Simultaneous multi-angle spectroscopy

Abstract

A metrology system (100) comprising: one or more illumination sources (110) configured to generate a quantity of broadband illumination light (117); a subsystem of the illumination optics configured to direct an amount of illumination light (117) from the illumination source (110) to a measurement spot (116) on a surface of a sample (120) to be measured at a plurality of angles of incidence, a plurality of azimuth angles, or a combination thereof; a subsystem of collection optics configured to collect an amount of collected light (127) from the measurement spot (116) on the surface of the sample (120), the subsystem of collection optics having a measurement pupil; one or more detectors (160A-C), each having a flat, two-dimensional surface sensitive to incident light; and a pupil segmentation and dispersion device (150) configured to segment an image of the measurement pupil into two or more pupil segments and to disperse the two or more pupil segments onto the one or more detectors (160A-C) over spatially separated regions, each pupil segment comprising signal information associated with distinct subregions of the plurality of angles of incidence, the plurality of azimuth angles, or a combination thereof, the pupil segmentation and dispersion device (150) comprising: a first diffractive element (150A) having an incident surface in an optical path of the collection optics subsystem arranged at or near an image plane (140) of the measurement pupil, wherein a first pupil segment is a portion of the collected light (127) on the incident surface of the first diffractive element (150A, 151A, 152A, 153A); and a second diffractive element (150B, 151B, 152B, 153B) having an incident surface in the optical path of the collection optics subsystem, which is arranged at or near an image plane (140) of the measuring pupil, wherein a second pupil segment is a portion of the collected light incident on the incident surface of the second diffractive element (150B, 151B, 152B, 153B), wherein a normal to the incident surface of the first diffractive element (150A, 151A, 152A, 153A) is oriented at a first angle with respect to a normal to the incident surface of the second diffractive element (150B, 151B, 152B, 153B).

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This patent application claims priority under 35 USC §119 from U.S. Provisional Patent Application Serial No. 62 / 348,870, entitled “Optics for Simultaneous Multi-Angel Spectroscopy,” filed June 11, 2016. TECHNICAL FIELD

[0002] The described embodiments relate to metrology systems and methods, and more particularly to methods and systems for improving the measurement of semiconductor structures. BACKGROUND INFORMATION

[0003] Semiconductor devices, such as logic and memory elements, are typically manufactured through a sequence of processing steps applied to a sample. The various features and multiple structural levels of the semiconductor devices are formed through these processing steps. For example, lithography, among others, is a semiconductor manufacturing process that involves creating a pattern on a semiconductor wafer. Other examples of semiconductor manufacturing methods include, but are not limited to, chemical mechanical polishing, etching, deposition, and ion implantation. Multiple semiconductor devices can be manufactured on a single semiconductor wafer and then separated into individual semiconductor devices.

[0004] Metrology processes are used at various steps during a semiconductor manufacturing process to detect defects on wafers and achieve higher yields. Optical metrology techniques offer the potential for high throughput without the risk of sample destruction. A variety of optical metrology techniques include implementations of scatterometry and reflectometry, and associated analysis algorithms are often used to characterize critical dimensions, layer thicknesses, composition, overlay, and other parameters of nanoscale structures.

[0005] Measurements taken across multiple angles yield information with greater accuracy and precision. For example, spectroscopic ellipsometry (SE) and spectroscopic reflectometry (SR) systems perform simultaneous measurements across a wide range of illumination wavelengths. However, many existing SR and SE systems determine the measurement signals at a single angle of incidence (AOI) at a time. This limits the throughput of such a system when multiple AOIs are required to accurately characterize the sample.

[0006] In one example, a multi-angle SE instrument available from JA Woollam Co., Lincoln, Nebraska (USA), includes mechanisms for rotating a sample to be measured, elements of the optical system, or both, to sequentially perform measurements of different AOI values. In another example, a multi-angle SE instrument available from KLA-Tencor Corp., Milpitas, California (USA), may be used, which uses a large numerical aperture (NA) optical system and acquires all AOIs of interest simultaneously without moving the sample or significant parts of the optical system.

[0007] In this example, the converging pupil contains the entire range of angles reflected by the sample. Depending on the NA of the system, the full angular range could range from a very small range (e.g., collimated) to a very large range (e.g., greater than five degrees). In existing metrology systems, reflected light across the entire angular range is not used to perform a measurement because the measurement signal information associated with too many angles of incidence is integrated at the detector. The resulting loss of signal accuracy limits the effectiveness of the measured signals. To mitigate this effect, the range of measured AOIs is limited to a few degrees above each nominal AOI being spectrally measured.

[0008] The multi-angle SE instrument, available from KLA-Tencor, uses mechanical shutters to measure sequential spectra at one or more AOI subregions. In this example, a sample with a large NA is illuminated across the entire wavelength range of interest, and the reflected light is collected by the system optics. The collecting pupil contains all angles of interest, but mechanical shutters or beam blockers are used to block the collected light except for a selected range of AOIs. This selected range is unblocked and is measured by the measurement sensor. In this approach, the optics are held in a stationary configuration, and AOI selection is achieved with mechanical shutters or masks. Sequential spectral measurements at different AOIs result in extended wafer exposure and total measurement time.Furthermore, time-dependent effects that manifest on the wafer can be captured by the sequential measurements and negatively influence the measurement results.

[0009] In summary, the ongoing reduction in feature size and the increasing depth of structural features place challenging demands on optical metrology systems. Optical metrology systems must meet high precision and accuracy requirements for increasingly complex measurement targets at high throughput to remain cost-effective. In this context, the speed of data acquisition and the range of angles of incidence are important factors in the design of optical metrology systems. Thus, it is desirable that improved metrology systems and methods overcome these limitations.

[0010] US 2015 / 0 153 165 A1 discloses an optical metrology device that simultaneously detects light at different angles of incidence and / or different azimuth angles to determine at least one parameter of a sample. For this purpose, a pupil plate is used that splits light from the sample into a plurality of partial beams, which are then analyzed, for example, spectroscopically.

[0011] US 2015 / 0 193 926 A1 concerns a device in which a sample is illuminated and the light emitted from the sample as a result of the illumination is captured via a pupil with multiple segments. Different segments correspond to different illumination or detection angles. For each segment, a separate evaluation of the radiation captured by that segment takes place.

[0012] US 2006 / 0 066 837 A1 describes the optical examination of small, moving objects, such as cells. Light emanating from the object is captured and split into components by a multitude of dichroic reflectors, each of which is directed to a corresponding detector. SUMMARY OF THE INVENTION

[0013] Methods and systems for performing simultaneous spectroscopic measurements of semiconductor structures over a wide range of angles of incidence, azimuth angles, or both are presented here. Spectra spanning two or more subranges of angles of incidence, azimuth angles, or both are measured simultaneously across different sensor areas at high throughput and under the same alignment conditions. In this way, machine errors, such as wavelength errors, are uniformly corrected across all measured wavelengths. The collected light is linearly dispersed across different light-sensitive areas by one or more detectors according to the wavelength for each subrange of AOIs, azimuth angles, or both.Each different light-sensitive area is arranged on the one or more detectors to perform a separate spectroscopic measurement of each different range of AOIs, azimuth angles, or both. In this way, a wide range of AOIs, azimuth angles, or both can be simultaneously acquired with a high signal-to-noise ratio. These features, individually or in combination, enable high-throughput measurements of high-aspect-ratio structures (e.g., structures with a depth of one micrometer or more) with high throughput, accuracy, and precision.

[0014] In one aspect, a device for segmenting and dispersing the pupil is designed such that an image of the measuring pupil is dispersed into two or more pupil segments, and the two or more pupil segments are dispersed onto one or more detectors via spatially separated sensor surfaces. Each pupil segment contains signal information associated with discrete sub-ranges of the multiple angles of incidence, the multiple azimuth angles, or a combination thereof.

