JP4950795B2 - Exposure apparatus, device manufacturing method, and correction method - Google Patents

Description

  The present invention relates to an exposure apparatus that exposes a pattern of an original on a substrate.

  Conventionally, a projection exposure apparatus for transferring a circuit pattern drawn on a reticle (mask) onto a wafer or the like has been used when manufacturing a fine semiconductor device such as a semiconductor memory or a logic circuit by using a photolithography technique. ing. A projection exposure apparatus generally includes an illumination optical system that illuminates a reticle using a light beam from a light source, and a projection optical system that projects a reticle pattern onto a wafer.

  In a projection exposure apparatus, various super-resolution techniques for transferring a pattern below the wavelength of an exposure light source have been proposed with the recent miniaturization of semiconductor devices. One such super-resolution technique is called a modified illumination method (oblique incidence illumination method). In the modified illumination method, the reticle is not illuminated with a light beam (illumination light) having a uniform angular distribution, but the light beam is incident on the reticle obliquely.

  The angular distribution of the light beam that illuminates the reticle corresponds to the light quantity distribution at the pupil plane position of the illumination optical system. In a projection exposure apparatus using a fly's eye lens as an optical integrator, the exit surface of the fly's eye lens is the pupil plane of the illumination optical system. The light intensity distribution at the pupil plane position of the illumination optical system is called an effective light source distribution or a secondary light source distribution. The effective light source distribution is also a light intensity distribution on the pupil plane of the projection optical system.

  Examples of the effective light source distribution used in the modified illumination method include an annular effective light source distribution and a quadrupole effective light source distribution. By arranging an aperture stop having an annular or quadrupole opening on the exit surface of the optical integrator, an effective light source distribution having an annular or quadrupole shape can be formed. However, if an effective light source distribution having an annular shape or a quadrupole shape is formed with an aperture stop, a part of the light beam is shielded, so that the light beam from the light source cannot be used efficiently and the reticle. Illuminance of the illumination light that illuminates is reduced. Therefore, productivity for transferring the circuit pattern to the wafer is reduced.

On the other hand, various techniques for forming an effective light source distribution used in the modified illumination method while efficiently using a light beam from a light source (that is, suppressing a light quantity deficit) have been proposed. Patent Documents 1 to 3 disclose a technique for converting a light intensity distribution using a diffractive optical element. The diffractive optical element can form an arbitrary effective light source distribution while suppressing the light quantity deficiency.
JP-A-7-201697 JP-A-11-176721 JP 2001-284212 A

  However, in an actual illumination optical system, since the condenser optical system and the zoom optical system include aberrations, even if the diffractive optical element emits diffracted light to form a predetermined light intensity distribution, The light intensity distribution at is blurred.

  For example, when forming an effective light source distribution in a ring shape, it is not a top hat shape having only a 100% light intensity region and a 0% light intensity region, but a blurred shape as shown in FIG. (Drawn shape). Such a phenomenon appears remarkably when an effective light source distribution is formed using a prism. This is because an optical system having a prism includes a larger aberration than an optical system having only a lens. Here, FIG. 10 is a diagram illustrating an effective light source distribution when a general annular light source distribution is formed in the related art.

  The shape of the effective light source distribution is generally expressed by a σ value called a coherence factor. Here, the σ value is a value obtained by dividing the NA of the illumination light (NA of the illumination optical system) by the NA of the projection optical system. The σ value is also used when the position from the center of the pupil when the pupil radius is 1 is indicated. For example, the effective light source distribution shown in FIG. 10 has an outer σ0 because the points of half the maximum light intensity in the effective light source distribution are 0.9 (outside) and 0.6 (inside) from the center point of the pupil plane. .90, σ 0.60 effective light source distribution (annular illumination). Note that σ1 indicates that the NA of the illumination light that illuminates the reticle is equal to the NA of the projection optical system. For example, in a projection exposure apparatus having an NA of 0.92 and a reduction ratio of 1/4, the NA of the projection optical system on the reticle surface is 0.23, so the NA of the illumination light that illuminates the reticle is 0.23. In some cases, σ1.

  In addition, the effective light source distribution may be blurred due to the wavefront division period of the optical integrator. When the diameter of σ1 on the optical integrator is φ100 and the wavefront division period of the optical integrator is 1 mm, the wavefront division period is represented by σ0.02. Therefore, even if the diffractive optical element forms a light intensity distribution having a fine shape equal to or smaller than the wavefront division period of the optical integrator, it is not reflected in the effective light source distribution formed on the exit surface of the optical integrator. In other words, even if a top hat-shaped effective light source distribution is formed on the incident surface of the optical integrator, an effective light source distribution including blur of σ 0.02 is formed on the exit surface of the optical integrator.

  In recent years, in order to further improve the resolving power of the projection exposure apparatus, an effective light source distribution with a large outer σ has been required. However, in the related art, when an effective light source distribution having an annular shape with a large outer σ (for example, an outer σ 0.98, an inner σ 0.72) is formed, the effective light source distribution is blurred, as shown in FIG. The skirt portion of the effective light source distribution exceeds σ1. Therefore, the 0th-order light is shielded by the NA stop disposed on the pupil plane of the projection optical system, which causes a problem that the projection (imaging) performance is deteriorated. Here, FIG. 11 is a diagram showing an effective light source distribution when an annular effective light source distribution having a large outer σ is formed in the prior art.

  FIG. 12 shows the distribution of diffracted light on the pupil plane of the projection optical system when the reticle is illuminated with a good effective light source distribution not exceeding σ1. In FIG. 12, OP indicates the aperture of the NA stop arranged on the pupil plane of the projection optical system.

The illumination light that illuminates the reticle is diffracted by a pattern (for example, line and space) on the reticle, and is emitted from the reticle as diffracted light. Since the 0th order light travels straight through the reticle, the distribution of the 0th order light is the effective light source distribution itself. In FIG. 12, an annular distribution DB ₀ existing in the aperture stop OP of the NA stop indicates zero-order light. The ± first-order light is emitted from the reticle symmetrically with a diffraction angle depending on the repetition period of the pattern on the reticle. In FIG. 12, two annular zone distributions DB ₊₁ and DB _-1 symmetrical with respect to the center of the aperture OP of the NA stop indicate ± first-order light. However, the sign of the order of the diffracted light is only given for convenience, and has no meaning in itself.

