JP2010062309A - Lighting optical system, exposure apparatus, and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the generation of irregularity in an illuminance on an irradiating face, and a change of a polarizing state caused by influences of a stress double refraction inside a lens. <P>SOLUTION: The lighting optical system which lights the irradiating face by a light from a light source includes: first fresnel lens faces (11a and 11b) and second fresnel lens faces (12a and 12b) arranged in an optical path. The lighting optical system is configured in such a way that a position of a step of the first fresnel lens faces is not overlapped with a position of a step of the second fresnel lens faces when viewing from an optical axis (AX) direction of the lighting optical system. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an illumination optical system, an exposure apparatus, and a device manufacturing method. More specifically, the present invention relates to an illumination optical system suitable for an exposure apparatus for manufacturing devices such as a semiconductor element, an image sensor, a liquid crystal display element, and a thin film magnetic head in a lithography process.

  In a typical exposure apparatus of this type, light emitted from a light source forms a secondary light source (predetermined light intensity distribution) composed of a number of light sources on the rear focal plane through a fly-eye lens. The light from the secondary light source illuminates the mask on which a predetermined pattern is formed via a condenser lens in a superimposed manner. The light transmitted through the mask forms an image on the wafer via the projection optical system, and the mask pattern is projected and exposed (transferred) onto the wafer.

  In recent years, with the increase in circuit pattern density, developments such as shortening the wavelength of exposure light, increasing the numerical aperture of projection optical systems, and increasing the sensitivity of resists have become active. In addition, with the increase in circuit pattern density, diversity is required for the light intensity distribution (secondary light source) formed on the illumination pupil on the rear focal plane of the fly-eye lens, that is, the shape and polarization state of the pupil intensity distribution. ing. Therefore, an illumination optical system has been proposed that uses a polarization controller, a diffractive optical element, a zoom lens, an axicon system, and the like to realize various illumination conditions for the shape of the pupil intensity distribution, the polarization state, and the like (for example, Patent Documents). 1).

JP 2005-243904 A

  In the illumination optical system disclosed in Patent Document 1, polarization control is performed using a wave plate or the like. However, for example, due to the influence of stress birefringence in the lens, the polarization state is likely to change from a required polarization state. Since the influence of stress birefringence in the lens increases according to the thickness of the lens, a configuration using a Fresnel lens capable of making the axial thickness relatively thin can be considered instead of a normal lens. However, if a normal lens is simply replaced with a Fresnel lens, the illumination distribution on the irradiated surface (mask pattern surface or wafer exposure surface in the case of an exposure apparatus) will be uneven due to the effect of the steps on the Fresnel lens surface. easy.

  The present invention has been made in view of the above-mentioned problems, and provides an illumination optical system capable of suppressing changes in the polarization state due to the occurrence of illuminance unevenness on the irradiated surface and the influence of stress birefringence in the lens. With the goal. In addition, the present invention uses an illumination optical system capable of suppressing changes in the polarization state due to the occurrence of illuminance unevenness on the surface to be irradiated and the influence of stress birefringence in the lens, and provides good exposure under desired illumination conditions. An object of the present invention is to provide an exposure apparatus and a device manufacturing method capable of performing the above.

In order to solve the above problems, in the first embodiment of the present invention, in the illumination optical system that illuminates the illuminated surface with light from a light source,
A first Fresnel lens surface and a second Fresnel lens surface disposed in the optical path;
The position of the step on the first Fresnel lens surface and the position of the step on the second Fresnel lens surface are configured not to overlap each other when viewed from the optical axis direction of the illumination optical system. An illumination optical system is provided.

  According to a second aspect of the present invention, there is provided an exposure apparatus comprising the illumination optical system according to the first aspect for illuminating a predetermined pattern, and exposing the predetermined pattern onto a photosensitive substrate.

In the third embodiment of the present invention, using the exposure apparatus of the second embodiment, an exposure step of exposing the predetermined pattern to the photosensitive substrate;
Developing the photosensitive substrate to which the predetermined pattern is transferred, and forming a mask layer having a shape corresponding to the predetermined pattern on the surface of the photosensitive substrate;
And a processing step of processing the surface of the photosensitive substrate through the mask layer.

