Improved dynamic geometry for one-dimensional leaf spring guidance

Abstract

Embodiments described herein include a guide stage and a lithographic system configured to measure a position of an objective lens on the guide stage by controlling the position of the objective lens. The guide platform may include flexure that reduces stiffness of the guide platform in the z-axis when the objective lens is positioned to improve overall focus accuracy of the objective lens. A flexure guide mechanism may be used to position the objective lens for overlap measurements.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. application 63 / 437,293, filed on January 5, 2023, which is incorporated herein by reference in its entirety. Technical Field

[0002] The present disclosure generally relates to a lithography system configured to measure the position of an objective lens on a guide platform by controlling the position of the objective lens. The guide platform may include a flexure that reduces the stiffness of the guide platform in the z-axis when the objective lens is positioned. Background Art

[0003] A lithographic apparatus is a machine that applies a desired pattern to a substrate (typically onto a target portion of the substrate). For example, a lithographic apparatus can be used in the manufacture of integrated circuits (ICs). In this case, a patterning device, alternatively referred to as a mask or reticle, is used to generate the circuit pattern to be formed on a single layer of the IC. This pattern can be transferred to a target portion (e.g., comprising a portion of a die, one or several dies) on a substrate (e.g., a silicon wafer). Typically, this transfer is performed by imaging the pattern onto a layer of radiation-sensitive material (resist) disposed on the substrate. Typically, a single substrate will contain a grid of adjacent target portions that are patterned sequentially. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing the entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the radiation beam across the target portion simultaneously, either parallel or antiparallel to a given direction (the "scanning" direction). A pattern can also be transferred from a patterning device to a substrate by impressing the pattern onto the substrate.

[0004] During a lithography operation, different processing steps may require sequential formation of different layers on a substrate. Therefore, the substrate may need to be positioned with high accuracy relative to a previously formed pattern on the substrate. Typically, alignment marks are placed on the substrate to allow alignment and positioning relative to a second object. A lithographic apparatus may use an alignment device to detect the position of the alignment marks and use them to align the substrate to ensure accurate exposure from the mask. Misalignment between alignment marks at two different layers is measured as overlay error.

[0005] To monitor the photolithography process, parameters of the patterned substrate are measured. These parameters may include, for example, the overlay error between successive layers formed in or on the patterned substrate and the critical linewidth of the developed photoresist. These measurements can be performed on production substrates and / or on specialized metrology targets. Various techniques exist for measuring the microstructures formed during photolithography, including the use of scanning electron microscopes and specialized tools. A rapid and non-invasive form of specialized inspection tool is a scatterometer: a radiation beam is directed onto a target on the surface of the substrate, and the properties of the scattered or reflected beam are measured. By comparing the properties of the beam before and after reflection or scattering by the substrate, the properties of the substrate can be determined. This can be accomplished, for example, by comparing the reflected beam with data stored in a library of known measurements of known properties. Spectral scatterometers direct a broadband radiation beam onto the substrate and measure the spectrum (intensity as a function of wavelength) of the radiation scattered into a specific narrow angular range. In contrast, angle-resolved scatterometers use a monochromatic radiation beam and measure the intensity of the scattered radiation as a function of angle.

[0006] Such optical scatterometers can be used to measure parameters such as the critical dimension of a developed photoresist or the overlay error (OV) between two layers formed in or on the patterned substrate. The properties of the substrate can be determined by comparing the properties of an irradiating beam before and after it is reflected or scattered by the substrate.

[0007] Photolithography systems can have performance issues due to the motion of the guide stage. The motion can cause focus control issues, which affects the beam. Summary of the Invention

[0008] The lithography system is configured to measure the position of an objective lens on a guide platform, wherein the guide platform may include a flexure arrangement that reduces the stiffness of the guide platform in the z-axis when the objective lens is positioned. The flexure guide mechanism may be used to position the objective lens for overlay measurement.

[0009] In some embodiments, a guide platform is provided. The objective lens can be arranged on the guide platform. The objective lens can include an optical device configured to focus the beam. A plurality of Lorentz motors can be arranged on the guide platform and configured to position the objective lens. The magnet assembly can include at least two magnets, wherein the at least two magnets can be configured to balance the guide platform. An encoder can be arranged on a support assembly, and the support assembly is arranged on the guide platform, wherein the encoder can be configured to measure the position of the objective lens. At least one flexure and at least one leaf spring can be attached to the guide platform and configured to provide the stiffness of the guide platform on the x-axis and y-axis when the objective lens is positioned, and the length of at least one flexure is such that the stiffness of the guide platform on the z-axis is reduced when the objective lens is positioned.

[0010] In some embodiments, the at least one flexure is configured to restrict motion in the z-axis.

[0011] In some embodiments, at least one flexure has a rotation mode (Rx) on the x-axis, wherein the Rx mode limits rocking of the guide platform about the x-axis.

[0012] In some embodiments, Rx mode is minimized.

[0013] In some embodiments, the guide platform further comprises a heat sink, wherein the heat sink provides additional stiffness to the flexure.

[0014] In some embodiments, the flexure comprises an L-shape.

[0015] In some embodiments, the L-shape is anchored at the objective lens to provide a rigid connection point.

[0016] In certain embodiments, method comprises using the objective lens that is arranged on the guide platform to focus the beam, wherein the objective lens comprises an optical device. The objective lens can be positioned using a plurality of Lorentz motors that are installed on the guide platform. A magnet assembly can be installed that comprises at least two magnets and is configured to balance the guide platform. The position of the objective lens can be measured with an encoder that is installed on the support assembly on the guide platform. At least one flexure and at least one leaf spring can be attached and can be configured to provide the rigidity of the guide platform on the x-axis and y-axis when the objective lens is positioned, and the length that at least one flexure has makes the rigidity of the guide platform on the z-axis be reduced when the objective lens is positioned.

[0017] In some embodiments, the lithographic apparatus may include an illumination system configured to illuminate a pattern of a pattern forming device. A support may be configured to support the pattern forming device and include a substrate. A projection system may be configured to project an image of the pattern onto the substrate. A measurement system having a guide platform may include an objective lens disposed on the guide platform, wherein the objective lens includes an optical device configured to focus a radiation beam. A plurality of Lorentz motors may be disposed on a guide platform configured to position the objective lens. A magnet assembly may include at least two magnets, wherein the at least two magnets are configured to balance the guide platform. An encoder may be disposed on a support assembly disposed on the guide platform, wherein the encoder is configured to measure the position of the objective lens. At least one flexure and at least one leaf spring may be attached to the guide platform and configured to provide stiffness of the guide platform in the x-axis and y-axis when the objective lens is positioned, and at least one flexure has a length such that the stiffness of the guide platform in the z-axis is reduced as the objective lens is further positioned.

[0018] Other features of the present disclosure and the structure and operation of various embodiments are described in detail below with reference to the accompanying drawings. It should be noted that the present disclosure is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Based on the teachings contained in the present invention, those skilled in the relevant art will understand additional embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate the disclosure and, together with the description, further serve to explain the principles of the disclosure and enable one skilled in the relevant art to make and use the embodiments described herein.

[0020] Figure 1A Schematic diagram illustrating a reflective lithography apparatus according to some embodiments.

[0021] Figure 1B Schematic diagram illustrating a transmissive lithographic apparatus according to some embodiments.

[0022] Figure 2 A more detailed schematic diagram illustrating a reflective lithographic apparatus according to some embodiments is shown.

[0023] Figure 3 Schematic diagram illustrating a lithography cell according to some embodiments.

[0024] Figure 4A and Figure 4B A schematic diagram illustrating an inspection apparatus according to some embodiments is shown.

[0025] Figure 5 Depicted is a front perspective view of a flexure for use in a guide stage in a lithography system, according to some embodiments.

[0026] Figure 6A Depicted is a side perspective view of a flexure for use in a guide stage in a lithography system, according to some embodiments.

[0027] Figure 6B Depicted is a side perspective view of a leaf spring for use in a photolithography system, according to some embodiments.

[0028] Figure 7 Depicted is a cross-sectional embodiment of a flexure 730 for use in a guide stage 710 in a lithography system 700 , according to some embodiments.

[0029] Figure 8 A method 800 for positioning an objective lens according to some embodiments is described.

[0030] Features of the present disclosure will become apparent from the detailed description set forth below when taken in conjunction with the accompanying drawings, in which like reference numerals identify corresponding elements throughout. In the drawings, similar reference numerals generally indicate identical, functionally similar, and / or structurally similar elements. Additionally, generally, the leftmost digit of a reference numeral identifies the drawing in which the reference numeral first appears. Unless otherwise indicated, the drawings provided throughout this disclosure should not be construed as being to scale. DETAILED DESCRIPTION

[0031] This specification discloses one or more embodiments that incorporate the features of the present disclosure. The disclosed embodiments are provided as examples. The scope of the present invention is not limited to the disclosed embodiments. The features that are claimed are defined by the claims appended hereto.

[0032] The described embodiments and references in the specification to "one embodiment," "an embodiment," "an example embodiment," etc. indicate that the described embodiments may include specific features, structures, or characteristics, but every embodiment may not necessarily include the specific features, structures, or characteristics. Furthermore, such phrases do not necessarily refer to the same embodiment. In addition, when specific features, structures, or characteristics are described in conjunction with an embodiment, it should be understood that, whether or not explicitly described, it is within the knowledge of those skilled in the art to implement such features, structures, or characteristics in combination with other embodiments.

[0033] For ease of description, spatially relative terms, such as "below," "beneath," "lower," "above," "on," and the like, may be used herein to describe the relationship of one element or feature to another element or feature as illustrated in the accompanying drawings. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the drawings. The device may be otherwise oriented (rotated 90 degrees or in other orientations) and the spatially relative descriptors used herein should be interpreted accordingly.

[0034] As used herein, the term "about" indicates that a value of a given amount varies based on a particular technology. Based on the particular technology, the term "about" can indicate a value of a given amount that varies within, for example, 10-30% of the stated value (e.g., ±10%, ±20%, or ±30%).

[0035] Embodiments of the present invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present disclosure may also be implemented as instructions stored on a machine-readable medium that can be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form that can be read by a machine (e.g., a computing device). For example, machine-readable media may include: read-only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustic, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), etc. Furthermore, herein, firmware, software, routines, and / or instructions may be described as performing certain actions. However, it should be understood that such descriptions are merely for convenience, and that these actions are actually performed by a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc.

[0036] However, before describing such embodiments in further detail, it is instructive to present an example environment in which embodiments of the present disclosure may be implemented.

[0037] Exemplary lithography systems

[0038] Figure 1A and Figure 1BSchematic diagrams of lithographic apparatuses 100 and 100', respectively, in which embodiments of the present disclosure may be implemented. Each of lithographic apparatuses 100 and 100' includes the following components: an illumination system (illuminator) IL configured to condition a radiation beam B (e.g., deep ultraviolet or extreme ultraviolet radiation); a support structure (e.g., a mask table) MT configured to support a patterning device (e.g., a mask, reticle, or dynamic patterning device) MA and connected to a first positioner PM configured to accurately position the patterning device MA; and a substrate table (e.g., a wafer stage) WT configured to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate W. Lithographic apparatuses 100 and 100' also have a projection system PS configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion (e.g., comprising one or more dies) C of the substrate W. In lithographic apparatus 100, the patterning device MA and projection system PS are reflective. In the lithographic apparatus 100', the patterning device MA and the projection system PS are transmissive.

[0039] The illumination system IL may include various types of optical components, such as refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping or controlling the radiation beam B.

[0040] The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device MA relative to a reference frame, the design of at least one of the lithographic apparatuses 100 and 100', and other conditions, such as whether the patterning device MA is held in a vacuum environment. The support structure MT can use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device MA. The support structure MT can be a frame or a stage, for example, which can be fixed or movable as desired. Using sensors, the support structure MT can ensure that the patterning device MA is in a desired position, for example relative to the projection system PS.

[0041] The term “patterning device” MA is to be broadly interpreted as referring to any device that can be used to impart a radiation beam B with a pattern in its cross-section, for example so as to create a pattern in a target portion C of a substrate W. The pattern imparted to the radiation beam B may correspond to a specific functional layer of a device to be created in the target portion C to form an integrated circuit.

[0042] The terms "inspection equipment," "metrology system," etc. may be used herein to refer to, for example, a device or system for measuring properties of a structure (e.g., overlay error, critical dimension parameters), or for use in a lithography apparatus to check the alignment of a wafer (e.g., alignment equipment).

[0043] The patterning device MA may be of the transmissive type (e.g. Figure 1B lithographic apparatus 100 ′) or reflective (as in Figure 1A lithographic apparatus 100). Examples of patterning devices MA include reticles / masks, programmable mirror arrays, or programmable LCD panels. Masks are well known in lithography and include mask types such as binary masks, alternating phase-shift masks, or attenuated phase-shift masks, as well as various hybrid mask types. One example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted to reflect an incident radiation beam in different directions. The tilted mirrors impart a pattern to the radiation beam B that is reflected by the matrix of small mirrors.

[0044] The term "projection system" PS includes any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic, and electrostatic optical systems, or any combination thereof, as long as it is suitable for the exposure radiation used or other factors such as the use of an immersion liquid or the use of a vacuum on the substrate W. A vacuum environment may be used for EUV or electron beam radiation, as other gases may absorb too much radiation or electrons. A vacuum environment may therefore be provided to the entire beam path by means of vacuum walls and a vacuum pump.

[0045] The lithographic apparatus 100 and / or the lithographic apparatus 100' may be of a type having two (dual stage) or more substrate tables WT (and / or two or more mask tables). In such a "multi-stage" machine, the additional substrate tables WT may be used in parallel, or preparatory steps may be performed on one or more tables while one or more other substrate tables WT are being used for exposure. In some cases, the additional tables may not be substrate tables WT.

[0046] 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, such as water, so as 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 for increasing the numerical aperture of projection systems. The term "immersion" as used herein does not imply that a structure, such as a substrate, is necessarily immersed in the liquid; rather, "immersion" simply means that the liquid is located between the projection system and the substrate during exposure.

[0047] refer to Figure 1A and Figure 1B , the illuminator IL receives a radiation beam from a radiation source SO. When the source SO is an excimer laser, the source SO and the lithographic apparatus 100, 100' may be separate physical entities. In this case, the source SO is not considered to form part of the lithographic apparatus 100 or 100', and the radiation beam is delivered to the lithographic apparatus 100 or 100' by means of a beam delivery system BD (in the embodiment of FIG. 1 ) comprising, for example, suitable directing mirrors and / or a beam expander. Figure 1B The radiation is transferred from the source SO to the illuminator IL (in the embodiment of FIG. 1 ). In other cases, the source SO may be an integral part of the lithographic apparatus 100, 100′, for example, when the source SO is a mercury lamp. The source SO and illuminator IL, and optionally a beam delivery system BD, may be collectively referred to as a radiation system.

[0048] The illuminator IL may comprise an adjuster AD (at Figure 1B Typically, at least the outer radial extent and / or the inner radial extent (commonly referred to as "σ-outer" and "σ-inner", respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. Furthermore, the illuminator IL may include various other components (in Figure 1B ), such as an integrator IN and a condenser CO. The illuminator IL may be used to condition the radiation beam B so as to have a desired uniformity and intensity distribution in its cross-section.

[0049] refer to Figure 1A The radiation beam B is incident on and patterned by the patterning device (e.g., mask) MA, which is held on the support structure (e.g., mask table) MT. In the lithographic apparatus 100, the radiation beam B reflects from the patterning device (e.g., mask) MA. After reflecting from the patterning device (e.g., mask) MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam B onto a target portion C of a substrate W. With the aid of a second positioner PW and a position sensor IF2 (e.g., an interferometer arrangement, a linear encoder, a 2D encoder, or a capacitive sensor), the substrate table WT can be accurately moved (e.g., to position a different target portion C in the path of the radiation beam B). Similarly, a first positioner PM and another position sensor IF1 can be used to accurately position the patterning device (e.g., mask) MA relative to the path of the radiation beam B. The patterning device (eg, mask) MA and substrate W may be aligned using mask alignment marks M1 , M2 and substrate alignment marks P1 , P2 .

[0050] refer to Figure 1BThe radiation beam B is incident on and patterned by the patterning device (e.g., mask MA), which is held on the support structure (e.g., mask table MT). Having traversed the mask MA, the radiation beam B passes through the projection system PS, which focuses the radiation beam onto a target portion C of the substrate W. The projection system has a pupil PPU that is conjugate with the illumination system pupil IPU. Portions of the radiation originate from the intensity distribution at the illumination system pupil IPU, traverse the mask pattern unaffected by diffraction at the mask pattern, and produce an image of the intensity distribution at the illumination system pupil IPU.

[0051] The projection system PS projects an image of the mask pattern MP onto a photoresist layer coated on the substrate W, wherein the image is formed by a diffraction beam generated from the marking pattern MP by radiation from the intensity distribution. For example, the mask pattern MP may include an array of lines and spaces. Diffraction of radiation at the array, other than the zeroth-order diffraction, generates a deflected diffraction beam having a change in direction perpendicular to the lines. The undiffracted beam (i.e., the so-called zeroth-order diffraction beam) traverses the pattern without any change in propagation direction. The zeroth-order diffraction beam passes through an upper lens or upper lens group of the projection system PS (located upstream of a conjugate pupil PPU of the projection system PS) to reach the conjugate pupil PPU. The portion of the intensity distribution in the plane of the conjugate pupil PPU and associated with the zeroth-order diffraction beam is an image of the intensity distribution in the illumination system pupil IPU of the illumination system IL. The aperture device PD is, for example, disposed at or approximately located in a plane including the conjugate pupil PPU of the projection system PS.

[0052] The projection system PS is arranged to capture not only the zeroth-order diffraction beam, but also first-order or first-and-higher-order diffraction beams (not shown), via a lens or lens group L. In some embodiments, dipole illumination can be used to image a line pattern extending perpendicular to the line, exploiting its resolution-enhancing effect. For example, the first-order diffraction beam interferes with the corresponding zeroth-order diffraction beam at the level of the wafer W to produce an image of the line pattern MP with the highest possible resolution and process window (i.e., the available depth of focus combined with the tolerable exposure dose deviation). In some embodiments, astigmatic aberrations can be reduced by providing radiation poles (not shown) in opposite quadrants of the illumination system pupil IPU. Furthermore, in some embodiments, astigmatic aberrations can be reduced by blocking the zeroth-order radiation beam associated with the radiation pole in the opposite quadrant of the conjugate pupil PPU of the projection system. This is described in more detail in US Pat. No. 7,511,799 B2, issued on March 31, 2009, the entire contents of which are incorporated herein by reference.

[0053] With the help of a second positioner PW and a position sensor IFD (e.g. an interferometer arrangement, a linear encoder, a 2D encoder or a capacitive sensor), the substrate table WT can be accurately moved (e.g. to position a different target portion C in the path of the radiation beam B). Similarly, the first positioner PM and another position sensor (not in use) can be moved (e.g. after mechanical retrieval from a mask library or during a scan). Figure 1B ) is used to accurately position the mask MA relative to the path of the radiation beam B.

[0054] Typically, movement of the mask table 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 with 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 mask table MT may be connected to a short-stroke actuator only, or may be fixed. The 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 in the figure occupy dedicated target portions, they may be located in the spaces between multiple target portions (these are called scribe lane alignment marks). Similarly, where more than one die is provided on the mask MA, the mask alignment marks may be located between these dies.

[0055] The mask table MT and patterning device MA can be located within a vacuum chamber, where an in-vacuum robot (IVR) can be used to move the patterning device (such as a mask or reticle) into and out of the vacuum chamber. Alternatively, when the mask table MT and patterning device MA are outside the vacuum chamber, an out-of-vacuum robot can be used for various transport operations similar to the in-vacuum robot (IVR). Both the in-vacuum and out-of-vacuum robots need to be calibrated to smoothly transfer any payload (e.g., a mask) to the fixed kinematic mount of the transfer station.

[0056] The lithographic apparatuses 100 and 100 ′ may be used in at least one of the following modes:

[0057] 1. In step mode, the support structure (e.g., mask table) MT and substrate table WT remain essentially stationary while an entire pattern imparted to the radiation beam is projected at once onto a target portion C (i.e., a single static exposure). The substrate table WT is then shifted in the X and / or Y direction so that a different target portion C can be exposed.

[0058] 2. In scan mode, the support structure (e.g., mask table) MT and substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e., a single dynamic exposure). The velocity and direction of the substrate table WT relative to the support structure (e.g., mask table) MT may be determined by the (de-)magnification and image reversal characteristics of the projection system PS.

[0059] 3. In another mode, the support structure (e.g., mask table) MT holding the programmable patterning device is held substantially stationary and the substrate table WT is moved or scanned, while a pattern imparted to the radiation beam B is projected onto a target portion C. A pulsed radiation source SO may be employed, with the programmable patterning device updated as required after each movement of the substrate table WT or between successive radiation pulses during a scan. This mode of operation may be readily applicable to maskless lithography utilizing a programmable patterning device, such as a programmable mirror array.

[0060] Combinations and / or variations of the described modes of use or entirely different modes of use may also be employed.

[0061] In another embodiment, the lithographic apparatus 100 includes an extreme ultraviolet (EUV) source configured to generate an EUV radiation beam for EUV lithography. Typically, the EUV source is configured in a radiation system, and a corresponding illumination system is configured to adjust the EUV radiation beam of the EUV source.

[0062] Figure 2The lithographic apparatus 100 is shown in more detail, comprising the source collector apparatus SO, the illumination system IL and the projection system PS. The source collector apparatus SO is constructed and arranged so as to maintain a vacuum environment within an enclosure 220 of the source collector apparatus SO. A plasma 210 emitting EUV radiation may be formed by a discharge-generated plasma source. EUV radiation may be generated by a gas or vapor (e.g., Xe gas, Li vapor, or Sn vapor) in which a very hot plasma 210 is generated to emit radiation in the EUV range of the electromagnetic spectrum. For example, the very hot plasma 210 may be generated by a discharge that causes an at least partially ionized plasma. For efficient radiation generation, a partial pressure of, for example, 10 Pa of Xe, Li, Sn vapor, or any other suitable gas or vapor may be required. In some embodiments, an excited tin (Sn) plasma is provided to generate EUV radiation.

[0063] Radiation emitted by the hot plasma 210 is transferred from the source chamber 211 to the collector chamber 212 via an optional gas barrier or contaminant trap 230 (also referred to as a contaminant barrier or fin trap in some cases) positioned in or behind an opening in the source chamber 211. The contaminant trap 230 can include a channel structure. The contaminant trap 230 can also include a gas barrier, or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier 230, as otherwise referred to herein, includes at least a channel structure.

[0064] The collector chamber 211 may include a radiation collector CO, which may be a so-called grazing incidence collector. The radiation collector CO has an upstream radiation collector side 251 and a downstream radiation collector side 252. Radiation traversing the collector CO may be reflected out of a grating spectral filter 240 to be focused at a virtual source point INIF. The virtual source point INTF is often referred to as an intermediate focus, and the source collector apparatus is arranged such that the intermediate focus INTF is located at or near an opening 219 in the enclosure 220. The virtual source point INTF is an image of the radiation emitting plasma 210. The grating spectral filter 240 is particularly used to suppress infrared (IR) radiation.

[0065] The radiation then traverses the illumination system IL, which may include a faceted field mirror arrangement 222 and a faceted pupil mirror arrangement 224 arranged to provide a desired angular distribution of the radiation beam 221 at the patterning device MA, and a desired uniformity of radiation intensity at the patterning device MA. When the radiation beam 221 is reflected at the patterning device MA, which is held by the support structure MT, a patterned radiation beam 226 is formed, and the patterned radiation beam 226 is imaged by the projection system PS via reflective elements 228, 229 onto a substrate W held by a wafer stage or substrate table WT.

[0066] There may typically be more elements than shown in the illumination optics unit IL and projection system PS. A grating spectral filter 240 may optionally be present, depending on the type of lithographic apparatus. Additionally, there may be more than Figure 2 More mirrors than the one shown in FIG. 4 may be present in the projection system PS. Figure 2 One to six additional reflective elements are shown.

[0067] Collector optics CO (such as Figure 2 As just one example of a collector (or collector mirror), the collector optics CO is depicted as a nested collector with grazing incidence reflectors 253, 254, and 255. The grazing incidence reflectors 253, 254, and 255 are arranged axially symmetrically around the optical axis O, and this type of collector optics CO is preferably used in conjunction with a discharge produced plasma source (often referred to as a DPP source).

[0068] Exemplary Lithography Cell

[0069] Figure 3A lithography cell 300, sometimes also referred to as a lithocell or cluster, according to some embodiments is shown. A lithography apparatus 100 or 100' may form part of a lithography cell 300. The lithography cell 300 may also include one or more devices for performing pre-exposure and post-exposure processes on a substrate. In some examples, these include a spin coater SC for depositing a resist layer, a developer DE for developing the exposed resist, a chill plate CH, and a bake plate BK. A substrate transport device or robot RO picks up substrates from input / output ports I / O1 and I / O2, moves them between the various process devices, and transfers them to a loading station LB of the lithography apparatus 100 or 100'. These devices are often collectively referred to as a track or coating and developing system and are controlled by a track or coating and developing system control unit TCU, which is itself controlled by a supervisory control system SCS, which in turn controls the lithography apparatus via a lithography control unit LACU. Thus, the various devices can be operated to maximize throughput and processing efficiency.

[0070] Exemplary inspection equipment

[0071] To control the lithography process and accurately place device features on the substrate, alignment marks are typically placed on the substrate, and the lithography apparatus includes one or more inspection devices to accurately locate the marks on the substrate. These alignment devices are effectively position measurement devices. Different types of marks and alignment devices and / or systems are known from different times and by different manufacturers. One type of system widely used in current lithography apparatus is based on a self-referencing interferometer, as described in U.S. Patent No. 6,961,116 (den Boef et al.). Typically, marks are measured separately to obtain the X and Y positions. However, combined X and Y measurements can be performed using the techniques described in U.S. Publication No. 2009 / 195768 A (Bijnen et al.). The entire contents of both publications are incorporated herein by reference.

[0072] Figure 4A A schematic diagram illustrating a cross-sectional view of an inspection apparatus 400, according to some embodiments, which can be implemented as part of a lithographic apparatus 100 or 100'. In some embodiments, the inspection apparatus 400 can be configured to align a substrate (e.g., substrate W) relative to a patterning device (e.g., patterning device MA). The inspection apparatus 400 can also be configured to detect the positions of alignment marks on the substrate and use the detected positions of the alignment marks to align the substrate relative to the patterning device or other components of the lithographic apparatus 100 or 100'. Such alignment of the substrate can ensure accurate exposure of one or more patterns on the substrate.

[0073] In some embodiments, inspection apparatus 400 may include an illumination system 412, a beam splitter 414, an interferometer 426, a detector 428, a radiation beam analyzer 430, and an overlap calculation processor 432. Illumination system 412 may be configured to provide an electromagnetic narrowband radiation beam 413 having one or more passbands. In one example, the one or more passbands may be within a spectrum of wavelengths between approximately 500 nm and approximately 900 nm. In another example, the one or more passbands may be discrete narrow passbands within a spectrum of wavelengths between approximately 500 nm and approximately 900 nm. Illumination system 412 may also be configured to provide one or more passbands having a substantially constant center wavelength (CWL) value over an extended period of time (e.g., over the lifetime of illumination system 412). As discussed above, in current alignment systems, this configuration of illumination system 412 may help prevent actual CWL values from drifting from desired CWL values. And, therefore, using a constant CWL value may improve the long-term stability and accuracy or precision of an alignment system (eg, inspection apparatus 400 ) compared to current alignment apparatuses.

[0074] In some embodiments, beam splitter 414 can be configured to receive radiation beam 413 and split radiation beam 413 into at least two radiation sub-beams. For example, radiation beam 413 can be split into radiation sub-beams 415 and 417, as shown in FIG. Figure 4A. The beam splitter 414 can also be configured to direct a radiation sub-beam 415 onto a substrate 420 placed on a platform 422. In one example, the platform 422 can be moved along a direction 424. The radiation sub-beam 415 can be configured to illuminate an alignment mark or target 418 located on the substrate 420. The alignment mark or target 418 can be coated with a radiation-sensitive film. In some embodiments, the alignment mark or target 418 can have a one hundred and eighty degree (i.e., 180°) symmetry. That is, when the alignment mark or target 418 is rotated 180° about an axis of symmetry perpendicular to the plane of the alignment mark or target 418, the rotated alignment mark or target 418 can be substantially identical to the unrotated alignment mark or target 418. The target 418 on substrate 420 can be: (a) a resist layer grating comprising bars formed of solid resist lines, or (b) a product layer grating, or (c) a composite grating stack in an overlay target structure comprising a resist grating superimposed or staggered on a product layer grating. The bars can alternatively be etched into the substrate. Such patterns are sensitive to chromatic aberrations and illumination symmetry in the lithographic projection apparatus (particularly the projection system PL), and the presence of such aberrations will manifest themselves as variations in the printed grating. One in-line method for measuring line width, pitch, and critical dimensions in device fabrication utilizes a technique known as "scatterometry." Scatterometry methods are described in Raymond et al., "Multiparameter Grating Metrology Using Optical Scatterometry," J. Vac. Sci. Tech. B, Vol. 15, No. 2, pp. 361-368 (1997), and Niu et al., "Specular Spectroscopic Scatterometry in DUV Lithography," SPIE, Vol. 3677 (1999), both of which are incorporated herein by reference in their entirety. In scatterometry, light is reflected by periodic structures in the target, and the resulting reflection spectrum at a given angle is detected. The structure that produced the reflection spectrum is reconstructed, for example, using rigorous coupled wave analysis (RCWA) or by comparison with a library of patterns derived from simulations. Thus, scatterometry data of the printed grating is used to reconstruct the grating. The parameters of the grating, such as line width and shape, can be input into the reconstruction process, which is performed by the processing unit PU based on knowledge of the printing step and / or other scatterometry processes.

[0075] In some embodiments, the beam splitter 414 may be further configured to receive the diffracted radiation beam 419 and split the diffracted radiation beam 419 into at least two radiation sub-beams, depending on the embodiment. The radiation beam 419 may be split into radiation sub-beams 429 and 439, as shown in FIG. Figure 4A As shown in .

[0076] It should be noted that even though beam splitter 414 is shown as directing radiation sub-beam 415 toward alignment mark or target 418 and directing diffracted radiation sub-beam 429 toward interferometer 426, the present disclosure is not limited thereto. Those skilled in the relevant art will appreciate that other optical arrangements may be used to achieve similar results of illuminating alignment mark or target 418 on substrate 420 and detecting an image of alignment mark or target 418.

[0077] like Figure 4A , the interferometer 426 can be configured to receive the radiation sub-beam 417 and the diffracted radiation sub-beam 429 that passed through the beam splitter 414. In an example embodiment, the diffracted radiation sub-beam 429 can be at least a portion of the radiation sub-beam 415 that can be reflected from the alignment mark or target 418. In an example of this embodiment, the interferometer 426 includes any suitable set of optical elements, such as a prism combination that can be configured to form two images of the alignment mark or target 418 based on the received diffracted radiation sub-beam 429. It should be understood that it is not necessary to form good quality images, but the features of the alignment mark 418 should be resolved. The interferometer 426 can also be configured to rotate one of the two images by 180° relative to the other of the two images and to interferometrically recombine the rotated image and the unrotated image.

[0078] In some embodiments, detector 428 can be configured to receive the recombined image via interferometer signal 427 when the alignment axis 421 of inspection apparatus 400 passes through the center of symmetry (not shown) of alignment mark or target 418, and detect interference resulting from the recombined image. This interference may be due to the 180° symmetry of alignment mark or target 418, and according to example embodiments, the recombined image interferes constructively or destructively. Based on the detected interference, detector 428 can also be configured to determine the position of the center of symmetry of alignment mark or target 418 and, therefore, detect the position of substrate 420. According to an example, alignment axis 421 can be aligned with an optical beam perpendicular to substrate 420 and passing through the center of image rotation interferometer 426. Detector 428 can also be configured to estimate the position of alignment mark or target 418 by implementing sensor characteristics and interacting with wafer marking process variations.

[0079] In another embodiment, the detector 428 determines the location of the center of symmetry of the alignment mark or target 418 by performing one or more of the following measurements: 1. Measure the position change (position shift between colors) for each wavelength; 2. Measure the position variation for each order (the position shift between diffraction orders); and 3. Measure the position change for each polarization (the position shift between the polarizations).

[0080] For example, this data can be acquired using any type of alignment sensor, such as a SMASH (SMart Alignment Sensor Hybrid) sensor, as described in U.S. Patent No. 6,961,116, which employs a self-referencing interferometer with a single detector and four different wavelengths and extracts the alignment signal in software, or ATHENA (Advanced Technology using High-Order Alignment Enhancement), as described in U.S. Patent No. 6,297,876, which directs each of the seven diffraction orders to a dedicated detector, both of which are incorporated herein by reference in their entirety.

[0081] In some embodiments, the radiation beam analyzer 430 can be configured to receive and determine the optical state of the diffracted radiation sub-beam 439. The optical state can be a measure of the beam wavelength, polarization, or beam profile. The radiation beam analyzer 430 can also be configured to determine the position of the platform 422 and correlate the position of the platform 422 with the position of the center of symmetry of the alignment mark or target 418. In this way, the position of the alignment mark or target 418 relative to the alignment platform 422, and therefore the position of the substrate 420 relative to the alignment platform 422, can be accurately known. Alternatively, the radiation beam analyzer 430 can be configured to determine the position of the inspection device 400 or any other reference element, so that the center of symmetry of the alignment mark or target 418 can be known relative to the inspection device 400 or any other reference element. The radiation beam analyzer 430 can be a point or imaging polarimeter with some form of wavelength band selectivity. In some embodiments, according to other embodiments, the radiation beam analyzer 430 can be directly integrated into the inspection device 400 or connected via several types of optical fibers: polarization-maintaining single-mode fiber, multimode fiber, or imaging fiber.

[0082] In some embodiments, the radiation beam analyzer 430 may also be configured to determine overlay data between two patterns on the substrate 420. One of the patterns may be a reference pattern on a reference layer. The other pattern may be an exposure pattern on an exposure layer. The reference layer may be an existing etching layer on the substrate 420. The reference layer may be generated by exposing a reference pattern on the substrate by the lithography apparatus 100 and / or 100'. The exposure layer may be an exposed resist layer adjacent to the reference layer. The exposure layer may be generated by exposing an exposure pattern on the substrate 420 by the lithography apparatus 100 or 100'. The exposure pattern on the substrate 420 may correspond to movement of the substrate 420 caused by the stage 422. In some embodiments, the measured overlay data may also indicate an offset between the reference pattern and the exposure pattern. The measured overlay data may be used as calibration data to calibrate the exposure pattern exposed by the lithography apparatus 100 or 100', such that, after calibration, the offset between the exposure layer and the reference layer is minimized.

[0083] In some embodiments, the radiation beam analyzer 430 may also be configured to determine a model of a product stack profile of the substrate 420 and may be configured to measure the overlay, critical dimensions, and focal length of the target 418 in a single measurement. The product stack profile contains information about the stack product, such as alignment marks, the target 418, or the substrate 420, and may include optical signature measurements caused by variations in the marking process, which are a function of illumination variations. The product stack profile may also include product raster profiles, mark stack profiles, and mark asymmetry information. An example of a radiation beam analyzer 430 is the Yieldstar manufactured by ASML of Veldhoven, The Netherlands. TM , as described in U.S. Patent No. 8,706,442, which is incorporated herein by reference in its entirety. The radiation beam analyzer 430 may also be configured to process information related to specific properties of the exposure pattern in the layer. For example, the radiation beam analyzer 430 may process: an overlay parameter (indicating the accuracy of positioning of the layer relative to the previous layer on the substrate, or the accuracy of positioning of the first layer relative to a mark on the substrate), a focus parameter, and / or critical dimension parameters of the image depicted in the layer (e.g., line width and its variation). Other parameters are image parameters related to the quality of the image of the depicted exposure pattern.

[0084] In some embodiments, a detector array (not shown) can be connected to the radiation beam analyzer 430 and allow the possibility of accurate stack profile detection, as discussed below. For example, the detector 428 can be a detector array. For the detector array, there are several options: multimode fiber bundles, discrete pin detectors per channel, or CCD or CMOS (linear) arrays. For stability reasons, the use of multimode fiber bundles allows any dissipative elements to be remotely located. Discrete pin detectors can provide a larger dynamic range, but each requires a separate preamplifier. Therefore, the number of elements is limited. CCD linear arrays provide many elements that can be read at high speed and are particularly noteworthy when phase-stepped detection is used.

[0085] In some embodiments, the second radiation beam analyzer 430' may be configured to receive and determine the optical state of the diffracted radiation sub-beam 429, such as Figure 4B . The optical state may be a measure of the radiation beam wavelength, polarization or radiation beam profile. The second radiation beam analyzer 430' may be identical to the radiation beam analyzer 430. Alternatively, the second beam analyzer 430' may be configured to perform at least all of the functions of the radiation beam analyzer 430, such as determining the position of the platform 422, and associating the position of the platform 422 with the position of the center of symmetry of the alignment mark or target 418. In this way, the position of the alignment mark or target 418 relative to the platform 422 may be accurately known, and therefore the position of the substrate 420 relative to the platform 422 may be known. The second radiation beam analyzer 430' may also be configured to determine the position of the inspection device 400 or any other reference element, so that the center of symmetry of the alignment mark or target 418 may be known relative to the inspection device 400 or any other reference element. The second radiation beam analyzer 430' may also be configured to determine overlap data between the two patterns and a model of the product stack profile of the substrate 420. The second radiation beam analyzer 430' may also be configured to measure overlay, critical dimension, and focus of the target 418 in one measurement.

[0086] In some embodiments, according to other embodiments, second radiation beam analyzer 430' may be directly integrated into inspection apparatus 400, or it may be connected via several types of optical fibers: polarization-maintaining single-mode fiber, multimode fiber, or imaging fiber. Alternatively, second radiation beam analyzer 430' and radiation beam analyzer 430 may be combined to form a single analyzer (not shown) configured to receive and determine the optical state of diffracted radiation sub-beams 429 and 439.

[0087] In some embodiments, processor 432 receives information from detector 428 and beam analyzer 430. For example, processor 432 may be an overlay calculation processor. The information may include a model of the product stack profile constructed by beam analyzer 430. Alternatively, processor 432 may use the received information about product markings to construct a model of the product marking profile. In either case, processor 432 uses or combines the model of the product marking profile to construct a model of the stacked product and the overlay marking profile. The overlay model is then used to determine the overlay offset and minimize spectral influences on the overlay offset measurement. Processor 432 may generate a basic correction algorithm based on the information received from detector 428 and beam analyzer 430, including but not limited to the optical state of the illumination beam, alignment signals, associated position estimates, and optical states in pupil, image, and other planes. The pupil plane is a plane where the radial position of the radiation defines the angle of incidence and the angular position defines the azimuth angle of the radiation. Processor 432 may utilize the basic correction algorithm to characterize the inspection apparatus 400 with reference to wafer marks and / or alignment marks 418.

[0088] In some embodiments, processor 432 can also be configured to determine, for each mark, an offset error in the printed pattern position relative to the sensor estimate based on information received from detector 428 and beam analyzer 430. This information includes, but is not limited to, the product stack profile, overlay, critical dimension, and focus measurements for each alignment mark or target 418 on substrate 420. Processor 432 can utilize a clustering algorithm to group marks into groups with similar constant offset errors and generate an alignment error offset correction table based on this information. The clustering algorithm can be based on overlay measurements, position estimates, and additional optical stacking process information associated with each group of offset errors. Overlay offsets are calculated for multiple different marks, such as overlay targets with positive and negative deviations around a predetermined overlay offset. The target with the smallest measured overlay offset is used as a reference (because it is measured with the best accuracy, i.e., precision). Based on this measured small overlay offset and the known predetermined overlay offset of its corresponding target, the overlay error can be derived. Table 1 illustrates how this is performed. In the example shown, the smallest measured overlay offset is -1 nm. However, this is relative to the preset target overlay offset of -30 nm. The process may have introduced an overlay error of 29 nm.

[0089]

[0090] The minimum value can be used as a reference point, relative to which the offset between the measured overlay offset and the overlay offset expected due to the preset overlay offset can be calculated. This offset determines the overlay error for each mark or set of marks with similar offsets. Therefore, in the example of Table 1, at the target position with a preset overlay offset of 30nm, the minimum measured overlay offset is -1nm. The difference between the expected overlay offset and the measured overlay offset at other targets is compared with the reference. A table such as Table 1 can also be obtained based on the marks and targets 418 under different illumination settings, and the illumination setting and its corresponding calibration factor that results in the minimum overlay offset error can be determined and selected. Thereafter, the processor 432 can group the marks into sets of similar overlay errors. The criteria for grouping the marks can be adjusted based on different process controls, for example, based on different error tolerances for different processes.

[0091] In some embodiments, the processor 432 can confirm that all or most members of the group have similar offset errors and apply a separate offset correction from the clustering algorithm to each mark based on its additional optical stack measurement. The processor 432 can determine the correction for each mark and feed the correction back to the lithographic apparatus 100 or 100' to correct the error in the overlay, for example, by feeding the correction into the inspection apparatus 400.

[0092] Exemplary Flexure Embodiments

[0093] An exemplary lithography system as described above may be configured to measure the position of an objective lens on a guide stage. The guide stage may include a flexure arrangement to reduce the stiffness of the guide stage in the z-axis when the objective lens is positioned.

[0094] For example, a typical photolithography system may include a guide stage, and within the guide stage, a flexure leaf spring structure is used to guide the objective lens in the vertical direction. Any parasitic motion or tilt in random directions can be limited within the operating range. This parasitic motion enables focus control of the photolithography system because the sensor can measure many points on the substrate.

[0095] Optics that improve sensor transmission and throughput can be positioned near the sensor objective. For example, a four-way non-polarizing beam splitter (NPBS) prism can be used to improve optical transmission and sensor throughput. However, the prism must be positioned close to the sensor objective, which requires changes to the leaf spring guide geometry, such as cutouts in the top flexure. Positioning the prism closer to the objective enables higher light transmission through the sensor, which results in higher throughput.

[0096] However, z-stage dynamics can affect the bandwidth of the focus controller. Removing a portion of the four-way NPB can negatively impact both z-stage dynamics and focus control bandwidth. Furthermore, because the dynamics can be improved, such as with better focus control bandwidth, this can lead to faster focus control of the sensor. This focus control also contributes to higher throughput.

[0097] Therefore, the leaf spring design can be modified, which can improve the performance of the lithography system. The leaf spring can be optimized for dynamics and can incorporate new constraints from the four-way NPBS cut.

[0098] The leaf spring design can anchor the shortened flexure, which can reduce the motion in the x-direction toward where the objective is located rather than outside the z-stage. This leaf spring design can result in a stiffer connection point, which can limit the dynamic performance limit R x This restriction does not increase the overall stiffness, such as making movement in the z-direction more difficult. In addition, the guidance accuracy of the flexure mechanism is not affected.

[0099] The frequency of the actuator's z-mode is between 20 Hz and 35 Hz. The theoretical frequency of the z-stage rigid body can be achieved by shifting the resonant modes or reducing the amplitude of these modes by using a stiffer encoder mount for the z-mode. x Modal improvement can be achieved by increasing damping, optimizing moving masses or flexure variations, which is proposed in this paper.

[0100] Figure 5 A front perspective view of a flexure 530 for use in a guide platform 510 in a lithography system 500 is shown, in accordance with some embodiments.

[0101] A guide platform 510 is shown. A sensor objective lens 520 is positioned below the objective lens (not shown). The sensor objective lens 520 can be mounted to the guide platform 510. The guide platform can include at least one actuator motor 540, such as a Lorentz motor or similar actuator motor, as will be appreciated by those skilled in the art, to achieve fine-tuning movement for focusing the objective lens. Alternatively, a piezoelectric actuator can be used. The actuator motor 540 can also generally contribute to the system's moving mass. A portion of the guide platform 510 has been removed to make room for optical elements of different sizes, such as the objective lens, but by varying the length of the flexure 530, there is no loss in performance.

[0102] The flexure 530 can have a shortened length in the x-axis and a long length in the y-axis. The shortened length of the flexure 530 reduces the stress caused by deformation in the x-axis. The longer length reduces stiffness and allows movement in the z-axis. The flexure 530 described herein can help limit rotation when the objective lens (not shown) moves to focus the radiation beam. Due to changes in the optics, the flexure 530 has been partially removed. By partially removing the flexure 530, the remaining flexure 530 can be used as an anchor so that less movement occurs and rotation is minimized. The flexure 530 is moved closer to the objective lens, which allows for better control of R x mode, but does not affect the stiffness in the z-axis. x The pattern was difficult to control, so this change provides better control.

[0103] R x The mode is a dynamic mode and describes a rocking motion about the x-axis. The amplitude of the rocking motion is reduced, and the mode is no longer a restricted motion in the system. In addition, the rotation about the x-axis is minimized.

[0104] Flexure 530 has been shortened and can be anchored on the objective side. This anchoring allows for a stiffer connection point while limiting R x The amplitude of the mode and improve dynamics. However, this change in flexure 530 improves dynamics without sacrificing guidance accuracy or z-actuation. By guiding in one direction, parasitic motion in the z-direction is prevented. In addition, this allows for finer movement in the z-direction and enables finer focusing of the objective lens.

[0105] At least one flexure 530 is described, but up to six flexures may be included. However, if flexure 530 is too stiff, the guide platform cannot easily move in the up and down directions. Flexure 530 has an L-shape that prevents excessive strain. If the flexure is overstretched without some yield, too much pressure is applied to the guide platform. Due to the number of cycles performed by the lithographic apparatus, the stress of the system should be low overall.

[0106] Guiding accuracy is one of the most important aspects of the objective, as the objective should not move around the system during measurement, as the entire system would be harder to control. The flexure 530 and its stiffness provide an overall improved focusing of the objective.

[0107] A magnet assembly 550 is provided to balance the guide platform 510. The magnet assembly 550 can provide a force to counteract gravity and, for example, provide an emergency retraction force. Additionally, a leaf spring 560 is provided to provide control for the flexure 530. Specifically, the leaf spring 560 helps the flexure 530 provide guiding stiffness in the x and y directions. The flexure 530 can be anchored to the leaf spring 560.

[0108] Apart from Figure 5 In addition to the proposed embodiment, a heat sink can also be used. A heat sink (not shown) can act as a passive heat exchanger, transferring heat. Here, the heat sink can also increase stiffness in certain modes. These modes can include, but are not limited to, resonant modes of the objective guide stage. This increases sensor throughput, enabling the system to perform more measurements per hour. By increasing the frequency of these resonant modes and / or reducing their amplitude, the bandwidth of the focus controller can be increased, enabling faster stage movement and, therefore, reducing the time between measurements.

[0109] Figure 6A A side perspective view of a flexure 530 for use in a guide platform 510 in a lithography system 500 is shown, in accordance with some embodiments.

[0110] The guide platform 510 is shown with a sensor objective 520. Flexures 530 are shown which provide stiffness to the guide platform 510. The guide platform 510 includes an actuator motor 540. A magnet assembly 550 is provided to balance the guide platform 510. A leaf spring 560 is provided with an encoder 570.

[0111] Figure 6B A side perspective view of a leaf spring 560 for use in a photolithography system 500 is shown, in accordance with some embodiments.

[0112] The guide platform 560 has a flexure 530 attached thereto. An objective lens (not shown) can be inserted into the hole 590. The offset view of the flexure 530 depicts the L-shaped flexure 530 that can be anchored at the objective lens to provide a rigid connection point.

[0113] Figure 7 Shown is a cross-sectional embodiment of a flexure 730 used in a guide platform 710 in a lithography system 700 , in accordance with some embodiments.

[0114] A guide platform 710 is shown with a sensor objective 720. The sensor objective 720 can receive a radiation beam from an objective 722. The objective 722 contains optics that can be used to focus the radiation beam. In addition, the objective 722 is one of the main masses of the system that needs to be controlled. A flexure 730 is shown that provides stiffness to the guide platform 710. The guide platform 710 includes a Lorentz motor 740 to focus the objective 722. A magnet assembly 750 is provided to balance the guide platform 710. A leaf spring 760 is provided with an encoder 770. The encoder 770 can help measure the z position of the objective 722. Since Figure 7 In a cross-sectional view, the leaf spring 760 is shown behind the Lorentz motor 740 and the magnet assembly 750.

[0115] Figure 8 A method 800 for positioning an objective lens according to some embodiments is described.

[0116] In step 802, a radiation beam is focused using an objective lens mounted on a guidance stage. The objective lens may comprise an optical device.

[0117] In step 804, the objective lens is positioned using a Lorentz motor. The Lorentz motor can be mounted on a guide stage and helps provide fine-tuning movement for focusing the objective lens. The Lorentz motor can also move the mass of the system.

[0118] In step 806, a magnet assembly is mounted on the guide platform and configured to balance the guide platform. The magnet assembly may include at least two magnets. The two magnets provide a force that counteracts gravity.

[0119] The position of the objective lens may be measured in step 808. The measurement may be performed using an encoder on a support assembly that may be mounted on a guide platform.

[0120] At least one flexure and at least one leaf spring are attached to the guide platform in step 810. The leaf spring can be configured to provide stiffness to the guide platform in the x-axis and y-axis when the objective lens is positioned. The flexure has a length such that the stiffness of the guide platform in the z-axis is reduced once the objective lens is positioned.

[0121] In step 812 , the stiffness of the guide platform may be reduced.

[0122] These embodiments can be further described using the following aspects: 1. A guidance platform comprising: an objective lens disposed on the guide platform, wherein the objective lens comprises optics configured to focus the radiation beam; a plurality of actuator motors disposed on the guide platform, the plurality of actuator motors being configured to position the objective lens; a magnet assembly comprising at least two magnets, wherein the at least two magnets are configured to balance the guide platform; and an encoder disposed on a support assembly disposed on the guide platform, wherein the encoder is configured to measure a position of the objective lens; and At least one flexure and at least one leaf spring are attached to the guide platform and are configured to provide stiffness of the guide platform in the x-axis and y-axis when the objective lens is positioned, and the at least one flexure has a length such that the stiffness of the guide platform in the z-axis is reduced when the objective lens is positioned. 2. The guiding platform of aspect 1, wherein the at least one flexure is configured to constrain motion in the z-axis. 3. The guiding platform of aspect 1, wherein the at least one flexure has a rotation mode (Rx), wherein the Rx mode limits rocking of the guiding platform about the x-axis. 4. The guide platform of aspect 1, wherein the guide platform further comprises a heat sink, wherein the heat sink provides additional stiffness to the flexure. 5. The guide platform of aspect 1, wherein the flexure comprises an L-shape. 6. The guiding platform of aspect 1, wherein the L-shape is anchored at the objective lens to provide a rigid connection point. 7. A method comprising: focusing the radiation beam using an objective lens disposed on the guiding platform, wherein the objective lens comprises optics; positioning the objective lens using a plurality of actuator motors mounted on the guide platform; installing a magnet assembly comprising at least two magnets and configured to balance the guide platform; and measuring the position of the objective lens using an encoder mounted on a bracket assembly on the guide platform; and At least one flexure and at least one leaf spring are attached, the at least one flexure and at least one leaf spring being configured to provide stiffness of the guide platform in the x-axis and y-axis when the objective lens is positioned, and the at least one flexure having a length such that the stiffness of the guide platform in the z-axis is reduced when the objective lens is positioned. 8. The method of clause 7, further comprising limiting the movement of the guide platform in the z-axis using the flexure. 9. The method of clause 8, further comprising limiting the rocking of the guide platform about the x-axis using the Rx mode of the flexure. 10. The method of clause 9, further comprising minimizing the Rx mode. 11. The method of aspect 8, further comprising attaching a heat sink to the guide platform to provide additional stiffness to the flexure. 12. The method of aspect 8, wherein the flexure comprises an L-shape. 13. The method of clause 8, further comprising positioning the flexure on the objective lens to provide a rigid connection point. 14. A lithographic apparatus comprising: an illumination system configured to illuminate the patterning device; a support configured to support the patterning device; substrate; a projection system configured to project an image of the pattern onto a substrate; and A metrology system having a guide platform, the guide platform comprising: an objective lens disposed on the guide platform, wherein the objective lens comprises optics configured to focus the radiation beam; a plurality of actuator motors disposed on the guide platform, the plurality of actuator motors being configured to position the objective lens; a magnet assembly comprising at least two magnets, wherein the at least two magnets are configured to balance the guide platform; and an encoder disposed on a support assembly disposed on the guide platform, wherein the encoder is configured to measure a position of the objective lens; and At least one flexure and at least one leaf spring are attached to the guide platform and are configured to provide stiffness of the guide platform in the x-axis and y-axis when the objective lens is positioned, and the at least one flexure has a length such that the stiffness of the guide platform in the z-axis is reduced as the objective lens is further positioned. 15. The lithographic apparatus of clause 14, wherein the at least one flexure is configured to constrain movement in the z-axis. 16. The lithographic apparatus of clause 15, wherein the at least one flexure has an Rx mode, wherein the Rx mode limits rocking of the guide platform about the x-axis. 17. The lithographic apparatus of clause 16, wherein the Rx mode is minimized. 18. The lithographic apparatus of clause 15, wherein the guide platform further comprises a heat sink, wherein the heat sink provides stiffness to the flexure. 19. The lithographic apparatus of clause 15, wherein the flexure comprises an L-shape. 20. The lithographic apparatus of clause 15, wherein the L-shape is anchored at the objective lens to provide a rigid connection point.

[0123] While specific reference is made herein to the use of lithographic apparatus in the fabrication of integrated circuits, it should be understood that the lithographic apparatus described herein may have other applications, such as the fabrication of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin-film magnetic heads, and the like. Those skilled in the art will appreciate that, in the context of such alternative applications, any use of the terms "wafer" or "die" herein may be considered as specific examples of the more general terms "substrate" or "target portion," respectively. References herein to substrates may be processed before or after exposure, for example, in a track unit or a coater-developer unit (a tool that typically applies a resist layer to a substrate and develops the exposed resist) and / or a metrology unit. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Furthermore, a substrate may be processed more than once, for example to produce a multi-layer IC, such that the term substrate as used herein may also refer to a substrate that already contains multiple processed layers.

[0124] Although specific reference has been made above to embodiments of the present disclosure in the context of optical lithography, it will be understood that the present disclosure can be used in other applications, such as imprint lithography, and is not limited to optical lithography where the context permits. In imprint lithography, the topography in a patterning device defines the pattern produced on a substrate. The topography of the patterning device can be imprinted into a resist layer supplied to the substrate, whereby the resist is cured by applying electromagnetic radiation, heat, pressure, or a combination thereof. After the resist is cured, the patterning device is removed from the resist, leaving a pattern therein.

[0125] It is to be understood that the phraseology or terminology herein is for the purpose of description and not limitation, so that the phraseology or terminology in this disclosure will be interpreted by those skilled in the relevant art in accordance with the teachings herein.

[0126] In addition, the terms "radiation," "radiation beam," or the like as used herein include all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g., having a wavelength λ of 365 nm, 355 nm, 248 nm, 193 nm, 157 nm, or 126 nm) and extreme ultraviolet (EUV or soft X-ray) radiation (e.g., having a wavelength in the range of 5 nm to 20 nm, such as, for example, a wavelength of 13.5 nm), or hard X-rays operating at less than 5 nm, as well as matter beams (such as ion beams or electron beams). The terms "light," "irradiation," and the like may refer to non-matter radiation (e.g., photons, UV, X-rays, etc.). Generally, radiation having a wavelength between about 400 nm and about 700 nm is considered visible radiation; radiation having a wavelength between about 780 nm and 3000 nm (or greater) is considered IR radiation. UV refers to radiation having a wavelength between about 100 nm and 400 nm. In photolithography, the term "UV" also applies to wavelengths that can be produced by mercury discharge lamps: the G-line, 436 nm; the H-line, 405 nm; and / or the I-line, 365 nm. Vacuum UV, or VUV (i.e., UV absorbed by gases), refers to radiation having a wavelength of approximately 100 nm to 200 nm. Deep UV (DUV) generally refers to radiation having a wavelength range from 126 nm to 428 nm, and in embodiments, excimer lasers can generate DUV radiation for use within photolithographic equipment. Radiation having a wavelength in the range of, for example, 5 nm to 20 nm should be understood to refer to radiation having a wavelength band at least partially within the range.

[0127] It will be understood that the Detailed Description section, rather than the Summary and Abstract sections, is intended to be used to interpret the claims. As contemplated by the inventors, the Summary and Abstract sections may set forth one or more, but not all, exemplary embodiments of the present disclosure, and thus, are not intended to limit the present disclosure and the appended claims in any way.

[0128] The present disclosure has been described above with reference to the functional building blocks illustrating the embodiments of the specified functions and their mutual relationships. For ease of description, the boundaries of these functional building blocks have been arbitrarily defined herein. As long as the specified functions and their relationships are properly performed, alternative boundaries can be defined.

[0129] Although specific embodiments of the present disclosure have been described above, it should be understood that the embodiments of the present disclosure may be practiced in ways other than those described. These descriptions are intended to be illustrative and not restrictive. Thus, those skilled in the art will appreciate that modifications may be made to the disclosed content without departing from the scope of the claims set forth below.

[0130] The foregoing description of the specific embodiments will sufficiently reveal the general nature of the present disclosure that others may readily modify and / or adapt these specific embodiments for various applications by applying knowledge within the skill of the art without departing from the general concept of the present disclosure and without undue experimentation. Therefore, such adaptations and modifications are intended to fall within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.

[0131] The breadth and scope of the claimed subject matter should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. A guidance platform comprising: an objective lens disposed on the guide platform, wherein the objective lens comprises optics configured to focus the radiation beam; a plurality of actuator motors disposed on the guide platform, the plurality of actuator motors being configured to position the objective lens; a magnet assembly comprising at least two magnets, wherein the at least two magnets are configured to balance the guide platform; as well as an encoder disposed on a support assembly disposed on the guide platform, wherein the encoder is configured to measure a position of the objective lens; as well as At least one flexure and at least one leaf spring are attached to the guide platform and are configured to provide stiffness of the guide platform in the x-axis and y-axis when the objective lens is positioned, and the at least one flexure has a length such that the stiffness of the guide platform in the z-axis is reduced when the objective lens is positioned.

2. The guide platform according to claim 1, wherein: The at least one flexure is configured to restrict motion in the z-axis.

3. The guide platform according to claim 1, wherein: The at least one flexure has a rotational mode (R x ), wherein the R x The mode limits the rocking of the guide platform about the x-axis. The guide platform according to claim 1 , wherein: The guide platform further includes a heat sink, wherein the heat sink provides additional stiffness to the flexure.

5. The guide platform according to claim 1, wherein: The flexure includes an L-shape. The guide platform according to claim 1 , wherein: The L-shape is anchored at the objective lens to provide a rigid connection point.

7. A method comprising: focusing the radiation beam using an objective lens disposed on the guiding platform, wherein the objective lens comprises optics; positioning the objective lens using a plurality of actuator motors mounted on the guide platform; installing a magnet assembly comprising at least two magnets and configured to balance the guide platform; as well as Measuring the position of the objective lens using an encoder mounted on a bracket assembly on the guide platform; as well as At least one flexure and at least one leaf spring are attached, the at least one flexure and at least one leaf spring being configured to provide stiffness of the guide platform in the x-axis and y-axis when the objective lens is positioned, and the at least one flexure having a length such that the stiffness of the guide platform in the z-axis is reduced when the objective lens is positioned.

8. The method of claim 7, further comprising limiting the movement of the guide platform in the z-axis using the flexure.

9. The method according to claim 8, further comprising utilizing the R x The mode limits the rocking of the guide platform about the x-axis.

10. The method according to claim 9, further comprising minimizing the R x model.

11. The method of claim 8, further comprising attaching a heat sink to the guide platform to provide additional stiffness to the flexure.

12. The method according to claim 8, wherein The flexure includes an L-shape.

13. The method of claim 8, further comprising positioning the flexure on the objective lens to provide a rigid connection point.

14. A lithographic apparatus comprising: an illumination system configured to illuminate the patterning device; a support configured to support the patterning device; substrate; a projection system configured to project an image of the pattern onto a substrate; as well as A metrology system having a guide platform, the guide platform comprising: an objective lens disposed on the guide platform, wherein the objective lens comprises optics configured to focus the radiation beam; a plurality of actuator motors disposed on the guide platform, the plurality of actuator motors being configured to position the objective lens; a magnet assembly comprising at least two magnets, wherein the at least two magnets are configured to balance the guide platform; and an encoder disposed on a support assembly disposed on the guide platform, wherein the encoder is configured to measure a position of the objective lens; and At least one flexure and at least one leaf spring are attached to the guide platform and are configured to provide stiffness of the guide platform in the x-axis and y-axis when the objective lens is positioned, and the at least one flexure has a length such that the stiffness of the guide platform in the z-axis is reduced as the objective lens is further positioned.

15. The lithographic apparatus of claim 14, wherein: The at least one flexure is configured to restrict motion in the z-axis.

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