Imprint apparatus, imprint method and method of manufacturing an article

The present invention provides an imprint apparatus including a control unit configured to perform detection process, wherein the detection process includes first process in which a detection optical system is caused to detect a mold-side mark in a state in which a substrate state is positioned such that a reference mark is located outside the field of view of the detection optical system, and second process in which the detection optical system is caused to detect the reference mark in a state in which the mold stage is positioned such that the mold-side mark is out of focus with respect to the detection optical system, and the substrate stage is positioned such that the reference mark is located inside the field of view of the detection optical system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an imprint apparatus, an imprint method, and a method of manufacturing an article.

2. Description of the Related Art

Demand for smaller semiconductor devices has increased, and in addition to conventional photolithography techniques, attention has been given to imprint technology according to which an imprint material (uncured resin) on a substrate is molded using a mold (die) so as to form a resin pattern on the substrate. Imprint technology makes it possible to form microstructures on the order of several nanometers on a substrate. Photocuring is known as one example of imprint technology.

With an imprint apparatus that employs photocuring, first, photocurable resin (e.g., ultraviolet curable resin) is applied to a shot region on a substrate, and this resin is molded using a mold. The resin is then cured by being irradiated with light (e.g., ultraviolet light), and the mold is then separated (detached), and thus a resin pattern is formed on the substrate.

This type of imprint apparatus is disclosed in Japanese Patent No. 4478424, and includes a substrate stage for positioning a substrate, an alignment substrate that is arranged on the substrate stage and includes a reference alignment mark formed thereon, and an alignment detection system, for example. The alignment detection system detects misalignment between the reference alignment mark and an alignment mark formed on the mold, for example. Alignment of the mold and the substrate can be performed based on the detection results from the alignment detection system.

However, in conventional imprint apparatuses, when detecting misalignment between the reference alignment mark and the alignment mark formed on the mold with the alignment detection system, it is necessary to bring the mold and the alignment substrate close together (i.e., reduce the gap between the mold and the alignment substrate) when detecting the alignment marks. Accordingly, if a foreign particle exists on the alignment substrate, there is a possibility of the mold becoming damaged due to coming into contact with the foreign particle (i.e., the foreign particle is sandwiched between the mold and the alignment substrate).

SUMMARY OF THE INVENTION

The present invention provides technology advantageous to the detection of a mold-side mark provided on a mold and a reference mark provided on a substrate stage.

According to one aspect of the present invention, there is provided an imprint apparatus that performs imprint process for forming a pattern on an imprint material on a substrate using a mold, the imprint apparatus including a mold stage configured to hold the mold, a substrate stage configured to hold the substrate, a detection optical system configured to detect a mold-side mark provided on the mold and a reference mark arranged on the substrate stage, a control unit configured to perform detection process by controlling positioning of the mold stage and the substrate stage and detection performed by the detection optical system, and a processing unit configured to perform the imprint process based on a detection result from the detection optical system, wherein the detection process includes first detection process in which the detection optical system is caused to detect the mold-side mark in a state in which the substrate stage is positioned such that the reference mark is located outside the field of view of the detection optical system, and second detection process in which the detection optical system is caused to detect the reference mark in a state in which the mold stage is positioned such that the mold-side mark is out of focus with respect to the detection optical system, and the substrate stage is positioned such that the reference mark is located inside the field of view of the detection optical system.

Further aspects of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

DESCRIPTION OF THE EMBODIMENTS

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Note that the same reference numerals denote the same members throughout the drawings, and a repetitive description thereof will not be given.

First Embodiment

FIG. 1is a schematic diagram showing the configuration of an imprint apparatus1according to an aspect of the present invention. The imprint apparatus1is a lithography apparatus that performs imprint process for using a mold (die) to form a pattern in an imprint material (uncured resin) on a substrate. As shown inFIG. 1, the imprint apparatus1includes an irradiation unit2, a detection optical system3, a mold stage4, a substrate stage5, a resin supply mechanism6, and a control unit19. In the following, the X axis direction and the Y axis direction are directions that are orthogonal to each other in a plane parallel to the substrate and the mold, and the Z axis direction is the direction that is perpendicular to the X axis and the Y axis.

The irradiation unit2includes a light source and a plurality of optical elements, and emits light for curing resin9on a substrate8in a state in which the resin9is in contact with a mold7that includes a mesa region provided with a concave-convex pattern7a(relief pattern) that corresponds to the pattern (e.g., circuit pattern) to be formed in the substrate8. The irradiation unit2uniformly irradiates the mold7, specifically the mesa region (irradiated face) in which the concave-convex pattern7ais formed, with light that is emitted from the light source with a predetermined shape.

The irradiation region (irradiation range) of the light from the irradiation unit2need only be, for example, a region with roughly the same area as the mesa region in which the concave-convex pattern7ais formed, or a region with a slightly larger area than the mesa region in which the concave-convex pattern7ais formed. This is for reducing the irradiation region of the light from the irradiation unit2to the minimum necessary size in order to suppress misalignment and distortion in the pattern to be transferred to the resin9due to expansion of the mold7and the substrate8caused by heat from irradiation with light. This also for suppressing abnormalities in the operation of the resin supply mechanism6caused by light reflected by the substrate8or the like reaching the resin supply mechanism6and curing residual resin9in the resin ejection opening of the resin supply mechanism6.

