JP6093525B2 - Illumination monitoring apparatus and exposure apparatus provided with the same - Google Patents

Description

  The present invention relates to illumination light of an exposure apparatus, and relates to an illumination apparatus that performs measurement and adjustment of illuminance and light amount, and particularly relates to monitoring of illumination light.

  In the exposure apparatus, light emitted from a light source such as a discharge lamp or a laser is transmitted to an illumination optical system on the substrate side through an optical fiber bundle (see, for example, Patent Document 1). When a plurality of light sources are used, optical fiber bundles are connected for each light source, and are bundled in the middle to make one output end.

  Further, in the exposure apparatus, a photodetector is provided in order to make the illuminance and light quantity to the substrate constant (for example, see Patent Document 2). In order to extract the light traveling through the optical fiber bundle, a part of the fiber bundle is branched to the photodetector side, or a beam splitter is arranged to extract a part of the light from the light source, and to measure the illuminance and light quantity. Make adjustments. Furthermore, it is possible to extract light by disposing a grating and a dielectric mirror inside the optical fiber (see Patent Document 3).

JP 2006-343684 A JP-A-7-183207 US Patent Application Publication No. 2010/0202726

  Since a part of the illumination light is taken out for light detection, a light loss occurs correspondingly, and exposure cannot be performed using the illumination light to the maximum. Further, by using the light extraction optical system in the middle of the optical fiber bundle, the fiber performance is adversely affected to the illuminance / light quantity measurement.

  Therefore, it is required to accurately measure the illuminance / light quantity while suppressing light loss as much as possible in the process of light transmission using the optical fiber bundle.

  The illumination monitor apparatus of the present invention is an illumination monitor apparatus applicable to an exposure apparatus, and performs illumination monitoring using a plurality of optical fibers that transmit illumination light from a light source unit to an exposure head provided in the exposure apparatus. Is possible. The exposure head represents a pattern forming device including an illumination optical system, a light modulation element array, a mask / reticle, or the like.

  As the light source unit, a laser, a discharge lamp, or the like can be applied. In particular, it is possible to connect a plurality of optical fibers to a plurality of light sources, respectively. In this case, it is possible to extend from the middle to the exposure head as a fiber cable. Various types of fiber can be applied as the optical fiber, and a small-diameter optical fiber in which a cladding is formed around the core can be applied.

  In the present invention, a plurality of optical fibers in which an unshielded region from which leakage light is emitted are formed on the outer peripheral surface of at least one of the plurality of optical fibers. The non-shielded region / section is a region where light that inevitably leaks from the clad or the like due to fiber characteristics or the like can be emitted to the outside without being blocked. For example, a configuration not covered with a shielding member such as a protective film is possible. The non-shield region may be formed to have a predetermined width along the axial direction, or the whole may be a non-shield region.

  Furthermore, the illumination monitor device of the present invention includes a photodetector that receives leaked light and a light guide that is disposed around the non-shielded region and guides the leaked incident light to the photodetector. If the light output is constant, the light leaking from the unshielded region is also substantially constant. By detecting the light amount / luminance value of this leaked light, it is possible to detect whether or not the light output is fluctuating.

  Various optical members can be applied as the light guide. In consideration of making the light incident on the light receiver as uniform as possible, it is possible to provide an optical member for diffusing the incident leakage light. Here, the light diffusion means that the light incident on the light receiver is dispersed so as to be uniform and includes reflection / scattering of light.

  The optical member may be shaped in consideration of taking in light leaking from the entire unshielded region and securing a light diffusion (scattering, reflection) space. For example, it is possible to configure a rectangular parallelepiped shape having an incident surface of a size that covers the entire unshielded region. As a specific optical member, a rectangular parallelepiped, block-like acrylic or glass, or an optical member having a sheet-like diffusion film as an incident surface can be applied.

  It is also possible to transmit light that matches the sensitivity characteristics of the light receiver. For example, it is possible to provide a phosphor that receives incident leaked light and emits fluorescence having a wavelength corresponding to the sensitivity characteristics of the light receiver. It is.

