Patent Description:
Demand for electronic logic and memory devices with ever-smaller footprints and features present a wide range of manufacturing challenges beyond fabrication at a desired scale. Increasingly complex structures result in increasing numbers of parameters which must be monitored and controlled to maintain device integrity. One important characteristic in the field of semiconductor fabrication is critical dimension uniformity (CDU) and the critical dimension(s) (CD) of device features. Monitoring CDU may help with monitoring process variations and identify process tool drift which needs to be fixed.

Traditionally, monitoring features of interest (e.g., CDU) involves defining patterns of interest (POIs), defining a region of interest (ROI) relative to the POIs within which a measurement (e.g., CDU measurement) is to be made, detecting the edges of the ROI, and performing the measurement. However, because current techniques involve aligning POIs with scanning electron microscopy (SEM) images and placing ROIs based on the POI location, the accuracy of the ROI placement is dependent upon SEM-to-SEM alignment, which may not be reliable. Furthermore, alignment accuracy is often low because the defined POI structure size within each image may vary considerably. Due to this misalignment, ROIs may be mis-placed, and thereby fail to include the entire region required for a particular measurement of interest.

Additionally, current techniques are not able to correct for process variations and/or structural variations which may affect alignment accuracy. Therefore, POI alignment within an SEM image, and therefore ROI alignment, may fail due to structural variations within the specimen itself. For example, target structure size variations may result in POI and ROI alignment failure, thereby preventing efficient monitoring of measurements of interest.

<CIT> discloses methods and systems for determining parameters of a process to be performed on a specimen.

<CIT> describes methods and systems for detecting anomalies in images of a specimen.

Therefore, it would be desirable to provide a system and method that cure the shortfalls of the previous approaches identified above.

A method as recited in claim <NUM> is disclosed.

It is noted herein that monitoring features of interest, including critical dimension uniformity (CDU), is an important step in monitoring process variations during semiconductor fabrication. Traditionally, monitoring features of interest (e.g., CDU) are based on conventional image processing procedures and involve the following steps: (<NUM>) defining patterns of interest (POIs), (<NUM>) defining a region of interest (ROI) relative to the POIs within which a measurement (e.g., CDU measurement) is to be made, (<NUM>) defining which measurement is to be made (e.g., CDU measurement, pattern width, contact, and the like), (<NUM>) detecting the edges of each ROI, and (<NUM>) performing the measurement. However, because current techniques involve aligning POIs with scanning electron microscopy (SEM) images and placing ROIs based on the POI location, the accuracy of the ROI placement is dependent upon SEM-to-SEM alignment, which may not be reliable. Furthermore, alignment accuracy is often low because the defined POI structure size within each image may vary considerably. Due to this misalignment, ROIs may be mis-placed, and thereby fail to include the entire region required for a particular measurement of interest.

Additionally, current ROI placement techniques based on conventional image processing procedures are not able to correct for process variations which may affect alignment accuracy. Therefore, POI alignment within an SEM image, and therefore ROI alignment, may fail due to structural variations within the specimen itself. For example, target structure size variations may result in POI and ROI alignment failure, thereby preventing efficient monitoring of measurements of interest.

Accordingly, embodiments of the present disclosure are directed to curing one or more shortfalls of the previous approaches identified above. Embodiments of the present disclosure are directed to a system and method for generating adaptive regions of interest (ROls) using machine learning techniques. More particularly, embodiments of the present disclosure are directed to using machine learning techniques to generate adaptive ROIs in order to more effectively monitor features of interest.

The various shortfalls of previous approaches based on conventional image processing procedures, as well as the significance of embodiments of the present disclosure, may be further understood with reference to <FIG>. It is contemplated herein that a brief discussion of traditional approaches may serve as a benchmark against which the advantages of the present disclosure may be compared.

<FIG> illustrates pattern of interest (POI) and region of interest (ROI) alignment on a specimen.

As noted previously herein, in the first step of traditional feature of interest monitoring using conventional image processing procedures, a POI <NUM> is defined/selected on a control image <NUM> of a specimen, as may be seen in <FIG>. The POI <NUM> may be drawn on any control image <NUM> including a design image of the specimen, an optical image, an SEM image, and the like. The POI <NUM> defines an area of specimen within which a measurement is to be made, and serves as an anchor point for ROI <NUM> placement. The POI <NUM> may include a unique pattern, a unit of a repeating structure, or the like. Following POI <NUM> selection, the ROI <NUM> is then selected on the control image <NUM> of the specimen within the area defined by the POI <NUM>. The ROI <NUM> defines an area of the specimen within which the measurement is to be made. In practice, POI <NUM> and ROI <NUM> selection shown in <FIG> may be carried out on a design image of a specimen (e.g., control image <NUM>).

After POI <NUM> and ROI <NUM> selection, a product image of a specimen is taken, and the POI <NUM> defined in the first step is identified and aligned in the product image. The product image taken in the second step is a different image from the control image <NUM> in which the POI <NUM> and ROI <NUM> were defined, and may include an image of a product specimen. The product image may include any image known in the art including, but not limited to, an optical image, a SEM image, and the like. After the POI <NUM> has been aligned in the product image, the ROI <NUM> is placed within the product image according to the placement of the POI <NUM>. In this regard, the alignment accuracy of the POI <NUM> may directly affect the alignment accuracy of the ROI <NUM>. Thus, the accuracy of the ROI <NUM> placement is dependent upon SEM-to-SEM alignment, which may not be reliable. Furthermore, alignment accuracy is often low because the defined POI <NUM> structure size within each image may vary considerably, thereby causing ROIs <NUM> to be mis-placed.

Following POI <NUM> and ROI <NUM> alignment in a product image, a measurement type may be defined. This may be further understood with reference to <FIG>.

<FIG> illustrates a pattern of interest (POI <NUM>) including a target site. The target site to be measured may include the measurement of interest defined as D4. The measurement D4 may include a critical dimension (CD) measurement, and may be defined by the expression <MAT>.

