Measuring contamination buildup on semiconductor samples

Abstract

A monitoring system is provided for monitoring the degree of contamination affecting the critical size of a specimen as measured by an inspection tool. The system includes a processor operatively connected to the inspection tool. The processor is configured to acquire multiple measurement cycles, each cycle including a measurement of the critical size (CD) of the specimen pattern while the specimen is contained within a cavity of the inspection tool. These measurement cycles are performed at discrete time intervals, such that the sequential measurement cycles are affected by variations in the CD measurements. A further configuration of the processor is to determine the degree of contamination as a function of the gradient of a linear approximation of the CD measurements.

Description

Technical Field

[0001] The technical topic disclosed in this article is largely related to measuring contaminants accumulated on test samples. Background Technology

[0002] Currently, the high density and high performance requirements associated with the integration of very large-scale integrated devices necessitate sub-micron features, higher transistor and integrated circuit speeds, and greater reliability. As semiconductor processes advance, pattern dimensions (such as linewidth) and other critical dimensions continue to shrink. This demand necessitates the formation of device features with high precision and uniformity, which in turn requires careful monitoring of the manufacturing process, including automated inspection of the device while it is still in semiconductor wafer form.

[0003] Non-destructive inspection tools can be used to inspect samples during or after their fabrication. Inspection generally involves directing light or electrons onto a wafer and detecting the light or electrons from the wafer, thereby generating some output (such as images, signals, etc.) for the sample. Various non-destructive inspection tools include (non-limiting examples) scanning electron microscopes, atomic force microscopes, optical inspection tools, etc.

[0004] The inspection process may include multiple inspection steps. The manufacturing process of a semiconductor device may include various procedures such as etching, deposition, planarization, growth (e.g., epitaxial growth), implantation, etc. Inspection steps may be performed multiple times, for example, after some processing steps, and / or after the fabrication of some layers, or similar cases. Additionally, or alternatively, each inspection step may be repeated multiple times, for example, for different wafer locations, or for the same wafer location with different inspection settings.

[0005] Inspection processes are used at various steps in the semiconductor manufacturing process to perform metrology-related and / or defect-related operations. The effectiveness of inspection can be improved through the automation of processes such as defect detection, automated defect classification (ADC), automated defect review (ADR), automated image segmentation, and metrology-related operations. Automated inspection systems ensure that manufactured parts meet expected quality standards and, based on the type of defects found, provide useful information that may require adjustments to manufacturing tools, equipment, and / or components to help improve yield. Summary of the Invention

[0006] Based on some aspects of the currently disclosed subject matter, a system is provided for monitoring the degree of contamination affecting the critical size of a specimen as measured by an inspection tool, the system including a processing and memory circuit (PMC) operably connected to the inspection tool; wherein the PMC is configured to: a. Obtaining multiple measurement cycles, each cycle comprising at least one measurement of the critical dimension (CD) of at least one pattern of a specimen housed within the chamber of an inspection tool; wherein the measurement cycles are performed at discrete time intervals, such that the sequential measurement cycles are affected by variations in the CD measurements; and b. Determine the degree of pollution based on a gradient function of a straight line approximating the CD measurements.

[0007] In addition to the features described above, systems according to this aspect of the subject matter of this disclosure may also include one or more of the features (i) to (ix) listed below, in any technically possible combination or arrangement: (i) The sample pattern is a line, and the gradient is increasing. The steeper the gradient, the larger the contamination range.

[0008] (ii) The sample pattern is a cavity, and the gradient therein is decreasing. The steeper the gradient, the larger the contamination range.

[0009] (iii) Several of the measurement cycles are greater than 3.

[0010] (iv) At least one of the measurement cycles is obtained in accordance with a dynamic procedure, thereby keeping the sample in the chamber for a portion (e.g., a smaller) of the time interval.

[0011] (v) wherein the time interval is 10 to 120 seconds inside the chamber and an additional 60 seconds outside the chamber.

[0012] (vi) At least one of the measurement cycles is obtained according to a static procedure, such that the sample remains in the chamber for at least two consecutive time intervals.

[0013] (vii) At least one of the measurement cycles is obtained according to a static procedure (e.g., keeping the sample continuously in the chamber for at least two consecutive time intervals), and the time intervals are less than a hypothetical time interval, which, if a dynamic procedure is used, would keep the sample in the chamber for a portion of the hypothetical time interval (e.g., a smaller time interval).

[0014] (viii) The time interval is between 10 and 120 seconds.

[0015] (vi) wherein, within at least one period, the measurement result is obtained within a small fraction of the time interval.

[0016] According to other aspects of the subject matter of this disclosure, a computerized method is provided for monitoring the degree of contamination affecting critical dimensions of a specimen measured by an inspection tool, the method comprising: [the following is missing from the original text: "through processor and memory circuitry (PMC) : "] a. Obtaining multiple measurement cycles, each cycle comprising at least one measurement of the critical dimension (CD) of at least one pattern of a specimen housed within the chamber of an inspection tool; wherein the measurement cycles are performed at discrete time intervals, such that the sequential measurement cycles are affected by variations in the CD measurements; and b. Determine the degree of pollution based on the linear gradient function of the approximate CD measurement value.

[0017] This aspect of the disclosed subject matter may include one or more of the features (i) to (ix) of the system described above, in any technically possible combination or arrangement of the features described above.

