as the refractive index of the lenses 41 to 47 as the optical members. This is not preferable because the change amount of the image magnification and the change amount of the distortion when the illumination condition is changed as shown in FIG.

Further, in the present embodiment, the plurality of lenses 41 to 47 are error shapes with respect to the transmitted wavefront of a light transmitting material (for example, a crystal material such as quartz glass or fluorite, or an ultraviolet transmitting glass) forming each lens. The protrusion shape and streak shape existing in the fitting residue shape remaining after fitting with a predetermined function,
(24) [Σ {Tm × (Dm / PD) ² } ² ] ^1/2 + [Σ {2 × Hn × Wn × Ln / PD ² } ² ] ^1/2 <0.026
Is preferably satisfied.

  Where Tm is the height of the projection shape (nm), Dm is the diameter of the circumscribed circle on the bottom surface of the projection shape, Hn is the height of the stripe shape (nm), Wn is the width of the stripe shape bottom surface, and Ln is the stripe shape. The length of the bottom surface, PD, is the size of a region when a light beam from a predetermined point on the object reaches the optical member. In the case of an optical member such as a lens or a plane-parallel plate, when considering the size of a region when a light beam from a predetermined point on the object reaches the optical member, the incident-side optical surface (lens surface) Although it is necessary to consider both the optical surface (lens surface) on the exit side, in the case of the condition (24), attention is focused on the smaller of the size of the area in both. And what satisfy | fills the said conditions (18)-(20) is made into protrusion shape, and what satisfies the said conditions (22) and (23) is made into stripe shape.

  Here, the protrusion shape and the streak shape existing in the fitting residue shape remaining after fitting the error shape with respect to the transmitted wavefront of the light transmitting material forming each lens (optical member) with a predetermined function are the above-mentioned Satisfying the condition (24) means that the transmitted wavefront of the light transmissive material is measured using a known interferometer or the like, and the difference shape (error wavefront) between the measured transmitted wavefront and the ideal transmitted wavefront is, for example, When fitting is performed with a predetermined function such as a Zernike function and the residue component (residue shape) that has not been fitted is cut out in an area having the size of the PD, the above condition (24 ).

  When the above condition (24) is not satisfied, due to internal inhomogeneities such as the refractive index of the lenses 41 to 47 as optical members, the projection component and the streak component in the wavefront aberration of the projection optical system This is not preferable because the amount of change in image magnification and the amount of change in distortion when the illumination conditions are changed as shown in FIG.

  In the above-described embodiment, the fringe-Zernike function is used as the predetermined function when fitting the wavefront aberration. However, in the present invention, any function is used without being limited to the fringe-Zernike function. However, it is preferable to use a function with high orthogonality.

Next, the above conditions (9) to (23) will be described from another viewpoint.
The above conditions (9) to (11) can be rewritten as the following conditions (25) to (27).
(25) [Σ {Tk × (Dk / 300) ² } ² ] ^1/2 <0.00035λ
(26) 3 ≦ DVk ≦ 30
(27) 3 ≦ DHk ≦ 30
The above conditions (13) to (15) can be rewritten as the following conditions (29) to (31).
(29) [Σ {2 × Hl × Wl × Ll / 300 ² } ² ] ^1/2 <0.00035λ
(30) 3 ≦ Wl ≦ 30
(31) λ / 100 ≤ Hl
The condition (16) can be rewritten as the following condition (32).
(32) [Σ {Tk × (Dk / 300) ² } ² ] ^1/2 + [Σ {2 × Hl × Wl × Ll / 300 ² } ² ] ^1/2 <0.00035λ
The above conditions (17) to (19) can be rewritten as the following conditions (33) to (35).
(33) [Σ {Tm × (Dm / 300) ² } ² ] ^1/2 <0.026
(34) 3 ≦ DVm ≦ 30
(35) 3 ≦ DHm ≦ 30
The above conditions (21) to (23) can be rewritten as the following conditions (37) to (39).
(37) [Σ {2 × Hn × Wn × Ln / 300 ² } ² ] ^1/2 <0.026
(38) 3 ≦ Wn ≦ 30
(39) λ / 100 ≤ Hn
The condition (24) can be rewritten as the following condition (40).
(40) [Σ {Tm × (Dm / 300) ² } ² ] ^1/2 + [Σ {2 × Hn × Wn × Ln / 300 ² } ² ] ^1/2 <0.026
When the optical member is disposed in the vicinity of the object plane or the image plane of the projection optical system, instead of the above conditions (25) to (27),
(41) [Σ {Tk × (Dk / 50) ² } ² ] ^1/2 <0.00035λ
(42) 0.5 ≤ DVk ≤ 5
(43) 0.5 ≦ DHk ≦ 5
Is preferably satisfied.

