Systems and methods suitable for uniform ion cutting

Abstract

The present invention provides a device and method that enable highly accurate and uniform removal of individual layers. [Solution] A system and method are provided for high-precision, uniform material removal or delamination of a large area of ​​a sample. The size of the cutting area can be controlled over a range from the sub-millimeter scale to the several-millimeter scale, and the depth resolution can be controlled on the nanometer scale. To achieve uniform delamination, a controlled single-charged ion beam is scanned across the sample surface to normalize the ion density distribution from the center to the periphery of the sample.

Description

Technical Field

[0001] The present invention relates to the controlled decomposition of samples such as integrated circuits or IC chips, optical devices, electronic devices, and combinations of any of these, for the identification of the structure and chemical properties of chips and / or defect analysis. More specifically, the present invention relates to a system and method for uniformly delaminating a relatively large area IC chip by using a controllable ion beam.

Background Art

[0002] In the semiconductor industry, IC chips are extremely complex, having billions of individual devices each containing transistors within each integrated circuit. IC chips include numerous layers each having a given thickness ranging from a single atomic plane to several microns. The layers may occupy the entire or a portion of the surface of the chip. Each layer may include a portion of the various components of an integrated circuit that may comprise metal, alloy, semiconductor material, ceramic, insulator, or any other material. Each layer is related to both logic devices and memory devices.

[0003] During the research and development stage and throughout the subsequent manufacturing process, it is essential to understand the properties of the materials related to the various devices contained within an integrated circuit. Generally, chips are formed by processes of growth, deposition, etching, and polishing to produce a physical electronic circuit derived from a circuit diagram. These processes are extremely complex and, if not controlled with high precision, can result in defects within the chip.

[0004] Generally, the yield of acceptable IC chips in the initial manufacturing process of new designs is low. Manufacturers require months to improve the processing to achieve high yields. Feedback from various analysis techniques is utilized for process control to improve both the performance and yield of the chips. For example, metrology deals with the high-precision measurement of devices within the chip. Electrical probe measurements are used in testing individual circuits.

[0005] Quality control is crucial during and after chip manufacturing. Reliability of semiconductor devices is paramount. When a failure occurs, significant effort is dedicated to failure analysis. Since chips are often returned from the site, it is essential to perform post-fault single-defect analysis by carefully removing material until the faulty area is exposed.

[0006] To improve yield and control quality during manufacturing, as well as to analyze defects after fabrication, it is essential to have access to individual device feature areas suitable for various property quantification techniques.

[0007] Access to individual feature components for testing can be achieved through reverse engineering or controlled decomposition of the device. For example, qualified and unqualified chips are reverse-engineered to determine whether these feature components meet expected specifications. Engineers will check the location, width, and thickness of internal feature components, including vias, chemical composition, transistor and / or memory well dimensions, and similar components. Furthermore, engineers will attempt to pinpoint the location of detailed defects and identify them. This reverse-engineered information will be fed into process engineering for yield improvement purposes.

[0008] Reverse engineering involves sequential layer delamination of a chip or sample and subsequent analysis of each layer. This process is extraordinarily complex, especially considering the number of feature regions dispersed across a large number of layers, sometimes exceeding 100. Further complicating matters is the fact that each of these layers has a thickness ranging from approximately 1 nm to 2000 nm and is often composed of multiple elements to accommodate various electronic circuits.

[0009] Currently, the 5nm technology node is being used commercially in the IC industry, and the 2-3nm scale is under development. Feature region sizes are constantly trending toward 1nm or smaller.

[0010] Various techniques exist for delamination. For example, mechanical polishing using micron-scale or submicron-scale abrasive particles to remove material from the sample surface is one method. However, these particles can generate micron-scale or submicron-scale artifacts or scratches on the sample surface, which can destroy important chip characteristics. Furthermore, mechanical methods lack high-precision control over the amount of material removed.

[0011] Chemical etching is used to remove materials by exposing the chip to various chemicals and inducing chemical reactions that remove the material from the chip surface. However, depending on the chemical action of the etching agent, the various materials within the chip react at different etching rates. This can result in differential or non-uniform material removal.

[0012] Plasma etching is another method for removing material from IC chips. This method uses a combination of a reactive ionized gas and / or a non-reactive gas ionized by a strong electric field under vacuum. Reactive ions cause both chemical reactions and impact or sputtering effects on the chip surface, thereby removing material from the surface. Non-reactive ions cause only physical impact, thereby sputtering off the material. Non-uniformity in elemental composition, material density, and etching chemical species can adversely affect the etching rate and uniformity of material removal.

[0013] Broad-beam ion cutting is also used to delaminate chip layers. Typically, in this process, the center of the ion beam has a higher energy density compared to the periphery or tail of the beam. Therefore, the center of the chip is generally cut faster than the edges, resulting in a concave cutting spot with the strongest ion beam at the center and a shallower depth with lower ion beam density at the edges. This concave geometric surface profile makes it impossible to image and analyze localized feature areas within a large area of ​​a single chip layer.

[0014] Recent developments in layer delamination techniques include focused ion beam (FIB) and plasma FIB (PFIB), where the ion beam is more strongly focused. However, the drawbacks of these methods are low cutting speeds, relatively small cutting areas, and the implantation of chemically reactive elements such as, but not limited to, gallium.

[0015] Three fundamental requirements for more uniform layer delamination are: 1) uniform flatness or planarity of the pretreatment area, 2) a large area of ​​up to 10 mm × 10 mm or larger, and 3) controllable depth resolution. Therefore, what is needed in this art is a device and method that can perform layer delamination of the entire chip with sufficient resolution and enable high-precision, uniform removal of individual layers. Furthermore, this system requires obtaining planarity within a given layer that enables surface property measurements to be performed within the area of ​​interest. [Overview of the project] [Means for solving the problem]

[0016] A system and method suitable for uniform layer removal across the entire surface of a sample by ion cutting are disclosed. Specifically, the system includes one or more ion beam sources in a vacuum chamber, a fixed or rotating sample stage, a control unit for controlling the ion beam sources to selectively and uniformly remove one or more layers across the entire surface of a sample such as an IC chip, and at least one detector such as an optical microscope, a CCD camera or CMOS camera, a scanning electron microscope (SEM), an energy-dispersive spectrometer (EDS), a secondary ion mass spectrometer (SIMS), and / or an Auger probe.

