Liquid metal ion source, method of producing a liquid metal ion source, and focused ion beam emitting device

Abstract

A liquid metal ion source comprising an emitter 5 with a cylindrical portion 6 and truncated cone shaped tip 7, the tip 7 having a trapezoidal recess with an annular flange (10, Figure 3) surrounding

Description

The invention relates to a liquid metal ion source, a method of producing a liquid metal ion source, and a device emitting a focused ion beam. The subject matter of the invention finds application in the field of precise imaging and examination of micro- and nanostructures in electronic and photonic materials, particularly in devices utilizing focused ion beams (FIB). Focused Ion Beam (FIB) is an advanced technology based on the precise steering of high-energy ion beams, enabling material modification and analysis at the nanometric level. This technique is employed in structural studies, thanks to its ability to remove material (ion milling) and deposit chemical compounds through ion beam-induced processes. FIB is a critical tool in materials engineering and semiconductor technology, enabling, among other applications, the precise preparation of samples for transmission electron microscopy (TEM). Often integrated with scanning electron microscopy (SEM), FIB allows simultaneous visualization and manipulation of structures, making it indispensable for research in nano- and microstructures. The ion source is a key component of a FIB device, as it determines the properties of the ion beam, the primary tool in this technology. The quality, composition, and energy of the ions directly affect the precision, efficiency, and range of applications of the device. The performance of the ion source, such as a liquid metal ion source (LMIS) or plasma source defines the operational capabilities of the FIB system and its ability to perform advanced tasks in nanotechnology, microelectronics, and materials research. LMIS devices are sophisticated systems that play a crucial role in modern FIB technologies. Their defining characteristic is the ability to generate ion beams with very high current density and low divergence, making them essential for applications such as ion microscopy, nanolithography, and ion implantation in semiconductor processes. The operating principle of LMIS relies on the properties of metals in their liquid state. In a strong electric field, the liquid metal deforms, forming a structure known as a Taylor cone. Ions are emitted from the apex of this cone and can be directed and controlled using electrostatic optics systems. A significant advantage of LMIS is its capacity to operate with various materials, including metal alloys such as gallium, indium, or tin. These metals are characterized by low vapor pressures, which minimize evaporation at high temperatures, and good electrical conductivity, making them particularly suitable for generating stable ion beams. A typical LMIS structure includes a holder with two connectors that enable the source to be connected to a voltage source. Between the connectors is a tungsten wire, which serves as a heater and supports source operation. This wire is coupled with a tungsten filament and a reservoir containing the ion-generating material, typically gallium. In its liquid state, the material in the reservoir wets the tungsten filament through capillary action. The filament tip, with a radius on the order of nanometers, exhibits a very high electric field. The application of high voltage causes a Taylor cone to form at the tip of the filament. Simultaneously, atoms of the liquid metal undergo ionization. The resulting ions are propelled by the electric field toward the apex of the Taylor cone. At this point, field evaporation occurs, whereby ions leave the material and enter the vacuum, forming a stable ion beam. The efficiency and stability of LMIS operation depend heavily on the surface properties of the tungsten wire supporting the liquid metal. Consequently, the prior art employs various surface modifications of the tungsten wire's tip to optimize LMIS performance. These modifications aim to enhance reliability, emission stability, and efficiency across diverse technological applications. The Japanese patent document JPS61179034A discloses a method for manufacturing an emitter tip for a liquid metal ion source. The emitter tip on the side of the liquid metal ion source has a spiral groove formed on the conical part of the tip. The manufacturing method includes a step of shaping the tip into a conical form, for example, using an electrolytic technique. Subsequently, a very thin electrode wire is spirally wound around the conical part of the tip, and the tip is immersed in an electrolytic solution, such as an aqueous sodium hydroxide solution. This process forms the spiral groove on the conical surface of the emitter tip for the liquid metal ion source. The pitch of the groove's spiral can be adjusted