Methods and systems to measure properties of products on a moving blade in electronic device manufacturing machines

Implementations disclosed describe an optical inspection device comprising a source of light to direct a light beam to a location on a surface of a wafer, the wafer being transported from a processing chamber, wherein the light beam is to generate, a reflected light, an optical sensor to collect a first data representative of a direction of the first reflected light, collect a second data representative of a plurality of values characterizing intensity of the reflected light at a corresponding one of a plurality of wavelengths, and a processing device, in communication with the optical sensor, to determine, using the first data, a position of the surface of the wafer; retrieve calibration data, and determine, using the position of the surface of the wafer, the second data, and the calibration data, a characteristic representative of a quality of the wafer.

TECHNICAL FIELD

This instant specification generally relates to controlling quality of wafer (substrate) yield of systems used in electronic device manufacturing, such as various processing chambers. More specifically, the instant specification relates to post-processing optical inspection of wafers while the wafers are being transported from a processing chamber.

BACKGROUND

Manufacturing of modern materials often involves various deposition techniques, such as chemical vapor deposition (CVD) or physical vapor deposition (PVD) techniques, in which atoms of one or more selected types are deposited on a wafer (substrate) held in low or high vacuum environments that are provided by vacuum processing (e.g., deposition, etching, etc.) chambers. Materials manufactured in this manner may include monocrystals, semiconductor films, fine coatings, and numerous other substances used in practical applications, such as electronic device manufacturing. Many of these applications depend critically on the purity of the materials grown in the processing chambers. The need to maintain isolation of the inter-chamber environment and to minimize its exposure to ambient atmosphere and contaminants therein gives rise to various robotic techniques of sample manipulation and chamber inspection. Improving precision, reliability, and efficiency of such robotic techniques presents a number of technological challenges whose successful resolution is crucial for continuing progress of electronic device manufacturing. This is especially important given that the demands to the quality of chamber manufacturing products are constantly increasing.

SUMMARY

In one implementation, disclosed is an optical device having a first source of light to direct a first light beam to a first location on a surface of a product, the product being transported from a processing chamber. The first light beam is to generate, at the first location, a first reflected light. The optical device further has an optical sensor. The optical sensor is to collect a first data representative of a direction of the first reflected light and a second data representative of a first plurality of values characterizing intensity of the first reflected light at a corresponding one of a first plurality of wavelengths, each of the first plurality of wavelengths belonging to a first range of wavelengths. The optical device further includes a processing device, in communication with the optical sensor. The processing device is to determine, using the first data, a position of the surface of the product, retrieve calibration data, and determine, using the position of the surface of the product, the second data, and the calibration data, a first characteristic representative of a quality of the product.

In another implementation, disclosed is an optical device having a plurality of n sources of light, each one of the n sources of light to direct a light beam to a plurality of m locations on a surface of a product being transported from a processing chamber. Each one of the n sources of light is to generate, at each one of the m locations, a reflected light. The optical device further has a plurality of n optical sensors, each of the n optical sensors configured to detect light having a wavelength within a respective range of a plurality of n ranges of wavelengths. Each of the n optical sensors is to detect a reflected light generated by a respective one of the n sources of light at each of the m locations on the surface of the product. Each of the n optical sensors is further to collect m intensity data, wherein each of the m intensity data is representative of a plurality of values characterizing intensity of the reflected light generated at the respective one of the m locations, the intensity of the reflected light corresponding to one of a plurality of wavelengths, wherein each of the plurality of wavelengths belongs to the respective range of the plurality of n ranges of wavelengths. The optical device further has a processing device in communication with each of the n optical sensors. The processing device is to determine, using the m intensity data from each of the n optical sensors, at least one characteristic representative of a quality of the product.

In another implementation, disclosed is a method that includes directing a first light beam, produced by a first source of light, to a first location on a surface of a product, the product being transported from a processing chamber. The first light beam is to generate, at the first location, a first reflected light. The method further includes collecting, by a first optical sensor, a first data representative of a direction of the first reflected light and a second data representative of a first plurality of values characterizing intensity of the first reflected light at a corresponding one of a first plurality of wavelengths, each of the first plurality of wavelengths belonging to a first range of wavelengths. The method further includes determining, using the first data obtained by the first optical sensor, a position of the surface of the product. The method further includes retrieving calibration data, and determining, using the position of the surface of the product, the second data, and the calibration data, a first characteristic representative of a quality of the product.

DETAILED DESCRIPTION

The implementations disclosed herein provide for contactless precision optical inspection of processed wafers while the wafers are being transferred from processing chambers (that may include deposition chambers, etching chambers, and so on). For example, the implementations disclosed may help accurately determine optical, physical, and morphological properties of the wafers, such as their uniformity, smoothness, thickness, refractive index, reflectivity, and so on, and provide an efficient quality control tool that does not require slowing down the manufacturing process.

The robotic systems allow a quick and efficient delivery of wafers for processing into a processing chamber and an automated retrieval of the processed wafers from the processing chamber. Robotic delivery/retrieval systems greatly increase a yield of the manufacturing process but pose some specific quality control challenges. At least some—and, ideally, all—processed wafers need to be examined for compliance to the process specification. Yet, stopping the manufacturing process (e.g., randomly or after processing of every n-th wafer) to test an occasional output wafer has a number of disadvantages. The wafer being tested is, as a consequence, being exposed to a testing environment (e.g, of a testing chamber) for a longer period of time compared to those output wafers that are not subjected to the same testing. This introduces intrinsic inaccuracy into the testing procedure and, additionally, results in a non-uniformity of the wafer yield where the untested wafers may have properties that are somewhat different from the tested wafers (e.g., the tested wafers may have more contaminants due to a longer exposure to the post-processing environment). Furthermore, stopping the manufacturing process and then restarting it, even if performed occasionally, reduces the speed of wafer manufacturing.

The problem of the yield non-uniformity, prolonged exposure to the testing environment, and slowing down of the manufacturing process may be solved by performing wafer testing (using optical inspection methods) while the wafer is being transported from the processing chamber to the loading/unloading chamber. An optical inspection device may have a light source, to direct a beam of light at one or more target locations on the surface of the wafer, and an optical sensor to detect a light reflected from the surface and obtain reflectivity R(λ) data for each target location on the surface, for a broad range of wavelengths λ. The reflectivity data may be obtained for some parts of visible, infrared (IR), and ultraviolet (UV) spectra, depending on the light source and the optical sensor used. Based on the reflectivity data, a processing device (e.g., a computing system equipped with a processor and a memory) may determine a variety of characteristics of the wafer: uniformity of the wafer, e.g., of the wafer thickness, (from comparison of the reflectivity R(λ) across multiple locations of the wafer), the amount of contaminants (from comparing the reflectivity R(λ) to a benchmark reflectivity stored in the memory), the smoothness of the surface of the wafer (from detecting a degree of non-specular—diffuse—reflection) from the wafer, and the like.