[0018] According to other aspects of the subject matter of this disclosure, a non-transitory 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 monitoring the degree of contamination affecting the critical dimensions of a specimen measured by an inspection tool, the method comprising: a. Obtaining multiple measurement cycles, each cycle comprising at least one measurement of the critical dimension of at least one pattern of a specimen housed within the chamber of an inspection tool; wherein the measurement cycles are performed at discrete time intervals, such that the sequential measurement cycles are affected by variations in the CD measurement; and b. Determine the degree of pollution based on the linear gradient function of the approximate CD measurement value.

[0019] This aspect of the disclosed subject matter may include one or more of the features (i) to (ix) of the system described above, in any technically possible combination or arrangement of the features described above. Attached Figure Description

[0020] To understand this disclosure and how to implement it in practice, specific embodiments will now be described by way of non-limiting example only, with reference to the accompanying drawings, in which: Figure 1 A general block diagram of an inspection system based on some specific embodiments of the subject matter of this disclosure is shown; Figure 2 A summary flowchart illustrating the sequence of operations for monitoring the degree of contamination affecting the critical size of a sample, according to some specific embodiments of the subject matter of this disclosure, is provided. Figure 3 The discrete time intervals according to some specific embodiments of the subject matter of this disclosure are illustrated, and the measurement period is obtained by scanning electron microscopy (SEM) within the discrete time intervals. Figure 4These are graphical representations of the gradients of linear approximations obtained using different procedures, based on some specific embodiments of the subject matter of this disclosure; and Figure 5 The sequence of operations for loading a semiconductor wafer into the vacuum chamber of an SEM is illustrated schematically according to some specific embodiments of the subject matter of this disclosure. Detailed Implementation

[0021] In a typical scenario involving the inspection of test specimens (such as semiconductor specimens like wafers), a robot picks up the wafer from a carrier and inserts it into the load-locked chamber of an inspection tool (such as a SEM based on semiconductor process diagnostics and control tools) for initial alignment and localized pumping. Another robot then loads the specimen into the SEM's main chamber, which is under high vacuum. The wafer is then aligned using optical and charged particle methods. The wafer is then moved and imaged using charged particle tools (such as the SEM). The images are used to measure the critical dimensions (CD) of various features on the wafer (lines, spacing, contacts, cavities, etc.). Next, the wafer is moved from the main chamber to a carrier through the load-locked chamber. Sometimes all of the above steps are repeated for repeatable measurements.

[0022] Molecular contamination is a well-known fundamental problem in semiconductor manufacturing processes, particularly in tools that include vacuum chambers, such as scanning electron microscopes. Organic molecules may originate from polymer components inside the vacuum chamber or from wafers previously inserted into it. These organic molecules adsorb onto the surface of the wafer being inspected, forming islands that cover small portions of the surface. This molecular contamination can lead to variations in CD measurement, wafer failure, eBeam pillar failure, or reduced electromagnetic immunity.

[0023] Vacuum cleanliness levels can vary over time due to tool maintenance activities and the level of gas release from the inspected wafers. Therefore, there is a growing need for a monitoring system to assess the cleanliness of vacuum chambers and determine the degree of contamination.

[0024] It should be further noted that, as is well known, exposing a surface in a vacuum to an electron beam results in the formation of a carbon-rich film in the exposed area. This is due to the interaction between the electron beam and organic contaminants on the sample surface (originating from the vacuum environment). Please note that the terms contamination and deposit are used interchangeably.

[0025] Therefore, according to some specific embodiments of the present invention, a system is provided for monitoring the degree of contamination of a sample critical size affecting the measurement of an inspection tool. The system includes a processing and memory circuit (PMC) operably connected to the inspection tool, wherein the PMC is configured as follows: a. Obtaining multiple measurement cycles, each measurement cycle comprising at least one measurement of the critical dimension (CD) of at least one pattern (e.g., line, contact, cavity, etc.) of a sample (e.g., a semiconductor sample) while housed within a vacuum chamber of an inspection tool. The measurement cycles are performed at discrete time intervals, thereby subjecting the sequential measurement cycles to variations in the CD measurement values; and b. Determine the contamination range based on the gradient function of a straight line approximating the CD measurements. Note that the terms "pattern" and "characteristic" are used interchangeably in this document.

[0026] In view of this, please note Figure 1 , Figure 1 A functional block diagram of an inspection system according to some specific embodiments of the subject matter of this disclosure is shown.

[0027] Figure 1 The inspection system 100 shown can be used to inspect samples (e.g., semiconductor wafers, dies, or components thereof) as part of the sample manufacturing process. Inspection as referred to herein can be understood to encompass any operation related to defect inspection / detection, defect classification, segmentation, and / or metrological operations, such as critical dimension (CD) measurement, overlay, etc., related to the sample. System 100 includes one or more inspection tools 120 configured to scan the sample and capture its image for further processing for various inspection applications.

[0028] Without limiting the scope of this disclosure, it should be noted that the inspection tool 120 can be implemented as various types of inspection machines, such as optical inspection machines, electron beam inspection machines (e.g., scanning electron microscopes (SEM) [e.g., defect inspection, CD inspection], atomic force microscopes (AFM), or transmission electron microscopes (TEM), etc.). In some cases, the same inspection tool can provide both low-resolution and high-resolution image data. The resulting image data (low-resolution image data and / or high-resolution image data) can be transmitted directly to system 101 or through one or more intermediate systems. This disclosure is not limited to any particular type of inspection tool and / or the resolution of the image data generated by the inspection tool.