[0015] In this way, two or more angular segments of the measurement pupil are spatially dispersed such that the measured spectra associated with each angular segment are spatially offset from each other. This allows simultaneous detection by multiple different detectors, a multi-zone detector, or a combination thereof. With this approach, the entire measurement pupil is imaged simultaneously, thus avoiding the limitations of sequential measurements.

[0016] In a further aspect of the invention, a fine focus sensor (FFS) is integrated into the detection subsystem to provide a measurement input for focus error correction during measurement.

[0017] In another further aspect of the invention, the metrology system described herein utilizes a multi-zone infrared detector that combines different bands of sensitivity at different locations on a single detector package. The detector is configured to provide a continuous spectrum of data with different sensitivities depending on the location of incidence. Collected light is dispersed linearly across the surface of the detector according to wavelength. Each different light-sensitive region is arranged on the detector to detect a different range of incident wavelengths. In this way, a broad spectrum of infrared wavelengths with a high signal-to-noise ratio is detected by a single detector.

[0018] In yet another aspect of the invention, the pupil segmentation and dispersion device in the metrology system is dynamically reconfigurable. In some embodiments, each of the plurality of grid segments is movable with respect to position or orientation, or both.

[0019] In yet another aspect of the invention, the pupil segmentation and dispersion device in the metrology system is interchangeable. This allows a suitable pupil segmentation and dispersion device to be selected and positioned in the path of the collection optics for a specific measurement application.

[0020] In yet another aspect, the size of the illumination field is adjusted to optimize the resulting measurement accuracy and speed depending on the type of target to be measured.

[0021] The foregoing is a summary and thus necessarily contains simplifications, generalizations, and omissions of detail. Accordingly, those skilled in the art will recognize that the summary is illustrative only and is not intended to be limiting in any way. Other aspects, inventive features, and advantages of the devices and / or methods described herein will become apparent in the non-limiting detailed description below. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows an exemplary metrology system 100 for performing simultaneous spectroscopic measurements of semiconductor structures at a wide range of angles of incidence, azimuth angles, or both. Fig. 2 shows a mask 141 in the plane of an image 145 of the measuring pupil of the metrology system 100. Fig. 3 shows a mask 143 in the plane of an image 145 of the measuring pupil of the metrology system 100. Fig. Figure 4 shows another representation of the device 150 for segmenting and dispersing the pupil and the subsystem 160 of the detector of Fig. 1. Fig. 5 shows another representation of the pupil segmentation and dispersion device 151 and the detector subsystem 162 according to another embodiment. Fig. 6 shows another representation of the pupil segmentation and dispersion device 152 and the detector subsystem 164 according to yet another embodiment. Fig. Figure 7 shows an illustration of the pupil segmentation and dispersion device 153 and the detector subsystem 164 according to another embodiment. Fig. Figure 8 shows a diagram of a multi-zone infrared detector 180. Fig. Figure 9 shows typical light sensitivity curves of four available indium gallium arsenide (InGaAs) sensors. Fig. 10 shows a NAND structure 300 with an exemplary high aspect ratio resulting from the low penetration of light into the structure to be measured. Fig. 11 illustrates a method 200 for performing simultaneous spectroscopic measurements of one or more structures over a wide range of angles of incidence, azimuth angles, or a combination of both, in accordance with at least one novel aspect described herein. DETAILED DESCRIPTION

[0022] Reference will now be made in detail to examples of the prior art and some embodiments of the invention, examples of which are illustrated in the accompanying drawings.

[0023] Methods and systems for performing simultaneous spectroscopic measurements of semiconductor structures across a wide range of angles of incidence, azimuth angles, or both are presented here. Spectra spanning two or more subranges of angles of incidence, azimuth angles, or both are measured simultaneously across different sensor areas at high throughput with the same alignment. In this way, machine errors, such as wavelength errors, are uniformly corrected across all measured wavelengths. Collected light is linearly dispersed across different photosensitive areas of one or more detectors according to the wavelength for each subrange of AOIs, azimuth angles, or both. Each different photosensitive area arranged on the one or more detectors performs a separate spectroscopic measurement of each different range of AOIs, azimuth angles, or both.In this way, a wide range of AOIs, azimuth angles, or both can be simultaneously acquired with a high signal-to-noise ratio. These features, individually or in combination, enable high-throughput measurements of high-aspect-ratio structures (e.g., structures with a depth of one micrometer or more) with high throughput, accuracy, and precision.

[0024] Fig. 1 shows an exemplary metrology system 100 for performing simultaneous spectroscopic measurements of semiconductor structures at a wide range of angles of incidence, azimuth angles, or both. In some examples, the one or more structures include at least one high aspect ratio (HAR) structure or at least one structure with a large lateral dimension. As shown in Fig. As shown in Figure 1, the metrology system 100 is configured as a broadband spectroscopic ellipsometer. However, in general, the metrology system 100 may be configured as a spectroscopic reflectometer, a scatterometer, an ellipsometer, or any combination thereof.

[0025] The metrology system 100 includes an illumination source 110 that generates a beam of illumination light 117 incident on the wafer 120. In some embodiments, the illumination source 110 is a broadband light source that emits illumination light in the ultraviolet, visible, and infrared spectra. In one embodiment, the illumination source 110 is a laser-sustained plasma (LSP) light source (also known as a laser-driven plasma source). The pump laser of the LSP light source can be a continuous-wave laser or a pulsed laser. A laser-driven plasma source can generate significantly more photons than a xenon lamp across the entire wavelength range from 150 nanometers to 2000 nanometers. The illumination source 110 can be a single light source or a combination of a plurality of broadband or discrete-wavelength light sources.The light generated by the illumination source 110 comprises a continuous spectrum or portions of a continuous spectrum from ultraviolet to infrared (e.g., vacuum ultraviolet to mid-infrared). Generally, the illumination light source 110 may comprise a supercontinuum laser, a helium-neon laser for infrared light, an arc lamp, or any other suitable light source.

[0026] In another aspect, the amount of illumination light can be broadband illumination light spanning a wavelength range of at least 500 nanometers. In one example, the broadband illumination light includes wavelengths below 250 nanometers and wavelengths above 750 nanometers. Generally, the broadband illumination light includes wavelengths between 120 nanometers and 3000 nanometers. In some embodiments, wavelengths below 3000 nanometers can be used for the broadband illumination light.

[0027] As in Fig. 1, the metrology system 100 includes an illumination subsystem configured to direct illumination light 117 onto one or more structures formed on the wafer 120. The illustrated illumination subsystem may include the light source 110, one or more optical filters 111, a polarizing component 112, a field stop 113, and illumination optics 115. The one or more optical filters 111 are used to control the light level, the spectral power, or both of the illumination subsystem. The polarizing component 112 creates the desired polarization state at the exit from the illumination subsystem. In some embodiments, the polarizing component may be a polarizer, a compensator, or both, and may include any commercially available polarizing component.The polarization component can be fixed, rotatable between fixed positions, or continuously rotatable. Although the illumination subsystem, as shown in . Fig. 1, contains a polarization component, the illumination subsystem may include more than one polarization component. The field stop 113 controls the field of view (FOV) of the illumination subsystem and may include any suitable commercially available field stop. The aperture stop 114 controls the numerical aperture (NA) of the illumination subsystem and may include any suitable commercially available aperture stop. The light from the illumination source 110 is directed through illumination optics 115 to be focused onto one or more structures on the wafer 120 (not shown). Fig. 1). The illumination subsystem may include any type and arrangement of optical filters 111, field stop 113, aperture stop 114, and illumination optics 115 as known in the art of spectroscopic ellipsometry, reflectometry, and scatterometry.

