BACKGROUND OF THE INVENTION

1 , Field of the invention

This invention generally relates to methods and systems for metrology optimized inspection in which metrology data for a wafer is used to alter one or more parameters of a wafer inspection process for the wafer or another wafer,

2, Description of the Related. ^' Art

The following description and examples are not admitted to be prior art by virtue of their inclusion in t is section.

Fabricating semiconductor devices swell as logic and memory devices typically includes processing a substrate such as a semiconductor wafer using a large umber of semicondtictor fabrication processes to form various features and multiple levels of the semiconductor dev ices. For example, lithography is a

semiconductor fabrication process that involves transferring a pattern from a reticle to a resist arranged on a semiconductor wafer. Additional examples of

semiconductor fabrication processes include, but are not limited to, chemical- mechanical polishing, etch, deposition, and ion implantation. Multiple

semiconductor devices may be fabricated in an arrangement on a single

semiconductor wafer and then separated into individual semiconductor devices.

Inspection processes are used at various steps during a semiconductor manufacturing process to detect defects on wafers. Inspection processes have always been an important part of fabricating semicon uctor devices such as i Integrated circuits. Bow ever, as the dimensions of semiconductor devices decrease. Inspection processes become even more important to the successful manufacture of acceptable semiconductor devices. For instance-, as the dimensions of semiconductor devices decrease, detection of defects of decreasing size has become necessary since even relatively small defects may cause unwanted aberrations in the semiconductor devices.

Many different types of inspection systems have adjustable output

acquisition (e.g., data, signal, and/or image acquisition) and sensitivity (or defect detection) parameters such that different parameters can be used to detect different defects or avoid sources of unwanted (nuisance) events. Although an inspection system that has adjustable output acquisition and sensitivity parameters presents significant advantages to a semiconductor device manufacturer, these inspection systems are essentially useless if the incorrect output acquisition and sensitivity parameters are used for an inspection process. Although using the correct output acquisition and sensitivity parameters will have a dramatic effect on the results of inspection. It is conceivable that many inspection processes are currently being performed with incorrect or non-optimized output acquisition and sensitivity parameters.

In currently used methods for wafer inspection process setup, a defect engineer may set up a wafer inspection recipe with several limitations. For example, the user may set up the inspection sensitivity based on a limited number of wafers that are available and Only selected areas on the wafers _* A user also may choose t use multiple wafers to set up sensitivity in an effort to accommodate wafer-to-wafer variation due to fabrication process variability. In other applications, a user may choose data from one or more die to define reference (nominal) images for the pu pose of setting up a reference die. in such applications, a user can guess the best place to collect data but that place may not represent true nominal conditions. In another application, a user may choose various defects for review sampling but the sampling population is based on die or locations where the noise level is often unknown.

In the area of inspection optimization, not knowing whe e the noisy areas are can restilt in setting up sensitivity based on only noisy regions or only quiet regions that may not truly reflect variations across wafers. If die row selection was done on a quiet region, additional nuisance defects may arise when additional wafers are scanned. If die selection was done in a noisy region, real defects may be missed during production wafer scans due to thresholds being set too high. With respect to nominal die selection, the challenge is to select dies that are at truly nominal conditions where average thickness, critical dimension (CD), etc, are present. Not having this data set can lead to selecting dies that do not represent the nominal signature. With regard to defect samp i g, delects that are sampled In a nois region can produce low signal-to-noise while an optimized sampling from a quiet region may yield more real defects.

Accordingly, it would be advantageous to develop systems and/or methods that do not have one or more of the disadvantages described above.

SUMMARY OF THE INVENTION

The following descri p tion of various embod iments is not to he constru ed in any way as limiting the subject matter of the appended claims.

One embodiment relates to a computer-implemented method for determining one or more parameters of a wafer inspection process. The method includes acquiring metrology data for a wafer generated by a wafer metrology system. The method also includes determining one or more parameters of a wafer inspection process fo the wafer or another wafer based on the metrologv data. The acquiring and determining steps are performed by a computer system. The method described above may be performed as described further herein.

In addition, the method described above may include any other step(s) of any other method(s) described herein. Furthermore, the method described above may be performed by any of the systems described herein.

Another embodiment relates to a non-transitory computer-readable medium storing program instructions executable on a computer system for performing a computer-implemented method for determining one or more parameters of a water inspection process. The co mp uter- im ! em en ted method includes 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 described further herein. In addition, the computer- implemented method for which the program instructions are executable may include any other stepfs) of any other method(s) described herein.