[0029] In some specific embodiments, at least one of the inspection tools 120 has metrological functionality and can be configured to capture images and perform metrological operations on the captured images. Such an inspection tool is also referred to herein as a metrological tool.

[0030] According to a specific implementation, the metrological tool can be an electron beam tool, such as a scanning electron microscope (SEM). A scanning electron microscope is an electron microscope that generates an image of a sample by scanning it with a focused electron beam. Electrons interact with atoms in the sample, producing various signals containing information about the sample's surface morphology and / or composition. Scanning electron microscopes can accurately measure features during semiconductor wafer manufacturing. For example, the metrological tool can be a critical-size scanning electron microscope (CD-SEM) configured to perform metrological operations on the structural features of the sample based on the captured image.

[0031] Semiconductor manufacturing processes may require measurements to monitor and control the process. Such measurements may include critical dimension (CD) measurements of specimen patterns / features, such as lines, contacts, cavities, etc. As is customary, a carbon-rich film may accumulate when the specimen is loaded into the vacuum chamber of a SEM tool, which can affect the accuracy of the measured pattern. There is a need in the art to identify contamination affecting CD measurements, to correct measurement errors caused by contamination, and to allow for post-processing steps such as cleaning the vacuum chamber.

[0032] According to some specific embodiments of the subject matter of this disclosure, the inspection system 100 includes a computer-based system 101 operatively connected to the inspection tool 120, including but not limited to online operation, wherein images acquired by the inspection tool are processed by various modules of the PMC 102, or according to other non-limiting embodiments, images acquired by the inspection tool 120 are received through I / O module 126 and stored in memory module 122 for later offline processing by the PMC 102, all of which will be explained in more detail below.

[0033] Specifically, system 101 includes a processor and memory circuitry (PMC) 102 operatively connected to a hardware-based I / O interface 126. The PMC 102 is configured to provide the processing required by the operating system, as per reference. Figures 2 to 5 As further detailed, the PMC 102 also includes one or more processors (not shown separately) operatively connected to memory (not shown separately). The processors of the PMC 102 are configured to execute multiple functional modules according to computer-readable instructions implemented on non-transitory computer-readable memory contained in the PMC. These functional modules are referred to below as functional modules contained in the PMC.

[0034] The functional modules included in the PMC 102 of system 101 may include measurement module 104 and pollution range calculation module 106, etc.

[0035] PMC 102 can be configured to acquire, during execution, an inspection image of the specimen (an image indicating at least one well and possibly other data) from the inspection tool 120 via the I / O interface 126. The image can be acquired by one (or more) tools (e.g., by a known VeritySEM tool).

[0036] The operation of systems 100, 101, 110 and their PMC, as well as their functional modules, will be referred to Figure 2-5 Further details.

[0037] In some cases, in addition to system 101, inspection system 100 may also include one or more inspection modules, such as a defect detection module and / or an automated defect review module (ADR), and / or an automated defect classification module (ADC) and / or additional metrology-related modules, and / or other inspection modules that can be used to inspect specimens. One or more inspection modules may be implemented as stand-alone computers, or their functions (or at least some functions) may be integrated with inspection tool 120. In some cases, the output of system 101, for example, an image associated with data on the bottom contour of an indicator hole, may be provided to one or more inspection modules for further processing.

[0038] According to some specific embodiments, system 101 may include a storage unit 122. Storage unit 122 may be configured to store any data required by operating system 101, such as data related to the inputs and outputs of system 101, and intermediate processing results generated by system 101. For example, storage unit 122 may be configured to store images of samples and / or their derivatives generated by inspection tool 120. Therefore, images can be retrieved from storage unit 122 and provided to PMC 102 for further processing. Outputs of system 101 may be sent to storage unit 122 for storage.

[0039] In some embodiments, system 100 may optionally include a computer-based graphical user interface (GUI) 124, which is configured to enable user-specified input associated with system 101. For example, a user can view a visual representation of the sample (e.g., via a display that forms part of the GUI 124), including image data of the sample. The user can access options for defining operational parameters through the graphical user interface. The user can also annotate reference images through the graphical user interface. The user can also view operational results on the graphical user interface.

[0040] In some cases, system 101 may be further configured to send output data via I / O interface 126 to one or more inspection tools 120 and / or one or more inspection modules for further processing. In some cases, system 101 may be further configured to send some output data to storage unit 122 and / or external systems (e.g., a production management system (YMS) of a semiconductor foundry (FAB)).

[0041] Those skilled in the art will readily understand that the teachings of this disclosure are not subject to... Figure 1 The constraints of the system shown are, in particular, not subject to the constraints of specified modules 104 and 106, and / or not subject to the constraints referred to below. Figure 2-5 The constraints on the operations performed thereby. Equivalent and / or modified functions may be combined or divided in other ways and may be implemented through any suitable combination of software and firmware and / or hardware.

[0042] It should be pointed out that, Figure 1 The system shown can be implemented in a distributed computing environment, where Figure 1 The components and functional modules shown above can be distributed across multiple local and / or remote devices and can be connected via a communication network. For example, the inspection tool 120 and the system 101 can be located in the same entity (or hosted by the same device in some cases) or distributed across different entities.