The diffracted light at the point A on the 0th order light distribution DB ₀ , the diffracted light at the point B on the -1st order light distribution DB- ₁ , and the diffracted light at the point C on the _{+ 1st} order light distribution DB _{+ 1} are the effective light source. It is generated from light at the same point on the distribution. Since each point on the effective light source distribution is incoherent with each other, only diffracted light generated from light at one point on the effective light source distribution interferes to form an interference pattern. In FIG. 12, the diffracted light at the point B on the -1st order light distribution DB _-1 is diffracted out of the opening OP of the NA stop and is therefore shielded by the NA stop. Accordingly, the diffracted light at the point A and the diffracted light at the point C existing in the aperture stop OP of the NA aperture form an interference pattern on the wafer, and the reticle pattern is projected onto the wafer.

  On the other hand, FIG. 13 shows the distribution of diffracted light on the pupil plane of the projection optical system when the reticle is illuminated with an effective light source distribution exceeding σ1. FIG. 13 shows an effective light source distribution having an annular shape larger than the aperture OP of the NA stop.

Referring to FIG. 13, the diffracted light at point A on 0th-order light distribution DB ₀ and the diffracted light at point B on -1st-order light distribution DB- ₁ are shielded by the NA stop, so the + 1st order Only the diffracted light at the point C on the light distribution DB _{+ 1} passes through the aperture OP of the NA stop. As described above, since only the diffracted light generated from the same point on the effective light source distribution can form an interference pattern, the interference pattern is formed only by the diffracted light at the point C on the + 1st order light distribution DB _{+ 1.} Can not do it. Therefore, the reticle pattern cannot be projected onto the wafer, and the projection (imaging) performance is degraded.

  In recent years, it is also required to illuminate the reticle with an effective light source distribution having a fine shape as shown in FIG. FIG. 14 is a diagram showing an effective light source distribution disclosed in US Pat. No. 7,057,709 (FIG. 13). However, even if such an effective light source distribution is formed using only the diffractive optical element, the effective light source distribution is blurred due to the aberration included in the illumination optical system and the wavefront division period of the optical integrator as described above. Therefore, an effective light source distribution having a fine shape cannot be formed, and a desired imaging performance cannot be obtained.

  Therefore, an object of the present invention is to provide an exposure apparatus capable of forming an effective light source distribution having a large outer σ and an effective light source distribution having a fine shape with high accuracy while suppressing light quantity deficiency.

  In order to achieve the above object, an exposure apparatus according to one aspect of the present invention includes an illumination optical system that illuminates an original using a light beam from a light source, and a projection optical system that projects a pattern of the original onto a substrate. In the exposure apparatus, the illumination optical system includes an optical integrator that forms a plurality of light sources, and a light shielding member that is inserted into and removed from a pupil plane of the illumination optical system and shields a part of a light beam from the optical integrator. And a telecentric correction unit that corrects off-axis telecentricity in the image plane of the projection optical system, and the telecentric correction unit is generated when the light shielding member is inserted into the pupil plane of the illumination optical system. It has a correction range equal to or greater than the difference between the off-axis telecentricity and the off-axis telecentricity generated when the light shielding member is taken out from the pupil plane of the illumination optical system.

  A device manufacturing method according to another aspect of the present invention includes a step of exposing a substrate using the exposure apparatus described above, and a step of developing the exposed substrate.

  According to still another aspect of the present invention, there is provided a correction method for illuminating an original with an illumination optical system, and projecting an image of the pattern on the original onto a substrate through the projection optical system. In the correction method for correcting the off-axis telecentricity, a determination step for determining whether or not to insert a light blocking member that blocks a part of the light beam from the optical integrator in the pupil plane of the illumination optical system; and The off-axis telecentricity in the image plane of the projection optical system generated when the light shielding member is inserted into the pupil plane of the illumination optical system according to the determined insertion / removal of the light shielding member, and the light shielding member A correction step of correcting the off-axis telecentricity in a correction range equal to or greater than the difference from the off-axis telecentricity generated when the illumination optical system is taken out from the pupil plane. To.

  Further objects and other features of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

  According to the present invention, for example, it is possible to provide an exposure apparatus capable of forming an effective light source distribution having a large outer σ and an effective light source distribution having a fine shape with high accuracy while suppressing a light quantity defect.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings. In addition, in each figure, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted.

  FIG. 1 is a schematic sectional view showing a configuration of an exposure apparatus 1 as one aspect of the present invention. In this embodiment, the exposure apparatus 1 is a projection exposure apparatus that exposes a pattern of a reticle (mask) 30 as an original to a wafer 50 as a substrate by a step-and-scan method. However, the exposure apparatus 1 can also apply a step-and-repeat method.

  The exposure apparatus 1 includes a light source 10, an illumination optical system 20, a reticle stage (not shown) that supports the reticle 30, a projection optical system 40, a wafer stage (not shown) that supports the wafer 50, and a control unit 60.

As the light source 10, for example, a KrF excimer laser with a wavelength of about 248 nm, an ArF excimer laser with a wavelength of about 193 nm, or the like is used. However, the light source 10 is not limited to the excimer laser, and for example, an F ₂ laser having a wavelength of about 157 nm may be used.

  The illumination optical system 20 is an optical system that illuminates the reticle 30 using a light beam from the light source 10. In this embodiment, the illumination optical system 20 includes a routing optical system 201, a beam shaping optical system 202, exit angle preserving optical elements 203 and 205, a condensing optical system 204, relay optical systems 206 and 208, and an aperture. A diaphragm 207 is included. Further, the illumination optical system 20 includes a diffractive optical element 209, a relay optical system 210, an aperture 211, a zoom optical system 212, an optical integrator 213, a light shielding member 214, a drive unit 215, an illumination unit 216, Drive unit 217.

  The routing optical system 201 includes a mirror, a relay lens, and the like, and guides the light beam emitted from the light source 10 to the beam shaping optical system 202. The beam shaping optical system 202 includes a cylindrical lens, a mirror, and the like, and shapes the cross-sectional shape of the light beam guided by the drawing optical system 201 into a predetermined shape.

