Converged ion beam polishing system using radio frequency based gridded ion source and applications thereof

Abstract

Converged ion beam polishing system using radio frequency based gridded ion source and applications thereof The present invention discloses a dual-source broad ion beam polishing system designed for high-precision surface and cross-section milling It features an ion milling chamber (01) and load lock chamber (02) connected via a transfer arm (03). Two inductively coupled plasma ion sources with gridded extraction are mounted on flanges (04): an EBSD ion source (05a) for flat milling and a cross-section ion source (05b) for cross-sectional polishing, each with dedicated specimen holders (09a, 09b) and adjustable ion incidence. The cross-section source includes a conical aperture (12) to produce a 3 mm collimated beam for high-resolution thinning. Dielectric plasma chambers (06), inductive coils (07), and focusing grids (08) ensure stable ion generation. Shutters (11a, 11b) serve as Faraday devices. Real-time monitoring is provided by an integrated CMOS camera. The system enables efficient, artifact-free sample preparation for EBSD and SEM analysis across fields like metallurgy, semiconductors, materials science, and geology.

Description

[0001] BEFORE THE INTERNATIONAL BUREAU OF THE WORLD INTELLECTUAL PROPERTY ORGANIZATION

[0002] NON-PROVISIONAL APPLICATION FOR PATENT

[0003] PCT Rule 19.1 (a)(iii)

[0004] *** Complete Specification ***

[0005] Converged ion beam polishing system using radio frequency based gridded ion source and applications thereof”

[0006] Cross references to related applications: This complete specification is filed further to patent application No. 202421064728 filed on 27 / 08 / 2024 with provisional specification, the entire contents of which are incorporated herein in their entirety by way of reference.

[0007] Field of the invention

[0008] The present invention relates to the field of materials processing and surface preparation, specifically to systems and methods for broad ion beam polishing of specimens. More particularly, the invention pertains to a dual-source ion beam polishing system incorporating inductively-coupled plasma (ICP) sources and gridded extraction mechanisms for controlled ion beam shaping, acceleration, and converging. The system facilitates both flat milling for Electron Backscatter Diffraction (EBSD) and cross-section milling of specimens in a controlled vacuum environment.

[0009] Definitions

[0010] Before undertaking the description of the invention below, it may be advantageous to set forth definitions of certain words or phrases used throughout this patent document. Also, as some technical terms are not used uniformly in the field of the instant invention, a few definitions are given in the following to clarify the meaning of terms as they are used in this paper. Accordingly, the following terms shall mean and refer, as under-

[0011] (1 ) “SEM” shall refer to Scanning Electron Microscopy.

[0012] (2) “TEM” shall refer to Transmission Electron Microscopy.

[0013] (3) “AFM” shall refer to Atomic Force Microscopy.

[0014] (4) “EBSD” shall refer to Electron Backscattered Diffraction, a technique used in SEM to analyze the crystallographic orientation of materials.

[0015] (5) “EDS” shall refer to Energy Dispersive Spectroscopy

[0016] (6) “Ar” refers to Argon.

[0017] (7) “Bakelite” (formally polyoxybenzylmethyleneglycolanhydride) shall refer to a thermosetting phenol formaldehyde resin, formed from a condensation reaction of phenol with formaldehyde.

[0018] (8) “FIB” shall refer to Focused Ion Beam. (9) “RPM” shall refer to Rotations Per Minute.

[0019] (10) “AC” shall refer to alternating current.

[0020] (1 1 ) “RF” shall refer to radio frequency.

[0021] (12) The terms “Ion Beam Milling” and “Ion Beam Polishing” are used synonymously.

[0022] (13) The terms “sample” and “specimen” are used synonymously.

[0023] Background of the invention

[0024] Ion beam polishing is a technique used to improve the surface finish of materials by using a converged beam of ions. Common ions used are Ar or other noble gases, which are accelerated to high energies. The ion beam is then focused and directed towards the material’s surface using electromagnetic lenses and other beam-shaping techniques. When the high-energy ions strike the sample surface, they cause atoms to be ejected from the surface through a process known as sputtering. This removes surface material and helps smooth out irregularities. The process can be finely tuned to remove material at a controlled rate, allowing for precise surface polishing.

[0025] Ion beam used for surface milling I polishing can be adjusted to remove material atom by atom, which leads to very smooth surfaces. This level of control is particularly useful for preparing samples for high-resolution imaging or precise applications in the semiconductor industry (e.g. polishing silicon wafers and other materials), optics (e.g. preparation of optical surfaces, such as lenses and mirrors), material sciences (e.g. preparation of samples for detailed surface analysis, such as SEM I AFM) and nanotechnology (e.g. polishing of nanostructures and devices to improve performance and reliability).

[0026] Broad ion beam milling and polishing systems have emerged as critical tools for surface treatment and preparation of specimens in high-resolution imaging and analytical techniques, including EBSD, SEM, and EDS. Conventionally, systems employ either focused ion beam (FIB) or broad-beam ion sources for milling operations. While FIB systems provide high resolution with nanoscale beam control, they are limited in throughput and spatial coverage.

[0027] Typically, the presently available ion beam milling I polishing systems for EBSD polishing and Cross-sectional milling for SEM applications incorporate hollow anode discharge I cold cathode discharge type ion sources. These ion sources incorporate high voltage plasma discharge and output a narrow beam of a diameter ranging from a few hundred microns up to a maximum of 2.5 millimeters. Thus, there is a lacuna for ion beams having larger diameters.

[0028] Further, the specimen is placed within a distance of 15 millimeters to 30 millimeters from the ion source beam exit aperture to get the 2.5 mm diameter ion beam generated as above on the specimen treatment surface. This leads to the heating of the specimen and thereby requiring active cooling of the specimen during the polishing process. It would be desirable thus to have some means to keep the ion source farther from the specimen treatment surface, therein avoiding excessive heating of the specimen and consequently the need for cooling systems for addressing said heat.

