Controlling the incident angle of the ion beam by specimen bias

Abstract

An ion beam milling system is provided. The ion beam milling system includes a vacuum chamber, an ion column for directing an ion beam toward a sample, and a stage disposed within the vacuum chamber and configured to mount a holder for supporting the sample. The stage includes a stage surface disposed at a first angle relative to an axis of the ion column. An electrical bias is applied to the stage to adjust the angle of incidence of the ion beam with respect to the stage surface. A method of milling a sample using the ion beam milling system includes providing an ion beam milling system that applies an electrical bias to the stage to adjust the angle of incidence of the ion beam with respect to the stage surface, and milling the sample surface of the sample using the ion beam after applying the electrical bias to the stage.

Description

[Technical Field]

[0001] The present disclosure is directed to low angle milling, and more particularly, the present disclosure describes a method and system for stage biasing to redirect an ion beam in low angle milling. [Background technology]

[0002] Focused ion beam scanning electron microscopy (FIB-SEM) is an important technique in life sciences and has become a popular method for high-resolution 3D analysis of biological samples. Plasma-FIB (PFIB) SEM tomography is based on a cross-sectional technique in which the sample is perpendicular to the ion beam and remains tilted during the imaging process. Summary of the Invention

[0003] According to one embodiment, an ion beam milling system includes a vacuum chamber, an ion column for directing an ion beam at a sample, and a stage disposed within the vacuum chamber and configured to mount a holder for supporting the sample. The stage includes a stage surface disposed at a first angle relative to an axis of the ion column. An electrical bias is applied to the stage to adjust the angle of incidence of the ion beam with respect to the stage surface.

[0004] The system may include various optional embodiments. The angle of incidence of the ion beam may be based at least in part on one or more of a bias level of an electrical bias or an energy level associated with the ion beam. The bias level of the electrical bias may be 3.0 kV or greater. The energy level associated with the ion beam may include a landing energy of 30 keV or less. The holder may include a pre-tilted holder for supporting the sample. The first angle may be 28 degrees or less. The system may further include an electron column for directing the electron beam toward the sample. A normal to the stage surface may be positioned at a second angle relative to the electron column. The second angle may be between 0 and -10 degrees. Applying an electrical bias to the stage may enable milling of substantially all of the sample surface of the sample using the ion beam without colliding the sample or sample holder with the end of the ion column. The stage may include a tilt stage configured to tilt the holder to adjust the first angle and the second angle. The system may be configured to mill samples with a diameter of 6 inches or less in any orientation.

[0005] According to another embodiment, a method for milling a specimen using an ion beam milling system includes providing an ion beam milling system including a vacuum chamber, an electron column for directing an electron beam at the specimen, an ion column for directing an ion beam at the specimen, and a stage disposed within the vacuum chamber and configured to mount a holder for supporting the specimen, the stage having a stage surface disposed at a first angle relative to an axis of the ion column, The method further includes applying an electrical bias to the stage to adjust an angle of incidence of the ion beam with respect to the stage surface, and milling a specimen surface of the specimen using the ion beam after applying the electrical bias to the stage.

[0006] The method may include various optional embodiments. Applying an electrical bias to the stage to adjust the angle of incidence of the ion beam relative to the stage surface may generate an electric field between the end of the electron column and the stage surface. The method may further include imaging the milled sample surface. The method may further include varying the electrical bias applied to the stage during milling. The system may be configured to mill samples up to six inches in diameter in any orientation.

[0007] According to yet another embodiment, the ion beam milling system includes a vacuum chamber, an ion column for directing an ion beam at a sample, an electron column for directing an electron beam at the sample, and a stage disposed within the vacuum chamber and including a stage surface for supporting the sample, wherein an electrical bias is applied to the stage to adjust the angle of incidence of the ion beam with respect to the stage surface.

[0008] The system may include various optional embodiments. The angle of incidence of the ion beam is based at least in part on one or more of a bias level of the electrical bias or an energy level associated with the ion beam. The system may be configured to mill samples up to 6 inches in diameter in any direction. [Brief explanation of the drawings]

[0009] The foregoing aspects and many of the attendant advantages of the present disclosure will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, in which: [Figure 1] FIG. 1 is a schematic diagram of an example dual beam system for preparing materials, according to some embodiments. [Figure 2A] FIG. 1 illustrates a PFIB and SEM on a sample in a PFIB-SEM spin mill system, according to some embodiments. [Figure 2B] FIG. 2B is a partial view of FIG. 2A including the geometry of a PFIB-SEM spin mill system according to some embodiments. [Figure 3] FIG. 2 is a schematic diagram of an exemplary stage bias system for redirecting an ion beam, according to some embodiments. [Figure 4] 10 is a graph illustrating the effect of applying a positive electrical bias to a stage, according to some embodiments. [Figure 5A] FIG. 1 illustrates a PFIB and SEM of a sample with a positive stage bias applied, according to some embodiments. [Figure 5B] FIG. 5B is a partial view of FIG. 5A including the geometry of a PFIB-SEM spin mill system according to some embodiments. [Figure 6] 1 is a flowchart of a method for milling a specimen using an ion beam milling system, according to some embodiments. [Figure 7] FIG. 1 is a block diagram of an exemplary computer system usable with systems and methods according to embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] While exemplary embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the disclosure.

[0011] Angle milling is a machining process used to remove material from a specimen at an angle other than 90° relative to the machine axis. An ideal ion-milled specimen contains a large, thinned area within the selected region, minimal amorphization of the top and bottom surfaces, and minimal preferential etching of adjacent material. Minimizing the angle of incidence of the ion beam relative to the specimen's surface can satisfy at least some of these requirements.

[0012] Low-angle milling is based on removing a thin layer from the sample surface at a near-glancing angle, which can also be described as a method of polishing a horizontal surface. In life science resin-embedded samples, large areas up to 1 mm in diameter can be irradiated with a plasma ion beam at a glancing angle using xenon, argon, nitrogen, or, most commonly, oxygen. Commonly used angles are 1°-5°, with 4° being the most common.

[0013] According to an exemplary application, the stage is periodically rotated to a series of predetermined milling sites, called spin mill positions. The number of milling positions can contribute to an optimized quality of the sample surface. Most commonly, five milling positions are used. A full 360° rotation under the ion beam constitutes a single milling slice.

[0014] Various known methods of low-angle milling may require a pretilt holder or a stage with a negative extended tilt to achieve small glancing angles. For example, spin milling methods using multidirectional low-angle milling may be limited to relatively small samples with a maximum diameter of 12.5 mm and an addressable area radius of only 4 mm from the center of rotation. Furthermore, processing occurs primarily near the center of the sample, rather than across the entire sample. Larger samples can also be processed with a pretilt holder, with the addressable area at the edge of the sample. However, the size of the sample is still limited due to potential interference with the ion column (e.g., the edge of a large sample may contact the ion column and prevent or disrupt its operation). Therefore, both pretilt holders and stages with a negative extended tilt have geometric limitations.

[0015] Various embodiments of the present disclosure enable spin milling at high angles, which further enables processing of relatively large samples. Additionally, biasing the stage according to the embodiments described herein improves the quality of the milled area and further enables spin milling on a tool without extending tilt in the negative direction. For example, embodiments of the present disclosure provide methods and systems for redirecting an ion beam by biasing a stage supporting a sample.

[0016] FIG. 1 is a schematic diagram of an example dual beam system 100, according to some embodiments. System 100 may be used to perform the low-angle milling discussed herein. In some embodiments, system 100 performs the sample milling. However, in other embodiments, milling algorithms may be performed by a computing system coupled to system 100, such as a user's desk-based or cloud-based computing system. While examples of suitable hardware are provided below, the present disclosure is not limited to being implemented on any particular type of hardware. Various embodiments of low-angle milling as described herein may be implemented using one or more algorithms executed by a computing system coupled to system 100.

[0017] The dual beam system 100 includes an SEM 141, along with a power supply and control unit 145. An electron beam 143 is emitted from a cathode 152 by applying a voltage between the cathode 152 and an anode 154. The electron beam 143 is focused to a fine spot by a condenser lens 156 and an objective lens 158. The electron beam 143 is scanned two-dimensionally over the specimen by a deflector 160. The operation of the condenser lens 156, the objective lens 158, and the deflector 160 is controlled by the power supply and control unit 145.

[0018] The electron beam 143 can be focused onto a sample 122 on a stage 125 in a lower chamber 126. The sample 122 can be located on the surface of the stage 125 or on a sample holder 124 that extends from the surface of the stage 125.

[0019] When electrons in the electron beam strike the sample 122, secondary electrons are emitted. These secondary electrons are detected by a secondary electron detector 140.

[0020] System 100 also includes a FIB system 111, which includes a vacuum chamber with an ion column 112 within which an ion source 114 and focusing elements 116, including extraction electrodes and an electrostatic optical system, are located. The axis of focusing column 116 may be tilted, for example, 52 degrees from the axis of electron column 141. Ion column 112 includes ion source 114, extraction electrodes 115, focusing elements 117, and deflection elements 120, which cooperate to form a focused ion beam 118. Focused ion beam 118 passes from ion source 114 through focusing elements 116, between electrostatic deflection means, shown schematically at 120, and toward a substrate 122, which may include, for example, a semiconductor wafer positioned on a movable stage 125 within a lower chamber 126.

[0021] Stage 125 can move in the horizontal plane (X and Y axes) and vertically (Z axis). Stage 125 can also tilt and rotate about the Z axis.

[0022] To insert the substrate 122 onto the stage 125, the door 161 is opened. Depending on the tilt of the stages 124 / 125, the Z axis will be in the direction of the optical axis of the associated column. For example, during the data collection phase of the disclosed technique, the Z axis will be in a direction parallel to the FIB optical axis, for example, as indicated by the ion beam 118. In such a coordinate system, the X and Y axes are referenced from the Z axis. For example, the X axis may be in or out of the page showing FIG. 1, while the Y axis is in the page, and all three axes maintain their perpendicular nature to one another at all times.

[0023] The chamber 126 is evacuated using a turbomolecular and mechanical pumping system 130 under the control of a vacuum controller 132. The vacuum system pumps approximately 1×10 volts of gas into the chamber 126. -7 Tor ~ 5 × 10 -4 Provide a vacuum of 1000 psi (3000 psi). If an etch-assisting gas, an etch-retarding gas, or a deposition precursor gas is used, the chamber background pressure is typically about 1×10 -5 The temperature can rise to 1000kJ / s.

[0024] A high voltage power supply provides an appropriate accelerating voltage to electrodes in the focusing column 116 to energize and focus the ion beam 118. When the ion beam strikes the sample 122, it sputters, i.e., physically ejects, material from the sample. Alternatively, the ion beam 118 can decompose a precursor gas to deposit material.

[0025] A high-voltage power supply 134 is connected to the ion source 114 and appropriate electrodes in the ion beam focusing component 116 to form an ion beam 118 of approximately 500 eV to 30 keV and direct it toward the sample. A deflection controller and amplifier 136, operating according to a predetermined pattern provided by a pattern generator 138, is coupled to the deflection plates 120, so that the ion beam 118 can be manually or automatically controlled to track a corresponding pattern on the top surface of the substrate 122. In some systems, the deflection plates are placed before the final lens, as is known in the art. Beam blanking electrodes (not shown) in the ion beam focusing column 116 direct the ion beam 118 to impinge on a blanking aperture (not shown) rather than the sample 122 when a blanking controller (not shown) applies a blanking voltage to the blanking electrodes.

[0026] The ion source 114 typically provides an ion beam based on the type of ion source. In some embodiments, the ion source 114 is a liquid metal ion source that can provide, for example, a gallium ion beam. In other embodiments, the ion source 114 may be a plasma-type ion source that can deliver several different ion species, such as oxygen, xenon, argon, nitrogen, etc. The ion source 114 is typically capable of being focused into a beam less than 1 / 10 of a micrometer wide at the substrate 122 for processing the substrate 122 by ion milling, ion-induced etching, material deposition, or for imaging the substrate 122.

[0027] A charged particle detector 140, such as an Everhart-Thornley detector or multichannel plate used to detect secondary ion or electron emissions, is connected to a video circuit 142, which provides drive signals to a video monitor 144 and receives deflection signals from the system controller 119. The location of the charged particle detector 140 within the lower chamber 126 may vary in different embodiments. For example, the charged particle detector 140 may be coaxial with the ion beam and include a hole to allow the ion beam to pass through. In other embodiments, secondary particles may be collected through a final lens and then deflected off-axis for collection.

[0028] A system controller 119 controls the operation of various parts of the dual beam system. Through the system controller 119, a user can cause the ion beam 118 or the electron beam 143 to be scanned in a desired manner through commands entered into a conventional user interface (not shown). Alternatively, the system controller 119 may control the dual beam system according to programmed instructions stored in memory 121. In some embodiments, the dual beam system incorporates image recognition software to automatically identify regions of interest, and the system can then manually or automatically extract samples in accordance with the present disclosure. For example, the system can automatically locate similar features on a semiconductor wafer containing multiple devices and acquire samples of those features on different (or the same) devices.

[0029] A layer of the sample 122 can be removed from the working surface. The layer can be removed in smaller "slices," according to certain embodiments, with successive slices of about 1 nm to 5 nm being removed. After a slice is removed, the newly exposed surface is imaged. The process of image acquisition and slice removal can be repeated 25, 50, 75, or 100 times, although any other number of slices is contemplated herein.

[0030] Removal of a layer of material from the specimen 122 can be achieved by directing the FIB 118 in a pattern toward a portion of the specimen 122. For example, the ion beam can be raster scanned across the surface of the specimen 122 in that portion to remove the desired layer. Embodiments of the present disclosure provide methods and systems for redirecting an ion beam and using the redirected ion beam to remove the desired layer from the specimen 122.

[0031] 2A shows a PFIB and SEM for a sample in a PFIB-SEM spin mill system. The system 200 can be configured to remove a thin layer from a sample surface 202 of a sample 204. Specifically, the system 200 includes an ion column 206 for directing an ion beam toward the sample surface 202 to polish a horizontal surface of the sample 204. The system 200 may further include an electron column 208 for directing an electron beam toward the sample surface 202. The system 200 may include a stage 210 configured to mount a holder 212 for supporting the sample 204 having the sample surface 202.

[0032] 2A, one or more test features 250 may be formed on the sample surface 202 and / or test sample (not shown) to illustrate the accuracy and / or effectiveness of milling parameters, etc. As shown, the one or more test features 250 may include a series of concentric circles with an "x" mark in the center, although any shape or combination of shapes may be used without limitation.

[0033] Figure 2B shows a partial view of Figure 2A, including the geometry of a PFIB-SEM spin mill system. As shown in Figure 2B, an ion column 206 directs an ion beam 216 toward the sample 204, and an electron column 208 directs an electron beam 218 toward the sample 204. The stage 210 includes a stage surface 220 positioned at an angle relative to the axis of the ion beam 216. For life science resin-embedded samples, a plasma ion beam can be used to irradiate a large area of ​​the sample surface 202, up to 1 mm in diameter, at a glancing angle using xenon, argon, nitrogen, or, most commonly, oxygen. Commonly used angles are between 1° and 5°, with 4° being the most common. The stage 210 is periodically rotated to a series of predetermined milling sites. As shown in Figure 2B, the stage 210 can be tilted to an angle θ2 of approximately -34°, with the ion beam forming a 4° angle θ1 with respect to the sample surface 202.

[0034] Low-angle milling methods, such as planar exfoliation or polishing as shown in Figures 2A and 2B, are limited by the geometry of the ion column and the dimensions of the sample. For example, spin milling using multi-directional low-angle milling may be limited to relatively small samples with an addressable area radius of up to 12.5 mm, as discussed above, and an addressable area radius of only 4 mm from the center of rotation; sample size may also be limited due to potential interference from the ion column.

[0035] To address these various limitations, various embodiments of the present disclosure enable spin milling at high angles, which further enables processing of relatively large samples. Additionally, biasing the stage according to the embodiments described herein improves the quality of the milled area and further enables spin milling on the tool without extending the tilt in the negative direction.

[0036] Embodiments of the present disclosure provide methods and systems for redirecting an ion beam by biasing a stage supporting a sample. According to various embodiments, the ion beam may be redirected by an electric field according to Coulomb's law. FIG. 3 is a schematic diagram of an exemplary stage bias system for redirecting an ion beam. According to various embodiments, a system 300 includes an ion column 302 for directing an ion beam 304 toward a sample 306. In at least some embodiments, the system 300 may further include an electron column 308 for directing an electron beam 310 toward the sample 306. As shown in FIG. 3 , a positive electrical bias may be applied to the sample 306 via the stage and / or to the stage itself to redirect the ion beam 304 away from an axis 312 of the ion column 302. An electric field is generated between conductive components of the system (e.g., between the electron column 308 and the sample 306). For example, applying a positive electrical bias generates an electric field 314 between the electron column 308 (e.g., specifically, the end of the electron column 308) and the sample 306. Specifically, applying a positive electrical bias generates an electric field 314 between the electron column 308 and the sample 306, which causes the path of the positively charged particles to curve relative to the sample 306 and redirect the ion beam 304 near the sample 306, as shown in FIG. 3. Accordingly, the angle of incidence between the sample 306 and the ion beam 304 is reduced based at least in part on the acceleration voltage of the ion beam 304 and / or the electrical bias applied to the stage and / or sample 306. For example, the angle of incidence may be reduced by increasing the electrical bias applied to the stage and / or sample 306 and / or by decreasing the acceleration voltage. According to various embodiments, an electrical bias is applied to the stage to adjust the angle of incidence of the ion beam relative to the stage surface.

[0037] Figure 4 is a graph showing the effect of applying a positive electrical bias to the stage. The y-axis represents the height above the sample (e.g., "height above stub [mm]"), and the x-axis represents the position of the sample relative to the ion beam (e.g., "stub position [mm]"). Ion beam 402-A represents particles impacting the surface of the sample with no potential applied to the sample and / or stage. Ion beam 402-B represents particles impacting the surface of the sample with a potential applied to the sample and / or stage. The potential applied during impact, represented by a square, is 3233 V. For each impact, an acceleration voltage of 12 kV was applied when the angle between the ion beam and the sample (e.g., θ1 shown in Figure 2B) was 28°. As shown, by biasing the stage to several thousand volts (e.g., approximately 3000 V), the ion beam, represented by a square, was deflected away from the sample, reducing the angle of incidence to geometric parallelism.

[0038] FIG. 5A illustrates a PFIB and SEM on a sample, according to some embodiments. The system 500 may be configured to remove a thin layer from a sample surface 502 of a sample 504. Specifically, the system 500 includes an ion column 506 for directing an ion beam 505 toward the sample surface 502 to polish horizontal surfaces of the sample 504. The system 500 may further include an electron column 508 for directing an electron beam 507 toward the sample surface 502. The system 500 may include a stage 510 configured to mount a holder 512 for supporting the sample 504 having the sample surface 502. The system 500 may also include a vacuum chamber (not shown), according to various embodiments. Various components described herein may be disposed at least partially within the vacuum chamber during milling, etc. In contrast to the one or more test features 250 shown in FIG. 5A, the one or more test features 550 have relatively jagged edges caused by non-uniform electric fields when compared to test features formed using embodiments of the present disclosure, which are described in more detail below.

[0039] FIG. 5B shows a partial view of FIG. 5A , including the geometry of a PFIB-SEM spin mill system. As shown in FIG. 5B , an ion column 506 directs an ion beam 505 toward a sample 504, and an electron column 508 directs an electron beam 507 toward the sample 504. A stage 510 includes a stage surface 520 disposed at a first angle θ1 relative to an axis 509 of the ion column 506. The first angle θ1 can be 28 degrees or less (e.g., 28°) according to various embodiments described herein. According to various embodiments, the first angle θ1 can be greater than 0° and between 90°. In still other embodiments, the first angle θ1 can be between 5° and 40°. In an exemplary embodiment, the first angle θ1 is 28°. In various embodiments, a normal 524 of the stage surface 520 is disposed at a second angle θ2 relative to the electron column 508. Normal 524 may coincide with the axis of stage 510 and the axis of rotation of stage 510. Second angle θ2 may be between −38° and 52°, according to at least some embodiments. A third angle θ3 is formed between sample surface 502 and redirected ion beam 505. According to at least some embodiments, second angle θ2 (and the resulting third angle θ3) may be adjusted by using a tilted sample holder and / or a tilted stage. Stage 510 may move in the horizontal plane (X-axis and Y-axis) and vertically (Z-axis), and stage 510 may also be tilted and rotated about the Z-axis.

[0040] According to various embodiments, an electrical bias is applied to the stage 510 to adjust the angle of incidence of the ion beam 505 relative to the stage surface 520. The angle of incidence is based at least in part on one or more of a bias level of the electrical bias or an energy level associated with the ion beam 505. In at least some embodiments, the bias level of the electrical bias is 3.0 kV or greater. For example, the bias level of the electrical bias may be between 1.0 keV and 5.0 kV. In yet other embodiments, the bias level of the electrical bias may be between 1.0 keV and 10.0 kV. In various embodiments, the energy level associated with the ion beam 505 includes a landing energy of 30 keV or less. By biasing the stage 510 (or the sample 504 via the stage 510), the ion beam 505 is redirected (e.g., curved) so that the charged ion beam 505 is approximately parallel to the sample surface 502 upon impact, as shown by the curved square in FIG. 4 . In one exemplary embodiment, applying an acceleration voltage of 12 kV can redirect the ion beam 505 by 28 degrees, thus enabling milling on samples tilted only down to -10 degrees (e.g., having a second angle θ2 of -10 degrees). Thus, embodiments of the present disclosure enable spin milling on products (e.g., stages) that do not have the ability to extend tilt in the negative direction (e.g., up to -38 degrees).

[0041] Applying an electrical bias to the stage 510 allows the ion beam 505 to mill substantially all of the sample surface 504 without causing the end 526 of the ion column 506 to collide with the sample 502 or other in-chamber accessories. Advantageously, embodiments of the present disclosure enable the processing of relatively large samples that may be processed with conventional techniques and systems. For example, the system 500 is configured to mill samples that are larger than ½ inch in the X and Y directions, and up to 6 inches in size. For example, the sample diameter may be at least 6 inches across the sample.

[0042] In some embodiments, the holder 512 may be a pre-tilted holder for supporting the sample 504. The stage 510 may include a tilt stage (not shown) configured to tilt the holder 512 to adjust the first angle θ1 and the second angle θ2.

[0043] FIG. 6 is a flowchart of a method for milling a specimen using an ion beam milling system. Method 600 may be performed using any of the embodiments described herein, particularly those described with respect to the ion beam milling system of FIGS. 5A and 5B. Additionally, various embodiments of method 600 may be implemented and / or performed by one or more components of computer system 700, described with respect to FIG. 7 below. Method 600 may include more or fewer operations than those described herein, and at least some steps described herein may be performed in an alternative order unless otherwise noted herein. Method 600 includes step 602, which includes providing an ion beam milling system. The system may include an embodiment of system 500, as described in detail above. For example, the system may include a vacuum chamber, an electron column for directing an electron beam at the specimen, an ion column for directing an ion beam at the specimen, and a stage disposed within the vacuum chamber and configured to mount a holder for supporting the specimen. The stage may have a stage surface disposed at a first angle relative to the axis of the ion column, shown and described as a first angle θ1 in at least FIG. 5B.

[0044] Method 600 further includes step 604. Step 604 includes applying an electrical bias to the stage to adjust the angle of incidence of the ion beam relative to the stage surface. The angle of incidence may be based at least in part on one or more of a bias level of the electrical bias or an energy level associated with the ion beam. According to various embodiments, a "bias level" refers to a unit of electrical bias, such as an electrical bias in kV, applied to the stage. As referred to herein, an "energy level" refers to a unit of landing energy of the ion beam. In at least some embodiments, the bias level of the electrical bias is 3.0 kV or greater. In various embodiments, the energy level associated with the ion beam includes a landing energy of 30 keV or less. As described with respect to FIG. 5 , applying an electrical bias to the stage to adjust the angle of incidence of the ion beam relative to the stage surface generates a uniform electric field between the end of the electron column and the stage surface.

[0045] Method 600 further includes step 606, which includes applying an electrical bias to the stage and then milling the sample surface of the sample using the ion beam. In various embodiments, method 600 may be performed in a spin-milling application in which the sample is rotated along an axis of rotation (e.g., as shown in FIG. 5B, normal 524 may coincide with the axis of stage 510 and the axis of rotation of stage 510). According to at least some embodiments, step 606 may include varying the electrical bias applied to the stage during milling. For example, the applied stage bias may be dynamically changed to correct the first angle, such as when the sample normal is not perfectly parallel to the stage axis of rotation. Thus, embodiments of the present disclosure provide fine-tuned control of the glancing angle of the ion beam. The system is configured to mill samples larger than ½ inch wide and up to 6 inches wide in any orientation.

[0046] The method 600 may further include imaging the milled sample surface. Imaging the milled surface can involve a variety of systems, as those skilled in the art will appreciate upon reading this disclosure. During conventional spin milling, the beam may chip away at the surface at an angle of 0.5 to 5 degrees. This often results in deep cuts around the sample periphery during relatively long spin mill runs, which can lead to redeposition on the target area. Furthermore, for crystallographic reasons, milling rates often vary from particle to particle. When an electrical bias is applied to the stage according to embodiments of the present disclosure, the ion beam is parallel to the sample surface, avoiding these deep cuts around the target area. This reduces contamination, which typically occurs during processing, and the surface remains flat. Essentially, the point of coincidence (impact point) between the ion beam and the sample surface is offset from the point of incidence between the electron beam and the sample surface, preventing contamination from reaching the electron pole, thereby reducing contamination during ion beam processing.

[0047] FIG. 7 is a block diagram of an exemplary computer system that can be used with systems and methods according to embodiments of the present disclosure. Any of the computer systems referred to herein can utilize any suitable number of subsystems. An example of such a subsystem is shown in computer system 700 of FIG. 7. In some embodiments, the computer system includes a single computer device, and the subsystems can be components of the computer device. In other embodiments, the computer system can include multiple computer devices, each of which is a subsystem and has internal components. The computer system can include desktop and laptop computers, tablets, mobile phones, and other mobile devices.

[0048] The subsystems shown in FIG. 7 are interconnected via a system bus 775. Additional subsystems are shown, such as a printer 774, a keyboard 778, storage device(s) 779, and a monitor 776 (e.g., a display screen, such as an LED) coupled to a display adapter 782. Peripherals and input / output (I / O) devices coupled to an I / O controller 771 can be connected to the computer system by any number of means known in the art, such as input / output (I / O) ports 777 (e.g., USB, FireWire). For example, the I / O ports 777 or an external interface 781 (e.g., Ethernet, Wi-Fi, etc.) can be used to connect the computer system 700 to a wide area network such as the Internet, a mouse input device, or a scanner. The interconnection via the system bus 775 allows a central processor 773 to communicate with each subsystem and control the execution of instructions from the system memory 772 or storage device(s) 779 (e.g., a fixed disk, such as a hard drive or optical disk), as well as the exchange of information between the subsystems. The system memory 772 and / or storage device(s) 779 may embody a computer-readable medium. Another subsystem is a data collection device 785, such as a camera, microphone, accelerometer, etc. Any of the data referred to herein may be output from one component to another, or may be output to a user.

[0049] A computer system may include multiple identical components or subsystems connected together, for example, by an external interface 781, by an internal interface, or through a removable storage device that can be connected and disconnected from one component to another. In some embodiments, computer systems, subsystems, or devices may communicate over a network. In such an example, one computer may be considered a client and another computer may be considered a server, each of which may be part of the same computer system. The client and server may each include multiple systems, subsystems, or components.

[0050] Aspects of the embodiments can be implemented in the form of control logic using hardware circuitry (e.g., application-specific integrated circuits or field-programmable gate arrays) and / or using computer software stored in memory with modular or integrated, generally programmable processors; thus, a processor can include a memory that stores software instructions that configure the hardware circuitry, as well as an FPGA or ASIC with the configuration instructions. As used herein, a processor can include a single-core processor, a multi-core processor on the same integrated chip, or multiple processing units on a single circuit board or networked, as well as dedicated hardware. Based on the disclosure and teachings provided herein, those skilled in the art will know and understand other ways and / or methods for implementing embodiments of the present disclosure using hardware and combinations of hardware and software.

[0051] Any of the software components or functions described in this application may be implemented as software code executed by a processor using any suitable computer language, such as, for example, Java, C, C++, C#, Objective-C, Swift, or a scripting language such as Perl or Python, using, for example, conventional or object-oriented techniques. The software code may be stored as a series of instructions or commands on a computer-readable medium for storage and / or transmission. Suitable non-transitory computer-readable media may include random access memory (RAM), read-only memory (ROM), magnetic media such as a hard drive or a floppy disk, or optical media such as a compact disc (CD) or DVD (Digital Versatile Disc) or Blu-ray disc, flash memory, etc. The computer-readable medium may also be any combination of such devices. Furthermore, the order of operations may be rearranged. A process may terminate when its operations are completed, but may have additional steps not included in a figure. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination corresponds to a return of the function to the calling function or the main function.

[0052] Such programs may also be encoded and transmitted using carrier signals adapted for transmission over wired, optical, and / or wireless networks conforming to various protocols, including the Internet. Thus, computer-readable media can be created using data signals encoded with such programs. Computer-readable media encoded with program code may be packaged with a compatible device or provided separately from other devices (e.g., via Internet download). Any such computer-readable medium may reside on or within a single computer product (e.g., a hard drive, CD, or entire computer system), or may reside on or within different computer products within a system or network. A computer system may include a monitor, printer, or other suitable display for providing a user with any of the results mentioned herein.

[0053] Any of the methods described herein can be performed in whole or in part using a computer system including one or more processors that can be configured to perform the steps. Any operation (e.g., aligning, determining, comparing, computing, calculating) performed using a processor can be performed in real time. The term "real time" can refer to a computing operation or process that is completed within a specific time constraint. The time constraint may be one minute, one hour, one day, or seven days. Accordingly, embodiments can be directed to a computer system configured to perform the steps of any of the methods described herein, potentially using different components that perform each step or each group of steps. Although presented as numbered steps, steps of the methods herein can be performed simultaneously, at different times, or in different orders. In addition, some of these steps may be used with some of other steps from other methods. Also, all or some of the steps may be optional. Furthermore, any of the steps of any of the methods can be performed using a system module, unit, circuit, or other means for performing these steps.

[0054] In the foregoing specification, embodiments of the present disclosure have been described with reference to numerous specific details that may vary from embodiment to embodiment. Accordingly, the specification and drawings should be regarded in an illustrative rather than a restrictive sense. The sole and exclusive indication of the scope of the present disclosure, and what the applicant intends the scope of the present disclosure to be, is the literal and equivalent scope of the set of claims issuing from this application, in the specific form in which such claims are issued, including any subsequent amendments. The specific details of particular embodiments can be combined in any suitable manner without departing from the spirit and scope of the embodiments of the present disclosure.

[0055] Additionally, spatially relative terms such as "bottom" or "top" can be used to describe the relationship of an element(s) and / or feature(s) to other elements and / or features, for example, as shown in the figures. It will be understood that spatially relative terms are intended to encompass different orientations of the device in use and / or operation in addition to the orientation depicted in the figures. For example, if a device in a figure is turned upside down, an element described as the "bottom" surface can then be oriented "above" the other element or feature. The device can be oriented differently (e.g., rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein can be interpreted accordingly.

[0056] As used herein, the terms "and," "or," and "and / or" can have a variety of meanings that are expected to depend, at least in part, on the context in which such terms are used. Typically, when "or," when used to associate a list such as A, B, or C, is intended to refer to A, B, and C, which are used herein in an inclusive sense, as well as A, B, or C, which are used herein in an exclusive sense. Additionally, as used herein, the term "one or more" can be used to describe any feature, structure, or characteristic in the singular, or it can be used to describe any combination of features, structures, or characteristics. However, it should be noted that this is merely an illustrative example, and claimed subject matter is not limited to this example. Furthermore, the term "at least one of," when used to associate a list such as A, B, or C, can be interpreted to mean any combination of A, B, and / or C, such as A, B, C, AB, AC, BC, AA, AAB, ABC, AABBCCC, etc.

[0057] References throughout this specification to "one example," "an example," "a particular example," or "an exemplary embodiment" mean that a particular feature, structure, or characteristic described in connection with a feature and / or example may be included in at least one feature and / or example of the claimed subject matter. Thus, appearances of the phrases "in one example," "in an example," "in a particular example," "in a particular embodiment," or other similar phrases throughout this specification do not necessarily all refer to the same features, examples, and / or limitations. Furthermore, particular features, structures, or characteristics may be combined in one or more examples and / or characteristics.

[0058] In some implementations, operations or processing may involve physical manipulations of physical quantities. Usually, though not necessarily, such quantities may take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to such signals as bits, data, values, elements, symbols, characters, terms, numbers, numerals, or the like. It should be understood, however, that all of these or similar terms are to be associated with the appropriate physical quantities and are merely convenient labels. Unless otherwise indicated, as will be apparent from a discussion of this specification, discussions throughout this specification utilizing terms such as “processing,” “computing,” “calculating,” “determining,” etc. should be understood to refer to operations or processes of a special purpose apparatus, such as a special purpose computer, a special purpose computing apparatus, or a similar special purpose electronic computing device. Thus, in the context of this specification, a special purpose computer or a similar special purpose electronic computing device can manipulate or transform signals that are typically represented as physical electronic or magnetic quantities in the memories, registers, or other information storage, transmission, or display devices of the special purpose computer or similar special purpose electronic computing device.

[0059] In the foregoing detailed description, numerous specific details are set forth to provide a thorough understanding of the claimed subject matter. However, it will be understood by those skilled in the art that the claimed subject matter may be practiced without these specific details. In other instances, methods and apparatuses that would be known by those skilled in the art have not been described in detail so as not to obscure the claimed subject matter. Therefore, it is intended that the claimed subject matter not be limited to the particular examples disclosed, but that such claimed subject matter also include all aspects falling within the scope of the appended claims and their equivalents.

Claims

1. 1. An ion beam milling system comprising: a vacuum chamber; an ion column for directing the ion beam toward the sample; a stage disposed within the vacuum chamber and configured to mount a holder for supporting the sample, the stage having a stage surface oriented at a first angle relative to an axis of the ion column; an electrical bias is applied to the stage to adjust the angle of incidence of the ion beam with respect to the stage surface; system.

2. The system of claim 1 , wherein the angle of incidence of the ion beam is based at least in part on one or more of a bias level of the electrical bias or an energy level associated with the ion beam.

3. 3. The system of claim 2, wherein the bias level of the electrical bias is 3.0 kV or greater.

4. The system of claim 2 , wherein the energy levels associated with the ion beam include landing energies of 30 keV or less.

5. The system of claim 1 , wherein the holder comprises a pre-tilted holder for supporting the sample.

6. The system of claim 1 , wherein the first angle is between 0 and 90 degrees.

7. The system of claim 1 further comprising an electron column for directing an electron beam toward the specimen.

8. The system of claim 7 , wherein a normal to the stage surface is disposed at a second angle relative to the electron column.

9. The system of claim 8 , wherein the second angle is between −38 and 52 degrees.

10. 8. The system of claim 7, wherein applying the electrical bias to the stage enables the ion beam to mill substantially all of a sample surface of the sample without colliding the sample or the sample holder with the end of the ion column.

11. The system of claim 7 , wherein the stage comprises a tilt stage configured to tilt the holder to adjust the first angle and the second angle.

12. 10. The system of claim 1, wherein the system is configured to mill samples up to 6 inches in diameter in any direction.

13. 1. A method for milling a specimen using an ion beam milling system, comprising:

1. An ion beam milling system comprising: a vacuum chamber; an electron column for directing an electron beam at the sample; an ion column for directing an ion beam at the sample; providing an ion beam milling system comprising: a stage disposed within the vacuum chamber and configured to mount a holder for supporting the sample, the stage having a stage surface disposed at a first angle relative to an axis of the ion column; applying an electrical bias to the stage to adjust the angle of incidence of the ion beam with respect to the stage surface; and milling a sample surface of the sample using the ion beam after applying the electrical bias to the stage. method.

14. 14. The method of claim 13, wherein applying the electrical bias to the stage to adjust the angle of incidence of the ion beam relative to the stage surface generates an electric field between the end of the electron column and the stage surface.

15. 14. The method of claim 13, further comprising imaging the milled sample surface.

16. The method of claim 13 , further comprising varying the electrical bias applied to the stage during the milling.

17. 14. The method of claim 13, wherein the system is configured to mill samples up to 6 inches in diameter in any direction.

18. 1. An ion beam milling system comprising: a vacuum chamber; an ion column for directing the ion beam toward the sample; an electron column for directing an electron beam at the sample; a stage disposed within the vacuum chamber and having a stage surface supporting the sample; an electrical bias is applied to the stage to adjust the angle of incidence of the ion beam with respect to the stage surface; system.

19. 20. The system of claim 18, wherein the angle of incidence of the ion beam is based at least in part on one or more of a bias level of the electrical bias or an energy level associated with the ion beam.

20. 20. The system of claim 18, wherein the system is configured to mill samples up to 6 inches in diameter in any direction.

Images