  The exit angle preserving optical element 203 has an aperture, a lens system, and the like, and even when the optical axis of the light beam is slightly changed and entered, the angle of the emitted light beam (emission angle) is constant (in this embodiment, the exit angle). a). The exit angle preserving optical element 203 may be a fly-eye lens composed of microlenses.

  The condensing optical system 204 condenses the light beam emitted from the emission angle storage optical element 203 at the emission angle α and guides it to the emission angle storage optical element 205. In addition, the condensing optical system 204 has a Fourier transform plane relationship between the exit surface of the exit angle preserving optical element 203 and the entrance surface of the exit angle preserving optical element 205 (relationship between the object plane and the pupil plane or the pupil plane and the image plane). I have to.

  The exit angle preserving optical element 205 has the same configuration and function as the exit angle preserving optical element 203. In this embodiment, the exit angle of the exiting light beam is maintained at β.

  The relay optical systems 206 and 208 collect the light beam emitted from the emission angle preserving optical element 205 at the emission angle β and guide it to the diffractive optical element 209. Note that an aperture stop 207 is disposed between the relay optical system 206 and the relay optical system 208.

The diffractive optical element 209 has a predetermined light intensity distribution (for example, an annular shape or a quadrupole shape) at the position of the aperture 211 (a position conjugate with the pupil plane of the illumination optical system 20) via the relay optical system 210. Form. In other words, the diffractive optical element 209 forms an effective light source distribution on the pupil plane of the illumination optical system 20 in cooperation with the optical integrator 213. The diffractive optical element 209 is configured by a computer generated hologram or kinoform such as an amplitude distribution type hologram or a phase distribution type hologram.
In this embodiment, the diffractive optical element 209 is configured to be switchable with a plurality of diffractive optical elements that form different light intensity distributions, and the controller 60 forms an optimal light intensity distribution according to the pattern of the reticle 30. A diffractive optical element is disposed in the optical path of the illumination optical system 20.

  The aperture 211 has a function of passing only the light intensity distribution formed by the diffractive optical element 209. The diffractive optical element 209 and the aperture 211 are arranged so as to have a Fourier transform plane relationship with each other.

  The zoom optical system 212 enlarges the light intensity distribution formed by the diffractive optical element 209 at a predetermined magnification and projects it onto the optical integrator 213.

  The optical integrator 213 is disposed in the vicinity of the pupil plane of the illumination optical system 20 and forms a light source image (effective light source distribution) corresponding to the light intensity distribution formed at the position of the aperture 211 on the exit surface. The optical integrator 213 includes, for example, a fly-eye lens, a cylindrical lens array, a microlens array, or the like.

  The light blocking member 214 is configured to be inserted into and removed from the exit surface of the optical integrator 213 (the pupil plane of the illumination optical system 20) by the driving unit 215. The light shielding member 214 shields a part of the light beam and changes the first light intensity distribution formed by the diffractive optical element 209 to the second light intensity distribution. In the present embodiment, the light shielding member 214 shields the blurring portion of the effective light source distribution generated due to the aberration included in the illumination optical system 20 and the wavefront division period of the optical integrator 213. Specifically, in the light shielding member 214, the effective light source distribution formed by the diffractive optical element 209 and the optical integrator 213 is blurred (smaller than a predetermined light intensity), and σ generated in the effective light source distribution is 1. Shade the excess part. Further, when an effective light source distribution with σ of 0.2 or less is formed, the light shielding member 214 is generated in the effective light source distribution due to blurring of the effective light source distribution formed by the diffractive optical element 209 and the optical integrator 213. The portion where σ exceeds 0.2 is shielded from light. As described above, the light shielding member 214 is positioned at or near the pupil plane of the illumination optical system 20, and partially adjusts the shape of the effective light source distribution on the pupil plane of the illumination optical system 20, thereby blurring the effective light source distribution. Make the shape with no part. However, the light shielding member 214 does not shield the light beam from the light source 10 by itself to form an effective light source distribution, but shields the blurring portion of the effective light source distribution formed by the diffractive optical element 209 and the optical integrator 213. Just doing. Therefore, the light quantity defect of the light beam emitted from the light source 10 is minimized.

  For example, the light shielding member 214 includes a plurality of apertures having different opening diameters and shapes arranged on the turret, and the plurality of apertures are selectively inserted into and removed from the exit surface of the optical integrator 213. Further, the light shielding member 214 may be configured by an iris diaphragm whose aperture diameter is variable. In this case, instead of configuring the iris diaphragm so that it can be inserted into and removed from the exit surface of the optical integrator 213, it is possible to prevent the light beam from being blocked by increasing the aperture diameter of the iris diaphragm.

  The drive unit 215 is controlled by the control unit 60 to drive the light shielding member 214 to the exit surface of the optical integrator 213 and the light shield member 214 disposed on the exit surface of the optical integrator 213 to the outside of the optical path of the illumination optical system 20. It has a function to drive.

  The illumination unit 216 includes a condenser optical system and the like, and illuminates the reticle 30 with an effective light source distribution formed on the exit surface of the optical integrator 213. The illumination unit 216 includes a zoom mechanism 216a including a plurality of lenses driven by the drive unit 217, and telecentric correction that corrects off-axis telecentricity in the illumination optical system 20 by driving the zoom mechanism 216a. It functions as a part. The driving unit 217 is controlled by the control unit 60 and has a function of driving a plurality of lenses constituting the zoom mechanism 216a.

  In the manufacture of semiconductor devices, several layers of circuit patterns are accumulated on the wafer 50 because one exposure is repeated a plurality of times. The pattern of each layer needs to be positioned and transferred with high accuracy. In actual semiconductor device manufacture, since the circuit accumulated on the wafer 50 has a step, the exposure apparatus 1 needs to accurately position and transfer the pattern including the step region. Therefore, it is necessary to reduce distortion (defocus distortion) at a position defocused from the best focus of the projection optical system 40. In particular, since it is necessary to correct the off-axis telecentricity, which is a magnification component of defocus distortion, in this embodiment, the illumination unit 216 (zoom mechanism 216a) has a function of correcting the off-axis telecentricity.

