JP2005158784A - Aligner and exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably conduct an excellent exposure by keeping the polarized state of an exposure light reaching a photosensitive substrate approximately constant during an exposure even when the polarized state of a transmitted light is varied by the effect of a light transmitting member formed of a fluorite. <P>SOLUTION: A mask (M) is illuminated on the basis of the exposure light from a light source (1), and a pattern on the mask is exposed on the photosensitive substrate (W). The polarized state of an incident light to the mask or the substrate is stabilized, and the pattern on the mask is exposed on the substrate. That is, the start of the exposure is stood by until the polarized state of the incident light to the mask or the substrate is stabilized after a time when the luminescence of the light source is started. When the mask or the substrate is exchanged, a light from the light source is interrupted at a specified place (10) without stopping the luminescence of the light from the light source. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exposure apparatus and an exposure method, and more particularly to an exposure apparatus used for manufacturing a microdevice such as a semiconductor element, an imaging element, a liquid crystal display element, and a thin film magnetic head in a lithography process.

  In a typical exposure apparatus of this type, a light beam emitted from a light source is used as a substantial surface light source composed of a large number of light sources via a fly-eye lens (or a micro fly-eye lens or the like) as an optical integrator. A secondary light source is formed. The light beam from the secondary light source is condensed by the condenser lens and then illuminates the mask on which a predetermined pattern is formed in a superimposed manner.

  The light transmitted through the mask pattern forms an image on the wafer via the projection optical system. Thus, the mask pattern is projected and exposed (transferred) onto the wafer. The pattern formed on the mask is highly integrated, and it is essential to obtain a uniform illuminance distribution on the wafer in order to accurately transfer this fine pattern onto the wafer.

Currently, a KrF excimer laser light source that supplies light with a wavelength of about 248 nm, an ArF excimer laser light source that supplies light with a wavelength of about 193 nm, and the like are used as the exposure light source. When the wavelength of the exposure light is shortened, the types of optical materials that can be practically used are limited due to light absorption. In particular, in an exposure apparatus that uses ArF excimer laser light as exposure light, a wide range of light-transmitting members (lenses, plane-parallel plates, etc.) formed of fluorite (calcium fluoride: CaF ₂ ), which is an optical material with a short absorption edge wavelength. It is used.

  As will be described later, the present inventor recently discovered that fluorite has a characteristic of changing the polarization state of transmitted light when irradiated with laser light. When the polarization state of the transmitted light changes due to the influence of the light transmission member formed of fluorite, the polarization state of the exposure light reaching the wafer changes with time. If the polarization state of exposure light changes during exposure, good exposure cannot be performed stably.

  The present invention has been made in view of the above-described problems. For example, even if the polarization state of transmitted light fluctuates due to the influence of a light transmitting member formed of fluorite, the exposure light that reaches the photosensitive substrate during exposure. It is an object of the present invention to provide an exposure apparatus and an exposure method capable of stably performing good exposure while maintaining the polarization state of the film substantially constant.

In order to solve the above problems, in the first embodiment of the present invention, in an exposure apparatus that illuminates a mask based on exposure light from a light source and exposes a pattern on the mask onto a photosensitive substrate,
Provided is an exposure apparatus comprising polarization stabilization means for stabilizing the polarization state of incident light on the mask or the photosensitive substrate prior to the exposure.

  According to a preferred aspect of the first aspect, the polarization stabilization means performs the exposure until the polarization state of the incident light on the mask or the photosensitive substrate is stabilized from the time when the light emission of the light source is started. Wait for start. In the first embodiment, the optical member is disposed in the optical path between the light source and the photosensitive substrate and has a characteristic of changing the polarization state of the transmitted light. Here, the optical member is formed of a crystal material.

  Further, according to a preferred aspect of the first aspect, the polarization stabilizing means is provided between the light source and the mask without stopping light emission of the light source when replacing the mask or the photosensitive substrate. The light from the light source is blocked at a predetermined position in the optical path. In this case, an illumination field stop for defining an illumination area on the mask is disposed at the predetermined position, and the polarization stabilizing means controls the illumination field stop to block light from the light source. It is preferable. Further, it is preferable that an optical member having a characteristic of changing a polarization state of transmitted light is not substantially disposed in an optical path between the predetermined position and the mask.