An additional embodiment relates to a system configured to determine one or more parameters of a wafer inspection process. The system includes an inspection subsystem configured to generate output for a wafer. The system also includes a computer subsystem configured for performing the acquiring and determining steps of the method described above. The system may be further configured as described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the accompanying drawings in which: Fig. I is a block diagram Illustrating ^' one embodiment of a non-transitory computer-readable medium that includes program instructions executable on a computer system for performing one or more of the computer-implemented, methods described herein; and

Fig. 2 is a schematic diagram illustrating a side view of one embodiment of a system configured to determine one or more parameters of a wafer inspection process.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail, it should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION iW THE PREFERRED EMBODIMENTS

Turning now to the drawings, it is noted that the .figures are not drawn to scale. I n particular, the scale of some of the elements of the figures is greatly exaggerated to emphasize characteristics of the elements. It is also noted that the figures are not drawn to the same scale. Elements shown in more than one figure that may be similarly configured have been Indicated usin the same reference numerals. Unless otherwise noted herein, any of the elements described and shown may include any suitable commercially available elements.

One embodiment relates to a computer-implemented method for determining one or more parameters of a water inspection process. The method includes acquiring metrology data for a wafer generated by a wafer metrology system. Acquiring the metrology data may include performing measurements on the wafer such as any of those described farther herein using a wafer metrology tool, which may be configured as described herein. In this manner, acquiring the metrolog data may include measuring the wafer. However, acquiring the metrology data does not necessarily include performing measurements of the wafer. For example, acquiring the metrology data may include acquiring the metrology data from a storage medium in which the metrology data has been stored (e.g., by the metrology system}. Acquiring the metrology data from the storage medium ma be performed in a»v suitable manner, and the storage medium from which the metroiogv data is acquired may include any of the storage media described herein.

In one embodiment, the metrolog data includes information for w arp of the wafer. In another embodiment, the metrology data includes information for bow of the wafer, in an additional embodiment, the metrology data includes a thickness of a film formed on the wafer. In a further embodiment, the metrology data includes a critical dimension (CD) of a patterned structure formed on the wafer. In some embodiments, the metrology data includes more than two million metrology dat points generated across the w afer. For example, relatively high resolution metrology points (i.e., millions of metrology data points acquired across a wafer) can be used to identify potential sources of inspection noise for recipe setup. The metrolog data described above may be generated by any suitable metrolog tool in any suitable manner.

With ever shrinking process windows and relatively large wafer diameters, a relatively small change in wafer bow and arp can have a significant effect on film thickness and CD variation. In inspection, often defect data can be inundated with nuisance defects due to such variations but has never been compensated for. By metrology-aware inspection described herein, parameter(s) of wafer inspection such as inspection sensitivit and/or die sampling may be optimized as described further herein. The method includes determining one or more parameters of a wafer inspection process for the wafer or another wafer based on the metrology data. For example, metrology data desc ibed herein (e.g., mask metrology, wafer film

thickness, water C D metrology) can be linked to inspection as described herein. In this manner, the metrology data may be fed forward to inspection. For example, a metrology tool such as one of those described herein can be configured to send metrology data for a wafer directly to an inspection system. The inspectio system may then use the metrology data to perform one or more steps of the methods described herein snch as recipe setup and/or defect sampling, which ma be performed as described further herein. in this manner, metrology data can be integrated into inspection t fine tune inspection and delect sampling. In one such example, data may be sent from a metrology system to inspection where inspection uses data to classify and/or group areas based on variation in the metrology data. Once the noisy and quiet areas are identified, an inspection strategy can be set accordingly. As such, the embodiments described herei are configured for metrolog optimized inspection (e.g., inspection having improved detection sensitivity and improved defect analysis based on metrology data), in this manner, metrology data such as wafer bow, warp, and thickness data can be used to improve inspection. The interaction of wafer metrology and inspection can help set up production worthy inspection processes white prioritizing potential real defects.