A high-pressure mercury lamp, various excimer lamps, an excimer laser, a light emitting diode, or the like can be used as the light source of the irradiation unit2. Since ultraviolet curable resin, which is cured when irradiated with ultraviolet light, is used in the present embodiment, ultraviolet light is emitted from the light source of the irradiation unit2. Note that the light (e.g., wavelength thereof) to be emitted from the light source of the irradiation unit2is determined according to the type of resin9.

The detection optical system3detects various marks in order to relatively align the mold7and the substrate8. For example, the detection optical system3optically detects an alignment mark10provided on the mold7(a mold-side mark) and an alignment mark11provided on the substrate8. This makes it possible to obtain the relative positions of the mold7(alignment mark10) and the substrate8(alignment mark11). The detection optical system3is arranged such that the optical axis thereof is perpendicular to the mold7or the substrate8. Also, the detection optical system3is arranged so as to be capable of moving in the X axis direction and the Y axis direction according to the position of a mark such as an alignment mark. Furthermore, the detection optical system3is arranged so as to be capable of moving in the Z axis direction as well, in order to match the focal plane (focal point) with the position of a mark such as an alignment mark.

The mold stage4includes a mold chuck that holds the mold7by attraction using vacuum suction force or electrostatic force. The mold stage4includes a mold driving mechanism for pressing the mold7against resin9that has been supplied to the substrate8. The mold driving mechanism moves the mold stage4(the mold7) in the Z axis direction. Also, a mold shape correction unit that corrects distortion of the concave-convex pattern7a(the shape of the mold7) by deforming the mold7in the X axis direction and the Y axis direction is arranged on the mold stage4. The mold shape correction unit corrects the shape of the mold7based on the relative positions of the mold7and the substrate8under control of the control unit19.

The substrate stage5includes a substrate chuck that holds the substrate8using vacuum suction force or electrostatic force. The substrate stage5includes a substrate driving mechanism for moving the substrate stage5(the substrate8) in the X axis direction and the Y axis direction (for enabling movement in the XY plane).

An alignment substrate (reference plate)12is arranged on the substrate stage5. An alignment mark (reference mark)13is provided on the alignment substrate12, and the alignment mark13can be positioned in the detectable region (field of view) of the detection optical system3by moving the substrate stage5. Accordingly, the detection optical system3can detect the alignment mark13provided on the alignment substrate12as well. This makes it possible to align the mold7and the alignment substrate12, that is to say align the mold7and the substrate stage5.

In the present embodiment, an imprint operation (operation for bringing the mold7into contact with the resin9) and a mold separation operation (operation for detaching the mold7from the resin9) performed by the imprint apparatus1are realized by moving the mold stage4(the mold7) in the Z axis direction. Note that the imprint operation and the mold separation operation may be realized by moving the substrate stage5(the substrate8) in the Z axis direction or moving both the mold stage4and the substrate stage5in the Z axis direction.

The resin supply mechanism6(dispenser) includes a nozzle that includes a resin ejection opening, for example, and supplies (applies) resin9to the substrate8. The resin supply mechanism6does not need to be arranged inside the imprint apparatus1, and may be arranged outside the imprint apparatus1. For example, a configuration is possible in which a substrate8to which resin9has been applied in advance by an external resin supply mechanism is conveyed to the imprint apparatus1. According to this configuration, the step for supplying the resin9inside the imprint apparatus1is eliminated, thus making it possible to reduce the time required for process performed by the imprint apparatus1(imprint process). Also, the need for the resin supply mechanism6is eliminated, thus making it possible to suppress the overall cost of the imprint apparatus1.

The surface of the mold7that opposes the substrate8includes a mesa region in which the concave-convex pattern7ais formed, and an off-mesa region that surrounds the mesa region. In order for light from the irradiation unit2to pass through the mold7and irradiate the resin9, the mold7is constituted by a material that transmits light from the irradiation unit2, such as quartz. In the mold7, the off-mesa region is the region in which the concave-convex pattern7ais not formed, and the mesa region is structured so as to protrude from the off-mesa region toward the substrate8. Accordingly, only the mesa region of the mold7comes into contact with the resin9on the substrate8in the imprint operation.

The substrate8includes a glass plate, a wafer made of single crystal silicon, or the like. Resin9is supplied to the upper surface of the substrate8by the resin supply mechanism6. Although the resin9is ultraviolet curable resin that is cured when irradiated with ultraviolet light in the present embodiment, the type of resin9is selected according to the type of semiconductor device, for example.

The control unit19includes a CPU, a memory, and the like, and performs overall control of the imprint apparatus1. The control unit19performs imprint process (functions as a processing unit) for forming a pattern on a substrate by controlling units of the imprint apparatus1. Also, as will be described later, the control unit19performs detection process by controlling the positioning of the mold stage4and the substrate stage5and detection by the detection optical system3in the alignment of the mold7and the substrate8and the alignment of the mold7and the alignment substrate12. The control unit19furthermore controls the substrate stage5and the mold shape correction unit based on the relative positions of the mold7and the substrate8.