[0029] Ion beams characterized in having diameter < 1 millimeters to 2.5 millimeters and lower beam current (typically ~ 2.5mA at source exit) also necessitate the use of more than one ion source in the system for treatment of the specimen requiring a larger treatment area. It would be desirable thus to have a single ion source suffice broad diameter requirements, and therefore avoid the need, procurement, operations, operational costs, and maintenance of a plurality of ion sources.

[0030] Smaller working chambers in some ion milling systems also limit the use of samples without Bakelite mount thereby adding an additional step of unmounting the specimen from Bakelite after mechanical polishing. It would be desirable thus to have some effective ion source capable of outputting broad width ion beams, yet amenable to smaller working chambers holding Bakelite mounted samples as well.

[0031] Another application of the RF inductively coupled type ion source is for cross sectional milling of SEM specimen. For the cross-sectional milling using a specially designed grid system and a conical graphite aperture, the converging ion beam can be further focused to a collimated ion beam of 3 mm beam diameter on the cross-sectional SEM specimen which is sandwiched in position between a specially designed backing plate and a front facing mask. The mask is manufactured from material of low sputter rate such as titanium or tungsten carbide. Only a very thin portion of the specimen typically around 100um to 200um is exposed to the ion beam such that the ion beam mills the cross-section of the exposed specimen.

[0032] On the other hand, broad-beam systems offer higher material removal rates but often suffer from limitations in beam shaping, energy control, and uniformity of milling — particularly across larger sample areas. There hence exists a pressing need for further research and development in their regard.

[0033] Prior art

[0034] Most prior art systems integrate DC or Kaufman-type ion sources, which offer limited control over beam uniformity and spot size, or require multiple beam alignment and adjustment steps for different specimen types. Additionally, transitioning between flat milling and cross-section milling often demands reconfiguration of the system or use of entirely different machines.

[0035] Existing EBSD sample preparation techniques also involve limitations in beam-induced heating, sample mounting complexity (especially for Bakelite-mounted specimens), and difficulties in achieving the low-angle polishing required for effective EBSD analysis.

[0036] Cross-section milling, particularly for multi-layer thin films on semiconductor substrates, faces challenges in generating a well-collimated ion beam for precise, high-aspect-ratio trenching. Prior solutions often fall short in beam collimation, angle-of-incidence flexibility, and area control — critical parameters for accurate microstructural and compositional analysis.

[0037] Patent prior art lists some scattered attempts to address the issues mentioned hereinabove. For example, US6759807 titled “Multi-Grid Ion Beam Source for Generating a Highly Collimated Ion Beam” describes a multi-grid ion beam source comprising an extraction grid, an acceleration grid, a focus grid, and a shield grid to produce a highly collimated ion beam. The focus grid adjusts the momentum of ions exiting the acceleration grid, enhancing beam collimation. This system provisions beam collimation using complex multi-grid optics, but lacks integration of sample tilt, rotation, or in-situ beam incident angle adjustment, which are critical for surface uniformity in milling applications like EBSD. Also, this system does not provide a dual-functionality system (flat + cross-section milling) with separate sources tailored to specific geometries or sample types, and has no consideration for thermal management (like liquid nitrogen cooling) or sample holders compatible with Bakelite-mounted specimens. Another reference, US6288357B1 titled “Ion Milling Planarization of Semiconductor Workpieces” outlines a method and apparatus for smoothing surfaces with fine irregularities using an ion beam in the presence of a radio frequency-generated plasma. The technique is applicable to planarizing semiconductor wafers and precision optical lenses. This system focuses on planarization of semiconductor substrates rather than dual-purpose ion milling for EBSD and material cross-sections but lacks advanced beam shaping or grid-based control mechanisms for varying beam diameters and focusing, and has no support for sample oscillation, masking, or precision angular milling, which are essential for cross-sectioning multilayer samples.

[0038] Yet another reference, US8168957B2 titled “Magnetically Enhanced, Inductively Coupled Plasma Source for a Focused Ion Beam System” presents an inductively coupled, magnetically enhanced ion beam source suitable for use with probe-forming optics to produce an ion beam without kinetic energy oscillations induced by the source. This system is focused on FIB systems, which typically use probe-forming optics for nanometer-scale precision, not suitable for broad-area polishing required in EBSD or large-area cross-sectioning. Also, this system is designed for low-current, tightly focused beams — not optimized for higher beam currents and large milling footprints. Beam shaping and control via magnetics rather than mechanical sample positioning and angle optimization.

[0039] Issues to be resolved

[0040] Therefore, the technical issues that remain to be resolved include:

[0041] (a) Inflexibility of Ion Beam Sources: Existing systems do not support interchangeable or integrated dual-mode operation for both EBSD and crosssection milling using a single compact platform. A need exists for an integrated system supporting dedicated and optimized ion sources for each application. Prior art devices are typically dedicated to either flat surface polishing or crosssectioning but do not support interchangeable or switchable configurations with separate optimized ion sources for each task.

[0042] (b) Beam Collimation and Control: Prior ion beam systems lack precise control over beam shaping, focusing, and extraction, especially when aiming to achieve narrow beam widths with consistent energy distribution. This limits spatial resolution and polishing uniformity. Prior art designs lack gridded extraction systems or mechanical angle adjustment features, which limits their ability to precisely control ion beam incidence and focus across diverse specimen types and geometries. (c) Sample Compatibility and Handling: Conventional systems do not accommodate Bakelite-mounted specimens without remounting, and fail to offer fine in-situ angle adjustments or height control for ensuring optimal beam incidence across varied specimen topographies. Prior art systems often do not support Bakelite-mounted specimens, require unmounting or reprocessing, and offer limited in-situ sample manipulation (e.g., tilt, rotation, oscillation) for uniform treatment.

[0043] (d) Beam-Induced Heating: Inadequate control over specimen temperature during milling leads to heat-induced damage or deformation, especially in sensitive samples. A solution is needed to ensure effective thermal management without compromising vacuum conditions. Existing ion milling setups typically lack integrated cooling mechanisms or beam-to-sample distance adjustments that help mitigate heat-related artifacts during prolonged milling.