[0028] As in Fig. As shown in Figure 1, the beam of illumination light 117 passes through at least one optical filter 111, the polarization component 112, the field stop 113, the aperture stop 114, and the illumination optics 115 as the beam propagates from the illumination source 110 to the wafer 120. The beam 117 illuminates a portion of the wafer 120 via a measurement spot 116.

[0029] In some examples, the beam size of the amount of illumination light 117 projected onto the surface of the wafer 120 is smaller than a size of a measurement target measured on the surface of the sample. Exemplary beam shaping techniques are described in detail in U.S. patent application US 2013 / 0114085 by Wang et al.

[0030] The metrology system 100 also includes a collection optics subsystem configured to collect light generated by the interaction between the one or more structures and the incident illumination beam 117. A beam 127 of collected light is collected from the measurement spot 116 by a collection optics 122. The collected light 127 enters the collection optics subsystem for collection through the aperture stop 123, the polarizing element 124, and the field stop 125.

[0031] The collection optics 122 includes any suitable optical element to collect light from the one or more structures on the wafer 120. The collection aperture stop 123 controls the NA of the collection optics subsystem. The polarizing element 124 analyzes the desired polarization state. The polarizing element 124 is a polarizer or a compensator. The polarizing element 124 can be fixed, rotatable at various fixed positions, or continuously rotatable. Although the Fig. 1 includes a polarizing element, the subsystem may include more than one polarizing element. The collection field stop 125 controls the FOV of the collection subsystem. The collection subsystem takes light from wafer 120 and directs the light through the collection optics 122 and the polarizing element 124 to be focused on the field stop 125. In some embodiments, the collection field stop 125 is used as the slit of the spectrometer for the detection subsystem. However, the collection field stop 125 may be located at or near the slit 126 of the detection subsystem spectrometer.

[0032] The collection subsystem may include any type and arrangement of the collection optics 122, the aperture stop 123, the polarizing element 124, and the field stop 125, as known from the prior art of spectroscopic ellipsometry, reflectometry, and scatterometry.

[0033] In the Fig. In the embodiment illustrated in Figure 1, the collection optics subsystem directs the light to one or more spectrometers of the detection subsystem. The detection subsystem generates an output that is a response to the light collected from the one or more structures illuminated by the illumination subsystem.

[0034] As in Fig. 1, the Z-axis is oriented perpendicular to the surface of wafer 120. The X and Y axes are coplanar with the surface of wafer 120 and thus perpendicular to the Z-axis. Similarly, the X' and Y' axes are coplanar with the surface of wafer 120 and thus perpendicular to the Z-axis. The X' and Y' axes are rotated with respect to the X and Y axes by an azimuth angle AZ. The azimuth angle specifies the orientation of the light delivery to wafer 120 about the Z-axis. The principal ray 118 of the beam of illumination light 117 and the principal ray 121 of the beam of collected light 127 define a plane of incidence. The X' axis is aligned with the plane of incidence, and the Y' axis is orthogonal to the plane of incidence. Thus, the plane of incidence lies in the X'Z plane. The beam of illumination light 117 strikes the surface of the wafer 120 at an angle of incidence α with respect to the Z-axis and lies within the plane of incidence.

[0035] In one aspect of the invention, a pupil segmentation and dispersion device is configured such that an image of the measurement pupil is segmented into two or more pupil segments, and the two or more pupil segments are dispersed onto one or more detectors via spatially separated sensor surfaces. Each pupil segment comprises an information signal associated with the different sub-ranges of the multiple angles of incidence, the multiple azimuth angles, or a combination thereof. In some embodiments, the pupil segmentation and dispersion device is arranged at or near an aperture stop of the metrology system or at or near a conjugate of an aperture stop of the metrology system.

[0036] In this way, two or more angular segments can be spatially dispersed in the measurement pupil, so that the measured spectra associated with each angular segment are spatially offset from each other. This allows simultaneous detection by multiple, different detectors, a multi-zone detector, or a combination thereof. With this approach, the entire measurement pupil is imaged simultaneously, thus avoiding the limitations of sequential measurements.

[0037] The measurement pupil (i.e., converging pupil) is typically mounted on or near the converging lens 122. The measurement pupil encompasses the full range of angles reflected by the wafer 120. The full spectrum of angles depends on the NA of the optical design, but it could be varied from very small (e.g., collimated) to very large (e.g., greater than five degrees). When all reflected light over a full range of angles is aggregated into a measured spectrum, the measured signal typically suffers from a loss of accuracy because too many angles are integrated into the measurement signal. Previously, it was common practice to limit the angular range of certain measured spectra to a few degrees around a nominal angle of incidence for the purposes of a particular measurement.

[0038] As described here, an image of the measurement pupil is separated in terms of angle and wavelength to simultaneously generate multiple spectra, each segment corresponding to a different target angle and a subrange of angles around the target angle. The generated spectra are spatially separated and detected separately by one or more detectors (such as separate detectors, a multi-zone detector, or a combination thereof).

[0039] In the Fig. 1, the collected light 127 passes through a slit 126 of the spectrometer and falls on the pupil of the segmentation and dispersion device 150. In the embodiment shown in Fig. 1, the pupil segmentation and dispersal device 150 comprises multiple reflection gratings. Each reflection grating is arranged at a different angle relative to each other. Light dispersed by each grating toward the detection subsystem 160 is spatially separated on the surface of the detection subsystem 160.

[0040] Fig. 2 shows an image 145 of the measuring pupil of the metrology system 100. As in Fig. 2, the image 145 of the measuring pupil contains the information of the angle of incidence distributed over one direction of the image and contains information of the azimuth angle over another direction of the image. Fig. 2 also shows a mask 141 in the plane of the image of the measuring pupil 145. As in Fig. As shown in Figure 2, the mask 141 obscures portions of the image, leaving three pupil segments 142A-C available for transmission. Each of these pupil segments contains the same information about the azimuth angle but different information about the angle of incidence. In this way, the mask 141 divides the image of the measuring pupil 145 into different segments, each associated with different ranges of angles of incidence.

[0041] Fig. 3 shows another representation of the image 145 of the measuring pupil of the metrology system 100. As in Fig. 3, the image 145 of the measuring pupil comprises information on the angle of incidence distributed over one direction of the image and the information on the azimuth angle distributed in another direction of the image. Fig. 3 shows a mask 143 in the plane of the image 145 of the measuring pupil. As in Fig. As shown in Figure 3, the mask 143 obscures portions of the image, leaving three pupil segments 144A-C available for transmission. Each of these pupil segments contains the same AOI information but different information about the azimuth angle. In this way, the mask 143 divides the image of the measuring pupil 145 into different segments, each associated with different ranges of the azimuth angle.

[0042] The images of the measuring pupil 145 shown are divided into three segments. However, in general, any number of different segments can be considered within the scope of this patent specification. Furthermore, the Fig. 2 and Fig. 3 Examples of segmentation along the directions of the AOI and azimuth angle. However, in general, segmenting the measuring pupil along any direction in the image plane of the measuring pupil can be considered within the scope of this patent application. In this way, each segment can contain different information regarding the AOI and azimuth angle. In one example, both masks 141 and 143 in the image plane can be used to divide the measuring pupil into nine different segments, each containing different information regarding the AOI and azimuth angle. In another example, mask 141 or mask 143 can be rotated within the image plane to contain different strips of information regarding the AOI and azimuth angle.

[0043] The Fig. 2 and Fig. 3 show representations of a mask in an image plane of the measurement pupil of the metrology system 100, which mask is located in front of the pupil of the segmentation and dispersion device. The mask defines segments of the angular information for separate and simultaneous measurement. Such a mask can be advantageous to enable precise subdivisions of the measurement pupil before it impinges on the pupil in the segmentation and dispersion device. However, the techniques for segmenting and dispersing the pupil described herein generally do not require a mask, since a mask is located in an image plane of the measurement pupil.If a mask is not used, the segmentation and dispersion device will segment the measurement pupil by directing different portions of the incoming beam to different areas of the detector subsystem based on the position of incidence of the collected beam on the segmentation and dispersion device. As such, the pupil segmentation and dispersion device can be arranged in any suitable manner to segment the measurement pupil in the desired manner.

[0044] Fig. Figure 4 shows another representation of the device 150 for segmenting and dispersing the pupil and the Fig. 1 shown subsystem 160 for detection. As in Fig. 4, the pupil segmentation and dispersion device 150 is arranged at or near an image plane 140 of the measurement pupil of the metrology system 100. At image plane 140, the collected beam 127 includes azimuth angle information dispersed in one direction and angle of incidence information dispersed in another direction. The pupil segmentation and dispersion device 150 has three reflection grating segments 150A-C. As shown in Fig. 4, the portion of the collected light 127 incident on each segment includes the same azimuth angle information but different angle of incidence information. In this embodiment, the three reflection grating segments correspond to the three pupil image segments of Fig. 2. By arranging the device for segmenting and dispersing the pupil at or near an image plane of the measuring pupil, the pupil segments, which have different angular information, are spatially differentiated and dispersed separately onto different sensor surfaces of a detection subsystem.

[0045] At the Fig. 4, each segment of the reflection grating is oriented at a different angle relative to each other. For example, segment 150B of the reflection grating is oriented in the image plane 140, segment 150A of the reflection grating is oriented at an angle Θ2 relative to the image plane 140, and segment 150C of the reflection grating is oriented at an angle Θ1 relative to the image plane 140. As shown in Fig. As shown in Figure 4, the different orientations cause each segment to disperse the incident light in a different direction.

[0046] In the embodiment of the Fig. 4, segment 150C of the reflection grating is tilted by an angle Θ1 about an axis A1, which lies within the image plane 140 and extends in a direction parallel to the blaze direction of the grating structures of segments 150A-C of the reflection grating. Similarly, segment 150A of the reflection grating is tilted by an angle Θ2 about axis A2, which lies within the image plane 140 and extends in a direction parallel to the blaze direction of the grating structures of segments 150A-C of the reflection grating. In this configuration, the measured spectrum 161A is dispersed by 150A of the reflection grating, so that it falls upon the detector 160A. The measured spectrum 161B is dispersed by segment 150B of the reflection grating, so that it falls upon the detector 160B. The measured spectrum 161C is dispersed by the segment 150C of the reflection grating so that it falls on the detector 160C. As in Fig. As shown in Figure 4, the detection subsystem 160 includes three detectors 160A-C, each arranged on top of the other in a direction orthogonal to the direction of wavelength dispersion. The magnitude of the angles Θ1 and Θ2 determines the magnitude of the spatial displacement at the detectors.

[0047] The diffractive gratings of the pupil segmentation and dispersion device 150 linearly disperse the first-order diffracted light according to the wavelength along one dimension of each of the respective two-dimensional detectors (ie, the direction of the Fig. 4 for each of the respective detectors). Each segment of the diffraction grating provides spatial separation between two different wavelengths of light projected onto the surface of each corresponding detector along the direction of wavelength dispersion.

[0048] In one example, the detectors of detection subsystem 160 are charge-coupled devices (CCDs) sensitive to ultraviolet and visible light (e.g., light with wavelengths between 190 nanometers and 860 nanometers). In other examples, one or more of the detectors of detection subsystem 160 may be implemented as a photodetector array (PDA) sensitive to infrared light (e.g., light with wavelengths between 950 nanometers and 2500 nanometers). However, other two-dimensional detector technologies may generally be considered (e.g., a position-sensitive detector (PSD), an infrared detector, a photovoltaic detector, etc.). Each detector converts the incident light into electrical signals indicative of the spectral intensity of the incident light.In general, detectors of subsystem 160 generate output signals 170 for light detected simultaneously by each detector of subsystem 160 for detection.

[0049] As in Fig. As shown in Figure 1, the detection subsystem is arranged so that the collected light propagates simultaneously to all detectors of the metrology system 100. The metrology system 100 also includes a computer system 130 configured to receive detected signals 170 and determine an estimate of a value of a parameter of interest 171 of the measured structure(s) based on the measured signals. By simultaneously collecting the spectra associated with different angular data, measurement times are reduced, and all spectra are measured under the same alignment conditions. This allows wavelength errors to be more easily corrected, as a common correction can be applied to all spectral data sets.

[0050] Fig. Figure 5 shows an illustration of a pupil segmentation and dispersion device 151 and a detection subsystem 162 in another embodiment. As shown in Fig. 5, the pupil segmentation and dispersion device 151 is arranged at or near an image plane 140 of the measurement pupil of the metrology system 100. In this embodiment, the pupil segmentation and dispersion device 151 comprises three segments 151A-C of a reflection grating. As shown in Fig. 5, the portion of the collected light 127 incident on each segment includes the same azimuth angle information but different angle of incidence information. In this embodiment, the three segments of the reflection grating correspond to the three segments of the pupil image from Fig. 2.

[0051] In the Fig. 5, each segment of the reflection grating is oriented at a different angle relative to each other. For example, segment 151B of the reflection grating is aligned in the image plane 140. Segment 151A of the reflection grating is oriented at an angle Φ1 relative to the image plane 140. Segment 151C of the reflection grating is oriented at an angle Φ2 relative to the image plane 140. As shown in Fig. As shown in Figure 5, the different orientations of each segment cause the incident light to be dispersed in a different direction.

[0052] In the Fig. 5, the segment 151C of the reflection grating is tilted by an angle Φ2 about the axis B, which lies within the image plane 140 and extends in a direction perpendicular to the blaze direction of the grating structures of the segments 151A-C of the reflection grating. Similarly, the segment 151A of the reflection grating is tilted by an angle Φ2 with respect to the axis B. In this configuration, the spectrum 163A dispersed by the segment 151A of the reflection grating is incident on the detector 162A. The spectrum 163B dispersed by the segment 151B of the reflection grating is incident on the detector 162B. The spectrum 163C dispersed by the segment 151C of the reflection grating is incident on the detector 162C. As in Fig. As shown in Figure 5, the detection subsystem 162 comprises three detectors 162A-C, each arranged adjacent to each other and parallel to the direction of wavelength dispersion. The size of the angles Φ1 and Φ2 determines the magnitude of the spatial shift on the detectors.

[0053] Fig. Figure 6 shows a representation of a device 152 for segmenting and dispersing the pupil and a subsystem 164 for detection in a further embodiment of the invention. As in Fig. 6, the pupil segmentation and dispersion device 152 is arranged at or near an image plane 140 of the metrology system 100. In this embodiment, the pupil segmentation and dispersion device 152 comprises three segments 152A-C of a reflection grating. As shown in Fig. As shown in Figure 6, the portion of the collected light 127 incident on each segment includes the same angle of incidence information, but different information on the azimuth angle. In this embodiment, the three segments of the reflection grating correspond to the three segments of the pupil image from Fig. 3.

[0054] In the Fig. 6, each segment of the reflection grating is oriented at a different angle relative to each other. For example, segment 152B of the reflection grating is oriented in the image plane 140. Segment 152A of the reflection grating is oriented at an angle α1 relative to the image plane 140. Segment 152C of the reflection grating is oriented at an angle α2 relative to the image plane 140. As in Fig. As shown in Figure 6, the different orientations cause each segment to disperse the incident light in a different direction.