  Further, according to a preferred aspect of the first aspect, there is provided a beam splitter provided so as to be detachable with respect to an optical path between the light source and the predetermined position, and a position detection system for detecting the position of the mask. The position detection system detects the position of the mask using light extracted from the optical path through the beam splitter inserted into the optical path when the mask is replaced or the photosensitive substrate is replaced. . In addition, the polarization stabilization means stops the light emission of the light source when the mask is replaced or the photosensitive substrate is replaced, and the incident light to the mask or the photosensitive substrate is restarted when the light emission of the light source is restarted. It is preferable to wait for the exposure to resume until the polarization state becomes substantially constant. In the first embodiment, the light source is, for example, an ArF excimer laser light source.

In the second embodiment of the present invention, in an exposure method of illuminating a mask based on exposure light from a light source and exposing a pattern on the mask onto a photosensitive substrate,
A polarization stabilization step of stabilizing the polarization state of incident light on the mask or the photosensitive substrate;
And an exposure step that is performed after the polarization stabilization step and exposes a pattern on the mask onto a photosensitive substrate.

  According to a preferred aspect of the second aspect, the polarization stabilization step is performed until the polarization state of incident light on the mask or the photosensitive substrate is stabilized from the time when the light emission of the light source is started. It includes a waiting step for waiting for the start. Further, the second mode includes a step of guiding light from the light source to the photosensitive substrate through an optical member having a characteristic of changing the polarization state of transmitted light. Here, the optical member is made of, for example, a crystal material.

  In addition, according to a preferred aspect of the second embodiment, the method further includes a replacement step of replacing the mask or the photosensitive substrate, and the polarization stabilization step is performed from the light source while the replacement step is being performed. The light from the light source is blocked at a predetermined position without stopping the light emission. In this case, in the polarization stabilization step, it is preferable to block light from the light source using an illumination field stop that is arranged at the predetermined position and defines an illumination area on the mask. Further, it is preferable that an optical member having a characteristic of changing a polarization state of transmitted light is not substantially disposed in an optical path between the predetermined position and the mask.

  Further, according to a preferred aspect of the second embodiment, a step of inserting a beam splitter into an optical path between the light source and the predetermined position while performing the replacement step, and via the beam splitter And a position detection step of detecting the position of the mask using light extracted from the optical path. The method further includes a replacement step of replacing the mask or the photosensitive substrate, and the polarization stabilization step stops light emission of the light source and resumes light emission of the light source during the replacement step. It is preferable to wait for the resumption of exposure from the time to the time when the polarization state of the incident light on the mask or the photosensitive substrate becomes substantially constant.

  In the present invention, the start of exposure is waited after the light emission of the light source is started until the polarization state of the light incident on the mask or the photosensitive substrate is stabilized. Typically, when replacing the mask or the photosensitive substrate, light from the light source is blocked by a mask blind disposed in the optical path between the light source and the mask without stopping light emission of the light source.

  In this case, even while the mask blind blocks light, the optical member disposed in the optical path between the light source and the mask blind and having the characteristic of changing the polarization state of the transmitted light continues to receive light irradiation. Therefore, the polarization state of the exposure light reaching the photosensitive substrate during the exposure is maintained almost constant. As a result, in the present invention, the polarization state of the exposure light reaching the photosensitive substrate during the exposure is maintained substantially constant even when the polarization state of the transmitted light fluctuates due to the influence of a light transmission member formed of, for example, fluorite. Good exposure can be performed stably.

Embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a drawing schematically showing a configuration of an exposure apparatus according to an embodiment of the present invention. In FIG. 1, the Z axis along the normal direction of the wafer W, which is a photosensitive substrate, the Y axis in the direction parallel to the plane of FIG. 1 in the plane of the wafer W, and the plane of the wafer W in FIG. The X axis is set in the direction perpendicular to the paper surface. The exposure apparatus of this embodiment includes a laser light source 1 for supplying exposure light. As the laser light source 1, for example, an ArF excimer laser light source that supplies light having a wavelength of 193 nm can be used.

