Matching pupil determination

Abstract

A method for reducing variations in device performance is described herein. The method comprises: (i) a reference performance (e.g., CD) of a reference device (e.g., a reference scanner); (ii) a set of initial leading degrees of freedom selected from a plurality of degrees of freedom of a plurality of pupil facet mirrors of a device selected to reproduce the reference performance (e.g., to match the scanner); and (iii) exposure data related to one or more parameters of a patterning process (e.g., CD, overlay, focus, etc.) representing the performance of the device based on the set of initial leading degrees of freedom; and determining a matching pupil of the device based on the set of initial leading degrees of freedom and the exposure data such that the matching pupil reduces the difference between the performance of the device and the reference performance.

Description

Technology Field

[0001] Cross-reference regarding related applications

[0002] This application claims priority to EP application 18190862.5 filed on August 24, 2018, the entire contents of which are referenced herein.

[0003] The present invention relates to a technology for improving the performance of a device manufacturing process. The present technology may be used in connection with a lithography device or a measuring device. Background Technology

[0004] A lithography device is a machine that applies a desired pattern onto a target portion of a substrate. A lithography device may be used, for example, in the manufacture of an integrated circuit (IC). In such cases, a patterning device, alternatively referred to as a mask or reticle, may be used to generate a pattern corresponding to an individual layer of the IC, and this pattern may be imaged onto a target portion (e.g., including part of one or several dies) on a substrate (e.g., a silicon wafer) having a layer of radiation-sensitive material (resist). Generally, a single substrate will comprise a network of multiple adjacent target portions that are transferred in succession. A known lithography device includes a so-called stepper, which irradiates each target portion by exposing the entire pattern onto the target portion at once, and a so-called scanner, which irradiates each target portion by scanning the pattern through a beam in a given direction ("scanning" direction) while simultaneously scanning the substrate parallel to or anti-parallel to this direction.

[0005] Before transferring the circuit pattern from the patterning device to the substrate, the substrate may undergo various procedures such as priming, resist coating, and soft baking. After exposure, the substrate may undergo other procedures such as post-exposure baking (PEB), development, hard baking, and measurement / inspection of the transferred pattern. These numerous procedures serve as the basis for creating individual layers of a device, for example, an IC. The substrate may then undergo various processes such as etching, ion implantation (doping), metallization, oxidation, and chemical-mechanical polishing, all of which are intended to finish the individual layers of the device. If multiple layers are required for the device, the entire procedure or a variation thereof is repeated for each layer. Eventually, the device will exist on each target portion of the substrate. These devices are then separated from each other by techniques such as dicing or sawing, where individual devices can be mounted on a carrier connected to pins, etc.

[0006] Accordingly, manufacturing devices, such as semiconductor devices, typically form various features and multiple layers of the device, including processing a substrate (e.g., a semiconductor wafer) using multiple manufacturing processes. These layers and features are typically manufactured and processed using, for example, deposition, lithography, etching, chemical-mechanical polishing, and ion implantation. Multiple devices may be manufactured on multiple dies on a substrate and subsequently separated into individual devices. This device manufacturing process may be considered a patterning process. The patterning process includes a patterning step, such as optical and / or nanoimprint lithography using a patterning device in a lithography device, to transfer a pattern on the patterning device to a substrate, and typically but optionally includes one or more associated pattern processing steps, such as resist development by a developing device, baking of the substrate using a baking tool, and etching of the pattern using an etching device.

[0007] According to an embodiment, a method for reducing changes in device performance is provided. The method comprises: (i) a reference performance of a reference device; (ii) a set of initial leading degrees of freedom selected from a plurality of degrees of freedom of a plurality of pupil facet mirrors of a device selected to reproduce the reference performance; and (iii) obtaining exposure data related to one or more parameters of a patterning process representing the performance of the device based on the set of initial leading degrees of freedom; and determining a matching pupil of the device by a computer system based on the set of initial leading degrees of freedom and the exposure data such that the matching pupil reduces the difference between the performance of the device and the reference performance.

[0008] In the embodiment, the matching pupil is a subset and / or whole set of multiple pupil facet mirrors corresponding to the initial leading degrees of freedom set.

[0009] In an embodiment, the determination of the matching pupil is an iterative process, and the iteration includes changing one or more degrees of freedom of a preceding set of degrees of freedom of a plurality of pupil facet mirrors based on the difference between the reference performance and the reference performance; obtaining the current performance from exposure data corresponding to the changed pupil facet mirror; and determining the current difference between the current performance and the reference performance.

[0010] In the embodiments, changing one or more degrees of freedom includes changing the orientation and / or intensity of one or more mirrors corresponding to a preceding set of degrees of freedom.

[0011] In the embodiment, the initial set of preceding degrees of freedom is selected based on the sensitivity of each degree of freedom of the degrees of freedom of the device's plurality of pupil facet mirrors to reproduce reference performance.

[0012] In the embodiment, the initial preceding set of degrees of freedom is a subset and / or whole set of degrees of freedom of multiple pupil facet mirrors of the device that match the reference performance.

[0013] In the example, exposure data is acquired for a linear combination of an initial preceding set of degrees of freedom.

[0014] In the example, the reference performance is the performance of the device and a different reference device.

[0015] In the example, the reference performance is the performance of the device determined at a specific time of the patterning process.

[0016] In the embodiments, the performance of the device and the reference performance of the reference device are related to parameters of the patterning process including critical dimensions and / or overlays.

[0017] In the embodiment, the matching pupil minimizes the difference between the device's performance and the reference performance.

[0018] In an embodiment, the present method further includes adjusting the performance of the device based on the matching pupil of the device in the patterning process.

[0019] In the example, the device for the patterning process is a lithography device.

[0020] Furthermore, according to an embodiment, a method for reducing a change in device performance is provided. The method comprises (i) obtaining a reference performance of a reference device and (ii) obtaining a pupil measurement of a mirror of a plurality of pupil facet mirrors of the device at the substrate level; determining imaging data based on the pupil measurement and performance based on the imaging data by a computer system; and determining a matching pupil of the device by a computer system such that the matching pupil reduces the difference between the performance of the device and the reference performance.

[0021] In an embodiment, the determination of the matching pupil is an iterative process, and the iteration includes changing one or more degrees of freedom of a plurality of pupil facet mirrors; calculating the current aerial image and current performance through modeling / simulation based on the changed pupil facet mirrors; and determining the current difference between the current performance and the reference performance.

[0022] In the embodiments, changing one or more degrees of freedom includes changing the orientation and / or intensity of one or more mirrors of a plurality of pupil facet mirrors.

[0023] In the examples, pupil measurement includes the intensity and / or orientation of one or more mirrors of a plurality of pupil facet mirrors.

[0024] In the example, the reference performance is measured from reference imaging data for the reference device, and the reference device is different from the device.

[0025] In the embodiment, the reference performance is measured from reference imaging data for the device, determined at a specific time of the patterning process.

[0026] In an embodiment, reference imaging data is generated by overlapping aerial images of each mirror of a plurality of pupil facet mirrors.

[0027] In the examples, the aerial image is generated by modeling and / or simulation of the raw field position at the substrate level.

[0028] In an embodiment, imaging data is generated by overlapping aerial images of each mirror of a plurality of pupil facet mirrors, and the aerial image is calculated based on intensity measurements of each mirror of the plurality of pupil facet mirrors.

[0029] In the embodiments, performance and reference performance are related to parameters of the patterning process including critical dimensions and / or overlays.

[0030] In the embodiment, the matching pupil minimizes the difference between the device's performance and the reference performance.

[0031] In an embodiment, the present method further includes adjusting the performance of the device based on the matching pupil of the device in the patterning process.

[0032] In the example, the device for the patterning process is a lithography device.

[0033] The present specification discloses a computer program product comprising a computer-readable medium having recorded instructions that implement the method within the present specification when executed by a computer.

[0034] The general description of exemplary implementations mentioned above and the following detailed description thereof are merely exemplary aspects of the teachings of the invention and are not limiting. Brief explanation of the drawing

[0035] FIG. 1 schematically illustrates a lithography apparatus according to an embodiment. FIG. 2 schematically illustrates an example of a lithography cell or cluster. Figure 3 schematically illustrates an exemplary inspection device and measurement technology. Figure 4 schematically illustrates an exemplary inspection device. Figure 5 illustrates the relationship between the light spot of the inspection device and the measurement target. Figure 6 schematically illustrates a process for deriving multiple variables of interest based on measurement data. Figure 7 shows exemplary categories of processing variables. Figure 8 schematically shows the flow of a method according to an embodiment. FIG. 9 schematically illustrates the flow of a method according to an embodiment. FIG. 10 is a flowchart for determining a matching pupil according to an embodiment. FIG. 11 is a flowchart of another method for determining a matching pupil according to an embodiment. FIG. 12a illustrates an exemplary reference pupil according to an embodiment. FIG. 12b illustrates an exemplary matching pupil according to an embodiment. Figure 13 is a block diagram of an exemplary computer system. Specific details for implementing the invention

[0036] Before describing the embodiments in detail, it is beneficial to present an exemplary environment in which the embodiments can be implemented.

[0037] FIG. 1 schematically illustrates an example of a lithography apparatus (LA). The apparatus comprises:

[0038] - A lighting system (illuminator) (IL) configured to control a radiation beam (B) (e.g., UV radiation, EUV or DUV radiation);

[0039] - A support structure (e.g., mask table) (MT) connected to a first positioner (PM) configured to support a patterning device (e.g., mask) (MA) and configured to accurately position the patterning device according to a predetermined parameter;

[0040] - A substrate table (e.g., wafer table) (WT) (e.g., WTa, WTb, or both) connected to a second positioner (PW) configured to hold a substrate (e.g., a resist-coated wafer) (W) and to accurately position the substrate according to a predetermined parameter; and

[0041] - It includes a projection system (e.g., a refractive projection lens system) (PS) that is configured to project a pattern applied to a radiation beam (B) by a patterning device (MA) onto a target portion (C) of a substrate (W) (e.g., including one or more dies, commonly referred to as a field) and is supported on a reference frame (RF).

[0042] As illustrated herein, the device is of the transmissive type (e.g., using a transmissive mask). Alternatively, the device may be of the reflective type (e.g., using a programmable mirror array of the type mentioned above or using a reflective mask).

[0043] The illuminator (IL) receives a radiation beam from a radiation source (SO). The source and the lithography device 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 lithography device, and the radiation beam travels from the radiation source (SO) to the illuminator (IL) with the help of a beam delivery system (BD), for example, which includes a suitable directional mirror and / or beam expander. In other cases, the source may be an integral part of the device, for example, when the source is a mercury lamp. The source (SO) and the illuminator (IL), together with the beam delivery system (BD), may be referred to as a radiation system if necessary.

[0044] The illuminator (IL) can change the intensity distribution of the beam. The illuminator may be positioned to limit the radial size of the radiation beam such that the intensity distribution is not zero within an annular region in the pupil plane of the illuminator (IL). Additionally or alternatively, the illuminator (IL) may be operable to limit the distribution of the beam in the pupil plane such that the intensity distribution is not zero in a plurality of evenly spaced sectors in the pupil plane. The intensity distribution of the radiation beam in the pupil plane of the illuminator (IL) may be referred to as an illumination mode.

[0045] Accordingly, the illuminator (IL) may include a regulator (AD) configured to adjust the (angle / spatial) intensity distribution of the beam. Generally, at least the outer and / or inner radial magnitudes (typically referred to as σ-outer and σ-inner, respectively) of the intensity distribution within the pupil plane of the illuminator may be adjusted. The illuminator (IL) may be operable to change the angular distribution of the beam. For example, the illuminator may be operable to change the number and angular range of sectors within the pupil plane where the intensity distribution is non-zero. By adjusting the intensity distribution of the beam in the pupil plane of the illuminator, different lighting modes may be achieved. For example, by limiting the radial and angular magnitudes of the intensity distribution within the pupil plane of the illuminator (IL), the intensity distribution may have a multi-pole distribution, such as a dipole, quadrupole, or hexapole distribution. For example, a desired illumination mode may be obtained by inserting an optical system that provides an illumination mode into the illuminator (IL) or by using a spatial light modulator.

[0046] The illuminator (IL) may be operable to change the polarization of the beam and may be operable to adjust the polarization using an adjuster (AM). The polarization state of the radiation beam across the pupil plane of the illuminator (IL) may be referred to as a polarization mode. The use of different polarization modes may allow greater contrast to be achieved in the image formed on the substrate (W). The radiation beam may not be polarized. Alternatively, the illuminator may be positioned to linearly polarize the radiation beam. The polarization direction of the radiation beam may vary across the pupil plane of the illuminator (IL). The polarization direction of the radiation may differ in different regions of the pupil plane of the illuminator (IL). The polarization state of the radiation may be selected according to the illumination mode. For multipole illumination modes, the polarization of each pole of the radiation beam can generally be perpendicular to the position vector of that pole in the pupil plane of the illuminator (IL). For example, for a dipole illumination mode, the radiation can be linearly polarized in a direction substantially orthogonal to the line dividing the two opposing sectors of the dipole. The radiation beam can be polarized in one of two different orthogonal directions, which may be referred to as X-polarization and Y-polarization states. For a quadrupole illumination mode, the radiation in the sector of each pole can be linearly polarized in a direction substantially perpendicular to the line dividing that sector. This polarization mode may be referred to as XY polarization. Similarly, for a sextupole illumination mode, the radiation in the sector of each pole can be linearly polarized in a direction substantially perpendicular to the line dividing that sector. This polarization mode may be referred to as TE polarization.

[0047] Additionally, the illuminator (IL) generally includes various other components such as an integrator (IN) and a capacitor (CO). The lighting 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, for directing, shaping, or controlling radiation.

[0048] Accordingly, the illuminator provides a beam (B) of adjusted radiation having the desired uniformity and intensity distribution in its cross section.

[0049] A support structure (MT) supports the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithography device, and other conditions, such as whether the patterning device is maintained in a vacuum environment, for example. The support structure may use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device. The support structure may be, for example, a frame or table that can be fixed or movable as needed. The support structure can ensure that the patterning device is in a desired position, for example, relative to a projection system. Any use of the terms "reticle" or "mask" in this specification may be considered synonymous with the more general term "patterning device."

[0050] As used herein, the term “patterning device” should be broadly interpreted to refer to any device that can be used to apply a pattern to a target portion of a substrate. In the embodiments, the patterning device is any device that can be used to apply a pattern to the cross-section of a radiation beam to create a pattern on a target portion of a substrate. For example, it should be noted that if the pattern includes a phase-shifting feature or a so-called assist feature, the pattern applied to the radiation beam may not exactly correspond to the desired pattern within the target portion of the substrate. Generally, the pattern applied to the radiation beam will correspond to a specific functional layer of the device created on the target portion, such as an integrated circuit.

[0051] Patterning devices can be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in the field of lithography and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array utilizes a matrix array of small mirrors, each of which can be individually tilted to reflect an incident radiation beam in different directions. The tilted mirrors impart patterns to the radiation beam reflected by the mirror matrix.

[0052] As used herein, the term "projection system" should be broadly interpreted to include any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic, and electrostatic optical systems, or any combination thereof, appropriate with respect to the exposure radiation used, or other factors such as the use of immersion liquid or vacuum. Any use of the term "projection lens" in this specification may be considered synonymous with the more general term "projection system."

[0053] The projection system (PS) has an optical transmission function that may be non-uniform, which can affect the pattern being imaged on the substrate (W). For unpolarized radiation, this effect can be quite well described by two scalar maps, which describe the transmission (apodization) and relative phase (aberration) of radiation exiting the projection system (PS) as a function of its position in the pupil plane. These scalar maps, which may be referred to as the transmission map and the relative phase map, can be expressed as a linear combination of a complete set of basis functions. A particularly convenient set is the Zernike polynomial, which forms a set of orthogonal polynomials defined on the unit circle. Determining each scalar map may involve determining the coefficients in these expansions. Since the Zernike polynomials are orthogonal on the unit circle, the Zernike coefficients can be determined by calculating the inner product of the measured scalar maps with respect to each Zernike polynomial and dividing it by the square of the norm of the Zernike polynomial.

[0054] The transmission map and relative phase map are field and system dependent. That is, generally, each projection system (PS) will have a different Zernike expansion for each field point (i.e., for each spatial location in its image plane). The relative phase of the projection system (PS) in the pupil plane can be determined, for example, by projecting radiation from a point-like source in the object plane of the projection system (PS) (i.e., the plane of the patterning device (MA)) through the projection system (PS) and by using a shearing interferometer to measure the wavefront (i.e., the locus of points having the same phase). The shearing interferometer is a common path interferometer, and therefore, advantageously, a secondary reference beam is not required to measure the wavefront. A shear interferometer may include a diffraction grating, for example, two two-dimensional grids, within the image plane of a projection system (i.e., a substrate table (WT)), and a detector positioned to detect an interference pattern within a plane conjugated to the pupil plane of the projection system (PS). The interference pattern is related to the derivative of the phase of the radiation with respect to the coordinates of the pupil plane in the shear direction. The detector may include an array of sensing elements, such as, for example, charge-coupled devices (CCDs).

[0055] The projection system (PS) of the lithography device may not generate visible fringes, and thus the accuracy of wavefront determination can be improved by using phase stepping techniques, such as moving the diffraction grating. Stepping can be performed in the plane of the diffraction grating and in a direction perpendicular to the scanning direction of the measurement. The stepping range may be one grating period, and at least three (uniformly distributed) phase steps may be used. Thus, for example, three scanning measurements may be performed in the y-direction, and each scanning measurement may be performed for a different position in the x-direction. This stepping of the diffraction grating allows phase information to be determined by effectively converting phase changes into intensity changes. The grating can be stepped in a direction perpendicular to the diffraction grating (z-direction) to calibrate the detector.

[0056] The diffraction grating can be scanned sequentially in two vertical directions, which may coincide with the axes (x and y) of the coordinate system of the projection system (PS) or be at an angle such as 45 degrees to these axes. Scanning can be performed over an integer number of grating periods, for example, one grating period. Scanning allows the phase change in one direction to be averaged to reconstruct the phase change in the other direction. This allows the wavefront to be determined as a function of both directions.

[0057] The transmission (apodization) of the projection system (PS) in the pupil plane can be determined, for example, by projecting radiation from a point source onto the object plane of the projection system (PS) (e.g., the plane of the patterning device (MA)) through the projection system (PS) and by measuring the intensity of the radiation in a plane conjugated with the pupil plane of the projection system (PS) using a detector. The same detector used to measure the wavefront may be used to determine the aberration.

[0058] A projection system (PS) may include a plurality of optical elements (e.g., lenses) and may further include an adjustment mechanism (AM) configured to adjust one or more of the optical elements to correct aberrations (phase changes across the pupil plane of the entire field). To achieve this, the adjustment mechanism may be operable to manipulate one or more optical elements (e.g., lenses) within the projection system (PS) in one or more different ways. The projection system may have a coordinate system, wherein its optical axis extends in the z-direction. The adjustment mechanism may be operable to perform any combination of the following: displace one or more optical elements; tilt one or more optical elements; and / or deform one or more optical elements. Displacement of an optical element may be in any direction (x, y, z, or a combination thereof). Tilt of an optical element typically deviates from a plane perpendicular to the optical axis by rotating about an axis in the x and / or y directions, but rotation about the z-axis may be used for non-rotationally symmetric aspherical optical elements. Deformation of the optical element may include low-frequency features (e.g., astigmatic) and / or high-frequency features (e.g., free-form aspheres). Deformation of the optical element may be performed, for example, by using one or more actuators to apply force to one or more sides of the optical element and / or by using one or more heating elements to heat one or more selected areas of the optical element. Generally, it may not be possible to adjust the projection system (PS) to correct apodization (transmission variation across the pupil plane). The transmission map of the projection system (PS) may be used when designing a patterning device (e.g., a mask) (MA) for a lithography device (LA).Using computational lithography technology, a patterning device (MA) can be designed to correct at least partially apodization.

[0059] The lithography device may be of the type having two (dual-stage) or more tables (e.g., two or more substrate tables (WTa, WTb), two or more patterning device tables, substrate table (WTa), and a table (WTb) under a projection system without a substrate dedicated to facilitating, for example, measurement and / or cleaning). In such a “multi-stage” machine, additional tables may be used simultaneously, or preparation steps may be performed on one or more other tables while one or more other tables are being used for exposure. For example, alignment measurements using an alignment sensor (AS) and / or level measurements (height, tilt, etc.) using a level sensor (LS) may be performed.

[0060] The lithography apparatus may also be of a type in which at least a portion of the substrate can be covered with a liquid having a relatively high refractive index, such as water, to fill the space between the projection system and the substrate. The immersion liquid may also be applied to other spaces within the lithography apparatus, for example, between the patterning device and the projection system. Immersion techniques for increasing the numerical aperture of the projection system are well known in the art. As used herein, the term "immersion" does not mean that a structure such as a substrate must be submerged in the liquid, but rather simply means that the liquid is positioned between the projection system and the substrate during exposure.

[0061] Accordingly, when the lithography device is operated, the radiation beam is regulated and provided by the illumination system (IL). The radiation beam (B) is incident on a patterning device (e.g., mask) (MA) held on a support structure (e.g., mask table) (MT) and is patterned by the patterning device. The radiation beam (B), having crossed the patterning device (MA), passes through a projection system (PS), and the projection system focuses the radiation beam onto a target portion (C) of the substrate (W). With the help of a second positioner (PW) and a position sensor (IF) (e.g., an interferometer device, a linear encoder, a 2-D encoder, or a capacitive sensor, etc.), the substrate table (WT) can be moved precisely to position, for example, different target portions (C) within the path of the radiation beam (B). Similarly, a first positioner (PM) and another position sensor (not clearly shown in FIG. 1) can be used to accurately position the patterning device (MA) relative to the path of the radiation beam (B), for example, after mechanical retrieval from a mask library or during scanning. Generally, movement of the support structure (MT) can be realized with the help of a long-stroke module (rough positioning) and a short-stroke module (fine positioning), and these modules form part of the first positioner (PM). Likewise, movement of the substrate table (WT) can be realized using a long-stroke module and a short-stroke module, and these modules form part of the second positioner (PW). In the case of a stepper (in contrast to a scanner), the support structure (MT) can be connected only to a short-stroke actuator or can be fixed. The patterning device (MA) and the substrate (W) can be aligned using patterning device alignment marks (M1, M2) and substrate alignment marks (P1, P2).As described, substrate alignment marks occupy a dedicated target portion, but they may be located in the space between the target portions (these are known as scribe lane alignment marks). Similarly, in a situation where one or more dies are provided on a patterning device (MA), patterning device alignment marks may be located between the dies.

[0062] The described device may be used in at least one of the following modes:

[0063] 1. In step mode, the support structure (MT) and the substrate table (WT) are essentially kept in a stationary state, while the entire pattern applied to the radiation beam is projected onto the target portion (C) at once (i.e., a single static exposure). The substrate table (WT) is then shifted in the X and / or Y directions so that a different target portion (C) can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion (C) being imaged during a single static exposure.

[0064] 2. In scan mode, the support structure (MT) and the substrate table (WT) are scanned simultaneously while the pattern applied to the radiation beam is projected onto the target portion (C) (i.e., single dynamic exposure). The speed and orientation of the substrate table (WT) relative to the support structure (MT) can be determined by the (reduction) magnification and image inversion features 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) during single dynamic exposure, whereas the length of the scanning motion determines the height of the target portion (in the scanning direction).

[0065] 3. In another mode, the support structure (MT) is kept in a essentially stationary state by holding the programmable patterning device, and the substrate table (WT) is moved or scanned while the pattern imparted by the radiation beam is projected onto the target portion (C). In this mode, a pulsed radiation source is typically used, and the programmable patterning device is updated as needed after each movement of the substrate table (WT) or between consecutive radiation pulses during a scan. This mode of operation can be easily applied to maskless lithography using a programmable patterning device, such as a programmable mirror array of the type mentioned above.

[0066] Combinations and / or variations of the usage modes described above, or completely different usage modes, may also be used.

[0067] While specific references may be made in this document regarding the use of lithography devices in the manufacture of ICs, it should be understood that the lithography devices described herein may have other applications, such as the manufacture of integrated optical systems, guide and detection patterns for magnetic domain memory, liquid crystal displays (LCDs), thin-film magnetic heads, etc. Those skilled in the art will recognize that any use of the terms “wafer” or “die” within this specification in relation to these alternative applications may be considered synonymous with the more general terms “substrate” or “target part,” respectively. The substrate referred to herein may be processed before or after exposure, for example, on a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist) or on a metrology or inspection tool. Where applicable, the disclosures within this specification may be applied to such and other substrate processing tools. Additionally, the substrate may be processed one or more times, for example, to create a multilayer IC; thus, the term substrate as used herein may also refer to a substrate comprising a number of already processed layers.

[0068] As used herein, the terms “radiation” and “beam” include all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g., having wavelengths of 365, 248, 193, 157, or 126 nm) and extreme ultraviolet (EUV) radiation (e.g., having wavelengths in the range of 5 to 20 nm), as well as particle beams such as ion beams or electron beams.

[0069] Various patterns on or provided by a patterning device may have different process windows, that is, spaces of processing variables within which the pattern is generated. Examples of pattern specifications related to potential systematic defects include checks for necking, line pull back, line thinning, CD, edge placement, overlapping, loss of the top of the resist, resist undercut, and / or bridging. The process window of all patterns on the patterning device or its area may be obtained by merging (e.g., overlapping) the process windows of each individual pattern. The boundary of the process window of all patterns includes the boundary of the process window of some of the individual patterns. That is, these individual patterns limit the process window of all patterns. This pattern may be referred to as a "hot spot" or "Process Window Limiting Pattern (PWLP)" as used interchangeably herein. When controlling a portion of the patterning process, it is possible and economical to focus on the hot spot. If there are no defects in the hot spots, it is most likely that all patterns will be defect-free.

[0070] As shown in FIG. 2, the lithography device (LA) may form part of a lithography cell (LC), sometimes also referred to as a lithocell or cluster, and also includes a device for performing pre-exposure and post-exposure processes on a substrate (W). Typically, these include one or more spin coaters (SC) for depositing one or more resist layers, one or more developers (DE) for developing the exposed resist, one or more cooling plates (CH) and / or one or more bake plates (BK). A substrate handler or robot (RO) picks up one or more substrates from input / output ports (I / O1, I / O2), moves the substrates between different process devices, and transfers the substrates to a loading bay (LB) of the lithography device. These devices, commonly collectively referred to as tracks, are under the control of a Track Control Unit (TCU), which is self-controlled by a supervisory control system (SCS) that also controls the lithography device through the Lithography Control Unit (LACU). Therefore, different devices can be operated to maximize throughput and processing efficiency.

[0071] In order to ensure that a substrate exposed by a lithography device is exposed accurately and consistently, and / or to monitor a part of a patterning process (e.g., a device manufacturing process) including at least one pattern transfer step (e.g., an optical lithography step), it is desirable to inspect the substrate or other objects to measure or determine one or more properties such as alignment, overlay (which may be between structures in layers above, e.g., or between structures in the same layer individually provided to the layer by a double patterning process), line thickness, critical dimension (CD), focus offset, material properties, etc. Accordingly, the manufacturing facility where the lithocell (LC) is located also typically includes a metrology system (MET) that measures some or all of the substrates (W) processed in the lithocell or other objects within the lithocell. The metrology system (MET) may be part of the lithocell (LC) and may be part of a lithography device (LA), for example (such as an alignment sensor (AS)).

[0072] One or more measured parameters may include, for example, overlay between consecutive layers formed in or on the patterned substrate, for example, critical dimension (CD) (e.g., critical line width) of features formed in or on the patterned substrate, focus or focus error of the optical lithography step, dose or dose error of the optical lithography step, optical aberration of the optical lithography step, etc. This measurement may be performed on a target on the product substrate itself and / or on a dedicated metrology target provided on the substrate. The measurement may be performed after development of the resist but before etching, or after etching.

[0073] Various techniques exist for measuring structures formed in a patterning process, including the use of scanning electron microscopes, image-based measurement tools, and / or various specialized tools. As discussed above, a fast and non-invasive type of specialized measurement tool is one in which a radiation beam is directed onto a target on the surface of a substrate and the characteristics of the scattered (diffracted / reflected) beam are measured. By evaluating one or more characteristics of the radiation scattered by the substrate, one or more characteristics of the substrate can be determined. This can be referred to as diffraction-based measurement. One such application of this diffraction-based measurement is the measurement of feature asymmetry within a target. This can be used, for example, as a measure of overlay, but other applications are also known. For example, asymmetry can be measured by comparing opposing parts of a diffraction spectrum (e.g., by comparing the -1st and +1st orders in the diffraction spectrum of a periodic grating). This can be done as described above and, for example, as described in U.S. Patent Application Publication US2006-066855, the entirety of which is incorporated herein by reference. Another application of diffraction-based metrology is the measurement of feature width (CD) within a target. This technique may utilize the apparatus and method described below.

[0074] Accordingly, in a device manufacturing process (e.g., a patterning process or a lithography process), a substrate or other object may undergo various types of measurements during or after the process. Measurements may be used to determine whether a specific substrate has defects, to establish adjustments for the process and the devices used in the process (e.g., aligning two layers on a substrate or aligning a patterning device with respect to the substrate), to measure the performance of the process and devices, or for other purposes. Examples of measurements include optical imaging (e.g., optical microscopy), non-imaging optical measurements (e.g., diffraction-based measurements such as the ASML YieldStar metrology tool or the ASML SMASH metrology system), mechanical measurements (e.g., profiling using a stylus or atomic force microscope (AFM)), and / or non-optical imaging (e.g., scanning electron microscopy (SEM)). A SMASH (SMart Alignment Sensor Hybrid) system as described in U.S. Patent No. 6,961,116, the entire contents of which are referenced herein, utilizes a self-referencing interferometer that generates two superimposed and relatively rotated images of an alignment marker, detects the intensity in the pupil plane where the Fourier transform of the images interferes, and extracts positional information from the phase difference between the diffraction orders of the two images, which appears as a change in intensity at the interfered order.

[0075] Measurement results may be provided to the Supervisory Control System (SCS) directly or indirectly. If an error is detected, adjustments may be made for the exposure of subsequent substrates and / or subsequent exposures of the exposed substrates (particularly, if the inspection can be performed sufficiently immediately and quickly enough for one or more other substrates in the batch to still be exposed). Additionally, already exposed substrates may be peeled off and reworked or discarded to improve yield, thereby avoiding further processing on substrates known to be defective. If defects exist only in certain target portions of the substrate, additional exposure may be performed only on the good target portions.

[0076] Within a metrology system (MET), a metrology device is used to determine one or more characteristics of a substrate, and in particular, how one or more characteristics of different substrates differ or how different layers of the same substrate differ from layer to layer. As mentioned above, the metrology device may be integrated into a lithography device (LA) or a lithocell (LC), or it may be a standalone device.

[0077] To enable measurement, one or more targets may be provided on the substrate. In an embodiment, the target may be specially designed and include a periodic structure. In an embodiment, the target is part of a device pattern, for example, a periodic structure of the device pattern. In an embodiment, the device pattern is a periodic structure of a memory device (for example, a structure such as a bipolar transistor (BPT), bit line contact (BLC), etc.).

[0078] In an example, the target on the substrate may comprise one or more 1-D periodic structures (e.g., gratings), which are printed such that after development, periodic structural features are formed as solid resist lines. In an example, the target may comprise one or more 2-D periodic structures (e.g., gratings), which are printed such that after development, one or more periodic structures are formed as solid resist pillars or vias within the resist. Alternatively, the bars, pillars, or vias may be etched into the substrate (e.g., into one or more layers on the substrate).

[0079] In the examples, one of the parameters of interest in the patterning process is the overlay. The overlay can be measured using dark-field scatterometry, where zero-order diffraction (corresponding to specular reflection) is blocked and only higher orders are processed. Examples of dark-field measurements can be found in PCT patent applications WO2009 / 078708 and WO2009 / 106279, the entire contents of which are incorporated herein by reference. Further developments of the technology are described in U.S. patent applications US2011-0027704, US2011-0043791, and US2012-0242970, the entire contents of which are incorporated herein by reference. Diffraction-based overlays utilizing dark-field detection of diffraction orders enable overlay measurements on smaller targets. These targets may be smaller than the illumination spot and may be surrounded by device product structures on the substrate. In the examples, multiple targets can be measured in a single radiation capture.

[0080] FIG. 3 shows an exemplary inspection device (e.g., a scatterometer). This device includes a broadband (white light) radiation projector (2) that projects radiation onto a substrate (W). The directed radiation passes to a scatterometer detector (4), which measures the spectrum (10) of specularly reflected radiation (i.e., intensity as a function of wavelength), as shown, for example, in the graph on the lower left. From this data, the structure or profile that generates the detected spectrum can be reconstructed by a processor (PU), for example, by rigorous coupled wave analysis and nonlinear regression, or by comparison with a library of simulated spectra, as shown on the lower right of FIG. 3. Generally, for reconstruction, a general form of the structure is known, and some parameters are assumed from information on the process in which the structure was made, so that only a few variables of the structure are determined from the measured data. Such an inspection device can be configured as a vertical-incident inspection device or an oblique-incident inspection device.

[0081] Another inspection device that can be used is shown in FIG. 4. In this device, radiation emitted by a radiation source (2) is collimated using a lens system (12), transmitted through an interference filter (13) and a polarizer (17), reflected by a partial reflective surface (16), and focused onto a spot (S) on a substrate (W) through an objective lens (15) having a high numerical aperture (NA), preferably at least 0.9 or at least 0.95. An immersion inspection device (using a fluid with a relatively high refractive index, such as water) may have a numerical aperture of 1 or more.

[0082] As in a lithography device (LA), one or more substrate tables may be provided to hold the substrate (W) during the measurement operation. The substrate tables may be similar in shape to or identical to the substrate table (WT) of FIG. 1. In an example where the inspection device is integrated with the lithography device, they may be the same substrate table. A rough and fine positioner may be provided on a second positioner (PW) configured to accurately position the substrate in relation to the measurement optical system. For example, various sensors and actuators are provided to acquire the position of a target of interest and bring it to a position below the objective lens (15). Typically, many measurements will be made for targets at different positions across the substrate (W). The substrate support may be moved in the X and Y directions to acquire different targets, and moved in the Z direction to acquire the desired position of the target relative to the focus of the optical system. For example, it is convenient to think of and describe the operation as if the optical system can be kept substantially stationary (typically in the X and Y directions, but perhaps also in the Z direction) and only when the substrate moves is the objective lens being brought to different positions relative to the substrate. As long as the relative positions of the substrate and the optical system are accurate, in principle it does not matter which of them is actually moving, whether both are moving, or whether a combination of parts of the optical system is moving (e.g., in the Z and / or oblique directions) while the rest of the optical system remains stationary and the substrate is moving (e.g., in the X and Y directions, but also optionally in the Z and / or oblique directions).

[0083] Radiation directed by the substrate (W) then passes through a partially reflective surface (16) to a detector (18) to detect the spectrum. The detector (18) may be positioned at a back-projected focal plane (11) (i.e., at the focal length of the lens system (15), or the plane (11) may be re-imaging onto the detector (18) with an auxiliary optical system (not visible). The detector may be a two-dimensional detector so that the two-dimensional angular scattering spectrum of the substrate target (30) can be measured. The detector (18) may be, for example, an array of CCD or CMOS sensors and may use, for example, an integration time of 40 milliseconds per frame.

[0084] For example, a reference beam may be used to measure the intensity of incident radiation. To do this, when a radiation beam is incident on a partial reflective surface (16), a portion of the radiation beam is transmitted through the partial reflective surface (16) as a reference beam directed toward a reference mirror (14). The reference beam is then projected onto a different part of the same detector (18) or, alternatively, onto a different detector (not visible).

[0085] One or more interference filters (13) may be used to select a wavelength of interest within a much lower range, such as, for example, 405 to 790 nm or 200 to 300 nm. The interference filters may be adjustable rather than comprising a set of other filters. A grating may be used instead of an interference filter. An aperture stop or a spatial light modulator (not visible) may be provided in the illumination path to control the range of the angle of incidence of radiation to the target.

[0086] The detector (18) can measure the intensity of the diverted radiation at a single wavelength (or a narrow wavelength range), separately at multiple wavelengths, or integrated across a wavelength range. Additionally, the detector can separately measure the intensity of the transverse magnetic- and transverse electric-polarized radiation and / or the phase difference between the transverse magnetic- and transverse electric-polarized radiation.

[0087] The target (30) on the substrate (W) may be an LD grid, which is printed so that after development, a bar is formed as a solid resist line. The target (30) may be a 2-D grid, which is printed so that after development, a grid is formed as a solid resist pillar or a via in the resist. The bar, pillar, or via may be etched into the substrate or on the substrate (e.g., into one or more layers on the substrate). The pattern (e.g., of a bar, pillar, or via) is sensitive to processing changes in the patterning process (e.g., optical aberrations, focus changes, dose changes, etc. of the lithography projection device (particularly, the projection system (PS))) and will appear as changes in the printed grating. Therefore, measurement data of the printed grating is used to reconstruct the grating. One or more parameters of the 1-D grating, such as line width and / or shape, or one or more parameters of the 2-D grating, such as pillar or via width or length or shape, can be input into a reconstruction process performed by a processor (PU) from information from the printing step and / or other inspection process.

[0088] In addition to the measurement of parameters by reconstruction, angle-resolved scatterometry is useful for measuring the asymmetry of features in a product and / or resist pattern. A specific application of asymmetry measurement is for overlay measurement, where the target (30) comprises a set of periodic features superimposed on another set. The concept of asymmetry measurement using the apparatus of FIG. 3 or FIG. 4 is described, for example, in U.S. Patent Application Publication US2006-066855, the entire contents of which are incorporated herein by reference. Briefly, the position of the diffraction order in the diffraction spectrum of the target is determined solely by the periodicity of the target, but the asymmetry of the diffraction spectrum indicates asymmetry in the individual features constituting the target. In the apparatus of FIG. 4, if the detector (18) may be an image sensor, this asymmetry in the diffraction order appears directly as asymmetry within the pupil image recorded by the detector (18). This asymmetry can be measured by digital image processing within the unit (PU) and corrected against a known overlay value.

[0089] FIG. 5 illustrates a plan view of a typical target (30) and the size of the illumination spot (S) within the device of FIG. 4. To obtain a diffraction spectrum free from interference from surrounding structures, in the embodiment, the target (30) is a periodic structure (e.g., a grating) larger than the width (e.g., diameter) of the illumination spot (S). The width of the spot (S) may be smaller than the width and length of the target. That is, the target is "underfilled" by the illumination, and the diffraction signal is essentially free of any signal from product features, etc., outside the target itself. The illumination array (2, 12, 13, 17) may be configured to provide illumination of uniform intensity across the back-focus plane of the objective lens (15). Alternatively, for example, by including an opening in the illumination path, the illumination may be restricted axially or out-of-axially.

[0090] FIG. 6 schematically illustrates an exemplary process for determining the value of one or more variables of interest of a target pattern (30') based on measurement data obtained using measurement. Radiation detected by the detector (18) provides a measured radiation distribution (108) for the target (30').

[0091] For a given target (30'), the radiation distribution (208) can be calculated / simulated from a parameterized model (206) using, for example, a numerical Maxwell solver (210). The parameterized model (206) shows exemplary layers of various materials that constitute the target and are associated with it. The parameterized model (206) may include one or more variables regarding the features and layers of the target portion under consideration, which may vary and be induced. As shown in FIG. 6, one or more variables may be the thickness of one or more layers ( t ), width of one or more features ( W ) (e.g., CD), height of one or more features ( h ), and / or sidewall angles of one or more features ( αIt may include ). Although not shown, one or more of the variables may further include, but are not limited to, one or more of the refractive indices of one or more of the layers (e.g., real or complex refractive indices, refractive index tensor, etc.), extinction coefficients of one or more layers, absorption of one or more layers, loss of resist during development, footing of one or more features, and / or line edge roughness of one or more features. The initial values ​​of the variables may be expected values ​​for the target being measured. The measured radiation distribution (108) is then compared with the radiation distribution (208) calculated in 212 to determine the difference between the two distributions. If there is a difference, the value of one or more of the variables of the parameterized model (206) may be varied, and a new calculated radiation distribution (208) may be calculated and compared with the measured radiation distribution (108) until there is sufficient matching between the measured radiation distribution (108) and the calculated radiation distribution (208). At that point, the value of the variable of the parameterized model (206) provides a good or best match of the geometric structure of the actual target (30'). In the embodiment, there is sufficient matching when the difference between the measured radiation distribution (108) and the calculated radiation distribution (208) is within an allowable threshold.

[0092] Variables of the patterning process are referred to as "processing variables." The patterning process may include upstream and downstream processes for the actual transfer of the pattern from the lithography device. FIG. 7 illustrates exemplary categories of processing variables (370). A first category may be variables (310) of the lithography device or any other device used in the lithography process. Examples of this category include variables of the lithography device, projection system, substrate stage, etc. A second category may be variables (320) of one or more procedures performed in the patterning process. Examples of this category include focus control or focus measurement, dose control or dose measurement, bandwidth, exposure period, development temperature, chemical composition used for development, etc. A third category may be variables (330) of the design layout and its implementation in or using the patterning device. Examples of this category may include the shape and / or position of assist features, adjustments applied by resolution enhancement technology (RET), CD of mask features, etc. The fourth category may be substrate variables (340). Examples include characteristics of structures under the resist layer, chemical composition and / or physical dimensions of the resist layer, etc. The fifth category may be characteristics (350) of temporal variation of one or more variables of the patterning process. Examples of this category include high-frequency stage shifts (e.g., frequency, amplitude, etc.), high-frequency laser bandwidth changes (e.g., frequency, amplitude, etc.), and / or high-frequency laser wavelength changes. These high-frequency changes or shifts are those that exceed the response time of the mechanism to adjust the basic variables (e.g., stage position, laser intensity). The sixth category may be characteristics (360) of upstream or downstream processes of pattern transfer in a lithography device, such as spin coating, post-exposure bake (PEB), development, etching, deposition, doping, and / or packaging.

[0093] As will be recognized, many, if not all, of these variables will affect the parameters of the patterning process, and often the parameters of interest. Non-limiting examples of parameters of the patterning process may include critical dimension (CD), critical dimension uniformity (CDU), focus, overlay, edge position or placement, sidewall angle, pattern shift, etc. Often, these parameters represent the error from nominal values ​​(e.g., design value, average value, etc.). Parameter values ​​may be characteristic values ​​of individual patterns or statistics regarding the characteristics of a pattern group (e.g., mean, variance, etc.).

[0094] The values ​​of some or all of the processing variables, or related parameters, may be determined by appropriate methods. For example, the values ​​may be determined from data acquired by various measurement tools (e.g., substrate measurement tools). The values ​​may be acquired from various sensors or systems of the device in the patterning process (e.g., sensors such as leveling sensors or alignment sensors of a lithography device, control systems of the lithography device (e.g., substrate or patterning device table control systems), sensors within a track tool, etc.). The values ​​may be provided by the operator of the patterning process.

[0095] An exemplary flowchart for modeling and / or simulating a part of the patterning process is shown in FIG. 8. As will be recognized, the model may represent different patterning processes and does not need to include all the models described below. The source model (1200) represents the optical properties of the illumination of the patterning device (including radiation intensity distribution, bandwidth and / or phase distribution). The source model (1200) may represent the optical properties of the illumination, including, but not limited to, numerical aperture settings, illumination sigma (σ) settings, as well as any specific illumination shape (e.g., annular, quadrupole, dipole, etc., and other out-of-axis radiation shapes). Here, σ (or sigma) is the outer radial range of the illuminator.

[0096] The projection optical system model (1210) represents the optical properties of the projection optical system (including changes in radiation intensity distribution and / or phase distribution caused by the projection optical system). The projection optical system model (1210) may represent the optical properties of the projection optical system, including aberrations, distortion, one or more refractive indices, one or more physical sizes, one or more physical dimensions, etc.

[0097] The patterning device / design model module (1220) captures how design features are placed on the pattern of the patterning device and may include a representation of the detailed physical properties of the patterning device, for example, as described in U.S. Patent No. 7,587,704, the entire contents of which are referenced herein. In an embodiment, the patterning device / design layout model module (1220) represents the optical properties of the design layout (e.g., device design layout corresponding to features of an integrated circuit, memory, electronic device, etc.) (including changes in radiation intensity distribution and / or phase distribution caused by the given design layout), which is a representation of an array of features on or formed by the patterning device. Since the patterning device used in the lithography projection device may change, it is desirable to separate the optical properties of the patterning device from the optical properties of the rest of the lithography projection device, including at least the illumination and projection optical systems. The purpose of the simulation is often to accurately predict, for example, edge placement and CD, which can then be compared with the device design. Device designs are generally defined by pre-OPC patterned device layouts and will be provided in standardized digital file formats such as GDSII or OASIS.

[0098] An aerial image (1230) can be simulated from a source model (1200), a projection optical system model (1210), and a patterning device / design layout model (1220). The aerial image (AI) is a radiation intensity distribution at the substrate level. Optical properties of the lithography projection device (e.g., lighting, properties of the patterning device and projection optical system) affect the aerial image.

[0099] A resist layer on a substrate is exposed by an aerial image, and the aerial image is transferred to the resist layer as a potential "resist image" (RI) within it. The resist image (RI) can be defined as a spatial distribution of the solubility of the resist within the resist layer. The resist image (1250) can be simulated from the aerial image (1230) using a resist model (1240). The resist model can be used to calculate the resist image from the aerial image, an example of which can be found in U.S. Patent Application Publication No. US2009-0157360, the entire contents of which are by reference in this specification. For example, to predict the contour of a resist feature formed on a substrate, the resist model typically accounts for the influence of chemical processes occurring during resist exposure, post-exposure bake (PEB), and development, and thus is typically only related to these properties of the resist (e.g., the influence of chemical processes occurring during exposure, post-exposure bake, and development). In the example, the optical properties of the resist layer, e.g., refractive index, film thickness, propagation, and polarization effects, can be captured as part of the projection optical system model (1210).

[0100] Therefore, generally, the connection between the optical model and the resist model is the simulated aerial image intensity within the resist layer, which arises from the projection of radiation onto the substrate, refraction at the resist interface, and multiple reflections within the resist film stack. The radiation intensity distribution (aerial image intensity) is transformed into a potential "resist image" by the absorption of incident energy, which is further altered by diffusion processes and various loading effects. An efficient simulation method sufficiently fast for full-chip applications approximates the actual 3-dimensional intensity distribution of the resist stack by the 2-dimensional aerial (and resist) image.

[0101] In an embodiment, the resist image can be used as an input to the pattern transfer post-process model module (1260). The pattern transfer post-process model (1260) defines the performance of one or more resist post-processes (e.g., etching, development, etc.).

[0102] Simulation of the patterning process can predict, for example, contours, CD, edge placement (e.g., edge placement error) within the resist and / or etched image. Thus, the purpose of the simulation is to accurately predict, for example, the edge placement of the printed pattern and / or aerial image intensity gradient and / or CD. These values ​​are compared with the intended design to, for example, correct the patterning process and identify locations where defects are expected to occur. The intended design is generally limited to a pre-OPC design layout that may be provided in a standardized digital file format such as GDSII, OASIS, or other file formats.

[0103] Therefore, the model formulation describes most, if not all, of the physical and chemical properties of the entire process, and each model parameter preferably corresponds to a distinct physical or chemical effect. Thus, the model formulation establishes an upper bound on how well the model can be used to simulate the entire manufacturing process.

[0104] An exemplary flowchart for modeling and / or simulating a measurement process is illustrated in FIG. 9. As will be recognized, the following models may represent different measurement processes and may not need to include all the models described below (e.g., some may be combined). The source model (1300) represents the optical properties of the illumination of the measurement target (including radiation intensity distribution, radiation wavelength, polarization, etc.). The source model (1300) may represent the optical properties of the illumination, including, but not limited to, wavelength, polarization, illumination sigma (σ) setting (where σ (or sigma) is the outer radial range of the illumination within the illuminator), and any specific illumination shape (e.g., an annular, quadrupole, dipole, etc., an off-axis radiation shape).

[0105] The measurement optical system model (1310) represents the optical properties of the measurement optical system (including changes in radiation intensity distribution and / or phase distribution caused by the measurement optical system). The measurement optical system (1310) may represent the optical properties of the illumination of the measurement target by the measurement optical system and the optical properties of the delivery of directed radiation from the measurement target toward the measurement device detector. The measurement optical model may represent various properties related to the illumination of the target and the delivery of directed radiation from the measurement target toward the measurement device detector, including aberrations, distortion, one or more refractive indices, one or more physical sizes, one or more physical dimensions, etc.

[0106] The measurement target model (1320) can represent the optical properties of the illumination directed by the measurement target (including changes in the intensity distribution and / or phase distribution of the illumination radiation caused by the measurement target). Thus, the measurement target model (1320) can model the conversion of illumination radiation by the measurement target into directed radiation. Thus, the measurement target model can simulate the resulting illumination distribution of directed radiation from the measurement target. The measurement target model can represent various properties related to the illumination of the target and the generation of directed radiation from the measurement, including one or more refractive indices, one or more physical sizes of the measurement, and the physical layout of the measurement target. Since the measurement target used may vary, it is desirable to separate the optical properties of the measurement target from the optical properties of the rest of the measurement device, including at least the illumination and projection optical systems and the detector. The purpose of the simulation is often to accurately predict, for example, intensity, phase, etc., which can then be used to derive parameters of interest for the patterning process, such as overlay, CD, focus, etc.

[0107] The pupil or aerial image (1330) can be simulated from the source model (1300), the measurement optical system model (1310), and the measurement target model (1320). The pupil or aerial image is a radiation intensity distribution at the detector level. Optical properties of the measurement optical system and the measurement target (e.g., illumination, properties of the measurement target and the measurement optical system) affect the pupil or aerial image.

[0108] The detector of the measuring device is exposed to a pupil or aerial image and detects one or more optical properties (e.g., intensity, phase, etc.) of the pupil or aerial image. The detection model module (1320) indicates how radiation from the measuring optical system is detected by the detector of the measuring device. The detection model can describe how the detector detects the pupil or aerial image and may also include signal versus noise, sensitivity to incident radiation on the detector, etc. Thus, generally, the connection between the measuring optical system model and the detector model is a simulated pupil or aerial image, which arises from the illumination of the measuring target by the optical system, the diversion of radiation by the target, and the delivery of the diverted radiation to the detector. The radiation distribution (pupil or aerial image) is converted into a detection signal by the absorption of incident energy on the detector.

[0109] Simulation of the measurement process can predict, for example, spatial intensity signals and spatial phase signals from the detector, or other calculated values ​​from the detection system such as overlays and CDs, as well as values ​​of pupil or aerial images based on detection by the detector. Therefore, the purpose of the simulation is to accurately predict, for example, detector signals or derived values ​​such as overlays and CDs corresponding to the measurement target. These values ​​are compared with intended design values ​​to, for example, correct the patterning process and identify locations where defects are expected to occur.

[0110] Therefore, the model formulation describes most, if not all, of the known physical and chemical properties of the entire metrology process, and each of the model parameters preferably corresponds to a distinct physical and / or chemical effect in the metrology process.

[0111] As previously mentioned, the patterning process may include one or more devices that can operate simultaneously to produce similar substrates. Over time, the performance of one or more devices may change, leading to discrepancies between substrates produced by different devices or the same device (e.g., in terms of CD of the same feature). The performance of the devices may be characterized in terms of parameters of the patterning process. In the embodiments, the performance of the devices may vary due to pupil difference between one device and another, or pupil difference of one device over a certain period / processing step.

[0112] The pupil of the device may be part of the illuminator (IL) of FIG. 1, more specifically the beam delivery system (BDS) as previously discussed. The pupil may consist of multiple pupil facet mirrors that can be adjusted (e.g., by an adjustment mechanism (AM)) to change the intensity and / or orientation of one or more mirrors to produce different illumination patterns, such as dipoles, quadrupoles, etc. Over time, as the pupil degrades, the same pattern may provide different performance for the same device. Additionally, the pupil on one device may not be the same as the pupil on another device, for example, due to the manufacturing process of the device itself or changes in the material of the pupil.

[0113] Pupil matching may be required to maintain a consistent output (for example, a substrate having a desired pattern with minimal variation between different substrates may be obtained from different devices or the same device over a period of time or during multiple patterning steps). The foregoing invention describes a method for obtaining pupil matching. Pupil matching refers to a pupil configuration of a device (e.g., a list of mirrors having a specific intensity and / or orientation) that produces device performance similar to reference performance (e.g., CD of a feature). In an embodiment, pupil matching may be performed between two devices or between the same device at different points in the patterning process.

[0114] FIG. 10 is a flowchart of a pupil matching method according to an embodiment of the present invention. Pupil matching may be based on determining an initial set of leading degrees of freedom of a pupil facet mirror and modifying / adjusting the initial leading DoF so that the device produces performance very similar to reference performance.

[0115] In process P10, a reference performance (1602) can be obtained for a reference device. The reference device may be one of a plurality of devices in the patterning process and may be compared with the performance of the remaining devices and / or the reference device may be the same device whose performance can be compared with itself at different points in the patterning process (e.g., at the beginning, in the middle, or at the end).

[0116] In the embodiments, the reference performance may be a performance that is very similar to the ideal and / or design intent (e.g., within 0 to 5% of the desired value). The performance may be expressed in terms of a value or a set of values ​​associated with one or more parameters of the patterning process (e.g., CD, overlay, etc.). For example, the reference performance may be a desired CD value of a feature (e.g., CD of 10 nm for a contact hole, or CD of 25 nm for a bar or pillar, etc.), a range of CD values ​​associated with one or more features, or other design specifications typically used to define the performance of the device. In the embodiments, the reference performance may be determined for a first device (e.g., a first scanner of the patterning process), and this reference performance may serve as a reference for a second device (e.g., a second scanner of the patterning process). This reference performance may or may not be close to the ideal value, but simply serves as a reference that can match the performance of the second device. In another embodiment, reference performance may be determined from the second device at a specific point in time, for example, at the beginning of the patterning process; such reference performance may serve as a reference for the same device at other points in time (for example, in the middle of the patterning process, at the point when 500, 1,000, 5,000, 10,000 wafers, etc. are produced). Additionally, the reference performance obtained from the second device may or may not be close to the ideal, but may simply serve as a reference that can match the performance of the second device at different points in time.

[0117] In the embodiments, reference performance may be measured from a substrate generated by the first device (or, for example, the second device at the start of the patterning process, etc.) (e.g., using a measurement tool). In the embodiments, reference data may be modeled and / or simulated by assuming ideal or realistic conditions based on the populations of the tool or its predictions.

[0118] When a reference performance (e.g., corresponding to a specific pupil facet mirror for a first device) is obtained, in process P20, pupil data (1620) (also referred to as the first set of degrees of freedom or reference pupil data) for a device (e.g., a second device) that generates a matching performance together with the reference performance (e.g., for a first device) may be obtained. The pupil has several degrees of freedom (e.g., 300×300, 400×400, 500×500, 1,000×1,000, 2,000×2,000, 3,000×3,000, etc.), and each degree of freedom corresponds to a specific (or possible) state of the mirror of the pupil facet mirror. A pupil facet mirror is a set of mirrors arranged in an array, wherein each mirror can be connected to an operating device controlled by a controller, and the controller can be configured to control the strength and / or orientation of the mirrors.

[0119] In the embodiments, the pupil data generally refers to the degrees of freedom of interest of the pupil facet mirror of the device (e.g., the second device) where the matching pupil is to be determined, or a list of mirrors. For example, the reference pupil data of the device may be a list of mirrors within the pupil facet mirror that generate a match with the reference performance and their configuration. The pupil data may include all mirrors of the pupil facet mirror or a subset thereof. Additionally, for each mirror in the pupil data, the intensity of each mirror and / or the orientation of each mirror may be included in the pupil data. In the embodiments, the mirrors of the pupil facet mirror have one or more discrete states (e.g., "on" or "off"), and thus the pupil data may include discrete states corresponding to specific mirrors. Additionally, each state of the mirror may correspond to an aerial image. Based on the individual aerial images corresponding to the pupil facet mirror, the entire aerial image of the pupil may be generated, for example, by the summation or superposition of the aerial images of the individual mirrors. Accordingly, pupil data may include the discrete state of each mirror of the pupil facet mirror, an aerial image corresponding to each mirror, and / or a total aerial image composed of the individual aerial images. In the embodiments, the discrete state of the mirror or the intensity value of the mirror may be associated with aspects of features of the substrate (e.g., edges of bars, circumferences of contact holes). In the embodiments, the correlation of the discrete state or intensity of the individual mirrors may be established, for example, through the simulation of a process model and / or etching model such as a resist, or based on measurements of the printed substrate.

[0120] In the embodiments, the aerial image generated by each mirror also depends on the pattern / feature to be imaged on the substrate and optical parameters (NA, aberration, magnification, apodization, focus, etc.). Accordingly, in the embodiments, the aerial image per mirror may also correspond to or be related to data / values ​​of optical parameters. Accordingly, pupil data may also include such aerial image data per mirror.

[0121] In the embodiments, the pupil data may be limited to a region of interest based on a merit function. The merit function may be a function of CD, overlay, or other parameters of the patterning process. Thus, if there is interest in comparing performance with respect to an aspect of a specific pattern or feature (e.g., an edge), then the pupil data may be limited or restricted to the mirror data associated with the region of interest (e.g., an edge). As such, according to the embodiments, the pupil data can directly generate an image (e.g., an aerial image) without using or referencing the design layout of the pattern to be printed on the substrate.

[0122] A list of mirrors can define the desired lighting pattern that will eventually result in the reference performance of the device. However, during the patterning process, the performance of the device (e.g., the second device) may drift / deviate / become incompatible with other device(s) (e.g., the first device) (e.g., due to collector degradation in EUV lithography or pupil degradation due to use), and thus one or more of these mirrors of the reference pupil data that match the reference performance may need to be adjusted to maintain the reference performance or be very similar to it.