[0055] In the Fig. 6, the segment 152C of the reflection grating is tilted by an angle α2 about the axis C2, wherein the axis lies within the image plane 140 and extends in a direction parallel to the blaze direction of the grating structures of the segments 152A-C 152C of the reflection grating. Similarly, the segment 152A of the reflection grating is tilted by the angle α1 about the axis C1. In this configuration, the measured spectrum 165A of the reflection grating is dispersed by the segment 152A of the reflection grating and incident on the detector 164A. The measured spectrum 165B is dispersed by the segment 152B of the reflection grating and incident on the detector 164B. The measured spectrum 165C is dispersed by the segment 152C of the reflection grating and incident on the detector 164C. As in Fig. As shown in Figure 6, the detection subsystem 164 comprises three detectors 164A-C, each arranged adjacent to each other and parallel to the direction of wavelength dispersion. The size of the angles α1 and α2 determines the magnitude of the spatial displacement at the detectors.

[0056] Fig. Figure 7 shows a representation of a device 153 for segmenting and dispersing a pupil and the detection subsystem 166 in a further embodiment. As in Fig. 7, the pupil segmentation and dispersion device 153 is arranged at or near an image plane 140 of the metrology system 100. In this embodiment, the pupil segmentation and dispersion device 153 comprises three segments 153A-C of a reflection grating. As shown in Fig. 7, the portion of the light incident on and collected by each segment 127 includes the same information about the angle of incidence, but different information about the azimuth angle. In this embodiment, the three segments of the reflection grating correspond to the three Fig. 3 shown segments of the image of the pupil.

[0057] In the Fig. In the embodiment illustrated in Figure 7, each segment of the reflection grating is oriented at a different angle relative to each other. For example, segment 153B of the reflection grating is oriented in the image plane 140. Segment 153A of the reflection grating is oriented at an angle β2 relative to the image plane 140. Segment 153C of the reflection grating is oriented at an angle β1 relative to the image plane 140. As shown in Fig. 7, different orientations cause each segment to disperse the incident light in a different direction.

[0058] In the Fig. 7, the segment 153C of the reflection grating is tilted by an angle β1 about the axis D, which lies within the image plane 140 and extends in a direction perpendicular to the blaze direction of the grating structures of the segments 153A-C of the reflection gratings. Similarly, the segment 153A of the reflection grating is tilted by an angle β1 relative to the axis D. In this configuration, the measured spectrum 167A is dispersed by segments 153A of the reflection grating and impinges on the detector 166A. The measured spectrum 167B is dispersed by the segment 153B of the reflection grating and impinges on the detector 166B. The measured spectrum 167C is dispersed by the segment 153C of the reflection grating and impinges on the detector 166C. As in Fig. As shown in Figure 7, the detection subsystem 166 comprises three detectors 166A-C, each arranged adjacent to each other, perpendicular to the direction of wavelength dispersion. The size of the angles β1 and β2 determines the magnitude of the spatial displacement at the detectors.

[0059] In the embodiments described with reference to the Fig. 4-7, the detector elements of each respective detection subsystem are separate detectors arranged in a stacked arrangement (e.g., one above the other or adjacent end to end). However, in general, the detector elements may be arranged in any suitable manner to receive dispersed light from each respective pupil segment generated by the pupil segmentation and dispersal device. Moreover, in some embodiments, multiple detector elements are configured to receive light from a particular pupil segment across different wavelength bands.In one embodiment, a measured spectrum dispersed by a particular pupil segment is captured by a charge-coupled device (CCD) in a wavelength band including ultraviolet wavelengths and captured by a photodetector array (PDA) in a wavelength band including infrared wavelengths. In general, any suitable combination of detection elements can be used to detect a measured spectrum dispersed by a particular pupil segment by the segmentation and dispersion device.

[0060] In some embodiments, a detection subsystem may include a multi-zone infrared detector that combines bands of different sensitivities at different locations on a single detector package. The detector is configured to provide a continuous spectrum of data at different sensitivities, depending on the location of incidence.

[0061] Fig. Figure 9 illustrates typical light sensitivity curves of available indium gallium arsenide (InGaAs) sensors. As in Fig. As shown in Figure 9, not a single available InGaAs sensor is capable of providing sufficient light sensitivity over a wavelength range from 1 micrometer to 2.5 micrometers. Thus, the individually available sensors are only suitable for detecting a narrow wavelength range.

[0062] In one aspect of the invention, multiple sensor chips are provided, each sensitive to a different wavelength range, and combined into a single detector package. This multi-zone detector is again implemented in the metrology system described here.

[0063] Fig. Figure 8 shows four sensor chips 180A-D, which originate from four different wavelength ranges to create a multi-zone infrared detector 180. The four sensor chips comprise different material compositions, each having a different property regarding light sensitivity. As shown in Fig. 9, the sensor chip 180A has a high sensitivity over a wavelength range A, the sensor chip 180B has a high sensitivity over a wavelength range B, the sensor chip 180C has a high sensitivity over a wavelength range C, and the sensor chip 180D has a high sensitivity over a wavelength range D. A metrology system including the detector 180 is configured to disperse wavelengths in the wavelength band A on the sensor chip 180A, disperse wavelengths in the wavelength range B on the sensor chip 180B, disperse wavelengths in the wavelength range C on the sensor chip 180C, and disperse wavelengths in the wavelength range D on the sensor chip 180D. In this way, a high light sensitivity (i.e., high SNR) is achieved over the entire wavelength range including the wavelength bands AD of the individual detectors.

[0064] In some examples, a multi-zone detector includes InGaAs sensors sensitive to different spectral regions combined in a single sensor package to produce a single, contiguous spectrum spanning spectral regions with wavelengths from 750 nanometers to 3,000 nanometers or beyond.

[0065] In general, any number of individual sensors can be assembled into a multi-zone detector along the direction of wavelength dispersion, potentially providing a contiguous spectrum from the detector. However, typically two to four individual sensors are used in a multi-zone detector, such as detector 180.

[0066] The embodiments of pupil segmentation and the dispersion device as shown in the Fig. 4-7 are provided by way of non-limiting example. Although the illustrated embodiments include three different segments of the reflection gratings, in general, any number of different segments greater than one may be envisaged and still be within the scope of this patent application. Additionally, the orientation angle between each grating and the image plane of the measurement pupils may be the same as for all grating elements, or it may be different. In this way, the tilt angles are configured to achieve the desired separation between the simultaneously measured spectra. In some embodiments, the pupil segments are tilted with respect to an axis parallel to the blaze direction and also with respect to an axis perpendicular to the blaze direction.

[0067] Furthermore, the shape and arrangement of the different segments are not limited to the Fig. 4-7. Any number of different shapes and arrangements of the segments may be contemplated within the scope of this patent application. In some examples, the segments are arranged such that each segment contains different AOI and azimuth angle information. In one example, a two-dimensional array of grating segments is arranged across the measurement pupil. In another example, a one-dimensional or two-dimensional array of grating segments may be oriented at an oblique angle with respect to a propagation direction of the angle of incidence or azimuth angle in the measurement pupil. In one example, a one-dimensional array of grating segments is oriented diagonally across the measurement pupil to allow for blending of angular information in a desired manner.

[0068] Although the illustrated embodiments include reflective grating segments, other dispersive elements are contemplated within the scope of this patent application. In some embodiments, transmissive grating elements are employed to disperse incident light. In another example, segmented prism optics are employed to disperse incident light. In some embodiments, the orientation of the gratings or prism elements determines the direction of dispersion of light from each pupil segment. However, in some other embodiments, mirror elements are employed to direct the light dispersed by the gratings or prism elements to different detector elements.

[0069] In some embodiments, each grating segment has the same period and reflectance function. However, in some other embodiments, one or more of the grating segments may comprise different grating periods and reflectance functions. In this way, different dispersion properties are created for different pupil segments. This approach can be advantageous for optimizing signal levels or sensor designs, and for meeting measurement system requirements.

[0070] In some embodiments, a sequential grating arrangement can be used to disperse different wavelength ranges of each pupil segment. In one embodiment, a reflective grating segment disperses ultraviolet light at the +1 / -1 diffraction order and reflects infrared light at the zeroth diffraction order. The reflected infrared light is then dispersed by a subsequent grating element.

[0071] In another aspect of the invention, the pupil segmentation and dispersion devices are dynamically reconfigured in metrology system 100. In some embodiments, each of the multiple grating segments is movable in position, orientation, or both. The position, orientation, or both of each of the grating segments is controlled by computer system 130. Computer system 130 communicates control signals to a dynamically reconfigurable pupil segmentation and dispersion device. In response, the pupil segmentation and dispersion device adjusts a position, orientation, or both of one or more of the pupil segments to select the desired angular information about the measurement pupil and disperse the corresponding spectra with the corresponding detector elements.

[0072] In some embodiments, a dynamically reconfigurable pupil segmentation and dispersal device comprises a microelectromechanical device (MEMS) array of reflective or transmissive grating elements configured to disperse light, including different angular information, to different detector elements.

[0073] In another aspect of the invention, the pupil segmentation and dispersion device is designed to be replaceable within the metrology system 100. In this way, a suitable pupil segmentation and dispersion device for a specific measurement application can be selected and inserted into the path of the collection optics.

[0074] In the Fig. In the embodiment illustrated in Figure 1, the pupil segmentation and dispersal device comprises a plurality of reflective grating segments. In addition to the pupil segmentation, the pupil segmentation and dispersal device may be configured such that the incident light is divided into different wavelength bands, the different wavelength bands propagate in different directions, and the light from one of the wavelength bands is appropriately dispersed onto one or more detectors. In some examples, a beam splitter element is used to divide the collection beam 127 into different wavelength bands, and separate reflective grating structures are employed to segment the measurement pupil in each wavelength band.

[0075] In the in the Fig. In the embodiments illustrated in Figures 4-7, a reflective grating is used because it has high diffraction efficiency in the +1 / -1 order. Using a reflective grating avoids inherent losses in beam splitting elements (such as a dichroic beam splitting element).

[0076] In another aspect, a fine focus sensor (FFS) is integrated into the detection subsystem to provide a measurement input for focus error correction during measurement. In some embodiments, the light diffracted by one or more of the reflective grating segments at the zeroth diffraction order can be directed to a fine focus sensor. In some embodiments, the FFS is a photodiode array. The output generated by the FFS (not shown) is communicated to computer system 130. Computer system 130 determines changes in the focus position (Z-position) of wafer 120 based on the output of the FFS. The desired changes in the focus position of wafer 120 are communicated to a wafer positioning system (not shown), which adjusts the Z-position of wafer 120 accordingly.

[0077] In a further aspect of the invention, the size of the field stop of the illumination field is selected such that the resulting measurement accuracy and speed are optimized for the type of target to be measured.

[0078] In a further aspect of the invention, the field stop of the illumination is adjusted to optimize the resulting measurement accuracy and speed with respect to the type of target to be measured.

[0079] In some examples, the size of the illumination field stop is adjusted to achieve the desired spectral resolution. In some examples, the size of the illumination field stop is adjusted to increase light throughput and reduce measurement time.

[0080] In the Fig. In the embodiment illustrated in Figure 1, computer system 130 is configured to receive signals 170 corresponding to the spectral sensitivity of detection subsystem 160. Computer system 130 is further configured to determine control signals 119 that are forwarded to programmable illumination field stop 113. Programmable illumination field stop 113 receives control signals 119 and adjusts the size of the illumination aperture to achieve the desired illumination field size.

[0081] In some examples, the illumination field stop is adjusted to optimize measurement accuracy and speed, as described above. In another example, the illumination field stop is adjusted to prevent clipping of the image by the spectrometer slit and the corresponding degradation of the measurement results. In this way, the illumination field size is adjusted so that the image of the measurement target underfills the spectrometer slit. In one example, the illumination field stop is adjusted so that the projection of the slit of the polarizer of the illumination optics underfills the slit of the spectrometer of the metrology system.

[0082] Fig. 11 illustrates a method 200 for performing spectroscopic measurements according to at least one novel aspect. The method 200 is adapted for implementation by a metrology system such as that described in Fig. 1 of the present invention. In one aspect, it has been recognized that the data processing blocks of method 200 may be performed by one or more processors of computer system 130 or any other general-purpose computer system using a preprogrammed algorithm. It should be noted that the particular structural aspects of metrology system 100 are not limiting and should be interpreted as illustrative only.

[0083] In block 201, a set of broadband illumination light from an illumination source is directed onto a measurement spot provided on the surface of a sample to be measured. The illumination light is directed onto the sample at multiple angles of incidence, multiple azimuth angles, or a combination thereof.

[0084] In block 202, an amount of light from the measurement spot on the surface of the sample is collected and an image of the measurement pupil is formed at or near a plane of the measurement pupil.

[0085] In block 203, the measured image of the pupil is segmented into two or more pupil segments, and the two or more pupil segments are distributed across spatially separated regions on one or more detectors. Each pupil segment contains signal information associated with different sub-regions of the multiple angles of incidence, the multiple azimuth angles, or a combination thereof.

[0086] In block 204, measurement spectra associated with the two or more pupil segments are detected simultaneously.

[0087] Example measurement techniques that may be configured as described herein include, but are not limited to, spectroscopic ellipsometry (SE), including Mueller Matrix Ellipsometry (MMSE), rotating polarizer SE (RPSE), rotating polarizer rotating compensator SE (RPRC), rotating compensator rotating compensator SE (RCRC), spectroscopic reflectometry (SR), including polarized SR, unpolarized SR, spectroscopic scatterometry, overlay scatterometry, beam profile reflectometry, both angle-resolved and polarization-resolved, beam profile ellipsometry, discrete single or multiple wavelength ellipsometry, etc. In general, any metrology technique that includes a wide range of angular information in the measurement signals may be considered individually or in any combination.For example, any SR or SE technique suitable for the characterization of semiconductor structures, including image-based metrology techniques, can be considered individually or in any combination.

[0088] In another embodiment, system 100 includes one or more computer systems 130 employed to perform measurements of the actual device structures based on collected spectroscopic measurement data in accordance with the methods described herein. The one or more computer systems 130 may be communicatively coupled to the spectrometer. In one aspect, the one or more computer systems 130 are configured to obtain measurement data 170 associated with the measurements of the sample structure 120.

[0089] It should be appreciated that one or more steps described throughout the present disclosure may be performed by a single computer system 130 or, alternatively, by a multiple computer system 130. Furthermore, various subsystems of system 100 may include a computer system suitable for performing a portion of the steps described herein. Therefore, the foregoing description should not be construed as a limitation of the present invention, but is merely an illustration of the invention.

[0090] Furthermore, the computer system 130 may be communicatively coupled to the spectrometer in any manner known in the art. For example, the one or more computer systems 130 may be coupled to the computer systems associated with the spectrometers. In another example, the spectrometers may be directly controlled by a single computer system coupled to the computer system 130.

[0091] The computer system 130 of the metrology system 100 can be configured to receive and / or acquire data or information from the system's subsystems (e.g., spectrometers, etc.) through a transmission medium that may include wired and / or wireless portions. In this way, the transmission medium can serve as a data connection between the computer system 130 and other subsystems of the system 100.

[0092] The computer system 130 of the metrology system 100 may be configured to receive and / or acquire data or information (e.g., measurement results, modeling inputs, modeling results, reference measurement results, etc.) from other systems through a transmission medium, where the transmission medium may include wired and / or wireless portions. In this way, the transmission medium may serve as a data connection between the computer system 130 and other systems (e.g., the memory of the metrology system 100, the external storage, or the other external systems). For example, the computer system 130 may be configured to receive measurement data from a storage medium (e.g., memory 132 or external storage) via a data connection. For example, spectral results obtained using the spectrometers described herein may be stored in a permanent or semi-permanent storage device (e.g., a flash drive).B. Memory 132 or an external storage). In this regard, the spectral results can be imported from the metrology system's memory or from an external storage system. Furthermore, the computer system 130 can send data to other systems via a transmission medium. For example, a measurement model or an estimated parameter value 171 determined by the computer system 130 can be transmitted to an external storage and stored there. In this regard, the measurement results can be exported to another system.