by varying the pitch of the electrode wire spiral. Furthermore, the depth and / or width of the groove is controlled by adjusting the current intensity and / or the duration of the current flow. The patent application WO2011122687A1 discloses a liquid metal ion source comprising a needle electrode formed from two metal wires arranged in parallel, with their external surfaces in contact. The needle electrode includes a guide passage and an emission end, both formed by the two metal wires. The guide passage extends continuously to the emission end. Toward the bottom of the guide passage, its width decreases to zero. When liquid metal is supplied to the guide passage, capillary forces arise near the bottom of the channel, resulting in volumetric flow of the liquid metal rather than conventional surface flow. This principle and phenomenon of volumetric flow correspond to the principle and phenomenon of a fountain pen. Thus, the flow of liquid metal toward the emission end is stably maintained, and the ion beam emission current is stabilized, even with liquid metals of low wettability. Moreover, the emission end is designed as a hypothetical single emission point, preserving the controllability of the ion beam's focal point and direction. The European patent EP1622184B1 discloses an emitter for a liquid metal ion source, comprising a wire that includes a substantially curved portion shaped as a U or V, formed by bending, and having an external surface. At least part of the external surface of the wire is tapered in the substantially curved portion to form the emitter tip. The wire further includes filament portions for connecting the wire to support means, with the angle between the filament portions ranging from 1° to 25°. The emitter also includes a reservoir containing the source material, with the reservoir being formed between the filament portions and loaded due to capillary forces. The technical problem faced by the present invention is to propose such a liquid metal ion source, particularly for use in a focused ion beam (FIB) microscope, that provides an ion beam with improved quality, specifically with high and stable intensity, while maintaining reduced emission current of the source. Additionally, it is desirable to provide a liquid metal ion source with enhanced reliability and durability of the emitter, contributing to an extended operational lifespan. The technical problem faced by the present invention is also to propose a method of manufacturing a liquid metal ion source that achieves a source capable of solving the aforementioned problems, while providing a reliable, repeatable, and precise process that minimizes the number of steps and required technical resources. According to a first aspect of the invention, there is provided a liquid metal ion source comprising an emitter configured to emit liquid metal ions, wherein the emitter includes a substantially cylindrical portion and a tip portion at the emission end, the tip portion being shaped as a truncated cone, characterized in that a trapezoidal-shaped recess is formed on the upper surface of the truncated cone of the tip portion, defining an annular flange surrounding the recess, and from the bottom surface of the recess extends an apex formed by a cone with a base diameter corresponding to the diameter of the bottom surface of the recess, wherein the height of the cone forming the apex exceeds the height of the flange, a plurality of grooves are formed on the lateral surface of the truncated cone of the tip portion, the grooves extending radially from the interface area between the cylindrical portion and the tip portion to the area of the flange. Preferably, the ratio of the height h of the cone forming the apex to the height of the tip portion is in the range of 0.2 to 0.25, and the cone angle a of the cone forming the apex is in the range of 45° to 55°. Preferably, the ratio of the height h of the cone forming the apex to the height of the tip portion is 0.23, and the cone angle a of the cone forming the apex is 49.3°. Preferably, the inclination angle p of the sidewall of the groove relative to a plane passing through the upper edges of the groove is in the range of 90° to 135°. Preferably, the inclination angle p of the sidewall of the groove relative to a plane passing through the upper edges of the groove is in the range of 90° to 120°. Preferably, the ratio of the width x of the groove to the diameter of the tip portion is in the range of 1 / 150 to 10 / 150. Preferably, the ratio of the width x of the groove to the diameter of the tip portion is 1 / 30. Preferably, the ratio of the depth y of the groove to the height of the tip portion is in the range of 0.01 to 0.1. Preferably, the ratio of the depth y of the groove to the height of the tip portion is 0.05. Preferably, the groove has a cross-sectional shape selected from the group comprising a trapezoid, rectangle, and triangle. Preferably, the