  In the illumination optical system of the present invention, instead of a normal lens, a Fresnel lens having a relatively thin on-axis thickness is used, so that a change in polarization state due to the influence of stress birefringence in the lens is suppressed. Can do. Also, for example, between a pair of adjacent Fresnel lenses, the position of the step on the Fresnel lens surface of one Fresnel lens overlaps the position of the step on the Fresnel lens surface of the other Fresnel lens when viewed from the optical axis direction. Since it is configured so that there is no illuminance unevenness due to the influence of the step on the Fresnel lens surface, it can be suppressed.

  That is, in the illumination optical system of the present invention, it is possible to suppress changes in the polarization state due to the occurrence of illuminance unevenness on the irradiated surface and the influence of stress birefringence in the lens. Further, the exposure apparatus of the present invention uses an illumination optical system capable of suppressing changes in the polarization state due to the occurrence of illuminance unevenness on the irradiated surface and the stress birefringence in the lens, under a desired illumination condition. Good exposure can be performed, and thus a good device can be manufactured.

  Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a drawing schematically showing a configuration of an exposure apparatus according to an embodiment of the present invention. In FIG. 1, the Z axis along the normal direction of the wafer W, which is a photosensitive substrate, the Y axis in the direction parallel to the plane of FIG. 1 in the plane of the wafer W, and the plane of the wafer W in FIG. The X axis is set in the direction perpendicular to the paper surface.

  Referring to FIG. 1, in the exposure apparatus of the present embodiment, exposure light (illumination light) is supplied from a light source 1. As the light source 1, for example, an ArF excimer laser light source that supplies light with a wavelength of 193 nm, a KrF excimer laser light source that supplies light with a wavelength of 248 nm, or the like can be used. The light emitted from the light source 1 enters the first fly-eye lens 4 via the beam transmission system 2 and the polarization controller 3 having a known configuration.

  The beam transmission system 2 has a function of guiding an incident light beam to the polarization controller 3 while converting the incident light beam into a light beam having a cross section having an appropriate size and shape. Further, the beam transmission system 2 has a function of actively correcting the position variation and the angle variation of the light beam incident on the polarization control unit 3 (and eventually the light beam incident on the first fly-eye lens 4).

  For example, the polarization controller 3 includes, in order from the light source side, a quarter-wave plate 3a that converts incident elliptically polarized light into linearly polarized light with a crystal optical axis that is rotatable about the optical axis AX. A half-wave plate 3b that changes the polarization direction of linearly polarized light that is incident on the optical axis AX so that the crystal optical axis is rotatable, and a depolarizer (non-polarizing element) that can be inserted into and removed from the illumination optical path. ) 3c.

  The polarization controller 3 has a function of converting the light from the light source 1 into linearly polarized light having a desired polarization direction and making it incident on the first fly-eye lens 4 with the depolarizer 3c retracted from the illumination optical path. . The polarization control unit 3 has a function of converting the light from the light source 1 into substantially non-polarized light and making it incident on the first fly-eye lens 4 in a state where the depolarizer 3 c is set in the illumination optical path.

  The first fly-eye lens 4 is, for example, a wavefront division type optical integrator composed of a plurality of lens elements arranged vertically and horizontally and densely, and forms a large number of light sources on the rear focal plane or in the vicinity thereof. Light from a large number of light sources illuminates the incident surface of the second fly-eye lens 6 in a superimposed manner, for example, via a relay optical system 5 composed of a plurality of Fresnel lenses.

  Similar to the first fly-eye lens 4, the second fly-eye lens 6 is a wavefront division type optical integrator made up of a plurality of lens elements arranged vertically and horizontally and densely, for example. In FIG. 1, for the sake of clarity, the number of lens elements constituting the fly-eye lenses 4 and 6 is considerably smaller than the actual number.

  Thus, a large number of lenses corresponding to the product of the number of lens elements of the first fly-eye lens 4 and the number of lens elements of the second fly-eye lens 6 are located at or near the rear focal plane of the second fly-eye lens 6. A substantial surface light source (secondary light source) composed of the light sources is formed. The light from the secondary light source illuminates the mask blind 8 in a superimposed manner via a condenser optical system 7 composed of a plurality of Fresnel lenses, for example.

  The light passing through the rectangular opening (light transmitting portion) of the mask blind 8 as an illumination field stop is subjected to the light condensing action of the imaging optical system 9 composed of a plurality of Fresnel lenses, and then a predetermined pattern is formed. The mask M is illuminated in a superimposed manner. That is, the imaging optical system 9 forms an image of the rectangular opening of the mask blind 8 on the mask M. The light transmitted through the pattern of the mask M held on the mask stage MS forms an image of the mask pattern on the wafer (photosensitive substrate) W held on the wafer stage WS via the projection optical system PL. .

