Reduced charging due to low negative voltage in FIB systems

Abstract

1. A method for processing a region of a sample, the method including: placing the sample in a vacuum chamber; generating an ion beam with a focused ion beam (FIB) column; focusing the ion beam on the sample and scanning the focused ion beam over a region of the sample, thereby generating secondary electrons that are emitted from a surface of the sample within the region; and applying a negative bias voltage to a conductive structure proximate to the region during the scanning to change the trajectory of the secondary electrons and repel them back toward the sample surface, the conductive structure being one of a gas injection nozzle, a voltage pin, or a nanomanipulator.

Description

[Technical field]

[0001] This application claims the benefit of U.S. Patent Application No. 17 / 725,023, filed April 20, 2022, the entire disclosure of which is incorporated herein by reference for all purposes. [Background technology]

[0002] In the study of electronic materials and processes for fabricating such materials into electronic structures, specimens of the electronic structures may be used for microscopic examination for failure analysis and device validation purposes. For example, a specimen such as a silicon wafer containing one or more integrated circuits (ICs) or other electronic structures formed thereon may be machined and imaged with a focused ion beam (FIB) to study the intrinsic properties of the circuits or other structures formed on the wafer.

[0003] As an example, a FIB may be used to machine holes or trenches in one or more layers formed on a sample. During such a machining process, ions bombard the sample, triggering a series of events that can generate free electrons that escape from the surface of the sample. When the material being machined is a conductive layer, electrons from within the sample can rapidly replace the escaping electrons, maintaining a relatively neutral charge in the machined area. However, when the material being machined is a non-conductive (i.e., electrically insulating) layer, electrons do not move freely through the material. Thus, during machining of a non-conductive material, electrons that escape or are otherwise released from the machined area may not be replaced, and the machined area may develop a positive charge that can adversely affect the machining process.

[0004] Therefore, improved techniques for mechanically processing non-conductive materials are desirable. Summary of the Invention

[0005] The embodiments disclosed herein provide improved techniques and processes for mechanically treating areas on a sample to reduce or prevent the formation of positive charges in the mechanically treated areas, even when the material being mechanically treated is non-conductive.

[0006] In some embodiments, a method of processing a region of a sample includes placing the sample in a vacuum chamber; generating an ion beam with a focused ion beam (FIB) column; focusing the ion beam on the sample and scanning the focused ion beam across a region of the sample, thereby generating secondary electrons that are emitted from a surface of the sample within said region; and applying a negative bias voltage to an electrically conductive structure proximate to said region during said scanning to change the trajectory of the secondary electrons and bounce them off the sample surface, where the electrically conductive structure is one of a gas injection nozzle, a voltage pin, or a nanomanipulator.

[0007] Various implementations of the embodiments described herein may include one or more of the following features: The conductive structure may be located 5 millimeters or less away from the region being machined. The conductive structure may include a gas injection nozzle located between a column cap of the FIB column and the sample. The gas injection nozzle may be heated during application of a negative bias voltage to the gas injection nozzle. During said scanning, a first end of the gas injection nozzle may be located adjacent to said region, and a second end of the gas injection nozzle may extend through a conductive wall of a component of the vacuum chamber and may be electrically insulated from, but thermally coupled to, said wall. The conductive structure may include a voltage pin operable to be moved adjacent to within 100 microns of said region. The sample may include a non-conductive layer formed on an upper surface of the sample, and the focusing step may scan the focused ion beam over the region of the sample to machine a portion of the non-conductive layer. The sample may include a semiconductor substrate, and during scanning. The conductive structure may be 5 microns to 1.5 millimeters away from said region.

[0008] Some embodiments relate to a non-transitory computer readable medium storing instructions that, when executed by one or more processors, cause the processor to: place a sample in a vacuum chamber; generate an ion beam with a focused ion beam (FIB) column; focus the ion beam on the sample and scan the focused ion beam across a region of the sample, thereby generating secondary electrons that are emitted from a surface of the sample within the region; and, during the scan, apply a negative bias voltage to a conductive structure proximate to the region to change the trajectory of the secondary electrons and repel them back toward the sample surface, where the conductive structure is one of a gas injection nozzle, a voltage pin, or a nanomanipulator.

[0009] Some embodiments relate to a system for performing mechanical processing of a region of a sample according to any of the methods described above or herein. For example, the system may include a vacuum chamber, a sample support configured to hold the sample in the vacuum chamber during processing operations, a focused ion beam (FIB) column configured to direct an ion beam into the vacuum chamber toward the region of the sample during processing operations, a conductive structure movable into position to be proximate to the region of the sample when the sample is disposed on the sample support, the conductive structure being one of a gas injection nozzle, a voltage pin, or a nanomanipulator, and a voltage source operable to apply a negative bias voltage to the conductive structure.

[0010] For a better understanding of the nature and advantages of the present disclosure, reference should be made to the following description and the accompanying drawings. It should be understood, however, that each of the figures is provided for illustrative purposes only and is not intended as a definition of the limits of the scope of the present disclosure. Also, as is customary, and unless otherwise clear from the description, when elements in different figures use the same reference numbers, those elements are generally identical or at least similar in function or purpose. [Brief description of the drawings]

[0011] [Figure 1] 1 is a simplified diagram of an exemplary focused ion beam (FIB) characterization system, according to some embodiments of the present disclosure. [Diagram 2] 1 is a simplified diagram of a portion of a known charged particle column. [Diagram 3] 1 is a simplified diagram of a portion of a known charged particle column. [Figure 4] 1 is a simplified diagram of an exemplary focused ion beam (FIB) characterization system, according to some embodiments of the present disclosure. [Diagram 5] 1 is a simplified flow chart illustrating steps associated with a method for mechanically processing a sample, according to some embodiments. [Figure 6A] 1 is a simplified diagram of a portion of a FIB column and gas nozzle, according to some embodiments. [Figure 6B] FIG. 6B is a simplified plan view of a portion of the gas injection nozzle shown in FIG. 6A positioned above a sample being machined. [Figure 6C] 1 is a simplified diagram of a gas injection nozzle according to some embodiments positioned above a sample being machined. [Figure 7] 1 illustrates a simplified diagram of a gas nozzle connection system according to some embodiments. [Figure 8A] 1 is a simplified diagram of an exemplary focused ion beam (FIB) characterization system, according to some embodiments. [Figure 8B] 1 is a simplified diagram of an exemplary focused ion beam (FIB) characterization system, according to some embodiments. [Figure 8C] 1 is a simplified diagram of an exemplary focused ion beam (FIB) characterization system, according to some embodiments. [Figure 9] 1 is a simplified diagram of an area on a semiconductor wafer where one or more regions may be machined according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The embodiments disclosed herein provide improved techniques and processes for mechanically treating areas on a sample to reduce or prevent the formation of positive charges in the mechanically treated areas, even when the material being mechanically treated is non-conductive.

[0013] Exemplary Focused Ion Beam (FIB) Characterization Tools To better understand and appreciate the present disclosure, reference is first made to FIG. 1, which is a simplified schematic diagram of a focused ion beam (FIB) characterization system 100 according to some embodiments of the present disclosure. As shown in FIG. 1, the system 100 can include, among other elements, a focused ion beam (FIB) column 110, a sample support element 140, and a secondary electron detector 150 (or in some embodiments a secondary ion detector, or a combination of two detectors operating in parallel). The FIB column 110 is operable to generate a charged particle beam 120 and direct the particle beam toward a sample 130 (sometimes referred to herein as a "target" or "specimen") to mechanically or otherwise process the sample. The sample, for example a semiconductor wafer, can be supported on the support element 140 within a vacuum chamber 105.

[0014] The FIB column 110 can machine the sample 130 (e.g., drill a recess in the sample 130) to form a cross section by irradiating the sample with the charged particle beam 120, and can also smooth the cross section if desired. The FIB machining process generally operates by placing the specimen in a vacuum environment and firing a focused beam of ions toward the specimen to etch or machine away material on the specimen. In some cases, the vacuum environment can be purged with a controlled concentration of background gas that serves to help control the etch rate and quality or to help control material deposition. The accelerated ions can be generated from xenon, gallium, or other suitable elements, and are accelerated toward the specimen by a voltage that generally falls within the range of 500 to 100,000 volts, more typically within the range of 3,000 to 30,000 volts. Beam currents are typically in the range of a few picoamps to a few microamps depending on the FIB instrument configuration and application, and pressures typically range from 10 to 100 MPa in different parts of the system and in different operating modes. -10 From 10 -5 It is controlled between mbar.