Because collection of optical inspection data may be performed while the wafer is moving, such motion may introduce errors resulting in imprecise characterization of the wafer. For example, as a result of the robot blade motion, the wafer may experience up-and-down (vertical) or side-to-side (horizontal) parallel displacements, and angular tilts around one of three spatial axes. For example, the wafer may experience a tilt around a horizontal direction (x direction, as depicted inFIG.2A) of the robot blade's velocity—a roll. The wafer may experience a tilt around the horizontal direction (y direction) that is perpendicular to the blade's velocity—a pitch. Additionally, the wafer may experience a tilt around the vertical direction (z direction)—a yaw. Any of these parallel displacements and/or angular tilts may be small and undetectable without precision instruments. However, an optical path, which requires a calibration to a high degree of precision, may nonetheless be significantly affected by a tilt and/or a displacement. For example, if the thickness of the wafer ranges between 1-100 nm, a displacement of only a few angstroms may result in a significant error in determining the reflectivity R(λ), or the refractive index n(λ), or any other optical quantity that may be used to characterize the wafer, such as a polarization dependence of the reflectivity, an angle rotation of the polarization plane upon reflection, luminescence intensity, and so on. As a result, a wafer that is within the desired specification may incorrectly appear to be outside it. Conversely, motional errors may mask the fact that the wafer is outside the specification.

Aspects and implementations of the present disclosure address this and other shortcomings of the optical inspection technology that may be used in wafer manufacturing. Described herein is an optical inspection device capable of measuring an optical response of a wafer during its transportation, detecting the wafer displacement/tilt, and analyzing the optical response using calibration data to compensate for the detected displacement. The optical inspection tool may be equipped with light sources to direct incident light at a surface of the wafer and may be further equipped with light sensors to detect light reflected from the wafer. The operation of the light sources and light sensors may be synchronized with the motion of the wafer so that the incident light is reflected from the wafer at a set of pre-determined testing locations that may be selected to maximize the scope and efficiency of the inspection process.

If a broadband optical sensor is used to collect a wafer optical response data within a wide range of wavelengths λ (such as 500-600 nm or greater), designing and calibrating such broadband sensor to detect and compensate for tilt/displacement in the entire range of wavelengths may be a very complex task. Accordingly, in some implementations of this disclosure, the optical inspection tool may have multiple “chromatic” optical sensors, each chromatic sensor detecting light within a range that is 50-100 nm wide (100-200 nm wide, in some implementations, or 20-50 nm wide, in other implementations). Each chromatic sensor may be designed and calibrated to detect and compensate, within a narrow range of wavelengths, for an error in the measured optical response of the wafer induced by the wafer's tilt and/or displacement. Using multiple chromatic sensor, instead of one broadband sensor, may offer a significant advantage by ensuring that each sensor is to detect light that travels over more homogenous optical paths within the narrower range of wavelengths λ. Additionally, chromatic sensors may be characterized by less dispersion of their various optical components, such as lens, mirrors, optical fibers, diffraction gratings, optical coatings, and so on. In some implementations, multiple chromatic sensors may be designed and operated to probe the same set of target testing locations. As a result, a number of narrow-range chromatic sensors may produce a set of complementary optical responses spanning a broad range of wavelengths λ (e.g., spanning an entire or a substantial part of the visible spectrum, an IR, and/or a UV spectrum).

The disclosed implementations pertain to a variety of manufacturing techniques that use processing chambers (that may include deposition chambers, etching chambers, and the like), such as chemical vapor deposition techniques (CVD), physical vapor deposition (PVD), plasma-enhanced CVD, plasma-enhanced PVD, sputter deposition, atomic layer CVD, combustion CVD, catalytic CVD, evaporation deposition, molecular-beam epitaxy techniques, and so on. The disclosed implementations may be employed in techniques that use vacuum deposition chambers (e.g, ultrahigh vacuum CVD or PVD, low-pressure CVD, etc.) as well as in atmospheric pressure deposition chambers. The disclosed implementations may be advantageous for determining the morphology of the materials being tested, such as a relative concentration of different materials being deposited (e.g., the ratio of silicon to nitrogen), or a relative presence of various types of the same material (e.g., crystalline vs. amorphous silicon). The disclosed implementations may also be advantageous for determining geometry of the systems being tested, such as the thickness (and composition) of various films deposited on wafers, and so on.

FIG.1Aillustrates one exemplary implementation of a manufacturing machine100capable of supporting accurate optical inspection of wafers transported on a moving blade. In one implementation, the manufacturing machine100includes a loading station102, a transfer chamber104, and one or more processing chambers106. The processing chamber(s)106may be interfaced to the transfer chamber104via transfer ports (not shown). The number of processing chamber(s) associated with the transfer chamber104may vary (with three processing chambers indicated inFIG.1A, as a way of example). The transfer chamber104may include a robot108, a robot blade110, and an optical inspection tool for accurate optical inspection of a wafer112that is being transported by the robot blade110after processing in one of the processing chambers106. The transfer chamber104may be held under pressure (temperature) that is higher (or lower) than the atmospheric pressure (temperature). The robot blade110may be attached to an extendable arm sufficient to move the robot blade110into the processing chamber106to retrieve the wafer in chamber116after the processing of the wafer is complete.

The robot blade110may enter the processing chamber(s)106through a slit valve port (not shown) while a lid to the processing chamber(s)106remains closed. The processing chamber(s)106may contain processing gases, plasma, and various particles used in deposition processes. A magnetic field may exist inside the processing chamber(s)106. The inside of the processing chamber(s)106may be held at temperatures and pressures that are different from the temperature and pressure outside the processing chamber(s)106.

The optical inspection tool (device) may have one or more measurement heads114. Each measurement head114may include a chromatic optical sensor. Some or all of the measurement heads114may include a dedicated chromatic light source to produce light within a range that may be detectable by the optical sensor of that measurement head114. In some implementations, a single light source may produce light spanning wavelengths detectable by more than one optical sensor. The plurality of optical sensors of the measurement heads114of the optical inspection device may be capable of sensing visible light, IR light, UV light, or other electromagnetic radiation coming from the wafer. In some implementations, the light sources may be mounted outside the inspection device, e.g., mounted inside the transfer chamber104, the loading station102or the processing chambers106.

