Apparatus and method for measuring deformation of a patterning device in a lithographic apparatus

Abstract

A system and method for measuring reticle deformation using a pneumatic sensor, wherein a nozzle is placed along a side of the reticle and the pneumatic sensor generates an output signal indicating the distance between the sensor and a portion of the side of the reticle. The reticle deformation measurement from the sensor can be used as an input for reticle heating control.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Application No. 62 / 755,590, filed on November 5, 2018, and the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to an apparatus and method for measuring deformation of an object, for example a patterning device such as a reticle in a lithographic apparatus. Background Art

[0004] A lithographic apparatus is a machine that applies a desired pattern to a substrate, usually to a target portion of the substrate. For example, a lithographic apparatus may be used in the manufacture of integrated circuits (ICs). In this case, a pattern forming device, optionally referred to as a mask or reticle, may be used to generate a circuit pattern to be formed on a single layer of the IC. The pattern may be transferred to a target portion (e.g., including a portion, one or more dies) on a substrate (e.g., a silicon wafer). Typically, the pattern is transferred to a layer of radiation-sensitive material (resist) disposed on the substrate via imaging. Typically, a single substrate will contain a network of adjacent target portions that are patterned in succession. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing the entire pattern to the target portion at once; and so-called scanners, in which each target portion is irradiated by scanning the pattern along a given direction (the "scanning" direction) with a radiation beam, while simultaneously scanning the substrate in a direction parallel or antiparallel to that direction. The pattern may also be transferred from the pattern forming device to the substrate by imprinting the pattern onto the substrate.

[0005] In a lithographic apparatus, a radiation beam may induce thermal effects (e.g., thermal expansion) in a reticle. These thermal effects may be due to absorption of the radiation beam by non-transmissive portions of the reticle and may result in, for example, alignment errors and / or overlay errors in a pattern formed on a substrate. To correct for these errors due to thermal expansion of the reticle, current lithographic apparatus may rely on correction systems, such as reticle or wafer alignment systems, magnification correction systems, feed-forward systems for expansion prediction, lens correction systems, or combinations thereof. However, with the continued trend toward shrinking device sizes, these correction systems may not provide the desired levels of alignment and / or overlay accuracy required to develop these shrinking devices.

[0006] In terms of feed-forward systems for expansion prediction, current lithography equipment can incorporate the use of a reticle temperature control system (heating and / or cooling system) to achieve higher levels of alignment and / or overlay accuracy. Deformations are estimated using a thermal prediction model (TPM) and a mechanical prediction model (MPM), which are input into the reticle heating control (RHC). However, there are limitations to this approach. For example, the input to the TPM may be a disposable reticle temperature sensor (RTS) measurement of the reticle in its "cold" state (i.e., the thermal state before any radiation-induced heating) and does not represent the reticle temperature state during exposure. Similarly, reticles may have different properties from each other, for example, positivity as opposed to negativity, and the prediction model may not be accurate for all types of reticles. In addition, variations in stiffness between fixture components can reduce the prediction accuracy of the MPM. Addressing these limitations gives rise to the subject matter disclosed herein. Summary of the invention

[0007] A simplified overview of one or more embodiments is given below to provide a basic understanding of the embodiments. This overview is not an exhaustive overview of all contemplated embodiments and is not intended to identify key or important elements of all embodiments, nor is it intended to delineate the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to a more detailed description that will be presented later.

[0008] According to one aspect of the embodiments, a pneumatic sensor is used to measure the deformation of a mask. The pneumatic sensor can be of the "air meter" type, where nozzles are placed near the edges of the mask along both sides (Y axis) of the mask. The mask deformation measurements from the sensor can be used as input for mask heating control.

[0009] Other features and advantages of the present invention and the structure and operation of various embodiments of the present invention are described in detail below with reference to the accompanying drawings. Note that the present invention is not limited to the specific embodiments described herein. Such embodiments are proposed here only for illustrative purposes. Based on the teachings contained herein, other embodiments will be apparent to those skilled in the relevant art. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and enable those skilled in the relevant art to make and use the invention.

[0011] Figure 1 A lithographic apparatus according to an aspect of an embodiment of the invention is depicted.

[0012] Figure 2Ais a schematic side view of an example system including a reticle sensing system according to an aspect of an embodiment.

[0013] Figure 2B is a schematic plan view of an example system including a reticle sensing system according to an aspect of the embodiments.

[0014] Figure 3 is a functional block diagram of a system for compensating for reticle deformation according to an aspect of an embodiment.

[0015] The features and advantages of the present invention will become more apparent from the detailed description set forth below in conjunction with the accompanying drawings, in which like reference numerals identify corresponding elements throughout. In the accompanying drawings, like reference numerals generally indicate identical, functionally similar, and / or structurally similar elements. DETAILED DESCRIPTION

[0016] This specification discloses one or more embodiments that incorporate features of the present invention. The disclosed embodiments merely illustrate the present invention. The scope of the present invention is not limited to the disclosed embodiments. The present invention is defined by the appended claims.

[0017] The described embodiments and references in the specification to "one embodiment," "an embodiment," "an example embodiment," etc. indicate that the described embodiments may include specific features, structures, or characteristics, but each embodiment may not necessarily include the specific features, structures, or characteristics. Moreover, such phrases do not necessarily refer to the same embodiment. In addition, when a specific feature, structure, or characteristic is described in conjunction with an embodiment, it should be understood that such feature, structure, or characteristic may be implemented in conjunction with other embodiments within the knowledge of those skilled in the art, whether or not explicitly described.

[0018] In the following description and in the claims, the terms "upper", "lower", "top", "bottom", "vertical", "horizontal" and similar terms may be used. These terms are intended to show relative orientations only, not any orientation with respect to gravity. Similarly, terms such as left, right, front, rear, etc. are intended to give relative directions only.

[0019] Before describing the embodiments in further detail, it is helpful to provide an example environment in which embodiments of the invention may be implemented. Figure 1A lithographic apparatus is schematically depicted, comprising: an illumination system (illuminator) IL configured to condition a radiation beam; a support structure (e.g., a mask table) MT configured to support a pattern forming device (e.g., a mask) MA and connected to a first positioning device PM configured to precisely position the pattern forming device MA according to determined parameters; a substrate table (e.g., a wafer table) WT configured to hold a substrate (e.g., a wafer coated with a resist) W and connected to a second positioning device PW configured to precisely position the substrate W according to determined parameters; and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by the pattern forming device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W.

[0020] The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof, to direct, shape, or control the radiation.

[0021] The support structure bears the weight of the pattern forming device. The support structure holds the pattern forming device in a manner that depends on the orientation of the pattern forming device, the design of the lithographic equipment, and other conditions such as whether the pattern forming device is maintained in a vacuum environment. The support structure can use mechanical, vacuum, electrostatic or other clamping techniques to hold the pattern forming device. The support structure can be a frame or a table, for example, which can be fixed or movable as required. The support structure can ensure that the pattern forming device is in a desired position (for example relative to the projection system). Any use of the term "reticle" or "mask" herein can be considered synonymous with the more general term "pattern forming device".

[0022] The term "patterning device" as used herein should be broadly interpreted as referring to any device that can be used to impart a radiation beam with a pattern in its cross-section so as to form a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate (for example if the pattern includes phase-shifting features or so called assist features). Typically, the pattern imparted to the radiation beam will correspond to a specific functional layer in a device being formed in the target portion, such as an integrated circuit.

[0023] The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in photolithography and include mask types such as binary mask types, alternating phase-shift mask types, attenuated phase-shift mask types, and various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be independently tilted to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern to the radiation beam reflected by the mirror matrix.

[0024] The term "projection system" as used herein should be broadly interpreted as covering any type of projection system, including refractive, reflective, catadioptric, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate to the exposure radiation used, or to other factors such as the use of immersion liquid or the use of a vacuum. Any use of the term "projection lens" herein may be considered synonymous with the more general term "projection system".

[0025] As depicted here, the device is of the transmissive type (eg, employing a transmissive mask). Alternatively, the device may be of the reflective type (eg, employing a programmable mirror array of the type described above, or employing a reflective mask).

[0026] The lithographic apparatus may be of a type having two (dual stage) or more substrate tables (and / or two or more mask tables). In such a "multi-stage" machine, the additional tables may be used in parallel, or preparatory steps may be carried out on one or more tables while one or more other tables are being used for exposure.

[0027] The lithographic apparatus may also be of a type in which at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, such as water, to fill the space between the projection system and the substrate. Immersion liquid may also be applied to other spaces in the lithographic apparatus, such as between the mask and the projection system. It is well known in the art that immersion techniques can be used to increase the numerical aperture of the projection system. The term "immersion" as used herein does not mean that structures such as the substrate must be submerged in the liquid, but only means that the liquid is between, for example, the projection system and the substrate during exposure.

[0028] Refer again Figure 1, the illuminator IL receives a radiation beam emitted by a radiation source SO. The source and the lithographic apparatus may be separate entities (for example when the source is an excimer laser). In this case, the source is not considered to form part of the lithographic apparatus, and the radiation is transferred from the source SO to the illuminator IL with the help of a beam delivery system comprising, for example, suitable directional mirrors and / or a beam expander. In other cases, the source may be an integral part of the lithographic apparatus (for example when the source is a mercury lamp). The source SO and the illuminator IL, and the beam delivery system BD provided if required, may be referred to together as a radiation system.

[0029] The illuminator IL may comprise an adjustment device AD ​​configured to adjust the angular intensity distribution of the radiation beam. Typically, at least the outer and / or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in a pupil plane of the illuminator may be adjusted. Furthermore, the illuminator IL may comprise various other components, such as an integrator IN and a condenser CO. The illuminator may be used to condition the radiation beam to have a desired uniformity and intensity distribution in its cross-section.

[0030] The radiation beam B is incident on the patterning device (e.g. mask MA) held on a support structure (e.g. mask table MT) and is patterned by the patterning device. After having passed through the mask MA, the radiation beam B passes through a projection system PS which focuses the beam onto a target portion C of the substrate W. With the help of a second positioning device PW and a position sensor IF (e.g. interferometer device, linear encoder or capacitive sensor), the substrate table WT can be precisely moved, for example in order to position different target portions C in the path of the radiation beam B. Similarly, the first positioning device PM and a further position sensor (in the example of FIG. 1 ) may be used, for example, after mechanical retrieval from a mask library or during scanning. Figure 1The first positioning device PM (not explicitly shown) can be used to accurately position the mask MA relative to the path of the radiation beam B. In general, movement of the mask table MT can be achieved with the help of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) which form part of the first positioning device PM. Similarly, movement of the substrate table WT can be achieved using a long-stroke module and a short-stroke module which form part of the second positioning device PW. In the case of a stepper (as opposed to a scanner), the mask table MT may be connected to a short-stroke actuator only, or may be fixed. Mask MA and substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks shown occupy dedicated target portions, they may be located in the spaces between target portions (these are known as scribe alignment marks). Similarly, where more than one die is provided on the mask MA, the mask alignment marks may be located between these dies.

[0031] The apparatus may be used in at least one step mode or a scan mode. In the step mode, an entire pattern imparted to the radiation beam is projected onto a target portion C at one time (i.e. a single static exposure) while the mask table MT and substrate table WT are held substantially stationary. The substrate table WT is then shifted in the X and / or Y direction so that a different target portion C can be exposed. In the step mode, the maximum size of the exposure field limits the size of the target portion C that is imaged in a single static exposure.

[0032] In scan mode, the mask table MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e. a single dynamic exposure). The speed and direction of the substrate table WT relative to the mask table MT may be determined by the (de-)magnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width of the target portion (in the non-scanning direction) in a single dynamic exposure, while the length of the scanning motion determines the height of the target portion (in the scanning direction).

[0033] In another mode, the mask table MT holding the programmable patterning device is held substantially stationary and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, a pulsed radiation source is typically employed and the programmable patterning device is updated as required after each movement of the substrate table WT or between successive radiation pulses during a scan. This mode of operation may be readily applicable to maskless lithography using a programmable patterning device, for example a programmable mirror array of the type described above.

[0034] Combinations and / or variations on the above described modes of use, or entirely different modes of use, may also be employed.

[0035] The lithography system also preferably includes a control system. Typically, the control system includes one or more of digital electronic circuits, computer hardware, firmware, and software. The control system also includes memory, which may be read-only memory and / or random access memory. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including, for example, semiconductor memory devices such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM disks.

[0036] When thermal energy is absorbed by the reticle, thermal stresses develop and thermal expansion occurs in the reticle. Due to the low thermal conductivity of the quartz material of a typical reticle, thermal gradients and stresses develop. Such stresses may cause localized reticle deformations. The fact that the reticle is typically clamped may cause additional higher order deformations. At least some of this deformation may be corrected by adjusting the scanning lens elements. Furthermore, heat may be added to portions of the reticle that do not experience exposure or portions that have a lower temperature than other portions of the reticle.