It is noted herein that traditional ROI placement techniques using conventional image processing procedures may suffer from alignment errors attributable to process variations during the specimen fabrication process. With shrinking design rules, even small process variations may lead to large structural variations of specimen. This may then lead to alignment inaccuracies and alignment failures, thereby causing inaccurate placement of ROIs within an image. These process variations and resulting alignment inaccuracies are especially problematic during ramp-up periods in the semiconductor fabrication process. During ramp-up periods, structures may vary considerably in shape, size, orientation, and the like. This may in turn lead to alignment inaccuracies for POI/ROI placement between a control image and a product image.

<FIG> illustrate an alignment error between a region of interest (ROI 104b) of a product image <NUM> and a region of interest (ROI 104a) of a control image <NUM>.

Using traditional POI/ROI placement techniques based on conventional image processing procedures, a user may desire to perform one or more measurements on product specimens within the left "lobe" illustrated in <FIG>, and may thereby define the left lobe as the target site at issue. In this regard, the target site may include one or more "measurements of interest," which may include any parameter which may be measured including, but not limited to, a critical dimension (CD) measurement. Using traditional techniques, a user may define the ROI 104a within a control image <NUM>, wherein the ROI 104a is located within the POI 102a and includes the target site including the one or more measurements of interest. Subsequently, a product image <NUM> may be taken, as shown in <FIG>.

As shown in <FIG>, one or more process variations in the layer including the target site may result in an enlarged target site (e.g., enlarged left lobe). This structural variation between the target site of the product image <NUM> and the target site of the control image <NUM> may lead to alignment inaccuracies, and incorrect ROI 104b placement. For example, the POI 102b of the product image <NUM> may be aligned with the POI 102a of the control image <NUM>, and the ROI 104b of the product image <NUM> may be placed according to the placement of the POI 102b within the product image <NUM>. As may be seen in <FIG>, the placement of the ROI 104b may be inaccurate in that it fails to encompass the target site (e.g., the left lobe). Due to the fact that the ROI 104b does not include the entirety of the target site, the desired measurements of interest within the target site may not be able to be acquired. Accordingly, under the traditional approach, conventional image processing procedures and alignment techniques are not capable of accounting for the process variation resulting in structural variations (e.g., enlarged left lobe).

<FIG> illustrate an additional example of an alignment error between a region of interest (ROI 104b) of a product image <NUM> and a region of interest (ROI 104a) of a control image <NUM>.

Similarly to the previous example, a user may desire to perform one or more measurements on product specimens within the left "lobe" illustrated in <FIG>, and may thereby define the left lobe as the target site at issue. Using traditional techniques, a user may define the ROI 104a within a control image <NUM>, wherein the ROI 104a is located within the POI 102a and includes the target site. Subsequently, a product image <NUM> may be taken, as shown in <FIG>.

As shown in <FIG>, one or more process variations in the layer including the target site may result in a thin and/or shifted target site (e.g., left lobe). This structural variation between the target site of the product image <NUM> and the target site of the control image <NUM> may lead to alignment inaccuracies, and incorrect ROI 104b placement. For example, the POI 102b of the product image <NUM> may be aligned with the POI 102a of the control image <NUM>, and the ROI 104b of the product image <NUM> may be placed according to the placement of the POI 102b within the product image <NUM>. As may be seen in <FIG>, the placement of the ROI 104b may be inaccurate in that it fails to encompass the target site (e.g., the left lobe) including the measurements of interest. Therefore, conventional image processing procedures relying on alignment techniques may fail to accurately place the ROI 104b in the product image <NUM>. This may result in the inability to perform the desired measurements of the target site.

As noted previously herein, embodiments of the present disclosure are directed to a system and method for generating adaptive regions of interest (ROls) using machine learning techniques. More particularly, embodiments of the present disclosure are directed to using machine learning techniques to generate adaptive ROIs in order to more effectively monitor features of interest. It is contemplated herein that embodiments of the present disclosure may allow for the accurate placement of ROIs despite the existence of process and/or structural variations.

<FIG> illustrates a system <NUM> for adaptive region of interest (ROI) selection, in accordance with one or more embodiments of the present disclosure. The system <NUM> may include, but is not limited to, one or more characterization sub-systems <NUM>. The system <NUM> may additionally include, but is not limited to, a controller <NUM> including one or more processors <NUM> and a memory <NUM>, and a user interface <NUM>.

The characterization sub-system <NUM> may include any characterization sub-system <NUM> known in the art including, but not limited to, an optical-based characterization system, a charged particle-based characterization system, and the like. For example, the characterization sub-system <NUM> may include a scanning electron microscopy (SEM) characterization system. In one embodiment, the controller <NUM> is communicatively coupled to the one or more characterization sub-systems <NUM>. In this regard, the one or more processors <NUM> of the controller <NUM> may be configured to generate one or more control signals configured to adjust one or more characteristics of the characterization sub-system <NUM>.

<FIG> illustrates a system <NUM> for adaptive region of interest (ROI) selection, in accordance with one or more embodiments of the present disclosure. In particular, <FIG> illustrates a system <NUM> including an optical characterization sub-system 202a.

The optical characterization sub-system 202a may include any optical-based characterization system known in the art including, but not limited to, an image-based metrology tool. For example, the characterization sub-system 202a may include an optical critical dimension metrology tool. The optical characterization sub-system 202a may include, but is not limited to, an illumination source <NUM>, an illumination arm <NUM>, a collection arm <NUM>, and a detector assembly <NUM>.

In one embodiment, optical characterization sub-system 202a is configured to inspect and/or measure the specimen <NUM> disposed on the stage assembly <NUM>. Illumination source <NUM> may include any illumination source known in the art for generating illumination <NUM> including, but not limited to, a broadband radiation source. In another embodiment, optical characterization sub-system 202a may include an illumination arm <NUM> configured to direct illumination <NUM> to the specimen <NUM>. It is noted that illumination source <NUM> of optical characterization sub-system 202a may be configured in any orientation known in the art including, but not limited to, a dark-field orientation, a light-field orientation, and the like.

Specimen <NUM> may include any specimen known in the art including, but not limited to, a wafer, a reticle, a photomask, and the like. In one embodiment, specimen <NUM> is disposed on a stage assembly <NUM> to facilitate movement of specimen <NUM>. In another embodiment, the stage assembly <NUM> is an actuatable stage. For example, the stage assembly <NUM> may include, but is not limited to, one or more translational stages suitable for selectably translating the specimen <NUM> along one or more linear directions (e.g., x-direction, y-direction and/or z-direction). By way of another example, the stage assembly <NUM> may include, but is not limited to, one or more rotational stages suitable for selectively rotating the specimen <NUM> along a rotational direction. By way of another example, the stage assembly <NUM> may include, but is not limited to, a rotational stage and a translational stage suitable for selectably translating the specimen <NUM> along a linear direction and/or rotating the specimen <NUM> along a rotational direction. It is noted herein that the system <NUM> may operate in any scanning mode known in the art.

The illumination arm <NUM> may include any number and type of optical components known in the art. In one embodiment, the illumination arm <NUM> includes one or more optical elements <NUM>, a beam splitter <NUM>, and an objective lens <NUM>. In this regard, illumination arm <NUM> may be configured to focus illumination <NUM> from the illumination source <NUM> onto the surface of the specimen <NUM>. The one or more optical elements <NUM> may include any optical elements known in the art including, but not limited to, one or mirrors, one or more lenses, one or more polarizers, one or more beam splitters, and the like.

In another embodiment, optical characterization sub-system 202a includes a collection arm <NUM> configured to collect illumination reflected or scattered from specimen <NUM>. In another embodiment, collection arm <NUM> may direct and/or focus the reflected and scattered light to one or more sensors of a detector assembly <NUM> via one or more optical elements <NUM>. The one or more optical elements <NUM> may include any optical elements known in the art including, but not limited to, one or mirrors, one or more lenses, one or more polarizers, one or more beam splitters, and the like. It is noted that detector assembly <NUM> may include any sensor and detector assembly known in the art for detecting illumination reflected or scattered from the specimen <NUM>.

In another embodiment, the detector assembly <NUM> of the optical characterization sub-system <NUM> is configured to collect metrology data of the specimen <NUM> based on illumination reflected or scattered from the specimen <NUM>. In another embodiment, the detector assembly <NUM> is configured to transmit collected/acquired images and/or metrology data to the controller <NUM>.

As noted previously herein, the controller <NUM> of system <NUM> may include one or more processors <NUM> and memory <NUM>. The memory <NUM> may include program instructions configured to cause the one or more processors <NUM> to carry out various steps of the present disclosure. In one embodiment, the program instructions are configured to cause the one or more processors <NUM> to adjust one or more characteristics of the optical characterization sub-system <NUM> in order to perform one or more measurements of the specimen <NUM>.

In additional and/or alternative embodiments, the characterization sub-system <NUM> may include a charged particle-based characterization sub-system <NUM>. For example, the characterization sub-system <NUM> may include an SEM characterization sub-system, as illustrated in <FIG>.

<FIG> illustrates a system <NUM> for adaptive region of interest (ROI) selection, in accordance with one or more embodiments of the present disclosure. In particular, <FIG> illustrates a system <NUM> including an SEM characterization sub-system 202b.

In one embodiment, the SEM characterization sub-system 202b is configured to perform one or more measurements on the specimen <NUM>. In this regard, the SEM characterization sub-system 202b may be configured to acquire one or more images of the specimen <NUM>. The SEM characterization sub-system 202b may include, but is not limited to, electron beam source <NUM>, one or more electron-optical elements <NUM>, one or more electron-optical elements <NUM>, and an electron detector assembly <NUM> including one or more electron sensors <NUM>.

In one embodiment, the electron beam source <NUM> is configured to direct one or more electron beams <NUM> to the specimen <NUM>. The electron beam source <NUM> may form an electron-optical column. In another embodiment, electron beam source <NUM> includes one or more additional and/or alternative electron-optical elements <NUM> configured to focus and/or direct the one or more electron beams <NUM> to the surface of the specimen <NUM>. In another embodiment, SEM characterization sub-system 202b includes one or more electron-optical elements <NUM> configured to collect secondary and/or backscattered electrons <NUM> emanated from the surface of the specimen <NUM> in response to the one or more electron beams <NUM>. It is noted herein that the one or more electron-optical elements <NUM> and the one or more electron-optical elements <NUM> may include any electron-optical elements configured to direct, focus, and/or collect electrons including, but not limited to, one or more deflectors, one or more electron-optical lenses, one or more condenser lenses (e.g., magnetic condenser lenses), one or more objective lenses (e.g., magnetic condenser lenses), and the like.

It is noted that the electron optical assembly of the SEM characterization sub-system 202b is not limited to the electron-optical elements depicted in <FIG>, which are provided merely for illustrative purposes. It is further noted that the system <NUM> may include any number and type of electron-optical elements necessary to direct/focus the one or more electron beams <NUM> onto the specimen <NUM> and, in response, collect and image the emanated secondary and/or backscattered electrons <NUM> onto the electron detector assembly <NUM>.

For example, the system <NUM> may include one or more electron beam scanning elements (not shown). For instance, the one or more electron beam scanning elements may include, but are not limited to, one or more electromagnetic scanning coils or electrostatic deflectors suitable for controlling a position of the one or more electron beams <NUM> relative to the surface of the specimen <NUM>. Further, the one or more scanning elements may be utilized to scan the one or more electron beams <NUM> across the specimen <NUM> in a selected pattern.

In another embodiment, secondary and/or backscattered electrons <NUM> are directed to one or more sensors <NUM> of the electron detector assembly <NUM>. The electron detector assembly <NUM> of the SEM characterization sub-system <NUM> may include any electron detector assembly known in the art suitable for detecting backscattered and/or secondary electrons <NUM> emanating from the surface of the specimen <NUM>. In one embodiment, the electron detector assembly <NUM> includes an electron detector array. In this regard, the electron detector assembly <NUM> may include an array of electron-detecting portions. Further, each electron-detecting portion of the detector array of the electron detector assembly <NUM> may be positioned so as to detect an electron signal from specimen <NUM> associated with one of the incident one or more electron beams <NUM>. In this regard, each channel of the electron detector assembly <NUM> may correspond to an electron beam <NUM> of the one or more electron beams <NUM>. The electron detector assembly <NUM> may include any type of electron detector known in the art. For example, the electron detector assembly <NUM> may include a micro-channel plate (MCP), a PIN or p-n junction detector array, such as, but not limited to, a diode array or avalanche photo diodes (APDs). By way of another example, the electron detector assembly <NUM> may include a high-speed scintillator/PMT detector.

While <FIG> illustrates the SEM characterization sub-system 202b as including an electron detector assembly <NUM> comprising only a secondary electron detector assembly, this is not to be regarded as a limitation of the present disclosure. In this regard, it is noted that the electron detector assembly <NUM> may include, but is not limited to, a secondary electron detector, a backscattered electron detector, and/or a primary electron detector (e.g., an in-column electron detector). In another embodiment, SEM characterization sub-system <NUM> may include a plurality of electron detector assemblies <NUM>. For example, system <NUM> may include a secondary electron detector assembly 234a, a backscattered electron detector assembly 234b, and an in-column electron detector assembly 234c.

In one embodiment, the one or more processors <NUM> are configured to analyze the output of detector assembly <NUM>/electron detector assembly <NUM>. In one embodiment, the set of program instructions are configured to cause the one or more processors <NUM> to analyze one or more characteristics of specimen <NUM> based on images received from the detector assembly <NUM>/electron detector assembly <NUM>. In another embodiment, the set of program instructions are configured to cause the one or more processors <NUM> to modify one or more characteristics of system <NUM> in order to maintain focus on the specimen <NUM> and/or the detector assembly <NUM>/electron detector assembly <NUM>. For example, the one or more processors <NUM> may be configured to adjust one or more characteristics of the illumination source <NUM>/electron beam source <NUM> and/or other elements of system <NUM> in order to focus of the illumination <NUM> and/or one or more electron beams <NUM> onto the surface of the specimen <NUM>. By way of another example, the one or more processors <NUM> may be configured to adjust the one or more elements of system <NUM> in order to collect illumination and/or secondary electrons <NUM> from the surface of the specimen <NUM> and focus the collected illumination on the detector assembly <NUM>/electron detector assembly <NUM>. By way of another example, the one or more processors <NUM> may be configured to adjust one or more focusing voltages applied to one or more electrostatic deflectors of electron beam source <NUM> in order to independently adjust the position or alignment of the one or more electron beams <NUM> and scan the electron beams <NUM> across the specimen <NUM>.

In one embodiment, the one or more processors <NUM> may be communicatively coupled to memory <NUM>, wherein the one or more processors <NUM> are configured to execute a set of program instructions stored on memory <NUM>, the set of program instructions configured to cause the one or more processors <NUM> to carry out various functions and steps of the present disclosure.

In another embodiment, as shown in <FIG> and in <FIG>, system <NUM> includes a user interface <NUM> communicatively coupled to the controller <NUM>. In another embodiment, the user interface <NUM> includes a user input device and a display. The user input device of the user interface <NUM> may be configured to receive one or more input commands from a user, the one or more input commands configured to input data into system <NUM> and/or adjust one or more characteristics of system <NUM>. For example, as will be described in further detail herein, the user input device of the user interface <NUM> may be configured to receive one or more POI and/or ROI selections from a user. In another embodiment, the display of the user interface <NUM> may be configured to display data of system <NUM> to a user.

As noted previously herein, the one or more processors <NUM> may be communicatively coupled to memory <NUM>, wherein the one or more processors <NUM> are configured to execute a set of program instructions stored on memory <NUM>, the set of program instructions configured to cause the one or more processors <NUM> to carry out various functions and steps of the present disclosure. In this regard, the controller <NUM> may be configured to: receive one or more training images of a specimen <NUM> from the characterization sub-system <NUM>; receive one or more training region-of-interest (ROI) selections within the one or more training images; generating a machine learning classifier based on the one or more training images and the one or more training ROI selections; receive one or more product images of a specimen <NUM> from the characterization sub-system <NUM>; generate one or more classified regions of interest with the machine learning classifier; and determine one or more measurements of the specimen <NUM> within the one or more classified regions of interest. Each of these steps will be addressed in turn.

In one embodiment, the controller <NUM> of system <NUM> is configured to receive one or more training images <NUM> of a specimen <NUM> from the characterization sub-system <NUM>. For the purposes of the present disclosure, the term "training images" may be regarded as images which will be used as inputs to train a machine learning classifier. <FIG> illustrates a training image <NUM> for training a machine learning classifier, in accordance with one or more embodiments of the present disclosure. For example, as shown in <FIG>, the controller <NUM> may be configured to receive one or more optical training images <NUM> of the specimen <NUM> from the optical characterization sub-system 202a. By way of another example, as shown in <FIG>, the controller <NUM> may be configured to receive one or more SEM training images <NUM> of the specimen <NUM> from the SEM characterization sub-system 202b. In this regard, the training image <NUM> depicted in <FIG> may include an optical training image <NUM>, an SEM training image <NUM>, and the like. In additional and/or alternative embodiments, the controller <NUM> may be configured to receive one or more training images <NUM> from a source other than the one or more characterization sub-systems <NUM>. For example, the controller <NUM> may be configured to receive one or more training images <NUM> of a specimen <NUM> from an external storage device. In another embodiment, controller may be further configured to store received training images <NUM> in memory <NUM>.