[0017] A key aspect of the process is the generation of a roughly cylindrical ion beam that maintains its profile over long working distances, typically up to 10 cm. In addition, it is essential that this beam has the ability to scan or raster-scan over a large area to uniformly expose the individual layer structures within the chip. For consistent cutting, it is generally important to guide the beam at a viewing angle that is preferably close to zero degrees relative to the chip surface. Furthermore, it is important to select the ion species within the beam to exclude neutral charged particles. Thus, preferably, a beam composed solely of charged particles (ions) is guided to the chip surface in a controllable manner.

[0018] To establish planarity within individual layers, it is crucial to control the ion beam so that it can uniformly remove material regardless of the device geometry and elemental composition. To achieve this objective, an in-situ sensing system can be applied, utilizing a detector with output data related to the performance of the ion source in a feedback control loop.

[0019] For effective delamination, maintaining a uniform ion density distribution across the sample surface is essential. Further rotation of the sample is used to minimize the different cutting speeds caused by various elements contained within the chip and ejected at different velocities. Generally, harder elements that are cut at lower speeds cover softer elements that are cut at higher speeds, resulting in a relatively flat surface.

[0020] The material removal method of the present invention uses a controlled ion beam scanned across the sample surface to normalize the ion density distribution. More specifically, the system includes an ion beam source that generates the ion beam. The ion source technique is preferably electron bombardment, but other types of ion source techniques such as electron cyclotron resonance (ECR) may be used.

[0021] An electron impulse ionization source consists of a filament cartridge that generates an electron stream and then guides them into an ionization chamber. Within the ionization chamber, electrons interact with a process gas also contained within the chamber to generate ions. These ions are then extracted and guided through a focusing lens component of the ion source.

[0022] The outlet of the ion beam source houses a beam guidance mechanism, such as a raster scanning electrode or a deflection electrode, and preferably comprises several individually controlled guidance rods. The beam guidance mechanism is designed to deflect ions in both the X and Y directions relative to the sample surface. Thus, both the beam direction and the raster scanning amplitude are preferably adjustable. The XX raster scanning capabilities of these electrodes scan the ion beam parallel to the sample surface. The ion beam source is mounted in the system such that the resulting ion beam emitted from it is substantially parallel to the sample surface and does not intersect the sample surface under zero deflection conditions. By applying Y deflection, the ion beam is guided toward the sample surface.

[0023] Furthermore, the inductive manipulation mechanism electrostatically separates uncharged particles from the ion beam by deflecting only charged particles. Neutral atoms continue unaffected in parallel paths above the sample surface. In this way, only ions are incident on the surface as a function of the applied Y-deflection.

[0024] Through the momentum transfer / scattering process, the material is ejected from the sample surface in the controlled manner described above, resulting in uniform layer delamination. The control unit drives the operation of the ion beam source and the induction mechanism, and controls and adjusts the raster scanning amplitude and scanning speed.

[0025] In controlled cutting, ion beam scanning relies on feedback from the outputs of various detectors. Surface data for characterizing the structure and chemical properties of a given layer can be composed of images, spectra, or other information. For example, various detectors capture signals from the cutting sample surface point by point, where the size of the point is approximately the size of either the ion beam or the electron beam. Such detectors can be used for the analytical determination of various devices present in the corresponding layer of the sample. The detector can include a camera such as an optical camera that captures the physical topography of this surface to determine the uniformity of the sample surface. A light source can assist in optical imaging.

[0026] Scanning of an electron beam over the sample surface causes a spatial region interaction between the incident electrons and the sample material. This interaction depends on both the accelerating voltage of the electron beam and the elemental composition of the sample. The interaction produces both X-rays and various types of electrons, such as backscattered electrons and secondary electrons. The characteristics of the generated electrons and X-rays depend on both the surface properties and the atomic interactions.

[0027] Depth profile information is generated by the interaction of the electrons generated by the SEM with the corresponding sample spatial region. Detector technology and state-of-the-art mathematics yield information regarding the depth profile of the cutting area. This information is obtained by a combination of the system electronics and the control of the cutting process.

[0028] By using a secondary electron detector or SED, such as an Everhart-Thornley type, either electrons generated by the incidence of an electron beam or ion-induced secondary electrons generated by the incidence of an ion beam can be captured and processed to generate information about the sample surface. By changing the acceleration voltage of the SEM in cooperation with a backscattered electron detector or BSE technology, depth information can be generated due to the change in the interaction volume of the material with respect to voltage. Further detectors can include EDS, SIMS, or Auger probes for analyzing the cut surface structure and chemical composition, as well as the scattered by-products derived from various layers during the layer stripping process.

[0029] The control unit receives and analyzes the outputs from various detector technologies during the layer stripping process, quantifies and determines the composition of individual device layers, and evaluates the cutting situation. For example, the control unit creates a depth profile map from the data generated at points in the center of the sample, the periphery of the sample, and any amount in between. Subsequently, the variation in the depth profile for the corresponding positions is input into a mathematical cutting algorithm. An algorithm has been developed such that the ion density distribution is adjustable when the beam moves across the sample to achieve uniform layer stripping. The cutting factor k of this algorithm is adjusted as more fully explained below, and the control unit sends real-time modified operation instructions to the ion source for modifying the cutting pattern that physically changes the ion beam raster scan pattern with respect to both the dwell time per point and the corresponding current density. This continuous feedback method then minimizes the depth change Δd, as more fully explained below, to produce a planar surface.

[0030] Accordingly, the control unit processes the data and issues commands to enable the uniform removal of layers of the entire IC chip, comprising one or more materials. To control the ion beam source to selectively remove each of these chip layers at their respective appropriate speeds, computer-controlled data can be loaded into memory and executed on one or more microelectronic devices.

[0031] In the semiconductor industry, layer geometry and elemental composition are widely known as the most fundamental aspects of chip architecture. Initial maps created during the chip design process are used to define features such as transistors, memory wells, and other components, as well as corresponding interconnects between these features, but not limited to these. These maps are then printed onto various chip layers using lithography, resulting in the device circuitry. While circuit maps are known to semiconductor device manufacturers as they are fundamental to chip creation, these maps are highly confidential.

[0032] The system is optionally given the ability to input surface maps of individual layers. Control electronics and corresponding software acquire and analyze data from various detectors to create a map of sample characteristics during the cutting process. By changing the acceleration voltage of the SEM electron beam, information from the surface layer and at least one underlying layer is generated during cutting. This real-time sample representation is then compared with the original device map. Subsequently, the cutting factor k is adjusted based on the relative material removal rate with respect to the surface to normalize the cutting across the sample surface in order to produce a uniform and planar profile across the entire area of ​​a given chip layer.

[0033] To obtain optimal sample characteristics, the ion beam performance characteristics must be variable. For example, laser beam energy increases cutting speed but can introduce artifacts. Lower energy generally produces a high-quality surface but results in a correspondingly lower cutting speed.

[0034] Ion cutting reveals hierarchical circuit information using data acquired from each layer. When the structure of a given layer is known, the image processing data may be in the form of a structure map. In this case, this data can be compared with real-time information to adjust and terminate the process.

[0035] Further techniques include acquiring images and corresponding data from each of the various layers, followed by reconstruction to provide information corresponding to the feature geometric structure and elemental composition. This results in a three-dimensional representation of the chip structure and chemical properties. This three-dimensional representation can also be used as an endpoint determination method to stop the layer delamination process.

[0036] Subsequently, observations and measurements performed during ion cutting can be adjusted using a self-supervised learning process or artificial intelligence that incorporates a feedback loop to adjust cutting parameters based on the observation results. Individual cutting plans can be created for unique part types and applied to all chips with equivalent characteristics using this learning technique.

[0037] The system includes the steps of: placing a chip or sample in a vacuum chamber; operating ion beams and electron beams; acquiring and processing signals from various detectors; and dynamically adjusting one or more operating parameters related to the ion beam source to selectively remove specific individual layers within the chip at their respective appropriate rates.

[0038] The present invention further includes a method for acquiring data from the top surface of a chip. The surface data may include photographs, images, chemical compositions, or other data representations that have the ability to characterize feature portions or other aspects of the chip. This method can be optionally performed, and the step of removing a layer of design thickness is performed in a single step, with the same removal rate for each material present in this layer. When the respective removal rates for each material are different, a series of iterative steps using ion beam sources operating with different characteristics will result in the uniform removal of a layer of design thickness. Both methods may further include a step of repeating the above steps until a predetermined number of layers or the entire predetermined thickness of the chip, as determined by the user, has been removed. Furthermore, the method may include a step of generating a hierarchical schematic using the data acquired from each layer.

[0039] The present invention allows for controllable cutting area size across a range from sub-millimeter to several-millimeter scales. Depth resolution is also controllable on a nanometer scale. The system and method of the present invention enable high-precision delamination of a chip to determine whether feature areas meet expected specifications regarding position, dimensions, and elemental composition. The combination of required analysis of the chip's structure and chemical properties with a high-speed, high-precision, consistent, and uniform delamination method makes the present invention essential. This type of delamination allows for subsequent imaging and analysis using methods such as optical / electron microscopy, measurement of electrical properties, and various forms of spectroscopic measurements.

[0040] The specific features and advantages of this ion cutting system and method will become clear from the detailed description that follows, with reference to the attached drawings. [Brief explanation of the drawing]

[0041] [Figure 1] This is a cross-sectional view of a layer delamination result produced by a conventional ion beam cutting device, exhibiting concave surface characteristics. [Figure 2] This is a cross-sectional view of the layer delamination result obtained by the present invention. [Figure 3] This is a schematic diagram of a raster scan of an ion beam along the X-axis of the sample surface and the corresponding ion density distribution. [Figure 4] This diagram illustrates the theoretical basis for the algorithm used to control the ion density distribution as a function of the cutting area radius in this invention. [Figure 5] This is a schematic diagram showing the relative positions of certain components of the present invention. [Figure 6] This is a schematic diagram of the present invention. [Figure 7] This is a schematic diagram of the present invention. [Figure 8] This is an exploded view of the electron source assembly of the present invention. [Figure 9A] Figure 8 shows the electron source assembly. [Figure 9B] Figure 9A is an end view of the electron source assembly shown. [Figure 10] This is a cross-sectional view of the electron source assembly shown along line 10-10 in Figure 9B. [Figure 11A] This is an isometric view of the filament assembly and bending tool. [Figure 11B] This is an isometric view of a filament assembly showing the use of pins for bending filament wire. [Figure 12] This is a partially exploded view of the filament assembly and loading stand. [Figure 13A] Figure 12 is a top view of the filament assembly and loading stand shown in the diagram. [Figure 13B] This is a cross-sectional view of the filament assembly and loading stand shown along the line 13B-13B in Figure 13A. [Figure 14] This is an exploded view of the ionization assembly of the present invention. [Figure 15] Figure 14 is a plan view of the end face of the ionization assembly shown. [Figure 16] This is a cross-sectional view of the ionization assembly shown along line 16-16 in Figure 15. [Figure 17] This is an exploded view of the focusing assembly and beam guidance assembly of the present invention. [Figure 18]Figure 17 is an end view of the converged assembly shown. [Figure 19] This is a cross-sectional view of the converged assembly shown along line 19-19 in Figure 18. [Figure 20] Figure 18 is a partially exploded view of the focusing assembly shown, illustrating the first electrical input. [Figure 21] Figure 18 is a partially exploded view of the focusing assembly shown, illustrating the second electrical input. [Figure 22] Figure 18 is a partially exploded view of the converged assembly shown.

[0042] Throughout several of the drawings, the same reference numerals indicate the same parts. These drawings are not intended to limit the invention to the specific embodiments they show. The drawings are not necessarily to scale. [Modes for carrying out the invention]

[0043] As shown in the accompanying drawings, the present invention relates to a system and method for delaminating a sample, such as an IC chip, using a raster scanning ion beam to achieve uniform delamination across the sample surface. As used herein, a layer means a uniform thickness of one or more materials laid on or dispersed across a surface. The thickness may be equal to one atomic plane or up to several microns. A layer may occupy all or part of the surface. A sample may mean a metal, alloy, semiconductor material, ceramic, insulator, or any other solid material. A sample may also mean, but is not limited to, a semiconductor device, an integrated circuit chip, layers of metal and dielectric of any thickness, one or more materials within an area of ​​any size, an optical device, an electronic device, or any combination thereof. Uniform delamination means the partial or total removal of one or more layers in a cutting process, in which case one or more layers or a portion thereof may comprise one or more materials, and one or more layers may have any desired uniform thickness.

[0044] Broadly characterized, the present invention provides a system and method for delaminating samples of integrated circuits and other solid materials on a large area scale. More specifically, several embodiments relate to apparatus and methods for facilitating the removal of one or more layers from an integrated circuit sample with a desired uniform thickness within an area with a maximum diameter of approximately 10 mm. Several embodiments also provide for beneficially maintaining the flatness of the sample surface during delamination of a given area. Furthermore, the overall delamination process may include many endpoints where feature areas, wire patterns, chemical composition, and other properties of interest can be analyzed and / or recorded for specification inspection, failure analysis, or 3D reconstruction.

