JP2004062091A - Holding apparatus, aligner, and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a holding apparatus, an aligner, and a device manufacturing method with which desired optical performance is obtained by reducing aberration due to deformation and dislocation of an optical member which cause degradation of imaging performance. <P>SOLUTION: The holding apparatus is provided with a supporting member which supports a mirror at six points via three spherical surfaces, a positioning means each of which is arranged at three places around the supporting member and movable to two axes as the optical axis direction and the circumference direction around the optical axis, and a coupling means which couples the supporting member to the positioning means and is movable to four axes except for the transfer direction of the positioning means. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention generally relates to a precision instrument on which an optical member is mounted, in particular, to a projection optical system such as an exposure apparatus, and more particularly, to a semiconductor device, an imaging device (such as a CCD) or a thin film magnetic head. In an exposure apparatus used in a lithography process, when an image of an original (for example, a mask or a reticle (the terms are used interchangeably in the present application)) is projected and exposed on an object to be processed, it is more accurate. TECHNICAL FIELD The present invention relates to a holding device for an optical member for obtaining a proper imaging relationship.
[0002]
[Prior art]
2. Description of the Related Art When manufacturing a device using a photolithography (printing) technique, a reduction projection exposure apparatus that transfers a circuit pattern by projecting a circuit pattern drawn on a mask onto a wafer or the like by a projection optical system has been conventionally used. . The projection optical system forms an image by causing the diffracted light from the circuit pattern to interfere with the wafer.
[0003]
In order to meet the recent demand for smaller and thinner electronic devices, it is necessary to highly integrate devices mounted on the electronic devices, and finer circuit patterns to be transferred, that is, higher resolution Are increasingly required. In order to obtain a high resolution, it is effective to shorten the wavelength of the exposure light and increase the numerical aperture (NA) of the projection optical system. At the same time, the aberration of the projection optical system must be extremely small.
[0004]
When an optical element such as a lens or a mirror that constitutes a projection optical system is deformed, an optical path is refracted before and after the deformation, and a ray to be imaged at one point does not converge at one point, causing an aberration. The aberration causes a displacement and a short circuit of the circuit pattern on the wafer. On the other hand, if the pattern size is increased in order to prevent a short circuit, it is against the demand for miniaturization.
[0005]
Therefore, in order to realize a projection optical system with small aberration, the shape and the position of the optical element constituting the projection optical system with respect to the optical axis are held in the projection optical system without changing, and the original It is necessary to maximize optical performance. In particular, with the recent increase in the NA of the projection optical system, the diameter of the projection lens has been increased, so that the volume of the lens has also been increased, and deformation due to its own weight has been likely to occur. An exposure apparatus using extreme ultraviolet (EUV) light (hereinafter, referred to as an EUV exposure apparatus), which has been actively researched recently, is one of the features of the exposure apparatus. For a wavelength of about 10 nm to 15 nm), the projection optical system must be composed of a small number of reflecting elements (that is, mirrors), and the shape of the mirror and the positional accuracy with respect to the optical axis are extremely severe.
[0006]
[Problems to be solved by the invention]
Since the EUV exposure apparatus is used for exposing a circuit pattern of 0.1 μm or less, the line width accuracy is very strict, and the mirror shape is allowed to deform only about 1 nm or less. Therefore, it is necessary to accurately reproduce the mirror processing shape when incorporating the mirror into an EUV exposure apparatus.
[0007]
However, the base material that constitutes the mirror is very soft, and the mirror is deformed by several nanometers only by the force (holding force) applied by the holding member that holds the mirror. In addition, the displacement of the mirror is caused by thermal expansion, vibration, and deformation of the holding member. Furthermore, the mirror does not reflect all of the exposure light, but absorbs more than 30% of the exposure light, so that the absorbed exposure light is split into heat and thermally expands the mirror. Changes the position with respect to. Therefore, the mirror cannot be held in the projection optical system without changing its shape and position with respect to the optical axis, and the desired optical performance cannot be exhibited.
[0008]
Accordingly, it is an exemplary object of the present invention to provide a holding apparatus, an exposure apparatus, and a device manufacturing method that provide desired optical performance by reducing aberration due to deformation and displacement of an optical member that deteriorates imaging performance. And
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a holding device according to one aspect of the present invention is provided with a support member that supports a mirror at six points via three spherical surfaces, and at three locations around the support member. Positioning means movable in two axes in the axial direction and in the circumferential direction around the optical axis, and the supporting member and the positioning means are connected to each other and movable in four axes other than the moving direction of the positioning means (elastically deformable) ) Connecting means. According to such a holding device, the mirror is kinematically supported, and the supporting member supporting the mirror can be moved about six axes, thereby reducing the deformation and displacement of the optical member which deteriorates the imaging performance. it can. The three spherical surfaces are arranged on the same circumference at a pitch of 120 °. The mirror has a conical concave portion in contact with the circumference of the three spherical surfaces. The support member has a groove having a V-shaped cross section that contacts two points of the spherical surface. The positioning means are arranged on the same circumference at a pitch of 120 °. An actuator (driving mechanism) for moving the positioning means in two axes in the optical axis direction and a circumferential direction around the optical axis is further provided. The image forming apparatus further includes a detection unit that detects a position of the support member. The apparatus further includes a measuring unit that measures the position of the mirror. It is characterized by further comprising a position reference portion for defining a relative position of the mirror. The positioning means has a guide of a parallel leaf spring.
[0010]
A mirror incorporating method according to another aspect of the present invention is a method of incorporating a mirror at a desired position of an optical system, wherein a holding device for attaching the mirror has a position reference unit for measuring a relative position of the mirror. Forming, attaching the mirror to the holding member, measuring the position of the position reference unit after the attaching step, and, after the first measuring step, holding the mirror attached to the holding member. A step of incorporating the unit into the optical system; and, after the incorporating step, a second measuring step of measuring a position of the position reference unit. Measuring the wavefront aberration of the optical system after the mirror has been incorporated into the optical system; and the mirror such that the wavefront aberration measured in the measuring step is reduced (preferably minimized). And adjusting the holding device. According to this method, the mirror can be held in a desired posture, and excellent optical performance can be achieved.
[0011]
An exposure apparatus as still another aspect of the present invention includes the holding device described above, and includes an optical system that exposes a pattern formed on a mask or a reticle to a target object via a mirror held by the holding device. It is characterized by the following. According to such an exposure apparatus, it is possible to prevent the occurrence of aberration due to the deformation and displacement of the optical member, which deteriorates the imaging performance, by including the holding device described above as a part of the constituent elements.
[0012]
A device manufacturing method as still another aspect of the present invention includes a step of projecting and exposing an object to be processed by using the above-described exposure apparatus, and a step of performing a predetermined process on the object to be subjected to projection exposure. It is characterized by. The claims of the device manufacturing method having the same operation as that of the above-described exposure apparatus extend to the device itself as an intermediate and final product. Such devices include semiconductor chips such as LSI and VLSI, CCDs, LCDs, magnetic sensors, thin-film magnetic heads, and the like.
[0013]
Further objects and other features of the present invention will become apparent from preferred embodiments described below with reference to the accompanying drawings.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a holding device and an exposure device that are exemplary embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to these embodiments, and each component may be replaced as long as the object of the present invention is achieved. For example, in the present embodiment, the holding device 100 is exemplarily applied to the projection optical system 530 of the exposure device 500, but may be applied to the illumination optical system 514 of the exposure device 500 or any other known optical system. . In each of the drawings, the same reference numerals indicate the same members, and redundant description will be omitted. Here, FIG. 1 is a schematic configuration perspective view showing a holding device 100 as one aspect of the present invention. The optical axis direction coincides with the Z-axis direction, and is indicated by an arrow in the drawing.
[0015]
As shown in FIG. 1, the holding device 100 includes a support member 120, a connecting unit 130, a positioning unit 140, and a base 150, and holds the mirror 110.
[0016]
The mirror 110 is mounted on a support member 120 described later, and forms an image of light using reflection. The reflection surface of the mirror 110 is provided with a multilayer film for reflecting light, and the multilayer film has an effect of enhancing light. The multilayer film applicable to the mirror 110 is, for example, a Mo / Si multilayer film in which a molybdenum (Mo) layer and a silicon (Si) layer are alternately stacked, or a Mo in which a Mo layer and a beryllium (Be) layer are alternately stacked. / Be multilayer film and the like are conceivable. However, the multilayer film of the present invention is not limited to the above-mentioned materials, and does not prevent the use of a multilayer film having the same operation and effect.
[0017]
The mirror 110 has three protrusions 112 on the outer circumference as shown in FIG. The protrusions 112 are formed integrally with the mirror 110 and are arranged at a pitch of 120 °. However, if the shape of the mirror 110 does not change due to the force applied when joining the protrusion 112 to the mirror 110, or if the change in the shape of the mirror 110 is within an allowable range, the protrusion 112 May be configured separately from the mirror 110. Here, FIG. 2 is a schematic configuration top view of the holding device 100 shown in FIG.
[0018]
As shown in FIG. 3, the protrusion 112 has a concave portion 114 on the lower surface. The recess 114 is formed in a conical shape and comes into contact with the circumference of a spherical member 122 described later. The mirror 110 is supported by a support member 120 via a spherical member 122 that comes into contact with a concave portion 114 formed in the protrusion 112. Here, FIG. 3 is a partially enlarged cross-sectional view of the holding device 100 shown in FIG. 1, and shows the protrusion 112 of the mirror 110 and the groove 122 of the support member 120.
[0019]
The support member 120 has a spherical member 122 that comes into contact with the mirror 110 and a groove 124 on which the spherical member 122 is placed, and supports the mirror 110. The support member 120 is an annular plate member centered on the optical axis, and is preferably made of, for example, a material having a linear expansion coefficient substantially equal to the linear expansion coefficient of the mirror 110.
[0020]
The spherical members 122 are arranged at a pitch of 120 ° according to the concave portions 114 formed on the protrusions 112 of the mirror 110. As described above, since the spherical members 122 are distributed at substantially equal intervals along the circumferential direction of the mirror 110, the mirror 110 is stabilized on the support member 120. The spherical member 122 is a member having a true spherical shape, and is in contact with the concave portion 114 formed on the projection 112 of the mirror 110 at the outer periphery. The spherical member 122 is mounted on the groove 124 so as to be movable in the radial direction of the support member 120 (that is, with a degree of freedom in the radial direction). Therefore, even if thermal expansion occurs in the mirror 110 when the temperature environment fluctuates, it is possible to allow expansion in the radial direction, and it is possible to prevent the center of the mirror from being displaced from the optical axis.
[0021]
The grooves 124 are formed at a pitch of 120 ° along the radial direction of the support member 120 and mount the spherical member 122 thereon. In other words, the groove 124 is formed at a position facing the concave portion 114 formed on the protrusion 112 of the mirror 110. Grooves 124 allow radial movement of spherical member 122 and define circumferential movement. The groove 124 has a V-shaped cross section as shown in FIG. 4, and contacts the spherical member 122 at two points (A1 and A2). That is, by the three grooves 124, the support member 120 supports the mirror 110 at six points via the spherical member 122 (kinematic support), and can maintain the posture without excessively restraining the mirror 110. . Here, FIG. 4 is a schematic sectional view showing the spherical member 122 and the groove 124 of the support member 120 shown in FIG.
[0022]
The spherical member 122 and the groove 124 prevent a change in the attitude of the mirror 110 due to deformation at the contact points A1 and A2, and minimize frictional force as much as possible in order to make contact at six ideal points. (Low coefficient of friction) is required. As the material of the spherical member 122 and the groove 124 satisfying high hardness and a low coefficient of friction, ceramics, a metal whose surface is hardened and heat-treated, and a film-formed coat by ion plating such as DLC can be used.
[0023]
Although the mirror 110 is stabilized on the support member 120 via the spherical member 122 and the groove 124 only by its own weight, for example, considering that vibration is applied when transporting the optical system on which the holding device 100 is mounted, the mirror 110 is used. It is preferable to provide a holding mechanism 170 that holds down 110. The pressing mechanism 170 presses the mirror 110 from the side facing the support member 120 with respect to the protrusion 112 of the mirror 110, and fixes the mirror 110 while maintaining the shape of the mirror 110 as much as possible. In detail, for example, as shown in FIG. 5, the pressing mechanism 170 is joined to the support member 120 by a pin P, applies an elastic force to the protrusion 112 of the mirror 110 via the elastic member 172, and To fix the mirror 110 in between. At this time, in order not to damage the mirror 110, a conical recess 114 is formed on the upper surface of the protrusion 112 of the mirror 110, and the elastic force is applied via the spherical member 122 having a spherical shape placed on the recess 114. Apply. The holding mechanism 170 may always clamp the mirror 110, and it is preferable to appropriately determine whether to always use the mirror 110 or to use it only during transportation from required mirror surface accuracy and vibration resistance. Here, FIG. 5 is a partially enlarged cross-sectional view of the holding device 100 having the pressing mechanism 170.
[0024]
On the other hand, in order to strengthen the fixation between the spherical member 122 and the groove 124, the spherical member 122 is made of a magnetic material, and a permanent magnet is embedded in a region R forming the groove 124 as shown in FIG. Further, if an electromagnet is embedded in the region R forming the groove 124, the fixing of the spherical member 122 and the groove 124 can be switched between reinforced and non-reinforced. Here, FIG. 6 is a schematic sectional view showing the spherical member 122 and the groove 124 of the support member 120.
[0025]
The connecting means 130 is joined to the outer periphery of the support member 120 and connects the support member 120 and a positioning means 140 described later. As shown in FIG. 7, the connecting means 130 may be, for example, using a leaf spring, in the X-axis direction (ΔX), the circumferential direction around the X-axis (θx), the circumferential direction around the Y-axis (θy), and Z The configuration is such that the rigidity of the four axes in the circumferential direction (θz) around the axis is smaller than that of the other two axes (Y-axis direction and Z-axis direction). In other words, the connecting means 130 has four directions: the X-axis direction (ΔX), the circumferential direction around the X-axis (θx), the circumferential direction around the Y-axis (θy), and the circumferential direction around the Z-axis (θz). It is configured to be able to move to the axis. Here, FIG. 7 is a schematic perspective view of the connecting means 130 and the positioning means 140 shown in FIG.
[0026]
When the connecting means 130 moves in the X-axis direction (ΔX) as shown in FIG. 8A, the support member 120 moves horizontally with respect to the XY plane. When the connecting means 130 moves in the circumferential direction (θx) around the X axis as shown in FIG. 8B, the support member 120 tilts around the X axis. When the connecting means 130 moves in the circumferential direction (θz) around the Z axis as shown in FIG. 8C, the support member 120 tilts around the Z axis. When the connecting means 130 moves in the circumferential direction (θy) around the Y axis as shown in FIG. 8D, the support member 120 tilts around the Y axis. Therefore, the connecting means 130 enables the movement of the support member 130 with respect to four axes. Here, FIG. 8 is a schematic diagram showing the connecting means 130 when moving about four axes.
[0027]
The positioning means 140 is arranged around the support member 120 at a pitch of 120 ° and is connected to the connecting means 130. As shown in FIG. 9, the positioning means 140 is constituted by an elastic hinge mechanism which is guided by the parallel leaf spring 142a and is movable in the Y-axis direction (Δy) and the parallel leaf spring 142b in the Z-axis direction (Δz). Is done. The positioning means 140 changes the thickness of the spacers 146a and 146b sandwiched between the push screws 144a and 144b for pressing and deforming the parallel leaf springs 142a and 142b, thereby changing the thickness in the Y-axis direction (Δy) and the Z-axis direction (Δz). Adjust the amount of movement. Further, a reduction elastic hinge mechanism (not shown) is provided for the push screws 144a and 144b, and the movement amount of the push screws 144a and 144b is reduced at a predetermined ratio and transmitted to the parallel leaf springs 142a and 142b. The resolution of the movement amount in the direction (Δy) and the Z-axis direction (Δz) can be improved. Preferably, the positioning means 140 is configured such that the parallel leaf springs 142a and 142b are deformed from the natural state only in one direction (pressing direction). According to such a configuration, the positioning mechanism has a small amount of components other than the moving direction and is a feed mechanism that does not involve friction, so that highly accurate positioning can be performed. Furthermore, by using the connecting means that can be elastically deformed in four axial directions, the posture and the position of the support member 120 are moved when the positioning mechanism moves, but the deformation of the support member can be minimized. Become. Further, by supporting the mirror kinematically on this support member, a holding mechanism that does not easily cause the mirror to be deformed when controlling the attitude of the mirror is achieved. When it is desired to increase the rigidity of the parallel leaf springs 142a and 142b in the moving direction or to deform the parallel leaf springs 142a and 142b in the pressing direction and the pulling direction, as shown in FIG. 10, for example, the coil springs 148a and 148b , It is also possible to pull the parallel leaf springs 142a and 142b in one direction. Here, FIG. 9 is a schematic sectional view of the positioning means 140 shown in FIG. 8, and FIG. 10 is a schematic perspective view of the connecting means 130 and the positioning means 140 shown in FIG.
[0028]
That is, the positioning means 140 enables the movement of the connecting means 130 with respect to two axes in the Y-axis direction (Δy) and the Z-axis direction (Δz). Accordingly, the connecting means 130 can cooperate with the positioning means 140 to make the support member 120 movable about six axes and minimize the deformation of the support member 120. Thus, the mirror 110 supported by the support member 120 can reduce aberrations due to deformation and displacement that degrade imaging performance, and can achieve desired optical performance.
[0029]
Further, the positioning means 140 may be moved in the Y-axis direction (Δy) and the Z-axis direction (Δz) by using an actuator 180 as shown in FIGS. 11 and 12, instead of the push screws 144a and 144b. . The actuator 180 is, for example, a piezo element or a pico motor to which the piezo element is applied, and presses the parallel leaf springs 142a and 142b in one direction. Note that a displacement meter 185 can be provided to measure the displacement amount of the parallel leaf springs 142a and 142b. As the displacement meter 185, a high-precision displacement meter such as a capacitance sensor or a differential transformer is used. Here, FIG. 11 is a schematic perspective view of the connecting means 130 and the positioning means 140 shown in FIG. 1, and FIG. 12 is a schematic sectional view of the positioning means 140 shown in FIG.
[0030]
Returning to FIG. 1 again, the base 150 is joined to the positioning means 140 and fixed to the lens barrel of the projection optical system 530 via the fixing hole 152. The base 150 is an annular plate member centered on the optical axis, and is made of, for example, a copper alloy such as brass, stainless steel, iron, metal such as Invar, carbon steel, or a ceramic such as carbon steel, or ceramics.
[0031]
With the above-described configuration, the holding device 100 allows the support member 120 to rotate the support member 120 along six axes (X-axis direction, circumferential direction around the X-axis, Y-axis direction, circumferential direction around the Y-axis, Z-axis direction, and circle around the Z-axis). (Circumferential direction) to perform positioning without changing the shape of the mirror 110.
[0032]
In addition, as shown in FIG. 13, the holding device 100 can control the driving of the support member 120 with higher accuracy by providing the base 150 with the detection unit 190 that detects the position of the support member 120. In the present embodiment, the detection unit 190 includes a displacement sensor 192 for detecting the position of the support member 120 in the Z-axis direction and a displacement sensor 194 for detecting the position of the support member 120 in the circumferential direction around the Z-axis at three positions. Are placed. Here, FIG. 13 is a schematic perspective view showing an example of the holding device 100.
[0033]
As shown in FIG. 14, the holding device 100 can control the position of the mirror 110 with higher accuracy by providing the base 150 with the measuring unit 200 that measures the position of the mirror 110. In the present embodiment, the measuring unit 200 is provided at three positions (two of which are not shown) for tilt measurement in the circumferential direction around the X-axis and in the circumferential direction around the Y-axis, and in the X-axis direction and the Y-axis of the mirror 110. Two positions are arranged for position measurement in the direction. As the measuring unit 200, a laser length measuring device may be used, or a capacitance sensor may be used to simplify the control system. However, when using a capacitance sensor, it is necessary to form a target electrode on at least the measurement surface of the mirror 110. Here, FIG. 14 is a schematic perspective view showing an example of the holding device 100.
[0034]
Hereinafter, a method of incorporating the mirror 110 held by the holding device 100 at a desired position in the optical system will be described with reference to FIG. FIG. 16 is a flowchart for explaining a method of incorporating the mirror 110 held by the holding device 100 at a desired position in the optical system. First, a position reference unit 210 that defines the relative position of the mirror 110 is formed on the holding device 100 to which the mirror 110 is attached (Step 1002).
Specifically, when processing a mirror, a reference portion whose position is three-dimensionally guaranteed with respect to the mirror surface is formed. The purpose of providing this position reference unit is to detect the mirror surface position with desired accuracy in an optical system assembling step described later. In this case, instead of the mirror surface measurement, this position reference unit can be measured. It is like that. Measuring the mirror surface may cause shape damage and contamination on the reflecting surface, and if the mirror surface has a complex shape such as an aspheric surface, many measurement points are required, which increases the number of assembly steps. It will be connected.
The position reference portion may have any shape as long as the position with respect to the mirror surface is three-dimensionally guaranteed. However, in order to increase the accuracy at the time of measurement, for example, as shown in FIG. A spherical member may be provided at the location.
Next, the mirror 110 is attached to the holding device 100. At this time, it is confirmed that the position reference unit 210 of the mirror 110 is within a predetermined allowable range with respect to a predetermined position of the holding device 100. If the value is out of the allowable range, perform the built-in adjustment work again, and finally make it within the default value
(Step 1004). Further, the holding device 100 to which the mirror 110 is attached is incorporated in the optical system. At this time, the position reference unit 210 is measured so that the position of the mirror 110 is at a predetermined position, and the mounting position of the holding device 100 is adjusted.
(Step 1006). Attachment of the mirror 110 to the mirror holding device 100 and incorporation of the holding device 100 to which the mirror 110 is attached into the optical system are always performed while referring to the position reference unit 210, thereby simplifying the process. In addition, the mirror 110 can be arranged at a desired position, and a highly accurate optical system can be provided. Next, the wavefront aberration of the optical system incorporating the holding device 100 to which the mirror 110 is attached is measured (step 1008), and the holding device 100 holding the mirror 110 is adjusted so that the measured wavefront aberration is minimized. (Step 1010). In this adjustment, high-precision adjustment can be performed by moving the positioning means 140 described above. Thus, the optical system incorporating the holding device 100 can achieve desired optical performance.
[0035]
Hereinafter, an exemplary exposure apparatus 500 of the present invention will be described with reference to FIG. Here, FIG. 17 is a schematic configuration diagram of an exemplary exposure apparatus 500 of the present invention. The exposure apparatus 500 of the present invention uses the EUV light (for example, a wavelength of 13.4 nm) as the exposure illumination light to convert the circuit pattern formed on the mask 520 by the step-and-scan method or the step-and-repeat method. This is a projection exposure apparatus that exposes an object to be processed 540. Such an exposure apparatus is suitable for a submicron or quarter-micron lithography process. Hereinafter, in this embodiment, a step-and-scan type exposure apparatus (also referred to as a “scanner”) will be described as an example. Here, in the step-and-scan method, the wafer is continuously scanned (scanned) with respect to the mask to expose the mask pattern to the wafer, and after the exposure of one shot is completed, the wafer is step-moved. This is an exposure method for moving to an exposure area. The step-and-repeat method is an exposure method in which the wafer is step-moved for each batch exposure of the wafer and moves to the exposure area of the next shot.
[0036]
Referring to FIG. 17, an exposure apparatus 500 mounts an illumination device 510, a mask 520, a mask stage 525 on which the mask 520 is mounted, a projection optical system 530, an object to be processed 540, and an object to be processed 540. It has a wafer stage 545 to be placed, an alignment detection mechanism 550, and a focus position detection mechanism 560.
[0037]
Further, as shown in FIG. 17, since the transmittance of EUV light to the atmosphere is low, it is preferable that at least the optical path through which the EUV light passes is a vacuum atmosphere VC.
[0038]
The illumination device 510 is an illumination device that illuminates the mask 520 with arc-shaped EUV light (for example, a wavelength of 13.4 nm) with respect to the arc-shaped field of view of the projection optical system 530, and includes an EUV light source 512 and an illumination optical system 514. Be composed.
[0039]
As the EUV light source 512, for example, a laser plasma light source is used. In this method, a high-intensity pulsed laser beam is irradiated to a target material in a vacuum vessel to generate high-temperature plasma, and EUV light having a wavelength of, for example, about 13 nm is emitted from the plasma. As the target material, a metal film, a gas jet, a droplet, or the like is used. In order to increase the average intensity of the emitted EUV light, the repetition frequency of the pulse laser is preferably high, and the operation is usually performed at a repetition frequency of several kHz.
[0040]
The illumination optical system 514 includes a condenser mirror 514a and an optical integrator 514b. The condensing mirror 514a collects EUV light that is emitted almost isotropically from the laser plasma. The optical integrator 514b has a role of illuminating the mask 520 uniformly with a predetermined numerical aperture. The illumination optical system 514 is provided with an aperture 514c at a position conjugate with the mask 520 to limit the illumination area of the mask 520 to an arc shape. The holding device 100 of the present invention can be used to hold optical members such as the condenser mirror 514a and the optical integrator 514b of the illumination optical system 514.
[0041]
The mask 520 is a reflective mask on which a circuit pattern (or image) to be transferred is formed, and is supported and driven by a mask stage 525. The diffracted light emitted from the mask 520 is reflected by the projection optical system 530 and projected onto the object 540. The mask 520 and the object to be processed 540 are arranged in an optically conjugate relationship. Since the exposure apparatus 500 is a step-and-scan exposure apparatus, it scans the mask 520 and the object 540 to reduce and project the pattern of the mask 520 onto the object 540.
[0042]
The mask stage 525 supports the mask 520 and is connected to a moving mechanism (not shown). As the mask stage 525, any configuration known in the art can be applied. The moving mechanism (not shown) is configured by a linear motor or the like, and can move the mask 520 by driving the mask stage 525 at least in the X direction. The exposure apparatus 500 scans the mask 520 and the object 540 in synchronization. Here, the scanning direction in the mask 520 or the object 540 is X, the direction perpendicular to the scanning direction is Y, and the direction perpendicular to the mask 520 or the object 540 is Z.
