Method for controlling patterning process, device manufacturing method

Abstract

A method of controlling a patterning process is disclosed. In one arrangement, tilt data is obtained from a measurement of a tilt in an etch path through a target layer of a structure on a substrate. The tilt indicates a deviation of the direction of the etch path from a perpendicular line to the plane of the target layer. The tilt data is used to control a patterning process for forming a pattern in a further layer.

Description

[0001] Notes on divisional applications

[0002] This application is a divisional application of an application with application number 201880060107.1, filed on August 8, 2018, and invention name “Method for controlling patterning process, device manufacturing method”. Technical Field

[0003] The present specification relates to a method of controlling a patterning process and a method of manufacturing a device. Background Art

[0004] A lithographic apparatus is a machine that applies a desired pattern to a substrate (usually to a target portion of a substrate). A lithographic apparatus may be used, for example, in the manufacture of an integrated circuit (IC) or other device designed to have a certain function. In that case, a patterning device, alternatively referred to as a mask or reticle, may be used to generate a circuit pattern to be formed on an individual layer of a device designed to have a certain function. The pattern may be transferred to a target portion (e.g., a portion including one or several dies) on a substrate (e.g., a silicon wafer). The transfer of the pattern is usually via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are patterned in succession. Known lithographic apparatus include: a so-called stepper, in which each target portion is irradiated by exposing the entire pattern to the target portion at once; and a so-called scanner, in which each target portion is irradiated by scanning the pattern in a given direction by a radiation beam while simultaneously scanning the substrate parallel to or antiparallel to the direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate. Summary of the invention

[0005] Manufacturing equipment such as semiconductor devices typically involves processing a substrate (e.g., a semiconductor wafer) using a number of manufacturing processes to form various features and typically multiple layers of the device. Such layers and / or features are typically manufactured and processed using, for example, deposition, lithography, etching, chemical mechanical polishing, and ion implantation. Multiple devices can be manufactured on multiple dies on a substrate and then separated into individual devices. The device manufacturing process can be considered a patterning process. The patterning process involves a pattern transfer step, such as optical and / or nanoimprint lithography using a lithographic apparatus, to provide a pattern on a substrate, and typically, optionally, involves one or more related pattern processing steps, such as resist development by a development apparatus, baking of the substrate using a baking tool, etching of the pattern by an etching apparatus, and the like. In addition, one or more metrology processes are involved in the patterning process.

[0006] Metrology processes are used at various steps during the patterning process to monitor and / or control the process. For example, metrology processes are used to measure one or more characteristics of a substrate, such as relative positions (e.g., registration, notching, alignment, etc.) or dimensions (e.g., line width, critical dimension (CD), thickness, etc.) of features formed on the substrate during the patterning process, so that, for example, the performance of the patterning process can be determined based on the one or more characteristics. If one or more characteristics are unacceptable (e.g., outside a predetermined range for (the one or more characteristics)), one or more variables of the patterning process can be designed or modified, for example, based on the measurement results of the one or more characteristics, so that the substrate manufactured by the patterning process has (the one or more) acceptable characteristics.

[0007] With the advancement of photolithography and other patterning process technologies, over the decades, the size of functional elements has been constantly reduced while the amount of functional elements such as transistors of each device has been steadily increased. The requirements for accuracy in engraving sleeves, critical dimensions (CD), etc. have become increasingly stringent. Errors such as errors in engraving sleeves, errors in CD, etc. will inevitably arise in the patterning process. For example, imaging errors can arise from optical aberrations, patterning device heating, patterning device errors, and / or substrate heating and can be characterized in, for example, engraving sleeves, CD, etc. Additionally, errors can be introduced into other parts of the patterning process such as during the etching step.

[0008] It is desirable to reduce errors in patterning processes used to manufacture semiconductor devices.

[0009] According to one aspect, a method for controlling a patterning process is provided, comprising: obtaining tilt data obtained from measuring a tilt in an etch path through a target layer of a structure on a substrate, the tilt representing a deviation of a direction of the etch path from a perpendicular line to a plane of the target layer; and using the tilt data to control a patterning process for forming a pattern in another layer.

[0010] According to one aspect, a device manufacturing method is provided, comprising: forming a structure including a target layer on a substrate; obtaining tilt data obtained from measuring a tilt in an etching path passing through the target layer, the tilt representing a deviation of a direction of the etching path from a perpendicular line to a plane of the target layer; and using the tilt data to control a patterning process for forming a pattern in another layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Embodiments will now be described, by way of example only, with reference to the accompanying schematic drawings, in which corresponding reference numerals indicate corresponding parts:

[0012] Figure 1 The photolithographic apparatus is depicted;

[0013] Figure 2 Describes the use Figure 1 lithography equipment and other equipment to form production facilities for semiconductor devices;

[0014] Figure 3A is a schematic diagram of a measurement apparatus for use in measuring a target according to one embodiment using a first pair of illumination apertures providing certain illumination patterns;

[0015] Figure 3B is a schematic detail of the diffraction spectrum of a target for a given illumination direction;

[0016] Figure 3C is a schematic illustration of a second pair of illumination apertures providing an additional illumination mode in using the measurement device for diffraction-based overlay measurement;

[0017] Figure 3D is a schematic illustration of a third pair of illumination apertures combining the first pair of apertures and the second pair of apertures to provide an additional illumination mode in using the measurement device for diffraction-based overlay measurement;

[0018] Figure 4 The form of a plurality of periodic structure (e.g., a plurality of grating) targets on a substrate and the profile of a measurement spot are schematically depicted;

[0019] Figure 5 The method obtained in the apparatus of FIG. 3 is schematically depicted. Figure 4 An image of the target;

[0020] Figure 6 Examples of metering devices and metering techniques are schematically depicted;

[0021] Figure 7 An example of a metering device is schematically depicted;

[0022] Figure 8 The diagram shows the relationship between the irradiation spot of the metering device and the metering target;

[0023] Fig. 9 schematically depicts the process of driving one or more variables of interest based on measured data;

[0024] Fig. 10A schematically depicts an example unit cell, an associated pupil representation, and an associated derived pupil representation;

[0025] Fig. 10B schematically depicts an example unit cell, an associated pupil representation, and an associated derived pupil representation;

[0026] Fig. 10Cschematically depicts an example target comprising one or more physical instances of a unit cell;

[0027] Fig.11 Schematically illustrates the sources of etching-induced overlay errors;

[0028] Fig.12 The tilt of the etch path through the target layer is depicted;

[0029] Fig.13 Describes the process of shifting the upper layer to Fig.12 Compensation for tilt;

[0030] Fig.14 Describes the effect of shifting the lower layer Fig.12 Compensation for tilt;

[0031] Fig.15 Describes the effects of controlling the etching process or stress distribution in the target layer or surrounding layers. Fig.12 Removal of tilt;

[0032] Figures 16 to 18 depicts the stages in an etching process that includes multiple steps;

[0033] Fig.19 Depicts the pronounced notching caused by a tilt in the etch path through a layer above the target layer;

[0034] Fig. 20 Comparison of control with (left) and without (right) direct measurement of the tilt in the target layer. Figures 16 to 18 The result of etching the target layer during the etching process; and

[0035] Fig.21 A computer system is schematically depicted upon which embodiments of the present disclosure may be implemented. DETAILED DESCRIPTION

[0036] Before describing embodiments of the invention in detail, it is instructive to present an example environment in which embodiments of the invention may be implemented.

[0037] Figure 1 A lithographic apparatus LA is schematically depicted. The apparatus comprises:

[0038] An illumination system (illuminator) IL is configured to condition a radiation beam B (eg, UV radiation or EUV radiation).

[0039] a support structure (e.g., mask table) MT constructed to support a patterning device (e.g., mask or reticle) MA and connected to a first positioner PM configured to accurately position the patterning device according to certain parameters;

[0040] a substrate structure (eg, wafer table) WT configured to hold a substrate (eg, a resist coated wafer) W and connected to a second positioner PW configured to accurately position the substrate according to certain parameters; and

[0041] A projection system (eg, a refractive projection lens system) PS is configured to project a pattern imparted to the radiation beam B by patterning the device MA onto a target portion C of the substrate W (eg, comprising one or more dies).

[0042] The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping or controlling the radiation.

[0043] The support structure supports (i.e., bears) the weight of the patterning device. It holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions (such as whether the patterning device is held in a vacuum environment). The support structure can ensure that the patterning device is at a desired position, for example, relative to a projection system. Any use of the term "reticle" or "mask" herein may be considered synonymous with the more general term "patterning device."

[0044] The term "patterning device" as used herein should be broadly interpreted as referring to any device that can be used to impart a pattern to a radiation beam in a cross section of the radiation beam to create a pattern in a target portion of a substrate. It should be noted that the pattern imparted to the radiation beam may not correspond exactly to the desired pattern in the target portion of the substrate, for example, if the pattern indicates a phase-shifting feature or a so-called assist feature. In general, the pattern imparted to the radiation beam will correspond to a specific functional layer in a device (or many devices) created in a target portion (such as an integrated circuit). Patterning devices can be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels.

[0045] The term "projection system" as used herein should be interpreted broadly to encompass any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, depending on the exposure radiation being used or other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term "projection lens" herein may be considered synonymous with the more general term "projection system".

[0046] As depicted herein, the device is of the transmissive type (eg, employing a transmissive mask). Alternatively, the device may be of the reflective type (eg, employing a programmable mirror array as one of the types mentioned above, or employing a reflective mask).

[0047] The lithographic apparatus may be of a type having two (dual stage) or more substrate tables (and / or two or more mask tables). In such a "multi-stage" machine, additional tables may be used in parallel, or preparatory steps may be performed on one or more tables while one or more other tables are being used for exposure.

[0048] The lithographic apparatus may also be of a type in which at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, such as water, so as to fill the space between the projection system and the substrate. Immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of a projection system. The term "immersion" as used herein does not mean that structures such as substrates must be submerged in liquid, but rather simply means that the liquid is located between the projection system and the substrate during exposure.

[0049] The illuminator IL receives a radiation beam from a radiation source SO. The source and the lithographic apparatus may be separate entities, for example when the source is an excimer laser. In such a case, the source is not considered to form part of the lithographic apparatus, and the radiation is transferred from the source SO to the illuminator IL with the aid of a beam delivery system BD comprising, for example, appropriate directing mirrors and / or a beam expander. In other cases, for example when the source is a mercury lamp, the source may be an integral part of the lithographic apparatus. The source SO and the illuminator IL and the beam delivery system BD may be referred to as a radiation system where necessary.

[0050] The illuminator IL may include an adjuster AD for adjusting the angular density distribution of the radiation beam. In general, at least the outer radial extent and / or the inner radial extent (collectively referred to as σ-outer and σ-inner, respectively) of the density distribution in a pupil plane of the illuminator may be adjusted. In addition, the illuminator IL may include various other components, such as an integrator IN and a condenser CO. The illuminator may be used to adjust the radiation beam to have a desired uniformity and density distribution in its cross-section.

[0051] The radiation beam B is incident on a patterning device (e.g. a mask MA), which is held on a support structure (e.g. a mask table MT) and is patterned by the patterning device. Having traversed the mask MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target position C on a substrate W. With the aid of a second positioner PW and a position sensor IF (e.g. an interferometer device, a linear encoder or a capacitive sensor), the substrate table WTa / WTb is accurately moved, for example in order to position different target positions C in the path of the radiation beam B. Similarly, a first positioner PM and a further position sensor (which is not explicitly depicted in FIG. 1 ) are provided. Figure 1The mask table MT is used to accurately position the mask MA relative to the path of the radiation beam B, for example after mechanical retrieval from a mask library or during scanning. In general, the movement of the mask table MT can be achieved with the help of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, the movement of the substrate table WTa / WTb can be achieved using a long-stroke module and a short-stroke module, which form part of the second positioner PM. In the case of a stepper (as opposed to a scanner), the mask table MT can be connected only to the short-stroke actuator, or can be fixed. The mask MA and the substrate W can be aligned using alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks as shown occupy dedicated target portions, they can be located in the space between target portions (fields) and / or between device areas (die) within the target portions. They are called scribe line alignment marks because individual product dies will eventually be cut from each other by dicing along these lines. Similarly, in cases where more than one die is provided on mask MA, mask alignment marks may be located between the dies.

[0052] The depicted device can be used in at least one of the following modes:

[0053] 1. In step mode, the mask table MT and substrate table WT are held substantially fixed while an entire pattern imparted to the radiation beam is projected at one time (i.e. a single static exposure) onto a target portion C. The substrate table WT is then shifted in the X and / or Y direction so that a different target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure.

[0054] 2. In scan mode, the mask table MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam (i.e. a single dynamic exposure) is projected onto a target portion C. The speed and direction of the substrate table WT relative to the mask table MT may be determined by the (de)magnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field is limited to the width (in the non-scanning direction) of the target portion in a single dynamic exposure, whereas the length of the scanning movement determines the height (in the scanning direction) of the target portion.