In some implementations, the radiation coming from the wafer112may be a reflected radiation generated in response to irradiation of the wafer112by the incident light from one or more light sources. The radiation may be reflected substantially from the surface of the wafer, if the wafer material is non-transparent to a specific wavelength being used and the thickness of the wafer exceeds the penetration depth for that wavelength. In other implementations, the reflected radiation may be originating from the entire cross-section of the wafer, such as in situations where the wafer is transparent to the specific wavelength being detected or where the thickness of the wafer is less that the penetration depth of light. In some implementations, the radiation coming from the wafer may be a radiation transmitted through the wafer. For example, the sources of light may be located on one side of the wafer112(e.g., above or below the wafer) whereas the optical sensors may be location on the other side of the wafer112(below or above the wafer, respectively). In such implementations, the robot blade110may cover only some portions of the bottom surface of the wafer112, leaving other portions of the bottom surface exposed to facilitate transmission of light across the thickness of the wafer112.

A computing device118may control operations of the robot108and the optical inspection device, including operation of the measurement heads114and processing of data obtained by the measurement heads114. The computing device118may communicate with an electronics module150of the robot108. In some implementations, such communication may be performed wirelessly.

FIG.1Billustrates the electronics module150capable of supporting accurate optical inspection of wafers transported on a moving blade inside the manufacturing machine100, in one exemplary implementation. The electronics module150may include a microcontroller152and a memory buffer154coupled to the microcontroller152. The memory buffer154may be used to collect and store optical inspection data before transmitting the inspection data to the computing device118. In some implementations, the inspection data may be transmitted using a wireless communication circuit. In other implementations, the data may be transmitted using a wired connection between the electronics module150and the computing device118. In some implementations, the optical inspection data may first be stored (buffered) in the memory buffer154prior to being transmitted to the computing device118. In other implementations, the inspection data may be transmitted to the computing device118as the data is collected, without being stored in the memory buffer154. In some implementations, the wireless or wired connection may be continuous. In other implementations, the wireless or wired connection may be established periodically or upon completion of the inspection or some other triggering event (e.g., when the memory buffer154is close to being full). The electronics module150may further include a power element156and a power-up circuit158. In some implementations, the power element156may be a battery. In some implementations, the power element156may be a capacitor. The power element156may be rechargeable from a power station180. For example, the battery or the capacitor may be recharged upon a contact (e.g., via a charging docking station) with the power station180. In some implementations, the charging station may be connected (e.g., via a wired connection) to the power element156. In some implementations, the connection between the charging station180and the power element156may be wireless. In some implementations, the charging station180may include a power transmitter and the power element156may include a power receiver. When the power element156is low on power, the power element156may send a beacon signal to the find the power station180and the power station180may provide a power signal to the power element156until the power element156is recharged to the required level.

The microcontroller152may be coupled to one or more measurement heads114(one exemplary measurement head is depicted inFIG.1B). The measurement head114may include a light source164and an optical sensor166. The electronics module150may also include an accelerometer168to facilitate accurate extension and angular rotation of the robot blade110. The electronics module150may also include a temperature sensor170to detect temperature near the wafer112.

The electronics module150may further include a wireless communication circuit, i.e. a radio circuitry for receiving wireless instructions from the computing device118and for transmitting optical inspection data to the computing device118. For example, the radio circuitry may include an RF front end module160and an antenna162(e.g., a UHF antenna), which may be an internal ceramic antenna, in one implementation. The batteries may be of a high temperature-tolerant type such as lithium ion batteries that can be exposed to a chamber temperature of 450 degrees C. for a short time period such as one to eight minutes.

Some components shown inFIG.1Bmay be located on or at the stationary part of the robot108. For example, the microcontroller152, the memory buffer154, and the RF front end160may be so located. Other components of the electronics module150may be located on the robot blade110. For example, the accelerometer168, and the temperature sensor170may be so located. In some implementations, some of the components of the electronics module150may be located both on the stationary part of the robot108and the extendable robot blade110, e.g., a power element156may be so located. In some implementations, two separate microcontrollers may be used, with one of the microcontrollers located on the stationary part of the robot108and the other microcontroller located on the optical inspection device. In some implementations, a temperature sensor167may be a part of the measurement head114(as shown by a dashed box displayed therein). The temperature sensor167may be separate from the global temperature sensor170and may independently measure substrate temperature and provide information to supplement optical data in order to compensate for temperature-induced variations in the optical properties of the wafer. In some implementations, the temperature sensor167may be included in every measurement head114, for precise measurement of temperature at the testing location(s) on the wafer. In some implementations, the temperature sensor167may be included in only some of the measurement heads114(e.g., only included in the leading sensor and/or the trailing sensor). In some implementations, the temperature sensor(s)167may not be included in the measurement heads114but instead may be positioned between the measurement heads114.

The wireless connection facilitated by the RF front end160and antenna162may support a communication link between the microcontroller152and the computing device118, in some implementations. In some implementations, the microcontroller152integrated with the robot108may have a minimal computational functionality sufficient to communicate information to the computing device118, where most of the processing of information may occur. In other implementations, the microcontroller152may carry out a significant portion of computations, while the computing device118may provide computational support for specific, processing-intensive tasks. Data received by the computing device118may be data obtained from the inside of the transfer chamber104, the processing chambers106, data generated by the optical inspection device, data temporarily or permanently stored in the memory buffer154, and so on. The data stored in the memory buffer154and/or transmitted to or from the computing device118may be in a raw or processed format.

In one implementation, the optical inspection device may direct (using the processing capabilities of the microcontroller152and/or the computing device118) light beams produced by the light sources to one or more locations on the surface of the wafer112(while the wafer is being transported by the robot blade110). The optical inspection device and collect reflected light data from each of the optical sensors of the measurement heads114. In some implementations, there may be n optical sensors, with each of the sensors collecting reflected light data (e.g., the reflectivity R(λ), the refractive index n(λ), polarization data, and so on), for each one of m locations of the wafer. Using the reflected light data from the measurement heads114, the microcontroller152and/or the computing device118may determine (e.g., using triangulation techniques), a tilt and displacement of the wafer at all or some of the m locations and retrieve calibration data, which may describe how a particular degree of tilt/displacement may affect the reflected light data. For example, a particular tilt angle may translate into a known error in determining the refractive index n(λ) of the wafer112. The microcontroller152and/or the computing device118may determine, based on the reflected light data and the calibration data one or more characteristics of the wafer112(e.g., one or more optical properties of the wafer), such as refractive index, extinction coefficient or optical attenuation (imaginary part of the refractive index), wafer thickness, and the like, at some or all of the m locations. The microcontroller152(or computing device118) may then output (and store in the memory buffer154) one or more characteristics of representative of a quality of the wafer112, such as a thickness of the wafer112, characterizing uniformity, smoothness, absence of contaminants, etc.

