Lateral recess measurement in a semiconductor specimen

Abstract

A system and method for measuring lateral recesses in a semiconductor sample are provided, comprising: acquiring a first image by collecting electron beams emitted from a surface of the sample and a second image by collecting electron beams scattered from an internal region of the sample between the surface and the target second layer, the sampling being scanned using an electron beam having a landing energy selected to penetrate to a depth corresponding to the target second layer; generating a first galvanic wave (GL) based on the first image and generating a second GL based on the second image; estimating a first width of a first layer based on the first GL waveform and generating a second width relative to at least the target second layer based on the second GL; and measuring the lateral recess based on the first width and the second width.

Description

Technical Field

[0001] The subject matter currently revealed generally relates to the field of inspection of semiconductor samples, and more specifically, to the metrology of critical dimensions (CD) relative to lateral recesses in the sample. Prior Technology

[0002] Current demands for high density and high performance associated with the ultra-large-scale integration of manufactured devices require submicron features, increased transistor and circuit speeds, and improved reliability. As semiconductor manufacturing processes advance, pattern dimensions (such as linewidth) and other types of critical dimensions continue to shrink. This demand necessitates the formation of device features with high precision and uniformity, which in turn necessitates careful monitoring of the manufacturing process, including automated inspection of the device while it is still in the form of a semiconductor wafer.

[0003] Inspection can be provided using non-destructive testing tools during or after the manufacturing process of the sample to be inspected. Inspection generally involves generating some output (e.g., an image, signal, etc.) for the sample by directing light or electrons onto the wafer and detecting the light or electrons from the wafer. As non-limiting examples, various non-destructive testing tools include scanning electron microscopes, atomic force microscopes, optical inspection tools, etc.

[0004] Inspection procedures may include multiple inspection steps. Inspection steps may be performed multiple times during the manufacturing process, such as after manufacturing or processing certain layers. Additionally or alternatively, each inspection step may be repeated multiple times, for example, for different wafer locations or for the same wafer location under different inspection settings.

[0005] Inspection procedures are used at various stages during semiconductor manufacturing to detect and classify defects in samples, as well as to perform metrology-related operations. The effectiveness of inspection can be improved through the automation of (multiple) procedures (e.g., defect detection, automated defect classification (ADC), automated defect inspection (ADR), automated metrology-related operations, etc.). Summary of the Invention

[0006] Based on certain aspects of the currently disclosed subject matter, a computerized system is provided for measuring lateral recesses in a semiconductor sample comprising a stack of one or more first layers of a first type and one or more second layers of a second type, deposited alternately to each other, the second layers being at least partially etched to form lateral recesses between each given second layer and its two adjacent first layers. The system includes: an electron beam tool configured to: scan the semiconductor sample using an electron beam having a landing energy specifically selected to penetrate to a predefined depth corresponding to a target second layer of the sample; and to acquire a first image by collecting secondary electrons (SE) emitted from the surface of the sample and by collecting electrons emitted from the sample at the surface and the target second layer. The method comprises: acquiring a second image by backscattering electrons (BSE) from the internal regions between the first and second images, the first image providing information on the surface profile of the sampled image and the second image providing information on the internal structure of the internal regions; and a processing and memory circuit (PMC) operatively connected to the electron beam tool and configured to: generate a first GL waveform providing information on the gray-level (GL) intensity distribution of the first image and a second GL waveform providing information on the GL intensity distribution of the second image; estimating a first width of the one or more first layers based on the first GL waveform and estimating a second width relative to at least the target second layer based on the second GL waveform; and measuring a lateral recess relative to the target second layer based on the first width and the second width.

[0007] In addition to the features described above, any technically possible combination or substitution of this type of system based on the currently disclosed subject matter may include one or more of the features (i) to (x) listed below: (i) The semiconductor sampling includes a gate-around-annular (GAA) device. The first layer is made of silicon, and the second layer is made of silicon-germanium. (ii) The target second layer is the top second layer of the one or more second layers, and the measured lateral recess is the top lateral recess formed between the top second layer and its adjacent first layer. (iii) The target second layer is the subsequent second layer after the top second layer, and the measured lateral recess is the average lateral recess formed between the top second layer and the adjacent first layer and the subsequent lateral recess formed between the subsequent second layer and the adjacent first layer. (iv) The PMC is further configured to measure the average lateral recess relative to the subsequent second layer after the top second layer, and to converge the lateral recess of the subsequent layer based on the average lateral recess and the top layer lateral recess. (v) The SE is collected by an SE detector array, and the BSE is collected by at least one BSE detector. (vi) The landing energy that penetrates to the predefined depth corresponding to the second layer of the target is specifically selected based on a comparison between the number of BSEs relative to the reference sample without lateral recesses and the number of BSEs relative to the semiconductor of interest. (vii) Estimating the first width includes estimating a first topological point on the first GL waveform by calculating a derivative along the first GL waveform, and applying a predefined derivative threshold on the first GL waveform to generate the first topological point, and measuring the first width between the first topological points. (viii) Estimating the second width includes estimating a second topology point on the second GL waveform by applying a predefined GL threshold to the second GL waveform, generating the second topology point, and measuring the second width between the second topology points. (ix) The PMC is further configured to calibrate the measured lateral recess relative to reference measurements obtained from the TEM. (x) The calibration is based on the correlation previously derived between the corresponding measurement data from the electron beam tool and the reference measurement data obtained from the TEM.

[0008] Based on other aspects of the currently disclosed subject matter, a method for measuring lateral recesses in a semiconductor sample is provided, the semiconductor sample comprising a stack of one or more first layers of a first type and one or more second layers of a second type deposited alternately, the second layers being at least partially etched to form a lateral recess between each given second layer and its two adjacent first layers, the method being performed by a processing and memory circuit (PMC) and comprising: obtaining a first image by collecting secondary electrons (SE) emitted from the surface of the sample and a second image by collecting backscattered electrons (BSE) scattered from an internal region of the sample between the surface and a target second layer, wherein a method is used with a... An electron beam with a landing energy specifically selected to penetrate to a predefined depth corresponding to the target second layer is used to scan the semiconductor sample, wherein the first image provides information on the surface profile of the sample, and the second image provides information on the internal structure of the internal region; a first GL waveform providing information on the grayscale (GL) intensity distribution of the first image and a second GL waveform providing information on the GL intensity distribution of the second image are generated; a first width of the first layer is estimated based on the first GL waveform, and a second width relative to at least the target second layer is estimated based on the second GL waveform; and a lateral recess relative to the target second layer is measured based on the first width and the second width.

[0009] This state of the subject matter can be any desired combination or substitution that is technically possible, including one or more of the features (i) to (x) listed above with respect to the system, and with necessary modifications.

[0010] According to other forms of the subject matter currently disclosed, a non-transient computer-readable storage medium is provided, which tangibly embodies an instruction program that, when executed by a computer, causes the computer to perform a method for measuring lateral recesses in a semiconductor sample, the semiconductor sample comprising a stack of one or more first layers of a first type and one or more second layers of a second type deposited alternately, the second layers being at least partially etched to form a lateral recess between each given second layer and its two adjacent first layers, the method comprising: obtaining a first image by collecting secondary electrons (SE) emitted from the surface of the sample and by collecting backscattered electrons scattered from the sample in an internal region between the surface and the target second layer. The second image acquired by the BSE (Browser Sequencer) is used to scan the semiconductor sample using an electron beam with a landing energy specifically selected to penetrate to a predefined depth corresponding to the target second layer, wherein the first image provides information on the surface profile of the sample, and the second image provides information on the internal structure of the internal region; a first GL waveform providing information on the grayscale (GL) intensity distribution of the first image and a second GL waveform providing information on the GL intensity distribution of the second image are generated; a first width of the first layer is estimated based on the first GL waveform, and a second width relative to at least the target second layer is estimated based on the second GL waveform; and a lateral recess relative to the target second layer is measured based on the first width and the second width.

[0011] This form of the subject matter disclosed in this invention can be achieved by any technically possible combination or substitution, including one or more of the features (i) to (x) listed above with respect to the system, with necessary modifications. Simple Explanation of the Diagram

[0012] To understand this case and how it can be implemented in practice, embodiments will be described by way of non-limiting example only with reference to the accompanying drawings, in which:

[0013] [picture] [1] The figure shows a generalized block diagram of an inspection system based on certain embodiments of the subject matter disclosed herein.

[0014] [picture] [2A] The figure shows a generalized flowchart of the measurement of a lateral recess in semiconductor sampling according to certain embodiments of the subject matter disclosed herein.

[0015] [picture] [2B] The figure shows a generalized flowchart of obtaining a first image and a second image according to certain embodiments of the subject matter currently disclosed.

[0016] [picture] [3] The figure shows a generalized flowchart of measuring the lateral recesses of each layer and / or measuring the average lateral recesses according to certain embodiments of the subject matter disclosed herein.

[0017] [picture] [4] The figure shows a schematic diagram of a GAA structure based on certain embodiments of the subject matter disclosed herein.

[0018] [picture] [5] The illustrations show examples of first and second images of GAA structures based on certain embodiments of the subject matter currently disclosed.

[0019] [picture] [6] The illustration shows examples of a first GL waveform and a second GL waveform according to certain embodiments of the subject matter currently disclosed.

[0020] [picture] [7] An exemplary graph illustrating the correlation between the number of BSEs received from a reference sample relative to the difference in the sample of interest, according to certain embodiments of the subject matter disclosed herein, and the level of landing energy used. Implementation

[0021] In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the subject matter. However, those skilled in the art will understand that the subject matter disclosed herein can be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to obscure the subject matter disclosed herein.

[0022] Unless otherwise specifically stated, it will be understood from the following discussion that throughout this specification, the use of terms such as “measurement,” “scanning,” “acquisition,” “generation,” “estimation,” “output,” “selection,” “calculation,” “application,” and “calibration” refers to the manipulation of data by a computer and / or the actions and / or procedures that transform data into other data, said data being physically represented, such as electronic, quantitative, and / or representing physical objects. The term “computer” should be broadly interpreted to encompass any kind of hardware-based electronic device with data processing capabilities, including, by way of non-limiting example, the inspection system, metrology system, and corresponding parts thereof disclosed in this case.

[0023] The term "inspection" as used in this specification should be broadly interpreted to encompass any kind of metrological operation and operations related to the detection and / or classification of defects in the sample during its manufacture. Inspection is provided by using non-destructive testing tools during or after the manufacture of the sample to be inspected. As a non-limiting example, an inspection procedure may include one or more of the following operations: performing a running scan (in a single or multiple scans) using the same or different testing tools, sampling, inspection, measurement, classification, and / or other operations relating to the sample or portions thereof. Similarly, inspection may be provided prior to the manufacture of the sample to be inspected and may include, for example, generating inspection schemes and / or other setup operations. It should be noted that, unless otherwise specifically stated, the term "inspection" or its derivatives as used in this specification are not limited in terms of the resolution or size of the area being inspected. As a non-limiting example, various non-destructive testing tools include scanning electron microscopes, atomic force microscopes, optical inspection tools, etc.

[0024] The term "metrology" as used in this specification should be broadly interpreted to encompass any kind of measurement characteristics and features of a sample provided during or after the manufacture of the sample to be inspected using inspection and / or metrology tools. As a non-limiting example, metrology procedures may include generating measurement protocols and / or performing runtime measurements, such as scanning (in single or multiple scans) using the same or different tools, inspection, measurement, and / or other operations provided with respect to the sample or portions thereof. For example, analyzing measurement results (such as measured images) using image processing techniques. It should be noted that, unless otherwise specifically stated, the term "metrology" or its derivatives as used in this specification are not limited to measurement techniques, measurement resolution, or the size of the inspection area.

[0025] The terms “non-transient memory” and “non-transient storage media” used in this document should be interpreted broadly to encompass any volatile or non-volatile computer memory suitable for the subject matter disclosed herein.

[0026] The term "sampling" as used in this specification should be interpreted broadly to cover any kind of wafer, mask, and other structure, as well as combinations thereof and / or portions thereof, used in the manufacture of semiconductor integrated circuits, magnetic heads, flat panel displays, and other semiconductor articles.

[0027] The term "defect" as used in this specification should be interpreted broadly to cover any kind of abnormality or undesirable feature formed on or within a sample.

[0028] It will be understood that, unless otherwise specifically stated, certain features of the subject matter currently disclosed, described in the context of individual embodiments, may also be provided in combination in individual embodiments. Conversely, various features of the subject matter currently disclosed, described in the context of individual embodiments, may also be provided individually or in combination of any suitable subgroups. Numerous specific details are set forth in the following detailed description in order to provide a thorough understanding of the methods and apparatus.

[0029] With this in mind, turn [picture] [1] The figure shows a functional block diagram of an inspection system according to certain embodiments of the subject matter disclosed herein.

[0030] As part of the sampling manufacturing process, it can be used [picture] The inspection system shown in [1]

[0100] To inspect semiconductor samples (e.g., their wafers and / or portions thereof). As mentioned above, inspection as referred to herein can be interpreted to encompass any kind of metrology-related operation, as well as operations related to the detection and / or classification of defects in the sample during the manufacturing process of the sample. According to certain embodiments of the subject matter currently disclosed, the illustrated inspection system...

[0100] Includes computer-based systems

[0101] Computer-based systems

[0101] The system is capable of automatically performing one or more metrological operations on images acquired during sampling manufacturing.

[0101] Also known as a measurement system, it is a testing system

[0100] subsystem. Specifically, according to some embodiments, the metrology operation may include critical dimension (CD) measurement relative to a lateral recess formed in a semiconductor sample.

[0031] system

[0101] Operable to connect to one or more inspection tools

[0120] The one or more testing tools

[0120] is configured to scan semiconductor samples and capture their images to inspect the samples. In some embodiments, the inspection tool At least one of

[0120] has metrological capabilities and can be configured to perform metrological operations on the captured image. Such a verification tool is also called a metrological tool.

[0032] The term "metrology operation" as used in this specification should be broadly interpreted to encompass any metrology operation procedure used to extract metrology information associated with one or more structural elements on a semiconductor sample. For example, the metrology information to be extracted may indicate one or more of the following: dimensions (e.g., linewidth, line spacing, contact diameter, element size, edge roughness, grayscale statistics, etc.), element shape, distances within or between elements, relevant angles, overlap information associated with elements corresponding to different design levels, etc. In some embodiments, a metrology operation may include measurement operations, such as, for example, CD measurements performed relative to certain structures on the sample.

[0033] The term "(multiple) inspection tools" as used herein should be broadly interpreted to encompass any tool that can be used to inspect related procedures, including, as a non-limiting example, imaging, scanning (in a single or multiple scans), sampling, inspection, measurement, classification, and / or other procedures relating to sampling or its components.

[0034] As an example, samples can be inspected using one or more low-resolution inspection tools (e.g., optical inspection systems, low-resolution SEMs, etc.). The resulting data (also known as low-resolution image data) providing information about the sampled low-resolution images can be transmitted directly to the system or via one or more intermediate systems.

[0101] . Alternatively, or additionally, the samples may be examined by high-resolution instruments (e.g., scanning electron microscope (SEM), atomic force microscope (AFM), or transmission electron microscope (TEM)). The resulting data (also known as high-resolution image data) providing information on the high-resolution images of the samples may be transmitted directly to the system or via one or more intermediate systems.

[0101] .

[0035] Without limiting the scope of this case in any way, it should also be noted that the testing tools...

[0120] It can be implemented as various types of inspection machines, such as optical imaging machines, electron beam machines, etc. In some cases, the same inspection tool can provide both low-resolution and high-resolution image data.

[0036] According to some embodiments, one of the inspection tools is an electron beam tool, such as, for example, a scanning electron microscope (SEM). An SEM is a type of electron microscope that produces an image of a sample by scanning it with a focused electron beam. Electrons interact with atoms in the sample, generating various signals containing information about the surface morphology and / or composition of the sample. The position of the beam and the intensity of the detected signals are combined to produce an image. SEMs enable accurate measurement of features during the fabrication of semiconductor wafers. As an example, an SEM tool could be a critical-dimensional scanning electron microscope (CD-SEM) used to measure critical dimensions of structural features in an image.

[0037] system

[0101] Includes an I / O interface operably connected to a hardware-based interface.

[0126] Processor and memory circuitry (PMC)

[0102] PMC

[0102] Configured to provide the processing necessary for the operating system (as per reference) [picture] [2A]、 [picture] [2B] and [picture] [3] Further details), and include the processor (not shown separately) and memory (not shown separately). PMC

[0102] The processor may be configured to execute several functional modules according to computer-readable instructions implemented on a non-transient computer-readable memory included in the PMC. Such functional modules are referred to below as included in the PMC.

[0038] As mentioned above, in some embodiments, the system

[0101] It can be configured to measure lateral recesses in a semiconductor sample. A lateral recess (also called a cavity recess) refers to a recess formed from the lateral side of a semiconductor sample. Specifically, in some embodiments, a semiconductor sample may include a stack of two types of layers: one or more first layers of a first type and one or more second layers of a second type, which are deposited alternately to form a superlattice layer stack. The two types of layers may be made of different materials. During the manufacturing process, it may be necessary to selectively recess only one type of material from the superlattice layer stack. For example, the second layers may be etched at least partially to form a lateral recess between each given second layer and the two first layers adjacent to the given second layer. In some cases, the sample manufacturer is particularly interested in measuring the lateral recess (e.g., the width of the lateral recess, also called the cavity depth), which is one of the geometric parameters that has a significant impact on the performance of the final device. It can also provide an indication of the etching progress, as well as facilitate fine-tuning and control of the manufacturing process.

[0039] The recess etched from the side of the sample is hidden and buried in the stack, and therefore cannot be seen from top-down images typically taken by inspection tools. Current program control relies on expensive, slow, and destructive cross-sectional electron microscopy (such as the use of metrological tools like TEM), or on optical inspection techniques (such as optical critical size (OCD) scattering instruments) that rely on specific spectra and provide indirect and less accurate measurements.

[0040] Semiconductor samples, which may include the aforementioned layered stacked structures, can be logic devices or memory devices. As an example, a sample can be a logic device, such as, for example, a gate-around field-effect transistor (GAAFET), also referred to herein as a gate-around (GAA) device or transistor. As another example, a sample can be a memory device, such as, for example, 3D NAND (NOT-AND), a type of non-volatile flash memory in which memory cells are vertically stacked in multiple layers. As a further example, a sample can be a memory device, such as, for example, a 3D storage-class memory (3D SCM).

[0041] For illustrative and exemplary purposes, certain embodiments of the subject matter disclosed herein are described with respect to GAA devices. This is in no way intended to limit the scope of the invention. It will be understood that the proposed methods and systems can be applied to the measurement of lateral recesses in other semiconductor sampling having structures similar to those described above.

[0042] A GAA device is a field-effect transistor (such as, for example, a nanosheet (NS), a fork-shaped (FS), and a complementary field-effect (CFET) transistor) in which the gate material surrounds the channel region on all sides. Figure 4 illustrates a schematic diagram of a GAA structure according to some embodiments of the subject matter disclosed herein.

[0043] GAA structure

[0410] It includes two types of layer stacking: formed on a semiconductor substrate

[0406] Multiple first layers

[0402] (i.e., silicon layer) and multiple second layers

[0404] (That is, silicon-germanium layers, also known as SiGe layers). The stacked structure comprises a periodic arrangement of silicon layers deposited on top of the silicon-germanium layers, thus forming a superlattice layer stack. Multiple such stacked structures can be formed on wafers spaced apart from each other, such as on… [picture] [4] shows the substrate The two exemplary GAA structures formed on

[0406]

[0400] and

[0410] . Once these layers are fully grown, special chemicals are used to selectively etch silicon germanium without reacting with silicon. The lateral sides of multiple silicon germanium layers are etched to remove at least a portion of these layers. The etching process can be progressive, and ultimately, only the silicon layer is suspended as a bridge between the source and drain.

[0044] During the etching process, a lateral recess is formed between each given second layer and two adjacent first layers. For example, a lateral recess or cavity recess is formed between a second silicon-germanium layer and its adjacent silicon layer.

[0408] As mentioned above, in some cases, the lateral recess is measured (e.g., the width of the lateral recess).

[0412] The cavity depth (also known as the cavity depth) is particularly important, as it has a significant impact on the performance of the final device. For illustrative purposes, the GAA structure...

[0400] and

[0410] is shown as a lateral recess with different widths to illustrate what happens to the GAA device at different etching time points during the etching process.

