JP2005140999A - Optical system, adjustment method of optical system, exposure device and exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high performance optical system capable of efficiently correcting a rotation-asymmetrical aberration component which is caused by the deformation of an optical member and the like due to the heat generation by light irradiation and the effect of long-term exposure. <P>SOLUTION: The optical system is provided with heat transfer bodies 31, 32 disposed inside a reflective member for forming a required temperature distribution over a reflection surface CMa of the reflective member CM and a control part 33 for controlling the heat transfer bodies 31, 32. The control part controls a plurality of the first heat transfer bodies 31 having a first characteristic (exothermic action) and a plurality of the second heat transfer bodies 32 having a second characteristic (endothermic action) different from the first characteristic independently. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical system, an optical system adjustment method, an exposure apparatus, and an exposure method, and more particularly, a reflection suitable for an exposure apparatus used when a microdevice such as a semiconductor element or a liquid crystal display element is manufactured in a photolithography process. The present invention relates to a refractive projection optical system.

  When a semiconductor element or a liquid crystal display element is manufactured using a lithography technique, an exposure illumination light is irradiated to a mask on which a pattern is formed, and an image of the mask pattern is transferred to a photosensitive substrate (photograph) via a projection optical system. An exposure apparatus that performs projection exposure on a semiconductor wafer or a glass plate coated with a photosensitive material such as a resist is used. In recent years, semiconductor elements have been increasingly integrated, and there is an increasing demand for miniaturization of circuit patterns.

In order to meet the demand for pattern miniaturization, the exposure light has a shorter wavelength (shortening the wavelength λ of the exposure light) and a projection optical system having a higher NA (higher image-side numerical aperture). Specifically, pulsed laser light such as KrF excimer laser light (λ = 248 nm), ArF excimer laser light (λ = 193 nm), and F ₂ laser light (λ = 157 nm) is used as exposure light. Further, in the projection optical system, an image-side numerical aperture of 0.75 or more has been realized in recent years.

  Further, in recent years, by adopting a scanning exposure method (for example, a step-and-scan method) in which exposure is performed while moving a mask and a photosensitive substrate relative to the projection optical system, an effective imaging region (stationary) of the projection optical system is adopted. The effective exposure area in the state is an elongated rectangular shape. Further, in the illumination optical system for illuminating the mask, for example, a secondary light source (light formed in or near the illumination pupil) composed of a substantial surface light source having an annular shape or a multipolar shape (bipolar shape, quadrupole shape, etc.). By adopting modified illumination that illuminates the mask with a light beam from the intensity distribution, it is possible to improve the depth of focus and resolution of the projection optical system and expose a finer pattern.

  Further, in the projection optical system, a part of the irradiated exposure light is absorbed by the optical member and the reflection protection film formed on the surface thereof, and as a result, the aberration of the projection optical system changes due to the influence of heat generated. It has been known. This type of aberration change is adjusted (corrected) by moving a lens in the projection optical system in the optical axis direction or in a direction perpendicular to the optical axis. In exposure apparatuses, the power of exposure light irradiated with increasing throughput and narrowing of laser light tends to increase, and aberrations in the projection optical system change due to the heat generated due to light absorption. Expected to grow.

  If the wavelength of the exposure light is shortened, the types of optical materials that can withstand practical use are limited, and it becomes difficult to correct chromatic aberration in a refractive projection optical system. On the other hand, the concave reflecting mirror corresponds to a positive lens as an optical element for converging light, but does not cause chromatic aberration and has a negative contribution to Petzval's condition that determines the amount of field curvature. Is different from the positive lens. Therefore, a concave reflector and lens are combined as an optical system that can correct chromatic aberration and correct various aberrations, including curvature of field, without increasing the lens diameter with a simple structure. It has been proposed to use a catadioptric projection optical system.

  By adopting the scanning exposure method, the effective imaging area (effective exposure area in the stationary state) of the projection optical system becomes a long and narrow rectangular shape. For example, the mask is illuminated with a luminous flux from an annular or multipolar secondary light source. When illumination is used, the projection optical system has an aberration that is not rotationally symmetric with respect to the optical axis, such as an astigmatism difference on the optical axis (an astigmatism on the optical axis) or an anisotropic distortion, that is, a rotationally asymmetric aberration. Will occur. In this case, the conventional aberration correction mechanism that moves the lens as described above can correct the rotationally symmetric aberration, but cannot correct the rotationally asymmetric aberration.

  Therefore, for example, it is conceivable to insert a toric lens in the projection optical system and correct the rotationally asymmetric aberration by the action of the toric lens. However, the toric lens is easily displaced in the direction orthogonal to the optical axis during rotation, and it is difficult to ensure reproducibility. In addition, the only aberration component that can be corrected by the action of the toric lens is a monotonous asphalt component (a two-fold rotationally symmetric aberration component), and it can cope with aberration changes that occur during modified illumination using a multipolar secondary light source. Can not do it. Furthermore, aberration changes due to deformation of the optical member such as compaction (local refractive index change due to volume shrinkage) caused by long-term exposure are not uniform depending on use conditions and their accumulation, and are difficult to correct.

  The present invention has been made in view of the above-described problems, and can efficiently correct rotationally asymmetric aberration components generated due to heat generation due to light irradiation or optical member deformation caused by the effects of long-term exposure. An object is to provide a high-performance optical system. The present invention also provides an exposure apparatus and an exposure method capable of performing good projection exposure with high resolution and high throughput by using a high-performance optical system capable of efficiently correcting rotationally asymmetric aberration components. The purpose is to do.

In order to solve the above problems, in the first embodiment of the present invention, in an optical system including at least one reflecting member,
A heat transfer body provided inside the reflecting member to form a required temperature distribution across the reflecting surface of the reflecting member;
An optical system comprising: a control unit for controlling the heat transfer body.

  According to a preferred aspect of the first aspect, a plurality of the heat transfer bodies are provided according to a predetermined distribution. In this case, it is preferable that the control unit independently controls the plurality of heat transfer bodies. Further, the plurality of heat transfer bodies include a plurality of first heat transfer bodies having a first characteristic and a plurality of second heat transfer bodies having a second characteristic different from the first characteristic. It is preferable. In this case, it is preferable that the plurality of first heat transfer bodies have a heat generating action, and the plurality of second heat transfer bodies have a heat absorbing action.

  According to a preferred aspect of the first aspect, the plurality of first heat transfer bodies are provided at a first distance from the reflection surface of the reflection member, and the plurality of second heat transfer bodies are the A second distance different from the first distance is provided at a distance from the reflecting surface of the reflecting member. In this case, it is preferable that the first distance is smaller than the second distance. Moreover, it is preferable that the said heat exchanger is a heat conductive member which has a softness | flexibility.

  Moreover, according to the preferable aspect of a 1st form, it is further provided with another heat exchanger provided in surfaces other than the reflective surface of the said reflection member. Moreover, it is preferable to further include a heat dissipating member provided on a surface other than the reflecting surface of the reflecting member. The reflecting surface of the reflecting member is preferably flat or curved. The distance D (m) between the heat transfer body and the reflecting surface of the reflecting member preferably satisfies the condition of 0.001 <D <0.3.

  According to a preferred aspect of the first aspect, the optical system is an imaging optical system, and is disposed on or near the pupil plane of the imaging optical system and provided with the heat transfer body. And a second reflecting member disposed substantially away from the pupil plane and provided with the heat transfer body.

  Further, according to a preferred aspect of the first mode, the optical system includes a first reflecting member having the first reflecting surface provided with the heat transfer body, and a second reflecting surface provided with the heat transferring body. And a second reflecting member having the second reflecting member, and the light beam from a predetermined point on the object plane of the image forming optical system is irradiated onto the first reflecting surface or the second reflecting surface. When the diameter of the region occupied by is a partial light beam diameter, the first reflecting member and the second reflecting member are positioned so that the partial light beam diameters differ from each other with respect to the effective diameter of the reflecting surface. The partial light beam diameter is the diameter when the region occupied by the light beam on the reflecting surface is circular, and the short diameter when the region is elliptical. The effective diameter of the reflection surface is the diameter when the shape of the reflection surface is circular, and the length in the short direction when the shape is rectangular.

In the second embodiment of the present invention, in the adjustment method of the optical system of the first embodiment,
A measuring step for measuring optical characteristics of the optical system;
An adjustment step of adjusting an optical characteristic of the optical system by forming a required temperature distribution over the reflection surface of the reflection member according to the measurement result obtained by the measurement step. Provide a method. In this case, it is preferable that the measurement step includes a step of measuring aberration of the optical system.

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

  According to a fourth aspect of the present invention, there is provided an exposure apparatus comprising the optical system of the first aspect, and projecting and exposing a mask pattern onto a photosensitive substrate via the optical system.

  According to a fifth aspect of the present invention, there is provided an exposure method characterized by illuminating a mask using the optical system of the first aspect and exposing a pattern of the mask onto a photosensitive substrate.

  According to a sixth aspect of the present invention, an exposure method is characterized in that a pattern formed on a mask is projected and exposed onto a photosensitive substrate through the optical system according to any one of claims 1 to 13. I will provide a.

  The optical system of the present invention includes a heat transfer body provided inside the reflection member in order to form a required temperature distribution over the reflection surface of the reflection member, and a control unit for controlling the heat transfer body. I have. Therefore, in the present invention, a required temperature distribution is formed over the reflecting surface of the reflecting member by the action of the heat transfer body, and by changing the reflecting surface to a desired surface shape, heat generation due to light irradiation or long-term exposure can be achieved. It is possible to efficiently correct rotationally asymmetric aberration components generated due to optical member deformation (deformation of a lens or the like) caused by the influence, particularly aberration components generated due to an unexpected cause.

  That is, in the present invention, it is possible to realize a high-performance optical system that can efficiently correct rotationally asymmetric aberration components generated due to optical member deformation caused by the effects of heat generation or long-term exposure due to light irradiation. it can. As a result, the exposure apparatus and exposure method of the present invention can perform good projection exposure with high resolution and high throughput using a high-performance optical system that can efficiently correct rotationally asymmetric aberration components. As a result, a good device can be manufactured with high throughput.

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 is parallel to the optical axis AX of the projection optical system PL, the Y axis is parallel to the paper surface of FIG. 1 in a plane perpendicular to the optical axis AX, and the plane is perpendicular to the optical axis AX. The X axis is set perpendicular to the paper surface of FIG.

The exposure apparatus shown in FIG. 1 includes, for example, an ArF excimer laser light source (wavelength 193 nm) or an F ₂ laser light source (wavelength 157 nm) as a light source LS for supplying illumination light (exposure light). The light emitted from the light source LS illuminates the reticle (mask) R on which a predetermined pattern is formed via the illumination optical system IL. The optical path between the light source LS and the illumination optical system IL is sealed with a casing (not shown), and the space from the light source LS to the optical member on the most reticle side in the illumination optical system IL absorbs exposure light. It is replaced with an inert gas such as helium gas or nitrogen, which is a low-rate gas, or is kept in a substantially vacuum state.

  The reticle R is held parallel to the XY plane on the reticle stage RS via the reticle holder RH. A pattern to be transferred is formed on the reticle R. For example, a rectangular pattern region having a long side along the X direction and a short side along the Y direction in the entire pattern region is illuminated. Reticle stage RS can be moved two-dimensionally along the reticle plane (ie, XY plane) by the action of a drive system (not shown), and its position coordinates are measured by interferometer RIF using reticle moving mirror RM. And the position is controlled.

  Light from the pattern formed on the reticle R forms a reticle pattern image on the wafer W, which is a photosensitive substrate, via the projection optical system PL. The wafer W is held parallel to the XY plane on the wafer stage WS via a wafer table (wafer holder) WT. A rectangular exposure area having a long side along the X direction and a short side along the Y direction on the wafer W so as to optically correspond to the rectangular illumination area on the reticle R. A pattern image is formed. The wafer stage WS can be moved two-dimensionally along the wafer surface (that is, the XY plane) by the action of a drive system (not shown), and its position coordinates are measured by an interferometer WIF using a wafer moving mirror WM. In addition, the position is controlled.

  In the illustrated exposure apparatus, the interior of the projection optical system PL is hermetically sealed between the optical member disposed on the most reticle side and the optical member disposed on the most wafer side among the optical members constituting the projection optical system PL. The gas inside the projection optical system PL is replaced with an inert gas such as helium gas or nitrogen, or is almost kept in a vacuum state. Further, a reticle R and a reticle stage RS are arranged in a narrow optical path between the illumination optical system IL and the projection optical system PL, but a casing (not shown) that hermetically surrounds the reticle R and the reticle stage RS. Is filled with an inert gas such as nitrogen or helium gas, or is kept in a vacuum state.

  A narrow optical path between the projection optical system PL and the wafer W includes a wafer W and a wafer stage WS. The inside of a casing (not shown) that hermetically encloses the wafer W and the wafer stage WS. Is filled with an inert gas such as nitrogen or helium gas, or is kept in a vacuum state. Thus, an atmosphere in which the exposure light is hardly absorbed is formed over the entire optical path from the light source LS to the wafer W. As described above, the illumination area on the reticle R and the exposure area on the wafer W (that is, the effective exposure area) defined by the projection optical system PL are rectangular shapes having short sides along the Y direction.

  Accordingly, the reticle stage RS is controlled along the short side direction of the rectangular exposure area and the illumination area, that is, the Y direction, while controlling the positions of the reticle R and the wafer W using a drive system and an interferometer (RIF, WIF). By moving (scanning) the wafer stage WS and thus the reticle R and the wafer W synchronously, the wafer W has a width equal to the long side of the exposure area and the scanning amount (movement amount) of the wafer W. The reticle pattern is scanned and exposed to an area having a length corresponding to). Alternatively, the pattern of the reticle R is sequentially exposed in each exposure region of the wafer W by performing batch exposure while controlling the wafer W in a two-dimensional manner within a plane orthogonal to the optical axis AX of the projection optical system PL. The

  FIG. 2 is a diagram schematically showing the configuration of the projection optical system according to the present embodiment. Referring to FIG. 2, the projection optical system PL of the present embodiment includes a refractive first imaging optical system G1 for forming a first intermediate image of the pattern of the reticle R arranged on the first surface. Yes. A first reflecting surface M1 is disposed in the vicinity of the position where the first intermediate image formed by the first imaging optical system G1 is formed. The first reflecting surface M1 deflects the light beam directed to the first intermediate image or the light beam from the first intermediate image toward the catadioptric second imaging optical system G2.

  The second imaging optical system G2 includes a concave reflecting mirror CM and two negative lenses, and is based on a light beam from the first intermediate image, and is a second intermediate image (an image of the first intermediate image having a pattern 2). Next image) is formed in the vicinity of the formation position of the first intermediate image. A second reflecting surface M2 is disposed in the vicinity of the formation position of the second intermediate image formed by the second imaging optical system G2. The second reflecting surface M2 deflects the light beam directed to the second intermediate image or the light beam from the second intermediate image toward the refractive third imaging optical system G3.

  Based on the light beam from the second intermediate image, the third imaging optical system G3 applies a reduced image of the pattern of the reticle R (the image of the second intermediate image and the final image of the projection optical system) to the second surface. Formed on the arranged wafer W. The first imaging optical system G1 has a linearly extending optical axis AX1, and the third imaging optical system G3 has a linearly extending optical axis AX3. The optical axis AX1, the optical axis AX3, and the like. Are set to coincide with the reference optical axis AX which is a common single optical axis.

  On the other hand, the second imaging optical system G2 also has a linearly extending optical axis AX2, and this optical axis AX2 is set to be orthogonal to the reference optical axis AX. Furthermore, the first reflecting surface M1 and the second reflecting surface M2 are both planar, and are formed on the reflecting member FM having a right prism shape, for example. The intersecting line of the two reflecting surfaces M1 and M2 (strictly speaking, the intersecting line of the virtual extension surface) is AX1 of the first imaging optical system G1, AX2 of the second imaging optical system G2, and the third imaging optical system. It is set to intersect with AX3 of G3 at one point.

  As described above, the projection optical system PL of the present embodiment is a three-fold imaging type catadioptric that forms the first intermediate image and the second intermediate image of the reticle R in the optical path between the reticle R and the wafer W. This is an imaging optical system. The concave reflecting mirror CM is disposed on or near the pupil plane of the projection optical system PL. The right-angle prism-shaped reflecting member FM is disposed substantially away from the pupil plane of the projection optical system PL.

  FIG. 3 is a diagram schematically showing the internal configuration of the concave reflecting mirror of FIG. FIG. 4 is a diagram schematically showing the internal configuration of the right-angle prism-like reflecting member of FIG. Referring to FIG. 3, a plurality of first heat transfer bodies having a heat generating action arranged in a predetermined distribution along a surface substantially parallel to the reflection surface CMa is provided in the concave reflecting mirror CM of the present embodiment. 31 and a plurality of second heat transfer bodies 32 having an endothermic action arranged according to a predetermined distribution along a plane substantially parallel to the reflection surface CMa.

  Here, the distance between the plurality of first heat transfer bodies 31 and the reflection surface CMa of the concave reflecting mirror CM is set to be smaller than the distance between the plurality of second heat transfer bodies 32 and the reflection surface CMa of the concave reflection mirror CM. ing. As the first heat transfer body 31, for example, an electric heating coil can be used. Further, as the second heat transfer body 32, for example, a Peltier element can be used. Each of the plurality of first heat transfer bodies 31 and each of the plurality of second heat transfer bodies 32 are respectively connected to the control unit 33. The control unit 33 independently controls the heat generation operation of the plurality of first heat transfer bodies 31 and the heat absorption operation of the plurality of second heat transfer bodies 32.

  Similarly, referring to FIG. 4, a plurality of second heating elements arranged in a predetermined distribution along a surface substantially parallel to the first reflecting surface M <b> 1 is provided in the reflecting member FM of the present embodiment. 1 heat transfer body 41a, a plurality of first heat transfer bodies 41b having a heat generating action arranged according to a predetermined distribution along a surface substantially parallel to the second reflection surface M2, and substantially parallel to the first reflection surface M1. A plurality of second heat transfer bodies 42a having endothermic action arranged along a predetermined surface along a predetermined distribution, and an endothermic action arranged according to a predetermined distribution along a plane substantially parallel to the second reflecting surface M2. And a plurality of second heat transfer bodies 42b.

  Here, the distance between the plurality of first heat transfer bodies 41a and the first reflection surface M1 is substantially equal to the distance between the plurality of first heat transfer bodies 41b and the second reflection surface M2, and the plurality of second heat transfer bodies 42a. And the first reflecting surface M1 are substantially equal to the distance between the plurality of second heat transfer bodies 42b and the second reflecting surface M2. The distance between the plurality of first heat transfer bodies 41a and 41b and the first reflection surface M1 is set to be smaller than the distance between the plurality of second heat transfer bodies 42a and 42b and the second reflection surface M2. As the first heat transfer body 41a and 41b, for example, an electric heating coil can be used as in the case of the first heat transfer body 31.

  Further, as the second heat transfer body 42a and 42b, for example, Peltier elements can be used as in the case of the second heat transfer body 32. Each of the plurality of first heat transfer bodies 41 a and 41 b and each of the plurality of second heat transfer bodies 42 a and 42 b are respectively connected to the control unit 43. The controller 43 independently controls the heat generation operation of the plurality of first heat transfer bodies 41a and 41b and the heat absorption operation of the plurality of second heat transfer bodies 42a and 42b.

  In the projection optical system PL of the present embodiment, the heat generation operation of the plurality of first heat transfer bodies 31 and the heat absorption operation of the plurality of second heat transfer bodies 32 provided inside the concave reflecting mirror CM as the reflecting member are independently performed. By controlling, a required temperature distribution can be formed over the curved reflecting surface CMa of the concave reflecting mirror CM. In addition, by independently controlling the heat generation operation of the plurality of first heat transfer bodies 31a and the heat absorption operation of the plurality of second heat transfer bodies 32a provided inside the reflection member FM, the planar first reflection surface M1 A required temperature distribution can be formed over the entire area. Further, by independently controlling the heat generation operation of the plurality of first heat transfer bodies 31b and the heat absorption operation of the plurality of second heat transfer bodies 32b provided inside the reflection member FM, the planar second reflection surface M2 A required temperature distribution can be formed over the entire area.

  Therefore, in the present embodiment, a required temperature distribution is formed over the reflecting surface CMa of the concave reflecting mirror CM and the first reflecting surface M1 and the second reflecting surface M2 of the reflecting member FM, and consequently the reflection of the concave reflecting mirror CM. By changing the surface CMa and the first reflecting surface M1 and the second reflecting surface M2 of the reflecting member FM to desired surface shapes, optical member deformation (deformation of a lens or the like) caused by heat generation due to light irradiation or long-term exposure, etc. It is possible to efficiently correct rotationally asymmetrical aberration components generated due to the above, particularly aberration components generated due to unexpected causes.

  Thus, the present embodiment realizes a high-performance projection optical system that can efficiently correct rotationally asymmetric aberration components generated due to optical member deformation caused by the effects of heat generation or long-term exposure due to light irradiation. be able to. As a result, the exposure apparatus of the present embodiment can perform good projection exposure with high resolution and high throughput by using a high-performance projection optical system that can efficiently correct rotationally asymmetric aberration components.

  By the way, Japanese Patent Application No. 2002-194974 specification and drawing concerning an application of this applicant propose the structure which has arrange | positioned the heat exchanger on the back surface side of a reflection member. However, in the proposed configuration, since the heat transfer body is not provided inside the reflecting member, the heat conduction efficiency during heating (cooling) is poor, and only a gentle temperature distribution can be formed on the reflecting surface. Furthermore, heat conduction or the like from the heat transfer body arranged on the back surface side of the reflecting member to the holding member (member holding the reflecting member) occurs, and the reflecting member is easily affected by the holding member. Other optical members and devices are easily affected.

  In this embodiment, since the heat transfer body (31, 32, 41, 42) is provided inside the reflection member (CM, FM), the heat transfer body provided with heat generated by light irradiation is provided. Thus, heat conduction is efficiently performed, and deformation of the reflecting member can be suppressed. Furthermore, since heat is absorbed via the second heat transfer bodies (32, 42), for example, almost no force is transmitted from the holding member. Moreover, since the heat transfer body (31, 32, 41, 42) is provided inside the reflecting member, for example, external influences from the holding member can be prevented as much as possible.

  In the present embodiment, since the first heat transfer body (31, 41) and the second heat transfer body (32, 42) are heat conductive members having flexibility, the reflection members (CM, FM) and The relative displacement between can be absorbed. Moreover, in this embodiment, the heat_generation | fever operation | movement of several 1st heat exchangers arrange | positioned so that the whole reflective surface of a reflecting member may be followed and the heat absorption operation | movement of several 2nd heat exchangers can be controlled independently. Therefore, the surface shape of the reflecting surface can be efficiently and freely changed by utilizing the thermal expansion or contraction of the reflecting member by heat transfer through the heat transfer body. In this way, it is possible not only to suppress the deformation of the reflecting member, but also to efficiently correct aberrations caused by deformation of other optical members, environmental changes, and the like.

  Further, since the operations of the plurality of heat transfer bodies arranged along the entire reflection surface of the reflection member (CM, FM) can be controlled independently, local surface deformation on the reflection surface becomes possible. As a result, it is possible to correct only the aberration corresponding to a partial region of the effective exposure region. Thus, it is possible to efficiently correct rotationally asymmetric aberration components such as astigmatic difference on the optical axis (astigmatism on the optical axis) and anisotropic distortion, which are difficult to correct with the prior art. In addition, it is possible to correct uncertain aberration changes or unexpected aberration changes caused by optical member deformation due to long-term exposure, differences in use conditions, and the like.

  In this embodiment, it is preferable to further include another heat transfer body provided on a surface (back surface or end surface) other than the reflection surface of the reflection member (CM, FM). With this configuration, it is easy to suppress and control the deformation of the reflecting surface of the reflecting member. Moreover, it is preferable to further include a heat radiating member provided on a surface (back surface or end surface) other than the reflective surface of the reflective member (CM, FM). In this configuration, the heat generated by the light irradiation is quickly dissipated by the action of the heat dissipating member, and is further efficiently dissipated through the heat transfer body provided inside, so that the reflecting surface of the reflecting member is deformed. Can be suppressed.

  Further, the heat transfer body (31, 32, 41, 42) provided inside the reflection member (CM, FM) and another heat transfer body provided on a surface (back surface or end surface) other than the above-described reflection surface It is desirable that there is a temperature difference between With this configuration, it is easy to control the deformation of the reflecting surface of the reflecting member. The larger the temperature difference between the temperature of the reflecting member and the heat transfer body provided inside, the more freely the surface shape of the reflecting surface can be changed, making it possible to efficiently form a surface shape rich in changes. Become. This is a side effect when an extremely bright and dark light intensity distribution is formed on or near the illumination pupil plane, as in annular illumination or multipolar illumination using an annular surface light source or a multipolar surface light source. It is effective to correct the aberration generated as follows.

  However, if aberration correction is performed by the action of only the heat transfer body provided inside the reflecting member, it is inefficient that a large amount of heat or cooling is required, and heat is not applied to the surrounding optical members and equipment. The adverse effect of conduction can occur. Therefore, for example, the reflecting member is cooled by the action of another heat transfer member or heat radiating member provided on a surface (back surface or end surface) other than the reflecting surface of the reflecting member (CM, FM), and is provided inside the reflecting member. If heated by the heat transfer body, the temperature difference necessary for the change in the shape of the reflecting surface can be maintained without extremely increasing the overall temperature of the reflecting member.

In the present embodiment, the distance D (m) between the heat transfer body (31, 32, 41, 42) and the reflecting surface of the reflecting member (CM, FM) satisfies the following conditional expression (1). desirable.
0.001 <D <0.3 (1)

In general, when there is a heat generation (endothermic) source inside an object, that is, at a distance D (m) from the surface, and a temperature difference Δt is generated between the surface and the surface, the surface deformation Δd (m ) Is expressed by the following equation (2) in proportion to the thermal expansion coefficient α (ppm / ° C) of the object. That is, the distance D (m) from the surface is expressed by the following equation (3).
Δd = α × D × Δt (2)
D = Δd / (α × Δt) (3)

On the other hand, since the heat generation (endothermic) amount Q (W) increases in proportion to the thermal conductivity β (W / m · K), the distance D (m) from the surface is expressed by the following equation (4). .
D = Q / (β × Δt) (4)
Therefore, the distance D (m) from the surface (the reflecting surface in the present embodiment) is limited by the above-described equations (3) and (4).

  As described above, high precision is required for a projection optical system used for manufacturing a semiconductor element, a liquid crystal display element, and the like in a photolithography process. In order to meet the demand for higher precision, it is common to use SiC (silicon carbide), Zerodur (registered trademark), ULE (registered trademark), or the like as a material for forming the reflecting member. The thermal expansion coefficient α and thermal conductivity β of each material are listed in the following table (1).

Table (1)
SiC ULE
Thermal expansion coefficient α 3.00 × 10 ⁻⁶ 3.00 × 10 ⁻⁸
Thermal conductivity β 166 1.31

However, ULETM (CORNING 7971) is made by the same manufacturing method as synthetic quartz and is designed to have a coefficient of thermal expansion of zero near room temperature by adding a small amount of titanium to silica (SiO ₂ ). It is a material unsuitable for forming the reflective member of the embodiment.

  When the required reflection surface deformation Δd (m), the temperature difference Δt that does not affect the surroundings, and the amount of heat generation (heat absorption) Q (W) are set to the first condition values (SiC, The distance D1 (m) from the reflecting surface determined by the equation (3) and the distance D2 (m) from the reflecting surface determined by the equation (4) are listed in the following table (2).

Table (2)
Δd 5.00 × 10 ^-8 m
Δt 10 K
Q 500 W
SiC ULE
D1 (m) 1.67 × 10 ⁻³ 1.67 × 10 ⁻¹
D2 (m) 3.01 × 10 ⁻¹ 3.82 × 10 ⁺¹

  Similarly, each material when the necessary deformation Δd (m) of the reflecting surface, the temperature difference Δt that does not affect the surroundings, and the amount of heat generation (heat absorption) Q (W) are set to the second condition value. For (SiC, ULE), the distance D1 (m) from the reflecting surface determined by equation (3) and the distance D2 (m) from the reflecting surface determined by equation (4) are listed in the following table (3).

Table (3)
Δd 5.00 × 10 ^-9 m
Δt 0.1 K
Q 1 W
SiC ULE
D1 (m) 1.67 × 10 ⁻² 1.67 × 10 ⁰
D2 (m) 6.02 × 10 ⁻² 7.63 × 10 ⁰

  Referring to Table (2) and Table (3), it can be seen that it is desirable that the distance D (m) from the reflecting surface satisfies the conditional expression (1). That is, if the lower limit value of the conditional expression (1) is not reached, the distance D from the reflecting surface becomes too small, and there is a high risk of causing problems when maintaining or processing the reflecting surface. On the other hand, if the upper limit value of conditional expression (1) is exceeded, the distance D from the reflecting surface becomes too large, and only a gradual temperature distribution with respect to the reflecting surface, and hence a gradual change in surface shape can be formed. This is not preferable because it is not suitable for correction of aberrations that occur when an intense light intensity distribution is formed on or near the illumination pupil plane as in annular illumination or multipole illumination.

  Furthermore, in this embodiment, it is desirable that at least two or more deformation peaks (at least curved peaks and valleys) can be formed within the effective diameter of the reflecting surface. Further, it is desirable that the heat transfer body be disposed at a substantially uniform distance from the reflection surface of the reflection member. Therefore, in the case of a curved reflecting surface, it is desirable to arrange the curved reflecting surface along a curved surface substantially parallel to the reflecting surface. If the heat transfer body is not arranged at a substantially uniform distance from the reflection surface, the heat transfer of each heat transfer body on the reflection surface is uneven, and a desired surface shape change cannot be obtained.

  Further, the first reflecting member (CM) disposed at or near the pupil plane of the imaging optical system as the projection optical system and provided with the heat transfer body (31, 32) is substantially separated from the pupil plane. It is preferable to include a second reflecting member (FM) disposed and provided with a heat transfer body (41, 42). In the projection optical system, deformation of the optical member and its surface due to light irradiation to cause aberration changes affects not only the reflecting member but also other optical members. Therefore, in order to efficiently correct the aberration change of the entire projection optical system, it is desirable that as many reflection members as possible to which the present invention is applied are included in the optical path.

  In the case of the reflecting surface of the first reflecting member (CM) disposed at or near the pupil surface and provided with the heat transfer body (31, 32), the on-axis partial diameter and the off-axis partial diameter are effective for the reflecting surface. Since they overlap within the diameter, it is effective in correcting aberrations over the entire exposure region (entire wafer field). On the other hand, in the case of the reflecting surface of the second reflecting member (FM) disposed substantially away from the pupil surface and provided with the heat transfer body (41, 42), the on-axis partial diameter and the off-axis partial diameter Since there is a gap between them, it is suitable for aberration correction for each part in the exposure area (for each image height of the wafer field).

  Here, the on-axis partial diameter is the diameter of the area occupied by the light beam from the object point on the optical axis within the effective diameter of the reflecting surface, and the off-axis partial diameter is the light beam reflected from the object point off the optical axis. This is the diameter of the area occupied within the effective diameter of the surface. In addition, about the general definition of "partial diameter (partial light beam diameter)", paragraph [0032] and FIG. 3 of Unexamined-Japanese-Patent No. 2002-151397, and paragraph [0087] and figure of Unexamined-Japanese-Patent No. 2002-258131 are shown. 14 can be referred to.

  As described above, in the projection optical system PL of the present embodiment, an aberration caused by an unexpected cause, for example, is caused by changing the reflecting surface to a desired surface shape by the action of the heat transfer body provided inside the reflecting member. The components can be corrected (adjusted) efficiently. FIG. 5 is a flowchart of the projection optical system adjustment method according to the present embodiment. Hereinafter, a method for adjusting the projection optical system PL according to the present embodiment will be briefly described with reference to FIG.

  In the adjustment method of the present embodiment, the aberration as the optical characteristic of the projection optical system PL is measured as necessary (S11). When measuring the aberration of the projection optical system PL, the wavefront aberration measuring method described in JP-A-10-170399, the Shack-Hartmann method wavefront aberration measuring method described in JP-A-2002-71514, and JP2002-2002. Aberration measurement method by aerial image detection described in JP-A No. 14005 and JP-A No. 2002-198303, Wavefront aberration measurement method by phase recovery method described in JP-A Nos. 2000-195782 and 2000-340488, A known aberration measuring method such as a wavefront aberration measuring method using an interferometer described in Japanese Patent Laid-Open Nos. 2000-277411 and 2000-277412 can be used.

  Next, the required amount of change in the surface shape of the reflecting surface (CMa, M1, M2) of the reflecting member (CM, FM) necessary for aberration correction is obtained according to the measurement result obtained in the measuring step (S11) (S12). ). Then, a required temperature distribution over the reflecting surface necessary for obtaining the required amount of change in the surface shape of the reflecting surface is obtained (S13). Finally, by controlling the heat transfer body (31, 32, 41, 42) via the control unit (33, 43), a required temperature distribution is formed across the reflecting surface, and the aberration of the projection optical system PL Is adjusted (corrected) (S14).

  In the exposure apparatus of the above-described embodiment, the reticle (mask) is illuminated by the illumination system (illumination process), and the transfer pattern formed on the mask is exposed to the photosensitive substrate using the projection optical system (exposure process). Thus, a micro device (semiconductor element, imaging element, liquid crystal display element, thin film magnetic head, etc.) can be manufactured. Hereinafter, referring to the flowchart of FIG. 6 for an example of a method for obtaining a semiconductor device as a micro device by forming a predetermined circuit pattern on a wafer or the like as a photosensitive substrate using the exposure apparatus of the present embodiment. I will explain.

  First, in step 301 of FIG. 6, a metal film is deposited on one lot of wafers. In the next step 302, a photoresist is applied on the metal film on the lot of wafers. Thereafter, in step 303, using the exposure apparatus of the present embodiment, the image of the pattern on the mask is sequentially exposed and transferred to each shot area on the wafer of one lot via the projection optical system. Thereafter, in step 304, the photoresist on the one lot of wafers is developed, and in step 305, the resist pattern is etched on the one lot of wafers to form a pattern on the mask. Corresponding circuit patterns are formed in each shot area on each wafer.

  Thereafter, a device pattern such as a semiconductor element is manufactured by forming a circuit pattern of an upper layer. According to the semiconductor device manufacturing method described above, a semiconductor device having an extremely fine circuit pattern can be obtained with high throughput. In steps 301 to 305, a metal is deposited on the wafer, a resist is applied on the metal film, and exposure, development, and etching processes are performed. Prior to these processes, on the wafer. It is needless to say that after forming a silicon oxide film, a resist may be applied on the silicon oxide film, and steps such as exposure, development, and etching may be performed.

  In the exposure apparatus of this embodiment, a liquid crystal display element as a micro device can be obtained by forming a predetermined pattern (circuit pattern, electrode pattern, etc.) on a plate (glass substrate). Hereinafter, an example of the technique at this time will be described with reference to the flowchart of FIG. In FIG. 7, in a pattern forming process 401, a so-called photolithography process is performed in which a mask pattern is transferred and exposed to a photosensitive substrate (such as a glass substrate coated with a resist) using the exposure apparatus of the present embodiment. By this photolithography process, a predetermined pattern including a large number of electrodes and the like is formed on the photosensitive substrate. Thereafter, the exposed substrate undergoes steps such as a developing step, an etching step, and a resist stripping step, whereby a predetermined pattern is formed on the substrate, and the process proceeds to the next color filter forming step 402.

  Next, in the color filter forming step 402, a large number of sets of three dots corresponding to R (Red), G (Green), and B (Blue) are arranged in a matrix or three of R, G, and B A color filter is formed by arranging a plurality of stripe filter sets in the horizontal scanning line direction. Then, after the color filter forming step 402, a cell assembly step 403 is executed. In the cell assembly step 403, a liquid crystal panel (liquid crystal cell) is assembled using the substrate having the predetermined pattern obtained in the pattern formation step 401, the color filter obtained in the color filter formation step 402, and the like.

  In the cell assembly step 403, for example, liquid crystal is injected between the substrate having the predetermined pattern obtained in the pattern formation step 401 and the color filter obtained in the color filter formation step 402, and a liquid crystal panel (liquid crystal cell) is obtained. ). Thereafter, in a module assembling step 404, components such as an electric circuit and a backlight for performing a display operation of the assembled liquid crystal panel (liquid crystal cell) are attached to complete a liquid crystal display element. According to the above-described method for manufacturing a liquid crystal display element, a liquid crystal display element having an extremely fine circuit pattern can be obtained with high throughput.

  In the above-described embodiment, a method of filling the optical path between the projection optical system and the photosensitive substrate with a medium (typically liquid) having a refractive index larger than 1.1, a so-called immersion method is applied. You may do it. In this case, as a method of filling the liquid in the optical path between the projection optical system and the photosensitive substrate, a method of locally filling the liquid as disclosed in International Publication No. WO99 / 49504, A method of moving a stage holding a substrate to be exposed as disclosed in Japanese Patent Laid-Open No. 6-124873 in a liquid bath, or a predetermined depth on a stage as disclosed in Japanese Patent Laid-Open No. 10-303114. A technique of forming a liquid tank and holding the substrate in the liquid tank can be employed.

As the liquid, it is preferable to use a liquid that is transmissive to exposure light and has a refractive index as high as possible, and is stable with respect to a photoresist applied to the projection optical system or the substrate surface, for example, KrF excimer laser light. When ArF excimer laser light is used as exposure light, pure water or deionized water can be used as the liquid. When F ₂ laser light is used as exposure light, a fluorine-based liquid such as fluorine oil or perfluorinated polyether (PFPE) that can transmit the F ₂ laser light may be used as the liquid.

In the above-described embodiment, an ArF excimer laser light source that supplies light with a wavelength of 193.3 nm or an F ₂ laser light source that supplies light with a wavelength of 157 nm is used. However, the present invention is not limited to this, and a wavelength of 248 nm is used. The present invention can also be applied to other suitable light sources such as a KrF excimer laser light source that supplies light. In the above-described embodiment, the present invention is applied to the projection optical system mounted on the exposure apparatus. However, the present invention is not limited to this, and the present invention is applied to other general optical systems. It can also be applied.

It is a figure which shows schematically the structure of the exposure apparatus concerning embodiment of this invention. It is a figure which shows schematically the structure of the projection optical system concerning this embodiment. It is a figure which shows schematically the internal structure of the concave reflecting mirror of FIG. It is a figure which shows schematically the internal structure of the reflection member of the right-angle prism shape of FIG. It is a flowchart of the adjustment method of the projection optical system concerning this embodiment. It is a flowchart of the method at the time of obtaining the semiconductor device as a microdevice. It is a flowchart of the method at the time of obtaining the liquid crystal display element as a microdevice.

Explanation of symbols

LS Light source IL Illumination optical system R Reticle RS Reticle stage PL Projection optical system W Wafer WS Wafer stage AX Optical axis CM Concave reflection mirror FM Right angle prism-like reflection members G1 to G3 Imaging optical systems CMa, M1, M2 Reflection surface 31, 41 1st heat transfer body 32,42 2nd heat transfer body 33,43 Control part

Claims (19)

In an optical system including at least one reflecting member,
A heat transfer body provided inside the reflecting member to form a required temperature distribution across the reflecting surface of the reflecting member;
An optical system comprising: a control unit for controlling the heat transfer body. The optical system according to claim 1, wherein a plurality of the heat transfer bodies are provided according to a predetermined distribution. The optical system according to claim 2, wherein the control unit independently controls the plurality of heat transfer bodies. The plurality of heat transfer bodies include a plurality of first heat transfer bodies having a first characteristic and a plurality of second heat transfer bodies having a second characteristic different from the first characteristic. The optical system according to claim 2 or 3, characterized in that 5. The optical system according to claim 4, wherein the plurality of first heat transfer members have a heat generating action, and the plurality of second heat transfer members have a heat absorbing action. The plurality of first heat transfer bodies are provided at a first distance from the reflection surface of the reflection member, and the plurality of second heat transfer bodies are separated from the reflection surface of the reflection member by the first distance. 6. The optical system according to claim 4, wherein the optical systems are spaced apart from each other by different second distances. The optical system according to claim 6, wherein the first distance is smaller than the second distance. The optical system according to any one of claims 1 to 7, wherein the heat transfer body is a heat conductive member having flexibility. The optical system according to claim 1, further comprising another heat transfer member provided on a surface other than the reflection surface of the reflection member. The optical system according to claim 1, further comprising a heat dissipating member provided on a surface other than the reflecting surface of the reflecting member. 11. The optical system according to claim 1, wherein the reflecting surface of the reflecting member is planar or curved. The distance D (m) between the heat transfer body and the reflecting surface of the reflecting member is
0.001 <D <0.3
The optical system according to claim 1, wherein the following condition is satisfied. The optical system is an imaging optical system;
A first reflecting member disposed at or near the pupil plane of the imaging optical system and provided with the heat transfer body; and a first reflecting member disposed substantially away from the pupil plane and provided with the heat transfer body. The optical system according to any one of claims 1 to 12, further comprising two reflecting members. The method for adjusting an optical system according to any one of claims 1 to 13,
A measuring step for measuring optical characteristics of the optical system;
An adjustment step of adjusting an optical characteristic of the optical system by forming a required temperature distribution over the reflection surface of the reflection member according to the measurement result obtained by the measurement step. Method. The adjustment method according to claim 14, wherein the measuring step includes a step of measuring an aberration of the optical system. An exposure apparatus comprising the optical system according to any one of claims 1 to 13 for illuminating a mask and exposing a pattern of the mask onto a photosensitive substrate. An exposure apparatus comprising the optical system according to any one of claims 1 to 13, wherein a mask pattern is projected and exposed onto a photosensitive substrate via the optical system. An exposure method comprising: illuminating a mask using the optical system according to claim 1, and exposing a pattern of the mask onto a photosensitive substrate. An exposure method, comprising: projecting and exposing a pattern formed on a mask onto a photosensitive substrate through the optical system according to claim 1.

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