The following describes imprint process performed by the imprint apparatus1. First, the substrate8is conveyed to the imprint apparatus1by a substrate conveying system, and the substrate8is held on the substrate stage5. Next, the substrate stage5is moved such that the substrate8held on the substrate stage5is located at a resin supply position of the resin supply mechanism6. The resin supply mechanism6then supplies resin9to a predetermined shot region on the substrate8. Next, the substrate stage5is moved such that the shot region (the substrate8) to which the resin9was supplied is located directly under the mold7. The mold stage4holding the mold7is then moved in the Z axis direction (vertically downward), and the resin9supplied to the substrate8and the mold7(the concave-convex pattern7a) are brought into contact (imprint operation). At this time, the resin9flows over the concave-convex pattern7aon the mold7and fills the spaces in the concave-convex pattern7a.

Next, while the mold7and the resin9are in contact with each other, the detection optical system3detects the alignment mark10provided on the mold7and the alignment mark11provided on the substrate8. The mold7and the substrate8are then aligned by moving the substrate stage5in the X axis direction and the Y axis direction based on the detection result from the detection optical system3. Also, the mold shape correction unit arranged on the mold stage4performs shape correction such as magnification correction on the mold7. When the mold7and the substrate8have been aligned, and magnification correction has been sufficiently performed on the mold7, the resin9is irradiated with light from the irradiation unit2so as to cure the resin9. At this time, the detection optical system3is moved out of the optical path so as to prevent the detection optical system3from blocking the optical path of the light from the irradiation unit2. Next, the mold7is detached from the cured resin9on the substrate8by moving the mold stage4holding the mold7in the Z axis direction (vertically upward) so as to widen the gap between the substrate8and the mold7. Accordingly, the concave-convex pattern7aon the mold7is transferred to the substrate8(i.e., a pattern corresponding to the concave-convex pattern7ais formed in the resin9).

FIG. 2is a schematic diagram showing an example of the configuration of the detection optical system3. The detection optical system3includes a detection system21and an illumination system22. The detection system21and the illumination system22are configured such that a portion of the optical members constituting them is common between them.

The illumination system22reflects light from the light source23with a prism24, guides the light onto the same optical axis as the detection system21, and illuminates the alignment marks10and11with this light. A halogen lamp, an LED, or the like can be used as the light source23. The light source23emits light having a different wavelength from the wavelength of the light emitted from the irradiation unit2. Since ultraviolet light is used as the light emitted from the irradiation unit2in the present embodiment, visible light or infrared light is used as the light emitted from the light source23.

The prism24is arranged at the pupil plane of the detection system21and the illumination system22, or in the vicinity thereof. The alignment marks10and11are each constituted by a diffraction grating. A pattern (moiré stripes) formed by diffracted light from the alignment marks10and11illuminated by the illumination system22is formed by the detection system21on an imaging element25constituted by a CCD sensor or a CMOS sensor.

At its affixed faces, the prism24includes a reflection film24afor reflecting light from the portion surrounding the pupil plane of the illumination system22. The reflection film24afunctions as an aperture stop that defines the light intensity distribution of the pupil plane of the illumination system22. Also, the reflection film24afunctions as an aperture stop that defines the size (numerical aperture) of the pupil of the detection system21. In this way, the reflection film24adefines the numerical aperture (detection pupil) NAo of the detection optical system3.

The prism24can be replaced with a half prism that includes a semipermeable film at its affixed faces, or an optical element other than a prism, such as a plate-shaped optical element that includes a reflection film on its upper surface. Also, in order to change the shape of the pupil of the detection system21or the illumination system22, a configuration is possible in which the prism24can be switched with another prism (a prism whose reflection film at its affixed faces includes a differently shaped aperture) by a switching mechanism such as a turret or a slide mechanism. In other words, the detection optical system3may include a switching mechanism that functions as a first change unit for changing the numerical aperture of the detection system21and a second change unit for changing the light intensity distribution of the pupil plane of the illumination system22.

Also, the arranged position of the prism24is not limited to the pupil plane of the detection system21and the illumination system22, or the vicinity thereof. Furthermore, the aperture stop that defines the light intensity distribution of the pupil plane of the illumination system22does not need to be arranged in the prism24. For example, as shown inFIG. 3, an aperture stop26may be arranged in the pupil plane of the detection system21, and an aperture stop27may be arranged in the pupil plane of the illumination system22. The aperture stop26defines the size of the pupil of the detection system21, and the aperture stop27defines the light intensity distribution of the pupil plane of the illumination system22. In this case, a half prism that includes a semipermeable film at its affixed faces or the like is used as the prism24. Furthermore, the aperture stop26and the aperture stop27may each be configured so as to be able to be switched with another aperture stop (an aperture stop having a differently shaped aperture) using a switching mechanism such as a turret.

The following describes details of the alignment mark10provided on the mold7and the alignment mark11provided on the substrate8. A rough alignment mark is provided in the vicinity of the alignment mark10, and the detection optical system3can detect this rough alignment mark at the same time as the alignment mark10. Also, a rough alignment mark is provided in the vicinity of the alignment mark11, and the detection optical system3can detect this rough alignment mark at the same time as the alignment mark11. Here, the alignment marks10and11are constituted by diffraction gratings having mutually different pitches. Diffracted light from the alignment marks10and11therefore forms moiré stripes whose periods are different according to the difference between the pitches of the diffraction gratings. Due to the properties of the moiré stripes formed by diffracted light from the alignment marks10and11, the detection optical system3cannot detect relative positional misalignment greater than or equal to one pitch of the diffraction gratings (several microns). In view of this, it is necessary to specify the positions of the mold7and the substrate8by detecting the rough alignment marks, and move the substrate stage5such that the relative positional misalignment of the mold7and the substrate8is within one pitch of the diffraction gratings. The rough alignment marks are used to specify rougher positions than the alignment marks10and11.