[0043] It should be further noted that, in some specific embodiments, at least some of the inspection tool 120, storage unit 122, and / or GUI 124 may be external to the inspection system 100 and communicate with the systems 100 and 101 via I / O interface 126. System 101 may be implemented as a standalone computer and used in conjunction with the inspection tool and / or the aforementioned additional inspection modules. Alternatively, the various functions of system 101 may be at least partially integrated with one or more inspection tools 120, thereby facilitating and enhancing the functionality of the inspection tools 120 in the inspection-related processes.

[0044] Although Figure 1 As explained in the document, in some cases, the functionality of System 110 can be at least partially integrated into System 100. For example, functional modules of System 110 can be integrated into PMC 102 in System 101.

[0045] While this may not be the case, the operating procedures of systems 101 and 100 can be compared with... Figure 2-5 Corresponding to some or all of the stages of the method. Similarly, regarding Figure 2-5 The described method and its possible implementations can be implemented by systems 101 and 100, possibly utilizing modules 104 and 106. Therefore, it should be noted that regarding... Figure 2-5 The specific implementation methods discussed can also be implemented by analogy to the various specific implementation methods of systems 101 and 100, and vice versa.

[0046] Please note now. Figure 2 This figure illustrates a general flowchart of the operational sequence for monitoring the degree of contamination affecting the measurement of the critical size of a sample, according to some specific embodiments of the subject matter of this disclosure. A detailed description will follow (with reference to...). Figure 5 The sample is inserted into the vacuum chamber of the inspection tool. In the first stage 201 (possibly implemented in module 104), multiple measurement cycles (e.g., more than 3) are obtained, for example using an inspection tool such as a SEM. In each cycle, the SEM obtains at least one critical dimension measurement of one or more patterns (e.g., lines, joints, cavities) of the sample. The measurement cycles are performed at discrete time intervals, such as T1, T2, T3...Tn, etc. (301-304 respectively, e.g., ...). Figure 3 (As shown). The time intervals may be the same, but this is not necessarily the case according to other specific embodiments of the subject matter of this disclosure, where two or more time intervals are different, one relative to another. The number of time intervals may vary depending on the application; for example, according to some specific embodiments, the number of time intervals falls in the range of 3-20. The duration of each time interval will be explained in detail below, as it affects the quality of the results obtained.

[0047] It should be noted that the sample can be loaded into the chamber according to a so-called dynamic procedure, or it can be measured according to another non-limiting embodiment, a so-called static procedure, which will be explained in more detail below. Intuitively, by following a dynamic procedure, each time interval T... i (Dynamic) and time interval T i (Static) procedures are longer because they involve removing the sample from the chamber of the inspection tool (e.g., SEM) at each time interval before performing a measurement cycle (consisting of one or more measurements). Removing the sample from the chamber requires some preparation stages, such as alignment, before the sample can be reinserted into the chamber (to perform the next measurement cycle), which obviously takes longer. In contrast, with a static procedure, preparations such as calibration are performed before the sample is first inserted into the chamber, and measurement cycles performed in subsequent time intervals do not require removing and reinserting the sample from the chamber, which obviously reduces the time because no preparation work needs to be done outside the chamber.

[0048] Please note that CD measurements are obtained for one or more semiconductor patterns (such as lines, contacts, cavities, etc.) in each cycle. As mentioned earlier, a carbon-rich film may accumulate on the tested pattern due to physical / chemical phenomena such as carbonization, affecting the accuracy of CD measurements. Please note that the terms "pattern" and "feature" are used interchangeably.

[0049] As mentioned above, the accumulation of carbon-rich films can affect the measured CD dimensions (e.g., the line width dimension increases while the cavity width dimension decreases).

[0050] After obtaining continuous measurements over a specified time interval, the obtained measurements can be approximated as a straight line, and its gradient can be calculated (step 202). Surprisingly, it was found that the degree of contamination in the chamber can be determined as a function of the specified gradient. The specified calculation stage 202 can be performed in... Figure 1 The pollution range calculation module 106 is implemented in this module.

[0051] To better understand the above, please note Figure 4 The figure shows the respective linear gradients of approximate CD measurements obtained using different procedures according to some specific embodiments of the subject matter of this disclosure.

[0052] Generally, the horizontal axis represents the number of time intervals (each time interval includes one or more measurement cycles), and the vertical axis represents the CD of the measurement pattern, such as the width of a given line in a given wafer (in ηm). Figure 4 As shown, for simplicity, (i) a small number of measurements are performed per cycle time [e.g., 20 times]; (ii) all time intervals have the same duration; and (iii) the CD of the same pattern on a single wafer is measured (in a given wafer) in all measurement cycles. Note that one or more specified constraints may differ in different embodiments of the subject matter of this disclosure.

[0053] Therefore, Figure 401 represents a linear approximation of CD measurements over, for example, 20 consecutive measurement cycles (e.g., approximately 20 measurements per cycle) according to a dynamic procedure. Note that in one specific implementation, the 20 measurements per cycle can be averaged to a single average for each cycle, and the linear approximation can be applied to that average for each cycle. However, this is not intended to be limiting; according to another non-limiting example, a function different from the average can be applied, or according to another non-limiting example, all (selected or any number) of the original measurements can be considered when calculating the linear approximation. The advantage of using more than one measurement per cycle may be improved reliability and avoidance of outliers.