  A substantially parallel light beam emitted from the laser light source 1 along the Z direction has a rectangular cross section extending along the X direction, and is incident on a beam expander 2 including a pair of lenses 2a and 2b. Each lens 2a and 2b has a negative refracting power and a positive refracting power in the plane of FIG. 1 (in the YZ plane), respectively. Therefore, the light beam incident on the beam expander 2 is enlarged in the paper surface of FIG. 1 and shaped into a light beam having a predetermined rectangular cross section. The substantially parallel light beam that has passed through the beam expander 2 as the shaping optical system is deflected in the Y direction by the bending mirror 3 and then enters the afocal zoom lens 5 through the first diffractive optical element 4.

  In general, a diffractive optical element is formed by forming a step having a pitch of the wavelength of exposure light (illumination light) on a substrate, and has a function of diffracting an incident beam to a desired angle. Specifically, the first diffractive optical element 4 has a function of forming a circular light intensity distribution in its far field (or Fraunhofer diffraction region) when a parallel light beam having a rectangular cross section is incident. . Therefore, the light beam that has passed through the first diffractive optical element 4 forms a circular light intensity distribution at the pupil position of the afocal zoom lens 5, that is, a light beam having a circular cross section.

  The first diffractive optical element 4 is configured to be retractable from the illumination optical path. The afocal zoom lens 5 is configured so that the magnification can be continuously changed within a predetermined range while maintaining an afocal system (non-focal optical system). The light beam that has passed through the afocal zoom lens 5 enters the second diffractive optical element 6. The afocal zoom lens 5 optically substantially conjugates the divergence origin of the first diffractive optical element 4 and the diffractive surface of the second diffractive optical element 6. Then, the numerical aperture of the light beam condensed on one point of the diffractive surface of the second diffractive optical element 6 or a surface in the vicinity thereof changes depending on the magnification of the afocal zoom lens 5.

  The second diffractive optical element 6 has a function of forming a ring-shaped light intensity distribution in the far field when a parallel light beam enters. The second diffractive optical element 6 is configured to be switchable with a second diffractive optical element having other characteristics. The light beam that has passed through the second diffractive optical element 6 enters the zoom lens 7. In the vicinity of the rear focal plane of the zoom lens 7, the incident surface of the micro fly's eye lens (or fly eye lens) 8 is positioned. The micro fly's eye lens 8 is an optical element composed of a large number of microlenses having positive refractive power arranged vertically and horizontally and densely. In general, a micro fly's eye lens is configured by, for example, performing etching treatment on a plane-parallel plate to form a micro lens group.

  Here, each micro lens constituting the micro fly's eye lens is smaller than each lens element constituting the fly eye lens. Further, unlike a fly-eye lens composed of lens elements isolated from each other, a micro fly-eye lens is formed integrally with a large number of micro lenses (micro refractive surfaces) without being isolated from each other. However, the micro fly's eye lens is the same wavefront division type optical integrator as the fly eye lens in that lens elements having positive refractive power are arranged vertically and horizontally.

  As described above, the luminous flux from the circular light intensity distribution formed at the pupil position of the afocal zoom lens 5 via the first diffractive optical element 4 is emitted from the afocal zoom lens 5 and then variously emitted. A light beam having an angle component enters the second diffractive optical element 6. That is, the first diffractive optical element 4 constitutes an optical integrator having an angular light beam forming function. On the other hand, the second diffractive optical element 6 has a function as a light beam conversion element that forms a ring-shaped light intensity distribution in the far field when a parallel light beam is incident. Therefore, the light beam that has passed through the second diffractive optical element 6 has an annular illumination field centered on the optical axis AX, for example, on the rear focal plane of the zoom lens 7 (and hence on the incident surface of the micro fly's eye lens 8). Form.

  As described above, the zoom lens 7 substantially connects the second diffractive optical element 6 and the incident surface of the micro fly's eye lens 8 in a Fourier transform relationship. The outer diameter of the annular illumination field formed on the incident surface of the micro fly's eye lens 8 changes depending on the focal length of the zoom lens 7. The light beam incident on the micro fly's eye lens 8 is divided two-dimensionally, and the rear focal plane of the micro fly's eye lens 8 has a large number of light sources (hereinafter referred to as “two” Next light source ") is formed.