[0045] In conventional ion beams, the ion flux density within the beam generally follows a Gaussian profile, resulting in a higher density in the central region and a lower density in the periphery or tail of the beam. Therefore, when using broad-beam ion cutting, the center of the sample is cut at a higher speed than the periphery, making it impossible to uniformly delaminate the semiconductor chip layer.

[0046] Referring to Figure 1, the results of layer delamination using a conventional ion beam are shown by curve 1 on sample 2. Typically, the cutting speed R in the layer delamination process is determined by the ion density Id per unit cutting area A, as follows: R = c*Id / A = c*Id / r*Δr (1) In the above equation, A = r * Δr, where r is the radius of the circular cutting mark and c is a constant.

[0047] The present invention addresses the aforementioned uneven delamination by generating a beam that is relatively small relative to the sample size and scanning or raster scanning this beam across the sample surface in a specific controlled manner that facilitates uniform cutting, as shown in Figure 2, which is independent of both the device position and elemental composition.

[0048] Referring to Figure 2, the trench D cut on sample 1 is equal to the sum of depths 3, 4, and 5 divided by 3. D = (D1 + D2 + D3) / 3 (2) Nonplanarity Δd=(|D1-D|+|D2-D|+|D3-D|) / 3 (3) Cutting error ΔE=Δd / D (4)

[0049] The System 500 and Method for exfoliating Sample 1 enable the exfoliation of large areas of Sample 1 while minimizing Δd to a few nanometers and keeping ΔE below 1%, generally 0.1%.

[0050] This technique produces an ion density distribution as shown in Figure 3. Specifically, the ion beam source 31 emits an ion beam 32, shown as a range in this figure, which is incident on the surface of sample 1 at an incident angle. Sample 1 rotates along direction 34 during the delamination process. Therefore, the resulting cutting area 33 is circular in shape.

[0051] The rotation speed range is variable within the range of 0 to 100 rpm. The rotation direction can be either clockwise or counterclockwise. The angular range of the incident beam 32 is from 0.0 degrees to 15 degrees. The size of the cutting area 33 is adjustable by changing the scanning parameters of the ion beam 32, and a typical cutting area is in the range of 1 mm to 10 mm in diameter or larger.

[0052] The ion density distribution along the X-axis is shown by one of the curves 35, 36, 37, or 38. Curve 35 represents a uniform density distribution with a high cutting speed in the center of the sample and a low cutting speed in the periphery.

[0053] Generally, cutting speed is a function of ion irradiation dose or density, with higher density beams resulting in higher cutting speeds. To achieve uniform cutting for delamination purposes, the cutting speed across the sample surface needs to be variable to compensate for geometric and elemental compositional differences within the chip layer.

[0054] The theoretical density distribution curve 36 shown in Figure 3 may not be sufficient to reduce the ion density in the central region. As a result, the cutting speed remains higher than that of the periphery. Another possible density distribution is curve 38 shown in Figure 3, which causes an excessively large reduction in beam density over the central region of the sample, and therefore results in a lower cutting speed in the central region compared to the periphery. Curve 37 has an ion density distribution that theoretically produces uniform layer delamination in the cutting region. This curve is specific to the given layer characteristics and needs to be determined for each layer and each chip. Due to this factor, it is important to develop a unique mathematical cutting control algorithm such that the corresponding ion density distribution curve 37 is effective in uniformly removing material from layers with various geometries and elemental compositions.

[0055] Figure 4 shows a diagram of the cutting area 41 on the sample surface. The diameter is on a millimeter scale. The goal is to obtain a uniform ion density distribution at all locations within the cutting area 41.

[0056] To achieve this objective, a sub-millimeter diameter ion beam is generated and scanned within the desired area, with the characteristic of uniformly distributing the ion beam density within the cutting area 41.

[0057] Based on the above, this system avoids the drawback of having a Gaussian ion density distribution within the ion beam itself, which is a characteristic of broad ion beam technology.

[0058] To perform the desired function, a sub-millimeter beam is raster-scanned point by point on the sample surface, and the beam intensity is determined by the moving speed, so that the residence time at each point on the sample surface is variable. The residence time Δt divided by the unit cutting area A must be equal to or equal to a constant C. Δt / A=C (5) Or, Δt = C * A (6) Factor r is the radius 42 within the cutting area 41, while Δr is the radius increment 43 shown in Figure 4, according to the following equation. Δt = C * A = C * 2πr * Δr dt = C * 2πr * dr ∫dt=C*2πr*∫dr t = C * πr 2 r = a*t 1 / 2 (a is a constant) (7) In practice, equation (7) needs to be extended as follows. r = a*t k (a is a constant, and k is 0 <k≦1である) (8) Here, k is the cutting factor. Equation (7) is a special case of equation (8) when k = 1 / 2. When k = 1, the ion density distribution is uniform with curve 35 in Figure 3. When k is reduced to a value slightly less than 1, the ion density distribution is uniform with curve 36 in Figure 3. When k is further reduced, the ion density distribution is uniform with curve 37 in Figure 3. Subsequent reductions in k result in an ion density distribution uniform with curve 38 in Figure 3. In practice, to achieve uniform delamination, it is necessary to determine the k value for various materials and layer configurations.

[0059] During the ionization and extraction processes, some ions may be neutralized by taking up electrons. These neutral charged particles move purely as a function of their momentum and cannot be guided. Therefore, incidence of these particles onto the sample surface generally results in uneven and uncontrolled cutting of the sample surface. To avoid this problem, the system and method include means for specifically guiding only charged ion particles. Figure 5 shows a basic diagram of the system 500. An initial ion beam 52 is generated and guided from at least one ion source 31 into a Faraday cup 53. In this state, the entire beam is guided into the Faraday cup 53 and no cutting occurs. In at least one embodiment, the Faraday cup 53 can also be used to measure the ion beam current.

[0060] To precisely control the ion beam for uniform layer delamination, the ion source 31 of the present invention includes a Y-deflection electrode, which, when a voltage is applied, generates an electrostatic field that deflects a portion of the initial ion beam 52 to produce an incident ion beam 32 that is guided off-axis and incident on the sample surface 55, as shown in Figure 5. Since only ions are affected by the electrostatic field, these ions are guided or induced by the Y-deflection to produce the incident ion beam 32. Neutral particles remain in the initial beam 52, unaffected by the electrostatic field, and collide with the Faraday cup 53 rather than the sample. In this manner, only charged particles collide with the sample surface 55 for layer delamination.

[0061] The sample is supported on a sample stage 56 whose height can be adjusted along axis 57 and can be moved in the XY direction. The ion source 31 further includes an XX beam deflection electrode that raster scans, scans, or guides the incident ion beam 32 with respect to the sample surface 55 according to equation (8). Under non-deflection conditions, the incident ion beam 32 is above the sample surface 55 and intersects the sample rotation axis in a plane parallel to the axial centerline of the ion source 31. The sample surface 55 is perpendicular to the sample rotation axis. The beam scanning direction along the X axis shown in Figure 3 must be parallel to the sample surface 55. During delamination, the sample 1 is either fixed or can rotate at an appropriate speed clockwise or counterclockwise. The rotation normalizes the cutting across the entire sample surface 55 and compensates for the incident ion beam 32 that is only raster scanned in the X direction.

[0062] The beam incidence angle relative to the sample surface 55 is determined by the bending signal intensity or bending signal voltage, because this signal or voltage is related to both the potential applied to the Y-bending electrode and the height of the stage. The incidence angle increases by using a higher voltage. The incidence angle is reduced by adjusting the height of the sample stage 56 upwards so that its height approaches the plane of the unbent initial ion beam 52. Typically, the beam incidence angle is adjustable within a range of 0 to 15 degrees.

[0063] Focusing on the overall system 500, as shown in Figures 6 and 7, the system 500 includes an ion beam source 31, a sample stage 56, a vacuum chamber 62, an ion source controller 61 (not shown), a control unit 69, and various detectors. The sample stage 56 is configured and positioned to support a sample 1, which may or may not be an IC chip, a part of an IC chip, multiple IC chips, any type of wafer, or other types of sample material. The sample stage 56 has a Z-stage height adjustment capability along axis 57 as shown in Figure 5, as well as the rotational capability and XY offset described earlier. Rotation is used to normalize the effect of the ion cutting process on the chip surface. The rotational speed range of the sample stage 56 can be between 0.0 rpm and 100 rpm. The stage 56 may also have a tilting capability. In some embodiments, the sample stage 56 can be cryogenically cooled to approximately liquid nitrogen temperature. Heaters, temperature sensors, and control electronics allow the sample temperature to be adjusted between cryogenic and room temperature.

[0064] The vacuum chamber 62 provides a hollow space that houses the ion beam source 31, the sample stage 56, the sample 1, and various detectors. The vacuum chamber 62 is part of a vacuum system that preferably includes a turbomolecular main pump, an auxiliary or backup pump, valves, a drive circuit, and a control system which may be electrically or pneumatic and used to generate a vacuum or negative pressure state inside the vacuum chamber 62 during use. The vacuum chamber can be mounted on a frame that provides appropriate vibration isolation. The vacuum system may include controllers and gauges for outputting a basic vacuum level and an operating vacuum level.

[0065] Sample 1 can be loaded into the system by incorporating a loading lock assembly that has both vacuum and inert gas transfer capabilities. This methodology allows the sample to be protected from the environment throughout the entire process, from sample preparation to subsequent imaging and analysis. This protection is particularly important for environmentally sensitive samples, such as but not limited to catalysts and lithium-ion battery materials.

[0066] The ion beam source 31 consists of a filament assembly 100, an ionizer assembly 200, and a focusing assembly 300, all of which are shown in more detail throughout Figures 8 to 21. In particular, the filament assembly 100 shown in Figures 8 to 13B is the main electron source. The filament assembly 100 includes a mount 110 connected to a filament cover 111 separated by a support rod 112 and a spring 113. At least one filament 120 is fixed to the mount 110 by a clamp 130 and a holder 140. The filament 120 can be yttrium-clad iridium, tungsten, or a material suitable for generating electrons. A connector 150 is in electrical communication with the filament 120 and supplies a current to the filament 120 that generates an electron flow. Preferably, there is one connector 150 for each filament lead. These filament leads can be bent or shaped into various forms by using a bending tool 170 to bend the filament leads around a pin 172 that can be pushed up or down to accommodate wire bending, as will be explained more fully with reference to Figure 11. A stand 180 can be used to load the filament assembly 100, as will be explained more fully with reference to Figure 13. One end of the filament 120 is surrounded by a Wehnelt electrode 160. An electrical bias applied to the Wehnelt electrode 160 draws electrons from the filament 120.

[0067] As shown in Figures 14 to 16, the filament assembly 100 is physically coupled to the ionizer assembly 200. The ionizer assembly 200 includes a Wehnert support 210 in which the filament assembly 100 is loaded and held. The Wehnert support 210 is mounted on an adjustment plate 214 via a spacer 211, and the adjustment plate 214 is further mounted on an ionizer flange 215 such that the Wehnert support 210 aligns with an opening within the ionizer flange 215.

[0068] The ionizer assembly 200 includes at least one ion source 220 between the end of the Wehnelt electrode 160 and the opening of the ionizer flange 215. For example, the ion source 220 may include a G2 electrode 222, also called a G2 opening, and an E electrode 224, separated from each other by an insulator 212. The ion source 220 may also include an F electrode 226 or an F opening, which is physically separated from the extractor 224 by an insulator 212.

[0069] The E electrode 224 has two input sections: an electrical bias receiving section and a capillary gas input section 250. The gas input section 250 is connected to a capillary tube 252 that is in fluid flow communication with a gas feedthrough 254 to supply a process gas flow into the ion source 220. A clamp 255 can secure the gas feedthrough 254 to the ionizer flange 215. The process gas supplied by the gas feedthrough 254 can be argon, xenon, or any other gas such as an inert gas, or a combination thereof. The gas flow rate is adjustable within a range from less than standard cubic centimeters per minute (SCCM) to several tens of SCCMs, preferably around 0.02 or higher, but other flow rates are also anticipated.

[0070] In a typical gaseous ion source, ionization occurs in a chamber held at a potential high above ground potential, at a pressure much lower than atmospheric pressure, typically a few pascals, which generates ions and subsequently accelerates the ion beam to a grounded system. The gas supply source is usually grounded and at a pressure much higher than atmospheric pressure. The gas is supposed to move from a high-pressure state at ground potential to a low-pressure state at high potential. One suitable configuration for gas delivery is a mass flow controller at ground potential, followed by an insulating tube, usually in vacuum. This tube has a large inner diameter such that the pressure drop at both ends can be ignored, and as a result, the pressure inside the tube is only slightly higher than that inside the ionization chamber. Most of the pressure drop occurs within the mass flow controller. Unfortunately, the optimal ionization pressure is usually close to the minimum of the Paschen curve, and therefore glow discharge is not easily prevented inside the insulating tube due to the corresponding voltage gradient. This generally imposes upper limits on the usable ionization chamber pressure and / or ion beam potential.

[0071] To solve this problem, the present invention delivers process gas using a capillary tube 252. The capillary tube 252 has a very small inner diameter. Considering the transition from laminar flow before the capillary tube 252 to molecular flow inside the capillary tube 252, the pressure profile inside the capillary tube 252 is not linear. Conversely, this pressure profile is almost flat until near the end of the tube, with a large pressure drop at the outlet. As a result, most of the length of the capillary tube 252 is considerably higher than the ionization chamber. When the pressure inside the capillary tube 252 is high, it is possible to accommodate the high voltage in the ionizer assembly 200 without the risk of gas discharge inside the tube. This allows for virtually any combination of voltage, ionization pressure, and flow rate to the ion source 220, resulting in improved performance and reliability.

[0072] Electrical biases are individually applied to the G2 electrode 222, E electrode 224, and F electrode 226. Electrons emitted from the Wehnelt electrode 160 collide with gas atoms in the region surrounding the ion source 220. Each collision results in the loss of electrons from the gas atoms. Multiple collisions generate a large amount of ions.

[0073] These ions are ejected from the ionizer assembly 200 and guided into the focusing assembly 300 shown in Figures 17 to 21. The focusing assembly 300 includes a support plate 310 that physically secures the lens. The opening structure of the support plate 310 allows for vacuum pumping of various regions of the ion source 220. A spacer 313 physically and electrically isolates the extractor from the ion source 220. An electrical bias is applied to the extractor to attract ions emitted from the region of the ion source 220. The ions are controlled by electrical biases applied to the drift tube 324 and the focusing electrode 322.

[0074] The focusing assembly 300 further houses an induction maneuvering assembly 330 having the ability to electrostatically guide the beam. Preferably, the induction maneuvering assembly 330 includes a plurality of individually electrically biased induction maneuvering electrodes, which are in the form of induction maneuvering rods 332 housed in induction maneuvering rod insulators 334. Some of the induction maneuvering rods 332 are X-deflection electrodes, and the others are Y-deflection electrodes. The induction maneuvering rods 332 can each be individually electrically biased to enable high-precision induction maneuvering and scanning of the resulting ion beam by deflection of approximately ±15 degrees. The induction maneuvering rods 332 and their corresponding insulators 334 are enclosed by an induction maneuvering rod cover 336. The focusing assembly 300 further includes electrical inputs 342 and 344 positioned along its housing 311. An illustrative configuration may include a first electrical input 342 supplying 12 kV and up to 20 amperes of power. The second electrical input 344 can supply 700V along with a current of up to 5 amperes. One of these electrical inputs can be used to generate the incident ion beam 32 described earlier. The other is used for raster scanning purposes, supplying an electrical bias to deflect the resulting ion beam toward the sample and to guide the incident ion beam 32 across the sample surface 55.

[0075] The ion beam source 31 described above has the ability to generate an ion beam with a beam energy in the range of 1 keV to 50 keV or higher, and can be continuously adjusted with an accuracy of 1 eV. High beam energy increases the cutting speed but may cause damage to the sample surface. Low energy produces a smooth sample surface with less damage, but may result in a lower cutting speed.

[0076] The resulting ion beam diameter can be in the range of 50 μm to 5 mm and can be adjusted depending on the energy level. For example, the beam size can be 50 μm at 10 keV and a current of 0.1 to 7 μA in some embodiments, and 1.0 mm at 1 keV and a current of 7 to 15 μA in other embodiments. The ion beam can have a current between 1 μA and 1000 μA, including these values. Preferably, the current is up to 200 μA. A strong current can increase the cutting speed. The current density of the ion beam is approximately 10 mA / cm². 2 This can be done. The ion source can be up to 12 mm 2 Alternatively, when the raster range is greater than or equal to that, it can be operated within a working distance range of 10 mm to 100 mm. In at least one embodiment, the raster range can be 10 mm in diameter when the working distance is 25 mm.

[0077] As can be seen from Figures 8 to 21, the modular design of the ion beam source 31 allows for both rapid replacement of the filament 120 and in-situ xy adjustment of the ionizer assembly 200 relative to the lens.

[0078] The direction of ions emitted from the ion beam source 31 is above the sample surface 55, preferably parallel to it, as shown in the initial ion beam 52 in Figure 5. The incident ion beam angle can be adjusted by changing the sample height along the Y-axis 57 and the Y-bending amplitude of the beam caused by the guiding manipulator assembly 300. Using a combination of these adjustments, the incident point of the incident ion beam 32 coincides with the sample rotation axis 34. By utilizing the XX deflection electrode of the guiding manipulator rod 332, the incident ion beam 32 is scanned between both edges of the sample surface 55.

[0079] Returning to Figures 6 and 7, the system 500 includes an ion source controller 61 that supplies operational commands to adjust the voltage, current, extraction voltage, beam size, gas flow rate, and filament emission of the ion beam. The ion source controller 61 controls various assemblies of the ion beam source 31 described above, including the energy, focus, and ion extraction of the ion beam, and in addition, it consists of several high-voltage power supplies that control a deflection amplifier for beam raster scanning in the X direction and for deflecting or bending the ion beam in the Y direction onto the sample surface 55 shown in Figure 5. Adjustable amplitude raster control distributes the ion density in the X direction so that uniform layer delamination is achieved over large areas. Furthermore, the ion source controller 61 controls and adjusts the raster scanning speed of the incident ion beam 32 for each location extending from the center of the sample to its maximum radius.

[0080] The ion beam source 31 can be mechanically moved and rotated in the X and Y directions. By physically changing the X adjustment without scanning, the ion beam 32 is positioned relative to the sample rotation axis. By changing the Y movement, it is ensured that the ion source is at the appropriate height relative to the cutting plane. Rotation adjustment without applying XX deflection ensures that the position of the ion beam is parallel to the sample surface when attached to the base 65. This alignment procedure can be performed during system configuration and calibration.

[0081] The system 500 may include various detectors that supply information about delamination during the cutting process. Each detector is in communication with the control unit 69 to supply data to the control unit 69. The detectors supply information about the type of feature of the chip, the location of the feature, the dimensions of the feature, and the chemical composition of the feature.

[0082] System 500 may include a camera 66 and a light source 67 to capture light reflected from the sample surface. During the cutting process, sample 1 can be periodically illuminated by the light source 67. An image is then acquired by the camera 66 and sent to the control unit 69. The camera 66 may include various receiving objects for imaging at higher or lower resolutions. The pattern exposed during layer delamination can be recognized by image recognition software installed on the control unit 69, both for identifying feature areas and for confirming or adjusting cutting process parameters. In addition, the light source 67 can be used to reveal the difference in vertical spacing between two layers. Interference fringes appear as cutting progresses, and these fringes correspond to the depth of the cutting area. Light reflection and the generation of interference fringes are influential ways in establishing the non-planarity of the sample surface, even when the non-planarity is only a few nanometers. Under ideal conditions, only one interference ring appears on the image, indicating very small depth variations between the center and periphery of the sample. An increase in the amount of rings corresponds to a greater variation in depth.

[0083] During cutting, the first ring to appear in the center of the sample indicates that the cutting speed in the center is higher than in the surrounding area. When rings appear near the periphery of the sample, these rings indicate that the center is being cut at a lower speed than the periphery. The appearance of many rings indicates a large difference in cutting speed between the center and periphery of the sample. If a single ring is wide, the difference in cutting speed is considered small. The reflected image can be analyzed by the human eye or by computer image recognition techniques. Accordingly, the cutting factor k can be adjusted manually or automatically.

[0084] System 500 may further include a secondary ion mass spectrometer or SIMS 64 that can be used to analyze the elemental composition of material scattered from the cutting surface. Generally, the sample layers are separated by semiconducting or nonconducting oxide layers and have a combination of light and heavy elements that can be quantified by SIMS when scattered. This quantification result can be sent to control unit 69 for analysis of the chemical interactions encountered within each layer with respect to the subsequent determination and identification of the chip layer components. Chemical composition analysis is performed at points, within areas, and by mapping.

[0085] As shown in Figure 7, the system 500 may include a SEM column 75. The SEM column 75 is positioned directly above the sample stage 56 and interacts with the sample surface 55 to generate an electron beam that produces secondary and backscattered electrons and X-rays, which are later used to quantify depth profile information, provide three-dimensional structural information, and further determine the elemental composition of the sample. A shutter can be positioned adjacent to the SEM objective lens that can be operated to protect the SEM lens and detector from the deposition of scattered particles generated by the delamination process. Data acquired from various layers by the SEM, working in conjunction with various detectors, can be used for 3D reconstruction of the sample by creating feature patterns during the delamination process. The delamination process can be adjusted or stopped when a specific feature pattern appears.

[0086] System 500 may include a sample stage that implements X and Y translation, thereby moving the sample position relative to the electron beam incidence point. If the desired resolution of the SEM image limits the field of view, the entire sample surface can be imaged by translating the sample to multiple positions.

[0087] The system may further include a secondary electron detector or SED for imaging electrons emitted from the sample surface excited by ion-induced secondary electrons generated by electrons from the electron column or ions emitted from the ion source 31. A backscatter electron detector or BSE detector may further be included to detect backscatter electrons from the sample surface. Backscatter electrons are produced by the elastic scattering of the primary electron beam by atomic nuclei. By changing the acceleration voltage of the incident electron beam, the electron penetration depth or interaction volume is changed. Since information is generated by atomic nuclei, the corresponding elemental index becomes known. This index is particularly useful when attempting to distinguish material differences between various layers within a chip.

[0088] The system 500 may further include an energy-dispersive spectrometer or EDS detector 74 that detects X-rays emitted from the sample surface 55 during impact by the incident electron beam to characterize the elemental composition of the spatial region under analysis. By combining the BSE information and the EDS information, depth profiles in the x and y dimensions of the surface and near-surface are generated.

[0089] Within this system, wavelength-dispersive spectroscopy (WDS) probes, Auger detectors, laser profilers, X-rays, and / or other probes may also be used, not all of which are shown in the diagram, but their inclusion is considered to be within the scope of those skilled in the art.

[0090] The system 500 further includes a control unit 69. The control unit 69 is in communication with all components of the system 500 and determines the relevant parameters of the system 500. This determination includes the vacuum conditions in the vacuum chamber 62, the adjustment of the stage movement, and the adjustment of the output of the mass flow controller to adjust the amount of process gas supplied to the ion source 31. Thus, the control unit 69 supplies operating parameters to the ion source controller 61 to operate the ion source 31. Furthermore, the control unit 69 also controls the movement / adjustment of the sample stage 56. The control unit 69 includes a user interface for interaction with the system operator. One or more displays capable of displaying output data from the detector may also be provided.

[0091] In addition, the control unit 69 receives input from various detectors and uses this data within a mathematical algorithm to control the ion beam density distribution across the chip surface.

[0092] Various signals can be captured point by point by the detector, and the size of the point is roughly the size of either the ion beam or the electron beam. The control unit 69 creates a depth profile map from the data generated at points in the sample center, the sample periphery, and any amount in between. A larger number of points means a higher resolution map. Subsequently, the variability of the depth profile with respect to the corresponding locations is input into the algorithm.

[0093] Analysis of the data from the detector allows for adjustment of the cutting factor k, as described in equation (8), to achieve uniform layer delamination. For example, when the cutting speed at the center of the sample is higher than at the periphery, the cutting factor k must be reduced. When the cutting speed at the center of the sample is lower than at the periphery, the cutting factor k must be increased. The amount of adjustment of k described in equation (8) is variable and is determined by the variation in cutting depth.

[0094] The raster scanning control can be modified to correspond with the type of sample material, raster scanning amplitude, ion beam energy, ion beam current, and other parameters. Based on this calculation, adjustments to the operating parameters required to achieve uniform delamination are sent to relevant system components such as the ion source controller 61 to adjust the raster scanning pattern and the current density at corresponding locations of the ion beam 32. The result is to physically modify the ion beam raster scanning pattern with respect to both the raster scanning speed and the corresponding point-by-point current density, with respect to Δd. Accordingly, the control unit 69 can adjust the cutting factor k in near real time by analyzing the outputs of various detectors.

[0095] When the material removal rate for a given layer of a given thickness is equivalent, the process can be repeated by using equivalent ion beam control parameters to remove subsequent layers stepwise. This method may include any of the predetermined steps for automatically removing multiple layers from the chip.

[0096] The objective of this system is to control the cutting speed with high precision in combination with the step of determining the process endpoint. The simplest form of endpoint determination is by time, but for this to be effective, both the layer thickness and the cutting speed must be fully understood. Since the cutting speed at a specific beam energy for various materials is known, the cutting time is calculated using a predetermined desired delamination depth. Once the endpoint is determined, the control unit 69 stops the process by deactivating the ion source 31.

[0097] The endpoint can also be determined by features or specific chemical compositions that appear in the image or analysis data during layer delamination. If a specific chemical composition at a particular depth is required, EDS74, SIMS64, or other chemical analysis data can be used to identify the endpoint.

[0098] For system calibration of cutting speed over a given area, a multilayer control sample with each layer having a different elemental composition must be used. The layer thickness of such a sample should be uniform, approximately 5-50 nanometers per layer. Thicker layers are acceptable, but this will increase the overall cutting / calibration time.

[0099] Since many modifications, changes, and substitutions can be made to the details of the preferred embodiments described herein, all things described in the foregoing description and shown in the accompanying drawings are intended to be interpreted as illustrative and not limiting. Accordingly, the scope of the invention should be determined by the appended claims and their legal equivalents. [Explanation of Symbols]

[0100] 1 sample 3 Depth D1 4 Depth D2 5 Depth D3

Claims

1. A system for exfoliating a sample, a. A sample stand that supports the sample housed in the vacuum chamber, b. An ion beam source having at least one ion source that generates a substantially cylindrical ion beam, c. A deflector for deflecting the charged ion beam from its initial beam path in order to raster scan the ion beam over a raster scanning range in at least one direction along the surface of the sample, d. A system comprising a control circuit that is in electronic communication with the deflector and the ion beam source and modifies at least one of the following to achieve substantially planar material removal: acceleration voltage, ion flux density, spot size, raster scanning speed, raster scanning dimensions, and residence time.

2. The system according to claim 1, wherein the ion beam source is selected from gaseous or liquid metal types.

3. The system according to claim 1, wherein the spot size of the ion beam is in the range of 50 μm to 5 mm.

4. The system according to claim 1, wherein the adjustment of the ion beam produces a uniformly cut sample surface that is independent of the sample composition and layer geometry.

5. The system according to claim 1, wherein the ion beam source is arranged to emit the ion beam substantially parallel to the sample stage and the sample.

6. The system according to claim 1, wherein the axis of the ion beam is substantially parallel to the planar surface of the sample and is offset therefrom.

7. The system according to claim 5, wherein the deflector guides the ion beam from a path substantially parallel to the planar surface of the sample to a path intersecting the planar surface.

8. The system according to claim 1, wherein the deflector selectively moves the ion beam across at least a portion of the sample surface.

9. The system according to claim 8, wherein the raster scanning range of the ion beam is selected from (i) substantially the entire surface of the sample or more, and (ii) a limited area within the surface of the sample.

10. The system according to claim 1, wherein the sample stage can be adjusted in at least one of the X, Y, Z, and rotation directions.

11. The system according to claim 10, wherein the adjustment of the rotation direction is within the range between 0 rpm and 100 rpm.

12. The system according to claim 1, wherein the sample stage is temperature-adjustable between ambient temperature and extremely low temperature.

13. The system according to claim 1, further comprising at least one detector for collecting data from the sample, the detector being in electronic communication with a feedback circuit, and selected from the group consisting of an optical microscope, a CCD camera, a CMOS camera, a scanning electron microscope, an energy-dispersive spectrometer, a secondary ion mass spectrometer, and an Auger probe.

14. The system according to claim 13, wherein the detector provides in-situ feedback regarding at least one of the topography of the sample surface and the depth of material removal across the sample surface.

15. The system according to claim 14, wherein the scanning electron microscope is configured to change the acceleration voltage of the scanning electron microscope in order to derive information from the sample surface and substructure.

16. The system according to claim 13, further comprising a secondary electron detector for detecting the relative beam position and the characteristics of the sample surface upon incidence of one of the ion beam and the electron beam.

17. The system according to claim 13, further comprising a backscatter electron detector for detecting characteristics of the sample surface and substructure by incidence of an electron beam operated at various voltages.

18. The system according to claim 1, wherein the ion beam source further comprises a filament, an ionization chamber, and a focusing lens.

19. The system according to claim 18, wherein the filament is mounted in a cartridge that is removable from the rest of the ion source.

20. The system according to claim 1, wherein the cutting speed at a given position on the sample is a function of the residence time of the ion beam at the position.

21. The system according to claim 1, wherein the ion beam has an incident cutting angle range of 0.0 to 15 degrees.

22. The system according to claim 1, wherein the ion beam has an incident cutting angle greater than 15 degrees.

23. The system according to claim 1, characterized in that the rate of change of the deflection of the ion beam is variable as the ion beam moves across the sample surface.

24. The system according to claim 1, wherein the ion beam has a selectively adjustable energy level between 1 keV and 50 keV, including these values.

25. The system according to claim 1, wherein the ion beam has a beam current between 1 μA and 1000 μA, including values ​​within these ranges.

26. A blocking device for transporting a flow of gaseous material between at least two conductors with different electrostatic potentials, a. An insulating tube having an input section, b. A circuit breaker comprising a current limiter that restricts the flow so as to maintain the pressure at the inlet of the insulating tube above a preselective limit in order to prevent arc discharge.

27. The current limiter is a throttling port, as described in claim 26.

28. The circuit breaker according to claim 26, wherein the insulating tube and the current limiter are combined as a capillary tube.

29. The blocking device according to claim 26, wherein the conductor is a component of the ion source.

30. A method for exfoliating a sample, a. The step of placing the sample on a stand inside the vacuum chamber, b. The step of determining the surface topography of the selected layer of the sample, c. A step of determining the thickness, depth profile, and corresponding removal rate for at least a portion of the layer of the sample, d. The step of scanning the controlled ion beam across the surface of the sample to remove each layer or at least one of a selected portion of each layer, e. A step of detecting the change in the surface topography of the sample, f. A method comprising the steps of adjusting the residence time of the ion beam as a function of the position of the ion beam on the sample based on the surface topography, wherein the adjustment causes a substantially planar removal of the material.

31. The method according to claim 30, further comprising the step of selecting a layer, an interface between two adjacent layers, a portion of a layer, one of several layers, a specified thickness, a specific amount of material to be removed, and a pre-selected endpoint with respect to at least one of the samples.

32. The method according to claim 31, wherein the layer of the sample is removed until the pre-selected endpoint is reached.

33. The method according to claim 30, wherein the ion beam comprises ions and neutral particles, the neutral particles being removed before the ion beam is incident on the sample surface.

34. The step of adjusting the residence time of the ion beam is r = a * t k This includes a step of determining the time-averaged ion flux per unit area using the following formula: a. The variable t corresponds to the above residence time, b. The variable k is a value determined by the relative removal rate of the material with respect to the position on the sample, c. Variable a is a constant, d. The method according to claim 30, wherein the variable r is a radius measured by the distance between the position of the ion beam on the sample and the center of the cutting area of ​​the sample.

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