Method for obtaining a sequence of cross-section images of a measurement site of a wafer parallel to one another, computer program product and one-chamber system

Abstract

A method for obtaining a sequence of multiple parallel cross-sectional images of a measurement region on a wafer, the method comprising the steps of: 1a) providing a focused ion beam (FIB) column and a charged particle beam (CPB) imaging column in an overlapping configuration, wherein an FIB optical axis of the FIB column and a CPB optical axis of the CPB imaging column coincide on a wafer surface, and a configuration angle GFE is formed between the FIB optical axis and the CPB optical axis; 1b) in the overlapping configuration, using the FIB column to remove the measurement region of the wafer. 1c) To form a new profile available for imaging at the measurement site; 1d) To shorten a working distance between the CPB imaging post and the wafer surface in a direction along the axis of the CPB imaging post; 1e) To image the new profile at the measurement site of the wafer with the CPB imaging post at the shortened working distance and therefore not in the overlapping configuration; 1f) To increase the working distance between the CPB imaging post and the wafer surface in the direction along the axis of the CPB imaging post until the overlapping configuration is achieved.

Description

Technical Field

[0001] The present invention relates to a dual beam device and three-dimensional circuit pattern inspection by cross-sectioning of an inspection volume. Prior Art

[0002] Semiconductor structures are among the most complex man-made structures and are susceptible to various defects. These defects are currently identified using quantitative 3D metrology, defect detection, or defect verification systems. Semiconductor structures are manufactured based on conventional knowledge. They are fabricated from sequential layers parallel to the substrate. For example, in logic-type samples, metal lines run parallel within the metal layers or in HAR (high aspect ratio) structures, and metal vias run perpendicular to the metal layers. The angles between metal lines in different layers are either 0° or 90°. On the other hand, VNAND-type structures are known to have, on average, a circular cross-section.

[0003] A semiconductor wafer has a diameter of, for example, 300 mm and consists of multiple locations (so-called dies), each of which contains at least one integrated circuit pattern, such as for a memory chip or a processor chip. During manufacturing, the semiconductor wafer undergoes approximately 1,000 process steps, resulting in approximately 100 or more parallel layers within the semiconductor wafer, including transistor layers, interposers, and interconnect layers, as well as multiple 3D memory cell arrays in memory devices. The size, shape, and layout of semiconductor structures and patterns are influenced by various factors. Etching and deposition are currently the key processes in the manufacture of 3D memory devices. Other process steps involved, such as lithography and implantation, also influence the characteristics of the IC components.

[0004] The aspect ratio and number of layers in integrated circuits continue to increase, and structures are evolving into the third (vertical) dimension. Currently, memory stack heights exceed tens of microns. In contrast, feature sizes are shrinking. Minimum feature sizes, or critical dimensions, are below 10nm, such as 7nm or 5nm, and in the near future, feature sizes will approach below 3nm. While the complexity and size of semiconductor structures are growing into the third dimension, the lateral dimensions of integrated semiconductor structures are shrinking. Consequently, measuring the shape, size, orientation, and overlay of 3D features and patterns with high precision is becoming increasingly challenging.

[0005] The inspection and 3D analysis of integrated semiconductor circuits on wafers are becoming increasingly challenging as the requirements for three-dimensional resolution in charged-particle imaging systems continue to increase. The lateral measurement resolution of charged-particle systems is typically limited by the sampling grating at each image point, or the dwell time per pixel on the sample, and the charged-particle beam diameter. The sampling grating resolution can be set within the imaging system and adapted to the charged-particle beam diameter at the sample. Typical grating resolutions are 2 nm or less, but in principle, the grating resolution limit can be lowered without physical limitations. The charged-particle beam diameter has a finite size, depending on the beam's operating conditions and lensing. Beam resolution is limited to approximately half the beam diameter. Resolutions below 2 nm, for example, can be achieved, even below 1 nm.

[0006] A common method for generating nanoscale 3D tomographic data from semiconductor samples is the so-called slice and image method, which is exemplified by dual-beam systems. These systems employ a charged-particle beam column for imaging and a FIB column for milling, operating at a so-called coincidence point, meaning that the charged-particle beam optical axis, the FIB optical axis, and the sample surface meet (coincide) at a single point. This is advantageous because it ensures that imaging is performed precisely at the sample point affected by milling.

[0007] For example, the slice and image method is described in WO 2020 / 244795 A1. According to the method of WO 2020 / 244795 A1, a 3D volumetric examination is obtained on an inspection sample extracted from a semiconductor wafer. A disadvantage of this method is that the wafer must be destroyed to obtain the inspection sample in bulk. On the other hand, an advantage of this method is that the working distance between a charged particle imaging device, such as a scanning electron microscope (SEM), or more precisely, its column, and the sample or wafer to be imaged can be relatively small, especially if the two columns are arranged perpendicular to each other and the optical axis of the SEM is positioned perpendicular to the sample surface. Generally speaking, the shorter the working distance, the better the resolution of the particle imaging device.

[0008] WO 2021 / 180600 A1 describes an alternative method for generating nanoscale 3D tomographic data from semiconductor samples. According to this document, the disadvantage of having to destroy the wafer is overcome by employing an alternative geometric configuration of a milling or FIB column on the one hand and a charged particle imaging column on the other. This configuration allows for navigating coincident points across the entire wafer without destroying the wafer. This so-called wedge-cut method utilizes a slicing and imaging method that accesses the semiconductor wafer surface at an oblique angle. However, due to the geometric constraints of the configuration of the two columns relative to each other, the working distance from the charged particle imaging column to the sample or wafer to be imaged is increased compared to the method described in WO 2020 / 244795 A1. This results in good imaging resolution, but still compromises resolution.

[0009] DE 10 2013 102 776 A1 discloses a cross-section processing and observation method for determining cut width using a dual-beam system. This system uses a different geometry than the wedge-cutting method. The FIB column is positioned perpendicular to the sample surface, while the SEM column is positioned at an oblique angle to the sample surface.

[0010] WO 2021 / 180600 A1 discloses a method for cross-sectional imaging of an inspection volume within a wafer. More specifically, it discloses a dual-beam device and a three-dimensional circuit pattern inspection technique performed by cross-sectioning an inspection volume extending to a depth exceeding 1 μm below the surface of a semiconductor wafer. Specifically, WO 2021 / 180600 A1 discloses a method, computer program product, and apparatus for generating 3D volumetric image data of a deep inspection volume within a wafer without removing the sample from the wafer. This method utilizes a wedge-cutting method. WO 2021 / 180600 A1 also relates to a method for generating 3D volumetric images and aligning cross-sectional images for three-dimensional circuit pattern inspection using a dual-beam device.

[0011] DE 10 2013 102 535 A1 discloses a dual-beam device in which the FIB column and the SEM column are arranged orthogonally to each other. The sample to be sectioned and imaged is placed on a special holder that allows edge cutting of the sample. Summary of the Invention

[0012] Therefore, the overall purpose to be solved by the present invention is to overcome the above-mentioned shortcomings of the prior art.

[0013] Another object of the present invention is to provide an improved sectioning and imaging method and a correspondingly adapted dual-beam system, in particular to enable better imaging resolution even in the presence of geometrical restrictions regarding the configuration of the columns of the dual-beam device, for example when applying the geometry of the wedge-cutting method.

[0014] Furthermore, it aims to increase workflow flexibility.

[0015] Furthermore, it is designed to provide a fast workflow.

[0016] This object is solved by the subject matter of the independent claims. The dependent claims relate to advantageous embodiments.

[0017] This patent application claims priority to U.S. Provisional Patent Application No. 63 / 365,548, filed May 31, 2022, the entire disclosure of which is hereby incorporated by reference into this patent application. This patent application also claims priority to German Patent Application No. 10 2022 117 601.0 10, filed July 14, 2022, the entire disclosure of which is hereby incorporated by reference into this patent application.

[0018] According to a first aspect of the present invention, the present invention relates to a method for obtaining a sequence of parallel cross-sectional images of a measurement site on a wafer. This method can also be used to image other types of samples; however, its application to wafers is particularly valuable because it does not require total destruction or damage of the wafer, yet allows for improved imaging resolution compared to a "normal" wedge-cut FIB / SEM configuration. This method comprises the following steps (1a) through 1e): 1a) providing a focused ion beam (FIB) column and a charged particle beam (CPB) imaging column in a coincident configuration, wherein a FIB optical axis of the FIB column and a CPB optical axis of the CPB imaging column coincide on a wafer surface, and a configuration angle GFE is formed between the FIB optical axis and the CPB optical axis; 1b) using the FIB column in the overlapped configuration to remove a surface layer of a cross section of the measurement portion of the wafer to form a new cross section that can be used for imaging; 1c) shortening a working distance between the CPB imaging column and the wafer surface in a direction along the axis of the CPB imaging column; 1d) imaging the new cross-section at the measurement location of the wafer with the CPB imaging column at the shortened working distance and therefore not in the coincident configuration; 1e) Increasing the working distance between the CPB imaging column and the wafer surface in the direction along the axis of the CPB imaging column until the coincident configuration is achieved.

[0019] The CPB imaging device can in principle be of any type. It can be, for example, a scanning electron microscope (SEM) or a helium ion microscope (HIM).

[0020] In principle, this method applies the configuration known from the wedge-cutting method. However, compared to the known workflow in the wedge-cutting configuration, the present invention implements some advantageous differences in the workflow. The inventors' overall considerations are as follows: The configuration angle GFE between the FIB column and the CPB imaging column cannot be completely freely selected. Generally, the larger the GFE angle, the smaller the working distance can be. However, the size of the GFE angle is limited by the available space in the system: at short working distances, the FIB column begins to block the CPB imaging column.

[0021] The inventors have discovered that temporarily abandoning the coincidence arrangement offers advantages overall, instead operating in the coincidence configuration throughout the entire workflow. According to the present invention, the milling process is still performed in the coincidence configuration, but with a smaller angular GFE. This results in reduced imaging resolution when monitoring milling (although, of course, the CPB imaging beam is focused on the wafer surface). However, this reduced imaging resolution is still sufficient for monitoring milling. Therefore, for such imaging processes, the coincidence arrangement is abandoned (while maintaining the angular GFE) and the working distance of the CPB imaging column can be reduced. Consequently, imaging is performed at a relatively short working distance, which enables better imaging resolution (although, of course, a different focus setting for the CPB imaging column is also required). The enhanced imaging resolution more than compensates for the slight disadvantage of lower imaging resolution during the milling process.

[0022] Relative movement between the CIP imaging column and the wafer surface along the optical axis of the CPB imaging column shortens the working distance. Since the working distance is shortened along the axis of the CPB imaging column, for example, by vertical stage movement, the alignment coincidence is only temporarily abandoned, making it easier to re-establish it later. Furthermore, if a high-precision stage is used, any vertical misalignment of the stage due to z-direction movement will be minimal compared to the typical dimensional variations in the z-direction within the wafer to be analyzed. Optionally, the method may include an additional alignment step. Alternatively, relative movement between the CPB imaging column and the wafer surface can be achieved by moving the CPB imaging column. However, before moving the CPB imaging column, the FIB column must be moved to "unblock" the CPB imaging column.