  The luminous flux from the annular secondary light source formed on the rear focal plane of the micro fly's eye lens 8 illuminates the mask blind 10 in a superimposed manner after passing through the condenser optical system 9. Thus, a rectangular illumination field corresponding to the shape and focal length of each microlens constituting the micro fly's eye lens 8 is formed on the mask blind 10 as an illumination field stop. The light beam that has passed through the rectangular opening (light transmitting portion) of the mask blind 10 is subjected to the light condensing action of the imaging optical system 11 and then superimposed on the mask (reticle) M on which a predetermined pattern is formed. Illuminate.

  As described above, the imaging optical system 11 forms an image of the rectangular opening of the mask blind 10 on the mask M supported by the mask stage MS. In other words, the mask blind 10 constitutes a field stop for defining an illumination area formed on the mask M (and thus the wafer W). The light flux that has passed through the pattern of the mask M forms an image of the mask pattern on the wafer W supported by the wafer stage WS via the projection optical system PL. In this way, the pattern of the mask M is formed in each exposure region of the wafer W by performing batch exposure or scan exposure while two-dimensionally driving and controlling the wafer W in a plane orthogonal to the optical axis AX of the projection optical system PL. Sequential exposure is performed.

  In addition, it can replace with the 2nd diffractive optical element 6 for annular illumination, and can perform 4 pole illumination by setting the 2nd diffractive optical element for 4 pole illumination in an illumination optical path. The second diffractive optical element for quadrupole illumination has a function of forming a four-point light intensity distribution in the far field when a parallel light beam is incident. Therefore, the light beam that has passed through the second diffractive optical element for quadrupole illumination is formed into a quadrupole illumination comprising, for example, four circular illumination fields centered on the optical axis AX on the incident surface of the micro fly's eye lens 8. Form a field. As a result, the same quadrupole secondary light source as the illumination field formed on the incident surface is also formed on the rear focal plane of the micro fly's eye lens 8.

  Further, the first diffractive optical element 4 is retracted from the illumination optical path, and a second diffractive optical element for circular illumination is set in the illumination optical path instead of the second diffractive optical element 6 for annular illumination. Circular illumination can be performed. In this case, a light beam having a rectangular cross section enters the afocal zoom lens 5 along the optical axis AX. The light beam incident on the afocal zoom lens 5 is enlarged or reduced in accordance with the magnification, and is emitted from the afocal zoom lens 5 along the optical axis AX as a light beam having a rectangular cross section, and is used for circular illumination. The light enters the two-diffractive optical element.

  Here, like the first diffractive optical element 4, the second diffractive optical element for circular illumination forms a circular light intensity distribution in the far field when a parallel light beam having a rectangular cross section is incident. It has a function. Therefore, the circular light beam formed by the second diffractive optical element for circular illumination forms a circular illumination field around the optical axis AX on the incident surface of the micro fly's eye lens 8 via the zoom lens 7. . As a result, a circular secondary light source centered on the optical axis AX is also formed on the rear focal plane of the micro fly's eye lens 8.

  FIG. 2 is a diagram schematically showing the internal configuration of the beam matching unit arranged between the light source and the first diffractive optical element in FIG. In the beam matching unit BMU shown in FIG. 2, a parallel beam supplied from a laser light source 1 (for example, a KrF excimer laser light source or an ArF excimer laser light source) passes through a pair of declination prisms 31 and a parallel plane plate 32, and then The light enters the expander 2. The laser light source 1 is installed on the floor slab A on the lower floor, for example.

  Here, at least one of the pair of declination prisms 31 is configured to be rotatable about the optical axis AX. Therefore, the angle of the parallel beam with respect to the optical axis AX can be adjusted by relatively rotating the pair of declination prisms 31 around the optical axis AX. That is, the pair of declination prisms 31 constitute beam angle adjusting means for adjusting the angle of the parallel beam supplied from the laser light source 1 with respect to the optical axis AX. The plane parallel plate 32 is configured to be rotatable around two axes orthogonal to each other in a plane perpendicular to the optical axis AX.

  Therefore, the parallel beam can be translated with respect to the optical axis AX by rotating the plane parallel plate 32 around each axis and inclining it with respect to the optical axis AX. That is, the plane parallel plate 32 constitutes a beam translation means for translating the parallel beam supplied from the laser light source 1 with respect to the optical axis AX. Thus, the parallel beam from the laser light source 1 via the pair of declination prisms 31 and the plane parallel plate 32 is enlarged and shaped into a parallel beam having a predetermined cross-sectional shape via the beam expander 2 and then the first right angle. The light enters the prism 33.

  The parallel beams deflected in the vertical direction by the first right-angle prism 33 as the back surface reflecting mirror are sequentially reflected by the second right angle prism 34 to the fifth right angle prism 37 as the back surface reflector, and then the upper floor slab. The light passes through the opening B and enters the sixth right-angle prism 38. As shown in FIG. 2, the second right-angle prism 34 to the fifth right-angle prism 37 are parallelly deflected by the first right-angle prism 33 and directed toward the sixth right-angle prism 38, for example, a pipe for supplying pure water. It arrange | positions so that the piping 39 for ventilation, etc. may be detoured.

  The beam deflected in the horizontal direction by the sixth right-angle prism 38 as the back reflecting mirror enters the half mirror 40. The beam reflected by the half mirror 40 is guided to the misalignment tilt detection system 41. On the other hand, the beam transmitted through the half mirror 40 is guided to the first diffractive optical element 4. The positional deviation inclination detection system 41 detects the positional deviation and inclination of the parallel beam incident on the first diffractive optical element 4 with respect to the optical axis AX.

  2, the beam splitter 12 is inserted into the optical path between the half mirror 40 and the first diffractive optical element 4 (corresponding to the optical path between the bending mirror 3 and the first diffractive optical element 4 in FIG. 1). It is provided so that it can be removed. When the beam splitter 12 is set in the optical path, as shown in FIG. 1, a part of the exposure light extracted from the optical path via the beam splitter 12 is a position for detecting the position of the mask M as alignment light. Guided to the detection system 13.

  The position detection system 13 guides the alignment light to the reference mark on the wafer stage WS via the mask M and the projection optical system PL, and photoelectrically detects the reflected light from the reference mark via the projection optical system PL and the mask M. . Thus, the position detection system 13 detects the relative position of the mask M with respect to the reference mark on the wafer stage WS based on the photoelectric detection result. Note that the detailed configuration and operation of the position detection system 13 can be referred to, for example, Japanese Patent Laid-Open No. 2000-270491.

  The exposure apparatus according to the present embodiment includes a control unit 20 for controlling the exposure of the pattern of the mask M onto the wafer W. The control unit 20 emits (oscillates) the laser light source 1, inserts and removes the beam splitter 12, inserts and removes the first diffractive optical element 6, zooming operation of the afocal zoom lens 5, and second diffractive optical element 6. Exchange operation, zoom lens 7 zooming operation, opening / closing operation of the opening of the mask blind 10, operation of the mask stage MS including replacement of the mask M, operation of the wafer stage WS including replacement of the wafer W, position detection system 13 The detection operation of each is controlled.

  By the way, when using, for example, an ArF excimer laser light source as the laser light source 1, it is common to ensure required transmittance and durability by using fluorite as a light transmitting member that is irradiated with light having a high energy density. Recently, the inventor of the present application has discovered that fluorite has a property of changing the polarization state of light transmitted through irradiation with laser light. In particular, the fluctuation of the polarization state is significant when receiving irradiation with high-power laser light in the vacuum ultraviolet region. Specifically, fluorite has a property that the polarization state of light transmitted through the fluorite gradually changes within several tens of seconds from the start of laser light irradiation, and then the polarization state of the transmitted light settles to a steady state. Have

In the present embodiment, the declination prism 31, the plane parallel plate 32, the lenses 2a and 2b of the beam expander 2, the first right-angle prism 33 to the sixth right-angle prism 38, the first diffractive optical element 4 and the mask blind 10 are used. There is a possibility that fluorite may be used for a light transmitting member (lens, plane parallel plate, diffractive optical element, etc.) that is irradiated with light having a high energy density. In this case, almost linearly polarized light (light having a degree of polarization of approximately 1.0) is supplied from the laser light source 1, and as shown in FIG. 3, the time T ₀ when the laser light source 1 starts to emit light (oscillate). The exposure light reaching the wafer W in FIG. 1 is almost linearly polarized light, but the polarization state of the exposure light reaching the wafer W gradually changes as the time T elapses (the degree of polarization gradually decreases). At the time T ₁ when the time has passed, the polarization state of the exposure light reaching the wafer W becomes almost constant and stabilized.

  Note that the change in the polarization state due to fluorite is almost restored in several tens of seconds when the irradiation of the laser beam is stopped. Therefore, when the laser irradiation to the fluorite and the irradiation stop are repeated, the polarization state of the light transmitted through the fluorite changes every time the laser irradiation is started. For example, as schematically shown in FIG. 3, when the polarization state of the exposure light reaching the wafer W changes with time due to the influence of the light transmitting member formed of fluorite, that is, the polarization state of the exposure light changes during the exposure. As a result, good exposure cannot be performed stably.

  FIG. 4 is a flowchart of a typical exposure process in this embodiment. In the present embodiment, as shown in FIG. 4, the control unit 20 closes the opening of the mask blind 10 via the driving unit 21 and sets it in a light-shielding state prior to the start of exposure (S11). Next, the control unit 20 starts the light emission of the laser light source 1, and waits for the start of exposure until the polarization state of the exposure light reaching the wafer W is stabilized (S12). When the polarization state of the exposure light reaching the wafer W is stabilized after a predetermined time has elapsed, the control unit 20 opens the opening of the mask blind 10 to set the light passing state, and the first shot on the wafer W is set. Exposure to the area is started (S13).

  Next, the control unit 20 sequentially repeats exposure on each shot area on the wafer W while moving the wafer stage WS two-dimensionally through the drive unit 22 (S14). Thus, when the exposure to all the shot areas on the wafer W is completed, the control unit 20 closes the opening of the mask blind 10 and sets the light shielding state without stopping the light emission of the laser light source 1 (S15). . Next, the control unit 20 drives the wafer stage WS to replace the wafer W (S16). Thus, when the exposure preparation for the new wafer W is completed, the control unit 20 opens the opening of the mask blind 10 to set the light passing state, and performs exposure to each shot area on the new wafer W. Start (S17).

  As described above, in the present embodiment, the control unit 20 constitutes a polarization stabilizing unit for stabilizing the polarization state of the incident light on the mask M or the wafer W prior to exposure. That is, the control unit 20 as the polarization stabilization unit stabilizes the polarization state of the exposure light (generally incident light on the mask M or the wafer W) reaching the wafer W from the time when the laser light source 1 starts to emit light. Until the start of exposure. Further, when exchanging the wafer W, the light from the laser light source 1 is blocked by the mask blind 10 disposed in the optical path between the laser light source 1 and the mask M without stopping the light emission of the laser light source 1.

  In this case, an optical member (for example, fluorite, for example) that has a characteristic of changing the polarization state of light that is disposed in the optical path between the laser light source 1 and the mask blind 10 while the mask blind 10 blocks light. Since the light transmitting member formed by (2) continues to receive the laser irradiation, the polarization state of the exposure light reaching the wafer W during the exposure is maintained substantially constant. As a result, in this embodiment, the polarization state of the exposure light reaching the wafer W during the exposure is almost the same even if the polarization state of the transmitted light changes with time due to the influence of the light transmission member formed of, for example, fluorite. Since it is maintained constant, good exposure can be performed stably.

  In the above-described embodiment, the mask M is not replaced during the exposure of one wafer W. However, for example, in the case of double exposure, the mask M needs to be replaced. Specifically, when exposure to all shot regions on the wafer W is completed, the opening of the mask blind 10 is closed and set to a light-shielding state without stopping the light emission of the laser light source 1, and then the driving unit 23 is turned on. Then, the mask stage MS is driven to exchange the mask M. Further, the control unit 20 sets the beam splitter 12 in the illumination optical path via the driving unit 24, and uses the alignment light extracted out of the optical path via the beam splitter 12 to perform a new mask by the position detection system 13. The position of M is detected.

  Further, the control unit 20 positions the new mask M by driving the mask stage MS based on the detection result of the position detection system 13. Thus, when the exposure preparation of a new mask M pattern is completed, the control unit 20 opens the opening of the mask blind 10 and starts exposure to each shot area on the wafer W. As described above, for example, when double exposure is performed, the mask blind disposed in the optical path between the laser light source 1 and the mask M without stopping the light emission of the laser light source 1 when the mask M is replaced. 10, the light from the laser light source 1 is blocked.

  In the above-described embodiment, when the mask M or the wafer W is replaced, the light from the laser light source 1 is blocked by the mask blind 10 without stopping the light emission of the laser light source 1. In this case, even while the mask blind 10 blocks light, an optical member (for example, by fluorite) that is disposed in the optical path between the laser light source 1 and the mask blind 10 and has a characteristic of changing the polarization state of transmitted light. Since the formed light transmitting member) continues to receive the laser irradiation, the polarization state of the exposure light reaching the wafer W during the exposure is maintained almost constant.

  However, when an optical member having a property of changing the polarization state of transmitted light is disposed in the optical path between the mask blind 10 and the mask M, these optical members are used while the mask blind 10 blocks light. Since the laser irradiation with respect to is stopped, there is a possibility that the polarization state of the exposure light reaching the wafer W will fluctuate for a certain time from the restart of exposure. Therefore, in the present embodiment, it is preferable that an optical member having a characteristic of changing the polarization state of transmitted light is not substantially disposed in the optical path between the mask blind 10 and the mask M.

  In the above-described embodiment, when the mask M or the wafer W is replaced, the light from the laser light source 1 is blocked by the mask blind 10 without stopping the light emission of the laser light source 1. However, the present invention is not limited to this, and a modification in which the light emission of the laser light source 1 is stopped when the mask M or the wafer W is replaced is also possible. In this case, it is necessary to wait for the resumption of exposure from the time when the light emission of the laser light source 1 is resumed until the time when the polarization state of the light incident on the mask M or the wafer W becomes substantially constant.

  In the above description, a light transmissive member formed of fluorite is considered as an optical member having a characteristic of changing the polarization state of transmitted light. However, without being limited to fluorite, other crystal materials having birefringence and light transmitting members formed of crystal materials such as quartz having optical rotation also have characteristics that change the polarization state of transmitted light. It should be noted that

  In the exposure apparatus according to the above-described embodiment, the illumination optical device illuminates the mask (reticle) (illumination process), and the projection optical system is used to expose the transfer pattern formed on the mask onto the photosensitive substrate (exposure). Step), a micro device (semiconductor element, imaging element, liquid crystal display element, thin film magnetic head, etc.) can be manufactured. Refer to the flowchart of FIG. 5 for an example of a technique 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 above-described embodiment. To explain.

  First, in step 301 of FIG. 5, 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, the image of the pattern on the mask is sequentially exposed and transferred to each shot area on the wafer of one lot through the projection optical system using the exposure apparatus of the above-described embodiment. 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 the exposure apparatus of the above-described 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. 6, in the pattern formation process 401, a so-called photolithography process is performed in which the 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 above-described 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 so-called immersion method is applied in which the optical path between the projection optical system and the photosensitive substrate is filled with a medium (typically liquid) having a refractive index greater than 1.1. 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 and 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, KrF excimer laser light (wavelength: 248 nm) or ArF excimer laser light (wavelength: 193 nm) is used as exposure light. However, the present invention is not limited to this, and other appropriate laser light sources are used. For example, the present invention can also be applied to an F ₂ laser light source that supplies laser light having a wavelength of 157 nm.