In another embodiment, the controller <NUM> is configured receive one or more training region-of-interest (ROI) selections within the one or more training images <NUM>. <FIG> illustrates a training image <NUM> including a training ROI selection <NUM>. In one embodiment, the one or more received training ROI selections <NUM> may include one or more measurements of interest. For example, as shown in <FIG>, a training ROI selection <NUM> may include a first measurement of interest (MOI 304a) indicating a length of the left lobe, and a second measurement of interest (MOI 304b) indicating a height of the left lobe. These measurements of interest (MOI 304a, MOI 304b) may include critical dimensions which may be desirable to monitor throughout a fabrication process in order to ensure critical dimension uniformity (CDU). Measurements of interest (MOI <NUM>) within the one or more training ROI selections <NUM> may include any feature which may be measured on a pattern, structure, or the like.

The one or more training ROI selections <NUM> may be received using any technique known in the art. For example, program instructions stored in memory <NUM> may be configured to automatically select one or more training ROI selections <NUM>. By way of another example, the one or more training ROI selections <NUM> may be received via the user interface <NUM>. For instance, a display device of the user interface <NUM> may display one or more training images <NUM> to a user. The user may then input, via a user input device of the user interface <NUM>, one or more input commands indicative of one or more training ROI selections <NUM>. In this regard, in some embodiments, a user may manually draw/select one or more training ROI selections <NUM> within a training image <NUM> via the user interface <NUM>. In another embodiment, the controller <NUM> is configured to store the one or more training ROI selections <NUM> in memory <NUM>.

In another embodiment, the controller <NUM> is configured to generate a machine learning classifier based on the one or more training images <NUM> and the one or more training ROI selections <NUM>. The machine learning classifier may include any type of machine learning algorithm/classifier and/or deep learning technique or classifier known in the art including, but not limited to, a convolutional neural network (CNN) (e.g., GoogleNet, AlexNet, and the like), an ensemble learning classifier, a random forest classifier, artificial neural network (ANN), and the like.

Training the machine learning classifier may include teaching the machine learning classifier to identify the one or more measurements of interest (MOI 304a, 304b) and/or features of interest to be measured based on the received training images <NUM> and training ROI selections <NUM>. As it is used herein, the term "measurement of interest" (MOI 304a, 304b) may be regarded as referring to any measurement which may be desired to be performed on the specimen <NUM>. In this regard, the machine learning classifier may be trained/generated such that it is configured to identify the first measurements of interest (MOI 304a) and/or the second measurement of interest (MOI 304b) based on the received training images <NUM> and the received training ROI selections <NUM>.

The controller <NUM> may be configured to generate the machine learning classifier via supervised learning and/or unsupervised learning. It is noted herein that the machine learning classifier may include any algorithm or predictive model configured to predict and/or identify one or more measurements of interest.

In another embodiment, the controller <NUM> may be configured to receive one or more product images <NUM> of a specimen <NUM> from the characterization sub-system <NUM>. <FIG> illustrates a product image <NUM>, in accordance with one or more embodiments of the present disclosure. As shown in <FIG>, the controller <NUM> may be configured to receive one or more optical product images <NUM> of the specimen <NUM> from the optical characterization sub-system 202a. By way of another example, as shown in <FIG>, the controller <NUM> may be configured to receive one or more SEM product images <NUM> of the specimen <NUM> from the SEM characterization sub-system 202b. In this regard, the product image <NUM> depicted in <FIG> may include an optical product image <NUM>, an SEM product image <NUM>, and the like. In additional and/or alternative embodiments, the controller <NUM> may be configured to receive one or more product images <NUM> from a source other than the one or more characterization sub-systems <NUM>. For example, the controller <NUM> may be configured to receive one or more product images <NUM> of a specimen <NUM> from an external storage device. In another embodiment, controller <NUM> may be further configured to store received product images <NUM> in memory <NUM>.

The term "product images" is used herein to describe images of a specimen <NUM> which include one or more measurements of interest (MOI <NUM>). In this regard, the one or more product images <NUM> may include one or more images of product wafers (e.g., product specimens <NUM>) which are to be monitored by measuring one or more measurements of interest (MOI <NUM>). This may be carried out in order to ensure critical dimension uniformity (CDU), as described previously herein.

In another embodiment, the controller <NUM> is configured to generate one or more classified regions of interest with the machine learning classifier. For example, <FIG> illustrates a product image <NUM> including a classified ROI <NUM>, in accordance with one or more embodiments of the present disclosure.

In one embodiment, the controller <NUM> is configured to generate the one or more classified ROIs <NUM> within the one or more product images <NUM> with the machine learning classifier. In another embodiment, the machine learning classifier may be configured to generate the one or more classified ROIs <NUM> within the product images <NUM> such that the classified ROIs <NUM> include one or more identified measurements of interest (MOI 304a, 304b). For example, as shown in <FIG>, the machine learning classifier may be configured to generate the classified ROI <NUM> such that the classified ROI <NUM> contains the first identified measurement of interest (MOI 304a) and/or the second identified measurement of interest (MOI 304b).

It is contemplated herein that generating ROIs based on machine learning algorithms (e.g., classified ROI <NUM>) may increase the probability that the ROIs will be correctly placed such that they include intended measurements of interest. It is further contemplated herein that generating classified ROIs <NUM> via machine learning algorithms may provide a number of advantages over previous approaches, which place ROIs (e.g., ROI 104b in <FIG> and <FIG>) based on conventional image processing alignment procedures. This may be illustrated by comparing the placement of the ROI 104b in <FIG> via conventional image processing alignment procedures, and the placement of the classified ROI <NUM> in <FIG> via a machine learning classifier. As shown in <FIG>, conventional image processing techniques may be unable to account for process and structural variations, which may then lead to misplacement of the ROI 104b and inability to carry out the desired measurements. Comparatively, as shown in <FIG>, it is contemplated herein that machine learning classifiers may be configured to identify measurements of interest (MOI 304a, 304b) such that the machine learning classifiers may generate adaptive classified ROIs <NUM> which may be more accurately placed to include identified measurements of interest (MOI 304a, 304b). In particular, characteristics of the classified ROIs <NUM> (e.g., shape, size, orientation) generated by the machine learning classifier may be modified according to the characteristics (e.g., shape, size, orientation) of relevant structures (e.g., left lobe) of the specimen <NUM>. In this regard, by generating adaptive classified ROIs <NUM> which are able to vary in size, shape, orientation, and the like, embodiments of the present disclosure may provide for more accurate and reliable ROI placement.

In another embodiment, the controller is configured to generate the one or more classified ROIs <NUM> by adaptively modifying one or more characteristics of one or more product ROI selections with the machine learning classifier. In this regard, generating one or more classified ROIs <NUM> with the machine learning classifier may include receiving one or more product ROI selections <NUM> within the one or more product images <NUM>, and adaptively modifying one or more characteristics of one or more product ROI selections <NUM> with the machine learning classifier to generate the one or more classified ROIs <NUM>. This may be further understood with reference to <FIG>.

<FIG> illustrates a product image <NUM> including a product ROI selection <NUM> and a classified ROI <NUM>, in accordance with one or more embodiments of the present disclosure. In this example, the controller <NUM> may receive a product ROI selection <NUM> indicative of a region of the product image <NUM>. For instance, a user may input the product ROI selection <NUM> via the user interface <NUM>. Continuing with the same example, the controller <NUM> may be configured to adaptively modify one or more characteristics of the product ROI selection <NUM> with the machine learning classifier to generate the classified ROI <NUM>. Characteristics of the product ROI selection <NUM> which may be adaptively modified by the machine learning classifier to generate the classified ROI <NUM> may include, but are not limited to, size, shape, orientation, and the like.

It is contemplated herein that generating the classified ROIs <NUM> by modifying received product ROI selections <NUM> may allow for the machine learning classifier to serve as a corrective tool which is activated on an as-needed basis. For example, in some embodiments, the machine learning classifier may only generate the classified ROI <NUM> by adaptively modifying a product ROI selection <NUM> when the received product ROI selection <NUM> is incorrectly placed (e.g., placed such that it fails to include the one or more MOIs 304a, 304b), as shown in <FIG>.

In one embodiment, the machine learning classifier may adaptively modify one or more characteristics of the one or more product ROI selections <NUM> based on one or more characteristics of a structure within the one or more product images <NUM>. For example, as shown in <FIG>, the machine learning classifier may adaptively modify the product ROI selection <NUM> based on a structural variation of the left lobe. In another embodiment, the machine learning classifier may adaptively modify one or more characteristics of the one or more product ROI selections <NUM> in response to one or more process variations. In this regard, the machine learning classifier may adaptively modify the product ROI selection <NUM> in order to correct for one or more process variations.

Similarly, in another embodiment, generation of the classified ROI <NUM> may be assisted by receiving one or more product POI selections (not shown). For example, similar to traditional approaches, the controller <NUM> may receive a product POI selection within a product image <NUM>, and then generate one or more classified ROIs <NUM> based, at least in part, on the one or more received POI selections.

<FIG> illustrates a product image <NUM>, in accordance with one or more embodiments of the present disclosure. <FIG> illustrates a product image <NUM> including a classified region of interest (ROI) <NUM>, in accordance with one or more embodiments of the present disclosure. In one embodiment, the machine learning classifier may generate one or more classified ROIs <NUM> such that the one or more classified ROIs <NUM> include one or more identified MOIs 304a, 304b. Comparing the placement of the ROI 104b in <FIG> against the classified ROI <NUM> in <FIG>, it may be seen that ROI placement via a machine learning classifier may provide for improved ROI placement over conventional image processing alignment procedures. Accordingly, it is contemplated herein that embodiments of the present disclosure may provide for more accurate and reliable ROI placement which are less susceptible and/or immune to structural/process variations. In particular, it is contemplated herein that the increased adaptability of classified ROIs <NUM> may be especially beneficial in the context of semiconductor fabrication ramp-ups.

<FIG> illustrates a product image <NUM> including an angular classified region of interest (ROI) <NUM>, in accordance with one or more embodiments of the present disclosure.

In one embodiment, as shown in <FIG>, the machine learning classifier may be configured to generate one or more angular classified ROIs <NUM>. The term "angular" may be used herein to describe a classified ROI <NUM> which is oriented at an offset angle <NUM> (defined by θ) with respect to a particular frame or object of reference. For example, an angular classified ROI <NUM> may be rotated with respect to a product ROI selection <NUM> such that the angular classified ROI <NUM> is disposed at an offset angle <NUM> with respect to the product ROI selection <NUM>. By way of another example, as shown in <FIG>, an angular classified ROI <NUM> may be rotated such that the angular classified ROI <NUM> is disposed at an offset angle <NUM> with respect to an edge or border of the product image <NUM>, as shown in <FIG>.

It is noted herein that it may be extremely difficult, or even impossible, to generate angular ROIs <NUM> with conventional image processing procedures. For example, where only a portion of a structure has been rotated, such as in <FIG>, conventional image processing procedures may be unable to generate and accurately align an angular ROI <NUM>. Additionally, even where angular ROIs <NUM> may potentially be generated by conventional image processing procedures, the process may be so computationally expensive as to make it impracticable and inefficient. Accordingly, it is contemplated herein that the ability to generate angular classified ROIs <NUM> with machine learning classifiers may provide for more accurate ROI placement for varying structures, and enable more complex and intricate critical dimension measurements.

In another embodiment, the controller <NUM> may be configured to determine one or more measurements of the specimen <NUM> within the one or more classified ROIs <NUM>. For example, as shown in <FIG>, the controller <NUM> may be configured to measure a first critical dimension indicated by the first measurement of interest (MOI 304a) and a second critical dimension indicated by the second measurement of interest (MOI 304b). The one or more measurements made within the one or more classified ROIs <NUM> may include any measurements known in the art including, but not limited to, critical dimension (CD) measurements.

It is noted herein that the one or more components of system <NUM> may be communicatively coupled to the various other components of system <NUM> in any manner known in the art. For example, the one or more processors <NUM> may be communicatively coupled to each other and other components via a wireline (e.g., copper wire, fiber optic cable, and the like) or wireless connection (e.g., RF coupling, IR coupling, WiMax, Bluetooth, <NUM>, <NUM>, <NUM> LTE, <NUM>, and the like). By way of another example, the controller <NUM> may be communicatively coupled to one or more components of characterization sub-system <NUM> via any wireline or wireless connection known in the art.

In one embodiment, the one or more processors <NUM> may include any one or more processing elements known in the art. In this sense, the one or more processors <NUM> may include any microprocessor-type device configured to execute software algorithms and/or instructions. In one embodiment, the one or more processors <NUM> may consist of a desktop computer, mainframe computer system, workstation, image computer, parallel processor, or other computer system (e.g., networked computer) configured to execute a program configured to operate the system <NUM>, as described throughout the present disclosure. It should be recognized that the steps described throughout the present disclosure may be carried out by a single computer system or, alternatively, multiple computer systems. Furthermore, it should be recognized that the steps described throughout the present disclosure may be carried out on any one or more of the one or more processors <NUM>. In general, the term "processor" may be broadly defined to encompass any device having one or more processing elements, which execute program instructions from memory <NUM>. Moreover, different subsystems of the system <NUM> (e.g., illumination source <NUM>, electron beam source <NUM>, detector assembly <NUM>, electron detector assembly <NUM>, controller <NUM>, user interface <NUM>, and the like) may include processor or logic elements suitable for carrying out at least a portion of the steps described throughout the present disclosure. Therefore, the above description should not be interpreted as a limitation on the present disclosure but merely an illustration.

The memory <NUM> may include any storage medium known in the art suitable for storing program instructions executable by the associated one or more processors <NUM> and the data received from the characterization sub-system <NUM>. For example, the memory <NUM> may include a non-transitory memory medium. For instance, the memory <NUM> may include, but is not limited to, a read-only memory (ROM), a random-access memory (RAM), a magnetic or optical memory device (e.g., disk), a magnetic tape, a solid-state drive and the like. It is further noted that memory <NUM> may be housed in a common controller housing with the one or more processors <NUM>. In an alternative embodiment, the memory <NUM> may be located remotely with respect to the physical location of the processors <NUM>, controller <NUM>, and the like. In another embodiment, the memory <NUM> maintains program instructions for causing the one or more processors <NUM> to carry out the various steps described through the present disclosure.

In one embodiment, a user interface <NUM> is communicatively coupled to the controller <NUM>. In one embodiment, the user interface <NUM> may include, but is not limited to, one or more desktops, tablets, smartphones, smart watches, or the like. In another embodiment, the user interface <NUM> includes a display used to display data of the system <NUM> to a user. The display of the user interface <NUM> may include any display known in the art. For example, the display may include, but is not limited to, a liquid crystal display (LCD), an organic light-emitting diode (OLED) based display, or a CRT display. Those skilled in the art should recognize that any display device capable of integration with a user interface <NUM> is suitable for implementation in the present disclosure. In another embodiment, a user may input selections and/or instructions responsive to data displayed to the user via a user input device of the user interface <NUM>.

<FIG> illustrates a flowchart of a method <NUM> for adaptive region of interest (ROI) selection, in accordance with one or more embodiments of the present disclosure. It is noted herein that the steps of method <NUM> may be implemented all or in part by system <NUM>. It is further recognized, however, that the method <NUM> is not limited to the system <NUM> in that additional or alternative system-level embodiments may carry out all or part of the steps of method <NUM>.

In a step <NUM>, one or more training images of a specimen are acquired with a characterization sub-system. For example, as shown in <FIG>, an optical characterization sub-system 202a and/or an SEM characterization sub-system 202b may be configured to acquire one or more training images <NUM> of a specimen <NUM> and transmit the one or more acquired training images <NUM> to a controller <NUM>.

In a step <NUM>, one or more training ROI selections are received. For example, as shown in <FIG>, the controller <NUM> may receive one or more training ROI selections <NUM> within the one or more training images <NUM>. The one or more training ROI selections <NUM> may include one or more measurements of interest (MOI 304a, 304b). The one or more training ROI selections <NUM> may be received using any technique known in the art. For example, program instructions stored in memory <NUM> may be configured to automatically select one or more training ROI selections <NUM>. By way of another example, the one or more training ROI selections <NUM> may be received via the user interface <NUM>. For instance, a display device of the user interface <NUM> may display one or more training images <NUM> to a user. The user may then input, via a user input device of the user interface <NUM>, one or more input commands indicative of one or more training ROI selections <NUM>.

In a step <NUM>, a machine learning classifier is generated based on the one or more training images and the one or more training ROI selections. Training the machine learning classifier may include teaching the machine learning classifier to identify the one or more measurements of interest (MOI 304a, 304b) and/or features of interest to be measured based on the received training images <NUM> and training ROI selections <NUM>. The machine learning classifier may include any type of machine learning algorithm/classifier and/or deep learning technique or classifier known in the art including, but not limited to, a deep learning classifier, a convolutional neural network (CNN) (e.g., GoogleNet, AlexNet, and the like), an ensemble learning classifier, a random forest classifier, artificial neural network (ANN), and the like.