When the optical member is disposed in the vicinity of the object plane or the image plane of the projection optical system, instead of the above conditions (29) to (31),
(44) [Σ {2 × Hl × Wl × Ll / 50 ² } ² ] ^1/2 <0.00035λ
(45) 0.5 ≦ Wl ≦ 5
Is preferably satisfied.

In the case where the optical member is disposed in the vicinity of the object plane or the image plane of the projection optical system, instead of the above condition (32),
(46) [Σ {Tk × (Dk / 50) ² } ² ] ^1/2 + [Σ {2 × Hl × Wl × Ll / 50 ² } ² ] ^1/2 <0.00035λ
Is preferably satisfied.

When the optical member is disposed in the vicinity of the object plane or the image plane of the projection optical system, instead of the above conditions (33) to (35),
(47) [Σ {Tm × (Dm / 50) ² } ² ] ^1/2 <0.026
(48) 0.5 ≤ DVm ≤ 5
(49) 0.5 ≤ DHm ≤ 5
Is preferably satisfied.

In the case where the optical member is disposed in the vicinity of the object plane or the image plane of the projection optical system, instead of the above conditions (37) to (39),
(50) [Σ {2 × Hn × Wn × Ln / 50 ² } ² ] ^1/2 <0.026
(51) 0.5 ≦ Wn ≦ 5
Is preferably satisfied.

When the optical member is disposed near the object plane or the image plane of the projection optical system, instead of the above condition (40),
(52) [Σ {Tm × (Dm / 50) ² } ² ] ^1/2 + [Σ {2 × Hn × Wn × Ln / 50 ² } ² ] ^1/2 <0.026
Is preferably satisfied.

  By satisfying at least one of the above conditions (41) to (52), or at least one set of conditions, the influence of the projection component and the streak component of the surface shape error of the optical member, and the inside of the optical member Even in the case of an optical member near the object surface / image surface that is easily affected by inhomogeneous protrusion components and streak components, the amount of change in image magnification and the amount of change in distortion can be kept extremely small.

  An immersion type projection exposure apparatus that performs exposure while filling a space between an optical member that is disposed closest to the image plane and a photosensitive substrate among a plurality of optical members that constitute a projection optical system. In the optical member in contact with the liquid, since the difference in refractive index between the optical member and the liquid is small even when the optical member is disposed in the vicinity of the image plane, the above conditions (25) to (27), It is preferable that the conditions (29) to (31) and / or the condition (32) are satisfied.

  In the above-described embodiment, the projection optical system that forms the mask pattern image on the photosensitive substrate at the reduction magnification, the enlargement magnification, or the equal magnification has been described. However, the present invention is an observation apparatus for forming an enlarged image of an object, for example. The present invention can also be applied to the objective optical system and telescope objective optical system.

It is the figure which showed the wavefront aberration of the optical system three-dimensionally. It is the schematic which shows a protrusion shape three-dimensionally. It is the schematic which shows a stripe shape three-dimensionally. It is a graph which shows the relationship between the volume of the projection component in a wavefront aberration, and a streak component, and the difference between the illumination conditions of distortion. It is a figure which shows roughly an example of a projection exposure apparatus.