[0043]
The projection optical system 530 uses a plurality of reflection mirrors (that is, multilayer mirrors) 530a to reduce and project the pattern on the mask 520 onto the object 540, which is the image plane. The number of mirrors 530a is about four to six. In order to realize a wide exposure area with a small number of mirrors, the mask 520 and the object 540 are simultaneously scanned by using only a thin arc-shaped area (ring field) separated by a certain distance from the optical axis. Transfer a large area. The numerical aperture (NA) of the projection optical system 530 is about 0.1 to 0.3.
[0044]
The holding device 100 of the present invention can be used for holding an optical member such as a mirror 530a constituting the projection optical system 530. The holding device 100 is connected to the lens barrel of the projection optical system 530 by a member (not shown). Therefore, the projection optical system 530 can reduce aberration due to deformation and displacement of the optical member, which deteriorates imaging performance, and can achieve desired optical performance.
[0045]
The target object 540 is a wafer in the present embodiment, but widely includes a liquid crystal substrate and other target objects. A photoresist is applied to the object 540. The photoresist application step includes a pretreatment, an adhesion improver application process, a photoresist application process, and a pre-bake process. The pretreatment includes washing, drying, and the like. The adhesion improver application treatment is a surface modification treatment (that is, a hydrophobic treatment by applying a surfactant) for increasing the adhesion between the photoresist and the base, and the organic film such as HMDS (Hexamethyl-disilazane) is treated. Coat or steam. Prebaking is a baking (firing) step, but is softer than that after development, and removes the solvent.
[0046]
The wafer stage 545 supports the object to be processed 540 by a wafer chuck 545a. The wafer stage 545 moves the object 540 in the XYZ directions using, for example, a linear motor. The mask 520 and the object 540 are scanned synchronously. The position of the mask stage 525 and the position of the wafer stage 545 are monitored by, for example, a laser interferometer, and both are driven at a constant speed ratio.
[0047]
The alignment detection mechanism 550 measures the positional relationship between the position of the mask 520 and the optical axis of the projection optical system 530, and the positional relationship between the position of the object 540 and the optical axis of the projection optical system 530, and measures the position of the mask 520. The positions and angles of the mask stage 525 and the wafer stage 545 are set so that the projected image matches a predetermined position of the object 540.
[0048]
The focus position detecting mechanism 560 measures the focus position in the Z direction on the surface of the object 540 and controls the position and angle of the wafer stage 545 so that the surface of the object 545 is constantly exposed by the projection optical system 530 during exposure. Keep at the imaging position.
[0049]
In the exposure, the EUV light emitted from the illumination device 510 illuminates the mask 520, and forms a pattern on the mask 520 on the surface of the object 540. In the present embodiment, the image plane is an arc-shaped (ring-shaped) image plane, and the entire surface of the mask 520 is exposed by scanning the mask 520 and the object 540 at a reduction ratio.
[0050]
Next, an embodiment of a device manufacturing method using the above-described exposure apparatus 500 will be described with reference to FIGS. FIG. 18 is a flowchart for explaining the manufacture of devices (semiconductor chips such as ICs and LSIs, LCDs, CCDs, etc.). Here, the manufacture of a semiconductor chip will be described as an example. In step 1 (circuit design), the circuit of the device is designed. Step 2 (mask fabrication) forms a mask on which the designed circuit pattern is formed. In step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is referred to as a preprocess, and an actual circuit is formed on the wafer by lithography using the mask and the wafer. Step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer created in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). Including. In step 6 (inspection), inspections such as an operation check test and a durability test of the semiconductor device created in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).
[0051]
FIG. 19 is a detailed flowchart of the wafer process in Step 4. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the surface of the wafer. Step 13 forms electrodes on the wafer. Step 14 (ion implantation) implants ions into the wafer. In step 15 (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the exposure apparatus 500 to expose a circuit pattern on the mask onto the wafer. Step 17 (development) develops the exposed wafer. Step 18 (etching) removes portions other than the developed resist image. Step 19 (resist stripping) removes unnecessary resist after etching. By repeating these steps, multiple circuit patterns are formed on the wafer. According to the device manufacturing method of the present embodiment, it is possible to manufacture a higher-quality device than before. As described above, the device manufacturing method using the exposure apparatus 500 and the resulting device also constitute one aspect of the present invention.
[0052]
Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the gist. For example, the holding device of the present invention may be used to support a mask or a wafer.
[0053]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the holding apparatus of this invention, desired optical performance can be achieved by reducing the aberration by the deformation | transformation and displacement of the optical member which deteriorates imaging performance.