  In this embodiment, the illumination unit 216 is generated when the off-axis telecentricity generated when the light blocking member 214 is inserted into the pupil plane of the illumination optical system 20 and when the light blocking member 214 is taken out from the pupil plane of the illumination optical system 20. The correction range is greater than the difference from the off-axis telecentricity. The case where the effective light source distribution is formed without using the light shielding member 214 and the case where the effective light source distribution is formed using the light shielding member 214 differ in the off-axis telecentricity generated in the illumination optical system 20. The unit 216 can cope with either case.

  Here, the off-axis telecentricity generated in the illumination optical system 20 will be described. There are two factors that cause off-axis telecentricity in the illumination optical system 20. One is that the off-axis telecentricity is generated depending on the distance between the position where the effective light source distribution is formed and the position of the pupil plane of the illumination optical system 20, and the other is due to the wavefront division period of the optical integrator 213. Thus, off-axis telecentricity is generated.

  So far, the light intensity distribution on the pupil plane of the illumination optical system 20 has been described as being the same as the light intensity distribution on the pupil plane of the projection optical system 40. However, in practice, the position where the same distribution as the effective light source distribution as the light intensity distribution on the pupil plane of the projection optical system 40 is formed may be different from the position of the pupil plane of the illumination optical system 20. For example, when the light shielding member 214 is used, the position where the same distribution as the effective light source distribution as the light intensity distribution on the pupil plane of the projection optical system 40 is formed is the position of the light shielding member 214. When the light shielding member 214 is not used, the parallel light beam incident on the optical integrator 213 is condensed at a position where the same distribution as the effective light source distribution as the light intensity distribution on the pupil plane of the projection optical system 40 is formed. This is the rear focal position of each element lens. Hereinafter, the light intensity distribution formed at the position of the light shielding member 214 or the rear focal position of each element lens of the optical integrator 213 is referred to as an effective light source distribution.

  The reason why the off-axis telecentricity occurs when the position where the effective light source distribution is formed and the position of the pupil plane of the illumination optical system 20 is different will be described with reference to FIG. FIG. 2 schematically shows the pupil plane PP of the illumination optical system 20 and the optical system and the projection optical system 40 that are subsequent to the pupil plane PP among the optical systems that constitute the illumination optical system 20. Here, the lens LG includes an optical system subsequent to the pupil plane PP and a projection optical system 40 among the optical systems constituting the illumination optical system 20, and has a focal length f (mm).

  Light emitted at an angle θ from the center of the pupil plane PP of the illumination optical system 20 reaches perpendicularly to an image height Y (mm) represented by f × sin θ = Y, as shown in FIG. . Since the shape of the effective light source distribution is symmetric with respect to the optical axis, if the effective light source distribution is formed at the position of the pupil plane PP of the illumination optical system 20, the light amount distribution of the exposure light is a line perpendicular to the image plane. The distribution is centered. Therefore, even if defocusing occurs, the imaging position does not shift and off-axis telecentricity does not occur.

On the other hand, as shown in FIG. 2B, when an effective light source distribution is formed at a position PP ′ shifted by X (mm) in the optical axis direction from the position of the pupil plane PP of the illumination optical system 20, the effective light source distribution is formed. The light emitted from the center of the light reaches the image plane with an angle (inclination angle φ). Therefore, off-axis telecentricity occurs. The inclination angle φ at the image height Y is expressed by sin φ = (X · tan θ) / f. The change in the image transfer position per 1 micrometer defocus is expressed by 0.001 × tan φ (mm). Since the tilt angle φ is a small value, sin φ≈φ≈tan φ may be satisfied, and the change in the image transfer position per 1 micrometer defocus is represented by (0.001 · X · tan θ) / f. The change in the image transfer position is divided by the image height as a magnification component, and becomes (0.001 · X · tan θ) / (f ² · sin θ) ≈ (0.001 · X) / f ² .

Since the change in the image transfer position is usually in units of nm, such a number is about 10 ⁻⁶ . Therefore, it is often representative of the off-axis telecentricity in a number of the magnification ¹⁰⁶ times the ppm display. According to such a notation, the amount of off-axis telecentricity due to the position of the pupil plane PP of the illumination optical system and the position where the effective light source distribution is shaped is separated by X (mm) is about 1 μm defocus. (X · 1000) / f ² (ppm).

Here, a case where the effective light source distribution is formed using the light shielding member 214 and a case where the effective light source distribution is formed without using the light shielding member 214 are considered. In this case, the position where the effective light source distribution is formed is different between the position of the light shielding member 214 and the position of the condensing point of the optical integrator 213. Therefore, as described above, a difference occurs in the amount of off-axis telecentricity caused by the difference between the position of the pupil plane of the illumination optical system 20 and the position where the effective light source distribution is formed. For example, the distance (the distance in the optical axis direction) between the position of the light shielding member 214 and the position of the condensing point of the optical integrator 213 is Z (mm). At this time, the difference between the off-axis telecentricity generated when the effective light source distribution is formed using the light shielding member 214 and the off-axis telecentricity generated when the effective light source distribution is formed without using the light shielding member 214. Is (Z · 1000) / f ² (ppm) per 1 μm defocus.

  Next, the off-axis telecentricity resulting from the wavefront division period of the optical integrator 213 will be described with reference to FIG. Such a phenomenon occurs when an effective light source distribution is formed without using the light shielding member 214. In FIG. 3, the case where the optical integrator 213 has a wavefront division period of a (mm) is considered.

  As described above, when the effective light source distribution is formed without using the light shielding member 214, the effective light source distribution in which the skirt portion is blurred is formed on the incident surface of the optical integrator 213. In other words, a trapezoidal light intensity distribution as illustrated on the left side of the optical integrator 213 is incident on the optical integrator 213. Accordingly, the light intensity incident on the wavefront splitting element that constitutes the optical integrator 213 disposed in the skirt portion of the light intensity distribution has a strong region on the optical axis side and a weak region on the peripheral side.