[0093] Computer system 130 may include, but is not limited to, a personal computer system, a mainframe computer system, a workstation, an image computer, a parallel processor, or any other device known in the art. In general, the term "computer system" can be broadly interpreted to include any device having one or more processors that execute instructions from a storage medium.

[0094] Program instructions 134 implementing methods such as those described herein may be transmitted over a transmission medium, such as a wire, a cable, or a wireless transmission link. For example, as in Fig. 1, program instructions 134 stored in memory 132 are transferred to processor 131 via bus 133. Program instructions 134 are stored in a computer-readable medium (e.g., memory 132). Example computer-readable media include read-only memory, random access memory, a magnetic or optical disk, or magnetic tape.

[0095] In some examples, the measurement models are implemented as an element of a SpectraShape® optical metrology system for critical dimensions, available from KLA-Tencor Corporation, Milpitas, California, USA. In this way, the model is created and ready for use immediately after the spectra are collected by the system.

[0096] In some other examples, the measurement models are implemented offline, such as by a computer system implementing AcuShape® software from KLA-Tencor Corporation, Milpitas, California, USA. The resulting trained model can be included as an element in an AcuShape® library accessible by a measurement system performing the measurements.

[0097] In another aspect of the invention, the methods and systems described herein for spectroscopic metrology of semiconductor devices can be applied to the measurement of high aspect ratio (HAR) structures, structures with large lateral dimensions, or both. The described embodiments enable optical critical dimension (CD) metrology, layer metrology, and compositional metrology of semiconductor devices, including three-dimensional NAND structures such as vertical-NAND (V-NAND) structures, dynamic random access memory (DRAM) structures, etc., manufactured by various semiconductor manufacturers such as Samsung Inc. (South Korea), SK Hynix Inc. (South Korea), Toshiba Corporation (Japan), and Micron Technology, Inc. (USA). These complex devices suffer from poor light penetration into the structure to be measured. Fig.10 shows, by way of example, a high aspect ratio NAND structure 300 that is affected by the weak penetration of light into the structure(s) to be measured. A spectroscopic ellipsometer with broadband capability and wide ranges of AOI, azimuth angle, or both, allowing simultaneous detection of the spectral band, as described herein, is suitable for measuring these high aspect ratio structures. HAR structures often include hard mask layers that facilitate the etching process for HARs. As described herein, the term "HAR structure" refers to any structure characterized by an aspect ratio exceeding 10:1, and can achieve an aspect ratio as high as 100:1 or higher.

[0098] In yet another aspect of the invention, the measurement results described herein can be used to provide active feedback for a process tool (e.g., lithography tool, etching tool, deposition tool, etc.). For example, the values ​​of the parameters measured using the measurement methods described herein can be communicated to a lithography tool for adjusting the lithography system to achieve a desired yield. Similarly, etching parameters (e.g., etch time, diffusivity, etc.) or deposition parameters (e.g., time, concentration, etc.) can be incorporated into a measurement model to provide active feedback to the etching tool or coating tools, respectively. In one example, the determined parameters can be transmitted to a lithography tool, an etching tool, or a deposition tool for process correction based on the measured values ​​of the device parameters and a trained measurement model.

[0099] As described herein, the term "critical dimension" includes any critical dimension of a structure (e.g., a bottom critical dimension, a middle critical dimension, a top critical dimension, a sidewall angle, a lattice height, etc.), a critical dimension between any two or more structures (e.g., a distance between two structures), and a displacement between two or more structures (e.g., an overlay displacement between two superimposed lattice structures, etc.). The structures may include three-dimensional structures, patterned structures, overlay structures, etc.

[0100] As described herein, the term “application of the critical dimension” or “application of the critical dimension measurement” includes any measurement of the critical dimension.

[0101] As described herein, the term "metrology system" includes any system that can be used, at least in part, to characterize a sample in any aspect, including metrology applications such as critical dimension metrology, overlay metrology, focus / dose metrology, and compositional metrology. However, these prior art terms do not limit the scope of the term "metrology system" described herein. Additionally, metrology system 100 can be configured to measure patterned wafers and / or unpatterned wafers.The metrology system can be configured as an LED inspection tool, an edge inspection tool, a backside inspection tool, a macro inspection tool, or a multi-mode inspection tool (incorporating data from one or more platforms simultaneously), and another metrology tool or inspection tool that benefits from calibrating system parameters based on critical dimensional data.

[0102] Various embodiments are described herein for a semiconductor measurement system that can be used to measure a sample within a semiconductor processing tool (e.g., an inspection system or a lithography system). The term "sample" is used herein to refer to a wafer, a reticle, or any other sample that can be processed (e.g., printed or inspected for defects) using state-of-the-art means.

[0103] As used herein, the term "wafer" generally refers to substrates made of a semiconductor or non-semiconductor material. Examples include, but are not limited to, single-crystal silicon, gallium arsenide, and indium phosphide. Such substrates may be commonly found and / or processed in semiconductor manufacturing facilities. In some cases, a wafer may comprise only the substrate (i.e., a bare wafer). Alternatively, a wafer may comprise one or more layers of different materials formed on a substrate. One or more layers formed on a wafer may be "patterned" or "unpatterned." For example, a wafer may include a plurality of dies comprising repeating features of a pattern.

[0104] A "reticle" can be a reticle at any stage of a reticle manufacturing process or a finished reticle that may or may not be released for use in a semiconductor fabrication facility. A reticle or "mask" is generally defined as a substantially transparent substrate having substantially opaque regions formed thereon and configuring a pattern. The substrate may, for example, comprise a glass material such as amorphous SiO2. A reticle may be disposed over a resist-covered wafer during an exposure step of a lithography process so that the pattern on the reticle can be transferred to the resist.

[0105] One or more layers formed on a wafer may be patterned or unpatterned. For example, a wafer may comprise a plurality of dies, each of which has repeatable pattern properties. The formation and processing of such material layers may ultimately result in finished devices. Many different types of devices may be formed on a wafer, and the term "wafer" as used herein is intended to encompass a wafer on which any type of device known in the art is fabricated.

[0106] In one or more embodiments, the functions described herein may be implemented in hardware, software, firmware, or any combination. If the functions are implemented in software, the functions may be transmitted on or to the computer-readable medium as one or more instructions or code. Computer-readable media includes both computer storage media and communications media, including any medium that supports transfer of computer programs from one location to another. Storage media may be any available media accessible by a general-purpose or special-purpose computer.By way of example, and not limitation, such computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Furthermore, each combination is properly referred to as a computer-readable medium.For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted-pair digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted-pair DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. The term "disc," as used herein, includes a compact disc (CD), a laser disc, an optical disc, a digital versatile disc (DVD), a floppy disk, and a Blu-ray disc, where disks typically reproduce data magnetically, while platters reproduce data optically using a laser. Combinations of the above should also be included within the scope of computer-readable media.

