Gas flow configuration for semiconductor inspection

Abstract

Methods and systems for inspecting a specimen are provided. One system includes an inspection subsystem configured to guide light into a region on the specimen and to generate an output that responds to light from the region on the specimen. The system further includes a first gas flow subsystem configured to replace a gas in a first local volume surrounding a region on the specimen with a first medium that scatters light less than the gas. Additionally, the system includes a second gas flow subsystem configured to replace a gas in a second local volume adjacent 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 specimen based on the output.

Description

Technology Field

[0001] The present invention generally relates to an inspection system comprising a gas flow subsystem for reducing non-specimen-induced light scattering and foreign substance contamination of a specimen under inspection. Background Technology

[0002] The following descriptions and examples are not to be recognized as prior art simply because they are included in this section.

[0003] Manufacturing semiconductor devices, such as logic and memory devices, typically involves processing a substrate, such as a semiconductor wafer, using a large number of semiconductor manufacturing processes to form various features and multiple levels of the semiconductor device. For example, lithography is a semiconductor manufacturing process that includes the step of transferring a pattern from a reticle onto a resist arranged on a semiconductor wafer. Further examples of semiconductor manufacturing processes include, but are not limited to, chemical-mechanical polishing (CMP), etching, deposition, and ion implantation. A number of semiconductor devices may be manufactured arranged on a single semiconductor wafer and then separated into individual semiconductor devices.

[0004] Inspection processes are used to detect defects on wafers and other substrates at various stages of the semiconductor manufacturing process, achieving higher yields and consequently generating higher profits. Inspection has always been a critical part of manufacturing semiconductor devices such as ICs. However, as the size of semiconductor devices decreases, inspection becomes even more critical for successfully manufacturing acceptable semiconductor devices, as smaller defects can cause the device to fail.

[0005] Particles are critical defects in semiconductor manufacturing. 10 nm particles can break or short-circuit in devices with a 20 nm critical dimension (CD). With the introduction of extreme ultraviolet (EUV) lithography, the scaling of CDs continues slowly but steadily. The need to inspect much smaller particles is approaching.

[0006] The method currently used to detect particles involves measuring scattered light under dark field (DF) optics. Laser light is shone obliquely onto the wafer. Mirror reflections are discarded, and the scattered light is collected through the objective lens. The scattered light includes particles, wafer irradiance, and light from the air through which the light passes. To achieve the required signal-to-noise ratio (SNR), light scattered from surface irradiance and air must be suppressed. Air scattering is generally small and is not a concern until the particles of interest are reduced to 10 nm or less. An effective method to reduce air scattering is to lower the air density by creating a vacuum between the objective lens and the wafer. Some next-generation particle inspection tools are expected to require a vacuum of approximately 10 Torr (about 1% of atmospheric pressure) from the specimen to about 1 mm above the specimen.

[0007] To create a vacuum, currently used methods and systems construct a sealed chamber and make its interior a vacuum. Inspection modules, such as chucks, stages, and objective lenses, will be placed inside the chamber or at least partially inside the chamber. Examples of currently used methods to create such a vacuum environment for semiconductor applications are U.S. Patent No. 5,536,330 of Chen et al., issued July 16, 1996, and

[0008] 7,001,491 of Lombardi et al., published on February 21, 2006, is described and incorporated by reference as fully specified herein.

[0009] The biggest problem with currently used vacuum configurations is the difficulty of maintaining cleanliness. For example, current semiconductor yield tools operating in a vacuum are typically two to three times dirtier than the cleanest particle inspection tools currently on the market. Currently, surface inspection tools achieve excellent cleanliness by using purging air to spray around the wafer, effectively pushing away any particles falling on it. In the case of current vacuum configurations, implementing air purification would be impossible because the entire wafer is under vacuum. Another problem is the cost of current vacuum configurations. Vacuum will dramatically increase the cost of the tool size, stage, chuck, and objective lens. Throughput will be severely impacted by the extra time required to create a vacuum every time a new wafer is loaded. While this may be less of a problem for relatively low-throughput tools such as electron beam inspectors and defect inspection tools, it can be a significant issue for high-throughput tools like particle inspection tools, as their throughput is typically around 10 to 100 wafers per hour.

[0010] Therefore, it would be advantageous to develop a system and / or method for inspecting specimens that are non-defective and / or have reduced particle light scattering and foreign substance contamination, and that do not have one or more of the disadvantages described above.

[0011] The following description of various embodiments should not be interpreted in any way as limiting the invention of the appended claims.

[0012] One embodiment relates to a system configured to inspect a specimen. One system includes an inspection subsystem configured to guide light into a region on the specimen and to generate an output that responds to light from the region on the specimen. The system further includes a first gas flow subsystem configured to replace a gas in a first local volume surrounding a region on the specimen with a first medium that scatters light less than the gas. Additionally, the system includes a second gas flow subsystem configured to replace a gas in a second local volume adjacent 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 specimen based on the output. The system may also be configured as disclosed herein.

[0013] Another embodiment relates to a method for inspecting a specimen. The method includes the steps of directing light onto an area on the specimen and generating an output that responds to the light from the area on the specimen. The method further includes the step of replacing a gas within a first local volume surrounding an area on the specimen with a first medium during directing and generating. The first medium scatters light less than the gas. Additionally, the method includes the step of replacing a gas within a second local volume located adjacent to the first local area with a second medium during directing and generating. The second medium is different from the first medium. The method further includes the step of detecting abnormalities on the specimen based on the output. The detection is performed by a computer system.

[0014] The steps of the method may also be performed as described herein. The method may include any other step(s) of any other method(s) described herein. The method may be performed by any system described herein.

[0015] Additional embodiments relate to a non-transient computer-readable medium storing program instructions executable on a computer system for performing a computer-implemented method for inspecting a specimen. The computer-implemented method comprises the steps of the method described above. The computer-readable medium may be further configured as described herein. The steps of the computer-implemented method may be performed as further described herein. Additionally, the computer-implemented method in which the program instructions are executable may include any other step(s) of any other method(s) described herein. Brief explanation of the drawing

[0016] Other objects and advantages of the invention will become apparent from reading the following detailed description and referring to the attached drawings: FIG. 1 is a schematic diagram illustrating a side view of an embodiment of a system configured to inspect a specimen. FIGS. 2 to 6 are schematic diagrams illustrating cross-sectional views of various embodiments of parts of a system configured to use different media to inspect a specimen and to reduce light scattering and the introduction of foreign substances during inspection. FIG. 7 is a block diagram illustrating an embodiment of a non-transient computer-readable medium storing program instructions executable on a computer system for performing one or more of the computer implementation methods disclosed herein. Although various modifications and alternative forms of the invention are possible, specific embodiments thereof are illustrated by way of example in the drawings and will be described in detail herein. However, it should be understood that the drawings and the detailed description thereof are not intended to limit the invention to the specific forms disclosed, but are intended to encompass all modifications, equivalents, and alternatives within the spirit and scope of the invention as defined by the appended claims. Specific details for implementing the invention

[0017] Moving on to the drawings, it should be noted that they are not drawn to scale. In particular, the scale of some of the components in the drawings is greatly exaggerated to emphasize the characteristics of those components. It should also be noted that the drawings are not drawn to the same scale. Components that may be similarly constructed and depicted in more than one drawing are indicated using the same reference number. Unless otherwise specified herein, any components described and depicted may include any suitable commercially available components.