  In this way, batch exposure or scan exposure is performed while the wafer stage WS is two-dimensionally driven and controlled in a plane (XY plane) orthogonal to the optical axis AX of the projection optical system PL, and thus the wafer W is two-dimensionally driven and controlled. As a result, the pattern of the mask M is sequentially exposed in each exposure region of the wafer W. In FIG. 1, for clarity of illustration, the relay optical system 5 and the condenser optical system 7 are represented by one Fresnel lens, and the imaging optical system 9 is represented by a pair of Fresnel lenses.

  In the above-described configuration, the optical system arranged downstream of the polarization control unit 3, that is, the relay optical system 5, the condenser optical system 7, and the imaging optical system 9 are used with a normal lens having a relatively large axial thickness. When configured, it easily changes to a polarization state different from the required polarization state due to, for example, the influence of stress birefringence in the lens. As a result, it becomes difficult to illuminate the wafer W with light having a required polarization state, and it becomes difficult to form a good image of a mask pattern having a desired contrast.

  In the present embodiment, the axial thickness of the relay optical system 5, the condenser optical system 7, and the imaging optical system 9 is made relatively thin in order to suppress the change in the polarization state due to the influence of stress birefringence in the lens. It is composed of Fresnel lenses that can be used. However, if a normal lens is simply replaced with a Fresnel lens, unevenness is likely to occur in the illuminance distribution on the irradiated surface (pattern surface of the mask M or exposure surface of the wafer W) due to the effect of the step on the Fresnel lens surface.

  For example, as shown in FIG. 2, the position of the step between the Fresnel lens surfaces 21a and 21b and the position of the step between the Fresnel lens surfaces 22a and 22b substantially coincide with each other between a pair of adjacent Fresnel lenses 21 and 22. In this case, the shadow (or the shadow is blurred) formed by the four steps that are approximately the same distance from the optical axis AX is easily transferred onto the wafer W, and the illuminance on the wafer W due to the additive effect of the four steps. Unevenness is likely to occur relatively large. Note that in a normal Fresnel lens, the positions of the steps between the Fresnel lens surface on the light incident side and the Fresnel lens surface on the exit side coincide with each other.

  In the present embodiment, in at least one of the relay optical system 5, the condenser optical system 7, and the imaging optical system 9, as shown in FIG. 3, between a pair of adjacent Fresnel lenses 11 and 12. The positions of the steps on the Fresnel lens surface are different from each other. In other words, the position of the step between the Fresnel lens surfaces 11a and 11b of the Fresnel lens 11 and the position of the step between the Fresnel lens surfaces 12a and 12b of the Fresnel lens 12 are configured so as not to overlap each other when viewed from the optical axis AX direction. is doing. In this case, as apparent from comparison between FIG. 2 and FIG. 3, the influence of the step on the Fresnel lens surface is dispersed, and the shadow transferred onto the wafer W corresponding to each step is reduced.

  As described above, the illumination optical system (2 to 9) of the present embodiment uses a Fresnel lens that can have a relatively thin axial thickness in the optical system disposed downstream of the polarization controller 3. Therefore, a change in the polarization state due to the influence of stress birefringence in the lens can be suppressed. In addition, the position of the step on the Fresnel lens surface is not overlapped between a pair of adjacent Fresnel lenses in a required optical system disposed downstream of the polarization control unit 3 when viewed from the optical axis AX direction. Therefore, it is possible to suppress the occurrence of uneven illuminance due to the effect of the step on the Fresnel lens surface.

  That is, in the illumination optical system (2-9) of the present embodiment, it is possible to suppress changes in the polarization state due to the occurrence of illuminance unevenness on the irradiated surface (M; W) and the influence of stress birefringence in the lens. Further, in the exposure apparatus (2 to WS) of the present embodiment, an illumination optical system capable of suppressing changes in the polarization state due to the occurrence of illuminance unevenness on the irradiated surface (M; W) and the influence of stress birefringence in the lens. Using (2-9), good exposure can be performed under desired illumination conditions.

  In the above-described embodiment, as shown in FIG. 3, the position of the step on the Fresnel lens surface is different between a pair of adjacent Fresnel lenses 11 and 12 in a required optical system. . However, the present invention is not limited to this, and as shown in FIG. 4, in at least one Fresnel lens 13 included in the required optical system, the position of the step of the Fresnel lens surface 13a on the light incident side and the light emission The effect of the present invention can be achieved by configuring so that the position of the step on the Fresnel lens surface 13b on the side does not overlap when viewed from the optical axis AX direction.

  Further, as shown in FIG. 5, in a pair of adjacent Fresnel lenses 14 and 15 in a required optical system, the position of the step of one Fresnel lens surface 14a of one Fresnel lens 14 and the other Fresnel lens surface 14b. The position of the step is different from each other, the position of the step on one Fresnel lens surface 15a of the other Fresnel lens 15 is different from the position of the step on the other Fresnel lens surface 15b, and between the Fresnel lenses 14 and 15. By configuring the step positions of the Fresnel lens surface to be different from each other, the effects of the present invention can be achieved even better.

  In the above-described embodiment, a variable pattern forming apparatus that forms a predetermined pattern based on predetermined electronic data can be used instead of a mask. By using such a variable pattern forming apparatus, the influence on the synchronization accuracy can be minimized even if the pattern surface is placed vertically. As the variable pattern forming apparatus, for example, a DMD (digital micromirror device) including a plurality of reflecting elements driven based on predetermined electronic data can be used. An exposure apparatus using DMD is disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-304135 and International Patent Publication No. 2006/080285. In addition to a non-light-emitting reflective spatial light modulator such as DMD, a transmissive spatial light modulator may be used, or a self-luminous image display element may be used. Note that a variable pattern forming apparatus may be used even when the pattern surface is placed horizontally.

  The exposure apparatus of the above-described embodiment is manufactured by assembling various subsystems including the respective constituent elements recited in the claims of the present application so as to maintain predetermined mechanical accuracy, electrical accuracy, and optical accuracy. Is done. In order to ensure these various accuracies, before and after assembly, various optical systems are adjusted to achieve optical accuracy, various mechanical systems are adjusted to achieve mechanical accuracy, and various electrical systems are Adjustments are made to achieve electrical accuracy. The assembly process from the various subsystems to the exposure apparatus includes mechanical connection, electrical circuit wiring connection, pneumatic circuit piping connection and the like between the various subsystems. Needless to say, there is an assembly process for each subsystem before the assembly process from the various subsystems to the exposure apparatus. When the assembly process of the various subsystems to the exposure apparatus is completed, comprehensive adjustment is performed to ensure various accuracies as the entire exposure apparatus. The exposure apparatus is preferably manufactured in a clean room where the temperature, cleanliness, etc. are controlled.

  Next, a device manufacturing method using the exposure apparatus according to the above-described embodiment will be described. FIG. 6 is a flowchart showing a semiconductor device manufacturing process. As shown in FIG. 6, in the semiconductor device manufacturing process, a metal film is vapor-deposited on a wafer W to be a semiconductor device substrate (step S40), and a photoresist, which is a photosensitive material, is applied on the vapor-deposited metal film. (Step S42). Subsequently, using the exposure apparatus of the above-described embodiment, the pattern formed on the mask (reticle) M is transferred to each shot area on the wafer W (step S44: exposure process), and the transfer of the wafer W after the transfer is completed. Development, that is, development of the photoresist to which the pattern has been transferred is performed (step S46: development process). Thereafter, using the resist pattern generated on the surface of the wafer W in step S46 as a mask, processing such as etching is performed on the surface of the wafer W (step S48: processing step).

  Here, the resist pattern is a photoresist layer in which unevenness having a shape corresponding to the pattern transferred by the exposure apparatus of the above-described embodiment is generated, and the recess penetrates the photoresist layer. is there. In step S48, the surface of the wafer W is processed through this resist pattern. The processing performed in step S48 includes, for example, at least one of etching of the surface of the wafer W or film formation of a metal film or the like. In step S44, the exposure apparatus of the above-described embodiment performs pattern transfer using the wafer W coated with the photoresist as the photosensitive substrate, that is, the plate P.

  FIG. 7 is a flowchart showing a manufacturing process of a liquid crystal device such as a liquid crystal display element. As shown in FIG. 7, in the manufacturing process of the liquid crystal device, a pattern formation process (step S50), a color filter formation process (step S52), a cell assembly process (step S54), and a module assembly process (step S56) are sequentially performed.

  In the pattern forming process of step S50, a predetermined pattern such as a circuit pattern and an electrode pattern is formed on the glass substrate coated with a photoresist as the plate P using the exposure apparatus of the above-described embodiment. In this pattern formation process, an exposure process for transferring the pattern to the photoresist layer using the exposure apparatus of the above-described embodiment and development of the plate P to which the pattern is transferred, that is, development of the photoresist layer on the glass substrate are performed. And a developing step for generating a photoresist layer having a shape corresponding to the pattern, and a processing step for processing the surface of the glass substrate through the developed photoresist layer.

  In the color filter forming step of step S52, a large number of sets of three dots corresponding to R (Red), G (Green), and B (Blue) are arranged in a matrix or three R, G, and B A color filter is formed by arranging a plurality of stripe filter sets in the horizontal scanning direction.

  In the cell assembly process in step S54, a liquid crystal panel (liquid crystal cell) is assembled using the glass substrate on which the predetermined pattern is formed in step S50 and the color filter formed in step S52. Specifically, for example, a liquid crystal panel is formed by injecting liquid crystal between a glass substrate and a color filter. In the module assembling process in step S56, various components such as an electric circuit and a backlight for performing the display operation of the liquid crystal panel are attached to the liquid crystal panel assembled in step S54.

  In addition, the present invention is not limited to application to an exposure apparatus for manufacturing a semiconductor device, for example, an exposure apparatus for a display device such as a liquid crystal display element formed on a square glass plate or a plasma display, It can also be widely applied to an exposure apparatus for manufacturing various devices such as an image sensor (CCD or the like), a micromachine, a thin film magnetic head, and a DNA chip. Furthermore, the present invention can also be applied to an exposure process (exposure apparatus) when manufacturing a mask (photomask, reticle, etc.) on which mask patterns of various devices are formed using a photolithography process.

In the above-described embodiment, ArF excimer laser light (wavelength: 193 nm) or KrF excimer laser light (wavelength: 248 nm) is used as the exposure light. However, the present invention is not limited to this, and other appropriate laser light sources are used. For example, the present invention can also be applied to an F ₂ laser light source that supplies laser light having a wavelength of 157 nm. In the above-described embodiment, the present invention is applied to the illumination optical system that illuminates the mask in the exposure apparatus. However, the present invention is not limited to this, and a general illumination surface other than the mask is illuminated. The present invention can also be applied to an illumination optical system.

It is a figure which shows schematically the structure of the exposure apparatus concerning embodiment of this invention. It is a figure explaining the disadvantage of the structure using a normal Fresnel lens. It is a figure which shows roughly the principal part structure of this embodiment. It is a figure which shows roughly the principal part structure of the 1st modification of this embodiment. It is a figure which shows roughly the principal part structure of the 2nd modification of this embodiment. It is a flowchart which shows the manufacturing process of a semiconductor device. It is a flowchart which shows the manufacturing process of liquid crystal devices, such as a liquid crystal display element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Beam transmission system 3 Polarization control part 4,6 Fly eye lens 5 Relay optical system 7 Condenser optical system 8 Mask blind 9 Imaging optical system 11-15 Fresnel lens M Mask PL Projection optical system W Wafer

Claims (5)

In the illumination optical system that illuminates the illuminated surface with light from the light source,
A first Fresnel lens surface and a second Fresnel lens surface disposed in the optical path;
The position of the step on the first Fresnel lens surface and the position of the step on the second Fresnel lens surface are configured not to overlap each other when viewed from the optical axis direction of the illumination optical system. Illumination optical system. The illumination optical system according to claim 1, wherein the first Fresnel lens surface and the second Fresnel lens surface are formed in one Fresnel lens. The first Fresnel lens surface is formed on a first Fresnel lens, and the second Fresnel lens surface is formed on a second Fresnel lens different from the first Fresnel lens. The illumination optical system according to claim 1. An exposure apparatus comprising the illumination optical system according to any one of claims 1 to 3 for illuminating a predetermined pattern, and exposing the predetermined pattern onto a photosensitive substrate. An exposure step of exposing the predetermined pattern to the photosensitive substrate using the exposure apparatus according to claim 4;
Developing the photosensitive substrate to which the predetermined pattern is transferred, and forming a mask layer having a shape corresponding to the predetermined pattern on the surface of the photosensitive substrate;
And a processing step of processing the surface of the photosensitive substrate through the mask layer.

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