A rough alignment mark is provided in the vicinity of the alignment mark13on the alignment substrate12as well for similar reasons. The rough alignment mark provided in the vicinity of the alignment mark13may have a different phase from the alignment substrate12even while having an uneven shape. The detection optical system3can detect scattered light from the rough alignment mark provided in the vicinity of the alignment mark13.

The following is a specific description of an issue regarding alignment mark detection in conventional technology.FIGS. 4A and 4Bare diagrams for describing alignment of the mold7and the alignment substrate12according to conventional technology. Note that a similar issue exists even when the alignment substrate12is replaced with the substrate8.

In conventional technology, as shown inFIG. 4A, the mold7(the mold stage4) is moved toward the focal plane16of the detection optical system3(i.e., in the focusing direction) in order to bring the mold7and the alignment substrate12close together. While the mold7and the alignment substrate12are close together with a gap on the order of microns, the alignment mark10provided on the mold7and the alignment mark13provided on the alignment substrate12are detected by the detection optical system3. In this way, the mold7and the alignment substrate12are brought close together in conventional technology, and therefore if a foreign particle14exists on the alignment substrate12, there is a possibility of the mold7coming into contact with the foreign particle14, and the mold7becoming damaged. This is a cause for difficulty in the alignment of the mold7and the alignment substrate12.

On the other hand, as shown inFIG. 4B, a case is conceivable in which the alignment mark10provided on the mold7and the alignment mark13provided on the alignment substrate12are detected by the detection optical system3while the mold7and the alignment substrate12are separated from each other. In this case, light (alignment light)15from the detection optical system3passes through an edge region that includes a step portion of the mold7, that is to say the step (boundary) between the mesa region and the off-mesa region, and therefore the detection light amount corresponding to the alignment mark13decreases. This is a cause for a reduction in alignment mark detection precision. Also, either the alignment mark10or the alignment mark13(inFIG. 4B, the alignment mark10) will be detected while being separated from the focal plane16of the detection optical system3. This is also a cause for a reduction in alignment mark detection precision, and there is a possibility of not being able to detect this one of the alignment marks.

The following describes the reduction in the detection light amount corresponding to an alignment mark caused by the step of the mold7.FIG. 5Ais a diagram showing a model in a two-dimensional wave optics simulation. In the present embodiment, the alignment substrate12and the mold7are constituted by quartz (SiO2). The mesa region32of the mold7protrudes 30 μm from the off-mesa region35. An edge region31that includes the step between the mesa region32and the off-mesa region35is modeled as a region having a curvature radius of 30 μm.FIG. 5Bis an enlarged view of the mesa region32. The concave-convex pattern7ahaving a level difference of 50 nm and a pitch of 100 nm is formed in the mesa region32.FIG. 5Cis an enlarged view of the alignment mark13. The alignment mark13is formed by Cr having a thickness of 100 nm.

Envisioning the case where the alignment mark13provided on the alignment substrate12is located below the mesa region32, the edge region31, and the off-mesa region35, the alignment mark13was moved at 10 μm intervals in the simulation. As shown inFIG. 5A, a center (an edge center)31aof the edge region31in the X axis direction is located between the edge of the mesa region32and the edge of the off-mesa region35. The two-dimensional wave optics simulation was performed in order to investigate how the waveform obtained by detecting the alignment mark13with the detection optical system3changes according to the position of the alignment mark13relative to the edge center31a(±0 μm at the position shown inFIG. 5A). In the model shown inFIG. 5A, alignment light15entered, and scattered light from the alignment mark13was detected by the detection optical system3. Note that the gap between the mesa region32of the mold7and the alignment substrate12(gap distance) was 100 μm.

The following describes illumination conditions and detection conditions with respect to the alignment mark13. The detection optical system3is optimized for detecting the alignment marks10and11(the moiré stripes formed by diffracted light from them) that need to be detected with higher precision than the alignment mark13.FIG. 6is a schematic diagram showing an example of the configuration of the pupil plane of the detection optical system3. IL1, IL2, IL3, and IL4used in reference toFIG. 6indicate poles (effective light sources) where the numerical aperture (NA) is NAp and the distance from the pupil center is NAil. The effective light sources including the poles IL1to IL4shown inFIG. 6are set as illumination conditions with respect to the alignment mark13, and scattered light from the alignment mark13is detected by the detection pupil of the detection optical system3whose numerical aperture is indicated by NAo. In the simulation that was performed in the present embodiment, the NAo was 0.1, the NAp was 0.05, the NAil was 0.2, and the wavelength of the alignment light15was 650 nm.