[0018] The embodiments described herein generally relate to systems and methods for inspecting specimens. For example, the embodiments described herein provide methods and systems for using two different media (e.g., applying purified air and creating a local vacuum or applying a helium medium) for particle inspection equipment. To manufacture next-generation particle inspection tools, the tool must be equipped with means for reducing air scattering (e.g., through a vacuum or another medium that scatters less light than air) and means for keeping the tool clean (e.g., through purified air). Although the two requirements may appear contradictory, the inventors have created the system architectures described herein that make it possible to satisfy both requirements. The embodiments described herein have numerous advantages and improvements over currently available inspection tools. For example, the embodiments allow for the creation of a substantially small volume vacuum between the specimen and the objective lens, eliminating the overhead time required to pump a large vacuum chamber. The embodiments also allow purified clean air around the specimen to keep the specimen clean.

[0019] While 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 specimen inspectors, metrology tools, optical defect inspection tools, etc.

[0020] In one embodiment, the specimen is a wafer. The wafer may include any wafer known in the semiconductor industry. While some embodiments may be described herein in relation to wafers or wafers, the embodiments are not limited to specimens in which they may be used. For example, the embodiments described herein may be used for specimens such as reticles, flat panels, personal computer (PC) boards, and other semiconductor specimens.

[0021] A system configured to inspect a specimen includes an inspection subsystem configured to direct light to a region on the specimen and to generate an output in response to light from the region on the specimen. The inspection subsystem includes, at least, a light source configured to generate light directed to a region on the specimen and a detection subsystem configured to detect light from the specimen and to generate an output in response to the detected light. An embodiment of such a system is illustrated in FIG. 1.

[0022] As illustrated in FIG. 1, the lighting subsystem includes a light source (100). The lighting subsystem is configured to direct light generated by the light source to an area (not shown) on a specimen at one or more angles of incidence, which may include one or more oblique angles and / or one or more vertical angles. The area may be a relatively large spot, one or more spots, a field, a line, etc. For example, as illustrated in FIG. 1, light from the light source (100) is directed at an oblique angle of incidence through an optical element (102) and then through a lens (104) to the specimen (106). The angle of incidence may include any suitable angle of incidence, which may vary, for example, depending on the characteristics of the specimen and the process to be performed on the specimen.

[0023] The illumination subsystem may be configured to direct light toward a specimen at different angles of incidence at different times. For example, the imaging subsystem may be configured to change one or more characteristics of one or more elements of the illumination subsystem so that light may be directed toward the specimen at an angle of incidence different from that shown in FIG. 1. As an example of this, the inspection subsystem may be configured to move the light source (100), optical element (102), and lens (104) to direct light toward the specimen at different angles of incidence.

[0024] In some cases, the inspection subsystem may be configured to direct light toward a specimen at more than one angle of incidence simultaneously. For example, the illumination subsystem may include more than one illumination channel, one of which may include a light source (100), an optical element (102), and a lens (104) as illustrated in FIG. 1, and another of which may include similar elements configured differently or identically, or at least a light source and possibly one or more other components such as those further described herein. When such light is directed toward a specimen as different light simultaneously, one or more characteristics (e.g., wavelength, polarization, etc.) of the light directed toward the specimen at different angles of incidence may differ, and thus the light from the illumination of the specimen at different angles of incidence may be distinguished from one another at the detector(s).

[0025] In another example, the lighting subsystem may include only one lighting source (e.g., the lighting source (100) shown in FIG. 1), and light from the light source may be separated into different light paths (e.g., based on wavelength, polarization, etc.) by one or more optical elements (not shown) of the lighting subsystem. Then, light in each of the different light paths may be directed toward a specimen. Multiple lighting channels may be configured to direct light toward the specimen simultaneously or at different times (e.g., when different lighting channels are used to sequentially illuminate the specimen). In other cases, the same lighting channel may be configured to direct light toward the specimen with different characteristics at different times. For example, the optical element (102) may be configured as a spectral filter, and the characteristics of the spectral filter may be changed in various different ways (e.g., by replacing the spectral filter) so that light of different wavelengths may be directed toward the specimen at different times. The illumination subsystem may have any other suitable configuration known in the art to direct light having different or identical characteristics onto a specimen sequentially or simultaneously at different or identical angles of incidence.

[0026] The light source (100) may include any suitable light source, such as any suitable laser known in the art, configured to generate light at any suitable wavelength(s) known in the art. The laser may be configured to generate monochromatic or nearly monochromatic light. Additionally, the laser may be a mode-locked laser. The light source may also include a polychromatic light source that generates light at a plurality of discrete wavelengths or wavelength bands.

[0027] Light from the optical element (102) can be focused onto the specimen (106) by the lens (104). Although the lens (104) is illustrated in FIG. 1 as a single refractive optical element, in practice, the lens (104) may include a plurality of refractive and / or reflective optical elements in combination to focus light from the optical element onto the specimen. The illumination subsystem illustrated in FIG. 1 and described herein may include any other suitable optical element (not shown). Examples of such optical elements include, but are not limited to, polarizing components(s), spectral filters(s), spatial filters(s), reflective optical elements(s), apodizer(s), beam splitters(s), aperture(s), etc., and may include any such suitable optical element known in the art. Additionally, the system may be configured to change one or more of the elements of the illumination subsystem based on the type of illumination to be used for imaging. Furthermore, the illumination subsystem may be configured to direct light to only one area on the specimen or to one or more areas on the specimen. The domain(s) may have all suitable characteristics known in the relevant technical field.

[0028] The inspection subsystem may also include a scanning subsystem configured to allow light to be scanned over a specimen. For example, the inspection subsystem may include a stage (not shown in FIG. 1) upon which the specimen (106) is placed. The scanning subsystem may include any suitable mechanical and / or robotic assembly (including the stage) configured to move the specimen so that light can be scanned over the specimen. Additionally or alternatively, the inspection subsystem may be configured such that one or more optical elements of the inspection subsystem perform partial scanning of the light over the specimen. The light may be scanned over the specimen in any suitable manner. The stage may be further configured as described herein.

[0029] The detection subsystem may include one or more detection channels. At least one of the detection channel(s) includes a detector configured to detect light from a specimen resulting from illumination of the specimen by an illumination subsystem and to generate an output in response to the detected light. For example, the detection subsystem illustrated in FIG. 1 includes a detection channel formed by an objective lens (112), a tube lens (116), an element (118), and a detector (120). As illustrated in FIG. 1, the detection channel is configured to detect light scattered from the specimen. In this way, the detection channel can be configured for dark-field (DF) imaging.

[0030] The detection subsystem may also include one or more detection channels (not shown) for collecting and detecting light at different collection angles. In some cases, 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 wafer. However, two or more of the detection channels may be configured to detect the same type of light (e.g., scattered light) from the specimen. Although the objective lens and the tube lens are illustrated in FIG. 1 as comprising a specific number of refractive optical elements having a specific shape, the objective lens and the tube lens may each comprise one or more refractive optical element(s) and / or one or more reflective optical element(s) having any suitable configuration known in the art.