[0054] With this in mind, returning to the dynamic procedure, it involves removing the sample and placing it into the chamber before each measurement cycle. Clearly, in a practical implementation, this requires relatively long time intervals, for example, approximately 1 to 10 minutes per interval. In this example, the calculated linear gradient for approximately 20 measurement cycles is 0.119 ηm / measurement cycle. Line 401 rises from ~77.6 ηm in the first measurement cycle to ~79.7 ηm in the 20th measurement cycle due to the long-term accumulation of carbon-rich film. The extent of contamination can be determined by calculating a function of the gradient (slope). Therefore, a steeper slope indicates a more severe level of contamination. Thus, the degree of contamination can be determined by calculating the gradient of a line approximating the CD measurement value, for example, by displaying the slope value, or by using another example as its function. Once the contamination is determined, the chamber can be cleaned using known methods.

[0055] In one improved embodiment, the measured feature is a cavity. A carbon-rich membrane may cause a decrease in CD measurements because contaminants accumulating on the cavity walls over time narrow the cavity width. This results in a straight line with a negative gradient (approximately a decreasing CD measurement). However, the same rule applies: the degree of contamination can be determined as a function of the defined gradient, such as a negative gradient. The deeper the straight line approximation of the measurement, the higher the degree of contamination.

[0056] Regardless of whether the gradient is positive or negative, the dynamic process takes a long time because of the extensive preparation steps required before the sample is reinserted into the chamber for the next measurement cycle. To better understand the dynamic procedure, please note... Figure 5 The figure schematically illustrates, according to some specific embodiments of the subject matter of this disclosure, the sequence of operations for loading a semiconductor wafer into the vacuum chamber of a scanning electron microscope (SEM) in a dynamic procedure.

[0057] Therefore, as Figure 5As shown, robot 501 (indicated by the arrow) removes wafer 502 from carrier 503 and inserts it into load-locking chamber 504 of the SEM, where it is initially aligned and partially pumped. This process is relatively time-consuming, and according to some examples, it may take a minute or longer, as further examples will be given below. Then, another robot (not shown) inserts (505) the wafer into the main chamber 506 of the SEM, which is under a high vacuum. The wafer is then aligned using optical and charged particle methods (507). Afterward, the wafer is moved (508) to a location 509, such as the imaging location of SEM 510. The image is used for measurements to obtain one or more measurements of the critical dimensions (CD) of one or more features (lines, gaps, contacts, etc.) on the wafer, all of which are discussed herein according to various specific embodiments of the subject matter of this disclosure. After obtaining the measurement results within this cycle time, the wafer is moved from the main chamber through the load-locking chamber to the carrier, and the entire process is repeated for the next measurement cycle in the next time interval. Please note that, depending on the dynamic procedure, the duration of the time interval may be in the range of several minutes, during which the wafer remains outside the main chamber for at least one minute, and possibly longer, because a relatively lengthy preparation procedure is required to align the wafer before it is reinserted into the main chamber. It should also be noted that, according to some specific implementations, the actual measurement cycle (20 measurements per cycle in this example) is in many cases significantly shorter than the time required to align the wafer in the main chamber. Therefore, the net effect is that the measurement cycle, i.e., the actual one or more measurements per cycle (20 in this example), may be much shorter than the entire time interval, which includes external wafer alignment outside the main chamber and internal alignment inside the chamber before the actual measurement (e.g., by SEM). Please note that the specified dynamic procedure operation sequence is for illustrative purposes only, and the invention is in no way bound by the specified stages or operation sequence. Also note that the specified SEM structure (including the load-locked chamber and the main chamber and the division between them) is provided for illustrative purposes only, and the invention is in no way bound by it.

[0058] In view of this, let's look at it again. Figure 4 Therefore, it is clear from the above discussion that the entire process of determining the extent of pollution can be quite lengthy, requiring, for example, 20 measurement cycles to obtain the desired slope.

[0059] Depending on the specific implementation, it may be desirable to reduce the overall duration of each time interval, thereby reducing the overall duration of obtaining measurements, deriving gradients, and combining them as functions. In this regard, it is worth noting that while accurately determining the degree of contamination and taking appropriate compensatory measures is essential, this could result in the main chamber being unable to perform its ongoing task for a relatively long period. Thus, for example, in a dynamic procedure, each time interval, including external sample calibration (outside the chamber), internal sample calibration (inside the chamber), and 20 measurements, takes 5 minutes. Further assuming 20 time intervals (each comprising 20 measurement cycles), this would result in the main chamber being unable to perform its designated ongoing activity for approximately 100 minutes.

[0060] Figure 5 Figure 402 illustrates an attempt to shorten each measurement cycle. In this specific implementation, the number of measurements per cycle is reduced to a minimum, i.e., once. Following the steps described above (now performing one measurement per cycle), the slope of the linear approximation of the CD measurement will be smaller, i.e., 0.069ηm / measurement cycle, compared to 0.119ηm / measurement cycle in Figure 401, due to the shorter residence time of the sample in the chamber. Note that this benefit is relatively limited because the alignment requirements inside and outside the chamber remain unchanged regardless of whether the number of measurements per cycle is significantly reduced, and considering that the alignment procedure may take longer than the measurement duration, the overall time saving per cycle is not much, for example, 10-120 seconds (one measurement per cycle), rather than at least 1 minute + 120 seconds / cycle second (20 measurements per cycle).