[0044] (e) Vacuum Integrity During Sample Exchange: Many systems disrupt the main chamber vacuum during sample loading / unloading, leading to downtime and contamination risks. A need exists for a load-lock-based or equivalent mechanism to preserve vacuum integrity. Sample transfer in many conventional systems necessitates venting the main chamber, leading to vacuum integrity loss and potential contamination.

[0045] (f) Lack of Real-Time Monitoring: Existing systems often lack high-resolution in- process imaging, making real-time process monitoring and feedback-based control infeasible.

[0046] (g) Complex and Inflexible System Configuration: There is a lack of a modular yet compact design that enables system reconfiguration (with or without a load-lock chamber) while maintaining all core functional parameters.

[0047] (h) Narrow Application Focus: Many prior art devices are highly application-specific (e.g., planarization of wafers or nanoscale FIB), and do not offer versatility for multimodal material analysis, including grain orientation, thin film stack analysis, and defect mapping.

[0048] What the art therefore needs, is a comprehensive, adaptable, and precise ion beam polishing solution, enabling efficient processing of a wide variety of samples, including for high-end analytical applications like EBSD and cross-sectional SEM / EDS.

[0049] As the reader shall appreciate, state-of-art therefore, does not list a single effective solution embracing all considerations mentioned hereinabove, thus preserving an acute necessity-to-invent for the present inventor / s who, as result of focused research, has come up with novel solutions for resolving all needs once and for all. Work of the applicant / s hereof, specifically directed against the technical problems recited hereinabove and currently part of the public domain including earlier filed patent applications, is neither expressly nor impliedly admitted as prior art against the present disclosures.

[0050] A better understanding of the objects, advantages, features, properties and relationships of the present invention will be obtained from the following detailed description which sets forth an illustrative yet-preferred embodiment.

[0051] Objectives of the present invention

[0052] The present invention is identified in addressing at least all major deficiencies of art discussed in the foregoing section by effectively addressing the objectives stated under, of which:

[0053] It is a primary objective to identify and address the disadvantages and technical shortcomings in existing ion beam polishing systems, particularly in beam width control, thermal stability, and system modularity.

[0054] It is another objective hereof to establish a standalone ion beam polishing system with dual-mode functionality - Flat Milling for EBSD applications, as well as Cross-Section Milling for materials like multilayer semiconductor stacks.

[0055] It is another objective hereof to ensure precise control over beam width.

[0056] It is another objective hereof two separately optimized, ICP-based Argon ion sources, One with a gridded extraction system for wide elliptical beam for flat milling, and another with a grounded conical aperture for 3 mm collimated beam for cross-section milling.

[0057] It is another objective hereof to establish an ion beam polishing system in a modular, standalone format that combines the flexibility of two ion sources within a compact footprint, with easy serviceability and integration into research and industrial environments. The manner in which the above objectives are achieved, together with other objects and advantages which will become subsequently apparent, reside in the detailed description set forth below in reference to the accompanying drawings and furthermore specifically outlined in the independent claims. Other advantageous embodiments of the invention are specified in the dependent claims.

[0058] Brief description of drawings

[0059] The present invention is explained herein under with reference to the following drawings, in which-

[0060] FIGURE 1 is a final assembly view of the system integrating the broad ion beam polishing system for EBSD milling (flat milling) and cross-sectional milling of the present invention.

[0061] FIGURE 2A is front view of the broad ion beam polishing system for EBSD milling (flat milling) of the present invention.

[0062] FIGURE 2B is top view of the broad ion beam polishing system for EBSD milling (flat milling) of the present invention.

[0063] FIGURE 3A is one cross-sectional view of the broad ion beam polishing system for EBSD milling (flat milling) of the present invention.

[0064] FIGURE 3B is another cross-sectional view of the broad ion beam polishing system for EBSD milling (flat milling) of the present invention.

[0065] FIGURE 4 is a schematic diagram illustrating the ion beam source incorporating an inductively coupled plasma and gridded extraction system for EBSD flat milling system, as per the present invention.

[0066] FIGURE 5A is front view of the broad ion beam polishing system for cross section milling of the present invention.

[0067] FIGURE 5B is top view of the broad ion beam polishing system for cross section milling of the present invention.

[0068] FIGURE 6A is one cross-sectional view of the broad ion beam polishing system for cross section milling of the present invention.

[0069] FIGURE 6B is another cross-sectional view of the broad ion beam polishing system for cross section milling of the present invention.

[0070] FIGURE 7 is a schematic diagram illustrating the ion beam source incorporating an inductively coupled plasma and gridded extraction system with conical aperture for cross section milling, as per the present invention.

[0071] FIGURE 8A is one cross-sectional view of the shutter of EBSD (flat milling) ion source with an integrated Faraday Cup for ion beam diagnostics. FIGURE 8B is the schematic diagram illustrating the EBSD (flat milling) ion beam source with the shutter having integrated Faraday Cup for ion beam diagnostics.

[0072] FIGURE 9A is one cross-sectional view of the cross-section ion source with a shutter cum Faraday plate for ion beam diagnostics.

[0073] FIGURE 9B is the schematic diagram illustrating the cross-section ion source with a shutter cum Faraday plate for ion beam diagnostics.

[0074] FIGURES 10A, 10B, 11 (A to H) and 12 show EBSD results of flat ion milled samples.

