DETECTION DEVICE, LITHOGRAPHY APPARATUS, AND ARTICLE MANUFACTURING METHOD

Detection device detects relative position between first and second marks overlapping each other. The device includes illumination system configured to illuminate the first and second marks with illumination light, and detection system configured to form image on imaging surface of image sensor from diffracted lights from the first and the second marks configured to form, on the imaging surface, optical information representing the relative position in first or second direction. The illumination light passes through only optical axis of the illumination system on pupil surface of the illumination system. Light blocking body provided on pupil surface of the detection system includes first light blocking portion crossing optical axis of the detection system in direction conjugate to the first direction, and second light blocking portion crossing the optical axis of the detection system in direction conjugate to the second direction.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a detection device, a lithography apparatus, and an article manufacturing method.

Description of the Related Art

An imprint apparatus brings a mold into contact with an imprint material arranged on a substrate, and cures the imprint material, thereby forming a pattern made of a cured product of the imprint material. In this imprint apparatus, it is important to correctly align the substrate and the mold. Japanese Patent Laid-Open No. 2008-522412 describes a technique of aligning a substrate and a mold using a mark formed by a diffraction grating provided on the substrate and a mark formed by a diffraction grating provided on the mold.

If the mark is illuminated, light reflected by an edge as the boundary between the mark and a region outside the mark enters an image sensor as noise light, and this may decrease the detection accuracy of the mark. Especially, if the area of the mark is reduced, the influence of the noise light on an image formed by light for detecting position information from the mark becomes large, and thus the decrease in detection accuracy may be conspicuous.

SUMMARY OF THE INVENTION

The present invention provides a technique advantageous in detecting the relative position between the first mark and the second mark provided on the first object and second object, respectively, with high detection accuracy.

One of aspects of the present invention provides a detection device for detecting a relative position between a first mark and a second mark respectively provided in a first object and a second object arranged to overlap each other, comprising: an illumination system configured to illuminate the first mark and the second mark with illumination light; and a detection system including an image sensor and configured to form an image on an imaging surface of the image sensor from diffracted lights from the first mark and the second mark illuminated by the illumination system, wherein the first mark and the second mark are configured to form, on the imaging surface, optical information representing the relative position in a first direction or a second direction orthogonal to the first direction, the illumination light is light that passes through only an optical axis of the illumination system and a vicinity of the optical axis on a pupil surface of the illumination system, a light blocking body including a first light blocking portion crossing an optical axis of the detection system in a direction parallel to a third direction and a second light blocking portion crossing the optical axis of the detection system in a direction parallel to a fourth direction is provided on a pupil surface of the detection system, and the third direction is a direction conjugate to the first direction and the fourth direction is a direction conjugate to the second direction.

DESCRIPTION OF THE EMBODIMENTS

FIG.2shows the arrangement of an imprint apparatus10as an example of a lithography apparatus that transfers a pattern of an original to a substrate. The imprint apparatus10is used to manufacture a device such as a semiconductor device, and forms a pattern made of a cured product of an imprint material18on a substrate17by molding the uncured imprint material18on the substrate17as a processing target object using a mold16. A pattern forming process of forming a pattern on the substrate17by the imprint apparatus10can include a contact step, a filling and alignment step, a curing step, and a separation step. In the contact step, the imprint material18on a shot region of the substrate17and a pattern region16aof the mold16are brought into contact with each other. In the filling and alignment step, a space defined by the shot region of the substrate17and the pattern region16aof the mold16is filled with the imprint material18, and the shot region of the substrate17and the pattern region16aof the mold16are aligned. The shot region is a region where the pattern is formed by one pattern forming process. In other words, the shot region is a region where the pattern region16aof the mold16is transferred by one pattern forming process.

As the imprint material, a curable composition (to be also referred to as a resin in an uncured state) to be cured by receiving curing energy is used. As the curing energy, an electromagnetic wave or heat can be used. The electromagnetic wave can be, for example, light selected from the wavelength range of 10 nm (inclusive) to 1 mm (inclusive), for example, infrared light, a visible light beam, or ultraviolet light. The curable composition can be a composition cured by light irradiation or heating. Among compositions, a photo-curable composition cured by light irradiation contains at least a polymerizable compound and a photopolymerization initiator, and may further contain a nonpolymerizable compound or a solvent, as needed. The nonpolymerizable compound is at least one material selected from the group consisting of a sensitizer, a hydrogen donor, an internal mold release agent, a surfactant, an antioxidant, and a polymer component. The imprint material can be arranged on the substrate in the form of droplets or in the form of an island or film formed by connecting a plurality of droplets. The imprint material may be supplied onto the substrate in the form of a film by a spin coater or a slit coater. The viscosity (the viscosity at 25° C.) of the imprint material can be, for example, 1 mPa·s (inclusive) to 100 mPa·s (inclusive). As the material of the substrate, for example, glass, a ceramic, a metal, a semiconductor (Si, GaN, SiC, or the like), a resin, or the like can be used. A member made of a material different from the substrate may be provided on the surface of the substrate, as needed. The substrate is, for example, a silicon wafer, a compound semiconductor wafer, or silica glass. An example of adopting a photo-curable composition as the imprint material will be described below but this is not intended to limit the type of the imprint material.

