Method of performing x-ray spectroscopy material analysis, system for evaluating region of sample, and non-transitory computer-readable memory

Abstract

A method for X-ray spectral material analysis of a region of interest within a cross-section of a sample using an evaluation system comprising a focused ion beam (FIB) column, a scanning electron microscope (SEM) column, and an X-ray detector, comprising: forming a sheet having first and second opposing side surfaces in the sample by milling first and second trenches in the sample using the FIB column to expose first and second side surfaces of a sheet, respectively; depositing a background material in the second trench, wherein the background material is selected such that it does not contain any chemical elements desired to be present within the region of interest of the sample; generating a charged particle beam using the SEM column and scanning the region of interest across the first side surface of the sheet such that the charged particle beam collides with the first side surface of the sheet at a non-perpendicular angle; and detecting the generated X-ray while scanning the region of interest with the charged particle beam.

Description

[Technical Field]

[0001] This application claims priority to U.S. Application No. 17 / 320,526, filed May 14, 2021. The disclosure of that application is incorporated herein by reference in its entirety for all purposes. [Previous Technology]

[0002] In the study of electronic materials and the processes used to manufacture such materials into electronic structures, samples of the electronic structures can be used for microscopic examination for purposes such as fault analysis and device verification. For example, samples of electronic structures, such as silicon wafers, can be analyzed using a scanning electron microscope (SEM) to study specific characteristic features within the wafer. These characteristic features may include fabricated circuitry and any defects formed during the manufacturing process. The electron microscope is one of the most useful pieces of equipment for analyzing the microstructure of semiconductor devices.

[0003] When a sample is examined using an electron beam from a SEM tool, X-rays are produced as a result of radiation when electrons strike the sample surface. One specific application where SEM tools can be used is for material analysis of the sample. For example, SEM tools can be used for X-ray imaging material analysis by bombarding the sample with a high-energy electron beam to ensure a strong signal. High-energy electron beams produce a relatively large interaction volume in samples from which X-rays can be emitted; however, this results in relatively poor spatial resolution for material analysis steps. While lower-energy electron beams can be used in some cases, some material analysis applications require a strong signal generated from a higher-energy beam.

[0004] Therefore, improvements to X-ray imaging are needed. [Summary of the Invention]

[0005] Some embodiments of this application relate to improved methods and techniques for performing X-ray imaging in a cross-section of a sample. Embodiments may include one or more initial steps of milling the sample to form a thin sheet. For example, milling may be performed using a focused ion beam column in a focused ion beam scanning electron microscope (FIB-SEM) tool. After the sample is milled to produce a sheet, background material may be deposited on one side of the sheet. Subsequently, as part of a materials analysis step, the sample may be bombarded with an electron beam generated by, for example, a scanning electron microscope column of a FIB-SEM tool. The electron beam may be guided onto the sample at a non-perpendicular angle (e.g., 45 degrees) on one side of the sheet, opposite the side where the background material is deposited. X-rays generated by the collision of the electron beam and the sample can be collected while the sample is bombarded with electrons, and the collected X-rays can be analyzed to determine the material present in the sample region being evaluated. In this way, some embodiments of this application enable high-resolution materials analysis of samples using standard FIB-SEM tools without removing the sheet and analyzing the sheet using a separate evaluation tool.

[0006] In some embodiments, a method is provided for X-ray spectroscopic material analysis of a region of interest within a cross-section of a sample using an evaluation system comprising a focused ion beam (FIB) column, a scanning electron microscope (SEM) column, and an X-ray detector. The method may include: forming a sheet having first and second opposing side surfaces in the sample by milling first and second trenches in the sample using the FIB column to expose first and second side surfaces of the sheet, respectively; depositing a background material in the second trench, wherein the background material is selected such that it does not contain any chemical elements desired within the region of interest of the sample; generating a charged particle beam using the SEM column and scanning the region of interest across the first side surface of the sheet such that the charged particle beam collides with the first side surface of the sheet at a non-perpendicular angle; and detecting the generated X-rays while scanning the region of interest with the charged particle beam.

[0007] Various implementations of the embodiments described herein may include one or more of the following features: A two-dimensional image of the scanned region of interest is generated based on the detected X-rays. The first and second side surfaces of the sheet may be substantially perpendicular, and a charged particle beam may scan over the region of interest on the substantially perpendicular first side surface of the sheet. Background material may be deposited in trenches at a level below the interaction region between the scanning charged particle beam and the sheet. SEM pillars and FIB pillars may be part of a SEM-FIB evaluation tool. The charged particle beam may be guided to collide with the first surface of the sheet at a 45-degree angle. The sample may be a semiconductor wafer.

[0008] Some embodiments relate to a non-transitory computer-readable medium storing instructions for performing X-ray spectral surface material analysis on a region of a sample according to any of the methods described above or herein. For example, by: forming a sheet having first and second opposing side surfaces in a sample by milling first and second trenches in the sample using a FIB column to expose first and second side surfaces of the sheet, respectively; depositing a background material in the second trench, wherein the background material is selected such that it does not include any chemical elements within known materials desired to be within the region of interest of the sample; generating a charged particle beam using a SEM column and scanning the charged particle beam across the region of interest on the first side surface of the sheet such that the charged particle beam collides with the first side surface of the sheet at a non-perpendicular angle; and detecting the generated X-rays while scanning the region of interest with the charged particle beam.

[0009] Some embodiments relate to systems for X-ray spectral surface material analysis of regions of a sample according to any of the methods described above or herein. For example, the system may include: a vacuum chamber; a sample support configured to hold the sample within the vacuum chamber during a sample evaluation process; a focusing particle beam (FIB) column configured to guide a charged particle beam toward the sample into the vacuum chamber; a scanning electron microscope (SEM) column configured to guide a charged particle beam toward the sample into the vacuum chamber; a detector configured to detect X-rays generated by collisions between the charged particle beam and the sample; and a processor and memory coupled to the processor. The memory may include a plurality of computer-readable instructions that, when executed by a processor, cause the system to perform the following steps: forming a sheet in the sample having first and second opposing side surfaces by milling first and second trenches in the sample using FIB pillars to expose first and second side surfaces of the sheet, respectively; depositing a background material in the second trench, wherein the background material is selected such that it does not contain any chemical elements desired to be within the region of interest of the sample; generating a charged particle beam using SEM pillars and scanning the charged particle beam across the region of interest on the first side surface of the sheet such that the charged particle beam collides with the first side surface of the sheet at a non-perpendicular angle; and detecting the generated X-rays while scanning the region of interest with the charged particle beam.

[0010] To better understand the nature and advantages of this application, reference should be made to the following description and figures. However, it should be understood that each figure is provided for illustrative purposes only and is not intended to be a definition of limitation on the scope of this application. Furthermore, as a general rule, and unless clearly contrary to the description, if elements in different figures use the same element symbol, such elements are generally identical or at least similar in function or purpose.

Implementation Method

[0019] Embodiments of this invention implement an improved X-ray imaging technique for material analysis of samples. Some embodiments enable high-resolution material analysis of samples using standard FIB-SEM tools without removing the sheet formed on the sample and without transferring the sheet to a separate evaluation tool for analysis. Exemplary sample evaluation tool

[0020] To better understand this case, reference is first made to Figure 1, which is a simplified schematic diagram of a sample evaluation system 100 according to some embodiments of this case. Among other operations, the sample evaluation system 100 can be used, in particular, for defect inspection and analysis (including X-ray imaging) of structures formed on samples (such as semiconductor wafers).

[0021] System 100 may include a vacuum chamber 110 and a scanning electron microscope (SEM) column 120 and a focused ion beam (FIB) column 130. A support element 140 (e.g., a sample support base) may support a sample 145 (e.g., a semiconductor wafer) within the chamber 110 during processing operations in which the sample 145 (sometimes referred to herein as "object" or "sample") is subjected to a beam of charged particles from either the FIB column or the SEM column. The support element 140 may also be able to move the sample within the vacuum chamber 110 between the fields of view of the two columns 120 and 130 as needed for processing.

[0022] The SEM column 120 and FIB column 130 are connected to the vacuum chamber 110 so that a beam of charged particles generated by either of the charged particle columns propagates through the vacuum environment formed within the vacuum chamber 110 before impacting the sample 145. The SEM column 120 can generate an image of a portion of the sample 145 by irradiating the sample with a beam of charged particles 125 (e.g., an electron beam 125), detecting particles emitted attribution to the irradiation, and generating a charged particle image based on the detected particles. For this purpose, the system 100 may include a detector 150, such as an energy-dispersive X-ray spectroscopy (EDX) detector or a wavelength-dispersive X-ray spectroscopy (WDX) detector, which can be used to determine the composition of one or more microstructures in the sample 145. EDX detector 150 can collect X-ray photons emitted due to electron beam 125 irradiating the structure, and EDX detector 150 can include an energy analyzer for determining the energy of the photons detected by the detector, thereby enabling system 100 to characterize the elements from which the X-ray photons are emitted.

[0023] The FIB column 130 can be used to mill the sample 145 (e.g., drill holes in the sample 145) by irradiating the sample with one or more beams of charged particles to form a cross section, and can also smooth the cross section. The cross section may include different materials that can be subsequently analyzed by the SEM column 120 at different locations along the cross section.

[0024] Particle imaging and milling processes typically involve scanning a beam of charged particles back and forth at a constant rate over a specific area of ​​the imaged or milled sample (e.g., using a raster scan pattern). One or more lenses (not shown) coupled to each charged particle column can implement a scanning pattern as known to those skilled in the art. The scanned area is typically a very small portion of the overall area of ​​the sample. For example, the sample may be a semiconductor wafer with a diameter of 100 mm or 300 mm, and each scanned area on the wafer may be a rectangular area with a width and / or length measured in micrometers or tens of micrometers.

[0025] System 100 may include one or more controllers 160, such as one or more processors or other hardware units, which can control the operation of system 100 by executing computer instructions stored in one or more computer-readable memories 170, as will be known to those skilled in the art. For example, computer-readable memories may include solid-state memories (such as random access memory (RAM) and / or read-only memory (ROM), which may be programmable, flash-updatable, and / or the like), disk drives, optical storage devices, or similar non-transitory computer-readable storage media.

[0026] Although not illustrated in Figure 1, the sample evaluation system 100 may include several additional components, including but not limited to one or more gas nozzles for delivering process gas to chamber 110, vacuum valves and other valves for controlling the pressure within chamber 110, and one or more lenses for guiding a beam of charged particles (as described above), and other components.

[0027] In some embodiments, to evaluate sample 145, the sample can be milled using a focused ion beam generated by charged particle column 130 to form a thin portion of the sample with grooves on opposite sides. As part of a materials analysis step described in more detail below, the thin portion of the sample (sometimes referred to herein as a sheet) can then be exposed at a non-perpendicular angle (e.g., in tilted operating mode) to an electron beam generated by SEM column 120. To enable the SEM column 120 to tilt, the column cap (not shown) may have a tapered shape, which allows the column to be positioned very close to sample 145 without the column cap interfering with the sample. Challenges of Cross-Sectional X-ray Analysis

[0028] Figure 2 is an example of an energy-dispersive X-ray spectrum 200 of a sample material based on X-ray emission collected by system 100. X-ray emission can be detected by the EDX detector 150 of system 100 when a solid target is bombarded by an electron beam. Some of the detected X-rays are characteristic X-rays, representing X-ray beams emitted after the inner shells of atoms in the sample material are ionized by bombarded electrons, and then the outer shell electrons fill the now empty inner shells. Characteristic X-rays have specific energies unique to the sample material, where the specific energy is equal to the energy difference between the two shells in which the electrons "jump". As an example, the various intensity peaks at different energy levels shown in Figure 200 indicate different chemical elements in the analyzed sample and demonstrate that the sample includes at least iron (Fe), chromium (Cr), carbon (C), molybdenum (Mo), nickel (Ni), and silicon (Si).

[0029] Figure 3 is a simplified cross-sectional view of sample 300, which can be processed to produce a view similar to Figure 200 shown in Figure 2. As shown in Figure 3, grooves 310 have been milled into the sample, exposing a cross-section of the sample including surface 320. During the material analysis step, surface 320 can be exposed to a high-energy electron beam 330 at a non-perpendicular angle, thereby creating a relatively large interaction volume 340. X-rays 350 can be emitted from the sample from various points within the interaction volume 340. The emitted X-rays can be detected by an evaluation tool such as system 100 to determine the type of material from which the X-rays are emitted. However, due to the size of the interaction volume 340, the resolution of the material analysis step is insufficient for some applications. That is, the evaluation system cannot determine where the X-rays are emitted within the interaction volume and therefore can only conclude that the material identified during the evaluation process is located somewhere within a relatively large interaction volume.

[0030] Furthermore, in some cases, the collision between the electron beam 330 and the sample can generate backscattered electrons 360, which can collide with the sample surface within the trench 310, thereby creating a smaller second interaction volume 342 within the trench. X-rays 352 can be generated from within the interaction volume 342 and detected by the evaluation system. However, in such cases, the detected X-ray signal represents a mixture of X-rays 350 and 352. Therefore, the evaluation system cannot determine whether any material identified by the X-ray signal originates from the portion of sample 300 within the interaction volume 340 or from the portion of sample 300 within the interaction volume 342.

[0031] Figure 4 is a simplified cross-sectional view of a sample 400 that can withstand an X-ray material analysis process, illustrating a technique that can reduce the interaction volume and provide improved material analysis results. As shown in Figure 4, the first and second trenches 410, 412 have been milled in the sample to form a thin portion 420 (referred to as a sheet 420) between the two trenches. During the material analysis step, the surface 422 of the sheet 420 can be exposed to a high-energy electron beam 430 at a non-perpendicular angle. The electron beam generates an interaction volume 440 within the sheet 420. X-rays 450 can exit from various points within the interaction volume 440 from the sample.

[0032] Because the sheet 420 is relatively thin, even when the electron beam 430 is generated at the same relatively high energy level as the electron beam 230 discussed above with respect to Figure 2, the interaction volume 440 is much smaller than the interaction volume 340. Compared with the process described with respect to Figure 2, the reduced interaction volume enables improved X-ray material analysis results. However, because the sheet 420 is relatively thin, some portions of the electron beam 430 can completely penetrate the sheet, so that the beam portion 432 impacts the bottom surface 414 of the trench 412, generating a second interaction volume 442 below the surface 414. X-rays 452 can therefore also be generated from the second interaction volume 442. In addition, as discussed above with respect to Figure 3, in some cases, X-rays 454 can be generated by the collision of backscattered electrons (not shown in Figure 4) with the sample surface within the trench 410, thereby generating a third interaction volume 444.

[0033] X-rays 450 and 452 (and, if present, X-ray 454) can be detected by an evaluation tool such as system 100 to determine the type of material from which the X-rays are emitted. However, the detected X-ray signals represent all generated X-rays 450 and 452 (and X-ray 454, if present) mixed together. Therefore, the evaluation system cannot determine whether any material identified by the X-ray signals originates from the portion of sample 400 within the interaction volume 440, or from the portion of sample 400 within the interaction volume 442 (or, when X-ray 454 is part of the signal, the portion of sample 400 within the interaction volume 444). X-ray imaging of cross-sections is performed according to this invention.

[0034] Embodiments of this invention provide an improved method for performing X-ray imaging in a cross-section of a sample within a region of interest when the material in that region is previously known. For better illustration of the embodiments, reference is made to Figures 6A, 6B, and 5, wherein Figure 5 is a simplified flowchart of the steps associated with method 500 according to some embodiments of this invention, and Figures 6A and 6B are simplified cross-sectional views of sample 600 at different stages of the X-ray material analysis process according to method 500. Method 500 is particularly useful for X-ray material analysis of samples in which the material is known, but can be used for any sample, provided that background material (as described below) not known to be present in the portion of the sample being analyzed can be selected.

[0035] Referring first to Figure 6A, method 500 includes forming a first groove 610 (Figure 5, block 510) within a sample 600. The groove 610 may be formed by milling the sample 600 in a region 605 in which a cross-section of the sample 600 will be imaged. Milling may be accomplished, for example, by positioning the sample in the evaluation tool 100 and moving the sample within the field of view of the FIB pillar 130.

[0036] Next, a second trench 612 (Figure 5, block 520) adjacent to the first trench 610 may be formed in region 605. The trench 612 may be formed by milling the sample 600 with the evaluation tool 100 in the same general manner as forming the trench 610. The trench 612 may be spaced apart from the trench 610 to form a thin region 620 in region 605 in which a cross-section of the sample 600 will be performed. The thin region 620, sometimes referred to herein as a sheet 620, includes a region of interest (ROI) in which X-ray material analysis of the cross-section of region 605 will be performed. The sheet 620 may include first and second opposing surfaces 622, 624 facing the first and second trenches 610, 612, respectively.

[0037] Next, prior to performing X-ray imaging, a layer of background material 614 (Figure 5, block 530) is deposited within trench 612. Since the material within sheet 620 is known, the background material should be selected such that it does not contain any of the same chemical elements found within the sheet. For example, if the sheet is known to consist of alternating layers of silicon oxide and silicon nitride, the background material should be selected such that it does not contain any silicon, nitrogen, or oxygen. As another example, if the sheet is known to consist of silicon oxide, polycrystalline silicon, and tungsten, the background material should be selected such that it does not contain any silicon, oxygen, or tungsten. For either example, the background material may be gold or copper. Furthermore, the background material 614 should be deposited within trench 612 to a sufficient depth to prevent the electron beam portion 632 from reaching the surface of sample 600 located beneath the background material 614. The precise depth will depend in particular on the thickness of sheet 620, the material within the sheet, and the energy of electron beam 630, which can be determined by those skilled in the art through experimentation or simulation. In some embodiments where the X-ray detector is located opposite the tilted SEM column, the background material 614 may be deposited at a height below the interaction region in the sheet (i.e., the region on the sheet to which the electron beam is guided during X-ray imaging). Otherwise, in such embodiments, the background material would interfere with the X-rays generated within the sheet, forcing some X-ray emission through the background material before reaching the detector, resulting in poor X-ray signal quality.

[0038] Referring now to Figure 6B, after the background material 614 has been deposited within the trench 612, an electron beam 630 may scan through a portion of the sheet (e.g., the region of interest) (Figure 5, block 540). The electron beam may advantageously scan across the sheet 620 with a tilted SEM column such that the electron beam 630 collides with the sheet 620 at a non-perpendicular angle, for example, 45 degrees relative to the upper surface of the sample (or alternatively expressed as 45 degrees relative to the vertical sidewall surface of the sheet).

[0039] During the scanning process, electrons generated from the interaction region 640 within the sample can be collected (block 550). Because the sheet 620 is relatively thin and the electron beam 630 can be a relatively high-energy beam, a portion 632 of the electron beam can completely penetrate the sheet 620 and collide with the deposited background material 614 in the second interaction region 642. Therefore, the X-rays collected during step 550 may include X-rays 650 generated from the sheet (interaction region 640) and X-rays 652 generated from the background material (second interaction region 642). Since the background material is known and consists entirely of chemical elements not within the sheet, characteristic X-ray signals indicating the background material can be ignored. Then, characteristic X-ray signals representing known chemical elements within the sheet can be used in the material analysis step to generate a high-resolution material analysis image of the scanned area (Figure 5, block 560).

[0040] As described above with respect to Figures 3 and 4, in certain circumstances, backscattered electrons may generate additional interaction volumes within trench 610, which could potentially generate additional X-rays that would otherwise be part of the detected X-ray signal. To address this possibility, some embodiments deposit background material 614 in both trench 610 and trench 612 (e.g., in step 530), as shown in Figure 6C. Thus, backscattered electrons 660 that would otherwise collide with surfaces within trench 610 may instead collide with background material 614 deposited within trench 610 in a third interaction region 644. In these embodiments, the X-rays collected during step 550 may include X-rays 650 generated from a sheet within interaction region 640, X-rays 652 generated from background material within second interaction region 642, and X-rays 654 generated from background material within third interaction region 644. Since the background material is known and consists entirely of chemical elements not present in the sheet, characteristic X-ray signals indicating the background material can be ignored as described above.

[0041] As described above, embodiments of this invention enable high-resolution material analysis in the cross-section of a sample without bending or cutting thin sections as required by some other known techniques. Examples of regions of interest.

[0042] To further illustrate exemplary regions of interest (ROIs) that can be analyzed according to method 500, reference is made to Figure 7, a simplified illustration of a semiconductor wafer 700. Figure 7 includes a top view of the wafer 700 and two enlarged views of specific portions of the wafer 700. The wafer 700 may be, for example, a 200 mm or 300 mm semiconductor wafer and may include a plurality of integrated circuits 710 (52 in the illustrated example) formed thereon. The integrated circuits 710 may be in an intermediate stage of manufacturing, and the X-ray analysis techniques described herein can be used to evaluate and analyze one or more regions of interest (ROIs) 720 of the integrated circuits. For example, an expanded view of Figure 7 illustrates multiple ROIs 720 of one of the integrated circuits 710 that can be evaluated and analyzed according to the techniques described herein. Expanded view B illustrates one of the ROIs 720 that include several different types of structures.

[0043] Within each ROI 720, the structure and different chemical elements within the ROI are known, enabling the analysis of the ROI using the cross-sectional X-ray imaging techniques described herein. Therefore, some embodiments may analyze and evaluate each ROI 720 by forming a sheet 730 (as shown in enlarged view B) between the first and second trenches 732, 734 and sequentially scanning the cross-sectional region of the sheet back and forth using an electron beam according to a grating pattern. During each scan, X-rays can be collected and analyzed to determine the chemical elements present at each location in the scanned pattern.

[0044] For illustrative purposes, the foregoing description uses specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to those skilled in the art that specific details are not required to practice the described embodiments. For example, while the above embodiments guide the electron beam to the sheet surface at a 45-degree angle, any non-perpendicular angle may be used in other embodiments. For instance, in a particular SEM-FIB tool, the SEM column may be adjusted to any angle between 45 and 90 degrees (referring to the upper surface of the sample), and therefore a non-perpendicular angle between 45 and 90 degrees may be used. In other tools, the SEM column may be adjusted to an angle less than 45 degrees, and a non-perpendicular angle less than 45 degrees may be used. Furthermore, while the above examples discuss the formation of the first trench before the second trench, the order in which the trenches are milled is not important, and in some embodiments, the second trench may be formed before the first trench. Furthermore, Figures 6A and 6B depict the trench 610 as having vertical sidewalls and angled sidewalls opposite the vertical sidewalls. The sidewalls, spaced apart from and opposite to the sheets in each of the grooves 610 and 612, are not limited to the details shown in Figures 1 and 2, and may be generally vertical, angled, or have any other suitable profile.

[0045] Therefore, for purposes of illustration and description, the foregoing description of the specific embodiments described herein is presented. The foregoing description is not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. Furthermore, while different embodiments of the present invention have been disclosed above, the specific details of particular embodiments may be combined in any suitable manner without departing from the spirit and scope of the embodiments of the present invention. Moreover, it will be apparent to those skilled in the art that many modifications and variations are possible in light of the foregoing teachings.

[0046] To the extent that most of the embodiments shown in this patent application can be implemented using electronic components and circuits known to those skilled in the art, the explanation of such details will not be more extensive than the above-deemed necessary in order to understand and comprehend the basic concepts of this patent application and in order not to confuse or distract from the teachings of this application. [Simplified Explanation of the Diagram]

[0011] Figure 1 is a simplified diagram of a sample evaluation system according to some embodiments of this case.

[0012] Figure 2 is an example of an energy dispersive X-ray spectrum of a sample material according to some embodiments;

[0013] Figure 3 is a simplified cross-sectional view of a sample that can undergo previously known X-ray material analysis processes;

[0014] Figure 4 is a simplified cross-sectional view of another sample that can undergo X-ray material analysis;

[0015] Figure 5 is a simplified flowchart of the steps related to the X-ray imaging material analysis process according to some embodiments;

[0016] Figures 6A and 6B are simplified cross-sectional views of a sample capable of undergoing X-ray material analysis according to an embodiment of the present invention;

[0017] Figure 6C is a simplified cross-sectional view of a sample capable of undergoing X-ray material analysis according to some additional embodiments of the present invention;

[0018] Figure 7 is a simplified diagram of a region on a semiconductor wafer that can be analyzed according to some embodiments. [Biomaterial Storage]

[0048] Domestic storage information (please note in order of storage institution, date, and number): None. International storage information (please note in order of storage country, institution, date, and number): None.

Claims

1. A method for X-ray spectral material analysis of a region of interest within a cross-section of a sample using an evaluation system comprising a focused ion beam (FIB) column, a scanning electron microscope (SEM) column, and an X-ray detector, the method comprising the steps of: forming a sheet having first and second opposing side surfaces in the sample by milling first and second trenches in the sample using the FIB column to expose first and second side surfaces of the sheet, respectively; depositing a background material in the second trench, wherein the background material is selected such that it does not contain any chemical elements desired to be present within the region of interest of the sample; generating a charged particle beam using the SEM column and scanning the charged particle beam across a region of interest on the first side surface of the sheet such that the charged particle beam collides with the first side surface of the sheet at a non-perpendicular angle; and detecting the generated X-ray while scanning the region of interest with the charged particle beam.

2. The method as described in claim 1 further includes the step of generating a two-dimensional image of the scanned region of interest based on the detected X-ray.

3. The method as described in claim 1, wherein the first and second side surfaces of the sheet may be substantially perpendicular, and the charged particle beam scans over a region of interest on the substantially perpendicular first side surface of the sheet.

4. The method as described in claim 1, wherein the background material is deposited in the trench at a quasi-position of an interaction region between the charged particle beam below the scan and the sheet.

5. The method as described in claim 1, wherein the SEM column and FIB column are part of a SEM-FIB evaluation tool.

6. The method as described in claim 1, wherein the charged particle beam is guided to collide with the first surface of the sheet at a 45-degree angle.

7. The method as described in any one of claims 1 to 6, wherein the sample comprises a semiconductor wafer.

8. A system for evaluating a region of a sample, the system comprising: a vacuum chamber; a sample support configured to hold a sample within the vacuum chamber during a sample evaluation process; a focused ion beam (FIB) column configured to guide a charged particle beam toward the sample into the vacuum chamber; a scanning electron microscope (SEM) column configured to guide a charged particle beam toward the sample into the vacuum chamber; a detector configured to detect X-rays generated by the collision between the charged particle beam and the sample; a processor and a memory coupled to the processor, the memory including a plurality of computer-readable instructions that, when executed by the processor, cause the system to: form a sheet having first and second opposing side surfaces in the sample by milling first and second trenches in the sample using the FIB column to expose first and second side surfaces of the sheet, respectively; Background material is deposited in the second trench, wherein the background material is selected such that it does not contain any chemical elements desired to be within the region of interest of the sample; a charged particle beam is generated using the SEM column and scanned across a region of interest on the first side surface of the sheet such that the charged particle beam collides with the first side surface of the sheet at a non-perpendicular angle; and the generated X-rays are detected while the region of interest is scanned with the charged particle beam.

9. The system as described in claim 8, further comprising: generating a two-dimensional image of the scanned region of interest based on the detected X-ray.

10. The system as claimed in claim 8, wherein the first and second side surfaces of the sheet may be substantially vertical, and the charged particle beam scans over a region of interest on the substantially vertical first side surface of the sheet.

11. The system as described in claim 8, wherein the SEM column and FIB column are part of a SEM-FIB evaluation tool.

12. The system as claimed in claim 8, wherein the charged particle beam can be guided to collide with the first surface of the sheet at a 45-degree angle.

13. The system as described in claim 8, wherein the sample comprises a semiconductor wafer.

14. The system as described in any one of claims 8 to 13, wherein the background material may be deposited in the trench at a quasi-position of an interaction region between the charged particle beam below the scan and the sheet.

15. A non-transitory computer-readable memory storing a plurality of computer-readable instructions for evaluating a sample region by: forming a sheet having first and second opposing side surfaces in the sample by milling first and second trenches in the sample using the FIB column to expose the first and second side surfaces of the sheet, respectively; depositing a background material in the second trench, wherein the background material is selected such that it does not contain any chemical elements desired within the region of interest in the sample; generating a charged particle beam using the SEM column and scanning the charged particle beam across a region of interest on the first side surface of the sheet such that the charged particle beam collides with the first side surface of the sheet at a non-perpendicular angle; and detecting the generated X-rays while scanning the region of interest with the charged particle beam.

16. The non-transitory computer-readable memory as described in claim 15, wherein the computer-readable instructions for evaluating a region of a sample further include instructions for generating a two-dimensional image of the scanned region of interest based on detected X-rays.

17. The non-transitory computer-readable memory as described in claim 15, wherein the first and second side surfaces of the sheet are substantially perpendicular, and the charged particle beam scans over a region of interest on the substantially perpendicular first side surface of the sheet.

18. The non-transitory computer-readable memory as described in claim 15, wherein the background material is deposited in the trench at a quasi-position of an interaction region between the charged particle beam below the scan and the sheet.

19. The method of claim 1, the non-transitory computer-readable memory of claim 15, wherein the computer-readable instructions for evaluating a region of a sample further include instructions for depositing background material in a first trench prior to scanning the charged particle beam through the region of interest.

20. A non-transitory computer-readable memory as described in any one of claims 15 to 19, wherein the computer-readable instructions for evaluating a region of a sample further include instructions for guiding the beam of charged particles to collide with the first surface of the sheet at a 45-degree angle.

Images