[0055] 3. In another mode, the mask table MT remains substantially fixed to hold the programmable patterning device, and the substrate table WT is moved or scanned whilst a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, typically a pulsed radiation source is employed and the programmable patterning device is updated as required after each movement of the substrate table WT or between successive radiation pulses during a scan. This mode of operation can readily be applied to maskless lithography which utilises a programmable patterning device such as a programmable mirror array of the type mentioned above.

[0056] Combinations and / or variations on the above-described modes of use or entirely different modes of use may also be employed.

[0057] A so-called dual-stage lithography apparatus having a substrate table and two stations (an exposure station and a measuring station, between which the substrate table can be exchanged). While one substrate on one substrate table is exposed at the exposure station, another substrate is loaded onto the other substrate table at the measuring station so that various preparation steps can be performed. The preparation steps may include using a height sensor to map the surface height of the substrate and using an alignment sensor to measure the position of an alignment mark on the substrate. Measurement is time-consuming, and the provision of two substrate tables enables a substantial increase in the throughput of the apparatus. If the position sensor IF cannot measure the position of the substrate table at the same time as it is at the measuring station and at the exposure station, a second position sensor may be provided so that the position of the substrate table can be tracked at both stations.

[0058] The device also includes a lithography device control unit LACU 206, which controls all movements and measurements of the various actuators and sensors described. LACU also includes signal processing and data processing capabilities to implement the desired calculations related to the operation of the device. In practice, the control unit LACU will be implemented as a system of many subunits, each processing real-time data acquisition, processing and control of the subsystems or components in the device. For example, a processing subsystem can be dedicated to the servo control of the substrate positioner PW. A separate unit can handle rough and fine actuators or different axes. Another unit can be dedicated to the readout of the position sensor IF. The overall control of the device can be controlled by a central processing unit communicating with these subsystem processing units, with an operator and with other devices involved in the lithography manufacturing process.

[0059] Figure 2At 200 is shown a lithography apparatus LA in the context of an industrial production facility for semiconductor products. Within the lithography apparatus (or simply "lithography tool" 200), a measurement station MEA is shown at 202 and an exposure station EXP is shown at 204. A control unit LACU is shown at 206. Within the production facility, the apparatus 200 forms part of a "lithography cell" or "lithography cluster" which also includes a coating device 208 for applying photoresist and other coatings to substrates W for patterning by the apparatus 200. On the output side of the apparatus 200, a baking device 210 and a developing device 212 are provided for developing the exposed pattern into a physical resist pattern.

[0060] Once the pattern has been applied and developed, the patterned substrate 220 is transferred to other processing devices such as those illustrated at 222, 224, and 226. A wide range of processing steps are implemented by various devices in common manufacturing facilities. In this embodiment, device 222 is an etching station, and device 224 performs post-etching cleaning and / or annealing steps. Additional physical and / or chemical processing steps are applied in additional devices 226, etc. Many types of operations may be required to make a real device, such as deposition of materials, modification of surface material properties (oxidation, doping, ion implantation, etc.), chemical mechanical polishing (CMP), etc. Device 226 can actually represent a series of different processing steps performed in one or more devices.

[0061] As is well known, the manufacture of semiconductor devices involves many repetitions of such a process to build up a device structure with suitable materials and patterns layer by layer on a substrate. Thus, the substrates 230 that arrive at the lithography cluster may be newly prepared substrates, or they may be substrates that have been previously processed in the cluster or in another device entirely. Similarly, depending on the desired processing, substrates 232 that leave device 226 may be returned for subsequent patterning operations in the same lithography cluster, they may go to patterning operations in a different cluster, or they may be finished products (substrates 234) to be sent for sawing and packaging.

[0062] Each layer of the product structure requires a different set of processing steps, and the equipment 226 used in each layer can be completely different in type. In addition, different layers require different etching processes, such as chemical etching, plasma etching, depending on the details of the material to be etched and special requirements (such as anisotropic etching).

[0063] The preceding and / or subsequent processes may be performed in other lithography apparatuses as just mentioned, and may be performed in different types of lithography apparatuses. For example, some layers in the device manufacturing process that have high requirements on parameters such as resolution and overlay may be performed with more advanced lithography tools than other layers with smaller requirements. Thus, some layers may be exposed with immersion lithography tools, while other layers are exposed with "dry" tools. Some layers are exposed with tools operating at DUV wavelengths, while other layers are exposed with EUV wavelength radiation.

[0064] The entire facility may operate under the control of a supervisory control system 238, which receives metrology data, design data, process recipes, etc. Supervisory control system 238 issues commands to each of the devices to perform a manufacturing process on one or more batches of substrates.

[0065] exist Figure 2 Also shown in , is a metrology device 240, which is provided for making measurements of parameters of a product at a desired stage in the manufacturing process. A common example of a metrology device in a modern lithography production facility is a scatterometer, such as an angle-resolved scatterometer or a spectral scatterometer, and which can be applied to measure the properties of a developed substrate at 220 before an etching device 222. Using the metrology device 240, it can be determined that, for example, important performance parameters such as the etch cap or critical dimension (CD) do not meet specified accuracy requirements in the developed resist. Prior to the etching step, there is an opportunity to strip the developed resist and reprocess the substrate 220 through the lithography cluster. As is also known, the metrology results 242 from the device 240 can be used in an advanced process control (APC) system 250 to generate a signal 252 by making small adjustments over time through the control unit LACU 206 to maintain accurate execution of patterning operations in the lithography cluster, thereby minimizing the risk of out-of-specification products and requiring rework. The metrology device 240 and / or other metrology devices (not shown) may be employed to measure properties of the processed substrates 232 , 234 and the incoming substrate 230 .

[0066] The advanced process control (APC) system 250 can, for example, be configured to calibrate individual lithography devices and allow different devices to be used more interchangeably. Improvements in the focus and engraving (layer-to-layer alignment) uniformity of the device have recently been achieved by implementing a stability module, resulting in an optimized process window for a given feature size and chip application, thereby enabling the continued creation of smaller, more advanced chips. In one embodiment, the stability module automatically resets the system to a predefined baseline at regular intervals (e.g., every day). More details of lithography and metrology methods including stability modules can be found in US2012008127A1.

[0067] To achieve metrology, one or more targets may be provided on the substrate. In an embodiment, the target is specially designed and may include a periodic structure. In an embodiment, the target is part of a device pattern, such as a periodic structure of a device pattern. In an embodiment, the device pattern is a periodic structure of a memory device (e.g., a bipolar transistor (BPT), a shared bit bus (BLC), etc. structure).

[0068] In an embodiment, the target on the substrate may include one or more 1-D periodic structures (e.g., gratings) that are printed such that, after development, the periodic structural features are formed by solid resist lines. In an embodiment, the target may include one or more 2-D periodic structures (e.g., gratings) that are printed such that, after development, the periodic structural features are formed by solid resist posts or vias in the resist. The bars, posts, or vias may alternatively be etched into the substrate (e.g., into one or more layers on the substrate).

[0069] In an embodiment, one of the parameters of interest of the patterning process is the engraving. The engraving can be measured using a dark field scatterometer, wherein the zero-order diffraction (corresponding to the specular reflection) is blocked and only higher orders are processed. Examples of dark field scatterometers can be found in PCT patent application publications WO 2009 / 078708 and WO 2009 / 106279, which are incorporated herein by reference in their entirety. Further developments of the present technology have been described in U.S. Patent Application Publications US2011-0027704, US2011-0043791, and US2012-0242970, which are incorporated herein by reference in their entirety. Diffraction-based engraving using dark field detection of these diffraction orders enables engraving measurements to be performed on smaller targets. These targets can be smaller than the irradiation spot and can be surrounded by the device product structure on the substrate. In an embodiment, multiple targets can be measured in one radiation capture.

[0070] exist Figure 3A A metering device suitable for use in an embodiment for measuring, for example, a sleeve is schematically shown in FIG. Figure 3B The target T (comprising a periodic structure such as a grating) and the diffracted rays are illustrated in more detail in . The metrology apparatus may be a stand-alone device or incorporated into the lithography apparatus LA (e.g. at a measuring station or lithography cell). An optical axis having several branches in the whole apparatus is indicated by a dashed line O. In the apparatus, radiation emitted by an output 11 (e.g. a source such as a laser or a xenon lamp or an opening connected to the source) is directed onto a substrate W via a prism 15 by an optical system comprising lenses 12, 14 and an objective lens 16. These lenses are arranged in a double sequence of a 4F arrangement. Different lens arrangements may be used provided that they still provide an image of the substrate onto the detector.

[0071] In an embodiment, the lens arrangement allows access to the intermediate pupil plane for spatial frequency filtering. Therefore, the angular range of radiation incident on the substrate is selected by defining the spatial density distribution in the plane (here called the (conjugate) pupil plane) that presents the spatial spectrum of the substrate plane. In particular, this can be done, for example, by inserting an aperture plate 13 of appropriate form between lenses 12 and 14 in the plane that is the back-projected image of the objective lens pupil plane. In the illustrated example, the aperture plate 13 has different forms, marked as 13N and 13S, allowing different illumination modes to be selected. The illumination system in the current example forms an off-axis illumination mode. In the first illumination mode, the aperture plate 13N provides off-axis illumination from a direction designated as "north" for descriptive purposes only. In the second illumination mode, the aperture plate 13S is used to provide similar illumination, but from the opposite direction marked as "south". Other illumination modes are possible by using different apertures. The rest of the pupil plane is desirably dark, because any unnecessary radiation outside the desired illumination mode may interfere with the desired measurement signal.

[0072] like Figure 3B As shown in , a target T is placed with a substrate W substantially perpendicular to the optical axis O of the objective lens 16. An illumination ray I striking the target T from an angle offset from the axis O produces a zeroth order ray (solid line 0) and two first order rays (dotted line +1 and dotted line -1). With a small, filled target T, these rays are just one of many parallel rays covering the area of ​​the substrate including the metrology target T and other features. Since the aperture in the plate 13 has a finite width (necessary to admit a useful amount of radiation), the incident ray I will actually occupy a certain angular range, and the diffracted rays 0 and +1 / -1 will be slightly spread out. Depending on the point spread function of the small target, each order +1 and -1 will be further spread out over a certain angular range, not a single ideal ray as shown. Note that the periodic structure spacing and the illumination angle can be designed or adjusted so that the first order rays entering the objective are closely aligned with the central optical axis. In Figure 3A and Figure 3B The rays illustrated in are shown slightly off-axis, purely so that they can be more easily distinguished in this figure. At least the 0th and +1st orders diffracted by the target on substrate W are collected by objective lens 16 and directed back through prism 15.

[0073] return Figure 3A, both the first and second illumination modes are illustrated by specifying diametrically opposite apertures labeled North (N) and South (S). When the incident ray I comes from the north of the optical axis, i.e. when the first illumination mode is applied using aperture plate 13N, the +1 diffracted ray, labeled +1 (N), enters objective lens 16. In contrast, when the second illumination mode is applied using aperture plate 13S, the -1 diffracted ray, labeled -1 (S), is the one that enters objective lens 16. Therefore, in an embodiment, the measurement result is obtained by the following operation: measuring the target under certain conditions, for example, rotating the target or changing the illumination mode or changing the imaging mode to obtain the -1 diffraction order intensity and the +1 diffraction order intensity respectively. Comparing these intensities for a given target provides a measure of the asymmetry in the target, and the asymmetry in the target can be used as an indicator of a parameter of the lithography process (e.g., engraving). In the case described above, the illumination mode is changed.

[0074] A beam splitter 17 splits the diffracted beam into two measurement branches. In the first measurement branch, an optical system 18 forms a diffraction spectrum (pupil plane image) of the target on a first sensor 19 (e.g., a CCD or CMOS sensor) using the zero-order and first-order diffracted beams. Each diffraction order hits a different point on the sensor so that image processing can compare and contrast the orders. The pupil plane image captured by the sensor 19 can be used to focus a metrology device and / or normalize intensity measurements. The pupil plane image can also be used for other measurement purposes such as reconstruction, as described further below.

[0075] In the second measurement branch, the optical systems 20, 22 form an image of the target on the substrate W on a sensor 23 (e.g., a CCD or CMOS sensor). In the second measurement branch, an aperture stop 21 is provided in a plane conjugate to the pupil plane of the objective lens 16. The aperture stop 21 is used to block the zero-order diffraction beam so that the image of the target formed on the sensor 23 is formed by the -1 or +1 first-order beam. Data about the image measured by the sensors 19 and 23 are output to a processor and controller PU, the function of which will depend on the specific type of measurement being performed. Note that the term "image" is used in a broad sense. If only one of the -1 and +1 orders is present, an image of periodic structural features (e.g., grating lines) will therefore not be formed.

[0076] The specific forms of aperture plate 13 and stop 21 shown in FIG3 are purely exemplary. In another embodiment, on-axis illumination of the target is used, and an aperture stop with an off-axis aperture is used to pass substantially only one first order diffracted radiation to the sensor. In still other embodiments, 2nd, 3rd and higher order beams (not shown in FIG3 ) may be used in the measurement instead of or in addition to a first order beam.

[0077] To adapt the illumination to these different types of measurements, the aperture plate 13 may include a number of aperture patterns formed around a disk that is rotated to achieve the desired pattern. Note that aperture plates 13N or 13S are used to measure periodic structures of a target oriented in one direction (X or Y, depending on the setup). For measurements of orthogonal periodic structures, rotations of the target by 90° and 270° may be implemented. Figure 3C A and D show different aperture plates. Figure 3C Two additional types of off-axis illumination modes are illustrated. Figure 3C In the first illumination mode, for purposes of description only, aperture plate 13E provides off-axis illumination from a direction designated as "East" relative to the previously described "North". Figure 3C In a second illumination mode, aperture plate 13W is used to provide similar illumination but from an opposite direction labeled "West." Figure 3D Two additional types of off-axis illumination modes are illustrated. Figure 3D In a first illumination mode, aperture plate 13NW provides off-axis illumination from directions designated as "North" and "West" as previously described. In a second illumination mode, aperture plate 13SE is used to provide similar illumination but from opposite directions labeled "South" and "East" as previously described. Use of these and many other variations and applications of the apparatus are described in, for example, the previously published patent application publications referenced above.

[0078] Figure 4An example composite metrology target T formed on a substrate is depicted. The composite target comprises four periodic structures (gratings in this case) 32, 33, 34, 35 positioned closely together. In one embodiment, the periodic structure layout can be made smaller than the measurement spot (i.e., the periodic structure layout is filled). Therefore, in one embodiment, the periodic structures are positioned closely enough together that they are all within the measurement spot 31 formed by the illumination beam of the metrology device. In that case, the four periodic structures are therefore all illuminated at the same time and imaged on the sensors 19 and 23 at the same time. In one example dedicated to overlay measurement, the periodic structures 32, 33, 34, 35 are themselves composite periodic structures (e.g., composite gratings) formed by overlaying periodic structures, i.e., the periodic structures are patterned in different layers of a device formed on a substrate W and such that at least one periodic structure in one layer overlays at least one periodic structure in a different layer. Such a target may have outer dimensions within 20 μm x 20 μm or within 16 μm x 16 μm. Additionally, all periodic structures are used to measure the notch between a pair of layers. To facilitate the target being able to measure more than a single pair of layers, the periodic structures 32, 33, 34, 35 may have differently biased notch offsets to facilitate measurement of notch between different layers in which different portions of the composite periodic structure are formed. Thus, all periodic structures on a target on a substrate will be used to measure a pair of layers and all periodic structures on another identical target on a substrate will be used to measure another pair of layers, wherein the different offsets facilitate differentiation between the layer pairs.

[0079] return Figure 4 , the periodic structures 32, 33, 34, 35 may also differ in their orientations, as shown, so as to diffract incoming radiation in the X and Y directions. In one example, the periodic structures 32 and 34 are X-direction periodic structures with deviations of +d, -d, respectively. The periodic structures 33 and 35 are Y-direction periodic structures with deviations of +d and -d, respectively. Although four periodic structures are illustrated, another embodiment may include a larger matrix to obtain the desired accuracy. For example, a 3x3 array of nine composite periodic structures may have deviations of 4d, -3d, -2d, -d, 0, +d, +2d, +3d, +4d. Individual images of these periodic structures may be identified in the image captured by the sensor 23.

[0080] Figure 5 It shows that the device of FIG. 3 can be used Figure 4 The goal is to use Figure 3DAn example of an image in which an aperture plate 13NW or 13SW is formed on the sensor 23 and detected by the sensor. Although the sensor 19 cannot resolve different individual periodic structures 32 to 35, the sensor 23 can operate in this way. The dark rectangle represents the field of the image on the sensor, within which the illumination spot 31 on the substrate is imaged into the corresponding circular area 41. Within this, the rectangular areas 42-45 represent the images of the periodic structures 32 to 35. The target can be positioned in the device product features instead of or in addition to the scribe grooves. If the periodic structure is positioned in the device product area, then the device features can also be visible in the periphery of the image field. The processor and controller PU use pattern recognition to process these images to identify individual images 42 to 45 of the periodic structures 32 to 35. In this way, the images do not have to be aligned very accurately at specific locations within the sensor frame, which greatly improves the throughput of the measurement device as a whole.

[0081] Once individual images of a periodic structure have been identified, the intensity of those individual images can be measured, for example, by averaging or summing the intensity values ​​of selected pixels within the identified region. The intensity and / or other properties of the images can be compared to each other. These results can be combined to measure different parameters of the lithography process. Overlay performance is an example of such a parameter.

[0082] In an embodiment, one of the parameters of interest for the patterning process is feature width (eg, CD). Figure 6 A highly schematic example metrology device (e.g., scatterometer) is depicted that can achieve feature width determination. It includes a broadband (high light) radiation projector 2 that projects radiation onto a substrate W. The redirected radiation is passed to a spectrometer detector 4, which measures the spectrum 10 (intensity according to wavelength) of the specularly reflected radiation as shown, for example, in the figure in the lower left. From this data, the structure or profile of the detected spectrum can be generated by a processor PU, for example by rigorous coupled wave analysis and nonlinear regression or by comparing with the above as in Figure 6 The scatterometer of the embodiment of the present invention is a kind of scatterometer of the present invention. ...

[0083] Figure 7 An example of an alternative metrology device is illustrated. The principle of operation of this type of metrology device is explained in more detail in U.S. Patent Application Nos. US 2006-033921 ​​and US 2010-201963, which are incorporated herein by reference in their entirety. An optical axis having several branches throughout the device is represented by a dashed line O. In the device, radiation emitted by a source 110 (e.g., a xenon lamp) is directed onto a substrate W by an optical system comprising: a lens system 120, an aperture plate 130, a lens system 140, a partially reflective surface 150, and an objective lens 160. In one embodiment, these lens systems 120, 140, 160 are arranged in a double sequence of a 4F arrangement. In an embodiment, the radiation emitted by the radiation source 110 is collimated using the lens system 120. Different lens arrangements may be used where desired. The angular range of radiation incident on the substrate may be selected by defining a spatial intensity distribution in a plane that presents a spatial spectrum of the substrate plane. In particular, this can be accomplished by inserting an aperture plate 130 of appropriate form between lenses 120 and 140 in the plane of the back-projected image of the objective pupil plane. By using different apertures, different intensity distributions (e.g., angular, dipole, etc.) are possible. The angular distribution of the illumination in radial and circumferential directions as well as properties such as wavelength, polarization and / or coherence of the illumination can all be adjusted to achieve the desired result. For example, one or more interference filters 130 (see Fig. 9 ) may be provided between the source 110 and the partially reflective surface 150 to rotate the wavelength of interest within a range of, for example, 400-900 nm or even lower, such as 200-300 nm. The interference filter may be tunable rather than comprising a set of different filters. A grating may be used instead of an interference filter. In an embodiment, one or more polarizers 170 (see Fig. 9 ) may be provided between the source 110 and the partially reflecting surface 150 to select the polarization of interest. The polarizer may be tunable rather than comprising a set of different polarizers.

[0084] like Figure 7 As shown in FIG, the target T is placed together with the substrate W perpendicular to the optical axis O of the objective lens 160. Therefore, the radiation from the source 110 is reflected by the partially reflective surface 150 and is focused via the objective lens 160 onto an illumination spot S on the target T on the substrate W (see FIG. Figure 8 In one embodiment, objective lens 160 has a high numerical aperture (NA), desirably at least 0.9 or at least 0.95. Immersion metering devices (using relatively high refractive index fluids, such as water) can even have a numerical aperture of 1.

[0085] Illumination rays 170, 172 focused from an angle off axis O onto the illumination spot produce diffracted rays 174, 176. It should be remembered that these rays are only one of many parallel rays covering the area of ​​the substrate including the target T. Each element within the illumination spot is within the field of view of the metrology device. Since the aperture in plate 130 has a finite width (necessary to admit a useful amount of radiation), the incident rays 170, 172 will actually occupy a range of angles, and the diffracted rays 174, 176 will be slightly spread out. Depending on the point spread function of a small target, each diffraction order will be further spread out over a range of angles, not a single ideal ray as shown.

[0086] At least the 0th order of the target diffraction on the substrate W is collected by the objective lens 160 and directed back through the partially reflective surface 150. The optical element 180 provides at least a portion of the diffracted beam to the optical system 182, which forms a diffraction spectrum (pupil plane image) of the target T on the sensor 190 (e.g., CCD or CMOS sensor) using the zeroth order and / or first order diffracted beam. In one embodiment, an aperture 186 is provided to filter out certain diffraction orders so that a specific diffraction order is provided to the sensor 190. In an embodiment, the aperture 186 allows substantially or mainly only zeroth order radiation to reach the sensor 190. In one embodiment, the sensor 190 can be a two-dimensional detector, so that the two-dimensional angular scattering spectrum of the substrate target T can be measured. The sensor 190 can be, for example, an array of CCD or CMOS sensors, and can use, for example, an integration time of 40 milliseconds per frame. The sensor 190 can be used to measure the intensity of the redirected radiation at a single wavelength (or a narrow wavelength range), the intensity integrated at multiple wavelengths alone or within a wavelength range. Additionally, the sensor may be used to measure the intensity of the radiation solely using the phase difference between the trans-magnetic and / or trans-electric polarization and / or trans-magnetic and trans-electric polarization radiation.

[0087] Optionally, the optical element 180 provides at least a portion of the diffracted beam to a measurement branch 200 to form an image of a target on the substrate W on a sensor 230 (e.g., a CCD or CMOS sensor). The measurement branch 200 may be used for various auxiliary functions, such as focusing a metrology device (i.e., enabling the substrate W to be in focus of the objective lens 160), and / or for dark field imaging of the type mentioned in the introduction.

[0088] To provide a customized field of view for gratings of different sizes and shapes, an adjustable field stop 300 is provided within the lens system 140 on the path from the source 110 to the objective 160. The field stop 300 contains an aperture 302 and is positioned in a plane conjugate to the plane of the target T so that the illumination spot becomes an image of the aperture 302. The image can be scaled according to the magnification factor, or the aperture and illumination spot can adopt a 1:1 size relationship. In order to adapt the illumination to different types of measurements, the aperture plate 300 can include many aperture patterns formed around a disk that rotates to achieve the desired pattern. Alternatively or additionally, a set of plates 300 can be provided and exchanged to achieve the same effect. Additionally or alternatively, a programmable aperture device (such as a deformable mirror array or a transmissive spatial light modulator) can also be used.

[0089] Typically, the target will be aligned with its periodic structural features extending parallel to the Y axis or parallel to the X axis. With respect to its diffraction behavior, a periodic structure having features extending in a direction parallel to the Y axis has periodicity in the X direction, while a periodic structure having features extending in a direction parallel to the X axis has periodicity in the Y direction. In order to measure the performance in two directions, two types of features are generally provided. Although reference is made to lines and spaces for simplicity, the periodic structure does not need to be formed by lines and spaces. In addition, each line and / or the space between the lines can be a structure formed by smaller substructures. In addition, the periodic structure can be formed with periodicity in two dimensions at once, for example, in the case where the periodic structure includes rods and / or through holes.

[0090] Figure 8 The diagram shows a plan view of a common target T and Figure 7 The range of the illumination spot S in the device of the invention is . In order to obtain a diffraction spectrum free from interference from surrounding structures, the target T is, in an embodiment, 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. In other words, the target is "not filled" by the illumination, and the diffraction signal is substantially free from any signal influence from analogs other than the product feature target itself. This simplifies the mathematical reconstruction of the target, since it can be considered infinite.

[0091] Fig. 9 An example process of determining values ​​of one or more variables of interest for a target pattern 30' based on measurement data obtained using metrology is schematically depicted.The radiation detected by the detector 190 provides a measured radiation distribution 108 for the target 30'.

[0092] For a given target 30', the radiation distribution 208 can be calculated / simulated according to the parameterized mathematical model 206 using, for example, a numerical Maxwell solver 210. The parameterized mathematical model 206 shows example layers of various materials that make up the target and are associated with the target. The parameterized mathematical model 206 may include one or more of the variables for the features and layers of the target under consideration that may be varied and derived. Fig. 9 As shown in , one or more of the variables may include the thickness t of one or more layers, the width w (e.g., CD) of one or more features, the height h of one or more features, the side wall angle α of one or more features, and / or the relative position between features (considered as notches herein). Although not shown, one or more of the variables may also include, but are not limited to, the refractive index of one or more of the layers (e.g., real or complex refractive index, refractive index tensor, etc.), the extinction coefficient of one or more layers, the absorptivity of one or more layers, the resist loss during development, the footprint of one or more features, and / or the line edge roughness of one or more features. One or more values ​​of one or more parameters of a 1-D periodic structure or a 2-D periodic structure (such as values ​​of width, length, shape, or 3-D profile characteristics) may be input to a reconstruction process based on knowledge of a patterning process and / or other measurement processes. For example, the initial values ​​of the variables may be those expected values ​​for one or more parameters of the target being measured, such as values ​​of CD, spacing, etc.

[0093] In some cases, the target may be divided into multiple instances of a unit cell. To facilitate easy calculation of the radiation distribution of the target in that case, the model 206 may be designed to calculate / simulate using a unit cell of the structure of the target, where the unit cell is repeated as an instance across the entire target. Thus, the model 206 may calculate using one unit cell and replicate the results to fit the entire target using appropriate boundary conditions in order to determine the radiation distribution of the target.

[0094] In addition to or as an alternative to calculating the radiation distribution 208 at reconstruction time, multiple radiation distributions 208 may be pre-calculated for multiple variations of the variable of the target portion under consideration to create a library of radiation distributions for use at reconstruction time.

[0095] The measured radiation distribution 108 is then compared to the calculated radiation distribution 208 (e.g., calculated or obtained from a library at approximately that time) at 212 to determine a difference between the two. If a difference exists, the values ​​of one or more of the variables of the parameterized mathematical model 206 may be changed, and a new calculated radiation distribution 208 is obtained (e.g., calculated or obtained from a library) and compared to the measured radiation distribution 108 until there is a sufficient match between the measured radiation distribution 108 and the radiation distribution 208. At this point, the values ​​of the variables of the parameterized mathematical model 206 provide a good or best match to the geometry of the actual target 30'. In one embodiment, a sufficient match exists when the difference between the measured radiation distribution 108 and the calculated radiation distribution 208 is within a tolerance threshold.

[0096] In these metrology devices, a substrate support may be provided to hold the substrate W during the measurement operation. The substrate support may be similar in form to Figure 1 The substrate table WT of the measuring device is similar or identical to that of the lithographic apparatus. In the example where the metrology device is integrated with the lithographic apparatus, it may even be the same substrate table. Coarse and fine positioners may be provided to accurately position the substrate relative to the measuring optical system. Various sensors and actuators are provided, for example, to obtain the position of an object of interest and put it into a suitable position under the objective. Typically, many measurements will be made on targets at different positions across the substrate W. The substrate support may be moved in the X and Y directions to obtain different targets, and in the Z direction to obtain the desired position of the target relative to the focus of the optical system. It is convenient to imagine and describe the operation as if the objective is being introduced into different positions relative to the substrate, when, for example, the optical system can actually remain substantially fixed (usually in the X and Y directions, but possibly also in the Z direction) and only the substrate moves. If the relative position of the substrate and the optical system is correct, then in principle it does not matter which of those, the substrate and the optical system, is moving in the real world or whether both the substrate and the optical system are moving or a combination of part of the optical system is moving (e.g., in Z and / or tilt direction) while the rest of the optical system is fixed and the substrate is moving (e.g., in X and Y directions, and optionally also in Z and / or tilt direction).

[0097] In one embodiment, the measurement accuracy and / or sensitivity of a target may vary with respect to one or more properties of a beam of radiation provided onto the target, such as the wavelength of the radiation beam, the polarization of the radiation beam, the intensity distribution of the radiation beam (e.g., angular or spatial intensity distribution), etc. Thus, a particular measurement strategy may be selected in order to obtain, for example, good measurement accuracy and / or sensitivity of a target.

[0098] In order to monitor a patterning process (e.g., a device manufacturing process) that includes at least one pattern transfer step (e.g., an optical lithography step), a patterned substrate is inspected and one or more parameters of the patterned substrate are measured / determined. The one or more parameters may include, for example, notching between successive layers formed in or on the patterned substrate, critical dimensions (CD) of features formed in or on the patterned substrate (e.g., critical line width), focus or focus error of the optical lithography step, dose or dose error of the optical lithography step, placement error (e.g., edge placement error), etc. The measurements may be performed on a target on the product substrate itself and / or on a dedicated metrology target provided on the substrate. The measurements may be performed after development of the resist but before etching, or may be performed after etching.

[0099] In one embodiment, the parameter obtained from the measurement process is a parameter derived from the parameter determined directly from the measurement process. As an example, the parameter obtained from the measurement parameter is an edge placement error for the patterning process. The edge placement error provides a change in the position of the edge of the structure created by the patterning process. In an embodiment, the edge placement error is derived from the cut-out value. In an embodiment, the edge placement error is derived from a combination of the cut-out value and the CD value. In an embodiment, the edge placement is derived from a combination of the cut-out value, the CD value, and a value corresponding to a local variation (e.g., edge roughness of an individual structure, shape asymmetry, etc.). In one embodiment, the edge placement error includes a limit value (e.g., 3 standard deviations, i.e., 3σ) of the combination of the cut-out and CD errors. In one embodiment, in a multi-patterning process involving the creation of a structure and involving "cutting" a structure by removing a portion of the structure through etching a pattern provided by a patterning process associated with the structure, the edge placement error has the following form (or includes one or more of the following items): Where σ is the standard deviation, σ overlay Corresponding to the standard deviation of the notch, σ CDU structures Corresponding to the standard deviation of critical dimension uniformity (CDU) created during the patterning process, σ CDU cuts corresponds to the standard deviation (if any) of the critical dimension uniformity (CDU) of the cuts created during the patterning process, σ OPE,PBA corresponds to the standard deviation of the optical proximity effect (OPE) and / or proximity bias average (PBA), which is the difference between the CD at the spacing and the reference CD, and σ LER,LPE corresponds to the standard deviation of the line edge roughness (LER) and / or the local placement error (LPE).Although the above formula relates to standard deviation, it can be formulated in a different equivalent statistical way, such as variance.

[0100] There are various techniques for making measurements of structures formed during the 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 form of a specialized metrology tool is that a beam of radiation is directed onto a target on the surface of a substrate and the properties of the scattered (diffracted / reflected) beam are measured. By evaluating one or more properties of the radiation scattered by the substrate, one or more properties of the substrate can be determined. This can be named diffraction-based metrology. One such application of this diffraction-based metrology is in the measurement of feature asymmetry within a target. This can be used as a measurement of a set, for example, but other applications are also known. For example, asymmetry can be measured by comparing opposite parts of the diffraction spectrum (e.g., comparing the -1 order and +1 order in the diffraction spectrum of a periodic grating). This can be accomplished as described above and as described, for example, in U.S. Patent Application Publication US2006-066855, which is incorporated herein in its entirety by application. Another application of diffraction-based metrology is in the measurement of feature width (CD) within a target. Such a technique can be used with reference to the above. Figure 6-9 The apparatus and method are described.

[0101] Now, while these techniques are effective, it is desirable to provide alternative measurement techniques that derive feature asymmetry within a target, such as notch, CD asymmetry, sidewall angle asymmetry, etc. Such techniques would be effective for specially designed metrology targets or perhaps more significantly for determining feature asymmetry directly on a device pattern.

[0102] Referring to Figure 10, the principle of this measurement technique is described in the context of an engraved embodiment. Fig. 10A , a geometrically symmetric unit cell of a target T is shown. The target T may include only a single physical instance of the unit cell or may include Fig. 10C Multiple physical instances of the unit cell are shown in .

[0103] The target T may be a specially designed target. In one embodiment, the target is for a scribe line. In an embodiment, the target may be an intra-die target, i.e., the target is within the device pattern (and therefore between the scribe lines). In one embodiment, the target may have a feature width or spacing comparable to the device pattern features. For example, the target feature width or spacing may be less than or equal to 300% of the minimum feature size or spacing of the device pattern, less than or equal to 200% of the minimum feature size or spacing of the device pattern, less than or equal to 150% of the minimum feature size or spacing of the device pattern, or less than or equal to 100% of the minimum feature size or spacing of the device pattern.

[0104] The target T may be a device structure. For example, the target T may be a portion of a memory device (which typically has one or more structures that are or may be geometrically symmetrical as discussed further below).

[0105] In one embodiment, a physical instance of a target T or unit cell may have an area less than or equal to 2400 square microns, an area less than or equal to 2000 square microns, an area less than or equal to 1500 square microns, an area less than or equal to 1000 square microns, an area less than or equal to 400 square microns, an area less than or equal to 200 square microns, an area less than or equal to 100 square microns, an area less than or equal to 50 square microns, an area less than or equal to 25 square microns, an area less than or equal to 10 square microns, an area less than or equal to 5 square microns, an area less than or equal to 1 square micron, an area less than or equal to 0.5 square microns, or an area less than or equal to 0.1 square microns. In one embodiment, a physical instance of a target T or unit cell may have a cross-sectional dimension parallel to a plane of the substrate of less than or equal to 50 microns, less than or equal to 30 microns, less than or equal to 20 microns, less than or equal to 15 microns, less than or equal to 10 microns, less than or equal to 5 microns, less than or equal to 3 microns, less than or equal to 1 micron, less than or equal to 0.5 microns, less than or equal to 0.2 microns, or less than or equal to 0.1 microns.

[0106] In one embodiment, the physical instance of the target T or unit cell has a structure having a pitch of less than or equal to 5 microns, less than or equal to 2 microns, less than or equal to 1 micron, less than or equal to 500 nm, less than or equal to 400 nm, less than or equal to 300 nm, less than or equal to 200 nm, less than or equal to 150 nm, less than or equal to 100 nm, less than or equal to 75 nm, less than or equal to 50 nm, less than or equal to 32 nm, less than or equal to 22 nm, less than or equal to 16 nm, less than or equal to 10 nm, less than or equal to 7 nm, or less than or equal to 5 nm.

[0107] In one embodiment, the target T has multiple physical instances of a unit cell. Therefore, the target T may generally have the higher dimensions listed herein, while the physical instances of the unit cell will have the lower dimensions listed herein. In an embodiment, the target T includes 50,000 or more physical instances of a unit cell, 25,000 or more physical instances of a unit cell, 15,000 or more physical instances of a unit cell, 10,000 or more physical instances of a unit cell, 5,000 or more physical instances of a unit cell, 1,000 or more physical instances of a unit cell, 500 or more physical instances of a unit cell, 200 or more physical instances of a unit cell, 100 or more physical instances of a unit cell, 50 or more physical instances of a unit cell, or 10 or more physical instances of a unit cell.

[0108] Desirably, a physical instance of a unit cell or multiple physical instances of a unit cell collectively fills a beam spot of a metrology device. In this case, the measured result includes substantially only information from the physical instance of the unit cell (or multiple instances thereof). In one embodiment, the beam spot has a cross-sectional width of 50 microns or less, 40 microns or less, 30 microns or less, 20 microns or less, 15 microns or less, 10 microns or less, 5 microns or less, or 2 microns or less.

[0109] Fig. 10A The unit cell in includes at least two structures that are or will be physically instantiated on a substrate. The first structure 1000 includes a line and the second structure 1005 includes an oval shape. Of course, the first structure 1000 and the second structure 1005 can be structures different from those depicted.

[0110] Additionally, in this example, there may be a relative shift between the first structure 1000 and the second structure 1005 from their intended positions due to their separate transfers onto the substrate, thereby having errors in notching. In this example, the first structure 1000 is located in a higher layer on the substrate than the second structure 1005. Therefore, in one embodiment, the second structure 1005 may be produced in a first lower layer in a first execution of the patterning process, and the first structure 1000 may be produced in a second higher layer than the first lower layer in a second execution of the patterning process. Now, the first structure 1000 and the second structure 1005 do not have to be located in different layers. For example, in a double patterning process (including, for example, an etching process as part thereof), the first structure 1000 and the second structure 1005 may be produced in the same layer to form a substantially single pattern but there may still be "notching" issues with respect to their relative placement within the same layer. In this single layer example, the first structure 1000 and the second structure 1005 may have a relative shift between the first structure 1000 and the second structure 1005. Fig. 10A 1000, but the lines of the second structure 1005 that have been provided on the substrate by the first pattern transfer process may be staggered with the lines of the structure 1000 provided in the second pattern transfer process.

[0111] Importantly, the unit cell has or can have geometric symmetry about an axis or point. For example, Fig. 10A The unit cell in has reflection symmetry with respect to, for example, axis 1010 and point / rotation symmetry with respect to, for example, point 1015. Similarly, it can be seen that Fig. 10C The physical instances of the unit cells in (and hence the combinations of physical instances of the unit cells) have geometric symmetries.

[0112] In one embodiment, the unit cell has a geometric symmetry for a certain property (such as notch). The embodiments herein focus on a unit cell having zero notch when it is geometrically symmetric. However, instead, the unit cell may have zero notch for a certain geometric symmetry. Appropriate offsets and calculations will then be used to illustrate a unit cell having zero notch when it has a certain geometric symmetry. Specifically, the unit cell should be able to change symmetry (e.g., become asymmetric, or become further asymmetric, or change from an asymmetric situation to a symmetric situation) according to a certain eigenvalue.

[0113] exist Fig. 10A In the example of FIG. 1 , the unit cell has geometric symmetry about a zero-trace nest (although it need not be a zero-trace nest). This is represented by arrows 1020 and 1025, which show that the lines of the first structure 1000 are uniformly aligned relative to the oval shape of the second structure 1005 (and their uniform alignment at least in part enables the unit cell to have a geometric symmetry about a zero-trace nest). Fig. 10A ). Thus, in this example, when the unit cell has geometric symmetry, there is a zero engraving. However, when there is an error in the engraving (e.g., a non-zero engraving), the unit cell is no longer geometrically symmetric and is no longer geometrically symmetric according to the defined objective.

[0114] Additionally, where the target comprises multiple physical instances of a unit, the instances of the unit cell are periodically arranged. In an embodiment, the instances of the unit cell are arranged in a lattice. In an embodiment, the periodic arrangement has geometric symmetry within the target.

[0115] Thus, in the present technique, as discussed further below, a change in geometric symmetry associated with a feature asymmetry of interest (e.g., a non-zero notch) (e.g., a change to geometric symmetry or a change to further geometric asymmetry or a change from geometric asymmetry to geometric symmetry) can be used to determine a feature asymmetry (e.g., a non-zero notch).

[0116] include Fig. 10A The physical instance of the unit cell of the target can be obtained using e.g. Figure 7 The metrology device of the target is illuminated with radiation. The radiation redirected by the target can be measured, for example, by a detector 190. In an embodiment, the pupil of the redirected radiation is measured, i.e., the Fourier transform plane. An example measurement of such a pupil is depicted as a pupil image 1030. Although the pupil image 1030 has a diamond shape, it does not have to have such a shape. Unless the context requires otherwise (e.g., where the pupil plane of a particular optical system is being identified), the terms pupil and pupil plane herein include any conjugate thereof. The pupil image 1030 is actually an image of the pupil of the redirected radiation specified in terms of optical properties (in this case, intensity).

[0117] For convenience, the discussion herein will focus on intensity as the optical property of interest. However, the techniques herein may be used with one or more alternative or additional optical properties, such as phase and / or reflectivity.

[0118] In addition, for convenience, the discussion herein focuses on detecting and processing images of redirected radiation and in particular pupil images. However, the optical properties of the redirected radiation can be measured and represented in a manner different from that of an image. For example, the redirected radiation can be processed in one or more spectral aspects (e.g., in terms of intensity of wavelengths). Thus, a detected image of the redirected radiation can be considered an example of an optical representation of the redirected radiation. Thus, in the case of a pupil plane image, the pupil image is an example of a pupil representation.

[0119] Additionally, the redirected radiation may be polarized or unpolarized.In an embodiment, the measurement beam radiation is polarized radiation.In an embodiment, the measurement beam radiation is linearly polarized.

[0120] In one embodiment, the pupil representation is primarily or substantially one diffraction order of radiation redirected from the target. For example, the radiation may be 80% or more, 85% or more, 90% or more, 95% or more, 98% or more, or 99% or more of the radiation of a particular order. In one embodiment, the pupil representation is primarily or substantially zero-order redirected radiation. This may occur, for example, when the spacing of the targets, the wavelength of the measured radiation, and optionally one or more other conditions cause the target to redirect primarily zero-order (although one or more higher-order radiation may be present). In one embodiment, the majority of the pupil representation is zero-order redirected radiation. In one embodiment, the pupil representation is zero-order radiation and some is 1st-order radiation, which may be linearly combined (cased). Figure 7The aperture 186 in can be used to select radiation of a particular order (eg, zeroth order).

[0121] Having referred to the pupil image 1030 corresponding to the geometrically symmetric unit cells of the first structure 1000 and the second structure 1005, it can be seen that the density distribution is substantially symmetric within the pupil image (e.g., having the same type of symmetry as the geometric structure). This is further confirmed by removing the symmetric density distribution portion from the pupil image 1030 (which results in the resulting pupil image 1035). To remove the symmetric density distribution portion, a particular pupil image pixel (e.g., a pixel) can have a symmetric density distribution portion removed by subtracting the intensity of the symmetrically located pupil image pixel from the intensity at the particular pupil image pixel, and vice versa. In one embodiment, the pixel can correspond to a pixel of a detector (e.g., detector 190), but it need not be so; for example, the pupil image pixel can be a plurality of pixels of the detector. In one embodiment, the symmetry point or axis from which the pixel intensity is subtracted corresponds to the symmetry point or axis of the unit cell. Thus, for example, considering pupil image 1030, the symmetric density distribution portion can be removed by, for example, subtracting the intensity Ii' from a symmetrically located pixel (i.e., symmetrically located with respect to axis 1032) from the intensity Ii at that particular pixel shown. Thus, the intensity Si at a particular pixel with the symmetric density intensity portion removed is then Si=Ii-Ii'. This can be repeated for multiple pixels of the pupil image (e.g., all pixels in the pupil image). As seen in the resulting pupil image 1035, the intensity distribution corresponding to the symmetric unit cell is substantially completely symmetric. Thus, a symmetric target having a symmetric unit cell geometry (and, where applicable, a particular periodicity of instances of the unit cell) results in a symmetric pupil response as measured by a metrology device.

[0122] Reference now Fig. 10B ,refer to Fig. 10A The unit cell depicted in FIG. 1 depicts an example of an error in the engraving. In this case, the first structure 1000 is displaced in the X direction relative to the second structure 1005. Specifically, the axis 1010 centered on the line of the first structure 1000 has been displaced to Fig. 10B1045. Thus, there is an error in the notch 1040 in the X direction; i.e., an X-direction notch error. Of course, the second structure 1005 may be displaced relative to the first structure 1000 or the two may be displaced relative to each other. In either case, the result is an X-direction notch error. However, as should be appreciated from the unit cell arrangement, a pure relative displacement in the Y direction between the first structure 1000 and the second structure 1005 will not change the geometric symmetry of the unit cell. However, with a suitable geometric arrangement, notch in both directions or between different combinations of portions of the unit cell may change the symmetry and may also be determined, as discussed further below.

[0123] Since the physical configuration of the unit cell changes from Fig. 10A The result of the change in the nominal physical configuration of the unit cell in the pupil image 1030 and represented by the error in the notch 1040 is that the unit cell has become geometrically asymmetric. This can be seen by arrows 1050 and 1055 having different lengths, which show that the oval shape of the second structure 1005 is non-uniformly positioned relative to the lines of the first structure 1000. The symmetry is checked relative to a symmetry point or axis of the pupil image 1030 (i.e., in this case, axis 1032 is now shown as axis 1034).

[0124] Fig. 10B The physical instantiation of the unit cell can be done using, for example, Figure 7 The metering device is illuminated with radiation. A pupil image of the redirected radiation can be recorded, for example, by detector 190. An example of such a pupil image is depicted as pupil image 1060. Pupil image 1060 is actually an image of intensity. Although pupil image 1060 has a diamond shape, it does not have to have such a shape; it can be a circular shape or any other shape. In addition, pupil image 1060 has substantially the same axis or coordinate position as pupil image 1030. That is, in this embodiment, Fig. 10A The symmetry axes in the unit cell are 1010 and Fig. 10B The same axis in the unit cell of is aligned with the symmetry axis 1032 of the pupil images 1030 , 1060 .

[0125] Reference has been made to the pupil image 1060 corresponding to the geometrically asymmetric unit cell of the first structure 1000 and the second structure 1005, which visually appears to have a density distribution that is substantially symmetrical within the pupil image. However, there is an asymmetric density distribution portion within the pupil image. The asymmetric density distribution portion is due to the asymmetry within the unit cell. In addition, the asymmetric density distribution is significantly lower in magnitude than the symmetric density distribution portion in the pupil image.

[0126] Thus, in one embodiment, in order to more effectively isolate the asymmetric density distribution portion, the symmetric density distribution portion may be removed from the pupil image 1060, which results in a derived pupil image 1065. Similar to obtaining the derived pupil image 1035, a particular pupil image pixel (e.g., a pixel) may have a symmetric density distribution portion removed by subtracting the intensity of a symmetrically positioned pupil image pixel from the intensity at that particular pupil image pixel, and vice versa, as discussed above. Thus, for example, considering the pupil image 1060, the symmetric density distribution portion may be removed by, for example, subtracting the intensity Ii' from a symmetrically positioned pixel (i.e., symmetrically positioned relative to the axis 1032) from the intensity Ii at that particular pixel shown to obtain Si. This may be repeated for multiple pixels of the pupil image (e.g., all pixels in the pupil image). In Fig. 10A and Fig. 10B , a complete resulting pupil image of Si is depicted for explanatory purposes. As will be appreciated, Fig. 10A or Fig. 10B One half of the derived pupil image is identical to the other half. Thus, in embodiments, only half of the values ​​from the pupil image may be used for further processing discussed herein and thus the derived image pupil used in further processing herein may be only half of the Si values ​​for the pupil.

[0127] As seen in the derived pupil image 1065, the density distribution measured using the physical instance of the asymmetric unit cell is not symmetric. As seen in regions 1075 and 1080, there are asymmetric density distribution portions that are visible once the symmetric density distribution portions are removed. As noted above, the complete derived pupil image 1065 is shown and therefore the asymmetric density distribution portions are shown on both halves (even though they are equal to each other in magnitude and density in their respective halves).

[0128] Thus, asymmetry in the geometric domain corresponds to asymmetry in the pupil. Thus, in one embodiment, a method is provided that uses the optical response of a periodic target that has or is capable of inherent geometric symmetry in its physical instance of a unit cell to determine parameters corresponding to a physical configuration change that causes a change in the geometric symmetry of the physical instance of the unit cell (e.g., causes asymmetry, or causes further asymmetry, or causes an asymmetric unit cell to become symmetric). Specifically, in one embodiment, an asymmetry (or lack thereof) caused by notching in the pupil as measured by a metrology device can be exploited to determine notching. That is, pupil asymmetry is used to measure notching within the physical instance of the unit cell and therefore within the target.

[0129] Asymmetry within the geometric domain can also be caused by tilt in the etch path through the target layer in the target, which is caused by errors in the etching process used to form the pattern in the target layer and / or stress in the target layer and / or surrounding layers. The asymmetry will result in a corresponding asymmetry in the pupil (or in another detected representation of the scattered radiation), which can be used to measure the tilt. In addition, the asymmetry in the pupil caused by the tilt is different from the asymmetry caused by the cut sleeve, thereby enabling the extraction of tilt independent of the cut sleeve and the extraction of the cut sleeve independent of the tilt. As will be described in further detail below, the measured tilt can be used to control the etching process and / or other patterning processes.

[0130] like Figure 2 As depicted in , in one embodiment, an etching controller 223 is provided for controlling the etching process performed by the etching station 222. Control of the etching process may include controlling one or more of the following etching parameters: a desired thermal pattern across the substrate, a desired chemical concentration pattern in the plasma used in the etching process, a desired electric field pattern around the substrate during the etching process, a voltage applied to one or more electrodes during the etching process. Each of these etching parameters can be changed to change the etching direction and / or etching rate and / or another etching factor in a position-dependent manner. By changing at least one of the etching parameters, the etching process can be optimized to reduce or eliminate errors introduced by the etching process, such as errors caused by tilted etching paths.

[0131] Fig.11 Illustrated is how errors can be introduced by the etching process. Fig.11 Specifically illustrated is how overlay errors may be introduced at the edge of the substrate. However, the etching process may introduce errors across the entire substrate or in areas other than or in addition to the edge region of the substrate. Overlay errors may be introduced by the etching process in an asymmetric manner.

[0132] As in Fig.11 , the substrate 220 generally includes a lower layer 310 having a pattern embedded therein. On top of the lower layer 310, one or more device layers 320 are applied. Before the photoresist layer 240 is applied on the pattern irradiated by the device 200 and developed into a physical resist pattern by the development device 212, one or more additional layers 330 may be applied. As shown, there is no overlay error between the physical resist pattern and the pattern in the lower layer 310.

[0133] In the etching station 222, a chemical (e.g., plasma) etches the device layer 320 and any additional layers 330 in the gaps in the physical resist pattern of the photoresist layer 340. Fig.11As illustrated in the top middle of , if the etching direction is not perfectly perpendicular to the top surface of substrate 220 as illustrated by arrow 350, then layers 320, 330 are not etched as rectangles but are etched as parallelograms. The parallelogram corresponds in position to the physical resist pattern at its upper end, but even if there is no overlay error between the physical resist pattern and the pattern in the lower layer 310, the parallelogram does not match in position the pattern of the lower layer 310 at the lower end. Therefore, when layers 330, 340 are removed (by further device 226) to reach the final substrate 234 or substrate 232 for application of further layers, an overlay error is introduced between the pattern in the lower layer 310 and the pattern etched in the device layer 320, as shown in FIG. Fig.11 As shown in the right-hand figure.

[0134] The picture is Fig.11 The overlay on the right hand side of is therefore an overlay error induced by the etching station 222 , which would not exist if the etching direction 350 was perfectly perpendicular to the top surface of the substrate 220 . Fig.11 The middle lower figure in illustrates how a flawed etching direction 350 may be induced. For example, at the edge of the substrate 220, the electric field 360 used during the etching process may change from being perfectly perpendicular to the surface of the substrate 220 (which is at the center of the substrate 220) to being angled relative to the perpendicular direction of the top surface of the substrate 220 at the edge of the substrate 220.

[0135] One etching parameter that can be changed to change the direction of the electric field (and thus change the etching direction 350) is the voltage that can be applied to the electrode around the outer edge of the substrate 220. This is an example of an etching parameter that can be changed to change the etching process (i.e., the etching direction 350 at the outer edge of the substrate 220) to reduce errors induced by the etching process. Similar concepts can be disclosed, for example, in US 6,767,844 (which relates to a temperature-controlled focus ring surrounding a substrate during etching) and US2006 / 0016561 (which discloses an edge ring member for achieving a uniform etching rate across the entire surface of a substrate).

[0136] Other causes for etching-induced overlay errors may include local variations in the concentration of chemical etching agents on the surface of substrate 220 during etching, thermal patterns present in substrate 220 during etching, etc. Variations in etching direction over the surface of substrate 220 may be reduced or eliminated by changing etching parameters.

[0137] Embodiments of the present disclosure provide ways to reduce or compensate for etch-induced errors, such as overlay errors.

[0138] According to one embodiment, a method for controlling a patterning process is provided. The method is applied to, for example, Fig.12 The situation schematically depicted in Fig.12 yes Fig.11 A simplified version of the configuration depicted in . Fig.12 4 is a side cross-sectional view of a small area of ​​a three-layer structure including a lower layer 401, a target layer 402, and an upper layer 403. Each of the lower layer 401, the target layer 402, and the upper layer 403 is depicted as a single uniform layer for simplicity, but may actually include one or more layers. Lower layer 401 includes lower reference features 411, which are part of a pattern formed in lower layer 401. Upper layer 403 includes upper reference features 413, which are part of a pattern formed in upper layer 403. Target layer 402 also includes a pattern. Features in the pattern are due to etching effects (such as the above reference features). Fig.11 410). The tilted features define a path followed by an etching step used to create a pattern in target layer 402 and referred to as etch path 420. Etch path 420 connects lower reference feature 411 to upper reference feature 413. Etch path 420 can define final product features, such as by providing an electrical connection between lower reference feature 411 and upper reference feature 413. The tilt θ in etch path 420 caused by errors in the etching process results in an imperfect connection between lower reference feature 411 and upper reference feature 413. In effect, tilt θ results in an overlay error OV at the junction between lower layer 401 and target layer 402. Tilt θ is the difference between the direction of etch path 420 and a perpendicular 430 (at Fig.12 Deviation of the vertical direction in the orientation.

[0139] The method includes obtaining tilt data obtained from the measurement of the tilt in the etch path 420 passing through the target layer 402. In one embodiment, the method includes performing a measurement of the tilt. In one embodiment, the measurement of the tilt is a direct measurement of the tilt. Alternatively or additionally, the measurement of the tilt is a non-destructive measurement of the tilt. The tilt data is used to control the patterning process. The controlled patterning process is used to form a pattern in another layer formed after the target layer 402 (at a later time). Various options can be used for control. The choice of control can depend on how fast the measured tilt changes according to the position on the substrate. Different control methods will have different capabilities according to their spatial resolution. For simplicity, the following discussion refers to a single etch path and the corresponding single tilt of the etch path. In practical applications, there will be many etch paths and there may be many different tilts associated with them. The method is capable of measuring the tilt at multiple locations. The method can, for example, provide a graph or fingerprint of the measured tilt, which shows the change across a die or multiple dies.

[0140] As mentioned above FIG. 10A to FIG. 10CAs discussed above, a particularly effective way to perform a measurement of tilt is by using asymmetries in the detected pupil representation (or other detected representation of scattered radiation). Thus, the measurement of tilt may comprise illuminating the structure with radiation and detecting radiation redirected (scattered) by the structure. The detected radiation may comprise primarily zero-order radiation. FIG. 10A to FIG. 10C The method discussed allows asymmetry information, such as tilt information or casing information, to be derived from zero-order radiation. The use of zero-order radiation allows measurements to be made on structures with small characteristic length scales or periodicities, thereby enabling the measurement of tilt in a device structure or in a non-device structure (i.e., a non-device structure having a characteristic length scale or periodicity of the same order of magnitude as the device structure) located within a substrate die comprising the device structure. In one embodiment, the tilt is extracted from an asymmetric component (e.g., an asymmetry in the density distribution in a pupil image) of a detected representation of radiation redirected by the structure (such as a detected pupil representation). The asymmetry can be a plane relative to mirror symmetry. The asymmetry is related to the tilt and thereby allows the tilt to be extracted. The method also allows the thickness of a layer to be extracted simultaneously with the tilt and / or casing. The thickness of a layer may be required in order to determine the size of the correction to be applied to a subsequently formed layer to correct the measured tilt.

[0141] In one class of embodiments, the measured tilt is used to control a patterning process for forming a pattern in a layer where the tilt has been measured but formed after the target layer 402 on the same instance of the structure. This scenario is schematically depicted in Fig.13 In this example, the patterning process is adjusted (controlled) to shift the pattern in the upper layer 403 to the left relative to the pattern in the lower layer 401. This shift is an example of a control that changes the nominal overlay between the patterns produced in different layers. This type of control can be implemented, for example, by controlling a photolithographic pattern transfer step. The result of the control is that the inclined etch path 420 (which is shifted to the left due to the shift of the reference feature 413) is better aligned with the lower reference feature 411.

[0142] In an alternative class of embodiments, the measured tilt is used to control a patterning process for forming a pattern in a layer in or on a subsequently formed instance of the structure (eg, on a different substrate or wafer). Fig.14 and Fig.15 An example of such a control is depicted.

[0143] exist Fig.14In the example of FIG. 4 , the patterning process is adjusted (controlled) to shift the pattern in the lower layer 401 to the right relative to the upper layer 403. This shift is another example of control that changes the nominal overlay between the patterns produced in different layers (in this case, the lower layer 401 and the upper layer 403). The result of the control is that the inclined etch path 420 is better aligned with the lower reference feature 411.

[0144] The patterning process being controlled may thus comprise a lithographic pattern transfer step. The lithographic pattern transfer step may impart a radiation beam with a pattern in its cross-section using a patterning device MA so as to define a pattern to be transferred to the substrate, as described above with reference to e.g. Figure 1 In this type of embodiment, the measured tilt θ is used to control the photolithographic pattern transfer step. This control can form a pattern in a layer 303 formed after the target layer on the structure (e.g. Fig.13 Alternatively or additionally, when a photolithographic pattern transfer step is applied to a subsequently formed instance of the structure, the control may be applied during patterning in a layer 401 formed before a target layer 402 of the subsequently formed instance of the structure, or during patterning in a layer 403 formed after the target layer 402 of the subsequently formed instance of the structure.

[0145] In one embodiment, the control of the lithographic pattern transfer step includes modifying the patterning device MA. The patterning device MA can be modified without recreating a completely new patterning device MA. In an embodiment, the modification is implemented by selectively heating the patterning device MA to induce local stress within the patterning device MA. Further details on how the patterning device MA can be modified are provided in WO 2017 / 067765A1, which is incorporated herein by reference in its entirety. The patterning device MA can be modified to correct the measured tilt that changes rapidly depending on the position within the die (i.e., tilt changes of relatively high spatial frequency).

[0146] As mentioned above, control of the lithographic pattern transfer step can include changing the nominal cut sleeve between the pattern formed in the layer and the pattern in the different layers by the lithographic pattern transfer step. When control is implemented by modifying the patterning device MA, the change in the nominal cut sleeve can be changed according to the position across the substrate (including in the die) to follow the change in the position according to the measured tilt. Alternatively or additionally, all of the changes in the nominal cut sleeve or the contribution to the change in the nominal cut sleeve can be applied uniformly for each die or even on the entire substrate. The technology for modifying the lithographic pattern transfer step to apply uniform displacement in the cut sleeve is well known in the art. Applying uniform displacement in the cut sleeve to correct the measured tilt can be effective for correcting the contribution to the tilt that changes relatively slowly with the position on the substrate. The uniform displacement in the applied cut sleeve can be different from one die to the next die, so that each die is subjected to the optimal cut sleeve displacement for the die.

[0147] Alternatively or additionally, the control of the lithographic pattern transfer step includes modifying one or more of: a dose applied by the radiation beam, a focus of the radiation beam, one or more optical aberrations applied to the radiation beam. For example, modification of the dose may be used to make selected features larger to increase the likelihood of making reliable electrical connections between different layers of the device in the presence of a tilted etch path.

[0148] In other embodiments, the patterning process to be controlled includes a deposition step in which a material layer is deposited. The deposition can be performed, for example, using the above reference Figure 2 The control of the patterning process may be implemented by the coating device 208 described in the embodiment. The control of the patterning process may therefore include the control of the coating device 208. In one embodiment, the measured tilt is used to control the deposition step during the formation of the layer 403 formed after the target layer 402 on the structure. Alternatively or additionally, when the deposition step is applied to the subsequently formed instance of the structure, the control may be applied during the formation of the layer 401 formed before the target layer 402 of the subsequently formed instance of the structure, during the formation of the target layer 402 of the subsequently formed instance of the structure, or during the formation of the layer 403 formed after the target layer 402 of the subsequently formed instance of the structure. In one embodiment, the control of the deposition process includes controlling the stress distribution in the layer of the material deposited by the deposition step. This can be achieved, for example, by controlling the temperature of the material during deposition, the speed at which the material is deposited, or any other factor that will affect the stress distribution. In one embodiment, the control of the deposition process alternatively or additionally includes controlling one or more of the following in the material layer deposited by the deposition step: height distribution, density distribution, composition distribution.

[0149] exist Fig.15In the example of FIG. 4 , the patterning process is adjusted (controlled) to change the tilt in the etching process 420 itself. In the example shown, the tilt is completely removed. The removal (or reduction) of the tilt results in better alignment of the etch path 420 with the lower reference feature 411. The tilt can be changed by controlling the etching process used to form the etch path 420 or by modifying the stress distribution in the target layer 402 or the layers surrounding the target layer 402.

[0150] In one embodiment, the measured tilt is used to control an etching process applied to a subsequently formed instance of a structure on a substrate. The control may be applied during formation of a pattern in layer 401 formed before target layer 402 in a subsequently formed instance of the structure, during formation of a pattern in layer 402 formed before target layer 402 in a subsequently formed instance of the structure, or during formation of a pattern in layer 403 formed after target layer 402 in a subsequently formed instance of the structure. In an embodiment, the measured tilt is used to control one or more etching parameters of the etching process. In one embodiment, as described above with reference to Figure 2 As described, the etching process is performed by etching station 222, and control is applied by passing control signals to etching controller 223. In one embodiment, control of the etching process includes controlling one or more of the following: a thermal pattern across the substrate, a chemical concentration pattern in a plasma used in the etching process, an electric field pattern surrounding the substrate during the etching process, and a voltage applied to one or more electrodes during the etching process.

[0151] exist Figure 2 In the process flow depicted in and described above, embodiments of the present disclosure may be implemented by performing measurements of tilt on a substrate output from an etching station 222 (path 420), on a substrate output from a post-etch cleaning and / or annealing station 224 (path 421), and / or on a substrate output from another downstream processing device 226 (path 422).

[0152] In an embodiment of the present disclosure, the tilt is measured directly. Tilt is thus determined without comparing measurements made at different times on different structures. For example, the measurement of the tilt does not require a comparison between a metrology measurement made on the target layer before etching the target layer to produce the tilted etch path and a metrology measurement made on the target layer while the tilted etch path exists or after the tilted etch path has been used to affect subsequent processing of the substrate. The measurement of the tilt does not require a comparison of overlay measurements made before and after the tilted etch path has been formed.

[0153] Direct measurement of tilt is particularly beneficial where multiple etch steps cumulatively contribute to errors such as overcut. Alternative methods that rely on comparing overcut values ​​obtained before all of the multiple etch steps with overcut values ​​obtained after all of the multiple etch steps will not be able to distinguish between overcuts caused by tilt in one of the etch steps and overcuts caused by tilt in another etch step. Any prediction of tilt in a structure formed by one of the etch steps obtained using such a method will therefore be prone to error due to the possibility of a different tilt in one of the other etch steps. Figures 16 to 20 Example scenarios are discussed.