groove has a variable width along its length, with the angle y between the sidewalls being in the range of 1° to 5°. Preferably, the angle y between the sidewalls is 3,82°. Preferably, the emitter is made of tungsten, and the liquid metal is liquid gallium. According to a second aspect of the invention, there is provided a method for producing a liquid metal ion source as defined in the first aspect of the invention, characterized in that material removal processing is carried out to form the apex in the form of a cone extending from the recess on the upper surface of the truncated cone of the tip portion and to form grooves on the lateral surface of the truncated cone of the tip portion, wherein the material removal step is performed using a focused ion beam technology with ions selected from the group consisting of xenon, argon, oxygen, or nitrogen. According to a third aspect of the invention, there is provided a focused ion beam emitting device, characterized in that it comprises a liquid metal ion source as defined in the first aspect of the invention. The liquid metal ion source according to the present invention is designed for use in devices emitting focused ion beams (FIB), such as scanning microscopes. The implementation of a cone-shaped apex of the tip portion, extending from a recess on the upper surface of the truncated cone of the tip portion, combined with grooves radiating outward on the lateral surface of the truncated cone, has resulted in an ion beam of improved quality, particularly characterized by high and stable intensity while maintaining reduced emission current levels of the source. The appropriately selected geometry of the grooves, including the inclination of the sidewall relative to the plane passing through the edges of the sidewalls, together with the width and depth of the grooves, promotes laminar flow of the liquid metal along the surface of the truncated cone of the tip portion. This configuration minimizes turbulent flow, thereby enhancing the parameters of the ion beam emitted from the liquid metal ion source of the present invention. As a result of the improved liquid metal flow and the reduction in emission current required to generate the ion beam, the wear on the liquid metal ion source has been significantly decreased. This improvement enhances the reliability and durability of the emitter, thereby ensuring an extended operational lifespan under optimal conditions. The solution according to the present invention has been shown in the embodiments below and illustrated in the drawing, in which: Fig. 1 is a schematic side view of a liquid metal ion source according to one embodiment of the present invention, Fig. 2 is a side view of the emitter, which forms a component of the liquid metal ion source shown in Fig. 1, Fig. 3 is a cross-sectional view with a magnified detail of the tip portion of the emitter shown in Fig. 2, Fig. 4 is a top view of the emitter, which forms a component of the liquid metal ion source shown in Fig. 2, Fig. 5 is a side view with a magnified detail of the conical portion of the emitter shown in Fig. 2, Fig. 6 A) - C) are cross-sectional views of grooves according to various embodiments of the liquid metal ion source, Fig. 7 is a side view with a magnified detail of the conical portion of the emitter which forms a component of the liquid metal ion source according to another embodiment of the invention, Fig. 8 is a top view of the emitter which forms a component of the liquid metal ion source shown in Fig. 7, Fig. 9 is a schematic representation of the liquid metal ion beam emitted from the liquid metal ion source according to the present invention. Example 1 An embodiment of the liquid metal ion source according to the present invention is illustrated schematically in Fig. 1-5. In this embodiment, the liquid metal ion source represents one of the components employed in ion beam-emitting devices, such as, but not limited to, a focused ion beam (FIB) microscope. As depicted in Fig. 1, the liquid metal ion source of the present invention comprises a holder 1, electrical contacts 2, a mounting system 3, exemplarily in the form of wires, a liquid metal reservoir 4, and an emitter 5. The liquid metal reservoir 4 stores the liquid metal, which, during the operation of the ion beam-emitting device, is supplied to the emitter 5. In one non-limiting embodiment of the invention, the liquid metal reservoir 4 contains liquid gallium. During operation, a voltage is applied to the electrical contacts 2, resulting in the generation of an ion beam from the emitter 5, which has a profile approximated by a Gaussian function. The ion beam profile generated by the liquid metal ion source according to this invention is schematically shown in Fig. 9, where the beam profile can be divided into a main emission profile 11 and a tail emission profile 12. The parameters of the emitted ion beam profile describe its quality, which