  Photodetectors can be placed in a variety of locations. In particular, when the optical member has a rectangular parallelepiped shape, the optical member can be disposed to face the side surface of the optical member. For example, the optical member is mounted inside so as not to be exposed on the surface of the light guide unit other than the incident surface, and light is reflected on the incident surface other than the side surface facing the light receiver and the side surface in contact with the inner wall of the light guide unit. The optical member can be configured to repeat scattering and reflection. According to this, the leakage light that has entered the optical member is all transmitted to the photodetector through the opposing side surface.

  When the unshielded region is formed in each of the plurality of optical fibers, the light guide unit can be provided with a guide unit that aligns the unshielded regions of the optical fibers together. The leaked light is guided to the light guide without being diffused as it is. For example, the guide portion can be configured to align a plurality of optical fibers in a flat shape while being in close contact with each other in the unshielded region.

  As the illumination monitor device, not only monitoring but also output adjustment is possible. For example, an output control unit that adjusts the output of illumination light based on a luminance signal output from a photodetector may be provided. The output control unit can perform output adjustment during the execution of the exposure process, that is, during irradiation of illumination light for pattern formation.

  For example, the output control unit can adjust the output so that the luminance signal is constant. That is, the light output is controlled so that the leaked light becomes constant, and the light output may be adjusted so as to compensate for the change in the luminance value / light quantity of the leaked light.

  Alternatively, the output control unit can adjust the output so that the target value and the luminance value determined according to the sensitivity characteristic of the non-exposed body coincide. It is empirically known that the leakage light and the light output have a substantially linear relationship, and the light output can be increased or decreased toward the target value.

  On the other hand, an illumination monitoring apparatus according to another aspect of the present invention is an apparatus for detecting leakage light of an optical fiber bundle, and a plurality of optical fibers that transmit illumination light from a light source unit to an exposure head provided in the exposure apparatus. Apply a bunch. The illumination monitor device includes a plurality of optical fiber bundles in which a non-shield region from which leakage light is emitted is formed on an outer peripheral surface of at least one optical fiber bundle, a photodetector that receives the leakage light, and a non-shield region. And a light guide unit that is arranged around and guides incident leaked light to a photodetector.

  In the illumination monitoring method of the present invention, in a plurality of optical fibers that transmit illumination light from a light source unit to an exposure head provided in an exposure apparatus, unshielded light leaks from the outer peripheral surface of at least one optical fiber. A region is formed, and leakage light emitted from the unshielded region is guided to the photodetector. Alternatively, in the illumination monitoring method according to another aspect of the present invention, in the plurality of optical fiber bundles that transmit the illumination light from the light source unit to the exposure head provided in the exposure apparatus, on the outer peripheral surface of at least one optical fiber bundle, A non-shielded region from which leaked light exits is formed, and the leaked light emitted from the non-shielded region is guided to the photodetector.

  As described above, according to the present invention, it is possible to accurately detect the illuminance and the light amount without reducing the output of the illumination light during the exposure process.

It is a schematic block diagram of the exposure apparatus which is this embodiment. It is a typical perspective view of a light guide part and a photodetector. It is a typical top view of a light guide part and a photodetector. It is a flowchart of the light output adjustment performed in a control part.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic block diagram of an exposure apparatus according to this embodiment.

The exposure apparatus 10 is a maskless exposure apparatus that directly forms a pattern on a substrate S on which a photosensitive material such as a photoresist is formed, and includes a light source unit 100 and an exposure head 30. The light source unit 100 includes a plurality of light sources 100 _{1 to} 100 _N. Here, a laser that emits light having a wavelength of 405 nm is applied.

A plurality of optical fibers 20 _{1 to} 20 _N are connected to the _N light sources 100 _{1 to} 100 _N , and these are gathered together to form an optical fiber group (hereinafter referred to as “optical fiber group” or “ Use one of the multiple optical fibers "). Illumination light emitted from the light sources 100 _{1 to} 100 _N is sent to the exposure head 30 via the plurality of optical fibers 20 _{1 to} 20 _N.

  Here, each of the plurality of optical fibers 20 is configured as a quartz-based multimode optical fiber, and light incident on each fiber travels inside the core while being reflected by the cladding. On the other hand, the outer peripheral surface of the optical fiber constituting each optical fiber is not covered with a protective film or the like, and light leaking from the outer peripheral surface of the clad in terms of fiber performance, that is, leaked light is emitted outside the fiber without being blocked. To do.