[0037] However, due to the fact that the reticle is usually clamped, thermal stresses may still develop. These stresses can be relieved periodically by loosening the reticle and allowing it to relax. After the stresses have been relieved in this way, the reticle can be re-clamped and realigned as needed. Alternatively, the selective heating device can be adjusted in space and time to minimize the uncorrectable portion of the deformation caused by heating. This may result in a non-uniform temperature distribution in the substrate, but with minimal uncorrected mask deformation.

[0038] Despite these measures, it is still necessary to be able to determine the deformations of the mask and control the system to compensate for these deformations so that they do not cause any production errors. As discussed, the deformation can be estimated using a thermal prediction model (TPM) and a mechanical prediction model (MPM) that feed into the mask heating control (RHC). A temperature sensor measures the temperature of the mask. The measured temperature is provided as an input to the TPM. The TPM uses a calculation matrix to predict the mask deformation caused by the thermal load of the mask, which is in turn fed into the MPM to obtain a feedforward control of the mask heating correction. The predicted thermal deformations are used to perform mask heating correction and / or control the compensating lens actuator. The MPM is an approximation of the mechanical properties of the mask and is used to predict the mechanical deformations of the mask caused by mechanical loads of the mask, such as clamps. Mask heating correction is performed by controlling the optical system to optically correct the calculated deformations in the mask. In this regard, see, for example, U.S. Patent No. 8,184,265, issued May 22, 2012, and entitled “Method for Correcting Non-Uniform Reticle Heating in a Lithographic Apparatus.”

[0039] According to one aspect of the embodiment, the sensor measures the position of the side of the mask. Typically, due to deformation, the side will not be straight, and the relative displacement of the sensor and the edge of the mask will change by tens of nanometers. The change in displacement between the sensor and the edge of the mask will result in a change in back pressure. Measuring this change in back pressure can be used to determine the change in edge displacement. Apparatus for determining position and measuring back pressure using a nozzle is disclosed, for example, in International Publication No. WO 2017 / 108336 A1 entitled “Height Meter” published on June 29, 2017, for example, in U.S. Patent No. 7,021,120 entitled “High Resolution Gas Pressure Gauge Proximity Sensor” issued on April 4, 2006, and in U.S. Patent No. 7,578,168 entitled “Using Surface Roughness Faced by Nozzle to Increase Gas Pressure Gauge Pressure Sensitivity” issued on August 25, 2009, all of which are hereby incorporated by reference in their entirety.

[0040] According to one aspect of an embodiment, as in Figure 2A As shown in FIG. 1 , a chuck 100 as a part of a mask table MT supports a patterning device 110. A film 120 may be inserted between the patterning device 110 and the chuck 100. Also shown are a sensor 130 located on one side of an edge of the patterning device 110, and a sensor 140 located near the opposite edge side of the patterning device 110. The sensors 130 and 140 are of an air meter type, in which an air flow indicated by an arrow “a” is used to detect a distance “d” between the patterning device 110 and the corresponding sensors 130 and 140.

[0041] Figure 2B yes Figure 2A 100a, 100b and 100c. Sensor 130 has a series of nozzles 132, 134, 136 and 138. Sensor 140 has a series of nozzles 142, 144, 146 and 148. Although Figure 2B Four nozzles are shown for each edge, but it will be apparent to one of ordinary skill in the art that more or fewer nozzles may be used. The nozzles blow a gas, such as air, onto the edge of the patterning device 110. The back pressure created by the flow there is measured by sensors 130 and 140 to determine the distance between the edge and the sensor.

[0042] In use, the sensors are moved out of the way during a reticle change. Then, after the reticle change is complete and the reticle is loaded onto the chuck 100, the sensors 130 and 140 are arranged to their operating positions laterally adjacent to either side of the patterning device 110. In the measuring position, the sensors 130 and 140 can continuously determine the edge profile, i.e., the deviation of the patterning device edge from a straight line in the Y direction, while the reticle is heated during exposure. The sensors can then be moved out of the way to avoid interfering with the change of the next reticle.

[0043] Figure 3 2 is a diagram illustrating a system for correcting lateral deformation in a patterning device using deformation measurement results produced by the arrangement just described. The system includes a deformation measurement system 200 as described above. A signal indicating the magnitude of the deviation of the reticle edge position obtained in the reticle deformation measurement performed by the deformation measurement system is provided to a reticle deformation compensation unit 210. The reticle deformation compensation unit 210 then uses the signal as at least part of the basis to control a lens actuator 220 in the optical system, thereby allowing optical compensation for reticle deformation.

[0044] The deformation measurement system 200 is able to provide sufficient information to the mask deformation compensation unit 210 to control the lens actuator 220. Therefore, components of conventional systems, such as mask temperature sensors, thermal prediction models and mechanical prediction models are not necessary. However, it may be advantageous for some applications to also make the predictions provided by these components available. Therefore, as also in Figure 3 As shown in FIG. 2 , the optional conventional reticle deformation prediction unit 230 includes a reticle sensor temperature sensor 240, whose output is input to a thermal prediction model 250. The output of the thermal prediction model 250 is fed as input to a mechanical prediction model 260. A software switch 270 selects which data is input to the reticle deformation compensation unit 210.

[0045] The embodiments may be further described using the following terms:

[0046] 1. A system for compensating for deformation in a patterning device in a lithographic apparatus, the system comprising:

[0047] a support for a patterning device;

[0048] at least one sensor positionable laterally adjacent an edge of the patterning device when the patterning device is mounted on the support, the sensor configured to generate an output signal indicative of a distance between the sensor and a portion of the edge; and

[0049] The reticle deformation compensation unit is arranged to receive the output signal and is configured to generate a compensation control signal based at least in part on the output signal.

[0050] 2. A system according to clause 1, wherein the sensor comprises: at least one nozzle for discharging an airflow at the portion of the edge and a measuring unit that measures the amount of back pressure exerted on the airflow by the portion of the edge.

[0051] 3. The system according to claim 1 further includes at least two sensors, a first sensor and a second sensor, wherein when the pattern forming device is mounted on the support, the first sensor can be positioned laterally adjacent to a first edge of the pattern forming device, and when the pattern forming device is mounted on the support, the second sensor can be positioned laterally adjacent to a second edge of the pattern forming device, the first sensor is configured to generate an output signal indicating the distance between the first sensor and a portion of the first edge, and the second sensor is configured to generate an output signal indicating the distance between the second sensor and a portion of the second edge.

[0052] 4. A system according to claim 1, wherein the first sensor comprises: at least one nozzle for discharging an airflow at the portion of the edge and a measuring unit that measures the amount of back pressure applied to the airflow by the portion of the first edge, and the second sensor comprises: at least one nozzle for discharging an airflow at the portion of the edge and a measuring unit that measures the amount of back pressure applied to the airflow by the portion of the second edge.

[0053] 5. The system of clause 1, 2, 3 or 4, further comprising an optical system comprising at least one optical element having an optical property that can be changed by an actuator based at least in part on the compensation control signal.

[0054] 6. The system of clause 1, wherein the at least one sensor comprises a linear array of sensor elements positioned adjacent to the edge and extending in a direction parallel to the edge.

[0055] 7. A system according to clause 5, wherein each of the sensor elements comprises: at least one nozzle for discharging an airflow at a corresponding portion of the edge; and a measuring unit that measures the amount of back pressure exerted on the airflow by the corresponding portion of the edge.

[0056] 8. The system of clause 6 or 7, further comprising an optical system comprising at least one optical element having an optical property that is changeable by an actuator based at least in part on the compensation control signal.

[0057] 9. A system for compensating for deformation in a patterning device in a lithographic apparatus, the system comprising:

[0058] a support for a patterning device;

[0059] a first sensor positionable laterally adjacent to a first edge of the patterning device when the patterning device is mounted on a support, the first sensor comprising a linear array of first sensor elements positioned adjacent to and extending in a direction parallel to the first edge of the patterning device, and the first sensor configured to generate a first output signal indicative of a deformation of a distance between the first sensor and a portion of the first edge;

[0060] a second sensor positionable laterally adjacent to a second edge of the patterning device when the patterning device is mounted on the support, the second sensor comprising a linear array of second sensor elements positioned adjacent to and extending in a direction parallel to the second edge of the patterning device, and the second sensor configured to generate a second output signal indicative of a deformation of a distance between the second sensor and a portion of the second edge; and

[0061] The reticle deformation compensation unit is arranged to receive the first output signal and the second output signal, and is configured to generate a compensation control signal based at least in part on the first output signal and the second output signal.

[0062] 10. A system according to claim 9, wherein each of the first sensor elements includes at least one nozzle for discharging a gas flow at a corresponding portion of the first edge and a first measuring unit, the first measuring unit measuring the amount of back pressure applied to the gas flow by the corresponding portion of the first edge, and each of the second sensor elements includes at least one nozzle for discharging a gas flow at a corresponding portion of the second edge and a second measuring unit, the second measuring unit measuring the amount of back pressure applied to the gas flow by the corresponding portion of the second edge.

[0063] 11. The system of clause 9 or 10, further comprising an optical system comprising at least one optical element having an optical property that is changeable by an actuator based at least in part on the compensation control signal.

[0064] 12. A method of compensating for deformation in a patterning device in a lithographic apparatus, the method comprising:

[0065] placing a patterning device in a support;

[0066] measuring a distance of a portion of the edge of the patterning device using at least one sensor positionable laterally adjacent to an edge of the patterning device to generate an output signal indicative of a distance between the sensor and the portion of the edge; and

[0067] A compensation control signal is generated based at least in part on the output signal.

[0068] 13. The method of clause 12, further comprising, after the generating step, a step of: changing an optical property of at least one optical element based at least in part on the compensation control signal.

[0069] 14. The method of clause 12, further comprising, after the generating step, the step of: using an actuator to change an optical property of the at least one optical element based at least in part on the compensation control signal.

[0070] 15. A method according to clause 12, 13 or 14, wherein the measuring step comprises: exhausting an airflow at the portion of the edge; and a measuring unit that measures the amount of back pressure exerted on the airflow by the portion of the edge.

[0071] Although specific reference may be made herein to the use of the lithographic apparatus for 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, liquid crystal displays (LCDs), thin film magnetic heads, etc. It should be understood by those skilled in the art that in the case of such alternative applications, any term "wafer" or "die" used herein may be considered synonymous with the more general term "substrate" or "target portion", respectively. The substrate referred to herein may be processed before or after exposure, such as in a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool, and / or an inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. In addition, the substrate may be processed more than once, such as to produce a multi-layer IC, so that the term "substrate" used herein may also refer to a substrate that already contains multiple processed layers.

[0072] Although specific embodiments of the present invention have been described above, it should be understood that the present invention may be practiced other than as described. The above description is intended to be illustrative rather than restrictive. Therefore, it will be apparent to those skilled in the art that modifications may be made to the described invention without departing from the scope of the appended claims.

[0073] It should be understood that the detailed description section is intended to be used to interpret the claims, rather than the summary and abstract sections. The summary and abstract sections may set forth one or more but not all exemplary embodiments of the invention contemplated by the inventor, and therefore, are not intended to limit the invention and the appended claims in any way.

[0074] The present invention has been described above by means of functional building blocks that illustrate the implementation of specific functions and their relationships. For ease of description, the boundaries of these functional building blocks have been arbitrarily defined here. Other boundaries may be defined as long as the specified functions and their relationships are properly performed.

[0075] The foregoing description of specific embodiments will fully reveal the general nature of the invention so that others can easily modify and / or adjust for various applications such as specific embodiments by applying knowledge within the art without departing from the general concept of the invention, without excessive experimentation. Therefore, based on the revelation and guidance set forth herein, such adjustments and modifications are intended to be within the meaning and scope of the equivalent forms of the disclosed embodiments. It should be understood that the wording or terminology herein is for the purpose of description rather than limitation, so that the terms or wording of this specification will be interpreted by the technician based on the revelation and guidance.

[0076] The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. A system for compensating for deformation in a patterning device in a lithographic apparatus, the system comprising: a support for a patterning device; at least one barometer-type sensor positionable laterally adjacent an edge of the patterning device when the patterning device is mounted on the support, the sensor being configured to generate an output signal indicative of a distance between the sensor and a portion of the edge; A mask deformation prediction unit, comprising a sensor for measuring the temperature of the mask and a prediction model for generating a predicted thermal deformation signal based on the temperature of the mask; as well as The reticle deformation compensation unit is arranged to selectively receive the output signal or the predicted thermal deformation signal, and is configured to generate a compensation control signal based at least in part on the output signal or the predicted thermal deformation signal.

2. The system of claim 1, wherein the sensor comprises: at least one nozzle for discharging a gas flow at the portion of the edge, and a measuring unit that measures the amount of back pressure exerted on the gas flow by the portion of the edge.