Explanation of symbols

10: light source, 20: illumination optical system, 30: mask, 40: projection optical system, 50: wafer, 60: wafer stage

Claims (29)

In a projection optical system that forms an image of an object illuminated with illumination light having a wavelength of 400 nm or less,
The projection optical system has a predetermined wavefront aberration,
The projection optical system according to claim 1, wherein the wavefront aberration of the predetermined shape has a shape of a residual component remaining after fitting the wavefront aberration of the predetermined shape with a predetermined function.   The projection optical system according to claim 1, wherein the shape of the residue component has at least one of a protrusion shape and a stripe shape.   The surface shape processing error of the optical member causing the projection-shaped and streak-shaped wavefront aberrations, and the manufacturing error existing inside the optical member causing the projection-shaped and streak-shaped wavefront aberrations. The projection optical system according to claim 2, wherein the projection optical system is limited within a predetermined range. The projection shape has a ratio of the size of the base of the projection shape to the NA of the wavefront aberration of the wavefront aberration of the predetermined shape as DVi in the vertical direction, and the base of the projection shape relative to the NA of the wavefront of the wavefront aberration of the predetermined shape. When the size ratio is DHi in the horizontal direction,
(1) 1/100 ≦ DVi ≦ 1/10 and (2) 1/100 ≦ DHi ≦ 1/10
And the wavelength of the illumination light is λ and the height of the protrusion shape is Ti,
(3) λ / 100 ≤ Ti
The projection optical system according to claim 2, wherein: When the ratio of the diameter of the circumscribed circle of the bottom surface of the projection shape to the NA of the wavefront is Di,
(4) [Σ {Ti × Di ² } ² ] ^1/2 <0.00035λ
The projection optical system according to claim 4, wherein:   The surface shape processing error of the optical member that causes the generation of the wavefront aberration of the projection shape and the refractive index non-uniformity existing inside the optical member are limited so as to satisfy the conditional expression (4). The projection optical system according to claim 5. When the streak shape is Wj, the ratio of the length of the short side of the bottom of the streak shape to the NA of the wavefront of the wavefront aberration of the predetermined shape is Wj.
(5) 1/100 ≦ Wj ≦ 1/10
And the wavelength of the illumination light is λ and the depth of the stripe shape is Hj,
(6) λ / 100 ≤ Hj
The projection optical system according to any one of claims 2 to 6, wherein: When the streak shape has a length ratio of the bottom of the streak shape to the NA of the wavefront of the wavefront aberration of the predetermined shape as Lj,
(7) [Σ {2 × Hj × Wj × Lj} ² ] ^1/2 <0.00035λ
The projection optical system according to claim 7, wherein:   The surface shape processing error of the optical member that causes the generation of the streak-shaped wavefront aberration and the refractive index nonuniformity existing inside the optical member are limited so as to satisfy the conditional expression (7). The projection optical system according to claim 8. The protrusion shape and the streak shape have a ratio of the diameter of the circumscribed circle of the bottom surface of the protrusion shape to the NA of the wavefront as Di, the height of the protrusion shape as Ti, and the NA of the wavefront of the wavefront aberration of the predetermined shape. The ratio of the length in the longitudinal direction of the base of the streak shape to Lj is Lj, and the ratio of the length in the short side of the base of the streak shape to the NA of the wavefront of the wavefront aberration of the predetermined shape is Wj. When the depth of the stripe shape is Hj and the wavelength of the illumination light is λ,
(5) 1/100 ≦ Wj ≦ 1/10
(6) λ / 100 ≤ Hj
(8) [Σ {Ti × Di ² } ² ] ^1/2 + [Σ {2 × Hj × Wj × Lj} ² ] ^1/2 <0.00035λ