[0045] According to certain embodiments, a novel method is proposed to measure lateral recesses in the aforementioned semiconductor samples using the penetration capability of an electron beam tool with a landing energy of relatively high voltage. The proposed measurement method is non-destructive and provides direct measurement with improved accuracy and throughput (TpT).

[0046] In some embodiments, testing tools

[0120] This could be an electron beam tool (e.g., SEM) configured to scan the semiconductor sample using an electron beam having a landing energy specifically selected to penetrate to a predefined depth corresponding to the target second layer being sampled. The electron beam tool is further configured to acquire a first image by collecting secondary electrons (SE) emitted from the sampled surface and a second image by collecting backscattered electrons (BSE) scattered from the sampled internal region between the surface and the target second layer. The first image provides information about the profile of the sampled surface, and the second image provides information about the internal structure of the internal region.

[0047] PMC

[0102] The functional modules included may include an image processing module.

[0104] and measurement module

[0106] The PMC 102 can be configured to operate via I / O interface.

[0126] A first image and a second image are obtained by an electron beam tool. The image processing module 104 can be configured to generate a first GL waveform providing information on the grayscale (GL) intensity distribution of the first image, and a second GL waveform providing information on the GL intensity distribution of the second image. Measurement module

[0106] It can be configured to estimate the first width of one or more first layers based on a first GL waveform, and to estimate the second width relative to at least a target second layer based on a second GL waveform. Measurement module

[0106] It can be further configured to measure the lateral recess relative to the target second layer based on the first width and the second width.

[0048] system

[0100] , System

[0101] , PMC

[0102] and the operation of the functional modules therein will refer to [picture] [2A]、 [picture] [2B] and [picture] [3] Further details.

[0049] According to some embodiments, the system

[0101] May include a storage unit

[0122] Storage unit

[0122] Can be configured as a storage operation system

[0100] and

[0101] Any required information, for example, with the system

[0100] and

[0101] The data related to the input and output of the system, and the data related to the system.

[0101] The intermediate processing results generated. As an example, storage unit.

[0122] Can be configured to store the inspection tools

[0120] The generated images (e.g., a first image and a second image) and / or their derivatives. Therefore, they can be retrieved from the storage unit.

[0122] Detect the image and provide it to the PMC

[0102] For further processing.

[0050] In some embodiments, the system

[0101] Optionally includes being configured to enable with the system

[0101] The relevant user-specified input is a computer-based graphical user interface (GUI).

[0124] For example, a sampled visual representation can be presented to the user (e.g., by forming a GUI).

[0124] A portion of the display includes sampled images and / or their corresponding waveforms. The GUI may provide the user with options to define certain operational parameters. In some cases, the user may also view operational results (such as lateral concave measurements) and / or further inspection results on the GUI.

[0051] As mentioned above, the system

[0101] Configured to be accessible via I / O interface

[0126] Receive the sampled image. The image may include data from the inspection tool.

[0120] The generated image data (and / or its derivatives) and / or stored in the storage unit

[0122] Image data in one or more data repositories. In some cases, image data may refer to images captured by inspection tools during the manufacturing process, and / or preprocessed images exported from images captured through various preprocessing stages, etc. It should be noted that in some cases, images may include associated digital data (e.g., relay data, handcrafted attributes, etc.). It should be further noted that some image data may include data related to the layer of interest and / or data related to one or more additional layers sampled.

[0052] system

[0101] is further configured to process the received image and via the I / O interface

[0126] The results (e.g., CD measurement on the image) are sent to the storage unit.

[0122] and / or inspection tools

[0120] .

[0053] In some embodiments, in addition to testing tools

[0120] In addition to the inspection system

[0100] It may include one or more inspection modules, such as, for example, a defect detection module and / or an automated defect inspection module (ADR) and / or an automated defect classification module (ADC) and / or a metrology-related module and / or other inspection modules that can be used to inspect semiconductor sampling. One or more inspection modules may be implemented as stand-alone computers, or their functions (or at least a portion thereof) may be compatible with inspection tools.

[0120] Integration. In some embodiments, from the system

[0101] The measurements obtained can be obtained by inspection tools.

[0120] and / or one or more inspection modules (or a portion thereof) are used for further inspection sampling.

[0054] Those skilled in the art will readily understand that the teachings of the subject matter presented herein are not subject to... [picture] The system constraints shown in [1]; equivalent and / or modified functions may be combined or divided in another way and may be implemented in any suitable combination of software and firmware and / or hardware.

[0055] It should be noted that [picture] The testing system shown in [1] can be implemented in a distributed computing environment, where PMC

[0102] The aforementioned functional modules included can be distributed across several local and / or remote devices and can be connected via a communication network. It should be further noted that in other embodiments, (multiple) inspection tools

[0120] Storage unit

[0122] and / or GUI At least some of

[0124] can be in the inspection system

[0100] External and via I / O interface

[0126] and system

[0101] Perform data communication. System

[0101] This can be implemented as multiple independent computers for use in conjunction with the testing tools. Alternatively, the system

[0101] The corresponding functions can be at least partially associated with one or more inspection tools.

[0120] Integrated together, thereby promoting and enhancing the inspection tools in inspection-related procedures.

[0120] Functionality.

[0056] Now for reference [picture] [2A], illustrating a generalized flowchart of a measurement of a lateral recess in semiconductor sampling according to certain embodiments of the subject matter currently disclosed.

[0057] As mentioned above, lateral recesses are measured relative to semiconductors with a specific type of structure. As an example, sampling may include a stack of one or more first layers of a first type and one or more second layers of a second type. The first and second layers are deposited alternately. The second layers are at least partially etched during the manufacturing process, thereby forming a lateral recess between each given second layer and its two adjacent first layers.

[0058] This type of sampling can be used with logic devices (such as GAA devices) or memory devices (such as, for example, 3D NAND, 3D SCM, etc.). As an example of this specialized structured sampling, GAA devices... [picture] [4] is illustrated schematically, as mentioned above.

[0059] It can be (e.g., through PMC)

[0102] Via I / O interface

[0126] From the inspection tool

[0120] Or from the storage unit

[0122] ) obtained (

[0202] The first and second images of the sample are obtained. The first and second images can be obtained using an electron beam tool (such as a SEM). For example, the SEM tool used herein could be a critical-size scanning electron microscope (CD-SEM) configured to measure the critical dimensions of the sampled structural elements / features based on the captured images. According to some embodiments, an electron beam (e.g., obtained by an electron beam tool) with a landing energy specifically selected to penetrate to a predefined depth corresponding to a second layer of the sampled target can be used.

[0120] ) to scan (

[0210] Sampling, such as [picture] As shown in [2B], a generalized flowchart of obtaining a first image and a second image is illustrated according to certain embodiments of the subject matter currently disclosed.

[0060] In SEM, different types of signals are generated when an electron beam strikes a sample. Secondary electrons (SEs) originate from the sampled surface or near-surface region. They are the result of an inelastic interaction between the primary electron beam and the sample, and have lower energy than backscattered electrons. Specifically, SEs are generated when incident electrons excite electrons in the sample and lose some energy in the process. The excited electrons move toward the sampled surface, and if they still have enough energy, they escape from the surface as secondary electrons. The shallow depth at which SEs are detected makes them ideal for examining the morphology of the sampled surface.

[0061] Alternatively, after the elastic interaction between the beam and the sample, backscattered electrons (BSEs) are reflected back. These electrons originate from a broad region within the interaction volume. They are the result of elastic collisions between electrons and atoms, causing a change in the electron's trajectory. Specifically, when the electron beam strikes the sample, the atoms in the sample elastically (without energy loss) deflect some of the electrons from their original paths. These essentially elastically scattered primary electrons (which are high-energy electrons) that bounce off the sample are called BSEs.

[0062] As mentioned earlier, BSE images originate from deeper regions of the sample, while SE images originate from the surface region. Therefore, BSE and SE carry different types of information. For example, BSE images are highly sensitive to differences in atomic number and can therefore carry information about the internal structure and / or composition of the sample (i.e., this is referred to as the penetrating power of BSE to probe deeper into the sample when sufficient landing energy is provided), while SE images provide more detailed surface information.

[0063] According to certain embodiments of the subject matter currently disclosed, secondary electrons (SE) emitted from a sampled surface can be collected (e.g., by an electron beam tool).

[0120] SE detector array) to obtain (

[0212] As described in the first image above. It should be noted that the sampled surface can refer to the outer surface of the sampled surface exposed to the electron beam, or it can be the surface region from the outer surface to a depth near the surface. Therefore, the first image is also referred to herein as an SE image. Backscattered electrons (BSE) scattered from the sampled internal region between the surface and the target second layer can be collected (e.g., by an electron beam tool).

[0120] At least one BSE detector acquires the second image as described above. Therefore, the second image is also referred to herein as a BSE image. Thus, the first image provides information on the sampled surface profile (e.g., surface morphology), while the second image provides information on the internal structure (and / or composition) of the sampled internal region.

[0064] like [picture] As shown in [4], sampling may include multiple first layers and multiple second layers deposited alternately with each other. As an example, the GAA structure

[0410] Includes three first layers

[0402] (i.e., silicon layer) and three second layers

[0404] (i.e., silicon-germanium layer), therefore three lateral recesses are formed on each lateral side of this structure, each lateral recess corresponding to a corresponding cavity formed between the corresponding second layer and its two adjacent first layers. For example, the lateral recesses shown

[0408] is the second of three lateral recesses, which is formed between the middle second layer (i.e., the second silicon-germanium layer) and the top first layer and bottom first layer adjacent to the middle second layer.

[0065] According to certain embodiments, lateral recesses relative to a target second layer can be measured using an electron beam with landing energy specifically selected to penetrate to a predefined depth corresponding to the target second layer. Specifically, the currently proposed method can be used to measure the average recess in a sample (i.e., the average recess of a plurality of lateral recesses included in the sample) and / or layer-specific lateral recesses (lateral recesses belonging to a particular target second layer (such as, for example, the top second layer, the middle second layer, etc.), as will be described in further detail below.

[0066] As an example, to measure the second layer from the top

[0404] The specific lateral recess can specifically select the landing energy of the electron beam to penetrate the second layer corresponding to the top.

[0404] (or its vicinity) predefined depth

[0414] For example, choosing landing energy to penetrate to a depth corresponding to the bottom (or vicinity) of the target's second layer (e.g., the top second layer in this example), such as... [picture] [4] As shown. In this case, the measured lateral concave portion is the lateral concave portion of each layer, that is, the top lateral concave portion belonging to the second-to-last layer.

[0067] As another example, in order to measure the average lateral concavity relative to the intermediate second layer, the landing energy of the electron beam can be specifically selected to penetrate a predefined depth corresponding to the intermediate second layer (or its vicinity).

[0416] In this case, the measured lateral concavity is the average lateral concavity between the top-layer lateral concavity and the middle-layer lateral concavity. Similarly, when the landing energy of the electron beam is set to a predefined depth corresponding to the bottom second layer...

[0418] At that time, the measured lateral concavity was the average lateral concavity of the three lateral concavities in each layer (top layer lateral concavity, middle layer lateral concavity, and bottom layer lateral concavity).

[0068] In some embodiments, the landing energy of the electron beam may first be set to be suitable for measuring the penetration depth of the top-layer lateral concave portion, as described above, and after the measurement is completed, the landing energy of the electron beam may be reset to be suitable for measuring the penetration depth of the average lateral concave portion between the top-layer and intermediate-layer lateral concave portions. The intermediate-layer lateral concave portion can then be derived based on these two measurements, as referenced... [picture] [3] Further detailed description.

[0069] In some embodiments, to select the level of landing energy that can penetrate to a specific expected depth corresponding to the target second layer of the sample to be examined, a reference sample having a similar structure to the sample but without recesses in any of the second layers can be used as a reference. A sample of interest with lateral recesses at a specific second layer can also be simulated. According to some embodiments, the landing energy penetrating to a predefined depth corresponding to the target second layer can be specifically selected based on a comparison between the number of BSEs relative to the reference sample (without lateral recesses) and the number of BSEs relative to the sample of interest (with lateral recesses at a specific layer).

[0070] [picture] [7] An exemplary graph illustrating the correlation between the number of BSEs received from a reference sample relative to the difference in the sample of interest, according to certain embodiments of the subject matter disclosed herein, and the level of landing energy used.

[0071] It can simulate having a reference [picture] [4] A reference GAA device with a similar structure to the described GAA (e.g., having a superlattice stack) but without lateral recesses in the second layer (SiGe layer) and a GAA of interest with lateral recesses in the first, second, and third SiGe layers, respectively, are plotted. Simulations can be performed to simulate scans of the reference GAA and the GAA of interest using different landing energies, and the number of BSEs received from the two analogous scans can be calculated and compared. [picture] The graphs in [7] illustrate the difference (Y-axis) between the number of BSEs received from two scans relative to different levels of landing energy (X-axis) used for scanning for different second layers. For example, the curve for layer 1 refers to the difference (Y-axis) between the number of BSEs received from a scan of a reference GAA relative to different levels of landing energy (X-axis) used for scanning and the number of BSEs received from a scan of a GAA of interest with a lateral recess at the first (i.e., top) SiGe layer. The curve for layer 2 refers to the difference (Y-axis) between the number of BSEs received from a scan of a reference GAA relative to different levels of landing energy (X-axis) used for scanning and the number of BSEs received from a scan of a GAA of interest with a lateral recess at the second SiGe layer. The curve for layer 3 refers to the difference (Y-axis) between the number of BSEs received from a scan of a reference GAA relative to different levels of landing energy (X-axis) used for scanning and the number of BSEs received from a scan of a GAA of interest with a lateral recess at the third SiGe layer.

[0072] As shown in the figure, when the landing energy is very low (e.g., less than 2 keV), the difference in BSE received from the two scans is close to 0, meaning that the landing energy is insufficient for electrons to penetrate to either of the second layers with the recess, and therefore there is no difference in the number of BSEs received from the two scans. As the landing energy increases, electrons begin to reach the top second layer of the sampled layer (e.g., the top SiGe layer), and a difference in the number of BSEs received from the two scans (the scan of the reference GAA and the GAA of interest with the recess at the top SiGe layer) is expected. This indicates the presence of a lateral recess in the top second layer of the GAA of interest relative to the reference GAA which has no recess at the top second layer (e.g., fewer electrons are received from the GAA of interest because there is less material interacting with the electrons, and electron scattering occurs due to the recess).

[0073] Therefore, in the curve for layer 1, it can be seen that as the landing energy increases from approximately 2 keV to 3.5 keV, the difference between the number of BSEs received from the two scans continuously increases, indicating that electrons with landing energies within this range are penetrating the top SiGe layer, but have not yet reached the second and third SiGe layers (as shown in the figure, the curves for layers 2 and 3 remain close to 0 in this energy range). An electron beam with a landing energy approximately selected within this range can be used to measure the recesses of each layer in the top SiGe layer.

[0074] As the landing energy continues to increase (e.g., from approximately 3.5 keV to 4.0 keV), electrons are able to reach the second SiGe layer, where, in the curve for layer 2, the difference between the number of BSEs received from two scans (a scan of the reference GAA and a scan of the GAA of interest with a concave portion in the second SiGe layer) continuously increases, as shown in the figure. An electron beam with a landing energy selected approximately within this range can be used to measure the average concavity of the top SiGe layer and the second SiGe layer.

[0075] As the landing energy increases between 4.0 keV and 6.0 keV, electrons are able to reach the third SiGe layer, where, in the diagram of layer 3, the difference between the number of BSEs received from two scans (the scan of the reference GAA and the scan of the GAA of interest with a recess in the third SiGe layer) begins to increase, as shown in the figure. Electron beams with landing energies selected approximately within this range can be used to measure the average recess in the top SiGe layer, the second SiGe layer, and the third SiGe layer. At relatively high landing energies (approximately 20 keV), [picture] [7] (not shown) Under these conditions, the electrons are almost equally sensitive to the three different layers, thus indicating that the BSE signal is only sensitive to the average concavity on the three layers. This relatively high level of landing energy can be used when measuring the average concavity of the GAA device.

[0076] continue [picture] [2A] describes that once the first and second images are obtained (as described in the reference box above),

[0202] and [picture] [2B](as described), then (for example, through the image processing module in Figure 1)

[0104] ) generates (

[0204] A first GL waveform provides information on the grayscale (GL) intensity distribution of a first image, and a second GL waveform provides information on the GL intensity distribution of a second image.

[0077] It can be based on the first GL waveform (e.g., via the measurement module in Figure 1).

[0106] ) to estimate (

[0206] The first width of one or more first layers can be estimated based on the second GL waveform.

[0206] ) relative to the second width of at least the target second layer. This can be based on the first width and the second width (e.g., via the measurement module in FIG1).

[0106] ) Measurement (

[0208] (The lateral recess relative to the second layer of the target)

[0078] Now for reference [picture] [5], showing examples of first and second images of GAA structures according to certain embodiments of the subject matter currently disclosed.

[0079] As shown in the figure, the image

[0502] An exemplary first image (i.e., an SE image) is obtained by collecting SE emitted from a sampled surface, and the image

[0504] An exemplary second image (i.e., a BSE image) is obtained by collecting BSE scattered from a sampled internal region between the surface and the target second layer. The first image provides information about the sampled surface profile (e.g., surface topography). As shown in the figure, the image...

[0502] SE image representations of four GAA structures are presented. For each GAA structure, the gray gradation intensity varies along a direction perpendicular to the longitudinal axis of the GAA structure, thus representing the variation of the surface profile of the GAA in that direction. For illustrative purposes, [picture] [4] An illustrative example illustrates GAA

[0400] Surface profile

[0420] As shown in the figure, the surface profile

[0420] This indicates the outer surface morphology of the first layer (i.e., silicon layer) exposed to the electron beam during scanning.

[0080] As mentioned above, the second image provides information on the internal structure (and / or composition) of the sampled internal region between the surface and the target second layer. Image

[0504] BSE image representations of four GAA structures are presented. For each GAA structure, the variation in grayscale intensity in the BSE image can reflect the hidden lateral recess structure (i.e., the penetration capability of the BSE) relative to the remainder of the second layer (i.e., the SiGe layer) during the etching process.

[0081] Now for reference [picture] [6], showing examples of first and second GL waveforms according to certain embodiments of the subject matter disclosed herein.

[0082] As shown in the figure, [picture] [5] generates a first image.

[0502] (e.g., its specific GAA structure) information of the first GL waveform of the GL intensity distribution

[0602] and generates a second image.

[0504] The second GL waveform of the GL intensity distribution information

[0604] The first GL waveform and the second GL waveform are generated along the longitudinal axis perpendicular to the GAA structure.

[0083] The first width (e.g., width) of one or more first layers can be estimated based on the first GL waveform.

[0512] ,like [picture] [5] (illustrated by example in the SE image). As an example, estimating the first width may include estimating a first topological point on the first GL waveform. A topological point is a point on a signal waveform (e.g., a GL waveform) that is identified as a specific location on the geometry corresponding to the sample. For example, the first topological point may represent the estimated edge / boundary of the first layer (e.g., the outer boundary of the widest silicon layer, or the average boundary of the three silicon layers). Specifically, in some embodiments, the first topological point may be estimated by calculating a derivative along the first GL waveform, applying a predefined derivative threshold to the first GL waveform, generating the first topological point, and measuring a first width between two topological points.

[0084] For example, in [picture] In this example of [6], the first waveform The two points on

[0602] corresponding to the derivative threshold are marked as

[0606] and

[0608] Topological points

[0606] and

[0608] This can represent the estimated edge / boundary of the first layer (i.e., the silicon layer). Two points can be measured.

[0606] and The first width between

[0608]

[0610] It represents the estimated width of the first layer of the GAA structure.

[0412] .

[0085] The second width (e.g., width) relative to at least the target second layer can be estimated based on the second GL waveform.

[0514] ,like [picture] [5] (illustrated by example in the BSE image). As mentioned above, when the target second layer is the top second layer, the estimated second width refers to the width of the target second layer. When the target second layer is a subsequent second layer after the top second layer (such as, for example, a middle second layer or a bottom second layer), the estimated second width refers to the average width of the second layer up to the target second layer. As an example, estimating the second width may include estimating a second topological point on the second GL waveform. For example, the second topological point may represent an estimated edge / boundary relative to at least the target second layer. Specifically, in some embodiments, the second topological point may be estimated by applying a predefined GL threshold on the second GL waveform and measuring the second width between the second topological points.

[0086] For example, in [picture] In this example of [6], in the second waveform

[0604] A predefined GL threshold (e.g., 70%) is applied to the two topological points.

[0616] and

[0618] Identified. Two points can be measured.

[0616] and The second width between

[0618]

[0620] Its representation is as follows [picture] The estimated width illustrated in [5]

[0514] .

[0087] Based on the first width

[0610] and second width

[0620] (For example, by subtracting the second width from the first width) to measure the lateral recess relative to the target second layer.

[0088] In some embodiments, the measured lateral recess can be further calibrated relative to reference measurements taken from a reference semiconductor sample obtained from a transmission electron microscope (TEM). This calibration can improve the accuracy of the measurement. In some cases, calibration can be performed based on a correlation previously derived between corresponding measurements from an electron beam instrument and reference measurements obtained from the TEM.

[0089] Turn now [picture] [3] The figure shows a generalized flowchart of measuring the lateral recesses of each layer and / or measuring the average lateral recesses according to certain embodiments of the subject matter disclosed herein.

[0090] As mentioned above, when the target second layer is the top second layer of one or more second layers, the above reference can be used. [picture] [2A] describes the method for measuring (

[0302] A lateral recess is formed in the top layer between the top second layer and its adjacent first layer. In this case, the landing energy of the electron beam needs to be specifically selected to penetrate to the depth corresponding to the top second layer. In other words, in this case, from [picture] [2A] The measured lateral concavity refers to the top lateral concavity.

[0091] In the square

[0302] After the measurement is completed, the landing energy of the electron beam can be reset to enable penetration of the depth corresponding to the subsequent second layer after the top second layer (e.g., the middle second layer or the bottom second layer, as illustrated in Figure 4), and the depth can be measured (

[0304] The lateral concavity is relative to the average lateral concavity of the subsequent second layer. For example, when the subsequent second layer is an intermediate second layer, the measured lateral concavity refers to the average lateral concavity averaged between the top layer lateral concavity and the intermediate layer lateral concavity. In this case, the lateral concavity can be calculated based on the average lateral concavity and the top layer lateral concavity.

[0306] The subsequent second layer has lateral recesses in each layer.

[0092] According to certain embodiments, as referenced above [picture] [2A]、 [picture] [2B] and [picture] [3] The measurement procedure described can be used as a system

[0101] and / or inspection tools

[0120] Part of the testing scheme used is for runtime testing sampling, such as performing a metrological operation on the sample (referred to as a metrological scheme in this case). Therefore, the subject matter disclosed herein also includes systems and methods for generating testing schemes during the scheme setup phase, wherein the formulation includes, as referenced [picture] [2A]、 [picture] [2B] and [picture] The steps described in [3] (and its various embodiments) should be noted. It should be noted that the term "testing protocol" should be broadly interpreted to encompass any protocol that can be used by testing tools to perform operations related to any kind of testing as described above.

[0093] It should be noted that the examples shown in this case, such as the exemplary GAA structure, the acquired first and second images, the generated GL waveform, and the specific manner in which the estimated width and / or topological points are presented, are for illustrative purposes only and should not be construed as limiting the scope of this case in any way. Other suitable examples / implementations may be used in addition to or in lieu of the foregoing.

[0094] It should be noted that while some embodiments of the measurement procedures disclosed in this invention are described in relation to measuring lateral recesses in semiconductor samples with a specific structure, i.e., samples comprising stacks of two types of layers: one or more first layers of a first type and one or more second layers of a second type deposited alternately, wherein the second layers are at least partially etched, this is not intended to limit the measurement procedures currently disclosed to only such structured samples. Alternatively, in some cases, samples comprising only one material and therefore not layered may have lateral recesses formed on their lateral sides, and the measurement procedures currently disclosed can be similarly applied to such samples for the purpose of measuring their lateral recesses.

[0095] As an example, the measurement procedure in this case may include: acquiring a first image by collecting secondary electrons (SE) emitted from the sampled surface and a second image by collecting backscattered electrons (BSE) scattered from an internal region of the sampled surface between the surface and a target depth (e.g., corresponding to the bottom (or vicinity) of a lateral recess in the sample), wherein the semiconductor sample is scanned using an electron beam having a landing energy specifically selected to penetrate to the target depth, wherein the first image provides information on the surface profile of the sample and the second image provides information on the internal structure of the internal region; generating a first GL waveform that provides information on the grayscale (GL) intensity distribution of the first image and a second GL waveform that provides information on the GL intensity distribution of the second image; estimating a first width of a first layer based on the first GL waveform and estimating a second width relative to at least a target second layer based on the second GL waveform; and measuring the lateral recess in the sample based on the first width and the second width.

[0096] One advantage of certain embodiments of the measurement procedure described herein is that it provides direct, non-destructive measurement of lateral recesses formed in the aforementioned semiconductor samples, with improved accuracy and throughput (TpT). This is achieved, at least by combining the SE signal of an electron beam tool with the penetration capability of a BSE signal, wherein the electron beam tool is configured with an electron beam having a landing energy of relatively high voltage.

[0097] It will be understood that the application of this case is not limited to the details set forth in the description contained herein or shown in the accompanying drawings.

[0098] It will also be understood that the system according to this case can be implemented at least partially on a suitably programmed computer. Similarly, this case envisions a computer program that can be read by a computer to execute the methods of this case. This case further envisions a non-transient computer-readable memory that tangibly embodies the instruction program that can be executed by a computer to execute the methods of this case.

[0099] The content of this application can have other embodiments and can be practiced or carried out in various ways. Therefore, it will be understood that the wording and terminology used herein are for descriptive purposes and should not be considered limiting. Consequently, those skilled in the art will appreciate that the concepts on which this application is based can be readily used as the basis for designing other structures, methods, and systems for carrying out several purposes of the subject matter currently disclosed.

[0100] Those skilled in the art will readily understand that various modifications and alterations can be applied to the embodiments of this case as described above without departing from the scope of the appended claims and as defined by the appended claims.

