Method and system for detecting and / or quantifying manufacturing inaccuracy

Abstract

The present disclosure relates to a method for detecting and / or quantifying manufacturing inaccuracies resulting from a lithographic process. The method includes providing at least one design for fabricating a structure on a substrate using a set of lithographic processes wherein the fabricated structure defines an array of metrology sensors wherein each metrology sensor is adapted to produce one of a known and limited set of possible different physical events when a physical process is applied, wherein the resulting physical event is unknown prior to application of the physical process, depending on the manufacturing inaccuracy resulting from at least one of the set of lithographic processes, and a shift state of the structure being manufactured, or has one or more physical entities associated with no structure being manufactured prior to application of the physical process; applying a group of photoetching processes; applying a physical process; and reading out the physical events generated by all the metering sensors. The disclosure also relates to a metering system.

Description

Technical Field

[0001] The present disclosure relates to a method for detecting and / or quantifying manufacturing inaccuracies resulting from a photolithography process. The present disclosure also relates to a metrology sensor assembly and a metrology system. Background Art

[0002] Lithographic equipment is commonly used in the manufacture of integrated circuits and applies a designed pattern to a substrate. A typical substrate is a semiconductor substrate, such as Si. The transfer of the pattern is performed by irradiating a radiation-sensitive layer of material (resist) uniformly deposited on the substrate.

[0003] Known lithography equipment includes electron beam writers, laser beam writers, steppers and scanners. Each of these tools converts computer-aided design (CAD) into a pattern on a resist on a substrate, which is an essential part of semiconductor device manufacturing. The electron beam writer uses rasterization of an electron beam focused to a single spot of a few nanometers to expose the portion of the resist that will form the feature of interest, while the scanner uses a wide-area beam modulated by a mask to achieve selective exposure of the resist. The image of the mask projected onto the substrate is reduced by an optical device such as a deep ultraviolet lens (DUV) or an extreme ultraviolet mirror (EUV). In the case of DUV, it is important that the light is transmitted through the mask, while in EUV, the mask is a mirror, and it is important that the light is reflected by the mask. In the semiconductor industry, electron beam lithography is mainly used to pattern features on a mask. The scanner uses a mask to perform lithography steps at high speed and wafer throughput. The mask is also a typical substrate, on top of which write-based lithography is performed to transfer the design of the pattern to the substrate where the device will be produced. There are multi-beam variants of beam writers.

[0004] All lithography equipment suffers from a variety of inaccuracies, which introduce small differences between what is designed in the CAD file and the pattern on the substrate. These inaccuracies affect the placement, shape, size, and roughness of the pattern produced on the wafer, which ultimately affects the performance and yield of semiconductor devices. Some of these types of inaccuracies are called edge placement errors (EPE) and include overlay (OV; a measurement of pattern-to-pattern shift between layers), critical dimension (CD, including local critical dimension LCD and critical dimension uniformity CDU), registration (REG; pattern position relative to an absolute grid), and any roughness type (including line edge roughness LER and line width roughness LWR) and random index.

[0005] Any EPE present at any level (from sub-device level, device level, system level, die level up to wafer and batch level) caused by any mask, lithography equipment, lithography process and other equipment or process steps involved in the creation of the structure accumulates after several masks to cause a potentially large mismatch between the expected design and the actual design on the substrate, which can strongly affect the yield of the manufactured device. A defect is defined as any physical, electrical or parametric deviation that can affect the yield. Due to the increase in the number of separate process steps and masks and the need for denser features, maintaining a low number of defects requires increasingly stringent EPE budgets, which requires strict measurement, control and mitigation schemes for EPE at each step and level for each mask and lithography equipment.

[0006] Electron beam lithography suffers from various sources of inaccuracy introduced into EPE, such as imperfect beam focusing and astigmatism, diffraction and spherical and chromatic aberrations, beam deflection lag, stage errors (including stitching, non-orthogonality and calibration errors), overlay misalignment, registration errors, proximity effects, charging effects, fogging effects, thermal effects, etc., as well as drift of several beam properties during exposure (such as focus, astigmatism, XY positioning and calibration of beam deflection, etc.).

[0007] In addition to the EPE originating from the written mask, mask-based lithography using scanners suffers from various sources of inaccuracy that may further affect the EPE, such as shot noise, overlay misalignment, optical proximity effects, phase shift effects, source mask optimization errors, illumination errors, pupil errors, flare effects, shadowing effects, imperfect focus, wafer and mask bending and thermal expansion, wafer clamping, mask clamping, distortion caused by filming, dose errors, imperfect rasterization, stage (mask and wafer stage) errors, tool matching, etc.

[0008] In addition to the inaccuracies that occur during resist exposure on the substrate, a variety of other inaccuracies and defects in the resist can be found due to resist baking and development, resist erosion during dry etching, and local random defects such as microbridges and broken lines, missing contacts and breaks, random effects, material quality, etc. Dry etching also introduces inaccuracies that affect overlay, CD and LCDU, etc., such as wafer edge effects, non-uniformity and drift in etch rate and etch direction, redeposition, resist hardening, microloading, pitch wandering, etch bias, etc. In addition, when many layers are stacked on top of each other, 3D effects also affect EPE.

[0009] All of these inaccuracy sources accumulate after each processing step and introduce various EPEs in the final device that affect the manufacturing yield and density of the manufactured device and must be detected, studied, and minimized to increase manufacturing yield and overall device performance.

[0010] Metrology tools that can detect and quantify any of these EPEs play an important role in process control and risk mitigation in the production of semiconductor devices. Metrology tools also play a key role in research and development activities and yield improvement efforts aimed at optimizing the operating conditions of lithography equipment and other equipment involved in the manufacture of semiconductor devices to maximize yield, reduce costs, increase device density, and improve performance. As the density of nanofabrication features increases and feature sizes decrease, the development of metrology tools for detecting and quantifying these errors at the single-digit nanometer and sub-nanometer levels is critical to determining whether the tool is working as expected (monitoring), and if not, what the source of the error or inaccuracy is (troubleshooting).

[0011] There are two main categories of technologies relevant to this context: inspection and metrology. Inspection techniques typically use optical microscopy to look for defects to detect defects at the nanometer, micrometer, or larger (such as particles), while metrology techniques measure the critical dimensions and coordinates (absolute and relative) of specific features or sub-features on a patterned substrate to assess the fidelity of pattern transfer or ensure proper overlap of subsequent patterns with pre-existing patterns, etc. As semiconductor manufacturing technology continues to advance to smaller and smaller critical dimensions, metrology must be performed on nano features and must be able to achieve extremely high resolution and accuracy at high throughput, otherwise significant sources of patterning variability may be detected too late in production and result in defective chips. It is important to the semiconductor industry to be able to measure EPE to perform process control or in order to utilize any actionable process corrections (such as high-order scanner corrections) in any tool or process step that can improve the final yield and performance of the manufactured devices.

[0012] Two broad types of techniques are used today to perform critical dimension and overlay metrology: (1) imaging-based (optical or scanning electron microscopy) and (2) scattering-based (scatterometry, OCD).

[0013] Metrology based on optical scattering (called scatterometry) derives shape, size and composition information from the scattering pattern observed in light that has interacted with the sample. A regular array of similar features is required, which can be features within a circuit (e.g., a line array) or specially designed measurement targets (also called scribes) typically located in the area between dies on a wafer. Scatterometry is often implemented using a dedicated grating structure (regularly spaced arrays of lines and spaces) as the measurement target, where the interference pattern of monochromatic light interacting with the grating is analyzed to derive information about critical dimensions and overlay with sub-nanometer accuracy. A typical metrology application involves performing a series of scatterometry measurements at different wavelengths of optical excitation.

[0014] Critical dimension scanning electron microscopy (CD-SEM) is a direct measurement technique and works by taking measurements using computational image processing of a scanning electron microscope (SEM) image of a pattern (typical examples are the width and pitch of an array of lines, or the diameter and pitch of an array of holes). This technique, which operates in a vacuum, is commonly used to measure critical dimensions of patterns as well as to quantify other types of important lithography defects such as random errors (missing holes, broken lines, etc.) and LER. Optical microscopy using a wavelength-tunable light source with a specific design target is used to perform overlay metrology in a technique called image-based overlay.

[0015] Scattering measurements and other OCD techniques require specialized optical equipment including coherent wavelength tunable light sources and spectrometers to work. They typically operate on a single point at a time rather than on an area. Some of these techniques also require special types of grating structures of certain micron sizes to work, which limits their practicality for device metrology. CD-SEMs are typically run on capital-intensive equipment and have very low throughput due to the very high magnification required to resolve sub-nanometer features. In addition, each of these techniques suffers from inherent noise, inaccuracies or origin errors in the imaging and detection components of the tool, calibration of the tool, and calculations (such as image processing, modeling, and fitting) that lead to the final metrology data.

[0016] In summary, available metrology technologies are low throughput and require complex and expensive tools and rely on sophisticated data analysis, which limits the frequency and density of metrology performed for process control and monitoring. Summary of the invention

[0017] Lithographic systems inevitably introduce errors in where and how the edges of a pattern are placed on a substrate, so-called edge placement errors (EPEs). The detection and quantification of EPEs is critical because they undesirably affect all micro- and nano-fabricated structures and have historically been the cause of major yield issues in the semiconductor industry. In the present disclosure, a new metrology method is described that binarizes EPEs into discrete, identifiable physical events on a substrate undergoing lithography. The method is compatible with all lithography systems and is independent of all other existing metrology techniques, which expands the toolbox available for sensing and quantifying errors in the lithography origin as well as SEM, TEM, AFM and diffraction-based techniques.

[0018] The present disclosure is directed to methods and systems that address at least some of the above-mentioned limitations.

[0019] According to a first embodiment, the present disclosure relates to a method for detecting and / or quantifying manufacturing inaccuracies resulting from a lithography process, comprising:

[0020] At least one design is provided for fabricating a structure on a substrate using a set of photolithography processes, wherein the fabricated structure defines an array of metrology sensors, wherein each metrology sensor is adapted to produce one of a known and finite set of possible different physical events upon application of a physical process, wherein the produced physical events:

[0021] is unknown before applying the physical process,

[0022] depending on manufacturing inaccuracies resulting from at least one of the set of lithographic processes, and

[0023] is a displaced state of said fabricated structure, or has one or more physical entities associated with said fabricated structure that did not exist prior to application of said physical process;

[0024] applying said set of photolithography processes to obtain said fabricated structure;

[0025] applying said physical process thereby producing one of said known and finite set of possible different physical events for each metrology sensor;

[0026] Reading physical events generated by all metering sensors; and

[0027] The resulting physical events of all metrology sensors are processed to detect and / or quantify manufacturing inaccuracies resulting from the lithography process.

[0028] Those skilled in the art are familiar with photolithography systems and processes and will be able to perform the examples of such processes mentioned in this disclosure.

[0029] The present disclosure also relates to a method for detecting and / or quantifying manufacturing inaccuracies produced by a lithographic apparatus, comprising the following steps:

[0030] providing at least one pattern for fabricating a structure on a substrate, the at least one pattern defining an array of metrology sensors, each metrology sensor comprising a displaceable substance configured to be in a stationary state and distributed over a local area, wherein the displaceable substance is adapted to reach a displaced state towards a predetermined discrete position within the local area during a displacement process upon application of a physical stressor;

[0031] obtaining the fabricated structure on the substrate from the lithographic apparatus, wherein the displaceable mass of the metrology sensor is in a stationary state;

[0032] applying the physical stressor to each metrology sensor for at least a predetermined period of time; and

[0033] The metrology sensor is read out to detect and / or quantify manufacturing inaccuracies produced by the lithographic apparatus.

[0034] By imaging a metrology sensor such as described in the last step of the previously disclosed method, metrology related to semiconductor manufacturing can be performed with nanometer resolution using a basic optical microscope. This is a cost and time effective approach compared to the existing metrology techniques previously described. The disclosed method can also be configured to generate a new metrology data stream that is independent of all other metrology techniques previously described, which can be used to effectively detect, study, control and minimize any of the aforementioned sources of EPE in masks, lithography equipment, etching and deposition processes and tools.

[0035] The disclosed method can be used in a scanner identification process. It can further be used in a patterning control process.

[0036] Advantageously, the method can be said to be conducting nanoscale experiments, each of whose results is the displacement of a substance (liquid or solid) to its displacement state, or the creation of one or more physical entities, the number or placement of which is sensitive to the lithographic pattern and its errors. The geometry and size of the lithographic pattern can be considered as an analog signal containing EPE, which will be processed by the experiment to detect EPE. The displacement of the substance or the number or placement of the physical entity constitutes the experimental result in the form of a binary (when the set of all possible physical events is equal to 2) or discrete (when the set of all possible physical events is greater than 2) signal generated by each metrology sensor and depends on the lithographic pattern and its deviation from the ideal design. After performing the different steps of the method, each metrology sensor contains data on the inaccuracies introduced by the entire lithographic process, including the contribution of the lithographic equipment, in a binary or discrete format, comparable to an analog-to-digital converter. When one of these lithographic processes has a dominant contribution to the metrology sensor, the metrology sensor contains data on this particular lithographic process. By manufacturing at least one pattern as described, and applying a physical process, it can be said that the method replaces computer-based data processing with multiple parallel physical processes that perform analog-to-digital conversion on a substrate. The method enables the optional use of imaging to collect data generated by the metrology sensor into a computer. As long as the resolution and signal-to-noise ratio of the imaging system (determined by the magnification, illumination intensity, camera and exposure settings used, etc.) are sufficient to detect the discretized data generated by the metrology sensor on the substrate, the metrology data becomes independent of the imaging technology, its associated calibration and computer-based data processing.

[0037] In the method disclosed herein, information related to the EPE is advantageously processed and binarized on the substrate by means of experiments on the sensitivity of the pattern on the substrate defined by the lithographic process and equipment. Imaging can be used to collect data that has been discretized on the substrate for statistical analysis in a computer. Therefore, the method described can be said to perform the measurement of the EPE before the data is digitized in the computer.

[0038] In the present method, the data processing of EPE is therefore said to be before the digitization of the data in the imaging or computer. This is in contrast to conventional metrology techniques, for which the data processing of EPE needs to be performed by computer algorithms or using machine learning methods after the data is digitized in the computer, and therefore follows the imaging or inspection steps. The present method generates universally readable metrology data, and after the creation of the binary experiment or physical entity involving the displaceable material has occurred on the substrate, there is no additional source of error or inaccuracy introduced in the metrology data. The only requirement is that the result of each binary experiment can be correctly aligned to the corresponding pattern in the original design. This is in sharp contrast to conventional metrology techniques, which are susceptible to the influence of multiple errors and inaccuracies introduced by the sensing / imaging system and computational modeling and analysis, and the final measurement extracted thereby depends on the steps involved in the creation of the metrology data, starting from the arrangement of the excitation and imaging system, the digitization process to the computer-based data processing, such as individual components (such as lenses and detectors), calibration methods, measurement conditions and parameters, and models and algorithms. For example, unlike the present method, model-based measurement techniques such as interferometry and scatterometry use experimental data and simulations of the underlying physics to extract quantitative estimates of the measured variables of a sample based on a parametric model of the sample. The uncertainty of these estimates is based not only on the uncertainty of the experimental data, but also on the sensitivity of the data to the model parameters, parametric correlations between those parameters, and fits, etc.

[0039] In the present disclosure, EPE measurement data written in a stable physical bitmap format on the chip can be collected by imaging at a spatial resolution much lower than the length scale of the error because they are encoded and binarized in much larger physical bits. Conceptually, this is similar to the principle of a barcode: data is encoded in a bit string and presented in a simple visual format that is machine-readable. The method of the present disclosure is similar to printing a two-dimensional barcode (such as a QR code) with ink on paper, where the actual printed barcode depends on the errors generated by the printer and the ink is only displayed after a specific process (in our case, a stress source, or more generally, a physical process) is applied. The deviation of the displayed barcode from the expected barcode can be easily determined and used to calculate the EPE. In this analogy, the printer is a lithographic printing tool, the paper is a semiconductor substrate with one or more layers of material that can be patterned, and the ink pattern encoding information is a physical bit generated by the binarization experiment on each metering sensor. Although the type of encoded EPE information (CDU, overlap, etc.) is determined by the design of the specific type of pattern printed on the substrate, the form of the physical bit remains the same for the same combination of substrate and physical process. In other words, the encoding and printing process of the barcode remains the same while allowing different types of EPE information to be encoded. Although the physical bit can be larger than 200nm and can therefore be read with a basic optical microscope (such as that found in some wafer inspection equipment), the data stored in the bitmap can encode metrological data about the EPE with an accuracy better than 10nm (i.e., even EPEs of 10nm and smaller sizes can be detected and quantified using this method). In addition, as long as the readout technology can distinguish the individual physical bits and align the bits to the patterns in the design used to produce them, the entire metrological data can be retrieved without error regardless of the imaging technology or microscope used, as long as the appropriate instructions are known or given to correctly interpret the bit string. Since the entire metrological data exists in the physical bits on the substrate, no improved calibration, magnification or contrast will improve the measurement accuracy and precision when imaging the physical bits: the measurement data becomes free of photon and electron deviations or origin noise in image acquisition. Different microscopes imaging the same bitmap will be able to read exactly the same metrological data. In this way, it can be said that the measurement of the EPE is performed before imaging. Imaging simply requires reading or digitizing already processed metrology data and processing it into qualitative or quantitative measurements.

[0040] The metrology data generated by the present method is independent of many of the limitations that typically plague optical techniques. For example, in the present invention, an optical microscope, whose resolution is typically limited by the wavelength of the light and the lenses used, can sense localized EPEs at sub-10nm levels on a single isolated structure. This is because if a metrology sensor is designed in such a way that we expect a specific bit, but after binarization, we find a different bit, then we know that a patterned error has been created in that particular metrology sensor.

[0041] The metrology data generated by the present method is independent of many of the limitations that usually plague CD-SEM and CD-AFM. For example, in the present invention, complex image processing is not required to obtain size and shape information about the pattern from the image, which is the case in CD-SEM and CD-AFM. In the present invention, only simple image processing is required, which can detect binary or discrete data from the metrology sensor, and its format is known. In addition, in the present invention, the size of the pixel used for imaging only needs to be large enough to distinguish the binary or discrete data from the metrology sensor, and can be several orders of magnitude larger than the pixel that needs to distinguish the nano features of interest in CD-SEM and CD-AFM. Therefore, in the current case, the effective physical size of each imaging pixel can be multiple orders of magnitude larger than the length scale of the EPE information. This leads to huge savings in data acquisition throughput, data storage and data processing. In addition, due to compatibility with high-throughput inspection optical microscopes or wafer inspection tools used in semiconductor foundries, the detection and measurement of nano or sub-nanometer EPE can be performed at the wafer level. Using this method, it is possible to capture wafer-level features of nano EPE with high wafer throughput. In addition, using the method currently described, different imaging systems will be able to read the same metrology data from the same EPE measurement without increased noise or deviation. This is in sharp contrast to all other metrology techniques, where the measurement data is inevitably sensitive to all downstream hardware components involved in the digitization of pattern information containing EPE and the software layer that calculates the measurement data from the digitized data. Such hardware can include illumination sources, filters, lenses, beam grating systems, mechanical stages, CMOS sensors, etc., and software can include physical equations, physical constants, CAD, meshing, edge detection algorithms, parameterization, fitting, etc. In other metrology techniques, any systematic or random errors introduced by any of these components or steps affect the accuracy and precision of the final metrology data. Therefore, if not properly calibrated, two different metrology tools can produce significantly different measurements of the same error. Two different image processing algorithms or physical models can produce different measurements from the same raw digitized data. The aberration caused by the tool optics can be said to be the main source of systematic errors in image-based metrology, and our method is insensitive to it in almost the same way as barcode readers.

[0042] The ability to generate data that is independent of other metrology techniques and their inherent errors strongly supports hybrid metrology and can be used to enhance, monitor or calibrate the execution of any existing metrology technique used with lithographic patterning and lithography processes.

[0043] In one embodiment, the metrology sensor comprises a plurality of mechanical actuators connected by at least one linking element in a strained state representing the rest state, wherein each mechanical actuator is adapted to trigger mechanical actuation upon initiation of an etching process to reach an end state within a predetermined amount of time, and wherein each linking element reaches an unstrained state representing the displaced state when one of the mechanical actuators reaches its end state, and wherein the step of simultaneously applying the physical stressor to each metrology sensor for at least the predetermined period of time comprises simultaneously etching the array of metrology sensors for at least the predetermined period of time.

[0044] In this embodiment, the expected result of the actuation of the mechanical actuators is known because the actuators are designed to behave in a specific way. The mechanical actuators can be thought of as timers. When the first of the timers reaches its end state, it can trigger a mechanical actuation, which will put the link element in a displaced state. When the mechanical actuation is triggered, the link element can be physically displaced toward one of the mechanical actuators (one that is not actuated or actuated later than the other). In this state, the optical microscope can provide an image covering the entire area of ​​multiple metrology sensors, thereby obtaining immediate detailed information about the manufacturing inaccuracies generated by the lithographic equipment by analyzing the deviations from the expected results.

[0045] The present disclosure also relates to a metrology sensor assembly, comprising:

[0046] substrate; and

[0047] An array of metrology sensors, each metrology sensor comprising a plurality of mechanical actuators connected by at least one linking element in a strained state, wherein each mechanical actuator is adapted to trigger mechanical actuation at the start of an etching process to reach an end state within a predetermined amount of time, and wherein each linking element reaches an unstrained state when one of the mechanical actuators reaches its end state.

[0048] As will be appreciated by those skilled in the art, any embodiment of the presently disclosed metrology sensor assembly may be used in any embodiment of the presently disclosed method to detect and / or quantify manufacturing inaccuracies produced by a lithographic apparatus, and vice versa.

[0049] The present disclosure also relates to a metering system, comprising:

[0050] A lithographic apparatus configured to pattern a radiation sensitive resist such as a polymer on a substrate to fabricate a structure using a design comprising an array of metrology sensors, wherein each metrology sensor is adapted to produce one of a known and finite set of possible different physical events upon application of a physical process, wherein the produced physical events:

[0051] is unknown before applying the physical process,

[0052] depends on the manufacturing inaccuracies produced by the lithographic apparatus, and

[0053] is a displaced state of said fabricated structure, or has one or more physical entities associated with said fabricated structure that did not exist prior to application of said physical process;

[0054] A system is provided, the system being adapted to apply the physical process to each metrology sensor.

[0055] The present disclosure also relates to a metering system, comprising:

[0056] a lithographic apparatus configured to pattern a radiation sensitive resist such as a polymer on a substrate using a design comprising an array of metrology sensors, each metrology sensor comprising a displaceable substance configured to be in a stationary state and distributed over a local area, wherein the displaceable substance is adapted to reach a displaced state towards a predetermined discrete position within the local area during a displacement process upon application of a physical stressor;

[0057] A physical stressor device, such as an etching device or system, adapted to apply a physical stressor for at least a predetermined period of time; and

[0058] An imaging device for imaging the metrology sensor to detect and / or quantify manufacturing inaccuracies produced by the lithographic apparatus.

[0059] Advantageously, by using the previously described metrology system, due to the a priori knowledge of the location of the metrology sensor on the surface of the patterned substrate being observed, metrology information obtained from the metrology sensor can be derived by a fast image recognition process (such as template matching) applied to a subset of pixels in the total imaging area. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The invention will be described below with reference to the accompanying drawings. The drawings are examples of embodiments and are not limited to the presently disclosed metrology sensor assembly, metrology system and method for detecting and / or quantifying manufacturing inaccuracies produced by a lithographic apparatus. As an example, it is generally considered that the metrology sensor is suitable for producing one of a known and limited set of possible different physical events when a physical process is applied. The drawings may show examples of mechanical actuators.

[0061] Figures 1A-1C Examples of metering sensors in different states are shown.

[0062] Figures 2A-2D An embodiment of the presently disclosed metrology sensor using a mechanical actuator is shown.

[0063] Figure 3 Another embodiment of the presently disclosed metering sensor is shown.

[0064] Figures 4A-4B An example of an array of metrology sensors distributed on a substrate after applying a physical process and the resulting bitmap conversion of binarized physical events after applying Boolean logic is shown.

[0065] Figures 5A-5H An embodiment of the presently disclosed metering sensor is shown wherein the displaceable substance is comprised of a liquid or a gel.

[0066] Figure 6 A diagram showing how a mechanical actuator or end region of a gel or liquid may be used to represent a timer for use in the presently disclosed metering sensor.

[0067] Figure 7A-7B A further illustration shows how a timer may be used to obtain a physical record or more generally a physical event on a substrate which may be used to detect and / or quantify manufacturing inaccuracies resulting from a lithographic process.

[0068] Figures 8A-8B An example of a pattern cut in two separate but complementary parts is shown, which can make an entire complete metrology sensor for detecting misalignment between two separate exposures.

[0069] Fig. 9 An example of a flow chart of the presently disclosed method for detecting and / or quantifying manufacturing inaccuracies resulting from a photolithography process is shown. DETAILED DESCRIPTION

[0070] The present disclosure relates to a method for detecting and / or quantifying manufacturing inaccuracies resulting from a photolithography process. Manufacturing inaccuracies may be, for example, edge placement errors, including CD, CDU, LCDU, overlay, registration, roughness, and random index.

[0071] Preferably, in a first step, at least one design is provided for manufacturing a structure on a substrate using a set of lithographic processes. The fabricated structure may define an array of metrology sensors, wherein each metrology sensor is adapted to produce one of a known and finite set of possible different physical events when a physical process is applied. The produced physical event may be unknown before the physical process is applied, depending on a manufacturing inaccuracy produced by at least one of the set of lithographic processes, and may be a shifted state of the fabricated structure, or have one or more physical entities associated with the fabricated structure that did not exist before the physical process was applied. The set of lithographic processes may then be applied to obtain the fabricated structure. The physical process may then be applied to produce one of a known and finite set of possible different physical events for each metrology sensor. The produced physical events of all metrology sensors may then be read out, and the produced physical events of all metrology sensors may be processed to detect and / or quantify the manufacturing inaccuracies produced by the lithographic processes. The produced physical events may be stored digitally. The produced physical events of all metrology sensors may be read out using, for example, imaging.

[0072] The metrology sensor may be configured such that the physical event produced is suitably larger than the inaccuracy itself. In this way, the inaccuracy may be read indirectly, for example by imaging at a much lower spatial resolution than the length scale of the error. Manufacturing inaccuracies may arise from edge placement errors, where the edge placement error is less than 5 nm, or where the edge placement error is less than 1 nm.

[0073] The photolithography process can generally be said to involve the transfer of the design pattern to the substrate using, for example, an exposure tool and the subsequent development of the resist. In a single run and without the use of a priori knowledge of metrology, the manufacturing inaccuracy caused by the entire photolithography process can be determined. When used in conjunction with other metrology tools as a whole, or in conjunction with a priori knowledge of the relative sizes of different error sources that produce manufacturing inaccuracies, the exact contribution of a specific device or process step can be quantified. In this way, a specific photolithography process and physical process can be performed so that the contribution to the overall manufacturing inaccuracy due to the exposure tool is dominant. Similarly, when using an extremely well calibrated and stable exposure tool, the inaccuracy caused by the dry etching or wet etching process can be quantified. In one embodiment, the set of photolithography processes includes at least exposure and development of a radiation-sensitive resist.

[0074] According to one example, at least one lithographic pattern for manufacturing a structure on a substrate is provided by a lithographic device, defining an array of metrology sensors. In this example, each metrology sensor includes a displaceable substance configured to be in a static state and distributed on a local area, wherein the displaceable substance is suitable for reaching a displaced state toward a predetermined discrete position within the local area during a displacement process when a physical stressor is applied. The physical stressor can be an etching process or any suitable physical process that causes the displaceable substance to reach a displaced state, including, for example, changing temperature or phase, or applying vibration or evaporation. The displaceable substance of the manufactured metrology sensor is initially manufactured in a static state. In another step, the physical stressor is applied to each metrology sensor for at least a predetermined period of time. In another step, the metrology sensor is imaged to collect data for detecting and quantifying any inaccuracies generated by the lithographic device.

[0075] The lithographic apparatus may be an electron beam writer, a laser beam writer, a nanoimprinter, a stepper, a scanner, or other apparatus used in the field of device nanofabrication. The lithographic apparatus is not necessarily an exposure tool, but may also be a pattern transfer tool, such as a tool for applying dry etching or wet etching. The photolithographic process should be interpreted as broadly covering any suitable use of one or more steps using the lithographic apparatus. An advantage of the currently disclosed method, system, and sensor is that any lithographic apparatus can be used, and therefore metrology data from any lithographic apparatus can be generated. The technology does not depend on a specific lithographic apparatus. It can be said that the currently disclosed method and system can transform any lithographic apparatus into a metrology apparatus that generates metrology data about itself, thereby not requiring other metrology tools other than itself to generate metrology data, that is, only using the lithographic process to generate metrology data. By moving data processing to the substrate, imaging such as an optical microscope can be used to evaluate the work of any lithographic apparatus or lithographic apparatus. The substrate on which the structure is placed may be a rigid semiconductor substrate, such as silicon or germanium, a metal (such as aluminum or gold), an oxide (such as SiO2 or sapphire or quartz), or any substrate used in the field of device nanofabrication and semiconductor manufacturing.

[0076] The structures fabricated in the context of the present disclosure may be resist, polymer, solid, liquid, gel or stacked or a combination of these materials.

[0077] The physical event can be a change in optical properties, a change in shape, a change in size, a change in placement in XY or Z, a buckling / bending pattern, etc. in the whole or part of a structure or an added visible entity. It may result from the removal or addition of material. The actual type of physical event is known to the operator before the physical process is applied and depends on the pattern, substrate and physical process. Different event types can be used alone or simultaneously, and the same combination of pattern, substrate and physical process can trigger more than one type of physical event. As described above, each metrology sensor is suitable for generating one of a known and limited set of possible different physical events when the physical process is applied. Examples of physical events include events in which the structure in the metrology sensor does not generate a visible entity, generates one visible entity, or generates several visible entities near a structure that did not exist before the physical process was applied, for example, a scattering point of light, such as a crack, a hole or a particle. Other examples of physical events include visible and discretely quantifiable changes in the structure itself or another structure derived from the structure, such as shrinkage-expansion of area, movement to the left or right, clockwise or counterclockwise twisting, bending up or down, etc. In one embodiment, the physical event is a change in shape, size or position of part or all of the structure, preferably wherein the change in shape, size or position of part or all of the structure is greater than 10 nm.

[0078] Physical processes in the context of the present disclosure may include mechanically applying stress, releasing internal stress, spin coating, selective deposition, selective exposure, selective etching, heating, freezing, applying stress by bending the substrate, bimorph displacement, exposure to radiation of a specific wavelength, ultrasound or megasonic vibrations, and combinations of one or more of the above physical processes, for example, selective etching followed by selective deposition.

[0079] The step of reading out the resulting physical events of all metrology sensors can be accomplished in several ways. Reading out can involve imaging-based reading, discrete sampling, including, for example, lasers used in the same way as barcode readers, scatterometry, or SEM used in local "probe" mode.

[0080] In one embodiment of the disclosed method for detecting and / or quantifying manufacturing inaccuracies produced by a lithographic process, the physical event produced is clearly distinguishable from other physical events in a known and limited set of possible different physical events. This can be achieved, for example, by having a metrological sensor, the metrological sensor comprising a displaceable substance configured to be in a stationary state and distributed over a local area, wherein the displaceable substance is suitable for reaching a displaced state in the local area during a displacement process when the physical process is applied. The displaceable substance can be in a stationary state when the manufactured structure on the substrate is obtained from the lithographic equipment. As described above, the physical process can involve many technologies. In one embodiment, the physical process is applied to each metrological sensor for a predetermined time period.

[0081] The step of processing the generated physical events may include computationally processing the generated physical events. For example, the processing may include the step of applying Boolean logic to the generated physical events from at least one design based on expected physical event outcomes, and / or the step of constructing probability distributions of counts of generated physical events for one or more varying design parameters of a design and comparing them to expected probability distributions based on a nominal design.

[0082] The step of reading out the generated physical events may comprise searching for physical events only at predetermined locations of the fabricated structure.

[0083] In one embodiment of the disclosed method for detecting and / or quantifying manufacturing inaccuracies resulting from a lithographic process, at least one design is configured such that a particular physical event is favorable. This can be accomplished, for example, by providing two or more designs, wherein at least one of the designs can be distinguished from another design by shifting at least one edge by an integer multiple of the minimum controllable step size of the lithographic apparatus. Alternatively, at least one design can be configured such that none of a known and limited set of different physical events is favorable.

[0084] Figure 1A A non-limiting conceptual example of a metering sensor 100 in a rest state is shown. The figure shows two possible displacement states 104 and 105, which correspond to possible different physical events. The displaceable substance 101 is in a rest state. From this position, a physical process can be applied to move the displaceable substance 101 in a predetermined direction 102 and 103 to reach one of the two possible displacement states 104 and 105. Figure 1B and Figure 1C The metering sensor 100 is shown with the displaceable mass 101 in each of the possible end states 104 and 105 .

[0085] As mentioned above, the step of reading out the physical events generated by all metering sensors can be accomplished, for example, by imaging. Imaging the metering sensors after the physical process has been applied to displace the displaceable material allows the position of the displaceable material to be identified in the end state. Such imaging includes determining the position of the connecting element preferably by means of an optical microscope. Other microscopy techniques (such as electron, ion, ultraviolet or X-ray microscopy) can also be used to perform the imaging step.

[0086] In an embodiment, the material comprising the mechanical actuator is isotropically or anisotropically etchable when in contact with an etchant in a wet or dry etching process. It will be appreciated that an isotropically etchable material is a material that is etched at a constant rate, regardless of properties such as size, crystal orientation, crystal polarity, or roughness. For example, aluminum oxide is a material that is isotropically etchable in contact with liquid HF or aluminum etchants. It will be appreciated that an anisotropically etchable material is a material that is etched at a rate that depends on crystal properties, such as crystal orientation, crystal polarity, or roughness. For example, specific crystal planes in crystalline Si can be etched at a much slower rate under certain etchants, such as the (111) plane in contact with KOH or TMAH.

[0087] Figure 2A An embodiment of a metrology sensor 200 is shown, which includes a mechanical actuator in the form of vertical nanopillars 202 and 203 disposed on a substrate 204. The mechanical actuator is fixed to a rigid substrate 204 and a linking element 201, such as Figure 2B The linking element 201 connecting two mechanical actuators comprises a rigid platform made of a material that is not reactive to etchants, thereby allowing the mechanical actuators to be selectively etched away.

[0088] initial, Figure 2A and Figure 2B The linking element 201 in is in a pre-strained state and connected to the mechanical actuators 202 and 203. Such a pre-strained state can be induced, for example, by manufacturing the linking element at a temperature above room temperature and making the linking element of a material having a higher thermal expansion coefficient than that of the substrate. Figure 2C The result is shown after an etching process removes at least one of the mechanical actuators of the metrology sensor 210, while the linking element 201 is preferably made of a material that is almost insensitive to the etchant. When a physical stressor is applied to the metrology sensor 210, the linking element is displaced from the strained state toward the remaining mechanical actuator 212 of the metrology sensor by a distance 211 to an unstrained position, as shown in FIG. Figure 2CAs shown in . The driving force for the displacement of the connecting element can be, for example, a tensile stress, such as thermal strain generated in the connecting element during the manufacturing process. The end state of the mechanical actuator corresponds to partial or complete etching of the mechanical actuator to the extent that it releases the connecting element to which it is connected. This may include physically separating the high-tensile connecting element from the mechanical actuator before complete release. The mechanical actuator is preferably etched laterally and isotropically by an etchant (e.g., hydrofluoric acid or aluminum etchant) in a wet etching process. Depending on the material composition of the nanopillars, other wet etchants such as KOH, TMAH, H2SO4 or piranha etching may be used. The etching process can be stopped at a desired time by drying or immersing the substrate in an etching stop liquid (e.g., deionized water, etc.).

[0089] In another embodiment, the linking element (which may alternatively be referred to as a beam) is a pre-strained element connected to at least two mechanical actuators within the metering sensor. The linking element may be disposed on top of the actuator in a pre-strained state. When the time required for the first actuator to function elapses, the linking element will be released from the substrate, and the tensile stress will pull it toward another actuator that has not yet elapsed and therefore remains attached to the substrate when displaced. The displacement experienced by the linking element from the actuator that elapsed first leaves a physical record on the substrate and simultaneously releases the stress in the metering sensor, thereby preventing another actuator from creating its own physical record once it has elapsed. The displacement of the linking element from the actuator that has elapsed first can be detected later, allowing to know which actuator elapsed first. When the stress is compressive, the displacement direction can be reversed. When the linking element has a stress gradient or is composed of a bimorph, the displacement direction can be out of plane. Therefore, in this disclosure a photolithographic method is described to define "timers" on a chip and create a system to make them mutually exclusive, so that of two or more connected actuators, only the actuator that disappears first can be displaced from its predetermined position and thus leave a physical record, while the other connected actuators will remain in the proper position even after they finally disappear.

[0090] The physical event can be a fracture generated by a fracture mechanism caused by the displacement of the displaceable material from a static state to a displaced state. The fracture can be generated by a connecting element pulling a mechanical actuator. The pulling may cause tearing in the layer to which it is attached, thereby leaving a fracture gap in the layer. The fracture gap can be used for the selective etching of the layer below, which forms an optically observable pit. The fracture gap can also be used for the selective growth of a material using the layer below as a seed material, thereby generating optically observable particles. Therefore, the fracture gap generated can be used to selectively and spatially amplify data about the displaced state, which simplifies the collection of data by imaging. Such gaps, pits and particles are non-limiting examples of physical entities generated in association with a manufactured structure that does not exist before the application of the physical process. The physical entity generated in association with the manufactured structure and the displaced state of the manufactured structure is an example of a known and limited set of possible different physical events triggered when the physical process is applied.

[0091] In the case of a link element metering device connecting two mechanical actuators, a one-dimensional displacement is achieved. However, multiple actuators can be linked to multiple link elements, allowing physical displacement in any direction within the plane of the surface of the recording substrate.

[0092] In another embodiment, the displaceable substance of each metering sensor comprises a liquid or gel, wherein upon application of a physical stressor, the liquid or gel displaces to a displaced state, and wherein the step of simultaneously applying the physical stressor to each metering sensor for at least a predetermined period of time comprises simultaneously changing the temperature or phase of the liquid or gel or the substrate, or applying vibration or evaporation.

[0093] FIG5 shows a schematic example of a metering sensor 500 in which the displaceable substance comprises a liquid or a gel. The sensor is photolithographically defined 500, such as Figure 5A 501 and is arranged in two end regions 501 and a connecting region 502 connecting the two end regions 501. "End regions" and "connecting regions" should be broadly interpreted as including any suitable shape having two ends toward which a liquid or gel can be displaced. This can include, for example, a single line region. Figure 5B Shows Figure 5A A side view of a sensor defined on a substrate by photolithography. Figure 5C A defined sensor 500 is shown with a liquid or gel 502 deposited on top of the sensor and occupying all available space. Figure 5D yes Figure 5C Side view of the sensor and liquid or gel shown in FIG. Figure 5EThe shape of a defined sensor is shown with a liquid or gel 502 deposited on top, which allows the liquid or gel to be displaced towards one of the end regions when a physical process 504 is applied. The physical process can be, for example, a drying process, a temperature change, a phase change or a vibration. Physical stressors can cause tension or instability in the liquid or gel. Fig. 5F yes Figure 5E Side view of a liquid or gel. Application of a physical stressor forces the liquid or gel to move toward one of the end regions, typically driven by minimization of the surface energy of the liquid or gel. This effectively creates an observable physical record of the displacement. Figure 5G The displacement of the liquid or gel 502 towards the left end region 505 is shown, while the right end region 506 is free of liquid or gel due to the displacement. The liquid or gel may be adapted to return to a resting state by a physical process (e.g., increasing water content in air or ultrasound treatment) when the physical stressor is released or inactivated. This may effectively allow the metering device to be reused multiple times by resetting the device to its initial state. Figure 5H Shows Figure 5G Side view of.

[0094] Preferably, in embodiments where the displaceable substance is composed of a liquid or gel or solid substance, the displaceable substance is displaceable in the plane of the surface of the substrate. Furthermore, the displacement of the substance can create an observable physical record in the displaced state. This can effectively convert nano-defects into the presence or absence of observable structures or changes in structures with a size greater than 100 nm, which can be easily detected optically.

[0095] In the case of mechanical actuators, each mechanical actuator or each two end regions of a gel or liquid can represent a timer. Each timer can define the expected trigger time for the mechanical actuator or end region to reach a displaced state when a physical stress source is applied. The concept of a "timer" can be as follows Figure 6 As shown in the example. Figure 6 In , an actuator is etched. The etching process starts at a given time. The actuator is etched laterally. Since the etching rate and the width of the actuator are known, an expected time for etching the entire actuator can be provided. FIG. 7 shows another illustration of how a timer can be used to obtain a physical record on a substrate that can be used to detect and / or quantify manufacturing inaccuracies produced by the lithographic equipment. In Fig. 7A In the embodiment, the two actuators 202 and 203 are designed so that 203 has a larger width, and therefore its "timer" has a larger predetermined timer value. Therefore, the expected result of the etching process is that actuator 202 reaches its end state before actuator 203, such as Figure 7B When the linking element 201 reaches its unstrained state, it creates an observable physical record.

[0096] Application of a physical stressor places the metrological sensor in a state in which the displaceable mass is displaced in the direction of the mechanical actuator with the longer trigger time, effectively imprinting the end state of the metrological sensor after actuation. The direction of displacement can be reversed depending on the physics of the experiment, for example, in the case of a compressively stressed displaceable mass. The displacement direction can be in the plane of the substrate, or out of plane, or a combination of both. A single metrological sensor comprises a minimum of two actuators, with the possibility of adding additional actuators in different directions on the substrate surface, allowing the fabrication of metrological sensors in which the displaceable mass can be displaced in two dimensions of the surface.

[0097] Figure 3 An illustration of a metrology sensor 300 is shown in which two actuators 302 and 303 are designed to have different widths and therefore have a predetermined trigger time difference when activated. Defining actuators with different trigger times allows quantification of manufacturing inaccuracies of the metrology sensor. Due to the higher trigger time of the right actuator 303, the displaceable material 301 will preferentially move to the right shift state 305 when the actuator is activated, rather than to the left shift state 304. If the shift state is to the left, it can be known that the lithography error in the metrology sensor is caused by the lithography system overcoming the deviation in the trigger time, which can be used to quantify the spatially generated error. Defining actuators with gradually smaller differences until they are the same allows identification of unknown physical deviations, such as edge placement errors caused by the lithography equipment during the manufacturing process. In one embodiment, each mechanical actuator or end region is designed so that its size is proportional to the predetermined amount of time it takes to reach the end state (corresponding to the expected trigger time of the actuator).

[0098] Figure 4A An example of an array 400 of binary metrology sensors 401 distributed on a substrate is shown. Such an array comprises metrology sensors arranged in an M×N matrix configuration, where M≥2 and N≥2. The pattern defines an array of at least 10 metrology sensors, allowing the end states of several metrology sensors to be measured to collect information on the inaccuracy of the lithographic equipment until a statistically significant result is obtained. Within the same array, different biases can be designed on each sensor, allowing the precision limits of lithography to be quantified and tested. Ideally, the precision limits of the lithographic equipment are achieved when the bias difference between actuators is sub-1 nm, giving the sensors random displacements when activated. An array may refer to a collection of discrete metrology sensors, which are not necessarily distributed over a continuous area, and are not necessarily arranged in any particular periodic or aperiodic pattern, with or without other intermediate structures. Figure 4BA bitmap or matrix barcode representation of an array 400 of metrology sensors 401 is shown. Similar to a barcode reader reading a matrix barcode, any optical system capable of distinguishing the end states of a metrology sensor can read the full encoded data therein, provided the proper instructions are known or given to interpret the bit string.

[0099] The metrology sensor disclosed herein can be run multiple times in parallel on a substrate, such as at least 5 times or at least 10 times, by patterning many metrology sensors and performing activation of all sensors at the same time. The number of times on a single substrate can be greater than 100, greater than one million or even up to a billion times or more. By detecting the results of multiple experiments, statistics that can be used to measure the inaccuracy of lithographic patterning can be obtained. This is because it is known which actuator will disappear first because their preset times are designed for lithography according to their size. If the statistics deviate from the expected results, the actuator has a preset time that is slightly different from the design, indicating that the tool has an error in lithography. For example, as shown in the first row of devices in Figure 4, a sensor containing actuators with the same preset time can be designed so that the probability of each actuator disappearing first is 50%. In this example, 50% of the actuators are shown as being in an upward or 50% in a downward final state. If an imbalance is detected in the statistics, where, for example, one of the actuators disappears first with an 80% probability, it can be understood that the lithographic equipment has introduced a bias that causes one of the actuators to have a larger island than the other.

[0100] The disclosed metrology sensors can also be configured to not only sense but also obtain quantitative measurements of inaccuracies introduced by the lithographic apparatus, such as edge placement errors. This is accomplished by patterning the sensor with a known bias for a preset time, or equivalently using Figure 6 The timer-based implementation (known size bias) is done. For example, patterning a sensor with a 4nm bias between end states and observing that one side disappears first with 100% probability means that the error accumulation in the tool is less than 4nm. Data from many sensors with different known nanometer or sub-nanometer biases can be compiled to compile a statistical output curve that can be used to evaluate the noise floor of the metrology technology under given process conditions involved in the construction of an individual metrology sensor.

[0101] The disclosed metrology sensors can generate independent statistics about different EPEs caused by the lithographic equipment. For example, it is possible to generate statistics that quantify the overlay error of X but independently of the overlay error of Y, as shown in Figure 8. It is also possible to quantify overlay independently of the quantification of CDU, as shown in Figure 8. In some cases, it is not possible to quantify one component of the EPE independently of another component of the EPE, in which case statistics from different metrology sensors designed to quantify a specific set of EPE components can be used to remove the contribution of those EPE components to obtain an accurate measurement of the remaining EPE components.

[0102] The step of imaging the metrology sensor to detect and / or quantify manufacturing inaccuracies generated by the lithographic apparatus may include microscopic imaging of structures on the substrate. Such imaging characterization techniques are preferably microscopic techniques, such as optical microscopy and alternative electron or ion microscopy, electrical characterization or ellipsometry or scatterometry. The use of an optical microscope allows multiple metrology sensors to be measured in a single frame due to the typical large field of view of the frames acquired using this technique compared to, for example, electron microscopy. An advantage of the disclosed metrology sensor and method of use thereof is that by using the sensor, nanometer differences induced during the lithographic process can be macroscopically detected using an optical microscope that does not initially have the spatial resolution to detect raw nanometer differences. Advantageously, the technique is compatible with generating metrology data at the single line level, which can be accomplished by CD-SEM rather than by interferometry, scatterometry and optical image measurement using statistical measurements that sample a large area of ​​at least a few micrometers of the side length surrounding at least several individual structures. In addition, the metrology data generated by the metrology sensor becomes independent of resolution limitations and sources of noise and uncertainty of the optical microscope used to read the data.

[0103] In one embodiment, a metrology sensor assembly comprises: a substrate; an array of metrology sensors, each metrology sensor comprising a plurality of mechanical actuators connected by at least one linking element in a strained state. In one embodiment, each mechanical actuator is adapted to trigger mechanical actuation at the start of an etching process to reach an end state within a predetermined amount of time, wherein each linking element reaches an unstrained state when one of the mechanical actuators reaches its end state. The substrate preferably comprises an out of plane crystal orientation semiconductor substrate having a defined out of plane crystal orientation, wherein each metrology sensor comprises two mechanical actuators or two liquid actuators.

[0104] The metrology sensors disclosed herein can be used in a "noise sensing mode" in which many sensors are patterned with actuators that are either identical or have multiple discrete known biases for quantization, the smallest of which is the smallest controllable increment that the lithographic apparatus can reliably produce, which can be the minimum step size or the minimum controllable stage step size in an electron beam lithography apparatus. The minimum step size can also be broadly interpreted as the typical minimum grid resolution used to design patterns in CAD, but can also be caused by controllable and known changes in the CD or CDU of a pattern or a portion of a pattern caused by a specific lithography process. This sensing mode can be used to characterize the noise floor of the lithographic apparatus in terms of EPE, which can be used to compare the performance of different lithographic apparatus or processes involved in the construction of the disclosed metrology sensors. For example, if changing a specific process parameter in the lithographic apparatus improves statistics (i.e., results in less error in the end state of the sensor), this means higher edge placement fidelity, and the same parameters can be used in other manufacturing processes to achieve closer to ideal results. By extension, the noise sensor can be used to optimize any process parameter of any lithographic apparatus or process step that results in less error in the end state of the sensor in order to minimize CD, LCDU, random index, and roughness such as LER and LWR. The noise sensing mode can be further used to characterize the noise floor of the metrology sensor patterned by the lithographic apparatus, the statistics of which can be used as a reference for the sensor in "shift sensing mode" (described below) to obtain higher accuracy and precision of EPE quantification.

[0105] The metrology sensors disclosed herein may alternatively or additionally be used in a "shift sensing mode," wherein the pattern of the metrology sensor is intentionally divided into two or more separate but complementary patterns that do not individually function as a metrology sensor, but when combined in two or more separate exposures in the same lithography step or in separate lithography steps can form a complete pattern that functions as a metrology sensor, such as Fig. 8A and 8BAs shown in . For example, the first pattern may define a portion of the actuator and the connecting element connecting the actuator, while the second exposure 802 only defines the remaining actuators. When a complete pattern is obtained in two exposures, due to, for example, overlap errors, the translation error of the alignment between the first exposure defining the pattern 801 and the second exposure defining the pattern 802 will produce a detectable imbalance in statistics, because, depending on the shift direction, the top island will always be smaller or larger than the bottom island. Complementary patterns may exist at different positions in the same mask, or at any position within the mask in two or more different masks. Complementary patterns may be spliced ​​together by the shift of the wafer stage or the mask stage or both. When complementary patterns are present in the same mask, the resulting metrology sensor can sense and quantify registration errors and CDU, etc. When present in different masks, metrology sensors can be used to sense overlap, etc. A variety of options for dividing the pattern into two or more complementary parts are possible, each potentially dependent on or independent of other EPEs to sense different EPEs. For example, the EPE contributions in X and Y can be sensed independently. In addition, complementary patterns can be exposed in many ways. For example, complementary patterns can be exposed so that the complete pattern becomes as originally designed, but can also be exposed with controlled misalignment to produce a bias that can be used to quantify errors. For example, a complete pattern as designed in CAD can be expected to produce statistically balanced results, such as due to mirror symmetry in the pattern, but can actually produce a systematic imbalance indicating overlap, registration or stage errors instead. Exposing complementary patterns with intentionally controlled translations in X or Y between exposures can produce more balanced statistics indicating a final pattern closer to CAD, which can be used to identify and quantify the errors that produce imbalances. In addition, complementary patterns can form many different metrology sensors by repeating complementary exposures. There can also be several complementary patterns to form several complete metrology sensors in parallel. There can also be more than one way to splice different complementary patterns in different exposures to obtain a complete pattern used as a metrology sensor. By dividing the pattern into one or more parts that affect metrology data when the components are misaligned relative to each other (e.g., due to overlap errors) or when the parts have different sizes (e.g., due to CD errors), the shift sensing mode can be used to sense EPE. The shift sensing mode can be used for various applications including sensing of EPEs such as overlay, rotation errors, registration errors, stage or beam drift over time, stage stitching errors, CDU and LCDU etc. The shift sensing mode can be of further interest for characterizing the lithographic apparatus or one of its sub-parts such as the stage, beam deflection system, overlay alignment system or mask etc. The strategy of dividing the pattern into multiple parts and noise sensing can also be used to optimize proximity effect correction strategies for optical and electron beam lithography using both single and multiple patterning approaches.

[0106] Fig. 8A and Figure 8B An example of a cut pattern of a metrology sensor with rectangular and square actuators in positive resist (a radiation-sensitive polymer used in photolithography patterning) is shown, which, when exposed individually to fabricate a complete metrology sensor, can sense and quantify misalignment (including overlay and registration) as well as dimensional differences (including CDU, etc.).

[0107] Fig. 8A A metrology sensor design 803 consisting of cutting patterns 801 and 802 is shown that is capable of sensing and quantifying misalignment in Y independently of misalignment in X. Rotating the structure 90° allows for sensing and quantifying misalignment in X independently of misalignment in Y. Another feature of the design is that misalignment contributes to changing the two actuators in opposite directions. In other words, the design amplifies the misalignment by a factor of two, thereby increasing the sensitivity of the metrology sensor by a factor of 2. Intentionally controlled stage shifts used to induce or compensate for imbalance between actuators can be used to quantify the error. Yet another feature of the design is that it is insensitive to CDU due to dual mirror symmetry, which enables the design to sense and quantify alignment inaccuracies independently of CD or CDU inaccuracies.

[0108] Figure 8B An example of cut patterns 811 and 812 of a metrology sensor 810 with square actuators in positive resist is shown, which when exposed alone into a full metrology sensor can sense and quantify CDU independent of small misalignment inaccuracies such as overlay and registration.

[0109] The metrology sensors disclosed herein may alternatively or additionally be used in a "fault sensing mode," where a displaceable material that does not reach a displaced state may be used to sense and quantify manufacturing inaccuracies, such as EPE. For example, if a manufacturing inaccuracy causes a physical discontinuity in a connecting element, the experiment may not produce a displacement of the material that can be interpreted as a displaced state of the metrology sensor, and is therefore interpreted as a failure of the metrology sensor. A failure of a metrology sensor produces useful data because it indicates that a pattern is not produced as expected. For example, it is well known that very narrow lines used in IC manufacturing may break randomly, which can have a negative impact on the yield of semiconductor devices, particularly in EUV scanners. A fault sensing mode may be used to sense randomly broken lines because a break in a connecting element will not result in an expected displaced state, such as when the connecting element is a beam. A metrology sensor may be intentionally designed to produce experiments that fail or have a chance of failure because any deviation from expected failure or non-failure behavior produces useful metrology data about the lithography equipment or process. For example, it can be known that when a certain dimension of the structure is less than 30 nm, the experiment cannot produce a displacement of the material that can be interpreted as a displacement state of the metrology sensor; if a metrology sensor designed to be above this dimension always fails to produce metrology data, it can be interpreted as the actual CD is less than 30 nm, which is less than the expected CD. The fault sensing mode can be used in the noise sensing mode or the displacement sensing mode, or vice versa, the noise and displacement sensing modes can be used in the fault sensing mode. By combining different sensing modes, the detection of metrology sensors that fail to produce metrology data enables further sensing and quantification of EPE.

[0110] Fig. 9 A flow chart of an example of a presently disclosed method 900 for detecting and / or quantifying manufacturing inaccuracies is shown. The method includes the following steps: providing at least one design for manufacturing a structure on a substrate using a set of lithographic processes, at least one pattern defining an array of metrology sensors, wherein each metrology sensor is adapted to produce one of a known and finite set of possible different physical events upon application of a physical process 901; applying the set of lithographic processes to obtain the fabricated structure 902; applying the physical process, thereby producing one of a known and finite set of possible different physical events for each metrology sensor 903; reading out the produced physical events of all metrology sensors and processing the produced physical events 904.

[0111] Further details

[0112] 1. A method for detecting and / or quantifying manufacturing inaccuracies produced by a lithographic apparatus, comprising:

[0113] providing at least one pattern for fabricating a structure on a substrate, the at least one pattern defining an array of metrology sensors, each metrology sensor comprising a displaceable substance configured to be in a stationary state and distributed over a local area, wherein the displaceable substance is adapted to reach a displaced state towards a predetermined discrete position within the local area during a displacement process upon application of a physical stressor;

[0114] obtaining the fabricated structure on the substrate from the lithographic apparatus, wherein the displaceable mass of the metrology sensor is in a stationary state;

[0115] applying the physical stressor to each metrology sensor for at least a predetermined period of time; and

[0116] The metrology sensor is read out to detect and / or quantify manufacturing inaccuracies produced by the lithographic apparatus.

[0117] 2. The method according to item 1, wherein the substrate is a semiconductor substrate.

[0118] 3. A method according to any of the preceding clauses, wherein the physical stressor is applied simultaneously to each metrology sensor.

[0119] 4. The method according to any of the preceding items, wherein the metrology sensor is read out by imaging.

[0120] 5. A method according to any of the preceding items, wherein each metrology sensor comprises a plurality of mechanical actuators connected by at least one linking element in a strained state representing the static state, wherein each mechanical actuator is adapted to trigger mechanical actuation at the start of an etching process to reach an end state within a predetermined amount of time, and wherein each linking element reaches an unstrained state representing the displaced state when one of the mechanical actuators reaches its end state, and wherein the step of applying the physical stressor to each metrology sensor simultaneously for at least a predetermined period of time comprises simultaneously etching an array of the metrology sensors for at least a predetermined period of time.

[0121] 6. The method of claim 5, wherein the step of imaging the metrology sensor comprises imaging the coupling element.

[0122] 7. The method according to any of the preceding items, wherein the mechanical actuator is made of an isotropically or anisotropically etchable material in contact with an etchant.

[0123] 8. The method according to any of the preceding items, wherein the mechanical actuator is a vertical nano-column arranged on the substrate.

[0124] 9. Method according to any of the preceding items, wherein the end state of the mechanical actuator corresponds to a partial or complete etching of the mechanical actuator to such an extent that it releases the link element to which it is connected.

[0125] 10. The method according to any of the preceding items, wherein the mechanical actuator is etched laterally.

[0126] 11. The method according to any of the preceding items, wherein the etching process is a wet etching process.

[0127] 12. The method according to any of the preceding items, wherein the etching process removes at least one of the mechanical actuators of the metrology sensor.

[0128] 13. The method according to item 12, wherein the link element is displaced from the strained state towards a position at a remaining mechanical actuator of the gauge sensor.

[0129] 14. The method according to any of the preceding items, wherein the connecting element is made of a material that is chemically stable in contact with an etchant for the mechanical actuator material.

[0130] 15. The method according to any of the preceding items, wherein the linking element is a pre-strained element connected to at least two mechanical actuators within a metrology sensor.

[0131] 16. The method according to any of the preceding items, wherein the connecting element is arranged on top of the actuator.

[0132] 17. The method according to any of the preceding items, wherein the connecting elements are beams.

[0133] 18. Method according to any of the preceding items, wherein the connecting element is a mechanical strain element which is released to an unstrained state when one of the mechanical actuators reaches its end state.

[0134] 19. A method according to any of the preceding items, wherein the joining element reaching its unstrained state creates an observable physical record.

[0135] 20. The method according to any of the preceding items, wherein the displaceable substance is photolithographically patterned.

[0136] 21. A method according to any one of items 1-2, wherein the displaceable material of each metering sensor comprises a liquid or a gel, wherein, upon application of the physical stress source, the liquid or gel is displaced to a displaced state, and wherein the step of simultaneously applying the physical stress source to each metering sensor for at least a predetermined period of time comprises simultaneously changing the temperature or phase of the liquid or gel or applying vibration or evaporation.

[0137] 22. The method according to item 21, wherein the liquid or gel is arranged in two end regions and a connecting region connecting the two end regions.

[0138] 23. A method according to item 22, wherein upon application of the physical stressor, the liquid or gel is displaced towards one of the end regions.

[0139] 24. A method according to any one of items 21-23, wherein the liquid or gel is adapted to return to a resting state when the physical stressor is released or inactivated.

[0140] 25. The method according to any of the preceding items, further comprising the step of interpreting the failure of the displaceable substance to reach the displaced state as a further manufacturing inaccuracy.

[0141] 26. The method according to any of the preceding items, wherein the displaceable substance is displaceable in the plane of the substrate.

[0142] 27. A method according to any of the preceding clauses, wherein the displaceable substance creates an observable physical record in a displaced state, the method further comprising the step of physically amplifying the observable physical record.

[0143] 28. A method according to any of the preceding items, wherein each mechanical actuator or each two end regions of the gel or liquid represents a timer.

[0144] 29. A method according to item 28, wherein the timer defines an expected trigger time for the mechanical actuator or end region to reach a displaced state when a physical stressor is applied.

[0145] 30. The method according to any of items 28-29, wherein each metering sensor comprises at least two timers.

[0146] 31. The method according to any one of item 30, wherein the at least two timers are designed to have the same expected triggering time.

[0147] 32. The method according to any one of item 30, wherein the at least two timers are designed to have a predetermined difference in triggering time.

[0148] 33. A method according to any one of clauses 30, wherein the difference is used to quantify manufacturing inaccuracies.

[0149] 34. A method according to any of items 32-33, wherein the predetermined difference corresponds to an unknown physical deviation, such as an edge placement error.

[0150] 35. A method according to any of items 28-35, wherein the pattern includes a plurality of timers.

[0151] 36. A method according to any one of items 28-35, wherein each mechanical actuator or end region is designed so that its size is proportional to a predetermined amount of time taken to reach the end state, corresponding to the expected trigger time of the timer.

[0152] 37. The method of any of the preceding items, wherein the array of metrology sensors is distributed on the substrate.

[0153] 38. The method of item 37, wherein the metrology sensors are arranged in an M×N configuration, where M>=2 and N>=2.

[0154] 39. The method of any of the preceding items, wherein the pattern defines an array of at least 10 metrology sensors.

[0155] 40. A method according to any of the preceding clauses, wherein the step of imaging the metrology sensor to detect and / or quantify manufacturing inaccuracies produced by the lithographic apparatus comprises a microscopy technique, such as optical microscopy, for imaging the structures on the substrate.

[0156] 41. A metrology sensor assembly comprising:

[0157] substrate;

[0158] An array of metrology sensors, each metrology sensor comprising a plurality of mechanical actuators connected by at least one linking element in a strained state, wherein each mechanical actuator is adapted to trigger mechanical actuation at the start of an etching process to reach an end state within a predetermined amount of time, and wherein each linking element reaches an unstrained state when one of the mechanical actuators reaches its end state.

[0159] 42. The metrology sensor assembly of clause 41, wherein the substrate comprises a semiconductor substrate having a defined out-of-plane crystal orientation.

[0160] 43. A metrology sensor according to any one of items 41-42, wherein the substrate is a semiconductor substrate having a defined out-of-plane crystal orientation, and wherein each metrology sensor comprises two mechanical actuators or two liquid actuators.

[0161] 44. A metering system comprising:

[0162] a lithographic apparatus configured to pattern a radiation sensitive resist such as a polymer on a substrate using a design comprising an array of metrology sensors, each metrology sensor comprising a displaceable substance configured to be in a stationary state and distributed over a local area, wherein the displaceable substance is adapted to reach a displaced state towards a predetermined discrete position within the local area during a displacement process upon application of a physical stressor;

[0163] A physical stressor device, such as an etching device or system, adapted to apply a physical stressor for at least a predetermined period of time; and

[0164] An imaging device for imaging the metrology sensor to detect and / or quantify manufacturing inaccuracies produced by the lithographic apparatus.

[0165] 45. A metrology system according to item 44, wherein the imaging device comprises a microscope, preferably an optical microscope.

Claims

1. A method for detecting and / or quantifying manufacturing inaccuracies resulting from a photolithography process, the method comprising: At least one design is provided for fabricating a structure on a substrate using a set of photolithography processes, wherein the fabricated structure defines an array of metrology sensors, wherein each metrology sensor is adapted to produce one of a known and finite set of possible different physical events upon application of a physical process, wherein the produced physical events: is unknown before applying the physical process, depending on manufacturing inaccuracies resulting from at least one of the set of lithographic processes, and is a displaced state of said fabricated structure, or has one or more physical entities associated with said fabricated structure that did not exist prior to application of said physical process; applying said set of photolithography processes to obtain said fabricated structure; applying said physical process thereby producing one of said known and finite set of possible different physical events for each metrology sensor; Reading physical events generated by all metering sensors; and The generated physical events of all metrology sensors are processed to detect and / or quantify manufacturing inaccuracies generated by the photolithography process.

2. The method according to claim 1, wherein: The generated physical event is visually distinguishable from other physical events in the set of possible different physical events.

3. A method according to any one of the preceding claims, wherein: The manufacturing inaccuracy arises from edge placement error, wherein the edge placement error is less than 5 nm, or wherein the edge placement error is less than 1 nm.

4. A method according to any one of the preceding claims, wherein: The step of processing the generated physical events includes computationally processing the generated physical events.

5. The method of claim 4, comprising the step of applying Boolean logic to the generated physical events based on expected physical results from the at least one design.

6. A method according to any one of claims 4-5, comprising the step of constructing a probability distribution of counts of resulting physical events for one or more varying design parameters of the design.

7. A method according to any one of the preceding claims, wherein: The set of photolithography processes includes at least exposure and development of a radiation sensitive resist.

8. A method according to any one of the preceding claims, wherein: The step of reading out said generated physical event comprises searching for said physical event only at predetermined locations of said manufactured structure.

9. A method according to any one of the preceding claims, wherein: The generated physical events are digitally stored.

10. A method according to any one of the preceding claims, wherein: Imaging is used to read out the physical events generated by all metrological sensors.

11. A method according to any one of the preceding claims, wherein: Each metering sensor comprises a displaceable mass configured in a rest state and distributed over a local area, wherein the displaceable mass is adapted to reach a displaced state within the local area during a displacement process upon application of the physical process.

12. The method according to claim 11, wherein: When the fabricated structure on the substrate is obtained from the photolithographic process, the displaceable substance is in a stationary state.

13. A method according to any one of the preceding claims, wherein: The physical process is applied to each metering sensor for a predetermined period of time.

14. A method according to any one of the preceding claims, wherein: The at least one design is configured such that a particular physical event is advantageous.

15. The method according to claim 14, wherein: Two or more designs are provided, wherein at least one of the designs is distinguishable from another design by at least one edge being shifted by an integer multiple of a minimum controllable step size of the lithographic apparatus.

16. A method according to any one of the preceding claims, wherein: The at least one design is configured such that none of the known and limited set of different physical events is favorable.

17. A method according to any one of the preceding claims, wherein: The physical event is a change in shape, size or placement of a part or all of the structure, preferably, wherein the change in shape, size or placement of a part or all of the structure is greater than 10 nm.

18. A method according to any one of the preceding claims, wherein: Each metrology sensor comprises a plurality of mechanical actuators connected by at least one linking element in a strained state representing the rest state, wherein each mechanical actuator is adapted to trigger mechanical actuation upon initiation of an etching process to reach an end state within a predetermined amount of time, and wherein each linking element reaches an unstrained state representing the displaced state when one of the mechanical actuators reaches its end state, and wherein the step of applying the physical process to each metrology sensor simultaneously for at least the predetermined period of time comprises etching the array of metrology sensors simultaneously for at least the predetermined period of time.

19. The method according to claim 18, wherein: The end state of the mechanical actuator corresponds to a partial or complete etching of the mechanical actuator to such an extent that it releases the link element to which it is connected.

20. The method according to claim 11, wherein: The displaceable substance of each metering sensor comprises a liquid or a gel, wherein upon application of the physical process, the liquid or gel is displaced to a displaced state, and wherein the step of applying the physical process to each metering sensor simultaneously for at least a predetermined period of time comprises simultaneously changing the temperature or phase of the liquid or gel or applying vibration or evaporation.

21. The method according to claim 20, wherein: The liquid or gel is arranged in two end regions and in a connecting region connecting the two end regions, wherein upon application of the physical process the liquid or gel is displaced towards one of the end regions.

22. The method according to any one of claims 18 to 21, wherein: Each mechanical actuator or each two end regions of the gel or liquid represents a timer.

23. The method according to claim 22, wherein: The timer defines an expected triggering time for the mechanical actuator or end region to trigger the displaceable mass to reach a displaced state upon application of the physical process.

24. The method according to any one of claims 22-23, wherein: Each mechanical actuator or end region is designed so that its size is proportional to a predetermined amount of time it takes to reach an end state, and the predetermined amount of time corresponds to an expected triggering time of the timer.

25. A metering system comprising: A lithographic apparatus configured to pattern a radiation sensitive resist such as a polymer on a substrate to fabricate a structure using a design comprising an array of metrology sensors, wherein each metrology sensor is adapted to produce one of a known and finite set of possible different physical events upon application of a physical process, wherein the produced physical events: is unknown before applying the physical process, depends on the manufacturing inaccuracies produced by the lithographic apparatus, and is a displaced state of said fabricated structure, or has one or more physical entities associated with said fabricated structure that did not exist prior to application of said physical process; A system is provided, the system being adapted to apply the physical process to each metrology sensor.

26. The metering system of claim 25, wherein: Each metering sensor comprises a displaceable substance configured in a rest state and distributed over a local area, wherein the displaceable substance is adapted to reach a displaced state in a displacing process towards predetermined discrete positions within the local area upon application of the physical process.

27. The metrology system according to any one of claims 25-26, further comprising an imaging device for imaging the metrology sensor to detect and / or quantify manufacturing inaccuracies produced by the lithographic apparatus.

Images