[0031] One or more detection channels may include any suitable detector known in the art, such as a photo-multiplier 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 detector may be configured to detect specific characteristics of scattered light, such as intensity, but may not be configured to detect these characteristics as a function of position within the imaging plane. Thus, the output generated by each detector included in each detection channel may be a signal or data, rather than an image signal or image data. In this case, a computer subsystem, such as the computer subsystem (122) of the system, may be configured to generate an image of the specimen from the non-imaging output of the detector. However, in other cases, the detector may be configured as an imaging detector configured to generate an imaging signal or image data. Accordingly, the system may be configured to generate the outputs and / or images described herein in a number of ways.

[0032] The inspection subsystem may be configured to generate outputs, e.g., images, of a specimen having multiple modes. Generally, a “mode” is defined by the value of a parameter of the inspection subsystem used to generate an output for the specimen. Thus, the modes may differ in the value for at least one of the parameters of the illumination and detection subsystems (other than the location on the specimen where the output is generated). For example, different modes may use different wavelengths of light for illumination. The modes may differ in illumination wavelength(s) 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. As such, different illumination channels may be used for different modes. The modes may also, or alternatively, differ in one or more acquisition / detection parameters of the detection subsystem. The modes may differ in any one or more modifiable parameters of the system (e.g., illumination polarization(s), angle(s), wavelength(s), etc.; detection polarization(s), angle(s), wavelength(s), etc.). The inspection subsystem may scan the specimen in different modes of the same scan or different scans, for example, depending on the ability to use multiple modes to scan the specimen simultaneously.

[0033] FIG. 1 is provided herein to schematically illustrate the configuration of an inspection subsystem that may be included in the system embodiments described herein. Clearly, the inspection subsystem configuration described herein may be modified to optimize the performance of the system as is typically done when designing commercial systems. Additionally, the systems described herein may be implemented using existing inspection systems, such as the SPx series tools commercially available from KLA Corp. in Milpitas, California, which are capable of detecting significantly small particles up to about 10 nm (e.g., by adding the functions described herein to existing optical systems). For some of these systems, the methods described herein may be provided as optional functions of the system (e.g., in addition to other functions of the system). Alternatively, the systems described herein may be designed "from scratch" to provide entirely new systems.

[0034] The system further includes a computer subsystem configured to detect abnormalities on a specimen based on output. For example, the system may include a computer subsystem (122) coupled to a 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 specimen. The computer subsystem may be configured to detect abnormalities on the specimen by applying a defect detection method to the output generated by the detector. Detecting abnormalities on the specimen may be performed in any suitable manner known in the art, accompanied by any suitable defect detection method and / or algorithm (e.g., applying a defect detection threshold to the output and determining that any output having a value above the threshold corresponds to an abnormality or potential abnormality). The computer subsystem (122) may be configured to perform any other functions further described herein. This computer subsystem may also be configured as described herein.

[0035] The term “anomaly” as used herein is defined as an example of specimen characteristics that differ from what is generally intended or expected. Examples of anomalies that may be detected by the embodiments described herein include the presence of particles on the specimen (e.g., droplets on particles, foreign matter, etc.), defects (e.g., defects in one or more materials formed on the specimen, whether patterned or unpatterned), etc. Generally, the embodiments described herein may be configured to detect different types of anomalies depending on the anomalies of interest and specimen characteristics (e.g., type, layer, etc.). In other words, the embodiments described herein are not limited to the types of anomalies that may be configured to detect.

[0036] 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 system(s) disclosed herein may take a number of forms, including personal computer systems, image computers, mainframe computer systems, workstations, network appliances, internet appliances, or other devices. Generally, the term “computing system” may be broadly defined to encompass any device having one or more processors that execute instructions from a memory medium. The computer subsystem(s) or system(s) may also include any suitable processor known in the art, such as a parallel processor. Additionally, the computer subsystem(s) or system(s) may include a computer platform equipped with high-speed processing and software as a standalone or networked tool.

[0037] As described in this specification, the system is configured as an inspection system. In other embodiments, the system may be configured as a measurement or defect review system. In particular, an embodiment of the system illustrated in FIG. 1 may be modified with one or more parameters to provide different imaging capabilities depending on the application in which it is to be used. In one such example, the optical subsystem illustrated in FIG. 1 may be configured to have higher resolution when it is used for measurement or defect review rather than inspection. In other words, the embodiments of the inspection subsystem illustrated in FIG. 1 describe somewhat general and varied configurations for the optical subsystem, which can be customized in a number of ways that will be obvious to a person skilled in the art to create systems with different imaging capabilities that are more or less suitable for different applications.

[0038] The system further comprises a first gas flow subsystem configured to replace the gas within a first local volume surrounding a region on the specimen with a first medium that scatters less light than the gas. The first local volume may have a height defined by the space between the objective lens of the inspection subsystem (e.g., the objective lens (112) shown in FIG. 1) and the upper surface of the specimen. The first local volume may be centered substantially on the region (or regions) illuminated on the specimen, but does not need to be centered precisely on the region (or regions). The first local volume preferably surrounds the region to the extent that any light from the specimen collected by the inspection subsystem travels entirely from the specimen to the objective lens within the first medium. Thus, the width of the first local volume may depend on the collection angles (angles at which light is collected from the specimen 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 region (or regions) on the specimen. Therefore, the dimensions of the first local volume may vary depending on the configuration of the inspection subsystem and how close the specimen is positioned to the objective lens.

[0039] In one embodiment, the first medium is a vacuum. For example, the vacuum may be aspirated by pumping air from the first local volume through one or more pumping channels. Generally, as illustrated in FIG. 1, the first gas flow subsystem comprises a housing block (108) having a plurality of channels (110) formed therein, through which the first gas flow subsystem can replace the gas within the first local volume surrounding the area illuminated on the specimen by the inspection subsystem with a first medium that scatters light less than the gas. The housing block (108) may be separate from the objective lens housing (114) illustrated in FIG. 1, but all of these elements, the plurality of channels (110), and the first gas flow subsystem may also be configured as described herein. The system embodiment illustrated in FIG. 1 may also be further configured as described herein using additional elements not illustrated in FIG. 1 for clarity only.

[0040] FIG. 2 illustrates a further detailed view of the first gas flow subsystem illustrated in FIG. 1, configured to create a local vacuum between the objective lens and the specimen. In particular, the first gas flow subsystem may include a plurality of channels (200, 202, 204) formed within a housing block (206). The vacuum channels may be perforated into the housing block (206), which may be formed from 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), so that the two housings are adjacent to and border each other, as shown by the dashed line between the housings in FIG. 2. In this case, the dashed line between the housing block (206) and the objective lens housing (208) can function as a boundary between the objective lens housing and the air channel housing. However, the housing block (206) and the objective lens housing (208) may be formed from a single piece of material and thus may be a single element within the system. For example, the air channels may be machined as an integrated part of the objective lens assembly. Generally, as long as the housing block (206) and the objective lens housing (208) can be configured not to allow air flow between the housings, the housing block and the objective lens housing may be manufactured in various ways depending, for example, the material requirements of the housings, the complexity of manufacturing both as a single part, the difficulty of combining separate housings to eliminate air flow between the housings, etc.

[0041] As additionally illustrated in FIG. 2, a plurality of channels are configured so that air (210) can be drawn out through the channels away from the specimen (212) and out of the volume (214) between the objective lens (216) and the specimen, thereby forming a vacuum between the objective lens (216) and the specimen. For example, each of the plurality of channels may be coupled to a vacuum pump (not shown in FIG. 2) that draws air through the channels in this manner. The vacuum pump may be any suitable vacuum pump known in the art and may be selected based on information regarding the volume between the specimen and the objective lens, the requested or required vacuum level, the configuration of the channels, etc. The first gas flow subsystem may include any other suitable element (not shown) typically included in a vacuum system, such as a valve, exhaust element, controller, etc. The vacuum created within 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 contained.

[0042] The objective lens (216) may also be configured as described herein, and the optical element of the objective lens (216) shown in FIG. 2 may be only one of the multiple optical elements of the objective lens shown in FIG. 1. For example, the optical element of the objective lens (216) shown in FIG. 2 may be the element of the objective lens (112) shown in FIG. 1 that is closest to the specimen. Alternatively, the objective lens (216) may include only the single optical element shown in FIG. 2. As further described herein, light (218) scattered from an area illuminated on the specimen may be collected by the objective lens and directed toward one or more other elements of the inspection subsystem. A vertical line (220) indicates the optical axis of the collection / detection subsystem of the inspection subsystem.

[0043] In an additional embodiment, the first gas flow subsystem comprises 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 characteristics close to two or more of the plurality of channels. In one such embodiment, the first medium is a vacuum, and the characteristic is pressure. In this way, the first gas flow subsystem may be configured to generate a vacuum of multiple stages using pumping of multiple stages. FIG. 3 illustrates the results of a numerical simulation performed on one embodiment of a vacuum of multiple stages achievable by the embodiments described herein. This figure illustrates the capabilities of the embodiments described herein estimated by simulation. In this figure, the first gas flow subsystem has three pumping stages. The first stage reduces the air pressure by 90% from 101 kPa at the edge position (300) of the housing block (302) to ~10 kPa at the position (304) near the inlet of the channel (306) of the first gas flow subsystem. The second stage reduces the air pressure from ~10 kPa at position (304) to ~1.3 kPa at position (308) near the inlet of channel (310) of the first gas flow subsystem, and the third stage reduces it by 56% from ~1.3 kPa at position (308) to ~0.6 kPa at position (312) near the inlet of channel (314) of the gas flow subsystem. The third stage may be less efficient than the first two stages because the air near the center becomes much thinner due to the first two stages.

[0044] The pressure values ​​described above are merely non-limiting examples of possible vacuum levels in the embodiments described herein. The vacuum pressure is adjustable based on the use case (e.g., the required amount of air scattering reduction, which may vary, for example, depending on the wafer haze level). Furthermore, the term “vacuum” as used in this document is not intended to mean a perfect or complete vacuum, as indicated by the vacuum pressure values ​​described above. Instead, “vacuum” as used herein is generally defined as a medium having a pressure below atmospheric pressure, and any vacuum pressure described herein may be selected by the user when configuring the first gas flow subsystem. “Vacuum” as defined herein is created by intentionally drawing one or more gases from the volume without intentionally replacing the gas(s) with one or more other gases. For example, intentionally replacing one or more gases in a volume with one or more other gases in a volume (identical or different from the original one or more gases) so that the pressure in the volume becomes lower than the original one or more gases (or is designed to be so) will not be considered as creating a vacuum in the volume as the term is used herein. A portion of the first gas flow subsystem illustrated in FIG. 3 may also be configured as described herein and may be coupled to an inspection subsystem (not shown in FIG. 3) as further described herein.

[0045] One new and important feature of the embodiments described herein is that they are therefore multiple pumping stages for creating a vacuum or can be configured for such purpose. Although three pumping stages are illustrated in FIG. 2 by three different channels within a housing block and three vacuum levels are illustrated in FIG. 3 at different pressures, different stages of pumping and vacuum may be used. For example, the embodiments described herein may be configured for one or more pumping stages and different vacuum levels. In some cases, the first gas flow subsystem may be composed of as many vacuum channels as is practically feasible, and if fewer vacuum stages are required, fewer vacuum channels than all vacuum channels may be used. For example, which channels are used to create a vacuum may be controlled by vacuum pumps attached to each of the channels. In one such case, the first gas flow subsystem configured for three vacuum stages can also be used for two vacuum stages by simply not activating the vacuum pump(s) connected to the channels for one of the three stages.

[0046] In the vacuum embodiments described herein, the specimen may be held by a vacuum chuck having a higher vacuum below than above, so that the specimen is not lifted from the chuck and comes into contact with the housing block and / or objective lens housing by a first medium. For example, the chuck (222) shown in FIG. 2 may be a vacuum chuck. The chuck may also be a vacuum chuck or an air / vacuum combination chuck. The system may also be configured to actively control the vacuum pressure of the vacuum chuck depending on the vacuum level above the top of the specimen. Alternatively, the chuck (222) may be an electrostatic chuck comprising any such chuck suitable for use in a vacuum environment. In this way, the chuck may be configured to hold the specimen by electrostatic force. Particle problems associated with electrostatic chucks may be acceptable, as further described herein, because air purification may be implemented to surround the chuck and prevent external particles from entering. The chuck may be coupled to a scanning subsystem as further described herein, which can be configured to allow light to be scanned over a specimen in any suitable manner. Additionally, the chuck may be an R-θ stage configured for spinning and linear motion.

[0047] In another embodiment, the first local volume includes a gap (236) between the housing block (206) and the specimen. For example, the housing block of the local vacuum subsystem may be positioned substantially close to the specimen without contacting the specimen, for example, with a gap of about 50 μm to 1 mm from the specimen. As further described herein, a vacuum may be created by pumping air out of the gap through one or more pumping channels. Due to such a small gap, a pressure gradient is formed as air flows from the outside of the objective lens to the center. By this, a vacuum is also formed within the volume (214) below the objective lens.

[0048] In some embodiments, the first medium has a refractive index at one or more wavelengths of light directed toward the region and light from the region, and the refractive index is lower than the refractive index of dry air at one or more wavelengths. As described above, the first gas flow subsystem is configured to replace the gas located adjacent to the region on the specimen with the first medium, which scatters light less than the gas, 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 light scattering-based surface inspection systems by replacing normal air adjacent to the region on the specimen with a light propagation medium having a Rayleigh scattering cross-section lower than that of normal air.

[0049] 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(s). For example, the inspection subsystem may operate at ultraviolet (UV) wavelengths. Accordingly, 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 UV wavelengths. In a preferred embodiment, the first medium is a gas having the lowest known Rayleigh cross-section for UV wavelengths (e.g., wavelengths up to about 200 nm).

[0050] In one embodiment, the first medium is essentially composed of helium (He). For example, the purpose of the vacuum in the embodiments described herein is to effectively reduce non-abnormal light scattering that would otherwise be detected by the system in the presence of clean dry air. Thus, if light scattering can be reduced to the same degree as a vacuum (or substantially the same degree depending on the application, such as when the cost of implementing a vacuum is unacceptable or impractical, etc.), other media may be used instead of a vacuum. In one such acceptable alternative, the vacuum may be replaced by a helium purification. Helium is as effective as a vacuum in reducing air scattering. In particular, helium molecules are smaller than air molecules, and therefore helium will scatter less light than air in the same way as a vacuum. The first gas flow subsystem may be configured to channel helium directly under the objective lens. The helium pressure can push air through the gap between the housing block and the specimen. One advantage of helium purification is that a lower pressure is required to make the flow smoother. Additionally, to reduce light scattering caused by air, it may be preferable to use helium instead of a vacuum, as this is easier to implement.

