JP2005109154A - Projection aligner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection aligner capable of realizing a higher NA while suppressing the upsizing of an apparatus scale by suppressing an increase of the number of optical parts used by deriving the optimum conditions for an incidence angle and reflectance to a reflecting mirror serving to bend an optical path. <P>SOLUTION: The projection aligner comprises a light source for emitting laser light, an optical path bending mirror for bending an optical path on the way, a lighting optical system for irradiating a reticle, and a projection optical system for imaging a pattern on the reticle on a wafer substrate. In the projection aligner, there can be dealt with a high NA aligner having an image space numerical aperture NAw of the projection optical system falls within a range 0.8≤NAw≤1.0 by satisfying ΔR≤3%, when an incidence angle α of a light ray with respect to a normal line of the optical path bending mirror is restricted within an angular range 30°≤α≤60°, and the maximum value of differences of reflectances over the whole range of the incidence angle. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a projection exposure apparatus configured to store a plurality of optical systems at a higher density, and more particularly to a projection exposure apparatus that manufactures a semiconductor element using a high NA projection optical system used in an immersion method or the like. Is.

  Conventionally, in a manufacturing process of a semiconductor device composed of an ultrafine pattern such as LSI or VLSI, a reduced projection in which a circuit pattern drawn on a reticle is reduced and projected onto a wafer substrate coated with a photosensitive agent to be printed. An exposure apparatus is used. As the mounting density of semiconductor elements increases, further miniaturization of patterns is required, and along with the development of the resist process, it is desired to cope with further miniaturization of the exposure apparatus, and various proposals have been made. (For example, refer to Patent Document 1).

  As a means for dealing with this problem, a higher NA is desired for a projection optical system in which the numerical aperture NA of the projection optical system of the projection exposure apparatus has already been significantly increased. In recent years, an immersion method in which a part of the wafer-side space is immersed in a light-transmitting liquid has come to be promising for further pattern miniaturization, and an ultra-high NA is expected. Along with such a demand for higher NA of the projection optical system, higher NA is required also in various parts of the illumination system (see, for example, Patent Document 2).

JP-A-5-217851 International Publication No. 99/49504 Pamphlet

  By the way, many optical units are incorporated in a projection exposure apparatus that has been used in the past, and reflection mirrors are provided at several places to bend the optical path so that it can be stored in a space as small as possible. As a general method for increasing the reflectance, this reflecting mirror is composed of an alternating layer of a thin film layer having a high refractive index and a thin film layer having a low refractive index on a metal thin film on an optical glass substrate. A dielectric thin film is coated.

  FIG. 11 shows the angle dependence characteristics of the reflectivity of a highly reflective mirror coated with a dielectric multilayer film as described above for an excimer laser having a wavelength of 193 nm. As can be seen from FIG. 11, the reflection mirror provided with such a dielectric thin film tends to have a sharp drop in reflectance at a light incident angle exceeding 60 degrees.

  2. Description of the Related Art Conventionally, in an illumination optical system of a projection exposure apparatus that has been used, light beams are divergent or convergent light beams in almost all optical paths, and form light beams having different angles with respect to the optical axis. As the NA of the projection optical system increases, the maximum angle formed by the optical axis of this light group tends to increase.

  Therefore, if a reflecting mirror for bending the optical path is arranged in a spatial region close to the Fourier transform relationship with the reticle surface having the circuit pattern, a difference in reflectance occurs between the upper line and the underline. When this reflectance difference is large, it causes an effective light source distortion in the irradiation light for irradiating the reticle, and as a result, a problem arises that the pattern printing line width becomes nonuniform on the wafer substrate.

  The present invention has been made in view of the above problems, and the purpose of the present invention is to derive optimum conditions for the incident angle and the reflectance to the reflecting mirror that bends the optical path, and to suppress the increase in the number of optical components to be used. It is an object of the present invention to provide a projection exposure apparatus capable of realizing a further increase in NA while suppressing an increase in size.

  The degree of asymmetry of the light intensity distribution in the plane equivalent to the pupil plane of the reticle irradiation light is called σ distortion of the effective light source. In the miniaturization of reticle patterns in recent projection exposure apparatuses, it is desirable that the σ distortion of this effective light source is within 3%. Therefore, it is necessary to set the reflectance difference within 3% due to the difference in the incident angle to the high reflection mirror disposed in the optical path bending portion. Further, as described above, a general high reflection mirror provided with a dielectric thin film tends to have a sharp drop in reflectance at a light incident angle exceeding 60 degrees.

  In view of this, in order to achieve the above-described object of the present invention, the invention described in claim 1 includes a light source that generates laser light, an optical path bending mirror that bends an intermediate optical path, and an illumination optical system that irradiates a reticle. In a projection exposure apparatus having a projection optical system that forms an image of the pattern on the reticle on a wafer substrate, the light incident angle α with respect to the normal of the optical path bending mirror is suppressed to an angle range of 30 ° ≦ α ≦ 60 °. When the maximum difference in reflectance over the entire range of incident angles is ΔR, ΔR ≦ 3% is satisfied, so that the image space numerical aperture NAw of the projection optical system is 0.8 ≦ NAw ≦ 1. It is characterized by being able to cope with an exposure apparatus with a high NA of 0.

  In particular, according to a second aspect of the present invention, in the immersion type projection exposure apparatus in which at least a part of the image space of the projection optical system is filled with a light-transmitting liquid, the light beam is incident on the normal of the optical path folding mirror. When the angle α is limited to an angle range of 30 ° ≦ α ≦ 60 ° and the maximum value of the difference in reflectance over the entire range of incident angles is ΔR, ΔR ≦ 3% is satisfied. The present invention is also applicable to an ultra high NA exposure apparatus in which the image space numerical aperture NAw of the system is 1.0 ≦ NAw ≦ 1.5.