[0101] 100: Inspection System 101: System 102:PMC 104: Image Processing Module 106: Measurement Module 120: Inspection tools 122: Storage Unit 124:GUI 126:I / O interface 202: Square 204: Square 206: Square 208: Square 210: Square 212: Square 302: Square 304: Square 306: Square 400:GAA structure 402: First Floor 404: Second layer 406: Semiconductor substrate 408: Lateral concave portion 410: GAA Structure 412: Width 414: Predefined depth 416: Predefined depth 418: Predefined depth 420: Surface Profile 502: First Image 504: Second Image 512: Width 514: Width 602: First waveform 604: Second waveform 606: points 608: points 610: First width 616: points 618: points 620: Second width

[0102] Domestic storage information (please note in order of storage institution, date, and number) none Overseas storage information (please note in the order of storage country, institution, date, and number) none

Claims

1. A computerized system for measuring a lateral recess in a semiconductor sample, the semiconductor sample comprising a stack of one or more first layers of a first type and one or more second layers of a second type deposited alternately, the second layers being at least partially etched to form a lateral recess between each given second layer and its two adjacent first layers, the system comprising: An electron beam tool configured to: scan a semiconductor sample using an electron beam having a landing energy specifically selected to penetrate to a predefined depth corresponding to a target second layer of the sample; acquire a first image by collecting secondary electrons (SE) emitted from a surface of the sample, and acquire a second image by collecting backscattered electrons (BSE) scattered from an internal region of the sample between the surface and the target second layer, the first image providing information on the contour of a surface of the sample, and the second image providing information on an internal structure of the internal region; and a processing and memory circuit (PMC) operatively connected to the electron beam tool and configured to: generate a first GL waveform providing information on the grayscale (GL) intensity distribution of the first image and a second GL waveform providing information on the GL intensity distribution of the second image; A first width of the one or more first layers is estimated based on the first GL waveform, and a second width relative to at least the target second layer is estimated based on the second GL waveform; and a lateral recess relative to the target second layer is measured based on the first width and the second width.

2. The computerized system as claimed in claim 1, wherein the semiconductor sampling includes a gate-around-annular (GAA) device, and wherein the first layer is made of silicon and the second layer is made of silicon-germanium.

3. The computerized system as claimed in claim 1, wherein the target second layer is a top second layer among the one or more second layers, and the measured lateral recess is a top lateral recess formed between the top second layer and its adjacent first layer.

4. The computerized system as claimed in claim 1, wherein the target second layer is a subsequent second layer following a top second layer, and the measured lateral recess is an average lateral recess formed between the top second layer and its adjacent first layer, and between a top lateral recess formed between the subsequent second layer and its adjacent first layer.

5. The computerized system as described in claim 3, wherein the PMC is further configured to measure an average lateral recess relative to a subsequent second layer following the top second layer, and to converge a subsequent layer lateral recess based on the average lateral recess and the top layer lateral recess.

6. The computerized system as described in claim 1, wherein the SEs are collected by an SE detector array and the BSEs are collected by at least one BSE detector.

7. The computerized system as claimed in claim 1, wherein the landing energy penetrating to the predefined depth corresponding to the second layer of the target is specifically selected based on a comparison between a number of BSEs relative to a reference sample without lateral recesses and a number of BSEs relative to the semiconductor sample.

8. The computerized system as claimed in claim 1, wherein estimating the first width includes estimating a first topological point on the first GL waveform by calculating a derivative along the first GL waveform, applying a predefined derivative threshold on the first GL waveform to generate the first topological point, and measuring the first width between such first topological points.

9. The computerized system as claimed in claim 1, wherein estimating the second width includes estimating second topological points on the second GL waveform by applying a predefined GL threshold to the second GL waveform, generating the second topological points, and measuring the second width between the second topological points.

10. The computerized system as claimed in claim 1, wherein the PMC is further configured to calibrate the measured lateral recess relative to reference measurement data obtained from a transmission electron microscope (TEM).

11. The computerized system as claimed in claim 10, wherein the calibration is based on a correlation previously derived between corresponding measurement data from the electron beam tool and reference measurement data obtained from the TEM.

12. A computerized method for measuring a lateral recess in a semiconductor sample comprising a stack of one or more first layers of a first type and one or more second layers of a second type deposited alternately, the second layers being at least partially etched to form a lateral recess between each given second layer and its two adjacent first layers, the method being performed by a processing and memory circuit (PMC) and comprising: A first image is obtained by collecting secondary electrons (SE) emitted from a sampled surface and a second image is obtained by collecting backscattered electrons (BSE) scattered from an internal region of the sampled surface between the surface and a target second layer, wherein the semiconductor sample is scanned using an electron beam having a landing energy specifically selected to penetrate to a predefined depth corresponding to the target second layer, and wherein the first image provides information on the surface profile of the sampled surface and the second image provides information on the internal structure of the internal region; a first GL waveform is generated providing information on the grayscale (GL) intensity distribution of the first image and a second GL waveform providing information on the GL intensity distribution of the second image; a first width of the first layers is estimated based on the first GL waveform, and a second width relative to at least the target second layer is estimated based on the second GL waveform; and a lateral recess relative to the target second layer is measured based on the first width and the second width.

13. The computerized method as described in claim 12, wherein the target second layer is a top second layer among the one or more second layers, and the measured lateral recess is a top lateral recess formed between the top second layer and its adjacent first layer.

14. The computerized method as described in claim 12, wherein the target second layer is a subsequent second layer following a top second layer, and the measured lateral recess is an average lateral recess formed between the top second layer and its adjacent first layer and between a top lateral recess formed between the subsequent second layer and its adjacent first layer.

15. The computerized method as described in claim 13 further includes measuring an average lateral recess relative to a subsequent second layer following the top second layer, and drawing a subsequent layer lateral recess based on the average lateral recess and the top layer lateral recess.

16. The computerized method as described in claim 12, wherein the landing energy penetrating to the predefined depth corresponding to the second layer of the target is specifically selected based on a comparison between a number of BSEs relative to a reference sample without lateral recesses and a number of BSEs relative to the semiconductor sample.

17. The computerized method as described in claim 12, wherein estimating the first width includes estimating a first topological point on the first GL waveform by calculating a derivative along the first GL waveform, applying a predefined derivative threshold on the first GL waveform to generate the first topological point, and measuring the first width between the first topological points.

18. The computerized method as described in claim 12, wherein estimating the second width includes estimating a second topological point on the second GL waveform by applying a predefined GL threshold to the second GL waveform, generating the second topological point, and measuring the second width between the second topological points.

19. The computerized method as described in claim 12 further includes calibrating the measured lateral recess relative to reference measurement data obtained from a transmission electron microscope (TEM).

20. A non-transient computer-readable storage medium tangibly embodies an instruction program that, when executed by a computer, causes the computer to perform a method for measuring a lateral recess in a semiconductor sample, the semiconductor sample comprising a stack of one or more first layers of a first type and one or more second layers of a second type deposited alternately, the second layers being at least partially etched to form a lateral recess between each given second layer and its two adjacent first layers, the method comprising the steps of: obtaining a first image by collecting secondary electrons (SE) emitted from a surface of the sample and a second image by collecting backscattered electrons (BSE) scattered from an internal region of the sample between the surface and a target second layer, wherein the semiconductor sample is scanned using an electron beam having a landing energy specifically selected to penetrate to a predefined depth corresponding to the target second layer, and wherein the first image provides information on a surface profile of the sample, and the second image provides information on an internal structure of the internal region; Generate a first GL waveform that provides information on the grayscale (GL) intensity distribution of the first image and a second GL waveform that provides information on the GL intensity distribution of the second image; estimate a first width of the first layer based on the first GL waveform, and estimate a second width relative to at least the target second layer based on the second GL waveform; and measure a lateral recess relative to the target second layer based on the first width and the second width.

Images