In one embodiment, the one or more parameters of the wafer inspection process that are determined for one or more areas on the wafer or the other wafer are different from the one or more parameters determined for one or more other areas on the wafer or the other wafer. For example, based on variations in the metrology data across the wafer (i.e., as a function of position or region on the w afer), the parameter(s) of the wafer inspection process can be set to vary across the wafer, in one such example, ased on metrology data for an edge region of the wafer, an edge yield inspection strategy can be defined. In addition, the metrolog data may indicate that different regions of the wafer proximate to the edge of the wafer may have different issues. Therefore, different inspection strategies can be implemented for different edge regions based on the potential yield issues that may be present in the different edge regions, which can be determined based on the metrology data. The variations in the metrology data across the wafer can also be used to determine different regions on the w afer having similar metrology data. The regions having similar metrology data (e.g., noisy regions or quiet regions) can then be grouped together or assigned the same classification. Regions in the same group or having the same assigned classification can then be assigned the same inspection process parameter^). In this manner, the wafer inspection process ca he optimized based on variations in the metrology data. in some embodiments, the one or more parameters of the wafer inspection process include one or more para meters of defect detection performed during the wafer inspection process. In this manner, the embodiments described herein can be used to improve defect detection by integrating metrology data from wafer measurement. The one or more parameters of defect detection may include any parameters of inspection system output processing (i.e., signal, image, or data processing) and any parameter(s) of any defect detection algorithm(s) and/or method(s) performed to detect defects on the wafer. For instance, as described further herein, the one or more parameters may include a sensitivity of t he inspection or defect detection. However, an other parameter(s) of defect detection ma be altered in a siradar manner including a complete change in defect detection algorithm and/or method.

In another embodiment, the one or more parameters of the wafer inspection process include one or more parameters that at leas partially determine a sensitivity of defect detection performed for one or more areas of the wafer or the other wafer. Jo this manner, metrolog data can be linked to inspection for recipe sensitivity. For example, wafer geometry and metrology can be used to optimize inspection sensitivity and to locate noisy/quiet regions for improved data analysis. By linking metrolog and inspection technologies, the embodiments described herein can deliver a unique solution in providing the most sensitive inspections. In addition, the embodiments described herein can help explain when there are relatively large amounts of nuisance defects and allow a user to determine how to address it. I» tills maimer, the close connectivity of metrology and Inspection described herein ca be leveraged to provide the most advanced inspection. The embodiments described herein also provide additional use cases and therefore additional value for metrology tools.

I an additional embodiment, the one or more parameters of the wafer inspection process include one or more parameters of defect sampling performed during the wafer inspection process. For example, the metrology-aware inspection described herein can provide clues to tune sampling so that real defects are likely t be selected for defect, review (e.g., scanning electron microscope (SEM) review). In addition, the metrology data described herein can be used tor predicting where nuisance defects may occur and therefore adjusting review sampling and predicting noise. In this manner, metrology data can be linked to inspection for review sample binning. As such, the embodiments described herein can be used to improve defect sampling by integrating metrology data from wafer measurement. in one embodiment, the one or more parameters of th wafer inspection process include a selection of one or more areas on the wafer or the othe wafe at which output is generated by a wafer inspection system during the wafer inspection process. For example, metrology data described herein may be linked to inspection to automatically determine die selection for recipe optimisation and review sampling. In addition, a good variety of quiet and noisy areas can be selected to optimize a production quality recipe. Furthermore, the metrology data described herein can be used to separate critical inspection ant! metrology regions such that Inspection can be performed where the signal is higher for defects of interest (DOIs) on the wafer. in some embodiments, determining the one or more parameters includes determining a probability of CD variation in one or more areas of the wafer or the other wafer based on the metrology data, determining at least one of the one or more areas in w hich the probability is higher than other of the one or more areas, and determining the one or more parameters such that the at least one of the one or more areas is sampled by wafer inspection system that performs the wafer inspection process more heavily than the other of the one or more areas. The probability of CD variation in different areas of the wafer may be determined in any suitable manner. For instance, If there is a bow or warp in the wafer, some portions of the w afe may be out of focus in a lithography step performed on the w afer and therefore may have CDs that vary from the designed CDs. Therefore, based on information about the wafer determined from the metrology data, areas of the wafer that may have relatively high CD variation can be determined and then sampled more heavily than areas that will not likely have high CD variations. In this manner, metrology data such as that described herein can be used to tone inspection sampling to look fo possible CD variation. As such, the metrology data described herein can be used to separate critical inspection and metrology regions such that areas on the water where variations may be high are measured.