directly impacts the resolution and contrast of imaging in a FIB microscope. Significant parameters include the full width at half maximum (FWHM) of the main profile (FWHMm) and the full width at half maximum of the tail profile (FWHMt) (see Fig. 9). The FWHMm of the main emission profile 11 refers to the width of the central portion of the main emission profile measured at half of its maximum intensity. This parameter indicates the region where the beam is most concentrated and intense. A smaller FWHMm corresponds to a more focused beam, enabling higher precision in processing. Preferably, the FWHMm of the main emission profile 11 does not exceed 510 nm. The FWHMtof the tail emission profile 12 describes the width of the beam's tail, measured at half of its maximum intensity, but relative to regions beyond the central maximum. This parameter indicates the degree of beam "spreading" around its core. A larger FWHMt signifies a broader area of beam influence, which may contribute to undesirable effects during processing, such as impacting surrounding material. Preferably, the FWHMt of the tail emission profile 12 does not exceed 1010 nm. The design of the emitter 5, which constitutes a component of the liquid metal ion source of the present invention, is crucial for ensuring the desired beam parameters. An embodiment is depicted in a side view in Fig. 2, in a longitudinal section of the tip portion 7 in Fig. 3, and in side and top views of the tip portion 7 in Figs. 4 and 5, respectively. The emitter 5 has a needle-like structure comprising a generally cylindrical portion 6 and a tip portion 7 shaped as a truncated cone. In this embodiment, the emitter 5 is made entirely of tungsten wire. However, the choice of material does not limit the scope of the invention, so alternative materials such as tantalum, niobium, or nickel may be used, provided they meet the required performance characteristics. In a non-limiting embodiment, the emitter 5 has a diameter of 150 pm and a height of 400 pm, with the cylindrical portion 6 being 300 pm height and the tip portion 7 100 pm height. As shown in Fig. 3, the tip portion 7 takes the form of a truncated cone topped with an apex 8. The apex 8 is formed by a conical structure extending from a recess on the upper plane of the truncated cone of the tip portion 7. More specifically, the upper plane of the truncated cone of the tip portion 7 has a cylindrical recess whose walls converge at an acute angle towards the axis of symmetry of the truncated cone, resulting in a recess surrounded by an annular flange 10. A centrally aligned cone extends from the recess, with its height exceeding the depth of the recess, forming the most protruding apex 8. In this embodiment, the height h of the cone forming the apex 8 is 23 pm, with an opening angle a of 49.3°, and a base diameter of 21.11 pm. The geometric dimensions of the cone forming the apex 8 do not limit the scope of the invention, and in alternative embodiments, the apex 8 may take the form of a cone with a height h ranging from 20 pm to 25 jim (corresponding to a height-to-tip portion ratio between 0.2 and 0.25), an opening angle a between 45° and 55°, and a base diameter between 20 pm and 25 pm. As illustrated in Figs. 4 and 5, the lateral surface of the truncated cone of the tip portion 7 is equipped with multiple grooves 9 through which liquid metal flows during device operation. In this embodiment, eighteen grooves 9 are evenly distributed along the lateral surface of the truncated cone. However, the number of grooves 9 is not a limiting factor, and alternative embodiments may include more or fewer grooves, depending on the emitter's geometry and the liquid metal's properties, such as viscosity, provided laminar flow of the liquid metal towards the apex 8 is ensured. The cross-sectional shapes of the grooves 9 are depicted in Figs. 6A-C, with trapezoidal (Fig. 6A), rectangular (Fig. 6B), and triangular (Fig. 6C) cross-sections shown. Various cross-sectional geometries represent individual embodiments of the invention. As depicted, the grooves 9 have specific dimensions, where x denotes the groove width, y denotes the groove depth, and 0 represents the angle between the groove sidewall and a plane passing through the upper groove edges. In this embodiment, the grooves 9 maintain a constant width along their entire length. According to the present invention, the geometric parameters of the groove 9 are within the following ranges: x from 1 pm to 10 pm (corresponding to a ratio of the width x of the groove 9 to the diameter of the tip portion 7 in the range of 1 / 150 to 10 / 150), y from 1 pm to 10 pm (corresponding to a ratio of the depth y of the groove 9 to the height of the tip portion 7 in the range of 0.01 to 0.1), and 0 from 90° to 135°. The method of manufacturing the liquid metal ion source includes modifying the emitter 5 in its tip portion 7 to achieve the described geometry. One exemplary method includes material removal processing to form the cone-shaped apex 8 extending from the recess on the upper plane of the truncated cone of the tip portion 7. Additionally, the lateral surface of the truncated cone is processed to form grooves 9 with the specified geometry. This material removal process can be performed using a focused ion beam, such as xenon, argon, oxygen, or nitrogen, which removes material by scanning over targeted areas. Detailed descriptions of such material removal techniques are omitted for clarity, as they are well-known by the skilled in the art. Within the scope of the embodiment of the present invention, the following examples of emitters 5 were fabricated and numerically simulated: MODI - eighteen grooves 9 of uniform width, evenly spaced along the lateral surface of the truncated conical of the tip section 7, wherein each groove 9 has a trapezoidal crosssection with a width (shorter base) x = 5 pm, a depth y = 5 pm, and a sidewall inclination angle p = 120°, M0D2 - eighteen grooves 9 of uniform width, evenly spaced along the lateral surface of the truncated conical of the tip section 7, wherein each groove 9 has a trapezoidal crosssection with a width (shorter base) x = 5 pm, a depth y = 5 pm, and a sidewall inclination angle p = 135°, M0D3 - eighteen grooves 9 of uniform width, evenly spaced along the lateral surface of the truncated conical of the tip section 7, wherein each groove 9 has a rectangular crosssection with a width x = 5 pm, a depth y = 5 pm, and a sidewall inclination angle p = 90°, M0D4 - eighteen grooves 9 of uniform width, evenly spaced along the lateral surface of the truncated conical of the tip section 7, wherein each groove 9 has a triangular crosssection with a width (triangle base) x = 5 pm, a depth y = 5 pm, and a sidewall inclination angle p = 120°. Numerical simulations were carried out using the method of Monte Carlo model and CFD, aimed at evaluating the stability of the emitted beam by assessing the FWHMm and FWHMt parameters at a specified emission current for various operating currents. The modifications defined above, namely M0D1-M0D4, were compared with a reference simulation (REF), where an emitter with identical geometry was used, but without the apex 8 and grooves 9 described in the present embodiment of the invention. The results of the numerical simulations are summarized in Table 1. Table 1. Results of numerical simulations for emitters 5 with modifications according to the present invention. Liquid metal ion source Working current [pA] Emission current [nA] FWHMm [nm] FWHMt [nm] REF 1 2500 191 408 7 2500 226 585 24 2500 248 634 40 2500 288 688 80 2500 300 780 MODI 1 1500 116 334 7 1500 136 389 24 1500 216 563 40 1500 326 919 80 1500 366 739 M0D2 1 1853 153 390 7 1853 179 380 24 1853 234 693 40 1853 327 782 80 1853 360 876 M0D3 1 1633 141 363 7 1633 147 318 24 1633 194 428 40 1633 317 909 80 1633 346 867 M0D4 1 1782 122 314 7 1782 182 433 24 1782 183 456 40 1782 289 789 80 1782 348 966 As confirmed by the results of the numerical simulations presented in Table 1, the 5 modifications to the emitter 5, which is a component of the liquid metal ion source according to the present invention, resulted in satisfactory parameters for the emitted ion beam, i.e., the full-width at half maximum (FWHMm) of the main emission profile 11 below 510 nm and the full-width at half maximum (FWHMt) of the tail emission profile 12 below 1010 nm across the entire range of operating currents. Importantly, the desired ion beam parameters were achieved at significantly lower emission currents, ranging from 1500 nA (for MODI) to 1853 nA (for MOD2), compared to the reference simulation (2500 nA). The reduction in emission current, while maintaining the desired ion beam parameters, ensures slower wear of the gallium ion source and extends its lifetime by at least 40%. Notably, the simulated stability of the ion beam included uninterrupted operation for a minimum of 100 hours. Example 2 Another embodiment of the liquid metal ion source according to the present invention is illustrated in a schematic view in Fig. 7 and Fig. 8. The liquid metal ion source depicted in this embodiment serves as one of the components used in an ion beam emitting device, such as, but not limited to, a focused ion beam (FIB) etching device. In general, the liquid metal ion source according to this embodiment has a structure essentially similar to the structure of the liquid metal ion source described in the first embodiment. Therefore, similar structural features will not be re-described here to maintain the clarity of the present disclosure. In contrast to the previous embodiment of the invention, the liquid metal ion source according to this embodiment has an emitter 5, the tip portion 7 of which is a truncated cone, on the lateral surface of which multiple grooves 9 have been formed. Each groove 9 has a variable width along its length (in