In the specification and the accompanying drawings, directions will be indicated on an XYZ coordinate system in which directions parallel to the surface of the substrate17are defined as the X-Y plane. Directions parallel to the X-axis, the Y-axis, and the Z-axis of the XYZ coordinate system are the X direction, the Y direction, and the Z direction, respectively. A rotation about the X-axis, a rotation about the Y-axis, and a rotation about the Z-axis are θX, θY, and θZ, respectively. Control or driving concerning the X-axis, the Y-axis, and the Z-axis means control or driving concerning a direction parallel to the X-axis, a direction parallel to the Y-axis, and a direction parallel to the Z-axis, respectively. In addition, control or driving concerning the θX-axis, the θY-axis, and the θZ-axis means control or driving concerning a rotation about an axis parallel to the X-axis, a rotation about an axis parallel to the Y-axis, and a rotation about an axis parallel to the Z-axis, respectively. In addition, a position is information that can be specified based on coordinates on the X-, Y-, and Z-axes, and an orientation is information that can be specified by values on the θX-, θY-, and θZ-axes. Positioning means controlling the position and/or orientation. Alignment (positioning) can include controlling the position and/or orientation of at least one of the substrate17and the mold such that the alignment error (overlay error) between the shot region of the substrate17and the pattern region of the mold16decreases. In addition, alignment can include control to correct or change the shape of at least one of the shot region of the substrate17and the pattern region of the mold16. The contact step and the separation step can be executed by driving the mold16by a mold driving mechanism13, but may be executed by driving the substrate17by a substrate driving mechanism14. Alternatively, the contact step and the separation step may be executed by driving the mold16by the mold driving mechanism13and driving the substrate17by the substrate driving mechanism14.

The imprint apparatus10can include a curing unit11, a detection device12, the mold driving mechanism13, the substrate driving mechanism14, and a control unit C. The imprint apparatus10may further include an application unit15. After the contact step of bringing the mold16into contact with the imprint material18on the substrate17, the curing unit11irradiates the imprint material18with light such as ultraviolet light as curing energy, thereby curing the imprint material18. The curing unit11includes, for example, a light source, and a plurality of optical elements for uniformly irradiating the pattern region16aof the mold16as an irradiated surface with light emitted from the light source in a predetermined shape. In particular, the irradiation region (irradiation range) with light by the curing unit11desirably has a surface area almost equal to the surface area of the pattern region16aor slightly larger than the area of the pattern region16a. This is to prevent, by making the irradiation region have a minimum necessary area, a situation in which the mold16or the substrate17expands due to heat generated by irradiation to cause a positional shift or distortion of the pattern transferred to the imprint material18. In addition, this is to prevent a situation in which light reflected by the substrate17or the like reaches the application unit15to cure the imprint material18remaining in the discharge portion of the application unit15, and an abnormality thus occurs in the operation of the application unit15. As the light source, for example, a high-pressure mercury lamp, various kinds of excimer lamps, an excimer laser, or a light-emitting diode can be adopted. The light source can appropriately be selected in accordance with the characteristic of the imprint material18as a light receiving object.

FIG.3shows an example of the arrangement of the detection device12. The detection device12is configured to optically detect or measure the relative position between a mold mark (first mark)19arranged on the mold (first object)16and a substrate mark (second mark)20arranged on the substrate (second object)17. The mold mark (first mark)19and the substrate mark (second mark)20are configured to form optical information representing the relative position in the X direction (first direction) or the Y direction (second direction) on the imaging surface of an image sensor25(to be described later). The detection device12can include an illumination system22and a detection system21. The illumination system22and the detection system21can share some components. The illumination system22includes a light source23, and generates illumination light using light from the light source23and illuminates measurement target objects (first mark and second mark) with the illumination light. This illumination light can be unpolarized light. The detection system21detects the relative position between the mold mark (first mark)19and the substrate mark (second mark)20as measurement target objects by detecting lights from the measurement target objects illuminated with the illumination light.

Among the optical axes of the detection device12, an optical axis at the positions of the substrate17and the mold16is vertical to the upper surface of the substrate17and the lower surface (pattern region16a) of the mold16, that is, parallel to the Z-axis. The detection device12can be configured to be driven in the X direction and the Y direction by a driving mechanism (not shown) in accordance with the positions of the mold mark19and the substrate mark20. The detection device12may be configured to be driven in the Z direction to align the focus of the detection system21with the position of the mold mark19or the substrate mark20. The detection device12may include an optical element or optical system for focus alignment. Based on the relative position between the mold mark19and the substrate mark20detected or measured using the detection device12, positioning of the substrate17by the substrate driving mechanism14and correction of the shape and magnification of the pattern region16aby a correction mechanism (not shown) can be controlled. The correction mechanism is mounted on the mold driving mechanism13, and can adjust the shape and magnification of the pattern region16aof the mold16by deforming the mold16. The mold mark19and the substrate mark20will be described in detail later.

The mold driving mechanism13can include a mold chuck (not shown) that holds the mold16by a vacuum suction force or an electrostatic force, and a mold driving unit (not shown) that drives the mold16by driving the mold chuck. The mold driving mechanism13can include the above-described correction mechanism. For example, the mold driving unit can be configured to drive the mold chuck or the mold16with respect to the Z-axis. The mold driving unit may be configured to further drive the mold chuck or the mold16with respect to at least one of the θX-axis, the θY-axis, the θZ-axis, the X-axis, and the Y-axis.

The substrate driving mechanism14can include a substrate chuck that holds the substrate17by a vacuum suction force or an electrostatic force, and a substrate driving unit (not shown) that drives the substrate17by driving the substrate chuck. For example, the substrate driving unit can be configured to drive the substrate chuck or the substrate17with respect to the X-axis, the Y-axis, and the θZ-axis. The substrate driving unit may be configured to further drive the substrate chuck or the substrate17with respect to at least one of the θX-axis, the and the Z-axis.

The application unit (dispenser)15applies or arranges the uncured imprint material18on the substrate17. The application unit15may be arranged outside the housing of the imprint apparatus10. In this case, the application unit15may be understood as a component that is not a component of the imprint apparatus10.

The mold16includes, in the pattern region16a, a pattern such as a circuit pattern to be transferred to the substrate17(the imprint material18thereon). The mold16can be made of a material that transmits light as curing energy, for example, quartz. The substrate17can be, for example, a semiconductor substrate such as a single-crystal silicon substrate or a substrate including at least one layer on a semiconductor substrate.

The control unit C can be configured to control the curing unit11, the detection device12, the mold driving mechanism13, the substrate driving mechanism14, and the application unit15. The control unit C can be formed by, for example, a Field Programmable Gate Array (FPGA), a computer embedded with a program, or a combination of all or some of these components. The FPGA can include a Programmable Logic Device (PLD) or an Application Specific Integrated Circuit (ASIC). The control unit C includes a memory and a processor, and can define the operation and function of the imprint apparatus10by operating based on arithmetic formulas, parameters, and computer programs stored (saved) in the memory. At least part of the function of the detection device12, for example, a function of processing an image captured by the image sensor25may be provided by a module incorporated in the control unit C. In this case, the module of the control unit C can be understood as part of the detection device12.

An imprint process or pattern forming process executed by the imprint apparatus10will now be described. First, the substrate17is conveyed to the substrate chuck of the substrate driving mechanism14by a substrate conveyance mechanism (not shown), and fixed to the substrate chuck. Subsequently, the substrate17is driven by the substrate driving mechanism14so that the shot region of the substrate17moves to an application position by the application unit15. After that, the application unit15applies, arranges, or supplies the imprint material18onto the shot region (imprint region) of the substrate (application step).

Next, the substrate17is driven by the substrate driving mechanism14so that the shot region where the imprint material18has been arranged is arranged at a position immediately below the pattern region16aof the mold16. Then, for example, the mold driving mechanism13lowers the mold16to bring the imprint material18on the substrate17and the pattern region16aof the mold16into contact with each other (contact step). This fills the space (including a concave portion of the pattern region16a) between the substrate17and the pattern region16aof the mold16with the imprint material18(filling step). Furthermore, with respect to a plurality of mark pairs each formed by the mold mark19and the substrate mark20, the detection device12is used to detect or measure the relative position between the mold mark19and the substrate mark20. Based on the result, the pattern region16aand the shot region of the substrate17are aligned (alignment step). At this time, the correction mechanism may be used to correct the shape of the pattern region16aof the mold16. In addition, a heating mechanism (not shown) may be used to correct the shape of the shot region of the substrate17.

Upon completion of the filling and alignment steps, the curing unit11irradiates the imprint material18with light via the mold16, thereby curing the imprint material18(curing step). At this time, the detection device12can be driven to retreat so as not to block the optical path of the curing unit11. Subsequently, the mold driving mechanism13raises the mold16to separate the mold16from the cured imprint material18on the substrate17(separation step).

The imprint apparatus10can be understood as an example of a lithography apparatus that includes the detection device12, aligns the original (or the pattern region) and the substrate (or the shot region) based on an output from the detection device12, and transfers the pattern of the original to the substrate. The imprint apparatus10aligns the mold16(first object or original) provided with the mold mark19(first mark) and the substrate17(second object) provided with the substrate mark20(second mark) based on an output from the detection device12.

Details of the detection device12will be described below with reference toFIG.3. As described above, the detection device12includes the illumination system22and the detection system21, and the illumination system22and the detection system21can share some components. The illumination system22guides illumination light generated by light from the light source23to a common optical axis via a prism24, thereby illuminating the mold mark19and the substrate mark20. The light source23can include, for example, at least one of a halogen lamp, an LED, a semiconductor laser (LD), a high-pressure mercury lamp, a metal halide lamp, a supercontinuum light source, and a Laser-Driven Light Source (LDLS). The wavelength of the illumination light generated by the light source23is selected not to cure the imprint material18.

The prism24is shared by the illumination system22and the detection system21, and can be arranged on or near a pupil surface1of the illumination system22or on or near a pupil surface2of the detection system21. Each of the mold mark19and the substrate mark20can include a mark formed by a diffraction grating. The detection system21can form, on the imaging surface of the image sensor25, an optical image of interference light (an interference fringe or moiré fringe) generated by interference between lights diffracted by the mold mark19and the substrate mark20which are illuminated by the illumination system22. The image sensor25can be formed by, for example, a CCD sensor or a CMOS sensor.

The prism24includes, as a reflective surface RS, a surface (bonding surface) obtained by bonding two members, and includes a reflective film24aon the bonding surface. The prism24may be replaced by a plate-shaped optical element having the reflective film24aon its surface. A position at which the prism24is arranged need not be on or near the pupil surface1of the illumination system22, or on or near the pupil surface2of the detection system21. An illumination aperture stop27(for example, a pinhole plate) can be arranged on the pupil surface1of the illumination system22. A detection aperture stop26can be arranged on the pupil surface2of the detection system21. The illumination aperture stop27defines the light intensity distribution of the pupil surface1of the illumination system22. Note that the illumination aperture stop27may be an arbitrary component, and illumination light parallel to the optical axis may be formed by defining the region of the reflective film24a.

FIG.4Ais a schematic view of the mold mark19as an alignment mark.FIG.4Bis a schematic view of the substrate mark20as an alignment mark. The mold mark19can be formed by, for example, a mark19aand diffraction gratings19band19b′. The substrate mark20can be formed by, for example, a mark20aand diffraction gratings20band20b′. The marks19aand20aare rough-detection marks, and the diffraction gratings19b,19b′,20b, and20b′ are fine-detection marks.

Each of the diffraction gratings19b,19b′,20b, and20b′ can include a periodic pattern. It is possible to obtain the relative position between the mold16and the substrate17from the detection result of the detection device12with reference to the geometrical center positions of the marks19aand20a. Since an interference fringe (moiré fringe) is generated by diffraction lights from the diffraction grating19b(19b′) of the mold mark19and the diffraction grating20b(20b′) of the substrate mark20, the light amount of the moiré fringe changes in accordance with the diffraction efficiency of the mold mark19and the substrate mark20. Especially, since the diffraction efficiency periodically changes in accordance with a change in wavelength, there can exist a wavelength at which it is possible to efficiently detect a moiré fringe and a wavelength at which it is difficult to detect a moiré fringe. Light of a wavelength at which it is difficult to detect a moiré fringe can be noise.

FIGS.5A to5Dare views each showing an example of a diffraction grating that generates a moiré fringe. The principle of generating a moiré fringe by diffraction lights from the diffraction gratings19band20band detection of the relative position between the diffraction gratings19band20busing the moiré fringe will be described below with reference toFIGS.5A to5D. The periods of the patterns (gratings) in the measurement direction of the diffraction grating19bprovided in the mold16and the diffraction grating20bprovided in the substrate17are slightly different from each other. If two diffraction gratings having different periods are superimposed on each other, a pattern having a period reflecting the difference in period between the diffraction gratings, that is, a so-called moiré fringe (moiré) appears due to interference between diffracted lights from the two diffraction gratings. At this time, since the phase of the moiré fringe changes in accordance with the relative position between the diffraction gratings, it is possible to obtain the relative position between the diffraction gratings19band20b, that is, the relative position between the mold16and the substrate17by detecting the moiré fringe.

More specifically, if the diffraction gratings19band20bhaving the slightly different periods are superimposed on each other, the diffracted lights from the diffraction gratings19band20boverlap each other, thereby generating a moiré fringe having a period reflecting the difference in period, as shown inFIG.5C. In the moiré fringe, the positions of bright and dark portions (the phase of the fringe) change in accordance with the relative position between the diffraction gratings19band20b. If, for example, one of the diffraction gratings19band20bis shifted in the X direction, the moiré fringe shown inFIG.5Cchanges to a moiré fringe shown inFIG.5D. Since the moiré fringe is generated as a fringe having a large period by enlarging the actual positional shift amount between the diffraction gratings19band20b, even if the resolution of the detection system21is low, it is possible to detect the relative position between the diffraction gratings19band20bwith high accuracy. The diffraction gratings19b,19b′,20b, and20b′ have been described using one-dimensional diffraction grating patterns. However, for example, checkerboard patterns can be used for the diffraction gratings20band20b′, as shown inFIG.6B. By using a checkerboard pattern as a diffraction grating pattern, it is possible to diffract light not only in the Y direction shown inFIGS.4A and4Bbut also in the X direction.

If there are scattered light from the pattern edge and scattered light from a foreign substance, they cause a measurement error in moiré measurement. If illumination light is made to enter the alignment mark from the Z direction perpendicular to the X-Y plane, noise light passes through the X-axis and the Y-axis of the pupil surface2of the detection system21. This is because the edges of the patterns of the mold mark19and the substrate mark20are parallel to one of the X-axis and the Y-axis. Therefore, it is preferable to detect, by the image sensor25, as a signal necessary to detect a moiré fringe, light having passed through a region decentered from the center of the pupil of the detection system21, and to block noise light entering the X-axis and the Y-axis of the pupil of the detection system21. This can reduce noise caused by scattered light from the pattern edge. Furthermore, if each of the two sides facing each other of the checkerboard pattern is not parallel to one of the X-axis and the Y-axis, the scattered light from the pattern edge can pass through an axis other than the X-axis and the Y-axis of the pupil surface2of the detection system21. Therefore, each pattern edge is desirably parallel to one of the X-axis and the Y-axis. This is not limited to a case where the diffraction grating pattern of the substrate mark20is a checkerboard pattern and the diffraction grating pattern of the mold mark19is a line-and-space pattern. For example, the diffraction grating pattern of the substrate mark20may be a line-and-space pattern, and the diffraction grating pattern of the mold mark19may be a checkerboard pattern.

Next, a method of deciding a relative position by detecting a moiré fringe will be described. The diffraction gratings19band20bare formed by periodic patterns, and have periods slightly different from each other in the measurement direction. Thus, if these diffraction gratings are superimposed on each other, a moiré fringe whose light intensity changes in the Y direction is formed. Because of the difference in period between the diffraction gratings19band20b, the shift direction of the moiré fringe when the relative position changes is different. For example, in a case where the period of the diffraction grating19bis slightly larger than the period of the diffraction grating20b, if the substrate17relatively shifts in the +Y direction, the moiré fringe also shifts in the +Y direction. On the other hand, in a case where the period of the diffraction grating19bis slightly smaller than the period of the diffraction grating20b, if the substrate17relatively shifts in the +Y direction, the moiré fringe shifts in the −Y direction.

The diffraction gratings19b′ and20b′ form another moiré fringe. The magnitude relationship between the periods of the diffraction gratings19band20bis reversed with respect to the magnitude relationship between the periods of the diffraction gratings19b′ and20b′. Therefore, if the relative position changes, the positions of the two measured moiré fringes change in the opposite directions. If the periodic marks on the mold side and the substrate side, that generate moiré fringes, are shifted by one period, it is impossible to detect the shift for one period in the moiré fringe detection principle. Therefore, by using the marks19aand20awith low detection accuracy, it can be confirmed that there is no relative positional shift for one period between the mold16and the substrate17.

Subsequently, the light intensity distributions on the pupil surface1of the illumination system22and the pupil surface2of the detection system21will be exemplarily described with reference toFIGS.1A and1B. As exemplified inFIG.1A, a light intensity distribution3having light intensity concentrated at the intersection point (that is, the optical axis) of the x-axis and the y-axis can be generated at the exit of the pupil surface1of the illumination system22.FIG.1Bexemplified a light intensity distribution formed on the pupil surface1of the detection system21by diffracted lights4ato4d,5ato5d, and6from the diffraction gratings19band20b(19b′ and20b′) illuminated by the light intensity distribution3. An xyz coordinate system is defined as the coordinate system of the pupil surface1of the illumination system22. The x-axis and the y-axis of the pupil surface1of the illumination system22coincide with the Z-axis and Y-axis of the XYZ coordinate system, respectively. The x direction parallel to the x-axis is a direction conjugate to the X direction parallel to the X-axis, and the y direction parallel to the y-axis is a direction conjugate to the Y direction parallel to the Y-axis. In the illumination system22, if the x direction and the X direction are conjugate to each other, this means that the x direction and the X direction coincide with each other in a case where there is no reflective surface (for example, the reflective surface RS) that bends the optical axis of the illumination system22between the mold16/substrate17and the pupil surface1of the illumination system22. In the illumination system22, if the x direction and the X direction are conjugate to each other, this means that the X direction mapped on the pupil surface1by the reflective surface coincides with the x direction in a case where there exists the reflective surface that bends the optical axis between the mold16/substrate17and the pupil surface1. In a case where there exists the reflective surface, the x direction may or may not coincide with the X direction. The same applies to conjugation of the y direction to the Y direction.

In the example shown inFIG.3, there is no reflective surface that bends the optical axis of the detection system21between the mold16/substrate17and the pupil surface2of the detection system21. Therefore, if an xyz coordinate system is defined as the coordinate system of the pupil surface2of the detection system21, the x-axis coincides with the X-axis and the y-axis coincides with the Y-axis. The x direction (third direction) parallel to the x-axis is a direction conjugate to the X direction (first direction) parallel to the X-axis, and the y direction (fourth direction) parallel to the y-axis is a direction conjugate to the Y direction (second direction) parallel to the Y-axis. In the detection system21, if the x direction and the X direction are conjugate to each other, this means that the x direction and the X direction coincide with each other in a case where there is no reflective surface that bends the optical axis of the detection system21between the mold16/substrate17and the pupil surface2of the detection system21. In the detection system21, if the x direction and the X direction are conjugate to each other, this means that the X direction mapped on the pupil surface2by the reflective surface coincides with the x direction in a case where there exists the reflective surface that bends the optical axis between the mold16/substrate17and the pupil surface2of the detection system21. In a case where there exists the reflective surface, the x direction may or may not coincide with the X direction. The same applies to conjugation of the y direction to the Y direction.

A case where the measurement direction (a direction in which the light intensity in the moiré fringe changes) coincides with the X direction (first direction) will now be described. The relative position between the diffraction grating19b(19b′) of the mold mark19and the diffraction grating20b(20b′) of the substrate mark20is equivalent to the relative position between the mold mark19and the substrate mark20. The detection system21forms an image on the imaging surface of the image sensor25from information representing the relative position between the diffraction grating19b(19b′) of the mold mark19and the diffraction grating20b(20b′) of the substrate mark20in the measurement direction.

Consider a case where the light intensity distribution3having light intensity concentrated at and near the intersection point (the optical axis of the illumination system22) of the X-axis and the Y-axis is formed at the exit of the pupil surface1of the illumination system22, in other words, a case where the illumination light passes through only the optical axis of the illumination system22and its vicinity on the pupil surface1of the illumination system22. In this case, it can be considered that only a light component, parallel to the optical axis, of the light emitted from the light source23enters the mold mark19(diffraction gratings19band19b′) as illumination light. In the mold mark19(diffraction gratings19band19b′), plus first-order diffracted light and minus first-order diffracted light are generated in the X-axis direction. Among the diffracted lights generated by the mold mark19(diffraction gratings19band19b′), the plus first-order diffracted light is light diffracted in the positive direction of the X-axis with respect to the optical axis, and the minus first-order diffracted light is light diffracted in the negative direction of the X-axis with respect to the optical axis. Each diffracted light enters the substrate mark20(diffraction gratings20band thereby generating plus first-order diffracted light and minus first-order diffracted light. Since the substrate mark20includes a checkerboard pattern, the traveling direction of the light diffracted by the substrate mark20has both an X-axis component and a Y-axis component. Among diffraction lights generated by the substrate mark20, the plus first-order diffracted light is diffracted light including a positive-direction component of the Y-axis with respect to the optical axis in the traveling direction, and the minus first-order diffracted light is diffracted light including a negative-direction component of the Y-axis with respect to the optical axis in the traveling direction.

Referring toFIGS.1A and1B, for example, on the pupil surface2of the detection system21, the diffracted light4arepresents light obtained when the illumination light enters the mold mark19, is diffracted in the minus first-order direction, and is diffracted in the plus first-order direction at the substrate mark20. The diffracted light4ais represented as (−1, +1). In accordance with this representation method, in addition to the diffracted light (−1, +1), the diffracted light4b(+1, +1), the diffracted light4c(−1, −1), and the diffracted light4d(+1, −1) enter the pupil surface2. An image is formed on the imaging surface of the image sensor25from the diffracted lights4aand4b, thereby generating an interference fringe (moiré fringe) whose light intensity changes in the X direction. Similarly, with the diffracted lights4cand4d, an interference fringe whose light intensity changes in the X direction is generated.

The pitch of the mold mark19(19band19b′) is represented by Pmx, and the pitches in the X direction and Y direction of the substrate mark20(20band20b′) are presented by Pwx and Pwy, respectively. The distance from the X-axis of the diffracted light4aon the pupil surface2of the detection system21can be given by f·tanθwy where f represents the focal length of a lens group arranged between the pupil surface2of the detection system21and the mold mark19/substrate mark20, and θwy represents a diffraction angle in the Y direction in the substrate mark20. The diffraction angle θwy is arcsin(λ/Pwy). This is because a diffraction angle θ can be given by sinθ=λ/p where λ represents the wavelength of light and p represents a mark pitch. The wavelength λ may be, for example, a single wavelength like in a case where a laser light source is used, or may have an intensity distribution in a wavelength band of 500 to 800 nm. On the other hand, the distance from the Y-axis of the diffracted light4acan be given by f·tan(θmx−θwx) where θmx represents a diffraction angle in the X-axis direction in the mold mark19, and θwx represents a diffraction angle in the X-axis direction in the substrate mark20. θmx−θwx is arcsin(λ/Pmx)−arcsin(λ/Pwx). This is because light entering the mold mark19/substrate mark20is diffracted by each of the mold mark19and the substrate mark20in the X-axis direction. Furthermore, the same applies to the mold mark19/substrate mark20in a case where the measurement direction is the same as the Y-axis (second direction) orthogonal to the X-axis of the pupil surface1or2, and the diffracted lights5a,5c, and5dcan be described.

The pattern edge light6will be described with reference toFIG.7. The pattern edge light6is diffracted light at each of the edges of the whole patterns of the diffraction gratings19b(19b′) and20b(20b′) of the mold mark19and the substrate mark20. Note that in the edge portion of each small pattern element forming the diffraction gratings19b(19b′) and20b(20b′), the pitch is small and thus diffracted light is not detected. The pattern edge light in the diffraction grating19bof the mold mark19will be described. Light entering the edge of the whole diffraction grating19bis diffracted only in an axis direction orthogonal to the edge. This is because the edge of the whole diffraction grating19bis parallel to one of the X-axis and the Y-axis. If, for example, light enters the edge in a direction parallel to the X-axis, diffracted light is in a direction parallel to the Y-axis direction. On the other hand, if light enters the edge in a direction parallel to the Y-axis direction, the light is diffracted in a direction parallel to the X-axis direction. The same applies to the diffracted lights from the diffraction grating19b′ of the mold mark19and the diffraction gratings20band20b′ of the substrate mark20. Therefore, the pattern edge light6passes through the X-axis and its vicinity and the Y-axis and its vicinity on the pupil surface2of the detection system21.

The illumination aperture stop27and the detection aperture stop26for removing the pattern edge light6as unnecessary light will be described with reference toFIGS.8A and8B. To make light parallel to the optical axis enter the mold mark19, it is advantageous to form a light intensity distribution having light intensity concentrated only at and near the intersection point (that is, the optical axis) of the X-axis and the Y-axis at the exit of the pupil surface1of the illumination system22. To do this, the illumination aperture stop27(pinhole plate) including an opening (pinhole) at the intersection point of the X-axis and the Y-axis can be arranged on the pupil surface1. This makes it possible to cause only light parallel to the optical axis of the light source23to enter the mold mark19(diffraction gratings19band19b′).

The diffracted lights4ato4dand5ato5dfrom which a moiré fringe is formed on the imaging surface of the image sensor25enter a region not on the X-axis and the Y-axis on the pupil surface2of the detection system21. On the other hand, the pattern edge light6enters the X-axis and its vicinity and the Y-axis and its vicinity on the pupil surface2of the detection system21. The pattern edge light6is noise light when measuring the relative position between the diffraction gratings19b(19b′) and20b(20b′) from the moiré fringe phase difference. To cope with this, the detection aperture stop26including a light blocking body260is arranged on and near the X-axis and on and near the Y-axis on the pupil surface2of the detection system21, thereby making it possible to block the pattern edge light6.

The light blocking body260arranged on the pupil surface2of the detection system21can include a first light blocking portion261crossing the optical axis of the detection system21in the direction (third direction) parallel to the x-axis, and a second light blocking portion262crossing the optical axis of the detection system21in the direction (fourth direction) parallel to the y-axis. The light blocking body260may further include a third light blocking portion263aligned with the optical axis. The third light blocking portion can have a circular shape. As described above, the direction (third direction) parallel to the x-axis is a direction conjugate to the direction (first direction) parallel to the X-axis, and the direction (fourth direction) parallel to the y-axis is a direction conjugate to the direction (second direction) parallel to the Y-axis. The illumination aperture stop27is a pinhole plate including a pinhole with a diameter d.

The pupil surface2of the detection system21includes a light transmitting region265in a region where no light blocking body260is arranged. The diffracted lights from the mold mark19(19band19b′) and the substrate mark20(20band20b′) illuminated with the illumination light pass through the light transmitting region265, thereby forming optical information representing the relative position between the mold16and the substrate17on the imaging surface of the image sensor25. Of the lights from the mold mark19(19band19b′) and the substrate mark20(20band20b′) illuminated with the illumination light, unnecessary light including no optical information representing the relative position can be blocked by the first light blocking portion261and the second light blocking portion262.

In a case where the diameter of the concentrated light intensity portion (that is, the pinhole) in the light intensity distribution3formed at the exit of the pupil surface1of the illumination system22is represented by d, the width of the pattern edge light6on the pupil surface2of the detection system21is also d. Therefore, to block the pattern edge light6, a width D of the first light blocking portion261and the second light blocking portion262of the detection aperture stop26is preferably equal to or larger than d. The diffracted lights4ato4dand5ato5dfor forming an image on the imaging surface of the image sensor25from the moiré fringe need to enter a region other than the light blocking body260on the pupil surface2of the detection system21. For example, with respect to the diffracted light4a, the distance |f·tanθwy| from the X-axis and the distance |f·tan(θmx−θwx)| from the Y-axis are preferably larger than the sum of half of the width D of the light blocking body260and a radius r of the diffracted light4aon the pupil surface2of the detection system21. In this example, the width D of the light blocking body260is the width in the X direction of the second light blocking portion262with respect to the X direction, and is the width in the Y direction of the first light blocking portion261with respect to the Y direction. If the condition is represented by formulas, the width D of the light blocking body260preferably satisfies the following expressions.

|f·tanθwy|−r≥D/2≥d/2, and

In this example, r is larger than d since the number of pitches of the mold mark19and the substrate mark20is infinite. For example, in the case of the diffracted light5a, the width D of the light blocking body preferably satisfies the following expressions.

|f·tanθwx|−r≥D/2≥d/2, and

Note that the mark that generates the diffracted light5ais a mark whose measurement direction is the Y direction.

The influence of the presence/absence of the pattern edge light6on moiré fringe phase difference measurement will be described with reference toFIGS.9A and9B. As shown in an arbitrary section31in the measurement direction of the moiré fringe including the pattern edge light6, if the pattern edge light6exists in each edge portion of the moiré fringe, this becomes a noise component, thereby degrading the measurement accuracy of the relative phase. As the moiré fringe is closer to the pattern edge light6, the influence of the noise component is larger. Thus, it is difficult to decrease the size of the alignment mark. On the other hand, as shown in an arbitrary section32in the measurement direction of the moiré fringe from which the pattern edge light6has been removed, if there is only a moiré signal, the measurement accuracy of the relative phase is improved. In addition, when the shot noise of the image sensor25is reduced, it is also expected to improve the measurement accuracy of the relative phase.

An article manufacturing method using an imprint apparatus represented by the above-described embodiment will be described next. The article can be, for example, a semiconductor device, a display device, a MEMS, or the like. The article manufacturing method can include a transfer step of transferring a pattern of an original to a substrate using a lithography apparatus or an imprint apparatus, and a processing step of processing the substrate so as to obtain an article from the substrate having undergone the transfer step. The transfer step can include a contact step of bringing the mold16and the imprint material18on the shot region of the substrate17into contact with each other. The transfer step can also include a measurement step of measuring the relative position between the mold16and the shot region (or the substrate mark) of the substrate17. The transfer step can also include an alignment step of aligning the mold16and the shot region of the substrate17based on the result of the measurement step. The transfer step can also include a curing step of curing the imprint material18on the substrate17and a separation step of separating the imprint material18from the mold16. This forms or transfers the pattern made of a cured product of the imprint material18on the substrate17. The processing step can include, for example, etching, resist peeling, dicing, bonding, and packaging.

The pattern made of the cured product formed using the imprint apparatus is used permanently for at least some of various kinds of articles or temporarily when manufacturing various kinds of articles. The articles are an electric circuit element, an optical element, a MEMS, a recording element, a sensor, a mold, and the like. Examples of the electric circuit element are volatile and nonvolatile semiconductor memories such as a DRAM, an SRAM, a flash memory, and an MRAM and semiconductor elements such as an LSI, a CCD, an image sensor, and an FPGA. Examples of the mold are molds for imprint.

The pattern of the cured product is directly used as the constituent member of at least some of the above-described articles or used temporarily as a resist mask. After etching or ion implantation is performed in the substrate processing step, the resist mask is removed.

An article manufacturing method in which an imprint apparatus forms a pattern on a substrate, processes the substrate on which the pattern has been formed, and manufactures an article from the processed substrate will be described next. As shownFIG.10A, a substrate1zsuch as a silicon wafer with a processed material2zsuch as an insulator formed on the surface is prepared. Next, an imprint material3zis applied to the surface of the processed material2zby an inkjet method or the like. A state in which the imprint material3zis applied as a plurality of droplets onto the substrate is shown here.

As shown inFIG.10B, a side of a mold4zfor imprint with a concave-convex pattern is directed to face the imprint material3zon the substrate. As shownFIG.10C, the substrate1zto which the imprint material3zhas been applied is brought into contact with the mold4z, and a pressure is applied. The gap between the mold4zand the processed material2zis filled with the imprint material3z. In this state, when the imprint material3zis irradiated with light as curing energy via the mold4z, the imprint material3zis cured.

As shown inFIG.10D, after the imprint material3zis cured, the mold4zis separated from the substrate1z, and the pattern of the cured product of the imprint material3zis formed on the substrate1z. In the pattern of the cured product, the concave portion of the mold corresponds to the convex portion of the cured product, and the convex portion of the mold corresponds to the concave portion of the cured product. That is, the concave-convex pattern of the mold4zis transferred to the imprint material3z.

As shown inFIG.10E, when etching is performed using the pattern of the cured product as an etching resistant mask, a portion of the surface of the processed material2zwhere the cured product does not exist or remains thin is removed to form a groove5z. As shown inFIG.10F, when the pattern of the cured product is removed, an article with the grooves5zformed in the surface of the processed material2zcan be obtained. Here, the pattern of the cured product is removed. However, instead of removing the pattern of the cured product after the process, it may be used as, for example, an interlayer dielectric film included in a semiconductor element or the like, that is, a constituent member of an article.

This application claims the benefit of Japanese Patent Application No. 2022-116575, filed Jul. 21, 2022, which is hereby incorporated by reference herein in its entirety.