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 internal structure of the beam matching unit arrange | positioned between a light source and the 1st diffractive optical element in FIG. It is a figure which shows typically a mode that the polarization state of the exposure light which reaches | attains a wafer changes with time by the influence of the light transmissive member formed with the fluorite. It is a flowchart of the typical exposure process in 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

DESCRIPTION OF SYMBOLS 1 Laser light source 4 1st diffractive optical element 5 Afocal zoom lens 6 2nd diffractive optical element 7 Zoom lens 8 Micro fly eye lens 9 Condenser optical system 10 Mask blind 11 Imaging optical system 12 Beam splitter 13 Position detection system 20 Control part M Mask PL Projection optical system W Wafer

Claims (18)

In an exposure apparatus that illuminates a mask based on exposure light from a light source and exposes a pattern on the mask onto a photosensitive substrate,
An exposure apparatus comprising polarization stabilization means for stabilizing the polarization state of incident light on the mask or the photosensitive substrate prior to the exposure. The polarization stabilization unit waits for the start of exposure until the polarization state of incident light on the mask or the photosensitive substrate is stabilized after the light emission of the light source is started. Item 4. The exposure apparatus according to Item 1. The exposure according to claim 1, further comprising an optical member disposed in an optical path between the light source and the photosensitive substrate and having a characteristic of changing a polarization state of transmitted light. apparatus. The exposure apparatus according to claim 3, wherein the optical member is made of a crystalline material. The polarization stabilizing means is configured to provide light from the light source at a predetermined position in the optical path between the light source and the mask without stopping light emission of the light source when replacing the mask or the photosensitive substrate. The exposure apparatus according to any one of claims 1 to 4, wherein the exposure apparatus is shielded. An illumination field stop for defining an illumination area on the mask is disposed at the predetermined position, and the polarization stabilizing means controls the illumination field stop to block light from the light source. An exposure apparatus according to claim 5. 7. The exposure according to claim 5, wherein an optical member having a characteristic of changing a polarization state of transmitted light is not substantially disposed in an optical path between the predetermined position and the mask. apparatus. A beam splitter provided to be removable with respect to an optical path between the light source and the predetermined position;
A position detection system for detecting the position of the mask,
The position detection system detects the position of the mask using light extracted from the optical path via the beam splitter inserted into the optical path when the mask is replaced or the photosensitive substrate is replaced. The exposure apparatus according to claim 5, wherein: The polarization stabilization means stops the light emission of the light source when the mask is replaced or the photosensitive substrate is replaced, and the polarization state of the incident light on the mask or the photosensitive substrate from the time when the light emission of the light source is restarted. 5. The exposure apparatus according to claim 1, wherein resumption of exposure is waited until a time point at which becomes substantially constant. In an exposure method of illuminating a mask based on exposure light from a light source and exposing a pattern on the mask onto a photosensitive substrate,
A polarization stabilization step of stabilizing the polarization state of incident light on the mask or the photosensitive substrate;
And an exposure step that is performed after the polarization stabilization step and exposes the pattern on the mask onto the photosensitive substrate. The polarization stabilization step includes a standby step of waiting for the start of the exposure until the polarization state of the incident light on the mask or the photosensitive substrate is stabilized after the light emission of the light source is started. The exposure method according to claim 10, wherein: The exposure method according to claim 10, further comprising a step of guiding light from the light source to the photosensitive substrate through an optical member having a characteristic of changing a polarization state of transmitted light. The exposure method according to claim 10, wherein the optical member is made of a crystalline material. A replacement step of replacing the mask or the photosensitive substrate;
11. The polarization stabilization process blocks light from the light source at a predetermined position without stopping light emission from the light source during the exchange process. 14. The exposure method according to any one of items 1 to 13. 15. The exposure according to claim 14, wherein in the polarization stabilization step, light from the light source is blocked using an illumination field stop disposed at the predetermined position to define an illumination area on the mask. Method. 16. The exposure according to claim 14, wherein an optical member having a characteristic of changing a polarization state of transmitted light is not substantially disposed in an optical path between the predetermined position and the mask. Method. Inserting a beam splitter into an optical path between the light source and the predetermined position while performing the exchange step;
The exposure method according to claim 14, further comprising: a position detection step of detecting a position of the mask using light extracted from the optical path through the beam splitter. . A replacement step of replacing the mask or the photosensitive substrate;
In the polarization stabilization step, the light emission of the light source is stopped while the replacement step is performed, and the polarization state of the incident light on the mask or the photosensitive substrate is almost the same as when the light emission of the light source is restarted. The exposure apparatus according to claim 10, wherein the exposure apparatus waits for the resumption of exposure until the time becomes constant.

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