Polarization switch

Abstract

Disclosed is an apparatus comprising a switch module configured to switch one or more optical elements in and out of a light path. The switch module includes a movable support assembly coupled to a first optical element, the movable support assembly configured to rotate the first optical element in and out of the light path along an axis of rotation that is not parallel to the light path. The switch module also includes a controller coupled to the movable support assembly, the controller moves a movable support structure of the movable support assembly to rotate the first optical element into or out of the light path.

Description

POLARIZATION SWITCHCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of US application 63 / 761,002 which was filed on February 20, 2025 and which is incorporated herein in its entirety by reference.TECHNICAL FIELD

[0002] The description herein relates generally to switches for components that alter the polarization of light utilized for lithographic processes. More particularly, the disclosure includes apparatus, methods, and computer programs for fast switching between different polarization states.BACKGROUND

[0003] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern (also often referred to as "design layout" or "design") of a patterning device (e.g., a mask) onto a layer of radiation- sensitive material (resist) provided on a substrate (e.g., a wafer).

[0004] As semiconductor manufacturing processes continue to advance, the dimensions of circuit elements have continually been reduced while the amount of functional elements, such as transistors, per device has been steadily increasing over decades, following a trend commonly referred to as 'Moore's law'. To keep up with Moore's law the semiconductor industry is chasing technologies that enable to create increasingly smaller features. To project a pattern on a substrate a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features which are patterned on the substrate. Typical wavelengths currently in use are 365 nm (i-line), 248 nm, 193 nm and 13.5 nm. A lithographic apparatus, which uses extreme ultraviolet (EUV) radiation, having a wavelength within a range of 4 nm to 20 nm, for example 6.7 nm or 13.5 nm, may be used to form smaller features on a substrate than a lithographic apparatus which uses, for example, radiation with a wavelength of 193 nm.

[0005] Products that may be produced by the above methods (e.g., wafers used with the production of computer chip components) often require measurements of surface features to quantify the quality of production or to find unacceptable errors or deviations.

[0006] Optical metrology sensors can be used to determine focus and / or dose utilizing various marks, which can be patterns or other structural features formed on a substrate that can be measured and compared to the expected pattern to evaluate the accuracy of the produced pattern. For example, an optical metrology sensor can be configured to project a radiation beam onto an mark and determine, based on a reflected radiation beam, a focus, dose, alignment, overlay, etc. Some optical metrology sensors can illuminate the mark with light at different wavelengths and / or polarizations as differenttypes of incident / scattered light can convey different information. The signals received from the light reflected or scattered from the mark can be dependent upon the wavelengths and polarizations. As such, received signals can be utilized to determine focus and / or dose.SUMMARY

[0007] In some aspects, the techniques described herein relate to an apparatus including: a switch module configured to switch one or more optical elements in and out of a light path, the switch module including: a movable support assembly coupled to a first optical element, the movable support assembly configured to rotate the first optical element in and out of the light path along an axis of rotation that is not parallel to the light path; and a controller coupled to the movable support assembly, wherein the controller moves a movable support structure of the movable support assembly to rotate the first optical element into or out of the light path.

[0008] In some aspects, the techniques described herein relate to an apparatus, wherein the axis of rotation is perpendicular to the light path.

[0009] In some aspects, the techniques described herein relate to an apparatus, further including a second optical element also coupled to the movable support structure, wherein the controller rotates the movable support structure to move either the first optical element or the second optical element into or out of the light path.

[0010] In some aspects, the techniques described herein relate to an apparatus, the movable support assembly including the movable support structure and a servo.

[0011] In some aspects, the techniques described herein relate to an apparatus, wherein the movable support structure is a bracket coupled to the servo and supporting the first optical element.

[0012] In some aspects, the techniques described herein relate to an apparatus, the servo including a motor configured to rotate the movable support structure in response to commands received from the controller.

[0013] In some aspects, the techniques described herein relate to an apparatus, wherein the motor is a stepper motor.

[0014] In some aspects, the techniques described herein relate to an apparatus, wherein the first optical element and the second optical element are polarizers.

[0015] In some aspects, the techniques described herein relate to an apparatus, wherein the first optical element is a V polarizer.

[0016] In some aspects, the techniques described herein relate to an apparatus, wherein the second optical element is an H polarizer.

[0017] In some aspects, the techniques described herein relate to an apparatus, wherein the first optical element and the second optical element are wave plates that alter a polarization state of light in the light path.

[0018] In some aspects, the techniques described herein relate to an apparatus, wherein the first optical element or the second optical element include a half-wave plate.

[0019] In some aspects, the techniques described herein relate to an apparatus, wherein the first optical element or the second optical element include two quarter-wave plates.

[0020] In some aspects, the techniques described herein relate to an apparatus, wherein the wave plates are achromatic.

[0021] In some aspects, the techniques described herein relate to an apparatus, wherein the wave plates operate to rotate an electric field of the light over a spectral range of 400-1600 nm.

[0022] In some aspects, the techniques described herein relate to an apparatus, wherein the first optical element has a first spectral range and the second optical element has a second spectral range that combine to cover a spectral range larger than either the first spectral range or the second spectral range.

[0023] In some aspects, the techniques described herein relate to an apparatus, wherein the first spectral range is 600-2000 nm and the second spectral range is 380-1100 nm.

[0024] In some aspects, the techniques described herein relate to an apparatus, wherein one or more of the wave plates is a half-wave plate.

[0025] In some aspects, the techniques described herein relate to an apparatus, further including a polarizer also coupled to the movable support structure.

[0026] In some aspects, the techniques described herein relate to an apparatus, wherein the polarizer is bonded to the half-wave plate.

[0027] In some aspects, the techniques described herein relate to an apparatus, wherein the first optical element and the second optical element are disposed on the switch module to move either of them utilizing a narrow range of actuation.

[0028] In some aspects, the techniques described herein relate to an apparatus, wherein the narrow range of actuation is less than ± 20 degrees of rotation of the movable support structure.

[0029] In some aspects, the techniques described herein relate to an apparatus, wherein the narrow range of actuation is less than ± 3 mm.

[0030] In some aspects, the techniques described herein relate to an apparatus, the switch module configured to cover at least half of the narrow range of actuation in 2 ms or less.

[0031] In some aspects, the techniques described herein relate to an apparatus including: a switch module configured to switch an optical element in and out of a light path, the switch module including: a movable support assembly coupled to the optical element; and a controller coupled to the movable support assembly, wherein the controller moves a movable support structure of the movable support assembly to move the optical element into or out of the light path utilizing a narrow range of actuation.

[0032] In some aspects, the techniques described herein relate to an apparatus, wherein the narrow range of actuation is less than ± 20 degrees of rotation of the movable support structure.

[0033] In some aspects, the techniques described herein relate to an apparatus, wherein the narrow range of actuation is less than ± 3 mm.

[0034] In some aspects, the techniques described herein relate to an apparatus, the switch module configured to cover at least half of the narrow range of actuation in 2 ms or less.

[0035] In some aspects, the techniques described herein relate to an apparatus, the movable support assembly including the movable support structure and a servo.

[0036] In some aspects, the techniques described herein relate to an apparatus, wherein the movable support structure is a bracket coupled to the servo and supporting the optical element.

[0037] In some aspects, the techniques described herein relate to an apparatus, the servo including a motor configured to actuate the movable support structure in response to commands received from the controller.

[0038] In some aspects, the techniques described herein relate to an apparatus, wherein the motor is a stepper motor.

[0039] In some aspects, the techniques described herein relate to an apparatus, wherein the optical element is a polarizer.

[0040] In some aspects, the techniques described herein relate to an apparatus, wherein the optical element is a V polarizer.

[0041] In some aspects, the techniques described herein relate to an apparatus, wherein the optical element is an H polarizer.

[0042] In some aspects, the techniques described herein relate to an apparatus, wherein the optical element is a wave plate.

[0043] In some aspects, the techniques described herein relate to an apparatus, wherein the wave plate is achromatic.

[0044] In some aspects, the techniques described herein relate to an apparatus, wherein the wave plate operates to rotate an electric field of light in the light path over a spectral range of 400-1600 nm.

[0045] In some aspects, the techniques described herein relate to an apparatus, wherein the wave plate is a half-wave plate.

[0046] In some aspects, the techniques described herein relate to an apparatus, further including a polarizer also coupled to the movable support structure.

[0047] In some aspects, the techniques described herein relate to an apparatus, wherein the polarizer is bonded to the half-wave plate.

[0048] In some aspects, the techniques described herein relate to a semiconductor device manufacturing method including: receiving a substrate with a photoresist layer; directing EUV or DUV radiation from a radiation source to transfer a pattern from a mask onto the photoresist layer, the directing including: switching a first optical element into or out of a light path of light from the radiation source utilizing a movable support structure coupled to the first optical element and configured to rotate the first optical element in and out of the light path along an axis of rotation that is not parallel to the light path; and removing a portion of the photoresist layer to form the pattern over the substrate.BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings, which are incorporated in and constitute a part of this specification, show certain aspects of the subject matter disclosed herein and, together with the description, help explain some of the principles associated with the disclosed implementations. In the drawings,

[0050] Figure 1 schematically depicts a lithography apparatus, according to an embodiment of the present disclosure.

[0051] Figure 2 schematically depicts an embodiment of a lithographic cell or cluster, according to an embodiment of the present disclosure.

[0052] Figure 3A is a schematic diagram illustrating a switch module for switching optical elements in and out of a light path, according to an embodiment of the present disclosure.

[0053] Figure 3B is a schematic diagram illustrating a switch module moving a polarizer into the light path, according to an embodiment of the present disclosure.

[0054] Figure 3C is a schematic diagram illustrating a switch module moving a different polarizer into the light path, according to an embodiment of the present disclosure.

[0055] Figure 4A is a diagram illustrating an example switch module, according to an embodiment of the present disclosure.

[0056] Figure 4B is a diagram illustrating a top view of switch module where no optical elements are in a light path, according to an embodiment of the present disclosure.

[0057] Figure 4C is a diagram illustrating a top view of switch module where first optical element is rotated into light path, according to an embodiment of the present disclosure.

[0058] Figure 4D is a diagram illustrating a top view of switch module where second optical element is rotated into light path, according to an embodiment of the present disclosure.

[0059] Figures 5A, 5B, and 5C are schematic diagrams of a switch module having a linear configuration with positions shown analogous to the examples of Figures 4B, 4C, and 4D, according to an embodiment of the present disclosure.

[0060] Figure 6A is a schematic diagram illustrating a switch module configured to rotate a wave plate in or out of a light path, according to an embodiment of the present disclosure.

[0061] Figure 6B is a schematic diagram illustrating a switch module rotating a wave plate into a light path, according to an embodiment of the present disclosure.

[0062] Figures 7A and 7B are schematic diagrams illustrating a single optical element switchable over a narrow range of actuation, according to an embodiment of the present disclosure.