In a step <NUM>, one or more product images of a specimen are acquired with the characterization sub-system. For example, as shown in <FIG>, an optical characterization sub-system 202a and/or an SEM characterization sub-system 202b may be configured to acquire one or more product images <NUM> of a specimen <NUM> and transmit the one or more acquired product images <NUM> to the controller <NUM>. The one or more product images <NUM> may include one or more images of product wafers (e.g., product specimens <NUM>) which are to be monitored by measuring one or more measurements of interest (MOI <NUM>). This may be carried out in order to ensure critical dimension uniformity (CDU), as described previously herein.

In a step <NUM>, one or more classified ROIs are generated with the machine learning classifier. For example, as shown in <FIG> and <FIG>, the machine learning classifier may be configured to generate the classified ROI <NUM> such that the classified ROI <NUM> contains the first identified measurement of interest (MOI 304a) and/or the second identified measurement of interest (MOI 304b).

In a step <NUM>, one or more measurements of the specimen are determined within the one or more classified regions of interest. For example, as shown in <FIG>, the controller <NUM> may be configured to measure a first critical dimension indicated by the first measurement of interest (MOI 304a) and a second critical dimension indicated by the second measurement of interest (MOI 304b). The one or more measurements made within the one or more classified ROIs <NUM> may include any measurements known in the art including, but not limited to, critical dimension (CD) measurements.

One skilled in the art will recognize that the herein described components (e.g., operations), devices, objects, and the discussion accompanying them are used as examples for the sake of conceptual clarity and that various configuration modifications are contemplated. Consequently, as used herein, the specific exemplars set forth and the accompanying discussion are intended to be representative of their more general classes. In general, use of any specific exemplar is intended to be representative of its class, and the non-inclusion of specific components (e.g., operations), devices, and objects should not be taken as limiting.

Those having skill in the art will appreciate that there are various vehicles by which processes and/or systems and/or other technologies described herein can be effected (e.g., hardware, software, and/or firmware), and that the preferred vehicle will vary with the context in which the processes and/or systems and/or other technologies are deployed. For example, if an implementer determines that speed and accuracy are paramount, the implementer may opt for a mainly hardware and/or firmware vehicle; alternatively, if flexibility is paramount, the implementer may opt for a mainly software implementation; or, yet again alternatively, the implementer may opt for some combination of hardware, software, and/or firmware. Hence, there are several possible vehicles by which the processes and/or devices and/or other technologies described herein may be effected, none of which is inherently superior to the other in that any vehicle to be utilized is a choice dependent upon the context in which the vehicle will be deployed and the specific concerns (e.g., speed, flexibility, or predictability) of the implementer, any of which may vary.

The previous description is presented to enable one of ordinary skill in the art to make and use the invention as provided in the context of a particular application and its requirements. As used herein, directional terms such as "top," "bottom," "over," "under," "upper," "upward," "lower," "down," and "downward" are intended to provide relative positions for purposes of description, and are not intended to designate an absolute frame of reference. Various modifications to the described embodiments will be apparent to those with skill in the art, and the general principles defined herein may be applied to other embodiments. Therefore, the present invention is not intended to be limited to the particular embodiments shown and described, but is to be accorded the widest scope consistent with the principles and novel features herein disclosed.

The various singular/plural permutations are not expressly set forth herein for sake of clarity.

All of the methods described herein may include storing results of one or more steps of the method embodiments in memory. The results may include any of the results described herein and may be stored in any manner known in the art. The memory may include any memory described herein or any other suitable storage medium known in the art. After the results have been stored, the results can be accessed in the memory and used by any of the method or system embodiments described herein, formatted for display to a user, used by another software module, method, or system, and the like. Furthermore, the results may be stored "permanently," "semi-permanently," temporarily," or for some period of time. For example, the memory may be random access memory (RAM), and the results may not necessarily persist indefinitely in the memory.

It is further contemplated that each of the embodiments of the method described above may include any other step(s) of any other method(s) described herein. In addition, each of the embodiments of the method described above may be performed by any of the systems described herein.

The herein described subject matter sometimes illustrates different components contained within, or connected with, other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. Likewise, any two components so associated can also be viewed as being "connected," or "coupled," to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being "couplable," to each other to achieve the desired functionality. Specific examples of couplable include but are not limited to physically mateable and/or physically interacting components and/or wirelessly interactable and/or wirelessly interacting components and/or logically interacting and/or logically interactable components.

Furthermore, it is to be understood that the invention is defined by the appended claims. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," and the like). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, and the like" is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., " a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, and the like). In those instances where a convention analogous to "at least one of A, B, or C, and the like" is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., " a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, and the like). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms.

Claim 1:
A system for adaptive region of interest (ROI) selection (<NUM>), comprising:
an inspection sub-system configured (<NUM>) to acquire one or more images of a specimen; and
a controller (<NUM>) including one or more processors (<NUM>) configured to execute a set of program instructions stored in memory, the set of program instructions configured to cause the one or more processors to:
receive one or more training images of a specimen from the inspection sub-system;
receive one or more training ROI selections within the one or more training images;
generate a machine learning classifier based on the one or more training images and the one or more training ROI selections, wherein the machine learning classifier is configured to identify one or more measurements of interest of a specimen based on the one or more training images and the one or more training ROI selections;
receive one or more product images of a specimen from the inspection sub-system;
generate one or more adaptive regions of interest with the machine learning classifier, wherein generating one or more adaptive regions of interest with the machine learning classifier comprises:
receiving one or more product ROI selections within the one or more product images;
adaptively modifying one or more characteristics of the one or more product ROI selections with the machine learning classifier to generate the one or more adaptive regions of interest;
determine one or more measurements of the specimen within the one or more adaptive regions of interest.