Airflow configuration for semiconductor inspection

Abstract

Methods and systems for inspecting a sample are provided. A system includes an inspection subsystem configured for directing light to a region on the sample and for generating an output in response to light from the region on the sample. The system also includes a first gas flow subsystem configured to replace a gas with a first medium that scatters less the light than the gas in a first local volume surrounding the region on the sample. In addition, the system includes a second gas flow subsystem configured for replacing the gas in a second local volume proximate to the first local volume with a second medium different from the first medium. The system further includes a computer subsystem configured to detect an anomaly on the sample based on the output.

Description

Technical Field

[0001] The present invention generally relates to an inspection system including an air flow subsystem for reducing non-sample induced light scatter and foreign matter contamination of an inspected sample. Background Art

[0002] The following description and examples are not admitted to be prior art by virtue of their inclusion in this section.

[0003] The manufacture of semiconductor devices, such as logic and memory devices, typically includes processing a substrate, such as a semiconductor wafer, using a number of semiconductor manufacturing processes to form the various features and multiple levels of the semiconductor devices. For example, photolithography is a semiconductor manufacturing process that involves transferring a pattern from a mask to a photoresist arranged on a semiconductor wafer. Additional examples of semiconductor manufacturing processes include, but are not limited to, chemical mechanical polishing (CMP), etching, deposition, and ion implantation. Multiple semiconductor devices can be manufactured in an arrangement on a single semiconductor wafer and then separated into individual semiconductor devices.

[0004] Various steps during the semiconductor manufacturing process use inspection processes to detect defects on wafers and other substrates to promote higher yields and therefore higher profits in the manufacturing process. Inspection has always been an important part of manufacturing semiconductor devices such as ICs. However, as the size of semiconductor devices decreases, inspection becomes even more important to the successful manufacture of acceptable semiconductor devices because smaller defects can cause device failure.

[0005] Particles are fatal defects in semiconductor manufacturing. A 10nm particle can destroy or short out circuitry in a device with a 20nm critical dimension (CD). Scaling of CD continues slowly but steadily with the introduction of extreme ultraviolet (EUV) lithography. The need to detect even smaller particles is imminent.

[0006] The currently used method for detecting particles is to measure the scattered light under dark field (DF) optics. The laser is directed at an angle onto the wafer. Specular reflections can be discarded and the scattered light is collected by an objective lens. The scattered light includes scattered light from the particles, the roughness of the wafer, and the air through which the light beam passes. In order to achieve the desired signal-to-noise ratio (SNR), the scattered light from the surface roughness and the air must be suppressed. Air scattering is usually small and does not become a problem until the particles of interest are reduced to 10nm and smaller. An effective way to reduce air scattering is to reduce the air density by evacuating the space between the objective lens and the wafer. Some next generation particle inspection tools anticipate that a vacuum of about 10 Torr (about 1% of atmospheric pressure) will be required from the sample to about 1mm above the sample.

[0007] To create a vacuum, currently used methods and systems construct an enclosed chamber and evacuate it. Inspection modules (such as chucks, stages, and objective lenses) will reside in the chamber or at least partially reside in the chamber. Examples of currently used methods for creating such a vacuum environment for semiconductor applications are described in U.S. Pat. No. 5,536,330 to Chen et al., issued on July 16, 1996, and U.S. Pat. No. 7,001,491 to Lombardi et al., issued on February 21, 2006, which are incorporated herein by reference as if fully set forth.

[0008] The biggest problem with the currently used vacuum configuration is that it is difficult to maintain cleanliness. For example, the currently used semiconductor yield-related tools operating in vacuum are usually 2 to 3 orders of magnitude dirtier than the cleanest particle inspection tools on the market today. Currently, surface inspection tools use flushing air to achieve superior cleanliness, which showers around the wafer and effectively pushes out all particles that will fall on the wafer. In the case of the currently used vacuum configuration, since the entire wafer is in a vacuum, it is impossible to implement air flushing. Another problem is the cost of the currently used vacuum configuration. The vacuum will greatly increase the size of the tool and the cost of the stage, chuck and objective lens. Due to the extra time required for vacuuming each time a new wafer is loaded, the throughput will be severely affected. For relatively low throughput tools (such as electron beam inspectors and defect re-inspection tools), this may not be a big problem, but for higher throughput tools (such as particle inspection tools), this will be a big problem because its throughput is usually close to 10 to 100 wafers per hour.

[0009] It would therefore be advantageous to develop systems and methods for inspecting samples with reduced non-defect and / or particle light scatter and foreign matter contamination that do not suffer from one or more of the above-mentioned disadvantages. Summary of the invention

[0010] The following description of various embodiments should not be construed in any way as limiting the subject matter of the appended claims.

[0011] One embodiment relates to a system configured for testing a sample. The system includes a testing subsystem configured to direct light to an area on the sample and to generate an output in response to light from the area on the sample. The system also includes a first gas flow subsystem configured to replace the gas with a first medium that scatters less light than the gas in a first local volume surrounding the area on the sample. In addition, the system includes a second gas flow subsystem configured to replace the gas in a second local volume proximate to the first local volume with a second medium different from the first medium. The system further includes a computer subsystem configured to detect anomalies on the sample based on the output. The system may be further configured as described herein.

[0012] Another embodiment relates to a method for examining a sample. The method includes directing light to an area on a sample and generating an output in response to the light from the area on the sample. The method also includes replacing a gas in a first local volume surrounding the area on the sample with a first medium during the directing and the generating. The first medium scatters the light less than the gas. Additionally, the method includes replacing the gas in a second local volume located proximate to the first local area with a second medium during the directing and the generating. The second medium is different from the first medium. The method further includes detecting an anomaly on the sample based on the output. The detecting is performed by a computer system.

[0013] The steps of the method may be performed as further described herein. The method may include any other step(s) of any other method(s) described herein. The method may be performed by any of the systems described herein.

[0014] Another embodiment relates to a non-transitory computer-readable medium storing program instructions that can be executed on a computer system for performing a computer-implemented method for testing a sample. The computer-implemented method includes the steps of the method described above. The computer-readable medium can be further configured as described herein. The steps of the computer-implemented method can be executed as further described herein. In addition, the computer-implemented method for which the program instructions can be executed can include any other step(s) of any other method(s) described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Other objects and advantages of the present invention will become apparent upon reading the following detailed description and referring to the accompanying drawings, in which:

[0016] Figure 1is a schematic diagram illustrating a side view of an embodiment of a system configured for testing a sample;

[0017] Figures 2 to 6 are schematic diagrams illustrating cross-sectional views of various embodiments of portions of a system configured for inspecting a sample and for using different media to reduce light scatter and introduction of foreign matter during the inspection; and

[0018] Figure 7 is a block diagram illustrating one embodiment of a non-transitory computer-readable medium storing program instructions executable on a computer system for performing one or more of the computer-implemented methods described herein.

[0019] Although the present invention is susceptible to various modifications and alternative forms, specific embodiments of the present invention are shown by way of example in the drawings and described in detail herein. However, it should be understood that the drawings and detailed description thereof are not intended to limit the present invention to the specific forms disclosed, but on the contrary, the present invention will cover all modifications, equivalents and substitutes falling within the spirit and scope of the present invention as defined by the appended claims. DETAILED DESCRIPTION

[0020] Referring now to the drawings, it should be noted that the drawings are not drawn to scale. In particular, the proportions of some elements of the drawings are greatly exaggerated to highlight the characteristics of the elements. It should also be noted that the drawings are not drawn to the same scale. The same element numbers have been used to indicate elements that may be similarly configured that are shown in more than one figure. Unless otherwise mentioned herein, any elements described and shown may include any suitable commercially available elements.