In another embodiment, determining the one or more parameters includes selecting one or more die on the wafer the other wafer based on the metrology data, acquiring output generated by a wafer inspection system for the one or more selected die, and generating a reference die from the output generated by the wafer inspection system for the one or more die. The reference die is used in the wafer inspection process to detect defects on the wafer or the other wafer. For example, the metrology data described herein can be used to identify a nominal condition area on the wafer, and then a set of reference die Le„ one or more reference dies) ma be selected from that area. By selecting die(s) in a quiet region of a wafer, the quality of the nominal image can be improved. In addition, the film thickness and CO metrology data can be used to identify a set of dies that are representative of nominal conditions. As such, the metrology data described herein can be used to identify iocation(s) of nominal iinage(s) for reference image selection to enhance die- to-reference image inspection. In this manner, metrology data can be linked to inspection for reference tile selection. in a further embodiment, determining the one or more parameters of the wafer inspection process includes determining, based on one or more first parameters of the wafer Inspection process and the metrology data, which one or more areas on the wafer or the other wafer will produce more noise than other areas on the waler or the other wafer in the wafer inspection process and which one or more additional areas on the wafer or the other wafer will produce less noise than other areas on the wafer or the other wafer and determining one or more second parameters of the wafer inspection process based on the on or more areas and the one or more additional areas. For example, metrology data such as wafer warp or bow data collection can be used to determin locations on a wafer where an inspection recipe is optimized. By utilizing millions of data points and identifying regions that are noisy versus quiet, wafer inspection parameters) such as recipe sensitivity setting and defect sampling can be optimised based on foreknowledge of the quality of the region. For example, the metrology data described herein can help understand the amount of variation In the wafer to anticipate variation to set inspection sensitivity accordingly. In one such example, the metrology data can be used to separate noisy and nominal areas and to set inspection sensitivity

independently for the different areas. In addition, the metrology data can be used to identify noisy inspection area(s) for nuisance data prioritization and filtering. Fo example, significantly more nuisance detects will typically be detected in a high noise region on the wafer, which can be determined from the metrology data as described herein, than a region having nominal o less noise. On the other hand, in relatively low noise regions, there is a higher probability of detecting real defects. Therefore, one or more parameters of noisance filtering can be determined based on the expected noise in different regions of the wafer.

In one snch embodiment, the one or more second parameters include one or more defect sampling parameters, and the one or more defect sampling parameters are determined to preferentially select random defects in the one or more additional areas that will produce less noise than the other areas. For exam le, by sampling defects from relatively quiet regions on the wafer, sampling of defects can show more random defects. In this maimer, quiet regions may be selected for random defect discovery. In addition, review sampling can be skewed toward quiet regions on the wafer to increase the chance of selecting real defects. in another such embodiment, the one or more second parameters include one or more defect sampling parameters, and the one or more defect sampling parameters are determined to preferentially select systematic defects in the one or more areas that will produce more noise than the other areas. For example, noisy regions may b a good proxy for sampling potential systematic defects.

In both of the embodiments described above, the defects that are detected in the wafer inspection process may foe assigned an IB that identifies the high/low variation region in which the defects were detected. In other words, defects detected in a region having a high variation, in the metrolog data may be assigned one ID, and defects detected in a region having a lo variation in the metrology data may be assigned a different ID. In this manner, the defects may be sampled and classified by regions in which they were detected. The defect detection results of the wafer inspection process may be correlated to the metrology data In any other suitable manner. For example, a defect map generated by inspection may be correlated to a metrology map. In one embodiment the method includes acquiring metrology or inspection data for a reticle, the reticle is used to print patterned features on the wafer, and determining the one or more parameters of the wafer inspection process is performed based on the metrology data for the wafer in combination with the metrology or inspection data for the reticle. In this manner, mask metrolog data may be used to identify within reticle anomalies that may contribute to inspection noise. For example, information about defects or potential def cts detected on a reticle bv reticle meiro!ogv and/or inspection ca be used to determine information about defects or potential defects that will be printed on a wafer by that reticle, in some such instances, information about the defects on the reticle that are

determined to be permissible by reticle inspection and/or metrology may be used to identify locations on the wafer where those permissible defects will be located.

Those locations may be scanned and checked for defects in wafer inspection to ensure that the defects are actually permissible. Alternatively, those locations may not be inspected at ail since presumably if wafer defects are detected there, those wafer defects will be permissible as a result of the permissible reticle defects.