[0154] Fig.16 An example structure is depicted before multiple etching processes. The structure includes a lower layer 401, a target layer 402, an upper layer 403, and a patterned layer 404. The patterned layer 404 is used as a mask in the first etching step. Fig.17 As shown, the first etching step etches a pattern into the upper layer 403. In this embodiment, the etched upper layer may be referred to as a hard mask layer 423. The first etching step forms an inclined etch path in the hard mask layer 423.

[0155] In the second etching step, a pattern is etched into the target layer 402. The pattern etched into the upper layer 403, which is the pattern within the hard mask layer 423, defines the pattern etched into the target layer 403. The hard mask layer 423 thus serves as a mask in the second etching step. Fig.18 The structure is depicted after completing the second etching step. The second etching step forms a tilted etch path in the target layer 402. The etching parameters used in the first etching step may be different from the etching parameters used in the second etching step. The tilt in the etch path produced by the first etching step may therefore be different from the tilt in the etch path produced by the second etching step.

[0156] Can Fig.16 The structure and Fig.18 The structure in the instrument is measured by engraving. Fig.16 Overlay measurement of the structure may result in an overlay error between layers 404 and 401. Fig.18 The overlay measurement of the structure may result in an overlay error between the centroid of layer 402 and layer 401. Combining the two measurements results in an overlay error between the centroid of layer 404 and layer 402. Fig.19 , such a measurement will show that the displacement 440 of layer 402 relative to layer 404 is less than what has actually occurred due to the tilt of layer 402, since the tilt of layer 423 is in the opposite direction to the tilt in layer 402 (so that the tilts compensate each other). Controlling the second etching step based on this result will simply result in the tilt being maintained in the target layer 402, as in Fig. 20As depicted in the right hand side path 441 shown in FIG.

[0157] If the method of the present disclosure is applied to directly measure the tilt in the target layer 402, this error can be avoided and a more accurate reduction of the tilt in the target layer 402 can be provided, such as in Fig. 20 As depicted in the left hand path 442 shown in FIG.

[0158] In one embodiment, the method further includes measuring the overlap between patterns in different layers of the structure independently of measuring the tilt in the etch path through the target layer 402. Figures 16 to 20 In the context of a patterning process with multiple etch steps discussed above, measurements of the overlay can be used in conjunction with measured tilt in the target layer 402 and geometric information (e.g., thickness) about the layer of interest to derive the relative position of the target layer in layers other than the target layer (e.g., thickness). Figure 16-20 The derived tilt is used to control a patterning process for forming patterns in layers other than the target layer during formation of subsequently formed instances of the structure. In the above example, the tilt induced by the first etching process can therefore be derived. The derived tilt can be used to control the patterning process in any of the ways discussed above with respect to the tilt in the target layer 402 (e.g., to reduce the tilt). Alternatively or additionally, the nominal overlay between the target layer 402 and the different layers is changed to compensate for the derived tilt in layers other than the target layer 402.

[0159] refer to Fig.21 , a computer system 3200 is shown. The computer system 3200 includes a bus 3202 or other communication mechanism for communicating information and a processor 3204 (or multiple processors 3204 and 3205) coupled to the bus 3202 for processing information. The computer system 3200 also includes a main memory 3206, such as a random access memory (RAM) or other dynamic storage device, which is coupled to the bus 3202 to store information and instructions to be executed by the processor 3204. The main memory 3206 can also be used to store temporary variables or other intermediate information during the execution of instructions to be executed by the processor 3204. The computer system 3200 also includes a read-only memory (ROM) 3208 or other static storage device coupled to the bus 3202 to store static information and instructions for the processor 3204. A storage device 3210, such as a magnetic disk or optical disk, is provided and coupled to the bus 3202 to store information and instructions.

[0160] The computer system 3200 can be coupled to a display 3212, such as a cathode ray tube (CRT) or a flat panel or touch panel display, via bus 3202 for displaying information to a computer user. An input device 3214 including alphanumeric and other keys is coupled to bus 3202 to communicate information and command selections to processor 3204. Any type of user input device is a cursor control 3216, such as a mouse, trackball, or cursor direction keys, for communicating directional information and command selections to processor 3204 and for controlling cursor movement on display 3212. The input device typically has two degrees of freedom on two axes, a first axis (e.g., x) and a second axis (e.g., y) that allow the device to specify a position within a plane. A touch panel (screen) display can also be used as an input device.

[0161] The computer system 3200 may be suitable for use as a processing unit herein in response to the processor 3204 executing one or more sequences of one or more instructions contained in the main memory 3206. Such instructions may be read into the main memory 3206 from another computer-readable medium such as the storage device 3210. The execution of the sequence of instructions contained in the main memory 3206 causes the processor 3204 to perform the processes described herein. One or more processors in a multi-processing arrangement may also be used to execute the sequence of instructions contained in the main memory 3206. In alternative embodiments, hard-wired circuits may be used in place of or in combination with various software instructions. Therefore, the embodiments are not limited to any specific combination of hardware circuitry and software.

[0162] As used herein, the term "computer-readable medium" refers to any medium that participates in providing instructions to the processor 3204 for operation. Such a medium can take many forms, including but not limited to non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical disks or disks, such as storage devices 3210. Volatile media include dynamic memory, such as main memory 3206. Transmission media include coaxial cables, copper wires, and optical fibers, including the lines that include bus 3202. Transmission media can also take the form of sound waves or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. 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 with patterns of holes, RAMs, PROMs, and EPROMs, FLASH-EPROMs, any other memory chips or cartridges, carriers as described below, or any other media that a computer can read from them.

[0163] Various forms of computer-readable media are involved in carrying one or more sequences of one or more instructions to the processor 3204 for execution. For example, the instructions may be carried on a disk of a remote computer. The remote computer may load the instructions into its dynamic memory and send the instructions over the phone using a modem. A modem local to the computer system 3200 may receive the data on the telephone line and convert the data into an infrared signal using an infrared transmitter. An infrared detector coupled to the bus 3202 may receive the data carried in the infrared signal and place the data on the bus 3202. The bus 3202 carries the data to the main memory 3206, from which the processor 3204 retrieves and executes the instructions. The instructions received by the main memory 3206 may optionally be stored on the storage device 3210 before or after being executed by the processor 3204.

[0164] The computer system 3200 may also include a communication interface 3218 coupled to the bus 3202. The communication interface 3218 provides a two-way data communication coupled to a network link 3220 connected to a local network 3222. For example, the communication interface 3218 may be an integrated services digital network (ISDN) card or a modem to provide a data communication connection to a telephone line of a corresponding type. As another example, the communication interface 3218 may be a local area network (LAN) card that provides a data communication connection to a compatible LAN. A wireless link may also be implemented. In any such implementation, the communication interface 3218 sends and receives electrical signals, electromagnetic signals, or optical signals that carry digital data streams representing various types of information.

[0165] The network link 3220 typically provides data communication through one or more networks to other data devices. For example, the network link 3220 can provide a connection through a local network 3222 to a host computer 3224 or to data equipment operated by an Internet service provider (ISP) 3226. The ISP 3226 in turn provides data communication services through the World Wide Web packet data communication network (now commonly referred to as the "Internet" 3228). Both the local network 3222 and the Internet 3228 use electrical, electromagnetic or optical signals that carry digital data streams. The signals through the various networks and the signals on the network link 3220 and through the communication interface 3218 (which carry the digital data to and from the computer system 3200) are exemplary forms of carrier waves that transport the information.

[0166] The computer system 3200 can send messages and receive data, including program code, through (one or more) networks, network links 3220, and communication interfaces 3218. In the Internet example, the server 3230 can send a request code for an application program through the Internet 3228, the ISP 3226, the local area network 3222, and the communication interface 3218. According to one or more embodiments, for example, one such downloaded application provides a method as disclosed herein. The received code can be executed by the processor 3204 when it is received, and / or stored in the storage device 3210 or other non-volatile storage device for later execution. In this way, the computer system 3200 can obtain application code in the form of a carrier wave.

[0167] Embodiments of the present disclosure may take the form of a computer program containing one or more sequences of machine-readable instructions describing the methods disclosed herein or a data storage medium (e.g., a semiconductor memory, a magnetic disk, or an optical disk) having such a computer program stored therein. For example, the machine-readable instructions may be embodied in two or more computer programs. The two or more computer programs may be stored on one or more different memories and / or data storage media.

[0168] Any controller described herein may operate individually or in combination when one or more computer programs are read by one or more computer processors located in at least one component of the lithographic apparatus. The controllers may have any suitable configuration for receiving, processing, and sending signals individually or in combination. One or more processors are configured to communicate with at least one of the controllers. For example, each controller may include one or more processors to run a computer program including machine-readable instructions for the methods described above. The controller may include a data storage medium for storing such a computer program and / or hardware to receive such a medium. Therefore, the (one or more) controllers may operate according to the machine-readable instructions of one or more computer programs.

[0169] Although specific reference may be made herein to the use of metrology apparatus in the manufacture of ICs, it should be understood that the metrology apparatus and processes described herein may have other applications, such as to the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, and the like. The skilled person will appreciate that in such alternative applications, any use of the term "wafer" or "die" herein may be considered synonymous with the more general term "substrate" or target portion, respectively. The substrates referenced herein may be processed, for example, before or after exposure, using a ruler (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool, and / or one or more of various other tools. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. In addition, a substrate may be processed more than once, for example to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[0170] Although specific reference may have been made above to using embodiments of the present disclosure in the context of a lithographic apparatus, it will be appreciated that the present disclosure may be used in other applications, such as nanoimprint lithography, and where the context permits, is not limited to optical lithography. In the case of nanoimprint lithography, the pattern pattern is an imprint template or mold.

[0171] As used herein, the terms "radiation" and "beam" include all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g., having or having a wavelength of approximately 365, 355, 248, 193, 157, or 126 nm) and extreme ultraviolet (EUV) radiation (e.g., having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.

[0172] The term "lens" may refer, where the context permits, to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic, and electrostatic optical components.

[0173] References herein to crossing or exceeding a threshold may include something having a value below a particular value or below or equal to a particular value, something having a value above a particular value or above or equal to a particular value, something being ranked above or below other things (by, for example, sorting) based on, for example, a parameter, and the like.

[0174] References herein to correcting an error or correction of an error include eliminating the error or reducing the error to within a tolerance range.

[0175] As used herein, the terms "optimizing" and "optimization" refer to or mean adjusting a lithographic apparatus, a patterning process, and the like so that the result and / or process of a lithographic or patterning process has more desirable characteristics, such as higher accuracy of projection of a design layout on a substrate, a larger process window, and the like. Thus, as used herein, the terms "optimizing" and "optimization" refer to or mean the process of identifying one or more values ​​of one or more variables that provide an improvement (e.g., a local optimum) on at least one relevant metric compared to one or more values ​​for an initial set of those one or more variables. "Optimal" and other related terms should be interpreted accordingly. In one embodiment, the optimization step may be applied iteratively to provide further improvements on one or more metrics.

[0176] In the optimization process of a system, the depiction of the advantages of a system or process can be expressed as a cost function. The optimization process is reduced to the process of finding a set of parameters (design variables) of a system or process that optimizes (e.g., minimizes or maximizes) the cost function. The cost function can have any appropriate form depending on the goal of the optimization. For example, the cost function can be the weighted square root (RMS) of the deviation of certain characteristics (evaluation points) of the system or process relative to the expected values ​​(e.g., ideal values) of these characteristics; the cost function can also be the maximum value (i.e., the worst deviation) of these deviations. The term "evaluation point" herein should be broadly interpreted as including any characteristic of a system or process. The design variables of a system can be limited to a limited range and / or are interdependent due to the practicality of the implementation of the system or process. In the case of a lithographic apparatus or patterning process, constraints are often associated with the physical properties and characteristics of the hardware (such as tunable range and / or patterning equipment manufacturing capability design rules), and the evaluation points can include physical points on the resist image on the substrate and non-physical characteristics such as dose and focus.

[0177] Although specific embodiments of the present disclosure have been described above, it will be appreciated that the present disclosure may be practiced in other ways than those described. For example, the present disclosure may take the form of a computer program containing one or more sequences of machine-readable instructions describing the methods as disclosed above, or a data storage medium (e.g., a semiconductor memory, a magnetic disk, or an optical disk) having such a computer program stored therein.