The projection optical system according to claim 4, wherein the projection optical system satisfies the following.   Limiting the surface shape processing error of the optical member that causes generation of the wavefront aberration of the protrusion shape and the streak shape and the refractive index nonuniformity existing inside the optical member so as to satisfy the conditional expression (8). The projection optical system according to claim 10. The projection optical system includes a plurality of optical members,
The protrusion shape existing in the fitting residue shape remaining after fitting the error shape from the design value for one or more optical surfaces of each optical member with a predetermined function is (9) [Σ {Tk × (Dk / PS) ² } ² ] ^1/2 <0.00035λ
The projection optical system according to claim 3, wherein the projection optical system satisfies the following.
Where Tk is the height of the protrusion shape, Dk is the diameter of the circumscribed circle on the bottom surface of the protrusion shape, and PS is the size of the region when the light beam from a predetermined point on the object reaches the optical member. , Λ is the wavelength of the illumination light,
The protrusion shape has a ratio of base sizes of the protrusion shape as DVk in the vertical direction and DHk in the horizontal direction.
(10) PS / 100 ≦ DVk ≦ PS / 10
(11) PS / 100 ≦ DHk ≦ PS / 10, and (12) λ / 100 ≦ Tk
Satisfied. The projection optical system includes a plurality of optical members,
A streak shape existing in a fitting residue shape remaining after fitting an error shape from a design value for one or more optical surfaces of each optical member with a predetermined function is (13) [Σ {2 × Hl × Wl × Ll / PS ² } ² ] ^1/2 <0.00035λ
The projection optical system according to claim 3, wherein the projection optical system satisfies the following.
Where Hl is the height of the stripe shape, Wl is the width of the bottom surface of the stripe shape, Ll is the length of the bottom surface of the stripe shape, and PS is when the light beam from a predetermined point on the object reaches the optical member. The size of the region, λ is the wavelength of the illumination light,
The streak shape is
(14) PS / 100 ≦ Wl ≦ PS / 10, and (15) λ / 100 ≦ Hl
Satisfied. The projection optical system includes a plurality of optical members,
Projection shapes and streak shapes existing in fitting residue shapes remaining after fitting an error shape from a design value for one or more optical surfaces of each optical member with a predetermined function
(16) [Σ {Tk × (Dk / PS) ² } ² ] ^1/2 + [Σ {2 × Hl × Wl × Ll / PS ² } ² ] ^1/2 <0.00035λ
The projection optical system according to claim 3, wherein the projection optical system satisfies the following.
Where Tk is the height of the protrusion shape, Dk is the diameter of the circumscribed circle on the bottom surface of the protrusion shape, and PS is the size of the region when the light beam from a predetermined point on the object reaches the optical member. , Hl is the height of the stripe shape, Wl is the width of the bottom surface of the stripe shape, Ll is the length of the bottom surface of the stripe shape, and PS is the light flux from a predetermined point on the object when reaching the optical member. The size of the region, λ is the wavelength of the illumination light,
The protrusion shape has a ratio of base sizes of the protrusion shape as DVk in the vertical direction and DHk in the horizontal direction.
(10) PS / 100 ≦ DVk ≦ PS / 10
(11) PS / 100 ≦ DHk ≦ PS / 10, and (12) λ / 100 ≦ Tk
And the streak shape is
(14) PS / 100 ≦ Wl ≦ PS / 10, and (15) λ / 100 ≦ Hl
Satisfied. The projection optical system includes a plurality of optical members,
The protrusion shape existing in the fitting residue shape remaining after fitting the error shape of the transmitted wavefront in the light transmissive material forming each optical member with a predetermined function is (17) [Σ {Tm × (Dm / PD ² } ² ] ^1/2 <0.026
The projection optical system according to claim 3, wherein the projection optical system satisfies the following.
Where Tm is the height (nm) of the protrusion shape, Dm is the diameter of the circumscribed circle on the bottom surface of the protrusion shape, and PD is the size of the region when the light beam from a predetermined point on the object reaches the optical member. Is the size of the smaller of
The protrusion shape has a ratio of the size of the bottom of the protrusion shape as DVm in the vertical direction, DHm in the horizontal direction, and λ as the wavelength of the illumination light.
