Confocal raman

Abstract

An optical measurement system that includes a confocal optics that includes an illumination path and a collection path. The illumination path is configured to illuminate, during a measurement iteration, a sample at an illumination angle with illuminating radiation. The collection path is configured to collect, during the measurement iteration, at a collection angle that differs from the illumination angle, from the sample, radiation resulting from the illumination of sample. The confocal optics includes a confocal filter. The Raman detector that is configured to acquire, during the measurement.

Description

CONFOCAL RAMANCROSS REFERENCE

[0001] This application claims priority from US provisional patent serial number 63 / 652,674 filing date May 28, 2024, which is incorporated herein by reference.BACKGROUND

[0002] There is a growing need to improve evaluation of samples.BRIEF DESCRIPTION OF THE DRAWINGS

[0003] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

[0004] FIGs. 1A and IB illustrate examples of samples;

[0005] FIG. 2 illustrates an example of a Raman spectrum;

[0006] FIG. 3A and 3B illustrate a part of a normal incidence normal collection optical system;

[0007] FIG. 4A illustrates an example of an illumination and a collection of a normal incidence normal collection optical system;

[0008] FIG. 4B illustrates an example of an illumination and a collection of a normal incidence and tilted collection optical system;

[0009] FIG. 4C illustrates an example of an illumination and a collection of a tilted incidence and normal collection optical system;

[0010] FIG. 4D illustrates an example of a normal incidence and tilted collection optical system;

[0011] FIG. 5 illustrates an example of a three layers stack z profiling result;

[0012] FIG. 6 illustrates an example of a method;

[0013] FIG. 7 illustrates an example of a sample and various measurements; and

[0014] FIG. 8 illustrates an example of a system.DETAILED DESCRIPTION OF THE DRAWINGS

[0015] Over recent years, semiconductor fabrication technology is increasingly using tall, 3D complex structures for continued technology development and scaling. This trend is most notable in memory devices, where devices such as 3D-NAND and in thecoming future 3D-DRAM are comprised of hundreds of multilayers reaching many microns of vertical extent. These highly-complex structures require correspondingly high-end metrology and characterization solutions, to measure their properties during fabrication. These properties include both dimensional and material attributes, and vertically-resolved information is required in order to accurately map the entire structure.

[0016] To clarify this gap in metrology offering, Figure 1 presents two examples for such critical needs: a. 3D-NAND aSi\pSi channel characterization (see sample 11 of Figure 1A): during the fabrication of 3D-NAND memory devices, an ultra-thin layer of amorphous Silicon (aSi) is deposited along high aspect-ratio (AR) channels. This layer is then turned into poly-Si (pSi) using dedicated fabrication processes. Characterization of the layer thickness, the ratio between aSi and pSi and their distribution along the channel height is of critical importance to ensure the device electrical performance. b. 3D-DRAM Si\SiGe multi-layer characterization (see sample 12 of Figure IB): the emerging technology of 3D-DRAM is based on a multi-layer structure made from Silicon (Si) and Silicon Germanium (SiGe), deposited in multiple interlacing bilayers. Characterization of these layer’s thickness, the Ge concentration in the SiGe and even induced strain and defectivity in these layers is required.

[0017] Of course, other structures of similar attributes exist, both in different stages of the fabrication process of these devices and in other device technologies (e.g. logic multilayer nanosheet-based devices).

[0018] The combined need for dimensional and material metrology, along with high- end profding of these attributes, poses a formidable characterization challenge.

[0019] According to an embodiment, there is provided a solution that combines confocal Raman metrology with one or more steps. Examples of a step include ameasurement sequence, an interpretation method, a hybrid information fusion with other optical tools, to address these needs.

[0020] measurement sequence, an interpretation method, a hybrid information fusion with other optical tools, to address these needs.

[0021] Alternative solutions addressing these challenges consist of slow, destructive methods, such as: a. Cross-sectional SEM: a group of methods by which the structure is cleaved or etched and Scanning Electron Microscopy information is collected, possibly including material-resolved readout such as Energy-Dispersive X-ray metrology (EDX). b. Transmission Electron Microscopy (TEM): requiring a preliminary stage by which a thin lamella is prepared out of the measured structure, in order to allow the TEM measurement. c. Secondary Ions Mass Spectrometry (SIMS): measuring secondary ions created during ion milling through the structure allows high-end profding of the stack.

[0022] All these can provide both dimensional and some material characterization. However, these are extremely slow, require extremely high-end equipment and most importantly - are destructive to the measured structure. As such, they are unsuitable for in-line metrology in the fab.

[0023] Another technique worth mentioning is optical scatterometry, and especially Spectral Interferometry (SI). Optical scatterometry serves the basis for Optical Critical Dimension (OCD) metrology, an extremely widespread used technique for dimensional characterization. The specific implementation of SI augments optical scatterometry by the ability to conduct vertical profiling through ultra-tall structures [see - for example - US Patent No. 11,029,258; US patent application US2024085805 and PCT patent application No. W02024003758, claiming priority from US. Provisional patent application 63 / 356,531 - all being incorporated herein by reference. As described below, this approach can provide significant benefit to the characterization solution, but on its own is insufficient due to two main gaps:

[0024] Low intra-layer profiling sensitivity: SI allows clear separation between reflections coming from vertically-separated regions in the stack. However, when travelling inside a homogeneous stack very little light is reflected, limited the sensitivity to gradual variations.

[0025] Material characterization: optical scatterometry is predominantly a dimensional metrology technique, with high sensitivity to layers’ lateral and verticaldimensions. However, it is not very sensitive to material characteristics, such as concentrations, strain\stress and defectivity.

[0026] There is provided a solution that involves using the technology of Raman Spectroscopy (RS) in a confocal-measurement scheme. To clarify the unique attributes involved in the current proposal, we include a brief outline of this technique.

[0027] RS is based on illuminating the sample by a narrow-band laser and blocking the laser wavelength at collection. While standard (elastic) light scattering is blocked, inelastically-scattered light is collected and analyzed by a high-resolution spectrometer.

[0028] Raman scattering is a specific type of inelastic scattering in which the reflected wavelength is different from the incident wavelength due to the excitation (or absorption) of a phonon - molecular vibrational excitation. The Raman spectrum reflects the distribution of vibrational modes, and is an extremely sensitive probe to a variety of material properties such as material composition, strain, doping, defectivity, molecular phase etc. These properties affect the positions and line shapes of different features (typically, peaks) and their positions. Figure 2 presents a typical Raman spectrum 20 obtained from a stack involving Si and SiGe, where the different peaks can be used to derive the Ge concentration and strain.

[0029] Figure 2 illustrates a typical Raman spectrum 20 from Si (lower) and a SiGe layer on Si substrate (upper). One peak 24 originates from Si, and other features - most notably three distinct peaks 21, 22 and 23 - are originate from SiGe.

[0030] In addition to characterization of material properties, the Raman peaks intensities relate to the dimensions (thicknesses, volume) of the different materials. This relation may not be trivial, due to the intricate interaction of the incident and scattered light with the measured structure. This concern is discussed further below.

[0031] In a confocal Raman measurement, the collection path includes an optical element limiting the collected signal to a narrow region on the sample. Typically, a pinhole is placed at the collection path, in a location conjugate to the sample plane. This pinhole blocks signal originating away from the focus point, selectively highlighting a specific region in the sample.

[0032] Figures 3A and 3B illustrate a part of a normal incidence normal collection optical system for confocal Raman microscopy that includes laser 31, first mirror 32, illumination objective lens 33, beam splitter 34 (shared by the illumination path and thecollection path), objective lens 35 (shared by the illumination path and the collection path), collection objective lens 36, pinhole 37 and detector 38.

[0033] According to an embodiment each of the systems of figures 3A, 3B, 4D and 8 includes optical for z-axis scanning - such as but not limited moving optics and / or z- stage form moving the sample along the Z-axis.

[0034] A laser beam from a laser source is focused on the sample plane. The pinhole 37 is placed at the collection path limits collection to the illuminated area. Reflections from out-of-focus parts are not focused on the collection pinhole, and their contribution to the collected signal is strongly attenuated.

[0035] According to an embodiment, the solution relates to using confocal Raman spectroscopy for combined dimensional and material metrology of tall (at least few microns) semiconductor structures.

[0036] According to an embodiment the solution involves a hardware configuration.

[0037] Providing (at least) IR excitation wavelengths and specific choice \ control over the angular span of collection and illumination channels.

[0038] Use of multiple wavelengths is also proposed, for further improved vertical resolution (allowing sub-micron resolutions) - especially at the top of the measured structure.

[0039] A specific implementation is proposed, by which a relative shift is introduced between the illumination and collection angles of incidence. As explained, this provides significantly improved vertical resolution as well as flexible access to stack properties.

[0040] Correct choice of excitation wavelength\s is of paramount importance.

[0041] Clearly, the used wavelength has to allow light penetration into the structure. For the examples described above, where materials of interest are Si (amorphous, poly-crystalline or crystalline) and SiGe, IR wavelengths - specifically, in excess of ~750nm, are of interest. For other materials, such as amorphous Carbon, even longer wavelengths are required.

[0042] However, a multi-wavelength solution can offer additional functionality, in the ability to profile top layers at ultra-high vertical resolution: using visible (and even UV) wavelengths, the light penetration depth can be significantly sub-micron (reaching few tens of nm and even few nm in DUV). Combining such wavelengths with the IR-confocal metrology can offer a huge span of resolutions - ultra-fine forthe top layers (using wavelength-resolved measurements) and confocally-resolved for deep regions.

[0043] Confocal Raman microscopy is implemented in many mainstream analytical products. In order to obtain high vertical resolution, small depth of focus (DOF) is desired. Correspondingly, large numerical aperture (NA) is commonly used at both illumination and collection, since the DOF is proportional to A / NA2(with A the wavelength). The negative impact of such small DOF is requirement for ultra-accurate alignment between the illumination and collection focus points and increased sensitivity to system instabilities. These aspects can be of crucial concern for industrial implementation.

[0044] A proposed alternative to the proposed approach involves using a relative angular difference between the illumination and collection channels (see Fig. 4). A possible implementation of such angular separation is outlined in Fig. 4c, where a moving mirror (here placed at illumination path) shifts the beam across the objective aperture, modifying the angle of incidence on the wafer.

[0045] Figure 4A illustrates an example of an illumination and a collection of a normal incidence normal collection optical system that may use large numerical aperture (NA) for illumination and collection channels providing small DOF at the risk of system stability.

[0046] The angular alignment of the illumination beam (denoted "illumination") and the collection beam (denoted "collection") when propagating within a sample (in this example the sample has a pair of layers) results in an overlap region that is relatively long (along the z-axis) - causing the detected signal to represent elements in this relatively long overlap region.

[0047] Figure 4B illustrates an example of an illumination and a collection of a normal incidence and tilted collection optical system that in turn is illustrated in figure 4C.

[0048] Figure 4C illustrates an example of an illumination and a collection of a tilted incidence and normal collection optical system.

[0049] It should be noted that the overlap may be obtained when both the illumination and the collection are tilted.

[0050] In figure 4D the first mirror 32 (which is fixed) is replaced by a movable mirror 38 the is movable in order the change the angle of illumination. Figure 4C illustrates a relationship between the linear movement ("Mirror movement 40a") ofthe mirror, to movements of beams in the collection path ("beam location change 40b" and " beam location change 40c") that are converted by the objective lens to a "beam angular change 40d").

[0051] Is should be noted that the illumination angle can be changed in any other manner - for example by rotating the mirror (instead of linear movement), tilting the location of illumination source 42, and the like.

[0052] It should be noted that the normal collection angle is merely a non-limiting example - and that the collection angle may be an oblique angle.

[0053] The angular misalignment between the illumination beam (denoted "illumination") and the collection beam (denoted "collection") when propagating within a sample (in this example the sample has a pair of layers) results in a much smaller overlap region that is relatively short (along the z-axis) - causing the detected signal to represent elements in this relatively much shorter overlap region - which dramatically increased the vertical resolution of the detected signal.

[0054] A relative tilt between the illumination and collection beams offers superior confocal performance but with reduced sensitivity to optical alignment.

[0055] Another possible implementation is to use two different optical paths for the illumination and collection. The incident light is focused on the sample at an angle and with a spatial offset with respect to the collection objective (similar to Figure 4B).

[0056] These type of techniques produce improved depth resolution as they minimize the overlapping volume of the illumination and collection point spread functions (PSF).

[0057] As depth resolution deteriorates with z, one plausible option to improve the results is to perform confocal measurements from both sides of the sample (i.e., turning the sample upside down). This method will be practical when the substrate is very thin.

[0058] Other system configuration that effects the system resolution should be set to optimize the confocal capabilities, such as the grating grooves density and CCD pixel size. Polarization configuration should be chosen accordingly to allow for deconvolution of adjacent peaks in cases where different materials with similar peaks position are subjected to depth profiling as their polarization dependence might differ.

[0059] According to an embodiment the solution includes an algorithmic analysis and supporting simulative framework: as explained below, by understanding the Ramaninteraction and its distribution inside the structure it is possible to conduct high-end interpretations.

[0060] Linear deconvolution: contrary to standard confocal microscopy, in Raman scattering it is possible to conduct deconvolution for the measured z-dependence of the signal. Such deconvolution can offer sub-diffraction vertical resolution, but requires good understanding of the beam distribution inside the measured structure. Modelbased analysis: a simulative engine, describing the illumination beam distribution inside the sample, the created Raman sources and the spatial distribution of the collection efficiency, is of high value. Such engine could provide accurate estimates for the deconvolution kernel (see below).

[0061] Furthermore, using standard regression methods such engine can allow conversion of the measured Raman intensity distributions into quantitative dimensional and material characterization.

[0062] Synergy with OCD, and specifically SI for full vertical characterization: as stated, SI technology offers the potential for vertically-resolved dimensional metrology. However, its sensitivities and parametric correlations are highly different from those of the proposed method. For example - SI is relatively insensitive to changes in strain or material composition, as well as gradual changes in dimensions along the stack height. However it is highly sensitive to nanostructure dimensions (‘Critical Dimensions’) such as hole diameters, layers’ thickness, over-etch\under-etch etc. Conversely, The proposed approach provides excellent selectivity along the entire stack height, while suffering from increased correlations between dimensional parameters. Using both measurement channels together can offer significantly advantageous performance.

[0063] Combining confocal Raman measurements with state-of-the-art notch filters in the collection path enables depth profiling of the the low-frequency range (to a few wavenumbers from incoming laser). This range includes valuable information such as layers thickness and quality of a superlattice (3D-DRAM), and doping concentration via electronic Raman.

[0064] Linear deconvolution

[0065] A key ingredient in the current invention relates to the basic applicability of linear interpretation of the measured confocal scan, namely - the ability to usedeconvolution for relating the measured signal with material distributions inside the stack.

[0066] To clarify this point, we compare the Raman measurement with standard confocal microscopy. The difference between the two cases arises from the coherence breaking involved in the Raman interaction.

[0067] The measured signal in such a layout, using the idealized assumptions of point illumination and detection size, is given by [Goodman, Introduction to Fourier Optics] :

[0068] dxdydz • EiU(x - x0, y - y0, z - z0) • Ecoi(x

[0069] Here, EiU(x, y, z) represents the spatial distributions of the illumination field and Ecol(x,y, z) the efficiency of collection. r(x, y, z) represents the reflectivity spatial distribution. While the integral represents a convolution, the measured signal is given by the absolute square of the integral.

[0070] Consequently, there is no linear operator relating the measured signal Mconfocai microscope to the reflectivity distribution r.

[0071] The Raman signal from a confocal measurement can be described by the following expression:

[0072] Mconfocal Raman(x, y, z) = J dxdydz | E (x - x0, y - y0, z - z0) |2|Ecol(x - x0, y - y0< z - z0) |2R(x,y, z).

[0073] Here, R(x, y, z) represents the spatial distribution of the Raman sources

[0074] Importantly, this expression can be separated in two parts:

[0075] MconfocalRaman (x> y, z) = J dxdydz • C(x - x0,y - y0, Z - z0) • R(x, y, z),

[0076] With C(x — x0, y — y0, z — z0) = |Eill(x - x0, y - y0, z - z0) |2|Ecol(x - x0, y — y0,z—zo) l2- We denote C the ‘probing efficiency’, as it dictates the contribution each point in the stack has to the measured signal.

[0077] The measured signal is given by a linear convolution of C with the spatial distribution of the Raman sources. Consequently, assuming C is known (or even controlled), it is possible to directly extact R providing full profiling of the probed material distribution.

[0078] The probing efficiency can often be estimated using ‘effective-medium’ approaches. For example, in a homogeneous structure, it can be directly extracted fromthe field distribution inside the stack - which is described by the effective refractive index.

[0079] A suggested measurement sequence is listed below.

[0080] Raman spectra is acquired for various z positions along the stack. Additional measurements focused above and below the region of interest are preferable as they offer significant benefits for the stability of the algorithmic deconvolution described below.

[0081] Next, the measured Raman spectra are fitted to specific line-shapes (e.g., Lorentzian, Voigt, Fano) to extract the peaks parameters (i.e., amplitude, position, width, asymmetry). Initial information can be used in the fitting process to fix some of the peaks’ parameters to extract those which vary with z, more accurately.

[0082] Figure 5 show an example of a three layers stack z profiling result. As the laser focus moves through z from one layer to the other, the relative intensities between the Raman peaks coming from each layer is changing. This difference between the intensity vs. z position can be used to extract the layers thickness.

[0083] Figure 5 illustrates a graph 60 that shows intensity variation with z of three different Raman peaks of three different curves - a first curve 61 that is related to Si, a second curve 62 that is related to a-Si, and a third curve 63 that is related to p-Si. The three peaks are coming from three different layers which are placed one on top of the other.

[0084] The extracted z dependent data is analyzed using an algorithmic analysis and a supporting simulative framework, and combined with an OCD / SI measurements as explained below.

[0085] When using notch filters to probe the low-frequency range of superlattices, the thickness of the layers can be extracted by using one of the proposed models in the literature such as Rytov’s model and Linear chain model (M. Cardona and G. Guntherodt, Light Scattering in Solids V, 1989).

[0086] According to an embodiment, the solution involves a model-based analysis

[0087] As stated, the probing distribution (C in Eq. 3) can be estimated from simple, homogeneous stacks. However, for pattered structures the field distributions (EiU, Ecol) can be highly nontrivial. A mitigation to this challenge is using a modeling engine tosimulated the illumination and collection near-field distributions, from which C is derived, and then calculating the deconvolution to extract the profding information.

[0088] Such capability can further benefit from synergy with other (mainly dimensional) metrology methods. For example, a dimensional metrology - such as Optical Critical Dimensions (OCD) - can be used to first characterize the structure layout. The resulting structure is then used for accurate simulation of the near-field distributions, from which C is found. Lastly, deconvolution is applied using the found field distributions.

[0089] Combining OCD and Spectral Interferometry - of specific benefit to the proposed approach is the addition of information obtained through Spectral Interferometry, specifically the ability of this technique to provide vertically-resolved metrology. An example of utilizing different types of measurements is illustrated in US patent application No. US2024085805 which is incorporated herein by reference.

[0090] Figure 6 illustrates an example of method 100 for optical measurement of a sample.

[0091] According to an embodiment, method 100 includes

[0092] Step 102 of illuminating, by an illumination path of a confocal optics and during a measurement iteration, the sample at an illumination angle with illuminating radiation.

[0093] Step 104 of collecting radiation resulting from the illumination of sample, by a collection path of the confocal optics, during the measurement iteration, and at a collection angle that differs from the illumination angle. The confocal optics includes a confocal filter.

[0094] Step 106 of acquiring, by a Raman detector, during the measurement iteration, a Raman spectrum based on radiation received from the confocal optics.

[0095] According to an embodiment, step 102 includes illuminating a 3-D illuminated region of the sample and step 104 includes collecting, by a collection path and from a three dimensional collection region of the sample, the radiation resulting from the illumination of sample.

[0096] According to an embodiment, a height of an overlap region between the 3-D illuminated region and the three dimensional collection region is smaller than 250 microns.

[0097] According to an embodiment, a height of an overlap region between the 3-D illuminated region and the three dimensional collection region is smaller than a depthof field associated with the confocal filter. The confocal filter is configured to strongly attenuate radiation received from outside the depth of field.

[0098] According to an embodiment, method 100 include performing multiple repetitions of steps 102, 104 and 106 to provide multiple Raman spectra. The repetitions are represented by the dashed arrow from step 106 to step 102.

[0099] According to an embodiment, the multiple measurement iterations are associated with different heights within the sample.

[0100] According to an embodiment, method 100 further includes step 110 of processing, by a processing circuit, at least some of the multiple Raman spectra.

[0101] According to an embodiment, step 110 includes step 111 of performing quantitative dimensional and material characterization of the sample based on the multiple Raman spectra.

[0102] According to an embodiment, the different heights cover an entirety of the sample.

[0103] According to an embodiment, the multiple Raman spectra are associated with different heights within the sample and step 110 includes step 112 of performing a hybrid analysis or fusing information.

[0104] According to an embodiment, step 112 includes or is preceded by receiving spectral interferometry measurement results regarding the different height.

[0105] In this case step 112 may further include step 113 of repeating, for each height of the different heights: determining, based on a Raman spectra associated with a sample region that is located at a range of heights that includes the height, a Raman based model of the sample region; and updating a spectral interferometry based model of the sample region, based on the Raman based model of the sample region.

[0106] According to an embodiment, step 112 includes step 114 of updating the Raman based model of the sample region based on the spectral interferometry based model of the sample region, following the update of the spectral interferometry based model of the sample region.

[0107] According to an embodiment step 114 may be followed by step 113 — and one or more iterations of steps 113 and 114 are executed.

[0108] According to an embodiment, during some of the multiple measurement iterations, step 102 includes illuminating the sample with illumination radiation that is of a first wavelength, and during some other of the multiple measurement iterationsstep 102 includes illuminating the sample with illumination radiation that is of a second wavelength that has a different penetration depth than the first wavelength.

[0109] According to an embodiment, the sample has a height that exceeds a penetrations depth of visible light, wherein the first wavelength is a visual light wavelength, and the second wavelength is an infrared wavelength.

[0110] According to an embodiment, the sample has a height that exceeds two microns and step 102 include illuminating the sample with infrared radiation.

[0111] According to an embodiment, method 100 include moving the sample between some of the multiple measurement iterations and some other of the multiple measurement iterations. For example the some of the multiple measurement iterations are executed while the sample is positioned at a first position in which a first end of the sample faces the confocal optics, and the some other of the multiple measurement iterations are executed while the sample is positioned at a second position in which a second end of the sample faces the confocal optics, the first end is opposite to the second end.

[0112] According to an embodiment, step 102 is preceded by positioning a movable mirror at a location that introduces an angular difference between the collection angle and the illumination angle.

[0113] According to an embodiment, the sample is a 4 3-D patterned semiconductor structure having a height that exceeds two microns.

[0114] According to an embodiment there is provided a non-transitory computer readable medium for optical measurement of a sample, the non-transitory computer readable medium stores instructions executable by a controller for executing method 100 or for controlling the execution of method 100. For example - the non- transitory computer readable medium stores instructions executable by a controller for controlling, by the controller: (a) an illuminating, by an illumination path of a confocal optics and during a measurement iteration, the sample at an illumination angle with illuminating radiation; (b) a collecting of radiation resulting from the illumination of sample, by a collection path of the confocal optics, during the measurement iteration, and at a collection angle that differs from the illumination angle; wherein the confocal optics includes a confocal filter; and (c) an acquiring, by a Raman detector, during the measurement iteration, a Raman spectrum based on radiation received from the confocal optics.

[0115] Figure 7 illustrates an example of a sample 200 that is measured at different heights - each measurement is related to a certain region.

[0116] Figure 8 illustrates an example of an optical measurement system 300 that includes confocal optics 301 that includes illumination path 302 and collection path 304. According to an embodiment the illumination path and the collection path have optical axes that differ from those illustrated in figure 8 - for example tilted optical axis of the collection path and / or normal optical axis of the illumination path.

[0117] According to an embodiment the confocal optics includes a confocal filter 303. In figure 8 and figure 4C the confocal filter is a part of the collection path 304.

[0118] System 300 is also illustrated as including controller 306, processing circuit 308, memory unit 310 configured to store instructions and / or sensed information and / or metadata and / or measurement results, and Raman detector 312.

[0119] According to an embodiment, illumination path 302 is configured to illuminate, during a measurement iteration, a sample at an illumination angle with illuminating radiation, and collection path 304 is configured to collect, during the measurement iteration, at a collection angle that differs from the illumination angle, from the sample, radiation resulting from the illumination of sample.

[0120] According to an embodiment, Raman detector 312 is configured to acquire, during the measurement iteration, a Raman spectrum based on radiation received from the confocal optics.

[0121] According to an embodiment, illumination path 302 is configured to illuminate a 3-D illuminated region of the sample, wherein collection path 304 is configured to collect from a three dimensional collection region of the sample, the radiation resulting from the illumination of sample.

[0122] According to an embodiment, a height of an overlap region between the 3-D illuminated region and the three dimensional collection region is smaller than 250 microns.

[0123] According to an embodiment, a height of an overlap region between the 3-D illuminated region and the three dimensional collection region is smaller than a depth of field associated with the confocal filter.

[0124] According to an embodiment, the optical measurement system is configured to execute multiple measurement iterations to provide multiple Raman spectra.

[0125] According to an embodiment, the multiple measurement iterations are associated with different heights within the sample.

[0126] According to an embodiment, processing circuit 308 is configured to perform quantitative dimensional and material characterization of the sample based on the multiple Raman spectra.

[0127] According to an embodiment, the different heights cover an entirety of the sample.

[0128] According to an embodiment, the multiple Raman spectra are associated with different heights within the sample, wherein processing circuit 308 further configured to: receive spectral interferometry measurement results regarding the different height; for each height of the different heights: determining, based on a Raman spectra associated with a sample region that is located at a range of heights that includes the height, a Raman based model of the sample region; and updating a spectral interferometry based model of the sample region, based on the Raman based model of the sample region.

[0129] According to an embodiment, processing circuit 308 is further configured to update the Raman based model of the sample region based on the spectral interferometry-based model of the sample region, following the update of the spectral interferometry based model of the sample region.

[0130] According to an embodiment, during some of the multiple measurement iterations the illumination radiation is of a first wavelength and during some other of the multiple measurement iterations the illumination radiation is of a second wavelength that has a different penetration depth than the first wavelength.

[0131] According to an embodiment, the sample has a height that exceeds a penetrations depth of visible light, wherein the first wavelength is a visual light wavelength, and the second wavelength is an infrared wavelength.

[0132] According to an embodiment, the sample has a height that exceeds two microns and wherein the radiation is an infrared radiation.

[0133] According to an embodiment, the optical measurement system is configured to execute a some of the multiple measurement iterations while the sample is positioned at a first position in which a first end of the sample faces the confocal optics, and to execute some other of the multiple measurement iterations when the sample is positioned at a second position in which a second end of the sample faces the confocal optics, the first end is opposite to the second end.

[0134] According to an embodiment, illumination path 302 includes a movable mirror configured to introduce an angular difference between the collection angle and the illumination angle.

[0135] According to an embodiment, the sample is a 3-D patterned semiconductor structure having a height that exceeds two microns.

[0136] The fact that this metrology approach allows profiling insight - mainly relating to dimensional characteristics of the measured structure - is highly synergic with the proposed invention which offers similar advantages for material characterization.

[0137] In the foregoing detailed description, numerous specific details are set forth to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention.

[0138] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings.

[0139] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

[0140] Because the illustrated embodiments of the present invention may for the most part, be implemented using electrooptic components known to those skilled in the art, details will not be explained in any greater extent than that considered necessary as illustrated above, for the understanding and appreciation of the underlying concepts of the present invention and in order not to obfuscate or distract from the teachings of the present invention.

[0141] Any reference in the specification to a method should be applied mutatis mutandis to a system capable of executing the method and / or should beapplied mutatis mutandis to computer readable medium that stores instructions for executing the method and / or for controlling an execution of the method.

[0142] Any reference in the specification to a system should be applied mutatis mutandis to a method that may be executed by the system and / or should be applied mutatis mutandis to computer readable medium that stores instructions for execution by the system.

[0143] In the foregoing specification, the invention has been described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made therein without departing from the broader spirit and scope of the invention as set forth in the appended claims.

[0144] Any reference to “comprising” or “Having” or “including” should be applied, mutatis mutandis to “consisting of’ and / or should be applied, mutatis mutandis to “consisting essentially of’.

[0145] Moreover, the terms “front,” “back,” “top,” “bottom,” “over,” “under” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein.

[0146] Any arrangement of components to achieve the same functionality is effectively "associated" such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality may be seen as "associated with" each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being "operably connected," or "operably coupled," to each other to achieve the desired functionality.

[0147] Furthermore, those skilled in the art will recognize that boundaries between the above-described operations merely illustrative. The multiple operations may be combined into a single operation, a single operation may be distributed in additional operations and operations may be executed at least partially overlapping in time. Moreover, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be altered in various other embodiments.

[0148] Also for example, in one embodiment, the illustrated examples may be implemented as circuitry located on a single integrated circuit or within a same device.Alternatively, the examples may be implemented as any number of separate integrated circuits or separate devices interconnected with each other in a suitable manner.

[0149] However, other modifications, variations and alternatives are also possible. The specifications and drawings are, accordingly, to be regarded in an illustrative rather than in a restrictive sense.

[0150] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word ‘comprising’ does not exclude the presence of other elements or steps then those listed in a claim. Furthermore, the terms “a” or “an,” as used herein, are defined as one or more than one. Also, the use of introductory phrases such as “at least one” and “one or more” in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim element to inventions containing only one such element, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an." The same holds true for the use of definite articles. Unless stated otherwise, terms such as “first" and “second” are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage.

[0151] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Claims

WE CLAIM1. An optical measurement system comprising: wherein the confocal optics comprises an illumination path and a collection path, wherein the illumination path is configured to illuminate, during a measurement iteration, a sample at an illumination angle with illuminating radiation, and the collection path is configured to collect, during the measurement iteration, at a collection angle that differs from the illumination angle, from the sample, radiation resulting from the illumination of sample; wherein the confocal optics comprises a confocal filter; and a Raman detector that is configured to acquire, during the measurement iteration, a Raman spectrum based on radiation received from the confocal optics.

2. The optical measurement system according to claim 1, wherein the illumination path is configured to illuminate a 3-D illuminated region of the sample, wherein the collection path is configured to collect from a three dimensional collection region of the sample, the radiation resulting from the illumination of sample.

3. The optical measurement system according to claim 2, wherein a height of an overlap region between the 3-D illuminated region and the three dimensional collection region is smaller than 250 microns.

4. The optical measurement system according to claim 2, wherein a height of an overlap region between the 3-D illuminated region and the three dimensional collection region is smaller than a depth of field associated with the confocal filter.

5. The optical measurement system according to claim 1, wherein the optical measurement system is configured to execute multiple measurement iterations to provide multiple Raman spectra.

6. The optical measurement system according to claim 5, wherein the multiple measurement iterations are associated with different heights within the sample.

7. The optical measurement system according to claim 5, wherein the optical measurement system further comprises a processing circuit.

8. The optical measurement system according to claim 7, wherein the processing circuit is configured to perform quantitative dimensional and material characterization of the sample based on the multiple Raman spectra.

9. The optical measurement system according to claim 8, wherein the different heights cover an entirety of the sample.

10. The optical measurement system according to claim 7, wherein the multiple Raman spectra are associated with different heights within the sample, wherein the processing circuit further configured to: receive spectral interferometry measurement results regarding the different height; for each height of the different heights: determining, based on a Raman spectra associated with a sample region that is located at a range of heights that comprises the height, a Raman based model of the sample region; and updating a spectral interferometry-based model of the sample region, based on the Raman based model of the sample region.

11. The optical measurement system according to claim 10, wherein the processing circuit is further configured to update the Raman based model of the sample region based on the spectral interferometry-based model of the sample region, following the update of the spectral interferometry based model of the sample region.

12. The optical measurement system according to claim 5, wherein during some of the multiple measurement iterations the illumination radiation is of a first wavelength and during some other of the multiple measurement iterations the illumination radiation is of a second wavelength that has a different penetration depth than the first wavelength.

13. The optical measurement system according to claim 12, wherein the sample has a height that exceeds a penetrations depth of visible light, wherein the first wavelength is a visual light wavelength, and the second wavelength is an infrared wavelength.

14. The optical measurement system according to claim 5, wherein the sample has a height that exceeds two microns and wherein the radiation is an infrared radiation.

15. The optical measurement system according to claim 5, wherein the optical measurement system is configured to execute a some of the multiple measurement iterations while the sample is positioned at a first position in which a first end of the sample faces the confocal optics, and to execute some other of the multiple measurement iterations when the sample is positioned at a second position in which a second end of the sample faces the confocal optics, the first end is opposite to the second end.

16. The optical measurement system according to claim 1, wherein the illumination path comprises a movable mirror configured to introduce an angular difference between the collection angle and the illumination angle.

17. The optical measurement system according to claim 1, wherein the sample is a 3-D patterned semiconductor structure having a height that exceeds two microns.

18. A method for optical measurement of a sample, the method comprising: illuminating, by an illumination path of a confocal optics and during a measurement iteration, the sample at an illumination angle with illuminating radiation; collecting radiation resulting from the illumination of sample, by a collection path of the confocal optics, during the measurement iteration, and at a collection angle that differs from the illumination angle; wherein the confocal optics comprises a confocal filter; and acquiring, by a Raman detector, during the measurement iteration, a Raman spectrum based on radiation received from the confocal optics.

19. The method for optical measurement of a sample, wherein the sample is a Si\SiGe multi-layer 3D-DRAM structure.

20. A non-transitory computer readable medium for optical measurement of a sample, the non-transitory computer readable medium stores instructions executable by a controller for: controlling, by the controller: an illuminating, by an illumination path of a confocal optics and during a measurement iteration, the sample at an illumination angle with illuminating radiation; a collecting of radiation resulting from the illumination of sample, by a collection path of the confocal optics, during the measurement iteration, and at a collection angle that differs from the illumination angle; wherein the confocal optics comprises a confocal filter; and an acquiring, by a Raman detector, during the measurement iteration, a Raman spectrum based on radiation received from the confocal optics.

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