3. The system according to claim 1 further includes at least two sensors, a first sensor and a second sensor, wherein when the pattern forming device is mounted on the support, the first sensor can be positioned laterally adjacent to a first edge of the pattern forming device, and when the pattern forming device is mounted on the support, the second sensor can be positioned laterally adjacent to a second edge of the pattern forming device, the first sensor is configured to generate an output signal indicating the distance between the first sensor and a portion of the first edge, and the second sensor is configured to generate an output signal indicating the distance between the second sensor and a portion of the second edge.

4. The system of claim 3, wherein the first sensor comprises: at least one nozzle for discharging an airflow at said portion of said edge, and a measuring unit that measures the amount of back pressure exerted on said airflow by said portion of said first edge, and the second sensor comprises: at least one nozzle for discharging an airflow at said portion of said edge, and a measuring unit that measures the amount of back pressure exerted on said airflow by said portion of said second edge.

5. The system of any one of claims 1, 2, 3 or 4, further comprising an optical system comprising at least one optical element having an optical property that can be changed by an actuator based at least in part on the compensation control signal.

6. The system of claim 1, wherein the at least one sensor comprises a linear array of sensor elements positioned adjacent to the edge and extending in a direction parallel to the edge.

7. The system of claim 5, wherein each of the sensor elements comprises: at least one nozzle for discharging a gas flow at a respective portion of the edge, and a measuring unit that measures an amount of back pressure exerted on the gas flow by the respective portion of the edge.

8. The system of claim 6 or 7, further comprising an optical system comprising at least one optical element having an optical property that is changeable by an actuator based at least in part on the compensation control signal.

9. A system for compensating for deformation in a patterning device in a lithographic apparatus, the system comprising: a support for a patterning device; a first sensor of a barometer type, the first sensor being positionable laterally adjacent to a first edge of the patterning device when the patterning device is mounted on the support, and the first sensor comprising a linear array of first sensor elements, the linear array being positioned adjacent to the first edge of the patterning device and extending in a direction parallel to the first edge of the patterning device, and the first sensor being configured to generate a first output signal indicative of a deformation in a distance between the first sensor and a portion of the first edge; a second sensor of the barometer type, the second sensor being positionable laterally adjacent to a second edge of the patterning device when the patterning device is mounted on the support, and the second sensor comprising a linear array of second sensor elements, the linear array being positioned adjacent to the second edge of the patterning device and extending in a direction parallel to the second edge of the patterning device, and the second sensor being configured to generate a second output signal indicative of a deformation in a distance between the second sensor and a portion of the second edge; A mask deformation prediction unit, comprising a sensor for measuring the temperature of the mask and a prediction model for generating a predicted thermal deformation signal based on the above; as well as The mask deformation compensation unit is arranged to selectively receive the first output signal and the second output signal or receive the predicted thermal deformation signal, and is configured to generate a compensation control signal based at least in part on the first output signal and the second output signal or the predicted thermal deformation signal.

10. The system of claim 9, wherein each of the first sensor elements comprises at least one nozzle for discharging an airflow at a corresponding portion of the first edge, and a first measuring unit measuring the amount of back pressure applied by the corresponding portion of the first edge to the airflow, and each of the second sensor elements comprises at least one nozzle for discharging an airflow at a corresponding portion of the second edge, and a second measuring unit measuring the amount of back pressure applied by the corresponding portion of the second edge to the airflow.

11. The system of claim 9 or 10, further comprising an optical system comprising at least one optical element having an optical property that is changeable by an actuator based at least in part on the compensation control signal.

12. A method of compensating for deformation in a patterning device in a lithographic apparatus, the method comprising: placing a patterning device in a support; measuring a distance of a portion of an edge of the patterning device using at least one barometer-type sensor positionable laterally adjacent an edge of the patterning device to generate an output signal indicative of a distance between the sensor and the portion of the edge; Measuring the temperature of the mask, and generating a predicted thermal deformation signal through a prediction model based on the measured temperature of the mask; as well as A compensation control signal is selectively generated based at least in part on the output signal or the predicted thermal deformation signal.

13. The method of claim 12, further comprising, after the generating step, a step of changing an optical characteristic of at least one optical element based at least in part on the compensation control signal.

14. The method of claim 12, further comprising, after the generating step, a step of using an actuator to change an optical characteristic of at least one optical element based at least in part on the compensation control signal.

15. The method according to any one of claims 12, 13 or 14, wherein the measuring step comprises: exhausting airflow at said portion of said edge; and a measuring unit that measures an amount of back pressure exerted on the airflow by the portion of the edge.

Images