In some implementations, the reflected light data may include information about polarization of the reflected light. For example, the light incident on the surface of the wafer may be linearly (circularly, elliptically) polarized. For example, the incident light may be an s-polarized light (or a p-polarized light). By detecting an amount of p-polarization (or s-polarization, respectively) in the reflected light, the optical inspection device may determine one of the tilt angles of the wafer. For example, if the incident light is s-polarized and the plane of incidence is parallel to the velocity of the blade's motion, the presence of the p-polarization in the reflected light may signal that the wafer has a roll tilt. Similarly, if the plane of incidence is perpendicular to the velocity of the blade's motion, the presence of the p-polarization in the reflected light may signal that the wafer has a pitch tilt. By measuring the amount of the p-polarization in these two examples, the optical processing device may determine the angle of the corresponding tilt.

Similarly, collection of polarization data may be performed using circularly or elliptically (left-hand or right-hand) polarized incident light. In some implementations, to facilitate collection of polarization data, some of the measurement heads114may be setup so that the planes of incidence/reflection of the respective light beams are oriented differently for different measurement heads. For example, the first measurement head114may operate using the plane of incidence/reflection that is parallel to the direction of the blade's motion, whereas the second measurement head may have the plane of incidence/reflection that is perpendicular to this direction. In some implementations, polarization information may also be used not only as positional data—to detect orientation of the surface of the wafer—but also to determine the morphology of the wafer, such as it uniformity and isotropy of its bulk as well as its surface (e.g., smoothness of the surface).

The computing device118of the manufacturing machine100may include a blade control module120, an inspection control module122(to control operations of the light sources and optical sensors), and a wafer quality control module124, in one implementation, as well as a central processing unit (CPU), software, and memory (as shown inFIG.9). In some implementations, some of the functionality of the blade control module120, the inspection control module122, and the wafer quality control module124may be implemented as part of the electronics module150by the microcontroller152and the memory buffer154.

FIG.2illustrates an optical inspection device setup200, as affected by a tilt of a wafer being transported by a moving robot blade110. The top picture inFIG.2illustrates an ideal situation where the wafer112is transported with its surface horizontal. The incident light produced by the light source210is making an angle α with a normal to the surface, which coincides with the vertical direction. The reflected light makes the same angle α with the vertical direction and is absorbed by an optical sensor220. The top picture inFIG.2illustrates a situation where the wafer112experiences a tilt due to the motion of the robot blade110. The tilt illustrated (for schematic exemplary purposes only) is a pitch tilt to an angle β from the horizontal direction (the tilt angle is exaggerated for the purpose of illustration). As a result, although the incident light makes the same angle α with the vertical direction, the reflected light makes the angle α+2β with the vertical direction. The reflected light, therefore, strikes the optical sensor220at a location that is different from the location shown in the top picture inFIG.2. Implementations of this disclosure, which employ narrow-band chromatic optical sensors, make it easier to design such optical sensors220where a different optical path followed by the light reflected from a tilted (or displaced) wafer112causes less detection error. For example, it may be easier to optimize coatings of various optical elements (lenses, mirrors, etc.) for a narrower range of wavelength used by a chromatic sensor, as opposed to optimizing a variety of optical paths for a broadband sensor.

FIG.3Aillustrates an optical inspection device setup300employing a diffraction grating. Shown inFIG.3Ais an ideal situation where the wafer112is transported with its surface horizontal. The light reflected from the wafer112may enter a spectrograph slit310and interact with the diffraction grating320. The diffraction grating320may split the reflected light into its spectral components that may follow different optical paths. For example, a first reflected light with wavelength λ1(depicted schematically with dashed lines) may take optical paths ABC and A1B1C1whereas a second reflected light with wavelength λ2(depicted schematically with dotted lines) may take optical paths ABE and A1B1E1. A focusing mirror330(which may be replaced with a focusing lens, in some implementations) may focus the first light to a location D of an optical detector340and may focus the second light to a location F of the optical detector340.

FIG.3Billustrates the optical inspection device setup ofFIG.3A, as affected by a tilt of a wafer being transported by the moving robot blade110. A modification of the optical path ABCD (shown with dashed line) of the first reflected light ofFIG.3Ais shown schematically inFIG.3B. As a result of the tilt angle, the optical path of the first reflected light is A′B′C′D′ (shown with solid line) so that the first reflected light strikes the optical detector340at a location D′ that is different from the original location D for reflection from a horizontal wafer. The length of the optical path ABCD (with, possibly, additional reflections/refractions that may be experienced by the reflected light from additional optical elements not shown explicitly inFIGS.3A-B) may be quite significant, reaching tens of centimeters, in some implementations. Consequently, the difference in the lengths of the paths ABCD and A′B′C′D′ may be substantial (tens or even hundredth of wavelengths) even for small tilt angles β, and the displacement of the detection point D′ from reference point D may also be quite significant.

Implementations described herein, which employ narrow-band chromatic optical sensors, allow for an easier and more accurate optimization of the optical paths for various wavelengths of the reflected light if each of the optical sensors is designed to detect reflected light within a more limited (compared with a broadband sensor range) range of wavelengths. Furthermore, making each of the optical sensors to detect light within its own limited range of wavelengths makes calibration of the sensors—for various tilt angles and/or parallel displacements—a more straightforward task and facilitates more accurate measurements when the wafer112deviates from an ideal horizontal transportation path.

FIGS.4A-Billustrates challenges of optimizing and calibrating broadband optical sensors to account for wafer tilt and displacement during robot blade transportation.FIG.4Adepicts one exemplary spectrum of a typical light source that emits light ranging from IR range (800 nm) and down to UV range (200 nm). The spectrum may have a number of sharp emission peaks (as shown) and a broad continuum of intensity that varies significantly with the wavelength (the continuum illustrated has intensity at 450 nm that is about four times that of the intensity at 800 nm).FIG.4Billustrates an effect of the wafer tilt on the reflectance measurements, in one exemplary implementation. Depending on a particular realization of an optical sensor, the optical paths of various wavelengths may be affected differently by the tilt. For example, in the implementation depicted, the detected reflectance in the UV range is suppressed whereas the reflectance in the IR range is enhanced. The relative error in detected reflectance may be several percent (±4%, in the situation depicted inFIG.4B) although in other implementations the error may be more or less significant. In particular, the error may increase near sharp emission peaks. Because, as illustrated byFIG.4B, the relative error may vary with the wavelength, calibrating such errors for various tilts may be more efficient where measurement heads114have chromatic optical sensors220dedicated to narrow optical ranges. Such chromatic sensors have significantly more uniform tilt-induced errors, and such errors may be easier to account for using a calibration procedure. For example, in a situation illustrated inFIG.4B, using five 100 nm narrow-range detectors configured to detect light within the ranges of 200-300 nm, 300-400 nm, 400-500 nm, 500-600 nm, and 600-700 nm may ensure that the variation of the relative error is within 0.1-0.2% across any of the 100 nm ranges.