Therefore, the one or more parameters of the wafer inspection process that are determined based, at least in part, on the metrolog or inspection data fo the reticle may include where to inspect on the wafer, types of inspection, classifications to be assigned to defects detected in certain areas of the wafer, etc. The reticle inspection and/or metrology data can be used in combination with the wafer metrology data for determining wafer inspection parameters) in a number of different ways such as via a set of roles that define suitable wafer inspection arameters) for different combinations of reticle inspection and/or metrology data and wafer metrology data. In addition, the wafer inspection parameters) can be defined based on the reticle inspection and/or metrology data as described in U.S. Patent Application

Publication No. 2005/000477 by Mareila et al. published on January 6, 21)05, which is incorporated by reference as if fully set forth herein. The embodiments described herein may be further configured as described in this patent application.

5 3 In a similar manner, information about "defects'* in design data may be used to determine the one or more parameters of the wafer inspection process in

combination with the wafer metrology data (and possibly the reticle inspection and/or metrology data). Information about the "'defects'* in the design data may be acquired using methods and systems such as those described in U.S. Patent No. 7,646,906 issued to Saidin et aL on January 12, 2010, which is incorporated by reference as if folly set forth herein. The embodiments described herein ma be further configured as described in this patent.

In some embodiments, the one or more parameters include one or more areas of the wafer or the other wafer used for field-to-field inspection performed within dies during the wafer inspection process, in this manner, the metrology data described herein may be used to define areas on a wafer that are suitable for field- to-field inspection within die. For example, the metrology data can be used to define one or more high noise regions on the wafer in which fieid-to~ field inspection should be performed. In particular, in relatively high noise regions, the noise variation from die-to-die may be much greater than the noise variation from field-to- ield. Therefore, in relatively high noise regions, die-to-die detection may result in the detection of significantly more nuisance defects than field-to-fteid detection. As such, parameters) of the wafer inspection process can be set such that the type of detection (e.g., die-to-die o field~to-field) that is performed is varied depending on the noise that is expected in different regions of the wafer.

In another embodiment, the method includes determining one or more parameters of a fabrication process for the wafer or the other wafer based on the metrolog data, the wafer inspection process is performed on the wafer or the other wafer after the fabrication process is performed on the wafer or the other wafer, and determining the one or more parameters of the w ater inspection process is performed based on the metrology data for the wafer in combination with the one or more parameters of the fabrication process, In some such embodiments* the fabrication process may be an etch process. However, the fabrication process may be any other fabrication process that can be performed on the wafer. In addition, the fabrication process that is performed on the wafer or other wafer may include one or more fabrication process steps (e.g., an etch process ste possibly with one or more other process steps). In one such example, the metrology data described herein such as within wafer field variation data can be used to optimize one or more etch .conditions and to use the combined dat to optimize Inspection of the wafer. in additional embodiments, determining the one or more parameters includes determining one or more characteristics of noise in output generated for one or more areas of the wafer or the other wafer by a wafer inspection system during the wafer inspection process based on the metrology data and determining one or more parameters of output noise reduction performed during the wafer inspection process based on the one or more determined characteristics of the noise. Therefore, the embodiments described herein may be configured for dynamic noise detection for inspection. For example, the metrology data described herein can be used for determination of high and low frequency noise, which can then be used to determine appropriate noise reduction technologies.

The acquiring and determining steps described herein are performed by a computer system, which may be configured as described further herein.

As will be clear from the description of the embodiment provided herein, the embodiments of the invention have a number of advantages over current methods and systems for setting up wafer inspection recipes. For example, manually

examining metrology data may help a user to pick regions on a wafer for inspection, but it wonid be time consuming and ineffective. There are currently no direct links between metrology and inspection and, therefore, use of external data sources such as mask metrology, film thickness, and CD metrology would not only be difficult to do but also leaves plenty of room for error. Unking the metrology data with an Inspection recipe to automatically ime the recipe and review sampling can make this flow efficient and production worthy.

Each of the embodiments of the method described above may i nclude any other step(s) of any other method(s) described herein. Furthermore _* each of the embodiments of the method described above may be performed by any of the systems described herein.

All of the methods described herein may include storing results of one or more steps of the method embodiments in 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 storage medium may include any storage medium described herein or any other suitable storage medium known in the art After the results have been stored, the results can be accessed in the storage medium and used by any of the method or system embodiments described herein, formatted for display to a user, us d by another software module, method _* or system, etc.

