Apparatus for imaging an object at multiple locations

Abstract

A system for imaging an object at any one of a plurality of positions (400; 410) is disclosed, the system comprising: one or more beam splitters (420), each beam splitter (420) splitting light from the object into an imaging beam and a continuous beam; and an optical element for each beam splitter, the optical element receiving the imaging beam and imaging the object when the object is at the corresponding position.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 684,839, filed on June 14, 2018, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to optical systems such as may be used in semiconductor lithography alignment systems. Background Art

[0004] The photolithographic apparatus applies the desired pattern to the substrate, usually to the target portion of the substrate. The photolithographic apparatus can be used, for example, in the manufacture of an integrated circuit (IC). In this application, a pattern forming device (alternatively referred to as a mask or reticle) can be used to generate a circuit pattern to be formed on a single layer of the IC. The pattern can be transferred to a target portion (e.g., including a portion, one or several dies) on a substrate (e.g., a silicon wafer). The transfer of the pattern is usually performed via imaging onto a radiation-sensitive material (resist) layer disposed on the substrate. Typically, a single substrate will contain a network of adjacent target portions that are continuously patterned.

[0005] Known lithographic apparatus include so-called steppers, in which each target portion is illuminated by exposing the entire pattern onto the target portion at once, and so-called scanners, in which each target portion is illuminated by scanning the pattern by a radiation beam in a given direction (the "scanning" direction) while simultaneously scanning the substrate parallel or antiparallel to that direction. A pattern may also be transferred from a patterning device to a substrate by imprinting the pattern onto the substrate.

[0006] During photolithography, a mask is used to transfer a desired pattern onto a substrate such as a wafer. The mask can be formed of a material that is transparent to the wavelength of the photolithography used, for example, in the case of visible light, the mask can be glass. In addition, the mask can also be formed of one or more materials that reflect the photolithography wavelength selected for the specific system in which the photolithography system is used. An irradiation source (e.g., an exposure optical element located in a photolithography apparatus) irradiates a mask disposed on a mask stage. The irradiation exposes an image to a substrate disposed on a substrate stage. The image exposed to the substrate corresponds to the image printed on the mask. Although exposure optical elements are used in the case of photolithography, different types of exposure devices can be used depending on the specific application. For example, as known to those skilled in the art, x-ray, ion, electron or photon lithography may all require different exposure devices. Specific examples of photolithography are discussed here only for illustrative purposes.

[0007] The mask is usually located between the semiconductor chip and the light source. A loading process is required to load the mask onto the mask exposure stage. The mask must be aligned very accurately at the predetermined position. Any alignment error must be within a correctable compliance range. Conventionally, alignment marks formed in the mask are used to align the mask by positioning the alignment marks. The alignment operation is performed by detecting the alignment marks of the mask.

[0008] In order to reduce the mask exchange time and thereby increase the output of the lithography system, it is desirable to perform pre-alignment, that is, to perform alignment of the mask at an offline alignment station. Once the mask is placed on the platen, the mask pre-alignment marks are used to position the mask in approximately the correct position. The stage is moved to position the special alignment marks attached to the stage in the correct position for fine mask alignment. The marks can be irradiated with a HeNe laser. The mask is then moved to provide the best alignment position, and the mask is held in this position until the mask is removed from the stepper / scanner.

[0009] Traditionally, reticle pre-alignment systems are only capable of imaging a reticle at a predetermined single working height. However, it would be advantageous to have the flexibility of being able to image a reticle not only at one height, but also at other heights. Therefore, there is a need for a system that is able to image a reticle at any one of a plurality of possible working heights. Summary of the invention

[0010] A simplified overview of one or more embodiments is given below to provide a basic understanding of the embodiments. This overview is not an exhaustive overview of all contemplated embodiments, and is not intended to identify key or important elements of all embodiments, nor is it intended to define the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to a more detailed description presented later.

[0011] According to one aspect of an embodiment, a system for imaging an object at a first position or a second position is disclosed, the system comprising a beam splitter and an optical element and other optical elements, the beam splitter being used to split light from the object into a first light beam and a second light beam, the optical element receiving the first light beam and imaging the object when the object is at the first position, and the other optical element receiving the second light beam and imaging the object when the object is at the second position.

[0012] According to another aspect of the embodiment, a device for imaging an object at one of a first position and a second position is disclosed, the device comprising: a beam splitter arranged to receive light from the object and for splitting the light into a first light beam and a second light beam, a first optical element arranged to receive the first light beam, and an arrangement including a folding mirror and a second optical element arranged to receive the second light beam. The device may also include a third optical element optically arranged between the beam splitter and the first optical element and a fourth optical element optically arranged between the folding mirror and the second optical element. The device may also include a third optical element optically arranged between the object and the beam splitter.

[0013] According to another aspect of the embodiment, a device for imaging an object at one of a first position and a second position is disclosed, the device comprising: a beam splitter arranged to receive light from the object and for splitting the light into a first light beam and a second light beam, the first beam passing through a first arm, the first arm comprising a first optical element arranged to receive the first light beam and a second optical element arranged to receive the first light beam from the first optical element; a folding mirror arranged to receive the second light beam and reflect the second light beam into the second arm, the second arm comprising a third optical element arranged to receive the reflected second light beam and a fourth optical element arranged to receive the second light beam from the third optical element.

[0014] According to another aspect of the embodiment, a device for imaging an object at one of a first position and a second position is disclosed, the device comprising: a first optical element arranged to receive light from the object; a beam splitter arranged to receive light from the first optical element and for splitting the light into a first light beam and a second light beam, the first beam passing through a first arm, the first arm comprising a second optical element arranged to receive the first light beam; and an arrangement comprising a folding reflector and a third optical element, arranged to receive the second light beam.

[0015] According to another aspect of the embodiment, a device for imaging an object in one of a first position and a second position is disclosed, the device comprising: a beam splitter arranged to split light from the object into a first light beam and a second light beam, a first optical system arranged to receive the first light beam and image the object when the object is in the first position, and a second optical system arranged to receive the second light beam and image the object when the object is in the second position. The first optical system may include a first optical element and a second optical element, and wherein the second optical system includes a folding mirror, a third optical element, and a fourth optical element. The device may also include a first optical element optically arranged between the object and the beam splitter, and wherein the first optical system includes the second optical element and the second optical system includes the folding mirror and the third optical element.

[0016] According to another aspect of the embodiment, a device for imaging an object in a first position or a second position is disclosed, the device comprising: a beam splitter arranged to split light from the object passing through a first optical path into a first light beam and a second light beam, a first optical module arranged to receive the first light beam and image the object when the object is in the first position, and a second optical module arranged to receive the second light beam and image the object when the object is in the second position.

[0017] According to another aspect of the embodiment, a device for imaging an object at one of a first position and a second position is disclosed, the device comprising: a first optical element configured to receive light from the object at a first working distance WD1 from the first position and a second distance WD2 from the second position; a beam splitter arranged to receive light from the first optical element and to split the light into a first light beam and a second light beam, the first beam passing through a first arm, the first arm comprising a first arm lens group having a focal length F1' arranged to receive the first light beam, and the second light beam passing through a second arm lens group, the second arm lens group having a focal length F2' and comprising a first lens and a second lens separated by a distance d; WD1, WD2, F2' and F1' satisfy the following relationship:

[0018]

[0019] Wherein k is a coefficient in the range of about 1 to about 4.

[0020] According to another aspect of the embodiment, a device for imaging an object at any one of a plurality of positions is disclosed, the device comprising: a first optical bifurcation module comprising a first beam splitter and a first imaging module, the first beam splitter being arranged to receive light from the object and for splitting the light into a first light beam and a second light beam, the first imaging module being arranged to receive the second light beam and for imaging the object when the object is at the farthest position among the plurality of positions; at least one additional optical bifurcation module comprising an additional beam splitter and an additional imaging module, the additional beam splitter being arranged to receive light from the first beam and for splitting the light into an imaging beam and a continuous beam, the additional imaging module being arranged to receive the imaging beam and for imaging the object when the object is at another position among the plurality of positions, the continuous beam propagating to a next additional optical bifurcation module and one of the final optical modules, the final optical module being arranged to receive light from the continuous beam and comprising a folding reflector and a final optical imaging module, the final optical imaging module being arranged to receive the second light beam and for imaging the object when the object is at the closest position among the plurality of positions.

[0021] Further embodiments, features, and advantages of the subject matter of the present disclosure, as well as the structure and operation of the various embodiments are described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A lithographic apparatus according to an aspect of an embodiment of the present invention is shown.

[0023] Figure 2 A pre-alignment system configured to pre-align a reticle according to an aspect of an embodiment of the present invention is shown.

[0024] Figure 3 is a diagram of an optical system for imaging a reticle in a single position.

[0025] Figure 4A is a diagram of an optical system for imaging a reticle at two positions as an example of multiple positions according to an aspect of an embodiment of the present invention.

[0026] Figure 4B is a diagram of an optical system for imaging a reticle at multiple positions in accordance with an aspect of an embodiment of the present invention.

[0027] Figure 5 is a diagram of an optical system for imaging a reticle at multiple positions in accordance with an aspect of an embodiment of the present invention.

[0028] Other features and advantages of the present invention and the structure and operation of various embodiments of the present invention are described in detail below with reference to the accompanying drawings. Note that the present invention is not limited to the specific embodiments described herein. Such embodiments are proposed herein for illustrative purposes only. Based on the teachings contained herein, other embodiments will be clear to those skilled in the relevant art. DETAILED DESCRIPTION

[0029] Various embodiments are now described with reference to the accompanying drawings, wherein throughout the text, like reference numerals are used to refer to like elements. In the following description, for the purpose of explanation, many specific details are set forth in order to facilitate a thorough understanding of one or more embodiments. However, it may be clear in some or all cases that any embodiment described below can be practiced without adopting the specific design details described below. In the following specification and in the claims, the terms "upper", "lower", "top", "bottom", "vertical", "horizontal" and similar terms may be used. Unless otherwise stated, these terms are intended to show only relative orientations, rather than any orientation relative to gravity.

[0030] Figure 1A lithographic apparatus 100 according to an embodiment of the invention is schematically depicted. The apparatus comprises an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. UV radiation or EUV radiation), a support structure or support or pattern support (e.g. mask table) MT constructed to support a pattern forming device (e.g. mask) MA and connected to a first positioner PM configured to accurately position the pattern forming device according to certain parameters, a substrate table (e.g. wafer stage) WT constructed to hold a substrate (e.g. a wafer coated with resist) W and connected to a second positioner PW configured to accurately position the substrate according to certain parameters, and a projection system (e.g. refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by the pattern forming device MA onto a target portion C (e.g. comprising one or more dies) of the substrate W.

[0031] The illumination system may include various types of optical components for directing, shaping, or controlling radiation, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof.

[0032] The support structure holds the weight of the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions such as, for example, whether the patterning device is held in a vacuum environment. The support structure can hold the patterning device using mechanical, vacuum, electrostatic, or other clamping techniques. The support structure can be, for example, a frame or table, which can be fixed or movable as desired. The support structure can ensure that the patterning device is in a desired position, for example, relative to a projection system. Any use of the term "reticle" or "mask" herein may be considered synonymous with the more general term "patterning device."

[0033] The term "patterning device" as used herein should be broadly interpreted as referring to any device that can be used to impart a radiation beam with a pattern in its cross-section so as to form a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase-shifting features or so called assist features. Typically, the pattern imparted to the radiation beam will correspond to a specific functional layer in a device such as an integrated circuit being created in the target portion.

[0034] The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography and include mask types such as binary, alternating phase shift, and attenuated phase shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam, which is reflected by the matrix of mirrors.

[0035] The term "projection system" as used herein should be broadly interpreted to cover any type of projection system, including refractive, reflective, refractive-reflective, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation used or other factors such as the use of immersion liquid or the use of a vacuum. Any use of the term "projection lens" herein may be considered synonymous with the more general term "projection system".

[0036] The support structure and substrate table may also be referred to as an article support hereinafter.Articles include, but are not limited to, patterning devices such as reticles and substrates such as wafers.

[0037] As depicted herein, the device is reflective (eg, employing a reflective mask). Alternatively, the device may be transmissive (eg, employing a transmissive mask).

[0038] The lithographic apparatus may be of a type having two (dual stage) or more substrate tables (and / or two or more mask tables). In such a "multi-stage" machine, the additional tables may be used in parallel, or a preparation step may be carried out on one or more tables while exposures are being taken on one or more other tables.

[0039] The lithographic apparatus may also be of a type in which at least a portion of the substrate may be covered by a liquid having a relatively high refractive index (e.g., water) to fill the space between the projection system and the substrate. Immersion liquid may also be applied to other spaces in the lithographic apparatus, such as between the mask and the projection system. Immersion techniques are well known in the art and are used to increase the numerical aperture of the projection system. The term "immersion" as used herein does not imply that structures such as the substrate are necessarily submerged in the liquid, but only that the liquid is located between the projection system and the substrate during exposure.

[0040] refer to Figure 1, the illuminator IL receives a radiation beam from a radiation source SO. The light source and the lithographic apparatus may be separate entities, for example when the light source is an excimer laser. In this case, the light source is not considered to form part of the lithographic apparatus, and the radiation beam is transferred from the source SO to the illuminator IL by means of a beam delivery system comprising, for example, suitable guide mirrors and / or a beam expander. In other cases, the light source may be an integral part of the lithographic apparatus, for example when the light source is a mercury lamp. The source SO and the illuminator IL, and the beam delivery system if required, may be referred to together as a radiation system.

[0041] The illuminator IL may include an adjuster for adjusting the angular intensity distribution of the radiation beam. Typically, at least the outer and / or inner radial extent of the intensity distribution in a pupil plane of the illuminator (commonly referred to as outer σ and inner σ, respectively) may be adjusted. In addition, the illuminator IL may include various other components, such as an integrator and a condenser. The illuminator may be used to adjust the radiation beam to have a desired uniformity and intensity distribution in its cross section.

[0042] A radiation beam B is incident on a patterning device (e.g. a mask) MA, which is held on a support structure (e.g. a mask table) MT, and is patterned by the patterning device. After being reflected by the patterning device (e.g. a mask) MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of a substrate W. With the aid of a second positioner PW and a position sensor IF1 (e.g. an interferometric device, a linear encoder or a capacitive sensor), the substrate table WT can be precisely moved, for example, in order to position a different target portion C in the path of the radiation beam B. Similarly, a first positioner PM and a further position sensor IF1 can be used to precisely position the patterning device (e.g. a mask) MA relative to the path of the radiation beam B, for example after mechanical retrieval from a mask library, or during scanning. Typically, movement of the support structure (e.g. a mask table) MT may be achieved with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) forming part of the first positioner PM. Similarly, movement of the substrate table WT may be achieved using a long-stroke module and a short-stroke module which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the support structure (e.g. mask table) MT may be connected to the short-stroke actuator only, or may be fixed. The patterning device (e.g. mask) MA and substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks shown occupy dedicated target portions, they may be located in the spaces between target portions (these are referred to as scribe alignment marks). Similarly, where more than one die is provided on the patterning device (e.g. mask) MA, the mask alignment marks may be located between the dies.

[0043] Figure 2 A system 200 configured to pre-align a reticle 202 is shown in accordance with an embodiment of the present invention. The system 200 includes an illumination source 208 and a pre-alignment system 206, which may include a plurality of optical elements 212, an optical detector 214, and a controller 216.

[0044] The illumination source 208 is configured to illuminate the reticle 202 with light of a predetermined wavelength for reticle pre-alignment. In one embodiment, the light generated by the illumination source 208 is in the near infrared region of 650nm to 1000nm. In another embodiment, light with a wavelength of 880nm is used. It should be understood that the wavelength of the light generated by the illumination source 208 for reticle alignment is a design choice, as understood by those skilled in the art. In the present embodiment, the illumination source 208 includes dual light sources 208a-b. In alternative embodiments, the illumination source 208 may include a single light source or more than two light sources. It should be understood that the number of light sources is a design choice, as understood by those skilled in the art. The illumination source 208 generates radiation beams 209a-b, which are used to illuminate the alignment targets 204a-b of the reticle 202. The interaction of the light beams 209a-b with the alignment target 204 generates imaging beams 210a-b, which are directed into the pre-alignment system 206. The imaging beams 210a-b are directed by optical element 212 onto an optical detector 214 controlled by controller 216. Controller 216 generates a control signal 218 for pre-aligning reticle 202 based on the imaging beams 210a-b. According to one aspect of the embodiment, reticle 202 is a reflective patterning device for extreme ultraviolet lithography (EUV). According to one aspect of the embodiment, reticle 202 is reticle MA, and alignment targets 204a-b are alignment targets M1 and M2, such as Figure 1 A similar system can be used for a transmissive patterning device in which illuminators 209a and 209b are placed above reticle 202.

[0045] Figure 3 is a diagram of a system for imaging an object (eg, a reticle) at a single object position 300 . Figure 3 The system is telecentric, where the chief ray is collimated and parallel to the optical axis in the image and / or object space. The key feature of telecentricity is the constant magnification regardless of the image and / or object position. The light from the object is partially focused by the first optical system (lens group) 310, and then the light path is folded by the folding mirror 320. The light in the folded light path is then additionally focused by the second optical system (lens group) 330 and imaged at the image plane 340.

[0046] Figure 3 The system is advantageously used to image objects that can be located at only a single height relative to the optical system. However, as described above, it is advantageous to minimize the time required for pre-alignment by possibly shortening or eliminating steps in the pre-alignment process. One technique for this minimization involves increasing the height (working distance) of a conventional reticle pre-alignment system and adding a second reticle position at a second working distance. According to one aspect of the embodiment, in order to meet this requirement, a multi-channel optical arrangement is used. The multi-channel optical arrangement involves multiple optical branches partially sharing an optical path.

[0047] According to one aspect of an embodiment, in one arrangement, referred to herein as a stacked arrangement, passive elements such as beam splitters and fold mirrors are in object space, and there are no shared active optical elements (e.g., lens groups) in the shared object space. A stacked version of the system involves using two identical branches or arms that share a common object space. In another arrangement, referred to herein as a bifurcated arrangement, some active optical elements are located in a shared (common) portion of the path and are therefore shared. This has the advantage that the design can be made more compact and use fewer lenses.

[0048] Figure 4A 4 is a diagram of a stacked system for imaging an object (e.g., a reticle) at multiple positions (object high position 400 or object low position 410). The system of FIG. 4 is telecentric, where the chief ray is collimated and parallel to the optical axis in image and / or object space. Light from the object is split by a beam splitter 420 (e.g., a 50% / 50% beam splitter), which splits the beam into an upper arm and a lower arm. Along the upper arm, there is a first upper arm lens group 430 and a second upper arm lens group 440, which together image the object at an image plane 450 when the object is in the high position 400. The lower arm is folded by a folding mirror 460 which redirects light to a first lower arm lens group 470 and a second lower arm lens group 480 which together image the object at an image plane 490 when the object is in a low position 410 .

[0049] In general, if desired, the number of branches can be greater than two for both stacked and bifurcated (multi-bifurcated) arrangements. In addition, different magnifications can be formed by different branches. Figure 4B is a diagram of a stacked system for imaging an object (eg, a reticle) at multiple positions (object high position 400, intermediate position 400', object low position 410, or other positions indicated by solid circles at the top of the diagram). Figure 4BThe system is telecentric, where the chief ray is collimated and parallel to the optical axis in the image and / or object space. The light from the object is split by a beam splitter 420 (e.g., a 50% / 50% beam splitter), which splits the beam into the upper arm and the lower arm. Along the upper arm, there is a first upper arm lens group 430 and a second upper arm lens group 440, which together image the object at an image plane 450 when the object is in a high position 400. The light from the object is again passed through a beam splitter 420' (e.g., a 50% / 50% beam splitter), which splits the beam into the intermediate arm and the continuous arm. Along the middle arm, there are first middle arm lens group 430' and second middle arm lens group 440', which together image the object at image plane 450' when the object is in the middle position 400'. The lower arm is folded by folding mirror 460, which redirects light to first lower arm lens group 470 and second lower arm lens group 480, which together image the object at image plane 490 when the object is in the low position 410. The solid circle in the lower portion of the figure is intended to indicate that additional arms may also be included for imaging objects at additional positions.

[0050] Figure 5 is a diagram of a bifurcated system for imaging an object (eg, a reticle) at either an object high position 500 or an object low position 510 . Figure 5 The system is telecentric, where the chief rays are collimated and parallel to the optical axis in image and / or object space. Light from the object is received by the front shared lens group 520 and then split by a beam splitter 530 (e.g., a 50% / 50% splitter mirror), which splits the beam into an upper arm and a lower arm. Along the upper arm, there is an upper arm rear lens group 540, which images the object at an image plane 550 when the object is in a high position 500. The lower arm is folded by a folding mirror 560, which redirects the rays to a lower arm lens group 570, which images the object at an image plane 580 when the object is in a low position 510.

[0051] In this arrangement, front lens group 520 is common to different working distances WD1 and WD2. The difference between these working distances ΔWD = WD1-WD2 is selected to be greater than the depth of field and may be greater than WD2.

[0052] The relationship between the focal length of the rear lens groups 540 and 570 and the working distances WD1 and WD2 can be defined by the following equation:

[0053]

[0054] Wherein F2′ is the focal length of the rear lens group 570 short through WD2, F1′ is the focal length of the rear lens group 540 long through WD1, and k is a coefficient that depends on ΔWD and the distance d between the two components in the rear lens group 570 and is in the range of about 1 to about 4.

[0055] Taking ΔWD>WD2 as an example, let WD1=75.5mm, WD2=35.5mm. In this case, the above formula gives:

[0056]

[0057] As another example, let WD1 = 66 mm and WD2 = 26 mm. In this case, the above formula gives:

[0058]

[0059] In this case, since the distances between the components in the rear lens group 570 have changed, the focal length F2', ie, the focal length of the rear lens group 570 short of the pass WD2, changes.

[0060] The embodiments may be further described using the following terms:

[0061] 1. An apparatus for imaging an object at one of a first position and a second position, the apparatus comprising:

[0062] a beam splitter arranged to receive light from the object and to split the light into a first light beam and a second light beam;

[0063] a first optical element arranged to receive the first light beam;

[0064] An arrangement comprising a folding mirror and a second optical element is arranged to receive the second light beam.

[0065] 2. The device according to clause 1 further comprises a third optical element optically arranged between the beam splitter and the first optical element, and a fourth optical element optically arranged between the folding mirror and the second optical element.

[0066] 3. The device according to clause 1 further comprises a third optical element optically arranged between the object and the beam splitter.

[0067] 4. An apparatus for imaging an object at one of a first position and a second position, the apparatus comprising:

[0068] a beam splitter arranged to receive light from the object and to split the light into a first beam and a second beam, the first beam passing through the first arm,

[0069] The first arm includes a first optical element arranged to receive the first light beam, and a second optical element arranged to receive the first light beam from the first optical element;

[0070] a folding mirror arranged to receive the second light beam and reflect the second light beam into the second arm,

[0071] The second arm comprises a third optical element arranged to receive the reflected second light beam, and a fourth optical element arranged to receive the second light beam from the third optical element.

[0072] 5. An apparatus for imaging an object at one of a first position and a second position, the apparatus comprising:

[0073] a first optical element arranged to receive light from the object;

[0074] a beam splitter arranged to receive light from the first optical element and for splitting the light into a first beam and a second beam, the first beam passing through a first arm, the first arm comprising a second optical element arranged to receive the first beam; and

[0075] An arrangement comprising a fold mirror and a third optical element is arranged to receive said second light beam.

[0076] 6. An apparatus for imaging an object at one of a first position and a second position, the apparatus comprising:

[0077] a beam splitter arranged to split light from the object into a first light beam and a second light beam;

[0078] a first optical system arranged to receive the first light beam and to image the object when the object is in the first position; and

[0079] A second optical system is arranged to receive the second light beam and to image the object when the object is in the second position.

[0080] 7. An apparatus according to clause 6, wherein the first optical system comprises a first optical element and a second optical element, and wherein the second optical system comprises a folding mirror, a third optical element and a fourth optical element.

[0081] 8. The apparatus of clause 6, further comprising a first optical element optically arranged between the object and the beam splitter, and wherein the first optical system comprises a second optical element and the second optical system comprises a folding mirror and a third optical element.

[0082] 9. A device for imaging an object at a first position or a second position, the device comprising:

[0083] a beam splitter arranged to split the light from the object through the first light path into a first light beam and a second light beam;

[0084] a first optical module arranged to receive the first light beam and to image the object when the object is in the first position; and

[0085] A second optical module is arranged to receive the second light beam and to image the object when the object is in the second position.

[0086] 10. An apparatus for imaging an object at one of a first position and a second position, the apparatus comprising:

[0087] a first optical element configured to receive light from the object at a first working distance WD1 from the first position and a second distance WD2 from the second position;

[0088] A beam splitter is arranged to receive light from the first optical element and is used to split the light into a first beam and a second beam, the first beam passes through a first arm, the first arm includes a first arm lens group with a focal length F1' arranged to receive the first beam, and the second beam passes through a second arm lens group, the second arm lens group has a focal length F2' and includes a first lens and a second lens separated by a distance d; WD1, WD2, F2' and F1' satisfy the following relationship

[0089]

[0090] Wherein k is a coefficient in the range of about 1 to about 4.

[0091] 11. An apparatus for imaging an object at any one of a plurality of positions, the apparatus comprising:

[0092] a first optical splitting module comprising a first beam splitter arranged to receive light from the object and for splitting the light into a first light beam and a second light beam, and a first imaging module arranged to receive the second light beam and for imaging the object when the object is at a farthest position among the plurality of positions;

[0093] at least one additional optical bifurcation module, comprising an additional beam splitter arranged to receive light from the first light beam and for splitting the light into an imaging beam and a continuous beam, the additional imaging module arranged to receive the imaging beam and for imaging the object when the object is in another one of the plurality of positions, the continuous beam propagating to one of a next additional optical bifurcation module and a final optical module, the final optical module arranged to receive light from the continuous beam and comprising a folding reflector and a final optical imaging module, the final optical imaging module arranged to receive the second light beam and for imaging the object when the object is in a nearest one of the plurality of positions.

[0094] It will be clear to one of ordinary skill in the art that the above principles can also be applied to systems for imaging an object at more than two positions. In addition, although the above description uses an optical system for semiconductor lithography as an example, it will be clear to one of ordinary skill in the art that the disclosed system can be used in other applications where it is desired to image an object, where the object may be in any one of a plurality of positions.

[0095] The present disclosure is made with the aid of functional building blocks that illustrate the implementation of specific functions and their relationships. For ease of description, the boundaries of these functional building blocks have been arbitrarily defined herein. Alternative boundaries may be defined so long as the specified functions and their relationships are properly performed. For example, the measurement module functions may be divided between several systems, or at least partially performed by the overall control system.

[0096] The above description includes examples of one or more embodiments. Of course, it is not possible to describe every possible combination of components or methods for the purpose of describing the aforementioned embodiments, but it will be appreciated by those of ordinary skill in the art that many other combinations and permutations of various embodiments are possible. Therefore, the described embodiments are intended to cover all such changes, modifications and variations that fall within the spirit and scope of the appended claims. In addition, to the extent that the term "includes" is used in the detailed description or claims, such terms are intended to be inclusive in a manner similar to the term "comprising" because when used as a transitional term in the claims, it is interpreted as "comprising". In addition, although the elements of the described aspects and / or embodiments may be described or claimed in the singular, the plural form is contemplated unless the limitation to the singular form is explicitly stated. In addition, unless otherwise stated, all or part of any aspect and / or embodiment may be used together with all or part of any other aspect and / or embodiment.

Claims

1. A device for imaging an object at one of a first position and a second position, the device include: a beam splitter arranged to receive light from the object and to split the light into a first light beam and a second light beam; a first arrangement comprising a first optical element arranged to receive the first light beam, wherein the first arrangement is configured to image the object when the object is in the first position; A second arrangement comprising a fold mirror and a second optical element, wherein the second arrangement is arranged to receive the second light beam and is configured to image the object when the object is in the second position.

2. The apparatus of claim 1, further comprising a third optical element optically arranged between the beam splitter and the first optical element and a fourth optical element optically arranged between the folding mirror and the second optical element. 3 . The apparatus of claim 1 , further comprising a third optical element optically arranged between the object and the beam splitter.

4. A device for imaging an object at one of a first position and a second position, the device include: a beam splitter arranged to receive light from the object and to split the light into a first light beam and a second light beam, the first light beam passing through the first arm, the first arm comprising a first optical element arranged to receive the first light beam, and a second optical element arranged to receive the first light beam from the first optical element, wherein the first arm is configured to image the object when the object is in the first position; a folding mirror arranged to receive the second light beam and reflect the second light beam into the second arm, The second arm includes a third optical element arranged to receive the reflected second light beam, and a fourth optical element arranged to receive the second light beam from the third optical element, wherein the second arm is configured to image the object when the object is in the second position.

5. A device for imaging an object at one of a first position and a second position, the device include: a first optical element arranged to receive light from the object; a beam splitter arranged to receive light from the first optical element and for splitting the light into a first light beam and a second light beam, the first light beam passing through a first arm, the first arm comprising a second optical element arranged to receive the first light beam, wherein the first arm is configured to image the object when the object is in the first position; as well as An arrangement comprising a fold mirror and a third optical element is arranged to receive the second light beam, wherein the arrangement is configured to image the object when the object is in the second position.

6. A device for imaging an object at one of a first position and a second position, the device include: a beam splitter arranged to split light from the object into a first light beam and a second light beam; a first optical system arranged to receive the first light beam and to image the object when the object is in the first position; as well as A second optical system is arranged to receive the second light beam and to image the object when the object is in the second position.

7. The apparatus of claim 6, wherein the first optical system comprises a first optical element and a second optical element, and wherein the second optical system comprises a folding mirror, a third optical element, and a fourth optical element.

8. The apparatus of claim 6, further comprising a first optical element optically disposed between the object and the beam splitter, and wherein the first optical system comprises a second optical element and the second optical system comprises a folding mirror and a third optical element.

9. A device for imaging an object at a first position or a second position, the device include: a beam splitter arranged to split the light from the object through the first light path into a first light beam and a second light beam; a first optical module arranged to receive the first light beam and to image the object when the object is in the first position; as well as A second optical module is arranged to receive the second light beam and to image the object when the object is in the second position.

10. A device for imaging an object at one of a first position and a second position, the device include: a first optical element configured to receive light from the object at a first working distance WD1 from the first position and a second distance WD2 from the second position; a beam splitter arranged to receive light from the first optical element and to split the light into a first beam and a second beam, the first beam passing through a first arm, the first arm comprising a first arm lens group having a focal length F1' arranged to receive the first beam and configured to image the object when the object is in the first position, and the second beam passing through a second arm comprising a second arm lens group, the second arm lens group having a focal length F2' and comprising a first lens and a second lens separated by a distance d, the second arm being configured to image the object when the object is in the second position; WD1, WD2, F2' and F1' satisfy the following relationship Where k is a coefficient in the range of 1 to 4.

11. A device for imaging an object at any one of a plurality of positions, the device include: a first optical splitting module comprising a first beam splitter arranged to receive light from the object and for splitting the light into a first light beam and a second light beam, and a first imaging module arranged to receive the second light beam and for imaging the object when the object is at a farthest position among the plurality of positions; at least one additional optical bifurcation module, comprising an additional beam splitter arranged to receive light from the first light beam and for splitting the light into an imaging beam and a continuous beam, the additional imaging module arranged to receive the imaging beam and for imaging the object when the object is in another one of the plurality of positions, the continuous beam propagating to one of a next additional optical bifurcation module and a final optical module, the final optical module arranged to receive light from the continuous beam and comprising a folding reflector and a final optical imaging module, the final optical imaging module arranged to receive the second light beam and for imaging the object when the object is in a nearest one of the plurality of positions.

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