[0123] Additionally, in process P30, the degrees of freedom of the reference pupil data (e.g., the number of mirrors and related parameters such as intensity and orientation) can be adjusted based on an initial set of leading degrees of freedom (DoF) within the reference pupil data. The initial leading DoF (1630) refers to one or more mirrors of the reference pupil data that have a relatively high sensitivity / influence on the performance of the device. These leading DoFs (1630) can be identified by modeling and / or simulating a defined relationship between the pupil data and the performance of the device. This relationship may be inherently statistical and / or may involve physically based modeling / simulation. Based on the modeling / simulation, the sensitivity of each mirror to the performance of the device can be determined. For example, a singular decomposition technique may be used to determine the sensitivity of each DoF to the performance. In another example, the following mathematical formula may be used to determine the sensitivity of each DoF:

[0124]

[0125] In the above mathematical formula (1), (i) P refers to a performance parameter (e.g., CD), and (ii) a n refers to the sensitivity of the nth mirror in the list of mirrors, and (iii) DoF n represents degrees of freedom. The present invention is not limited to the above mathematical formula (1) to determine the sensitivity of DoF, and other techniques related to sensitivity analysis, such as variance decomposition, partial derivative effects, scatter plot, regression analysis, screening, etc., may be used.

[0126] Additionally, based on the sensitivity of each DoF, an initial leading DoF having a relatively high sensitivity compared to other DoFs in the list of mirrors may be selected. In an embodiment, a determined number of DoFs, such as up to 100 DoFs, up to 10% of the total degrees of freedom, may be selected as leading DoFs. In an embodiment, the leading DoF may be based on the sensitivity value itself, for example, a leading DoF having a sensitivity greater than a predetermined threshold (e.g., 90%) may be selected. In another embodiment, the leading DoF may be selected based on the position of the mirrors within the pupil facet mirror. For example, mirrors around the center of the pupil facet mirror may have a greater preference (e.g., a relatively higher weight) compared to mirrors around the pupil facet mirror. In an embodiment, for example, within a pupil facet mirror having 400×400 DoFs, the selected leading DoFs may be 10, 20, 30, 45 mirrors, etc.

[0127] Furthermore, in process P40, exposure data (1640) of one or more parameters (e.g., CD, overlay, focus, etc.) may be acquired for one or more substrates. The substrates may be exposed to determine or probe the influence of the preceding DoF (e.g., 10) of the pupil on the performance of the device. In an embodiment, one or more substrates may be exposed using pupil data (1620) and / or the preceding DoF (1630) of the pupil data (1620). In an embodiment, the probe may include selecting a linear combination of the preceding DoFs (1630), exposing one or more substrates to a linear combination of the preceding DoFs, and measuring the performance (e.g., CD value) of one or more substrates for a single exposure. For example, if the preceding DoF includes 10 mirrors, then the linear combination may include all 10 mirrors and / or a subset (or subcombination) of the 10 mirrors, such as the first, third, and ninth mirrors among the 10 mirrors, which may be expressed in terms of sets, e.g. [1,3,9], [2,4,6], [5,6,7,8], [1,2,3,4], etc. Each linear combination of the preceding DoF may result in different performance of the device. Such exposure data (1640) may be collected for further determination, and a matching pupil may be determined in process P50. A matching pupil refers to a set of mirrors of the pupil facet mirrors selected in the preceding DoF that makes the device performance very similar to the reference performance.

[0128] In process P50, based on the exposure data (1640), a matching pupil (1650) (e.g., one of linear combinations of mirrors) may be determined based on the difference (e.g., ACD) between the performance obtained based on a linear combination of preceding DoFs (11630) and the reference performance (1602). For example, the matching pupil (1650) may be a list of mirrors that reduce, and preferably minimize, the difference. Thus, by controlling the matching pupil, the performance of the device (e.g., the second device) may be substantially similar to that of the reference device (e.g., the first device). By this, consistent performance throughout the patterning process may be observed and / or achieved based on the matching pupil for one or more devices of the patterning process using the method as discussed above.

[0129] In an embodiment, the determination of the matching pupil (1650) may involve an iterative process. Each iteration includes changing one or more degrees of freedom among the preceding DoFs (1630) of the pupil facet mirrors; obtaining the current performance from the exposure data corresponding to the changed pupil facet mirror; and determining the current difference between the current performance and the reference performance. Changing one or more degrees of freedom may include changing the orientation and / or intensity of one or more mirrors of the preceding degrees of freedom. In an embodiment, one or more degrees of freedom may be a linear combination of the preceding DoFs (1630). In an embodiment, one or more degrees of freedom for change may be selected based on the position of the mirrors of the pupil facet mirrors. For example, the intensity of the mirrors may be changed to form illumination types such as dipole, quadrupole, etc. For each illumination type, different performance may be observed. The difference in performance with respect to the reference performance for each linear combination may be stored and used to determine the matching pupil associated with the minimum difference.

[0130] In the embodiments, the minimum difference may be based on performance (e.g., CD) associated with a specific feature (e.g., a contact hole with a diameter of 10 nm) or a plurality of features (e.g., contact holes of sizes such as 10 nm, 15 nm, 20 nm, 25 nm, 40 nm, 50 nm, etc.). In the embodiments, the performance difference for each of the plurality of features (e.g., contact holes of sizes such as 10 nm, 15 nm, 20 nm, 25 nm, 40 nm, 50 nm, etc.) may be calculated. Then, in the examples, the minimum difference may be defined as the minimum value of the sum of the differences for each feature. For example, for each linear combination of preceding DoFs, the sum of the differences for a plurality of features may be calculated, and the linear combination having the smallest sum of differences may be selected as the matching pupil.

[0131] In the embodiments, other appropriate methods for calculating the difference may be used. For example, statistical means or variances may be used to calculate the performance difference of each feature. In such cases, the minimum difference may be related to a linear combination showing the minimum change in performance for each feature.

[0132] Furthermore, the performance parameter may be a combination of patterning process parameters, for example, CD and overlay. For example, for a CD of 25 nm, the overlay may be ±0.5 nm. In this case, the difference can be calculated for each parameter, and the minimum difference can be determined based on a single parameter and / or a combination of parameters. For example, to determine the minimum difference, the difference in CD, the difference in overlay, or the difference in both CD and overlay may be considered.

[0133] It may be recognized that the present invention is not limited to the performance parameter CD, but other appropriate parameters of the patterning process (e.g., overlay, focus, etc.) may be selected to determine the performance of the device.

[0134] In the embodiments, the pupil data (or matching pupil data) may be further used in the source optimization (SO) process or source mask optimization (SMO). For example, the matching pupil may be an input to a source mask optimization model that determines the optimal source based on the matching pupil. In the embodiments, during SO or SMO, the pupil may be further optimized. In the embodiments, the optimized pupil may be further used to determine optical proximity correction through process model simulation.

[0135] In the embodiments, pupil matching may be performed according to the method of FIG. 11. According to the method of FIG. 11, pupil matching may be based on the computation and comparison of aerial imaging data, for example, in the far field (e.g., at the substrate level). In the embodiments, pupil matching may be based on the appearance of the pupil, and, for example, it may be desirable to have all pupil facet mirrors have a specific intensity; however, due to degradation over a certain period, for example, some mirrors may have a low or zero intensity. The intensity in the pupil may be measured using a tool such as LEUP, for example, and the aerial image may be reconstructed from the intensity measurement data by modeling and / or simulation (e.g., using a projection optical system model, an aerial imaging model, etc.). The method of FIG. 11 may provide inline calibration and / or correction to the pupil to maintain and / or reduce the performance of the device over a certain period, preferably minimizing the degradation of the device's performance.

[0136] In process P100, imaging data (1710) may be acquired and / or generated for all mirrors of the pupil facet mirror. In an embodiment, the imaging data (1710) may include a collection of raw-field aerial images generated by one or more mirrors of the pupil facet mirror (as previously discussed) corresponding to a mask that may be used during the patterning process. In an embodiment, such imaging data may be acquired by modeling and / or simulation of a projection optical system model / aerial image model / patterning process using, for example, a computational tool (e.g., a Tachyon tool). In an embodiment, optionally, pupil rendering may be performed (e.g., using a corrected case predictor (Zeiss predictor)) to acquire accurate imaging data.

[0137] Based on imaging data (1710), in process P200, reference performance (1720) corresponding to parameters of the patterning process (e.g., CD, overlay) can be acquired and / or generated. For example, image data corresponding to each of the pupil facet mirrors can be superimposed (or combined / added) to obtain a reference image. In the reference image, reference performance (1720) (e.g., CD) can be measured and / or acquired.

[0138] In the embodiment, processes P100 and P200 can be performed offline, for example, at the step-up stage of the device.

[0139] During production, in process P300, measurements (1730) of the pupil facet mirrors may be obtained from a pupil measurement instrument (e.g., LEUP) that measures pupil-related parameters, such as the intensity of each pupil facet mirror at the wafer level. These measurements may indicate that one or more of the pupil facet mirrors may have an intensity different from the ideal intensity / desired intensity / starting intensity used to acquire reference image data (e.g., as used in process P100). For example, one or more mirrors may be dark (i.e., have an intensity of approximately 0), one or more mirrors may have a low intensity (e.g., less than 25% of the full intensity initially set in process P100) or an intermediate intensity (e.g., about 50% of the full intensity), etc. This change in intensity of the pupil facet mirror can be attributed to the degradation of the pupil facet mirror. This degradation can be attributed, for example, to collector degradation in EUV lithography or simply to the repeated use of the pupil mirror. For this reason, degraded performance of the device can be observed, causing parameters, for example, the CD, to deviate from the desired / design intent.

[0140] Based on the measurement data (1730), in process P400, imaging data (1740) may be acquired and / or generated by modeling / or simulation similar to that in process P100. Depending on the measurement of each mirror of the pupil facet mirror, the image data per mirror may vary, for example, as a function of the intensity of the pupil facet mirror. For example, if the mirror has an intensity of 0, no image may be generated, and if the mirror has a low intensity, the image may be distorted or other variations may be observed in the image data of each image corresponding to the pupil facet mirror. When these imaging data are superimposed, they generate a raw field aerial image, which may not match the reference image. Based on this imaging data (1740), the performance (1742) of the device (e.g., CD) may be measured and / or acquired. This performance may differ from the reference performance (1720).

[0141] Additionally, in process P500, the difference between the performance (1742) and the reference performance (1720) may be calculated and / or obtained. Based on the difference, in process P600, a matching pupil (1760) may be determined. To reduce, preferably minimize, the difference between the performance and the reference performance, the determination of the matching pupil (1760) may include adjustment / correction for one or more mirrors in the list of mirrors. Process P600 may be an iterative process (similar to process P50 discussed above) that includes several optimization steps during the simulation process.

[0142] In each iteration, process P600 may include changing one or more degrees of freedom of the pupil facet mirror and calculating the current aerial image and current performance through modeling / simulation based on the changed pupil facet mirror. Additionally, the current difference between the current performance and the reference performance may be determined. In the embodiment, for each iteration, the change may include adjustment / correction of the orientation of one or more mirrors (e.g., x / y coordinates, tilt, etc.) of the mirrors having a low intensity to zero intensity, and the current CD may be determined for the change. Then, based on the CD, the difference between the calculated CD and the reference CD may be obtained. Additionally, from these iterations, a list of mirrors having the minimum CD difference may be selected as the matching pupil (1760) in a manner similar to that discussed for process P50 above. In the embodiment, the optimization or selection of the list of mirrors may be based on a Monte Carlo or Branch Bound algorithm.

[0143] Furthermore, the above method may include a process for adjusting the performance of the device based on the matching pupil of the device in the patterning process. For example, adjustment of critical dimensions or overlays may be performed by changing the intensity of one or more mirrors of the device according to the matching pupil determined herein.

[0144] FIGS. 12a and 12b respectively illustrate an exemplary reference pupil (1802) on a pupil facet mirror (1800) (e.g., of a reference device) and a matching pupil (1812) on a pupil facet mirror (1810) (e.g., of a device). In FIG. 12a, the reference pupil (1802) may comprise a mirror array having most of the mirrors having high intensity (e.g., about 100%), excluding mirrors (M24, M25, M26, M27, M34, M37, M44, M47, M54, M55, M56, and M57) having intensity of about 0 (i.e., dark). Such a reference pupil can generate reference performance as previously discussed in relation to FIGS. 10 and 11.

[0145] However, after performing the method of FIG. 10 and / or FIG. 11, a matching pupil (e.g., matching pupil (1812)) that enables matching with reference performance may be generated. The matching pupil may be different from the reference pupil (1812) or (e.g., under ideal conditions) may not be. The matching pupil (1812) appears different from the reference pupil (1802). The matching pupil (1812) may include most mirrors having high intensity (e.g., 1), mirrors (M22, M23, M37, M38, M47 and M48) having medium intensity (e.g., within the range of 40% to 60% or generally lower than high intensity but greater than 0), and mirrors (M24, M25, M26, M27, M34, M44, M54, M55, M56 and M57) may have an intensity of about 0 (i.e., dark). As shown in the example, the creation of the matching pupil (1812) resulted in a change in intensity of some mirrors (i.e., M22, M23, M37, M38, M47, M48) compared to the reference pupil (1802).

[0146] In an embodiment, a method for reducing changes in device performance is provided. The method comprises: (i) a reference performance of a reference device; (ii) an initial set of preceding degrees of freedom selected from a plurality of degrees of freedom of a plurality of pupil facet mirrors of a device selected to reproduce the reference performance; and (iii) obtaining exposure data related to one or more parameters of a patterning process representing the performance of the device based on the initial set of preceding degrees of freedom; and determining a matching pupil of the device by a computer system based on the initial set of preceding degrees of freedom and the exposure data such that the matching pupil reduces the difference between the performance of the device and the reference performance.

[0147] In the embodiment, the matching pupil is a subset and / or whole set of multiple pupil facet mirrors corresponding to an initial preceding set of degrees of freedom.

[0148] In an embodiment, the determination of the matching pupil is an iterative process, and the iteration includes changing one or more degrees of freedom of a preceding set of degrees of freedom of a plurality of pupil facet mirrors based on the difference between the performance of the device and the reference performance; obtaining the current performance from exposure data corresponding to the changed pupil facet mirror; and determining the current difference between the current performance and the reference performance.

[0149] In the embodiments, changing one or more degrees of freedom includes changing the orientation and / or intensity of one or more mirrors corresponding to a preceding set of degrees of freedom.

[0150] In an embodiment, an initial set of degrees of freedom is selected based on the sensitivity of each degree of freedom of the degrees of freedom of the plurality of pupil facet mirrors of the device to reproduce reference performance. In an embodiment, the initial set of degrees of freedom is a subset and / or whole set of degrees of freedom of the plurality of pupil facet mirrors of the device that matches the reference performance.

[0151] In the example, exposure data is acquired for a linear combination of an initial preceding set of degrees of freedom.

[0152] In the embodiments, the reference performance is the performance of the device and a reference device different from the device. In the embodiments, the reference performance is the performance of the device determined at a specific time in the patterning process. In the embodiments, the performance of the device and the reference performance of the reference device are related to parameters of the patterning process including critical dimensions and / or overlays.

[0153] In the embodiment, the matching pupil minimizes the difference between the device's performance and the reference performance.

[0154] In an embodiment, the present method further includes adjusting the performance of the device based on the matching pupil of the device in the patterning process.

[0155] In the example, the device for the patterning process is a lithography device.

[0156] Furthermore, according to an embodiment, a method for reducing a change in device performance is provided. The method comprises (i) obtaining a reference performance of a reference device and (ii) obtaining a pupil measurement of a mirror of a plurality of pupil facet mirrors of the device at the substrate level; determining imaging data based on the pupil measurement and performance based on the imaging data by a computer system; and determining a matching pupil of the device by a computer system such that the matching pupil reduces the difference between the performance of the device and the reference performance.

[0157] In an embodiment, the determination of the matching pupil is an iterative process, and the iteration includes changing one or more degrees of freedom of a plurality of pupil facet mirrors; calculating the current aerial image and current performance through modeling / simulation based on the changed pupil facet mirrors; and determining the current difference between the current performance and the reference performance.

[0158] In the embodiments, changing one or more degrees of freedom includes changing the orientation and / or intensity of one or more mirrors of a plurality of pupil facet mirrors.

[0159] In the examples, pupil measurement includes the intensity and / or orientation of one or more mirrors of a plurality of pupil facet mirrors.

[0160] In an embodiment, reference performance is measured from reference imaging data for a reference device, and the reference device is different from the device. In an embodiment, reference performance is measured from reference imaging data for the device, determined at a specific time of the patterning process.

[0161] In an embodiment, reference imaging data is generated by overlapping aerial images of each mirror of a plurality of pupil facet mirrors.

[0162] In the examples, the aerial image is generated by modeling and / or simulation of the raw field position at the substrate level.

[0163] In an embodiment, imaging data is generated by overlapping aerial images of each mirror of a plurality of pupil facet mirrors, and the aerial image is calculated based on intensity measurements of each mirror of the plurality of pupil facet mirrors.

[0164] In the embodiments, performance and reference performance are related to parameters of the patterning process including critical dimensions and / or overlays.

[0165] In the embodiment, the matching pupil minimizes the difference between the device's performance and the reference performance.

[0166] In an embodiment, the present method further includes adjusting the performance of the device based on the matching pupil of the device in the patterning process.

[0167] In the example, the device for the patterning process is a lithography device.

[0168] FIG. 13 is a block diagram illustrating a computer system (100) that can help implement the method and flow disclosed herein. The computer system (100) includes a bus (102) or other communication mechanism for transmitting information, and a processor (104) (or a plurality of processors (104, 105)) connected to the bus (102) to process information. The computer system (100) also includes a main memory (106), such as random access memory (RAM) or other dynamic storage device, connected to the bus (102) to store instructions and information to be executed by the processor (104). The main memory (106) may also be used to store temporary variables or other intermediate information during the execution of instructions to be executed by the processor (104). The computer system (100) further includes a read-only memory (ROM) (108) or other static storage device connected to the bus (102) to store static information and instructions for the processor (104). A storage device (110), such as a magnetic disk or an optical disk, is provided to store information and commands and is connected to a bus (102).

[0169] A computer system (100) may be connected via a bus (102) to a display (112), such as a cathode ray tube (CRT) or a flat panel or touch panel display, to display information to a computer user. An input device (114), including alphanumeric keys and other keys, is connected to the bus (102) to transmit information and command selections to a processor (104). Another type of user input device is a cursor control unit (116), such as a mouse, trackball, or cursor direction key, for transmitting directional information and command selections to the processor (104) and for controlling cursor movement on the display (112). This input device typically has two degrees of freedom on two axes, namely a first axis (e.g., x) and a second axis (e.g., y), which allow the device to specify a position within a plane. A touch panel (screen) display may also be used as an input device.

[0170] According to an embodiment, parts of the process may be performed by a computer system (100) in response to a processor (104) that executes one or more sequences of one or more instructions contained in main memory (106). These instructions may be read into main memory (106) from another computer-readable medium, such as a storage device (110). Execution of the sequence of instructions contained in main memory (106) causes the processor (104) to perform the process steps described in the specification. One or more processors in a multiprocessing array may also be used to execute the sequence of instructions contained in main memory (106). In an alternative embodiment, hard-wired circuits may be used instead of or in combination with software instructions. Accordingly, the description in this specification is not limited to any specific combination of hardware circuits and software.

[0171] The term “computer-readable medium” as used herein refers to any medium that participates in providing instructions to the processor (104) for execution. Such media may take many forms, including but not limited to non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks such as storage devices (110). Volatile media include dynamic memory such as main memory (106). Transmission media include coaxial cables, copper wires, and optical fibers, including wires that include a bus (102). Transmission media may also take the form of acoustic waves or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communication. Common forms of computer-readable media include, for example, floppy disks, flexible disks, hard disks, magnetic tapes, any other magnetic media, CD-ROMs, DVDs, any other optical media, punch cards, paper tapes, any other physical media having a pattern of holes, RAM, PROM and EPROM, FLASH-EPROM, any other memory chip or cartridge, carriers as described below, or any other media that can be read by a computer.

[0172] Various types of computer-readable media may be involved in transporting one or more sequences of one or more instructions to the processor (104) for execution. For example, the instructions may initially be borne on a magnetic disk of a remote computer. The remote computer may load the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to the computer system (100) may receive data over the telephone line and convert the data into an infrared signal using an infrared transmitter. An infrared detector connected to the bus (102) may receive the data transmitted as an infrared signal and place the data on the bus (102). The bus (102) transmits the data to the main memory (106), and the processor (104) retrieves and executes the instructions from the main memory. The instructions received by the main memory (106) may be optionally stored in a storage device (110) before or after execution by the processor (104).

[0173] The computer system (100) also preferably includes a communication interface (118) connected to a bus (102). The communication interface (118) provides bidirectional data communication coupling to a network link (120) connected to a local network (122). For example, the communication interface (118) may be an Integrated Services Digital Network (ISDN) card or a modem to provide a data communication connection to a corresponding type of telephone line. As another example, the communication interface (118) may be a Local Area Network (LAN) card to provide a data communication connection to a compatible LAN. A wireless link may also be implemented. In any such implementation, the communication interface (118) transmits and receives electrical, electromagnetic, or optical signals that carry a digital data stream representing various types of information.

[0174] A network link (120) typically provides data communication to another data device through one or more networks. For example, a network link (120) may provide a connection to a host computer (124) or to data equipment operated by an Internet service provider (ISP) (126) through a local network (122). The ISP (126) consequently provides data communication services through a worldwide packet data communication network, which is now commonly referred to as the "Internet" (128). Both the local network (122) and the Internet (128) use electrical, electromagnetic, or optical signals to transmit digital data streams. Signals through various networks transmitting digital data to and from the computer system (100), and signals on the network link (120) and through the communication interface (118), are exemplary forms of carriers that transmit information.

[0175] A computer system (100) can transmit messages containing program code and receive data through network(s), network links (120), and communication interfaces (118). In the Internet example, a server (130) can transmit requested code for an application program through the Internet (128), an ISP (126), a local network (122), and communication interfaces (118). One such downloaded application provides, for example, lighting optimization of the embodiment. The received code can be executed by a processor (104) upon receipt and / or stored in a storage device (110) or other non-volatile storage for subsequent execution. In this way, the computer system (100) can obtain application code in the form of a carrier wave.

[0176] Examples may be further described using the following clauses:

[0177] 1. A method for reducing changes in device performance is,

[0178] (i) reference performance of a reference device, (ii) an initial set of preceding degrees of freedom selected from a plurality of degrees of freedom of a plurality of pupil facet mirrors of a device selected to reproduce the reference performance, and (iii) acquiring exposure data related to one or more parameters of a patterning process representing the performance of the device based on the initial set of preceding degrees of freedom; and

[0179] It includes determining the matching pupil of the device by a computer system based on an initial preceding set of degrees of freedom and exposure data so that the matching pupil reduces the difference between the performance of the device and the reference performance.

[0180] 2. In the method according to Clause 1, the matching pupil is a subset and / or whole set of multiple pupil facet mirrors corresponding to an initial preceding set of degrees of freedom.

[0181] 3. In the method according to either Clause 1 or Clause 2, the determination of the matching pupil is an iterative process, and the iteration is

[0182] Changing one or more degrees of freedom of a preceding set of degrees of freedom of multiple pupil facet mirrors based on the difference between the performance of the device and the reference performance;

[0183] Acquiring current performance from exposure data corresponding to the changed pupil facet mirror; and

[0184] It includes determining the current difference between current performance and reference performance.