  The exposure head 30 includes an illumination optical system, a DMD (Digital Micro-mirror Device), a projection optical system, and the like, and each micromirror of the DMD is ON / OFF controlled based on drawing pattern data. Thereby, the pattern light is projected onto the substrate S.

  The substrate S is mounted on a drawing table (not shown), and scanning is performed as the drawing table moves relative to the exposure head 30. When the drawing process for one substrate S is completed, the next substrate is transported and the drawing process is started. Each time a predetermined number of substrates are drawn, the drawing process is temporarily suspended for a predetermined time.

  The optical fiber group 20 extends as a single unit from the middle, and a light guide 40 is provided around a region partitioned in a part thereof (hereinafter referred to as a measurement region / non-shield region). The light guide unit 40 guides leaked light from each optical fiber bundle to the photodetector 50 disposed near the light guide unit 40.

  The photodetector 50 has one or a plurality of photodiodes (not shown) that receive leaked light, and outputs a luminance signal. The control unit 80 detects the light amount and illuminance of the light source unit 100 based on the luminance signal sent from the photodetector 50 and controls the light output. As described above, the arrangement of the optical fiber group 20 in which the unshielded region K is formed, the light guide unit 40, and the photodetector 50 detects a part of the light traveling through the optical fiber bundle without providing an optical member or the like. can do.

  Here, the leakage light is monitored during the drawing process, and the input power to each light source is adjusted so that the illuminance is constant. When the drawing process is temporarily suspended, the light receiving unit 90 in which the photodiodes are arranged moves above the table. Then, the illuminance / light quantity of the light actually irradiated onto the substrate S is detected.

  FIG. 2 is a schematic perspective view of the light guide and the photodetector. FIG. 3 is a schematic plan view of the light guide and the photodetector. However, in FIG. 3, the optical fiber, the light guide, and the photodetector are indicated by hatching for convenience.

  As shown in FIG. 2, the light guide 40 includes a cuboid / block-shaped light transmission member 45 and a base 60 that supports the light transmission member 45. A recess 60G extending in the longitudinal direction is formed on the base 60, and the measurement region K of the optical fiber group 20 is mounted in a flat state on the recess 60G in a dense and aligned state.

That is, the plurality of optical fiber bundles 20 _{1 to} 20 _N are arranged in a horizontal row in close contact on the bottom surface of the recess 60G that guides the fiber arrangement direction, and do not overlap in the vertical direction perpendicular to the arrangement direction. Note that the measurement region K of the optical fiber group 20 may be bound or bonded to be integrated.

  As shown in FIG. 3, the light transmission member 45 is disposed above the measurement region K of the optical fiber group 20 and attached to the base 60. The length of the measurement region K is defined according to the length of the light transmission member 45 in the longitudinal direction. Here, the light transmission member 45 is configured as a phosphor folder, and a plate-like fluorescent glass 70 is included therein.

  The fluorescent glass 70 has a size of a width D1 larger than the width of the measurement region K of the optical fiber group 20, and the measurement region K of the optical fiber group 20 is sandwiched between the fluorescent glass 70 and the base 60. The measurement area K is entirely covered. Leakage light that exits from the measurement region K to the outside of each optical fiber enters the incident surface 70 </ b> S of the fluorescent glass 70.

  The fluorescent glass 70 has a phosphor having an excitation spectrum peak near 400 nm and a peak wavelength of 610 nm. When leakage light having a wavelength of 405 nm is incident on the incident surface 70S, light having a peak wavelength of 610 nm is emitted from the phosphor. The phosphors are scattered in the fluorescent glass 70, and the leaked light strikes them. Therefore, light diffusion occurs together with the conversion from illumination light to fluorescence.

  Further, the light is scattered / reflected inside the fluorescent glass 70, and the light is reflected at the boundary surface (including the incident surface 70S) with the inside of the light transmission member 40. The light transmission member 40 is configured so that light other than leakage light does not reach the fluorescent glass 70. Thereby, the leakage light or fluorescence in the fluorescent glass is scattered and reflected, and diffused inside the glass.

  The photodetector 50 is disposed in contact with one side surface 70 </ b> D of the fluorescent glass 70. The photodetector 50 has a width D2 larger than the width D1 of the fluorescent glass 70, and has a size that covers the entire side surface 70D. The photodiodes are arranged in parallel in the horizontal direction so as to face the side surface 70D. The photodiode has twice the sensitivity around 610 nm than around 405 nm.

  As described above, the fluorescence of the fluorescent glass 70 is reflected at the boundary surface except the side surface 70D, scattered inside the glass, and finally reaches the photodiode of the photodetector 50 while diffusing. As a result, even if there is unevenness in the amount of light in the leaked light that enters the fluorescent glass 70 from the optical fiber group 20, the amount of light is made uniform when the photodiode is incident.

  FIG. 4 is a flowchart of light output adjustment executed in the control unit. Here, it is performed at predetermined time intervals.

  In the present embodiment, light output adjustment based on leakage light is performed during the drawing process. If it is determined that the pattern forming process is being performed on the substrate during the drawing process (S101), a luminance signal corresponding to the leaked light transmitted from the photodetector 50 is detected (S102).

Then, the input power is adjusted so that the luminance level is always constant (S103). The control unit 80 increases or decreases the input power by the same value or the same ratio with respect to each of the light sources 100 _{1 to} 100 _N.

  On the other hand, when the drawing process is completed, the light receiving unit 90 is moved to the table side. Then, based on the luminance signal detected by the light receiving unit 90, light output is performed (S105). When the exposure amount is changed by changing the sensitivity characteristic of the substrate S or the like, the input power is adjusted so that the target value matches the detected luminance signal.

  Thus, according to this embodiment, it is comprised so that leakage light may leak from each of the some optical fiber 20. FIG. That is, the measurement regions (non-shielded regions) K of the plurality of optical fibers 20 are closely arranged in one row in the recess 60G formed in the base 60. A light transmission member 45 provided with a fluorescent glass 70 is disposed above the measurement region K, and a photodetector 50 is disposed near the light transmission member 45.

  The fluorescent glass 70 absorbs leakage light and emits fluorescence. Incident leakage light and fluorescence enter the photodiode of the photodetector 50 while being reflected and scattered at the boundary surface and inside of the fluorescent glass 70. In the light output adjustment process, the input power to each light source is adjusted according to the detected light amount / luminance level so that the illuminance during the drawing process is constant.

  In general, optical fibers have optical loss due to Rayleigh scattering and non-uniform fiber structure. Part of the lost light that has not been absorbed inside the fiber is emitted outside the cladding. This leakage light is always generated when an optical fiber is used.

  In the present embodiment, since the output level of the illumination light is detected using this leakage light, there is no light loss caused by taking out a part of the illumination light using the optical device, and the drawing process is in progress. It is possible to detect the illuminance and light quantity.

  In addition, the fluorescent glass converts the spectral characteristics of light into spectral characteristics that match the sensitivity characteristics of the photodiode, and the light that has been diffused in the fluorescent glass to equalize the amount of light is incident on the photodetector 50. By doing so, accurate illuminance and light amount can be detected.

  In particular, the block-shaped fluorescent glass 70 is accommodated inside the light transmission member 45 so as to expose only the incident surface 70S, and the photodetector 50 is disposed on the side surface 70D. As a result, the leaked light is dispersed by reflection / scattering, and the uniformized light is guided to the photodetector 50.

  The light source may be a light source other than a laser such as a discharge lamp or LED. Moreover, the spectral characteristics of light are also arbitrary and may have a plurality of peak wavelengths. The material and propagation mode of the optical fiber are also arbitrary.

  About each optical fiber, the clad exposure area | region (non-shielding area | region) which does not interrupt | block leakage light only in a part of range may be formed, and you may make it coat | cover with a protective film other than that. In this case, it is preferable to form the non-shield region at the same position so that the fluorescent glass 70 can cover the entire non-shield region. Further, the unshielded region may be formed only for some of the optical fibers instead of all of the optical fibers.

