CN116762042A

CN116762042A - Fast uniformity drift correction

Info

Publication number: CN116762042A
Application number: CN202280012410.0A
Authority: CN
Inventors: R·B·维纳; K·K·曼卡拉; 托德·R·丹尼
Original assignee: ASML Holding NV
Current assignee: ASML Holding NV
Priority date: 2021-01-28
Filing date: 2022-01-16
Publication date: 2023-09-15

Abstract

Systems, apparatuses, and methods for adjusting illumination slit uniformity in a lithographic apparatus are provided. An example method may include illuminating a portion of a finger assembly with radiation by a radiation source. The example method may also include receiving, by a radiation detector, at least a portion of the radiation in response to the illumination of the portion of the finger assembly. The example method may also include determining, by a processor, a change in shape of the finger assembly based on the received radiation. The example method may also include generating, by the processor, a control signal configured to modify a position of the finger assembly based on the determined change in the shape of the finger assembly. Subsequently, the example method may include transmitting, by the processor, the control signal to a motion control system coupled to the finger assembly.

Description

Fast uniformity drift correction

Cross Reference to Related Applications

The present application claims priority from U.S. application 63/142,581, filed on day 28 of 1 in 2021, and U.S. application 63/144,798 filed on day 2 of 2021, and the entire contents of these U.S. applications are incorporated herein by reference.

Technical Field

The present disclosure relates to systems and methods for correcting illumination non-uniformities in lithographic apparatus and systems.

Background

A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. Lithographic apparatus can be used, for example, in the manufacture of Integrated Circuits (ICs). In that case, a patterning device, which is interchangeably referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the formed IC. Such a pattern may be transferred onto a target portion (e.g., a portion including a die, or several dies) on a substrate (e.g., a silicon wafer). Transfer of the pattern is typically performed via imaging onto a layer of radiation-sensitive material (e.g., resist) disposed on the substrate. Typically, a single substrate will include a network of adjacent target portions that are continuously patterned. A conventional lithographic apparatus comprises: a so-called stepper in which each target portion is irradiated by exposing the entire pattern onto the target portion at one time; and so-called scanners, in which each target portion is irradiated by scanning the pattern through the radiation beam in a given direction (the "scanning" direction) while simultaneously scanning the target portion parallel or anti-parallel (opposite) to such scanning direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

As semiconductor manufacturing processes continue to advance, the size of circuit elements has been continuously reduced for decades, while the amount of functional elements such as transistors per device has steadily increased, following a trend commonly referred to as "moore's law. To follow the Moire's law, the semiconductor industry is pursuing technologies that can produce smaller and smaller features. To project a pattern onto a substrate, a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the features patterned on the substrate. Typical wavelengths currently in use are 365nm (i-line), 248nm, 193nm and 13.5nm.

Extreme Ultraviolet (EUV) radiation, such as electromagnetic radiation having a wavelength of about 50 nanometers (nm) or less (sometimes also referred to as soft x-rays) and including light at a wavelength of about 13.5nm, may be used in or with a lithographic apparatus to produce very small features in or on a substrate, such as a silicon wafer. A lithographic apparatus using EUV radiation having a wavelength in the range of 4nm to 20nm (e.g., 6.7nm or 13.5 nm) may be used to form smaller features on a substrate than a lithographic apparatus using radiation, for example, having a wavelength of 193 nm.

Methods for generating EUV light include, but are not necessarily limited to, converting a material having an element such as xenon (Xe), lithium (Li), or tin (Sn) into a plasma state using an emission line in the EUV range. For example, in one such method, referred to as Laser Produced Plasma (LPP), a plasma may be produced by illuminating a target material, for example in the form of droplets, plates, ribbons, streams or clusters of material, interchangeably referred to as fuel in the context of an LPP source, with an amplified light beam, which may be referred to as a drive laser. For such processes, a plasma is typically generated in a sealed container, such as a vacuum chamber, and various types of metrology equipment are used to monitor the plasma.

The lithographic apparatus generally includes an illumination system that conditions radiation generated by the radiation source before it is incident on the patterning device. For example, the illumination system may modify one or more properties of the radiation, such as polarization and/or illumination mode. The illumination system may include a uniformity correction system that corrects or reduces non-uniformities (e.g., intensity non-uniformities) present in the radiation. The uniformity correction device may employ actuated finger assemblies that are inserted into the edges of the beam to correct for intensity variations. The spatial extent of the illumination that can be adjusted by the uniformity correction system depends inter alia on, i.e. depends on, the size of the finger assembly and the size of the actuation means for moving the finger assembly in the uniformity correction system. Modifying finger parameters according to known working designs is not trivial, as such modifications may lead to undesired changes in one or more properties of the radiation beam.

In order to achieve tolerances, i.e. tolerances, for the image quality on the patterning device and the substrate, an illumination beam with a controlled uniformity is required. It is common for an illumination beam to have a non-uniform intensity distribution before being reflected off of, or transmitted through, the patterning device. At various stages of the lithographic process, the illumination beam needs to be controlled to achieve improved uniformity. Uniformity may refer to a constant intensity across the relevant cross section of the illumination beam, but may also refer to the ability to control the illumination to achieve a selected uniformity parameter. The patterning device imparts a pattern to the beam of radiation that is then projected onto the substrate. The image quality of such a projected beam is affected by the uniformity of the beam.

Therefore, there is a need to control the illumination uniformity so that the lithography tool performs the lithography process as efficiently as possible for maximizing manufacturing capacity and yield, minimizing manufacturing defects, and reducing the cost per device.

Disclosure of Invention

The present disclosure describes various aspects of systems, apparatus, and methods for adjusting illumination slit uniformity in a lithographic apparatus.

In some aspects, the disclosure describes a system. The system may include a radiation source configured to generate radiation and transmit the generated radiation toward the finger assembly. The system may also include a radiation detector configured to receive at least a portion of the transmitted radiation. The system may also include a processor configured to determine a change in shape of the finger assembly based on the received radiation. The processor may be further configured to generate a control signal configured to modify a position of the finger assembly based on the determined change in the shape of the finger assembly. The processor may also be configured to transmit the control signal to a motion control system coupled to the finger assembly.

In some aspects, the determined change in the shape of the finger assembly may include: based on growth of the finger tip in response to exposure of the finger tip of the finger assembly to Deep Ultraviolet (DUV) radiation or Extreme Ultraviolet (EUV) radiation, a position of an optical edge of the finger tip changes.

In some aspects, the radiation source may be configured to transmit the radiation during a wafer exchange operation of the lithographic apparatus. In other aspects, the radiation source may be configured to transmit the radiation during a wafer exposure operation of the lithographic apparatus.

In some aspects, the generated radiation may include a laser curtain, and the radiation detector may be configured to receive at least a portion of the transmitted radiation in response to illumination of the portion of the finger assembly by the laser curtain. In some aspects, the portion of the finger assembly may include a mechanical edge of a fingertip of the finger assembly, the mechanical edge being disposed separate from an optical edge of the fingertip of the finger assembly.

In some aspects, the received radiation may include radiation reflected from a surface of a fingertip of the finger assembly in response to the surface of the fingertip being irradiated by the transmitted radiation.

In some aspects, the processor may be further configured to measure a change in a position of a reference marker disposed on the finger assembly based on the received radiation. In some aspects, the processor may be further configured to determine the change in the shape of the finger assembly based on the measured change in the position of the reference mark. In some aspects, the reference mark may be applied to a region of multilayer mirror material disposed on a fingertip of the finger assembly. For example, in these aspects, the radiation detector may be configured to sense a reflected portion of the actinic EUV light used during a wafer exposure operation of the lithographic apparatus.

In some aspects, the disclosure describes an apparatus. The apparatus may include a finger assembly. The finger assembly may include a finger body, a fingertip, a multilayer mirror material disposed on a surface of the fingertip, and a set of reference marks applied to regions of the multilayer mirror material. In some aspects, the set of reference marks may include two or more reference marks. In some aspects, the multilayer mirror material may be configured to reflect DUV radiation or EUV radiation towards a radiation detector during an exposure operation of the lithographic apparatus. In some aspects, the multilayer mirror material may include molybdenum.

In some aspects, the present disclosure describes a method for adjusting illumination slit uniformity in a lithographic apparatus. The method may include illuminating a portion of the finger assembly with radiation by a radiation source. The method may further include receiving, by a radiation detector, at least a portion of the radiation in response to the illumination of the portion of the finger assembly. The method may further include determining, by a processor, a change in shape of the finger assembly based on the received radiation. The method may further include generating, by the processor, a control signal configured to modify a position of the finger assembly based on the determined change in the shape of the finger assembly. The method may also include transmitting, by the processor, the control signal to a motion control system coupled to the finger assembly.

In some aspects, the determining the change in the shape of the finger assembly may include determining, by the processor, a change in a position of an optical edge of the fingertip of the finger assembly, the change based on a growth of the fingertip in response to exposure of the fingertip to DUV radiation or EUV radiation.

In some aspects, the irradiating the portion of the finger assembly may include irradiating the portion of the finger assembly with the radiation by the radiation source during a wafer exchange operation of the lithographic apparatus. In other aspects, the irradiating the portion of the finger assembly may include irradiating the portion of the finger assembly with radiation by a radiation source during a wafer exposure operation of the lithographic apparatus.

In some aspects, the radiation may include a laser curtain, and the receiving at least the portion of the radiation may include receiving at least the portion of the transmitted radiation by the radiation detector in response to illuminating the portion of the finger assembly with the laser curtain. In some aspects, the portion of the finger assembly includes a mechanical edge of a fingertip of the finger assembly, the mechanical edge being disposed separate from an optical edge of the fingertip of the finger assembly.

In some aspects, the receiving at least the portion of the radiation may include: radiation reflected from a surface of a fingertip of the finger assembly is received by the radiation detector in response to illuminating the surface of the fingertip with the radiation.

In some aspects, the determining the change in the shape of the finger assembly may include: the change in the position of the reference mark disposed on the finger assembly is measured by the processor based on the received radiation. In some aspects, determining a change in shape of the finger assembly may further include determining, by the processor, the change in shape of the finger assembly based on the measured change in the position of the reference mark. In some aspects, the reference mark is applied to a region of multilayer mirror material disposed on a fingertip of the finger assembly. For example, in these aspects, the method may include sensing, by a radiation detector, a reflected portion of actinic EUV light used by a lock during a wafer exposure operation of a lithographic apparatus.

Further features, as well as the structure and operation of various aspects, are described in detail below with reference to the accompanying drawings. It should be noted that the present disclosure is not limited to the particular aspects described herein. Such aspects are presented herein for illustration or example purposes only. Additional aspects will be apparent to those of ordinary skill in the relevant art based on the teachings contained herein.

Drawings

The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of the various aspects of the disclosure and to enable a person skilled in the pertinent art to make and use the various aspects of the disclosure.

FIG. 1A is a schematic illustration of an example reflective lithographic apparatus according to some aspects of the present disclosure.

FIG. 1B is a schematic illustration of an example transmission lithographic apparatus according to some aspects of the present disclosure.

FIG. 2 is a more detailed schematic illustration of the reflective lithographic apparatus shown in FIG. 1A, according to some aspects of the present disclosure.

FIG. 3 is a schematic illustration of an example lithographic cell according to some aspects of the present disclosure.

FIG. 4 is a schematic illustration of an example radiation source for an example reflective lithographic apparatus, according to some aspects of the present disclosure.

Fig. 5A and 5B are schematic illustrations of an example illumination uniformity correction system in accordance with some aspects of the present disclosure.

Fig. 6 is a schematic illustration of an example illumination uniformity correction system in accordance with some aspects of the present disclosure.

Fig. 7 is a schematic illustration of another example illumination uniformity correction system in accordance with some aspects of the present disclosure.

Fig. 8 is a schematic illustration of another example illumination uniformity correction system in accordance with some aspects of the present disclosure.

Fig. 9 is a schematic illustration of an example set of reference numerals in accordance with some aspects of the present disclosure.

Fig. 10 is a schematic illustration of another example illumination uniformity correction system in accordance with some aspects of the present disclosure.

FIG. 11 is an example method for adjusting illumination slit uniformity in a lithographic apparatus or portion thereof, according to some aspects of the present disclosure.

FIG. 12 is an example computer system for implementing some aspects of the present disclosure or portions thereof.

Features and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like or similar reference characters identify corresponding elements throughout. In the drawings, like or similar reference numbers generally indicate identical, functionally similar, and/or structurally similar elements unless otherwise indicated. In addition, generally, the leftmost digit(s) of a reference number identifies the figure in which the reference number first appears. The drawings provided throughout this disclosure should not be construed as being drawn to scale unless otherwise indicated.

Detailed Description

This specification discloses one or more embodiments that incorporate the features of this disclosure. The disclosed embodiments merely describe the present disclosure. The scope of the present disclosure is not limited to the disclosed embodiments. The breadth and scope of the present disclosure are defined by the claims appended hereto and their equivalents.

References in the specification to "one embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

Spatially relative terms, such as "under … …," "under … …," "lower," "above … …," "over … …," "upper," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or feature as illustrated in the figures. In addition to the orientations depicted in the drawings, the spatially relative terms are intended to encompass different orientations of the device in use or operation. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The term "about" as used herein indicates a given number of values that may vary based on a particular technology. The term "about" may indicate a given number of values that vary, for example, within 10% to 30% of the value (e.g., ±10%, ±20% or ±30%) above and below the value, based on a particular technology.

SUMMARY

An example illumination uniformity correction system, referred to as "Unicom," may adjust slit uniformity in the cross-scan direction to attenuate illumination "hot spots" by introducing a set of finger assemblies or "fingers" into the illumination slit. Unicom can be configured to operate in one of two "modes": (1) A first mode involving uniformity correction per wafer to correct the effect of irradiation; and (2) a second mode in which slit uniformity is modified by die (i.e., for each die) to correct for wafer and process effects, and in which uniformity correction is changed in parallel with stepping the dies. As incident light (e.g., EUV radiation) heats up the Unicom finger tips, the unmeasured distance from the Unicom position measurement to the fingertip can change, resulting in a drift in slit uniformity. For example, as power increases in a lithographic apparatus, the expected Critical Dimension (CD) impact of uniformity drift may increase from about 0.06nm (< 600W power supply power) to greater than or equal to about 0.1nm (. Gtoreq.600W power supply power). The CD effect may be equal to about 0.3 times the percent uniformity. CD uniformity (CDU) requirements may be between about 0.7nm and about 1.2 nm. In some examples, the slot uniformity drift may not be compensated for.

In one example, slit uniformity drift can be measured and corrected once every approximately 900 seconds, or in another example, once per wafer lot, thereby introducing uncorrectable CD effects. In some aspects, CD effects may be reduced by performing more frequent measurements. However, each Uniformity Refresh (UR) measurement can take about 2 seconds and use sensors in the platen. Therefore, these measurements cannot be performed in parallel with the platen chuck exchange. In addition, to reduce slit uniformity drift by half, at least two additional uniformity refresh measurements may be required in the first lot, increasing the lot time of 25 wafers from about 900 seconds to about 904 seconds and thus reducing overall machine yield.

In contrast, some aspects of the present disclosure may provide for correcting Unicom uncorrected thermal drift using a reference measurement near the fingertip. By periodically measuring a single reference surface in the fingertip, the actual fingertip growth can be periodically measured without the need for a sensor in the platen, thus introducing no yield impact. To measure and estimate fingertip growth relative to a position sensor (such as an encoder scale), some aspects of the present disclosure may provide for measuring changes to encoder index pulses in distance to one or more reference points in or associated with a Unicom fingertip. In some aspects, the raw distance from the Unicom fingertip to the encoder reference mark may be calibrated periodically or measured once during Unicom creation.

In some aspects, the present disclosure may provide a fingertip sensor that includes a single beam that spans all finger assemblies, which minimizes the number of sensors. In these aspects, each finger may have to move through its complete travel path until the position of the fingertip is measured. For example, each finger may move through its full travel path in about 200 ms. As such, measuring all 28 finger assemblies may take about 6 seconds, and thus the measurement may be performed in parallel with the wafer exchange.

In some aspects, an algorithm may be used to maximize the number of finger assemblies measured during a batch because the wafer chuck exchange time is about 2.5 seconds with a "shadow time" of about 0.43 seconds that may be used for Unicom movement. For example, some aspects of the present disclosure may measure only the most inserted, i.e., the most inserted, finger assembly and the least inserted finger assembly, and interpolate the measurement. Additionally or alternatively, some aspects of the disclosure may include: etching a mark on the fingertip (or creating a new surface in the fingertip to make such a mark), and measuring the displacement of such a mark as the finger thermally grows.

In some aspects, fingertip growth may be proportional to the change in encoder index from the distance of the selected reference point in the fingertip assembly. In some aspects, the measuring and adjusting may occur once per wafer or per die. In some aspects, the "room temperature" or reference distance from the fingertip to the encoder may be calibrated periodically or only once during construction of the fingertip assembly. In some aspects, fingertip growth of less than or equal to about 8 μm may be detected.

In some aspects, the present disclosure provides methods for adjusting illumination slit uniformity in a lithographic apparatus by, for example: illuminating a portion of the finger assembly with radiation by a radiation source; receiving, by a radiation detector, at least a portion of the radiation in response to the illumination of the portion of the finger assembly; determining, by a processor, a change in shape of the finger assembly based on the received radiation; generating, by the processor, a control signal configured to modify a position of the finger assembly based on the determined change in shape of the finger assembly; and transmitting, by the processor, the control signal to a motion control system coupled to the finger assembly.

There are many exemplary aspects to the systems, devices, methods, and computer program products disclosed herein. For example, aspects of the present disclosure provide for reducing CD drift and CDU effects from Unicom from greater than or equal to about 0.1nm (e.g., for all generations of tools having a source power greater than about 350W) to below about 0.06 nm. Since CDU requirements may be less than or equal to about 0.6nm, a 40% reduction in CDU impact from about 0.1nm to about 0.06nm may be important. In another example, aspects of the present disclosure do not require sensors in the platen, and thus there is substantially no yield impact on reducing CD drift. In another example, aspects of the present disclosure do not require sensors external to Unicom (e.g., accurate pressure sensors). In another example, aspects of the present disclosure do not require a priori knowledge of finger component insertion.

Before describing these aspects in more detail, however, it is instructive to present an example environment in which aspects of the present disclosure may be implemented.

Example lithography System

FIGS. 1A and 1B are schematic illustrations of a lithographic apparatus 100 and a lithographic apparatus 100', respectively, that may be used to implement aspects of the present disclosure. As shown in fig. 1A and 1B, the lithographic apparatus 100 and 100' are illustrated from a perspective (e.g., a side view) perpendicular to the XZ plane (e.g., the X axis points to the right, the Z axis points to the top, and the Y axis points away from the viewer's page), while the patterning device MA and the substrate W are presented from an additional perspective (e.g., a top view) perpendicular to the XY plane (e.g., the X axis points to the right, the Y axis points to the top, and the Z axis points to the viewer's page).

In some aspects, lithographic apparatus 100 and/or lithographic apparatus 100' may include one or more of the following structures: an illumination system IL (e.g., an illuminator) configured to condition a radiation beam B (e.g., a Deep Ultraviolet (DUV) radiation beam or an Extreme Ultraviolet (EUV) radiation beam); a support structure MT (e.g. a mask table) configured to support a patterning device MA (e.g. a mask, reticle or dynamic patterning device) and connected to a first positioner PM configured to accurately position the patterning device MA; and a substrate holder, such as a substrate table WT (e.g. a wafer table), configured to hold a substrate W (e.g. a resist coated wafer) and connected to a second positioner PW configured to accurately position the substrate W. The lithographic apparatus 100 and 100' also have a projection system PS (e.g., a refractive projection lens system) configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g., a portion including one or more dies) of the substrate W. In lithographic apparatus 100, patterning device MA and projection system PS are reflective. In lithographic apparatus 100', patterning device MA and projection system PS are transmissive.

In some aspects, in operation, the illumination system IL may receive a radiation beam from a radiation source SO (e.g., via a beam delivery system BD shown in fig. 1B). The illumination system IL may include various types of optical structures, such as refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic and other types of optical components for directing, shaping, or controlling radiation, or any combination thereof. In some aspects, the illumination system IL may be configured to condition the radiation beam B to have a desired spatial and angular intensity distribution in its cross-section at the plane of the patterning device MA.

In some aspects, the support structure MT may hold the patterning device MA in a manner that depends on the orientation of the patterning device MA with respect to a reference frame, the design of at least one of the lithographic apparatus 100 and 100', and other conditions, such as for example whether or not the patterning device MA is held in a vacuum environment. The support structure MT may use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device MA. The support structure MT may be, for example, a frame or a table, which may be fixed or movable as required. By using a sensor, the support structure MT may ensure that the patterning device MA is at a desired position, for example with respect to the projection system PS.

The term "patterning device" MA should 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 such as to create a pattern in a target portion C of the substrate W. The pattern imparted to the radiation beam B may correspond to a particular functional layer in a device being created in the target portion C to create an integrated circuit.

In some aspects, the patterning device MA may be of a transmissive type (as in lithographic apparatus 100' of fig. 1B) or of a reflective type (as in lithographic apparatus 100 of fig. 1A). Patterning device MA may include various structures, such as a reticle, a mask, a programmable mirror array, a programmable LCD panel, other suitable structures, or a combination thereof. Masks include mask types such as binary, alternating phase-shift, or attenuated phase-shift, as well as various hybrid mask types. In one example, the programmable mirror array may comprise a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in a radiation beam B which is reflected by the matrix of small mirrors.

The term "projection system" PS should be broadly interpreted as encompassing any type of projection system, including refractive, reflective, catadioptric, magnetic, anamorphic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, and/or for other factors such as the use of an immersion liquid (e.g. over a substrate W), or the use of a vacuum. Vacuum environments may be used for EUV or electron beam radiation, as other gases may absorb too much radiation or electrons. Thus, a vacuum environment can be provided to the entire beam path by means of the vacuum wall and the vacuum pump. Furthermore, in some aspects, any use of the term "projection lens" herein may be interpreted as synonymous with the more general term "projection system" PS.

In some aspects, the lithographic apparatus 100 and/or the lithographic apparatus 100' may be of a type having two (e.g., "dual stage") or more substrate tables WT and/or two or more mask tables. In these "multiple stage" machines the additional substrate tables WT may be used in parallel, or preparatory steps may be carried out on one or more tables while one or more other substrate tables WT are being used for exposure. In one example, a preliminary step of a subsequent exposure of the substrate W may be performed on the substrate W located on one of the substrate tables WT while another substrate W located on the other of the substrate tables WT is being used to expose a pattern on another substrate W. In some aspects, the additional table may not be the substrate table WT.

In some aspects, the lithographic apparatus 100 and/or the lithographic apparatus 100' may comprise a measurement platform in addition to the substrate table WT. The measurement platform may be arranged to hold the sensor. The sensor may be arranged to measure a property of the projection system PS, a property of the radiation beam B, or both. In some aspects, the measurement platform may hold a plurality of sensors. In some aspects, the measurement platform may move under the projection system PS as the substrate table WT moves away from the projection system PS.

In some aspects, the lithographic apparatus 100 and/or the lithographic apparatus 100' may also be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index (e.g. water) so as to fill a space between the projection system PS and the substrate W. The immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the patterning device MA and the projection system PS. Immersion techniques are used to increase the numerical aperture of projection systems. The term "immersion" as used herein does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that liquid is located between the projection system and the substrate during exposure. Various immersion techniques are described in U.S. Pat. No. 6,952,253 issued at 4/10/2005 and entitled "LITHOGRAPHIC APPARATUS AND DEVICE MANUFACTURING METHOD," which is incorporated herein by reference in its entirety.

Referring to fig. 1A and 1B, the illumination system IL receives a radiation beam B from a radiation source SO. For example, when the source SO is an excimer laser, the source SO and the lithographic apparatus 100 or 100' may be separate physical entities. In such cases, the source SO is not considered to form part of the lithographic apparatus 100 or 100' and the radiation beam B is passed from the source SO to the illumination system IL with the aid of a beam delivery system BD (e.g. shown in FIG. 1B) comprising, for example, suitable directing mirrors and/or a beam expander. In other cases, the source SO may be an integral part of the lithographic apparatus 100 or 100', for example when the source SO is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system.

In some aspects, the illumination system IL may include an adjuster AD for adjusting the angular intensity distribution of the radiation beam. In general, at least an outer radial extent and/or an 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. IN addition, the illumination system IL may include various other components, such as an integrator IN and a radiation collector CO (e.g., a condenser or collector optics). In some aspects, the illumination system IL may be used to condition the radiation beam B to have a desired uniformity and intensity distribution in its cross-section.

Referring to fig. 1A, in operation, a radiation beam B may be incident on a patterning device MA (e.g., a mask, a reticle, a programmable mirror array, a programmable LCD panel, any other suitable structure, or combination thereof), which may be held on a support structure MT (e.g., a mask table), and may be patterned by a pattern (e.g., a design layout) present on the patterning device MA. In lithographic apparatus 100, radiation beam B may be reflected from patterning device MA. Having traversed the patterning device MA (e.g., after being reflected from the patterning device MA), the radiation beam B may pass through the projection system PS, which may focus the radiation beam B onto a target portion C of the substrate W or onto a sensor arranged at the stage.

In some aspects, the substrate table WT may be accurately moved by means of the second positioner PW and position sensor IFD2 (e.g. an interferometric device, linear encoder or capacitive sensor), e.g. so as to position different target portions C in the path of the radiation beam B. Similarly, the first positioner PM and another position sensor IFD1 (e.g., an interferometric device, linear encoder or capacitive sensor) can be used to accurately position the patterning device MA with respect to the path of the radiation beam B.

In some aspects, the patterning device MA and the substrate W may be aligned using the mask alignment marks M1 and M2 and the substrate alignment marks P1 and P2. Although fig. 1A and 1B illustrate the substrate alignment marks P1 and P2 as occupying dedicated target portions, the substrate alignment marks P1 and P2 may be positioned in a space between the target portions. When the substrate alignment marks P1 and P2 are located between the target portions C, these substrate alignment marks are referred to as scribe-lane alignment marks. The substrate alignment marks P1 and P2 may also be arranged as intra-die marks in the area of the target portion C. These intra-die marks may also be used as metrology marks, for example, for overlay measurements.

In some aspects, for purposes of illustration and not limitation, one or more of the figures herein may utilize a cartesian coordinate system. The cartesian coordinate system includes three axes: an X axis; a Y axis; and a Z axis. Each of the three axes is orthogonal to the other two axes (e.g., the X-axis is orthogonal to the Y-axis and the Z-axis is orthogonal to the X-axis and the Z-axis, and the Z-axis is orthogonal to the X-axis and the Y-axis). The rotation about the X-axis is called Rx rotation. The rotation about the Y-axis is referred to as Ry rotation. The rotation about the Z axis is referred to as Rz rotation. In some aspects, the X-axis and the Y-axis define a horizontal plane, while the Z-axis is in a vertical direction. In some aspects, the direction of the cartesian coordinate system may be different, for example such that the Z-axis has a component along the horizontal plane. In some aspects, another coordinate system, such as a cylindrical coordinate system, may be used.

Referring to fig. 1B, a radiation beam B is incident on, and patterned by, a patterning device MA held on a support structure MT. 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. In some aspects, the projection system PS may have a pupil that is conjugate to the illumination system pupil. In some aspects, portions of the radiation may diverge from the intensity distribution at the illumination system pupil and traverse the mask pattern without being affected by diffraction at the mask pattern MP, and produce an image of the intensity distribution at the illumination system pupil.

The projection system PS projects an image MP 'of the mask pattern MP onto a resist layer coated on the substrate W, wherein the image MP' is formed by a diffracted beam resulting from radiation of intensity distribution from the mask pattern MP. For example, the mask pattern MP may include an array of lines and spaces. Diffraction of radiation at the array and other than zero order diffraction produces a diverted diffracted beam having a change of direction in a direction perpendicular to the line. The reflected light (e.g., a zero order diffracted beam) traverses the pattern without any change in the propagation direction. The zero order diffracted beam traverses an upper lens or upper lens group of the projection system PS upstream of the pupil conjugate of the projection system PS to reach the pupil conjugate. The portion of the intensity distribution in the plane of the pupil conjugate and associated with the zero-order diffracted beam is an image of the intensity distribution in the illumination system pupil of the illumination system IL. In some aspects, the aperture arrangement may be disposed at or substantially at a plane including a pupil conjugate of the projection system PS.

The projection system PS is arranged to capture not only the zero order diffracted beam, but also the first order, or first and higher order diffracted beams (not shown) by means of a lens or a lens group. In some aspects, dipole illumination for imaging a line pattern extending in a direction perpendicular to the line may be used to take advantage of the resolution enhancement effect of dipole illumination. For example, the first order diffracted beams interfere with the corresponding zero order diffracted beams at the level of the substrate W, while an image of the mask pattern MP is produced with the highest possible resolution and process window (e.g., available depth of focus combined with allowable exposure dose bias). In some aspects, astigmatic aberration can be reduced by providing an emitter (not shown) in opposite quadrants of the illumination system pupil. Additionally, in some aspects, astigmatic aberration can be reduced by blocking a zero order beam in a pupil conjugate of the projection system PS associated with the radiation poles in opposite quadrants. This is described in more detail in U.S. patent No. 7,511,799 issued 3/31/2009 and entitled "LITHOGRAPHIC PROJECTION APPARATUS AND A DEVICE MANUFACTURING METHOD," which is incorporated herein by reference in its entirety.

In some aspects, the substrate table WT may be accurately moved by means of the second positioner PW and position measurement system PMS (e.g. comprising a position sensor, such as an interferometric device, linear encoder or capacitive sensor), e.g. so as to position different target portions C at focused and aligned positions in the path of the radiation beam B. Similarly, the first positioner PM and another position sensor (e.g., an interferometric device, linear encoder, or capacitive sensor) (not shown in fig. 1B) 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). Mask alignment marks M1 and M2 and substrate alignment marks P1 and P2 may be used to align patterning device MA and substrate W.

In general, movement of the support structure MT may be realized with the aid of a long-stroke positioner (coarse positioning) and a short-stroke positioner (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT may be realized using a long-stroke positioner and a short-stroke positioner, 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 short-stroke actuator only, or may be fixed. Mask alignment marks M1 and M2 and substrate alignment marks P1 and P2 may be used to align patterning device MA and substrate W. While the substrate alignment marks (as illustrated) occupy dedicated target portions, they may be located in spaces between target portions (e.g., scribe-lane alignment marks). Similarly, in the case where more than one die is provided on the patterning device MA, the mask alignment marks M1 and M2 may be located between the dies.

The support structure MT and the patterning device MA can be in a vacuum chamber V, in which an in-vacuum robot can be used to move a patterning device, such as a mask, in and out of the vacuum chamber. Alternatively, when the support structure MT and patterning device MA are outside of a vacuum chamber, an out-of-vacuum robot may be used in various transport operations, similar to an in-vacuum robot. In some cases, it is desirable to calibrate both the in-vacuum and out-vacuum robots for smooth transfer of any payload (e.g., mask) to the fixed motion mount of the transfer station.

In some aspects, the lithographic apparatus 100 and 100' may be used in at least one of the following modes:

1. in step mode, the support structure MT and the substrate table WT are kept essentially stationary (e.g. a single static exposure) while an entire pattern imparted to the radiation beam B is projected onto a target portion C at one time. Next, the substrate table WT is shifted in the X and/or Y direction so that a different target portion C can be exposed.

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

3. In another mode, the support structure MT is kept essentially stationary to hold a programmable patterning device MA, 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. The pulsed radiation source SO may be used and the programmable patterning device updated as required after each movement of the substrate table WT or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device MA, such as a programmable mirror array.

In some aspects, lithographic apparatus 100 and 100' may employ combinations and/or variations on the above described modes of use or entirely different modes of use.

In some aspects, as shown in fig. 1A, the lithographic apparatus 100 may include an EUV source configured to generate an EUV radiation beam B for EUV lithography. In general, the EUV source may be configured in a radiation source SO, and the corresponding illumination system IL may be configured to condition an EUV radiation beam B of the EUV source.

FIG. 2 depicts in more detail a lithographic apparatus 100 that includes a radiation source SO (e.g., a source collector apparatus), an illumination system IL, and a projection system PS. As shown in fig. 2, the lithographic apparatus 100 is illustrated from a perspective or viewpoint (e.g., a side view) perpendicular to an XZ plane (e.g., the X axis pointing to the right and the Z axis pointing upwards).

The radiation source SO is constructed and arranged such that a vacuum environment can be maintained in the enclosure 220. The radiation source SO comprises a source chamber 211 and a collector chamber 212 and is configured to generate and transmit EUV radiation. EUV radiation may be generated from a gas or vapor, such as xenon (Xe) gas, lithium (Li) vapor, or tin (Sn) vapor, wherein the EUV radiation-emitting plasma 210 is generated to emit radiation in the EUV range of the electromagnetic spectrum. The at least partially ionized EUV radiation emitting plasma 210 may be generated by, for example, an electrical discharge or a laser beam. Partial pressures of, for example, about 10.0 pascals (pa) of Xe gas, li vapor, sn vapor, or any other suitable gas or vapor may be used to efficiently generate radiation. In some aspects, a plasma of excited tin is provided to generate EUV radiation.

Radiation emitted by the EUV radiation emitting plasma 210 is transferred from the source chamber 211 into the collector chamber 212 via an optional gas barrier or contaminant trap 230 (e.g., also referred to as a contaminant barrier or foil trap in some cases) positioned in or behind an opening in the source chamber 211. The contaminant trap 230 may include a channel structure. The contaminant trap 230 may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap 230 further indicated herein comprises at least a channel structure.

The collector chamber 212 may include a radiation collector CO (e.g., a condenser or collector optics) that 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 radiation collector CO may be reflected from the grating spectral filter 240 to be focused in the virtual source point IF. The virtual source point IF is commonly referred to as an intermediate focus and the source collector apparatus is arranged such that the virtual source point IF is located at or near the opening 219 in the enclosure 220. The virtual source point IF is an image of the EUV radiation emitting plasma 210. The grating spectral filter 240 may be used to suppress Infrared (IR) radiation.

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

There may generally be more elements in the illumination system IL and the projection system PS than shown. Alternatively, depending on the type of lithographic apparatus, there may be a grating spectral filter 240. In addition, there may be more mirrors than those shown in fig. 2. For example, there may be up to six additional reflective elements in the projection system PS than the reflective elements shown in fig. 2.

The radiation collector CO as illustrated in fig. 2 is depicted as a nest-like collector with grazing incidence reflectors 253, 254 and 255, merely as an example of a collector (or collector mirror). The grazing incidence reflectors 253, 254 and 255 are arranged axially symmetrically about the optical axis O and a radiation collector CO of this type is preferably used in combination with a discharge-generating plasma (DPP) source.

Example lithography Unit

Fig. 3 illustrates a lithography unit 300, which is sometimes also referred to as a lithography unit or a lithography manufacturing cluster. As shown in fig. 3, the lithography unit 300 is illustrated from a perspective (e.g., a top view) perpendicular to the XY plane (e.g., the X-axis pointing to the right and the Y-axis pointing upwards).

The lithographic apparatus 100 or 100' may form part of a lithographic cell 300. The lithography unit 300 may also include one or more devices to perform pre-exposure and post-exposure processes on the substrate. For example, these apparatuses may include a spin coater SC for depositing a resist layer, a developer DE for developing an exposed resist, a chill plate CH, and a bake plate BK. A substrate transport apparatus RO (e.g., a robot) picks up a substrate from input/output ports I/O1 and I/O2, moves the substrate between different processing apparatuses, and transfers the substrate to a feed station LB of the lithographic apparatus 100 or 100'. These devices, often collectively referred to as track or coating development systems, are under the control of a track or coating development system control unit TCU, which itself is controlled by a supervisory control system SCS, which also controls the lithographic apparatus via a lithographic control unit LACU. Thus, different equipment can be operated to maximize yield and process efficiency.

Example radiation Source

An example of a radiation source SO for use in an example reflective lithographic apparatus (e.g., lithographic apparatus 100 of FIG. 1A) is shown in FIG. 4. As shown in fig. 4, the radiation source SO is illustrated from a perspective or viewpoint (e.g., a top view) perpendicular to the XY plane, as described below.

The radiation source SO shown in fig. 4 is of a type that may be referred to as a Laser Produced Plasma (LPP) source. May for example comprise carbon dioxide (CO) ₂ ) The laser system 401 of the laser is arranged to deposit energy via one or more laser beams 402 into a fuel target 403 '(such as one or more discrete tin (Sn) droplets), which fuel target 403' is provided by a fuel target generator 403 (e.g. fuel emitter, droplet generator, for example). According to some aspects, laser system 401 may be a pulsed, continuous wave or quasi-continuous wave laser or may operate in the manner previously described. The trajectory of the fuel target 403' (e.g., an example, a droplet) emitted from the fuel target generator 403 may be parallel to the X-axis. According to some aspects, one or more laser beams 402 propagate in a direction parallel to a Y-axis, which is perpendicular to an X-axis. The Z-axis is perpendicular to both the X-axis and the Y-axis and generally extends into (or out of) the plane of the page, but in other aspects other configurations are used. In some embodiments, the laser beam 402 may propagate in a direction other than parallel to the Y-axis (e.g., in a direction other than orthogonal to the X-axis direction of the trajectory of the fuel target 403').

In some aspects, the one or more laser beams 402 may include a pre-pulse laser beam and a main pulse laser beam. In these aspects, the laser system 401 may be configured to emit a pre-pulsed laser beam at each of the fuel targets 403' to produce modified fuel targets. The laser system 401 may also be configured to impinge each of the modified fuel targets with a main pulsed laser beam to generate a plasma 407.

Although tin is mentioned in the following description, any suitable target material may be used. The target material may for example be in liquid form and may for example be a metal or an alloy. The fuel target generator 403 may include a nozzle configured to direct tin along a trajectory toward the plasma formation region 404, for example, in the form of fuel targets 403' (e.g., discrete droplets). Throughout the remainder of this specification, references to "fuel", "fuel target" or "fuel droplet" are understood to refer to a target material (e.g., droplet) emitted by the fuel target generator 403. The fuel target generator 403 may include a fuel emitter. One or more laser beams 402 are incident on a target material (e.g., tin) at a plasma formation region 404. Deposition of laser energy in the target material generates plasma 407 at plasma formation region 404. During de-excitation and recombination of ions and electrons of the plasma, radiation including EUV radiation is emitted from the plasma 407.

EUV radiation is collected and focused by a radiation collector 405 (e.g., radiation collector CO). In some aspects, the radiation collector 405 may include a near normal incidence radiation collector (sometimes more commonly referred to as a normal incidence radiation collector). The radiation collector 405 may be a multi-layer structure arranged to reflect EUV radiation (e.g., EUV radiation having a desired wavelength such as about 13.5 nm). According to some aspects, the radiation collector 405 may have an elliptical configuration with two foci. As discussed herein, the first focus may be at the plasma formation region 404 and the second focus may be at the intermediate focus 406.

In some aspects, the laser system 401 may be located at a relatively long distance from the radiation source SO. In such cases, one or more laser beams 402 may be transferred from laser system 401 to radiation source SO by means of a beam transfer system (not shown) comprising, for example, suitable directing mirrors and/or a beam expander and/or other optics. The laser system 401 and the radiation source SO may together be regarded as a radiation system.

The radiation reflected by the radiation collector 405 forms a radiation beam B. The radiation beam B is focused at a point (e.g., intermediate focus 406) to form an image of the plasma formation zone 404, which serves as a virtual radiation source for the illumination system IL. The point at which the radiation beam B is focused may be referred to as an Intermediate Focus (IF) (e.g., intermediate focus 406). The radiation source SO is arranged such that the intermediate focus 406 is located at or near an opening 408 in an enclosure 409 of the radiation source SO.

The radiation beam B passes from the radiation source SO into the illumination system IL, which is configured to condition the radiation beam B. The radiation beam B is delivered from the illumination system IL and is incident on the patterning device MA, which is held by the support structure MT. Patterning device MA reflects and patterns the radiation beam B. After reflection from patterning device MA, patterned radiation beam B enters projection system PS. The projection system includes a plurality of mirrors configured to project a radiation beam B onto a substrate W held by a substrate table WT. The projection system PS can apply a reduction factor to the radiation beam to form an image having features smaller than corresponding features on the patterning device MA. For example, a reduction factor of four may be applied. Although the projection system PS is shown in fig. 2 as having two mirrors, the projection system may include any number of mirrors (e.g., six mirrors).

The radiation source SO may also comprise components not shown in fig. 4. For example, a spectral filter may be provided in the radiation source SO. The spectral filter may substantially transmit EUV radiation, but substantially block radiation of other wavelengths, such as infrared radiation.

The radiation source SO (or radiation system) may also include a fuel target imaging system to obtain an image of a fuel target (e.g., a droplet) in the plasma formation region 404, or more particularly, to obtain an image of a shadow of the fuel target. The fuel target imaging system may detect light diffracted from an edge of the fuel target. Reference hereinafter to an image of a fuel target should also be understood to refer to an image of a shadow of the fuel target or a diffraction pattern caused by the fuel target.

The fuel target imaging system may include a photodetector such as a CCD array or CMOS sensor, but it should be appreciated that any suitable imaging device for obtaining an image of the fuel target may be used. It should be appreciated that in addition to the photodetector, the fuel target imaging system may also include optical components, such as one or more lenses. For example, the fuel target imaging system may include a camera 410, such as a light sensor or light detector in combination with one or more lenses. The optical components may be selected such that the light sensor or camera 410 obtains near field images and/or far field images. The camera 410 may be positioned at any suitable location within the radiation source SO from which the camera has a line of sight to the plasma formation zone 404 and one or more markers (not shown in fig. 4) disposed on the collector 405. In some aspects, however, it may be necessary to position the camera 410 away from the propagation path of the one or more laser beams 402 and away from the trajectory of the fuel target emitted from the fuel target generator 403 in order to avoid damage to the camera 410. According to some aspects, the camera 410 is configured to provide an image of the fuel target to the controller 411 via the connection 412. The connection 412 is shown as a wired connection, but it should be appreciated that the connection 412 (and other connections mentioned herein) may be implemented as a wired connection or a wireless connection, or a combination thereof.

As shown in fig. 4, the radiation source SO may include a fuel target generator 403 configured to generate fuel targets 403 '(e.g., discrete Sn droplets) and emit the fuel targets 403' toward the plasma formation area 404. The radiation source SO may also include a laser system 401 configured to impinge one or more of the fuel targets 403' with one or more laser beams 402 to generate a plasma 407 at a plasma formation region 404. The radiation source SO may also include a collector 405 (e.g., a radiation collector CO) configured to collect radiation emitted by the plasma 407.

Example illumination uniformity correction System

Fig. 5A and 5B are schematic illustrations of an example illumination uniformity correction system 500 in accordance with some aspects of the present disclosure.

As shown in fig. 5A, an example illumination uniformity correction system 500 may include a set of finger assemblies 502 (e.g., 28 finger assemblies at a pitch of about x 4 mm), a set of fingertips 504 (e.g., each finger assembly includes a respective fingertip), a frame 528, a set of flexures 530, and a set of flexures 532. In some aspects, the example illumination uniformity correction system 500 may individually control (e.g., using a motion control system including, but not limited to, one or more magnet assemblies) the position of each finger assembly of the set of finger assemblies 502 to modify the intensity of the illumination slit in order to achieve a target uniformity.

As shown in fig. 5B, an example illumination uniformity correction system 500 can include a radiation source 540 and a radiation detector 560. In some aspects, radiation source 540 may be configured to generate radiation 542 and emit radiation 542 toward radiation detector 560 across the set of finger assemblies 502. In some aspects, radiation 542 may include a laser curtain. In some aspects, the example illumination uniformity correction system 500 may be configured to move one or more finger assemblies of the set of finger assemblies 502 into a laser curtain to check for fingertip thermal growth during a wafer exchange operation (e.g., during a wafer exposure operation). In some aspects, radiation detector 560 may be configured to receive at least a portion of radiation 542. In some aspects, the received portion of radiation 542 may include radiation reflected from a surface of a fingertip of the finger assembly (e.g., a mechanical edge disposed opposite the optical edge) in response to the surface of the fingertip being illuminated by the transmitted radiation 542.

In some aspects, during a wafer exposure operation of the lithographic apparatus, an optical edge of one or more of the set of fingertips 504 may be exposed to radiation 580 (e.g., DUV or EUV radiation), which may cause one or more fingertips to grow as a result of the exposure (or during the course of multiple exposures). In some aspects, the example illumination uniformity correction system 500 may further include a processor (not shown) configured to determine a change in shape of one or more finger assemblies of the set of finger assemblies 502 based on the received radiation 542.

Fig. 6 is a schematic illustration of an example illumination uniformity correction system 600 in accordance with some aspects of the present disclosure.

As shown in fig. 6, a set of finger assemblies may include finger assembly 620. Finger assembly 620 may include a finger body 622, a fingertip 624, an actuator 626 (e.g., to adjust the position of finger assembly 620), a position sensor 628 (e.g., including but not limited to encoder dimensions), a flexure 630, and a flexure 632. Fingertip 624 may include an optical edge 624a and a mechanical edge 624b. In some aspects, the optical edge 624a of the fingertip 624 may be exposed to radiation 680 (e.g., DUV or EUV radiation) during a wafer exposure operation of the lithographic apparatus, which may cause the fingertip 624 to grow due to the exposure (or during a process of multiple exposures).

In some aspects, the radiation source may be configured to emit radiation 642 toward the finger assembly 620 (e.g., toward the mechanical edge 624b of the fingertip 624). In some aspects, the radiation source may be configured to emit radiation 642 during a wafer exchange operation of the lithographic apparatus (e.g., after a wafer exposure operation) during which the mechanical edge 624b of the fingertip 624 moves across the radiation 642.

In some aspects, the radiation detector may be configured to receive at least a portion of the radiation 642 in response to a portion of the finger assembly 620 being illuminated by the radiation 642. In some aspects, the portion of the finger assembly 620 may include a mechanical edge 624b of the fingertip 624 of the finger assembly 620 that is disposed separate from an optical edge 624a of the fingertip 624 of the finger assembly 620.

In some aspects, the example illumination uniformity correction system 600 may further include a processor (not shown) configured to determine a change in shape of one or more finger assemblies of the set of finger assemblies based on the received radiation 642. For example, the processor may be configured to determine a change in the position of the optical edge 624a of the fingertip 624 of the finger assembly 620 based on the growth of the fingertip 624 caused in response to the exposure of the fingertip 624 to radiation 680.

In some aspects, the processor may be further configured to measure a change in the position of a reference marker disposed on the finger assembly 620 based on the received radiation. In some aspects, the processor may be further configured to determine a change in shape of the finger assembly 620 based on the measured change in the position of the reference mark.

In some aspects, the processor may be further configured to generate a control signal configured to modify the position of one or more finger assemblies of the set of finger assemblies based on the determined change in shape of the one or more finger assemblies. For example, the processor may be configured to generate control signals configured to modify the position of the finger assembly 620 based on the determined change in shape of the finger assembly 620.

The processor may also be configured to transmit the control signals to a motion control system (e.g., including, but not limited to, one or more magnet assemblies) coupled to one or more finger assemblies of the set of finger assemblies. For example, the processor may be configured to transmit the control signals to a motion control system including, but not limited to, an actuator 626 coupled to the finger body 622.

Fig. 7 is a schematic illustration of an example illumination uniformity correction system 700 in accordance with some aspects of the present disclosure.

As shown in fig. 7, an example illumination uniformity correction system 700 can include a finger assembly having a fingertip 724, a radiation source 740, and a radiation detector 760 per finger assembly (e.g., 28 radiation detectors for 28 finger assemblies). In some aspects, the radiation source 740 may be configured to generate radiation and transmit the generated radiation toward a set of reference marks 722 (e.g., one or more reference marks) disposed on a surface 725 of the finger assembly (e.g., on an optical side of the finger assembly). In some aspects, the radiation source 740 may be configured to transmit the radiation during a wafer swap operation of the lithographic apparatus (e.g., after a wafer exposure operation). In some aspects, radiation detector 760 may be configured to receive at least a portion of the radiation reflected from surface 725.

In some aspects, the example illumination uniformity correction system 700 may further include a processor (not shown) configured to determine a change in shape of the finger assembly based on the received radiation. For example, the processor may be configured to determine a change in the position of the optical edge of the fingertip 724 of the finger assembly based on growth of the fingertip 724 caused in response to exposure of the fingertip 724 to EUV or DUV radiation.

In some aspects, the processor may be further configured to measure a change in the position of the set of reference markers 722 disposed on the surface 725 of the finger assembly based on the received radiation. In some aspects, the processor may be further configured to determine the change in the shape of the finger assembly based on the measured change in the position of the set of reference markers 722.

In some aspects, the processor may be further configured to generate a control signal configured to modify the position of the finger assembly based on the determined shape change of the finger assembly. In some aspects, the processor may be further configured to transmit the control signal to a motion control system (e.g., including, but not limited to, an actuator such as a magnet assembly) coupled to the finger assembly.

Fig. 8 is a schematic illustration of an example illumination uniformity correction system 800 in accordance with some aspects of the present disclosure.

As shown in fig. 8, an example illumination uniformity correction system 800 may include a finger assembly having a fingertip 824, a radiation source 840, and a radiation detector 860 per finger assembly (e.g., 28 radiation detectors for 28 finger assemblies). In some aspects, the radiation source 840 may be configured to generate radiation and transmit the generated radiation toward a set of reference marks 822 (e.g., one or more reference marks) disposed on a surface 823 of the finger assembly (e.g., on a mechanical (non-optical) side of the finger assembly). In some aspects, the radiation source 840 may be configured to transmit the radiation during a wafer swap operation of the lithographic apparatus (e.g., after a wafer exposure operation). In some aspects, radiation detector 860 may be configured to receive at least a portion of radiation reflected from surface 823.

In some aspects, the example illumination uniformity correction system 800 may further include a processor (not shown) configured to determine a change in shape of the finger assembly based on the received radiation. For example, the processor may be configured to determine a change in the position of the optical edge of the finger tip 824 of the finger assembly based on growth of the finger tip 824 in response to exposure of the finger tip 824 to EUV or DUV radiation.

In some aspects, the processor may be further configured to measure a change in the position of the set of reference marks 822 disposed on the surface 823 of the finger assembly based on the received radiation. In some aspects, the processor may be further configured to determine a change in shape of the finger assembly based on the measured change in the position of the set of reference markers 822.

In some aspects, the processor may be further configured to generate a control signal configured to modify the position of the finger assembly based on the determined change in shape of the finger assembly. In some aspects, the processor may be further configured to transmit the control signal to a motion control system (e.g., including but not limited to an actuator) coupled to the finger assembly.

Fig. 9 is a schematic illustration of an example set of reference marks 900 in accordance with some aspects of the present disclosure.

As shown in fig. 9, an example set of reference marks 900 may include reference marks 902 disposed on a surface of a finger assembly (e.g., at time t ₀ Referred to as 902a, and at time t ₁ Referred to as 902 b). In some aspects, the reference mark 902 may be referred to as a fingertip reference. The set of example reference marks 900 may also include index marks 904 disposed on a surface of a finger assembly, such as, but not limited to, a surface of a position sensor (e.g., encoder) disposed on or attached to the finger assembly. In one illustrative and non-limiting example, index marker 904 may be To be referred to as an "encoder index".

In some aspects, time t ₀ May correspond to a time associated with a calibration process performed during fabrication of the example illumination uniformity correction system, and reference mark 902a may correspond to time t ₀ A reference position on the measured fingertip, wherein the value D ₀ Corresponding to the distance from the reference mark 902a to the index mark 904.

In some aspects, time t ₁ May correspond to a time associated with measurements performed during an operation (e.g., wafer exchange operation, wafer exposure operation), and reference mark 902b may correspond to a time t ₁ The reference position on the fingertip measured, wherein a value D ₁ Corresponding to the distance from the reference mark 902b to the index mark 904. In some aspects, the value D is due to fingertip growth during operation of the lithographic apparatus ₁ Can be greater than the value D ₀ . In some aspects, the value D may be based on ₀ AND value D ₁ The difference between them to determine the slave time t of the reference mark 902 ₀ To time t ₁ Is a change in position of (c). For example, time t ₀ The position of reference mark 902a at time t ₁ The change in the position of the reference mark 902b at can be related to the value D ₀ AND value D ₁ The difference between them is proportional.

Fig. 10 is a schematic illustration of an example illumination uniformity correction system 1000 in accordance with some aspects of the present disclosure.

As shown in fig. 10, an example illumination uniformity correction system 1000 may include a finger assembly having a fingertip 1024. In some aspects, the fingertip 1024 may include an optical edge 1024a and a mechanical edge 1024b. In some aspects, an optical edge 1024a of a fingertip 1024 can be exposed to incident radiation 1080 (e.g., DUV or EUV radiation, such as actinic EUV light) during a wafer exposure operation of a lithographic apparatus, which can cause the fingertip 1024 to grow due to the exposure (or during a process of multiple exposures).

In some aspects, the fingertip 1024 may also include a multilayer mirror material disposed on a surface 1025 of the fingertip 1024. In some aspects, the multilayer mirror material may include alternating layers of molybdenum and silicon. In some aspects, the maximum steady state fingertip temperature can be reduced to allow the multilayer mirror material to remain substantially stable. In some aspects, the multilayer mirror material can reflect a majority of incident radiation to reduce thermal effects while improving drift compensation capabilities and reducing the risk of non-viable loss of fingertip attachment as radiation source power increases. In some aspects, the fingertip 1024 may be an angled fingertip, and the multilayer mirror material disposed on the surface 1025 may reflect greater than 60% of the incident radiation 1080 (e.g., as reflected radiation 1082) toward the radiation detector 1090. Accordingly, the thermal load on the fingertip 1024 may be reduced and the reliability, lifetime, and performance of the example illumination uniformity correction system 1000 may be increased.

In some aspects, the example illumination uniformity correction system 1000 may also include a radiation detector 1090 (e.g., a one-or two-dimensional sensor array, "beam+fingertip motion sensor"). In some aspects, the example illumination uniformity correction system 1000 may include one radiation detector per finger assembly. In some aspects, the multilayer mirror material may be configured to reflect incident radiation 1080 toward a radiation detector 1090 during an exposure operation of the lithographic apparatus. In some aspects, the radiation detector 1090 may be configured to sense a reflected portion of the incident radiation 1080 (e.g., reflected radiation 1082) used during wafer exposure operations of the lithographic apparatus.

In some aspects, a set of reference marks may be applied to the regions of the multilayer mirror material. In some aspects, the set of reference marks may include two or more reference marks. In some aspects, a marker (e.g., composed of thin lines, and the thin lines have a particular shape (e.g., a series of lines) formed of absorber material, as implemented for EUV reticles), or a set of markers may be applied to multiple particular regions of the multilayer mirror material to enhance the detectability, accuracy, or both the detectability and accuracy of the location of the fingertip 1024. In some aspects, data from other radiation detectors described herein may be combined with data from radiation detector 1090 to remove individual effects of radiation beam motion.

In some aspects, the example illumination uniformity correction system 1000 may further include a processor (not shown) configured to determine a change in shape of the fingertip 1024 based on the received radiation. For example, the processor may be configured to determine a change in the position of the optical edge 1024a of the fingertip 1024 based on a growth of the fingertip 1024 caused in response to an exposure of the fingertip 1024 to the radiation 1080. In some aspects, the processor may be further configured to measure a change in the location of the reference mark disposed on the surface 1025 of the fingertip 1024 based on the received radiation. In some aspects, the processor may be further configured to determine a change in shape of the fingertip 1024 based on the measured change in position of the reference mark. In some aspects, the processor may be further configured to generate a control signal configured to modify the position of the fingertip 1024 based on the determined change in shape of the fingertip 1024. In some aspects, the processor may be further configured to transmit the control signal to a motion control system (e.g., including but not limited to an actuator) coupled to the finger assembly. In some aspects, the processor may be configured to compare the reflected radiation 1082 with a previously obtained and saved dataset to determine finger position and thereby reduce dose and uniformity errors. Thus, the performance of the example illumination uniformity correction system 1000 may be increased based on the increased accuracy and availability of such beam movement data.

Example procedure for adjusting illumination slit uniformity

FIG. 11 is an example method 1100 for adjusting illumination slit uniformity of a lithographic apparatus, in accordance with aspects of the present disclosure or portions thereof. The operations described with reference to the example method 1100 may be performed by, or in accordance with, any of the systems, devices, components, techniques, or combinations thereof described herein (such as those described with reference to fig. 1-10 above and fig. 12 below).

At operation 1102, the method may include moving one or more finger assemblies to correct slit uniformity. In some aspects, movement of one or more finger assemblies may be accomplished using suitable mechanical or other methods, and include moving one or more finger assemblies according to any aspect or combination of aspects described with reference to fig. 1-10 above and fig. 12 below.

At operation 1104, the method may include steps performed in parallel with a wafer exchange operation (or in some aspects, a wafer exposure operation), including, but not limited to, measuring and estimating fingertip growth at operation 1106 and correcting finger assembly position if needed at operation 1108.

At operation 1106, the method may include measuring and estimating fingertip growth. For example, at operation 1106, the method may include illuminating, by a radiation source, a portion of the finger assembly with radiation. In some aspects, the radiation may comprise a laser curtain, and receiving at least the portion of the radiation may comprise: at least the portion of the transmitted radiation is received by the radiation detector in response to illuminating the portion of the finger assembly with the laser curtain. In some aspects, the portion of the finger assembly may include a mechanical edge of a fingertip of the finger assembly, the mechanical edge being disposed separate from an optical edge of the fingertip of the finger assembly. In some aspects, the irradiating of the portion of the finger assembly may be accomplished using suitable mechanical methods or other methods, and includes irradiating the portion of the finger assembly according to any aspect or combination of aspects described with reference to fig. 1-10 above and fig. 12 below.

Additionally, at operation 1106, the method may include: at least a portion of the radiation is received by a radiation detector in response to the illumination of the portion of the finger assembly. In some aspects, the irradiating the portion of the finger assembly may include irradiating the portion of the finger assembly with the radiation by the radiation source during a wafer exchange operation of the lithographic apparatus. In other aspects, the irradiating the portion of the finger assembly may include irradiating the portion of the finger assembly with the radiation by the radiation source during a wafer exposure operation of the lithographic apparatus. In some aspects, the receiving at least the portion of the radiation may include: radiation reflected from a surface of a fingertip of the finger assembly in response to illuminating the surface of the fingertip with radiation is received by the radiation detector. In some aspects, the receiving the radiation may be accomplished using suitable mechanical methods or other methods, and includes receiving the radiation according to any aspect or combination of aspects described with reference to fig. 1-10 above and fig. 12 below.

Additionally, at operation 1106, the method may include determining, by a processor, a change in shape of the finger assembly based on the received radiation. In some aspects, the determining a change in shape of the finger assembly may include determining, by the processor, a change in a position of an optical edge of a fingertip of the finger assembly, the change based on a growth of the fingertip in response to exposure of the fingertip to DUV radiation or EUV radiation. In some aspects, the determining a change in the shape of the finger assembly may include measuring, by the processor, a change in the position of a reference marker disposed on the finger assembly based on the received radiation. In some aspects, the determining the change in the shape of the finger assembly may further comprise: the change in the shape of the finger assembly is determined by the processor based on the measured change in the position of the reference mark. In some aspects, the reference mark is applied to a region of multilayer mirror material disposed on a fingertip of the finger assembly. For example, in these aspects, the method may include sensing, by the radiation detector, a reflected portion of actinic (actinic) EUV light used during a wafer exposure operation of a lithographic apparatus. In some aspects, the determining the change may be accomplished using suitable mechanical methods or other methods, and includes determining the change according to any aspect or combination of aspects described with reference to fig. 1-10 above and fig. 12 below.

At operation 1108, the method may include correcting the finger assembly position if desired. For example, at operation 1106, the method may include generating, by the processor, a control signal configured to modify a position of the finger assembly based on the determined change in shape of the finger assembly. Additionally, at operation 1106, the method may include transmitting, by the processor, the control signal to a motion control system coupled to the finger assembly. In some aspects, correction of the finger assembly positions described above may be accomplished using suitable mechanical or other methods, and include correcting the finger assembly positions according to any of the aspects or combinations of aspects described above with reference to fig. 1-10 and below with reference to fig. 12.

At operation 1110, the method may include determining whether a wafer lot is complete. If not, the method may proceed to operation 1102. If so, the method may continue to operation 1112. At operation 1112, the method may include determining whether to perform a Uniformity Refresh (UR). If not, the method may proceed to operation 1102. If so, the method may proceed to operation 1114. At operation 1114, the method may include performing UR correction.

Example computing System

Aspects of the present disclosure may be implemented in hardware, firmware, software, or any combination thereof. Aspects of the disclosure may also be implemented as instructions stored on a machine-readable medium, which may 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 readable by a machine (e.g., a computing device). For example, a machine-readable medium may include: read Only Memory (ROM); random Access Memory (RAM); a disk storage medium; an optical storage medium; a flash memory device; electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.); etc. Additionally, firmware, software, routines, instructions, and combinations thereof may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing firmware, software, routines, instructions, or a combination thereof, and thereby cause actuators or other devices (e.g., server motors, robotic devices) to interact with the physical world.

The various aspects may be implemented, for example, using one or more computing systems, such as the example computing system 1200 shown in fig. 12. The example computing system 1200 may be a special purpose computer capable of performing the functions described herein, such as: the example illumination uniformity correction system 500 shown in fig. 5A and 5B; the example illumination uniformity correction system 600 shown in fig. 6; the example illumination uniformity correction system 700 shown in fig. 7; an example illumination uniformity correction system 800 shown in fig. 8; the example illumination uniformity correction system 1000 shown in fig. 10; any of the systems, subsystems, or components described with reference to fig. 11; any other suitable system, subsystem, or component; or any combination thereof. The example computing system 1200 may include one or more processors (also referred to as central processing units or CPUs), such as the processor 1204. The processor 1204 is connected to a communication infrastructure 1206 (e.g., a bus). The example computing system 1200 may also include a user input/output device 1203, such as a monitor, keyboard, pointing device, etc., that communicates with the communication infrastructure 1206 via the user input/output interface 1202. The example computing system 1200 may also include a main memory 1208 (e.g., one or more main storage devices), such as Random Access Memory (RAM). Main memory 1208 may include one or more levels of cache. Main memory 1208 has control logic (e.g., computer software) and/or data stored therein.

The example computing system 1200 may also include a secondary memory 1210 (e.g., one or more secondary storage devices). For example, secondary memory 1210 may include a hard disk drive 1212 and/or a removable memory 1214. Removable storage 1214 may be a floppy disk drive, magnetic tape drive, compact optical drive, optical storage, tape backup, and/or any other storage/disk drive.

The removable memory drive 1214 may interact with a removable storage unit 1218. Removable storage unit 1218 includes a computer usable or readable storage device having stored therein computer software (control logic) and/or data. Removable storage unit 1218 may be a floppy disk, magnetic tape, optical disk, DVD, optical storage disk, and/or any other computer data storage device. The removable memory drive 1214 reads from and/or writes to a removable storage unit 1218.

According to some aspects, secondary memory 1210 may include other means, tools, or other methods for allowing computer programs and/or other instructions and/or data to be accessed by the example computing system 1200. For example, such devices, tools, or other methods may include a removable storage unit 1222 and an interface 1220. Examples of removable storage units 1222 and interfaces 1220 can include process cartridges and cartridge interfaces (such as those found in video game devices), removable memory chips (such as EPROM or PROM) and associated sockets, memory sticks and USB ports, memory cards and associated memory card slots, and/or any other removable storage units and associated interfaces.

The example computing system 1200 may also include a communication interface 1224 (e.g., one or more network interfaces). Communication interface 1224 enables the example computing system 1200 to communicate and interact with any combination of remote devices, remote networks, remote entities, etc. (individually and collectively referred to as remote devices 1228). For example, the communication interface 1224 may communicate with a remote device 1228 using the example computing system 1200 via a communication path 1226, which may be wired and/or wireless and may include any combination of LANs, WANs, the internet, and the like. Control logic, data, or both may be transmitted to and from the example computing system 1200 by the communication path 1226.

The operations in the foregoing aspects of the present disclosure may be implemented in a wide variety of configurations and architectures. Thus, some or all of the operations in the foregoing aspects may be performed in hardware, in software, or both. In some aspects, a tangible, non-transitory apparatus or article of manufacture comprises a tangible, non-transitory computer usable or readable medium having control logic (software) stored thereon, also referred to herein as a computer program product or process storage device. Such tangible devices or articles include, but are not limited to: example computing system 1200, main memory 1208, secondary memory 1210, and removable storage units 1218 and 1222, as well as tangible articles of manufacture embodying any combination of the preceding. Such control logic, when executed by one or more data processing devices (such as the example computing system 1200), causes the data processing devices to operate as described herein.

Based on the teachings included herein, those of ordinary skill in the relevant art will appreciate how to make and use aspects of the disclosure using data processing apparatus, computer systems, and/or computer architectures other than those illustrated in FIG. 12. In particular, aspects of the present disclosure may operate with software, hardware, and/or operating system implementations other than those described herein.

Embodiments of the present disclosure may be further described by the following aspects.

1. A system, comprising:

a radiation source configured to:

generating radiation; and

transmitting the generated radiation toward the finger assembly;

a radiation detector configured to:

receiving at least a portion of the transmitted radiation; and

a processor configured to:

determining a change in shape of the finger assembly based on the received radiation;

generating a control signal configured to modify a position of the finger assembly based on the determined change in the shape of the finger assembly; and

the control signal is transmitted to a motion control system coupled to the finger assembly.

2. The system of aspect 1, wherein the determined change in the shape of the finger assembly comprises: based on growth of the finger tip in response to exposure of the finger tip of the finger assembly to Deep Ultraviolet (DUV) radiation or Extreme Ultraviolet (EUV) radiation, a position of an optical edge of the finger tip changes.

3. The system of claim 1, wherein the radiation source is configured to transmit the radiation during a wafer swap operation of a lithographic apparatus.

4. The system of aspect 1, wherein:

the generated radiation includes a laser curtain; and

the radiation detector is configured to receive at least a portion of the transmitted radiation in response to illumination of the portion of the finger assembly by the laser curtain.

5. The system of aspect 4, wherein the portion of the finger assembly includes a mechanical edge of a fingertip of the finger assembly, the mechanical edge being disposed separate from an optical edge of the fingertip of the finger assembly.

6. The system of aspect 1, wherein the received radiation comprises radiation reflected from a surface of a fingertip of the finger assembly in response to the surface of the fingertip being illuminated by the transmitted radiation.

7. The system of aspect 1, wherein the processor is configured to:

measuring a change in the position of a reference mark disposed on the finger assembly based on the received radiation; and

the change in the shape of the finger assembly is determined based on the measured change in the position of the reference mark.

8. The system of aspect 7, wherein the reference mark is applied to a region of multilayer mirror material disposed on a fingertip of the finger assembly.

9. A method for adjusting illumination slit uniformity in a lithographic apparatus, the method comprising:

illuminating a portion of the finger assembly with radiation by a radiation source;

receiving, by a radiation detector, at least a portion of the radiation in response to the illumination of the portion of the finger assembly;

determining, by a processor, a change in shape of the finger assembly based on the received radiation;

generating, by the processor, a control signal configured to modify a position of the finger assembly based on the determined change in the shape of the finger assembly; and

the control signal is transmitted by the processor to a motion control system coupled to the finger assembly.

10. The method of aspect 9, wherein the determining the change in the shape of the finger assembly comprises: a change in the position of an optical edge of the fingertip of the finger assembly is determined by the processor, the change based on a growth of the fingertip in response to exposure of the fingertip to Deep Ultraviolet (DUV) radiation or Extreme Ultraviolet (EUV) radiation.

11. The method of claim 9, wherein the irradiating the portion of the finger assembly comprises irradiating the portion of the finger assembly with the radiation by the radiation source during a wafer exchange operation of the lithographic apparatus.

12. The method according to aspect 9, wherein:

the radiation includes a laser curtain; and

the receiving at least the portion of the radiation includes receiving, by the radiation detector, at least the portion of the transmitted radiation in response to illuminating the portion of the finger assembly with the laser curtain.

13. The method of aspect 12, wherein the portion of the finger assembly includes a mechanical edge of a fingertip of the finger assembly, the mechanical edge being disposed separate from an optical edge of the fingertip of the finger assembly.

14. The method of aspect 9, wherein said receiving at least said portion of said radiation comprises: radiation reflected from a surface of a fingertip of the finger assembly is received by the radiation detector in response to illuminating the surface of the fingertip with the radiation.

15. The method of aspect 9, wherein the determining the change in the shape of the finger assembly comprises:

measuring, by the processor, a change in a position of a reference mark disposed on the finger assembly based on the received radiation; and

the change in the shape of the finger assembly is determined by the processor based on the measured change in the position of the reference mark.

16. The method of aspect 15, wherein the reference mark is applied to a region of multilayer mirror material disposed on a fingertip of the finger assembly.

17. An apparatus, comprising:

a finger assembly, the finger assembly comprising:

a finger body;

a fingertip;

a multilayer mirror material disposed on a surface of the fingertip; and

a set of reference marks applied to regions of the multilayer mirror material.

18. The apparatus of aspect 17, wherein the set of reference marks comprises two or more reference marks.

19. The apparatus of claim 17, wherein the multilayer mirror material is configured to reflect Deep Ultraviolet (DUV) radiation or Extreme Ultraviolet (EUV) radiation toward a radiation detector during an exposure operation of the lithographic apparatus.

20. The apparatus of aspect 17, wherein the multilayer mirror material comprises molybdenum.

Although specific reference may be made in this text to the use of a lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, LCDs, thin-film magnetic heads, etc. 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 synonymous with the more general terms "substrate" or "target portion", respectively. The substrates referred to herein may be processed, before or after exposure, in for example a track unit (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology unit and/or an inspection unit. Where applicable, the disclosure herein may be applied to these and other substrate processing tools. In addition, the substrate may be processed more than once, for example, in order to produce a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already includes multiple processed layers.

It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings herein.

The term "substrate" as used herein describes a material to which a layer of material is added. In some aspects, the substrate itself may be patterned, and material added on top of the substrate may also be patterned, or material added on top of the substrate may remain unpatterned.

Examples disclosed herein illustrate, but are not limiting of, embodiments of the present disclosure. Other suitable modifications and adaptations of the various conditions and parameters normally encountered in the field and which will be apparent to those skilled in the relevant art are within the spirit and scope of the disclosure.

While specific aspects of the disclosure have been described above, it should be appreciated that the aspects may be practiced otherwise than as described. The description is not intended to limit embodiments of the present disclosure.

It should be appreciated that the detailed description section, rather than the prior art, summary and abstract sections, is intended to be used to interpret the claims. The summary and abstract sections may set forth one or more, but not all exemplary embodiments as contemplated by the disclosure, and thus are not intended to limit the present embodiments and the appended claims in any way.

Some aspects of the disclosure have been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. For ease of description, the present disclosure has arbitrarily defined the boundaries of these functional building blocks. As long as the specified functions and relationships thereof are appropriately performed

To define alternate boundaries.

The foregoing description of the specific aspects of the present disclosure will so fully reveal the general nature of the aspects that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific aspects without undue experimentation, without departing from the general concept of the present disclosure. Accordingly, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed aspects, based on the teaching and guidance presented herein.

The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary aspects or embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. A system, comprising:

a radiation source configured to:

generating radiation; and

transmitting the generated radiation toward the finger assembly;

A radiation detector configured to:

receiving at least a portion of the transmitted radiation; and

a processor configured to:

2. The system of claim 1, wherein the determined change in the shape of the finger assembly comprises: based on growth of the finger tip in response to exposure of the finger tip of the finger assembly to Deep Ultraviolet (DUV) radiation or Extreme Ultraviolet (EUV) radiation, a position of an optical edge of the finger tip changes.

4. The system of claim 1, wherein:

the generated radiation includes a laser curtain; and

5. The system of claim 4, wherein the portion of the finger assembly includes a mechanical edge of a fingertip of the finger assembly, the mechanical edge being disposed separate from an optical edge of the fingertip of the finger assembly.

6. The system of claim 1, wherein the received radiation comprises radiation reflected from a surface of a fingertip of the finger assembly in response to the surface being irradiated by the transmitted radiation.

7. The system of claim 1, wherein the processor is configured to:

8. The system of claim 7, wherein the reference mark is applied to a region of multilayer mirror material disposed on a fingertip of the finger assembly.

10. The method of claim 9, wherein the determining the change in the shape of the finger assembly comprises: a change in the position of an optical edge of the fingertip of the finger assembly is determined by the processor, the change based on a growth of the fingertip in response to exposure of the fingertip to Deep Ultraviolet (DUV) radiation or Extreme Ultraviolet (EUV) radiation.

12. The method according to claim 9, wherein:

the radiation includes a laser curtain; and

13. The method of claim 12, wherein the portion of the finger assembly includes a mechanical edge of a fingertip of the finger assembly, the mechanical edge being disposed separate from an optical edge of the fingertip of the finger assembly.

14. The method of claim 9, wherein the receiving at least the portion of the radiation comprises: radiation reflected from a surface of a fingertip of the finger assembly is received by the radiation detector in response to illuminating the surface of the fingertip with the radiation.

15. The method of claim 9, wherein the determining the change in the shape of the finger assembly comprises:

16. The method of claim 15, wherein the reference mark is applied to a region of multilayer mirror material disposed on a fingertip of the finger assembly.