JP2009145724A - Projection optical system and exposure device with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a relatively compact projection optical system excellent in imaging performance. <P>SOLUTION: The projection optical system 100 for projecting an image of a first object 101 onto a second object 102 includes: a first imaging optical system for forming a first intermediate image of the first object 101; a second imaging optical system G2 for forming a second intermediate image of the first object 101 based on a luminous flux from the first intermediate image, and having a concave mirror CM21; a third imaging optical system G3 for forming a third intermediate image of the first object 101 based on a luminous flux from the second intermediate image, and having a concave mirror CM31; a fourth imaging optical system G4 for forming an image of the first object 101 on the second object 102 based on a luminous flux from the third intermediate image; and a flat mirror FM1 which is disposed between a refractive member located closest to the third imaging optical system G3 along the optical path in the second imaging optical system G2 and a refractive member located closest to the second imaging optical system G2 along the optical path in the third imaging optical system G3, and reflects the luminous flux from the second imaging optical system G2 toward the third imaging optical system G3. The third imaging optical system G3 and the fourth imaging optical system G4 share the optical axis OA<SB>2</SB>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a projection optical system and an exposure apparatus having the same.

  In recent years, in addition to the demand for high resolution, exposure apparatuses are increasingly required to improve imaging performance and downsize the apparatus. In order to improve the imaging performance, it is necessary to stably reduce the influence of aberration and to secure a wide projection image formable region (good image range) on the object plane used for these corrections. Further, in order to reduce the size of the apparatus, it is necessary to keep the diameter of the lens and mirror as small as possible.

As one means for satisfying these requirements, a catadioptric projection optical system using a mirror and a lens is conventionally known. Chromatic aberration can be reduced by using a mirror. Further, by using a concave mirror having a negative Petzval sum, field curvature can be corrected and the lens can be miniaturized. As conventional techniques, there are Patent Documents 1 to 5.
JP-A-2005-107362 JP 2006-119244 A JP 2002-83766 A Japanese Patent Laid-Open No. 2005-37896 JP 2007-5558 A

  However, it is difficult to correct the Petzval sum with a single concave mirror. If the number of concave mirrors is one, it is necessary to provide a function for correcting the Petzval sum to other concave lenses. Then, an increase in the lens diameter and an increase in the distance between the object images due to an increase in the number of concave lenses is contrary to the demand for downsizing the exposure apparatus. Alternatively, the power of the concave lens is increased and higher-order aberrations are increased, so that it may be difficult to correct aberrations in the entire optical system.

  In addition, when the projection optical system is composed of a plurality of imaging optical systems and is coupled by a plane mirror, the reflection angle difference between the upper ray and the lower ray of the incident light beam at the plane mirror increases with the number of plane mirrors. become. Then, the projection optical system becomes a system that is easily affected by the angle characteristics of the reflection film of the plane mirror. As a result of the amplification of the transmittance difference between the upper and lower rays, the transmittance distribution (pupil transmittance distribution) in the exit pupil of the optical system is deteriorated, and the line width (critical dimension: CD) uniformity is improved. Getting worse.

  Further, in the configuration in which the image plane is arranged almost directly below the object plane, the distance between the object images increases, and if this problem is to be prevented, the power of the concave lens increases and the higher order aberrations increase.

  An object of the present invention is to provide a relatively small projection optical system having excellent imaging performance and an exposure apparatus having the same.

  A projection optical system according to one aspect of the present invention is a projection optical system that forms an image of a first object on a second object, and a first imaging optical system for forming a first intermediate image of the first object. And a second imaging optical system that forms a second intermediate image of the first object based on the light beam from the first intermediate image and has a first concave mirror, and the light beam from the second intermediate image. And forming a third intermediate image of the first object, a third imaging optical system having a second concave mirror, and an image of the first object based on a light beam from the third intermediate image. A fourth imaging optical system to be formed thereon; a refractive member closest to the third imaging optical system along an optical path in the second imaging optical system; and the optical path in the third imaging optical system. Between the refractive member closest to the second imaging optical system and the light beam from the second imaging optical system. Has a first plane mirror for reflecting the third imaging optical system, wherein the third imaging optical system and the fourth image-forming optical system is characterized by sharing the optical axis.