contrast to the constant width grooves 9 described in Example 1). As schematically shown in the top view in Fig. 8, each groove 9 converges towards the apex 8, meaning its width decreases from the edge area (i.e., at the interface of the cylindrical portion 6 and the tip portion 7) to the area surrounding the apex 8, and more specifically, up to the flange 11. In this embodiment, the width x of groove 9 is defined in the most external area, i.e., at the interface of the cylindrical portion 6 and the tip portion 7, and due to the circular nature of the structure, it is determined as a chord. As mentioned, the width x of grooves 9 decreases linearly as the distance from the apex 8 decreases, with the angle y between the sidewalls in the top view (see Fig. 7) ranging from 1° to 5°, depending on the geometry of the entire emitter 5. Within the scope of the embodiment of the present invention, the following examples of emitters 5 were fabricated and numerically simulated: M0D5 - eighteen grooves 9 of variable width, evenly spaced along the lateral surface of the truncated conical of the tip section 7, wherein each groove 9 has a trapezoidal crosssection with a width (shorter base) x = 5 pm, a depth y = 5 pm, a sidewall inclination angle P = 120°, and y the angle between the sidewalls is 3,82°; M0D6 - eighteen grooves 9 of variable width, evenly spaced along the lateral surface of the truncated conical of the tip section 7, wherein each groove 9 has a trapezoidal crosssection with a width (shorter base) x = 5 pm, a depth y = 5 pm, a sidewall inclination angle P = 135°, and y the angle between the sidewalls is 3,82°; M0D7 - eighteen grooves 9 of variable width, evenly spaced along the lateral surface of the truncated conical of the tip section 7, wherein each groove 9 has a rectangular crosssection with a width x = 5 pm, a depth y = 5 pm, a sidewall inclination angle p = 90°, and y the angle between the sidewalls is 3,82°; M0D8 - eighteen grooves 9 of variable width, evenly spaced along the lateral surface of the truncated conical of the tip section 7, wherein each groove 9 has a triangular crosssection with a width (triangle base) x = 5 pm, a depth y = 5 pm, a sidewall inclination angle P = 120°, and y the angle between the sidewalls is 3,82°. Numerical simulations were carried out using the method of Monte Carlo model and CFD, aimed at evaluating the stability of the emitted beam by assessing the FWHMm and FWHMt parameters at a specified emission current for various operating currents. The modifications defined above, namely MOD5-MOD8, were compared with a reference simulation (REF), where an emitter with identical geometry was used, but without the apex 8 and grooves 9 described in the present embodiment of the invention. The results of the numerical simulations are summarized in Table 1. Table 2. Results of numerical simulations for emitters 5 with modifications according to the present invention. Liquid metal ion source Working current [pA] Emission current [nA] FWHMm [nm] FWHMt [nm] REF 1 2500 191 408 7 2500 226 585 24 2500 248 634 40 2500 288 688 80 2500 300 780 M0D5 1 1848 116 334 7 1848 136 389 24 1848 216 563 40 1848 326 919 80 1848 366 739 MODS 1 1805 127 277 7 1805 162 384 24 1805 176 482 40 1805 256 641 80 1805 312 627 M0D7 1 1812 153 327 7 1812 233 550 24 1812 237 589 40 1812 241 615 80 1812 310 675 M0D8 1 1635 142 292 7 1635 224 547 24 1635 247 500 40 1635 261 604 80 1635 331 987 As confirmed by the results of the numerical simulations presented in Table 2, the 5 modifications to the emitter 5, which is a component of the liquid metal ion source according to the present invention, resulted in satisfactory parameters for the emitted ion beam, i.e., the full-width at half maximum (FWHMm) of the main emission profile 11 below 510 nm and the full-width at half maximum (FWHMt) of the tail emission profile 12 below 1010 nm across the entire range of operating currents. Importantly, the desired ion beam parameters were achieved at significantly lower emission currents, ranging from 1635 nA (for M0D8) to 1848 nA (for M0D5), compared to the reference simulation (2500 nA). The reduction in emission current, while maintaining the desired ion beam parameters, ensures slower wear of the gallium ion source and extends its lifetime by at 5 least 40%. Notably, the simulated stability of the ion beam included uninterrupted operation for a minimum of 100 hours. Reference numbers: 1 - holder 2 - electrical contact 3 - mounting system 4- liquid metal reservoir 5 - emitter 6 - cylindrical portion of the emitter 7 - tip portion of the emitter 8- apex 9 - groove 10-flange 11 - main emission profile of the ion beam 12 - tail emission profile of the ion beam h - height of the apex-forming cone x - width of the groove y - depth of the groove a - opening angle of the cone forming the apex P - inclination angle of the sidewall of the groove y - the angle between the sidewalls of the groove