[0023] According to an example, the method steps 1b), 1c), 1d), and 1e) are repeated in sequence, for example, 2, 3, 10, 100, or 500 times.

[0024] According to an example, the method further comprises imaging the removed cross-sectional surface layer with the CPB imaging column in the coincident configuration. The imaging can monitor the milling process and ensure that milling is started / stopped at the correct position.

[0025] According to an embodiment, shortening the working distance between the CPB imaging column and the wafer surface includes moving a stage supporting the semiconductor sample, particularly vertically. Stage movement in the z-direction (vertical direction) can be performed with relatively high precision. Furthermore, this stage movement is relatively fast compared to the total imaging time (e.g., only one second of stage movement compared to a 20-30 second imaging time). Therefore, the overall process is not significantly slowed down. The stage movement in the z-direction can be, for example, approximately 2 to 3 mm. Therefore, if the working distance is, for example, approximately 5 to 6 mm, stage movement can shorten the working distance to approximately half of the original working distance in the overlapped configuration. This can, for example, improve imaging resolution by more than an order of magnitude.

[0026] According to an example, the CPB optical axis is aligned with a normal to the wafer surface.

[0027] According to an example, the FIB optical axis is set at an inclined angle relative to the wafer surface (ie, the wafer top surface).

[0028] According to an example, the configuration angle GFE is equal to or less than 45°, preferably equal to or less than 40°, and most preferably equal to or less than 35°. Preferably, the angle GFE is not less than 30°, because imaging highly inclined surfaces with CPB imaging can cause problems.

[0029] According to an example, shortening the working distance between the PCB imaging columns includes moving the PCB imaging columns along the PCB optical axis. Here, the platform can remain partially fixed.

[0030] The present invention further relates to a computer program product having a program code adapted to perform the method described in the various examples above. The program code may be segmented or divided into multiple parts or modules. In principle, any computer language may be used as the programming language.

[0031] The present invention further provides a single-chamber system comprising: A focused ion beam (FIB) column and a charged particle beam (CPB) imaging column adapted to be arranged in a coincident configuration, wherein a FIB optical axis of the FIB column and a CPB optical axis of the CPB imaging column coincide with a wafer surface, forming a configuration angle GFE between the FIB optical axis and the CPB optical axis, wherein the CPB optical axis is arranged in a direction perpendicular to the wafer surface; a platform for carrying a wafer and configured to be movable along the direction perpendicular to the surface of the wafer; and A control member; The control component is configured to control the FIB column, the CPB imaging column and the platform to execute the methods described in the above different examples.

[0032] The platform can directly or indirectly support a wafer or sample. In one example, a chuck is placed on the platform itself, with the wafer resting on the chuck. The chuck can be used to position the wafer flatly, for example, by utilizing electrostatic attraction. The platform can not only move perpendicular to the wafer surface (typically defined as the z-direction), but can also move in other directions and / or rotate.

[0033] Other systems may also be used to perform the methods described in the various examples above.

[0034] According to a second main aspect of the present invention, the present invention is directed to a method for obtaining a sequence of parallel cross-sectional images of a measurement portion of a wafer, wherein the wafer is supported by a platform, the method comprising the following steps: 2a) providing a focused ion beam (FIB) column and a charged particle beam (CPB) imaging column in an offset configuration, wherein in the offset configuration a FIB column optical axis and a CPB optical axis intersect a wafer surface at two different locations, the difference between the two different locations defining an offset on the wafer surface, the offset allowing independent setting of working distances of the FIB column and the CPB imaging column without being subject to geometric limitations due to shapes and / or locations of the FIB column and the CPB imaging column; 2b) using the FIB column to remove a cross-sectional surface layer at a first measurement location of the wafer to form a new cross-sectional surface that can be used for imaging; 2c) moving the wafer surface by moving a stage relative to the FIB column and the CPB imaging column according to the offset; 2d) Imaging the new cross-section of the first measurement location of the wafer with the CPB imaging column.

[0035] According to a second major aspect of the present invention, the concept of coincidence is abandoned, and an offset arrangement is used instead. This has the advantage that the working distances of the FIB column and the CPB imaging column can be set independently of each other, allowing for optimization. In particular, the short working distance of the CPB imaging column is not obstructed by the FIB column. Consequently, imaging resolution is improved compared to a "normal" wedge-cutting configuration with coincidence. Additional stage movement can also be performed relatively quickly. Using a high-precision stage is advantageous. Optionally, one or more registration or alignment steps can be performed. Also according to the second major aspect of the present invention, there is no need to completely destroy or damage the wafer. In one example, as in the "normal" wedge-cutting method, the method can be performed using a configuration in which the FIB optical axis is set at an oblique angle relative to the top wafer surface.

[0036] According to an example, the method further comprises the following steps: 2e) moving the wafer surface by moving a stage relative to the FIB column and the CPB imaging column according to the offset.

[0037] In principle, step 2e can be implemented in two different ways: According to an example, step 2e) reverses step 2c), so that the measurement site is milled at a first position, moved to a second position for imaging, and then moved back to the first position for further milling. Overall, only two different columns are used here. However, according to another method, more than two columns can be used, and these columns can be arranged alternately in a line, for example, each column offset by the same amount. Processing can then be carried out on the processing line. Each offset advances the measurement site from one column to the next.

[0038] According to the example, the sequence of method steps 2b), 2c), 2d) and 2e) is repeated.

[0039] According to an example, the relative motion includes lateral platform motion or platform rotation. Platform rotation allows for relatively clear and rapid switching between two positions, one for milling and the other for imaging. Lateral movement is preferred, for example, in machining line implementations.

[0040] According to examples, a working distance of the FIB column is optimized, and / or wherein a working distance of the CPB imaging column is optimized.

[0041] According to an example, the offset matches a distance between the first measurement location on the wafer surface and a second measurement location on the wafer surface.

[0042] According to an example, the method further comprises obtaining a sequence of a plurality of cross-sectional images of the second measurement portion of the wafer parallel to each other by repeatedly performing the sequence of method steps 2b), 2c) and 2d) at the second measurement portion. wherein the step of removing a cross-sectional surface layer at the second measurement portion of the wafer and imaging the new cross-sectional surface of the first measurement portion of the wafer using the CPB imaging column are performed simultaneously, and The step of removing a cross-sectional surface layer at the first measurement portion of the wafer and imaging the new cross-section of the second measurement portion of the wafer using the CPB imaging column are performed simultaneously.

[0043] This example allows the entire process to be parallelized, thereby increasing overall speed. The milling (removal of the cross-sectional image layer) and imaging method steps are performed at least partially simultaneously. The processing steps at least partially overlap in time. For example, the milling and imaging process steps may begin at the same time, but one process may end earlier (faster) than the other. A common starting point facilitates process synchronization. Other implementations are also possible.

[0044] According to another aspect of the present invention, the invention is directed to a computer program product having a program code suitable for executing the method as described in the above different examples.

[0045] According to another aspect of the present invention, the invention is directed to a single-chamber system comprising: A focused ion beam (FIB) column and a charged particle beam (CPB) imaging column adapted to be arranged in an offset configuration, wherein in the offset configuration, a FIB optical axis and a CPB optical axis intersect a wafer surface at two different locations, the difference between the two different locations defining an offset on the wafer surface, the offset being large enough to allow independent setting of working distances of the FIB column and the CPB imaging column without being subject to geometric limitations due to shapes and / or positions of the FIB column and the CPB imaging column; A platform for carrying a wafer and configured to move along a plane parallel to the surface of the wafer; and A control member; The control component is configured to control the FIB column, the CPB imaging column and the platform to perform the method described in the different examples described above in the second main aspect of this invention.

[0046] The platform can move in a plane parallel to the wafer surface. Thus, for example, the platform can rotate about an axis perpendicular to the wafer surface. Additionally or alternatively, the platform can be configured for lateral movement, such as in the x-direction and / or the y-direction. The platform can also additionally be capable of vertical movement (in the z-direction).

[0047] Other systems may also be used to execute the methods described in the various examples described above in relation to the second main aspect of the invention.

[0048] According to a third aspect of the present invention, the present invention provides a method for obtaining a sequence of multiple cross-sectional images of a measurement portion of a wafer that are parallel to each other, the method comprising the following steps: 3a) providing a focused ion beam (FIB) column and a charged particle beam (CPB) imaging column in a coincident configuration, wherein a FIB optical axis of the FIB column and a CPB optical axis of the CPB imaging column coincide on a wafer surface, and a configuration angle GFE is formed between the FIB optical axis and the CPB optical axis; 3b) determining an optimized working distance for the FIB column and a tradeoff working distance for the CPB imaging column, or determining a tradeoff working distance for the FIB column and an optimized working distance for the CPB imaging column; 3c) moving the FIB column along its optical axis to position the FIB column within the determined working distance (which is also optimized or traded off) and / or moving the CPB imaging column along its optical axis to position the CPB imaging column within the determined working distance (which is also traded off or optimized); 3d) using the FIB column disposed within its working distance to remove a cross-sectional surface layer at the measurement portion of the wafer to form a new cross-sectional surface that can be used for imaging; and 3e) imaging the new cross-section at the measurement location of the wafer using the CPB imaging column configured within its working distance.

[0049] According to this embodiment, a decision is made as to which of the "milling" or "imaging" aspects is of greater importance in a particular step. The more important aspect is then given a higher weight or priority by optimizing the respective assigned working distances for one of the columns. Another working distance, referred to as a "tradeoff" working distance, is less optimal but still good and / or is selected based on the best remaining probability. For example, in a use case where imaging resolution is more important than milling quality, the working distance of the CPB imaging column can be shortened at the expense of the working distance of the FIB column. An algorithm for determining the tradeoff working distance can be applied. Also according to the third main aspect of the present invention, it is not necessary to completely destroy or damage the wafer. In one example, as in the "normal" wedge dicing method, the method can be performed using a setup in which the FIB optical axis is arranged at an oblique angle relative to the top wafer surface.

[0050] According to the example, the sequence of method steps 3d) and 3e) is repeated.

[0051] According to an example, step 3c) comprises: Shorten the working distance of the FIB column and increase the working distance of the CPB imaging column, or The working distance of the FIB column is increased and the working distance of the CPB imaging column is shortened.

[0052] According to one aspect of the present invention, the invention is directed to a computer program product having a program code suitable for executing the method as described in the aforementioned different examples of the third main aspect of the present invention.

[0053] According to one aspect of the present invention, the invention is directed to a single-chamber system comprising: A focused ion beam (FIB) column and a charged particle beam (CPB) imaging column adapted to be arranged in a coincident configuration, wherein a FIB optical axis of the FIB column and a CPB optical axis of the CPB imaging column coincide on a wafer surface, and a configuration angle GFE is formed between the FIB optical axis and the CPB optical axis; wherein the FIB column is configured to be movable along its FIB optical axis and wherein the CPB imaging column is configured to be movable along its CPB axis; a platform for carrying a wafer; and A control member; The control component is configured to control the FIB column, the CPB imaging column, and the platform to execute the method described in the aforementioned different examples of the third main aspect of the present invention.

[0054] Other systems may also be used to execute the methods described in the various examples described above in the third main aspect of the invention.

[0055] According to a fourth main aspect of the present invention, the invention is directed to a method for obtaining a sequence of a plurality of first cross-sectional images of a first measurement location on a first wafer and a sequence of a plurality of second cross-sectional images of a second measurement location on a second wafer, the method comprising: 4a) providing the first wafer on a first platform and positioning the first wafer on the first platform; 4b) providing the second wafer on a second platform and positioning the second wafer on the second platform; 4c) removing a first cross-sectional surface layer of the first measurement portion of the first wafer using a FIB column operating at a set FIB working distance, so that a first new cross-sectional surface layer is available for imaging; 4d) exchanging the positions of the first platform and the second platform; 4e) imaging the first new cross-section at the first measurement location of the first wafer using a CPB imaging column at a set working distance, and simultaneously removing a surface layer of a second cross-section at the second measurement location of the second wafer using the FIB column at the set FIB working distance, so that a second new cross-section is available for imaging; 4f) exchanging the positions of the first platform and the second platform; 4g) imaging the second new cross-section at the second measurement portion of the second wafer using the CPB imaging column at the set working distance, and simultaneously removing a surface layer of another first cross-section at the first measurement portion of the first wafer using the FIB column at the set FIB working distance, so that another first new cross-section can be used for imaging

[0056] According to an example, the set working distance of a CPB imaging column can be the optimal working distance for a specific use case. Similarly, the set working distance of a FIB imaging column can be the optimal working distance for a specific use case. The working distances can be set independently of each other because the columns do not block each other and can be used in combination with different platforms.

[0057] The positions of the first and second platforms can be exchanged or switched using methods known in the art and similar methods described in, for example, US7161659 BB. The positions of the exchange platforms can be parallelized, thereby speeding up the process.

[0058] According to an example, the sequence of method steps 4d), 4e), 4f), and 4g) is repeated. Preferably, the method steps are repeated until the measurement locations in both wafers have been milled and imaged with the desired slice thickness.

[0059] According to an example, a plurality of first measurement locations on the first wafer are milled and imaged sequentially; and a plurality of second measurement locations on the second wafer are milled and imaged sequentially. Therefore, before the platform position is changed, preferably all measurement locations on a wafer are milled (single slice) or imaged separately. Milling and imaging are again performed in parallel, so at least partially simultaneously.

[0060] According to an example, monitoring the removal of the surface layer of the first or / and second cross-section using low-resolution imaging; and / or imaging the new first or / and second cross-section includes high-resolution imaging. The terms "high-resolution" and "low-resolution" imaging are relative terms and should not be interpreted in an absolute sense. However, these terms indicate that one resolution is better or worse than the other. This may have an impact on the column used and its working distance: due to the configuration of the FIB column used for milling, a relatively low imaging resolution is sufficient to monitor or control milling. Alternatively, a different CPB imaging column can be used, which can be configured, for example, according to the symmetry of a normal wedge cut. However, since the more important process in this cross-beam arrangement is the milling process, the working distance of the FIB column can be optimized, and the CPB imaging column working distance can be adapted to the preferred FIB column working distance setting. In contrast, for imaging processes that generate real images, the optimal working distance can be set for the imaging measurement site on the wafer located on the platform where the CPB imaging column is actually located.

[0061] According to an example, low-resolution imaging is performed using a low-resolution scanning electron microscope (SEM) in a cross-beam configuration with the FIB column used to remove the first and second cross-sectional surface layers; and / or high-resolution imaging is performed using a high-resolution scanning electron microscope (SEM), a helium ion microscope (HIM), or a multi-beam scanning electron microscope (MultiSEM). The high-resolution scanning electron microscope may include, for example, a corrected scanning electron microscope with an additional electrostatic lens to correct for imaging aberrations.

[0062] According to an example, exchanging the positions of the first and second platforms includes transferring positioning information. Therefore, there is no need to position the wafer separately on the corresponding platform of each column, but in principle, a single positioning step is sufficient. Optionally, additional alignment steps can be implemented to correct for minor positional deviations.

[0063] According to an example, the FIB column is arranged in a first chamber, and wherein the CPB imaging column is arranged in a second chamber. This has the advantage that milling and redeposition do not interfere with the imaging quality of the (high resolution) CPB imaging column.

[0064] According to an example, exchanging the positions of the first platform and the second platform includes transferring one of the platforms from the first chamber to the second chamber, or vice versa. The transfer can be achieved using one or two vacuum locks.

[0065] According to one aspect of the present invention, the present invention is directed to a computer program product having a program code suitable for executing the method described in the aforementioned different examples of the fourth main aspect of the present invention.

[0066] According to one aspect of the present invention, the present invention is directed to a dual-chamber system comprising: a first chamber having a focused ion beam (FIB) column and a low-resolution charged particle beam (CPB) imaging column and adapted to be arranged in a wedge-cut coincident configuration, wherein a FIB optical axis of the FIB column and a CPB optical axis of the low-resolution CPB imaging column coincide on a wafer surface, and a configuration angle GFE is formed between the FIB optical axis and the CPB optical axis; a second chamber having a high-resolution CPB imaging column with an optical axis configured perpendicular to a wafer surface; a first platform for carrying a first wafer; a second platform for carrying a second wafer; a platform exchange mechanism configured to exchange positions of the first platform and the second platform; and A control member; The control unit is configured to control the first chamber having the FIB column and the low-resolution CPB imaging column, the second chamber having the high-resolution CPB imaging column, the first platform, the second platform, and the platform exchange mechanism to perform the method described in the aforementioned different examples of the fourth main aspect of the present invention.

[0067] Other systems may also be used to execute the methods described in the different examples described above in the fourth main aspect of the invention.

[0068] According to a fifth main aspect of the present invention, the invention is directed to a method for obtaining at least one sequence of multiple parallel cross-sectional images of at least one measurement location of a wafer, the method comprising the following steps: 5a) providing a first focused ion beam (FIB) column and a first charged particle beam (CPB) imaging column in a first chamber in a wedge-cut coincident configuration, wherein in the coincident configuration, a FIB optical axis of the FIB column and a CPB optical axis of the CPB imaging column coincide on a wafer surface, and a configuration angle GFE is formed between the FIB optical axis and the CPB optical axis; 5b) providing a second FIB column and a second CPB imaging column in a second chamber in an edge-cutting coincident configuration, wherein in the edge-cutting coincident configuration, a FIB optical axis of the second FIB column and a CPB optical axis of the second CPB imaging column are coincident and perpendicular to each other at a wafer or sample surface, the optical axis of the second CPB imaging column is arranged perpendicular to the wafer or sample surface, and the CPB imaging column is configured at a short working distance to allow high-resolution imaging; 5c) positioning the first wafer at least one measurement location on a first platform; 5d) performing milling around the at least one measurement location with the first FIB column in the first chamber to generate at least one raw material block, and monitoring the milling with the first CPB imaging column in the first chamber; 5e) lifting the at least one raw material block from the wafer and placing the at least one raw material block on a sample holder such that a measurement portion of each raw material block is located at an edge of the sample holder; 5f) transferring the support with the at least one raw material block to the second chamber; 5g) positioning the at least one measurement portion included in the at least one raw material block on a second platform; 5h) repeatedly milling the at least one raw material block with the second FIB column in the second chamber and repeatedly imaging the at least one raw material block with the second CPB imaging column to obtain at least one sequence of parallel cross-sectional images of the at least one measurement site.

[0069] This lifting-out process and positioning the chunk adequately on the sample holder (at the edge) ensures that the region of interest or measurement location is close to the edge of the sample holder. This enables the PCB imaging column to be configured perpendicular to the wafer or chunk surface, which in turn results in a shorter possible working distance and enhanced imaging resolution.

[0070] According to an example, the method further comprises: 5i) The second platform is moved to allow a second measurement location to be used for milling and imaging. The second measurement location is typically included in the second raw material block. The second raw material block is also located at the edge of the sample holder. The second platform can be moved in various ways, depending on its geometry. If the second platform is circular (having a rounded surface), the movement is preferably rotational. If the second platform is ramp-shaped (e.g., implemented using a belt), the movement is preferably lateral. In general, the raw material blocks can be arranged linearly on the ramp so that all blocks are located at the edge.

[0071] According to an example, the method further includes providing a plurality of sample holders and sequentially processing the plurality of sample holders in the first chamber and the second chamber according to steps 5d) to 5h). Thus, it is possible to extract more raw material pieces from a wafer than can be placed on a single sample holder. Of course, the entire process can be repeated for a second or additional wafer.

[0072] According to one aspect of the present invention, the present invention is directed to a computer program product having a program code suitable for executing the method described in the above different examples of the fifth main aspect of the present invention.

[0073] According to another aspect of the present invention, the present invention is directed to a dual-chamber system comprising: A first room, comprising: A first focused ion beam (FIB) column and a first charged particle beam (CPB) imaging column are adapted to be arranged in a wedge-cut coincident configuration, wherein a FIB optical axis of the FIB column and a CPB optical axis of the low-resolution CPB imaging column coincide on a wafer surface, and a configuration angle GFE is formed between the FIB optical axis and the CPB optical axis. a first platform for carrying a wafer; a sample holder adapted to carry at least one raw material block, a manipulator configured to extract a plurality of raw material blocks milled from the wafer and configured to place the raw material blocks on the sample holder; A second room, including: a second FIB column and a second CPB imaging column in an edge-cutting coincident configuration, wherein in the edge-cutting coincident configuration, a FIB optical axis of the second FIB column and a CPB optical axis of the second CPB imaging column are coincident on a wafer or sample surface and are perpendicular to each other, the optical axis of the second CPB imaging column is arranged perpendicular to the wafer or sample surface, and the CPB imaging column is configured at a short working distance to allow high-resolution imaging; a second platform for carrying the sample holder; a sample holder transfer mechanism configured to transfer the sample holder from the first chamber to the second chamber and place the sample holder on the second platform; and A control element, The control unit is configured to be used in the first chamber having the first FIB column, the first CPB imaging column, the first platform, the sample holder, and the manipulator, the second chamber having the second FIB column, the second CPB imaging column, and the second platform, and the sample holder transfer mechanism, to perform the method described in the aforementioned different examples of the fifth main aspect of the present invention.

[0074] This example allows for efficient batch processing.

[0075] Other systems may also be used to execute the methods described in the different examples described above in the fifth main aspect of the invention.

[0076] As long as no technical contradiction occurs, the above embodiments or examples can be combined with each other in whole or in part. This also applies to examples or embodiments that describe different aspects or main aspects of the present invention. Simple diagram description

[0077] The present invention will be more fully understood with reference to the following drawings:

[0078] Figure 1 is a diagram of a cross-sectional imaging technique for explaining a sample extracted from a wafer;

[0079] Figure 2 is a diagram of a dual-beam apparatus configured for cross-sectional imaging technology applied to a wedge-cut geometry of a wafer;

[0080] Figure 3 shows detailed information on the cross-sectional imaging technique of the wedge-cut geometry;

[0081] Figure 4 shows an oblique cross-sectional image slice through a plurality of HAR structures;

[0082] Figure 5 shows a first workflow according to the present invention;

[0083] Figure 6 schematically illustrates a system for executing a first workflow;

[0084] Figure 7 shows a second workflow according to the present invention;

[0085] Figure 8 schematically illustrates a system for executing a second workflow;

[0086] Figure 9 shows a third workflow according to the present invention;

[0087] Figure 10 shows a fourth workflow according to the present invention;

[0088] Figure 11 schematically shows a dual-chamber system for performing the fourth workflow;

[0089] Figure 12 shows a fifth workflow according to the present invention;

[0090] Figure 13 schematically illustrates a dual chamber system for performing the fifth workflow; and

[0091] FIG. 14 schematically illustrates geometric features and limitations in a dual-beam system according to the prior art and according to one aspect of the present invention. Implementation Method

[0092] Identical reference numerals in the figures denote identical features, even if not further described in the text.

[0093] Figure 1 illustrates a schematic diagram of a common cross-sectional imaging method for acquiring a 3D volumetric image of an integrated semiconductor sample. Using the cross-sectional method (also known as the slice and image method), three-dimensional (3D) volumetric image acquisition is achieved using a "step-and-repeat" approach. First, the integrated semiconductor sample is prepared for the common cross-sectional imaging method using methods known in the art. A small piece or block of material is extracted from the wafer and then further analyzed. Throughout this disclosure, the terms "cross-sectional image" and "slice" will be considered synonymous. In one step, a thin surface layer or "slice" of material is removed. This slice of material can be removed using several methods known in the art, including milling using a focused ion beam or polishing at a glancing angle using a focused ion beam (FIB) column 50. For example, a focused ion beam 51 propagates nearly parallel to the z-axis and scans in the y-direction to mill through the top surface 55 of the sample 10 (which may be, for example, a portion of a wafer) and expose a new cross-sectional surface 52 in the yz plane. Consequently, the newly exposed cross-sectional surface 52 is available for imaging. In a subsequent step, the cross-sectional surface layer 52 is raster-scanned using a charged particle beam (CPB) imaging system 40 (e.g., a scanning electron microscope (SEM) or a second FIB) to obtain a cross-sectional image slice 100.1. The optical axis 42 of the charged particle imaging system 40 can be configured parallel to the x-direction or tilted at a certain angle to the x-direction. Secondary electrons and backscattered electrons are collected by a detector (not shown) to reveal material contrast within the integrated semiconductor sample and are visible in cross-sectional image slice 100.1 at varying grayscale levels. Metallic structures produce brighter measurements. The milling to remove the surface layer and the cross-sectional imaging process are repeated using cross-sectional surfaces 53 and 54 and other cross-sectional surfaces at equal distances d to obtain a series of 2D cross-sectional image slices 1000, including, for example, N cross-sectional image slices 100.2, 100.3, ..., 100.N at different depths, to create a three-dimensional (3D) data set. Representative cross-sectional image slice 100.1 was obtained by measuring a commercial Intel processor integrated circuit semiconductor chip using 14 nm technology.

[0094] Using this method, at least first and second cross-sectional image slices are generated by subsequently milling a cross section into an integrated semiconductor sample using a focused ion beam to expose or make accessible a series of cross-sectional surfaces for imaging, allowing each cross-sectional surface of the integrated semiconductor sample to be imaged using a charged particle beam imaging system 40. A 3D image of the integrated semiconductor structure is reconstructed based on the sequence of N 2D cross-sectional image slices 1000. The distance d between the cross-sectional image slices 100.1, 100.2, and 100.3 can be controlled using a FIB milling or polishing process and can be controlled to be between 1 nm and 30 nm.

[0095] Aperture stop 9 can be implemented so as to follow the movement of the hexapod actuator of pivot drive 7. Specifically, aperture stop 9 can be coupled to the hexapod actuator. As an alternative or in addition to aperture stop 9, an aperture-limiting stop can be arranged between hollow waveguide 11 and downstream optical components of illumination optics unit 1. Another aperture stop of this type can also be arranged in the beam path of illumination light 3 downstream of hollow waveguide 11, between two downstream optical components of illumination optics unit 1.

[0096] Of course, the positions of the FIB column 50 and the CPB imaging column 40 can also be swapped. The CPB optical axis can then be oriented perpendicular to the top surface 55 of the sample 10. This configuration is preferred for imaging HAR structures that extend deep into the sample 10.

[0097] In both configurations described above, the working distances of the FIB column and the CPB imaging column can be set independently. This allows for optimization of both working distances. Generally speaking, the shorter the working distance, the better the imaging resolution. Therefore, since a short working distance can be set without geometrical limitations, high-resolution imaging is possible using the CPB imaging column 40.

[0098] However, a general problem remains: the measurement site of the wafer needs to be located close to the edge of the wafer to allow measurement using the geometric configuration of the depicted posts 40, 50. Otherwise, the wafer must be destroyed and the sample 10 or block of material must be extracted from the wafer to artificially create an edge and thus a situation suitable for further analysis.

[0099] FIG2 illustrates a method for generating 3D volumetric images using a slice-and-image method, applied to an inspection volume within a wafer using a so-called "wedge-cut" method or wedge-cut geometry, without removing the sample 10 from the wafer 8. The slice-and-image method is applied to an inspection volume measuring a few micrometers, for example, extending 5 to 10 μm laterally in a 200 mm or 300 mm wafer, without removing the sample from the wafer 8. A groove or edge is milled into the top surface 55 of the integrated semiconductor wafer 8 to enable access to a cross-section angled relative to the top surface 55. A 3D volumetric image of the inspection volume is acquired at a limited number of measurement locations, such as representative locations on the wafer, at a process control monitor (PCM), or at locations identified by other inspection tools. The slice-and-image method only locally disrupts the wafer, and other dies can still be used or the wafer can be processed further.

[0100] FIG2 illustrates a wafer inspection system 500 configured for performing a slicing and imaging method using a dual-beam apparatus 1 with a wedge-cut geometry. For wafer 8, multiple measurement locations, including measurement locations 6.1 and 6.2, are defined in a location map or inspection list generated by an inspection tool or design information. Wafer 8 is placed on a wafer support table 15. Wafer support table 15 is mounted on a platform 155 with actuators and position control. Actuators and devices for precise control of the wafer platform, such as laser interferometers, are known in the art. A control unit 16 is configured to control wafer platform 155 and adjust measurement location 6.1 of wafer 8 at intersection point 43 of the dual-beam apparatus 1. The dual-beam apparatus 1 includes a FIB column 50 having a FIB optical axis 48 and a charged particle beam (CPB) imaging system 40 having an optical axis 42. At the intersection point 43 of the optical axes of the FIB and CPB imaging system, the wafer top surface 55 is configured to form an inclination angle GF with respect to the FIB axis 48. FIB axis 48 and CPB imaging system axis 42 include an angle GFE, and CPB imaging optical axis 42 forms an angle GE with the normal to wafer top surface 55. In the coordinate system of FIG1 , the normal to wafer top surface 55 is provided by the z-axis. A focused ion beam (FIB) 51 is generated by FIB column 50 and impinges on surface 55 of wafer 8 at an angle GF. Using ion beam milling, an inclined cross-sectional surface is milled into the wafer at measurement location 6.1 at approximately a tilt angle GF. In the example of FIG2 , the tilt angle GF is approximately 30°. Due to the beam divergence of a focused ion beam (e.g., a gallium ion beam), the actual tilt angle of the inclined cross-sectional surface can deviate from the tilt angle GF by 1° to 4°. Images of the milled surface are acquired using charged particle beam imaging system 40 tilted at an angle GE relative to the wafer normal. In the example of FIG2 , the angle GE is approximately 15°. However, other arrangements are possible, such as GE=GF, such that the CPB imaging system axis 42 is perpendicular to the FIB axis 48, or GE=0°, such that the CPB imaging system axis 42 is perpendicular to the wafer top surface 55.

[0101] During imaging, the charged particle beam 44 is scanned by the scanning unit of the charged particle beam imaging system 40 along a scanning path across the cross-sectional surface of the wafer 8 at the measurement site 6.1, generating secondary particles and scattered particles. The particle detector 17 collects at least some of the secondary and scattered particles and communicates the particle count to the control unit 19. Other detectors for other types of interactive products may also be present. The control unit 19 controls the charged particle beam imaging column 40 of the FIB column 50 and is connected to the control unit 16 to control the position of the wafer 8 mounted on the wafer support table 15 via the wafer stage 155. The control unit 19 communicates with the operation control unit 2, which uses the movement of the wafer stage to trigger, for example, the placement and alignment of the measurement site 6.1 of the wafer 8 at the intersection 43, and triggers the repetitive operations of FIB milling, image acquisition, and stage movement.

[0102] Each new intersection surface is milled by the FIB beam 51 and imaged by a charged particle imaging beam 44, such as a scanning electron beam or a helium ion beam of a helium ion microscope (HIM).

[0103] However, because both the FIB column 50 and the CPB imaging column 40 are located above the wafer top surface 55, their configuration faces geometric limitations. It's no longer possible to optimize the two working distances independently, as the columns 40 and 50 begin to block each other at short working distances. As a general rule of practice, the position of the FIB column 50 limits, and therefore "defines," the working distance of the CPB imaging column 40. The working distance of the CPB imaging column 40 typically cannot be shorter than 4 to 5 mm. In contrast, the working distance of the CPB imaging column 40, as shown in Figure 1, can be as short as approximately 2 mm. Consequently, in the wedge-cut configuration shown in Figure 2, imaging resolution is typically reduced by an order of magnitude compared to the edge configuration shown in Figure 1.

[0104] FIG3 illustrates further details of the slicing and imaging method in a wedge-cut geometry. By repeating the slicing and imaging method in the wedge-cut geometry, a plurality of J cross-sectional image slices, including image slices of cross-sectional surfaces 52, 53.i, 53.J, are generated, and a 3D volume image of the inspection volume 160 at measurement location 6.1 of wafer 8 is generated. FIG3 illustrates a wedge-cut geometry in an example of a 3D memory stack. Cross-sectional surfaces 53.1, 53.N are milled using FIB beam 51 at an angle GF of approximately 30° to wafer surface 9, although other angles GF are possible, such as between GF = 20° and GF = 60°. FIG3 illustrates the situation when surface 52 is the last new cross-sectional surface milled by FIB 51. Cross-sectional surface 52 is scanned, for example, using SEM beam 44, which, in the example of FIG3 , is configured for normal incidence on wafer surface 55, and high-resolution cross-sectional image slices are generated. The cross-sectional image slices include a first cross-sectional image feature, a second cross-sectional image feature formed by intersections with high aspect ratio (HAR) structures or vias (e.g., the first cross-sectional image features of HAR structures 4.1, 4.2, and 4.3), and a second cross-sectional image feature formed by intersections with layers L.1…LM, which include, for example, SiO2, SiN, or tungsten lines or wordline layers. The maximum number of layers, M, is typically greater than 50, e.g., greater than 100 or even greater than 200. HAR structures and layers extend throughout most of the wafer volume but may include gaps. HAR structures typically have diameters below 100 nm, e.g., approximately 80 nm, or, for example, 40 nm. Thus, the cross-sectional image slices include first cross-sectional image features as intersections or cross-sections of the HAR structure footprint at different depths (Z) at corresponding XY locations. In the case of cylindrical perpendicular memory HAR structures, the first cross-sectional image features obtained are circular or elliptical structures at different depths as determined by the structure's position on the inclined cross-sectional surface 52. The memory stack extends in the Z direction perpendicular to the wafer surface 55. The thickness d, or minimum distance d, between two adjacent cross-sectional image slices is adjusted to a value typically on the order of a few nanometers, such as 30 nm, 20 nm, 10 nm, 5 nm, 4 nm, or even less. Once the material layer of predetermined thickness d is removed using the FIB, the next cross-sectional surface 53.i…53.J is exposed and can be imaged using the charged particle imaging beam 44.

[0105] FIG4 illustrates oblique cross-sectional image slices through multiple HAR structures. More specifically, FIG4 shows a cross-sectional image slice 311.1 generated by imaging charged particle beam 41 and corresponding to cross-sectional surface 301.1. Cross-sectional image slice 311.1 includes edge line 315 between the oblique cross section and wafer surface 55 at edge coordinate y1. Just at the edge, image slice 311.1 shows several cross sections 307.1…307.S through the HAR structure that intersect cross-sectional surface 301.1. Furthermore, image slice 311.1 includes cross sections of multiple word lines 313.1–313.3 at different depths or z-positions. Using these word lines 313.1–313.3, a depth map Z1(x, y) of oblique cross-sectional surface 301.1 can be generated.

[0106] In an example, image processing methods are used (e.g., from the HAR centroid) to detect features and 3D positions of semiconductor structures of interest (e.g., the positions of HAR channels). 3D volumetric image generation, including image processing methods and feature-based alignment, is further described in U.S. Provisional Application No. 62 / 858,470 and German Patent Application No. 102019006645.6, the contents of which are hereby fully incorporated by reference into this disclosure. It should be noted that the layers and HAR structures do not need to extend through the entire measurement volume.

[0107] To improve 3D tomographic data and 3D metrology measurement problems, improved imaging resolution is required. At the same time, the wafer containing the measurement area of ​​interest should remain intact so that the 3D image of the measurement area is still usable after it is generated.

[0108] The present invention addresses these issues by decoupling the working distance of the CPB imaging column from the limitations imposed by the FIB geometry, as explained in the general description. Several examples are provided below to further illustrate the present invention. However, these examples should not be construed as limiting the present invention.

[0109] FIG5 illustrates a first workflow according to the present invention, and FIG6 schematically illustrates a dual-beam apparatus 1 suitable for performing the first workflow. FIG6a schematically illustrates a slightly modified wedge-cut configuration compared to the wedge-cut configuration shown in FIG2 . As shown in FIG2 , a wafer 8 having multiple measurement locations 6 (here: two measurement locations) is arranged on a wafer support table 15 supported by a platform 155. The platform in the illustrated example is movable in all three spatial dimensions (x, y, z), as indicated by the arrows. Furthermore, the platform 155, or at least the wafer support table 15, can rotate. These movements can be controlled by a platform control unit 16 (not shown in FIG6 ).

[0110] In the depicted example, CPB imaging optical axis 42 is configured perpendicular to wafer top surface 55. In principle, this allows for top-down imaging of HAR structures in a sample or wafer 8. FIB column 50.1 is configured at an oblique angle relative to wafer top surface 55. FIB optical axis 48 and CPB optical axis 42 intersect at a coincidence point 43 located on wafer top surface 55. However, compared to the configuration shown in FIG2 , the configuration angle GFE between FIB optical axis 48 and CPB optical axis 42 is shortened in FIG6a . Imaging at this position increases the working distance of the CPB imaging column. However, according to the present invention, only milling processes using FIB column 50.1 can be performed in the depicted coincident configuration. In the depicted example, the working distance of FIB column 50.1 can be selected to be optimal.

[0111] After removing the surface layer of the cross-section using FIB 50.1, the FIB is stopped or inhibited. The configuration of columns 50.1 and 40 is then changed to that shown in Figure 6b: the working distance of CPB imaging column 42 is shortened along the CPB optical axis. In the depicted case, this shortening is achieved by moving the stage in the z-direction, indicated by the large arrow on stage 155. However, in principle, the CPB imaging column 40 itself can also be moved, either additionally or alternatively. After shortening the working distance, imaging is performed at a shorter working distance. A shorter working distance allows for better imaging resolution. Furthermore, stage movement in the z-direction can be performed relatively quickly and with considerable precision. After imaging an accessible cross-section, stage 155 (or CPB imaging column 40) can be moved back down again until the overlap configuration is achieved. The next slice can then be milled using FIB 50.1, and the process can be repeated for measurement site 6 and other measurement sites.

[0112] FIG14 further illustrates the geometric features and limitations of the dual-beam system 1: FIG14a) depicts a wedge-cut geometry according to the prior art, and FIG14b) depicts the geometric features and advantages of the first aspect of the present invention. In practice, the last lens in the lens sequence in the focused ion beam column 50 and the charged particle beam column 40 limits the available space between the columns 50, 40 and the sample or wafer 8: the outer shape of the columns 50, 40 near the wafer 8 can be approximated as a truncated cone with aperture angles α FIB and α CPB, respectively. Obviously, the FIB column 50 and the CPB imaging column 40 must not obstruct each other; in particular, the FIB column 50 must not be positioned within the available space below the CPB imaging column 40.

[0113] Furthermore, according to the prior art dual-beam device 1 configuration shown in FIG14 a, the bottom edge 49 of the FIB column 50 is arranged parallel to the wafer 8 and the wafer top surface 55. The distance h between the bottom edge 49 and the wafer top surface 55 is selected to be small, so that the working distance WD1 between the CPB imaging column 40 can also be made small. This, in principle, allows for high-resolution imaging (the smaller the working distance, the better the resolution, in principle). However, in practice, a minimum distance h exists, and therefore a minimum possible working distance WD1, as otherwise the FIB column 50 would contact the wafer 8. Furthermore, it must be remembered that the wafer 8 must generally be moved in a plane perpendicular to the optical axis of the CPB imaging column 40 (here: the z-axis), and that the wafer 8 cannot contact the FIB column 50 during this movement.

[0114] According to a first aspect of the present invention, the dual-beam apparatus 1 has a different geometric configuration: as shown in FIG14b , the FIB column 50 is retracted from the wafer 8 , with its bottom edge 49 no longer parallel to the wafer top surface 55 , and the configuration angle GFE2 is smaller than the configuration angle GFE1 . Therefore, during the milling process, the working distance WD2 of the CPB imaging column 40 is greater than the working distance WD1 shown in FIG14a . During milling in the coincident configuration (corresponding to the first position Pos1 of the wafer 8 and the wafer top surface 55 ), the resolution of the CPB imaging column 40 is reduced. However, this resolution remains sufficient for monitoring the milling process.

[0115] On the other hand, after milling, the relative distance between wafer top surface 55 and CPB imaging column 40 can now be shortened in the new configuration according to the first aspect of the present invention, for example, by moving the stage in the z-direction dz. A second shortened position Pos2 is also shown in FIG. 14b . In second position Pos2, high-resolution imaging can be performed using a working distance WD3 that is smaller than working distance WD1.

[0116] Figure 5 summarizes an exemplary workflow: In step S1, a focused ion beam (FIB) column 50.1 and a charged particle beam (CPB) imaging column 40 are provided in a coincident configuration. In step S2, in a coincident configuration, the FIB column 50.1 is used to remove surface layers from a cross-section of measurement location 6 of wafer 8 to form a new cross-section suitable for imaging. In step S3, the working distance between the CPB imaging column 40 and the wafer top surface 55 is shortened along the optical axis 42 of the CPB imaging column 40, for example, by stage movement in the z-direction. The new cross-section at measurement location 6 of wafer 8 is imaged using the CPB imaging column 40 at the shortened working distance and, therefore, out of the coincident configuration. In step S5, the working distance between the CPB imaging column 40 and the wafer top surface 55 is increased along the axis 42 of the CPB imaging column 40 until a coincident configuration is achieved. Steps S2 through S5 can be repeated until the measurement location is completely milled and imaged. The process then ends in step S6. Of course, this workflow can be repeated for the next measurement location 6.

[0117] FIG7 illustrates a second workflow according to the present invention, and FIG8 schematically illustrates a dual-beam apparatus 1 suitable for executing the second workflow. In contrast to the first workflow, which still uses coincidence points during milling, coincidence points are completely abandoned in the second workflow. Instead of a coincident configuration, an offset configuration of two columns 50.1 and 40 is employed. According to the offset configuration depicted, the FIB column optical axis 48 and the CPB optical axis 42 intersect the wafer surface 55 at two different points or locations. The difference between the two different locations defines the offset level from the wafer top surface 55, indicated by the double arrow. This offset allows the working distances of the FIB column 50.1 and the CPB imaging column 40 to be independently set, without geometric limitations imposed by their shape and / or position. Thus, optimal working distances can be set for both the FIB column 50.1 and the CPB imaging column 40. However, before imaging or milling can be performed, the wafer must be moved relative to the two columns 50.1 and 40 by the offset amount. One possibility for such a relative movement is a platform movement, for example a lateral platform movement (in the depicted example, the y direction).

[0118] It should be noted that the offset can be set flexibly within a certain range. In practice, the offset has a minimum dimension below which columns 50.1 and 40 no longer obstruct each other. However, the offset can be larger than this minimum dimension. Therefore, it is preferable to adjust the distance offset between the two measurement locations 6 on wafer 8. The first measurement location can then be milled and the second imaged. Using more columns further parallelizes milling and imaging. It is also possible to rotate platform 155 (or at least the wafer support table 15) to switch between the two measurement locations 6. This also allows for parallel milling and imaging of the two measurement locations 6.

[0119] Figure 7 summarizes an exemplary workflow: In step S10, a focused ion beam (FIB) column 50.1 and a charged particle beam (CPB) imaging column 40 are provided in an offset configuration; both working distances are selected to be optimal. In step S11, a cross-sectional surface layer is removed at a first measurement location 6 of wafer 8 using FIB column 50.1 to form a new cross-sectional surface suitable for imaging. In step S12, the wafer surface is relatively moved, for example, using lateral stage movement or stage rotation according to an offset. In step S13, the new cross-sectional surface of the first measurement location 6 of wafer 8 is imaged using CPB imaging column 40. In step S14, wafer 8 is again relatively moved (returned) according to the offset. Then, in step S11, the next cross-sectional surface layer can be removed, and steps S12 through S14 are repeated. When the entire location 6 has been milled and imaged, the process ends, for example, in step S15. Another location 6 can then be milled and imaged. As mentioned above, the process can also be parallelized if the offset is adjusted to the distance between different measuring locations 6.

[0120] FIG9 illustrates a third workflow according to the present invention. In step S20, a focused ion beam (FIB) column 50.1 and a charged particle beam (CPB) imaging column 40 are provided in an overlapping configuration. In step S21, the optimized working distance of the FIB column and the trade-off working distance of the CPB imaging column are determined, or the trade-off working distance of the FIB column and the optimized working distance of the CPB imaging column are determined. In step S22, the FIB column is moved along its optical axis to position the FIB column at the determined working distance (optimized or trade-off), and / or the CPB imaging column is moved along its optical axis to position the CPB imaging column at the determined working distance (trade-off or optimized). In step S23, a cross-sectional surface layer is removed from the measurement portion of wafer 8 using FIB column 50.1 positioned within the working distance to form a new cross-section suitable for imaging. In step S24, the new cross-section is used to image the measurement portion 6 of wafer 8 using CPB imaging column 40 positioned within the working distance. Milling and imaging can be repeated (steps S23 and S24). The process ends in step S25. The working distances of both the FIB column and the CPB imaging column are not optimal simultaneously; rather, one is selected as optimal (meaning best under given circumstances or constraints), and the other is chosen as preferred over the other, given the circumstances and constraints, whenever possible. This now includes the optimization of the other column and, therefore, the given working distance. For example, if imaging resolution is more important than milling quality, the working distance of the CPB imaging column 40 can be shortened at the expense of the working distance of the FIB column 50.1. This can be incorporated into the algorithm used to determine the trade-off between working distances.

[0121] Figure 10 illustrates a fourth workflow according to the present invention, and Figure 11 schematically illustrates a dual-chamber system suitable for performing the fourth workflow. The dual-chamber system includes a first chamber 70.1 and a second chamber 70.2. This dual-chamber solution spatially separates milling and high-resolution imaging. Milling is performed in the first chamber 70.1. High-resolution imaging is performed in the second chamber 70.2. Wafer 8 is transferred between the two chambers 70.1 and 70.2, allowing milling and high-resolution imaging to be performed alternately.

[0122] In more detail, first chamber 70.1 includes a dual-beam system 1.1 having a FIB column 50.1 and a CPB imaging column 40.1 configured in a coincident configuration. However, the CPB imaging column 40.1 itself is not used to image the cross-section; rather, the FIB 50.1 is utilized solely for monitoring / supervising the milling process. For such monitoring or surveillance purposes, a lower imaging resolution is generally sufficient. Therefore, the working distance of the FIB column 50.1 can be optimized at the expense of the imaging resolution (greater working distance) of the CPB imaging column 40.

[0123] When the cross-sectional surface layer is readily milled, wafer 8 is transferred to second chamber 70.2 for high-resolution imaging. According to the depicted example, second chamber 70.2 includes a high-resolution CPB imaging device 40.2. In principle, device 40.2 can be identical to device 40.1 in the first chamber; however, due to the ability to optimize the working distance, imaging resolution is improved. However, it is preferred to utilize a CPB imaging device 40.2 in second chamber 70.2 that is different and more advanced than that used in first chamber 70.1. For example, a high-resolution scanning electron microscope (SEM), a corrected SEM with an additional electrostatic lens to reduce imaging aberrations, or a multi-beam scanning electron microscope (MultiSEM or mSEM).

[0124] The wafer 8 can be transferred between the two chambers 70.1 and 70.2 in various ways. One possibility is to transfer the wafer support table 15, on which the wafer 8 is already positioned. Alternatively, the complete platform 155.1 can be transferred from one chamber to the other. Using a second platform 155.2 further refines the method: it is then possible to work on both wafers 8.1 and 8.2 in parallel. For example, while one wafer 8.1 is being ground in the first chamber 70.1, the second wafer 8.2 can be imaged in the second chamber 70.2, and vice versa. The platform exchange can be performed using a platform transfer interface 80. Optionally, this transfer interface 80 can be equipped with one or two vacuum locks (not shown), for example to prevent the grinding deposit material from entering the imaging chamber or the second chamber 70.2.

[0125] Figure 10 exemplarily summarizes a possible workflow for a method for obtaining a first cross-sectional image sequence of a first measurement location 6.1 on a first wafer 8.1, and a possible workflow for a method for obtaining a second cross-sectional image sequence of a second measurement location 6.2 on a second wafer 8.2. In step S30, first wafer 8.1 is placed on and positioned on first platform 155.1. In step S31, second wafer 8.2 is placed on and positioned on second platform 155.2. In step S32, a first cross-sectional surface layer of first measurement location 6.1 of first wafer 8.1 is removed using FIB column 50.1 operating at a set FIB working distance, making a first new cross-sectional image available for imaging. In step S33, the positions of first platform 155.1 and second platform 155.2 are swapped. In step S34, a first new cross-section at first measurement site 6.1 of first wafer 8.1 is imaged using CPB imaging column 40.2 at a set working distance. Simultaneously, a second cross-section surface layer of second measurement site 6.2 of second wafer 8.2 is milled using FIB column 50.1 at the set FIB working distance, making the second new cross-section available for imaging. In step S35, the positions of first stage 155.1 and second stage 155.2 are again changed, and wafers 8.1 and 8.2 are transferred from one chamber to the other. In step S36, a second new cross-section at second measurement site 6.2 of second wafer 8.2 is imaged using CPB imaging column 40.2 at the set working distance. Simultaneously, another first cross-section surface layer of first measurement site 6.1 of first wafer 8.1 is removed using FIB column 40.1 at the set FIB working distance, making another first new cross-section available for imaging. Steps S33 to S36 can be repeated until both measurement locations 6.1 and 6.2 are completely milled and imaged. The exemplary process ends in step S37. It is also possible to sequentially mill and image multiple measurement locations 6 on each wafer 8.1, 8.2. In this case, the transfer time from chamber 70.1 to chamber 70.2 can be kept low, and the entire process becomes faster.

[0126] FIG. 12 illustrates a fifth workflow according to the present invention, and FIG. 13 schematically illustrates a dual-chamber system suitable for performing the fifth workflow.

[0127] The first chamber 70.1 includes a first focused ion beam (FIB) column 50.1 and a first charged particle beam (CPB) imaging column 40.1, arranged in a wedge-cut configuration. The chamber 70.1 also includes a first platform 155.1, on which a wafer 8 having multiple measurement locations 6 is positioned. The first chamber 70.1 is used solely for sample preparation. Sample preparation involves extracting a 3D block or raw material block 61 from the wafer: the first FIB column 50.1 is used for milling around the measurement locations 6 and is not used for slicing and removing. The first CPB imaging column 40.1 is used only to monitor milling; therefore, the lower imaging resolution of the first CPB imaging column 40.1 is sufficient. In this example, the first chamber 70.1 also includes a manipulator 21 for extracting raw material blocks 61 milled from the wafer 8. The manipulator 21 can arrange one or more raw material blocks 61 on a sample holder 60, with the raw material blocks 61 positioned at the edges of the sample holder 60. Milling, extraction, and raw material block positioning can be controlled directly or indirectly by the operation control unit 2.

[0128] One or more raw material blocks 61 placed on the sample holder 60 can then be transferred from the first chamber 70.1 to the second chamber 70.2 for milling and imaging. For example, this transfer can be performed via a sample transfer interface 80 having two vacuum locks. It is possible to transfer the sample holder 60 with the raw material blocks 61 using this method and then place the sample holder 60 on the second platform 155.2 in the second chamber 70.2. However, it is also possible to transfer the holder 60 together with a correspondingly configured platform (not shown in FIG. 13 ). More than one sample holder 60 can also be provided. Providing more than one sample holder 60 can facilitate process parallelization: while a raw material block 61 is being placed on the first holder 60 in the first chamber 70.1, for example, a raw material block 61 placed on the second holder 60 can already be imaged in the second chamber 70.2.

[0129] In this example, the second chamber 70.2 includes a second FIB column 50.2 and a second CPB imaging column 40.2 in a coincident configuration. Because the measurement site 6 has been extracted and positioned at the edge of the sample holder 60, a high-resolution configuration of the FIB column 50.2 and CPB column 40.2 can be used, allowing for edge cutting. Milling using the FIB column 50.2 can be performed alternately with high-resolution imaging using the CPB imaging column 40.2 in a manner generally known in the art. Further details have been explained, for example, with reference to FIG. 1 .

[0130] Another possibility is to provide another chamber (not shown) with an additional FIB / CPB configuration for milling and high-resolution imaging. This can further speed up the workflow.

[0131] FIG12 shows an exemplary workflow for obtaining at least one parallel cross-sectional image sequence of at least one measurement location 6 of a wafer 8:

[0132] In step S40, a first focused ion beam (FIB) column 50.1 and a first charged particle beam (CPB) imaging column 40.1 are arranged in a wedge-cut coincident configuration in a first chamber 70.1, in which the FIB optical axis 48 of the FIB column 50.1 and the CPB optical axis 42 of the CPB imaging column 40.1 coincide at the wafer surface 55 and form a configuration angle GFE between the FIB optical axis and the CPB optical axis.

[0133] In step S41, the second FIB column 50.2 and the second CPB imaging column 40.2 are arranged in the second chamber 70.2 in an edge-cutting coincident configuration. In the edge-cutting coincident configuration, the FIB optical axis of the second FIB column and the CPB optical axis of the second CPB imaging column coincide with each other at the wafer 8 or sample surface 55 and are perpendicular to each other, the optical axis of the second CPB column 40.2 is configured to be perpendicular to the wafer or sample surface 55, and the second CPB column 40.2 is configured at a short working distance that allows high-resolution imaging.

[0134] In step S42 , the first wafer 8 having at least one measurement location 6 is positioned on the first platform 155 .

[0135] In step S43, the first FIB column 50.1 in the first chamber 70.1 is used to perform milling around the at least one measurement location 6, thereby generating at least one raw material block 61, and the milling is supervised by the first CPB imaging column 40.1 in the first chamber 70.1.

[0136] In step S44 , at least one raw material block 61 is lifted out of the wafer 8 and placed on the sample holder 60 such that the measurement portion 6 of each raw material block 61 is placed at the edge of the sample holder 60 .

[0137] In step S45 , the sample holder 60 with the at least one raw material block 61 is transferred into the second chamber 70 . 2 .

[0138] In step S46, at least one measuring location 6 included in at least one raw material block 61 is positioned on the second platform 155.2.

[0139] In step S47, at least one parallel cross-sectional image sequence of at least one measurement site 6 is obtained by repeatedly milling at least one material block 61 using second FIB column 50.2 and repeatedly imaging at least one material block 61 using second CPB column 40.2 in second chamber 70.2. Due to the geometric arrangement of material block 61, high-resolution imaging is possible.

[0140] In optional step S48 , the second platform 155 . 2 is rotated so that it is positioned at the second measurement location 6 . 2 on the second raw material block 61 for milling and imaging.

[0141] Alternatively, a plurality of sample holders 60 may be performed and processed sequentially in the first chamber 70 . 1 and the second chamber 70 . 2 according to steps S43 to S47 .

[0142] Other workflows and systems may be envisioned by those skilled in the art without departing from the scope of the invention as defined by the claims.

[0143] Examples of the present invention will be provided below.

[0144] Example 1: A method for obtaining a sequence of multiple parallel cross-sectional images of a measurement portion of a wafer, the method comprising the following steps: 1a) providing a focused ion beam (FIB) column and a charged particle beam (CPB) imaging column in a coincident configuration, wherein a FIB optical axis of the FIB column and a CPB optical axis of the CPB imaging column coincide on a wafer surface, and a configuration angle GFE is formed between the FIB optical axis and the CPB optical axis; 1b) using the FIB column in the overlapped configuration to remove a surface layer of a cross section of the measurement portion of the wafer to form a new cross section that can be used for imaging; 1c) shortening a working distance between the CPB imaging column and the wafer surface in a direction along the axis of the CPB imaging column; 1d) imaging the new cross-section at the measurement location of the wafer with the CPB imaging column at the shortened working distance and therefore not in the coincident configuration; 1e) Increasing the working distance between the CPB imaging column and the wafer surface in the direction along the axis of the CPB imaging column until the coincident configuration is achieved.

[0145] Example 2: The method according to Example 1, wherein the sequence of method steps 1b), 1c), 1d) and 1e) is repeated.

[0146] Example 3: The method as described in Example 1 further includes imaging the removed cross-sectional surface layer with the CPB imaging column in the overlapping configuration.

[0147] Example 4: The method of Example 1, wherein shortening the working distance between the CPB imaging column and the wafer surface comprises moving a platform carrying the semiconductor sample, particularly moving the platform vertically.

[0148] Example 5: The method of Example 1, wherein the CPB optical axis is aligned with a normal to the wafer surface.

[0149] Example 6: The method as described in Example 1, wherein for the configuration angle GFE, the following relationship holds: 30°≤GFE≤45°, in particular 30°≤GFE≤40° or 30°≤GFE≤35°.

[0150] Example 7: The method of Example 1, wherein shortening the working distance between the PCB imaging columns comprises moving the PCB imaging columns along the PCB optical axis.

[0151] Example 8: A computer program product having a program code suitable for executing the method according to Example 1.

[0152] Example 9: A single-chamber system comprising: A focused ion beam (FIB) column and a charged particle beam (CPB) imaging column adapted to be arranged in a coincident configuration, wherein a FIB optical axis of the FIB column and a CPB optical axis of the CPB imaging column coincide with a wafer surface, forming a configuration angle GFE between the FIB optical axis and the CPB optical axis, wherein the CPB optical axis is arranged in a direction perpendicular to the wafer surface; a platform for carrying a wafer and configured to be movable along the direction perpendicular to the surface of the wafer; and A control member; Wherein, the control component is configured to control the FIB column, the CPB imaging column and the platform to perform the method described in Example 1.

[0153] Example 10: A method for obtaining a sequence of parallel cross-sectional images of a measurement portion of a wafer, wherein the wafer is supported by a platform, comprising the following steps: 2a) providing a focused ion beam (FIB) column and a charged particle beam (CPB) imaging column in an offset configuration, wherein in the offset configuration a FIB column optical axis and a CPB optical axis intersect a wafer surface at two different locations, the difference between the two different locations defining an offset on the wafer surface, the offset allowing independent setting of working distances of the FIB column and the CPB imaging column without being subject to geometric limitations due to shapes and / or locations of the FIB column and the CPB imaging column; 2b) using the FIB column to remove a cross-sectional surface layer at a first measurement location of the wafer to form a new cross-sectional surface that can be used for imaging; 2c) moving the wafer surface by moving a stage relative to the FIB column and the CPB imaging column according to the offset; 2d) Imaging the new cross-section of the first measurement location of the wafer with the CPB imaging column.

[0154] Example 11: The method of Example 10, further comprising: 2e) moving the wafer surface by moving a stage relative to the FIB column and the CPB imaging column according to the offset.

[0155] Example 12: The method of Example 10, wherein the sequence of method steps 2b), 2c), 2d) and 2e) is repeated.

[0156] Example 13: The method of Example 10, wherein the relative movement comprises a lateral platform movement or a platform rotation.

[0157] Example 14: The method of Example 10, wherein a working distance of the FIB column is optimized, and / or wherein a working distance of the CPB imaging column is optimized.

[0158] Example 15: The method of Example 10, wherein the offset matches a distance between the first measurement location on the wafer surface and a second measurement location on the wafer surface.

[0159] Example 16: The method described in Example 15, The method further comprises obtaining a sequence of a plurality of cross-sectional images of the second measurement portion of the wafer parallel to each other by repeatedly performing the sequence of steps 2b), 2c), and 2d) at the second measurement portion. wherein the step of removing a cross-sectional surface layer at the second measurement portion of the wafer and imaging the new cross-sectional surface of the first measurement portion of the wafer using the CPB imaging column are performed simultaneously, and The step of removing a cross-sectional surface layer at the first measurement portion of the wafer and imaging the new cross-section of the second measurement portion of the wafer using the CPB imaging column are performed simultaneously.

[0160] Example 17: A computer program product having a program code suitable for executing the method according to Example 10.

[0161] Example 18: A single-chamber system comprising: A focused ion beam (FIB) column and a charged particle beam (CPB) imaging column adapted to be arranged in an offset configuration, wherein in the offset configuration, a FIB optical axis and a CPB optical axis intersect a wafer surface at two different locations, the difference between the two different locations defining an offset on the wafer surface, the offset being large enough to allow independent setting of working distances of the FIB column and the CPB imaging column without being subject to geometric limitations due to shapes and / or positions of the FIB column and the CPB imaging column; a platform for supporting a wafer and configured to move along a plane parallel to the surface of the wafer; and A control member; Wherein, the control component is configured to control the FIB column, the CPB imaging column and the platform to perform the method described in Example 10.

[0162] Example 19: A method for obtaining a sequence of parallel cross-sectional images of a measurement portion of a wafer, the method comprising the following steps: 3a) providing a focused ion beam (FIB) column and a charged particle beam (CPB) imaging column in a coincident configuration, wherein a FIB optical axis of the FIB column and a CPB optical axis of the CPB imaging column coincide on a wafer surface, and a configuration angle GFE is formed between the FIB optical axis and the CPB optical axis; 3b) determining an optimized working distance for the FIB column and a trade-off working distance for the CPB imaging column, or determining a trade-off working distance for the FIB column and an optimized working distance for the CPB imaging column; 3c) moving the FIB column along its optical axis to place the FIB column within the determined working distance and / or moving the CPB imaging column along its optical axis to place the CPB imaging column within the determined working distance; 3d) using the FIB column disposed within its working distance to remove a cross-sectional surface layer at the measurement portion of the wafer to form a new cross-sectional surface that can be used for imaging; and 3e) imaging the new cross-section at the measurement location of the wafer using the CPB imaging column configured within its working distance.

[0163] Example 20: The method of Example 19, wherein the sequence of method steps 3d) and 3e) is repeated.

[0164] Example 21: The method of Example 19, wherein step 3c) comprises: Shorten the working distance of the FIB column and increase the working distance of the CPB imaging column, or The working distance of the FIB column is increased and the working distance of the CPB imaging column is shortened.

[0165] Example 22: A computer program product having a program code suitable for executing the method according to Example 19.

[0166] Example 23: A single-chamber system comprising: A focused ion beam (FIB) column and a charged particle beam (CPB) imaging column adapted to be arranged in a coincident configuration, wherein a FIB optical axis of the FIB column and a CPB optical axis of the CPB imaging column coincide on a wafer surface, and a configuration angle GFE is formed between the FIB optical axis and the CPB optical axis; wherein the FIB column is configured to be movable along its FIB optical axis and wherein the CPB imaging column is configured to be movable along its CPB axis; a platform for carrying a wafer; and A control member; Wherein, the control component is configured to control the FIB column, the CPB imaging column and the platform to perform the method described in Example 19.

[0167] Example 24: A method for obtaining a sequence of multiple first cross-sectional images of a first measurement location on a first wafer and a sequence of multiple second cross-sectional images of a second measurement location on a second wafer, the method comprising: 4a) providing the first wafer on a first platform and positioning the first wafer on the first platform; 4b) providing the second wafer on a second platform and positioning the second wafer on the second platform; 4c) removing a first cross-sectional surface layer of the first measurement portion of the first wafer using a FIB column operating at a set FIB working distance, so that a first new cross-sectional surface layer is available for imaging; 4d) exchanging the positions of the first platform and the second platform; 4e) imaging the first new cross-section at the first measurement location of the first wafer using a CPB imaging column at a set working distance, and simultaneously removing a surface layer of a second cross-section at the second measurement location of the second wafer using the FIB column at the set FIB working distance, so that a second new cross-section is available for imaging; 4f) exchanging the positions of the first platform and the second platform; 4g) imaging the second new cross-section at the second measurement portion of the second wafer using the CPB imaging column at the set working distance, and simultaneously removing a surface layer of another first cross-section at the first measurement portion of the first wafer using the FIB column at the set FIB working distance, so that another first new cross-section can be used for imaging.

[0168] Example 25: The method of Example 24, wherein the method steps 4d), 4e), 4f) and 4g) are repeated in this order.

[0169] Example 26: The method described in Example 24, wherein the plurality of first measurement locations on the first wafer are sequentially milled and imaged; and Wherein, the plurality of second measurement locations on the second wafer are milled and imaged in sequence.

[0170] Example 27: The method described in Example 24, wherein the removal of the first and / or the second cross-sectional surface layer is supervised by low resolution imaging; and / or Wherein imaging the new first and / or second cross-section comprises high-resolution imaging.

[0171] Example 28: The method described in Example 27, wherein low-resolution imaging is performed by the FIB column used to remove the first and second cross-sectional surface layers, or by a low-resolution scanning electron microscope (SEM) in a cross-beam configuration with the FIB column used to remove the first and second cross-sectional surface layers; and / or High-resolution imaging is performed using a high-resolution scanning electron microscope (SEM), a helium ion microscope (HIM), or a multi-beam scanning electron microscope (MultiSEM).

[0172] Example 29: The method of Example 24, wherein exchanging the locations of the first platform and the second platform includes transferring positioning information.

[0173] Example 30: The method described in Example 24, The FIB column is arranged in a first chamber, and the CPB imaging column is arranged in a second chamber.

[0174] Example 31: The method described in Example 30, Wherein exchanging the positions of the first platform and the second platform includes transferring one of the platforms from the first chamber to the second chamber, or vice versa.

[0175] Example 32: A computer program product having a program code suitable for executing the method described in Example 24.

[0176] Example 33: A dual-chamber system comprising: a first chamber having a focused ion beam (FIB) column and a low-resolution charged particle beam (CPB) imaging column and adapted to be arranged in a wedge-cut coincident configuration, wherein a FIB optical axis of the FIB column and a CPB optical axis of the low-resolution CPB imaging column coincide on a wafer surface, and a configuration angle GFE is formed between the FIB optical axis and the CPB optical axis; a second chamber having a high-resolution CPB imaging column with an optical axis configured perpendicular to a wafer surface; a first platform for carrying a first wafer; a second platform for carrying a second wafer; a platform exchange mechanism configured to exchange positions of the first platform and the second platform; and A control member; The control component is configured to control the first chamber having the FIB column and the low-resolution CPB imaging column, the second chamber having the high-resolution CPB imaging column, the first platform, the second platform and the platform exchange mechanism to perform the method described in Example 28.

[0177] Example 34: A method for obtaining at least one sequence of multiple parallel cross-sectional images of at least one measurement location on a wafer, the method comprising the following steps: 5a) providing a first focused ion beam (FIB) column and a first charged particle beam (CPB) imaging column in a first chamber in a wedge-cut coincident configuration, wherein in the coincident configuration, a FIB optical axis of the FIB column and a CPB optical axis of the CPB imaging column coincide on a wafer surface, and a configuration angle GFE is formed between the FIB optical axis and the CPB optical axis; 5b) providing a second FIB column and a second CPB imaging column in a second chamber in an edge-cutting coincident configuration, wherein in the edge-cutting coincident configuration, a FIB optical axis of the second FIB column and a CPB optical axis of the second CPB imaging column are coincident and perpendicular to each other at a wafer or sample surface, the optical axis of the second CPB imaging column is arranged perpendicular to the wafer or sample surface, and the CPB imaging column is configured at a short working distance to allow high-resolution imaging; 5c) positioning the first wafer at least one measurement location on a first platform; 5d) performing milling around the at least one measurement location with the first FIB column in the first chamber to generate at least one raw material block, and monitoring the milling with the first CPB imaging column in the first chamber; 5e) lifting the at least one raw material block from the wafer and placing the at least one raw material block on a sample holder such that a measurement portion of each raw material block is located at an edge of the sample holder; 5f) transferring the support with the at least one raw material block to the second chamber; 5g) positioning the at least one measurement portion included in the at least one raw material block on a second platform; 5h) repeatedly milling the at least one raw material block with the second FIB column in the second chamber and repeatedly imaging the at least one raw material block with the second CPB imaging column to obtain at least one sequence of parallel cross-sectional images of the at least one measurement site.

[0178] Example 35: The method of Example 34, further comprising: 5i) Moving the second stage to make a second measurement location available for milling and imaging.

[0179] Example 36: The method of Example 34 further comprises providing a plurality of sample holders and sequentially processing the plurality of sample holders in the first chamber and the second chamber according to steps 5d) to 5h).

[0180] Example 37: A computer program product having a program code suitable for executing the method described in Example 34.

[0181] Example 38: A dual-chamber system comprising: A first room, comprising: A first focused ion beam (FIB) column and a first charged particle beam (CPB) imaging column are adapted to be arranged in a wedge-cut coincident configuration, wherein a FIB optical axis of the FIB column and a CPB optical axis of the low-resolution CPB imaging column coincide on a wafer surface, and a configuration angle GFE is formed between the FIB optical axis and the CPB optical axis; a first platform for carrying a wafer; a sample holder adapted to carry at least one raw material block, a manipulator configured to extract a plurality of raw material blocks milled from the wafer and configured to place the raw material blocks on the sample holder; A second room, including: a second FIB column and a second CPB imaging column in an edge-cutting coincident configuration, wherein in the edge-cutting coincident configuration, a FIB optical axis of the second FIB column and a CPB optical axis of the second CPB imaging column are coincident on a wafer or sample surface and are perpendicular to each other, the optical axis of the second CPB imaging column is arranged perpendicular to the wafer or sample surface, and the CPB imaging column is configured at a short working distance to allow high-resolution imaging; a second platform for carrying the sample holder; a sample holder transfer mechanism configured to transfer the sample holder from the first chamber to the second chamber and place the sample holder on the second platform; and A control element, Wherein, the control component is configured to be used for the first chamber having the first FIB column, the first CPB imaging column, the first platform, the sample holder and the manipulator, the second chamber having the second FIB column, the second CPB imaging column and the second platform, and the sample holder transfer mechanism, to perform the method described in Example 34.

[0182] 1: Dual beam device 1.1: Dual-beam system 4.1: First cross-sectional image features of HAR structure 4.2: First cross-sectional image features of HAR structure 4.3: First cross-sectional image features of HAR structure 6: Measurement location 6.1: First measurement site 6.2: Second measurement site 8: Wafer 8.1: First Wafer 8.2: Second Wafer 10: Sample 15: Wafer support table 16: Control unit 17: Particle Detector 19: Control Unit 21: Operator 40: Charged Particle Beam (CPB) Imaging Column 40.1: First Charged Particle Beam (CPB) Imaging Column 40.2: Second Charged Particle Beam (CPB) Imaging Column 42: Optical axis 43: Intersection 44: Charged Particle Imaging Beam 48: FIB column optical axis 50:FIB column 50.1: First Focused Ion Beam (FIB) Column 50.2: Second FIB column 51: Focused Ion Beam (FIB) 52: Sectional surface 53: Sectional surface 53.1: Sectional Surface 53.J: Sectional surface 54: Sectional surface 55: wafer top surface; wafer surface; sample surface 60: Sample holder 61: Raw material block 70.1: Room 1 70.2: Second Chamber 80:Platform transfer interface 100.1: Cross-sectional image slices 100.2: Cross-sectional image slices 100.3: Cross-sectional image slices 155: Platform 155.1: Complete the platform 155.2: Second Platform 160: Check volume 301.1: Sectional Surface 307.1: Section 307.S: Section 311.1: Image Slicing 313.1: Word Line 313.2: Word Line 313.3: Word line 315: Edge line 500:Wafer Inspection System 1000: 2D cross-sectional image slice sequence d: distance dz: platform movement GF: tilt angle GFE: angle GFE1: Configuration Angle GFE2: Configuration Angle h: distance h': distance L.1: Layer LM: Layer Offset: Pos1: first position Pos2: Second position S1: Steps S2: Step S3: Steps S4: Step S5: Step S6: Step S10: Step S11: Step S12: Step S13: Step S14: Step S15: Step S20: Step S21: Step S22: Step S23: Step S24: Step S25: Step S30: Step S31: Step S32: Step S33: Step S34: Step S35: Steps S36: Steps S37: Steps S40: Step S41: Step S42: Step S43: Step S44: Steps S45: Steps S46: Step S47: Steps S48: Steps S49: Steps WD1: Working distance WD2: Working distance WD3: Working distance y1: edge coordinates

Claims

1. A method for obtaining a sequence of multiple parallel cross-sectional images of a measurement portion of a wafer, the method comprising the steps of: 1a) providing a focused ion beam (FIB) column and a charged particle beam (CPB) imaging column in an overlapping configuration, wherein an FIB optical axis of the FIB column and a CPB optical axis of the CPB imaging column coincide on a wafer surface, and a configuration angle GFE is formed between the FIB optical axis and the CPB optical axis; 1b) in the overlapping configuration, removing a cross-sectional surface layer of the measurement portion of the wafer by milling with the FIB column in a scanning manner to form a new cross-section usable for imaging, wherein the FIB column is positioned relative to a top surface of the wafer at an angle GF and the new cross-section is therefore positioned relative to the top surface of the wafer at the same angle GF; 1c) shortening a working distance between the CPB imaging column and the wafer surface in a direction along the axis of the CPB imaging column; 1d) At the shortened working distance and therefore not in the overlapping configuration, image the new profile at the measurement location of the wafer with the CPB imaging post; 1e) Increase the working distance between the CPB imaging post and the wafer surface in the direction along the axis of the CPB imaging post until the overlapping configuration is achieved; wherein method steps 1b), 1c), 1d), and 1e) are repeated in sequence; wherein for the configuration angle GFE, the following relationship holds: 30° ≤ GFE ≤ 40°.

2. The method as described in claim 1, further comprising, in the overlapping configuration, imaging the removed cross-sectional surface layer with the CPB imaging column.

3. The method as described in claim 1 or 2, wherein shortening the working distance between the CPB imaging column and the wafer surface includes moving a platform carrying the semiconductor sample, particularly moving the platform vertically.

4. The method as described in claim 1 or 2, wherein the CPB optical axis is aligned with a normal to the wafer surface.

5. The method as described in request item 1 or 2, wherein for the configuration angle GFE, the following relationship holds: 30°≤GFE≤35°.

6. The method as described in claim 1 or 2, wherein shortening the working distance between the PCB imaging pillars includes moving the PCB imaging pillars along the PCB optical axis.

7. A computer program product having program code adapted to perform the method according to any one of claims 1 to 6.

8. A single-chamber system comprising: A focused ion beam (FIB) column and a charged particle beam (CPB) imaging column, adapted to be configured in an overlapping configuration, wherein an FIB optical axis of the FIB column and a CPB optical axis of the CPB imaging column coincide on a wafer surface, and a configuration angle GFE is formed between the FIB optical axis and the CPB optical axis, wherein the CPB optical axis is disposed in a direction perpendicular to the wafer surface; a platform for carrying a wafer and configured to be movable along the direction perpendicular to the wafer surface; and a control element; wherein the control element is configured to control the FIB column, the CPB imaging column, and the platform to perform the method according to any one of claims 1 to 6.

Images