[0178] In the block diagrams, the illustrated components are depicted as discrete functional blocks, but the embodiments are not limited to the systems in which the functions described herein are organized as illustrated. The functions provided by each of the components may be provided by software or hardware modules organized differently than currently depicted, for example such software or hardware may be mixed, combined, replicated, decomposed, distributed (e.g., within a data center or geographically) or otherwise organized differently. The functions described herein may be provided by one or more processors of one or more computers executing code stored on a tangible, non-transient machine-readable medium. In some cases, a third-party content delivery network may host some or all of the information communicated over the network, in which case the information (e.g., content) may be provided by sending instructions to retrieve the information from the content delivery network, assuming that the information (e.g., content) is supplied or otherwise provided.

[0179] Unless specifically stated otherwise, as will be apparent from the discussion, it should be appreciated that throughout this specification, discussions utilizing terms such as "process," "compute," "calculate," "determine," or the like refer to the actions or processes of a specific apparatus, such as a special purpose computer or similar special purpose electronic processing / computing device.

[0180] The reader should be aware that this application describes several inventions. Rather than separating those inventions into multiple isolated patent applications, the applicant has grouped these inventions into a single document because their related themes contribute to economy in the application process. However, the different advantages and aspects of such inventions should not be combined. In some cases, the embodiments solve all the shortcomings mentioned herein, but it should be understood that the present invention is independently useful, and some embodiments only solve a subset of professional problems or provide other unmentioned benefits that will be apparent to those skilled in the art who review this disclosure. Due to cost constraints, some inventions disclosed herein may not be claimed for protection now and may be claimed in a later submission (such as a continuation application) or by amending the current claims. Similarly, due to space constraints, the content of the invention of the invention paragraph of either the abstract or this document should not be regarded as a comprehensive enumeration of all such inventions or all aspects of such inventions.

[0181] Further embodiments of the invention are disclosed in the following ordered list of embodiments.

[0182] 1. A method for controlling a patterning process, comprising:

[0183] obtaining tilt data derived from a measurement of a tilt in an etch path through a target layer of a structure on a substrate, the tilt representing a deviation of a direction of the etch path from a perpendicular to a plane of the target layer; and

[0184] The tilt data is used to control a patterning process for forming a pattern in a further layer.

[0185] 2. The method of embodiment 1, wherein the patterning process includes an etching process, and the tilt data is used to control the etching process.

[0186] 3. The method of embodiment 2, wherein the controlling of the etching process is applied during formation of a pattern in a layer above the target layer by the etching process.

[0187] 4. The method of embodiment 2 or 3, wherein the controlling of the etching process is applied during formation of a pattern by the etching process in a layer in or on a subsequently formed instance of the structure.

[0188] 5. A method according to any one of embodiments 2-4, wherein the control of the etching process includes controlling one or more of the following: a thermal pattern across the substrate, a chemical concentration pattern in the plasma used in the etching process, an electric field pattern surrounding the substrate during the etching process, and a voltage applied to one or more electrodes during the etching process.

[0189] 6. The method of any preceding embodiment, wherein:

[0190] the patterning process comprises a lithographic pattern transfer step in which a patterning device is used to impart a pattern to the radiation beam in its cross-section so as to define a pattern to be transferred by the lithographic pattern transfer step; and

[0191] The tilt data is used to control the photolithographic pattern transfer step.

[0192] 7. The method of embodiment 6, wherein the controlling of the photolithographic pattern transfer step is applied during formation of a pattern in a layer above the target layer by the photolithographic pattern transfer step.

[0193] 8. The method of embodiment 6 or 7, wherein the control of the photolithographic pattern transfer step is applied during formation of a pattern by the photolithographic pattern transfer step in a layer in or on a subsequently formed instance of the structure.

[0194] 9. The method of any one of embodiments 6-8, wherein the controlling of the photolithographic pattern transfer step comprises modifying the patterning equipment.

[0195] 10. The method of any one of embodiments 6-9, wherein the controlling of the photolithographic pattern transfer step comprises modifying one or more of: a dose applied by the radiation beam, a focus of the radiation beam, one or more optical aberrations applied to the radiation beam.

[0196] 11. The method of any one of embodiments 6-10, wherein the controlling of the photolithographic pattern transfer step comprises varying a nominal overlap between a pattern formed in a layer by the photolithographic pattern transfer step and a pattern in a different layer.

[0197] 12. The method of any preceding embodiment, wherein the patterning process comprises a deposition step in which a layer of material is deposited, and the measured tilt is used to control the deposition step.

[0198] 13. The method according to embodiment 12, wherein the controlling of the depositing step is applied during the formation of a layer above the target layer by the depositing step.

[0199] 14. The method of embodiment 12 or 13, wherein the controlling of the depositing step is applied during formation of a layer in or on a subsequently formed instance of the structure by the depositing step.

[0200] 15. The method according to any one of embodiments 12-14, wherein the control of the deposition step includes controlling one or more of the following in the material layer deposited by the deposition step: stress distribution, height distribution, density distribution, and composition distribution.

[0201] 16. The method of any preceding embodiment, wherein the structure is formed by an etching process, the etching process comprising:

[0202] a first etching step in which a pattern is etched into a layer above the target layer; and

[0203] a second etching step, in which a pattern is etched into the target layer,

[0204] wherein the pattern etched into the layer above the target layer defines the pattern etched into the target layer.

[0205] 17. The method of embodiment 16, further comprising measuring overlay between patterns in different layers of the structure independently of the measuring of tilt in the etch path through the target layer.

[0206] 18. The method of embodiment 17, wherein:

[0207] The measured overlay is used in combination with the measured tilt in the target layer to derive the tilt in the etch path in the layer etched by the first etching step.

[0208] 19. The method of embodiment 18, wherein the derived tilt is used to control the first etching process during formation of subsequently formed instances of the structure.

[0209] 20. The method of embodiment 18 or 19, wherein a nominal overlay between the target layer and a different layer is changed to compensate for the resulting tilt.

[0210] 21. The method of any one of embodiments 1-15, further comprising measuring overlay between patterns in different layers of the structure independently of the measuring of tilt in the etch path through the target layer.

[0211] 22. The method of any preceding embodiment, wherein the measurement of tilt comprises a direct measurement of tilt.

[0212] 23. The method of any preceding embodiment, wherein the measuring of tilt comprises a non-destructive measurement of tilt.

[0213] 24. The method of any preceding embodiment, comprising performing said measurement of tilt.

[0214] 25. The method of any preceding embodiment, wherein the measuring of tilt comprises illuminating the structure with radiation and detecting radiation redirected by the structure.

[0215] 26. The method of embodiment 25, wherein the detected radiation is primarily zero-order radiation.

[0216] 27. The method of any one of embodiments 25-26, wherein the tilt is extracted from an asymmetric component of a detected representation of radiation redirected by the structure.

[0217] 28. The method of embodiment 27, wherein the detected representation comprises a detected pupil representation.

[0218] 29. The method of any preceding embodiment, wherein the structure comprises a device structure.

[0219] 30. The method of any preceding embodiment, wherein the structures include non-device structures within a substrate die that includes device structures.

[0220] 31. A method for manufacturing a device, comprising:

[0221] forming a structure including a target layer on a substrate;

[0222] obtaining tilt data derived from measuring a tilt in an etch path through the target layer, the tilt representing a deviation of the direction of the etch path from a perpendicular to the plane of the target layer; and

[0223] The tilt data is used to control a patterning process for forming a pattern in a further layer.

[0224] 32. A computer program product comprising a computer non-transitory readable medium having instructions thereon, the instructions, when executed by a computer, implementing the method of any one of embodiments 1-30.

[0225] It should be understood that the specification and drawings are not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

[0226] In view of this specification, modifications and alternative embodiments of various aspects of the present invention will be obvious to those skilled in the art. Therefore, this specification and the accompanying drawings should be understood to be merely illustrative and for the purpose of teaching those skilled in the art to perform the general mode of the present invention. It should be understood that the form of the present invention shown and described herein should be taken as an example of an embodiment. Elements and materials can replace the elements and materials illustrated and described herein, parts and processes can be reversed or omitted, certain features can be utilized independently, and the features of embodiments or embodiments can be combined, all of which will be apparent to those skilled in the art after benefiting from this specification of the present invention. Changes can be made in the elements described herein without departing from the spirit and scope of the present invention as described in the appended claims. The titles used herein are only for organizational purposes and are not intended to be used to limit the scope of this specification.

[0227] As used throughout this application, the word "may" is used in a permissive sense (i.e., meaning with possibility) rather than a mandatory sense (i.e., meaning must). The words "include", "including", and "includes" and the like are meant to include but are not limited to. As used throughout this application, unless the content clearly indicates otherwise, the singular forms of "one", "an", and "the" include plural references. Thus, for example, although other terms and phrases are used for one or more elements, such as "one or more", references to "an" element or "an" element include combinations of two or more elements. Unless otherwise indicated, the term "or" is non-exclusive, i.e., includes both "and" and "or". Terms describing conditional relationships, such as "in response to X, Y," "after X, Y," "if X, Y," "when X, Y," and the like, include causal relationships in which the antecedent is a necessary causal condition, the antecedent is a sufficient causal condition, or the antecedent is a contributing causal condition of the consequent, e.g., "statement X occurs after condition Y is satisfied" is common to "X occurs only after Y" and "X occurs after Y and Z." Such conditional relationships are not limited to consequences that follow immediately after the antecedent is satisfied, as some consequences may be delayed, and in conditional statements, the antecedents are connected to their consequents, e.g., the antecedent is related to the likelihood of the consequent occurring. Unless otherwise indicated, statements in which multiple attributes or functions are mapped to multiple objects (e.g., one or more processors that perform steps A, B, C, and D) include both all such attributes or functions being mapped to all such objects and subsets of attributes or functions being mapped to subsets of attributes or functions (e.g., both all processors each perform steps AD), as well as cases in which processor 1 performs step A, processor 2 performs steps B and portions of step C, and processor 3 performs steps C and portions of step D. In addition, unless otherwise indicated, a statement that a value or action is "based on" another condition or value includes both instances where the condition or value is the only factor and instances where the condition or value is one of multiple factors. Unless otherwise indicated, a statement that "each" instance in some set has a certain property should not be understood to exclude the case where some other identical or similar member of the larger set does not have the property, that is, each does not necessarily mean every one.

[0228] In the event that certain U.S. patents, U.S. patent applications, or other materials (e.g., articles) have been incorporated by reference, the text of such U.S. patents, U.S. patent applications, and other materials is incorporated by reference only to the extent that there is no conflict between such materials and the statements and drawings set forth herein. In the event of such a conflict, any such conflicting text in such U.S. patents, U.S. patent applications, and other materials incorporated by reference is not specifically incorporated by reference herein.

[0229] The above description is intended to be illustrative rather than limiting. It will therefore be apparent to those skilled in the art that modifications may be made to the present disclosure as described without departing from the scope of the claims set forth below.

Claims

1. A computer program product comprising a computer non-transitory readable medium having instructions thereon, the instructions being configured to cause a computer system to perform at least the following operations when executed by the computer system: obtaining tilt data derived from a measurement of a tilt in an etch path through a structure of a target layer located on a substrate, the tilt representing a deviation of the direction of the etch path from a perpendicular to a plane of the target layer; and The tilt data is used to configure a patterning process or a deposition step for forming a pattern in a further layer, the configuration of the patterning process or the deposition step being associated with controlling the overlapping between patterns produced in different layers. 2 . The computer program product of claim 1 , wherein the patterning process comprises an etching process, and the tilt data is used to configure the etching process. 3 . The computer program product of claim 2 , wherein the configuration of the etching process is applied during formation of a pattern in a layer above the target layer by the etching process.

4. A computer program product according to claim 2 or 3, wherein the configuration of the etching process is applied during formation of a pattern in a layer in or on a subsequently formed instance of the structure by the etching process.

5. A computer program product according to claim 2 or 3, wherein the configuration of the etching process includes configuring one or more of the following: a thermal pattern across the substrate, a chemical concentration pattern in the plasma used in the etching process, an electric field pattern surrounding the substrate during the etching process, and a voltage applied to one or more electrodes during the etching process.

6. The computer program product of claim 1, wherein: The patterning process comprises a lithographic pattern transfer step in which a patterning device is used to impart a pattern to the radiation beam in its cross-section so as to define a pattern to be transferred by the lithographic pattern transfer step; and The tilt data is used to configure the photolithographic pattern transfer step.

7. The computer program product of claim 6, wherein the configuration of the photolithographic pattern transfer step is applied during formation of a pattern in a layer above the target layer by the photolithographic pattern transfer step.

8. A computer program product according to claim 6 or 7, wherein the configuring of the lithographic pattern transfer step comprises modifying the patterning equipment.

9. The computer program product of claim 1, wherein the patterning process comprises a deposition step in which a layer of material is deposited, and the measured tilt is used to configure the deposition step.

10. The computer program product of claim 9, wherein the configuring of the depositing step comprises controlling one or more of the following in the material layer deposited by the depositing step: a stress distribution, a height distribution, a density distribution, a composition distribution.

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