  The light beams emitted from each of the wavefront splitting elements of the optical integrator 213 are collected at the rear focal position (near the emission surface) of the optical integrator 213, and an illumination region (for example, the reticle 30) via the subsequent optical system BL. Illuminate. In FIG. 3, among the light beams emitted from the wavefront splitting element arranged in the skirt portion of the light intensity distribution, the light beam from the region with a high light intensity on the optical axis side is L1, and the light beam from the region with a low light intensity on the peripheral side. Are indicated by L2. As is apparent from FIG. 3, in the illumination area, the light ray L1 inward with respect to the optical axis is stronger than the light ray L2 outward with respect to the optical axis. Therefore, since the center of gravity of the light amount is shifted inward by φ, off-axis telecentricity is generated.

Since the amount of off-axis telecentricity is shifted on the effective light source distribution by half of the wavefront division period a of the optical integrator 213, (a · 1000) / (2 · f ² · sin θ) per 1 μm defocus. It becomes. Here, θ is the maximum emission angle of the light beam emitted from the optical integrator. Further, assuming that the focal length of the optical integrator is F (mm), since there is a relationship of sin θ = a / (2F), the amount of off-axis telecentricity is (F · 1000) / f ² per 1 μm defocus. .

  In the case of a step-and-scan exposure apparatus, the wavefront division period a of the optical integrator 213 is a wavefront division period in the non-scanning direction. Further, the maximum emission angle θ is the maximum emission angle of the optical integrator 213 in the non-scanning direction, and the focal length F is the focal length of the optical integrator 213 in the non-scanning direction.

In this way, the off-axis telecentricity changes between when the effective light source distribution is formed using the light shielding member 214 and when the effective light source distribution is formed without using the light shielding member 214. The amount of change is ((Z · 1000) / f ² + (a · 1000) / (2 · f ² · sin θ)) (ppm) per 1 μm defocus. Here, Z (mm) is the distance between the position of the light shielding member 214 and the position of the condensing point of the optical integrator 213, and f (mm) is an optical system downstream of the pupil plane of the illumination optical system 20. This is the focal length of the projection optical system. Further, a (mm) is the wavefront division period of the optical integrator 213, and θ is the maximum emission angle of the light beam emitted from the optical integrator 213.

  Therefore, in the present embodiment, the illumination unit 216 (zoom mechanism 216a) is configured so that the correction range α (ppm / 1 μm defocus) of the off-axis telecentricity satisfies the following formula 1. Thereby, the off-axis telecentricity (off-axis telecentricity with a wide range of generation amount) in the illumination optical system 20 can be sufficiently corrected.

  Returning to FIG. 1, the reticle 30 has a circuit pattern and is supported and driven by a reticle stage (not shown). Diffracted light emitted from the reticle 30 is projected onto the wafer 50 via the projection optical system 40. Since the exposure apparatus 1 is a step-and-scan type exposure apparatus, the pattern of the reticle 30 is transferred to the wafer 50 by scanning the reticle 30 and the wafer 50.

  The projection optical system 40 is an optical system that projects the pattern of the reticle 30 onto the wafer 50. The projection optical system 40 can use a refractive system, a catadioptric system, or a reflective system. In addition, the projection optical system 40 has a diaphragm 42 on the pupil plane that controls the numerical aperture (NA) of the projection optical system.

  The wafer 50 is a substrate onto which the pattern of the reticle 30 is projected (transferred), and is supported and driven by a wafer stage (not shown). However, a glass plate or other substrate can be used instead of the wafer 50. A resist is applied to the wafer 50.

  The control unit 60 includes a CPU and a memory (not shown) and controls the operation of the exposure apparatus 1. The control unit 60 is electrically connected to the light source 10, the diffractive optical element 209 (mechanism for switching a plurality of diffractive optical elements), the drive unit 215, the drive unit 217, and the NA aperture 42 (mechanism for changing the aperture thereof). . In the present embodiment, the control unit 60 controls the light shielding member 214 to pass through the drive unit 215 based on the shape of the effective light source distribution formed by the diffractive optical element 209 and the multi-beam forming unit 213, and the exit surface of the optical integrator 213. Inserted into and removed from the optical path of the illumination optical system 20.

  Specifically, the control unit 60 determines whether or not a portion where σ exceeds 1 occurs in the effective light source distribution due to blurring of the effective light source distribution formed by the diffractive optical element 209 and the optical integrator 213. When a portion where σ exceeds 1 occurs in the effective light source distribution, the control unit 60 inserts the light shielding member 214 into the exit surface of the optical integrator 213. Even if the effective light source distribution is blurred, a portion where σ does not exceed 1 does not occur. The maximum outside σ of the effective light source distribution depends on the aberration included in the illumination optical system 20 and the wavefront division period of the optical integrator 213. 95. In other words, an effective light source distribution having an outer σ of 0.95 or less can be formed without using the light shielding member 214. Accordingly, when the diffractive optical element 209 and the optical integrator 213 form an effective light source distribution having a σ of 0.95 or more, the control unit 60 moves the light shielding member 214 of the illumination optical system 20 through the driving unit 215. Insert into the optical path. The control unit 60 stores the maximum σ of the effective light source distribution that can be formed without using the light shielding member 214 as a threshold value in the memory.

  On the other hand, let us consider a case where an effective light source distribution having a small σ, that is, a small σ is formed. In this case, the control unit 60 determines whether or not the effective light source distribution formed by the diffractive optical element 209 and the optical integrator 213 is blurred, so that a portion exceeding the σ value defined as the small σ is generated in the effective light source distribution. to decide. When a portion exceeding the σ value defined as the small σ occurs in the effective light source distribution, the control unit 60 inserts the light shielding member 214 on the exit surface of the optical integrator 213. In general, an effective light source distribution having σ greater than 0.20 can be formed without using the light blocking member 214. In other words, when forming an effective light source having a σ of 0.2 or less, the light shielding member 214 is necessary. Therefore, when the diffractive optical element 209 and the optical integrator 213 form an effective light source distribution having σ of 0.2 or less, the control unit 60 moves the light shielding member 214 of the illumination optical system 20 through the driving unit 215. Insert into the optical path. Note that the control unit 60 stores the minimum σ of the effective light source distribution that can be formed without using the light shielding member 214 in the memory as a threshold value. Further, for example, the same can be said for forming an effective light source distribution having a fine shape as shown in FIG. When the effective light source distribution shown in FIG. 14 is formed, assuming that the radius of the pupil plane of the projection optical system 40 is 1, the length, width, or minimum dimension (σ) of these effective light source shapes is 0.2 or less. If it is, blurring occurs in the effective light source distribution. Therefore, it is necessary to insert the light shielding member 214 on the exit surface of the optical integrator 213. At that time, the opening shape of the light shielding member 214 is a shape cut out along the outer shape of the effective light source distribution indicated by the solid line in FIG. Further, the control unit 60 stores the minimum dimension of the effective light source distribution that can be formed without using the light shielding member 214 in the memory as a threshold value. Note that the minimum dimension stored in the memory of the control unit 60 may be a predetermined length such as the length of each side or the length of a diagonal line, which is divided by a solid line in FIG.