[0051] As an alternative to elemental helium, the first medium may be composed essentially of neon (Ne). As used herein, the term “composed essentially” refers to a medium comprising one of the gases described above, which may be combined with other gases present in an amount that does not substantially affect the fundamental characteristics of light scattering caused by the first medium. For example, a first medium composed essentially of elemental helium or neon may contain a negligible amount of dry air that does not substantially affect the fundamental characteristics of light scattering caused by the medium. Further information regarding how helium and neon reduce light scattering in inspection systems and increase the sensitivity of the systems is described in U.S. Patent No. 7,372,559 of Haller et al., issued May 13, 2008, which is incorporated by reference as fully described herein. The embodiments described herein may also be configured as described in this patent.

[0052] FIG. 4 illustrates an embodiment of helium purification. In particular, the first gas flow subsystem may include channels (400) formed within a housing block (402). The housing block (402) may be coupled to an objective lens housing (404) as further described herein, so that the two housings are adjacent and bordering, as indicated by the dashed lines between the housings in FIG. 4. In this way, the helium channels may be machined in a separate assembly attached to the objective lens assembly. However, the housing block (402) and the objective lens housing (404) may be formed from a single piece of material and thus may be a single element within the system. The housing block (402) and the objective lens housing (404) may also be configured as described herein. Although a specific number of helium flow channels are shown in FIG. 4, the first gas flow subsystem may include any suitable number of channels of any suitable configuration as described herein.

[0053] Instead of drawing air away from the specimen (406) as in the embodiment illustrated in FIG. 2, the channels (400) are configured such that helium (408) displaces any air or gas of volume (410) so between the objective lens (412) and the specimen, thereby forming a reduced scattering medium within the volume. For example, each of the channels may be coupled to a helium source (not shown) and one or more other elements that push helium through the channels in this manner. The helium source and other elements (not shown) included in this first gas flow subsystem may include any suitable source and elements known in the art and may be selected based on information regarding the volume between the specimen and the objective lens, the required or desired helium pressure level, the configuration of the channels, etc. The first gas flow subsystem may include other suitable elements (not shown) typically included in gas flow subsystems, such as valves, exhaust elements, controllers, etc.

[0054] The objective lens (412) may also be configured as described herein, and the optical element of the objective lens (412) shown in FIG. 4 may be only one of several optical elements of the objective lens as shown in FIG. 1. Alternatively, the objective lens (412) may include only the single optical element shown in FIG. 4. As further described herein, light (414) scattered from the specimen may be collected by the objective lens and directed toward one or more other elements of the inspection subsystem (not shown in FIG. 4). A 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 of the embodiments described herein.

[0055] The system also includes a second gas flow subsystem configured to replace a gas in a second local volume adjacent to a first local volume with a second medium different from the first medium. For example, as illustrated in FIG. 2, the second gas flow subsystem, schematically illustrated by channels (224), can thereby direct the second medium (226) to a second local volume adjacent to the first local volume to replace any gas in the second local volume with the second medium. In another example, as illustrated in FIG. 4, the second gas flow subsystem, schematically illustrated by channels (420), can thereby direct the second medium (422) to a second local volume adjacent to the first local volume to replace any gas in the second local volume with the second medium. As illustrated in these figures, the second gas flow subsystem is configured such that the second medium is in close proximity to and showers around the objective lens and the objective lens housing. The objective lens and the specimen may be placed within a closed scanning chamber (not shown). A second medium may be introduced into the chamber from above while being exhausted from below (not shown). In some cases, the second medium may generate a positive pressure within the chamber outside the first local volume that is about 10 Pascals to about 100 Pascals higher than the ambient pressure. Accordingly, one novel and important feature of the embodiments described herein is that they are configured to purify the objective lens / specimen from the outside while creating a reduced scattering medium (e.g., a local vacuum) within the space between the specimen and the objective lens. In this way, the embodiments described herein may use a purification medium outside the different medium (e.g., a local vacuum) to keep the specimen clean while also reducing scattering. The inventors also do not recognize any other architecture capable of keeping the specimen clean while creating a vacuum.

[0056] In one embodiment, the second medium essentially consists of clean dry air (CDA). In this way, the embodiments described herein may be configured for air purification using a local vacuum. Alternatively, the embodiments described herein may be configured for air purification accompanied by helium purification. In either case, the system may use different first and second media. In particular, helium may be used for the first and second media, but this is not necessary for the second medium and would unnecessarily increase the cost of the system compared to using CDA for the second medium. Therefore, preferred combinations of media for the embodiments described herein are vacuum or helium used in combination with CDA.

[0057] In another embodiment, the second gas flow subsystem is configured not to direct the second medium into the light path directed toward the region and the light path from the region. In some embodiments, the second gas flow subsystem is configured to move foreign matter away from the specimen by the second medium. For example, the purpose of the second gas flow subsystem and the second medium is not related to the imaging performance of the inspection subsystem. In particular, unlike the first gas flow subsystem and the first medium, which are intended to improve the sensitivity of the inspection subsystem by reducing light scattering from abnormal sources, the second gas flow subsystem and the second medium are used primarily (and if possible, only) to keep the specimen clean. In other words, the second gas flow subsystem and the second medium are preferably configured to reduce the drop of particles or other foreign matter that could otherwise be deposited on the specimen during the inspection process. This foreign matter can come from any possible source, such as foreign matter within the clean room, foreign matter from the inspection subsystem, etc. The second gas flow subsystem and the second medium may be configured to have gas flow characteristics, such as gas flow rate and gas pressure, that move foreign matter away from the specimen and facilitate its movement to an exhaust subsystem (not shown) included in or coupled to the second gas flow subsystem. Therefore, there is no reason to configure the second gas flow subsystem to direct the second medium into any optical path directed toward the specimen and / or returning from the specimen. Additionally, when the second medium is a medium similar to CDA, directing the medium into an optical path within the inspection subsystem may actually be detrimental to the performance of the system.

[0058] The first gas flow subsystem may also be configured in such a manner that it effectively prevents the second medium from being placed within a first local volume surrounding an illuminated area on the specimen. For example, if the first medium is a vacuum, then if any of the second medium enters the first local volume, the second medium will also be removed by the first gas flow subsystem when creating and / or maintaining the vacuum. If the first medium is essentially composed of helium, the first gas flow subsystem may be configured such that helium properties, such as flow rate and pressure, cause the helium to effectively push the second medium out of the first local volume. In this way, the embodiments described herein can be easily configured so that the second medium does not interfere with the performance of the inspection subsystem.

[0059] In another embodiment, the first gas flow subsystem and the second gas subsystem do not alter the gas outside the second local volume. For example, except for individually performing the generation, control, maintenance, etc. of the first and second media within the first and second local volumes, the first and second gas flow subsystems are not configured to alter the ambient gas or other gases in other parts of the tool. One reason for this is the design purpose of the gas flow subsystems, namely, they are configured to perform the generation, control, maintenance, etc. of the first and second media within a relatively specific local volume within the inspection subsystem. Any area within or surrounding the rest of the inspection subsystem, such as outside the second local volume and possibly within the housing of the inspection subsystem, is not substantially affected by the first gas flow subsystem and the second gas flow subsystem. Such areas outside the second local volume may be allowed to be maintained under the surrounding conditions where the entire inspection subsystem is located. These configurations are possible because the first gas flow subsystem and the second gas flow subsystem are intended to replace the gas in such a relatively small local volume for specific reasons. Therefore, the first gas flow subsystem and the second gas flow subsystem can be much cheaper than other systems configured to control the entire environment in which the inspection subsystem and the entire specimen are located.