An additional embodiment relates to a non-transitor computer-readable medium storing program instructions executable on a computer system for performing a computer-implemented method for determining one or more parameters of a wafer inspection process. One such embodiment is shown in Fig. 1. In particular, as shown in Fig. 1, computer-readable medium 100 includes program Instructions 102 executable On computer system 104. The computer-implemented method includes the steps of the method described above. The computer- implemented method for which the program instructions are executable may include any other step(s) described herein.

Program instructions 102 implementing methods such as those described herein may be stored on computer-readable mediu 100. The computer-readable medium may be a storage medium such as a magnetic or optical disk, or a magnetic tape or any other suitable non-transitory computer-readable medium known in the art.

The program instructions may be implemented in any of various ways, including procedure-based techniques, component-based techniques, and/or object- oriented techniques, among others. For example, the program instructions may be implemented using ActiveX controls, C++ objects, JavaBeans, Microsoft Foundation Classes ("MFC"), or other technologies or methodologies, as desired.

The compute system may take various forms, including a personal computer system, image computer, mainframe computer system, workstation, network appliance, Internet appliance, or other device, in general, the term

"computer system' ^* may he broadly defined to encompass any device having one or more processors, which executes Instructions from a memory medium. The computer system may also include any suitable processor known in the art such as a parallel processor. In addition, the computer system may include a. computer platform with high speed processing and software, either as a standalone or a networked tool.

An additional embodiment relates to a system configured to determine one or more parameters of a w afer inspection process. One embodiment of such a system is shown in Fig. 2. System 2110 includes inspection subsystem 202 configured to generate output for a wafer, which is configured in this embodiment as described further herein. The system also includes computer subsystem 204 configured for performing the acquiring and determining steps described herein. The computer subsystem may be configured to perform these steps according to any of the embodiments described herein. The computer subsystem and the system may be configured to perforin any other step(s) described herein and may he further configured as described herein. The inspection subsystem ma be configured, to generate the output for the wafer by scanning the wafer with light and detecting light from the wafer during the scanning. For example, as shown in Fig, 2, the inspection subsystem includes Iight source 206, which ma include any suitable light source known in the art. Light from the light source may be directed to beam splitter 208, which may be configured to direct the light from the light source to wafer 210. The light source may be coupled to any other suitable elements (not shown) such as one or more condensing lenses, cellimating lenses _* relay lenses, objective lenses, apertures, spectral filters, polarizing components and the like. As show n in Fig. 2, the iight may be directed to the wafer at a normal angle of incidence. How ever, the f ight may be directed to the w afer at any suitable angle of incidence including near norma and oblique incidence. In addition, the light or multiple light beams may be directed to the wafer at more than one angle of incidence sequentially or simultaneously. The inspection subsystem may be configured to scan the light over the wafer in any suitable manner.

Light from wafe 210 may be collected and detected b one or more channels of the inspection subs stem during scanning. For example, light reflected from wafer 210 at angles relatively close to normal (i.e., specularly reflected light when the incidence is normal) may pass through beam splitter 208 to lens 212. Lens 212 may include a refractive optical element as shown in Fig. 2. In addition, lens 212 may include one or more refractive optical elements and/or one or more reflective optical elements. Light collected by lens 21 may be focused to detector 14.

Detector 214 may include any suitable detector known in the art such as a charge coupled device (CCD) or another type of imaging detector. Detector 214 is

configured to generate output that is responsive to the reflected light collected by lens 212. Therefore, lens 212 and detector 214 form one channel of the inspection subsystem. This channel of the inspection subsystem may include an other suitable optical components (not shown) known in the art. Since the inspection subsystem shown in Fig, 2 is configured to detect light specularly reflected from the wafer, the inspection subsystem is configured as a bright, field (BF) inspection subsystem. Such an inspection subsystem may, however, also be configured for other types of wafer inspection _* For example, the inspection subsystem shown in Fig. 2 may also include one or more other channels (not shown). The other channel(s) may include any of the optical components described herein such as a lens and a detector, configured as a scattered light channel. The lens and the detector may be further configured as described herein. In this manner, the Inspection subsystem may also be configured for dark field (BF) inspection.

Computer subsystem 204 is coupled to the inspection subsystem such that output generated by the deteetor(s) during scanning may be provided to computer subs stem 204. For example, the computer subsystem may be coupled to detector 21 (e.g., by one or more transmission media shown by the dashed line In Fig. 2, which may include any suitable transmission media known in the art) such that the computer subsystem may receive the output generated by the detector.

The computer subsystem may be configured to perform an step(s) described herein, For example, computer subsystem 204 may be configured for performing the acquiring and determining steps as described herein, in addition, computer subsystem 204 may be configured to perform any other steps described herein. The computer subsystem may also be configured to perform one or more steps of a wafer inspection process based on the one or more parameters described herein. For instance, any defect detection, defect sampling, etc. performed by the computer subsystem may be performed according to any parameter^) determined by the embodiments described herein.

In some embodiments, the systems described herein may include, or ma simply be coupled to, a metrology system. For example, as will be described further

5 herein, a computer subsystem of an inspection system such as that described above ma be coupled to a computer subsystem of a metrology system such that the computer subsystem of the inspection system can receive metrology data from the computer subsystem of the metrology system.

One embodiment of a metrology system that can generate the metrology data described herein is shown in Wig. 2. In this embodiment, metrology system 216 include Sight source 218 that is configured to generate light that is directed from the light source to beam splitter 220. The beam splitter is configured to reflect one portion of the light from the light source to refractive optical element 222 that focuses that portion of the light to w afer 224· The beam splitter is also configured to transmit another portion of the light from the tight source to reflective optical element 226 that serves as a reference in the metrology system. The light reflected from the wafe that passes through the refractive optical element and tbe light reflected from the reflective optical element may be combined by the beam splitter and directed to detector 228. In this manner, the two reflected beams (one from the wafer and the other from the reference) may interfere with each other, and the resulting interference may be detected by the detector. As such, the metrology system shown in Fig. 2 is configured as an interferometer. Computer subsystem 230 may be coupled to the detector as described herein such that the computer subsystem can receive output generated b the detector and determine one or more characteristics of the w afer (i.e., the metrology data) from the received output. The metrolog data determined in this manner ma include any of the metrology data described herein and may he determined in any suitable manner known i the art.

Although the metrology system is shown in Fig. 2 as an interferometer, any metrolog system included in, or coupled to, the systems described herein may have any other suitable configuration known in the art. For example, the metrology system may also or alternatively be configured as a seatterometer, a reflectometer, an eliipsometer, a diffractometen or some combination or variation thereof. The metrology system may also be further configured as described in U.S. Patent os. 7,711 ,51 ^' issued to Park et al. on May 4, 2010, 8,559,001 issued to Chang et a!. on October 15, 2 1 J. and 8,786,842 issued to Midler et ai. on July 22, 2014, and U.S. Patent Application Publication No. 2013/0310966 by MacNaughton et al. published November 21, 013, all of which are incorporated b reference as if fully set forth herein, The embodiments described herein may be further configured as described in these patents and patent application.

Computer subsystems 204 and 230 may be coupled by one or more transmission media shown by the dashed line between the computer subsystems in Fig. 2. In this manner, the two computer subsystems may send and receive information to and from each other. As such, the metrology data may be fed forward to an inspection system by a metrology system. However, the metrology data may also be stored in a storage medium such as that described and shown further herein by the metrology system, and then the computer subsystem of the inspection system can retrieve the metrology data from that storage medium.

It is noted that Fig. is provided herein to generally illustrate a configuration of an inspection system and a metrology system that may be included in the system embodiments described herein. Obviously, the inspection and metrology system configurations described herein may be altered to optimize the performance of the inspection system and metrology system as is normally performed when designing commercial inspection and metrology systems. In addition, the systems described herein may be implemented using an existing inspection system and/or existing metrology system (e.g., by adding functionality described herein to an existing inspection or metrology system) such as the 29sx 28xx series of wafer inspection tools and the WaferSight PWG metrology tools that are commercially available from KLA-Tencor, Milpitas, Calif. For some such systems, the methods described herein may be provided as optional functionality of the system (e.g., in addition to other functionality of the system). Alter atively,, the system described herein may be designed *from scratch** to provide a completely new system.

Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. For example, methods and systems for determining one or more parameters of a wafer inspection process are provided. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general, manner of carrying out the in vention. It is to be understood that the forms of the i vention shown and described herei are to be taken as the presentl preferred embodiments. Elements and materials mav be substituted for those iihistrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims.