Optical device for measuring thick films and aspect ratio structures

Abstract

Presented herein are methods and systems for performing spectral ellipsometry of semiconductor structures using reflection collection relay optics that have a zoom from a spectrometer slit to a detector. The zoom effectively increases the NA at the detector and reduces the measurement spot size at the wafer imaged onto the detector. In this manner, the magnification maintains a high spectral resolution at the detector, in particular within the ultraviolet wavelength range, such as 120 to 400 nanometers, while maintaining a small collection NA at the wafer, such as a collection NA of less than 0.05. The small collection NA achieves high fringe contrast, signal fidelity, and sensitivity when measuring a thick multi-layer stack, such as 200 to 300 layers.

Description

Technical Field

[0001] The described embodiments relate to metrology systems and methods, and more particularly, to methods and systems for improving the measurement of semiconductor structures. Background Art

[0002] Semiconductor devices such as logic and memory devices are typically fabricated through a series of processing steps applied to a sample. Various features and multiple structural levels of the semiconductor device are formed through these processing steps. For example, lithography is a semiconductor manufacturing process that involves generating patterns on a semiconductor wafer. Additional examples of semiconductor manufacturing processes include, but are not limited to, chemical mechanical polishing, etching, deposition, and ion implantation. Multiple semiconductor devices can be fabricated on a single semiconductor wafer and then separated into individual semiconductor devices.

[0003] Metrology processes are used at various steps during semiconductor manufacturing processes to detect defects on the wafer to facilitate a higher yield. Optical metrology techniques offer the potential for high throughput without the risk of sample damage. Several optical metrology-based techniques, including scatterometry and reflectometry implementations and their associated analysis algorithms, are commonly used to characterize critical dimensions, film thickness, composition, overlay, and other parameters of nanoscale structures.

[0004] Flash memory and dynamic random access memory (DRAM) architectures have transitioned from two-dimensional floating gate architectures to fully three-dimensional geometries. In some instances, the film stacks and etched structures are very deep (e.g., up to 6 microns in depth) and contain many layers. For example, state-of-the-art NAND memory structures contain 200 to 300 layers. Such high aspect ratio multi-layer structures pose challenges for film and CD measurements. The ability to measure the critical dimensions of the shapes of the holes and trenches that define these structures is crucial for achieving the desired performance levels and device yields. Additionally, many semiconductor architectures employ thick layers of opaque materials, such as amorphous carbon layers, tungsten layers, and hard mask layers. Illumination light in the vacuum ultraviolet, ultraviolet, visible, and short infrared wavelength ranges (i.e., wavelengths below approximately 1 micron) does not sufficiently penetrate these opaque layers, resulting in measurement signals with low signal-to-noise ratios or no measurable signals at all.

[0005] Many optical techniques suffer from low signal-to-noise ratio (SNR) because only a small fraction of the illumination light can reach the bottom of the high aspect ratio features and be reflected back up to the detector. As a result, many available high throughput metrology techniques cannot reliably perform CD and film measurements on high aspect ratio structures. Critical dimension, small angle X-ray scattering measurement (CD-SAXS), normal incidence reflectometry, and scatterometry have been explored as measurement solutions for high aspect ratio structures, but development is still ongoing.

[0006] Cross-sectional scanning electron microscopy (SEM) is a low throughput destructive technique not suitable for in-line metrology. The capabilities of atomic force microscopy (AFM) are limited to measuring high aspect ratio structures and have a relatively low throughput. CD-SAXS has not been demonstrated to achieve the high throughput capabilities required by the semiconductor industry. Model-based infrared reflectometry (MBIR) has been used for metrology of high aspect ratio DRAM structures, but the technique lacks the resolution provided by shorter wavelengths and the measurement spot size is too large for semiconductor metrology. See Gostein et al., "Measuring deep-trench structures with model-based IR," Solid State Technology, Vol. 49, No. 3, March 1, 2006, which is incorporated herein by reference as if fully set forth.

[0007] Optical CD metrology currently lacks the ability to measure in detail the profiles of structures with micron-scale depth and lateral dimensions in a relatively small spot (e.g., less than 50 microns or even more preferably less than 30 microns) with high throughput. U.S. Patent No. 8,860,937 (which is incorporated herein by reference as if fully set forth) describes an infrared spectroscopic ellipsometry technique suitable for characterizing high aspect ratio structures. However, the described technique suffers from long measurement times for measurements spanning ultraviolet and infrared wavelengths, wavelength stability limitations, and a limited range of infrared wavelengths during operation.

[0008] Existing metrology tools manufactured by KLA Corporation include the SpectraShape TM SS10k, SS11K, and S12k tools that focus on critical dimension and shape metrology, and the SpectraFilm TM F1 - F20 tools. These tools include a relatively large collection NA in the AOI direction, which limits the sensitivity to deep structures with a relatively large number of layers (e.g., 200 to 300 layers). Existing tools have a relatively large collection NA in the AOI direction and lack sensitivity at 200 to 300 layers of NAND. Additionally, the illumination wavelength range of existing tools is limited to 170 nm or higher because the tools employ refractive collection relay optics that are not compatible with shorter wavelength radiation.

[0009] In summary, the ever-decreasing feature sizes, increasing depth and number of structural features, and increasing use of opaque material layers pose difficult requirements on optical metrology systems. The optical metrology systems must meet the high-precision and accuracy requirements for meeting increasingly complex targets at high throughput to remain cost-effective. In this context, the collection NA of the collection relay optics and the limited short-wavelength capabilities have become key performance-limiting issues in the design of optical metrology systems suitable for high aspect ratio structures with a relatively large number of layers (e.g., more than 200 layers). Accordingly, improved metrology systems and methods are desired to overcome these limitations. SUMMARY OF THE INVENTION

[0010] Methods and systems are presented herein for performing spectroscopic ellipsometry of semiconductor structures using a reflective collection relay optic with demagnification from a spectrometer slit to a detector. Demagnification effectively increases the NA at the detector and decreases the measurement spot size at the wafer imaged onto the detector. In this way, demagnification maintains high spectral resolution at the detector, particularly in the ultraviolet wavelength range (e.g., 120 to 400 nanometers), while maintaining a small collection NA at the wafer (e.g., a collection NA less than 0.05). When measuring thick multi-layer stacks (e.g., 200 to 300 layers), the small collection NA enables high fringe contrast, signal fidelity, and sensitivity.

[0011] In one aspect, the optical elements of the collection relay optic 126 are reflective optical elements and the collection relay optic has a field-of-view demagnification greater than 1, i.e., a field-of-view magnification less than 1. In some embodiments, the field-of-view demagnification of the collection relay optic is between 1.1x and 10x, i.e., the field-of-view magnification is between 0.1x and 0.9x.

[0012] Generally, a reflective collection relay optic may include any number of reflective optical elements configured with a field-of-view demagnification greater than 1. A reflective collection relay optic with a field-of-view demagnification greater than 1 improves the optical resolution at the detector(s) without adding chromatic aberration inherent in reflective optical elements. Additionally, the reflective collection relay optic enables collection of shorter wavelength light, e.g., wavelengths less than 190 nanometers. In some embodiments, the reflective collection relay optic enables collection of light having wavelengths in the range from 140 nanometers to 2,500 nanometers.

[0013] In some embodiments, the collection optical subsystem includes a collection mask disposed near the pupil of the collection optical subsystem. The collection mask includes one or more apertures (i.e., openings) configured to transmit collection light from the wafer at one or more angles of incidence (AOI) and block light from other AOIs. In some embodiments, the collection mask includes three apertures that transmit collection light from three different AOIs from the wafer. Additionally, the collection mask is configured to transmit collection light at each of the one or more angles of incidence with a numerical aperture (NA) less than 0.05 in the AOI direction. In some embodiments, the collection mask transmits collection light at each of the one or more angles of incidence with an NA in the range from 0.02 to 0.05 in the AOI direction. Sampling with a relatively small NA in the AOI direction enables high fringe contrast and sensitivity to thick films and HAR structures. In this way, the collection mask controls the NA of the collection subsystem.

[0014] The collection field stop controls the field of view of the collection optical subsystem. In some other embodiments, a spectrometer slit is used to define the field of view of the collection optical subsystem.

[0015] In some embodiments, the dispersive element of the spectrometer includes one or more segments and each segment receives light from one or more corresponding apertures of the collection mask. In this way, the light dispersed onto the detector by the dispersive element includes light corresponding to one or more discrete angles of incidence at the wafer.

[0016] Generally, the detector receives light collected from the wafer at one or more angles of incidence, multiple wavelengths, and one or more polarization states. The detector generates an output signal in response to light collected from one or more structures illuminated by the illumination subsystem. In some embodiments, the dispersive element disperses the diffracted light linearly according to wavelength along one dimension of the detector, thereby causing a spatial separation among the light of different wavelengths projected onto the surface of the detector. In this way, light of a particular wavelength collected from a measurement spot is projected onto the detector at a spatial location different from that of light of another different wavelength collected from the measurement spot.

[0017] On the other hand, the methods and systems for spectroscopic metrology of semiconductor devices described herein are applied to the measurement of high aspect ratio (HAR) structures, large lateral dimension structures, or both. The described embodiments enable optical critical dimension (CD), film, and composition metrology of semiconductor devices fabricated by various semiconductor manufacturers such as Samsung Corporation (South Korea), SK Hynix Inc. (South Korea), Toshiba Corporation (Japan), and Micron Technology, Inc. (USA), etc., which include three-dimensional NAND structures such as vertical NAND (V-NAND) structures, dynamic random access memory structures (DRAM), etc. These complex devices suffer from the problem of weak light penetration into the (several) structures to be measured. Figure 3 FIG. 160 depicts an exemplary high aspect ratio structure where there is a problem of weak light penetration into the (several) structures to be measured. A spectroscopic ellipsometer with broadband capabilities and a wide range of AOI, azimuth, or both with synchronous spectroscopic band detection as described herein is suitable for measuring these high aspect ratio structures. The HAR structure typically includes a hard mask layer for facilitating the etching process for HAR. As described herein, the term "HAR structure" refers to any structure characterized by an aspect ratio exceeding 2:1 or 10:1 and can be as high as 100:1 or higher.

[0018] The foregoing is a summary and thus necessarily contains simplifications, generalizations, and omissions of detail; accordingly, those skilled in the art will appreciate that the summary is illustrative only and is not limiting in any way. Other aspects, inventive features, and advantages of the devices and / or processes described herein will become apparent in the non-limiting detailed description set forth herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 FIG. 100 depicts an exemplary metrology system for performing broadband spectroscopic measurements of semiconductor structures using collection relay optics with a demagnification greater than 1 as described herein.

[0020] Figure 2 FIG. 180 depicts an embodiment of a combined illumination source.

[0021] Figure 3 FIG. 160 depicts an exemplary high aspect ratio semiconductor structure where there is a problem of weak light penetration into the (several) structures to be measured.

[0022] Figure 4A FIG. 200 depicts another embodiment of a combined illumination source.

[0023] Figure 4B FIG. 220 depicts another embodiment of a combined illumination source.

[0024] Figure 4CDepict another embodiment 240 of a combined light source.

[0025] Figure 5 Depict a graph showing the specific detectivity of various detector technologies operating at a specified temperature.

[0026] Figure 6 Depict an illustration of a multi - zone infrared detector 270.

[0027] Figure 7 Illustrate the typical photosensitivity curves of four available indium gallium arsenide (InGaAs) sensors.

[0028] Figure 8 Illustrate a method 300 for performing spectroscopic measurements of one or more structures using a collection relay optic having a demagnification greater than 1 as described herein. Detailed Description

[0029] Reference will now be made in detail to the background examples and some embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

[0030] Methods and systems are presented herein for performing spectroscopic ellipsometry of semiconductor structures using a reflective collection relay optic having a demagnification from the spectrometer slit to the detector. The demagnification effectively increases the NA at the detector and decreases the measurement spot size at the wafer imaged onto the detector. In this way, the demagnification maintains a high spectral resolution at the detector, particularly in the ultraviolet wavelength range (e.g., 120 to 400 nanometers), while maintaining a small collection NA at the wafer (e.g., a collection NA less than 0.05). When measuring thick multi - layer stacks (e.g., 200 to 300 layers), the small collection NA enables high fringe contrast, signal fidelity, and sensitivity.

[0031] Figure 1 Depict an exemplary metrology system 100 for performing broadband spectroscopic measurements (e.g., film thickness, critical dimension, overlay, etc.) of semiconductor structures. In some examples, one or more structures include at least one high aspect ratio (HAR) structure or at least one large lateral dimension structure. In some of these examples, one or more structures include at least 200 different layers. As Figure 1 depicted, metrology system 100 is configured as an oblique - incidence broadband spectroscopic ellipsometer. However, generally, metrology system 100 may also include additional spectroscopic ellipsometers, spectroscopic reflectometers, scatterometers, or any combination thereof.

[0032] The metrology system 100 includes an illumination source 110 that generates an illumination light beam 101 incident on a wafer 120. The illumination source 110 includes one or more illumination sources that emit illumination light having wavelengths in the range from 140 nanometers to 2,500 nanometers. In some embodiments, the illumination source 110 is a combined illumination source that emits illumination light in the ultraviolet, visible, and infrared spectra (including ultraviolet wavelengths as low as 140 nanometers and infrared wavelengths greater than 2 microns, e.g., illumination wavelengths in the range from 140 nanometers to 2,500 nanometers). In some other embodiments, the illumination source 110 is a combined illumination source that emits illumination light having wavelengths in the range from 140 nanometers to 7,000 nanometers.

[0033] In a preferred embodiment, the combined illumination source 110 includes a supercontinuum laser source and a laser sustained plasma light source. The supercontinuum laser source provides illumination light having wavelengths greater than 2 microns and in some embodiments up to 5 microns or greater. The laser sustained plasma (LSP) light source (also known as a laser-driven plasma source) generates photons across the entire wavelength range from 120 nanometers to 2500 nanometers and higher. The pump laser of the LSP light source can be continuous wave or pulsed. In some embodiments, the combined illumination source 110 includes a supercontinuum laser source and an arc lamp (e.g., a xenon arc lamp). However, the laser-driven plasma source generates significantly more photons across the entire wavelength range from 120 nanometers to 2500 nanometers than a xenon lamp and is therefore preferred.

[0034] Generally, the combined illumination source 110 includes a combination of multiple broadband or discrete wavelength light sources. The light generated by the combined illumination source 110 includes a continuous spectrum or a portion of a continuous spectrum: from ultraviolet to infrared (e.g., vacuum ultraviolet to long infrared). Generally, the combined illumination light source 110 can include a supercontinuum laser source, an infrared helium-neon laser source, a silicon carbide glow bar source, a tungsten halogen source, one or more infrared LEDs, one or more infrared lasers, or any other suitable infrared light source that generates wavelengths greater than 2 microns, and an arc lamp (e.g., a xenon arc lamp), a deuterium lamp, an LSP light source, or any other suitable light source that generates wavelengths less than 2 microns (including visible and ultraviolet wavelengths).

[0035] Generally, the combined illumination source 110 includes multiple illumination sources optically coupled in any suitable manner. In some embodiments, the light emitted by the supercontinuum laser source is directly coupled through a plasma generated by an ultraviolet / visible light source.

[0036] Figure 2 An embodiment 180 of the combined illumination source 110 is depicted. As Figure 2As depicted, the LSP pump laser source 181 generates pump light 182 that is focused by focusing optics 183 to sustain the plasma 184 contained by the bulb 185. The plasma 184 generates broadband spectral light in the wavelength range from ultraviolet to short infrared. The bulb 185 includes an exit port 186. The LSP output light 187 is the portion of the light from the plasma 184 that passes through the exit port 186 and is directed toward the illumination optical device subsystem as referenced Figure 1 described. Additionally, the supercontinuum laser source 191 generates infrared light 192 that is focused by focusing optics 193 to a focal point 194 at or near the plasma 184. The supercontinuum output light 197 is the portion of the light from the focal point 194 that passes through the exit port 186 and is directed toward the illumination subsystem as referenced Figure 1 described. In one example, the LSP output light 187 and the supercontinuum output light 197 are collocated. In this manner, the infrared light 197 from the supercontinuum source 191 is effectively combined with the ultraviolet / infrared light 187 from the LSP laser source 181. In one example, the LSP output light 187 and the supercontinuum output light 197 have the same or similar numerical apertures. In another example, the LSP output light 187 and the supercontinuum output light 197 have different numerical apertures. In some examples, the bulb 185 is composed of calcium fluoride or magnesium fluoride to transmit wavelengths greater than 2.5 microns generated by the supercontinuum laser source 191. In some other examples, the bulb 185 includes one or more exit ports 186 made of calcium fluoride or magnesium fluoride to transmit wavelengths greater than 2.5 microns generated by the supercontinuum laser source 191. Conventional bulbs made of fused silica do not transmit significant light greater than 2.5 microns and are thus not suitable for combining the light generated by the supercontinuum laser source 191 in the manner described herein. In some embodiments, the LSP pump laser source 181 is a continuous wave laser. In some other embodiments, the LSP pump laser source 181 is a pulsed laser.

[0037] As Figure 1 depicted, the metrology system 100 includes an illumination subsystem configured to direct illumination light 101 to one or more structures formed on a wafer 120. The illumination subsystem may include any type and arrangement of (several) optical filters, polarization components, field stops, pupil stops, etc. known in the field of spectral metrology. As Figure 1 depicted, the illumination subsystem includes a light source 110, beam shaping optics 111, 112, 115, and 121, a polarization component 113, and a pupil stop 114. As depicted, in Figure 1In, when the beam of illumination light 101 propagates from the illumination source 110 to the wafer 120, the beam is reflected from beam shaping optics 111, 112, 115, and 121 and passes through polarization components 113 and the pupil aperture 114. The beam 101 illuminates a portion of the wafer 120 above the measurement spot 116.

[0038] In Figure 1 In the embodiment depicted in, the pupil aperture 114 controls the numerical aperture (NA) of the illumination subsystem and may include any suitable commercially available aperture stop. In one aspect, the illumination subsystem is configured to direct the illumination light 101 onto the wafer 120 with an illumination numerical aperture (NA) of at least 0.1 (e.g., between 0.1 and 0.25) at the wafer surface. In one aspect, the illumination NA provides an illumination spot at the wafer 120 that fits within the scribe lane. This enables the measurement of scribe lane metrology targets. In some embodiments, the illumination light 101 is focused on a 50 micron by 50 micron scribe lane target area. In some embodiments, the illumination light 101 is focused on a 50 micron by 100 micron scribe lane target area. In some embodiments, the illumination light 101 is focused on a 50 micron by 150 micron scribe lane target area. In some embodiments, the illumination light 101 is incident on the wafer 120 at an incident angle α (65 degrees or near 65 degrees from normal incidence).

[0039] Additionally, the illumination subsystem may include filters, masks, apodizers, etc. For example, the illumination subsystem may include an illumination field stop (not shown) and one or more optical filters (not shown). The illumination field stop controls the field of view (FOV) of the illumination subsystem and may include any suitable commercially available field stop. The optical filters are used to control the brightness, spectral output, or both from the illumination subsystem. In some instances, one or more multi-zone filters are used as the optical filter. As Figure 1 depicted in, the beam shaping optics 111, 112, 115, and 121 include one or more optical elements having reflective focusing capabilities.

[0040] In some instances, the beam size of the amount of illumination light 101 projected onto the surface of the wafer 120 is smaller than the size of the measurement target measured on the surface of the sample. For example, exemplary beam shaping techniques are described in U.S. Patent Application Publication No. 2013 / 0114085 to Wang et al., the disclosure of which is incorporated herein by reference in its entirety.

[0041] In some instances, noise and polarization optimization are performed to improve the performance of the illumination source 110. In some instances, depolarization is achieved by using a multimode fiber, a Hanle depolarizer, or an integrating sphere. In some instances, the illumination source light spread is optimized by using light guides, optical fibers, and other optical elements (e.g., lenses, curved mirrors, apodizers, etc.). In some instances, source coherence or coherence effects are mitigated by coherent blocking techniques or otherwise addressed through modeling and simulation.

[0042] The polarization component 113 generates the desired polarization state exiting the illumination subsystem. In some embodiments, the polarization component includes a polarizer, a compensator, or both, and may include any suitable commercially available polarization component. The polarizer, compensator, or both may be fixed, rotatable to different fixed positions, or continuously rotatable. Although Figure 1 the illumination subsystem depicted in

[0043] includes one polarization component, the illumination subsystem may include more than one polarization component. In some embodiments, the polarizer of the polarization component 113 is a Magnesium Fluoride Rochon polarizer. In some embodiments, the compensator of the polarization component 113 includes a quartz waveplate, a Magnesium Fluoride waveplate, a Calcium Fluoride K-prism, a Calcium Fluoride double Fresnel rhomb, or any combination thereof. In some embodiments, the compensator of the polarization component 113 includes one or more waveplates. In some of these embodiments, the first waveplate includes a desired delay in a first wavelength range and the second waveplate includes a desired delay in a second wavelength range, etc.

[0044] As Figure 1 depicted in

[0045] AsFigure 1 As depicted in, the collection optical subsystem includes a polarization component that analyzes the polarization state of the collected light. In some embodiments, the polarization component includes an analyzer, a compensator, or both, and may include any suitable commercially available polarization component. The analyzer, compensator, or both may be fixed, rotatable to different fixed positions, or continuously rotatable. Figure 1 The collection subsystem depicted in includes compensator 123 and analyzer 124. Generally, the collection optical subsystem may include any number of polarization elements.

[0046] In some embodiments, compensator 123 includes a quartz waveplate, a magnesium fluoride waveplate, a calcium fluoride K prism, a calcium fluoride double Fresnel rhomb, or any combination thereof. In some embodiments, compensator 123 includes one or more waveplates. In some of these embodiments, the first waveplate includes a desired delay in a first wavelength range and the second waveplate includes a desired delay in a second wavelength range, etc. In some embodiments, analyzer 124 is a magnesium fluoride Rochon analyzer.

[0047] As Figure 1 depicted in, the collection optical subsystem includes a collection mask 125 disposed near the pupil of the collection optical subsystem. Collection mask 125 includes one or more apertures (i.e., openings) configured to transmit collected light from wafer 120 at one or more angles of incidence (AOI) and block light from other AOIs. In some embodiments, collection mask 125 includes three apertures that transmit collected light from wafer 120 at three different AOIs. Additionally, collection mask 125 is configured to transmit collected light at each of the one or more angles of incidence with a numerical aperture (NA) less than 0.05 in the AOI direction. In some embodiments, collection mask 125 transmits collected light at each of the one or more angles of incidence with an NA in the range from 0.02 to 0.05 in the AOI direction. Sampling at a relatively small NA in the AOI direction enables high fringe contrast and sensitivity to thick films and HAR structures. In this way, collection mask 125 controls the NA of the collection subsystem.

[0048] The collection field stop 103 controls the field of view of the collection optical subsystem. In some other embodiments, a spectrometer slit is used to define the field of view of the collection optical subsystem.

[0049] In Figure 1 the embodiment depicted in, the spectrometer subsystem includes a collection field stop 103, a dispersive element 127, and one or more optical devices (not shown) having reflective focusing capabilities. The collection field stop 103 receives light from the collection optical subsystem that includes relay optics 126 and transmits a portion of the collected light to the dispersive element 127. The dispersive element 127 disperses the light into discrete wavelengths on the active surface of the detector 128.

[0050] The dispersion element 127 is typically located at or near the pupil plane of the collection optics subsystem. The relay optics 126 receives light from the collection mask 125 and images the light from the collection mask 125 onto the pupil plane at or near the dispersion element 127. In this way, the collection relay optics 126 serves as a pupil repeater and images the collection mask 125 at the dispersion element 127.

[0051] In one aspect, the optical elements of the collection relay optics 126 are reflective optical elements and the collection relay optics 126 has a field-of-view reduction greater than 1, i.e., a field-of-view magnification less than 1. The reduction of the collection relay optics enables the detector 128 to have a higher NA and spectral resolution. In some embodiments, the field-of-view reduction of the collection relay optics 126 is between 1.1x and 10x, i.e., the field-of-view magnification is between 0.1x and 0.9x. In some embodiments, the field-of-view reduction of the collection relay optics 126 is between 2x and 10x, i.e., the field-of-view magnification is between 0.1x and 0.5x. As described herein, the field-of-view magnification of the collection relay optics is the input NA of the relay optics in the imaging space compared to the output NA, and the field-of-view reduction of the collection relay optics is the output NA of the relay optics in the imaging space compared to the input NA.

[0052] As Figure 1 depicted, the reflective collection relay optics 126 includes reflective optical elements 126A and 126B. However, in general, the reflective collection relay optics 126 can include any number of reflective optical elements configured with a field-of-view reduction greater than 1. The reflective collection relay optics with a field-of-view reduction greater than 1 improves the optical resolution at the (a) detector(s) without adding the chromatic aberration inherent in refractive optical elements. The increased spectral resolution offsets the loss of spectral resolution at the detector caused by using a collection mask with a relatively small NA (i.e., less than 0.05) at the wafer. Additionally, the reflective collection relay optics enables collection of light at shorter wavelengths, e.g., wavelengths less than 190 nanometers. In some embodiments, the reflective collection relay optics enables collection of light having wavelengths in the range from 140 nanometers to 2,500 nanometers.

[0053] The dispersion element 127 is typically a diffraction grating or a dispersion prism. In some embodiments, the dispersion element 127 includes one or more segments and each segment receives light from one or more corresponding apertures of the collection mask 125. In this manner, the light dispersed by the dispersion element 127 includes light corresponding to one or more discrete angles of incidence at the wafer. In some embodiments, the dispersion element 127 is a planar diffraction grating. In some of these embodiments, the planar diffraction grating is segmented to split the pupil into segments each corresponding to a different set of discrete angles of incidence at the wafer. Further details regarding pupil splitting are described in U.S. Patent No. 10,690,602 to KLA-Tencor Corporation, the content of which is incorporated herein by reference in its entirety.

[0054] As Figure 1 depicted, the detector 128 receives light collected from the wafer 120 at one or more angles of incidence, multiple wavelengths (e.g., 140 nanometers to 2,500 nanometers), and one or more polarization states. In Figure 1 the depicted embodiment, the collection optical subsystem directs the light to the detector 128 and the detector 128 generates an output signal 154 in response to light collected from one or more structures illuminated by the illumination subsystem. The dispersion element 127 disperses the diffracted light linearly according to wavelength along one dimension of the detector 128 (i.e., Figure 1 the wavelength dispersion direction shown). The dispersion element 127 causes a spatial separation among the different wavelengths of the light projected onto the surface of the detector 128. In this manner, light having a particular wavelength collected from the measurement spot 116 is projected onto the detector 128 at a spatial location different from that of light having another different wavelength collected from the measurement spot 116.

[0055] The metrology system 100 further includes a computing system 130 configured to receive the detection signal 154 and determine an estimate 155 of the value of the parameter(s) of interest of the measurement structure(s) based on the detection signal.

[0056] Generally, the collection optical subsystem may direct the light to more than one detector. In these embodiments, two or more detectors are each configured to simultaneously detect the collected light in different wavelength ranges.

[0057] In one example, one detector is a charge-coupled device (CCD) sensitive to ultraviolet and visible light (e.g., light having wavelengths between 190 nanometers and 860 nanometers), and the other detector is a photodetector array (PDA) sensitive to infrared light (e.g., light having wavelengths between 950 nanometers and 5000 nanometers). However, in general, other two-dimensional detector technologies (e.g., position-sensitive detectors (PSD), infrared detectors, photovoltaic detectors, etc.) can be considered. Each detector converts the incident light into an electrical signal indicative of the spectral intensity of the incident light. In some embodiments, the detection subsystem is arranged such that the collected light is simultaneously propagated to all detectors of the metrology system 100. By collecting the UV and IR spectra simultaneously, the measurement time is reduced and all spectra are measured under the same alignment conditions. This allows for easier correction of wavelength errors since a common correction can be applied to all spectral data sets.

[0058] In general, the dispersive element 127 can be configured to split the incident light into different wavelength bands, propagate the different wavelength bands in different directions, and disperse the light of one of the wavelength bands onto one or more detectors in any suitable manner. In one example, the dispersive element 127 is configured as a transmission grating. In some other examples, the dispersive element 127 includes a beam splitting element for splitting the beam into different wavelength bands and a reflective or transmissive grating structure for dispersing the light of one of the wavelength bands onto the detector.

[0059] In some embodiments, the dispersive element 127 is a reflective grating configured to diffract a subset of the wavelengths of the incident light into the + / −1 diffraction orders towards one detector and a different subset of the wavelengths of the incident light into the 0 diffraction order towards another detector.

[0060] By measuring the target with infrared, visible, and ultraviolet light in a single system, accurate characterization of complex three-dimensional structures is achieved. In general, relatively long wavelengths penetrate deeply into the structure and provide suppression of high diffraction orders when measuring structures with relatively large pitches. Relatively short wavelengths provide accurate dimensional information about the structure, such as relatively small CDs and roughness features. In some examples, the longer wavelengths enable measurement of the dimensional characteristics of targets having relatively rough surfaces or interfaces due to the lower sensitivity of the longer wavelengths to roughness. In general, measuring the target with infrared, visible, and ultraviolet light in a single system improves the sensitivity to some measurement parameters and reduces the correlation among the parameters (e.g., parameters characterizing the top and bottom layers).