Claims

1. A liquid metal ion source comprising an emitter (5) configured to emit liquid metal ions, wherein the emitter (5) includes a substantially cylindrical portion (6) and a tip portion (7) at the emission end, the tip portion (7) being shaped as a truncated cone, characterized in thata trapezoidal-shaped recess is formed on the upper surface of the truncated cone of the tip portion (7), defining an annular flange (10) surrounding the recess, and from the bottom surface of the recess extends an apex (8) formed by a cone with a base diameter corresponding to the diameter of the bottom surface of the recess, wherein the height of the cone forming the apex (8) exceeds the height of the flange (10),a plurality of grooves (9) are formed on the lateral surface of the truncated cone of the tip portion (7), the grooves (9) extending radially from the interface area between the cylindrical portion (6) and the tip portion (7) to the area of the flange (10).

2. The liquid metal ion source according to claim 1, characterized in that the ratio of the height h of the cone forming the apex (8) to the height of the tip portion (7) is in the range of 0.2 to 0.25, and the cone angle a of the cone forming the apex (8) is in the range of 45° to 55°.

3. The liquid metal ion source according to claim 2, characterized in that the ratio of the height h of the cone forming the apex (8) to the height of the tip portion (7) is 0.23, and the cone angle a of the cone forming the apex (8) is 49.3°.

4. The liquid metal ion source according to any one of claims 1-3, characterized in that the inclination angle p of the sidewall of the groove (9) relative to a plane passing through the upper edges of the groove (9) is in the range of 90° to 135°.

5. The liquid metal ion source according to claim 4, characterized in that the inclination angle p of the sidewall of the groove (9) relative to a plane passing through the upper edges of the groove (9) is in the range of 90° to 120°.

6. The liquid metal ion source according to any one of claims 1-5, characterized in that the ratio of the width x of the groove (9) to the diameter of the tip portion (7) is in the range of 1 / 150 to 10 / 150.

7. The liquid metal ion source according to claims 6, characterized in that the ratio of the width x of the groove (9) to the diameter of the tip portion (7) is 1 / 30.

8. The liquid metal ion source according to any one of claims 1-7, characterized in that the ratio of the depth y of the groove (9) to the height of the tip portion (7) is in the range of 0.01 to 0.1.

9. The liquid metal ion source according to claim 8, characterized in that the ratio of the depth y of the groove (9) to the height of the tip portion (7) is 0.05.

10. The liquid metal ion source according to any one of claims 1-9, characterized in that the groove (9) has a cross-sectional shape selected from the group comprising a trapezoid, rectangle, and triangle.

11. The liquid metal ion source according to any one of claims 1 - 10, characterized in that the groove (9) has a variable width along its length, with the angle y between the sidewalls being in the range of 1° to 5°.

12. The liquid metal ion source according to claim 11, characterized in that the angle y between the sidewalls is 3,82°.

13. The liquid metal ion source according to any one of claims 1 - 12, characterized in that the emitter (5) is made of tungsten, and the liquid metal is liquid gallium.

14. A method for producing a liquid metal ion source as defined in any one of claims 1 - 13, characterized in that material removal processing is carried out to form the apex (8) in the form of a cone extending from the recess on the upper surface of the truncated cone of the tip portion (7) and to form grooves (9) on the lateral surface of the truncated cone of the tip portion (7), wherein the material removal step is performed using a focused ion beam technology with ions selected from the group consisting of xenon, argon, oxygen, or nitrogen.

15. A focused ion beam emitting device, characterized in that it comprises a liquid metal ion source as defined in any one of claims 1 -13.

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