  An exposure apparatus according to another aspect of the present invention is the above-described projection optical system that projects the pattern of the original plate as the first object onto the substrate as the second object in the exposure apparatus that exposes the pattern of the original plate onto the substrate. It is characterized by having a system.

  According to the present invention, it is possible to provide a relatively compact projection optical system having excellent imaging performance and an exposure apparatus having the same.

  Hereinafter, a projection optical system 100 and an exposure apparatus 200 as one aspect of the present invention will be described with reference to the accompanying drawings. Here, FIG. 1 is an optical path diagram of the projection optical system 100. In the figure, 101 is a first object (for example, a reticle) placed on the object plane, 102 is a second object (for example, a wafer) placed on the image plane, and the projection optical system 100 is the first object. An image is formed on the second object. The projection optical system 100 is a four-time imaging system having a first imaging optical system G1 to a fourth imaging optical system G4 in order from the object side along the optical path.

First imaging optical system G1 has a first intermediate image is a real image of the first object 101 is formed on the point P _1, in FIG. 1 includes a lens group (or a refractive member group).

  However, as shown in FIG. 2, the first imaging optical system G1 is composed of lens groups L11 and L12, and a plane mirror (second plane mirror) FM2 is arranged between the lens groups L11 and L12, and the first The optical axis of the imaging optical system G1 may be bent. The lens group L11 is a refractive system having at least one refractive member and has a positive refractive power. The lens group L11 is disposed on the side closest to the first object 101 along the optical path. The lens group L12 has at least one refractive member and has positive refractive power. The lens group L12 is disposed on the side closest to the second object 102 along the optical path. The plane mirror FM2 is disposed between the lens groups L11 and L12, preferably in the vicinity of the pupil of the first imaging optical system.

  With such a configuration, the first object 101 and the second object 102 can be arranged in parallel, and the stage drive mechanism is configured in an apparatus configuration, particularly in a step-and-scan exposure apparatus. There is a merit that it is easy. In this case, the first object 101 and the second object 102 are arranged in parallel, but the first imaging optical system G1 and the fourth imaging optical system G4 share one linear optical axis. Each has a different optical axis. For this reason, the problem that the distance between object images becomes long can be solved. Further, when the plane mirror FM2 is in the vicinity of the pupil, the incident angle and the emission angle of all the light beams out of the light beam emitted from a certain object point are substantially the same. For this reason, even if the reflectance angle characteristic of the reflective film is taken into consideration, the transmittance at each point of the pupil becomes a uniform value, and the pupil transmittance distribution does not deteriorate. In the present application, the expression that the plane mirror FM2 is “arranged at the pupil of the first imaging optical system G1” is intended to include a state slightly deviated from the pupil.

The second imaging optical system G2, a second intermediate image is a real image of the first object 101 is formed on the point P ₂ based on the light flux from the first intermediate image. The second imaging optical system G2 is a catadioptric system having a lens group L21 and a concave mirror CM21 (first concave mirror). The lens unit L21 includes at least one refractive member and has a positive refractive power. Preferably, the lens unit L21 includes at least one convex lens and at least one concave lens. Thereby, it becomes a structure advantageous for correction | amendment of Petzval sum. The concave mirror CM21 is disposed in the vicinity of the pupil of the second imaging optical system G2 to avoid the generation of astigmatism. In the present application, the expression that the concave mirror CM21 is “arranged in the pupil of the second imaging optical system G2” is intended to include a state slightly deviated from the pupil.

Third imaging optical system G3, the third intermediate image is real image of the first object 101 is formed on the point P ₃ on the basis of the light flux from the second intermediate image. The second imaging optical system G2 is a catadioptric system having a lens group L31 and a concave mirror CM31 (second concave mirror). The lens group L31 includes at least one refractive member and has a positive refractive power. Preferably, the lens group L31 includes at least one convex lens and at least one concave lens. Thereby, it becomes a structure advantageous for correction | amendment of Petzval sum. The concave mirror CM31 is disposed in the vicinity of the pupil of the third imaging optical system G3 to avoid the generation of astigmatism. In the present application, the expression that the concave mirror CM31 is “arranged in the pupil of the third imaging optical system G3” is intended to include a state slightly deviated from the pupil.

  The fourth imaging optical system G4 forms a real image of the first object 101 on the second object 102 based on the light beam from the third intermediate image. The fourth imaging optical system G4 is a refractive system composed of at least one refractive member. The fourth imaging optical system G <b> 4 forms a final image (final image) on the second object 102.

  A plane mirror (deflection reflecting mirror, bending mirror) FM1 is disposed between the lens group L21 of the second imaging optical system G2 and the lens group L31 of the third imaging optical system G3 along the optical path. More specifically, the plane mirror (first plane mirror) FM1 includes the refractive member closest to the third imaging optical system G3 along the optical path in the second imaging optical system G2, and the third imaging. In the optical system G3, the optical system G3 is disposed between the refractive member closest to the second imaging optical system G2 along the optical path.

The plane mirror FM1 reflects the light beam from the second imaging optical system G2 to the third imaging optical system G3. However, the light beam from the third imaging optical system G3 to the fourth imaging optical system G4 is not reflected. In this respect, the flat mirror FM3 is different from the flat mirrors (M1, M2) of FIG. The projection optical system shown in FIG. 3 of Patent Document 1 has one plane mirror, and the plane mirror uses the front and back surfaces as a reflection surface. On the other hand, the plane mirror FM1 of the present embodiment uses only one reflecting surface. The plane mirror FM1 is disposed at a position off the optical path from the third imaging optical system G3 to the fourth imaging optical system. Further, no reflecting surface is disposed between the third imaging optical system G3 and the fourth imaging optical system G4. As a result, the third imaging optical system G3 and the fourth imaging optical system G4 sharing linear optical axis OA ₂ common one. In this embodiment, the optical axis from the first object 101 to the second imaging optical system G2 is OA ₁ , and the optical axis OA ₂ from the third imaging optical system G3 to the second object 102 is used.

The plane mirror FM1 is disposed in the vicinity of the formation points P _{1 to} P ₃ of the _{first to} third intermediate images. Light fluxes are collected at points P _{1 to} P ₃ , and by arranging these in the vicinity of the plane mirror FM 1, the plane mirror FM 1 moves from the first imaging optical system G 1 to the second imaging optical system G 2. It does not interfere with the light beam or the light beam traveling from the third imaging optical system G3 to the fourth imaging optical system G4. In the present embodiment, although the planar mirror FM1 is arranged upstream along the optical path of the forming point P ₂ of the second intermediate image may be located downstream. The plane mirror FM1 does not contribute to image formation. In this embodiment, orthogonal to the optical axis OA ₁ and the optical axis OA _2, the angle with respect to the optical axis OA ₁ of the plane mirror FM1 is 45 degrees. However, the present invention does not limit the bending angle of the plane mirror FM1.

  As described above, the projection optical system 100 has several features.

  First, the projection optical system 100 is a four-time imaging system, and the four-time imaging system ensures a long optical path length to reduce the amount of aberration generated in each imaging optical system and increase the degree of freedom of aberration correction. Therefore, it is effective for aberration correction. The projection optical system 100 includes a refraction system and a catadioptric system such as a first image formation optical system G1 and a second image formation optical system G2, a third image formation optical system G3, and a fourth image formation optical system G4. Pairs are arranged consecutively. The projection optical system 100 has two or more pairs to facilitate correction of Petzval sum and axial chromatic aberration.

  Furthermore, since the Petzval sum can be easily corrected, the first image forming optical system G1 and the fourth image forming optical system G4 can be configured without using many concave lenses for correcting the Petzval sum. For this reason, it is possible to reduce the diameter of the lens. In the case of a single glass material, it becomes difficult to correct asymmetric chromatic aberrations such as chromatic coma and lateral chromatic aberration. On the other hand, asymmetrical chromatic aberration can be easily achieved by facilitating the control of the upper ray, the lower ray and the principal ray of the light beam by the two refractive systems of the first imaging optical system G1 and the fourth imaging optical system G4. It is corrected to. Further, the projection optical system 100 is a multiple-time imaging optical system that forms an image using only an off-axis light beam whose pupil center is not shielded.

  Since the projection optical system 100 includes the two concave mirrors CM21 and CM31, the Petzval sum can be easily corrected. Since the proportion of the concave lens having the function of correcting the Petzval sum is reduced as compared with the case where the number of concave mirrors is one, the projection optical system 100 is configured to be small by preventing an increase in the lens diameter and an increase in the number of concave lenses. be able to. In addition, since it is not necessary to use a powerful concave lens, it is possible to easily correct aberrations by preventing an increase in higher-order aberrations.

  The projection optical system 100 has only one plane mirror FM1 or only one reflecting surface. As the number of plane mirrors or reflecting surfaces increases, the transmittance difference between the upper and lower rays is amplified, the transmittance distribution (pupil transmittance distribution) in the exit pupil of the optical system deteriorates, and CD uniformity However, this embodiment minimizes this problem.

  In addition, the projection optical system 100 prevents all optical elements of the projection optical system from sharing a single linear optical axis by using the plane mirror FM1. If all the optical elements share the optical axis, the distance between object images tends to increase. In this case, the second object 102 is likely to be arranged directly below the first object 101. In particular, when the projection optical system is a catadioptric system, the reflected light from the mirror will pass outside the other mirrors, making it difficult to secure a wide good image range or to secure a wide good image range. For example, since the luminous flux passing outside the other mirror becomes higher, the lens diameter of the subsequent stage increases. The plane mirror FM1 of this embodiment solves this problem.

  A positive Petzval sum is generated from a refractive member having a positive refractive power (for example, a convex lens), and a negative Petzval sum is generated from a refractive member having a negative refractive power (for example, a concave lens). Further, a negative Petzval sum is generated from a reflecting member having a positive refractive power (for example, a concave mirror). The Petzval sums of the first to fourth imaging optical systems expressed as the sum of Petzval sums from the respective members are as follows. The Petzval sum of the first imaging optical system and the fourth imaging optical system is a positive value. This is corrected (cancelled) by the negative Petzval sum of the second imaging optical system and the third imaging optical system. At this time, the Petzval sum P11 of the first imaging optical system and the Petzval sum P14 of the fourth imaging optical system satisfy Equation 1, respectively, and the Petzval sum P12 of the second imaging optical system, the third imaging optical system. It is preferable that the Petzval sum P13 of the above satisfies Expression 2.

  The absolute value of the paraxial lateral magnification of the first imaging optical system G1 is preferably 0.9 times or more and 1.7 times or less, and more preferably about 1.3 times. If the absolute value of the paraxial lateral magnification of the first imaging optical system G1 is larger than 1.7 times, the lens diameter near the first intermediate image becomes enormous, and if the lens is constructed while avoiding interference, the entire system becomes enormous. This is because the cost becomes disadvantageous. In addition, if the absolute value of the paraxial lateral magnification of the first imaging optical system G1 is smaller than 0.9 times, the NA in the first intermediate image increases, making it difficult to construct a lens avoiding interference. Because.

  The absolute value of the product of the paraxial lateral magnifications of the second imaging optical system G2 and the third imaging optical system G3 is preferably 0.8 or more and 1.2 or less, and more preferably 1.0. This is because it is advantageous for securing a wide screen size while avoiding interference of light beams around the plane mirror FM1.

  This will be described in detail below. The height measured in the direction perpendicular to the optical axis between an arbitrary point on the object plane and the optical axis is called an object height. The projection optical system 100 has a minimum object height, so-called minimum object height, and a maximum object height, so-called maximum object height, due to its configuration. It is clear that a wider screen size can be secured as the difference between the maximum height and the minimum height increases. The maximum height is subject to constraints such as the glass material that can be manufactured and the size of the lens, and the minimum height is subject to the interference of light rays around the plane mirror FM1.

FIG. 12 is an optical path diagram for explaining the relationship between the plane mirror FM1 and the light beam in FIG. The height measured perpendicularly to the optical axis OA ₁ of the formation position (point P ₁ ) of the first intermediate image formed by the first imaging optical system G1 from the off-axis object point of the object height h0 is measured. Let h1. The high light flux emitted from the off-axis object point of the object height h0 is measured perpendicular to the optical axis OA ₂ forming position of the third intermediate image formed by the third imaging optical system G3 (the point P ₃₎ Let h3 be. In order to prevent the light beam traveling from the first imaging optical system G1 to the second imaging optical system G2 from being vignetted (not interfered) by the plane mirror FM1, it is necessary to secure h1 to some extent, for example, 5 mm or more. Similarly, in order for the light beam traveling from the third imaging optical system G3 to the fourth imaging optical system G4 not to be vignetted (does not interfere) by the plane mirror FM1, h3 must be ensured to some extent, for example, 5 mm or more. On the other hand, since the object heights h0, h1, and h3 are proportional to each other because they are conjugate points, the smallest possible object height h0 is determined by making h1 and h3 as small as possible. become.

  Here, when the paraxial magnification of the second imaging system is β2, and the paraxial magnification of the third imaging system is β3, the relationship of Formula 3 is established between h1 and h3.

  That is, the magnitude relationship between h1 and h3 is determined by the product of the paraxial magnifications of the second imaging optical system G2 and the third imaging optical system G3. Using this relational expression, if a condition where h1 and h3 are as small as possible is, for example, 5 mm or more is calculated, the values taken by h1 and h3 for each value of β2 × β3 are as shown in FIG. When β2 × β3 = 1, h1 = h3 = 5 mm, h1 and h3 are the smallest, and at other values, h1 or h3 gradually increases as β2 × β3 moves away from 1. That is, the smallest minimum height can be obtained when β2 × β3 = 1, and the minimum height is gradually increased as the condition is deviated. Here, the interference constraint is set to 5 mm as an example, but the same behavior is naturally shown at other values. It should be noted that β2 × β3 is preferably in the range of 0.8 to 1.2, assuming that it is allowed to increase by about 20% from the best state.

  FIG. 3 is a schematic block diagram of an exposure apparatus 200 as one aspect of the present invention. As illustrated in FIG. 3, the exposure apparatus 200 includes an illumination apparatus 210 and the above-described projection optical system 100 that projects the pattern of the original 220 onto the substrate 230.

  The exposure apparatus 200 is a projection exposure apparatus that exposes a substrate 230 with a pattern formed on an original plate 220 by a step-and-scan method. The illumination device 210 illuminates the original 220 on which a transfer circuit pattern is formed, and includes a light source unit 212 and an illumination optical system 214. The light source unit 212 uses a laser as a light source. The illumination optical system 214 illuminates the original 220 uniformly. The original 220 is a reticle (mask) on which a circuit pattern (or image) to be transferred is formed, and is supported and driven by a stage (not shown). The diffracted light emitted from the original 220 is projected onto the substrate 230 through the projection optical system 100. As the substrate 230, a wafer or a glass plate may be used. The substrate 230 is coated with a photoresist. The original plate 220 and the substrate 230 are arranged in a conjugate relationship. Since the exposure apparatus 200 is a step-and-scan exposure apparatus, the pattern is reduced and projected onto the substrate 230 by scanning the original 220 and the substrate 230.

  FIG. 4 is an optical path diagram of the catadioptric projection optical system 100A of the first embodiment. Referring to FIG. 4, the projection optical system 100A includes first to fourth imaging optical systems G1 to G4 in order from the first object 101 side along the optical path.

  The first imaging optical system G1 is a refractive system that does not form a reciprocating optical system, and has a refractive lens group that includes at least one lens. The second imaging optical system G2 is a catadioptric system that forms a reciprocating optical system. The second imaging optical system G2 includes a lens group L21 that forms a reciprocating optical system, and a concave mirror CM21. The lens unit L21 forming the reciprocating optical system includes a lens unit L211 having a positive refractive power and a lens unit L212 having a negative refractive power. The third imaging optical system G3 is a catadioptric system that forms a reciprocating optical system. The catadioptric third imaging optical system G3 includes a lens group L31 that forms a reciprocating optical system and a concave mirror CM31. The lens group L31 forming the reciprocating optical system includes a lens group L311 having a positive refractive power and a lens group L312 having a negative refractive power. The fourth imaging optical system G3 is a refractive system that does not form a reciprocating optical system, and includes a refractive lens group that includes at least one lens.

  In this embodiment, the first imaging optical system includes a plane mirror FM2, so that the first object (reticle) and the second object (wafer) face each other.

  The projection optical system 100 preferably determines the mirror shape and the lens power so that the sum of Petzval terms is zero or close to zero in the entire optical system. The shape of the aspherical mirror and lens is expressed by a general aspherical expression shown in Equation 4.

  In Equation 4, Z is the coordinate in the optical axis direction, c is the curvature (the reciprocal of the radius of curvature r), h is the height from the optical axis, and k is the cone coefficient. A, B, C, D, E, F, G, H, J,... Are 4th order, 6th order, 8th order, 10th order, 12th order, 14th order, 16th order, 18th order, Aspherical coefficients of the 20th order,.

  Table 1 shows numerical data such as the radius of curvature, surface spacing, and material of each surface in this lens configuration. Table 2 shows coefficient data of aspheric surfaces included in this lens configuration.

  The specifications of this lens configuration are as follows. This is a projection optical system of an immersion exposure apparatus in which pure water is filled between the final lens and the second object (wafer), and NA is 1.35. The distance (working distance) between the final lens and the wafer is 2 mm. The exposure light source is assumed to be an ArF excimer laser, and the exposure wavelength is 193 nm. The projection magnification is 1/4. The distance between the object images (not the optical path length but the actual distance) is 1705 mm. In this embodiment, synthetic quartz is used as a glass material, and the refractive index of synthetic quartz (indicated as “sio2” in Table 1) at a wavelength of 193 nm is 1.56029, and the wavelength of pure water (indicated in the table as “water”). The refractive index at 193 nm is 1.43669.

  An aberration diagram showing the optical performance of this example is shown in FIG. FIG. 5A shows spherical aberration, curvature of field, and distortion, and FIG. 5B shows wavefront aberration at five object points between the minimum object point and the maximum object point. In addition, the wavefront aberration RMS in the present embodiment achieves 0.007λ or less over the entire use region, and good aberration correction is performed. In addition, the paraxial magnification of each partial system in the present embodiment is −1.397 for the first imaging optical system, −0.997 for the second imaging optical system G, and the third imaging optical system. G3 is -1.018, and the fourth imaging optical system G4 is -0.176. The product of the paraxial magnifications of the second imaging optical system G2 and the third imaging optical system G3 is 1.015 and falls within the range of 0.8 to 1.2.

  In the present embodiment, there is no interference in the optical path and good aberration correction is performed for an object point having a height on the first object plane (reticle plane) of 12.5 mm to 68.5 mm. Accordingly, as shown in FIG. 6A, a rectangular area of 26 mm × 8 mm can be used for exposure on the second object plane (wafer surface). Further, as shown in FIG. 6B, a further wide 26 mm × 11 mm region may be used for exposure by making the two corresponding sides of the rectangle into an arc shape.

  Further, in this embodiment, an aperture stop is provided in the fourth imaging optical system G4 (75th surface in Table 1), and NA is controlled by this. Of course, the aperture stop is not limited to one, and a plurality of aperture stops may be provided in the fourth imaging optical system G4, or may be provided in other first to third imaging optical systems. Absent.

  In the present embodiment, a lens group L212 having negative refractive power is disposed immediately before the concave mirror CM21 of the second imaging optical system G2, and further, a lens group L312 having negative refractive power is disposed on the third imaging optical system G3. It is arranged immediately before the concave mirror CM31. As a result, the axial chromatic aberration is efficiently corrected without increasing the size of the optical system. Further, a lens group L211 having a positive refractive power is arranged in the second imaging optical system G2, and is formed by a light beam guided from the first intermediate image to the second imaging optical system G2 and the second imaging optical system G2. The light beam guided from the second intermediate image to the third imaging optical system G3 is prevented from excessively spreading. Thereby, size reduction of an optical system can be achieved. In addition, a lens unit L311 having a positive refractive power is disposed in the third imaging optical system G3, a light beam guided from the second intermediate image to the third imaging optical system G3, and the third imaging optical system to the fourth. The light beam guided to the imaging optical system is prevented from transiently spreading. Thereby, size reduction of an optical system can be achieved.

  FIG. 7 is an optical path diagram of the projection optical system 100B having a configuration different from that in FIG. 4 for avoiding interference between the flat mirror FM1 and the optical path. The object height used for the exposure is different between the two, and therefore there is a difference in the arrangement of the plane mirror FM1. 4 and 7 is determined in consideration of comprehensive conditions such as ease of lens barrel configuration and conditions for designing the reflecting film.

  FIG. 8 is an optical path diagram of the catadioptric projection optical system 100C of the second embodiment. The specifications of this lens configuration are as follows. The projection optical system of the immersion exposure apparatus as in Example 1, NA is 1.35, the working distance is 2 mm, and the exposure wavelength is 193 nm. Further, the projection magnification is 1/4, the distance between the object images is 1705 mm, the refractive index of the material is the same as in Example 1, and the range of the object height in which the aberration is corrected is also the same as in Example 1. is there.