[0185] 4. In the method according to Clause 3, changing one or more degrees of freedom includes changing the orientation and / or intensity of one or more mirrors corresponding to the preceding set of degrees of freedom.

[0186] 5. In the method according to any one of clauses 1 to 4, an initial set of preceding degrees of freedom is selected based on the sensitivity of each degree of freedom of the degrees of freedom of a plurality of pupil facet mirrors of the device to reproduce reference performance.

[0187] 6. In a method according to any one of provisions 1 through 5, the initial preceding set of degrees of freedom is a subset and / or whole set of degrees of freedom of a plurality of pupil facet mirrors of the device to reproduce reference performance.

[0188] 7. In the method according to any one of clauses 1 to 6, exposure data is obtained for a linear combination of an initial preceding set of degrees of freedom.

[0189] 8. In the method according to any one of Clauses 1 through 7, the reference performance is the performance of the device and a different reference device.

[0190] 9. In the method according to any one of clauses 1 through 7, the reference performance is the performance of the device determined at a specific time of the patterning process.

[0191] 10. In a method according to any one of provisions 1 through 9, the performance of the device and the reference performance of the reference device are related to parameters of a patterning process including critical dimensions and / or overlays.

[0192] 11. In the method according to any one of Clauses 1 through 10, the matching pupil minimizes the difference between the device's performance and the reference performance.

[0193] 12. The method according to Clause 1 further includes adjusting the performance of the device based on the matching pupil of the device in the patterning process.

[0194] 13. In the method according to Clause 12, the device for the patterning process is a lithography device.

[0195] 14. Methods to reduce changes in device performance are:

[0196] (i) obtaining reference performance of a reference device and (ii) obtaining pupil measurements of a plurality of pupil facet mirrors of the device at the substrate level;

[0197] Determining imaging data based on pupil measurements and performance based on imaging data by a computer system; and

[0198] It includes determining the matching pupil of a device by a computer system so that the matching pupil reduces the difference between the device's performance and the reference performance.

[0199] 15. In the method under Clause 14, the determination of the matching pupil is an iterative process, and the iteration is:

[0200] Changing one or more degrees of freedom of multiple pupil facet mirrors;

[0201] Computing the current aerial image and current performance through modeling / simulation based on the changed pupil facet mirror; and

[0202] It includes determining the current difference between current performance and reference performance.

[0203] 16. In the method according to Clause 15, changing one or more degrees of freedom includes changing the orientation and / or intensity of one or more mirrors of a plurality of pupil facet mirrors.

[0204] 17. In a method according to any one of provisions 14 through 16, the pupil measurement includes the intensity and / or orientation of one or more mirrors of a plurality of pupil facet mirrors.

[0205] 18. In the method according to any one of provisions 14 through 17, the reference performance is measured from reference imaging data for a reference device, and the reference device is different from the device.

[0206] 19. In the method according to any one of provisions 14 through 18, reference performance is measured from reference imaging data for the device determined at a specific time of the patterning process.

[0207] 20. In the method according to either clause 18 or 19, reference imaging data is generated by overlapping aerial images of each mirror of a plurality of pupil facet mirrors.

[0208] 21. In the method according to Clause 20, the aerial image is generated by modeling and / or simulation of the raw field position at the substrate level.

[0209] 22. In the method according to Clause 14, imaging data is generated by overlapping aerial images of each mirror of a plurality of pupil facet mirrors, and the aerial image is calculated based on the intensity measurement of each mirror of a plurality of pupil facet mirrors.

[0210] 23. In a method according to any one of provisions 14 through 22, performance and reference performance are related to parameters of a patterning process including critical dimensions and / or overlays.

[0211] 24. In the method according to any one of provisions 14 through 20, the matching pupil minimizes the difference between the performance of the device and the reference performance.

[0212] 25. The method according to Clause 14 further includes adjusting the performance of the device based on the matching pupil of the device in the patterning process.

[0213] 26. In the method according to Clause 25, the device for the patterning process is a lithography device.

[0214] 27. A computer program product comprises a computer-readable medium having recorded instructions that implement the methods of provisions 1 through 26 when executed by a computer.

[0215] Embodiments of the present invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present invention may also be implemented as instructions stored in 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); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustic, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.) and other media. Additionally, firmware, software, routines, and instructions may be described herein as performing specific operations. However, it should be recognized that such descriptions are merely for convenience and that such operations are actually derived from a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc.

[0216] In the block diagram, the illustrated components are illustrated as individual functional blocks, but embodiments are not limited to systems in which the functions described herein are configured as illustrated. The functions provided by each of the components may be provided by software or hardware modules configured differently from those currently illustrated, and, for example, such software or hardware may be mixed, combined, replicated, separated, distributed (e.g., within a data center or geographically), or otherwise configured differently. The functions described herein may be provided by one or more processors of one or more computers executing code stored on a type of non-transient machine-readable medium. In some cases, a third-party content delivery network may host some or all of the information delivered over the network, in which case the information (e.g., content) may be provided by transmitting a command to retrieve the information from the content delivery network to the extent that the information is supplied or otherwise provided.

[0217] Unless otherwise specifically stated, as is evident from the discussion, it is recognized that throughout this specification, terms such as “processing,” “computing,” “calculation,” “decision,” etc. refer to the operation or process of a specific device, such as a special-purpose computer or a similar special-purpose electronic processing / computation device.

[0218] Readers of this specification should recognize that this application describes several inventions. Instead of separating these inventions into several separate patent applications, the applicants have grouped them into a single document because the subject matter of their invention is suitable for saving costs in the filing process. However, the distinct advantages and aspects of these inventions should not be combined. It should be understood that while in some cases the embodiments address all the defects mentioned in this specification, the inventions are useful independently, and some embodiments address only a subset of these problems or provide other unmentioned advantages that would be apparent to a person skilled in the art reviewing the invention. Due to cost constraints, some inventions disclosed in this specification may not be claimed at present and may be claimed in a future application, such as a continuation application, or by amending the claims. Similarly, due to space constraints, the Abstract or Summary sections of this document should not be construed as containing a comprehensive list of all such inventions or all aspects of such inventions.

[0219] It should be understood that the description and drawings are not intended to limit the invention to the specific form disclosed, but on the contrary, to include all variations, equivalents, and alternatives within the technical spirit and scope of the invention as defined by the appended claims.

[0220] Variations and alternative embodiments of various aspects of the present invention will be apparent to those skilled in the art by consideration of this description. Accordingly, this description and drawings are to be interpreted merely as illustrative and intended to teach those skilled in the art a general manner of carrying out the present invention. The forms of the present invention shown and described herein should be understood as being taken as examples of embodiments. Elements and materials may be substituted for those shown and described herein, parts and processes may be reversed, changed in order, or omitted, specific features may be used independently, and embodiments or features of embodiments may be combined, as will be apparent to those skilled in the art after taking advantage of this description of the present invention. Modifications to the elements described herein may be made without departing from the spirit and scope of the present invention as described in the following claims. Headings used herein are for configuration purposes only and are not intended to be used to limit the scope of the description.

[0221] As used throughout this application, the word "may" is used in a sense of permission (i.e., having the possibility) rather than in a sense of obligation (i.e., having to). Words such as "include" and "include" mean that they include, but are not limited to. As used throughout this application, the singular forms "a," "an," and "the" include multiple objects unless the content explicitly indicates otherwise. Thus, for example, a reference to an element of "one" includes a combination of two or more elements, despite the use of other terms and phrases for one or more elements such as "one or more." Unless otherwise specified, the term "or" is non-exclusive, i.e., encompasses both "and" and "or." Terms describing conditional relationships, such as "in response to X, Y," "when X, Y," "if X, Y," and "in the case of X, Y," encompass causal relationships where the antecedent is a necessary causal condition, a sufficient causal condition, or a contributing causal condition of the result; for example, "when condition Y is obtained, state X occurs" is general to "X occurs only in Y" and "X occurs in Y and Z." Because some results may be delayed, these conditional relationships are not limited to the result immediately following the obtained antecedent; in conditional statements, the antecedent is linked to the result, for example, the antecedent is related to the probability of the result occurring.A statement that multiple attributes or functions map to multiple objects (e.g., one or more processors performing steps A, B, C, and D) encompasses, unless otherwise indicated, both that all such attributes or functions map to all such objects and that a subset of attributes or functions maps to a subset of attributes or functions (e.g., all processors each performing steps A through D, and both cases where processor 1 performs step A, processor 2 performs part of steps B and C, and processor 3 performs part of step C and step D). Furthermore, unless otherwise indicated, a statement that one value or action “is based” on another condition or value encompasses both cases where the condition or value is a single instance and cases where the condition or value is one of multiple instances. Unless otherwise indicated, a statement that "each" case of a collection has some property should not be read as excluding cases where some other identical or similar members of the larger collection do not have that property; that is, "each" does not necessarily mean "each and every."

[0222] To the extent that a given U.S. patent, U.S. patent application, or other material (e.g., paper) is cited, the text of such U.S. patent, U.S. patent application, and other material is cited only to the extent that there is no conflict between such material and the descriptions and drawings set forth in this specification. In the event of such a conflict, any such conflicting content in such cited U.S. patent, U.S. patent application, and other material is not specifically cited in this specification.

[0223] Although specific embodiments of the present invention have been described above, it will be recognized that the embodiments may be practiced differently from those described.

Claims

Claim 1 A method comprising: (i) obtaining a reference performance and (ii) obtaining a pupil measurement specific to one or more of the multiple pupil facet mirrors from one or more of the multiple pupil facet mirrors of the device, wherein the pupil measurement is a measurement of radiation emitted from a projection system configured to project radiation received from a patterning device, and wherein the patterning device is configured to receive radiation from a lighting system and generate patterned radiation; determining imaging data based on the pupil measurement and performance based on the imaging data by a computer system; and determining the pupil of the device by a computer system such that the pupil reduces the difference between the performance of the device and the reference performance. Claim 2 A method according to claim 1, wherein the determination of the pupil is an iterative process, and the iteration comprises: changing one or more degrees of freedom of the plurality of pupil facet mirrors; calculating the current performance based on the changed one or more degrees of freedom of the plurality of pupil facet mirrors and through modeling and / or simulation; and determining the current difference between the current performance and the reference performance. Claim 3 A method according to paragraph 2, wherein changing one or more degrees of freedom includes changing the orientation and / or intensity of one or more of the plurality of pupil facet mirrors. Claim 4 A method according to claim 1, wherein the pupil measurement comprises the intensity and / or orientation of one or more of the plurality of pupil facet mirrors. Claim 5 In paragraph 1, the reference performance is obtained from reference imaging data for a reference device, and the reference device is a different method from the device. Claim 6 In claim 1, the reference performance is a method obtained from reference imaging data for the device determined at a specific time of the patterning process. Claim 7 In claim 1, the reference performance is a method generated from the overlap of aerial images of each mirror of the plurality of pupil facet mirrors. Claim 8 In claim 7, the aerial image is generated by modeling and / or simulation of the raw field position at the substrate level. Claim 9 In claim 1, the imaging data is generated by overlapping aerial images of each mirror of a plurality of pupil facet mirrors, and each aerial image is calculated based on the intensity measurement of each mirror. Claim 10 A method according to claim 1, wherein the performance of the device and the reference performance are related to parameters of the patterning process including critical dimensions and / or overlay. Claim 11 In claim 1, the determined pupil is a method for minimizing the difference between the performance of the device and the reference performance. Claim 12 A method according to claim 1, further comprising adjusting the performance of the device based on the determined pupil. Claim 13 In paragraph 12, the device of the patterning process is a lithography device. Claim 14 A non-transient computer-readable, non-volatile medium storing a computer program, wherein the computer program includes instructions, and the instructions implement any one of the methods of claims 1 to 13 when executed by a computer.

Images