[0063] Figures 8A and 8B are schematic diagrams of a switch module having a linear configuration with positions shown analogous to the examples of Figures 7A and 7B, according to an embodiment of the present disclosure.

[0064] Figure 9 is a block diagram of an example computer system, according to an embodiment of the present disclosure.DETAILED DESCRIPTION

[0065] Figure 1 schematically depicts an embodiment of a lithographic apparatus LA. The apparatus comprises an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. UV radiation, DUV radiation, or EUV radiation); a support structure (e.g. a mask table) MT constructed to support a patterning device (e.g. a mask) MA and connected to a first positioner PM configured to accurately position the patterning device in accordance with certain parameters; a substrate table (e.g. a wafer table) WT (e.g., WTa, WTb or both) configured to hold a substrate (e.g. a resist coated wafer) W and coupled to a second positioner PW configured to accurately position the substrate in accordance with certain parameters; and a projection system (e.g. a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g. comprising one or more dies and often referred to as fields) of the substrate W. The projection system is supported on a reference frame RF.

[0066] The illuminator IL may comprise adjuster AD configured to adjust the (angular / spatial) intensity distribution of the beam. Generally, at least the outer and / or inner radial extent of the intensity distribution in a pupil plane of the illuminator can be adjusted. The illuminator IL may be operable to alter the polarization of the beam and may be operable to adjust the polarization using adjuster AD. The polarization state of the radiation beam across a pupil plane of the illuminator IL may be referred to as a polarization mode. The use of different polarization modes may allow greater contrast to be achieved in the image formed on the substrate W. In addition, the illuminator IL generally comprises various other components, such as an integrator IN and a condenser CO.

[0067] The support structure MT supports 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 or not the patterning device is held in a vacuum environment. The support structure may use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The support structure may be a frame or a table, for example, which may be fixed or movable as required. The support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system.

[0068] Any use of the terms "reticle" or "mask" herein may be considered synonymous with the more general term "patterning device." The term "patterning device" used herein should be broadly interpreted as referring to any device that can be used to impart a pattern in a target portion of the substrate. In an embodiment, a patterning device is any device that can be used to impart a radiation beam with a pattern in its cross-section to create 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. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device being created in a target portion of the device, such as anintegrated circuit. A patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels.

[0069] The term "projection system" (PS) should be broadly interpreted as encompassing any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic, and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, or for other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term "projection lens" herein may be considered as synonymous with the more general term "projection system."

[0070] The projection system PS may comprise a plurality of optical (e.g., lens) elements and may further comprise an adjustment mechanism configured to adjust one or more of the optical elements to correct for aberrations (phase variations across the pupil plane throughout the field). The lithographic apparatus may be of a type having two (dual stage) or more tables (e.g., two or more substrate tables WTa, WTb, two or more patterning device tables, a substrate table WTa and a table WTb below the projection system without a substrate that is dedicated to, for example, facilitating measurement, and / or cleaning, etc.). In such "multiple stage" machines, the additional tables may be used in parallel, or preparatory steps may be conducted on one or more tables while one or more other tables are being used for exposure. For example, alignment measurements using an alignment sensor AS and / or level (height, tilt, etc.) measurements using a level sensor LS may be made.

[0071] In operation of the lithographic apparatus, a radiation beam is conditioned and provided by the illumination system IL. The radiation beam B is incident on the patterning device (e.g., mask) MA, which is held on the support structure (e.g., mask table) MT, and is patterned by the patterning device. Having traversed the patterning device MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor IF (e.g. an interferometric device, linear encoder, 2-D encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. to position different target portions C in the path of the radiation beam B. Similarly, the first positioner PM and another position sensor (which is not explicitly depicted in Figure 1) can be used to accurately position the patterning device MA with respect to the path of the radiation beam B, e.g. after mechanical retrieval from a mask library, or during a scan. In general, movement of the support structure MT may be realized with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT may be realized 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 MT may be connected to a shortstroke actuator only, or may be fixed. Patterning device MA and substrate W may be aligned using patterning device alignment marks Ml, M2 and substrate alignment marks Pl, P2. Although the substrate alignment marks as illustrated occupy dedicated target portions, they may be located in spaces between target portions (these are known as scribe-lane alignment marks). Similarly, in situations inwhich more than one die is provided on the patterning device MA, the patterning device alignment marks may be located between the dies.

[0072] Between processing steps, alignment sensor AS can be utilized to confirm that the wafer is properly aligned relative to the reticle. The alignment sensor AS can provide illumination (e.g., light of varying wavelengths and / or polarizations) to an alignment mark and the diffraction pattern of the reflected light may be captured and analyzed to determine the position of the alignment mark. Errors in alignment can then be corrected before processing continues. One example of an alignment sensor AS can be a dual self -referencing interferometer, as described in further detail herein.

[0073] Also, as part of a manufacturing process (i.e., in-line operation) or before / after / between processing steps (i.e., offline operation), additional metrology can occur utilizing an overlay sensor to determine errors in alignment between process layers - overlay. An overlay sensor can also be diffraction-based but may utilize different or additional wavelengths and polarizations of light to obtain measurements of reference marks (overlay marks) at different process layers in order to determine the overlay.

[0074] The substrate may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist) or a metrology or inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already includes multiple processed layers.

[0075] The terms "radiation" and "beam" used herein with respect to lithography encompass all types of electromagnetic radiation, including ultraviolet (UV) or deep ultraviolet (DUV) radiation (e.g. having a wavelength of 365, 248, 193, 157 or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.

[0076] The lithographic apparatus LA and radiation source SO described herein can be used in a method for manufacturing a semiconductor device. A semiconductor device manufacturing method comprises receiving a substrate W with a photoresist layer. The method further comprises directing a radiation beam from radiation source SO to transfer a pattern from a mask onto the photoresist layer. This could be achieved by a patterning device which is configured to form a patterned radiation beam, imparting the patterned radiation beam onto the photoresist layer. The method for manufacturing a semiconductor device further comprises the step of removing a portion of the photoresist layer to form the pattern over the substrate W.

[0077] The substrate W may be made of silicon or other semiconductor materials. Alternatively or additionally, the substrate W may include other semiconductor materials such as germanium (Ge) or carbon (C). In some embodiments, the semiconductor substrate is made of a compound semiconductor such as IILV compound semiconductors, ILV compound semiconductors, and / or any suitableintegration of Group IV materials. In some embodiments, the substrate W may be a silicon-on-insulator (SOI) or a germanium-on-insulator (GOI) substrate.

[0078] The semiconductor device made from the substrate W may have various device elements. Examples of semiconductor device elements that are formed over the substrate W include transistors (e.g., planar or non-planar metal oxide semiconductor field effect transistors (MOSFET), bipolar junction transistors (BJT), high-voltage transistors, high-frequency transistors, etc.), diodes, CMOS image sensors, passive devices, and / or other applicable elements. Various processes may be performed to form the semiconductor device elements, such as deposition, etching, implantation, epitaxial growth, polishing, thermal treatment, and / or other suitable processes. In some embodiments, the substrate W is coated with a photoresist layer sensitive to the EUV light.

[0079] As shown in Figure 2, the lithographic apparatus LA may form part of a lithographic cell LC, also sometimes referred to a lithocell or cluster, which also includes apparatuses to perform pre- and post-exposure processes on a substrate. Conventionally these include one or more spin coaters SC to deposit one or more resist layers, one or more developers to develop exposed resist, one or more chill plates CH and / or one or more bake plates BK. A substrate handler, or robot, RO picks up one or more substrates from input / output port I / O I , I / O2, moves them between the different process apparatuses and delivers them to the loading bay LB of the lithographic apparatus. These apparatuses, which are often collectively referred to as the track, are under the control of a track control unit TCU which is itself controlled by the supervisory control system SCS, which also controls the lithographic apparatus via lithography control unit LACU. Thus, the different apparatuses can be operated to maximize throughput and processing efficiency.

[0080] In order that a substrate that is exposed by the lithographic apparatus is exposed correctly and consistently and / or in order to monitor a part of the patterning process (e.g., a device manufacturing process) that includes at least one pattern transfer step (e.g., an optical lithography step), it is desirable to inspect a substrate or other object to measure or determine one or more properties such as alignment, overlay (which can be, for example, between structures in overlying layers or between structures in a same layer that have been provided separately to the layer by, for example, a double patterning process), line thickness, critical dimension (CD), focus offset, a material property, etc. Accordingly, a manufacturing facility in which lithocell LC is located also typically includes a metrology system that measures some or all of the substrates W (Figure 1) that have been processed in the lithocell or other objects in the lithocell. The metrology system may be part of the lithocell LC, for example it may be part of the lithographic apparatus LA (such as alignment sensor AS (Figure 1)).

[0081] The one or more measured parameters may include, for example, alignment, overlay between successive layers formed in or on the patterned substrate, critical dimension (CD) (e.g., critical linewidth) of, for example, features formed in or on the patterned substrate, focus or focus error of an optical lithography step, dose or dose error of an optical lithography step, optical aberrations of an optical lithography step, etc. This measurement is often performed on one or more dedicated metrologymarks provided on the substrate. The measurement can be performed after-development of a resist but before etching, after-etching, after deposition, and / or at other times.

[0082] A fast and non-invasive form of specialized metrology tool is one in which a beam of radiation, which may have varying polarizations and / or wavelengths, is directed onto a target on the surface of the substrate and properties of the scattered (diffracted / reflected) beam are measured. By evaluating one or more properties of the radiation scattered by the substrate, one or more properties of the substrate can be determined. Traditionally, this may be termed diffraction-based metrology. Applications of this diffraction-based metrology include the measurement of overlay, alignment, etc. For example, overlay and / or alignment can be measured by comparing parts of the diffraction spectrum (for example, comparing different diffraction orders in the diffraction spectrum of a periodic grating).

[0083] Thus, in a device fabrication process (e.g., a patterning process or a lithography process), a substrate or other objects may be subjected to various types of measurement during or after the process. The measurement may determine whether a particular substrate is defective, may establish adjustments to the process and apparatuses used in the process (e.g., aligning two layers on the substrate or aligning the patterning device to the substrate), may measure the performance of the process and the apparatuses, or may be for other purposes.

[0084] Metrology results may be provided directly or indirectly to the supervisory control system SCS. If an error is detected, an adjustment may be made to exposure of a subsequent substrate (especially if the inspection can be done soon and fast enough that one or more other substrates of the batch are still to be exposed) and / or to subsequent exposure of the exposed substrate. Also, an already exposed substrate may be stripped and reworked to improve yield, or discarded, thereby avoiding performing further processing on a substrate known to be faulty. In a case where only some target portions of a substrate are faulty, further exposures may be performed only on those target portions which meet specifications. Other manufacturing process adjustments are contemplated.

[0085] Throughput in a metrology system can be an important factor in the overall throughput of a manufacturing process that utilizes such systems. When different types of light (e.g., wavelengths, polarizations, etc.) need to be delivered or received in a metrology system it can be beneficial to have the ability to quickly and robustly switch optical elements suitable for the type of light used. Figure 3 A is a schematic diagram illustrating a switch module 300 for switching optical elements in and out of a light path 390 (see, e.g., Figures 3B and 3C). In some embodiments, the switching can be performed by a movable support assembly 301 that can include servo 305 and movable support structure 310. As shown in Figure 3A, switch module 300 can include a movable support assembly 301 coupled to first optical element 320 (e.g., a polarizer, wave plate, etc.). Movable support assembly 301 can be configured to rotate first optical element 320 in and out of light path 390 along axis of rotation 340 that is not parallel to light path 390. In the example of Figure 3A, axis of rotation 340 is depicted as perpendicular to light path 390. However, this is not essential as some embodiments can have axis of rotation 340 be at other angles, such as 80 degrees, 60 degrees, 45 degrees, 30 degrees, etc.

[0086] Controller 350 can be operatively coupled to movable support structure 310 of movable support assembly 301 and can cause movement of movable support structure 310 via servo 305 to rotate first optical element into or out of light path 390. In various embodiments, controller 350 can include one or more computer processors configured to provide electronic instructions or signals to movable servo 305 (or other intervening apparatus operatively coupled to movable support structure 310) to control actuation (e.g., rotation or linear motion) of movable support structure 310. Controller 350 can also include associated hardware components to generate the electrical signals of the needed voltage, current, etc. to trigger or control switching elements in servo 305 that cause actuation. Controller 350 can also provide appropriate electronic signals to servo 305 to control the speed of rotation. In some embodiments, by controller operating to cause servo 305 to actuate at or below a given speed, the inertial force on the optical elements can be limited to an acceptable value that does not damage the optical element(s). Servo 305 can be, for example, a high-speed rotary switch, actuated by a motor configured to respond to commands from controller 350. The motor can be AC or DC and include stepper motors, etc.

[0087] In some embodiments, second optical element 330 can also be coupled to movable support structure 310. In this way, controller 350 can cause rotation of movable support structure 310 to move either first optical element 320 or second optical element 330 into or out of light path 390. While numerous embodiments herein describe the optical elements as polarizers or wave plates, the present disclosure contemplates that any other sort of optical element (or any other element) can be used instead to be rapidly switched in or out of a light path.

[0088] Figure 3B is a schematic diagram illustrating a switch module moving a polarizer into the light path. Figure 3C is a schematic diagram illustrating a switch module moving a different polarizer into the light path. Because some metrology devices can utilize light of different polarizations, in some embodiments first optical element 320 and second optical element 330 can be polarizers. For purposes of this example, the input light along light path 390 can be non-polarized light. Accordingly, first optical element 320 can be a vertical (V) vertical polarizer. Similarly, second optical element 330 can be a horizontal (H) polarizer. As a result, the example switch module 300 can have three settings, the one shown in Figure 3A where non-polarized light is allowed to pass because neither polarizer is in the light path, the one in Figure 3B where the V polarizer allows only V polarized light to pass, and the one in Figure 3C where the H polarizer allows only H polarized light to pass. The sizes of the arrows before and after the optical element shows that transmission can thereby be reduced (e.g., 50%) due to blocking of the respective components of the unpolarized light.

[0089] Figure 4A is a diagram illustrating an example switch module 400. Switch module 400 can be implemented in a variety of designs, in accordance with the present disclosure. The example in Figure 4A depicts a design of switch module 400 where the location and angle of first optical element 420 and second optical element 430 are arranged such that they can be switched in and out of light path 490 quickly due to the relatively small angle over which the elements need to be actuated. Switch module400 can include movable support assembly 401 that can include servo 405. The optical elements can be supported by bracket 410 (analogous to movable support structure 310) and coupled to servo 405 that actuates bracket 410. Bracket 410 can include apertures or removed portions 412 to allow light to pass through the optical elements when rotated around axis of rotation 440 to bring either of them into light path. Bracket 410 with the optical elements can be coupled to a single servo 405 that can rotate both optical elements as needed. Such a design can further be beneficial by not requiring individual actuators for the two optical elements.

[0090] Figure 4B is a diagram illustrating a top view of switch module 400 where no optical elements are in light path 490. Figure 4C is a diagram illustrating a top view of switch module 400 where first optical element 420 is rotated into light path 490. Figure 4D is a diagram illustrating a top view of switch module 400 where second optical element 430 is rotated into light path 490. As shown in Figure 4B, switch module can have optical elements are close to light path and angled such that when rotated around axis of rotation 440 over angle A (in either direction) that first optical element 420 or second optical element 430 is rotated into light path 490 such that they are at a desired orientation in the light path (e.g., perpendicular). Due to the reduced amount of movement needed to position optical elements in or out of light path, the required acceleration and / or top speed of the optical elements can be reduced. The reduced forces can then result in reduced drift over time and the ability to use more fragile optical elements that need not be constructed to withstand high acceleration. As shown in Figures 4C and 4D, the single servo 405 can quickly swap out first optical element 420 or second optical element 430 into light path 490 responsive to commands, such as from a controller (not shown).

[0091] Figures 5A, 5B, and 5C are schematic diagrams of a switch module 500 having a linear configuration with positions shown analogous to the examples of Figures 4B, 4C, and 4D. It is not essential that a switch module rely on rotation to switch optical elements. Figure 5A shows first optical element 520 and second optical element 530 separated by a gap 512 (which can be any sort of aperture or space), such that in the depicted state, neither optical element is in light path 590. As with other embodiments, first optical element 520 and second optical element 530 can be mounted on movable support structure 510, which can be coupled to servo 505. With switch module 500 configured to have a similar, but linear, narrow range of actuation, first optical element 520 can be translated into light path 590 as shown in Figure 5B. Similarly, second optical element 530 can be translated into light path 590 as shown in Figure 5C.

[0092] As shown by the examples herein, a first optical element and a second optical element can be disposed on the switch module to move either of them utilizing a narrow range of actuation, for example, rotationally as shown in Figures 4A-D or linearly as shown in Figures 5A-C. In some embodiments, the narrow range of actuation can be less than ± 20 degrees of rotation of the movable support structure and / or less than ± 3 mm. In some embodiments, this fast switching can include, for example, a switch module being configured to cover at least half of the narrow range of actuation in 2 ms or less.

[0093] Figure 6A is a schematic diagram illustrating a switch module 600 configured to rotate a wave plate in or out of a light path. Figure 6B is a schematic diagram illustrating a switch module 600 rotating a wave plate into a light path. While the examples above depicted the use of two optical elements, in some embodiments, only a single optical element may be mounted to a servo and switch in or out of a light path. In some applications, for example, digital holographic microscopy (DHM), a first optical element (and / or) a second optical element can be wave plates that alter a polarization state of light in the light path. Figure 6A shows a single optical element, for example, first optical element 620 (or an optional second optical element 630 shown in dashed) that can include a half-wave plate, which as in Figure 6B, rotates the polarization of light in light path 690 (e.g., changing polarization from V to H). In some embodiments, first optical element 620 (or second optical element 630) can include two quarter-wave plates that can combine to achieve the same effect. As indicated by the sizes of the arrows shown in light path 690, the transmission is the same due to the change in polarization of the incoming light rather than blocking a portion of the light as in the embodiment of Figures 3A-C.

[0094] Because some embodiments can require modifying light that can potentially span a relatively large wavelength range, the wave plates can be achromatic. By the wave plates being achromatic, this can include for example, where the wave plates operate to rotate an electric field of the light over a spectral range of 400-1600 nm. However, in some embodiments, such a large wavelength range may not be available for a single optical element and the needed spectral range may require utilization of multiple optical elements each having smaller wavelengths ranges. In this way, in some embodiments, first optical element 620 can have a first spectral range and a second optical element 630 can have a second spectral range that can combine to cover a spectral range larger than either the first spectral range or the second spectral range. For example, the first spectral range can be 600-2000 nm and the second spectral range can be 380-1100 nm., which then combined cover use between 380 nm and 2000 nm.

[0095] In some embodiments, different types of optical elements can be combined. For example, one or more of the wave plates can be a half-wave plate. A polarizer can also be coupled to the movable support structure. In some embodiments, the polarizer can be bonded to the half-wave plate to form a single optical element.

[0096] Figures 7A and 7B are schematic diagrams illustrating a single optical element switchable over a narrow range of actuation. The depicted embodiments illustrate that it is not essential to have a switch module actuate multiple optical elements in or out of a light path. Figure 7A shows switch module 700 configured to switch optical element 720 in and out of light path 790. Switch module 700 can include movable support assembly 701 coupled to movable support structure 710 which is in turn coupled to optical element 720. Controller 750 can be coupled to movable support structure 710 via movable support assembly 701, where controller 750 can move movable support structure 710 of movable support assembly 701 to move optical element 720 into or out of light path 790 utilizing a narrow range of actuation.

[0097] Similar to other embodiments detailed herein, movable support assembly 701 can include movable support structure 710 and servo 705. Movable support structure 710 can include a bracket coupled to servo 405 and supporting optical element 720. Servo 705 can include a motor configured to actuate movable support structure 710 in response to commands received from controller 750. In some embodiments, the motor can be a stepper motor.

[0098] Figure 7B shows a small rotation of switch module 700 placing optical element 720 in light path 790. Similar to other embodiments herein, the narrow range of actuation can be less than ± 20 degrees of rotation of the movable support structure and / or less than ± 3 mm. Switch module 700 can be configured to cover at least half of the narrow range of actuation in 2 ms or less. Optical element 720 can be a polarizer, e.g., a V polarizer or an H polarizer.

[0099] In some embodiments, optical element 720 can be a wave plate, which may be achromatic. In some embodiments, the wave plate can operate to rotate an electric field of light in the light path over a spectral range of 400-1600 nm. In some embodiments, wave plate can be a half- wave plate. There can be a polarizer also coupled to movable support structure 710 and the polarizer can be bonded to the half-wave plate.

[0100] Figures 8 A and 8B are schematic diagrams of a switch module 800 having a linear configuration with positions shown analogous to the examples of Figures 7A and 7B. Figure 8A shows first optical element 820 such that in the depicted state, first optical element 820 is not in light path 890. With switch module 800 configured to have a similar, but linear, narrow range of actuation, first optical element 820 can be translated into light path 890 as shown in Figure 8B. Similar to other embodiments, first optical element 820 can be mounted on movable support structure 810 that can be coupled to servo 805.

[0100] Figure 9 is a block diagram of an example computer system CS, according to an embodiment of the present disclosure. Computer system CS includes a bus BS or other communication mechanism for communicating information, and a processor PRO (or multiple processor) coupled with bus BS for processing information. Computer system CS also includes a main memory MM, such as a random access memory (RAM) or other dynamic storage device, coupled to bus BS for storing information and instructions to be executed by processor PRO. Main memory MM also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor PRO. Computer system CS further includes a read only memory (ROM) ROM or other static storage device coupled to bus BS for storing static information and instructions for processor PRO. A storage device SD, such as a magnetic disk or optical disk, is provided and coupled to bus BS for storing information and instructions.

[0101] Computer system CS may be coupled via bus BS to a display DS, such as a cathode ray tube (CRT) or flat panel or touch panel display for displaying information to a computer user. An input device ID, including alphanumeric and other keys, is coupled to bus BS for communicating information and command selections to processor PRO. Another type of user input device is cursor control CC,such as a mouse, a trackball, or cursor direction keys for communicating direction information and command selections to processor PRO and for controlling cursor movement on display DS. This input device typically has two degrees of freedom in two axes, a first axis (e.g., x) and a second axis (e.g., y), that allows the device to specify positions in a plane. A touch panel (screen) display may also be used as an input device.

[0102] According to one embodiment, portions of one or more methods described herein may be performed by computer system CS in response to processor PRO executing one or more sequences of one or more instructions contained in main memory MM. Such instructions may be read into main memory MM from another computer-readable medium, such as storage device SD. Execution of the sequences of instructions contained in main memory MM causes processor PRO to perform the process steps described herein. One or more processors in a multi-processing arrangement may also be employed to execute the sequences of instructions contained in main memory MM. In an alternative embodiment, hard-wired circuitry may be used in place of or in combination with software instructions. Thus, the description herein is not limited to any specific combination of hardware circuitry and software.

[0103] In the following, further features, characteristics, and exemplary technical solutions of the present disclosure will be described in terms of clauses that may be optionally claimed in any combination:1. An apparatus comprising:a switch module configured to switch one or more optical elements in and out of a light path, the switch module comprising:a movable support assembly coupled to a first optical element, the movable support assembly configured to rotate the first optical element in and out of the light path along an axis of rotation that is not parallel to the light path; anda controller coupled to the movable support assembly, wherein the controller moves a movable support structure of the movable support assembly to rotate the first optical element into or out of the light path.2. The apparatus of clause 1, wherein the axis of rotation is perpendicular to the light path. 3. The apparatus of clause 1, further comprising a second optical element also coupled to the movable support structure, wherein the controller rotates the movable support structure to move either the first optical element or the second optical element into or out of the light path.4. The apparatus of clause 1, the movable support assembly comprising the movable support structure and a servo.5. The apparatus of clause 4, wherein the movable support structure is a bracket coupled to the servo and supporting the first optical element.6. The apparatus of clause 4, the servo comprising a motor configured to rotate the movable support structure in response to commands received from the controller.7. The apparatus of clause 6, wherein the motor is a stepper motor.8. The apparatus of clause 3, wherein the first optical element and the second optical element are polarizers.9. The apparatus of clause 8, wherein the first optical element is a V polarizer10. The apparatus of clause 8, wherein the second optical element is an H polarizer.11. The apparatus of clause 3, wherein the first optical element and the second optical element are wave plates that alter a polarization state of light in the light path.12. The apparatus of clause 11, wherein at least one of the first optical element and the second optical element comprises a half-wave plate.13. The apparatus of clause 11, wherein at least one of the first optical element and the second optical element comprises two quarter-wave plates.14. The apparatus of clause 11, wherein the wave plates are achromatic.15. The apparatus of clause 11, wherein the wave plates operate to rotate an electric field of the light over a spectral range of 400-1600 nm.16. The apparatus of clause 15, wherein the first optical element has a first spectral range and the second optical element has a second spectral range that combine to cover a spectral range larger than either the first spectral range or the second spectral range.17. The apparatus of clause 16, wherein the first spectral range is 600-2000 nm and the second spectral range is 380-1100 nm.18. The apparatus of clause 11, wherein one or more of the wave plates is a half-wave plate. 19. The apparatus of clause 18, further comprising a polarizer also coupled to the movable support structure.20. The apparatus of clause 19, wherein the polarizer is bonded to the half-wave plate.21. The apparatus of clause 3, wherein the first optical element and the second optical element are disposed on the switch module to move either of them utilizing a narrow range of actuation.22. The apparatus of clause 21, wherein the narrow range of actuation is less than ± 20 degrees of rotation of the movable support structure.23. The apparatus of clause 21, wherein the narrow range of actuation is less than ± 3 mm. 24. The apparatus of clause 21, the switch module configured to cover at least half of the narrow range of actuation in 2 ms or less.25. An apparatus comprising:a switch module configured to switch an optical element in and out of a light path, the switch module comprising:a movable support assembly coupled to the optical element; anda controller coupled to the movable support assembly, wherein the controller moves a movable support structure of the movable support assembly to move the optical element into or out of the light path utilizing a narrow range of actuation.26. The apparatus of clause 25, wherein the narrow range of actuation is less than ± 20 degrees of rotation of the movable support structure.27. The apparatus of clause 25, wherein the narrow range of actuation is less than ± 3 mm.28. The apparatus of clause 25, the switch module configured to cover at least half of the narrow range of actuation in 2 ms or less.29. The apparatus of clause 25, the movable support assembly comprising the movable support structure and a servo.30. The apparatus of clause 29, wherein the movable support structure is a bracket coupled to the servo and supporting the optical element.31. The apparatus of clause 29, the servo comprising a motor configured to actuate the movable support structure in response to commands received from the controller.32. The apparatus of clause 31, wherein the motor is a stepper motor.33. The apparatus of clause 25, wherein the optical element is a polarizer.34. The apparatus of clause 33, wherein the optical element is a V polarizer.35. The apparatus of clause 33, wherein the optical element is an H polarizer.36. The apparatus of clause 25, wherein the optical element is a wave plate.37. The apparatus of clause 36, wherein the wave plate is achromatic.38. The apparatus of clause 36, wherein the wave plate operates to rotate an electric field of light in the light path over a spectral range of 400-1600 nm.39. The apparatus of clause 36, wherein the wave plate is a half-wave plate.40. The apparatus of clause 39, further comprising a polarizer also coupled to the movable support structure.41. The apparatus of clause 40, wherein the polarizer is bonded to the half-wave plate.42. A semiconductor device manufacturing method comprising:receiving a substrate with a photoresist layer;directing EUV or DUV radiation from a radiation source to transfer a pattern from a mask onto the photoresist layer, the directing comprising:switching a first optical element into or out of a light path of light from the radiation source utilizing a movable support structure coupled to the first optical element and configured to rotate the first optical element in and out of the light path along an axis of rotation that is not parallel to the light path; andremoving a portion of the photoresist layer to form the pattern over the substrate.

[0104] The term “computer-readable medium” as used herein refers to any medium that participates in providing instructions to processor PRO for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as storage device SD. Volatile media include dynamic memory, such as main memory MM. Transmission media include coaxial cables,copper wire and fiber optics, including the wires that comprise bus BS. Transmission media can also take the form of acoustic or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Computer-readable media can be non-transitory, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge. Non-transitory computer readable media can have instructions recorded thereon. The instructions, when executed by a computer, can implement any of the features described herein. Transitory computer-readable media can include a carrier wave or other propagating electromagnetic signal.

[0105] Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to processor PRO for execution. For example, the instructions may initially be borne on a magnetic disk of a remote computer. The remote computer can load the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to computer system CS can receive the data on the telephone line and use an infrared transmitter to convert the data to an infrared signal. An infrared detector coupled to bus BS can receive the data carried in the infrared signal and place the data on bus BS. Bus BS carries the data to main memory MM, from which processor PRO retrieves and executes the instructions. The instructions received by main memory MM may optionally be stored on storage device SD either before or after execution by processor PRO.

[0106] Computer system CS may also include a communication interface CI coupled to bus BS. Communication interface CI provides a two-way data communication coupling to a network link NDL that is connected to a local network LAN. For example, communication interface CI may be an integrated services digital network (ISDN) card or a modem to provide a data communication connection to a corresponding type of telephone line. As another example, communication interface CI may be a local area network (LAN) card to provide a data communication connection to a compatible LAN. Wireless links may also be implemented. In any such implementation, communication interface CI sends and receives electrical, electromagnetic or optical signals that carry digital data streams representing various types of information.

[0107] Network link NDL typically provides data communication through one or more networks to other data devices. For example, network link NDL may provide a connection through local network LAN to a host computer HC. This can include data communication services provided through the worldwide packet data communication network, now commonly referred to as the “Internet” INT. Local network LAN (Internet) both use electrical, electromagnetic or optical signals that carry digital data streams. The signals through the various networks and the signals on network data link NDL and through communication interface CI, which carry the digital data to and from computer system CS, are exemplary forms of carrier waves transporting the information.

[0108] Computer system CS can send messages and receive data, including program code, through the network(s), network data link NDL, and communication interface CL In the Internet example, hostcomputer HC might transmit a requested code for an application program through Internet INT, network data link NDL, local network LAN and communication interface CI. One such downloaded application may provide all or part of a method described herein, for example. The received code may be executed by processor PRO as it is received, and / or stored in storage device SD, or other non-volatile storage for later execution. In this manner, computer system CS may obtain application code in the form of a carrier wave.

[0109] The combinations and sub-combinations of the elements disclosed herein constitute separate embodiments and are provided as examples only. Also, the descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made as described without departing from the scope of the claims set out below.

Claims

CLAIMS1. An apparatus comprising:a switch module configured to switch one or more optical elements in and out of a light path, the switch module comprising:a movable support assembly coupled to a first optical element, the movable support assembly configured to rotate the first optical element in and out of the light path along an axis of rotation that is not parallel to the light path; anda controller coupled to the movable support assembly, wherein the controller moves a movable support structure of the movable support assembly to rotate the first optical element into or out of the light path.

2. The apparatus of claim 1, wherein the axis of rotation is perpendicular to the light path.

3. The apparatus of claim 1, further comprising a second optical element also coupled to the movable support structure, wherein the controller rotates the movable support structure to move either the first optical element or the second optical element into or out of the light path.

4. The apparatus of claim 1, the movable support assembly comprising the movable support structure and a servo.

5. The apparatus of claim 4, wherein the movable support structure is a bracket coupled to the servo and supporting the first optical element.

6. The apparatus of claim 4, the servo comprising a motor configured to rotate the movable support structure in response to commands received from the controller.

7. The apparatus of claim 6, wherein the motor is a stepper motor.

8. The apparatus of claim 3, wherein the first optical element and the second optical element are polarizers.

9. The apparatus of claim 8, wherein the first optical element is a V polarizer.

10. The apparatus of claim 8, wherein the second optical element is an H polarizer.

11. The apparatus of claim 3, wherein the first optical element and the second optical element are wave plates that alter a polarization state of light in the light path.

12. The apparatus of claim 11, wherein at least one of the first optical element and the second optical element comprises a half-wave plate.

13. The apparatus of claim 11, wherein at least one of the first optical element and the second optical element comprises two quarter-wave plates.

14. The apparatus of claim 11, wherein the wave plates are achromatic.

15. The apparatus of claim 11, wherein the wave plates operate to rotate an electric field of the light over a spectral range of 400-1600 nm.

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