  Table 3 shows numerical data such as the radius of curvature, surface spacing, and material of each surface in this lens configuration. Table 4 shows coefficient data of an aspheric surface included in this lens configuration. The definition of the aspherical surface shape is the same as in the first embodiment.

  Also in the present embodiment, the plane mirror FM2 is included in the vicinity of the pupil of the first imaging optical system G1, so that the first object (reticle) and the second object (wafer) face each other.

  An aberration diagram showing the optical performance of this example is shown in FIG. FIG. 9A shows spherical aberration, curvature of field, and distortion, and FIG. 9B shows wavefront aberration at five object points from the minimum object point to the maximum object point. In addition, the wavefront aberration RMS in the present embodiment is 0.005λ or less over the entire use region, and by adding one aspheric lens in the second imaging optical system G2, the wavefront aberration RMS is higher than that in the first embodiment. Furthermore, good aberration correction is performed.

  The paraxial magnification of each partial system in the present embodiment is -1.322 for the first imaging optical system G1, -0.992 for the second imaging optical system G1, and the third imaging optical system. The system G3 is −1.027, and the fourth imaging optical system G4 is −0.186. The product of the paraxial magnifications of the second imaging optical system and the third imaging optical system is 1.019, which falls within the range of 0.8 to 1.2.

  FIG. 10 is an optical path diagram of the catadioptric projection optical system 100D of the third embodiment. The specifications of this lens configuration are as follows. The projection optical system of the immersion exposure apparatus as in Example 1, NA is 1.35, the working distance is 2 mm, and the exposure wavelength is 193 nm. Further, the projection magnification is 1/4, the refractive index of the material is the same as that of the first embodiment, and the range of the height of the object whose aberration is corrected is the same as that of the first embodiment.

  Table 5 shows numerical data such as the radius of curvature, surface spacing, and material of each surface in this lens configuration. Table 6 shows coefficient data of an aspheric surface included in this lens configuration. The definition of the aspherical surface shape is the same as in the first embodiment.

  The projection optical system 100D has a straight configuration without arranging the plane mirror FM2 in the first imaging optical system G1. Accordingly, the first object (reticle) and the second object (wafer) are orthogonal to each other without facing each other. If the exposure apparatus is configured such that the wafer stage is parallel to the ground, the height of the projection optical system is from the second object plane (wafer surface) to the convex reflecting mirror in the third imaging optical system. It is determined by the distance, and its value is 1370 mm. That is, there is an advantage that the height of the exposure apparatus can be kept low compared to other embodiments.

  Further, since the first imaging optical system G1 has a straight configuration, there is also a feature that it is easy to provide an aperture stop in the first imaging optical system G1. The NA may be controlled by providing a stop only in the first imaging optical system G1, or the NA may be controlled with higher accuracy in conjunction with the aperture stop in the fourth imaging optical system G4.

  FIG. 11 is an aberration diagram showing the optical performance of this example. FIG. 11A shows spherical aberration, field curvature, and distortion, and FIG. 11B shows wavefront aberration at five object points from the minimum object point to the maximum object point. In addition, the wavefront aberration RMS in the present embodiment achieves 0.005λ or less over the entire use region, and the aberration correction is further improved as compared with the first embodiment.

  Further, the paraxial magnification of each partial system in the present embodiment is -1.398 for the first imaging optical system, -0.993 for the second imaging optical system, and is about -0.993 for the third imaging optical system. -1.022, and the fourth imaging optical system is -0.176. The product of the paraxial magnifications of the second imaging optical system and the third imaging optical system is 1.015, which falls within the range of 0.8 to 1.2.

  Hereinafter, an embodiment of a device manufacturing method using the exposure apparatus 200 will be described with reference to FIGS. FIG. 14 is a flowchart for explaining how to fabricate devices (such as 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 of forming a semiconductor chip using the wafer created in step 4, and includes steps 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. 15 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 200 to expose a reticle circuit pattern 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 repeatedly performing these steps, multiple circuit patterns are formed on the wafer. According to the device manufacturing method of the present embodiment, it is possible to manufacture a higher quality device than before by using a projection optical system having excellent imaging performance. Thus, the device manufacturing method using the exposure apparatus 200 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. For example, the catadioptric projection optical system can be applied without using an immersion exposure apparatus. Further, the present invention can also be applied to a higher NA projection optical system using a high refractive material such as LuAG.

It is an optical path diagram of the projection optical system as one aspect of the present invention. It is an optical path diagram of the modification of the projection optical system shown in FIG. 1 is an optical path diagram of an exposure apparatus having a projection optical system as one aspect of the present invention. FIG. 3 is an optical path diagram of the projection optical system of Example 1. FIGS. 5A and 5B are aberration diagrams of the projection optical system shown in FIG. FIG. 6A is a plan view showing the relationship between the projection image formable region (good image region) on the object plane of the projection optical system shown in FIG. 4 and the optical axis. FIG. 6B is a plan view showing another relationship between the projected image formable region (good image region) on the object plane of the projection optical system shown in FIG. 4 and the optical axis. It is an optical path figure of the modification of the projection optical system shown in FIG. 6 is an optical path diagram of the projection optical system of Example 2. FIG. FIGS. 9A and 9B are aberration diagrams of the projection optical system shown in FIG. FIG. 7 is an optical path diagram of the projection optical system of Example 3. 11A and 11B are aberration diagrams of the projection optical system shown in FIG. It is an optical path diagram for demonstrating the interference state of the plane mirror shown in FIG. 2, and a light beam. 13 is a graph showing the relationship between the height from the optical axis at the intermediate image forming position shown in FIG. 12 and the paraxial magnification. It is a flowchart of the device manufacturing method using the exposure apparatus shown in FIG. It is a flowchart which shows the detail of step 4 shown in FIG.

Explanation of symbols

FM1 (first) plane mirror FM2 (second) plane mirror G1 first imaging optical system G2 second imaging optical system G3 third imaging optical system G4 fourth imaging optical system OA ₁ , OA ₂ light Axis 101 First object 102 Second object 100 to 100D Projection optical system 200 Exposure apparatus

Claims (10)

In a projection optical system that projects an image of a first object onto a second object,
A first imaging optical system for forming a first intermediate image of the first object;
A second imaging optical system that forms a second intermediate image of the first object based on a light beam from the first intermediate image and has a first concave mirror;
A third imaging optical system that forms a third intermediate image of the first object based on a light flux from the second intermediate image and has a second concave mirror;
A fourth imaging optical system for forming an image of the first object on the second object based on a light beam from the third intermediate image;
A refraction member closest to the third imaging optical system along an optical path in the second imaging optical system, and a refraction member closest to the second imaging optical system along the optical path in the third imaging optical system. A first plane mirror that is disposed between the first imaging mirror and the third imaging optical system, and reflects the light beam from the second imaging optical system to the third imaging optical system,
A projection optical system, wherein the third imaging optical system and the fourth imaging optical system share an optical axis.   The first imaging optical system and the fourth imaging optical system are refractive systems, and the second imaging optical system and the third imaging optical system are catadioptric systems. Item 4. The projection optical system according to Item 1.   3. The projection optical system according to claim 1, wherein each of the first and fourth imaging optical systems has a positive Petzval sum, and each of the second and third imaging optical systems has a negative Petzval sum. system.   4. The absolute value of the paraxial lateral magnification of the first imaging optical system is in the range of 0.9 times or more and 1.7 times or less. 5. Projection optics.   The absolute value of the product of the paraxial magnification of the second imaging optical system and the paraxial magnification of the third imaging optical system is in the range of 0.8 to 1.2. The projection optical system according to any one of 1 to 4.   6. The projection optical system according to claim 1, wherein the first concave mirror is disposed on a pupil of the second imaging optical system.   The projection optical system according to claim 1, further comprising a second plane mirror disposed on a pupil of the first imaging optical system.   The first object and the second object are arranged in parallel, and the first imaging optical system and the fourth imaging optical system have different optical axes, respectively. The projection optical system according to any one of claims. In an exposure apparatus that exposes an original pattern onto a substrate,
9. An exposure apparatus comprising the projection optical system according to claim 1, wherein the pattern of the original plate as a first object is projected onto the substrate as a second object. Exposing the substrate using the exposure apparatus according to claim 9;
And developing the exposed substrate. A device manufacturing method comprising: