Dual-beam system and method for decoupling working distance of charged particle beam device from limitations caused by focused ion beam geometry

Abstract

A method of obtaining a sequence of multiple cross-sectional images of a measurement site of a wafer parallel to each other, the method comprising the steps of: 1a) providing a focused ion beam (FIB) column and a charged particle beam (CPB) imaging column in a coincident configuration in which the FIB optical axis of the FIB column and the CPB optical axis of the CPB imaging column coincide at the wafer surface, 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 a profile surface layer of the measurement site of the wafer to form a new profile for imaging; 1c) shortening the 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 profile at the measurement site of the wafer with the CPB imaging column at the shortened working distance and thus not in the coincident configuration; 1e) increasing the working distance between the CPB imaging column and the wafer surface in a direction along the axis of the CPB imaging column until the coincident configuration is achieved.

Description

Technical Field

[0001] The present invention relates to dual beam devices and three-dimensional circuit pattern inspection by cross-sectional imaging of an inspection volume. Background Art

[0002] Semiconductor structures are among the most delicate man-made structures and are subject to different defects. These defects are currently found using quantitative 3D metrology, defect detection or defect verification systems. The manufactured semiconductor structures are based on existing technologies. The semiconductor structures are manufactured from sequential layers parallel to the substrate. For example, in logic type samples, metal lines extend parallel in metal layers or HAR (high aspect ratio) structures and metal vias extend perpendicular to the metal layers. The angles between metal lines in different layers are 0° or 90°. On the other hand, for VNAND type structures, it is known that on average their cross-section is circular.

[0003] The semiconductor wafer has a diameter of, for example, 300 mm and consists of a plurality of parts (so-called bare cores), each of which includes at least one integrated circuit pattern, for example for a memory chip or for a processor chip. During the manufacturing process, the semiconductor wafer undergoes about 1000 process steps, forming about 100 or more parallel layers in the semiconductor wafer, including transistor layers, line intermediate layers and interconnect layers, as well as multiple 3D memory cell arrays in the memory device. The size, shape and layout of the semiconductor structure and pattern are subject to various influences. In the manufacture of 3D memory devices, the key processes currently are etching and deposition. Other process steps involved, such as photolithography exposure or implantation, also have an impact on the characteristics of the IC components.

[0004] The aspect ratio and number of layers of integrated circuits are increasing, and the structures are constantly developing into the third (vertical) dimension. The height of the current memory stack is more than a dozen microns. In contrast, the feature size is getting smaller. The minimum feature size or critical dimension is below 10nm, such as 7nm or 5nm, and in the near future the feature size will approach below 3nm. The complexity and size of semiconductor structures are growing into the third dimension, while the lateral dimensions of integrated semiconductor structures are becoming smaller. Therefore, it becomes challenging to measure the shape, size and orientation of 3D features and patterns and their overlap with high accuracy.

[0005] Inspection and 3D analysis of integrated semiconductor circuits in wafers are becoming increasingly challenging as requirements for the three-dimensional resolution of charged particle imaging systems continue to increase. The lateral measurement resolution of charged particle systems is usually limited by the sampling grating of the individual image points or the residence time of each pixel on the sample and the diameter of the charged particle beam. The sampling grating resolution can be set within the imaging system and can be adapted to the diameter of the charged particle beam on the sample. Typical grating resolutions are 2 nm or less, but in principle the grating resolution limit can be reduced and there is no physical limit. The size of the charged particle beam diameter is limited, depending on the operating conditions of the charged particle beam and the lens. The beam resolution is limited to approximately half the beam diameter. The resolution can be lower than 2 nm, for example even lower than 1 nm.

[0006] A common method for generating nanoscale 3D tomography data from semiconductor samples is the so-called slice and image method, which is, for example, elaborated in detail by a dual-beam system. The dual-beam system has a charged particle beam column for imaging and a FIB column for milling, which runs at a so-called coincidence point, that is, the charged particle beam optical axis, the FIB optical axis and the sample surface meet (coincidence) at a single point. This is advantageous because it is ensured in this way that imaging can be performed at the sampling point affected by milling.

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

[0008] An alternative method for generating nanoscale 3D tomography data from semiconductor samples is described in WO 2021 / 180600A1. According to the document, the disadvantage of having to destroy the wafer is overcome by another geometric configuration of a milling or FIB column on the one hand and a charged particle imaging column on the other hand. With this configuration, coincidence points can be navigated across the entire wafer without destroying the wafer. The so-called wedge-cut method utilizes a slicing and imaging method that enters the surface of the semiconductor wafer at an oblique angle. However, due to the geometric constraints of the configuration of the two columns relative to each other, the working distance of the charged particle imaging column to the sample or wafer to be imaged is increased compared to the method described in WO2020 / 244795A1. This results in good imaging resolution, but still reduces the imaging resolution.

[0009] DE 10 2013 102 776 A1 discloses a cross-section processing and observation method for determining the cutting width using a dual beam system. The system uses a different geometry from the wedge cutting method. The FIB column is set to be orthogonal to the sample surface, and the SEM column is set to be at an inclined angle to the sample surface.

[0010] WO 2021 / 180600 A1 discloses a method for cross-sectional imaging of an inspection volume in a wafer. In more detail, it discloses a dual-beam device and a three-dimensional circuit pattern inspection technique, which is performed by cross-sectioning an inspection volume extending at a large depth of more than 1 μm below the surface of a semiconductor wafer. Specifically, WO 2021 / 180600 A1 discloses a method, a computer program product and a device for generating 3D volumetric image data of a deep inspection volume inside a wafer without removing a sample from the wafer. A wedge cutting method is used. WO 2021 / 180600 A1 also relates to a 3D volumetric image generation and cross-sectional image alignment method 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, which allows edge-cutting of the sample. Summary of the invention

[0012] Therefore, the general object to be solved by the present invention is to overcome the above-mentioned disadvantages of the prior art.

[0013] Another object of the present invention is to provide an improved slicing and imaging method and a correspondingly adapted dual-beam system, in particular to achieve better imaging resolution even in the presence of geometrical limitations 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 / 365548, filed May 31, 2022, the entire scope of which is 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 scope of which is incorporated by reference into this patent application.

[0018] According to a first aspect of the invention, the invention relates to a method for obtaining a sequence of mutually parallel cross-sectional images of a measurement site of a wafer. The method can also be used for imaging other types of samples; however, when applied to wafers, it is more valuable because it does not require the entire wafer to be destroyed or damaged, but the imaging resolution can be improved compared to a "normal" wedge-cut FIB / SEM configuration. The method comprises the following steps 1a) to 1e):

[0019] 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;

[0020] 1b) in the overlapped configuration, using the FIB column to remove a surface layer of the cross-section of the measurement portion of the wafer to form a new cross-section that can be used for imaging;

[0021] 1c) shortening the working distance between the CPB imaging column and the wafer surface in a direction along the axis of the CPB imaging column;

[0022] 1d) imaging the new cross-section at the measurement location of the wafer with the CPB imaging column at a reduced working distance and thus not in the coincident configuration;

[0023] 1e) Increasing the working distance between the CPB imaging column and the wafer surface in a direction along the axis of the CPB imaging column until the coincident configuration is (again) achieved.

[0024] 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).

[0025] The method applies in principle a configuration known from the wedge cutting method. However, the present invention achieves some advantageous differences in the workflow compared to the known workflow in the wedge cutting configuration. The inventors' overall considerations are as follows: The configuration angle GFE between the FIB column and the CPB imaging column cannot be chosen completely freely. In general, the larger the angle GFE, the smaller the working distance can be, but the size of the angle GFE is limited by the available space in the system: for short working distances, the FIB column starts to block the CPB imaging column.

[0026] The inventors have found that temporarily abandoning the coincidence arrangement has advantages overall, and instead working in the coincidence arrangement during the entire workflow as known from the prior art. According to the invention, the milling process is still carried out in the coincidence arrangement, but with a smaller angle GFE, resulting in a reduction in the imaging resolution when supervising the milling (although of course the CPB imaging beam is focused onto the wafer surface). However, the reduced imaging resolution is still sufficient to monitor the milling. Then, for such an imaging process, the coincidence arrangement is abandoned (while maintaining the angle GFE) and the working distance of the CPB imaging column can be reduced. As a result, imaging is carried out at a relatively short working distance, which enables a better imaging resolution to be achieved (of course with another focus setting of the CPB imaging column). The enhanced imaging resolution overcompensates the slight disadvantage of the lower imaging resolution in the milling process.

[0027] The 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 moving the vertical platform, only the coincidence point of the arrangement is temporarily abandoned, and it is easier to find it again later. In addition, if a high-precision platform is used, any misalignment of the platform in the vertical direction due to the movement of the platform in the z direction is small compared to the typical dimensional changes in the z direction within the wafer to be analyzed. Optionally, the method may include an additional alignment step. Alternatively, the 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, it is also necessary to move the FIB column in order to "unblock" the CPB imaging column.

[0028] According to an example, the sequence of method steps 1b), 1c), 1d) and 1e) is repeated, for example, 2 times, 3 times, 10 times, 100 times or 500 times.

[0029] According to an example, the method further comprises: in the coincident configuration, imaging the removed surface layer of the cross section with the CPB imaging device. The imaging can monitor the milling process and ensure that milling is started / stopped at the correct position.

[0030] According to an embodiment, shortening the working distance between the CPB imaging device and the wafer surface includes moving the platform carrying the semiconductor sample, in particular moving the platform vertically. The platform movement along the z direction (vertical direction) can be performed with relatively high accuracy. In addition, compared with the entire imaging time, this platform movement is relatively fast (for example, compared with an imaging time of 20 seconds to 30 seconds, the platform moves only 1 second). Therefore, the entire process will not be significantly slowed down. The size of the platform moving in the z direction can be, for example, about 2 to 3 mm, so if the working distance is, for example, about 5 to 6 mm, the platform movement can allow the working distance to be shortened to about half of the original working distance in the overlap configuration. For example, this can improve the imaging resolution by more than an order of magnitude.

[0031] According to an example, the CPB optical axis is aligned to the normal to the wafer surface. The above facilitates operation.

[0032] According to an example, the FIB optical axis is set at an inclined angle relative to the wafer surface (ie, the wafer top surface).

[0033] 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°, since imaging highly inclined surfaces with CPB imaging may cause problems.

[0034] According to an example, shortening the working distance between the CPB imaging columns includes moving the PCB imaging columns along the PCB optical axis. Here, the platform can remain partially fixed.

[0035] The invention further relates to a computer program product having a program code suitable for executing the method as described in the different examples above. The program code can be segmented or divided into a plurality of parts or modules. In principle, any computer language can be used as a program language.

[0036] The present invention further relates to a single chamber system comprising:

[0037] A focused ion beam (FIB) column and a charged particle beam (CPB) imaging column adapted to be arranged in a coincident configuration, in which a FIB optical axis of the FIB column and a CPB optical axis of the CPB imaging column coincide on 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;

[0038] a platform for supporting a wafer and configured to be movable in a direction perpendicular to a surface of the wafer; and

[0039] Controls;

[0040] Wherein, the control component is configured to control the FIB column, the CPB imaging column and the platform to execute the methods described in the aforementioned different examples.

[0041] The platform can carry a wafer or a sample directly or indirectly. In an example, a chuck is placed on the platform itself, and the wafer is placed on the chuck. The chuck can be used to configure the wafer in a flat manner, for example using electrostatic attraction. The platform can not only move in a direction perpendicular to the wafer surface (usually defined as the z direction), but can also move and / or rotate in other directions.

[0042] Other systems may also be used to perform the methods described in the various examples above.

[0043] According to a second main aspect of the invention, the invention relates to a method for obtaining a sequence of mutually parallel cross-sectional images of a measurement location of a wafer, wherein the wafer is carried by a platform, the method comprising the following steps:

[0044] 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, the FIB column optical axis and the CPB optical axis intersect the wafer surface at two different locations, the difference between the two different locations defining an offset on the wafer surface, the offset allowing the working distances of the FIB column and the CPB imaging column to be independently set without being subject to geometrical limitations due to the shape and / or position of the FIB column and the CPB imaging column;

[0045] 2b) using the FIB column to remove a surface layer of the cross-section at the first measurement location of the wafer to form a new cross-section that can be used for imaging;

[0046] 2c) moving the wafer surface by moving the stage relative to the FIB column and the CPB imaging column according to the offset;

[0047] 2d) Imaging the new cross section of the first measurement location of the wafer with the CPB imaging column.

[0048] According to a second main aspect of the invention, the concept of coincidence is abandoned and an offset arrangement is used instead. The advantage is that the working distances of the FIB column and the CPB imaging column can be set independently of each other and can therefore be optimized. In particular, the short working distance of the CPB imaging column is not blocked by the FIB column. Therefore, the imaging resolution can be improved compared to a "normal" wedge cutting configuration with coincidence. Additional stage movements can also be implemented relatively quickly. It is advantageous to use a high-precision stage. Optionally, one or more registration or alignment steps can be implemented. Also according to the second main aspect of the invention, it is not necessary to completely destroy or destroy the wafer. In an example, as in the "normal" wedge cutting method, such a configuration can be used to perform the method, according to which the FIB optical axis is set at an inclined angle relative to the top wafer surface.

[0049] According to an example, the method further comprises the following steps:

[0050] 2e) moving the wafer surface according to the offset by stage movement relative to the FIB column and the CPB imaging column.

[0051] In principle, this 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, transferred to a second position for imaging and transferred 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, which can be arranged alternately in a line, for example, each column is offset from each other by the same value. The processing can then be carried out in the processing line. Each offset will advance the measurement site from one column to the next.

[0052] According to the example, the sequence of method steps 2b), 2c), 2d) and 2e) is repeatedly performed.

[0053] According to an example, the relative movement comprises a lateral platform movement or a platform rotation. Platform rotation allows a relatively clear and fast switch between two positions, in which milling is performed and in which imaging is performed. For example, in a processing line implementation, a lateral movement is preferred.

[0054] According to an example, the working distance of the FIB column is optimized, and / or the working distance of the CPB imaging column is optimized.

[0055] 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.

[0056] According to an example, the method further comprises obtaining a sequence of mutually parallel cross-sectional images of the second measurement location of the wafer by repeatedly performing a sequence of method steps 2b), 2c) and 2d) at the second measurement location,

[0057] wherein the step of removing the cross-sectional surface layer at the second measurement position of the wafer and imaging the new cross-sectional surface of the first measurement position of the wafer with the CPB imaging column are performed simultaneously, and

[0058] The step of removing the cross-sectional surface layer at the first measuring position of the wafer and imaging the new cross-section of the second measuring position of the wafer with the CPB imaging column are performed simultaneously.

[0059] This example allows the entire process to be parallelized, thereby increasing the overall speed. The method steps of milling (removing the cross-sectional image layer) and imaging are performed at least partially simultaneously. In terms of time, the processing steps are at least partially overlapped. For example, the milling and imaging processing steps may start at the same point in time, but one process ends earlier (faster) than the other process. A common starting point facilitates synchronization of the processes. Other implementations are also possible.

[0060] According to another aspect of the invention, the invention relates to a computer program product having a program code adapted to execute the method as described in the different examples above.

[0061] According to another aspect of the present invention, the present invention relates to a single chamber system, comprising:

[0062] 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, the FIB optical axis and the CPB optical axis intersect the 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 the working distances of the FIB column and the CPB imaging column without being subject to geometrical limitations due to the shape and / or position of the FIB column and the CPB imaging column;

[0063] a platform for supporting a wafer and configured to be movable in a plane parallel to a surface of the wafer; and

[0064] Controls;

[0065] Wherein, the control component is configured to control the FIB device, the CPB imaging device and the platform to perform the method as described in the aforementioned different examples of the second main aspect of the present invention.

[0066] The platform can be movable in a plane parallel to the wafer surface. Thus, the platform can, for example, be rotated about an axis perpendicular to the wafer surface. Additionally or alternatively, the platform can be configured for lateral movement, for example in the x-direction and / or the y-direction. The platform can also additionally be moved vertically (in the z-direction).

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

[0068] According to a third aspect of the present invention, the present invention relates to a method for obtaining a sequence of cross-sectional images parallel to each other of a measurement portion of a wafer, the method comprising the following steps:

[0069] 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;

[0070] 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;

[0071] 3c) moving the FIB column along its optical axis to place the FIB column within its determined working distance (which is optimized or traded off) and / or moving the CPB imaging column along its optical axis to place the CPB imaging column within its determined working distance (which is traded off or optimized);

[0072] 3d) using the FIB column configured within its working distance to remove a surface layer of the cross section at the measurement location of the wafer to form a new cross section that can be used for imaging; and

[0073] 3e) imaging the new cross section at the measurement location of the wafer using the CPB imaging column configured within its working distance.

[0074] According to this embodiment, it is decided which of the aspects "milling" or "imaging" has a higher importance in a specific step. Then, by optimizing the respectively assigned working distance of one of the columns, a higher weight or priority is given to the more important aspect. Other working distances, called "trade-off" working distances, are not optimal, but are still good and / or are selected according to the best remaining possibilities. For example, if 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 reducing the working distance of the FIB column. An algorithm for determining the trade-off working distance can be applied. Also according to the third main aspect of the invention, it is not necessary to completely destroy or destroy the wafer. In an example, as in the "normal" wedge cutting method, the method can be performed with a setup in which the FIB optical axis is configured at an inclined angle relative to the top wafer surface.

[0075] According to the example, the sequence of method steps 3d) and 3e) is repeatedly performed.

[0076] According to an example, step 3c) comprises:

[0077] shorten the working distance of the FIB column and increase the working distance of the CPB imaging column, or

[0078] Increase the working distance of the FIB column and shorten the working distance of the CPB imaging column.

[0079] According to one aspect of the invention, the invention relates to a computer program product having a program code adapted to execute the method as described in the different examples described above according to the third main aspect of the invention.

[0080] According to one aspect of the present invention, the present invention relates to a single chamber system, comprising:

[0081] A focused ion beam (FIB) column and a charged particle beam (CPB) imaging column adapted to be arranged in a coincident configuration, in which 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;

[0082] 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;

[0083] a platform for supporting a wafer; and

[0084] Controls;

[0085] Wherein, the control component is configured to control the FIB column, the CPB imaging column and the platform to perform the method described in the aforementioned different examples regarding the third main aspect of the present invention.

[0086] Other systems may also be used to perform the methods described in the above different examples of the third main aspect of the present invention.

[0087] According to a fourth main aspect, the invention relates to a method for obtaining a sequence of first cross-sectional images of a first measurement location on a first wafer and a sequence of second cross-sectional images of a second measurement location on a second wafer, the method comprising:

[0088] 4a) providing a first wafer on a first platform and positioning the first wafer on the first platform;

[0089] 4b) providing a second wafer on a second platform and positioning the second wafer on the second platform;

[0090] 4c) removing a first cross-sectional surface layer of the first measurement location of the first wafer using a FIB column operating at a set FIB working distance so that a first new cross section is available for imaging;

[0091] 4d) exchanging the positions of the first platform and the second platform;

[0092] 4e) imaging the first new cross section at the first measurement location of the first wafer with the CPB imaging column at the set working distance, and simultaneously removing a second cross section surface layer at the second measurement location of the second wafer with the FIB column at the set FIB working distance, so that the second new cross section can be used for imaging;

[0093] 4f) exchanging the positions of the first platform and the second platform;

[0094] 4g) imaging the second new cross section at the second measurement location of the second wafer with the CPB imaging column at the set working distance, and simultaneously removing another first cross section surface layer of the first measurement location of the first wafer with the FIB column at the set FIB working distance, so that another first new cross section can be used for imaging

[0095] 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, but are used in combination with different platforms.

[0096] The exchange or switching of the positions of the first platform and the second platform can be achieved by using methods known in the art and similar methods described in, for example, US7161659 BB. The exchange of platform positions can be parallelized, thereby speeding up the process.

[0097] According to the example, the sequence of method steps 4d), 4e), 4f) and 4g) is repeatedly performed. Preferably, the method steps are repeated until the measurement locations in both wafers have been milled and imaged with the desired slice thickness.

[0098] According to an example, a plurality of first measurement locations on the first wafer are milled sequentially and imaged sequentially; and a plurality of second measurement locations on the second wafer are milled sequentially and imaged sequentially. Thus, before exchanging the position of the platform, preferably all measurement locations present on one wafer are milled (one slice) or imaged, respectively. Milling and imaging are again performed in parallel, so at least partially simultaneously.

[0099] According to an example, monitoring the removal of the first or / and the second profile surface layer by low-resolution imaging; and / or imaging the new first or / and the second profile comprises high-resolution imaging. The terms "high-resolution" and "low-resolution" imaging are relative terms; they should not be interpreted in an absolute sense. However, these terms indicate that one of the resolutions is better or worse than the other. This may have an impact on the applied column / its working distance: due to the configuration of the FIB column used for milling, a relatively low imaging resolution is sufficient to monitor or monitor the milling, and another CPB imaging column can be applied, which can be arranged according to the normal wedge cutting symmetry, for example. Nevertheless, since the more important process in this cross-beam configuration 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 the imaging process as a real image generation process, the optimal working distance can be set for the imaging measurement site on the wafer located on the platform at the location of the CPB imaging column that is actually present.

[0100] According to an example, low-resolution imaging is performed by a low-resolution scanning electron microscope (SEM) in a cross-beam configuration with the FIB column for removing 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 for correcting imaging aberrations.

[0101] According to an example, exchanging the positions of the first platform and the second platform comprises transferring positioning information. Thus, it is not necessary to position the wafer separately on the corresponding platform of each column, but in principle one positioning is sufficient. Optionally, additional alignment steps can be implanted to correct minor position deviations.

[0102] 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 redeposition does not disturb the imaging quality of the (high resolution) CPB imaging column.

[0103] According to an example, exchanging the positions of the first platform and the second platform comprises transferring one of the platforms from the first chamber to the second chamber or vice versa. The transfer may be achieved using one or two vacuum locks.

[0104] According to one aspect of the invention, the invention relates to a computer program product having a program code adapted to execute a method as described in the different preceding examples according to the fourth main aspect of the invention.

[0105] According to one aspect of the present invention, the present invention relates to a dual chamber system comprising:

[0106] A first chamber having a focused ion beam (FIB) column and a low-resolution charged particle beam (CPB) imaging column adapted to be arranged in a wedge-cut coincident configuration, in which 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;

[0107] a second chamber having a high-resolution CPB imaging column with its optical axis configured perpendicular to the wafer surface;

[0108] A first platform, which is used to carry a first wafer;

[0109] A second platform, which is used to carry a second wafer;

[0110] a platform exchange mechanism configured to exchange positions of the first platform and the second platform; and

[0111] Controls;

[0112] Wherein, the control member 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 as described in the aforementioned different examples of the fourth main aspect of the present invention.

[0113] Other systems may also be used to perform the methods described in the above different examples of the fourth main aspect of the present invention.

[0114] According to a fifth main aspect, the invention relates to a method for obtaining at least one sequence of parallel cross-sectional images of at least one measurement location of a wafer, the method comprising the following steps:

[0115] 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 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;

[0116] 5b) providing a second FIB column and a second CPB imaging column in a second chamber in an edge-cut coincident configuration, wherein the FIB optical axis of the second FIB column and the CPB optical axis of the second CPB imaging column are coincident and perpendicular to each other at the 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;

[0117] 5c) positioning the first wafer at at least one measurement location on the first platform;

[0118] 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;

[0119] 5e) taking out the at least one raw material block from the wafer and placing the at least one raw material block on a sample holder so that the measurement site of each raw material block is located at an edge of the sample holder;

[0120] 5f) transferring the sample holder with the at least one feedstock block into the second chamber;

[0121] 5g) positioning the at least one measurement site included in the at least one raw material block on a second platform;

[0122] 5h) obtaining at least one sequence of parallel cross-sectional images of the at least one measurement site by 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.

[0123] By this lifting-out process and positioning the chunk adequately on the sample holder (at the edge), the region of interest or measurement site can be kept close to the edge of the sample holder, thereby enabling the PCB imaging column to be configured perpendicular to the wafer surface or the surface of the chunk, which in turn results in a shorter possible working distance and enhanced imaging resolution.

[0124] According to an example, the method further comprises:

[0125] 5i) Moving the second platform so that the second measurement site can be used for milling and imaging. The second measurement site is usually 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 different ways and the movement mode may depend on the geometric characteristics of the second platform. If the second platform is circular (the surface is circular), the movement is preferably a rotation. If the second platform is ramp-shaped (for example, using a belt), the movement is preferably a lateral movement. In general, the raw material blocks can therefore be arranged linearly on the ramp so that all blocks are located at the edge.

[0126] According to an example, the method 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). Thus, it is possible to extract more raw material pieces from one wafer than placed on one sample holder. Of course, the entire procedure can be repeated for a second or additional wafer.

[0127] According to another aspect of the present invention, the present invention relates to a computer program product having a program code adapted to execute the method as described in the different aforementioned examples of the fifth main aspect of the present invention.

[0128] According to yet another aspect of the present invention, the present invention relates to a dual chamber system comprising:

[0129] The first room includes:

[0130] The first focused ion beam (FIB) column and the first charged particle beam (CPB) imaging column are adapted to be arranged in a wedge-cut coincidence configuration, in which the FIB optical axis of the FIB column and the CPB optical axis of the low-resolution CPB imaging column coincide on the wafer surface, and a configuration angle GFE is formed between the FIB optical axis and the CPB optical axis.

[0131] A first platform, which is used to carry a wafer;

[0132] a sample holder adapted to carry at least one raw material block,

[0133] a manipulator configured to extract a block of stock milled from the wafer and configured to place the block of stock on the sample holder;

[0134] The second room includes:

[0135] a second FIB column and a second CPB imaging column in an edge-cut coincident configuration, wherein the FIB optical axis of the second FIB column and the CPB optical axis of the second CPB imaging column coincide at 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 second CPB imaging column is arranged at a short working distance to allow high-resolution imaging;

[0136] A second platform, which is used to carry the sample holder;

[0137] 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

[0138] Controls,

[0139] The control member 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 the aforementioned different examples of the fifth main aspect of the present invention.

[0140] This example allows for efficient batch processing.

[0141] Other systems may also be used to perform the methods described in the above different examples of the fifth main aspect of the present invention.

[0142] As long as no technical contradiction occurs, the above-mentioned embodiments or examples can be combined with each other in whole or in part. This also applies to the examples or embodiments that describe different aspects or main aspects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0143] The present invention will be more fully understood with reference to the following drawings:

[0144] Figure 1 is an illustration of the cross-sectional imaging technique used to interpret samples extracted from a wafer;

[0145] Figure 2 is an illustration of a dual beam apparatus configured for a profile imaging technique applied to a wedge cut geometry of a wafer;

[0146] Figure 3 Details of the cross-sectional imaging technique showing the wedge-cut geometry;

[0147] Figure 4 showing oblique cross-sectional image slices through a plurality of HAR structures;

[0148] Figure 5 Showing a first workflow according to the present invention;

[0149] Figure 6 A system for performing a first workflow is schematically shown;

[0150] Figure 7 A second workflow according to the present invention is shown;

[0151] Figure 8 schematically illustrates a system for performing a second workflow;

[0152] Fig. 9 A third workflow according to the present invention is shown;

[0153] Fig.10 A fourth workflow according to the present invention is shown;

[0154] Fig.11 schematically illustrates a dual chamber system for performing a fourth workflow;

[0155] Fig.12 A fifth workflow according to the present invention is shown;

[0156] Fig.13 schematically illustrates a dual chamber system for performing a fifth workflow; and

[0157] Fig.14 The geometrical features and limitations in a dual beam system according to the prior art and according to one aspect of the present invention are schematically illustrated. DETAILED DESCRIPTION

[0158] Identical reference numerals in the figures denote identical features, even if not further described in the text.

[0159] Figure 1A schematic diagram of a common cross-sectional image method for acquiring a 3D volume image of an integrated semiconductor sample is shown. Using the cross-sectional method (also known as the slice and image method), three-dimensional (3D) volume image acquisition is achieved using a "step-and-repeat" approach. First, an integrated semiconductor sample is prepared for a common cross-sectional image method by methods known in the art. Small pieces or raw material blocks are extracted from a wafer and then further analyzed. Throughout the disclosure, "cross-sectional image" and "slice" will be considered synonymous. In one step, a thin surface layer or "slice" of material is removed. The material slice can be removed in several ways known in the art, including milling using a focused ion beam or polishing at a grazing angle using a focused ion beam (FIB) column 50. For example, a focused ion beam 51 propagates almost parallel to the z-axis and scans in the y direction to mill through the top surface 55 of the sample 10 (which may, for example, be a portion of a wafer) and expose a new cross-sectional surface 52 in the yz plane. As a result, the new exposed cross-sectional surface 52 can be used for imaging. In a subsequent step, the profile 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 profile image slice 100.1. The optical axis 42 of the charged particle imaging system 40 can be configured to be parallel to the x-direction or tilted at a certain angle with respect to the x-direction. Secondary electrons and backscattered electrons are collected by a detector (not shown) to reveal the material contrast inside the integrated semiconductor sample and are visible in the profile image slice 100.1 at different gray levels. Metal structures produce brighter measurements. Milling is repeated through the profile surfaces 53 and 54 and other profiles at equal distances d to remove the surface layer and the profile imaging process to obtain a series of 2D profile image slices 1000, including, for example, N profile image slices 100.2, 100.3, ..., 100.N at different depths to establish a three-dimensional 3D data set. Representative cross-sectional image slice 100.1 was obtained by measuring a commercial Intel processor integrated semiconductor chip using 14 nm technology.

[0160] With this method, at least first and second cross-sectional image slices are generated by subsequently milling the cross-sectional surface into the integrated semiconductor sample with a focused ion beam to expose or make accessible a series of cross-sectional surfaces for imaging, so that each cross-sectional surface of the integrated semiconductor sample is imaged with a charged particle beam imaging system 40. A 3D image of the integrated semiconductor structure is reconstructed from the sequence of N 2D cross-sectional image slices 1000. The distance d of the cross-sectional image slices 100.1, 100.2, 100.3 can be controlled by a FIB milling or polishing process and can be controlled between 1 nm and 30 nm.

[0161] In the above example, the cross-sectional image plane is oriented perpendicular to the top surface 55 of the integrated semiconductor wafer, and the normal to the top surface 55 of the wafer is oriented parallel to the z-direction, as shown in FIG. Figure 1 This results in the 2D cross-sectional image slices being oriented parallel to the yz plane, or in other words, the cross-sectional image plane includes the z-axis or wafer normal axis, and the imaging direction x is parallel to the wafer surface. Therefore, the conventional slice and image method in this conventional geometry is only applicable to samples extracted from the wafer.

[0162] 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 extending into the depth of the sample 10.

[0163] In both configurations described above, the working distances of the FIB column and the CPB imaging column can be set independently. Thus, both working distances can be optimized. Generally speaking, the shorter the working distance, the better the imaging resolution. Therefore, high-resolution imaging using the CPB imaging column 40 is possible because a short working distance can be set without geometrical restrictions.

[0164] However, there remains a general problem: the measurement site of the wafer needs to be located close to the edge of the wafer to allow measurement using the depicted geometry of 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 condition suitable for further analysis.

[0165] Figure 2 A method for generating a 3D volume image using a slice and image method is disclosed, which is applied to an inspection volume within a wafer in a so-called "wedge cut" method or wedge cut geometry without removing a sample 10 from the wafer 8. The slice and image method is applied to an inspection volume of a few micrometers in size, for example, extending 5um to 10um laterally in a 200mm or 300mm wafer, without removing the sample from the wafer 8. A groove or edge is milled in the top surface 55 of the integrated semiconductor wafer 8 to enable access to a cross section at an angle to the top surface 55. The 3D volume image of the inspection volume is acquired at a limited number of measurement locations, such as representative locations of a die, such as at a process control monitor (PCM), or at locations identified by other inspection tools. The slice and image method only locally destroys the wafer, and other dies can still be used, or the wafer can still be used for further processing.

[0166] Figure 2A wafer inspection system 500 is disclosed, which is configured for performing a slicing and imaging method under a wedge-cutting geometry using a dual-beam device 1. For a wafer 8, a plurality of 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. The wafer 8 is placed on a wafer support table 15. The wafer support table 15 is mounted on a platform 155 having an actuator and position control. Actuators and devices such as laser interferometers for precise control of the wafer platform are known in the art. A control unit 16 is configured to control the wafer platform 155 and adjust the measurement location 6.1 of the wafer 8 at the intersection 43 of the dual-beam device 1. The dual-beam device 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 43 of the two optical axes of the FIB and the CPB imaging system, the wafer surface 55 is configured to be at an inclined angle GF to the FIB axis 48. The FIB axis 48 and the CPB imaging system axis 42 include an angle GFE, and the CPB imaging optical axis 42 forms an angle GE with the normal to the wafer surface 55. Figure 1 In the coordinate system of , the normal to the wafer surface 55 is provided by the z-axis. A focused ion beam (FIB) 51 is generated by the FIB column 50 and impinges on the surface 55 of the wafer 8 at an angle GF. Using ion beam milling at the measurement location 6.1, an inclined profile surface is milled into the wafer at approximately the tilt angle GF. Figure 2 In the example of FIG. 4 , the tilt angle GF is about 30°. Due to the beam divergence of a focused ion beam (e.g., a gallium ion beam), the actual tilt angle of the tilted profile surface may deviate from the tilt angle GF by 1° to 4°. An image of the milled surface is acquired using a charged particle beam imaging system 40 tilted at an angle GE relative to the wafer normal. Figure 2 In the example of , the angle GE is about 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 surface 55.

[0167] During imaging, the charged particle beam 44 is scanned by a scanning unit of the charged particle beam imaging system 40 along a scanning path on the cross-sectional surface of the wafer 8 at the measurement site 6.1, and secondary particles as well as scattered particles are generated. The particle detector 17 collects at least some of the secondary particles and scattered particles and communicates the particle counts 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 platform 155. The control unit 19 communicates with the operation control unit 2, which uses the wafer platform movement to trigger, for example, the placement and alignment of the measurement site 6.1 of the wafer 8 at the intersection 43, and triggers repeated operations of FIB milling, image acquisition and platform movement.

[0168] 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).

[0169] However, since both the FIB column 50 and the CPB imaging column 40 are located above the wafer top surface 55, there are geometric limitations on their configuration. It is no longer possible to optimize the two working distances separately, because the columns 40, 50 begin to block each other at short working distances. As a general rule of practice, the location 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 cannot typically be shorter than 4 to 5 mm. In contrast, if Figure 1 The working distance of the CPB imaging column 40 shown can be as short as about 2 mm. Figure 2 In the wedge-cut configuration shown, Figure 1 Compared to the edge configuration shown, imaging resolution is typically reduced by an order of magnitude.

[0170] Figure 3 More details of the slicing and imaging method in a wedge-cut geometry are described. By repeating the slicing and imaging method in a wedge-cut geometry, a plurality of J sectional image slices including image slices of the sectional surfaces 52, 53.i ... 53.J are generated and a 3D volume image of the inspection volume 160 at the measurement location 6.1 of the wafer 8 at the measurement location 6.1 is generated. Figure 3 The wedge cutting geometry in the 3D memory stack example is shown. The profile surfaces 53.1 ... 53.N are milled using the FIB beam 51 at an angle GF of about 30° to the wafer surface 9, but other angles GF are possible, for example between GF = 20° and GF = 60°. Figure 3The situation is shown when the surface 52 is a new section that was last milled by the FIB 51. For example, the section surface 52 is scanned by the SEM beam 44, which is Figure 3 In the example of , a cross-sectional image slice is configured to be incident perpendicularly to the wafer surface 55 and to generate a high-resolution cross-sectional image slice. The cross-sectional image slice includes a first cross-sectional image feature formed by an intersection with a high aspect ratio (HAR) structure or via (e.g., the first cross-sectional image feature of the HAR structures 4.1, 4.2, and 4.3); and a second cross-sectional image feature formed by an intersection with a layer L.1...LM, the layer L.1...LM including, for example, a SiO2, SiN- or tungsten line or word line layer. The maximum number of layers M is typically greater than 50, for example, greater than 100 or even greater than 200. The HAR structures and layers extend throughout most of the volume in the wafer, but may include gaps. The HAR structure typically has a diameter of less than 100 nm, for example, about 80 nm, or for example 40 nm. Therefore, the cross-sectional image slice includes a first cross-sectional image feature as an intersection or cross-section of the HAR structure footprint at different depths (Z) at corresponding XY positions. In the case of cylindrical vertical memory HAR structures, the first cross-sectional image features obtained are circular or elliptical structures at different depths determined by the location of the structure 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 the minimum distance d between two adjacent cross-sectional image slices is adjusted to a value of the order of a few nm, such as 30 nm, 20 nm, 10 nm, 5 nm, 4 nm or even less. Once the material layer of a predetermined thickness d is removed using the FIB, the next cross-sectional surface 53.i ... 53.J is exposed and can be used for imaging using the charged particle imaging beam 44.

[0171] Figure 4 An oblique cross-sectional image slice through multiple HAR structures is shown. In more detail, Figure 4 A cross-sectional image slice 311.1 generated by the imaging charged particle beam 41 and corresponding to the cross-sectional surface 301.1 is shown. The cross-sectional image slice 311.1 includes an edge line 315 at the edge coordinate y1 between the oblique cross section and the surface 55 of the wafer. Just at the edge, the image slice 311.1 shows several cross sections 307.1 ... 307.S through the HAR structure, which intersect the cross-sectional surface 301.1. In addition, the image slice 311.1 includes cross sections of a plurality of word lines 313.1 to 313.3 at different depths or z positions. Using these word lines 313.1 to 313.3, a depth map Z1 (x, y) of the oblique cross-sectional surface 301.1 can be generated.

[0172] In an example, features and 3D positions of semiconductor structures of interest (e.g., positions of HAR channels) are detected using image processing methods (e.g., from the HAR centroid). 3D volume 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 102019006645.6, which are hereby fully incorporated by reference into the present invention. It should be mentioned that the layers and HAR structures do not need to extend through the entire measurement volume.

[0173] To improve 3D tomography data and 3D metrology measurement problems, improved imaging resolution is required. At the same time, the wafer containing the measurement site of interest should remain intact and therefore still usable after the 3D image of the measurement site is generated.

[0174] The present invention solves these problems by decoupling the working distance of the CPB imaging column from the limitations caused by the FIB geometry, as explained in the general part of the specification. The present invention is further illustrated below using several embodiments. However, these embodiments should not be considered as limiting the present invention.

[0175] Figure 5 A first workflow according to the present invention is shown, and Figure 6 A dual-beam device 1 suitable for carrying out a first workflow is schematically shown. Figure 6 a In principle, it reveals Figure 2 The wedge cutting configuration shown is slightly modified compared to the wedge cutting configuration. Figure 2 As shown, a wafer 8 with a plurality of measurement locations 6 (here: two measurement locations) is arranged on a wafer support table 15 supported by a platform 155. The platform in the example shown can be moved in all three dimensions (x, y, z) of space, as indicated by the arrows. In addition, the platform 155 can be rotated or at least the wafer support table 15 can be rotated. The platform control unit 16 ( Figure 6 (not shown) controls these movements.

[0176] In the depicted example, the CPB imaging optical axis 42 is configured perpendicular to the wafer top surface 55. In principle, this allows for top-down imaging of HAR structures in the sample or wafer 8. The FIB column 50.1 is configured at an oblique angle relative to the wafer top surface 55. The FIB optical axis 48 and the CPB optical axis 42 intersect each other at a coincidence point 43 located at the wafer top surface 55. However, unlike Figure 2 Compared to the configuration shown in Figure 6The configuration angle GFE between the FIB optical axis 48 and the CPB optical axis 42 in a is reduced. If imaging is performed in this position, this will increase the working distance of the CPB imaging column. However, according to the present invention, only the milling process using the FIB column 50.1 is performed in the depicted coincident configuration. In the depicted example, the working distance of the FIB column 50.1 can be selected as optimal.

[0177] After removing the surface layer of the cross section using FIB 50.1, the FIB is stopped or blanked. The configuration of columns 50.1 and 40 is then changed to Figure 6 Configuration shown in b: The working distance of the CPB imaging column 42 is shortened in the direction of the CPB optical axis. In the described case, this shortening is achieved by moving the platform in the z direction, which is indicated by the large arrow at the platform 155. However, in principle, in addition or alternatively, a movement of the CPB imaging column 40 itself can also be performed. After shortening the working distance, imaging is performed at a shorter working distance. A shorter working distance allows for better imaging resolution. In addition, the movement of the platform in the z direction can be performed quite quickly and also with quite high precision. After imaging an accessible section, the platform 155 (or the CPB imaging column 40) can be moved back down again until a coincident configuration is reached again. Then, the next slice can be milled using the FIB 50.1, and the process can be repeated for the measurement site 6 as well as for other measurement sites.

[0178] Fig.14 The geometric features and limitations in the dual beam system 1 are further illustrated: Fig.14 a) depicts the geometric configuration of a wedge cut according to the prior art, and Fig.14 b) depicts the geometrical features and advantages according to the first aspect of the 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 close to the wafer 8 can be approximated as having an opening angle α FIB and α CPB Obviously, the FIB column 50 and the CPB imaging column 40 must not block each other, and in particular, the FIB column 50 must not be arranged in the available space below the CPB imaging column 40.

[0179] In addition, according to Fig.14In the prior art dual beam device 1 configuration shown in FIG. a, the bottom edge 49 of the FIB column 50 is configured 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 columns 40 can also become small, which in principle allows 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 also exists, because otherwise the FIB column 50 will contact the wafer 8. In addition, it must be remembered that generally the wafer 8 must be moved in a plane perpendicular to the optical axis of the CPB imaging column 40 (here: z-axis), and the wafer 8 cannot contact the FIB column 50 during the movement.

[0180] According to a first aspect of the invention, the geometrical configuration of the dual beam device 1 is different: Fig.14 As shown in b), the FIB column 50 is retracted from the wafer 8, the bottom edge 49 is no longer configured to be parallel to the wafer top surface 55, and the configuration angle GFE2 is smaller than the configuration angle GFE1. Therefore, in the milling process, the working distance WD2 of the CPB imaging column 40 is greater than Fig.14 a) Working distance WD1 shown. 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 as a result. However, this resolution is still sufficient to monitor the milling.

[0181] On the other hand, after milling, the relative distance between the wafer top surface 55 and the CPB imaging column 40 can now be shortened in the new configuration according to the first aspect of the invention, for example by moving the stage dz in the z direction. The second shortened position Pos2 is also Fig.14 In the second position Pos2, a working distance WD3 can be used for high-resolution imaging, which is smaller than the working distance WD1.

[0182] Figure 5An exemplary workflow is summarized: 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 the coincident configuration, a surface layer of a cross section of a measurement site 6 of a wafer 8 is removed using the FIB column 50.1 to form a new cross section that can be used for imaging. In step S3, the working distance between the CPB imaging column 40 and the wafer top surface 55 in the direction along the optical axis 42 of the CPB imaging column 40 is shortened, for example using a stage movement in the z direction. In step S4, the new cross section at the measurement site 6 of the wafer 8 is imaged using the CPB imaging column 40 at the shortened working distance and is therefore not in a coincident configuration. In step S5, the working distance between the CPB imaging column 40 and the wafer top surface 55 is increased in the direction along the axis 42 of the CPB imaging column 40 until a coincident configuration is reached (again). Steps S2 to S5 may be repeated until the measurement site is completely milled and imaged. The process is then terminated in step S6. Of course, this workflow can be repeated for the next measurement location 6 .

[0183] Figure 7 A second workflow according to the present invention is shown, and Figure 8 A dual beam device 1 suitable for performing a second workflow is schematically shown. In contrast to the first workflow, where coincidence points are still used during milling, coincidence points are completely abandoned in the second workflow. Instead of a coincidence configuration, an offset configuration of the two columns 50.1, 40 is applied: 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 positions, the difference between the two different positions defining an offset level from the wafer top surface 55, which is indicated by a double arrow. This offset allows the working distances of the FIB column 50.1 and the CPB imaging column 40 to be set independently without geometrical restrictions due to the shape and / or position of the FIB column 50.1 and the CPB imaging column 40. Thus, an optimal working distance can be set for both the FIB column 50.1 and the CPB imaging column 40. However, before performing imaging or milling, the wafer needs to be relatively moved relative to the two columns 50.1, 40 according to the offset. One possibility for such a relative movement is a stage movement, for example a lateral stage movement (in the depicted example, in the y direction).

[0184] It should be noted that the offset can be set flexibly within a certain range. In practice, the offset has a minimum size below which the columns 50.1 and 40 can no longer block each other. However, the offset can be larger than this minimum size. Therefore, it is preferred to adjust the offset to the distance between two measurement locations 6 on the wafer 8. Then, the first measurement location can be milled and the second measurement location can be imaged. The use of other columns can make milling and imaging more parallel. It is also possible to rotate the platform 155 (or at least the wafer support table 15) so that switching between the two measurement locations 6 is possible. This also allows parallel milling and imaging of the two measurement locations 6.

[0185] Figure 7 An exemplary workflow is summarized: 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 can be selected as optimal. In step S11, a profile surface layer is removed at a first measurement site 6 of a wafer 8 using the FIB column 50.1 to form a new profile that can be used for imaging. In step S12, the wafer surface is relatively moved, for example, by lateral stage movement or by stage rotation according to the offset. In step S13, the new profile of the first measurement site 6 of the wafer 8 is imaged using the CPB imaging column 40. In step S14, the wafer 8 is relatively moved (back) again according to the offset. Then, in step S11, the next profile surface layer can be removed, and steps S12 to S14 are repeated. When a complete site 6 has been milled and imaged, the process ends, for example, in step S15. Then, another site 6 can be milled and imaged. As described above, the process can also be parallelized if the offset is adjusted to the distance between different measurement sites 6.

[0186] Fig. 9A third workflow according to the present invention is shown. 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 configure the FIB column in its determined working distance (which is optimized or trade-off) and / or the CPB imaging column is moved along its optical axis to configure the CPB imaging column in its determined working distance (which is trade-off or optimized). In step S23, a surface layer of a cross section is removed at a measurement site of a wafer 8 using a FIB column 50.1 configured within its working distance to form a new cross section that can be used for imaging. In step S24, the new cross section at the measurement site 6 of the wafer 8 is imaged using the CPB imaging column 40 configured in its working distance. Milling and imaging (steps S23 and S24) can be repeated. In step S25, the process ends. The working distances of the FIB column and the CPB imaging column are not both optimal at the same time; but one of them is selected as optimal (which means the best under given circumstances or constraints) and the other is selected as much as possible under given circumstances and constraints, which now includes the optimization of the other column and thus the given working distance. For example, if in a use case where imaging resolution is more important than milling quality, the working distance of the CPB imaging column 40 can be shortened at the expense of shortening the working distance of the FIB column 50.1. This can be applied in the algorithm for determining the trade-off working distance.

[0187] Fig.10 A fourth workflow according to the present invention is shown, and Fig.11 A dual chamber system suitable for performing the fourth workflow is schematically shown. The dual chamber system comprises a first chamber 70.1 and a second chamber 70.2. According to this dual chamber solution, milling and high-resolution imaging are spatially separated. Milling is performed in the first chamber 70.1. High-resolution imaging is performed in the second chamber 70.2. The wafer 8 is transferred between the two chambers 70.1, 70.2 so that milling and high-resolution imaging can be performed alternately.

[0188] In more detail, the first chamber 70.1 comprises a dual beam system 1.1 having a FIB column 50.1 and a CPB imaging column 40.1 arranged according to a coincident configuration. However, the CPB imaging column 40.1 itself is not used for imaging the cross-section, but the FIB 50.1 is only used for supervising / monitoring the milling process. For such supervision or monitoring purposes, a lower imaging resolution is usually sufficient. Therefore, the working distance of the FIB column 50.1 can be optimized at the expense of the imaging resolution of the CPB imaging column 40 (greater working distance).

[0189] When the profile surface layer is easily milled, the wafer 8 is transferred to the second chamber 70.2 for high-resolution imaging. According to the depicted example, the second chamber 70.2 includes a high-resolution CPB imaging device 40.2. In principle, the device 40.2 can be the same as the device 40.1 in the first chamber; however, since the working distance can be optimized, there will be a better imaging resolution. However, it is preferred to apply a CPB imaging device 40.2 in the second chamber 70.2, which is different from and more advanced than that used in the 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).

[0190] The transfer of the wafer 8 between the two chambers 70.1 and 70.2 can be carried out in different ways. One possibility is to transfer the wafer support table 15, according to which the wafer 8 is already positioned. Alternatively, the complete platform 155.1 can be transferred from one chamber to the other. If a second platform 155.2 is applied, the method can be further improved: it is then possible to work on the two wafers 8.1 and 8.2 in parallel. When, for example, one wafer 8.1 is milled 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 carried out using a platform transfer interface 80. Optionally, the transfer interface 80 can be provided with one or two vacuum locks (not shown), for example to prevent the grinding deposition material from entering the imaging chamber or the second chamber 70.2.

[0191] Fig.10A possible workflow of a method for obtaining a first cross-sectional image sequence of a first measurement location 6.1 located on a first wafer 8.1 and a possible workflow of a method for obtaining a second cross-sectional image sequence of a second measurement location 6.2 located on a second wafer 8.2 are summarized by way of example. In step S30, the first wafer 8.1 is arranged on a first platform 155.1 and the first wafer 8.1 is positioned on the first platform 155.1. In step S31, the second wafer 8.2 is arranged on a second platform 155.2 and the second wafer 8.2 is positioned on the second platform 155.2. In step S32, a first cross-sectional surface layer of the first measurement location 6.1 of the first wafer 8.1 is removed using a FIB column 50.1 operating at a set FIB working distance so that a first new cross section is available for imaging. In step S33, the positions of the first platform 155.1 and the second platform 155.2 are exchanged. In step S34, the first new cross section at the first measurement site 6.1 of the first wafer 8.1 is imaged at the set working distance using the CPB imaging column 40.2, and simultaneously the second cross section surface layer of the second measurement site 6.2 of the second wafer 8.2 is milled at the set FIB working distance using the FIB column 50.1, so that the second new cross section is available for imaging. In step S35, the positions of the first platform 155.1 and the second platform 155.2 are changed again, and the wafers 8.1 and 8.2 are transferred from one chamber to another, respectively. In step S36, the second new cross section at the second measurement site 6.2 of the second wafer 8.2 is imaged at the set working distance using the CPB imaging column 40.2, and simultaneously the other first cross section surface layer of the first measurement site 6.1 of the first wafer 8.1 is removed at the set FIB working distance using the FIB column 40.1, so that the other first new cross section is available for imaging. Steps S33 to S36 can be repeated until both measurement locations 6.1 and 6.2 are completely milled and imaged. In step S37, the exemplary process ends. It is also possible to sequentially mill and sequentially 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 lower and the entire process becomes faster.

[0192] Fig.12 A fifth workflow according to the present invention is shown, and Fig.13 A dual chamber system suitable for performing the fifth workflow is schematically shown.

[0193] The first chamber 70.1 comprises a first focused ion beam (FIB) column 50.1 and a first charged particle beam (CPB) imaging column 40.1 arranged in a wedge-cutting coincident configuration. The chamber 70.1 further comprises a first platform 155.1 on which a wafer 8 with a plurality of measurement sites 6 is positioned. The first chamber 70.1 is used only for sample preparation. Sample preparation comprises 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 sites 6 and is not used for slice removal. The first CPB imaging column 40.1 is used only for supervising milling; therefore, the lower imaging resolution of the first CPB imaging column 40.1 is sufficient. According to this example, the first chamber 70.1 further comprises an operator 21 for bringing out the raw material block 61 milled from the wafer 8. The operator 21 can arrange one or more raw material blocks 61 on the sample holder 60, wherein the raw material block 61 is placed at the edge of the sample holder 60. Milling, bringing out and raw material block positioning can be controlled directly or indirectly by the operation control unit 2.

[0194] Then, one or more raw material blocks 61 placed on the sample holder 60 can be transferred from the first chamber 70.1 to the second chamber 70.2 for milling and imaging. For example, the transfer can be carried out 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 with a correspondingly configured platform ( Fig.13 It is also possible to provide more than one sample holder 60. Providing more than one sample holder 60 can help parallelize the process: while placing the raw material block 61 on the first holder 60 in the first chamber 70.1, for example, the raw material block 61 placed on the second holder 60 can already be imaged in the second chamber 70.2.

[0195] In the present example, the second chamber 70.2 comprises a second FIB column 50.2 and a second CPB imaging column 40.2 in a coincident configuration. Since 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 the CPB column 40.2 can be used which allows edge cutting. Milling with the FIB column 50.2 can be performed alternately with high-resolution imaging by the CPB imaging column 40.2 in a manner known in principle in the art. For example, reference has been made to Figure 1 Further details are explained.

[0196] 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.

[0197] Fig.12An exemplary workflow for obtaining at least one parallel cross-sectional image sequence of at least one measurement location 6 of a wafer 8 is shown in FIG.

[0198] In step S40, the first focused ion beam (FIB) column 50.1 and the first charged particle beam (CPB) imaging column 40.1 are arranged in a wedge-cut coincidence configuration in the 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.

[0199] 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 coincidence configuration, in which the FIB optical axis of the second FIB column and the CPB optical axis of the second CPB imaging column coincide and are perpendicular to each other at the wafer 8 or the sample surface 55, the optical axis of the second CPB column 40.2 is configured to be perpendicular to the wafer or the sample surface 55, and the second CPB column 40.2 is configured at a short working distance that allows high-resolution imaging.

[0200] In step S42 , the first wafer 8 having at least one measurement location 6 is positioned on the first platform 155 .

[0201] In step S43, milling is performed around at least one measurement location 6 using the first FIB column 50.1 in the first chamber 70.1 to generate 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.

[0202] In step S44 , at least one raw material block 61 is lifted out of the wafer 8 , and at least one raw material block 61 is arranged on the sample holder 60 such that the measurement site 6 of each raw material block 61 is placed at the edge of the sample holder 60 .

[0203] In step S45 , the sample holder 60 with the at least one raw material block 61 is transferred into the second chamber 70 . 2 .

[0204] 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.

[0205] In step S47, at least one parallel section image sequence of at least one measurement site 6 is obtained by repeatedly milling at least one raw material block 61 with the second FIB column 50.2 and repeatedly imaging at least one raw material block 61 with the second CPB column 40.2 in the second chamber 70.2. Here, due to the geometric arrangement of the raw material block 61, high-resolution imaging is possible.

[0206] In optional step S48, the second platform 155.2 is rotated so that the second measuring location 6.2 on the second raw material block 61 can be used for milling and imaging.

[0207] 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 .

[0208] Other workflows and systems may be envisioned by those skilled in the art without departing from the scope of the present invention as defined by the claims.

[0209] Examples of the present invention will be provided below.

[0210] Example 1: A method for obtaining a sequence of mutually parallel cross-sectional images of a measurement portion of a wafer, the method comprising the following steps:

[0211] 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;

[0212] 1b) in the overlapped configuration, using the FIB column to remove a surface layer of a cross-section of a measurement portion of the wafer to form a new cross-section that can be used for imaging;

[0213] 1c) shortening the working distance between the CPB imaging column and the wafer surface in a direction along the axis of the CPB imaging column;

[0214] 1d) imaging the new cross-section at the measurement location of the wafer with the CPB imaging column at a reduced working distance and thus not in the coincident configuration;

[0215] 1e) Increasing the working distance between the CPB imaging column and the wafer surface in a direction along the axis of the CPB imaging column until the coincident configuration is achieved.

[0216] Example 2: A method as described in Example 1, wherein the sequence of method steps 1b), 1c), 1d) and 1e) is repeated.

[0217] 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 overlap configuration.

[0218] 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, in particular moving the platform vertically.

[0219] Example 5: A method as described in Example 1, wherein the CPB optical axis is aligned with the normal to the wafer surface.

[0220] Example 6: A 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°.

[0221] Example 7: A method as described in Example 1, wherein shortening the working distance between the PCB imaging columns includes moving the PCB imaging columns along the PCB optical axis.

[0222] Example 8: A computer program product having a program code suitable for executing the method according to Example 1.

[0223] Example 9: A single chamber system comprising:

[0224] A focused ion beam (FIB) column and a charged particle beam (CPB) imaging column adapted to be arranged in a coincident configuration, in which a FIB optical axis of the FIB column and a CPB optical axis of the CPB imaging column coincide on 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;

[0225] a platform adapted to carry a wafer and configured to be movable in a direction perpendicular to a surface of the wafer; and

[0226] Controls;

[0227] Wherein, the control component is configured to control the FIB column, the CPB imaging column and the platform to perform the method according to Example 1.

[0228] Example 10: A method for obtaining a sequence of cross-sectional images parallel to each other of a measurement portion of a wafer, wherein the wafer is supported by a platform, the method comprising the following steps:

[0229] 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, the FIB column optical axis and the CPB optical axis intersect the wafer surface at two different locations, the difference between the two different locations defining an offset on the wafer surface, the offset allowing the working distances of the FIB column and the CPB imaging column to be independently set without being subject to geometrical limitations due to the shape and / or position of the FIB column and the CPB imaging column;

[0230] 2b) using the FIB column to remove a surface layer of the cross-section at the first measurement location of the wafer to form a new cross-section that can be used for imaging;

[0231] 2c) moving the wafer surface by moving the stage relative to the FIB column and the CPB imaging column according to the offset;

[0232] 2d) Imaging the new cross section of the first measurement location of the wafer with the CPB imaging column.

[0233] Example 11: The method as described in Example 10 further comprises:

[0234] 2e) moving the wafer surface according to the offset by stage movement relative to the FIB column and the CPB imaging column.

[0235] Example 12: A method as described in Example 11, wherein the sequence of method steps 2b), 2c), 2d) and 2e) is repeated.

[0236] Example 13: A method as described in Example 10, wherein the relative movement includes lateral platform movement or platform rotation.

[0237] Example 14: The method of Example 10, wherein the working distance of the FIB column is optimized, and / or wherein the working distance of the CPB imaging column is optimized.

[0238] Example 15: The method of Example 10, wherein the offset matches the distance between the first measurement location on the wafer surface and the second measurement location on the wafer surface.

[0239] Example 16: The method as described in Example 15,

[0240] further comprising obtaining a sequence of mutually parallel cross-sectional images of the second measurement location of the wafer by repeatedly performing a sequence of method steps 2b), 2c) and 2d) at the second measurement location,

[0241] wherein the step of removing the cross-sectional surface layer at the second measurement position of the wafer and imaging the new cross-sectional surface of the first measurement position of the wafer with the CPB imaging column are performed simultaneously, and

[0242] The step of removing the cross-sectional surface layer at the first measuring position of the wafer and imaging the new cross-section of the second measuring position of the wafer with the CPB imaging column are performed simultaneously.

[0243] Example 17: A computer program product having a program code adapted to execute the method according to Example 10.

[0244] Example 18: A single chamber system comprising:

[0245] 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, the FIB optical axis and the CPB optical axis intersect the 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 the working distances of the FIB column and the CPB imaging column without being subject to geometrical limitations due to the shape and / or position of the FIB column and the CPB imaging column;

[0246] a platform adapted to carry a wafer and configured to move in a plane parallel to a surface of the wafer; and

[0247] Controls;

[0248] Wherein, the control component is configured to control the FIB device, the CPB imaging device and the platform to perform the method according to Example 10.

[0249] Example 19: A method for obtaining a sequence of cross-sectional images parallel to each other of a measurement portion of a wafer, the method comprising the following steps:

[0250] 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;

[0251] 3b) determining an optimized working distance for the FIB column and a tradeoff working distance for the CPB imaging column, or determining the tradeoff working distance of the FIB column and the optimized working distance of the CPB imaging column;

[0252] 3c) moving the FIB column along its optical axis to place the FIB column within its determined working distance and / or moving the CPB imaging column along its optical axis to place the CPB imaging column within its determined working distance;

[0253] 3d) using the FIB column configured within its working distance to remove a surface layer of the cross section at the measurement location of the wafer to form a new cross section that can be used for imaging; and

[0254] 3e) imaging the new cross section at the measurement location of the wafer using the CPB imaging column configured within its working distance.

[0255] Example 20: A method as described in Example 19, wherein the sequence of method steps 3d) and 3e) is repeated.

[0256] Example 21: The method of Example 19, wherein step 3c) comprises:

[0257] shorten the working distance of the FIB column and increase the working distance of the CPB imaging column, or

[0258] Increase the working distance of the FIB column and shorten the working distance of the CPB imaging column.

[0259] Example 22: A computer program product having a program code adapted to execute the method according to Example 19.

[0260] Example 23: A single chamber system comprising:

[0261] A focused ion beam (FIB) column and a charged particle beam (CPB) imaging column adapted to be arranged in a coincident configuration, in which 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;

[0262] 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 optical axis;

[0263] a platform for supporting a wafer; and

[0264] Controls;

[0265] 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.

[0266] Example 24: A method for obtaining a sequence of first cross-sectional images of a first measurement location on a first wafer and a sequence of second cross-sectional images of a second measurement location on a second wafer, the method comprising:

[0267] 4a) providing a first wafer on a first platform and positioning the first wafer on the first platform;

[0268] 4b) providing a second wafer on a second platform and positioning the second wafer on the second platform;

[0269] 4c) removing a first cross-sectional surface layer of the first measurement location of the first wafer using a FIB column operating at a set FIB working distance so that a first new cross section is available for imaging;

[0270] 4d) exchanging the positions of the first platform and the second platform;

[0271] 4e) imaging the first new cross section at the first measurement location of the first wafer with the CPB imaging column at the set working distance, and simultaneously removing a second cross section surface layer at the second measurement location of the second wafer with the FIB column at the set FIB working distance, so that the second new cross section can be used for imaging;

[0272] 4f) exchanging the positions of the first platform and the second platform;

[0273] 4g) imaging the second new cross-section at the second measurement location of the second wafer using the CPB imaging column at the set working distance, and simultaneously removing another first cross-section surface layer of the first measurement location 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.

[0274] Example 25: A method as described in Example 24, wherein the sequence of method steps 4d), 4e), 4f) and 4g) is repeated.

[0275] Example 26: The method as described in Example 24,

[0276] wherein a plurality of first measurement locations on the first wafer are milled and imaged sequentially; and

[0277] The plurality of second measuring locations on the second wafer are milled and imaged sequentially.

[0278] Example 27: The method as described in Example 24,

[0279] wherein the first and / or the second cross-sectional surface layer is removed using low resolution imaging supervision; and / or

[0280] Wherein imaging the new first and / or second profile comprises high resolution imaging.

[0281] Example 28: The method described in Example 27,

[0282] wherein low resolution imaging is performed by the FIB column for removing 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 for removing the first and second cross-sectional surface layers; and / or

[0283] 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).

[0284] Example 29: A method as described in Example 24, wherein exchanging the positions of the first platform and the second platform includes transferring positioning information.

[0285] Example 30: The method as described in Example 24,

[0286] Wherein the FIB column is disposed in a first chamber, and wherein the CPB imaging column is disposed in a second chamber.

[0287] Example 31: The method as described in Example 30,

[0288] Wherein exchanging the positions of the first platform and the second platform comprises transferring one of the platforms from the first chamber to the second chamber, or vice versa.

[0289] Example 32: A computer program product having a program code adapted to execute the method according to Example 24.

[0290] Example 33: A dual chamber system comprising:

[0291] A first chamber having a focused ion beam (FIB) column and a low-resolution charged particle beam (CPB) imaging column adapted to be arranged in a wedge-cut coincident configuration, in which 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;

[0292] a second chamber having a high-resolution CPB imaging column with its optical axis configured perpendicular to the wafer surface;

[0293] A first platform, which is used to carry a first wafer;

[0294] A second platform, which is used to carry a second wafer;

[0295] a platform exchange mechanism configured to exchange positions of the first platform and the second platform; and

[0296] Controls;

[0297] Wherein, 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.

[0298] Example 34: A method for obtaining at least one sequence of parallel cross-sectional images of at least one measurement location of a wafer, the method comprising the steps of:

[0299] 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 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;

[0300] 5b) providing a second FIB column and a second CPB imaging column in a second chamber in an edge-cut coincident configuration, wherein the FIB optical axis of the second FIB column and the CPB optical axis of the second CPB imaging column are coincident and perpendicular to each other at the 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;

[0301] 5c) positioning the first wafer having at least one measurement location on a first platform;

[0302] 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;

[0303] 5e) taking out the at least one raw material block from the wafer and placing the at least one raw material block on a sample holder so that the measurement site of each raw material block is located at an edge of the sample holder;

[0304] 5f) transferring the support with the at least one raw material block into the second chamber;

[0305] 5g) positioning the at least one measurement site included in the at least one raw material block on a second platform;

[0306] 5h) obtaining at least one sequence of parallel cross-sectional images of the at least one measurement site by 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.

[0307] Example 35: The method as described in Example 34 further comprises:

[0308] 5i) Moving the second platform to make the second measurement site available for milling and imaging.

[0309] Example 36: The method as described in Example 34 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).

[0310] Example 37: A computer program product having a program code suitable for executing the method according to Example 34.

[0311] Example 38: A dual chamber system comprising:

[0312] The first room includes:

[0313] 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, in which 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;

[0314] A first platform, which is used to carry a wafer;

[0315] a sample holder adapted to carry at least one raw material block,

[0316] a manipulator configured to extract a block of stock milled from the wafer and configured to place the block of stock on the sample holder;

[0317] The second room includes:

[0318] a second FIB column and a second CPB imaging column in an edge-cut coincident configuration, wherein the FIB optical axis of the second FIB column and the CPB optical axis of the second CPB imaging column coincide at 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 arranged at a short working distance to allow high-resolution imaging;

[0319] A second platform, which is suitable for carrying the sample holder;

[0320] 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

[0321] Controls,

[0322] Wherein, the control member 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 operator, the second chamber having the second FIB column, the second CPB imaging column and the second platform, and the sample holder transfer mechanism, so as to perform the method described in Example 34.

[0323] Reference numerals list

[0324] 1 Dual beam device

[0325] 2 Operating the control unit

[0326] 4. First section image feature 6. Measurement location

[0327] 8 chips

[0328] 10 Sample (e.g. extracted from a wafer)

[0329] 15 Wafer support

[0330] 16 Platform control unit

[0331] 17 Secondary electron detector

[0332] 19 Control Unit

[0333] 21 Operator

[0334] 40 Charged Particle Beam (CPB) Imaging Column

[0335] 42 Optical axis of imaging system

[0336] 43 intersection

[0337] 44 Imaging Charged Particle Beams

[0338] 46 Scan Path

[0339] 48 FIB optical axis

[0340] 49 bottom edge

[0341] 50 FIB column

[0342] 51 Focused Ion Beam

[0343] 52 Section Surface

[0344] 53 Section surface

[0345] 54 Section Surface

[0346] 55 Wafer top surface

[0347] 60 Sample holder

[0348] 61 Raw material block

[0349] Room 70

[0350] 80 Transfer interface

[0351] 100 cross-sectional image slices

[0352] 155 Chip Platform

[0353] 160 Check volume

[0354] Measured cross-sectional image of 307 HAR structure

[0355] 311 cross-sectional image slices

[0356] 313 Word Line

[0357] 315 Surface Edge

[0358] 500 Wafer Inspection System

[0359] 1000 2D image slice sequences

[0360] L.1…LM layer

[0361] d is the distance between adjacent sections or adjacent section image slices.

[0362] GF milling angle (angle between the wafer surface and the FIB axis at the intersection)

[0363] GE imaging angle (the angle between the CPB imaging system axis and the wafer surface normal at the intersection point)

[0364] GFE configuration angle (angle between FIB axis and CPB imaging system axis)

[0365] GFE1 configuration angle (angle between FIB axis and CPB imaging system axis)

[0366] GFE2 configuration angle (angle between FIB axis and CPB imaging system axis)

[0367] WD1 Working distance

[0368] WD2 Working Distance

[0369] WD3 Working Distance

[0370] dz height difference, platform movement

[0371] h Height

[0372] h' Height

[0373] Pos1 Position 1 during milling

[0374] Pos2 Position 2 during high-resolution imaging

[0375] α FIB Angle FIB Column

[0376] α CPB CPB imaging column

Claims

1. A method for obtaining a sequence of mutually 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) in the overlapped configuration, using the FIB column to remove a surface layer of a cross-section of a measurement portion of the wafer to form a new cross-section that can be used for imaging; 1c) shortening the 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 reduced working distance and thus 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.

2. The method as claimed in claim 1, wherein the sequence of method steps 1b), 1c), 1d) and 1e) is repeatedly performed.

3. The method of any of the preceding claims, further comprising imaging the removed cross-sectional surface layer with the CPB imaging column in the coincident configuration.

4. The method of any of the preceding claims, wherein shortening the working distance between the CPB imaging column and the wafer surface comprises moving a platform carrying the semiconductor sample, in particular moving the platform vertically.

5. The method of any of the preceding claims, wherein the CPB optical axis is aligned to the normal to the wafer surface.

6. The method of any one of the preceding claims, wherein the FIB optical axis is arranged at an oblique angle relative to the wafer top surface. 7 . The method as claimed in claim 1 , wherein for the configuration angle GFE the following relationship holds: 30°≤GFE≤45°, in particular 30°≤GFE≤40° or 30°≤GFE≤35°.

8. The method of any one of the preceding claims, wherein shortening the working distance between the PCB imaging columns comprises moving the PCB imaging columns along the PCB optical axis.

9. A computer program product having a program code adapted to perform the method according to any of the preceding claims.

10. 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, in which a FIB optical axis of the FIB column and a CPB optical axis of the CPB imaging column coincide on 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 adapted to carry a wafer and configured to be movable in a direction perpendicular to a surface of the wafer; and Controls; Wherein, the control component 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 8.

11. A method for obtaining a sequence of cross-sectional images parallel to each other 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, the FIB column optical axis and the CPB optical axis intersect the wafer surface at two different locations, the difference between the two different locations defining an offset on the wafer surface, the offset allowing the working distances of the FIB column and the CPB imaging column to be independently set without being subject to geometrical limitations due to the shape and / or position of the FIB column and the CPB imaging column; 2b) using the FIB column to remove a surface layer of the cross-section at the first measurement location of the wafer to form a new cross-section that can be used for imaging; 2c) moving the wafer surface by moving the 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.

12. The method of claim 11, further comprising: 2e) moving the wafer surface according to the offset by stage movement relative to the FIB column and the CPB imaging column.

13. The method as claimed in claim 12, wherein the sequence of method steps 2b), 2c), 2d) and 2e) is repeatedly performed.

14. The method of any one of claims 12 to 13, wherein the relative movement comprises lateral platform movement or platform rotation.

15. The method of any one of claims 12 to 14, wherein the working distance of the FIB column is optimized, and / or wherein the working distance of the CPB imaging column is optimized.

16. The method of any one of claims 12 to 15, wherein the offset is matched to a distance between the first measurement location on the wafer surface and a second measurement location on the wafer surface.

17. The method of claim 16, further comprising obtaining a sequence of mutually parallel cross-sectional images of the second measurement location of the wafer by repeatedly performing a sequence of method steps 2b), 2c) and 2d) at the second measurement location, in, The step of removing the cross-sectional surface layer at the second measurement location of the wafer and imaging the new cross-section of the first measurement location of the wafer with the CPB imaging column are performed simultaneously, and The step of removing the cross-sectional surface layer at the first measuring position of the wafer and imaging the new cross-section of the second measuring position of the wafer with the CPB imaging column are performed simultaneously.

18. The method of any one of claims 12 to 17, wherein the FIB optical axis is arranged at an oblique angle relative to the wafer top surface.

19. A computer program product having a program code adapted to perform the method according to any one of claims 12 to 18.

20. 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, the FIB optical axis and the CPB optical axis intersect the 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 the working distances of the FIB column and the CPB imaging column without being subject to geometrical limitations due to the shape and / or position of the FIB column and the CPB imaging column; a platform adapted to carry a wafer and configured to be movable in a plane parallel to a surface of the wafer; as well as Controls; Wherein, the control part is configured to control the FIB device, the CPB imaging device and the platform to perform the method according to any one of claims 12 to 18.

21. A method for obtaining a sequence of cross-sectional images parallel to each other 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 tradeoff working distance for the CPB imaging column, or determining the tradeoff working distance of the FIB column and the optimized working distance of the CPB imaging column; 3c) moving the FIB column along its optical axis to place the FIB column within its determined working distance and / or moving the CPB imaging column along its optical axis to place the CPB imaging column within its determined working distance; 3d) using the FIB column configured within its working distance to remove a surface layer of the cross section at the measurement location of the wafer to form a new cross section 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.

22. The method of claim 21, wherein the sequence of method steps 3d) and 3e) is performed repeatedly.

23. The method of any one of claims 21 to 22, 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.

24. The method of any one of claims 21 to 23, wherein the FIB optical axis is arranged at an oblique angle relative to the wafer top surface.

25. A computer program product having a program code adapted to perform the method according to any one of claims 21 to 24.

26. 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, in which 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 adapted to carry a wafer; and Controls; Wherein, the control member is configured to control the FIB column, the CPB imaging column and the platform to perform the method according to any one of claims 21 to 24.

27. A method for obtaining a sequence of first cross-sectional images of a first measurement location on a first wafer and a sequence of second cross-sectional images of a second measurement location on a second wafer, the method comprising: 4a) providing a first wafer on a first platform and positioning the first wafer on the first platform; 4b) providing a 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 location of the first wafer using a FIB column operating at a set FIB working distance so that a first new cross section 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 with the CPB imaging column at the set working distance, and simultaneously removing a second cross section surface layer at the second measurement location of the second wafer with the FIB column at the set FIB working distance, so that the second new cross section can be used 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 location of the second wafer using the CPB imaging column at the set working distance, and simultaneously removing another first cross-section surface layer of the first measurement location 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.

28. The method of claim 27, wherein the sequence of method steps 4d), 4e), 4f) and 4g) is performed repeatedly.

29. The method according to any one of claims 27 to 28, in, Milling and imaging a plurality of first measurement locations on the first wafer sequentially; and The plurality of second measuring locations on the second wafer are milled and imaged sequentially.

30. The method according to any one of claims 27 to 29, wherein the first cross-sectional surface layer and / or the second cross-sectional surface layer are removed by low-resolution imaging supervision; and / or The imaging of the new first section and / or the second section comprises high-resolution imaging.

31. The method of claim 30, wherein low resolution imaging is performed by the FIB column for removing the first cross-sectional surface layer and the second cross-sectional surface layer, or by a low resolution scanning electron microscope (SEM) in a cross-beam configuration with the FIB column for removing the first cross-sectional surface layer and the second cross-sectional surface layer; 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).

32. The method of any one of claims 27 to 31, wherein exchanging the positions of the first platform and the second platform comprises transferring positioning information.

33. The method of any one of claims 27 to 31, Wherein the FIB column is disposed in a first chamber, and wherein the CPB imaging column is disposed in a second chamber.

34. The method of claim 33, Wherein exchanging the positions of the first platform and the second platform comprises transferring one of the platforms from the first chamber to the second chamber, or vice versa.

35. A computer program product having a program code adapted to perform the method according to any one of claims 27 to 34.

36. 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, wherein the focused ion beam (FIB) column and the low-resolution charged particle beam (CPB) imaging column are adapted to be arranged in a wedge-cut coincident configuration, in which 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 its optical axis configured perpendicular to the wafer surface; A first platform, used for carrying a first wafer; A second platform, used for carrying a second wafer; a platform exchange mechanism configured to exchange positions of the first platform and the second platform; and Controls; Wherein, the control member 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 according to any one of claims 27 to 34.

37. A method for obtaining at least one sequence of parallel cross-sectional images of at least one measurement location of a wafer, the method comprising the steps of: 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 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-cut coincident configuration, wherein the FIB optical axis of the second FIB column and the CPB optical axis of the second CPB imaging column are coincident and perpendicular to each other at the 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 at least one measurement location on the 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) taking out the at least one raw material block from the wafer and placing the at least one raw material block on a sample holder so that the measurement site 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 into the second chamber; 5g) positioning the at least one measurement site included in the at least one raw material block on a second platform; 5h) obtaining at least one sequence of parallel cross-sectional images of the at least one measurement site by 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.

38. The method of claim 37, further comprising: 5i) Moving the second platform to make the second measurement site available for milling and imaging.

39. The method of any one of claims 37 to 38, further comprising 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).

40. A computer program product having a program code adapted to perform the method according to any one of claims 37 to 39.

41. A dual chamber system comprising: The first room includes: 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, in which 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, used for carrying a wafer; a sample holder adapted to carry at least one raw material block, a manipulator configured to extract a block of raw material milled from the wafer and configured to place the block of raw material on the sample holder; The second room includes: a second FIB column and a second CPB imaging column in an edge-cut coincident configuration, wherein the FIB optical axis of the second FIB column and the 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 second CPB imaging column is arranged at a short working distance to allow high-resolution imaging; A second platform, used 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 Controls, Wherein, the control member 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 operator, the second chamber having the second FIB column, the second CPB imaging column and the second platform, and the sample holder transfer mechanism, so as to perform the method according to any one of claims 37 to 39.

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