Claims

A metrology system (100) comprising: one or more illumination sources (110) configured to generate a quantity of broadband illumination light (117); a subsystem of illumination optics configured to direct a quantity of illumination light (117) from the illumination source (110) to a measurement spot (116) on a surface of a sample (120) to be measured at multiple angles of incidence, multiple azimuth angles, or a combination thereof; a subsystem of collection optics configured to collect a quantity of collected light (127) from the measurement spot (116) on the surface of the sample (120), the subsystem of collection optics having a measurement pupil; one or more detectors (160A-C), each having a planar, two-dimensional surface sensitive to incident light;anda pupil segmentation and dispersion device (150) configured to segment an image of the measurement pupil into two or more pupil segments and to disperse the two or more pupil segments onto the one or more detectors (160A-C) over spatially separated regions, wherein each pupil segment comprises signal information associated with distinct sub-regions of the plurality of incidence angles, the plurality of azimuth angles, or a combination thereof, wherein the pupil segmentation and dispersion device (150) comprises:a first diffractive element (150A) having an incidence surface in an optical path of the collection optics subsystem arranged at or near an image plane (140) of the measurement pupil, wherein a first pupil segment is a portion of the collected light (127) on the incidence surface of the first diffractive element (150A, 151A, 152A, 153A);anda second diffractive element (150B, 151B, 152B, 153B) having an incident surface in the optical path of the collection optics subsystem, which is arranged at or near an image plane (140) of the measuring pupil, wherein a second pupil segment is a portion of the collected light incident on the incident surface of the second diffractive element (150B, 151B, 152B, 153B), wherein a normal to the incident surface of the first diffractive element (150A, 151A, 152A, 153A) is oriented at a first angle with respect to a normal to the incident surface of the second diffractive element (150B, 151B, 152B, 153B); The metrology system (100) of claim 1, wherein each of the first diffractive element (150A, 151A, 152A, 153A) and the second diffractive element (150B, 151B, 152B, 153B) is a reflective grating structure, a transmissive grating structure, or a dispersive prism structure. Metrology system (100) according to claim 2 , wherein an axis angle is associated with the first angle between the first diffractive element (150A, 153A) and the second diffractive element (150B, 153B) and is aligned parallel to a blaze direction of the first diffractive element (150A, 153A). Metrology system (100) according to claim 2, wherein an axis angle is associated with the first angle between the first diffractive element (151A, 152A) and the second diffractive element (151B, 152B) and is oriented perpendicular to a blaze direction of the first diffractive element (151A, 152A). The metrology system (100) of claim 2, wherein an axis angle is associated with the first angle between the first diffractive element and the second diffractive element and is oriented at an oblique angle with respect to a blaze direction of the first diffractive element. The metrology system (100) of claim 1, wherein the device for segmenting and dispersing the pupil (150) further comprises: a third diffractive element (150C, 151C, 152C, 153C) having an incident surface in an optical path of the collection optics subsystem near the image plane (140) of the measurement pupil, wherein a third pupil segment is a portion of the collected light incident on the incident surface of the third diffractive element (150C, 151C, 152C, 153C), wherein a normal to the incident surface of the first diffractive element (150A, 151A, 152A, 153A) is at a second angle with respect to a normal to the incident surface of the third diffractive element (150C, 151C, 152C, 153C). Metrology system (100) according to claim 6, wherein an axial angle associated with the second angle between the first diffractive element (150A, 151A, 152A, 153A) and the third diffractive element (150C, 151C, 152C, 153C) is equal to and opposite in direction to the axial angle associated with the first angle between the first diffractive element (150A, 151A, 152A, 153A) and the second diffractive element (150B, 151B, 152B, 153B). Metrology system (100) according to claim 2, wherein a grating pitch of the first diffractive element (150A, 151A, 152A, 153A) differs from a grating pitch of the second diffractive element (150B, 151B, 152B, 153B). Metrology system (100) according to claim 1, wherein the pupil segmentation and dispersion device (150) in the metrology system (100) is configurable, interchangeable with another pupil segmentation and dispersion device, or both. The metrology system (100) of claim 1, wherein a first of the one or more detectors comprises two or more different surface areas each having a different light sensitivity, the two or more of the different surface areas being aligned in a direction of wavelength dispersion along the surface of the first detector. The metrology system (100) of claim 1, wherein a second of the one or more detectors measures the background noise. The metrology system (100) of claim 1, wherein the amount of broadband illumination light (117) comprises a wavelength range including infrared, visible, and ultraviolet wavelengths. Metrology system (100) according to claim 1, wherein the metrology system (100) is configured as a spectroscopic ellipsometer, as a spectroscopic reflectometer, or as a combination thereof. The metrology system (100) of claim 1, further comprising:a computer system (130) configured to generate an estimated value of a parameter of interest of the sample (120) to be measured based on an analysis of the output signal of the one or more detectors. A metrology system (100) comprising: a subsystem of illumination optics configured to direct the amount of broadband illumination light (117) from the illumination source (110) to a measurement spot (116) on a surface of a sample (120) to be measured at multiple angles of incidence, multiple azimuth angles, or a combination thereof; a subsystem of collection optics configured to collect an amount of collected light (121) from the measurement spot (116) on the surface of the sample (120), the subsystem of collection optics having a measurement pupil; one or more detectors, each having a planar, two-dimensional surface sensitive to incident light;a first diffractive element (150A, 151A, 152A, 153A) having an incident surface in an optical path of the collection optics subsystem arranged at or near an image plane (140) of the measurement pupil, wherein a first pupil segment is a portion of the collected light on the incident surface of the first diffractive element (150A, 151A, 152A, 153A), wherein the first diffractive element (150A, 151A, 152A, 153A) disperses a portion of the first pupil segment over a first light-sensitive area of the one or more detectors;and a second diffractive element (150B, 151B, 152B, 153B) having an incident surface in the optical path of the collection optics subsystem, which is arranged at or near an image plane (140) of the measuring pupil, wherein a second pupil segment is a portion of the collected light incident on the incident surface of the second diffractive element (150B, 151B, 152B, 153B), wherein the second diffractive element (150B, 151B, 152B, 153B) disperses the second pupil segment over a second light-sensitive region of the one or more detectors that is spatially separated from the first light-sensitive region, and a normal to the incident surface of the first diffractive element (150A, 151A, 152A, 153A) at a first angle is oriented with respect to a normal to the incident surface of the second diffractive element (150B, 151B, 152B, 153B); Metrology system (100) according to claim 15, wherein each of the first diffractive element (150A, 151A, 152A, 153A) and the second diffractive element (150B, 151B, 152B, 153B) is a reflective grating structure, a transmissive grating structure, or a dispersive prism structure. The metrology system (100) of claim 15, wherein a first of the one or more detectors comprises two or more different surface areas, each having a different light sensitivity, the two or more of the different surface areas being aligned in a direction of wavelength dispersion along the surface of the first detector. A method comprises the steps of: directing a quantity of broadband illumination light (117) from an illumination source (110) to a measurement spot (116) on a surface of a sample (120) to be measured at multiple angles of incidence, multiple azimuth angles, or a combination thereof; collecting a quantity of collected light (121) from the measurement spot (116) on the surface of the sample (120) and generating an image of the measurement pupil at or near an image plane (140) of the measurement pupil; segmenting the image of the measurement pupil into two or more pupil segments and dispersing the two or more pupil segments onto one or more detectors over spatially separated regions, each pupil segment containing signal information associated with different sub-regions of the multiple angles of incidence, the multiple azimuth angles, or a combination thereof;andsimultaneous detection of measurement spectra associated with two or more pupil segments, wherein the segmenting and dispersing of a first of the two or more pupil segments involves a first diffractive element (150A, 151A, 152A, 153A) having an incident surface in an optical path of the subsystem of collection optics near an image plane (140) of the measurement pupil, and wherein the segmenting and dispersing of a second of the two or more pupil segments involves a second diffractive element (150B, 151B, 152B, 153B) having an incident surface in the optical path of the subsystem of collection optics near the image plane (140) of the measurement pupil, wherein a normal to the incident surface of the first diffractive element (150A, 151A, 152A, 153A) is oriented at a first angle with respect to a normal to the incident surface of the second diffractive element (150B, 151B, 152B, 153B); Method according to claim 18, wherein the sample (120) to be measured is a three-dimensional NAND structure or a dynamic random access memory structure.

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