[Brief description of the drawings]
FIG. 1 is a schematic configuration perspective view showing a holding device as one aspect of the present invention.
FIG. 2 is a schematic plan view of the holding device shown in FIG. 1;
FIG. 3 is a partially enlarged sectional view of the holding device shown in FIG. 1;
FIG. 4 is a schematic sectional view showing a spherical member and a groove of the support member shown in FIG. 1;
FIG. 5 is a partially enlarged sectional view of a holding device 100 having a pressing mechanism.
FIG. 6 is a schematic sectional view showing a spherical member and a groove of the support member shown in FIG. 1;
FIG. 7 is a schematic perspective view of the connecting means and the positioning means shown in FIG.
FIG. 8 is a schematic diagram showing the connecting means when moving about four axes.
9 is a schematic sectional view of the positioning means shown in FIG.
FIG. 10 is a schematic perspective view of the connecting means and the positioning means shown in FIG. 1;
FIG. 11 is a schematic perspective view of the connecting means and the positioning means shown in FIG.
FIG. 12 is a schematic sectional view of the positioning means shown in FIG.
FIG. 13 is a schematic perspective view showing an example of a holding device.
FIG. 14 is a schematic perspective view showing an example of a holding device.
FIG. 15 is a schematic perspective view showing an example of a holding device.
FIG. 16 is a flowchart for explaining a method of incorporating a mirror held by a holding device at a desired position in an optical system.
FIG. 17 is a schematic configuration diagram of an exemplary exposure apparatus of the present invention.
FIG. 18 is a flowchart for explaining the manufacture of devices (semiconductor chips such as IC and LSI, LCDs, CCDs, and the like).
19 is a detailed flowchart of the wafer process in Step 4 shown in FIG.
[Explanation of symbols]
100 holding device
110 mirror
112 Projection
114 recess
120 support member
122 spherical member
124 grooves
130 connecting means
140 positioning means
142a and b parallel leaf springs
144a and b set screw
146a and b spacer
148a and b Coil spring
150 base
170 Holding mechanism
172 elastic member
180 Actuator
185 displacement meter
190 detector
200 Measuring unit
210 Position Reference Unit
500 exposure equipment
510 Lighting device
514 Illumination optical system
520 mask
530 Projection optical system
540 object
550 Alignment detection mechanism
560 Focus position detection mechanism

Claims (14)

A support member for supporting the mirror at six points via three spherical surfaces,
Positioning means disposed at three places around the support member, each of which is movable in two axes in an optical axis direction and a circumferential direction around the optical axis;
A holding device, comprising: a connecting unit that connects the support member and the positioning unit and is movable in four axes other than the moving direction of the positioning unit. The holding device according to claim 1, wherein the three spherical surfaces are arranged on the same circumference at a pitch of 120 °. The holding device according to claim 1, wherein the mirror has a conical concave portion that contacts the circumference of the three spherical surfaces. 2. The holding device according to claim 1, wherein the support member has a groove having a V-shaped cross section that contacts two points of the spherical surface. 3. The holding device according to claim 1, wherein the positioning means are arranged on the same circumference at a pitch of 120 °. 2. The holding device according to claim 1, further comprising an actuator for moving the positioning means in two axes in the optical axis direction and a circumferential direction around the optical axis. The holding device according to claim 1, further comprising a detection unit configured to detect a position of the support member. The holding device according to claim 1, further comprising a measuring unit that measures a position of the mirror. The holding device according to claim 1, further comprising a position reference unit that defines a relative position of the mirror. 2. The holding device according to claim 1, wherein said positioning means has a guide of a parallel leaf spring. A method of incorporating a mirror at a desired position in an optical system,
Forming a position reference unit for measuring a relative position of the mirror on a holding device to which the mirror is attached;
Attaching the mirror to the holding member;
A first measuring step of measuring the position of the position reference unit after the attaching step;
After the first measurement step, incorporating the holding unit to which the mirror is attached into the optical system;
A second measuring step of measuring a position of the position reference unit after the assembling step. Measuring the wavefront aberration of the optical system after the mirror has been incorporated into the optical system;
Adjusting the mirror and the holding device such that the wavefront aberration measured in the measuring step is reduced. An optical system comprising the holding device according to any one of claims 1 to 10 and exposing a pattern formed on a mask or a reticle to an object to be processed via a mirror held by the holding device. An exposure apparatus characterized by the following. Projecting and exposing an object to be processed using the exposure apparatus according to claim 13;
Performing a predetermined process on the object subjected to the projection exposure.

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