  In the present embodiment, the control unit 60 drives the zoom mechanism 216a via the drive unit 217 to correct the off-axis telecentricity in the illumination optical system 20. For example, the control unit 60 calculates a driving amount of the zoom mechanism 216a for correcting the off-axis telecentricity in the illumination optical system 20 (a table indicating the relationship between the amount of off-axis telecentricity generated and the driving amount of the zoom mechanism 216a). Pre-stored in memory. The control unit 60 may actually detect the off-axis telecentricity in the illumination optical system 20 via a detection unit (not shown), and drive the zoom mechanism 216a based on the detection result.

  Hereinafter, the exposure method in the exposure apparatus 1 will be described with reference to FIG. First, in step S1100, the control unit 60 acquires the exposure conditions given to the exposure apparatus 1 by the user. The exposure conditions include the reticle 30 to be used, the shape of the effective light source distribution, the NA of the projection optical system 40, the exposure amount, the exposure range, the area on the wafer 50 to be exposed, and the like.

  Next, the control unit 60 prepares for exposure based on the exposure conditions acquired in step S1100. Specifically, the control unit 60 forms an effective light source distribution in step S1200. The formation of the effective light source distribution (step S1200) will be described in detail later. Further, in step S1300, the control unit 60 prepares other exposures necessary in addition to the formation of the effective light source distribution (for example, setting of the NA of the projection optical system 40, loading of the reticle 30, loading of the wafer 50, reticle 30). And alignment of the wafer 50). In this embodiment, after the effective light source distribution is formed, other exposure preparations are performed. However, the order may be reversed or may be performed in parallel. In other words, it is sufficient that preparation for necessary exposure is completed before performing exposure.

  When the preparation for exposure is completed, the control unit 60 performs exposure in step S1400.

  The formation of the effective light source distribution in step S1200 will be described in detail with reference to FIG. First, in step S1210, the control unit 60 compares the effective light source distribution shape (maximum σ, minimum σ, and minimum dimension) acquired in step S1100 with the threshold values stored in the memory. Here, the threshold values stored in the memory are the maximum σ, the minimum σ, and the minimum dimension of the effective light source distribution that can be formed without using the light shielding member 214 as described above.

  Next, in step S1220, the control unit 60 forms the effective light source distribution acquired in step S1100 without using the light shielding member 214 based on the comparison result between the shape of the effective light source distribution acquired in step S1100 and the threshold value. Determine if you can.

  If it is determined that the effective light source distribution can be formed without using the light shielding member 214, the control unit 60 does not insert the light shielding member 214 into the optical path of the illumination optical system 20 in step S1230, or illumination. The light shielding member 214 is taken out from the optical path of the optical system 20. In other words, the effective light source distribution is formed without using the light shielding member 214.

  On the other hand, if it is determined that the effective light source distribution cannot be formed without using the light shielding member 214, the control unit 60 inserts the light shielding member 214 into the optical path of the illumination optical system 20 in step S1240. In other words, the effective light source distribution is formed using the light shielding member 214.

  In the present embodiment, the control unit 60 determines whether or not the light shielding member 214 is inserted / removed based on the shape of the effective light source distribution acquired in step S1100, but may be determined by an apparatus outside the exposure apparatus 1. . In particular, when the effective light source distribution having a fine shape is formed using the light shielding member 214, it is necessary to separately manufacture the light shielding member 214. Therefore, the light shielding member 214 is designed at the stage of designing the optical system for forming the effective light source distribution. It is preferable to determine the necessity of use. In this case, the necessity of using the light shielding member 214 is included in the exposure conditions acquired in step S1100.

  As described above, the exposure apparatus 1 shields the blurring portion of the effective light source distribution caused by the aberration included in the illumination optical system 20 and the wavefront division period of the optical integrator 213 by the light shielding member 214. Therefore, an effective light source distribution having an effective light source shape or a fine shape with a large outer σ can be formed with high accuracy without reducing the resolution. In addition, since only the blurring portion of the effective light source distribution formed using the diffractive optical element 209 is shielded by the light shielding member 214, light quantity deficiency can be suppressed compared to the case where the effective light source distribution is formed only by the light shielding member. Can do.

  Next, in step S1260, the control unit 60 performs illumination optics regardless of whether an effective light source distribution is formed using the light blocking member 214 or an effective light source distribution is formed without using the light blocking member 214. The off-axis telecentricity in the system 20 is corrected (optimized). Specifically, the control unit 60 drives the zoom mechanism (optical system) 216a of the illumination unit 216 via the driving unit 217, and corrects the off-axis telecentricity generated in the effective light source distribution. The zoom mechanism 216a of the illumination unit 216 is configured to have a correction range equal to or greater than the above-described change amount of the off-axis telecentricity as the correction range of the off-axis telecentricity. In addition, it is preferable to obtain in advance the drive position of the zoom mechanism 216a of the illumination unit 216 for correcting the off-axis telecentricity.

  When an effective light source distribution having a large outer σ is formed, it is preferable to shield not only the outer σ of the effective light source distribution but also the inner σ of the effective light source distribution with a light shielding member. This is because, when only the outer σ of the effective light source distribution is shielded by the light shielding member 214, the position defining the outer σ of the effective light source distribution is the position of the light shielding member 214, and the position defining the inner σ of the effective light source distribution is the optical integrator. It is because it becomes a condensing point of 213. In this case, since the position where the effective light source distribution is formed differs between the outer σ and the inner σ, different off-axis telecentricities are generated in the inner σ shape and the outer σ shape, which affects the imaging performance. .

  As described above, an off-axis telecentricity is generated when the effective light source distribution is formed using the light blocking member 214 and when the effective light source distribution is formed without using the light blocking member 214, and the generated off-axis telecentricity is generated. The telecentricity is a predetermined amount determined by a design value. However, if the off-axis telecentricity is to be corrected only by the zoom mechanism 216a of the illumination unit 216, the correction amount becomes remarkably large. For example, it is preferable to reduce the correction amount using a parallel plane plate.

  Therefore, as shown in FIG. 6, it is preferable that the light shielding member 214 and the plane-parallel plate 218 are configured to be exchangeable via the drive unit 215. In the exposure apparatus 1 shown in FIG. 6, the off-axis telecentricity generated when the effective light source distribution is formed using the light shielding member 214 and when the effective light source distribution is formed without using the light shielding member 214 is illuminated. Correction is performed by inserting a plane-parallel plate 218 in the vicinity of the pupil position of the optical system 20. In the present embodiment, the vicinity of the pupil position of the illumination optical system 20 into which the plane-parallel plate 218 is inserted is the exit surface of the optical integrator 213. Then, the off-axis telecentricity in the illumination optical system 20 is corrected with higher accuracy using the zoom mechanism 216a of the illumination unit 216. Here, FIG. 6 is a schematic sectional view showing a configuration of the exposure apparatus 1 as one aspect of the present invention.

  In the exposure apparatus 1 shown in FIG. 6, in the formation of the effective light source distribution in step S1200, as shown in FIG. 7, when the effective light source distribution is formed without using the light shielding member 214, the parallel flat plate 218 is illuminated with illumination optics. It is inserted in the vicinity of the pupil position of the system 20 (step S1250). Specifically, the control unit 60 inserts the parallel plane plate 218 into the exit surface of the optical integrator 213 via the drive unit 215. Here, FIG. 7 is a detailed flowchart of the formation of the effective light source distribution in step S1200 shown in FIG.

  When the plane-parallel plate 218 is inserted in the vicinity of the pupil position of the illumination optical system 20, if the transmittance of the plane-parallel plate 218 has an angular characteristic, unevenness in illuminance occurs in the illumination area. It is preferable that the angle characteristic is small. Therefore, in this embodiment, the angular characteristic of the transmittance of the plane parallel plate 218 is 0.5% or less so as not to adversely affect the illuminance unevenness of the exposure region.

  Moreover, since it is preferable that the plane parallel plate 218 can correct the above-described off-axis telecentricity, the thickness of the plane parallel plate 218 is d (mm), and the refractive index of the plane parallel plate 218 with respect to the wavelength of the light beam from the light source 10 is set. N satisfies ((N−1) · d) / N = Z + a / (2 · sin θ).

If the magnification telecentricity is 0.5 ppm or less per 1 micro defocus, the pattern of the reticle 30 can be satisfactorily transferred to the wafer 50. Therefore, as an error in the thickness of the parallel flat plate 218, (0.5 F ² · N) / ((N-1) · 1000) (mm) is allowed.

Further, in consideration of the zoom mechanism 216a of the illumination unit 216 that can continuously correct the off-axis telecentricity, the error of the thickness of the plane parallel plate 218 is (α · f ² · N) / ((N− 1) · 1000) (mm) is allowed. Here, α is a correction range (ppm / 1 μm defocus) of the off-axis telecentricity of the illumination unit 216 (zoom mechanism 216a).

  Therefore, in this embodiment, the plane parallel plate 218 is configured so that the thickness d (mm) of the plane parallel plate 218 satisfies the following mathematical formula 2.

  Moreover, since the position where the plane parallel plate 218 is inserted is near the pupil position of the illumination optical system 20, the light intensity is high. Therefore, in order to obtain sufficient durability, the plane parallel plate 218 is made of fluorite when the wavelength of the light beam from the light source 10 is 200 nm or less, and when the wavelength of the light beam from the light source 10 is 300 nm or less. Is preferably made of quartz.

  In the present embodiment, the example in which the parallel plane plate 218 is inserted when the effective light source distribution is formed without using the light shielding member 214 has been described. However, parallel plane plates having different thicknesses may be inserted depending on whether the effective light source distribution is formed using the light shielding member 214 or when the effective light source distribution is formed without using the light shielding member 214.

  As described above, the exposure apparatus 1 can shield the blurring portion (for example, a portion exceeding σ1) of the effective light source distribution caused by the aberration of the illumination optical system 20 and the wavefront division period of the optical integrator 213 with the light shielding member 214. . At that time, since the exposure apparatus 1 has the illumination unit 216 (zoom mechanism 216) having a wide correction range of the off-axis telecentricity, the off-axis telecentricity in the illumination optical system 20 can be sufficiently corrected. Yes, excellent exposure performance can be realized. Specifically, the illumination unit 216 corrects the off-axis telecentricity that occurs when the effective light source distribution is formed using the light blocking member 214 and when the effective light source distribution is formed without using the light blocking member 214. be able to. Therefore, the exposure apparatus 1 performs exposure with a good off-axis telecentricity regardless of the case where the effective light source distribution is formed using the light shielding member 214 and the case where the effective light source distribution is formed without using the light shielding member 214. be able to.

  Next, an embodiment of a device manufacturing method using the exposure apparatus 1 will be described with reference to FIGS. FIG. 8 is a flowchart for explaining the manufacture of devices (semiconductor devices and liquid crystal devices). Here, an example of manufacturing a semiconductor device will be described. In step 1 (circuit design), a device circuit is designed. In step 2 (reticle fabrication), a reticle on which the designed circuit pattern is formed is fabricated. In step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the reticle and wafer. Step 5 (assembly) is called a post-process, and is a process for forming a semiconductor chip using the wafer created in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). Including. In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device created in step 5 are performed. Through these steps, the semiconductor device is completed and shipped (step 7).

  FIG. 9 is a detailed flowchart of the wafer process in Step 4. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed on the surface of the wafer. In step 13 (electrode formation), an electrode is formed on the wafer by vapor deposition or the like. In step 14 (ion implantation), ions are implanted into the wafer. In step 15 (resist process), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the exposure apparatus 1 to expose a circuit pattern on the reticle onto the wafer. In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer. According to this device manufacturing method, it is possible to manufacture a higher quality device than before. Thus, the device manufacturing method using the exposure apparatus 1 and the resulting device also constitute one aspect of the present invention.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist. In this embodiment, the off-axis telecentricity is corrected using the zoom mechanism 216a of the illumination unit 216, but any correction mechanism configuration known in the art can be applied. For example, the off-axis telecentricity may be corrected using a parallel flat plate, or the off-axis telecentricity may be corrected by defocusing the diaphragm. However, also in this case, it is necessary that the correction range of the off-axis telecentricity has a correction range similar to that of the zoom mechanism 216a included in the illumination unit 216.

It is a schematic sectional drawing which shows the structure of the exposure apparatus as one side surface of this invention. It is a figure for demonstrating the reason why an off-axis telecentricity generate | occur | produces when the position where an effective light source distribution is formed, and the position of the pupil plane of an illumination optical system differ. It is a figure for demonstrating the off-axis telecentricity resulting from the wavefront division | segmentation period of an optical integrator. It is a flowchart for demonstrating the exposure method in the exposure apparatus in FIG. It is a detailed flowchart of formation of the effective light source distribution of step S1200 shown in FIG. It is a schematic sectional drawing which shows the structure of the exposure apparatus as one side surface of this invention. It is a detailed flowchart of formation of the effective light source distribution of step S1200 shown in FIG. It is a flowchart for demonstrating manufacture of a device. 9 is a detailed flowchart of the wafer process in Step 4 shown in FIG. 8. It is a figure which shows effective light source distribution at the time of forming the general ring shaped effective light source distribution in a prior art. It is a figure which shows effective light source distribution at the time of forming the effective light source distribution of the annular zone shape with large outside (sigma) in a prior art. It is a figure which shows distribution of the diffracted light in the pupil plane of a projection optical system at the time of illuminating a reticle with the favorable effective light source distribution which does not exceed (sigma) 1. It is a figure which shows distribution of the diffracted light in the pupil plane of a projection optical system at the time of illuminating a reticle with the effective light source distribution exceeding (sigma) 1. It is a figure which shows an example of the effective light source distribution which has a fine shape.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exposure apparatus 10 Light source 20 Illumination optical system 201 Routing optical system 202 Beam shaping optical system 203 and 205 Emission angle preservation | save optical element 204 Condensing optical system 206, 208, and 210 Relay optical system 207 Aperture stop 209 Diffraction optical element 211 Aperture 212 Zoom Optical system 213 Optical integrator 214 Light shielding member 215 Drive unit 216 Illumination unit 216a Zoom mechanism 217 Drive unit 218 Parallel plane plate 30 Reticle 40 Projection optical system 50 Wafer 60 Control unit

Claims (10)

An exposure apparatus comprising: an illumination optical system that illuminates an original using a light beam from a light source; and a projection optical system that projects a pattern of the original onto a substrate,
The illumination optical system includes:
An optical integrator that forms multiple light sources;
A light shielding member that is inserted into and removed from the pupil plane of the illumination optical system and shields a part of the light beam from the optical integrator;
A telecentric correction unit for correcting off-axis telecentricity in the image plane of the projection optical system,
The telecentric correction unit is generated when the off-axis telecentricity generated when the light shielding member is inserted into the pupil plane of the illumination optical system, and when the light shielding member is taken out from the pupil plane of the illumination optical system. An exposure apparatus having a correction range equal to or greater than a difference from the off-axis telecentricity. The distance between the position of the light shielding member inserted in the pupil plane of the illumination optical system and the position of the condensing point of the optical integrator is Z (mm), and the illumination optical system among the optical systems constituting the illumination optical system The focal length of the optical system downstream of the pupil plane and the projection optical system is f (mm), the wavefront division period of the optical integrator is a (mm), and the maximum emission angle of the light beam emitted from the optical integrator Is θ,
The off-axis telecentricity correction range α (ppm / 1 μm defocus) of the telecentric correction unit is
The exposure apparatus according to claim 1, wherein:   The exposure apparatus according to claim 1, wherein the telecentric correction unit includes a zoom optical system, and corrects the off-axis telecentricity by driving the zoom optical system.   The exposure apparatus according to claim 1, further comprising a plane-parallel plate inserted into the pupil plane of the illumination optical system so as to be exchangeable with the light shielding member. When the refractive index of the plane parallel plate with respect to the wavelength of the light beam from the light source is N,
The thickness d (mm) of the plane parallel plate is:
The exposure apparatus according to claim 4, wherein: The wavelength of light from the light source is 300 nm or less,
The exposure apparatus according to claim 4, wherein the plane-parallel plate is made of quartz. The wavelength of light from the light source is 200 nm or less,
The exposure apparatus according to claim 4, wherein the plane-parallel plate is made of fluorite. Exposing the substrate using the exposure apparatus according to any one of claims 1 to 7,
And developing the exposed substrate. A device manufacturing method comprising: In a correction method for correcting off-axis telecentricity in the image plane of the projection optical system when illuminating the original with an illumination optical system and projecting an image of the pattern of the original on a substrate via the projection optical system,
A determination step of determining whether or not to insert a light blocking member that blocks a part of the light beam from the optical integrator on the pupil plane of the illumination optical system;
Off-axis telecentricity in the image plane of the projection optical system that occurs when the light blocking member is inserted into the pupil plane of the illumination optical system according to the insertion / removal of the light blocking member determined in the determining step; A correction step for correcting the off-axis telecentricity in a correction range that is equal to or greater than the difference from the off-axis telecentricity that occurs when the light shielding member is taken out from the pupil plane of the illumination optical system. Method. The distance between the position of the light shielding member inserted in the pupil plane of the illumination optical system and the position of the condensing point of the optical integrator is Z (mm), and the illumination optical system among the optical systems constituting the illumination optical system The focal length of the optical system downstream of the pupil plane and the projection optical system is f (mm), the wavefront division period of the optical integrator is a (mm), and the maximum emission angle of the light beam emitted from the optical integrator Is θ,
The correction range α (ppm / 1 μm defocus) of the off-axis telecentricity is
The correction method according to claim 9, wherein: