Methods for extended infrared spectroscopic ellipsometry

Abstract

To provide methods and systems for performing simultaneous spectroscopic measurement of semiconductor structures at ultraviolet, visible and infrared wavelengths.SOLUTION: Wavelength errors are reduced by orienting a direction of wavelength dispersion on a detector 141 surface perpendicularly to the projection of a plane of incidence onto the detector 141 surface. A broad range of infrared wavelengths are detected by the detector 141 that includes multiple photosensitive areas having different sensitivity characteristics. Collected light is linearly dispersed on the detector 141 surface according to the wavelength. Each different photosensitive area is arranged on the detector 141 to sense a different range of incident wavelengths. In this manner, a broad range of infrared wavelengths are detected with a high signal-to-noise ratio by a single detector. These features enable high throughput measurement of high aspect ratio structures with high throughput, precision and accuracy.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The described embodiments relate to metrology systems and methods, and more particularly to advanced metrology methods and systems for three-dimensional semiconductor structures. [Background technology]

[0002] (CROSS-REFERENCE TO RELATED APPLICATIONS) This patent application claims priority under 35 U.S.C. § 119 from U.S. Provisional Patent Application No. 62 / 279,469, entitled “Apparatus and Methods of Extended Infrared Ellipsometry,” filed January 15, 2016, the subject matter of which is incorporated herein by reference in its entirety.

[0003] Semiconductor devices, such as logic and memory devices, are typically fabricated by applying a series of processing steps to a specimen that creates the features and structural layers of the semiconductor device. For example, lithography is one of the semiconductor manufacturing processes that involves creating patterns on a semiconductor wafer. Other examples of semiconductor manufacturing processes include, but are not limited to, chemical mechanical polishing, etching, deposition, and ion implantation. Multiple semiconductor devices may be fabricated on a single semiconductor wafer, which may then be separated into individual semiconductor devices.

[0004] Metrology processes are used at various steps during semiconductor manufacturing processes to detect defects on wafers and facilitate improved yield. Optical metrology techniques offer the promise of high throughput without the risk of sample destruction. A number of optical metrology-based techniques, such as scatterometry and reflectometry instruments and their associated analysis algorithms, are widely used to characterize the critical dimensions, film thickness, composition, overlay and other parameters of nanoscale structures.

[0005] Flash memory architectures are transitioning from 2D floating gate architectures to full 3D geometries. In some instances, film stacks and etched structures are becoming very deep (e.g., as deep as 6 μm). Such high aspect ratio structures present challenges for film metrology and CD metrology. The ability to measure the critical dimensions and define the hole and trench geometries of these structures is critical to achieving desired performance levels and device yields.

[0006] Many optical techniques suffer from low signal-to-noise ratio (SNR) and only a small fraction of the illumination light can reach the bottom of high aspect ratio features and be reflected upwards to the detector. Thus, while many high-throughput metrology techniques are available, they cannot reliably perform CD and film metrology on high aspect ratio structures. Critical dimension small-angle X-ray scatterometry (CD-SAXS), normal incidence reflectometry and scatterometry are being explored as metrology solutions for high aspect ratio structures but are still under development.

[0007] Cross-sectional scanning electron microscopy (SEM) is a destructive technique with low throughput and is not suitable for in-line metrology. Atomic force microscopy (AFM) has poor measurement capabilities for high aspect ratio structures and relatively low throughput. It is unclear whether CD-SAXS can achieve the high throughput capabilities required by the semiconductor industry. Model-Based Infrared Reflectometry (MBIR) has been used to metrology high aspect ratio DRAM structures, but this technique does not offer the resolution available at shorter wavelengths and has a measurement spot size that is too large for semiconductor metrology. See, "Crystalline Electron Microscopy: A Novel Technique for Measuring High Aspect Ratio Structures," vol. 13, No. 1, pp. 1171-1175, 2002, which is incorporated herein by reference as if fully set forth.

[0008] Optical CD metrology currently lacks the ability to measure detailed profiles of structures with μm-scale depth and lateral dimensions in a relatively small spot (e.g., less than 50 μm, more preferably less than 30 μm) with high throughput. US Pat. No. 6,393,633, 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 technique described therein suffers from long measurement times across ultraviolet and infrared wavelengths, poor wavelength stability, and a narrow infrared wavelength range of operation. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Pat. No. 8,860,937 [Patent Document 2] US Patent Application Publication No. 2013 / 0114085 [Non-patent literature]

[0010] [Non-Patent Document 1] "Measuring deep-trench structures with model-based IR," by Gostein et al., Solid State Technology, vol. 49, no. 3, Mar. 1, 2006 Summary of the Invention [Problem to be solved by the invention]

[0011] In summary, the shrinking feature size and increasing depth of structural features impose challenging requirements on optical metrology systems. Optical metrology systems must meet the high precision and accuracy requirements to be able to cost-effectively measure increasingly complex targets at high throughput. In this context, broadband illumination and data collection speed, focusing error, and infrared wavelength range have emerged as critical performance constraints in designing optical metrology systems suitable for high aspect ratio structures. Therefore, a superior metrology system and method that can overcome these constraints is desirable. [Means for solving the problem]

[0012] In this application, a method and system are presented for performing simultaneous spectroscopic metrology of semiconductor structures at ultraviolet, visible, and infrared wavelengths. Spectra including ultraviolet, visible, and infrared wavelengths are measured with high throughput at the same alignment conditions. In this configuration, machine errors, such as wavelength errors, are uniformly corrected across all measurement wavelengths. Simultaneous measurement of targets with infrared, visible, and ultraviolet light in a single system allows precise characterization of complex three-dimensional structures. In general, longer wavelengths penetrate deeper into structures, thereby allowing structures with longer pitches to be measured while suppressing higher order diffractions. Shorter wavelengths provide precise dimensional information for structures accessible at shorter wavelengths (i.e., higher hierarchies) and for smaller CD and roughness features. Longer wavelengths, according to certain examples, allow measurement of dimensional characteristics of targets with rougher surfaces or interfaces, since longer wavelengths are less sensitive to roughness.

[0013] Additionally, in one embodiment, a fine focus sensor (FFS) is incorporated into the detection subsystem to provide metrology input for focus error correction during metrology.

[0014] Also, in one embodiment, the broadband spectrometer metrology system is configured such that the metrology spot is imaged onto the detector and the direction aligned with the plane of incidence on the wafer surface is oriented perpendicular to the wavelength dispersion direction on the detector surface. This arrangement significantly reduces the metrology system's sensitivity to focusing errors. Because of the reduced sensitivity to focusing errors, precise metrology results can be obtained with shorter MAM times and therefore higher throughput.

[0015] Also, in one aspect, a multi-zone infrared detector that combines several sensitivity bands at different locations on a single detector package is employed in the metrology system described herein. The detector is configured to provide a continuous spectrum of data with different sensitivities depending on the location of incidence. The collected light is linearly dispersed on the detector surface according to wavelength. Several light-sensitive areas are arranged on the detector such that each is sensitive to a different range of incident wavelengths. In this configuration, a wide range of infrared wavelengths can be detected by a single detector with a high signal-to-noise ratio.

[0016] In a further aspect, the size of the illumination field projected onto the wafer plane along a direction perpendicular to the plane of incidence is adjusted based on the properties of the target under measurement to optimize the measurement accuracy and speed obtained.

[0017] The foregoing is a summary, and as such contains various simplifications, generalizations, and omissions of detail; as such, those skilled in the art will appreciate that this summary is illustrative only and is not intended to be limiting in any way. Other aspects, unique 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]

[0018] [Figure 1] FIG. 1 illustrates an example metrology system 100 that performs simultaneous spectroscopic measurements of one or more structures at ultraviolet, visible, and infrared wavelengths according to one embodiment. [Diagram 2]FIG. 2 illustrates an example metrology system 200 for performing simultaneous spectroscopic measurements of one or more structures at ultraviolet, visible, and infrared wavelengths according to another embodiment. [Diagram 3] FIG. 3 illustrates an example metrology system 300 that performs simultaneous spectroscopic measurements of one or more structures at ultraviolet, visible, and infrared wavelengths according to yet another embodiment. [Figure 4] FIG. 4 illustrates an example metrology system 400 for performing simultaneous spectroscopic measurements of one or more structures at ultraviolet, visible, and infrared wavelengths according to yet another embodiment. [Figure 5A] 2 is a top view of a wafer 120 including a depiction of a metrology spot 116 illuminated by illumination light beam 117 of FIG. [Figure 5B] FIG. 2 is a direct view of the surface of a detector 23 in a weighing system having a conventional configuration. [Figure 6] FIG. 13 is a diagram showing the occurrence of a focus position error due to a wafer 120. [Figure 7] FIG. 2 shows a focused light beam that has been wavelength dispersed in a conventional manner and imaged onto the surface of a detector 23. [Figure 8] 2 is a direct view of the surface of the detector 141 shown in FIG. 1. [Figure 9] FIG. 2 is a front view of the surface of the detector 150 shown in FIG. 1 according to one embodiment. [Figure 10] FIG. 1 shows typical light sensitivity curves for four available indium gallium arsenide (InGaAs) sensors. [Figure 11] FIG. 5 illustrates a method 500 for performing simultaneous spectroscopic measurements of one or more structures at ultraviolet, visible, and infrared wavelengths according to at least one aspect described herein. [Figure 12] FIG. 6 shows an example 600 of a high aspect ratio NAND structure that suffers from poor light transmission to the structure(s) being measured. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Reference will now be made in more detail to background and certain embodiments of the invention, examples of which are illustrated in the accompanying drawings.

[0020] In the present application, a method and system for performing simultaneous spectroscopic measurements of semiconductor structures at ultraviolet, visible, and infrared wavelengths are presented. Spectra including ultraviolet, visible, and infrared wavelengths are measured with high throughput under the same alignment conditions. In this configuration, machine errors, such as wavelength errors, are uniformly corrected across all measurement wavelengths. In one embodiment, wavelength errors are reduced by making the wavelength dispersion direction on the detector surface perpendicular to the projection of the incident plane onto the detector surface. In one embodiment, a wide range of infrared wavelengths is detected by a detector having multiple light-sensitive areas exhibiting different sensitivity characteristics. The collected light is linearly dispersed on the detector surface according to wavelength. Several light-sensitive areas are arranged on the detector so that each is sensitive to a different incident wavelength range. In this configuration, a wide range of infrared wavelengths is detected by a single detector with a high signal-to-noise ratio. Each of these features, or a combination thereof, allows high throughput metrology of high aspect ratio structures (eg, structures having depths of 1 μm or greater) with high throughput, precision and accuracy.

[0021] Simultaneous measurement of a target with infrared, visible, and ultraviolet light in a single system allows for precise characterization of complex three-dimensional structures. In general, longer wavelengths penetrate deeper into structures, thereby allowing measurement of structures with longer pitches while suppressing higher diffraction orders. Shorter wavelengths provide precise dimensional information for structures accessible with shorter wavelengths (i.e., higher levels) and for smaller CD and roughness features. Longer wavelengths are less sensitive to roughness, and in certain instances, longer wavelengths allow measurement of dimensional characteristics of targets with rough surfaces or interfaces.

[0022] In certain embodiments, the semiconductor device spectroscopic methods and systems described herein are applied to metrology of high aspect ratio (HAR) structures, large lateral dimension structures, or both. These embodiments allow for optical critical dimension (CD), film, and composition metrology of semiconductor devices (e.g., NAND, VNAND, TCAT, DRAM, etc.) with HAR structures, and more generally, complex devices that suffer from low optical transmission into the structure(s) being measured. HAR structures often include a hard mask layer to perform HAR-specific etch processes. The term "HAR structure" as used herein refers to any structure characterized by an aspect ratio greater than 10:1 and that can be as high as 100:1 or more.

[0023] FIG 1 illustrates an example metrology system 100 that performs simultaneous spectroscopic measurements of one or more structures at ultraviolet, visible, and infrared wavelengths. The one or more structures may include, for example, at least one HAR structure or at least one large lateral dimension structure. The metrology system 100 illustrated in FIG 1 is configured as a broadband spectroscopic ellipsometer. However, in general, the metrology system 100 may be configured as a spectroscopic reflectometer, scatterometer, ellipsometer, or any combination thereof.

[0024] The metrology system 100 includes an illumination source 110 that generates an illumination light beam 117 that is incident on the wafer 120. The illumination source 110 is a broadband illumination source that emits illumination light in the ultraviolet, visible, and infrared spectrum. In one embodiment, the illumination source 110 is a laser-sustained plasma (LSP) light source (also called a laser-driven plasma light source). The pump laser of the LSP light source can be continuous wave or pulsed. A laser-driven plasma light source can provide a significantly larger number of photons than a xenon lamp over the entire wavelength range from 150 nm to 2000 nm. The illumination source 110 can be a single light source or a combination of multiple broadband or discrete wavelength light sources. The light generated by the illumination source 110 can include a continuous spectrum from ultraviolet to infrared (e.g., vacuum ultraviolet to mid-infrared) or several parts of a continuous spectrum. In general, illumination source 110 may comprise any suitable light source, such as a supercontinuum laser source, an infrared helium neon laser source, an arc lamp, or the like.

[0025] In a further aspect, the illumination light group is broadband illumination light having a wavelength range with a width of at least 500 nm. An example of broadband illumination light includes wavelengths less than 250 nm and wavelengths greater than 750 nm. In general, broadband illumination light includes wavelengths between 120 nm and 3000 nm. In some embodiments, broadband illumination light including wavelengths greater than 3000 nm may be used.