[0075] FIGURE 13 shows results of multilayer thin films milled using the cross-section ion beam milling

[0076] In above drawings, wherever possible, the same references and symbols have been used throughout to refer to the same or similar parts. In FIGURES 2A, 2B, 3A, 3B, 4, 8A and 8B below reference numerals have been used-

[0077] 01 . Ion milling chamber

[0078] 02. Load lock chamber

[0079] 03. Transfer arm

[0080] 04. Ion source mounting flange

[0081] 5a. EBSD Ion source

[0082] 06. Dielectric Plasma Chamber

[0083] 07. Inductive coil

[0084] 08. Focusing grids

[0085] 09a. EBSD (Flat Milling) specimen holder

[0086] 10a. EBSD Specimen

[0087] 11 a. Shutter cum Faraday Cup

[0088] In FIGURES 5A, 5B, 6A, 6B, 7, 9A & 9B below reference numerals have been used-

[0089] 01. Ion milling chamber

[0090] 02. Load lock chamber

[0091] 03. Transfer arm

[0092] 04. Ion source mounting flange

[0093] 05b. Cross-section Ion source

[0094] 06. Dielectric Plasma Chamber

[0095] 07. Inductive coil

[0096] 08. Focusing grids

[0097] 09b. Cross-section specimen holder

[0098] 10b. Cross-section Specimen 1 1 b. Shutter cum Faraday Plate

[0099] 12. Conical Aperture

[0100] The above drawings are illustrative of particular examples of the present invention but are not intended to limit the scope thereof. The drawings are not to scale (unless so stated) and are intended for use solely in conjunction with their explanations in the following detailed description. Though numbering has been introduced to demarcate reference to specific components in relation to such references being made in different sections of this specification, all components are not shown or numbered in each drawing to avoid obscuring the invention proposed.

[0101] Attention of the reader is now requested to the detailed description to follow which narrates a preferred embodiment of the present invention and such other ways in which principles of the invention may be employed without parting from the essence of the invention claimed herein.

[0102] Statement / Summary of the invention

[0103] The present invention introduces a versatile, standalone dual-mode ion beam polishing system featuring two optimized argon ion sources for EBSD surface polishing and high- resolution cross-section milling. It includes interchangeable sample holders (9a / 9b) with full in-situ control, a dual-chamber vacuum system for seamless sample handling, integrated liquid nitrogen cooling for thermal management, and real-time monitoring via an HD camera. A touchscreen HMI with PLC control ensures precision, repeatability, and user safety, delivering a modular, user-friendly solution that overcomes limitations of existing systems and enhances material analysis capabilities.

[0104] Detailed description

[0105] Principally, general purpose of the present invention is to assess disabilities and shortcomings inherent to known systems comprising state of the art and develop new systems incorporating all available advantages of known art and none of its disadvantages.

[0106] Evolution and approach of the invention: Through experiential learning and literature surveys, the inventors named herein have identified the following factors affecting beam width in ion beam polishing systems- (a) Type of ion source used - Different types of ion sources, such as broad-beam sources or FIBs have varying capabilities in terms of beam width. Broad-beam sources generally have larger beam widths, while FIB systems can achieve much smaller diameters.

[0107] (b) Components used for beam focusing - The ability to focus the ion beam to a small spot is influenced by the quality of the ion optics, including magnetic or electrostatic lenses used to shape and direct the beam.

[0108] (c) Ion energy - Higher energy ions can be focused to smaller spots, but this also increases the potential for surface damage and may require careful adjustment.

[0109] (d) Current density (current per unit area) - This can affect the effective beam width and the uniformity of polishing.

[0110] (e) Surface topography of specimens - Variations in the specimen surface can influence the effective beam width, as uneven surfaces may require adjustments to maintain a consistent spot size.

[0111] (f) Variations in specimen characteristics - Different materials might interact differently with the ion beam, affecting how the beam width is perceived during polishing.

[0112] Accordingly, the disclosures herein are directed towards a dual-mode, broad ion beam polishing system capable of both flat milling for Electron Backscatter Diffraction (EBSD) and cross-section milling of materials. The system includes two distinct ion sources with independent beam shaping mechanisms, sample manipulation capabilities, and vacuum chamber configurations.

[0113] The first ion source is tailored for flat milling applications. It employs an inductively coupled plasma (ICP) source combined with a gridded ion extraction system to generate a wide, elliptical ion beam. This configuration is particularly effective for planar surface polishing, such as that required for EBSD analysis. The system allows precise control over the ion beam's incidence angle, ranging from 1 to 15 degrees, thereby optimizing beam uniformity and minimizing damage to the specimen surface.

[0114] The second ion source is designed for cross-section milling. It also uses an ICP-based architecture but integrates a conical aperture at the exit to shape a focused, collimated ion beam approximately 3 mm in diameter. This configuration is especially useful for preparing detailed cross-sections of materials, including multilayer thin-film stacks on semiconductor substrates. The cross-section ion source enables high-resolution milling by maintaining beam coherence over a shorter working distance.

[0115] The system includes customized sample holders for each milling application. The EBSD sample holder supports both mounted and unmounted EBSD specimens, including those mounted in Bakelite, and provides full 360-degree rotation. Additionally, it allows for in-situ tilt adjustments between 1 and 15 degrees to optimize the angle of beam incidence. The cross-section sample holder sandwiches the cross-section sample between a sputter-resistant backing plate and a titanium or tungsten carbide mask, exposing only a thin strip of the sample surface for ion milling. This holder also permits oscillation within ±45 degrees and precise tilt adjustment to facilitate uniform milling across a broader area.

[0116] To ensure thermal stability during prolonged milling operations, the system incorporates an optional liquid nitrogen cooling unit. Thermally conductive contacts connect the Dewar to the specimen holder, helping maintain the sample at or near room temperature and preventing heat-induced artifacts or damage.

[0117] Vacuum management in the system is achieved through two alternative configurations. The first employs a dual-chamber setup, including a main Ion milling chamber and a load-lock chamber for transferring samples without breaking vacuum. The load-lock chamber is connected to a mechanical Transfer arm, allowing for clean and precise sample insertion and retrieval. The second, simplified configuration eliminates the loadlock chamber by integrating the sample holder directly onto a vacuum-sealed sliding door. This approach still allows the sample to be accurately aligned with either of the ion sources by repositioning the door.

[0118] A high-definition CMOS camera is integrated into the system to provide real-time visual monitoring of the ion beam milling process. This enables users to observe surface changes and ensure precise control throughout the procedure. Operation is managed through a user-friendly 7-inch touchscreen human-machine interface (HMI), which is powered by a programmable logic controller (PLC) for consistent, repeatable results.

[0119] To appreciate in the key novelty of this invention lies in its dual-mode ion beam polishing capability within a standalone system, uniquely integrating two independent ICP-based argon ion sources — each specifically optimized for EBSD (flat milling) and cross-sectional milling. The inventive step includes a modular design with full in-situ sample manipulation (360° rotation, tilt, and oscillation), real-time HD monitoring, and thermal management via liquid nitrogen cooling, all controlled through an intuitive touchscreen interface. This configuration enables precise, damage-minimized polishing and high-resolution milling, offering a significantly more versatile and usercentric solution compared to prior art systems.

[0120] Construction

[0121] Final assembly view of the system integrating the broad ion beam polishing system of the present invention is shown in FIGURE 1 . System has two Argon ion sources, one for EBSD (Flat milling) and second for cross-section milling. Either of the two sources i.e. EBSD (Flat milling) or cross-section milling can be used at one single time considering that they have dedicated sample holders (09a / 09b).

[0122] Construction of the ion beam source for EBSD application (flat milling) (5a) incorporating an inductively coupled plasma and gridded extraction system was constructed / assembled is now explained hereinbelow in combined reference to the accompanying drawings FIGURE 2A, FIGURE 2B, FIGURE 3A, FIGURE 3B, FIGURE 4, FIGURE 8A and FIGURE 8B. An Ion milling chamber (01 ) is seen here, which serves in preparing the specimen (10a) to be processed, by sputtering away material from said specimen (10a). Here, the specimen (10a), mounted on a holder (9a), is bombarded with an ion beam (i.e. energetic Argon ions), which erodes the surface and can be used to achieve a desired surface morphology. Said ion beam is generated by an ion source (5a). Said ion source (5a) is mounted fixedly on a mounting flange (04). FIGURE 4 also shows the EBSD flat milling sample holder with its manipulation i.e. 360 degrees rotation axis of sample and in situ sample tilt axis to enable setting and adjusting ion beam incident angle with specimen (10a) surface. The sample holder also has provision to adjust height of the sample with respect to the ion beam. This enables achieving best uniformity of the ion milling process over the sample surface.

[0123] An Inductive coil (07) is used to create and control a plasma within the ion source (05a). The coil is placed around a dielectric chamber (06) of the ion source (05a) and is powered by an RF Power Supply. This induces an electromagnetic field that excites the Argon gas fed through the ion source (05a) within the dielectric chamber (06) to form plasma. Although the ionization gas used in the art is Argon, ions of other gases such as Krypton, Xenon, Neon, Helium, Redon, Oxygen, Nitrogen, Hydrogen and / or their combinations can be also be used for flat EBSD milling.

[0124] Focusing grids (08), carrying a charged potential are arranged in a pattern that helps shape and direct the ion beam and provisioned to refine the beam's focus and improve its spatial resolution. The grid applies electric fields to manipulate the trajectory of ions, effectively converging the beam onto the sample. By controlling the electric field distribution, the grid ensures that the ion beam remains well-defined.

[0125] The ion polishing chamber houses a Shutter cum Faraday Cup (1 1 a) in front of the EBSD (flat milling) ion source (05a). This arrangement of the Shutter (1 1 a) avoids any sputtered particulate contamination of the EBSD (flat milling) ion source arising from operation of the cross-section ion source mounted on the opposite side of the chamber. Additionally, the Shutter cum Faraday Cup (1 1 a) faces the EBSD (flat milling) ion source which can be used for beam diagnostics i.e. precise measurement of ion beam current and profile prior to the actual EBSD (flat milling) process on the sample.

[0126] Introduction and processing of the specimen (10a) as mentioned above is facilitated in a controlled vacuum environment by means of a Load lock chamber (02). Said Load lock chamber (02) acts as an intermediary between the atmosphere and the main ion beam polishing chamber. Its primary purpose is to facilitate sample transfer without disrupting the vacuum in the main chamber. The specimen (10a) is first loaded into the Load lock chamber (02), which is then sealed off from the outside environment. The Load lock chamber (02) is evacuated to create a vacuum before transferring the sample, by means of a vacuum-sealed mechanical Transfer arm (03) into the Ion milling chamber (01 ) with precision and care without introducing contaminants or damaging the specimen (10a). This step prevents the introduction of contaminants and maintains the required vacuum conditions in the ion beam chamber.

[0127] Construction of Ion Source for Cross Section Milling: Construction of the ion beam source for cross-section milling incorporating an inductively coupled plasma and gridded extraction system with a conical aperture was constructed I assembled is now explained hereinbelow in combined reference to the accompanying drawings FIGURE 5A, FIGURE 5B, FIGURE 6A, FIGURE 6B, FIGURE 7, FIGURE 9A and FIGURE 9B. An Ion milling chamber (01 ) is seen here, which serves in preparing the specimen (10b) to be processed, by sputtering away material from said specimen (10b). Here, the specimen (10b), mounted on a holder (9b), is bombarded with an ion beam (i.e. energetic Argon ions), which erodes the surface and can be used to achieve a desired surface morphology. Said ion beam is generated by an ion source (5b). Said ion source (5b) is mounted fixedly on a mounting flange (04).

[0128] FIGURE 7 also shows the cross-section milling sample holder with its manipulation. The specimen (10b) for cross-section milling is sandwiched in position between a specially designed backing plate and a front facing mask. The mask is manufactured from material of low sputter rate such as titanium or tungsten carbide. Only a very thin portion of the specimen (10b) typically around 100um to 200um is exposed to the ion beam such that the ion beam mills the cross-section of the exposed specimen (10b).

[0129] The sample can be oscillated within + / - 45 degrees if and when required to have larger than 3mm ion beam exposure area on the sample. The sample can also be tilted in situ to enable setting and adjusting ion beam incident angle within 90 degrees + / - 5 degrees with specimen (10b) surface. The sample holder also has provision to adjust height of the sample with respect to the ion beam.

[0130] An Inductive coil (07) is used to create and control a plasma within the ion source (05b). The coil is placed around a dielectric chamber (06) of the ion source and is powered by an RF Power Supply. This induces an electromagnetic field that excites the Argon gas fed through the ion source (05b) within the dielectric chamber (06) to form plasma.

[0131] Although the ionization gas used in the art is Argon, ions of other gases such as Krypton, Xenon, Neon, Helium, Redon, Oxygen, Nitrogen, Hydrogen and / or their combinations can be also be used for cross section milling.

[0132] Focusing grids (08), carrying a charged potential are arranged in a pattern that helps shape and direct the ion beam and provisioned to refine the beam's focus and improve its spatial resolution. The grid applies electric fields to manipulate the trajectory of ions, effectively converging the beam. By controlling the electric field distribution, the grid ensures that the ion beam remains well-defined. The ion beam source for cross-section milling also houses a grounded conical aperture (12) mounted on the grounded shield of the ion source (5b) to enable shaping the ion beam to generate a collimated ion beam of 3mm diameter. The ion polishing chamber houses a shutter cum Faraday plate (1 1 b) in front of the cross-section ion source (5b). This arrangement of this Shutter (1 1 b) avoids any sputtered particulate contamination of the cross-section ion source arising from operation of the EBSD (flat milling) ion source mounted on the opposite side of the chamber. Additionally, the shutter cum Faraday plate (1 1 b) faces the conical aperture (12) of the cross-section ion source (5b) which can be used for beam diagnostics i.e. precise measurement of ion beam current prior to the cross-section milling process on the sample.

[0133] Introduction and processing of the specimen (10b) as mentioned above is facilitated in a controlled vacuum environment by means of a Load lock chamber (02). Said Load lock chamber (02) acts as an intermediary between the atmosphere and the main ion beam polishing chamber. Its primary purpose is to facilitate sample transfer without disrupting the vacuum in the main chamber. The specimen (10b) is fixed in the crosssection specimen holder (9b) and loaded into the Load lock chamber (02), which is then sealed off from the outside environment. The Load lock chamber (02) is evacuated to create a vacuum before transferring the sample, by means of a vacuum-sealed mechanical Transfer arm (03) into the Ion milling chamber (01 ) with precision and care without introducing contaminants or damaging the specimen (10b). This step prevents the introduction of contaminants and maintains the required vacuum conditions in the ion beam chamber.

[0134] The standalone broad ion beam polishing system (BIPS-1503) of this invention is broadly classified into two variants - (a) Model: IS203 (EBSD - Flat Milling) and (b) Model: IS203CS (Cross-Sectional Milling). Their technical specifications are as summarized in Table 1 below.

[0135] Table 1

[0136] Use-cases of the present invention: (a) EBSD Ion Milling (Flat Milling): The ion beam source incorporating an inductively coupled plasma and gridded extraction system as propounded herein allows polishing I milling of the specimen (10a) at high energies with a higher beam spot and with longer distance between source beam exit and specimen (10a) thereby limiting the heat generated in the specimen (10a). This also facilitates direct use of Bakelite mount samples in said system directly after mechanical polishing without need of unmounting the sample from Bakelite. Furthermore, the spot size so enabled is sufficient enough to mill EBSD samples by itself and does not need additional sources to increase the milling area as is seen in SEM EBSD ion millers being used in the art. (b) The ion beam polished EBSD sample (Flat milled) when characterized using SEM with EBSD & EDS, can be used for impurities and defect studies, plastic deformation, and statistical analysis for average misorientation, grain size, and crystallographic texture. FIGURES 9, 10, and 1 1 (A to H) and 12 show results of EBSD flat milled samples.

[0137] (c) Cross-section Ion Milling: The ion beam source incorporating an inductively coupled plasma and gridded extraction system as propounded herein allows milling of the specimen (10b) at high energies with a collimated beam of 3mm diameter generated at the exit of conical aperture. The cross-section ion source (05b) allows milling of stack of multilayer thin films deposited on semiconductor samples to be able to have qualitative and quantitative analysis of thin films using a Scanning Electron Microscope with EDS. FIGURE 13 shows results for cross section of multilayer thin films. Experimental studies for proof of concept: In an exemplary non-limiting experimental run of the system hereof, undertaken for validation I proof-of-concept, the following values were determined by the applicant as listed in the Tables 2 and 3 below.

[0138] Table 2 (For EBSD (Flat sample Milling) application)

[0139] Table 3. (For Cross Section Milling application)

[0140] Note: The above description of the system is the one with two argon ion sources one for EBSD (Flat Ion Milling) and second for cross-section milling. The system incorporates two chambers, one an Ion milling process chamber and second load-lock chamber with a manually operated vacuum sealed sample transfer mechanism having sample rotation and tilt function In another design concept the Load lock chamber (02) and the sample transfer mechanism (03) can be eliminated by incorporating the sample holder arrangement (with sample rotation / oscillation and manually operated vacuum sealed in-situ tilt function to enable setting and adjusting ion beam incident angle exactly as stated in the above art.) directly on the vacuum sealed sliding door of the ion milling process chamber. The sample can be positioned facing any of the desired ion sources (EBSD Flat Milling / Cross-section Ion Source) by merely closing the sliding door. In this case, the construction of the Ion Milling process chamber, pumping systems, vacuum conditions, construction of both the ion sources (EBSD Flat Ion Milling and crosssection milling) and their corresponding sample holders, EBSD sample holder and cross-section sample holder, specimen to source distance as well as the range of ion beam angle of incidences as described in the above art would remain exactly the same.

[0141] Experimental validations of implementation of the present invention:

[0142] FIGURES 10A, 10B, 1 1 (A— H), and 12 illustrate the EBSD (Electron Backscatter Diffraction) results obtained from flat ion-milled samples.

[0143] FIGURE 10A depicts a phase map of a W-Ni-Co composite, showing the distribution of tungsten particles within a nickel-cobalt matrix. FIGURE 10B illustrates a composite sample comprising a soft matrix phase embedded with hard tungsten-based particles. Preparation of such composite materials for EBSD analysis is challenging due to the differing polishing responses of the constituent phases. Experimental validation confirms that the ion polishing system described herein successfully produces a surface wherein both soft and hard regions exhibit high-quality diffraction patterns suitable for EBSD analysis. Inverse pole figure showing crystal orientation of both matrix and W particles can be seen here.

[0144] Aluminum, a relatively soft material, poses additional challenges for EBSD sample preparation. As demonstrated in FIGURE 10C, the system of the present invention enables acquisition of EBSD data over a sufficiently large area of an aluminum sample, overcoming conventional preparation difficulties.

[0145] With reference to FIGURE 1 1 , Image A presents an Image Quality (IQ) map superimposed on an Inverse Pole Figure (IPF) map, concurrently displaying grain orientation and pattern quality at each pixel. Image B shows an IPF map representing the grain orientations, along with an associated IQ map. Bright regions correspond to areas from which high-quality diffraction patterns were obtained. The sample is a multiphase alloy, which is traditionally difficult to prepare for EBSD analysis via mechanical polishing or electropolishing. The results demonstrate that the ion polishing system effectively facilitates EBSD data acquisition from such challenging materials.

[0146] FIGURE 12 shows EBSD results from a broad ion beam-polished Hastelloy sample, achieved under the following conditions: magnification of 800,000x, step size of 0.21 pm, scan area of 250 x 200 pm2, and an indexing success rate of 99%.

[0147] FIGURE 13 illustrates the results obtained from multilayer thin films prepared using cross-sectional ion beam milling.

[0148] Industrial Applicability

[0149] The invention offers a versatile, efficient, and precise solution for material surface preparation. It supports a wide range of analytical applications, including EBSD, SEM, and EDS characterization, while minimizing downtime and maximizing analytical quality. By integrating multiple functional modules and offering high levels of control, the system represents a significant improvement over prior art ion beam polishing technologies. Overall, the present invention offers a robust, adaptable solution for any industry or research domain requiring controlled, contamination-free, and artifact- minimized ion beam polishing and therefore holds wide-ranging industrial applicability across several sectors that demand high-precision surface preparation and cross- sectional analysis. Its ability to deliver both flat and cross-section milling with enhanced beam control, minimized thermal damage, and improved uniformity makes it particularly suited for advanced material characterization techniques such as Electron Backscatter Diffraction (EBSD), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDS). Sectors applicable include:

[0150] (a) In the semiconductor industry, the system is highly valuable for failure analysis, thin-film characterization, and process quality control. The cross-section milling function allows precise exposure of multilayer semiconductor stacks, enabling detailed inspection and compositional analysis of interconnects, barrier layers, and dielectric films. The flat milling mode is equally beneficial in preparing large-area EBSD-ready surfaces from integrated circuits or wafer cross-sections.

[0151] (b) The materials science and metallurgy sector benefits from the flat milling capability, particularly in EBSD sample preparation for grain boundary analysis, crystallographic texture mapping, and phase identification. The ability to directly polish Bakelite-mounted metallographic samples reduces preparation time and complexity, enhancing throughput in research labs and quality assurance units in alloy and metal component manufacturing.

[0152] (c) In the automotive and aerospace industries, where fatigue analysis, failure root cause identification, and material integrity assessments are crucial, the system aids in producing high-quality surfaces for EBSD and SEM. It enables engineers and researchers to study deformation zones, crack propagation paths, and microstructural transformations with high clarity and minimal artifacts.

[0153] (d) The academic and research institutions engaged in nanotechnology, microelectronics, and advanced materials research can leverage the system for both routine and advanced sample preparation. Its flexibility, precision, and control features support a wide array of experimental protocols across disciplines such as solid-state physics, thin-film technology, and crystallography.

[0154] (e) Additionally, the forensic and archaeological sciences can utilize the system for delicate polishing of layered or aged specimens without introducing contamination or heat-related degradation. The vacuum-integrated handling system preserves the integrity of sensitive samples, making the tool valuable in disciplines where preservation of fine structural details is critical.

[0155] Modifications and variations of the system and apparatus described herein will be obvious to those skilled in the art. Accordingly, the foregoing description will be regarded as illustrative in nature and not as restrictive in any form whatsoever, bound only by the appended claims.

[0156] Dated this 01stDay of May 2025

[0157] Duly constituted agent for the applicant,

[0158] Rohit Nitin Deshpande

[0159] Advocate [MAH / 4858 / 2012] & Patent Agent [IN / PA-1389]

[0160] Address for service: Inventillect Consultants, Office No. 307, Business Guild Condominium, Apex Colony, ILS Law College Road, Erandwane, Pune, Maharashtra, India - 41 1004 Phone: +91 -9422944630 Email: rd@inventillect.com

Claims

ClaimsWe claim,1 ) An ion beam polishing system, comprising:(a) a main Ion milling chamber (01 );(b) a first ion source (05a) having a for flat surface polishing applications, configured with an inductively coupled plasma (ICP) generator and a gridded ion extraction system to produce a broad, elliptical ion beam;(c) a second ion source (05b) for cross-section milling applications, configured with an ICP generator, gridded ion extraction system, and a conical aperture (12) to produce a collimated ion beam;(d) at least one sample holder (09a / 09b) configured for selective engagement with either of the corresponding ion sources (05a / 05b), and providing in- situ tilt, rotation, or oscillation control for sample manipulation;(e) a vacuum system comprising a turbomolecular pump backed by a dry scroll pump for maintaining vacuum conditions in the Ion milling chamber (01 );(f) a real-time imaging system including a high-definition complementary metal-oxide semiconductor (CMOS) camera; and(g) a programmable logic controller (PLC)-based touchscreen humanmachine interface (HMI) for control of the system.Wherein the system is operable to selectively activate either the first or the second ion source for targeted polishing or milling of a specimen (10a / 10b) mounted on the corresponding sample holder (09a / 09b).2) The ion beam polishing system as claimed in claim 1 , wherein the first ion source (5a) is positioned to emit ions at an adjustable angle of incidence relative to a sample surface between 1 ° and 15° for Electron Backscatter Diffraction (EBSD) preparation.3) The ion beam polishing system as claimed in claim 1 , wherein the second ion source (05b) emits a collimated beam of approximately 3 mm diameter, at a beam incidence angle adjustable between 85° and 95° to the sample surface for cross-sectional analysis.4) The ion beam polishing system as claimed in claim 1 , further comprising a load-lock chamber connected to the Ion milling chamber (01 ) via a vacuum-sealed mechanical Transfer arm (03) for introducing and removing samples without breaking vacuum in the Ion milling chamber (01 ).5) The ion beam polishing system as claimed in claim 1 , wherein the sample holder for EBSD (09a) applications is configured to accommodate both mounted and unmounted specimens (10a), including Bakelite-mounted samples, and provides 360° rotation and in-situ tilt adjustment from 1 ° to 15°.6) The ion beam polishing system as claimed in claim 1 , wherein the sample holder for cross-section milling (09b) sandwiches a specimen (10) between a backing plate and a low-sputter-rate front mask, and is operable to oscillate within ±45° and tilt in-situ within ±5° from normal beam incidence.7) The ion beam polishing system as claimed in claim 1 , further comprising a liquid nitrogen cooling assembly thermally coupled to the sample holder for controlling the sample temperature and minimizing thermal artifacts during milling.8) The ion beam polishing system as claimed in claim 1 , wherein each ion source is equipped with a dedicated Shutter 1 1 a or 1 1 b mechanism that includes a Faraday Cup or Faraday Plate respectively for beam current diagnostics and for protecting the inactive ion source from contamination during operation of the other.9) The ion beam polishing system as claimed in claim 1 , wherein the gridded ion extraction systems in both ion sources (05a / 05b) comprise Focusing grids (08) that shape and refine the ion beam to improve spatial resolution.10) The ion beam polishing system as claimed in claim 1 , wherein the water-cooled conical aperture (12) of the second ion source (05b) consists of a conical shape mounted on a grounded shield of the ion source (05b), said conical aperture (12) being made of a material with a low sputter rate selected from graphite or titanium, optionally coated with a pyrolytic carbon film to enhance aperture life; and said conical aperture configured to generate a collimated ion beam with a diameter of approximately 3 mm for cross-sectional milling of specimens (10b), wherein the aperture (12) is part of the cross-sectional milling ion source (05b),ensuring that the ion beam is focused to produce a precise milling area on the specimen (10b).1 1 ) The ion beam polishing system as claimed in claim 1 , wherein the ion beam energy is controllable up to 1000 eV, and beam current is adjustable up to 10 mA for EBSD mode and up to 15 mA for cross-section mode.12) The ion beam polishing system as claimed in claim 1 , wherein the vacuum system maintains a base pressure of < 2 x 10“6mbar and an operating pressure of < 8 x 10“5mbar.13) The ion beam polishing system as claimed in claim 1 , wherein the system is operable in a dual-variant configuration, comprising:(a) a first variant including a load-lock chamber with manual Transfer arm (03); and(b) a second variant without a load-lock chamber, wherein the sample holder (09a / 09b) is mounted directly on a vacuum-sealed sliding door capable of repositioning the sample relative to either ion source.14) The ion beam polishing system as claimed in claim 13, wherein both variants share identical configurations for ion source construction, sample holders, ion beam incidence angles, and vacuum conditions.15) A method for ion beam polishing a sample, comprising :(a) providing an ion beam polishing system as claimed in claim 1 ;(b) selecting between a first ion source for EBSD (05a) or a second ion source for cross-section milling (05b) for activation based on desired application;(c) mounting the specimen (10a / 10b) on a dedicated holder (09a / 09b) with in- situ adjustment for tilt, rotation, or oscillation;(d) transferring the mounted specimen (10a / 10b) into the Ion milling chamber (01 ) from the Load lock chamber (02) without disrupting vacuum conditions, in event the ion beam polishing system is a variant conforming to claim 13a).(e) operating the selected ion source to generate an ICP-based ion beam through a gridded extraction system to control beam width and energy, thereby being directed onto the specimen (1 Oa / 1 Ob) surface;(f) adjusting the angle of incidence of the ion beam with respect to the specimen (10a) surface, thereby achieving an elliptical beam with an effective spot size ranging from 7 mm to 20 mm, depending on the beam incidence angle;(g) exposing the sample surface to the ion beam under vacuum, with beam energy and current controlled via a PLC interface;(h) performing milling operations to achieve a desired surface morphology or cross-sectional structure, therein rotating or oscillating the specimen(10a / 1 Ob) during the milling process to achieve uniform milling across the specimen (10a / 1 Ob) surface; and(i) monitoring the polishing process in real-time using a CMOS camera.16) The ion beam polishing system as claimed in claim 1 , wherein the gridded extraction system comprises a set of Focusing grids (08) arranged to manipulate ion trajectories via electric fields, enabling control of beam width and enhancement of spatial resolution on the sample surface, wherein:(a) at least one grid among the said set of Focusing grids (08) being maintained at a defined electric potential; and(b) the grids are positioned within the ion source to facilitate ion extraction, acceleration, and focusing wherein the grid configuration shapes and directs the ion beam to achieve a well-defined, convergent geometry.17) The ion beam polishing system as claimed in claim 1 , wherein the ion source (05a / 05b) can use an ionization gas selected from among Argon, Krypton, Xenon, Neon, Helium, Redon, Oxygen, Nitrogen, Hydrogen and / or their combinations.18) The ion beam polishing system as claimed in claim 17, wherein the ionization gas is supplied via a dedicated gas inlet through each ion source (05a / 05b) using dedicated mass flow controllers.Dated this 01stDay of May 2025Duly constituted agent for the applicant,Rohit Nitin DeshpandeAdvocate [MAH / 4858 / 2012] & Patent Agent [IN / PA-1389]Address for service: Inventillect Consultants, Office No. 307, Business Guild Condominium, Apex Colony, ILS Law College Road, Erandwane, Pune, Maharashtra, India - 411004 Phone: +91 -9422944630 Email: rd@inventillect.com

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