[0061] According to some specific embodiments, it has been found that the carbon-rich film accumulating on the sample pattern, if not all, is predominantly found inside the vacuum-sealed main chamber, rather than in the air-exposed chamber. Therefore, according to some specific embodiments, the specified contamination determination is performed according to a so-called static procedure, where the sample is inserted into the main chamber once (at the beginning), and multiple measurement cycles are performed while the sample remains in the chamber, eliminating the time-consuming process of removing and realigning the sample before reinserting it into the chamber in each measurement cycle (as is the case with a dynamic procedure). The sample is only removed after the measurement cycle is completed.

[0062] To better illustrate the above situation, please note Figure 4 Figure 403 shows the result of 20 measurements per cycle. As shown in the figure, the slope calculated for the straight line (approximately the CD measurement value) is 0.103 (ηm / measurement cycle), which is very similar to the corresponding 0.119ηm / measurement cycle in the dynamic program. Therefore, the slope calculated according to the static program can well illustrate the degree of pollution.

[0063] Therefore, unlike dynamic procedures, significant time can be saved by eliminating the process of removing and re-inserting the sample from the chamber before at least one (or each in other embodiments) measurement cycle, for example, 60 seconds per time interval, with the entire contamination determination process taking 20 minutes, compared to 100 minutes for the corresponding dynamic procedure. This allows the main chamber of the inspection tool to be used more efficiently for its known, self-defined task.

[0064] Please note that the numerical examples provided are for reference only and are not binding. Depending on the type of inspection tool and the characteristics of the static procedure, the cycle time for each static procedure may be between 10 and 120 seconds.

[0065] It is important to note that following the static process not only avoids alignment outside the main chamber, but also, depending on the specific implementation, avoids alignment within the chamber during different cycles. For example, alignment can be performed once before the start of the first measurement cycle and skipped in the remaining measurement cycles. Therefore, theoretically, omitting internal alignment before each cycle and instantaneously moving from one measurement cycle to the next can significantly shorten the time interval. For instance, with 20 measurements per cycle, assuming each measurement lasts approximately 1 second, the total duration of each measurement cycle can be extended to ~20 seconds (the entire processing time for 20 cycles can be completed in less than 7 minutes). When calculating the slope of the approximate measurement value, the slope is 0.024 (ηm / measurement cycle), which is quite mild (much smaller than the slope of 0.119ηm / measurement cycle calculated in Figure 403). This is because the duration of each time interval is short, and only a small amount of film accumulates on the measured feature within 20 (shorter) time intervals.

[0066] If we try to further shorten the cycle time, for example by performing one measurement per cycle and immediately moving to the next cycle, it would obviously further and significantly reduce the overall time the inspection tool takes to determine the degree of contamination. However, this comes at the cost of obtaining a meaningless slope, for example... Figure 4 As shown in Figure 404, the duration of each cycle is less than 10 seconds.

[0067] Therefore, when using a static procedure, each cycle time obviously needs to be long enough to accumulate sufficient film and reflect it as increasing (or decreasing) CD measurements, so that the linear approximation of the measurements produces a meaningful gradient (slope), as in the case of Figure 403 above.

[0068] Therefore, it should be noted that, according to some specific implementations, if the measurement cycle is too short (e.g., extended over the duration "1" of time interval 301), a correspondingly longer time interval (301) should still be maintained (e.g., the system is placed in a "hold" state for the remaining duration "2" of time interval "301"), thereby allowing further film accumulation before performing the next measurement cycle. Thus, in some specific implementations, the actual duration measured in each cycle is a small fraction (e.g., less than 50%) of the duration of the corresponding time interval.

[0069] Please note that although the present invention has been described with reference to specific embodiments of dynamic or static programs, those skilled in the art will readily understand that the invention is not limited to these specific embodiments and other measurement paradigms may be used, which are not necessarily the specified static or dynamic programs. According to another modified embodiment, a hybrid paradigm consisting of static and dynamic programs may be used; for example, several cycles follow a dynamic program while other cycles follow a static program, all depending on the specific application.

[0070] It should be noted that the examples described in this disclosure, such as extracted measurements and the gradient of a straight line approximating the CD measurement, various processing techniques, numerical values, etc., are for illustrative purposes only and should not be construed as limiting the scope of this disclosure in any way. Other suitable examples / implementations may be used in addition to the foregoing, or may replace the foregoing.

[0071] One of the advantages of some specific embodiments of the subject matter described herein is that it provides data indicating characteristic contamination of the sample.

[0072] Numerous specific details are set forth in the detailed description to provide a thorough understanding of the subject matter of this disclosure. However, those skilled in the art will understand that the subject matter of this disclosure 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 of this disclosure.

[0073] Unless otherwise specifically stated, it will be apparent from the discussion that, throughout the discussion of this specification, the use of terms such as monitor, embody, determine, and include, or similar terms, refers to the operation and / or processes of a computer that convert data into other data, said data being represented as physical quantities, such as electronic quantities, and / or said data representing physical objects. The term "computer" should be interpreted broadly to encompass any kind of hardware-based electronic device with data processing capabilities, as referenced in the [reference] section. Figure 1 As stated above.

[0074] The processor mentioned in this disclosure may represent one or more general-purpose processing devices, such as microprocessors, central processing units, or similar devices. More specifically, a processor may be a Complex Instruction Set Computing (CISC) microprocessor, a Reduced Instruction Set Computing (RISC) microprocessor, a Very Long Instruction Word (VLIW) microprocessor, a processor that executes other instruction sets, or a processor that executes combinations of instruction sets. A processor may also be one or more special-purpose processing devices, such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs), network processors, etc. The processor is configured to execute instructions to perform the operations and steps discussed herein.

[0075] The memory mentioned here may include main memory (such as read-only memory (ROM), flash memory, dynamic random access memory (DRAM), such as synchronous DRAM (SDRAM) or Rambus DRAM (RDRAM), etc.) and static memory (such as flash memory, static random access memory (SRAM), etc.).

[0076] The terms “non-transitory memory” and “non-transitory storage medium” as used herein should be interpreted broadly to cover any volatile or non-volatile computer memory applicable to the subject matter of this disclosure. These terms should be considered to include a single medium or multiple media (e.g., a centralized or distributed database, and / or associated caches and servers) that store one or more sets of instructions. These terms should also include any medium capable of storing or encoding a set of instructions for execution by a computer, enabling the computer to perform any one or more methods of this disclosure. Therefore, the terms should be considered to include, but are not limited to, read-only memory (“ROM”), random access memory (“RAM”), disk storage media, optical storage media, flash memory devices, etc.

[0077] The term "sample" as used in this specification shall be interpreted broadly to encompass any kind of physical object or substrate, including but not limited to semiconductor samples, such as wafers, masks, meshes, and other structures, assemblies, and / or components, which may be used, for example, in the manufacture of semiconductor integrated circuits, magnetic heads, flat panel displays, and other semiconductor manufactured articles. Samples are also exemplified herein as semiconductor samples that may be produced by manufacturing apparatus performing the appropriate manufacturing processes.

[0078] The term "inspection" as used in this specification should be interpreted broadly to encompass any kind of operation related to defect detection, defect review, and / or various defect classification, segmentation, and / or metrological operations during and / or after specimen fabrication. Inspection is performed using non-destructive inspection tools during or after specimen fabrication. As a non-limiting example, the inspection process may include performing on-time scanning (single or multiple scans), imaging, sampling, testing, re-inspection, measurement (e.g., including measurements of specimen bores and bore bottom features), classification, and / or other operations on the specimen or its components using the same or different inspection tools. Similarly, inspection may be provided prior to the fabrication of the specimen to be inspected, and may include, for example, generating an inspection formulation and / or other setup operations. It should be noted that, unless otherwise specified, the term "inspection" or its derivatives as used in this specification are not limited in terms of resolution or the size of the inspection area. By way of non-limiting examples, various non-destructive inspection tools include scanning electron microscopes (SEM), atomic force microscopes (AFM), optical inspection tools, etc.

[0079] The term “inspection tool” as used herein should be interpreted broadly to encompass any tool that may be used to inspect the relevant process, including (by way of non-limiting example) scanning (in a single or multiple scans), imaging, sampling, examination, measurement, classification and / or other processes provided for the specimen or portions thereof.

[0080] It should be noted that the term "image" as used herein can refer to the original image of the specimen captured by the inspection tool during the manufacturing process, derivatives of the captured image obtained through various preprocessing stages, and / or computer-generated images based on design data. It should also be noted that in some cases, the image mentioned herein can include image data (e.g., captured images, processed images, etc.) and related numerical data (e.g., meta-data, handcrafted properties, etc.). Furthermore, image data can include data related to one or more layers of interest of the specimen.

[0081] The term “approximation” as used in this specification should be interpreted broadly to encompass any well-known approximation technique used to approximate a straight line, such as polynomial least squares regression.

[0082] It is understood that, unless otherwise specifically stated, some features of the subject matter of this disclosure described in the context of individual embodiments may also be provided in combination in a single embodiment. Conversely, various features of the subject matter of this disclosure described in a single specific embodiment may also be provided individually or in any suitable sub-combination. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the methods and apparatus.

[0083] Please note that, depending on the specific implementation, the order of the calculation stages described herein with reference to the accompanying drawings is not necessarily binding. For example, the order of the steps may be changed, steps may be modified or deleted, and / or other steps may be added to replace or supplement the steps disclosed herein.

[0084] It should be understood that the application of this disclosure is not limited to the details illustrated in the description or figures contained herein.

[0085] Furthermore, it is understood that the system according to this disclosure can be implemented, at least in part, on a suitably programmed computer. Similarly, this disclosure also contemplates computer-readable programs for executing methods of this disclosure. This disclosure further contemplates a non-transitory computer-readable memory, specifically a computer-executable instruction program, for executing methods of this disclosure.

[0086] This disclosure can be implemented and carried out in various ways and with other specific embodiments. Therefore, it should be understood that the wording and terminology used herein are for descriptive purposes only and should not be considered limiting. Consequently, those skilled in the art will understand that the concepts upon which this disclosure is based can be readily used as the basis for designing other structures, methods, and systems to achieve several objectives of the subject matter of this disclosure.

[0087] Those skilled in the art will readily understand that various modifications and alterations can be made to the specific embodiments of the present disclosure described herein without departing from the scope defined by the appended claims.

Claims

1. A system for monitoring the degree of contamination affecting the critical size of a specimen as measured by an inspection tool, the system comprising a processing and memory circuit (PMC) operably connected to the inspection tool; wherein the PMC is configured to: (i) Obtaining a plurality of measurement cycles, each measurement cycle comprising at least one measurement of the critical dimension (CD) of at least one pattern of the specimen when housed within the chamber of the inspection tool; wherein the measurement cycles are performed at discrete time intervals such that the successive measurement cycles are affected by variations in the CD measurements; and (ii) Determine the degree of contamination based on the gradient function of a straight line approximating the CD measurement value.

2. The system of claim 1, wherein the sample pattern is a line, and wherein the gradient is upward, such that the steeper the gradient, the larger the contamination range.

3. The system of claim 1 or 2, wherein the sample pattern is a cavity and wherein the gradient has a decreasing trend, so the steeper the gradient, the larger the contamination range.

4. The system as described in any of the preceding claims, wherein the plurality of measurement cycles is greater than 3.

5. The system as claimed in any of the preceding claims, wherein at least one measurement cycle of the measurement period is obtained according to a dynamic procedure, thereby keeping the sample in the chamber for a portion of the time interval.

6. The system as claimed in any of the preceding claims, wherein the time interval falls within the range of 10 to 120 seconds inside the chamber, and there is at least an additional 60 seconds outside the chamber.

7. The system of any one of claims 1 to 4, wherein at least one measurement cycle of the measurement period is obtained according to a static procedure, such that the sample remains in the chamber for at least two sequential time intervals.

8. The system of any one of claims 1 to 4 and 7, wherein at least one measurement cycle of the measurement period is obtained according to a static procedure, and wherein if a dynamic procedure is used, the time interval is less than a hypothetical time interval, wherein the sample remains in the chamber for a portion of the hypothetical time interval.

9. The system of claim 7 or 8, wherein the time interval is between 10 and 120 seconds.

10. The system of any one of claims 5 to 9, wherein the measurement is obtained over at least one period of time within a fraction of the time interval.

11. A computerized method for monitoring the degree of contamination affecting the critical size of a specimen as measured by an inspection tool, the method comprising being performed by a processor and memory circuitry (PMC): a. Obtaining multiple measurement cycles, each measurement cycle comprising at least one measurement of the critical dimension (CD) of at least one pattern of the specimen when housed within the chamber of the inspection tool; wherein the measurement cycles are performed at discrete time intervals, such that the successive measurement cycles are affected by variations in the CD measurements; and b. Determine the degree of contamination based on the gradient function of a straight line approximating the CD measurement value.

12. A non-transitory computer-readable storage medium tangibly implements an instruction program that, when executed by a computer, causes the computer to perform a monitoring method for monitoring the degree of contamination affecting a critical dimension of a sample, as measured by an inspection tool, the method comprising: a. Obtaining multiple measurement cycles, each measurement cycle including at least one measurement of the critical dimension of at least one pattern of the specimen when housed in the chamber of the inspection tool; wherein the measurement cycles are performed at discrete time intervals, such that the sequential measurement cycles are affected by variations in the CD measurement values; as well as b. Determine the degree of contamination based on the gradient function of a straight line approximating the CD measurement value.

13. The non-transient computer-readable storage medium of claim 12, wherein the sample pattern is a line and wherein the gradient is upward, such that the steeper the gradient, the larger the contamination range.

14. The non-transient computer-readable storage medium of claim 12 or 13, wherein the sample pattern is a cavity and wherein the gradient has a decreasing trend, so that the steeper the gradient, the larger the contamination range.

15. The non-transient computer-readable storage medium as claimed in any one of claims 12 to 14, wherein the plurality of measurement cycles is greater than three.

16. The non-transient computer-readable storage medium of any one of claims 12 to 15, wherein at least one measurement cycle of the measurement period is obtained according to a dynamic program, thereby causing the sample to be held in the chamber for a portion of the time interval.

17. The non-transient computer-readable storage medium of any one of claims 12 to 16, wherein the time interval falls within the range of 10 to 120 seconds within the cavity and has at least an additional 60 seconds outside the cavity.

18. The non-transient computer-readable storage medium of any one of claims 12 to 15, wherein at least one measurement cycle of the measurement period is obtained according to a static procedure, such that the sample remains continuously in the chamber for at least two sequential time intervals.

19. The non-transient computer-readable storage medium of any one of claims 12 to 15 and 18, wherein at least one measurement period of the measurement cycle is obtained according to a static program, and wherein if a dynamic program is used, the time interval is less than a hypothetical time interval, wherein the sample remains in the chamber for a portion of the hypothetical time interval.

20. The non-transient computer-readable storage medium of claim 18 or 19, wherein the time interval is in the range of 10-120 seconds.

21. The non-transient computer-readable storage medium of any one of claims 16 to 20, wherein the measurement is obtained during a fraction of the time interval within at least one cycle.

22. The system according to any one of claims 1 to 10, wherein the sample is a semiconductor sample.

23. The system of claim 11, wherein the sample is a semiconductor sample.

24. The non-transitory computer-readable storage medium according to any one of claims 12 to 21, wherein the sample is a semiconductor sample.

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