Having a more uniform optical performance within the working range of each of the chromatic optical sensors improves the accuracy of tilt/displacement compensation by, e.g., optimizing a signal-to-noise performance within each spectral range. For example, coatings and geometry (e.g., arrangement of the optical elements, design of the optical paths to be used) of each chromatic sensors may be optimized in view of the specific working range of the sensor. The use of chromatic sensors may allow replacing some elements (such as spectrograph gratings) that are characterized by a heightened sensitivity of their optical paths to the tilt/displacement of the wafer with less path-sensitive element. The use of chromatic sensors may also address a problem of oversaturation of some parts of the spectrum. For example, the use of a broadband sensor in situations depicted inFIG.4AandFIG.4Bof a strong UV emission of the light source and a lower long-wavelength reflectance of the waver may result in a lowered sensitivity of the broadband sensor to the long-wavelength part of the spectrum. Chromatic sensors, on the other hand, allow a variety of approaches to address this saturation. For example, signals that correspond to wavelengths with low reflectance may be selectively enhanced. This may be achieved by using optical filters (to filter out light outside the working range of the sensor), by increasing intensity of the light sources within the working wavelength range of the sensor, including making use of narrow-range light sources (such as lasers, light-emitting diodes, in some implementations), and so on.

The calibration process may be performed using one or more benchmark wafers. The benchmark wafers may be tilted (or given parallel displacements) in a controlled way and optical responses (e.g., dependence of the reflectance, index of refraction, etc.) of such wafers may be measured and stored (e.g., in the memory of the computing device118). In some implementations, the calibration process may be performed using benchmark wafers that have various degree of chemical and morphological uniformity, smoothness of the surface, thickness, and other relevant characteristics of the wafers. The calibration process may be performed for each of the chromatic sensors used in wafer inspection. During wafer inspection, a processing device may determine a position of the surface of the inspected wafer, for example, using methods of triangulation described below. The position of the surface may be specified in terms of a displacement of the surface from a reference position (e.g., from a horizontal reference plane). The position of the surface may further be specified in terms of the tilt (roll, pitch, yaw) angles.

FIG.5Aillustrates a top view of one exemplary implementation500of an optical inspection device capable of supporting accurate optical inspection of wafers transported on a moving blade. The optical inspection device may include n measurement heads114(a device with n=5 heads shown inFIG.5A), arranged in a single file, collinear with the direction of the motion of the robot blade110as (indicated by the arrow). Each measurement head114may have an optical sensor having a working range of wavelengths of 50-100 nm, in various implementations. In some implementations, the range of wavelength may be greater, e.g., 100-200 nm. In some implementation, one or more of the measurement heads114may include a broadband sensor with a working range of 500-700 nm. Some or all of the measurement heads114may include a light source to produce incident light within the working range of the respective optical sensor. Some of the measurement heads114may use light from the same (e.g., broadband) light source and filter out the light reflected from the wafer that happens to be outside the working range of the respective sensor. In some implementations, a single light source may be used with all measurement heads114.

As the robot blade110is transporting the wafer112(e.g., after processing in one of the processing chambers106), the measurement heads114may come in proximity to m measurement locations510on the surface of the wafer112(m=4 locations are shown inFIG.5A). This may happen sequentially, so that the rightmost measurement head114first comes in proximity to the leftmost measurement location, then to the second location from the left, to the third location and so on. In some implementations, the distance between two measurement heads114may be the same as the distance between two measurement locations510, so that two (or more) measurement heads may perform data collection simultaneously. In other implementations, the distance between two measurement heads114may be different from the distance between two measurement locations510, and some or all of the measurement heads114may be collecting data from various measurement locations510at different (e.g., staggered) times. In some implementations, the inspection control module122may time operations of the measurement heads114, based on timing information provided by the blade control module120, which indicates precise moments of time when the measurement locations510are in proximity with the measurement heads114. The operations of the blade control module120may be precisely synchronized with the operations of the measurement heads114so that optical data acquisition is performed at the correct moments of time when the targeted measurement locations on the wafer are aligned with acquisition areas of the measurement heads114. In some implementations, the operations of the blade control module120may be precisely synchronized with the operations of the measurement heads114in such a way that the first (last) target measurement locations coincide with the edges of the wafers, to determine the properties of the edges. In some implementations, when patterned wafers are being tested, the operations may be synchronized to determine the precision with which the regularity of the patterns has been achieved.

The inspection control module122may determine a precise moment of time when a j-th measurement location510is aligned with a k-th measurement head114. The alignment may be such that a light produced by an appropriate light source (e.g., a dedicated narrow-range light source of the k-th measurement head or a shared, among multiple heads, broadband light source) is reflected from the aligned location510so that the reflected light strikes the optical sensor of the k-th measurement head114. The light source may be activated for a short duration of time, in anticipation of the measurement location510arriving near the alignment point, and turned off when the measurement location510departs from the alignment point. Alternatively, the light source may provide a pulse having a fixed duration and an intensity that are selected based on the speed of the robot blade110. For example, for faster blade operations, the duration of the pulse may be shorter whereas the intensity may be increased proportionately so that the same (or approximately the same) amount of reflected light is reaching the optical sensor. In some implementations, the fixed duration of the pulse may be in the microsecond range whereas the interval between consecutive pulses is increased with speed of the robot blade to maintain the same sampling density.

In some implementations, synchronization of the operations of the measurement heads114and optical data acquisition may be performed of the blade control module120(e.g., using a robot software). For example, the blade control module120may be aware of the dimensions of the product (e.g., a wafer with films deposited thereon), the locations of the measurement heads114, and the layout of the processing chamber106. The blade control module120may, therefore, communicate to the inspection control module122the precise times when the measurement locations are aligned with the measurement heads114, and the inspection control module122may cause the measurement heads114to emit light towards the measurement locations. In some implementations, synchronization of the operations of the measurement heads114and the optical data acquisition may be performed using one or more dedicated optical sensors that detect arrival of an edge of the product (or some other representative feature of the product) into an optical inspection area. Based on the speed of the robot blade110(e.g., provided by the blade control module120), and the distance from the dedicated optical sensors to the measurement heads114, the inspection control module122may operate the measurement heads114at the precise instances when the measurement locations are aligned with the measurement heads114. In some implementations, the measurement heads114may operate continuously and provide a continuous (or quasi-continuous) stream of optical data. The synchronization information may then be used to associate (e.g., to map) measured optical data to specific locations on the product.

In some implementations, one or more of the measurement heads114may play the role of the one or more dedicated optical sensors. For example, the first measurement head114may output a light signal continuously and may detect when the product's edge aligns with the first measurement head114(e.g., by detecting a moment when a light reflected from the edge is incident on the optical sensor of the first measurement head114). In some implementations, the second, third, etc., measurement heads114may similarly output continuous light signals. The edge arrival times for these measurement heads114may be used for more accurate estimates (compared with a situation where only the first measurement head114is used to detect edge arrival) of the motion of the product and for more precise estimation when the target measurement locations are going to be aligned with the measurement heads114. In some implementations, the product arrival times for the first, second, third, etc., measurement head114may be used to correct the expected times of arrival provided by the inspection control module122(operating in conjunction with the blade control module120). For example, this may be performed as follows. Initially, the times of alignment of the target measurement locations with the measurement heads114may be known from the estimates made by the inspection control module122(based on the speed of the robot blade110, as provided by the blade control module120, and on the spatial layout of the chamber106). Subsequently, when the edge of the product is aligned with the first measurement head114, the inspection control module122may detect a discrepancy between the expected edge arrival time and the actual edge arrival time and introduce a first correction into the estimated dynamics of the blade/product. Likewise, when the edge of the product is aligned with the second measurement head114, the inspection control module122may detect another discrepancy between the new expected edge arrival time (corrected based on the edge detection by the first measurement head114) and the actual edge arrival time and may introduce a second correction into the estimated dynamics of the blade/product. The second correction may be smaller than the first correction. This process may be repeated with each subsequent measurement head providing a more accurate determination of the dynamics of the product. In other implementations, the synchronization information may be used to map measured optical data to specific locations on the product.

In the above example, an edge of the product is used as a detection reference. In some implementations, other features of the product may be used as detection references. For example a ridge, a groove, a boundary between two parts of the product (e.g., a boundary between two dies), a specific pattern on the surface of the product, and the like, may be so used.

FIG.5Billustrates another exemplary implementation550of the optical inspection device capable of supporting accurate optical inspection of wafers transported on a moving blade. The optical inspection device shown inFIG.5Amay have n measurement heads114(n=10 in the example depicted), arranged in a non-collinear fashion and designed to probe a two-dimensional distribution of the measurement locations510. Because some of the measurement locations510may be probed by only some (and not all) of the measurement heads114, some of the optical sensors and/or light sources in the measurement heads114may be duplicative (e.g., having the same working range of wavelengths). For example, the sensors in the rightmost measurement heads114in each of the three rows of measurement heads114inFIG.5Bmay be IR sensors with the same working range of 600-700 nm. In some implementations, the robot blade110may be capable of rotating the wafer112(e.g., around the wafer's center) so that a combination of a parallel motion of the wafer and its rotational motion may be used for optimization of the measurement process. For example, in some implementations, the combination of the two motions may be used to maximize the number or various measurement locations510accessible to the measurement heads114so that as wide area of the wafer112as possible may be inspected.

FIGS.6A-Cillustrate a side view of operations of one exemplary implementation600of an optical inspection device capable of supporting accurate optical inspection of wafers transported by a moving blade. For the sake of brevity and conciseness, only two measurement locations510and two measurement heads114are depicted and the tilt of the wafer is implied but not indicated explicitly. As illustrated inFIG.6Ain an exemplary fashion (the actual optical paths may differ, in various implementations), when the robot blade110transports the wafer sufficiently far to the left, so that a first measurement location510-1is aligned with a first measurement head114-1, a light source of the first measurement head114-1may be activated to produce a light incident on the first measurement location510-1. The incident light (having a first range of wavelengths) may generate a light reflected from the first measurement location510-1to be detected by the first measurement head114-1. At the same time, a second measurement head510-2may be in an idle state and the light source of the second measurement head114-2may be turned off (e.g., to optimize power consumption).

As illustrated inFIG.6B, when the robot blade110transports the wafer so that the first measurement location510-1is aligned with the second measurement head114-2, a light source of the second measurement head114-2may be activated to produce a light incident on the first measurement location510-1. This allows to probe the optical response of the first measurement location510-1for a second range of wavelengths (the ranges indicated schematically with symbols λ1and λ2). If the distance between the measurement locations is the same as between the measurement heads, the first measurement head114-1may be simultaneously activated to collect data (for the first range of wavelengths) from the second measurement location510-2.

As illustrated inFIG.6C, when the robot blade110transports the wafer so that the second measurement location510-2is aligned with the second measurement head114-2, a light source of the second measurement head114-2may be activated again to produce a light incident on the second measurement location510-2. This allows to probe the optical response of the second measurement location510-1within the second range of wavelengths. At the same time, the first measurement head510-1may be in an idle state and its light source may be turned off.

The operations depicted inFIGS.6A-Bare intended to illustrate a general concept of sequential probing of multiple locations of the wafer using multiple optical sensors; the number of locations and optical sensors as well as the geometric arrangement of the actual elements may differ from those depicted inFIGS.6A-B. Even though the depictions of show a near normal incidence/reflection of light from the wafer, this may not need be the case in some implementations, where angled incidence/reflection may be used instead.

FIG.7illustrates exemplary implementation700of light delivery system of the optical inspection device capable of supporting accurate optical inspection of wafers transported by a moving blade. A first measurement head may include a light source710-1and an optical sensor720-1. The light source710-1may be a dedicated source intended to be used only with the optical sensor720-1. In some implementations, the light source710-1may be a narrow-band light source, such as a light-emitting diode, a laser, etc. In some implementations, the light source710-1may be a broadband source whose spectral distribution is narrowed by additional optical elements (e.g., filters, absorbers, etc.). The light generated by the light source710-1may be, upon reflection from the wafer112, detected by the optical sensor720-1.

A second measurement head may include a light source710-2and an optical sensor720-2. The light source710-2may be a dedicated source to be used only with the optical sensor720-2. In some implementations, the light from the light source710-2may be delivered to the surface of the wafer112by an optical fiber730-1, in order to achieve enhanced directionality of the light incident on the wafer112. The optical fiber730-1may be designed to support delivery of a specific range of wavelengths, such as a working range wavelengths for the optical sensor720-2. For example, the material of the optical fiber may have the index of refraction n(λ) that is sufficiently small in the IR range so that IR light can escape from the fiber. On the other hand, the index of refraction may have a substantial imaginary part (responsible for light attenuation) in the UV range, so that UV light is absorbed inside the optical fiber730-1and is prevented from reaching the wafer112.

In some implementations, a third measurement head and a fourth measurement head may have separate optical sensors (sensors720-3and720-4, respectively) but share a common light source710-3. The light from the light source710-3may be delivered to the wafer using separate optical fibers730-2and730-3. The light delivered through the optical fibers730-2and730-3may have a substantially similar spectral content, in some implementations. In some implementations, while the light delivered to the wafer112(incident light) may be similar, optical filters may be used to narrow the spectral distribution of the reflected light before the reflected light reaches the optical sensors720-3and720-4. In some implementations, optical fibers may be used not only to deliver an incident light to the wafer112, but also to propagate the reflected light to the optical sensors. For example, as shown inFIG.7, the optical fiber740may be used to deliver the reflected light to the optical sensor720-4.

The light produced by the light sources710(e.g., any or all of the light sources710-1through710-4) may be coherent beams, such as laser beams, in some implementations. In other implementations, the light sources710may produce natural light, linearly, circularly, or elliptically polarized light, partially-polarized light, focused light, and so on. The light sources710may produce a continuous beam of light or a plurality of discrete pulsed signals. The light sources710may produce a collimated beam of light, a focused beam of light, or an expanded beam of light. The light sources710may include one or more monochromatic beams having a frequency/wavelength within a narrow region of frequencies/wavelengths near some central frequency/wavelength, in some implementations.

The optical sensors720(e.g., any or all of the sensors720-1through720-4) may be complementary metal oxide semiconductor (CMOS) sensors, or may use a charge coupled device (CCD), or any other known light detection technology. The optical sensors720may include any number of known optical elements, such as mirrors, lenses, absorbers, polarizers, gratings, collimators, etc. In some implementations, some or all of the optical sensors720may have working ranges of wavelength that are centered differently than some or of the other optical sensors720. In some implementations, the optical sensors720may have a partial overlap of their working ranges.

The optical sensors720may communicate with the microcontroller152(and/or computing device118) and may be capable of facilitating triangulation measurements. Namely, in addition to intensity data, at least some of the optical sensors may be capable of collecting positional data to determine positional data representative of a direction of the reflected light generated at the measurement locations. This positional data may be used to determine a positon of the surface of the wafer at least at some of the measurement locations510.

For example, in the optical triangulation method, the inspection control module122may infer a point where the line corresponding to the axis of the beam incident on the surface of the wafer112(produced, e.g., by any of the light sources710) intersects the axis of the beam reflected from the wafer112. The direction of the incident beam may be calibrated into the optical triangulation method and the direction of the reflected beam may be determined from the maximum reflected beam intensity, using an angular distribution of the reflected beam intensity, e.g., as captured by the corresponding optical sensor720, in one implementation.

Having determined the coordinates (x, y, z) of the intersection point, the inspection control module122may associate this point with the measurement location on the wafer (e.g., a location on the surface of the wafer). The inspection control module122may also retrieve data from the blade control module120, to determine the expected position of this measurement location at the present moment of time (given the location of the robot blade110). By comparing the difference between the expected coordinates and the actual coordinates, the inspection control module122may compare this difference with similar differences determined using triangulation data from other locations and/or other optical sensors. From a plurality of such measurements, the inspection control module may determine the tilt angles (e.g., roll, pitch, and yaw) angles and parallel displacements (along three spatial directions) of the wafer at some or all of the measurement locations510.

The wafer quality control module124may then retrieve the calibration data. The calibration data may contain a (set of) table(s), or a (set of) a mathematical formula(s), or any other type of correspondence between a tilt angle or displacement distance for various wavelengths λ and a tilt/displacement correction to the measured optical response of the wafer (e.g., reflectivity). Such correspondence may be for a discrete set of wavelengths, such as 10 (20, or any other number) per working range for the respective speaker. In some implementation, the discrete set of wavelengths may be quasi-continuous. In some implementations, tilt/displacement correction retrieved with the calibration data may be used by the wafer quality control module124to compensate for the detected tilt/displacement. Additionally, in some implementations, the tilt/displacement data may be used by the blade control module120to adjust position of the robot blade110to reduce tilt/displacement. In such implementations, the tilt/displacement may change (as the blade control module120controls to reduce them) while the wafer is being transferred between various measurement heads. Accordingly, each subsequent measurement head may collect additional tilt/displacement data to ensure that the current data reflects the actual current positioning of the wafer as accurately as possible.

FIG.8is a flow diagram of one possible implementation of a method800of accurate optical inspection of wafers transported by a moving blade. Method800may be performed using systems and components shown inFIGS.1-7or any combination thereof. Method800may be performed using a single optical sensor or a plurality of light sensors. Method800may be performed using a single light source or a plurality of light sources. Some of the blocks of method800may be optional. Some or all blocks of the method800may be performed responsive to instructions from the computing device118or the microcontroller152, in some implementations. The computing device118may have one or more processing devices (e.g. central processing units) coupled to one or more memory devices. The method800may be performed without taking a manufacturing system (such as the manufacturing machine100) off the production process. In some implementations, the method800may be implemented when a wafer is being retrieved from the processing chamber by a robot blade of a robot, for example while the robot blade110is transporting the processed wafer through the transfer chamber104towards the loading stations102. For example, the robot108may extend the robot blade110from the transfer chamber104into the processing chamber106(through a transfer port) and retrieve the processed wafer from its position (116) in the processing chamber106. The robot blade110may subsequently withdraw back into the transfer chamber104. The robot108may then rotate the robot blade110towards the loading station102where the processed wafer112may be cooled down, purged from contaminants by a flow of a purging gas, deposited a receiving pod, etc. The optical inspection may be performed while the wafer is inside the transfer chamber104or while the wafer is inside the loading station102. In some implementations, the optical inspection may be performed before purging; in other implementations, the optical inspection may be performed after purging. The optical inspection may be performed while the robot blade110implements a standard retrieval procedure, without slowing down the robot blade's motion. Accordingly, the optical inspection may be performed without delaying the manufacturing process.

The method800may involve a processing device (a microcontroller152, alone or in communication with the computing device118) causing a first light beam, produced by a first source of light, to be directed to a first location on a surface of the wafer while the wafer is being transported from the processing chamber by the moving blade (block810). The first light beam incident on the surface of the wafer may generate, at the first location, a first reflected light.

A first optical sensor may detect the first reflected light and collect a first data representative of a direction of the first reflected light (block820). The first data may include positional data, such as the information about the angular distribution of the first reflected light, for example the direction of the maximum intensity of the first reflected light, the width of the angular distribution, and so on. The first optical sensor may also collect a second data, which may be intensity data. The intensity data may be representative of a first plurality of values I(λj) characterizing intensity I of the first reflected light at a corresponding one of a first plurality of wavelengths λj, each of the first plurality of wavelengths belonging to a first range of wavelengths Λ1(block830).

At block840, method800may continue with the processing device determining, using the first data obtained from the optical sensor, a position of the surface of the wafer. The position of the surface may be determined relative to some reference position, such as a reference plane. For example, the position of the surface may be specified with one, two, or three tilt angles describing some or all of the roll, pitch, and yaw. The displacement of the surface of the wafer may be specified, for example, as a vertical offset from the reference plane.