(18) PD / 100 ≦ DVm ≦ PD / 10
(19) PD / 100 ≦ DH m ≦ PD / 10, and (20) λ / 100 ≦ Tm
Satisfied. The projection optical system includes a plurality of optical members,
The streak shape existing in the fitting residue shape remaining after fitting the error shape of the transmitted wavefront in the light transmissive material forming each optical member with a predetermined function is (21) [Σ {2 × Hn × Wn × ^{ln / PD 2} 2] 1/2} <0.026
The projection optical system according to claim 3, wherein the projection optical system satisfies the following.
Where Hn is the height of the stripe shape (nm), Wn is the width of the bottom surface of the stripe shape, Ln is the length of the bottom surface of the stripe shape, and PD is the light beam from a predetermined point on the object to the optical member. It is the smaller size of the size of the area when reaching, the streak shape is
(22) PD / 100 ≦ Wn ≦ PD / 10
(23) λ / 100 ≦ Hn
Satisfied. The projection optical system includes a plurality of optical members,
Projection shapes and streak shapes existing in fitting residue shapes remaining after fitting an error shape with respect to a transmitted wavefront in a light transmissive material forming each optical member with a predetermined function
(24) [Σ {Tm × (Dm / PD) ² } ² ] ^1/2 + [Σ {2 × Hn × Wn × Ln / PD ² } ² ] ^1/2 <0.026
The projection optical system according to claim 3, wherein the projection optical system satisfies the following.
Where Tm is the height of the projection shape (nm), Dm is the diameter of the circumscribed circle on the bottom surface of the projection shape, Hn is the height of the stripe shape (nm), Wn is the width of the stripe shape bottom surface, and Ln is the stripe shape. The length of the bottom surface, PD is the size of a region when a light beam from a predetermined point on the object reaches the optical member,
The protrusion shape has a ratio of the size of the bottom of the protrusion shape as DVm in the vertical direction, DHm in the horizontal direction, and λ as the wavelength of the illumination light.
(18) PD / 100 ≦ DVm ≦ PD / 10
(19) PD / 100 ≦ DH m ≦ PD / 10, and (20) λ / 100 ≦ Tm
And the streak shape is
(22) PD / 100 ≦ Wn ≦ PD / 10, and (23) λ / 100 ≦ Hn
Satisfied.   The projection optical system according to claim 1, wherein the predetermined function is a Zernike function. In a projection exposure apparatus that projects a predetermined pattern onto a photosensitive substrate,
A projection exposure apparatus comprising the projection optical system according to any one of claims 1 to 18. In a projection exposure method for projecting a predetermined pattern onto a photosensitive substrate,
A projection exposure method, wherein the predetermined pattern is projected onto a photosensitive substrate using the projection optical system according to any one of claims 1 to 18. In an optical member for lithography used with light having a wavelength of 400 nm or less,
The optical member comprises one or more optical surfaces;
The projection shape existing in the fitting residue shape remaining after fitting the error shape from the design value of the optical surface with a predetermined function is (25) [Σ {Tk × (Dk / 300) ² } ² ] ^{1 / 2} <0.00035λ
An optical member characterized by satisfying
Where Tk is the height of the protrusion shape, Dk is the diameter of the circumscribed circle on the bottom surface of the protrusion shape, and λ is the wavelength of the light.
The protrusion shape has a ratio of base sizes of the protrusion shape as DVk in the vertical direction and DHk in the horizontal direction.
(26) 3 ≦ DVk ≦ 30
(27) 3 ≦ DHk ≦ 30, and (28) λ / 100 ≦ Tk
Satisfied. In an optical member for lithography used with light having a wavelength of 400 nm or less,
The optical member comprises one or more optical surfaces;
A streak shape existing in the fitting residue shape remaining after fitting the error shape from the design value of the optical surface with a predetermined function is (29) [Σ {2 × Hl × Wl × Ll / 300 ² } ² ]. ^1/2 <0.00035λ
An optical member characterized by satisfying
Where Hl is the height of the stripe shape, Wl is the width of the bottom surface of the stripe shape, Ll is the length of the bottom surface of the stripe shape, and λ is the wavelength of the light,
The streak shape is
(30) 3 ≦ Wl ≦ 30
(31) λ / 100 ≦ Hl is satisfied. In an optical member for lithography used with light having a wavelength of 400 nm or less,
The optical member comprises one or more optical surfaces;
The protrusion shape and streak shape existing in the fitting residue shape remaining after fitting the error shape from the design value of the optical surface with a predetermined function is (32) [Σ {Tk × (Dk / 300) ² } ² ] ^1/2 + [Σ {2 × Hl × Wl × Ll / 300 ² } ² ] ^1/2 <0.00035λ
An optical member characterized by satisfying
Where Tk is the height of the projection shape, Dk is the diameter of the circumscribed circle of the bottom surface of the projection shape, Hl is the height of the stripe shape, Wl is the width of the bottom surface of the stripe shape, and Ll is the length of the bottom surface of the stripe shape. , Λ is the wavelength of the light,
The protrusion shape has a ratio of base sizes of the protrusion shape as DVk in the vertical direction and DHk in the horizontal direction.
(26) 3 ≦ DVk ≦ 30
(27) 3 ≦ DHk ≦ 30, and (28) λ / 100 ≦ Tk
And the streak shape is
(30) 3 ≦ Wl ≦ 30, and (31) λ / 100 ≦ Hl
Satisfied. In an optical member for lithography used with light having a wavelength of 400 nm or less,
The projection shape existing in the fitting residue shape remaining after fitting the error shape of the transmitted wavefront in the light transmissive material forming the optical member with a predetermined function is (33) [Σ {Tm × (Dm / 300) ² } ² ] ^1/2 <0.026
An optical member characterized by satisfying
Where Tm is the height of the projection shape (nm), Dm is the diameter of the circumscribed circle on the bottom surface of the projection shape,
The protrusion shape is such that when the ratio of the size of the base of the protrusion shape is DVm in the vertical direction, DHm in the horizontal direction, and the wavelength of the light is λ,
(34) 3 ≦ DVm ≦ 30
(35) 3 ≦ DHm ≦ 30, and (36) λ / 100 ≦ Tm
Satisfied. In an optical member for lithography used with light having a wavelength of 400 nm or less,
The streak shape existing in the fitting residue shape remaining after fitting the error shape of the transmitted wavefront in the light transmissive material forming the optical member with a predetermined function is (37) [Σ {2 × Hn × Wn × Ln / 300 ² } ² ] ^1/2 <0.026
An optical member characterized by satisfying
However, Hn is the height (nm) of the stripe shape, Wn is the width of the bottom surface of the stripe shape, Ln is the length of the bottom surface of the stripe shape,
(38) 3 ≦ Wn ≦ 30
(39) λ / 100 ≤ Hn
Satisfied. In an optical member for lithography used with light having a wavelength of 400 nm or less,
The projection shape and streak shape existing in the fitting residue shape remaining after fitting the error shape of the transmitted wavefront in the light transmissive material forming the optical member with a predetermined function is (40) [Σ {Tm × (Dm ^{/ 300) 2} 2] 1/2} + [Σ {2 × Hn × Wn × Ln / 300 2} 2] 1/2 <0.026
An optical member characterized by satisfying
Where Tm is the height of the projection shape (nm), Dm is the diameter of the circumscribed circle on the bottom surface of the projection shape, Hn is the height of the stripe shape (nm), Wn is the width of the stripe shape bottom surface, and Ln is the stripe shape. The length of the bottom,
The protrusion shape is such that the ratio of the size of the base of the protrusion shape is DVm in the vertical direction and DHm in the horizontal direction.
(34) 3 ≦ DVm ≦ 30
(35) 3 ≦ DHm ≦ 30, and (36) λ / 100 ≦ Tm
And the streak shape is
(38) 3 ≦ Wn ≦ 30, and (39) λ / 100 ≦ Hn
Satisfied. In a projection optical system that forms an image of an object illuminated with illumination light having a wavelength of 400 nm or less,
A projection optical system comprising the optical member according to any one of claims 21 to 26. In a projection exposure apparatus that projects a predetermined pattern onto a photosensitive substrate,
A projection exposure apparatus comprising the projection optical system according to claim 27. In a projection exposure method for projecting a predetermined pattern onto a photosensitive substrate,
28. A projection exposure method, wherein the predetermined pattern is projected onto a photosensitive substrate using the projection optical system according to claim 27.