[0026] The metrology system 100 shown in FIG. 1 includes an illumination subsystem configured to direct illumination light 117 to one or more structures formed on a wafer 120. The illumination subsystem includes a light source 110, one or more optical filters 111, a polarizing member 112, a field stop 113, an aperture stop 114, and illumination optics 115. The optical filter or filters 111 can be used to control the amount of light emitted into the illumination subsystem, the spectral output, or both. In certain examples, one or more multi-zone filters are employed as the optical filter 111. The polarizing member 112 generates a desired polarization state that is output from the illumination subsystem. The polarizing member in certain embodiments is a polarizer, a compensator, or both, and can include any suitable commercially available polarizing member. The polarizing member can be fixed, rotatable with several fixed positions, or continuously rotatable. Although the illumination subsystem shown in FIG. 1 includes one polarizing member, the illumination subsystem can include multiple polarizing members. Field stop 113 controls the field of view (FOV) of the illumination subsystem, which may include any suitable commercially available field stop. Aperture stop 114 controls the numerical aperture (NA) of the illumination subsystem, which may include any suitable commercially available aperture stop. Light from illumination source 110 is directed into illumination optics 115, which focus it onto one or more structures (not shown in FIG. 1 ) on wafer 120. The illumination subsystem may include any type and arrangement of optical filter(s) 111, polarizing member 112, field stop 113, aperture stop 114, and illumination optics 115 known in the art of spectroscopic ellipsometry, reflectometry, and scatterometry.

[0027] 1 passes through optical filter(s) 111, polarizing member 112, field stop 113, aperture stop 114, and illumination optics 115, and propagates as a beam from illumination source 110 to wafer 120. Beam 117 illuminates a portion of wafer 120 that is on measurement spot 116.

[0028] In certain instances, the beam size of the illumination light constellation 117 projected onto the surface of the wafer 120 will be smaller than the size of the metrology target measured on the surface of the specimen. Examples of beam shaping techniques are described in detail in U.S. Patent No. 6,399,363 to Wang et al., which is incorporated herein by reference in its entirety.

[0029] The metrology system 100 also includes a collection optics subsystem configured to collect light generated by interaction between one or more structures and the incident illumination beam 117. A collected light beam 127 is collected from the measurement spot 116 by collection optics 122. The collected light 127 passes through a collection aperture stop 123, a polarizing element 124, and a field stop 125 in the collection optics subsystem.

[0030] The collection optics 122 includes any suitable collection element for collecting light from one or more structures formed 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 compensator. The polarizing element 124 may be fixed, rotatable with several fixed positions, or continuously rotatable. Although the collection subsystem shown in FIG. 1 includes one polarizing element, the collection subsystem may include multiple polarizing elements. The collection field stop 125 controls the FOV of the collection subsystem. The collection subsystem captures the light from the wafer 120 and directs it into the collection optics 122 and polarizing element 124 to focus it onto the collection field stop 125. In certain embodiments, the collection field stop 125 is used as a spectrometer slit instead of a spectrometer in the detection subsystem. However, the collection field stop 125 may also be located at or near the spectrometer slit 126 of the spectrometer of the detection subsystem.

[0031] The collection subsystem may include any type and arrangement of collection optics 122, aperture stop 123, polarizing element 124, and field stop 125 known in the art of spectroscopic ellipsometry, reflectometry, and scatterometry.

[0032] In the embodiment shown in Figure 1, a collection optics subsystem directs light to a number of spectrometers in a detection subsystem that generates an output in response to light collected from one or more structures illuminated by the illumination subsystem.

[0033] In one embodiment, the detector subsystem includes two or more detectors, each configured to simultaneously detect collected light across several wavelength ranges, including infrared.

[0034] In the embodiment shown in FIG. 1, the collected light 127 passes through the spectrometer slit 126 and is incident on the diffraction element 128. The diffraction element 128 is configured to diffract a set of wavelengths of the incident light in ±1 order, while diffracting another set of wavelengths of the incident light in 0 order. Portion 129 shown in FIG. 1 is the portion of the incident light that includes the ultraviolet spectrum, which is dispersed by the diffraction element 128 in ±1 diffraction orders toward the detector 141. In addition, the diffraction element 128 is configured to reflect a portion 140 of the incident light that includes infrared wavelengths in the direction of a grating 147 with a diffraction order of 0. The light 140 is incident on the diffraction element 147, which disperses a portion 148 of the incident light 140 that includes infrared wavelengths in ±1 diffraction orders toward the detector 150.

[0035] In the embodiment shown in FIG. 1, the diffractive element 128 is a reflective grating element. However, in general, the diffractive element 128 may be configured to subdivide the incident light into several wavelength bands, propagate the several wavelength bands along different directions, and disperse one of the wavelength bands and direct it onto the detector 141 in any suitable manner. In one example, the diffractive element 128 is configured as a transmission grating. In certain other examples, the diffractive element 128 includes a beam splitting element that divides the beam into several wavelength bands and a reflective or transmission grating structure that disperses one of the wavelength bands and directs it onto the detector 141.

[0036] The reflective grating 128 is employed because it exhibits high ±1st order diffraction efficiency in the ultraviolet spectral region and high zeroth order diffraction efficiency for the infrared spectral region, and avoids losses associated with beam splitting elements (e.g., dichroic beam splitting elements).

[0037] Diffractive elements 128 and 147 linearly disperse the first order diffracted light according to wavelength along one dimension of their respective two-dimensional detectors (i.e., the wavelength dispersion direction noted in FIG. 1 for their respective detectors). For illustrative purposes, detected light at two wavelengths is shown on the surface of detector 141. Diffractive element 128 creates a spatial separation between the two wavelengths of light projected onto the surface of detector 141. In this manner, light having one particular wavelength collected from measurement spot 116 is projected onto detector 141 as spot 142A, and light having another wavelength collected from measurement spot 116 is projected onto detector 141 as spot 142B.

[0038] Exemplary detector 141 is a charge-coupled device (CCD) sensitive to ultraviolet and visible light (e.g., light having wavelengths between 190 nm and 860 nm). Exemplary detector 150 is a photodetector array (PDA) sensitive to infrared light (e.g., light having wavelengths between 950 nm and 2500 nm). In general, however, other two-dimensional detector technologies are contemplated (e.g., position sensitive detectors (PSDs), infrared detectors, photovoltaic detectors, etc.). Each detector converts incident light into an electrical signal indicative of the spectral intensity of the incident light. For example, UV detector 141 generates output signal 154A indicative of incident light 129, and IR detector 150 generates output signal 154B indicative of incident light 148.

[0039] The detection subsystem shown in Figure 1 is arranged such that collected light propagates simultaneously to all detectors of the metrology system 100. The metrology system 100 also includes an information processing system 130 configured to receive a detection signal 154 that includes both UV and IR signals and to derive an estimate of a parameter of interest of the measured structure(s) based on both the UV and IR signals. The simultaneous collection of the UV and IR spectra reduces measurement time and all spectra are measured with the same alignment conditions. This allows wavelength errors to be more easily corrected since a common correction can be applied to the entire spectral data set.

[0040] In a further aspect, a fine focus sensor (FFS) is incorporated into the detection subsystem to provide a metrology input for focus error correction during metrology.

[0041] FIG. 2 illustrates another embodiment of a metrology system 200 having an FFS 146. Elements in FIG. 2 that are configured similarly to the metrology system 100 illustrated in FIG. 1 are indicated with the same reference numerals. The zeroth order diffracted light 140 illustrated in FIG. 2 is diffracted by the diffractive element 128 and is incident on the beam-splitting element 143. The beam-splitting element 143 can be transmissive or reflective. The beam-splitting element 143 directs a portion of the light 145 in the IR range to the IR grating 147 and a portion of the light below the IR range (i.e., in the UV-visible range) 144 to the FFS 146. The UV-visible light diffracted in the zeroth order by the diffractive element 128 is then detected by the FFS 146. In some embodiments, the FFS 146 is a photodiode array and the beam-splitting element 143 is a dichroic beam splitter capable of highly efficient reflection of IR and highly efficient transmission of UV. In certain other embodiments, the beam splitting element 143 is a neutral density filter, a partially reflecting mirror, an uncoated substrate, or any other focusing element suitable for splitting the beam into two or more beams of lower intensity for individual channels.

[0042] The output (not shown) generated by FFS 146 is sent to information processing system 130. Information processing system 130 determines changes in the focal position (z position) of wafer 120 based on the output of FFS 146. Any desired changes in the focal position of wafer 120 are sent to a wafer positioning system (not shown) which adjusts the z position of wafer 120 accordingly.

[0043] FIG 3 illustrates another embodiment of a metrology system 300 having an FFS 146. Elements illustrated in FIG 3 that are configured similarly to the metrology system 100 illustrated in FIG 1 are indicated with the same reference numerals. FIG 3 illustrates that the zeroth order diffracted light 149 is diffracted by the diffractive element 147 and is incident on the FFS 146, while the first order diffracted light 148 is incident on the IR detector 150.

[0044] The output (not shown) generated by FFS 146 is sent to information processing system 130. Information processing system 130 determines changes in the focal position (z position) of wafer 120 based on the output of FFS 146. Any desired changes in the focal position of wafer 120 are sent to a wafer positioning system (not shown) which adjusts the z position of wafer 120 accordingly.

[0045] According to another further aspect, a metrology system includes two or more detectors configured to simultaneously detect light in separate ranges of the IR spectrum.

[0046] FIG. 4 illustrates another embodiment of a metering system 400 having multiple cascaded IR detectors. Elements in FIG. 4 that are configured similarly to the metering system 100 illustrated in FIG. 1 are designated with the same reference numerals. As illustrated in FIG. 4, light 145 is incident on an IR grating 147. The IR grating 147 is configured to diffract a portion 148 of the incident light 145 in a first order. The first diffracted order 148 includes a portion of the IR wavelength range of the incident light 145. The IR grating 147 is further configured to diffract a portion 149 of the incident light 145 in a zero order. The zero diffracted order 149 includes IR wavelengths outside the IR wavelength range that comprises the first diffracted order 148. The zero diffracted order 149 propagates to an IR grating 151, which diffracts the incident light in a first order toward an IR detector 153. The first diffracted order 152 in the embodiment illustrated in FIG. 4 includes all IR wavelengths of the incident light 149. On the other hand, in certain other embodiments, IR grating 151 is configured to diffract only a portion of the incident light into the first order, and the remaining zeroth order light is directed to yet another IR grating. In this manner, any number of IR detectors can be cascaded to detect distinct IR wavelength bands of collected light 127.

[0047] The embodiments described with reference to Figures 1-4 are presented by way of non-limiting example, and many other configurations for simultaneous detection of UV, visible, and IR wavelengths can be envisioned. According to one example, the metrology system can be configured to disperse the IR wavelengths of the collected light 127 in a first diffraction order, and to diffract the UV wavelengths of the collected light 127 in a zeroth diffraction order toward the UV grating and detector. According to certain examples, beam splitting elements can be employed to subdivide the full spectrum of the collected light into two or more sub-spectra. However, it can be beneficial to employ diffractive elements as described herein, thereby avoiding losses associated with beam splitting elements such as dichroic beam splitters, neutral density filters, partial reflectors, or uncoated substrates.

[0048] 1 is delivered at an oblique angle to the surface of wafer 120. In general, illumination light may be delivered to the surface of wafer 120 at any oblique angle or at any number of oblique angles. In certain embodiments, illumination light beams are delivered to the surface at normal incidence (i.e., aligned with the surface normal) in addition to oblique illumination.

[0049] As shown in FIG. 1, the Z axis is oriented normal to the surface of the wafer 120. The X and Y axes are in the same plane as the surface of the wafer 120 and are therefore normal to the Z axis. The chief ray 118 of the illumination light beam 117 and the chief ray 121 of the focused light beam 127 define a plane of incidence. The X axis is aligned with the plane of incidence and the Y axis is perpendicular to the plane of incidence. In this configuration, the plane of incidence lies in the XZ plane. The illumination light beam 117 is incident on the surface of the wafer 120 at an angle of incidence α with respect to the Z axis and lies in the plane of incidence. The projection of the illumination light beam shape onto the specimen surface is performed at an oblique angle, resulting in an elongation of the illumination beam cross section along a direction aligned with the plane of incidence. By way of non-limiting example, a circular illumination light beam is projected onto the wafer surface, resulting in an elliptical illumination area. Thus, oblique illumination of a surface generally results in a projected illumination area that is elongated compared to the illumination cross section, and the elongation direction is aligned with the plane of incidence. Furthermore, the larger the angle of incidence, the greater the degree of elongation. More specifically, the beam shape is inversely proportional to the cosine of the angle of incidence along the direction of the plane of incidence. In the absence of diffraction and aberration effects, the incident illumination light remains undistorted along the direction perpendicular to the illumination plane (e.g., the Y direction).

[0050] Figure 5A is a top view of wafer 120 including an illustration of metrology spot 116 illuminated by illumination light beam 117 of Figure 1. In the embodiment shown in Figure 1, illumination light beam 117 has a circular cross section (e.g., due to illumination field stop 113). With a circular illumination light beam, the projection of metrology spot 116 on the surface of wafer 120 will be elliptical, as shown in Figure 5A.

[0051] The measurement spot 116 shown in FIG. 1 is projected onto the surface of the detectors 141 and 150 in a wavelength dispersive manner. Also, in one embodiment, the dispersing elements of the metrology system described herein are configured such that the plane of light dispersion onto each detector is oriented perpendicular to the projection of the plane of incidence on each detector. In this configuration, the measurement spot 116 is imaged onto each detector such that the direction aligned with the plane of incidence on the wafer surface is oriented perpendicular to the wavelength dispersion direction on the detector surface. Such an arrangement significantly reduces the sensitivity of the metrology system to focusing errors. The reduced sensitivity to focusing errors allows for accurate metrology results with shorter MAM times and therefore higher throughput. A notable advantage of this architecture is the ability to measure thick films and multi-layer film stacks without introducing wavelength errors.

[0052] Conventionally, metrology systems are configured such that the long dimension projection of the measurement spot on the detector surface is aligned with the wavelength dispersion direction. Figure 5B shows the conventional configuration. As shown in Figure 5B, the long dimension projection of the measurement spot 116 (i.e., X-axis on the wafer and X'-axis on the detector) on the detector 23 is aligned with the wavelength dispersion direction on the detector 23 surface. For example, the long dimensions of spots 24A and 24B are aligned with the wavelength dispersion direction. By integrating these wavelength-dependent images (e.g., spots 24A and 24B) on the detector 23 surface along a direction perpendicular to the wavelength dispersion direction, a spectrum is obtained, i.e., the intensity as a function of wavelength along the wavelength dispersion axis. In the case of a CCD-based detector, the spectrum is obtained by integrating the charge along a direction perpendicular to the wavelength dispersion.

[0053] When a measurement spot is imaged onto a detector such that the direction aligned with the plane of incidence on the wafer surface is aligned with the wavelength dispersion direction on the detector surface, the resulting point spread function (PSF) exhibits a strong wavelength dependence. The resulting PSF is highly peaked because the image intensity varies significantly along the long dimension for a given wavelength. To adequately capture this highly peaked PSD, the spectrometer must capture the spectral data with high resolution, which increases measurement time and reduces throughput.

[0054] Also, for example, if a long image and its corresponding long intensity distribution are aligned in the direction of the spectral dispersion, the resulting PSF for a particular wavelength will depend on the angle of incidence: the resulting PSF will be wider or narrower depending on the angle of incidence.

[0055] Also for example, the resulting PSF is highly sensitive to focus errors. As the measurement targets on the wafer move in and out of focus, the detected images of the measurement spots on the wafer change in size and shift in position. In addition, the positions of the measurement spots on the wafer shift. As shown in FIG. 6, when the wafer 120 is in focus, the illumination light beam 117 illuminates a portion A of the wafer. When the focused light beam 127 is conventionally wavelength-dispersed and imaged onto the detector 23, the images appear at spots 24A and 24B as shown in FIG. 7. When the wafer 120 is moved upwards in the z-direction and defocused by an amount ΔZ greater than 0, the illumination light beam 117 illuminates a portion C of the wafer. When the focused light beam 127' is conventionally wavelength-dispersed and imaged onto the detector 23, the images appear at spots 24A' and 24B'. The image appears larger as the wafer moves away from the focal plane of the optical system, and the center position of the image shifts along a direction aligned with the wavelength dispersion direction. This shift along the wavelength dispersion direction changes the wavelength-to-pixel mapping, resulting in spectral measurement errors. When wafer 120 is moved downward along the z direction and defocused by an amount ΔZ less than zero, illumination light beam 117 illuminates location B of the wafer. When focused light beam 127" is conventionally wavelength dispersed and imaged onto detector 23, the image appears at spots 24A" and 24B". Again, as the wafer moves away from the focal plane of the optical system, the image appears larger and its center shifts along a direction aligned with the wavelength dispersion direction.

[0056] In this situation, any measurement spot movement on wafer 120 due to focus error with ΔZ≠0 will result in an image shift along the spectrometer dispersion axis as a function of wavelength. Since the wavelength calibration is performed at the focal plane, i.e., Z=0, any focus error induced image shift along the spectrometer dispersion direction will make the measurement spectrum very sensitive to deviations from the wavelength calibration.

[0057] In contrast, by projecting the plane of incidence onto the detector perpendicular to the wavelength dispersion direction as described herein, the dispersion plane is separated from the plane of incidence, and therefore focusing errors do not affect the spectral position on the detector.

[0058] As shown in Figure 1, the measurement spot 116 is projected in a wavelength dispersive manner onto the surfaces of the detectors 141 and 150. The metrology system 100 is configured such that the long dimension projection of the measurement spot 116 is oriented perpendicular to the wavelength dispersion direction on the surfaces of the detectors 141 and 150. The X' axis shown in Figure 1 represents the long dimension (i.e., X-axis) projection of the measurement spot 116 onto the detectors 141 and 150. The X' axis shown in Figure 1 is oriented perpendicular to the wavelength dispersion direction on the surfaces of the detectors 141 and 150.

[0059] In one example, a 20-fold reduction in sensitivity to focus position is achieved by imaging the measurement spot onto the detector such that its direction aligned with the plane of incidence on the wafer surface is oriented perpendicular to the wavelength dispersion direction on the detector surface. This reduction in focus error sensitivity allows for relaxed focus accuracy and repeatability requirements, faster focus times, and reduced sensitivity to wavelength errors without compromising measurement accuracy. These effects are particularly evident in large numerical aperture optical metrology systems.

[0060] FIG. 8 is a direct view of the surface of detector 141. As shown in FIG. 8, the long dimension projection (i.e., X'-axis) of measurement spot 116 is oriented perpendicular to the wavelength dispersion direction on the surface of detector 141. For example, spots 142A and 142B have their long dimensions oriented perpendicular to the wavelength dispersion direction. By integrating these wavelength-dependent images (e.g., spots 142A and 142B) on the surface of detector 141 along a direction perpendicular to the wavelength dispersion direction, a spectrum is obtained, i.e., intensity as a function of wavelength along the wavelength dispersion axis. In the case of a CCD-based detector, the spectrum is obtained by integrating the charge along a direction perpendicular to the wavelength dispersion.

[0061] The image projected onto the surface of a detector (e.g. CCD 141) is integrated at each wavelength along a direction perpendicular to the spectrometer wavelength dispersion axis to obtain the measured spectrum. The individual spectral shape at each wavelength is the point spread function (PSF) of the system at that particular wavelength.

[0062] When the measurement spot is imaged onto the detector such that the direction aligned with the plane of incidence on the wafer surface is oriented perpendicular to the wavelength dispersion direction on the detector surface, the resulting point spread function (PSF) is much less wavelength dependent than conventional configurations. The resulting PSF exhibits low peaks because the image intensity does not vary significantly along the direction perpendicular to the long dimension for a given wavelength (e.g., along the short axis of the ellipse). Furthermore, although the image intensity does vary significantly along the long dimension (e.g., along the long axis of the ellipse), such variations are integrated and smoothed because the long dimension is aligned with the charge integration direction of the CCD. This configuration eliminates the need for a spectrometer to capture spectral data at high resolution to accurately construct a PSF, thereby reducing measurement time and increasing throughput.

[0063] Also, for example, if a long image is oriented perpendicular to the direction of the spectral dispersion, the resulting PSF for a particular wavelength will be independent of the angle of incidence. The image and the corresponding intensity distribution along the direction perpendicular to the long dimension (i.e. across the minor axis of the ellipse) will be approximately invariant to the angle of incidence. That is, the image and the corresponding intensity distribution, due to projection along the direction of the spectral dispersion, will be approximately invariant to the angle of incidence. Thus, the calculated PSF will exhibit little dependence on the angle of incidence.

[0064] Also, for example, the resulting PSF exhibits much less sensitivity to focus errors than the conventional configuration. As the measurement target on the wafer moves in and out of focus, a position shift occurs in the detected image of the measurement spot on the wafer. When the wafer 120 is in focus, as shown in FIG. 6, the illumination light beam 117 illuminates the wafer at location A. The collected light beam 127 is wavelength dispersed and imaged onto the detector 141 as spots 142A and 142B, as shown in FIG. 8. When the wafer 120 moves upward along the z-direction and becomes defocused by an amount ΔZ greater than 0, the illumination light beam 117 illuminates the wafer at location C. The collected light beam 127′ is wavelength dispersed and imaged onto the detector 141 as spots 142A′ and 142B′. This image position shift perpendicular to the wavelength dispersion direction does not change the wavelength-to-pixel mapping, thereby reducing the focus error induced spectral measurement error. When wafer 120 is moved downward along the z direction and defocused by an amount ΔZ less than 0, wafer portion B is illuminated by illumination light beam 117. Focused light beam 127″ is wavelength dispersed and imaged onto detector 141 as spots 142A″ and 142B″. Again, the image position shift is perpendicular to the wavelength dispersion direction, reducing the spectrum measurement error induced by the focusing error.

[0065] In this configuration, focusing errors cause the image on the detector to shift along a direction perpendicular to the wavelength dispersion axis. Since the calculated spectrum is obtained by integrating the image perpendicular to the spectrometer dispersion axis, the image shift induced by focusing errors is integrated and smoothed, and does not induce substantial spectrum measurement errors. This reduction in sensitivity to focusing errors eliminates the need to track and correct focusing errors based on atomic beam emission. In this configuration, a broadband light source, such as a high-brightness laser-driven light source (LDLS), can be employed as the light source in the spectrometer system, such as system 100, with relaxed focus positioning requirements.

[0066] As mentioned above, the PSF produced by the projection of the spectrometer is mostly determined by the light distribution along the direction perpendicular to the incidence plane (i.e., the XZ plane). Therefore, the PSF is independent of the oblique incidence angle. That is, the wavelength dependency of the PSF is much less than that of the conventional configuration.

[0067] As described herein, any normal incidence or oblique incidence broadband optical metrology system can be configured to image a measurement spot onto a detector surface such that the direction aligned with the plane of incidence on the wafer surface is oriented perpendicular to the wavelength dispersion direction on the detector surface. Orienting the spectrometer dispersion axis perpendicular to the wafer focus axis (e.g., the z-axis in FIGS. 1-4) according to certain embodiments can further reduce the system sensitivity to focus errors.

[0068] Additionally, in some aspects, multi-zone infrared detectors that combine several sensitivity bands at different locations on a single detector package are employed in the metrology systems described herein, configured to provide a continuous spectrum of data with different sensitivities depending on the location of incidence.

[0069] FIG. 10 shows a typical optical sensitivity curve of available Indium Gallium Arsenide (InGaAs) sensors. As shown in FIG. 10, none of the available InGaAs sensors provide adequate optical sensitivity over the wavelength range of 1 μm to 2.5 μm. That is, taken individually, the available sensors are only capable of sensing over a narrow waveband. In some embodiments, the individual sensors are arranged in a cascade arrangement, such as that shown in FIG. 4. However, this requires the use of individual grating structures or a combination of beam splitting elements and grating structures to subdivide the collected light into individual spectral ranges and distribute each spectral range onto a separate detector. This results in unnecessary optical loss and optical system complexity.

[0070] In one embodiment, multiple sensor chips, each sensitive to a different waveband, are combined into a single detector package, and the multi-zone detector is then implemented in a metrology system as described herein.

[0071] FIG. 9 shows four sensor chips 150A-D from four different wavebands forming a multi-zone infrared detector 150. As shown in FIG. 10, the four sensor chips have different material compositions that provide different light sensitivity characteristics. As shown in FIG. 10, sensor chip 150A is highly sensitive in waveband A, sensor chip 150B is highly sensitive in waveband B, sensor chip 150C is highly sensitive in waveband C, and sensor chip 150D is highly sensitive in waveband D. A metrology system incorporating detector 150 is configured to distribute wavelengths in waveband A onto sensor chip 150A, wavelengths in waveband B onto sensor chip 150B, wavelengths in waveband C onto sensor chip 150C, and wavelengths in waveband D onto sensor chip 150D. In this way, high optical sensitivity (ie, high SNR) across an integrated waveband that includes wavebands A-D is achieved with a single detector.

[0072] Certain example multi-zone detectors have InGaAs sensors sensitive to different spectral regions assembled into a single sensor package, providing a single, consistent spectrum covering wavelengths from 750 nm to 3000 nm or beyond.

[0073] In general, any number of individual sensors may be assembled along the wavelength dispersion direction of a multi-zone detector to obtain a consistent spectrum from the detector, although typically, two to four individual sensors are employed in a multi-zone detector, such as detector 150.

[0074] According to another further aspect, by adjusting the dimension of the illumination field stop's projection onto the wafer plane along a direction perpendicular to the plane of incidence, the measurement accuracy and speed obtained can be optimized based on the properties of the target being measured.

[0075] By adjusting the projection of the illumination aperture on the wafer plane along the orthogonal direction, the PSF can be shaped for each measurement application to achieve a flat-top profile that is nearly wavelength insensitive. In addition, the spectral resolution can be adjusted to optimize measurement accuracy and speed based on the flat-top profile.

[0076] In some examples, for example, when the sample is a very thick film or a lattice structure, the projection of the illumination field stop on the wafer plane along the direction perpendicular to the incident surface can be adjusted to reduce the field size and improve the spectral resolution. In some examples, for example, when the sample is a thin film, the projection of the illumination field stop on the wafer plane along the direction perpendicular to the incident surface can be adjusted to expand the field size and shorten the measurement time without losing the spectral resolution.

[0077] 1-4, information processing system 130 is configured to receive signal 154 indicative of the spectral responses detected by detectors 141, 150 and 153 (if applicable). Information processing system 130 is further configured to determine and send a control signal 119 to programmable illumination field diaphragm 113. Programmable illumination field diaphragm 113 receives control signal 119 and adjusts the size of the illumination aperture to achieve a desired illumination field size.

[0078] In certain examples, the illumination field diaphragm can be adjusted to optimize measurement accuracy and speed as described above. In some examples, the illumination field diaphragm can be adjusted to prevent image clipping by the spectrometer slit and the corresponding degradation of the measurement results. In this case, the illumination field size is adjusted so that the image of the measurement target does not fill the spectrometer slit. In some examples, the illumination field diaphragm is adjusted so that the projection of the polarizer slit of the illumination optics does not fill the spectrometer slit of the metrology system.

[0079] 11 illustrates a method 500 for performing spectroscopic measurements in accordance with at least one embodiment. Method 500 is suitable for implementation in a metrology system, such as metrology systems 100, 200, 300, and 400 of the present invention, as illustrated in FIGS. 1-4, respectively. In accordance with certain embodiments, it will be appreciated that the data processing blocks of method 500 may be implemented by pre-programmed algorithms executed by one or more processors in information processing system 130, or any other general-purpose information processing system. As will be appreciated herein, the specific structural aspects of metrology systems 100, 200, 300, and 400 are not intended to be limiting, but should be construed as illustrative only.

[0080] In block 501, broadband illumination light from an illumination source is directed to a measurement spot on the surface of a specimen under measurement at one or more angles of incidence in a plane of incidence.

[0081] In block 502, a constellation of light is collected from a measurement spot on the specimen surface.

[0082] In block 503, a first portion of the collected light group within a first wavelength range is directed to a surface of a first detector, and a second portion of the collected light group within a second wavelength range is directed to a surface of a second detector.

[0083] In block 504, a response of the specimen to the set of illumination lights in a first wavelength range is detected.

[0084] In block 505, the response of the specimen to the set of illumination lights in the second wavelength range is detected at the same time that the response of the specimen to the set of illumination lights in the first wavelength range is detected.

[0085] Examples of metrology techniques that can be configured as described herein include, but are not limited to, spectroscopic ellipsometry (SE) such as Mueller matrix ellipsometry (MMSE), rotating polarizer SE (RPSE), rotating polarizer rotating compensator SE (RPRC), rotating compensator rotating compensator SE (RCRC), spectroscopic reflectometry (SR) such as polarized SR, non-polarized SR, spectroscopic scatterometry, scatterometry overlay, beam profile reflectometry, angle-resolved or polarization-resolved beam profile ellipsometry, single or multiple discrete wavelength ellipsometry, etc. In general, any metrology technique that includes illumination with UV and IR wavelengths can be envisioned, either individually or in any combination. For example, any SR or SE technique applicable to characterization of semiconductor structures, including image-based metrology techniques, can be envisioned, either individually or in any combination.

[0086] Further embodiments of the systems 100, 200, 300, and 400 utilize one or more information processing systems 130 that may be communicatively coupled to a spectrometer to perform measurements of real device structures based on spectroscopic metrology data collected according to the methods described herein. In some aspects, the one or more information processing systems 130 are configured to receive metrology data 154 relating to measurements of structures of the specimen 120.

[0087] It should be appreciated that one or more steps described throughout this disclosure may be performed by a single computer system 130 or, alternatively, by multiple computer systems 130. Additionally, the various subsystems of systems 100, 200, 300, and 400 may include computer systems suitable for performing at least some of the steps described herein. Thus, the above description should be taken as merely illustrative and not limiting on the present invention.

[0088] In addition, computer system 130 may be communicatively coupled to the spectrometers in any manner known in the art, for example, one or more information processing systems 130 may be coupled to the spectrometers, or the spectrometers may be directly controlled by a single computer system coupled to computer system 130.

[0089] The computer system 130 of the metrology systems 100, 200, 300 and 400 may be configured with a transmission medium, such as a wired section and / or a wireless section, to receive and / or capture data or information from the subsystems (e.g., spectrometer, etc.) of the system. In this configuration, the transmission medium may act as a data link between the computer system 130 and the other subsystems of the systems 100, 200, 300 and 400.

[0090] The computer system 130 of the metrology systems 100, 200, 300 and 400 may be configured with a transmission medium, such as a wired section and / or a wireless section, so that the computer system 130 can receive and / or capture data or information (e.g., measurement results, modeling inputs, modeling results, reference measurement results, etc.) from other systems. In this configuration, the transmission medium can act as a data link between the computer system 130 and other systems (e.g., on-board memory of the metrology systems 100, 200, 300 and 400, external memory, or other external systems). For example, the information processing system 130 may be configured to receive metrology data from a storage medium (i.e., memory 132 or an external memory) via a data link. For example, spectroscopy results obtained using the spectrometers described herein may be stored in a permanent or semi-permanent storage device (e.g., memory 132 or an external memory). In this configuration, spectroscopy results can be imported from the on-board memory or from an external memory system. Furthermore, it is preferable that the computer system 130 transmits data to another system via a transmission medium. For example, the measurement model or estimated parameter values ​​obtained by the computer system 130 may be transmitted and stored in an external memory. With this configuration, the measurement results can be exported to another system.

[0091] Information handling 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 "information handling system" may be broadly defined to include any device having one or more processors, which executes instructions obtained from a storage medium.

[0092] Program instructions 134 for implementing methods, such as those described herein, may be transmitted over a transmission medium, such as a wire, cable, or wireless transmission link. For example, as depicted in Figure 1, program instructions 134 stored in memory 132 are transmitted over bus 133 to processor 131. Program instructions 134 are stored in a computer-readable medium, such as memory 132. Examples of computer-readable media include read-only memory, random-access memory, magnetic or optical disks, and magnetic tape.

[0093] In one example, the metrology model is implemented as a component of a SpectraShape™ optical critical dimension metrology system available from KLA-Tencor Corporation, Milpitas, Calif. In this configuration, the model is generated and prepared for use immediately after a spectrum is collected by the system.

[0094] In another example, the metrology model is realized offline, for example by an information processing system running AcuShape® software available from KLA-Tencor Corporation, Milpitas, Calif. The resulting trained model can be incorporated as a component of an AcuShape® library that can be accessed by a metrology system to perform the metrology.

[0095] In some embodiments, the semiconductor device spectroscopic metrology methods and systems described herein are applied to metrology of high aspect ratio (HAR) structures, large lateral dimension structures, or both. Examples of structures suitable for metrology with the systems and methods described herein include three-dimensional NAND structures, such as vertical NAND (V-NAND®) structures, dynamic random access memory structures (DRAM), and the like, which are manufactured by various semiconductor manufacturers, such as Samsung Inc. (Korea), SK Hynix Inc. (Korea), Toshiba Corporation (Japan), Micron Technology, Inc. (USA), and others. These complex devices suffer from low light transmission into the structure(s) to be measured. FIG. 12 shows an example 600 of a high aspect ratio NAND structure that suffers from low light transmission into the structure(s) to be measured. A spectroscopic ellipsometer with broadband capability into the infrared and simultaneous spectral band detection with a multi-zone sensor as described herein is suitable for metrology of such high aspect ratio structures.

[0096] According to yet another aspect, the metrology results described herein can be used to provide active feedback to a process tool (e.g., a lithography tool, an etch tool, a deposition tool, etc.). For example, metrology parameter values ​​derived using the metrology methods described herein can be sent to a lithography tool to adjust the lithography system to achieve a desired output. Similarly, etch parameters (e.g., etch time, diffusivity, etc.) and deposition parameters (e.g., time, concentration, etc.) can be incorporated into metrology models to provide active feedback to an etch tool or a deposition tool, respectively. According to one example, corrections to process parameters based on the trained metrology model and device parameter measurements can be sent to a lithography tool, an etch tool, or a deposition tool.

[0097] The term "critical dimension" as used herein includes any critical dimension of a structure (e.g., bottom critical dimension, middle critical dimension, top critical dimension, sidewall angle, grid height, etc.), the critical dimension between any two or more structures (e.g., the distance between two structures), and the misregistration between two or more structures (e.g., overlay misregistration between overlapping grid structures, etc.). Example structures include three-dimensional structures, patterned structures, overlay structures, etc.

[0098] As used herein, the terms "critical dimension application" and "critical dimension metrology application" are intended to encompass any critical dimension metrology application.

[0099] The term "metrology system" as used herein encompasses any system employed at least in part to characterize a specimen in any manner, including metrology applications such as critical dimension metrology, overlay metrology, focus / dose metrology, and composition metrology. However, these technical terms do not limit the scope of the term "metrology system" as used herein. Additionally, the metrology system 100 can be configured for metrology of patterned 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 (with simultaneous data acquisition from one or more platforms), or any other metrology or inspection tool that benefits from calibration of system parameters based on critical dimension data.

[0100] Various embodiments are described herein in relation to a semiconductor metrology system that can be used to measure specimens in any semiconductor processing tool (e.g., an inspection system or a lithography system). The term "specimen" is used herein to refer to a wafer, reticle, or any other sample that can be processed (e.g., printed or inspected for defects) by means known in the art.

[0101] The term "wafer" as used herein generally refers to a substrate formed of a semiconductor or non-semiconductor material. Examples of such materials include, but are not limited to, monocrystalline silicon, gallium arsenide, and indium phosphide. Such substrates are often found and / or processed in semiconductor manufacturing facilities. In some cases, a wafer may consist of only the substrate (a so-called bare wafer). Alternatively, a wafer may have one or more layers formed of other materials on the substrate. One or more layers formed on a wafer may be "patterned" or "unpatterned." For example, a wafer may have multiple dies with repeatable pattern features.

[0102] A "reticle" may refer to a reticle at any stage in the reticle manufacturing process or to a finished reticle, which may or may not have been released for use in a semiconductor manufacturing facility. A reticle or "mask" is generally defined as a substantially transparent substrate having a pattern of substantially opaque regions formed thereon. The substrate may, for example, comprise a glass material such as amorphous SiO2. The reticle may be placed on a resist-coated wafer and the pattern on the reticle may be transferred to the resist through an exposure step in the lithography process.

[0103] The layer or layers formed on the wafer may be patterned or unpatterned. For example, each of the multiple dies that make up the wafer may have repeatable pattern features. The formation and processing of such layers of material may ultimately result in a completed device. Many types of devices may be formed on a wafer, and the term wafer as used herein is intended to encompass a wafer having any type of device fabricated thereon as known in the art.

[0104] In accordance with one or more exemplary embodiments, the functions described above may be implemented in hardware, software, firmware, or any combination thereof. When implemented in software, the functions are stored on or transmitted over a computer-readable medium as one or more instructions or code. Computer-readable media includes both computer storage media and communication media, and includes any medium that facilitates the transfer of a computer program from one place to another. A storage medium may be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable media may 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 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. Any connection may be referred to as a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio frequency, or microwave, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio frequency, or microwave would fall within the definition of the medium. The term disk / disc in this application encompasses disks on which data is typically reproduced magnetically and disks on which data is reproduced optically with a laser, including compact disks (CDs), laser disks, optical disks, digital versatile disks (DVDs), floppy disks, and Blu-ray disks. Combinations of the above should also be included within the scope of computer-readable media.

[0105] Although specific embodiments have been described above for instructional purposes, the teachings of this patent application are of general applicability and are not limited to the specific embodiments described above. Thus, various modifications, adaptations and combinations of the features of the embodiments described above can be made without departing from the spirit and scope of the invention as set forth in the claims.

Claims

1. directing broadband illumination light from an illumination source to a measurement spot on a surface of the specimen under measurement at one or more angles of incidence within a plane of incidence; collecting a group of collected light from a measurement spot on the surface of the specimen; directing a first portion of the collected light beam within a first wavelength range toward a surface of a first detector and a second portion of the collected light beam within a second wavelength range toward a surface of a second detector; detecting a response of the specimen to a set of illumination lights within a first wavelength range; detecting a response of the specimen to the set of illumination lights in the second wavelength range simultaneously with detecting the response of the specimen to the set of illumination lights in the first wavelength range; having a cross-sectional shape of the beam of the broadband illumination light group incident on the surface of the measurement target specimen is elliptical; A method comprising a step of imaging the measurement spot on the surfaces of the first detector and the second detector so that an alignment direction, which is the long axis direction of the ellipse of the incident surface projected onto the first detector, is oriented perpendicular to a wavelength dispersion direction, which is a direction in which focused light having different wavelengths is spatially separated on the surfaces of the first detector and the second detector, wherein the wavelength dispersion direction on the surfaces of the first detector and the second detector is a direction perpendicular to a focusing axis of the sample to be measured, and the second detector is an infrared detector that is configured as a single sensor package by arranging two or more sensor chips each exhibiting different light sensitivity along the wavelength dispersion direction.

2. 2. The method of claim 1 , the second detector comprises first to fourth sensor chips having different material compositions each exhibiting different light sensitivity characteristics, the first sensor chip exhibiting high sensitivity in a first wavelength band, the second sensor chip exhibiting high sensitivity in a second wavelength band, the third sensor chip exhibiting high sensitivity in a third wavelength band, and the fourth sensor chip exhibiting high sensitivity in a fourth wavelength band, and the method comprises distributing wavelengths in the first wavelength band onto the first sensor chip, distributing wavelengths in the second wavelength band onto the second sensor chip, distributing wavelengths in the third wavelength band onto the third sensor chip, and distributing wavelengths in the fourth wavelength band onto the fourth sensor chip.

3. 10. The method of claim 1 further comprising: directing a third portion of the collected light within a third wavelength range onto a surface of a third detector; detecting a response of the specimen to the set of illumination lights in a third wavelength range simultaneously with detecting the response of the specimen to the set of illumination lights in the first wavelength range; wherein the third detector is configured with the second detector as the single sensor package.

4. 2. The method of claim 1, wherein the specimen under test is a three-dimensional NAND structure or a dynamic random access memory structure.

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