[0061] In some embodiments, the methods and systems for spectroscopic metrology of semiconductor devices described herein are applied to the measurement of high aspect ratio (HAR), large lateral dimension structures, opaque film layers, or combinations thereof. These embodiments enable optical critical dimension (CD), film, and composition metrology of semiconductor devices having HAR structures (e.g., NAND, VNAND, TCAT, DRAM, etc.) and (more generally) complex devices where there is a problem of weak light penetration into the (several) structures to be measured. HAR structures typically include a hard mask layer for facilitating the etching process for HAR. As described herein, the term "HAR structure" refers to any structure characterized by an aspect ratio exceeding 2:1 or 10:1 and that can be as high as 100:1 or higher.

[0062] Figure 3 Depicts a vertical integrated memory structure 160 including a tungsten layer 161 sandwiched between oxide layers 162. As Figure 3 depicted, the etching process leaves horizontal grooves in each tungsten layer 161 with respect to the oxide layers 162 above and below each tungsten layer 161. The tungsten grooves at or near the top of structure 160 are referred to as top_grooves. The tungsten grooves at or near the middle of structure 160 are referred to as middle_grooves. The tungsten grooves at or near the bottom of structure 160 are referred to as bottom_grooves. The opening of the oxide layer 162 at or near the bottom of structure 160 is referred to as the bottom critical dimension (HM_BCD).

[0063] In some embodiments, the spectroscopic measurement system includes a combined illumination source that includes a first illumination source that generates ultraviolet, visible, and near-infrared wavelengths (e.g., wavelengths less than 2 microns) and a second illumination source that generates mid-infrared and long-infrared wavelengths (e.g., wavelengths 2 microns or greater). In some instances, the combined illumination source generates illumination light having a wavelength as low as 140 nanometers. In some instances, the combined illumination source generates illumination light having a wavelength up to and including 4.2 microns. In some instances, the combined illumination source generates illumination light having a wavelength up to and including 5 microns. In some instances, the combined illumination source generates illumination light having a wavelength greater than 5 microns. Additionally, the spectroscopic measurement system includes one or more measurement channels spanning the range of illumination wavelengths for performing measurements of semiconductor structures. The one or more measurement channels can operate in parallel (i.e., measure the sample simultaneously over the entire wavelength range) or sequentially (i.e., measure the sample sequentially over the entire wavelength range).

[0064] Figure 4A Depicts an embodiment 200 of a combined illumination source 110. As Figure 4AAs depicted, a voltage applied across cathode 208 and anode 209 generates plasma 204 contained within bulb 205. Additionally, LSP pump laser source 201 generates pump light 202 that is focused by focusing optics 203 to sustain plasma 204 contained within bulb 205. Plasma 204 generates broadband spectral light in the wavelength range from ultraviolet to short infrared. The ultraviolet / visible / short infrared light 207 generated by plasma 204 is provided to an illumination optical device subsystem as referenced Figure 1 as described. Additionally, supercontinuum laser source 211 generates infrared light 212. Infrared light 212 is focused by focusing lens 213 and forms a focal point 214 at or near plasma 204. Infrared light 217 from focal point 214 is provided to an illumination optical device subsystem as referenced Figure 1 as described. In one example, the UV / visible / short infrared light 207 and the infrared light 217 are collocated and effectively combined. In some examples, bulb 205 is made of calcium fluoride or magnesium fluoride to transmit wavelengths greater than 2.5 microns generated by supercontinuum laser source 211. In some other examples, bulb 205 includes one or more exit ports 206 made of calcium fluoride or magnesium fluoride to transmit wavelengths greater than 2.5 microns generated by supercontinuum laser source 211. Conventional bulbs made of fused silica do not transmit significant light above 2.5 microns and are thus not suitable for combining the light generated by supercontinuum laser illumination source 211 in the manner described herein.

[0065] Figure 4B Depicts an embodiment 220 of combined illumination source 110. As Figure 4B depicted, a voltage applied across cathode 228 and anode 229 generates plasma 224 contained within bulb 225. Additionally, LSP pump laser source 221 generates pump light 222 that is focused by focusing optics 223 to sustain plasma 224 contained within bulb 225. Plasma 224 generates broadband spectral light in the wavelength range from ultraviolet to short infrared. The ultraviolet / visible / short infrared light 227 generated by plasma 224 exits bulb 225 through exit port 226 and is provided to an illumination optical device subsystem as referenced Figure 1 as described. Additionally, supercontinuum laser source 231 generates infrared light 232. Infrared light 232 is focused by focusing lens 233. Infrared light 237 from supercontinuum laser source 231 is provided to an illumination optical device subsystem as referenced Figure 1 as described.

[0066] As Figure 4BAs depicted, the UV light / visible light / short infrared light 227 and the infrared light 237 are combined by the beam combiner 234. Thus, the beam combiner 234 combines the light generated by the ultraviolet light source 221 (e.g., the LSP light source 221) with the light generated by the infrared light source 234 (e.g., the supercontinuum laser light source 231). In one example, the beam combiner 234 has a splitting wavelength of, for example, 900 nanometers or near 900 nanometers. The beam combiner minimizes the loss of the light generated by the LSP light source (LSP loss is less than 10) and minimizes the depolarization effect across all illumination wavelengths (e.g., less than 0.1%).

[0067] Figure 4C Depicts an embodiment 240 of the combined illumination source 110. As Figure 4C depicted, the voltage provided across the cathode 248 and the anode 249 generates the plasma 244 contained in the bulb 245. Additionally, the LSP pump laser source 241 generates pump light 242 that is focused by the focusing optics 243 to sustain the plasma 244 contained in the bulb 245. The plasma 244 generates broadband spectral light in the wavelength range from ultraviolet to short infrared. The UV light / visible light / short infrared light 247 generated by the plasma 244 exits the bulb 245 through the exit port 246 and is provided to the illumination optical device subsystem as described in reference Figure 1 . Additionally, the supercontinuum laser source 251 generates infrared light 252. The infrared light 252 is focused by the focusing lens 253. The infrared light 257 from the supercontinuum laser source 251 is provided to the illumination optical device subsystem as described in reference Figure 1 .

[0068] As Figure 4C depicted, the combined illumination source 110 selectively provides ultraviolet and infrared illumination light to the wafer 120. In these examples, the measurements are time multiplexed. The mirror 254 is a movable mirror. In one example, the movable mirror 254 is mounted to a galvanometer that is used to selectively direct the UV light / visible light 247 and the infrared light 257 to the wafer 120 based on whether the movable mirror 254 is in the optical path of the UV light / visible light 247 or not. In another example, a movable total internal reflection prism is used to selectively direct the UV light / visible light 247 and the infrared light 257 to the wafer 120. In this way, the spectral measurements that include the ultraviolet / visible light spectrum are performed at a different time than the spectral measurements that include the infrared light spectrum.

[0069] Figure 5 Depicts a graph 260 that illustrates the specific detectivity of various detector technologies operating at a specified temperature. As Figure 5As described, both photovoltaic and photoconductive detector technologies are suitable for detecting radiation in the infrared wavelength range of greater than 1 micron and up to 5 microns. In some examples, metrology system 100 includes detectors such as lead sulfide (PbS), lead selenide (PbSe), indium antimonide (InSb), indium arsenide (InAs), mercury cadmium telluride (HgCdTe), indium gallium arsenide (InGaAs), x-InGaAs, thermoelectric, and bolometric detectors.

[0070] Thermoelectric and bolometric detectors are not quantum detectors. Therefore, these detectors can accept unsaturated high brightness and thus reduce noise sensitivity.

[0071] In some embodiments, the detector subsystem is shot noise limited rather than dark noise limited. In these examples, it is preferred to perform multiple measurements at high brightness to reduce measurement system noise.

[0072] In some embodiments, time-dependent measurements (e.g., pulsed light source, chopper, etc.) are performed in coordination with a lock-in amplifier or other phase-locked loop to increase the measurement signal-to-noise ratio.

[0073] In some embodiments, one or more of the detectors are cooled to a temperature of -20°C, 210°K, 77°K, or other low temperature to reduce measurement noise. Generally, any suitable cooling element can be used to maintain the temperature of the detector at a constant temperature during operation. By way of non-limiting example, any of a multi-stage Peltier cooler, a rotating disk cooler, a Stirling cycle cooler, an N2 cooler, a He cooler, etc. can be considered within the scope of this patent document.

[0074] In some embodiments, a wide range of wavelengths is detected by a detector that includes multiple photosensitive regions having different sensitivity characteristics. The collected light is linearly dispersed across the surface of the detector according to wavelength. Each different photosensitive region is arranged on the detector to sense a different range of incident wavelengths. In this way, a wide range of wavelengths is detected by a single detector with a high signal-to-noise ratio. These features are implemented individually or in combination to perform high-throughput measurements of high aspect ratio structures (e.g., structures having a depth of 1 micron or greater) with high throughput, precision, and accuracy.

[0075] In some embodiments, the detector subsystem includes a multi-region infrared detector that combines different sensitivity bands at different locations on a single detector package. The detector is configured to deliver a continuous data spectrum at different sensitivities depending on the incident location.

[0076] Figure 7 Illustrate a typical sensitivity curve of an indium gallium arsenide (InGaAs) sensor. As Figure 7As depicted, none of the available InGaAs sensors can provide sufficient photosensitivity across a wavelength band from 1 micron to 2.5 microns. Thus, individually, the available sensors are only capable of sensing within a narrow band.

[0077] In some embodiments, multiple sensor chips, each sensitive in a different band, are combined into a single detector package. This multi-region detector is then implemented in the metrology systems described herein.

[0078] Figure 6 Depicted are four sensor chips 270A - D derived from four different bands to fabricate the multi-region infrared detector 180. The four sensor chips comprise different material compositions each exhibiting different photosensitive characteristics. As Figure 6 depicted, sensor chip 270A exhibits high sensitivity within band A, sensor chip 270B exhibits high sensitivity within band B, sensor chip 270C exhibits high sensitivity within band C, and sensor chip 270D exhibits high sensitivity within band D. The metrology system incorporating detector 270 is configured to disperse the wavelengths within band A onto sensor chip 270A, the wavelengths within band B onto sensor chip 270B, the wavelengths within band C onto sensor chip 270C, and the wavelengths within band D onto sensor chip 270D. In this way, high photosensitivity (i.e., high SNR) is achieved within the aggregate band comprising bands A - D from a single detector. Thus, the measurement noise across the entire measurement range is reduced by limiting the use of a particular sensor to the narrow band where the measurement sensitivity is high and the measurement noise is low.

[0079] In some instances, the multi-region detector comprises InGaAs sensors sensitive to different spectral regions, which are assembled in a single sensor package to produce a single continuous spectrum covering wavelengths from 750 nanometers to 3,000 nanometers or higher.

[0080] Generally, any number of individual sensors can be assembled along the wavelength dispersion direction of the multi-region detector such that a continuous spectrum can be derived from the detector. However, typically two to four individual sensors are used in a multi-region detector (such as detector 270).

[0081] In one embodiment, three individual sensors are employed, where the first segment spans a range between 800 nanometers and 1600 nanometers, the second segment spans a range between 1600 nanometers and 2200 nanometers, and the third segment spans a range between 2200 nanometers and 2600 nanometers.

[0082] Although the use of an InGaAs-based infrared detector is specifically described herein, generally any suitable material exhibiting a narrow sensitivity range and a sharp sensitivity cutoff can be integrated into a multi-region detector as described herein.

[0083] As Figure 1 depicted, the illustrated measurement channel includes a polarizer on the illumination side and an analyzer on the collection side. However, generally speaking, any measurement channel may or may not include an illumination polarizer, a collection analyzer, an illumination compensator, a collection compensator (in any combination) to perform measurements of the polarized reflectivity of a sample, the unpolarized reflectivity of a sample, or both.

[0084] In some embodiments, one or more measurement channels of a metrology system are configured to measure a wafer at different azimuth angles plus different wavelength ranges and angles of incidence. In some embodiments, a metrology system including an infrared spectrometer as described herein is configured to perform measurements of a wafer at azimuth angles of 0 degrees and 90 degrees relative to a metrology target. In some embodiments, the metrology system is configured to simultaneously measure the wafer reflectivity within one or more wavelength ranges, one or more AOI ranges, and one or more azimuth angles. In some embodiments, the metrology system utilizes one or more combinations of one or more of a spectroscopic ellipsometer, a spectroscopic reflectometer, a discrete wavelength ellipsometer, a rotating polarizer ellipsometer, a rotating compensator ellipsometer, a rotating polarizer rotating compensator ellipsometer, a Mueller matrix ellipsometer, or any combination thereof with an LSP and a supercontinuum source.

[0085] In yet a further aspect, the size of the illumination field stop projected onto the wafer plane is adjusted to optimize the resulting measurement accuracy and speed based on the nature of the measurement target.

[0086] In yet a further aspect, the size of the illumination field stop is adjusted to achieve the desired spectral resolution for each measurement application.

[0087] In some instances, for example, if the sample is a very thick film or a grating structure, then the illumination field stop projected onto the wafer plane in a direction perpendicular to the plane of incidence is adjusted to reduce the field of view size to achieve increased spectral resolution. In some instances, for example, if the sample is a thin film, then the illumination field stop projected onto the wafer plane in a direction perpendicular to the plane of incidence is adjusted to increase the field of view size to achieve reduced measurement time without loss of spectral resolution.

[0088] In Figure 1In the illustrated embodiment, computing system 130 is configured to receive signal 154 indicative of the spectral response detected by the detector subsystem. Computing system 130 is further configured to determine control signal 119 communicated to programmable illumination field stop 117. Programmable illumination field stop receives control signal 119 and adjusts the size of the illumination aperture to achieve a desired illumination field size.

[0089] In some instances, the illumination field stop is adjusted to optimize measurement accuracy and speed, as described above. In another instance, the illumination field stop is adjusted to prevent image cropping of the spectrometer slit and the corresponding degradation of the measurement results. In this manner, the illumination field size is adjusted such that the image of the measurement target underfills the spectrometer slit. In one instance, the illumination field stop is adjusted such that the projection of the polarizer slit of the illumination optics underfills the spectrometer slit of the metrology system. In another instance, the illumination field stop is adjusted such that the projection of the polarizer slit of the illumination optics overfills the spectrometer slit of the metrology system.

[0090] Figure 8 Method 300 for performing spectral measurements is illustrated in at least one novel aspect. Method 300 is adapted to be implemented by a metrology system (e.g., Figure 1 the metrology system 100 of the present invention illustrated herein). In one aspect, it should be recognized that the data processing blocks of method 300 may be implemented via a pre-programmed algorithm executed by one or more processors of computing system 130 or any other general purpose computing system. It should be recognized herein that the specific structural aspects of metrology system 100 do not represent a limitation and should be construed as merely illustrative.

[0091] In block 301, a quantity of broadband illumination light having a wavelength less than 150 nanometers is directed from an illumination source to a measurement spot on the surface of a sample to be measured at one or more angles of incidence, one or more azimuth angles, or a combination thereof.

[0092] In block 302, a quantity of light is collected from the measurement spot on the surface of the sample in response to the quantity of illumination light. Collection involves a collection mask disposed at or near the pupil plane of the reflective collection optics subsystem.

[0093] In block 303, the quantity of collected light is imaged from the collection mask to a dispersive element. Imaging involves a plurality of reflective relay optics configured to image the quantity of collected light from the collection mask to the dispersive element with a field reduction factor greater than 1.0.

[0094] In block 304, the quantity of collected light is dispersed onto at least one detector.

[0095] In block 305, a measurement spectrum associated with the quantity of collected light is detected by at least one detector.

[0096] In a further embodiment, system 100 includes one or more computing systems 130 for performing measurements of an actual device structure based on spectroscopic measurement data collected according to the methods described herein. The one or more computing systems 130 may be communicatively coupled to a spectrometer. In one aspect, the one or more computing systems 130 are configured to receive measurement data associated with the measurement of the structure of the sample being measured.

[0097] It should be appreciated that the one or more steps described throughout this invention may be implemented by a single computer system 130 or alternatively by multiple computer systems 130. Additionally, different subsystems of system 100 may include computer systems adapted to implement at least a portion of the steps described herein. Accordingly, the foregoing description should not be construed as a limitation on the invention but merely as an illustration.

[0098] Additionally, the computer system 130 may be communicatively coupled to the spectrometer in any manner known in the art. For example, the one or more computing systems 130 may be coupled to a computing system associated with the spectrometer. In another example, the spectrometer may be directly controlled by a single computer system coupled to the computer system 130.

[0099] The computer system 130 of metrology system 100 may be configured to receive and / or obtain data or information from subsystems of the system (such as a spectrometer and the like) via a transmission medium that may include wired and / or wireless portions. In this manner, the transmission medium may serve as a data link between the computer system 130 and other subsystems of system 100.

[0100] The computer system 130 of metrology system 100 may be configured to receive and / or obtain data or information (such as measurement results, modeling inputs, modeling results, reference measurement results, etc.) from other systems via a transmission medium that may include wired and / or wireless portions. In this manner, the transmission medium may serve as a data link between the computer system 130 and other systems (such as a metrology system 100 on a memory board, an external memory, or other external systems). For example, the computing system 130 may be configured to receive measurement data from a storage medium (i.e., memory 132 or an external memory) via a data link. For example, spectroscopic results obtained using the spectrometers described herein may be stored in a permanent or semi-permanent memory device (such as memory 132 or an external memory). In this regard, spectroscopic results may be imported from on-board memory or from an external memory system. Additionally, the computer system 130 may send data to other systems via the transmission medium. For example, a measurement model or estimated parameter value 171 determined by the computer system 130 may be communicated and stored in an external memory. In this regard, measurement results may be exported to another system.

[0101] The computing 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 "computing system" may be broadly defined to cover any device having one or more processors that execute instructions from a memory medium.

[0102] The program instructions 134 for implementing a method, such as the methods described herein, may be transmitted via a transmission medium, such as a wire, a cable, or a wireless transmission link. For example, as Figure 1 illustrated, the program instructions 134 stored in the memory 132 are transmitted to the processor 131 via the bus 133. The program instructions 134 are stored in a computer-readable medium (e.g., the memory 132). Exemplary computer-readable media include read-only memory, random access memory, magnetic disks or optical disks, or magnetic tapes.

[0103] In some instances, the measurement model is implemented as an element of an optical critical dimension metrology system commercially available from KLA-Tencor Corporation, Milpitas, California, USA. In this way, the model is created and ready to be used immediately after the spectrum is collected by the system. In some other instances, the measurement model is implemented offline by a computing system implementing software commercially available from KLA-Tencor Corporation, Milpitas, California, USA. The resulting trained model may be incorporated as an element of a library accessible by a metrology system performing the measurement.

[0104] In another aspect, the methods and systems for spectroscopic metrology of semiconductor devices described herein are applied to the measurement of high aspect ratio (HAR) structures, large lateral dimension structures, or both. The described embodiments enable optical critical dimension (CD), film, and composition metrology of semiconductor devices including three-dimensional NAND structures (e.g., vertical NAND (V-NAND) structures, dynamic random access memory structures (DRAM), etc.) manufactured by various semiconductor manufacturers such as Samsung (South Korea), SK Hynix (South Korea), Toshiba (Japan), and Micron Technology (USA), etc. These complex devices suffer from the problem of weak light penetration into the (several) structures to be measured. The resulting trained model may be incorporated as an element of a library accessible by a metrology system performing the measurement. library.

[0105] In another aspect, the methods and systems for spectroscopic metrology of semiconductor devices described herein are applied to the measurement of high aspect ratio (HAR) structures, large lateral dimension structures, or both. The described embodiments enable optical critical dimension (CD), film, and composition metrology of semiconductor devices including three-dimensional NAND structures (e.g., vertical NAND (V-NAND) structures, dynamic random access memory structures (DRAM), etc.) manufactured by various semiconductor manufacturers such as Samsung (South Korea), SK Hynix (South Korea), Toshiba (Japan), and Micron Technology (USA), etc. These complex devices suffer from the problem of weak light penetration into the (several) structures to be measured. Figure 3Depict an exemplary high aspect ratio structure 160 that presents the problem of weak light penetration into (a number of) measured structures. A spectroscopic ellipsometer with broadband capabilities and a wide range of AOI, azimuth, or both, with synchronous spectral band detection as described herein, is suitable for measuring these high aspect ratio structures. HAR structures typically include a hard mask layer for facilitating the etching process for HAR. As described herein, the term "HAR structure" refers to any structure characterized by an aspect ratio exceeding 2:1 or 10:1 and that can be as high as 100:1 or higher.

[0106] In yet another aspect, the measurement results described herein can be used to provide active feedback to process tools (e.g., lithography tools, etching tools, deposition tools, etc.). For example, the values of measurement parameters determined based on the measurement methods described herein can be communicated to a lithography tool to adjust the lithography system to achieve the desired output. In a similar manner, etching parameters (e.g., etching time, diffusivity, etc.) or deposition parameters (e.g., time, concentration, etc.) can be included in the measurement model to provide active feedback to the etching tool or deposition tool, respectively. In some instances, corrections to process parameters determined based on measurement device parameter values and a trained measurement model can be communicated to a lithography tool, an etching tool, or a deposition tool.

[0107] As described herein, the term "critical dimension" includes any critical dimension of a structure (e.g., bottom critical dimension, middle critical dimension, top critical dimension, sidewall angle, grating height, etc.), any critical dimension between any two or more structures (e.g., distance between two structures), and displacement between two or more structures (e.g., overlay displacement between overlay grating structures, etc.). Structures can include three-dimensional structures, patterned structures, overlay structures, and so on.

[0108] As described herein, the term "critical dimension application" or "critical dimension measurement application" includes any critical dimension measurement.

[0109] As described herein, the term "metrology system" includes any system that is at least partially used to characterize a sample in any aspect (including measurement applications such as critical dimension metrology, overlay metrology, focus / dose metrology, and composition metrology). However, such technical terms do not limit the scope of the term "metrology system" as described herein. Additionally, the 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 (involving data from one or more platforms simultaneously) and any other metrology or inspection tool that benefits from calibration of system parameters based on critical dimension data.

[0110] Described herein are various embodiments of a semiconductor measurement system (e.g., an inspection system or a lithography system) that can be used to measure a sample within any semiconductor processing tool. 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) in a manner known in the art.

[0111] As used herein, the term "wafer" generally refers to a substrate formed of semiconductor or non-semiconductor material. Examples include, but are not limited to, single crystal silicon, gallium arsenide, and indium phosphide. Such substrates are typically found and / or processed in a semiconductor fabrication facility. In some cases, a wafer may consist only of the substrate (i.e., a bare wafer). Alternatively, a wafer may include one or more different material layers formed on the substrate. The one or more layers formed on the wafer may be "patterned" or "unpatterned". For example, a wafer may include a plurality of die each having repeatable pattern features.

[0112] A "reticle" can be a reticle at any stage of the reticle manufacturing process or a finished reticle that can be released or not released for use in a semiconductor manufacturing facility. A reticle or "mask" is generally defined as a substantially transparent substrate having a substantially opaque region formed thereon and configured to be patterned. The substrate can include, for example, a glass material such as amorphous SiO2. The reticle can be placed above a resist-covered wafer during the exposure step of a lithography process such that the pattern on the reticle can be transferred to the resist.

[0113] The one or more layers formed on the wafer may be patterned or unpatterned. For example, a wafer may include a plurality of die each having repeatable pattern features. The formation and processing of such material layers can ultimately result in a finished device. Many different types of devices can be formed on a wafer, and the term wafer as used herein is intended to encompass wafers on which any type of device known in the art is fabricated.

[0114] In one or more exemplary embodiments, the described functionality may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functionality may be stored on or transmitted via a computer-readable medium as one or more instructions or code. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise 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 embody 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. Also, any connection is properly termed a computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technology such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technology such as infrared, radio, and microwave is included in the definition of media. As used herein, disk and disc include optical discs (CD), laser discs, optical discs, digital versatile discs (DVD), floppy disks, and Blu-ray discs where disks typically reproduce data magnetically and discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0115] Although certain specific embodiments have been described above for purposes of illustration, the teachings of this patent document are of general applicability and are not limited to the specific embodiments described above. Accordingly, various modifications, adaptations, and combinations of the various features of the described embodiments may be practiced without departing from the scope of the invention as set forth in the claims.

Claims

1. A spectroscopic metrology system, comprising: An illumination source configured to generate an amount of illumination light that includes wavelengths less than 150 nanometers; An illumination optics subsystem configured to direct the amount of illumination light from the illumination source to a measurement spot on a surface of a sample under measurement at one or more incident angles, one or more azimuth angles, or a combination thereof; A reflection collection optics subsystem configured to collect an amount of collection light from the measurement spot on the surface of the sample, the reflection collection optics subsystem including a collection mask disposed at or near a pupil plane of the reflection collection optics subsystem and a plurality of reflective relay optical elements configured to image the amount of collection light from the collection mask to a dispersive element of the spectroscopic metrology system with a field-of-view reduction factor greater than 1.0; At least one detector having a planar two-dimensional surface sensitive to incident light, the at least one detector configured to detect the amount of collection light dispersed by the dispersive element and generate an output signal indicative of the detected light; And A computing system configured to generate an estimate of a parameter of interest of the sample under measurement based on an analysis of the output signal.

2. The metrology system according to claim 1, wherein an illumination numerical aperture (NA) of the illumination optics subsystem at the measurement spot is at least 0.

1.

3. The metrology system according to claim 1, wherein a collection numerical aperture (NA) of the reflection collection optics subsystem at the measurement spot is less than 0.

05.

4. The metrology system according to claim 1, the plurality of reflective relay optical elements configured to image the amount of collection light from the collection mask to the dispersive element with a field-of-view reduction factor greater than 2.

0.

5. The metrology system according to claim 1, wherein the collection mask includes a plurality of apertures, each aperture configured to transmit the amount of collection light associated with an incident angle different from that of the sample under measurement.

6. The metrology system according to claim 1, wherein the illumination source is a combined illumination source including a laser sustained plasma (LSP) illumination source and a supercontinuum laser illumination source.

7. The metrology system according to claim 1, wherein the at least one detector includes two or more detectors, each of the two or more detectors detecting a portion of the amount of collection light in a different spectral range.

8. The metrology system according to claim 7, wherein each of the two or more detectors simultaneously detects each portion of the amount of collection light in a different spectral range.

9. The metrology system according to claim 1, wherein the at least one detector includes two or more different surface regions each having a different photosensitivity, the two or more different surface regions being aligned with a direction of wavelength dispersion across the surface of the at least one detector.

10. The metrology system according to claim 1, wherein the sample under measurement includes a three-dimensional NAND structure or a dynamic random access memory structure.

11. A method, comprising: Directing a quantity of broadband illumination light having a wavelength less than 150 nanometers from an illumination source to a measurement spot on a surface of a sample to be measured at one or more angles of incidence, one or more azimuth angles, or a combination thereof; Collecting a quantity of collected light from the measurement spot on the surface of the sample in response to the quantity of illumination light, the collecting involving a collection mask disposed at or near a pupil plane of a reflective collection optical subsystem; Imaging the quantity of collected light from the collection mask to a dispersive element, the imaging involving a plurality of reflective relay optical elements configured to image the quantity of collected light from the collection mask to the dispersive element with a field-of-view reduction factor greater than 1.0; Dispersing the quantity of collected light onto at least one detector; And Detecting a measurement spectrum associated with the quantity of collected light with the at least one detector.

12. The method according to claim 10, wherein an illumination numerical aperture (NA) of the illumination optical subsystem at the measurement spot is at least 0.

1.

13. The method according to claim 10, wherein a collection numerical aperture (NA) of the reflective collection optical subsystem at the measurement spot is less than 0.

05.

14. The method according to claim 10, wherein the plurality of reflective relay optical elements are configured to image the quantity of collected light from the collection mask to the dispersive element with a field-of-view reduction factor greater than 2.

0.

15. The method according to claim 10, wherein the collection mask includes a plurality of apertures, each aperture being configured to transmit the quantity of collected light associated with an angle of incidence different from that of the sample to be measured.

16. The method according to claim 10, wherein the illumination source is a combined illumination source including a laser sustained plasma (LSP) illumination source and a supercontinuum laser illumination source.

17. The method according to claim 10, wherein the at least one detector includes two or more detectors, and each of the two or more detectors detects a portion of the quantity of collected light in a different spectral range.

18. The method according to claim 17, wherein each of the two or more detectors simultaneously detects each portion of the quantity of collected light in a different spectral range.

19. The method according to claim 10, wherein the at least one detector includes two or more different surface regions each having a different photosensitivity, and the two or more different surface regions are aligned with a direction of wavelength dispersion across the surface of the at least one detector.

20. A spectroscopic metrology system, comprising: An illumination source configured to generate a quantity of illumination light having a wavelength less than 150 nanometers; An illumination optical subsystem configured to direct the quantity of illumination light from the illumination source to a measurement spot on a surface of a sample to be measured at one or more angles of incidence, one or more azimuth angles, or a combination thereof; A reflection collection optical device subsystem configured to collect a quantity of collected light from the measurement light spot on the surface of the sample, the reflection collection optical device subsystem including a collection mask disposed at or near the pupil plane of the reflection collection optical device subsystem and a plurality of reflective relay optical elements configured to image the quantity of collected light from the collection mask to a dispersion element of the spectroscopic metrology system with a field-of-view reduction factor greater than 1.0; At least one detector having a planar two-dimensional surface sensitive to incident light, the at least one detector configured to detect the quantity of collected light dispersed by the dispersion element and generate an output signal indicative of the detected light; And A non-transitory computer-readable medium storing instructions that, when executed by one or more processors, cause the one or more processors to: Generate an estimate of a parameter of interest of the measured sample based on an analysis of the output signal.

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