Expression (1) below obtains the spread amount of the alignment light15when the alignment light15has traveled a distance equal to the gap between the alignment substrate12and the off-mesa region35of the mold7.
Spread amount of alignment light 15=NAo×(gap between mesa region 32 of mold 7 and alignment substrate 12+protruding amount of mesa region 32 of mold 7)  (1)

In the simulation, the NAo was 0.1, the protruding amount of the mesa region32of the mold7was 30 μm, and the gap between the mesa region32of the mold7and the alignment substrate12was 100 μm, and therefore the spread amount of the alignment light15was 13 μm. The detection optical system3can detect the alignment mark13with high precision if the scattered light from the alignment mark13and the scattered light from the edge region31of the mold7do not overlap.

FIG. 7is a diagram showing results of a simulation performed with the model shown inFIGS. 5A to 5C and 6(waveforms obtained by detecting the alignment mark13with the detection optical system3). InFIG. 7, the position of the alignment mark13relative to the edge center31aof the edge region31(range of ±30 μm in the X axis direction from the edge center31a) is plotted on the horizontal axis, and the light amount when the alignment mark13was detected by the detection optical system3is plotted on the vertical axis. It can be understood fromFIG. 7that scattered light from the alignment mark13was detected in the off-mesa region35and the mesa region32separated from the edge center31aof the edge region31.

In the case where the gap between the mesa region32of the mold7and the alignment substrate12is 100 μm, the spread amount of the alignment light15is 13 μm as described above (based on Expression (1)). Accordingly, if the alignment mark13provided on the alignment substrate12is located at a position 13 μm or less away from the edge region31of the mold7(a range of ±15 μm from the edge center31a), detection is influenced by scattering in the edge region31. For this reason, it is thought that alignment mark13imaging performance decreases in the vicinity of the edge center31aof the edge region31of the mold7as shown inFIG. 7.

Also, the alignment light15undergoes scattering in the edge region31of the mold7also when the alignment mark13provided on the alignment substrate12is illuminated. Accordingly, the light amount decreases in the portion corresponding to the shadow of the edge region31of the mold7, and therefore if the alignment mark13is located underneath this portion, the light amount of the alignment light15illuminating the alignment mark13decreases. Accordingly, the light amount of scattered light from the alignment mark13also decreases, and this is thought to make detection of the alignment mark13difficult.

In the case where the alignment mark13is located at a position −10 μm from the edge center31aof the edge region31of the mold7, it is thought that scattered light from the alignment mark13is influenced by scattering caused by the edge region31. However, in the simulation, the alignment mark13(a peak corresponding thereto) was detected as shown inFIG. 7. This is thought to be due to the fact that the illumination condition with respect to the alignment mark13is oblique incident illumination (11.5 degrees), and at a position −10 μm from the edge center31aof the edge region31of the mold7, the influence of scattering caused by the edge region31on the alignment light15is small.

Also, the light amount of light detected by the detection optical system3(scattered light from the alignment mark13) changes according to the wavelength of the alignment light15and the thickness (step amount) of the alignment mark13as well. Accordingly, the light amount of the scattered light from the alignment mark13detected by the detection optical system3can be adjusted by changing the wavelength of the alignment light15.

The following describes alignment of the mold7and the alignment substrate12according to the present embodiment with reference toFIGS. 8A and 8B. In the alignment of the mold7and the alignment substrate12, as described above, the detection optical system3needs to perform detection process for detecting the alignment mark10provided on the mold7and the alignment mark13provided on the alignment substrate12. This detection process is performed by the control unit19controlling the positioning of the mold stage4and the substrate stage5and the detection performed by the detection optical system3.

In the present embodiment, first, the substrate stage5is moved so as to move the alignment substrate12out of the way as shown inFIG. 8A. Due to moving the alignment substrate12out of the way, the alignment mark13(reference mark) can be positioned outside the field of view of the detection optical system3. The direction in which the substrate stage5is moved may be a horizontal direction (the X axis direction or the Y axis direction), or the vertical direction (the Z axis direction). Also, the mold stage4is positioned such that mold7(the alignment mark10provided thereon) is located in the focal plane16of the detection optical system3(i.e., the mold stage4is moved so as to bring the mold7close to the focal plane16). Since the alignment substrate12has been moved out of the way at this time, even if a foreign particle exists on the alignment substrate12, the mold7will not become damaged. In this state, the alignment mark10provided on the mold7is detected by the detection optical system3and acquired as a position relative to the detection optical system3(the imaging element25). In this way, the detection optical system3is caused to detect the alignment mark10in the state in which the substrate stage5has been positioned such that the alignment mark13is located outward of a field of view47(i.e., outside the field of view) of the detection optical system3(first detection process).

Next, as shown inFIG. 8B, the mold stage4is moved in the vertical direction so as to move the mold7out of the way. Here, the mold stage4(the mold7) is moved in the vertical direction by a distance longer than the distance corresponding to the dimensions of a foreign particle (envisioned foreign particle) that exists on the alignment substrate12or the alignment mark13. Also, the substrate stage5is positioned such that the alignment substrate12(the alignment mark13provided thereon) is located in the focal plane16of the detection optical system3(i.e., the mold stage4is moved so as to bring the alignment substrate12close to the focal plane16). In this state, the alignment mark13provided on the alignment substrate12is detected by the detection optical system3and acquired as a position relative to the detection optical system3(the imaging element25). In this way, the mold stage4is positioned such that the alignment mark10is out of focus with respect to the detection optical system3, and the substrate stage5is positioned such that the alignment mark13is located inward of the field of view47(in the field of view) of the detection optical system3. The detection optical system3is then caused to detect the alignment mark13in this state (second detection process).

In the present embodiment, the detection optical system3is fixed at the same position (i.e., the detection optical system3is not moved) in the first detection process shown inFIG. 8Aand the second detection process shown inFIG. 8B. This therefore makes it possible to obtain the relative positions of the alignment mark10detected in the first detection process and the alignment mark13detected in the second detection process. Also, since error does not occur due to movement of the detection optical system3, the alignment marks10and13can be detected with high precision. Note that even in the case where the detection optical system3is moved between the first detection process and the second detection process, it is possible to obtain the relative positions of the alignment mark10and the alignment mark13if the amount of movement is obtained, and thus there is no need to fix the detection optical system3at the same position.

Also, when performing the second detection process, the substrate stage5is positioned such that light (alignment light15) from the alignment mark13passes through the region of the mold7other than the edge region that includes the step between the mesa region and the off-mesa region of the mold7. Specifically, in the present embodiment, as shown inFIG. 8B, the substrate stage5is positioned such that light from the alignment mark13passes through the off-mesa region of the mold7. Accordingly, there is no influence of dispersion by the edge region of the mold7, and the alignment mark13imaging performance does not decrease. Note that when performing the second detection process, the substrate stage5may be positioned such that light from the alignment mark13passes through the mesa region of the mold7. Note that in this case, the substrate stage5needs to be positioned such that the light passes through a region of the mesa region of the mold7in which the pitch of the concave-convex pattern7ais lower than or equal to the wavelength of the light (alignment light15) from the alignment mark13.

The field of view of the detection optical system3can be changed using the magnification ratio of the detection system21and the size of the imaging element25, and is set to 500 μm2in the present embodiment. The spread amount of the alignment light15is obtained using Expression (1), and is 13 μm to 23 μm in the case where the NAo is 0.1, the gap between the mesa region of the mold7and the alignment substrate12is 100 μm to 200 μm, and the protruding amount of the mesa region32of the mold7is 30 μm, for example. Accordingly, within the field of view of the detection optical system3, the alignment mark10provided on the mold7and the alignment mark13provided on the alignment substrate12can be sufficiently detected using the position of the detection optical system3(the imaging element25) as a reference.

FIG. 9is a diagram in which the positional relationship between the mold stage4and the substrate stage5in first detection process is shown from the Z axis direction. The mold stage4(the mold7) and the substrate stage5(the substrate8and the alignment substrate12) move independently from each other. In the first detection process, the substrate stage5is moved out of the way to a position of not interfering with the mold stage4and the mold7, the alignment mark10provided on the mold7is arranged in the field of view47of the detection optical system3, and then the alignment mark10is detected by the detection optical system3. Then, in the second detection process, the mold stage4(the mold7) is moved in the vertical direction, thereafter the substrate stage5is moved so as to arrange the alignment mark13in the field of view47of the detection optical system3, and then the alignment mark13is detected by the detection optical system3.

InFIG. 9, one alignment mark13is provided on the alignment substrate12, and one alignment mark10is provided on the mold7. Note that a plurality of alignment marks13may be provided on the alignment substrate12, and a plurality of alignment marks10may be provided on the mold7. In this case, the imprint apparatus1includes a plurality of detection optical systems3, and these detection optical systems3detect corresponding alignment marks13and10. This therefore makes it possible to obtain error such as a shift component and a rotation component between the alignment marks13provided on the alignment substrate12and the alignment marks10provided on the mold7. Accordingly, it is possible to obtain the shape of the mold7based on the detection results from the plurality of detection optical systems3, and correct the shape of the mold7using the mold shape correction unit arranged on the mold stage4based on the obtained shape of the mold7.

FIGS. 10A and 10Bare diagrams showing examples of the configuration of the mold shape correction unit40arranged on the mold stage4. The mold shape correction unit40is constituted with a spring structure arranged (sandwiched) between the mold7and the mold stage4as shown inFIG. 10A, for example. The mold shape correction unit40shown inFIG. 10Acan deform the shape of the mold7by changing the intensity of the clamping of the spring structure. Also, the mold shape correction unit40may be constituted with a plurality of spring structures arranged (sandwiched) between the mold7and the mold stage4as shown inFIG. 10B, for example. The mold shape correction units40shown inFIG. 10Bcan deform the shape of the mold7with higher precision by changing the intensity of the sandwiching of the respective spring structures.

Also, although the second detection process is performed after performing the first detection process in the present embodiment, there is no influence on the precision of detection of the alignment marks10and13even if the first detection process is performed after performing the second detection process. Accordingly, it may be possible to select one of multiple detection modes in which detection process is performed, including a mode of performing the second detection process after performing the first detection process, and a mode of performing the first detection process after performing the second detection process. This selection need only be made with consideration given to throughput, for example.

In this way, according to the imprint apparatus1, it is possible to highly precisely align the mold7and the alignment substrate12without damaging the mold7. Accordingly, the imprint apparatus1enables highly precisely aligning the mold7and the substrate8, and makes it possible for articles such as high-quality semiconductor devices to be provided economically and with high throughput.