  Next, as a first condition for achieving the object of the present invention, the invention according to claim 3 is the projection exposure apparatus according to claim 1 or 2, wherein the object plane and the image plane are conjugate to each other in the illumination optical system. The optical path bend between the position where the principal ray of the off-axis light beam of the re-imaging optical system intersects the optical axis and the lens group having the most positive power on the image plane side. A mirror is arranged.

  As a second condition for achieving the object of the present invention, the invention according to claim 4 is the projection exposure apparatus according to any one of claims 1 to 3, wherein an object plane and an image plane are included in the illumination optical system. A re-imaging optical system having a conjugate relationship, and a lens group having a positive power and a negative power in order from the object plane between the object plane of the re-imaging optical system and the optical path bending mirror. And a lens group having a positive power.

  In order to achieve the object of the present invention with the σ continuously variable optical system, the invention according to claim 5 is the projection exposure apparatus according to claim 3 or 4, wherein the re-imaging optical system has a widened irradiation irradiation area. Is an irradiation region variable optical system capable of continuously changing the irradiation region, and the irradiation region variable optical system includes a first fixed group having a positive power and a first moving group having a negative power in order from the object plane. A second moving group having a positive power; a second fixed group having a negative power; and a third fixed group having a positive power. The second fixed group and the third fixed group; By arranging the mirror in between, the maximum height from the optical axis of the irradiation light in the object plane is H1, and the maximum height from the optical axis of the irradiation light in the image plane when the emission irradiation range is maximum is H2. Even with a high magnification variable magnification optical system such that 4.2 ≦ H2 / H1 ≦ 15.0 Characterized in that it allows the achievement of the object of the.

  Furthermore, in order to achieve the object of the present invention more effectively while performing optimum exposure amount control, the invention according to claim 6 is the projection exposure apparatus according to claim 3 or 4, wherein A condensing optical system that irradiates an object plane of the re-imaging optical system in front of the system, and either in the condensing optical system or between the condensing optical system and the re-imaging optical system. An optical branching member for branching a part of the light beam of the condensing optical system, and an angle formed between a plane for splitting the light and a plane perpendicular to the optical axis in the optical branching member, θ, When the absolute value of the imaging magnification between object images of the optical system is Bm and the object space numerical aperture of the re-imaging optical system is NAm, 21.2 ° ≦ θ ≦ 34.0 °, 1.0 ≦ Bm ≦ 2.0, 0.2 ≦ NAm ≦ 0.45.

In order to achieve the object of the present invention more effectively while performing optimum exposure amount control in an immersion type projection exposure apparatus, the invention according to claim 7 is a projection exposure apparatus according to claim 2. In the illumination optical system, there is a re-imaging optical system in which the object plane and the image plane are in a conjugate relationship, and the position where the principal ray of the off-axis light beam intersects the optical axis in the re-imaging optical system, The optical path bending mirror is disposed between lens groups having positive power on the image plane side, and a condensing optical system that irradiates an object plane of the re-imaging optical system, and A light branching member for branching a part of the light beam of the condensing optical system is provided between any one of the condensing optical system and the re-imaging optical system. The angle formed by a plane perpendicular to the axis is θ, and the absolute value of the imaging magnification between object images of the re-imaging optical system is Bm. When the object space numerical aperture of the re-imaging optical system is NAm, 21.2 ° ≦ θ ≦ 34.0 °, 1.0 ≦ Bm ≦ 1.8, 0.25 ≦ NAm ≦ 0.45. In order to achieve the object of the present invention more effectively in an immersion type projection exposure apparatus, the invention according to claim 8 is the projection exposure apparatus according to claim 7, wherein A lens group having a positive power, a lens group having a negative power, and a lens group having a positive power are arranged between the object plane of the imaging optical system and the optical path bending mirror in order from the object plane. And

  According to the present invention, the optical path bending mirror is arranged between the position where the principal ray of the off-axis light beam of the re-imaging optical system intersects with the optical axis and the lens group having the positive power closest to the image plane. By constructing the illumination optical system, the light incident angle on the bending mirror can be kept small, and the σ distortion of the effective light source in the reticle irradiation light can be reduced even if there is a demand for further NA. It is possible to suppress the variation in the line width of the projection pattern satisfactorily, and to burn a circuit pattern finer than the conventional device onto the semiconductor element.

  Further, according to the present invention, it is possible to provide a projection exposure apparatus that can prevent the increase in optical components, suppress the increase in the cost of the apparatus, and suppress the apparatus scale to the current level, while obtaining the above effects. Therefore, an increase in manufacturing cost can be suppressed when producing a semiconductor element with higher performance than before.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1>
A first embodiment of the present invention will be described with reference to FIGS. In the present embodiment, as shown in FIG. 1, in an illumination system having a mask irradiation optical system 104 that irradiates a mask surface 103 between a fly-eye lens 101 and a reticle 102, the irradiation light from the mask surface 103 This is an example in which a re-imaging optical system that irradiates the pattern surface on the reticle 102 with the mask surface 103 and the pattern surface on the reticle 102 in a conjugate relationship.

  The mask irradiation optical system 104 is composed of a plurality of lens groups, and is an optical system that condenses in the vicinity of the mask surface 103 when a parallel light beam enters. The exit pupil position of the mask irradiation optical system 104 is incident on the rear of the re-imaging optical system. It is matched with the pupil position.

  The re-imaging optical system of the present embodiment has an object space numerical aperture NAm of 0.38, an imaging magnification of -1.6 times, and has a positive power at the intersection of the principal ray of the off-axis light beam and the optical axis. Between the last lens group, there is provided an optical path bending portion for disposing an optical path bending mirror for bending the optical path. With such a configuration, in an exposure apparatus with a high NA in which the object space numerical aperture NAw of the projection optical system is 0.8 or more, the incident angle of the incident light on the optical path bending mirror is set with respect to the normal of the mirror. 30 degrees or more and 60 degrees or less.

  Therefore, the re-imaging optical system according to the present embodiment includes, in order from the object space, the first lens group having a positive power, the second lens group having a negative power, and the third lens group having a positive power. , And a fourth lens group having a positive power. The first lens group includes a cover glass CG1 for dust-proofing the immediately following lens, and the entire optical system with a minimum number of lenses, and a concave lens G101 and three lenses for correcting spherical aberration among various aberrations. Consists of convex lenses G102, G103, and G104. Later, a second lens group consisting of only one concave lens G105, a third lens group consisting of only one convex lens G106, and a fourth lens group consisting of convex lens G107, concave lens G108 and convex lens G109 are provided. It is arranged. Therefore, the fourth lens group is the final lens group on the image plane side having a positive power.

  As shown in the present embodiment, a lens group having a positive power and a lens group having a negative power in order from the object space between the object space 103 and the optical path bending unit 106 of the re-imaging optical system, and By disposing a lens group having a positive power, the intersection point 108 where the principal ray 107 of the off-axis light beam intersects the optical axis 105 can be moved to the object space side. As a result, between the optical path bending portions 106 of the third lens group and the fourth lens group, the angle formed by the principal ray of the off-axis light beam and the optical axis is relaxed, and the optical path bending that bends the optical axis 105 at a right angle. Space is secured to place the mirror. A reticle cover glass CG3 for dust prevention is disposed just before the reticle 102 as in the first lens group.

  While securing a space for bending the optical path, with a minimum lens configuration, particularly spherical aberration among the various aberrations is corrected well, and the parallelism of the principal ray with respect to the optical axis in the off-axis emitted light beam, that is, the exit telecentricity is obtained. In order to maintain a good level, the light exit side of the convex lens G106 constituting the third lens group is an aspherical surface.

  In this embodiment, in order to maintain the distortion aberration and the exit telecentricity at a favorable level, an optical system having a triplet structure is arranged as the fourth lens group which is the final lens group. That is, a convex lens G107, a concave lens G108, and a convex lens G109 are arranged from the incident light side.

  FIG. 2 shows the lateral aberration in the meridional direction, the lateral aberration in the sagittal direction, the distortion aberration, and the exit telecentricity when the maximum image height on the reticle side is 57 mm in the re-imaging optical system used in this embodiment. FIG. The distortion and the exit telecentricity are satisfactorily corrected while suppressing the lateral aberration within a practically allowable range.

  Table 1 shows values of specifications in the re-imaging optical system used in this example.

表１のレンズデータにおいて、ｒは各面の曲率半径（単位：ｍｍ）、ｄは各面間隔（単位：ｍｍ）、ｎは波長１９３ｎｍの入射光に対する媒質の屈折率をそれぞれ示す。

In the lens data in Table 1, r represents the radius of curvature (unit: mm) of each surface, d represents the spacing between the surfaces (unit: mm), and n represents the refractive index of the medium for incident light having a wavelength of 193 nm.

  Α1 and α2 indicate the minimum angle and the maximum angle of the light beam when the mirror is inclined at 45 degrees with respect to the optical axis in the optical path bending portion. In this embodiment, α1 = 33.5 ° and α2 = 56.5 °, and the incident angle α to the mirror can be suppressed to 30 degrees or more and 60 degrees or less with respect to the total luminous flux. G indicates the intersection 108 between the principal ray 107 of the off-axis light beam and the optical axis 105, and indicates the distance from the light incident side surface of the convex lens G106, which is the closest lens surface, that is, the 13th surface. Yes.

  The various coefficients related to the aspherical surface shown in Table 1 are as follows: the height in the direction perpendicular to the optical axis at any point on the aspherical surface is h, the distance in the direction along the optical axis is x, the radius of curvature of the apex is r, When the curved surface coefficient is K and the aspheric coefficient is an alphabet from A to F, it is expressed by the following equation (1).

^{x = h 2 / r / [} 1+ {1- (1+ K) (h / r) 2} 1/2] + Ah 4 + Bh 6 + Ch 8 + Dh 10
+ Eh ¹²
+ Fh ¹⁴
... (1)
The re-imaging optical system described in the present embodiment has an object space numerical aperture NAm of 0.38 and an image forming magnification Bm of -1.6, so that the image-to-object image forming magnification is -0.25, the image space. This can be applied to a projection optical system having a numerical aperture NAw of 0.95.

  By applying the re-imaging optical system configured as described above to the illumination device as a mask imaging optical system, an incident light beam that does not cause effective light source distortion in the irradiation light on the reticle surface while being configured with a smaller number of lenses. At an angle, an optical path folding mirror can be placed in the re-imaging optics.

  The re-imaging optical system described in the present embodiment can be applied as a mask imaging optical system of a projection exposure apparatus adopting a step-and-scan method as shown in FIG. 3, for example. That is, the irradiation light emitted from the excimer laser 111 having an oscillation wavelength of 193 nm is shaped into a desired beam shape via the beam shaping optical system 112 and then converted into a hexagonal columnar glass 114 by the condensing optical system 113. Incident.

  The columnar glass 114 forms a plurality of light sources from one light source by multiple reflection by the glass inner surface. Irradiation light from the columnar glass 114 is irradiated to the fly-eye lens 101 by the σ continuously variable optical system 115. Irradiation light from the fly-eye lens 101 is applied to the mask surface 103 by the mask irradiation optical system 104. Irradiation light from the mask surface 103 irradiates the circuit pattern surface of the reticle 102 by a mask imaging optical system. The irradiation light is collected by the projection optical system 119, and the circuit pattern of the reticle 102 is reduced and projected onto the base surface of the wafer 120 coated with the photosensitive material.

  The re-imaging optical system described in the present embodiment is replaced with a mask imaging optical system including the front group optical system 116, the optical path bending mirror 117, and the rear group optical system 118 in the projection exposure apparatus described above. Can be applied. That is, in the mask imaging optical system of the projection exposure apparatus shown in FIG. 3, the rear group optical system 116 is replaced with the lens groups of the cover glasses CG1 and G101 to G106, and the rear group optical system 118 is replaced with the convex lens G107, the concave lens G108, and the convex lens G109. It replaces with the optical system of this triplet structure, and cover glass CG2.

  An optical path bending mirror 117 that bends the optical axis 121 at a right angle within the cross section including the scanning direction of the reticle 102 and the wafer 120 and the optical axis 121 is disposed between the front group optical system 116 and the rear group light optical system 118.

  By applying the projection exposure apparatus configured as described above, the circuit pattern on the reticle can be faithfully maintained even when the projection optical system has a higher NA while accommodating the angle optical system in a smaller space. A projection exposure apparatus capable of performing projection exposure on a wafer can be provided.

<Embodiment 2>
A second embodiment of the present invention will be described with reference to FIGS.

  This embodiment is an example of a re-imaging optical system capable of continuously changing the size of a light irradiation region in an image space, as shown in FIG. 4, and an object plane 209 and an image plane 210 are In this example, an optical path bending mirror is arranged between the principal ray of the off-axis light beam and the final lens group having a positive power so that the incident angle of the light beam to the bending mirror is kept small.

  The re-imaging optical system capable of continuously changing the size of the light irradiation region includes a parallel plate G201, a first fixed group having a positive power, and a first movement having a negative power in order from the object space side. And a second moving group having a positive power and a second fixed group, and a third fixed group which is a final fixed group having a positive power.

  The first fixed group has G202 and G203 which are both convex lenses, the first moving group has a concave lens G204, and the second moving group has both G205 and G206 which are both convex lenses, The second fixed group has a concave lens G207, and the third fixed group has a convex lens G208. Here, the parallel flat plate G201 is incorporated in a turret mechanism that can be moved in and out of the optical path so that it can be exchanged with other optical elements for the purpose of changing the illuminance distribution state of the irradiation region.

  Here, the concave lens G207 as the second fixed group and the convex lens G208 as the third fixed group are arranged with a certain distance therebetween. With such a configuration, it is possible to secure a space in which the incident light angle to the mirror can be kept small, and at the same time, there is a practical problem with the parallelism of the principal ray incident on the fly-eye lens 203 with respect to the optical axis, that is, telecentricity. It can be maintained at a level with no.

  In order to maintain the uniformity of the irradiation light to the fly-eye lens 201, the second movement is used for suppressing distortion, particularly for suppressing the fluctuation amount of distortion in the zooming state on the large irradiation area side. In the lens group having negative power on the light incident side constituting the group, the curvature of the surface on the light incident side is stronger than the curvature of the surface on the light exit side, and there is a concave lens G207 with the concave surface facing the light incident side. It is desirable.

  The state when the irradiation range is minimum in the re-imaging optical system of the present embodiment is shown in P1 of FIG. In this state, the intersection position 208 where the principal ray 207 of the off-axis light beam intersects the optical axis 205 is located between the first moving group having negative power and the second moving group having positive power. I am letting. With such an arrangement, when the irradiation area in the image plane is expanded, the first moving group is moved to the image plane side along the optical axis 205 to provide a zooming function, and at the same time, the second moving group is By moving to the object plane side along the optical axis 209, control is performed so that a desired spot size is obtained on the incident surface of the fly-eye lens 210.

  And the state at the time of the irradiation range maximum in the re-imaging optical system of this Embodiment is shown to P3 of FIG. In this state, an intersection position 208 where the principal ray 207 of the off-axis light beam intersects the optical axis 205 is positioned between the first fixed group and the first moving group.

  Table 2 shows values of specifications in the re-imaging optical system used in this embodiment.

表２において、ｒは各面の曲率半径（単位：ｍｍ）、ｄは各面間隔（単位：ｍｍ）、ｎは入射光（波長０．２４８μｍ）に対する媒質の屈折率をそれぞれ示す。又、ｄ７は第１の固定群と第１の移動群との光軸２０５上の可変間隔、ｄ９は第１の移動群と第２の移動群との光軸２０９上の可変間隔、ｄ１３は第２の移動群と第２の固定群との光軸上２０９の可変間隔を示している。

In Table 2, r represents the radius of curvature (unit: mm) of each surface, d represents the spacing between the surfaces (unit: mm), and n represents the refractive index of the medium for incident light (wavelength 0.248 μm). D7 is a variable interval on the optical axis 205 between the first fixed group and the first moving group, d9 is a variable interval on the optical axis 209 between the first moving group and the second moving group, and d13 is The variable interval on the optical axis 209 between the second moving group and the second fixed group is shown.

  P1 is the minimum irradiation range position, P2 is the intermediate irradiation range position, P3 is the maximum irradiation range position, F1 is the focal length at each position of the re-imaging optical system of the present embodiment, and f1 is the first fixed group. The focal length, f2 indicates the focal length of the first moving group, and f3 indicates the focal length of the second moving group. G1, G2, and G3 indicate the intersection position 208 where the principal ray 207 of the off-axis light beam and the optical axis 209 intersect at each position, and the ninth surface or the eighth surface that is the surface on the light exit side of the concave lens G204. The distance from the surface is shown.

  Further, H2 / H1 is a light beam diameter on the evaluation surface at a position 67 mm from the final surface after the parallel light beam that has entered the opening of φ10 mm in the object space passes through the re-imaging optical system of the present embodiment. Indicates the enlargement ratio. In this case, the fly-eye lens 201 is not inserted. In this embodiment, the enlargement ratio H2 / H1 is 2.6 to 9.4, and the irradiation range in the image space is continuously changed from 2.6 to 9.4 times the irradiation range in the object space. It is an optical system that can be made to.

  Α1 and α2 indicate the minimum angle and the maximum angle of incident light when the optical path bending mirror is inclined 45 degrees with respect to the optical axis in the optical path bending section at each position. In the present embodiment, at the position P1, the minimum and maximum over the entire zoom range are α1, 35.7 °, and α2 = 54.3 °, and the incident angle α to the mirror over the entire luminous flux and all positions. Can be suppressed to 30 degrees or more and 60 degrees or less.

  FIG. 5 is a diagram showing meridional lateral aberration, sagittal lateral aberration, and distortion at the minimum irradiation range position P1 of the re-imaging optical system used in the present embodiment. FIG. 6 is a diagram showing transverse aberration and distortion in the meridional direction and the sagittal direction at the maximum irradiation range position P3 of the re-imaging optical system used in the present embodiment. While suppressing the lateral aberration within a practically acceptable range, the distortion is corrected well.

  As described above, the present embodiment uses a re-imaging optical system which is the simplest variable power optical system called a two-group movement system, and between the object space and the optical path bending unit 206, from the object space. By arranging a lens group having a positive power, a lens group having a negative power, and a lens group having a positive power in order, the intersection position 208 between the off-axis principal ray and the optical axis can be further moved to the object space side. Move to. Thereby, it is possible to secure an optical path in which the light incident angle to the optical path bending mirror becomes gentle. In addition, the telecentricity of the light emitted from the re-imaging variable optical system is maintained at a level that causes no practical problems while suppressing various aberrations.

  When the NA of the projection optical system is increased, the maximum effective beam diameter of the mask irradiation optical system disposed immediately after the fly-eye lens 201 is about twice the incident light beam. Quartz and fluorite currently used for excimer lasers can be supplied with a diameter of about 340 mm. Therefore, the maximum value allowed as the effective diameter of the fly-eye lens 201 is about 150 mm in diameter. Moreover, the irradiation range of 10 mm to 35 mm in diameter is optimal as the object space because of the thickness of the columnar glass that irradiates the object space and the spread of the diffraction image from the diffraction element that performs modified illumination.

Therefore, H2 / H1 is 4.
It needs to be 2 or more and 15.0 or less.

  With the power of each group constituting the optical system, if a re-imaging optical system having the same sign arrangement as shown in the present embodiment is used, an optical path that can suppress the light incident angle to the optical path folding mirror can be secured. It is possible to do.

  The re-imaging optical system described in the present embodiment can be applied as a σ continuously variable optical system of a projection exposure apparatus adopting a step-and-scan method as shown in FIG. 7, for example. In other words, the irradiation light emitted from the excimer laser 211 having an oscillation wavelength of 248 nm is shaped into a desired beam shape via the beam shaping optical system 212, and then formed into a columnar glass 214 having a hexagonal cross section by the condensing optical system 213. Incident.

  The columnar glass 214 forms a plurality of light sources from one light source by multiple reflection by the inner surface of the glass, as described in the first embodiment. The irradiation light from the columnar glass 214 is irradiated to the fly-eye lens 201 by the σ continuously variable optical system. The σ continuously variable optical system includes a front group optical system 215, a bending mirror 216, and a rear group optical system 217.

  Irradiation light from the fly-eye lens 201 is applied to the mask surface 203 by the mask irradiation optical system 204. Irradiation light from the mask surface 203 irradiates the circuit pattern surface of the reticle 202 by a mask imaging optical system. The mask imaging optical system includes the front group optical system 218, the optical path bending mirror 219, and the rear group optical system 220, which are the same as those described in the first embodiment. The circuit pattern of the reticle 202 is reduced and projected onto the substrate surface of the wafer 223 coated with a photosensitive material by the projection optical system 221.

  In the projection exposure apparatus in FIG. 7 described above, the σ continuously variable optical system can be replaced with the re-imaging optical system described in the present embodiment. That is, the front group optical system 215 is configured by lenses G201 to G207 in the re-imaging optical system described in the present embodiment. The rear group optical system 217 is configured by the convex lens G208 in the re-imaging optical system described in the present embodiment. Further, an optical path bending mirror 216 that bends the optical axis 223 at a right angle within the cross section including the scanning direction of the reticle 202 and the wafer 222 and the optical axis 223 is disposed between the two condensing optical systems. Configure the system.

  Therefore, by applying the re-imaging optical system configured as shown in the present embodiment to the projection exposure apparatus as a σ continuously variable optical system, the incident light condition that does not cause effective light source distortion while having a smaller number of lenses. Thus, the optical path bending mirror can be arranged in the σ-continuous variable optical system. In addition, according to the present invention, it is possible to provide a projection exposure apparatus that can satisfy a structural constraint condition and a constraint condition of an optical material diameter and can finely print a fine pattern with a larger σ value.

<Embodiment 3>
Next, a third embodiment of the present invention will be described with reference to FIGS. In the present embodiment, as shown in FIG. 8, a fly-eye lens exit surface and a mask surface 303 are used as a condensing optical system for irradiating the mask surface 303 between the fly-eye lens 301 and the mask surface 303. And a mask irradiation optical system 304 having a Fourier transform relationship, and further, a mask irradiation is applied to the light receiving surface of the sensor 306 for detecting an exposure amount between the mask irradiation optical system 304 and the mask surface 303. A half mirror 307 for guiding a part of light is arranged at a predetermined angle θ with respect to a plane perpendicular to the optical axis.

  An example in which the set angle θ of the light branching reflection surface 307a with respect to the surface perpendicular to the optical axis 302 is made as small as possible in order to reduce the difference in reflectance between the upper line and the lower line of incident light on the light branching reflection surface 307a as much as possible. It is.

  In the embodiment shown in FIG. 8, the sensor 306 is directed downward from the optical axis, but may be directed upward.

  The half mirror 307 is disposed on the image space side outside the mask irradiation optical system 304. Instead, the half mirror 307 is disposed in the mask irradiation optical system 304, and A lens that also serves as a seal glass for sealing the optical system may be provided on the image space side, and one surface of the seal glass may have a gentle curvature.

  Further, the present embodiment is an example applicable to the following projection exposure apparatus.

  That is, with respect to the mask imaging optical system, an illuminating device in which the object space numerical aperture NAm is set to 0.2 and the object-image imaging magnification Bm is set to -1.0 is used. The projection optical system can be applied to a projection exposure apparatus in which the image space maximum numerical aperture NAw is set to 0.8 and the image-to-object imaging magnification is set to -1/4, that is, -0.25.

  In FIG. 8, the distance L from the position where the light splitting reflecting surface 307a intersects the optical axis 305 to the condensing point position of the mask irradiation optical system 304 is set to 100 mm, and the slit width D in the scanning direction of the mask surface is set to 32 mm. For example, the mask irradiation system can be configured in a state where the half mirror 307 does not interfere with the mask surface 303, and the irradiation slit width on the wafer side can be applied to a projection exposure apparatus of 26 mm × 8 mm.

  In FIG. 8, the distance from the position where the light splitting reflecting surface 307a intersects with the optical axis 305 to the condensing point position of the mask irradiation optical system 304 is L, the slit width in the scanning direction of the mask surface is D, and mask irradiation is performed. Reflected light from the reflection surface 307a for light branching, where γ is the angle formed by the maximum aperture light beam of the optical system 304 and the optical axis 305, and β is the angle formed by the light branching reflection surface 307a perpendicular to the optical axis 305. The condensing point 308 is located on the maximum aperture light beam that is the most off-axis. At that time, the following equation (2) holds.

L · sin 2β = (L + L · cos 2β) · tan γ + D / 2 (2)
Substituting L = 100 mm and D = 32 mm into this conditional expression, and solving the equation relating to β by the numerical substitution method, β becomes 16.2 degrees. Then, if a margin angle for preventing the sensor 306 and the accompanying optical system barrel from blocking the effective light beam is expected to be 5 degrees, the set angle θ of the light branching reflection surface 307a with respect to the surface perpendicular to the optical axis 305 is set. 21. Set to 2 degrees.

  Here, since the object space numerical aperture NAm of the mask imaging optical system described above is 0.2, the angle formed by the maximum aperture light beam of the mask irradiation optical system 304 and the optical axis 305 is 11.5 degrees. Accordingly, the angles formed by the outermost upper line and the outermost lower line of the light beam emitted from the mask irradiation optical system 304 with respect to the normal line of the light splitting reflecting surface 307a are 32.7 degrees and -9.7 degrees, respectively. . FIG. 9 shows the angle dependence characteristics of the spectral reflectance by the half mirror 307 at this time.

  As shown in FIG. 9, if the reflectance difference between the upper line and the underline of the maximum aperture light beam according to the present embodiment is expressed by an average value difference ΔRM between the S-polarized component RS and the P-polarized component RP, it becomes 0.2%. This reflectance difference is an order of magnitude smaller than the maximum value of the reflectance difference due to the difference in the incident angle in the optical path bending mirror in the above-described embodiment.

  The upper limit and the lower limit in the conditional expression shown in claim 6 of the claims of the present invention will be described.

  First, the lower limit value of the second conditional expression shown in claim 6 will be described.

  In order to keep the overall height of the exposure apparatus lower, the optical path bending mirror in the mask imaging optical system is preferably arranged in the latter half of the optical system. At this time, in order to loosen the incident light beam angle to the optical path bending mirror part, it is desirable to position the intersection point where the off-axis principal ray intersects the optical axis as close to the object plane as possible. Therefore, the absolute value of the object image forming magnification Bm of the mask imaging optical system is preferably 1 or more.

  Next, lower limit values of the first and third conditional expressions shown in claim 6 will be described.

  As described above, assuming that the imaging magnification Bm between object images of the mask imaging optical system is -1.0 or more, the maximum numerical aperture NAw of the projection optical system is 0.8 or more, and the imaging magnification between object images is- Assume a projection exposure apparatus that is set to 1/4 or -0.25. Then, as described in the present embodiment, the minimum value of the object space numerical aperture NAm of the mask imaging optical system is 0.2, and at that time, the light branching reflecting surface 307a related to the mask irradiation optical system 304 is obtained. Is set to a minimum value of 21.2 degrees.

  Further, the upper limit value of the conditional expression shown in claim 6 will be described.

For the mask imaging optical system, the object space numerical aperture NAm is 0.45, and the imaging magnification Bm between object images is -2.
Assume a lighting device set to zero. Further, the present embodiment is applied to a projection exposure apparatus in which the image space maximum numerical aperture NAw is set to 0.9 and the object-to-object imaging magnification is set to -1/4, that is, -0.25, with respect to the projection optical system. explain.

  In FIG. 8, the distance L from the position where the light splitting reflecting surface 307a intersects the optical axis 305 to the condensing point position of the mask irradiation optical system 304 is 100 mm, and the slit width D in the scanning direction of the mask surface is 16.0 mm. If set, the mask irradiation system can be configured in a state where the half mirror 307 does not interfere with the mask surface 303, and the irradiation slit width on the wafer side can be applied to a projection exposure apparatus of 26 mm × 8 mm.

  By substituting such conditions, L = 100 mm, D = 16.0 mm, into the above equation (2) and solving the equation for β by the numerical substitution method, β becomes 29.0 degrees. If a margin angle for preventing the effective ray from being blocked by the sensor 306 and the lens barrel of the optical system associated therewith is expected to be 5 degrees, the set angle θ of the light branching reflection surface 307a with respect to the plane perpendicular to the optical axis 302 is set. 34. It can be set to 0 degrees.

  Since the object space numerical aperture NAm of the mask imaging optical system is 0.45, the angle γ formed by the maximum aperture light beam in the light beam emitted from the mask irradiation optical system 304 and the optical axis 305 is 26.7 degrees. Therefore, the angles formed by the outermost upper line and the outermost lower line in the light beam emitted from the mask irradiation optical system 304 with respect to the normal line of the light splitting reflecting surface 307a are 60.7 degrees and -7.3 degrees, respectively. . At this time, if the reflectance difference between the upper line and the underline of the maximum aperture light beam by the half mirror 307 is expressed by an average value difference ΔRM between the S-polarized component RS and the P-polarized component RP, it becomes 5.1%.