[0021] The embodiments described herein generally relate to systems and methods for inspecting samples. For example, the embodiments described herein provide methods and systems for particle inspection equipment using two different media (e.g., applying flushing air and creating a partial vacuum or applying a helium medium). In order to manufacture the next generation of particle inspection tools, the tools must have means to reduce air scattering (e.g., via a vacuum or another medium that scatters less light than air) and means to keep the tools clean (e.g., via flushing air). The two requirements appear to be contradictory, but the inventors have produced the system architecture described herein that makes it possible to meet both requirements. The embodiments described herein have many advantages and improvements over currently available inspection tools. For example, the embodiments allow a substantially small volume of vacuum to be created between the sample and the objective lens, which eliminates the excess time for a step-down pump to pump up a large vacuum chamber. The embodiments also allow clean air to be flushed around the sample to keep it clean.

[0022] Although the embodiments described herein may be particularly useful for wafer inspectors designed for particle inspection, the embodiments may be useful for other wafer inspectors, other types of sample inspectors, metrology tools, optical defect review tools, and the like.

[0023] In one embodiment, the sample is a wafer. The wafer may include any wafer known in the semiconductor field. Although some embodiments may be described herein with respect to one or more wafers, the embodiments are not limited to the samples that they can be used for. For example, the embodiments described herein can be used for samples such as masks, flat panels, personal computer (PC) boards, and other semiconductor samples.

[0024] A system configured for testing a sample includes a testing subsystem configured for directing light to an area on the sample and for generating an output in response to light from the area on the sample. The testing subsystem includes at least an illumination subsystem including a light source configured to generate light directed to an area on the sample and a detection subsystem including a detector configured to detect light from the sample and generate an output in response to the detected light. Figure 1 An embodiment of this system is shown in FIG.

[0025] like Figure 1 , the illumination subsystem includes a light source 100. The illumination subsystem is configured to direct light generated by the light source to an area (not shown) on the sample at one or more incident angles that may include one or more oblique angles and / or one or more normal angles. The area may be a relatively large light spot, one or more light spots, a field, a line, etc. For example, Figure 1 , light from light source 100 is directed at an oblique angle of incidence through optical element 102 and then through lens 104 to sample 106. The angle of incidence may include any suitable angle of incidence that may vary depending on, for example, the characteristics of the sample and the process to be performed on the sample.

[0026] The illumination subsystem may be configured to direct light to the sample at different incident angles at different times. For example, the inspection subsystem may be configured to modify one or more characteristics of one or more elements of the illumination subsystem so that different Figure 1 The light is directed to the sample at an incident angle of the angle shown in FIG. 1. In one such example, the inspection subsystem can be configured to move the light source 100, the optical element 102, and the lens 104 so that the light is directed to the sample at different incident angles.

[0027] In some examples, the inspection subsystem may be configured to direct light to the sample at more than one incident angle simultaneously. For example, the illumination subsystem may include more than one illumination channel, one of which may include, for example, Figure 1, and another of the illumination channels (not shown) may include similar elements that may be configured differently or identically, or may include at least a light source and possibly one or more other components (such as those described further herein). If this light is directed to the sample simultaneously with other light, one or more characteristics (e.g., wavelength, polarization, etc.) of the light directed to the sample at different incident angles may be different, such that light resulting from illumination of the sample at different incident angles may be distinguished from one another at the detector(s).

[0028] In another example, the illumination subsystem may include only one light source (e.g., Figure 1 ) and the light from the light source may be separated into different optical paths by one or more optical elements (not shown) of the illumination subsystem (e.g., based on wavelength, polarization, etc.). The light in each of the different optical paths may then be directed to the sample. Multiple illumination channels may be configured to direct light to the sample simultaneously or at different times (e.g., when different illumination channels are used to sequentially illuminate the sample). In another example, the same illumination channel may be configured to direct light with different characteristics to the sample at different times. For example, the optical element 102 may be configured as a spectral filter and the properties of the spectral filter may be changed in various ways (e.g., by swapping out the spectral filter) so that light of different wavelengths may be directed to the sample at different times. The illumination subsystem may have any other suitable configuration known in the art for directing light with different or the same characteristics to the sample sequentially or simultaneously at different or the same angles of incidence.

[0029] Light source 100 may include any suitable light source, such as any suitable laser known in the art configured to produce light of any suitable wavelength(s). The laser may be configured to produce monochromatic or near-monochromatic light. Additionally, the laser may be a mode-locked laser. The light source may also include a polychromatic light source that produces light of multiple discrete wavelengths or bands.

[0030] Light from optical element 102 may be focused onto sample 106 by lens 104. Although lens 104 is Figure 1 1 is shown as a single refractive optical element, but in reality, lens 104 may include several refractive and / or reflective optical elements that combine to focus light from the optical element onto the sample. Figure 1The illumination subsystem shown in and described herein may include any other suitable optical elements (not shown). Examples of such optical elements include, but are not limited to, polarizing components, spectral filter(s), spatial filter(s), reflective optical element(s), apodizer(s), beam splitter(s), aperture(s), and the like, which may include any such suitable optical elements known in the art. Additionally, the system may be configured to alter one or more of the elements of the illumination subsystem based on the type of illumination to be used. Furthermore, the illumination subsystem may be configured to direct light to only one area on the sample or to more than one area on the sample. The areas may have any suitable characteristics known in the art.

[0031] The inspection subsystem may also include a scanning subsystem configured to cause light to scan over the sample. For example, the inspection subsystem may include a stage ( Figure 1 The scanning subsystem may include any suitable mechanical and / or robotic assembly (including a stage) that may be configured to move the sample so that light may be scanned over the sample. Additionally or alternatively, the inspection subsystem may be configured so that one or more optical elements of the inspection subsystem perform some scan of light over the sample. The light may be scanned over the sample in any suitable manner. The stage may be further configured as described herein.

[0032] The detection subsystem may include one or more detection channels. At least one of the detection channels includes a detector configured to detect light from the sample due to illumination of the sample by the illumination subsystem and to generate an output in response to the detected light. For example, Figure 1 The detection subsystem shown in FIG. 1 includes a detection channel formed by an objective lens 112, a tube lens 116, an element 118, and a detector 120. Figure 1 As shown in , the detection channel is configured to detect scattered light from the sample. In this way, the detection channel can be configured for dark field (DF) imaging.

[0033] The detection subsystem may also include more than one detection channel (not shown) that collects and detects light at different collection angles. In some examples, one detection channel is configured to detect specularly reflected light and another detection channel is configured to detect light that is not specularly reflected (e.g., scattered, diffracted, etc.) from the sample. However, two or more detection channels may be configured to detect the same type of light (e.g., scattered light) from the sample. Although Figure 1 The objective and tube lenses are shown in as having a specific number of refractive optical elements of a specific shape, but the objective and tube lens may each include one or more refractive optical elements and / or one or more reflective optical elements having any suitable configuration known in the art.

[0034] One or more detection channels may include any suitable detector known in the art, such as a photomultiplier tube (PMT), a charge coupled device (CCD), and a time delay integration (TDI) camera. The detector may also include a non-imaging detector or an imaging detector. If the detector is a non-imaging detector, each of the detectors may be configured to detect a specific characteristic of light (e.g., intensity) but may not be configured to detect such characteristics that vary depending on the position within the imaging plane. Thus, the output generated by each of the detectors included in each of the detection channels may be a signal or data rather than an image signal or image data. In such examples, a computer subsystem of the system (e.g., computer subsystem 122) may be configured to generate an image of the sample from the non-imaging output of the detector. However, in other examples, the detector may be configured as an imaging detector configured to generate an image signal or image data. Thus, the system may be configured to generate the output and / or images described herein in a number of ways.

[0035] The inspection subsystem may be configured to generate output (e.g., image) of the sample with multiple modes. In general, a "mode" is defined by the value of a parameter of the inspection subsystem used to generate the output of the sample. Therefore, the mode may differ in the value of at least one of the parameters of the illumination and detection subsystems (except for the location on the sample where the output is generated). For example, different modes may use light of different wavelengths for illumination. The mode may differ in (several) illumination wavelengths as further described herein (e.g., by using different light sources, different spectral filters, etc. for different modes). In another example, different modes may use different illumination channels of the illumination subsystem. For example, as mentioned above, the illumination subsystem may include more than one illumination channel. Thus, different illumination channels may be used for different modes. The mode may also or alternatively differ in one or more collection / detection parameters of the detection subsystem. The mode may differ in any one or more modifiable parameters of the system (e.g., (several) illumination polarizations, (several) angles, (several) wavelengths, etc., (several) detection polarizations, (several) angles, (several) wavelengths, etc.). For example, depending on the ability to scan a sample using multiple modes simultaneously, the inspection subsystem may scan the sample with different modes in the same scan or in different scans.

[0036] This article provides Figure 1to generally illustrate the configuration of an inspection subsystem that may be included in an embodiment of the system described herein. Obviously, the inspection subsystem arrangement described herein may be modified to optimize the performance of the system as normally performed when designing a commercial system. In addition, the system described herein may be implemented using an existing inspection system (e.g., by adding the functionality described herein to an existing optical system), such as the SPx series of tools commercially available from KLA Corp., Milpitas, Calif., which may be capable of detecting substantially small particles as low as about 10 nm. For some such systems, the methods described herein may be provided as optional functionality of the system (e.g., in addition to other functionality of the system). Alternatively, the system described herein may be designed "from scratch" to provide an entirely new system.

[0037] The system further includes a computer subsystem configured for detecting anomalies on the sample based on the output. For example, the system may include a computer subsystem 122 that is coupled to the detector 120 in any suitable manner (e.g., via one or more transmission media, which may include "wired" and / or "wireless" transmission media) so that the computer subsystem can receive output, images, etc. generated by the detector during scanning of the sample. The computer subsystem may be configured for detecting anomalies on the sample by applying a defect detection method to the output generated by the detector. Detecting anomalies on the sample may be performed in any suitable manner known in the art (e.g., applying a defect detection threshold to the output and determining that any output having a value above the threshold corresponds to an anomaly or potential anomaly) with any suitable defect detection method and / or algorithm. The computer subsystem 122 may be configured to perform any other functions further described herein. This computer subsystem may be further configured as described herein.

[0038] As used herein, the term "anomaly" is generally defined as an example of a sample characteristic that is different from what is expected or desired. Examples of anomalies that may be detected by the embodiments described herein include the presence of particles on the sample (e.g., falling particles, foreign matter, etc.), defects (e.g., defects in one or more materials formed on the sample, whether patterned or unpatterned), etc. In general, depending on the anomaly of interest and the sample characteristics (e.g., type, layer, etc.), the embodiments described herein may be configured to detect different kinds of anomalies. In other words, the embodiments described herein are not limited to the types of anomalies that they may be configured to detect.

[0039] This computer subsystem (as well as other computer subsystems described herein) may also be referred to herein as computer system(s). Each of the computer subsystem(s) or systems described herein may take various forms, including personal computer systems, image computers, mainframe computer systems, workstations, network appliances, Internet appliances, or other devices. In general, the term "computer system" may be broadly defined to encompass any device having one or more processors that execute instructions from a storage medium. The computer subsystem(s) or system(s) may also include any suitable processor known in the art, such as a parallel processor. In addition, the computer subsystem(s) or system(s) may include a computer platform with high-speed processing and software as a stand-alone tool or a networked tool.

[0040] As described herein, the system is configured as an inspection system. In another embodiment, the system may be configured as a metrology or defect recheck system. In particular, Figure 1 The embodiments of the system shown in can be modified in one or more parameters to provide different imaging capabilities depending on the application in which it will be used. In one such example, Figure 1 The optical subsystem shown in FIG. 1 can be configured to have higher resolution in the case where it is to be used for metrology or defect rechecking rather than for inspection. In other words, Figure 1 The embodiments of the inspection subsystem shown in describe some general configurations for the optical subsystem and various configurations that can be customized in a number of ways that will be apparent to those skilled in the art to produce systems with different imaging capabilities that are more or less suitable for different applications.

[0041] The system includes a first gas flow subsystem configured to replace the gas with a first medium that scatters less light than the gas in a first local volume surrounding an area on the sample. The first local volume may have a portion of the gas that is passed through an objective lens (e.g., Figure 1 The first local volume is defined by the height defined by the space between the objective lens 112 shown in FIG. 1 and the upper surface of the sample. The first local volume may be generally centered on the illuminated area (or areas) on the sample, but it need not be precisely centered on the area (or areas). The first local volume preferably surrounds the area to the extent that any light from the sample collected by the inspection subsystem travels entirely within the first medium from the sample to the objective lens. Thus, the width of the first local volume may depend on the collection angle (the angle at which light is collected from the sample by the objective lens). The width of the first local volume may also be configured so that light from the illumination subsystem is directed through the first medium to the area (or areas) on the sample. Thus, the size of the first local volume may vary depending on the configuration of the inspection subsystem and how close the sample is positioned to the objective lens.

[0042] In one embodiment, the first medium is a vacuum. For example, the vacuum may be created by pumping air out of the first local volume through one or more pumping channels. Figure 1 , the first gas flow subsystem includes a housing block 108 having a plurality of channels 110 formed therein, through which the first gas flow subsystem can replace the gas with a first medium that scatters less light than the gas in a first local volume surrounding an area on the sample illuminated by the inspection subsystem. The housing block 108 can be connected to Figure 1 1 and 12. The objective lens housing 114 is shown separated in , but these two elements, the plurality of channels 110 and the first airflow subsystem may be further configured as described herein. Figure 1 The system embodiment shown in FIG. 1 may also be further configured as described herein for clarity only. Figure 1 Additional elements are not shown.

[0043] Figure 2 illustrate Figure 1 , which is configured to create a partial vacuum between the objective lens and the sample. Specifically, the first airflow subsystem may include a plurality of channels 200, 202, and 204 formed in a housing block 206. The vacuum channels may be bored into the housing block 206, which may be formed of any suitable material, such as stainless steel. The housing block 206 may be a separate assembly attached to the objective lens housing. In this way, the air channels may be machined in a separate assembly attached to the objective lens assembly. The housing block 206 may be coupled to the objective lens housing 208 (e.g., via screws, adhesives, etc.) such that the two housings are adjacent to each other and abut each other, such as by Figure 2 206 and the objective lens housing 208. In this case, the dotted line between the housing block 206 and the objective lens housing 208 can be used as the boundary between the objective lens housing and the air channel housing. However, the housing block 206 and the objective lens housing 208 can be formed by a single piece of material and can therefore be a single element in the system. For example, the air channel can be machined as an integrated part of the objective lens assembly. In general, as long as the housing block 206 and the objective lens housing 208 can be configured to not allow the airflow between the housings, the housing block and the objective lens housing can be manufactured in various ways depending on, for example, the material requirements of the housing, the complexity of manufacturing the housing block and the objective lens housing by a single piece of material, the difficulty of coupling a separate housing to eliminate the airflow between the housings, etc.

[0044] like Figure 2 As further shown in FIG. 1 , the plurality of channels are configured so that air 210 can be drawn through the channels away from the sample 212 and out of the volume 214 between the objective lens 216 and the sample, thereby forming a vacuum between the objective lens and the sample. For example, each of the plurality of channels can be coupled to a vacuum pump ( 100 ) that draws air through the channels in this manner. Figure 2The vacuum pump may be any suitable vacuum pump known in the art and may be selected based on information about the volume between the sample and the objective lens, the required or desired level of vacuum, the configuration of the channels, etc. The first gas flow subsystem may include any other suitable elements (not shown) typically included in a vacuum system, such as valves, exhaust elements, controllers, etc. The vacuum created in the local volume between the objective lens and the wafer may be about 10 Torr or any other suitable value, depending on the requirements of the inspection system in which the first gas flow subsystem is included.

[0045] Objective lens 216 may be further configured as described herein, and Figure 2 The optical elements of the objective lens 216 shown in FIG. 2 may be as follows: Figure 1 For example, Figure 2 The optical elements of the objective lens 216 shown in FIG. Figure 1 The element of the objective lens 112 shown in FIG. 1 that is closest to the sample. Alternatively, the objective lens 216 may only include Figure 2 21. As further described herein, light 218 scattered from the illuminated area on the sample can be collected by the objective lens and directed to one or more other elements of the inspection subsystem. Vertical line 220 indicates the optical axis of the collection / detection subsystem of the inspection subsystem.

[0046] In additional embodiments, the first gas flow subsystem includes a plurality of channels for replacing gas with a first medium, and the first gas flow subsystem is configured to cause the first medium to have different values ​​of a characteristic proximate two or more of the plurality of channels. In one such embodiment, the first medium is a vacuum, and the characteristic is a pressure. In this manner, the first gas flow subsystem can be configured to generate a plurality of vacuum levels using a plurality of pumping stages. Figure 3 The results of numerical simulations performed for one embodiment of the multi-stage vacuum that can be achieved by the embodiments described herein are described. This figure shows the capabilities of the embodiments described herein estimated by simulation. In this figure, the first airflow subsystem has three pumping stages. The first stage reduces the air pressure by 90%, from 101 kPa at position 300 at the edge of the housing block 302 to ~10 kPa at position 304 near the entrance of the channel 306 of the first airflow subsystem. The second stage reduces the air pressure from ~10 kPa at position 304 to ~1.3 kPa at position 308 near the entrance of the channel 310 of the first airflow subsystem, and the third stage reduces by 56%, from ~1.3 kPa at position 308 to ~0.6 kPa at position 312 near the entrance of the channel 314 of the airflow subsystem. The efficiency of the third stage may be lower than the first two stages because the air is thinner closer to the center due to the first two stages.

[0047] The values ​​of pressure described above are only non-limiting examples of possible vacuum levels through the embodiments described herein. The vacuum pressure may be adjusted based on the use case (e.g., the amount of air scattering reduction required, which may vary depending on, for example, the wafer haze level). In addition, "vacuum" when the term is used herein does not necessarily mean a perfect or complete vacuum as seen by the vacuum pressure values ​​described above. Alternatively, "vacuum" when the term is used herein is generally defined as a medium having a pressure lower than atmospheric pressure, and any of the vacuum pressures described herein may be selected by the user when configuring the first gas flow subsystem. "Vacuum" when the term is defined herein is created by intentionally extracting one or more gases from a volume without intentionally replacing the gas with one or more other gases. For example, intentionally replacing one or more gases in the volume with one or more other gases (same or different from the original one or more gases) that happen to (or are designed to) have a pressure lower than the original one or more gases in the volume will not be considered to create a vacuum in the volume (when the term is used herein). Figure 3 The portion of the first gas flow subsystem shown in FIG. 1 may be further configured as described herein and may be coupled to a detection subsystem ( Figure 3 not shown).

[0048] Thus, a new and important feature of the embodiments described herein is that the embodiments are configured or configurable for multiple pumping stages for evacuating a vacuum. Figure 2 The three pumping stages are shown through three different channels in the housing block and Figure 3 , but different pumping stages and vacuum stages may be used. For example, the embodiments described herein may be configured for one or more pumping stages and different vacuum levels. In some examples, the first gas flow subsystem may be configured with as many vacuum channels as seems practical, and if fewer vacuum stages are needed, less than all of the vacuum channels may be used. For example, which channels are used to create a vacuum may be controlled by a vacuum pump attached to each of the channels. In one such case, a first gas flow subsystem configured for three vacuum stages may also be used for two vacuum stages by simply deactivating the vacuum pump(s) of the channels connected to one of the three stages.

[0049] In the vacuum embodiments described herein, the sample may be held by a vacuum chuck having a higher vacuum below than above, such that the sample is not lifted from the chuck and is in contact with the housing block and / or objective housing through the first medium. Figure 2The chuck 222 shown in the figure can be a vacuum chuck. The chuck can also be a vacuum chuck or an air / vacuum combination chuck. The system can also be configured to actively control the vacuum pressure of the vacuum chuck depending on the vacuum level on the top of the sample. The chuck 222 can alternatively be an electrostatic chuck, including any such chuck suitable for use in a vacuum environment. In this way, the chuck can be configured to hold the sample by electrostatic force. The particle problems associated with electrostatic chucks can be tolerable because, as further described herein, air flushing can be implemented to enclose the chuck and prevent foreign particles from entering. The chuck can be coupled to a scanning subsystem as further described herein, which can be configured to cause light to scan over the sample in any suitable manner. In addition, the chuck can be an R-θ stage configured for rotation and linear motion.

[0050] In another embodiment, the first local volume includes a gap 236 between the housing block 206 and the sample. For example, the housing block of the local vacuum subsystem can be positioned substantially close to the sample without contacting the sample, for example, with an approximately 50um to 1mm gap from the sample. As further described herein, the vacuum can be evacuated by pumping air out of the gap through one or more pumping channels. Due to this small gap, a pressure gradient is established as the air flows from the outside to the center of the objective lens. Thereby, a vacuum is also formed in the volume 214 below the objective lens.

[0051] In some embodiments, the first medium has a refractive index at one or more wavelengths of light directed to and from the region that is less than a refractive index of dry air at the one or more wavelengths. As described above, the first gas flow subsystem is configured to replace the gas with a first medium that scatters less light than gas positioned proximate to the region on the sample, thereby increasing the sensitivity of the system. More specifically, in some embodiments, the first gas flow subsystem is configured to suppress atmospheric Rayleigh light scattering interference in a light scattering-based surface inspection system by replacing normal air present proximate to the region on the sample with a light propagation medium having a lower Rayleigh scattering cross section than normal air.

[0052] In this way, the first medium preferably has a refractive index at the operating wavelength(s) of the inspection subsystem that is lower than the refractive index of dry air at the operating wavelength. For example, the inspection subsystem may operate at ultraviolet (UV) wavelengths. Thus, in one embodiment, the first medium preferably has a refractive index at UV wavelengths that is lower than the refractive index of dry air at the UV wavelengths. In a preferred embodiment, the first medium is a gas with the lowest known Rayleigh cross section for UV wavelengths (e.g., wavelengths down to about 200 nm).

[0053] In one embodiment, the first medium is substantially composed of helium (He). For example, the purpose of the vacuum in the embodiments described herein is to effectively reduce the non-anomalous light scattering that would otherwise be detected by the system in the presence of clean dry air. Therefore, if other media can reduce light scattering to the same extent as vacuum (or, depending on the application, substantially the same extent, if the cost of vacuum implementation is unacceptable, if vacuum implementation is impractical, etc.), other media can be used instead of vacuum. In one such acceptable alternative, vacuum can be replaced with helium flushing. Helium is just as effective in reducing air scattering as vacuum. Specifically, helium molecules are smaller than air molecules, and therefore helium will scatter less light than air in the same manner as vacuum. The first airflow subsystem can be configured to direct helium directly under the objective lens. Helium pressure can push out air through the gap between the housing block and the sample. One advantage of helium flushing is the low pressure required to make the airflow smoother. In addition, using helium instead of vacuum to reduce light scattering due to air may be preferred because it is easier to implement.

[0054] As an alternative to elemental helium, the first medium may consist essentially of neon (Ne). As used herein, the term "consisting essentially of" means comprising one of the gases described above, possibly in combination with other gases present in amounts that do not substantially affect the basic properties of light scattering caused by the first medium. For example, a first medium consisting essentially of elemental helium or neon may include a negligible amount of dry air that does not substantially affect the basic properties of light scattering caused by the first medium. Additional information about how helium and neon can reduce light scattering in an inspection system, thereby increasing the sensitivity of the system, is described in U.S. Patent No. 7,372,559 to Haller et al., issued on May 13, 2008, which is incorporated herein by reference as if set forth in its entirety. The embodiments described herein may be further configured as described in this patent.

[0055] Figure 4 One embodiment of a helium flush is described. Specifically, the first gas flow subsystem may include a channel 400 formed in a housing block 402. The housing block 402 may be coupled to an objective housing 404 as further described herein, such that the two housings are adjacent and abutting, such as by Figure 4 404. In this way, the helium channel can be machined in a separate assembly attached to the objective lens assembly. However, the housing block 402 and the objective lens housing 404 can be formed from a single piece of material and can therefore be a single element in the system. The housing block 402 and the objective lens housing 404 can be further configured as described herein. Although Figure 4 A particular number of helium gas flow channels are shown in FIG. 1 , but the first gas flow subsystem may include any suitable number of channels in any suitable configuration described herein.

[0056] Instead of Figure 2 In the embodiment shown in FIG. 4 , air is generally evacuated from the sample 406, and the channel 400 is configured so that the helium 408 displaces any air or other in the volume 410 between the objective lens 412 and the sample, thereby forming a reduced scattering medium in the volume. For example, each of the channels may be coupled to a helium source (not shown) and one or more other elements that propel the helium through the channel in this manner. The helium source and any other elements (not shown) included in this first gas flow subsystem may include any suitable sources and elements known in the art, and may be selected based on information about the volume between the sample and the objective lens, the required or desired helium pressure level, the configuration of the channel, etc. The first gas flow subsystem may include any other suitable elements (not shown) typically included in gas flow subsystems, such as valves, exhaust elements, controllers, etc.

[0057] Objective lens 412 may be further configured as described herein, and Figure 4 The optical elements of the objective lens 412 shown in FIG. Figure 1 Alternatively, objective 412 may include only one of the several optical elements of the objective shown in FIG. Figure 4 As further described herein, light 414 scattered from the sample may be collected by an objective lens and directed to one or more other elements of the inspection subsystem ( Figure 4 4. (not shown in FIG. 4.) Vertical line 416 indicates the optical axis of the collection / detection subsystem of the inspection subsystem. This embodiment may also include a chuck 418, which may be configured according to any embodiment described herein.

[0058] The system also includes a second gas flow subsystem configured to replace gas in a second local volume proximate to the first local volume with a second medium different from the first medium. Figure 2 , a second gas flow subsystem schematically shown through channel 224 can direct a second medium 226 to a second local volume proximate to the first local volume to thereby replace any gas in the second local volume with the second medium. In another example, as shown in Figure 4, a second gas flow subsystem schematically shown by channel 420 can direct a second medium 422 to a second local volume proximate to the first local volume to thereby replace any gas in the second local volume with the second medium. As shown in such figures, the second gas flow subsystem is configured so that the second medium is close to the objective lens and the objective lens housing and showers around it. The objective lens and sample can be placed in a closed scanning chamber (not shown). The second medium can be brought into the chamber from above and exhausted from below (not shown). In some cases, the second medium can generate a positive pressure (e.g., a pressure of about 10 Pascals to about 100 Pascals above the environment) in the chamber outside the first local volume. Therefore, a new and important feature of the embodiments described herein is that the embodiments are configured to flush the objective lens / sample from the outside while generating a reduced scattering medium (e.g., a partial vacuum) inside between the sample and the objective lens. In this way, the embodiments described herein can use a flushing medium outside a different medium (e.g., a partial vacuum) to keep the sample clean while also reducing scattering. The inventors are not aware of any other architecture that can keep the sample clean while also generating a vacuum.

[0059] In one embodiment, the second medium consists essentially of clean dry air (CDA). In this way, the embodiments described herein may be configured for air flushing with a partial vacuum. Alternatively, the embodiments described herein may be configured for air flushing with a helium flush. In either case, the system may use first and second mediums that are different from each other. In particular, although helium may be used for the first and second mediums, helium is not required for the second medium and would unnecessarily increase the cost of the system compared to using CDA for the second medium. Therefore, the preferred combination of mediums for the embodiments described herein is vacuum or helium used in conjunction with CDA.

[0060] In another embodiment, the second airflow subsystem is configured not to guide the second medium into the path of light guided to the area and the path of light from the area. In some embodiments, the second airflow subsystem is configured to move foreign matter away from the sample with the second medium. For example, the purpose of the second airflow subsystem and the second medium is independent of the imaging performance of the inspection subsystem. Specifically, unlike the first airflow subsystem and the first medium that are intended to improve the sensitivity of the inspection subsystem by reducing light scattering from non-abnormal sources, the second airflow subsystem and the second medium are mainly (and possibly only) used to keep the sample clean. In other words, the second airflow subsystem and the second medium are preferably configured to reduce any falling particles or other foreign matter that may otherwise be deposited on the sample during the inspection process. This foreign matter may come from any possible source, such as foreign matter in a clean room, foreign matter from the inspection subsystem, etc. The second airflow subsystem and the second medium may be configured to have airflow characteristics (e.g., airflow rate, gas pressure, etc.) that promote the movement of foreign matter away from the sample and into an exhaust subsystem (not shown) contained in the second airflow subsystem or coupled to the second airflow subsystem. Therefore, there is no reason to configure the second gas flow subsystem so that it directs the second medium into the path of either the light directed to the sample and / or returned from the sample. In addition, when the second medium is a medium such as CDA, directing the medium into the path of the light in the inspection subsystem may actually be detrimental to the performance of the system.

[0061] The first gas flow subsystem may also be configured so as to effectively prevent the second medium from being positioned in the first local volume surrounding the illuminated area on the sample. For example, if the first medium is a vacuum, then if any of the second medium enters the first local volume, then when the vacuum is created and / or maintained, the second medium will also be removed by the first gas flow subsystem. If the first medium consists essentially of helium, then the first gas flow subsystem may be configured so that the helium properties (e.g., flow rate, pressure, etc.) are such that the helium effectively pushes the second medium out of the first local volume. In this way, the embodiments described herein may be easily configured so that the second medium does not interfere with the performance of the inspection subsystem.

[0062] In a further embodiment, the first and second gas flow subsystems do not change the gas outside the second local volume. For example, in addition to producing, controlling, maintaining, etc. the first and second media in the first and second local volumes, respectively, the first and second gas flow subsystems are not configured to change the gas (ambient gas or other gas) in other parts of the tool. One reason for this is the designed purpose of the gas flow subsystem, that is, it is configured to produce, control, maintain, etc. the first and second media in a relatively specific local volume within the inspection subsystem. Any area in or around the rest of the inspection subsystem (for example, an area outside the second local volume and possibly within the housing of the inspection subsystem) is generally not affected by the first and second gas flow subsystems. The area outside the second local volume can be allowed to remain under the environmental conditions in which the entire inspection subsystem is located. Such a configuration is possible because the first and second gas flow subsystems wish to replace the gas in such a relatively small local volume and for a specific reason. Therefore, the first and second gas flow subsystems can be much cheaper than other systems configured to control the entire inspection subsystem and the entire environment in which the sample is located.

[0063] In additional embodiments, the entire inspection subsystem is not positioned under vacuum. For example, a new and important feature of the embodiments described herein is that the embodiments are configured to create a vacuum only in a localized volume of the inspection tool (i.e., only in a relatively small volume between the objective lens and the sample). Because the vacuum is created in this small volume, the entire sample and inspection subsystem are not necessarily located within the vacuum. This overcomes many disadvantages of currently used inspection systems, such as reduced throughput (e.g., the embodiments described herein do not require time to create a vacuum after the sample is moved into the inspection tool), higher cost (e.g., the embodiments described herein do not require a vacuum housing that is large enough to enclose all of the optical hardware of the tool except the sample and to allow space for the sample to move within the housing), etc. For example, the embodiments described herein are configured to create a vacuum that is sufficient to reduce air scattering detected by the inspection subsystem and thereby achieve a higher sensitivity of the inspection subsystem, while still maintaining a distance between the objective lens and the sample that allows the sample to move and / or rotate.

[0064] In an embodiment, the first and second gas flow subsystems are configured to simultaneously replace the gas in the first and second local volumes, respectively. For example, if such a configuration is desired, one of the gas flow subsystems can be turned off so that it can be used alone. As further described above, the two gas flow subsystems can be used simultaneously without a physical barrier between the different media and the first and second local volumes are directly adjacent to each other because (1) the first gas flow subsystem can be configured to keep the second media outside the first local area, and (2) if the first medium is essentially composed of helium, then if some helium migrates into the second local area, then the performance of the second gas flow subsystem and the second media will not be hindered. In this way, the embodiments described herein can use different media and different gas flow subsystems to achieve superior performance while minimizing cost by customizing the media and gas flow subsystems for specific functions in specific volumes of the inspection subsystem.

[0065] In another embodiment, the first and second gas flow subsystems are configured to control the first and second media during the introduction and generation, respectively. For example, at the beginning of an inspection process performed on a sample, the first and second gas flow subsystems can replace the gas in the first and second partial volumes, respectively. Typically, in the embodiments described herein, the characteristics of the first and second media in the first and second partial volumes should not substantially change during the inspection process. Therefore, the parameters of the first and second gas flow subsystems can be set at the beginning of the process and then not adjusted again until the inspection is completed.

[0066] However, the first and second airflow subsystems may include any sensors or other equipment for monitoring one or more characteristics of the first and second media in the first and second partial volumes, respectively, during the inspection process. A control subsystem (not shown) and / or system of the first and / or second airflow subsystems may then change one or more parameters of the first and / or second airflow subsystems based on any output in response to the monitored one or more characteristics. In this way, the first and second airflow subsystems may be configured to have different values ​​of at least one parameter (e.g., flow rate) of the airflow subsystems during the inspection process. In one such example, if the thickness of the sample changes substantially across the sample, the distance between the objective lens and the sample may change as the inspection subsystem scans across the sample. In such cases, it may be desirable to change the settings of one or more vacuum pumps of the first airflow subsystem during the scan so that the vacuum pressure in the first partial volume is substantially the same throughout the scan of the sample despite changes in the sample thickness.

[0067] In one embodiment, the system includes a chuck configured to support the sample during guiding and generating, the chuck including a recess in which the sample is disposed during guiding and generating, and the recess is configured such that the upper surface of the sample when disposed in the recess is flush with the upper surface of the chuck outside the recess. Figure 2As shown in FIG. 1 , a sample 212 can be placed on a chuck 222 during inspection, and the chuck has a recess 228 in which the sample is placed so that an upper surface 230 of the sample is substantially flush with an upper surface 232 of the chuck outside the recess. In this way, the diameter of the chuck is larger than the diameter of the sample. A groove in the middle seats the sample. The depth of the recess is made close to the thickness of a conventional sample (e.g., a wafer) so that the top surface of the sample is flush with the chuck. Different types of samples may vary in thickness, but such variations will be small relative to the gap between the housing block and the sample and relative to the distance between the objective lens and the sample. The performance of the vacuum can be maintained. The flush design enables the vacuum to be maintained even when scanning at the edge of the sample.

[0068] Figure 5 Further details of the chuck configuration possibilities for the embodiments described herein are described. As described above, the chuck can extend beyond the sample, and the upper surface of the portion of the chuck that extends beyond the sample is preferably flush with the upper surface of the sample. In particular, in order to maintain the vacuum when the objective lens 500 is moved close to the edge of the sample, an extension wing 502 from the chuck and a mount for a spindle element 504 that can rotate about an axis 506 can be included in the chuck assembly. The top surface of the wing 502 is preferably flush with the top surface of the sample 508, as shown in FIG. Figure 5 In this way, a relatively small gap between the housing block and the sample and / or between the housing block and the top surface of the wing can be maintained across the entire diameter (and area) of the sample.

[0069] Being able to maintain this small gap between the housing block and the sample and / or chuck across the entire sample facilitates creating and maintaining a vacuum between the objective lens and the sample, as further described herein, without having to position the entire inspection subsystem and sample in a vacuum. Specifically, the extended wings can help maintain a vacuum seal between the sample and the objective lens even when scanning is performed close to the edge of the sample. Thus, during the entire inspection process performed on the sample, the vacuum can be maintained even if the inspection process scans the edge of the sample, scans close to the edge of the sample, or even scans beyond the edge of the sample. Different types of samples may vary in thickness, but the variation should be small (e.g., about 0.5 mm) compared to the height of the gap. In this way, different parts of the chuck assembly can be fixedly attached to each other without the need for adjustment as further described herein.

[0070] although Figure 5 Objective 500 is shown in a simplified version of housing 510 which together includes the objective housing and vacuum passage 512 formed therein, but the housing is only shown in such a way that it can be shown with enhanced detail relative to the chuck assembly. Figure 5The inspection subsystem and the first and second gas flow subsystems in the system embodiment of the chuck assembly shown in FIG. 1 can be further configured as described herein. In addition, the extended wing included in the chuck assembly can surround the entire sample and only be shown in FIG. 1 for simplicity. Figure 5 In addition, although the chuck and mandrel are Figure 5 1 is shown as a single element in FIG. 1 , but the chuck and spindle may be separate elements coupled in any suitable manner known in the art. Figure 5 The chuck assembly shown in may be further configured as described herein and may be part of a scanning subsystem configured as described herein.

[0071] The chuck may also include two different parts (not shown) that can be adjusted in height relative to each other so that the top surface of a sample having a different thickness is flush with the top surface of a portion that is not below the sample. The system may be configured to control the different parts of the chuck based on a priori information about the sample, such as the expected sample thickness or the thickness of the sample as measured by another tool. The system may also control the different parts of the chuck based on some visual feedback generated by the system itself about the position of the upper surface of the sample relative to the upper surface of the chuck external to the sample. For example, during alignment of the sample to the inspection tool or during a stage of a process performed prior to an inspection scan, the system may illuminate an area of ​​the sample near and beyond the edge of the sample and detect light reflected from the area. The reflected light image may be used to determine whether the upper surface of the sample and the chuck external to the sample are flush and / or whether the depth of the recess should be adjusted so that the two surfaces can be made flush. This function may be similar to the slave focus function performed to focus the sample prior to scanning, but in this case, instead of the chuck moving as a single unit, at least one portion of the chuck moves relative to each other and the height of the upper surface of the sample is positioned relative to the height of the upper surface of the chuck external to the sample rather than relative to the optical hardware.

[0072] Some embodiments of the system include an air bearing positioned outside the first local volume and configured to prevent the first and second airflow subsystems from contacting the sample. For example, the air bearing may be used as a safety guard at the outer ring of the housing block and may also be used to reduce the air gap. In this way, the air bearing may prevent the vacuum housing block from contacting the sample. The outlet of the air bearing may be an array of relatively small holes positioned outside the outermost vacuum stage. The air bearing may include any suitable commercially available vacuum preloaded air bearing known in the art. The air bearing is optional but may provide significant benefits to the embodiments described herein. For example, without an air bearing, a relatively large gap (e.g., hundreds of microns) may be required between the housing block and the sample to prevent the housing block from colliding into the sample. With an air bearing, the gap may be reduced to tens of microns.

[0073] Figure 6One possible implementation including an air bearing is shown. As with other embodiments described herein, the first airflow subsystem may include a housing block 600. A plurality of channels 602 are formed in the housing block and connected to a vacuum pump 604 so that it can, in combination, push air out of the housing block (and the objective lens ( Figure 6 The air bearing may include a first local volume 606 between the housing block (not shown) and the sample 608. The air bearing may include a channel 610 formed in the housing block and positioned outside any channels included in the first gas flow subsystem (e.g., outside any vacuum channels or helium flush channels). The channel may be coupled to a pressurized air source 612 and any other suitable gas flow elements (not shown), such as those further described herein.

[0074] The air bearing can be configured to direct pressurized air from the source through the channel and out of the outlet of the channel formed in the housing block. In this way, the pressurized air 614 can be forced into the gap between the outer edge of the housing block and the sample, which should reduce the possibility of the housing block contacting the sample for any reason (such as the vacuum created by the first air flow medium).

[0075] This pressurized air is preferably different from any CDA used by the second air flow subsystem. For example, the pressurized air of the air bearing is used to maintain a suitable gap between the housing block and the sample, especially near the edge of the housing block, while the CDA used as the second medium is used to reduce extraneous contamination on the sample. Thus, the pressurized air and CDA can have different characteristics (such as pressure, airflow direction, composition, etc.).

[0076] In some embodiments, the first gas flow subsystem includes a housing block through which the gas is replaced with the first medium, and the inspection subsystem is configured to direct light to the area through one or more passages formed through the housing block. For example, the housing block and any of the first and second gas flow subsystems formed therein and / or coupled thereto (including any pump outlets, gas flow channels, channel inlets, etc.) may be configured so that light can be directed to the sample and collected from the sample in any configuration selected. In one such example, the pump outlet of the channel for the first gas flow subsystem formed in the housing block may be solid in a certain azimuthal region to allow a hole to be drilled through which illumination passes and a reflected light beam exits. For example, in Figure 1 In the embodiment shown in , light from the light source 100 is shown as being directed to the sample through the housing block 108, which may include a passageway (not shown) configured to allow light to pass therethrough. The passageway may be an open channel having a window proximate the sample end of the channel so that the channel does not affect the first medium formed in the first local volume. The passageway may be formed in the housing block in any of the same manners described herein with respect to the channel of the first gas flow subsystem, except that it is sealed in some manner at the sample end of the passageway.

[0077] In another embodiment, the system includes a window element positioned between the objective lens of the inspection subsystem and the sample and configured to transmit light from the region without modifying the light. For example, a hemispherical dome window may be used with a stronger glass such as sapphire, independent of the lens housing. Examples of such a window element are respectively Figure 2 and 4 4 and 5. As shown in these figures, the hemispherical dome window is positioned between the objective lens and the sample, so the first medium will replace any gas inside the dome window and between the dome window and the sample. The benefit of using an additional dome window is to reduce any stress on the optical element by using stronger glass. The additional dome window can have two conformal and concentric surfaces with the center of curvature at the sample surface to minimize optical aberrations.

[0078] The computer subsystem may be configured to generate results for the sample, which may include any information described herein, such as any defect and / or particle information, mapping of defect and / or particle information across samples, etc. Results for anomalies may include, but are not limited to, the location of the anomaly, a detection score, information about the defect and / or particle classification (e.g., a class label or ID, etc.), or any such suitable information known in the art. Results for the sample may be generated by the computer subsystem in any suitable manner.

[0079] All embodiments described herein can be configured to store the result of one or more steps of the embodiment in a computer-readable storage medium. The result can include any one of the result described herein and can be stored in any manner known in the art. The result of the sample can have any suitable form or format (such as standard file type). The storage medium can include any storage medium described herein or any other suitable storage medium known in the art. After the result has been stored, the result can be accessed in the storage medium and used by any one of the method described herein or the system embodiment, formatted to be displayed to the user, used by another software module, method or system, etc., to perform one or more functions of another sample of the sample or the same type.

[0080] Such functions include, but are not limited to, changing a process (e.g., a manufacturing process or step) that has been or will be performed on a sample in a feedback or feedforward manner, etc. For example, the computer subsystem may be configured to determine one or more changes to a process that has been performed on a sample and / or a process that will be performed on a sample based on an anomaly. The change in process may include any suitable change to one or more parameters of the process. The computer subsystem preferably determines the change so that the anomaly can be reduced or prevented on other samples on which the revised process is performed, the anomaly can be corrected or eliminated on the sample in another process performed on the sample, the anomaly can be compensated in another process performed on the sample, etc. The computer subsystem may determine such changes in any suitable manner known in the art.

[0081] Those changes may then be sent to a semiconductor manufacturing system (not shown) or a storage medium (not shown) accessible to both the computer subsystem and the semiconductor manufacturing system. The semiconductor manufacturing system may or may not be part of the system embodiments described herein. For example, the inspection subsystem and / or computer subsystem described herein may be coupled to the semiconductor manufacturing system, for example, via one or more common elements such as a housing, a power supply, a sample handling device or mechanism, etc. The semiconductor manufacturing system may include any semiconductor manufacturing system known in the art, such as a lithography tool, an etching tool, a chemical mechanical polishing (CMP) tool, a deposition tool, and the like.

[0082] Unless otherwise mentioned herein, each embodiment described herein can be combined together into a single embodiment. The embodiments described herein can also be configured as described in each of the following patents: U.S. Patent No. 6,813,026 to McAninch, issued on November 2, 2004; U.S. Patent No. 7,359,052 to Fielden et al., issued on April 15, 2008; U.S. Patent No. 7,420,681 to Wang et al., issued on September 2, 2008; U.S. Patent No. 7,564,552 to Fielden et al., issued on July 21, 2009; U.S. Patent No. 20 No. 7,623,239 to Fielden et al., issued on November 4, 2009; No. 7,755,764 to Kwak et al., issued on July 13, 2010; No. 7,764,376 to Fielden et al., issued on July 27, 2010; and No. 11,315,816 to Pressburger et al., issued on April 26, 2022, all of which are incorporated herein by reference as if fully set forth.

[0083] Another embodiment relates to a method for inspecting a sample. The method includes directing light to an area on the sample and generating an output in response to the light from the sample, which can be detected by an inspection subsystem (e.g., Figure 1 The method also includes replacing the gas in a first local volume surrounding the area on the sample with a first medium during the introduction and generation, which can be performed by a first gas flow subsystem (e.g. Figure 2 and 4 The first medium scatters less light than the gas. In addition, the method includes replacing the gas in the second local volume positioned proximate to the first local volume with the second medium during the guiding and generating, which can be performed by the second gas flow subsystem (e.g., Figure 2 and 4 The second medium is different from the first medium. The method further includes detecting an abnormality on the sample based on the output. The detection is performed by a computer system (e.g., Figure 1 Executed by the computer subsystem 122 shown in FIG.

[0084] Each step of the method may be performed as further described herein. The method may also include any other step(s) that may be performed by the system(s) described herein. The steps of the method may be performed by the system described herein, which may be configured according to any embodiment described herein.

[0085] Additional embodiments relate to a non-transitory computer-readable medium storing program instructions executable on a computer system for performing a computer-implemented method for testing a sample. Figure 7 In particular, as shown in Figure 7 , a non-transitory computer-readable medium 700 includes program instructions 702 executable on a computer system 704. The computer-implemented method may include any step(s) of any method(s) described herein.

[0086] Program instructions 702 implementing methods such as those described herein may be stored on computer readable medium 700. The computer readable medium may be a storage medium such as a magnetic or optical disk, tape, or any other suitable non-transitory computer readable medium known in the art.

[0087] The program instructions may be implemented in any of a variety of ways, including process-based techniques, component-based techniques, and / or object-oriented techniques, etc. For example, the program instructions may be implemented using ActiveX controls, C++ objects, JavaBeans, Microsoft Foundation Classes ("MFC"), SSE (Streaming SIMD Extensions), or other techniques or methodologies as appropriate.

[0088] Computer system 704 may be configured according to any of the embodiments described herein.

[0089] In view of this description, further modifications and alternative embodiments of various aspects of the present invention will be understood by those skilled in the art. For example, methods and systems for testing samples are provided. Therefore, this description should be understood only as illustrative and for the purpose of teaching those skilled in the art to implement the general mode of the present invention. It should be understood that the form of the present invention shown and described herein should be regarded as the current preferred embodiment. All as those skilled in the art will understand after benefiting from this description of the present invention, elements and materials can replace the elements and materials illustrated and described herein, parts and processes can be reversed, and certain features of the present invention can be utilized independently. Without departing from the spirit and scope of the present invention as described in the appended claims, changes can be made to the elements described herein.

Claims

1. A system configured for testing a sample, comprising: an inspection subsystem configured for directing light to an area on the sample and for generating an output in response to light from the area on the sample; a first gas flow subsystem configured to replace the gas with a first medium that scatters the light less than the gas in a first local volume surrounding the area on the sample; a second gas flow subsystem configured to replace the gas in a second local volume proximate the first local volume with a second medium different from the first medium; and A computer subsystem is configured to detect an anomaly on the sample based on the output.

2. The system of claim 1, wherein the first medium consists essentially of helium. The system of claim 1 , wherein the first medium is a vacuum.

4. The system of claim 1, wherein the first gas flow subsystem includes a plurality of channels for replacing the gas with the first medium, and wherein the first gas flow subsystem is further configured to cause the first medium to have different values ​​of a characteristic proximate two or more of the plurality of channels.

5. The system of claim 4, wherein the first medium is a vacuum, and wherein the property is pressure.

6. The system of claim 1, wherein the first medium has a refractive index at one or more wavelengths of the light directed to and from the region that is less than a refractive index of dry air at the one or more wavelengths.

7. The system of claim 1, wherein a height of the first local volume is defined by a distance between an objective lens of the inspection subsystem and the sample.

8. The system of claim 1, wherein the second medium consists essentially of clean dry air.

9. The system of claim 1, wherein the second airflow subsystem is further configured to not direct the second medium into a path of the light directed to and from the area.

10. The system of claim 1, wherein the second gas flow subsystem is further configured to move foreign matter away from the sample with the second medium.

11. The system of claim 1, wherein the first and second gas flow subsystems do not modify the gas outside the second local volume.

12. The system of claim 1, wherein the entire inspection subsystem is not positioned within a vacuum.

13. The system of claim 1, wherein the first and second gas flow subsystems are further configured to simultaneously replace the gas in the first and second local volumes, respectively.

14. The system of claim 1, wherein the first and second airflow subsystems are further configured for controlling the first and second media, respectively, during the directing and the generating.

15. The system of claim 1 , further comprising a chuck configured to support the sample during the guiding and the generating, wherein the chuck comprises a recess in which the sample is disposed during the guiding and the generating, and wherein the recess is configured such that an upper surface of the sample, when disposed in the recess, is flush with an upper surface of the chuck outside the recess.

16. The system of claim 1, further comprising an air bearing positioned outside of the first local volume and configured to prevent the first and second air flow subsystems from contacting the sample.

17. A system according to claim 1, wherein the first gas flow subsystem includes a housing block through which the gas is replaced with the first medium, and wherein the inspection subsystem is further configured to direct the light to the area through one or more passages formed through the housing block.

18. The system of claim 1, further comprising a window element positioned between an objective lens of the inspection subsystem and the sample and configured to transmit the light to and from the area without altering the light.

19. A non-transitory computer readable medium storing program instructions executable on a computer system for performing a computer-implemented method for testing a sample, wherein the computer-implemented method comprises: directing light to an area on a sample and generating an output in response to light from the area on the sample; replacing gas in a first local volume surrounding the area on the sample with a first medium during the directing and the generating, wherein the first medium scatters the light less than the gas; replacing the gas in a second partial volume located proximate to the first partial volume with a second medium during the directing and the generating, wherein the second medium is different from the first medium; and Anomalies are detected on the sample based on the output.

20. A method for testing a sample, comprising: directing light to an area on a sample and generating an output in response to light from the area on the sample; replacing gas in a first local volume surrounding the area on the sample with a first medium during the directing and the generating, wherein the first medium scatters the light less than the gas; replacing the gas in a second partial volume located proximate to the first partial volume with a second medium during the directing and the generating, wherein the second medium is different from the first medium; and An abnormality is detected on the sample based on the output, wherein the detecting is performed by a computer system.

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