In some implementations, method800may be performed using an optical inspection device having more than one optical sensor (and, optionally, more than one source of light). In such implementations, method800may continue, at an optional block850, with the processing device causing a second light beam to be directed to the first location on the surface of the wafer. In some implementations, the second light beam may be produced by a second source of light that is different from the first source of light (e.g., the second light beam may have a different spectral distribution). In other implementations, the second light beam may be produced by the same first source of light. The second light beam may be delivered (e.g., by an optical fiber or by a direct propagation) to the first location on the surface of the wafer when the first location is aligned (or about to be aligned) with the second optical sensor. The second light beam may generate, at the first location, a second reflected light. In implementations with n>2 optical sensors, the processing device may similarly direct a third (fourth, etc.) light beam to the first location on the surface of the wafer, when the first location is aligned with the respective sensor(s), and the third (fourth, etc.) light beam may generate a third (fourth, etc.) reflected light from the first location.

At an optional block860, method800may continue with collecting, by a second optical sensor, a third data that may be intensity data. The intensity data may be representative of a second plurality of values I(λk) characterizing intensity of the second reflected light at a corresponding one of a second plurality of wavelengths λk, each of the second plurality of wavelengths belonging to a second range of wavelengths Λ2. The second range of wavelengths Λ2may be centered differently than the first range of wavelengths Λ1. In some implementations, the third data may further include positional data obtained from the second location, which may be used to supplement the positional data obtained from the first location. In some implementations, the positional data from the second location may be used to more accurately determine the tilt/displacement of the wafer. For example, if the wafer is rigidly supported by the robot blade, the tilt angles may be expected to be the same at both locations. Therefore, if positional data from two (or more) locations indicate that the tilt angles are different, this may be attributed to a measurement error. To reduce the effect of such an error, the tilt angle may be computed as some average (e.g., as the mean) of the tilt angles determined using the positional data from multiple locations. In other implementations, where the blade allows the wafer to bend during transportation, various values of the determined tilt angles may be treated as the actual tilt angles at the corresponding locations. In some implementations, the third data may only include the intensity data but not positional data. For example, the processing device may determine the tilt of the wafer based on the first data collected by the first sensor but not by the second sensor. For example, only the first sensor may include a triangulation setup whereas the remaining sensors may only collect intensity data.

Similarly, method800may employ additional (third, etc.) sensors that may collect additional (fourth, etc.) data representative of a further (third, etc.) plurality of values characterizing intensity of the additional (third, etc.) reflected light at a corresponding one of a (third, etc.) plurality of wavelengths belonging to additional (third, etc.) range of wavelengths (Λ3, Λ4, etc.).

At block870, method800may continue with the processing device retrieving calibration data. The calibration data may be stored in one or more memory devices, such as the memory buffer154or a memory device of the computing device118. Using the calibration data, the position of the surface of the wafer, and the second data, the processing device performing method800may determine one or more characteristics representative of a quality of the wafer (880). “Quality of the wafer” herein means any properties of the wafer or materials attached thereon, such as a quality of (one or more) film(s) deposited on the surface of the wafer. For example among the characteristics representative of the quality of the wafer may be a thickness of the wafer at the first location, a thickness of a film deposited on the wafer at the first location, a uniformity of the wafer at the first location, a uniformity of a film deposited on the wafer at the first location, a smoothness of the surface of the wafer at the first location, or a smoothness of a surface of a film deposited on the wafer at the first location.

FIG.9depicts a block diagram of an example processing device900operating in accordance with one or more aspects of the present disclosure and capable of supporting accurate optical inspection of wafers transported on a moving blade. The processing device900may be the computing device118ofFIG.1Aor a microcontroller152ofFIG.1B, in one implementation.

Example processing device900may be connected to other processing devices in a LAN, an intranet, an extranet, and/or the Internet. The processing device900may be a personal computer (PC), a set-top box (STB), a server, a network router, switch or bridge, or any device capable of executing a set of instructions (sequential or otherwise) that specify actions to be taken by that device. Further, while only a single example processing device is illustrated, the term “processing device” shall also be taken to include any collection of processing devices (e.g., computers) that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methods discussed herein.

Example processing device900may include a processor902(e.g., a CPU), a main memory904(e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM) such as synchronous DRAM (SDRAM), etc.), a static memory906(e.g., flash memory, static random access memory (SRAM), etc.), and a secondary memory (e.g., a data storage device918), which may communicate with each other via a bus930.

Processor902represents one or more general-purpose processing devices such as a microprocessor, central processing unit, or the like. More particularly, processor902may be a complex instruction set computing (CISC) microprocessor, reduced instruction set computing (RISC) microprocessor, very long instruction word (VLIW) microprocessor, processor implementing other instruction sets, or processors implementing a combination of instruction sets. Processor902may also be one or more special-purpose processing devices such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), network processor, or the like. In accordance with one or more aspects of the present disclosure, processor902may be configured to execute instructions implementing method800of accurate optical inspection of wafers transported by a moving blade.

Example processing device900may further comprise a network interface device908, which may be communicatively coupled to a network920. Example processing device900may further comprise a video display910(e.g., a liquid crystal display (LCD), a touch screen, or a cathode ray tube (CRT)), an alphanumeric input device912(e.g., a keyboard), an input control device914(e.g., a cursor control device, a touch-screen control device, a mouse), and a signal generation device916(e.g., an acoustic speaker).

Data storage device918may include a computer-readable storage medium (or, more specifically, a non-transitory computer-readable storage medium)928on which is stored one or more sets of executable instructions922. In accordance with one or more aspects of the present disclosure, executable instructions922may comprise executable instructions implementing method800of accurate optical inspection of wafers transported by a moving blade.

Executable instructions922may also reside, completely or at least partially, within main memory904and/or within processing device902during execution thereof by example processing device900, main memory904and processor902also constituting computer-readable storage media. Executable instructions922may further be transmitted or received over a network via network interface device908.

The implementations of methods, hardware, software, firmware or code set forth above may be implemented via instructions or code stored on a machine-accessible, machine readable, computer accessible, or computer readable medium which are executable by a processing element. “Memory” includes any mechanism that provides (i.e., stores and/or transmits) information in a form readable by a machine, such as a computer or electronic system. For example, “memory” includes random-access memory (RAM), such as static RAM (SRAM) or dynamic RAM (DRAM); ROM; magnetic or optical storage medium; flash memory devices; electrical storage devices; optical storage devices; acoustical storage devices, and any type of tangible machine-readable medium suitable for storing or transmitting electronic instructions or information in a form readable by a machine (e.g., a computer).

In the foregoing specification, a detailed description has been given with reference to specific exemplary implementations. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the disclosure as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense. Furthermore, the foregoing use of implementation, implementation, and/or other exemplarily language does not necessarily refer to the same implementation or the same example, but may refer to different and distinct implementations, as well as potentially the same implementation.