  By the way, as described at the beginning of “Means for Solving the Problems”, it is desirable that the σ distortion of the effective light source on the reticle irradiation surface is within 3%. By inserting a filter for correcting the deviation of the transmittance distribution in the pupil plane in the vicinity of the entrance pupil of the mask irradiation optical system 304, the σ distortion in the effective light source can be reduced, but when the value of ΔRM exceeds 5%. If an attempt is made to reduce the σ distortion in the effective light source by this method, it will affect the illuminance deterioration and cause a reduction in the throughput of the exposure apparatus.

  Therefore, the angle θ between the reflecting surface for splitting light and the surface perpendicular to the optical axis is 34.0 degrees, the absolute value of the imaging magnification Bm between object images of the mask imaging optical system is 2.0, and the object space The case where the numerical aperture NAm is set to 0.45 is the upper limit value in the conditional expression shown in claim 6 of the claims of the present invention.

  Finally, upper and lower limits in the conditional expression shown in claim 7 of the claims of the present invention will be described.

  As an exposure apparatus in the near future, in the image space of the projection optical system, for example, a method of filling the space between the final lens of the projection optical system and the wafer substrate with a light transmissive liquid and further increasing the NA is being studied. . In such an immersion projection optical system, an attempt is made to increase the image space numerical aperture NAw from 1.0 to 1.5 while maintaining the object-to-object imaging magnification of -1/4. Yes.

  In the above-described liquid immersion projection exposure apparatus, 21.2 ° ≦ θ ≦ 34.0 ° with respect to the angle θ between the light branching surface of the light branching member and the surface perpendicular to the optical axis. In order to satisfy the above, the object space numerical aperture NAm of the re-imaging optical system is set to 0.25 ≦ NAm ≦ 0.45, and the absolute value Bm of the image-to-object imaging magnification of the re-imaging optical system is 1 It is necessary to satisfy 0 ≦ Bm ≦ 1.8.

  Further, in the illumination optical system in such a liquid immersion type projection exposure apparatus, the object plane between the object plane of the re-imaging optical system and the optical path bending mirror is the same as described in the above embodiment. Having a lens group having a positive power, a lens group having a negative power, and a lens group having a positive power in this order makes the angle between the light incident on the optical path folding mirror and the optical axis more obtuse. This is particularly effective.

  By setting the above conditions in the mask irradiation optical system and the mask imaging optical system, it is possible to configure an illumination optical system that can cope with an ultra high NA projection optical system called an immersion method. it can.

  The condensing optical system described in the present embodiment can be applied as a mask irradiation optical system of a projection exposure apparatus adopting a step-and-scan method as shown in FIG. 10, for example. That is, the irradiation light emitted from the excimer laser 311 having an oscillation wavelength of 248 nm is shaped into a desired beam shape via the beam shaping optical system 312, and then formed into a columnar glass 314 having a hexagonal cross section by the condensing optical system 313. Incident.

  As described in Embodiment 1, the columnar glass 314 forms a plurality of light sources from one light source by multiple reflection by the inner surface of the glass. Irradiation light from the columnar glass 314 is irradiated to the fly-eye lens 301 by the σ continuously variable optical system. The σ continuously variable optical system includes a front group optical system 315, a bending mirror 316, and a rear group optical system 317 similar to those described in the second embodiment.

  Irradiation light from the fly-eye lens 301 is applied to the mask surface 303 by a mask irradiation system. Here, the mask irradiation system is replaced with the mask irradiation optical system 304, the half mirror 307, and the sensor 306 described in this embodiment. The irradiation light from the mask surface 303 is applied to the circuit pattern surface of the reticle 302 by the mask imaging optical system. Here, the mask imaging optical system includes the front group optical system 318, the optical path bending mirror 319, and the rear group optical system 320 which are the same as those described in the first embodiment. The circuit pattern of the reticle 302 is reduced and projected onto the substrate surface of the wafer 322 coated with a photosensitive material by the projection optical system 321.

  The sensor 306 receives the reflected light from the half mirror 307, and after the signal is amplified by the amplifier 324, it is output to the control unit 325. Based on the detection result of the sensor 306, the control unit 324 can control the output of the excimer laser 311 so that the exposure amount on the wafer substrate is optimized.

  Therefore, in a projection exposure apparatus to which the re-imaging optical system of the first embodiment is applied as a mask imaging optical system, or a projection exposure apparatus to which the re-imaging optical system of the second embodiment is applied as a σ-continuous variable optical system. If the mask irradiation optical system described in this embodiment is applied to each mask irradiation optical system 104 or 204, the exposure amount can be optimally controlled while suppressing the effective light source distortion in the reticle irradiation light. A projection exposure apparatus can be provided.

  In particular, in an immersion exposure apparatus that has been attracting attention in recent years, i.e., an exposure apparatus that is intended to realize an ultra-high NA by immersing the image space of the projection optical system, if the technique related to the optical path bending mirror according to the present invention is applied, In the irradiation light for irradiating the reticle, not only the absolute value difference of the light amount between the upper and lower lines of the light beam can be suppressed, but also the difference between the polarization components of the S component and the P component can be suppressed. Therefore, it is possible to provide a projection exposure apparatus capable of faithfully printing a finer circuit pattern when manufacturing a future highly accurate semiconductor element.

It is explanatory drawing of Embodiment 1 of this invention. It is an aberration diagram of the re-imaging optical system used in Embodiment 1 of the present invention. It is the schematic at the time of applying the re-imaging optical system used for Embodiment 1 of this invention as a mask imaging optical system in a projection exposure apparatus. It is explanatory drawing of Embodiment 2 of this invention. FIG. 10 is an aberration diagram at a position P1 of the re-imaging optical system used in Embodiment 2 of the present invention. FIG. 6 is an aberration diagram at a position P3 of the re-imaging optical system used in Embodiment 2 of the present invention. It is the schematic at the time of applying the re-imaging optical system used for Embodiment 2 of this invention as (sigma) continuous variable optical system in a projection exposure apparatus. It is explanatory drawing of Embodiment 3 of this invention. It is a figure which shows the angle dependence characteristic of the spectral reflectance in the half mirror of Embodiment 3 of this invention. It is the schematic at the time of applying the technique regarding the condensing optical system used for Embodiment 3 of this invention as a relay optical system in a projection exposure apparatus. It is a figure which shows the angle dependence characteristic of the reflectance in a common high reflection mirror.

Explanation of symbols

101, 201, 301 Fly's eye lens 102, 202, 302 Reticle 103, 203, 303 Mask surface 104, 204, 304 Mask irradiation optical system 105, 121, 205, 223, 305, 323 Optical axis 106, 206 Optical path bending portion 107,207 chief ray of off-axis light beam 108,208 intersection position of chief ray of off-axis light beam and optical axis 111, 211, 311 excimer laser 112, 212, 312 beam shaping optical system 114, 214, 314 columnar glass 115 sigma continuous Variable optical system 116,215,218,315,318 Front group optical system 117,216,219,316,319 Optical path bending mirror 118,217,220,317,320 Rear group optical system 119,221,321 Projection optical system 120 , 222, 322 Wafer 209 Object plane 10 image plane 306 sensor 307 half mirror 307a light branching reflecting surface 324 amplifier 325 control unit

Claims (8)

In a projection exposure apparatus having a light source that generates laser light, an optical path bending mirror that bends an optical path in the middle, an illumination optical system that irradiates a reticle, and a projection optical system that forms an image of a pattern on the reticle on a wafer substrate.
The incident angle of light with respect to the normal of the optical path bending mirror is α, the maximum difference in reflectance of the optical path bending mirror over the entire range of the incident angle is ΔR, and the image space numerical aperture of the projection optical system is NAw. When
30 ° ≦ α ≦ 60 °
ΔR ≦ 3%
0.8 ≦ NAw ≦ 1.0
A projection exposure apparatus characterized by satisfying A light source that generates laser light, an optical path bending mirror that bends an optical path in the middle, an illumination optical system that irradiates the reticle, and a projection optical system that forms an image of the pattern on the reticle on a wafer substrate; In an immersion type projection exposure apparatus that fills at least part of the image space of the system with a light-transmitting liquid,
The incident angle of light with respect to the normal of the optical path bending mirror is α, the maximum difference in reflectance of the optical path bending mirror over the entire range of the incident angle is ΔR, and the image space numerical aperture of the projection optical system is NAw. When
30 ° ≦ α ≦ 60 °
ΔR ≦ 3%
1.0 ≦ NAw ≦ 1.5
A projection exposure apparatus characterized by satisfying   The illumination optical system has a re-imaging optical system in which the object plane and the image plane are in a conjugate relationship, and the position where the principal ray of the off-axis light beam intersects the optical axis in the re-imaging optical system and the image plane side most 3. The projection exposure apparatus according to claim 1, wherein the optical path bending mirror is disposed between lens groups having a positive power.   The illumination optical system includes a re-imaging optical system in which the object plane and the image plane are in a conjugate relationship, and the object plane and the optical path folding mirror are sequentially arranged in order from the object plane. 4. The projection exposure apparatus according to claim 1, further comprising a lens group having a negative power, a lens group having a negative power, and a lens group having a positive power. The re-imaging optical system is an irradiation area variable optical system capable of continuously changing the spread of the emission irradiation area, and the irradiation area variable optical system is a first fixed group having a positive power in order from the object plane. And a first moving group having negative power, a second moving group having positive power, a second fixed group having negative power, and a third fixed group having positive power. The optical path bending mirror is arranged between the second fixed group and the third fixed group, the maximum height from the optical axis of the irradiation light on the object plane is H1, and the emission irradiation range is the maximum. When the maximum height from the optical axis of the irradiation light on the image plane is H2,
4. 2 ≦ H2 / H1 ≦ 15.0
The projection exposure apparatus according to claim 3, wherein: A condensing optical system for irradiating an object plane of the re-imaging optical system, and the condensing optical system either in the condensing optical system or between the condensing optical system and the re-imaging optical system. In a projection exposure apparatus having a light branching member that branches a part of a light beam,
The angle between the light branching surface of the light branching member and the surface perpendicular to the optical axis is θ, and the absolute value of the imaging magnification between object images of the reimaging optical system is Bm. When the object space numerical aperture of the image optical system is NAm,
21.2 ° ≦ θ ≦ 34.0 °
1.0 ≦ Bm ≦ 2.0
0.2 ≦ NAm ≦ 0.45
5. The projection exposure apparatus according to claim 3, wherein the projection exposure apparatus is a projection exposure apparatus. The illumination optical system includes a re-imaging optical system in which the object plane and the image plane are in a conjugate relationship, and the position where the principal ray of the off-axis light beam intersects the optical axis and the most image plane in the re-imaging optical system A converging optical system that irradiates an object plane of the re-imaging optical system, and a condensing optical system that irradiates an object plane of the re-imaging optical system. In a projection exposure apparatus having a light branching member for branching a part of a light beam of the condensing optical system between an optical system and the re-imaging optical system,
The angle between the light branching surface of the light branching member and the surface perpendicular to the optical axis is θ, and the absolute value of the imaging magnification between object images of the reimaging optical system is Bm. When the object space numerical aperture of the image optical system is NAm,
21.2 ° ≦ θ ≦ 34.0 °
1.0 ≦ Bm ≦ 1.8
0.25 ≦ NAm ≦ 0.45
The projection exposure apparatus according to claim 2, wherein:   Between the object plane of the re-imaging optical system and the optical path bending mirror, a lens group having a positive power, a lens group having a negative power, and a lens group having a positive power are sequentially arranged from the object plane. The projection exposure apparatus according to claim 6.

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