  The fluorescent material is not limited to fluorescent glass, and fluorescent acrylic or the like may be used. Moreover, you may affix a sheet-like light-diffusion member, such as a film (polymer film etc.) which scatters light, with respect to the incident surface or boundary surface of fluorescent glass. In this case, since light is made uniform by entering the film, it is suitable for the case where a phosphor with insufficient diffusion is used.

  Or you may comprise so that a fluorescent substance, such as fluorescent glass and fluorescent acrylic, may not be used but leakage light may be guide | induced to a photodetector as it is. In this case, the photodiodes and photosensors of the photodetector are configured to have a relatively large sensitivity with respect to the vicinity of the peak wavelength of the leaked light. Alternatively, when the light output for drawing is sufficiently high with respect to the performance of the photodiode, there is no problem even if the photodiode has low sensitivity to the wavelength.

  When a glass member other than fluorescent glass is used, a ground glass-like surface is formed on the incident surface, so that light is scattered and reflected on the incident surface or inside thereof, so that the diffused light enters the photodetector. You can do it.

  In this embodiment, the input power to each light source is adjusted so that the output value of leakage light is kept constant, but the target exposure amount is set according to the sensitivity characteristics of the substrate or the operator's intention. It is also possible to determine the value and adjust the light amount so that the output value of the leaked light detected matches the target value.

  It is empirically known that the output of light emitted from the optical fiber group 20, that is, the output of light applied to the substrate S and the output of leakage light have substantially linearity. Therefore, it is possible to calculate in advance a ratio between the light amount of light emitted from the output end of the optical fiber group and the light amount of leaked light, and determine the target value based on the ratio.

  Specifically, the value obtained by multiplying the amount of light leaked per mm, the PD (photodiode) current ratio, and the number of fiber bundles is the total amount of light leaked, so the target value can be set based on the above-described ratio. Is possible. PD current ratio is the luminous efficiency of phosphor, light receiving length ratio between phosphor and PD, critical ratio of phosphor, emission (light receiving) area ratio between phosphor and PD, and light receiving sensitivity ratio between phosphor and PD. It is calculated by multiplying each.

  By adjusting the amount of light, a target value is set according to the sensitivity characteristics of the substrate to be drawn, and the light output is fed back so that it matches the target value immediately before the start of exposure or when changing the substrate type. It becomes possible to control.

  In the present embodiment, the light output is adjusted in the maskless exposure apparatus, but the present invention is also applicable to an exposure apparatus that uses other masks / reticles.

  Further, an optical fiber bundle in which a plurality of small-diameter optical fibers are bundled with respect to one light source is prepared, and a plurality of optical fiber bundle groups are arranged. In this case, it is possible to form an unshielded region that does not form a protective film from which leakage light is emitted, with respect to the optical fiber bundle.

DESCRIPTION OF SYMBOLS 10 Exposure apparatus 20 Several optical fiber 40 Light guide part 45 Light transmission member 50 Photodetector 60G Concave part (guide part)
70 Fluorescent glass 70D Side surface 70S Incident surface 80 Control unit 100 Light source unit K Measurement region (unshielded region)

Claims (14)

A plurality of optical fibers for transmitting illumination light from a light source unit comprising a plurality of light sources to an exposure head provided in an exposure apparatus, connected to the plurality of light sources and extending to the exposure head; On the outer peripheral surface of each optical fiber, a plurality of optical fibers in which an unshielded region from which leakage light is emitted is formed along the fiber axis direction;
A photodetector for receiving leakage light from the unshielded region;
A light guide disposed around the non-shielded region and guiding incident leaked light to the photodetector;
The unshielded areas, Ri region der leakage light is emitted to the outside so as not to cover the outer circumferential surface along the fiber axis direction in the shield member,
The unshielded region is formed in the entirety of each of the plurality of optical fibers,
The plurality of optical fibers extend as one from the middle, and are aligned in a flat shape in close contact with each other in a measurement region partitioned in a part thereof,
The exposure apparatus , wherein the light guide part guides leaked light leaking from the measurement region to the photodetector . The light guide portion has a plane of incidence of the size that covers the measuring area, the exposure apparatus according to claim 1, characterized in that it comprises an optical member having a rectangular parallelepiped shape, which are disposed above the measuring area. The exposure apparatus according to claim 2 , wherein the photodetector is disposed to face a side surface of the optical member. The light guide portion, the exposure device according to any one of claims 1 to 3, characterized in that it has a guide portion to align the flat shape closely while together the plurality of optical fibers in the measuring area. The exposure apparatus according to claim 4 , wherein the guide portion is a concave portion. Based on the luminance signal outputted from the photodetector, an exposure apparatus according to any one of claims 1 to 5, further comprising an output control unit for adjusting the output of the illumination light. The exposure apparatus according to claim 6 , wherein the output control unit adjusts the output so that the luminance signal is constant. The exposure apparatus according to claim 6 , wherein the output control unit adjusts the output so that the luminance signal matches a target value determined according to the sensitivity characteristic of the object to be exposed. An apparatus according to any one of claims 6-8 wherein the output control unit, characterized in that adjusting the output during the exposure process execution. 3. The exposure apparatus according to claim 2 , wherein the optical member has the incident surface on which leakage light is incident, and has a phosphor that emits fluorescence by the incident leakage light. The exposure apparatus according to claim 10 , wherein the phosphor is in a block shape and is accommodated in the optical member so that only the incident surface is exposed. A plurality of optical fiber bundles for transmitting illumination light from a light source unit composed of a plurality of light sources to an exposure head provided in an exposure apparatus, connected to the plurality of light sources and extending to the exposure head; A plurality of optical fiber bundles in which an unshielded region from which leakage light exits is formed along the fiber axis direction on the outer peripheral surface of each optical fiber bundle;
A photodetector for receiving leakage light from the unshielded region;
A light guide disposed around the non-shielded region and guiding incident leaked light to the photodetector;
The non-shield region is a region where leakage light is emitted to the outside in order not to cover the outer peripheral surface along the fiber axis direction with a shield member ,
The unshielded region is formed in the entirety of each of the plurality of optical fiber bundles,
The plurality of optical fiber bundles extend as one from the middle, and are aligned in a flat shape in close contact with each other in a measurement region partitioned in a part thereof,
The exposure apparatus , wherein the light guide part guides leaked light leaking from the measurement region to the photodetector . A plurality of optical fibers for transmitting illumination light from a light source unit comprising a plurality of light sources to an exposure head provided in an exposure apparatus, connected to the plurality of light sources and extending to the exposure head; On the outer peripheral surface of each optical fiber, there is an illumination monitor device of an exposure apparatus including a plurality of optical fibers in which a non-shield region from which leakage light is emitted is formed along the fiber axis direction,
The non-shield region is a region where leakage light is emitted to the outside in order not to cover the outer peripheral surface along the fiber axis direction with a shield member,
A photodetector for receiving leakage light from the unshielded region;
A light guide disposed around the non-shielded region and guiding incident leaked light to the photodetector ;
The unshielded region is formed in the entirety of each of the plurality of optical fibers,
The plurality of optical fibers extend as one from the middle, and are aligned in a flat shape in close contact with each other in a measurement region partitioned in a part thereof,
An illumination monitor apparatus for an exposure apparatus , wherein the light guide section guides leaked light leaking from the measurement region to the photodetector . A plurality of optical fiber bundles for transmitting illumination light from a light source unit composed of a plurality of light sources to an exposure head provided in an exposure apparatus, connected to the plurality of light sources and extending to the exposure head; An illumination monitor device of an exposure apparatus including a plurality of optical fiber bundles in which an unshielded region from which leakage light is emitted is formed along the fiber axis direction on the outer peripheral surface of each optical fiber bundle,
The non-shield region is a region where leakage light is emitted to the outside in order not to cover the outer peripheral surface along the fiber axis direction with a shield member,
A photodetector for receiving leakage light from the unshielded region;
A light guide disposed around the non-shielded region and guiding incident leaked light to the photodetector ;
The unshielded region is formed in the entirety of each of the plurality of optical fiber bundles,
The plurality of optical fiber bundles extend as one from the middle, and are aligned in a flat shape in close contact with each other in a measurement region partitioned in a part thereof,
An illumination monitor apparatus for an exposure apparatus , wherein the light guide section guides leaked light leaking from the measurement region to the photodetector .

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