Second Embodiment

FIG. 11is a schematic diagram showing another configuration of the imprint apparatus1according to an aspect of the present invention. As shown inFIG. 11, in the present embodiment, the imprint apparatus1further includes a projection optical system41. The projection optical system41includes a dichroic mirror42, and is arranged above the mold7, specifically between the mold7and the detection optical system3. The projection optical system41projects light from the irradiation unit2onto the substrate. Also, the projection optical system41projects images of the alignment mark10provided on the mold7, the alignment mark11provided on the substrate8, and the alignment mark13provided on the alignment substrate12onto the projection plane. Here, the projection plane is provided between the detection optical system3and the projection optical system41, and the detection optical system3detects the alignment marks10,11, and13projected on the projection plane.

The dichroic mirror42is an optical member that selectively reflects or transmits light according to the wavelength. In the present embodiment, the dichroic mirror42is configured so as to reflect light for curing the resin9on the substrate8(ultraviolet light from the irradiation unit2), and transmit alignment light15corresponding to the alignment marks10,11, and13(visible light or infrared light from the detection optical system3).

The detection optical system3detects the alignment marks10,11, and13via the projection optical system41that includes the dichroic mirror42(i.e., detects images of moiré stripes projected on the projection plane of the projection optical system41). In other words, the detection optical system3detects the relative positions of the mold7and the substrate8, the relative positions of the mold7and the alignment substrate12, and the like via the projection optical system41.

The irradiation unit2irradiates the dichroic mirror42with ultraviolet light from beside the projection optical system41. The ultraviolet light reflected by the dichroic mirror42passes through the projection optical system41, and the concave-convex pattern7aon the mold7is irradiated with this ultraviolet light evenly with a predetermined shape. Accordingly, in the projection optical system41, the optical members arranged between the dichroic mirror42and the mold7are constituted by quartz or the like that transmits ultraviolet light.

According to this configuration, in the present embodiment, even when using the detection optical system3arranged such that the optical axis is perpendicular to the mold7and the substrate8, the detection optical system3does not need to be moved out of the way when emitting ultraviolet light from the irradiation unit2. This eliminates the need for time to move the detection optical system3out of the way when curing the resin9on the substrate8, thus making it possible to improve the throughput of the imprint apparatus1.

Note that the dichroic mirror42may be configured so as to transmit light for curing the resin9on the substrate8(ultraviolet light), and reflect alignment light15corresponding to the alignment marks10,11, and13(visible light or infrared light). In this case, the optical path of the projection optical system41is bent by the dichroic mirror42, and the positional relationship between the irradiation unit2and the detection optical system3is the opposite of that shown inFIG. 11. In other words, the irradiation unit2is arranged above the mold7.

Also, in the present embodiment, bending mirrors48are arranged in the vicinity of the projection plane of the projection optical system41. Light from the detection optical system3and diffracted light from the alignment marks10,11, and13are bent by the bending mirrors48to a direction parallel with the XY plane at a position at which the luminous flux diameter is small. Accordingly, even in the case where the diameter of the projection optical system41is increased by increasing the size of the projection optical system41and the numerical aperture of the detection optical system3in order to increase the width of the detected wavelength range and the illumination light amount, the detection optical system3can be arranged so as to be adjacent in the X axis direction and the Y axis direction. This therefore makes it possible to raise the degree of freedom in the layout of the alignment marks10,11, and13.

In the case where the projection optical system41is not provided, the detection optical system3needs to be arranged at a position separated from the mold7, or the diameter needs to be reduced, in order to avoid interfering with the mold shape correction unit and the mold driving mechanism included in the mold stage4. If the detection optical system3is arranged at a position separated from the mold7, the diameter of luminous flux increases, and therefore the detection optical system3increases in size, the cost of the detection optical system3rises, and the limitations on the arrangement of the alignment marks10,11, and13become stricter. On the other hand, if the diameter of the detection optical system3decreases, the numerical aperture of the detection optical system3decreases, thus inviting a decrease in the amount of illumination light that illuminates the alignment marks and a narrower range of detected wavelengths, and reducing the precision of detection of the alignment marks10,11, and13.

In the present embodiment, the provision of the projection optical system41makes it possible to avoid interference between the detection optical system3and the mold driving mechanism and the mold shape correction unit and avoid limitations on the arrangement of the alignment marks10,11, and13, and to increase the numerical aperture of the detection optical system3. Accordingly, in the present embodiment, it is possible to widen the detected wavelength range of the detection optical system3and increase the illumination light amount, and it is possible to highly precisely detect the alignment marks10,11, and13.

With the imprint apparatus shown inFIG. 11as well, similarly to the first embodiment (seeFIGS. 8A and 8B), the mold7and the alignment substrate12can be aligned highly precisely. The following describes the gap between the mesa region32of the mold7and the alignment substrate12when detecting light from the alignment mark13that has passed through the off-mesa region of the mold7. If the numerical aperture NAo of the detection optical system3is sufficiently small, the spread amount of the alignment light15is obtained by Expression (1) as described above. For example, if the NAo is 0.1, and the gap between the mesa region32of the mold7and the alignment substrate12is 200 μm, the spread amount of the alignment light15is 23 μm based on Expression (1). Accordingly, if the gap between the edge center of the edge region of the mold7and the alignment mark13in the X axis direction is set to 23 μm or more, the alignment light15is not influenced by diffusion by the edge region of the mold7, thus making it possible to avoid a reduction in the alignment mark13imaging performance.