[0060] In additional embodiments, the entire inspection subsystem is not positioned in a vacuum. For example, one new and important feature of the embodiments described herein is that they are configured to create a vacuum only within a local volume of the inspection tool, that is, only within a relatively small volume between the objective lens and the specimen. Because the vacuum is created within such a small volume, the specimen and the entire inspection subsystem do not need to be positioned in a 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 specimen is moved to the inspection tool) and higher costs (e.g., the embodiments described herein do not require a vacuum housing large enough to surround all the optical hardware of the tool in addition to the specimen and allow space for the specimen to move within the housing). For example, the embodiments described herein are configured to create a vacuum sufficient to reduce air scattering detected by the inspection subsystem, and thus enable increased sensitivity of the inspection subsystem while maintaining a distance between the objective lens and the specimen that allows the specimen to move and / or rotate.

[0061] In the embodiments, the first gas flow subsystem and the second gas flow subsystem are individually configured to simultaneously replace the gas in the first local volume and the second local volume. For example, it may be possible to turn off one of the gas flow subsystems so that it can be used separately if such a configuration is required. As described in more detail above, the two flow subsystems can be used simultaneously in a state where there is no physical barrier between the different media and the first local volume and the second local volume are in direct proximity to each other, because (1) the first gas flow subsystem can be configured to place the second medium outside the first local area and (2) if the first medium is essentially composed of helium, the performance of the second gas flow subsystem and the second medium is not hindered even if some of the helium moves into the second local area. In this way, the embodiments described herein may use different media and different gas flow subsystems to achieve superior performance while minimizing costs by customizing the media and gas flow subsystems for specific functions within specific volumes of the inspection subsystems.

[0062] In another embodiment, the first gas flow subsystem and the second gas flow subsystem are configured to control the first medium and the second medium, respectively, during orientation and generation. For example, at the start of an inspection process performed on a specimen, the first gas flow subsystem and the second gas flow subsystem may replace the gas within the first local volume and the second local volume, respectively. Generally, in the embodiments described herein, the characteristics of the first medium and the second medium within the first and second local volumes should not change substantially during the inspection process. Accordingly, the parameters of the first gas flow subsystem and the second gas flow subsystem may be set at the start of the process and may not be readjusted thereafter until the inspection is completed.

[0063] However, the first gas flow subsystem and the second gas flow subsystem may include any sensors or other equipment for monitoring one or more characteristics of the first medium and the second medium in the first and second local volumes during the inspection process. The first and / or second gas flow subsystem and / or the control subsystem of the system (not shown) may then change one or more parameters of the first and / or second gas flow subsystem based on any output responding to one or more characteristics being monitored. In this way, the first gas flow subsystem and the second gas flow subsystem may be configured to have different values ​​of at least one parameter of the gas flow subsystem, for example, flow rate, during the inspection process. In one such example, if the thickness of the specimen varies substantially over the entire specimen, the distance between the objective lens and the specimen may vary when the inspection subsystem scans the specimen. In such a case, it may be desirable to change the settings of one or more vacuum pumps of the first gas flow subsystem during the scan so that the vacuum pressure in the first local volume remains substantially the same throughout the entire scan of the specimen despite the variation in specimen thickness.

[0064] In one embodiment, the system comprises a chuck configured to support a specimen during orientation and generation, the chuck comprising a recess into which the specimen is placed during orientation and generation, and the recess configured such that the upper surface of the specimen is at the same height as the upper surface of the chuck outside the recess while the upper surface of the specimen is placed within the recess. For example, as illustrated in FIG. 2, a specimen (212) may be placed on the chuck (222) during inspection, the chuck having a recess (228) into which the specimen is placed, so that the upper surface (230) of the specimen is at substantially the same height as the upper surface (232) of the chuck outside the recess. In this way, the diameter of the chuck is larger than the diameter of the specimen. The specimen is seated in the middle recess. The depth of the recess is close to the thickness of regular specimens, e.g., wafers, so that the top surface of the specimen is at the same height as the chuck. Different types of specimens may have slightly different thicknesses, but such variations will be small compared to the gap between the housing block and the specimen and the distance between the objective lens and the specimen. Vacuum performance can be maintained. The planar design enables the vacuum to be maintained even when scanning at the edge of the specimen.

[0065] FIG. 5 illustrates additional details regarding the configuration possibilities of the chuck for the embodiments described herein. As previously mentioned, the chuck may extend beyond the specimen, and the upper surface of the portion of the chuck beyond the specimen is preferably at the same height as the upper surface of the specimen. In particular, to maintain a vacuum when the objective lens (500) moves close to the edge of the specimen, an extension wing (502) may be included within the chuck assembly from the mount of the chuck and spindle element (504) which can rotate about an axis (506). The upper surface of the wing (502) is preferably at the same height as the upper surface of the specimen (508), as illustrated in FIG. 5. In this way, a relatively small gap between the housing block and the specimen and / or between the housing block and the upper surface of the wing can be maintained over the entire diameter (and area) of the specimen.

[0066] Being able to maintain such a small gap between the housing block spanning the entire specimen and the specimen and / or chuck facilitates creating and maintaining a vacuum between the objective lens and the specimen, as further described herein, without the need to position the entire inspection subsystem and the specimen under vacuum. In particular, the extension wing can help maintain a vacuum seal between the specimen and the objective lens even when scanning is performed near the edge of the specimen. Accordingly, the vacuum can be maintained throughout the entire inspection process performed on the specimen, even if the inspection process scans the edge of the specimen, close to the specimen edge, or even beyond the specimen edge. Different types of specimens may vary slightly in thickness, but such variation should be small relative to the height of the gap, such as, for example, about 0.5 mm. 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.

[0067] FIG. 5 illustrates an objective lens (500) in a simplified version of a housing (510) that collectively includes an objective lens housing and vacuum channels (512) formed therein, but the housing is illustrated in a manner that allows for improved details of the chuck assembly to be illustrated. The inspection subsystem, the first gas flow subsystem, and the second gas flow subsystem included in the system embodiment having the chuck assembly illustrated in FIG. 5 may also be configured as described herein. Additionally, the extension wing included in the chuck assembly may surround the entire specimen and is illustrated on only one side of the specimen in FIG. 5 for simplification. Furthermore, although the chuck and spindle are illustrated as a single element in FIG. 5, the chuck and spindle may be separate elements coupled in any suitable manner known in the art. The chuck assembly illustrated in FIG. 5 may also be configured as described herein and may be part of a scanning subsystem configured as described herein.

[0068] The chuck may also include two different parts (not shown) that may be height-adjustable relative to each other so that the top surface of specimens having different thicknesses is at the same height as the top surface of the part not located beneath the specimen. The system may be configured to control the different parts of the chuck based on prior information regarding the specimen, such as the expected thickness of the specimen or the thickness of the specimen as measured by another tool. The system may also be configured to control the other parts of the chuck based on some visual feedback generated by the system itself regarding the position of the top surface of the specimen relative to the top surface of the chuck outside the specimen. For example, during the phase of the process performed while aligning the specimen to the inspection tool or prior to the inspection scan, the system may illuminate the area of ​​the specimen near the edge of the specimen and the area of ​​the specimen beyond the edge of the specimen and detect light reflected from those areas. The reflected light image may be used to determine whether the top surfaces of the specimen and the chuck outside the specimen are at the same height and / or whether adjustments to the depth of the recess should be made so that the two surfaces are at the same height. This function may be similar to the autofocus function performed to focus the specimen before scanning, but in this case, instead of the chuck moving as a single unit, at least one part of the chuck will move relative to another part, and the height of the top surface of the specimen is positioned relative to the height of the top surface of the chuck outside the specimen, rather than the optical hardware.

[0069] Some embodiments of the system include an air bearing positioned outside the first local volume and configured to prevent the first and second gas flow subsystems from coming into contact with the specimen. For example, the air bearing may be used as a safety guard on the outer ring of the housing block and, if possible, may also be used to reduce the air gap. In this way, the air bearing can prevent the vacuum housing block from coming into contact with the specimen. The outlet of the air bearing may be an array of relatively small holes located outside the outermost vacuum stage. The air bearing may include any suitable commercial vacuum preload air bearing known in the art. The air bearing is optional but can provide significant advantages for the embodiments described herein. For example, without an air bearing, a relatively large gap, such as hundreds of microns, may be required between the housing block and the specimen to prevent the housing block from colliding with the specimen. With the use of an air bearing, that gap can be reduced to tens of microns.

[0070] FIG. 6 illustrates one possible embodiment including an air bearing. As with other embodiments described herein, the first gas flow subsystem may include a housing block (600). A plurality of channels (602) are formed within the housing block and connected to a vacuum pump (604), so that they can be combined to draw air from a first local volume (606) between the housing block (and an objective lens (not shown in FIG. 6) located therein) and a specimen (608). The air bearing may include channels (610) formed within the housing block and located outside all channels included in the first gas flow subsystem (e.g., outside vacuum channels or helium purification channels). The channels may be coupled to a pressurized air source (612) and any other suitable gas flow elements (not shown) such as those further described herein.

[0071] The air bearing can be configured to direct pressurized air from a source through channels and out of the outlets of channels formed within the housing block. In this way, compressed air (614) can be forced into the gap between the outer edge of the housing block and the specimen, which can reduce the possibility of the housing block coming into contact with the specimen for any reason, such as a vacuum created by the first gas flow medium.

[0072] This compressed air is preferably different from any CDA used by the second gas flow subsystem. For example, the compressed air of the air bearing is used to maintain a suitable gap between the housing block and the specimen, particularly near the edges of the housing block, and the CDA used as the second medium is used to reduce foreign matter contamination on the specimen. Thus, the pressurized air and the CDA may have different characteristics such as pressure, air flow directions, composition, etc.

[0073] In some embodiments, the first gas flow subsystem comprises a housing block through which the gas is replaced with the first medium, and the inspection subsystem is configured to direct light into an area through one or more passages formed through the housing block. For example, the housing block and the first and second gas flow subsystems (including pump outlets, gas flow channels, channel inlets, etc.) formed within or coupled thereto may be configured so that light is directed toward a specimen and collected from the specimen according to a selected configuration. In one such example, the pump outlets of the channels formed within the housing block for the first gas flow subsystem may be rigid in some azimuth regions so that holes are perforated to allow the light to pass through and the reflected beam to escape. In the embodiment illustrated in FIG. 1, for example, light from a light source (100) is illustrated as being directed toward a specimen through a housing block (108) which may include a passage (not shown) configured to allow the light to pass through itself. The passage may be an open channel with a window near the end of the channel specimen, so that the channel does not affect the first medium formed within the first local volume. In addition to the end of the channel specimen being sealed in some way, the passage may be formed within the housing block in the same manner as described herein in relation to the channel of the first gas flow subsystem.

[0074] In another embodiment, the system includes a window element positioned between the objective lens of the inspection subsystem and the specimen and configured to transmit light from the area without altering the light. For example, a hemispherical dome window may be used with a stronger glass, such as sapphire, separate from the lens housing. Examples of such window elements are individually illustrated by the hemispherical dome windows (234, 424) in FIGS. 2 and FIGS. 4. As illustrated in these figures, the hemispherical dome window is positioned between the objective lens and the specimen, and a first medium will replace any gas inside the dome window and between the dome window and the specimen. The advantage of using an additional dome window is to reduce the stress applied to the optical element by using stronger glass. The additional dome window may have two conformal and concentric surfaces such that the center of curvature is located on the surface of the specimen to minimize optical aberrations.

[0075] A computer subsystem may be configured to generate results for a specimen, which may include all information described herein, such as defect and / or particle information, a map of defect and / or particle information across the entire specimen, etc. Results for anomalies may include, but are not limited to, the locations of the anomalies, detection scores, information on defect and / or particle classification, such as class labels or IDs, or such suitable information known in the art. Results for a specimen may be generated by the computer subsystem in any suitable manner.

[0076] All embodiments described herein may be configured to store the results of one or more steps of the embodiments on a computer-readable storage medium. The results may include any of the results described herein and may be stored in any manner known in the art. The results for the specimen may have a suitable form or format, such as a standard file format. The storage medium may include any of the storage media described herein or any other suitable storage medium known in the art. After the results are stored, the results may be accessed from the storage medium and used by any method or system embodiment described herein, formatted for display to a user, and used in another software module, method, or system, etc., to perform one or more functions on the specimen or another specimen of the same type.

[0077] These functions also include, but are not limited to, modifying processes, such as manufacturing processes or steps performed or to be performed on a specimen, in a feedback or feedforward manner. For example, the computer subsystem may be configured to determine one or more modifications to the process performed on the specimen and / or to be performed on the specimen based on determined information. Modifications to the process may include any suitable modifications to one or more parameters of the process. The computer subsystem preferably determines these modifications so that anomalies may be reduced or prevented in another specimen where the modified process is performed, so that anomalies may be corrected or eliminated in another process performed on the specimen, so that anomalies may be compensated in another process performed on the specimen, and so on. The computer subsystem may determine these modifications in any suitable manner known in the art.

[0078] Then, these changes may be sent to a semiconductor manufacturing system (not shown) or a storage medium (not shown) that is 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 through one or more common elements, such as a housing, a power supply, a specimen handling device, or a mechanism. 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, etc.

[0079] Each of the embodiments described herein may be combined into one embodiment unless otherwise stated herein. The embodiments described herein are also based on U.S. Patent No. 6,813,026 granted to McAninch (November 2, 2004), No. 7,359,052 granted to Fielden et al. (April 15, 2008), No. 7,420,681 granted to Wang et al. (September 2, 2008), No. 7,564,552 granted to Fielden et al. (July 21, 2009), No. 7,623,239 granted to Fielden et al. (November 4, 2009), No. 7,755,764 granted to Kwak et al. (July 13, 2010), No. 7,764,376 granted to Fielden et al. (July 27, 2010), and the patent granted to Pressburger et al. It may be configured as described in No. 11,315,816 (April 26, 2022), all of which are incorporated by reference as fully specified in this specification.

[0080] Another embodiment relates to a method for inspecting a specimen. The method includes the steps of directing light onto an area on the specimen and generating an output in response to the light emanating from the specimen, which may be performed by an inspection subsystem such as that shown in FIG. 1. The method also includes the step of replacing a gas within a first local volume surrounding an area on the specimen with a first medium during directing and generating, which may be performed by a first gas flow subsystem such as that shown in FIG. 2 and FIG. 4. The first medium scatters light less than the gas. Additionally, the method includes the step of replacing a gas within a second local volume located adjacent to the first local volume with a second medium during directing and generating, which may be performed by a second gas flow subsystem such as that shown in FIG. 2 and FIG. 4. The second medium is different from the first medium. The method further includes the step of detecting anomalies on the specimen based on the output. Detection is performed by a computer system, for example, the computer subsystem (122) shown in FIG. 1.

[0081] Each of the steps 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 systems described herein, which may be configured according to any of the embodiments described herein.

[0082] Additional embodiments relate to a non-transient computer-readable medium storing program instructions executable on a computer system for performing a computer-implemented method for inspecting a specimen. One such embodiment is illustrated in FIG. 7. In particular, as illustrated in FIG. 7, the non-transient 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.

[0083] Program instructions (702) for implementing the method described herein may be stored on a computer-readable medium (700). The computer-readable medium may be a storage medium such as a magnetic or optical disk, a magnetic tape, or any other suitable non-transient computer-readable medium known in the art.

[0084] Program instructions can be implemented in any variety of ways, including procedure-based technologies, component-based technologies, and / or object-oriented technologies. For example, program instructions can be implemented using ActiveX controls, C++ objects, JavaBeans, Microsoft Foundation Classes (MFC), Streaming SIMD Extension (SSE), or other technologies or methods as desired.

[0085] The computer system (704) may be configured according to any of the embodiments disclosed herein.

[0086] Considering this specification, additional modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art. For example, a method and system for inspecting specimens are provided. Accordingly, this description is merely illustrative and should be interpreted as intended to teach those skilled in the art a general method for carrying out the invention. The forms of the invention shown and disclosed herein are to be understood as currently considered preferred embodiments. As will be fully apparent to those skilled in the art after taking advantage of the description of the invention, elements and materials may be substituted with respect to those exemplified and described herein, parts and processes may be reversed, and specific features of the invention may be used independently. Modifications of the elements described herein may be made without departing from the spirit and scope of the invention as set forth in the following claims.

Claims

Claim 1 A system configured to inspect a specimen, comprising: an inspection subsystem configured to direct light to a region on the specimen and generate an output in response to light from the region on the specimen, wherein all optical hardware of the inspection subsystem is not located in a vacuum; a first gas flow subsystem configured to replace a gas in a first local volume surrounding a region on the specimen with a first medium that scatters light less than the gas, wherein the first medium is a vacuum; a second gas flow subsystem configured to replace a gas in a second local volume adjacent to the first local volume with a second medium different from the first medium; and a computer subsystem configured to detect abnormalities on the specimen based on the output. Claim 2 A system configured to inspect a specimen, wherein, in claim 1, the first gas flow subsystem comprises a plurality of channels for replacing the gas with the first medium, and the first gas flow subsystem is also configured to cause the first medium to have different characteristic values ​​close to two or more of the plurality of channels. Claim 3 A system configured to inspect a specimen, wherein the characteristic of paragraph 2 is pressure. Claim 4 A system configured to inspect a specimen according to claim 1, wherein the first medium has a refractive index at one or more wavelengths of light directed toward the region and light from the region, and the refractive index is lower than the refractive index of dry air at one or more wavelengths. Claim 5 A system configured to inspect a specimen, wherein, in claim 1, the height of the first local volume is defined by the distance between the objective lens of the inspection subsystem and the specimen. Claim 6 A system configured to inspect a specimen, wherein, in paragraph 1, the second medium is essentially composed of clean, dry air. Claim 7 A system configured to inspect a specimen, wherein, in claim 1, the second gas flow subsystem is also configured not to direct the second medium into a light path directed toward the region and a light path from the region. Claim 8 In claim 1, the second gas flow subsystem is also configured to use the second medium to move foreign substances away from the specimen, and is a system configured to inspect the specimen. Claim 9 A system configured to inspect a specimen, wherein the first gas flow subsystem and the second gas flow subsystem do not change the gas outside the second local volume. Claim 10 A system configured to inspect a specimen, wherein the entire inspection subsystem is not located in a vacuum, in accordance with claim 1. Claim 11 A system configured to inspect a specimen, wherein, in claim 1, the first gas flow subsystem and the second gas flow subsystem are also configured to simultaneously replace the gas within the first local volume and the second local volume, respectively. Claim 12 A system configured to inspect a specimen, wherein, in claim 1, the first gas flow subsystem and the second gas flow subsystem are also configured to control the first medium and the second medium, respectively, during the orientation and generation. Claim 13 A system configured to inspect a specimen according to claim 1, further comprising a chuck configured to support the specimen during the orientation and generation, wherein the chuck comprises a recess into which the specimen is placed during the orientation and generation, and the recess is configured such that the upper surface of the specimen is at the same height as the upper surface of the chuck outside the recess while the upper surface of the specimen is placed within the recess. Claim 14 A system configured to inspect a specimen according to claim 1, further comprising an air bearing positioned outside the first local volume and configured to prevent the first gas flow subsystem and the second gas flow subsystem from coming into contact with the specimen. Claim 15 A system configured to inspect a specimen, wherein, in claim 1, the first gas flow subsystem comprises a housing block through which the gas is replaced with the first medium, and the inspection subsystem is also configured to direct the light to the area through one or more passages formed through the housing block. Claim 16 A system configured to inspect a specimen according to claim 1, further comprising a window element positioned between the objective lens of the inspection subsystem and the specimen and configured to transmit the light into and from the area without changing the light. Claim 17 A non-transient computer-readable medium storing program instructions executable on a computer system for performing a computer implementation method for inspecting a specimen, wherein the computer implementation method comprises: a test subsystem, the step of directing light onto an area on the specimen and generating an output in response to light from the area on the specimen, wherein all optical hardware of the test subsystem is not located in a vacuum; the step of replacing a gas in a first local volume surrounding an area on the specimen during the directing and generating with a first medium, wherein the first medium scatters light less than the gas and the first medium is a vacuum; the step of replacing a gas in a second local volume located adjacent to the first local volume during the directing and generating with a second medium, wherein the second medium is different from the first medium; and the step of detecting abnormalities on the specimen based on the output. Claim 18 A method for inspecting a specimen, comprising: an inspection subsystem, the step of directing light onto an area on the specimen and generating an output in response to light from the area on the specimen—wherein all optical hardware of the inspection subsystem is not located in a vacuum—; the step of replacing a gas in a first local volume surrounding the area on the specimen during the directing and generating with a first medium—wherein the first medium scatters the light less than the gas and the first medium is a vacuum—; the step of replacing a gas in a second local volume located in proximity to the first local volume during the directing and generating with a second medium—wherein the second medium is different from the first medium—; and the step of detecting abnormalities on the specimen based on the output—wherein the detecting step is performed by a computer system. Claim 19 delete Claim 20 delete

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