Note that in this case, the effective diameter of the common optical path of the detection system21and the illumination system22of the detection optical system3needs to be increased according to the position of the alignment mark13. As shown inFIG. 12, in the case of detecting light from the alignment mark13(alignment light15) that has traveled inward of the mesa region of the mold7, the width of the alignment light15when passing through the projection optical system41is schematically indicated by a width43. Also, in the case of detecting light from the alignment mark13that has passed through the off-mesa region of the mold7, the width of the alignment light15when passing through the projection optical system41is schematically indicated by a width44. Accordingly, in order to detect light from the alignment mark13that has passed through the off-mesa region of the mold7, the effective diameter of the projection optical system41needs to be increased by an amount corresponding to the gap between the edge center of the edge region of the mold7and the alignment mark13. The amount of increase in the effective diameter of the projection optical system41is determined according to the position of the alignment mark13and the spread amount of the alignment light15obtained by Expression (1).

FIG. 13is a diagram in which the positional relationship between the alignment mark10provided on the mold7and the alignment mark13provided on the alignment substrate12in second detection process is shown from the Z axis direction.FIG. 13shows the alignment mark10provided on the mold7, the alignment mark13provided on the alignment substrate12, the effective diameter45of the projection optical system41, the step (edge)46between the mesa region and the off-mesa region of the mold7, and the field of view47of the detection optical system3. As shown inFIG. 13, the alignment marks10and13are arranged in the vicinity of the edge46of the mold7. In the case where the alignment marks10and13are arranged at a corner of the edge46of the mold7, the field of view47of the detection optical system3does not entirely fit within the effective diameter45of the projection optical system41, and there is a possibility of not being able to detect an alignment mark with the detection optical system3. If the alignment mark13is arranged in this range, the alignment mark13cannot be detected. In view of this, as shown inFIG. 13, if the alignment mark13is arranged (positioned) in the detectable range of the detection optical system3, the alignment mark13can be detected. In this way, the positions of the alignment marks10and13with respect to the field of view47of the detection optical system3can be changed according to the position of the alignment mark10.

Also, if the imprint apparatus1includes two or more detection optical systems3, corresponding alignment marks10and13can be detected in the fields of view of the respective detection optical systems3. The shape of the mold7can be obtained by detecting the gap between the mold7and the alignment substrate12at two or more positions. Here, the higher the number of locations at which the gap between the mold7and the alignment substrate12is measured, the more highly precisely the shape of the mold7can be obtained. The mold shape correction unit corrects the shape of the mold7to a predetermined shape based on the shape of the mold7obtained in this way.

Third Embodiment

The present embodiment describes error when detecting the alignment mark13(detection error) in the first embodiment and the second embodiment. In the second detection process shown inFIG. 8B, if the mold7becomes inclined when the mold7is moved out of the way, detection error will arise with respect to the alignment mark13. For example, as shown inFIG. 14, if the mold7is inclined at an angle53relative to the horizontal direction, light51from the alignment mark13is refracted by the mold7and becomes shifted by a gap52. Accordingly, when the alignment mark13is detected in the alignment of the mold7and the alignment substrate12, an amount of detection error corresponding to the gap52arises. For this reason, when the mold7is moved out of the way (i.e., when the mold7is moved in the Z axis direction), the mold stage4needs to be able to suppress the inclination angle (inclination amount) of the mold7to a low angle.

Letting θ1 be the inclination angle of the mold7, t be the thickness of the mold7, n be the refractive index of the mold7, and θ2 be the angle of refraction of light incident on the mold7, the shift amount of the light51from the alignment mark13is obtained by Expression (2) below.
shift amount=t×sin(θ1−θ2)/cos θ2  (2)

Also, taking Snell's law (sin θ1=n×sin θ2) into consideration, if θ1 is 1 minute, t is 1 mm, and n is 1.45, the shift amount of the light51from the alignment mark13is obtained as 90 nm according to Expression (2). The shift amount of the light51from the alignment mark13hinders highly precise alignment of the mold7and the alignment substrate12(becomes alignment error), and therefore the inclination angle of the mold7needs to be suppressed according to the alignment precision that is needed.

Fourth Embodiment

The present embodiment describes a method of manufacturing a device (semiconductor device, magnetic storage medium, liquid crystal display element, or the like) as an article. This manufacturing method includes a step of forming a pattern on a substrate (wafer, glass plate, film-like substrate, or the like) using the imprint apparatus1. This manufacturing method further includes a step of processing the substrate provided with the pattern. This processing step can include a step of removing a remaining film of the pattern. It can also include other widely-known steps, such as a step of etching the substrate using the pattern as a mask. The method of manufacturing an article of the present embodiment is advantageous over conventional technology in at least one of article performance, quality, productivity, and production cost.

This application claims the benefit of Japanese Patent Application No. 2014-000651 filed on Jan. 6, 2014, which is hereby incorporated by reference herein in its entirety.