[0015] The mechanical treatment process may be performed, for example, by (i) locating a location at which the sample should be mechanically treated to remove a portion of material (e.g., a portion of one or more layers) from the sample, (ii) moving the sample (e.g., by mechanical support element 140) so that it is under the field of view of the FIB unit, and (iii) mechanically treating the sample to remove the desired amount of material at the location. The mechanical treatment process may include forming an indentation in the sample (typically a few microns to a few hundred microns in size in a lateral dimension).

[0016] Mechanical processing generally involves scanning a charged particle beam back and forth (e.g., in a raster or other scanning pattern) over a particular area of ​​the sample being imaged or machined. One or more lenses (not shown) coupled to the charged particle column can implement the scanning pattern, as known to those skilled in the art. The scanned area is generally a very small fraction of the total area of ​​the sample. For example, the sample may be a semiconductor wafer with a diameter of 150, 200 or 300 mm, but each scanned area on the wafer (i.e., the machined area) may be a rectangular area with a width and / or length measured in microns or tens of microns. Each repetition (or frame) in which the ion beam is scanned over the area being machined is typically measured in microseconds and removes an extremely small amount of material (e.g., as low as 0.01 atomic layers using a low i probe (e.g., 10 pA), or as much as 1000 atomic layers using a high i probe (e.g., 1000 nA)), and the scan pattern is then repeated thousands or even millions of times to etch holes to the desired depth.

[0017] During mechanical processing operations, the charged particle beam 120 generated by the FIB column 110 propagates through a vacuum environment formed in the vacuum chamber 105 before striking the sample 130. The mechanical processing process produces by-products such as molecules, atoms and ions of the material being mechanically processed along with secondary electrons. For example, when ions strike the sample surface with a relatively high energy level, they can initiate a collision cascade that transfers momentum and energy from the ion to the sample until the ion is stopped and implanted. The momentum and energy transfer during the collision cascade can cause the rearrangement of atoms, the ionization of atoms, and the generation of phonons (heat). The cascade can reach the sample surface and cause sputtering of atoms that have sufficient momentum and energy to escape the solid sample, producing secondary ions and secondary electrons as a combination of ionization and sputtering, which also escape the sample surface. The secondary ions or electrons (shown in FIG. 1 as secondary ions / electrons 125) can be detected by a suitable detector 150. The detected secondary ions or electrons can then be used to analyze the properties of the machined layers and structures.

[0018] 1, the FIB evaluation system 100 may include several additional components, including, but not limited to, one or more gas nozzles for supplying process gases to the chamber 105, vacuum and other valves for controlling the pressure within the chamber 105, and one or more lenses for directing the charged particle beam, among other components. The system 100 may also include one or more controllers, processors, or other hardware units that control the operation of the system 100 by executing computer instructions stored in one or more computer-readable memories, as would be known to one of ordinary skill in the art. By way of example, the computer-readable memories may include solid-state memories (such as random access memories (RAM) and / or read-only memories (ROM), which may be programmable, flash-updateable, etc.), disk drives, optical storage devices, or similar non-transitory computer-readable storage media.

[0019] Accumulation of positive charge on the sample As mentioned above, when a sample is bombarded by an ion beam during a focused ion beam (FIB) mechanical processing process, secondary electrons may be generated that escape from the sample. For purposes of illustration, reference is made to FIG. 2, which is a simplified schematic diagram of a portion of a FIB column 200 spaced from a sample 230. The FIB column 200 may represent the FIB column 120 shown in FIG. 1. For ease of illustration, only selected elements of the FIB column 200 are shown in FIG. 2. As shown, the FIB column 200 includes a column cap 210 at a distal end of the column.

[0020] During a mechanical processing operation, the FIB column 200 generates an ion beam 220 and directs an electron beam so that the beam strikes the sample 230. The interaction of the ion beam with the sample 230 generates various secondary electrons, some of which are emitted from the sample, as shown by secondary electrons 240. When the layer being mechanically processed in the sample 230 is a non-conductive layer, the emitted secondary electrons are not easily replaced by other electrons in the sample 230. Thus, a positive charge may build up in the region 250 of the sample being mechanically processed. As mentioned above, the positive charge may adversely affect the ion beam 220, for example, by deflecting the ion beam 220 away from its intended trajectory.

[0021] In some known exemplary characterization systems, a negative voltage may be applied to the charged particle column to repel secondary electrons toward the sample and maintain a neutral charge at the surface of the sample. For example, FIG. 3 is a simplified schematic diagram of a portion of a charged particle column 300 spaced apart from a sample 330. The charged particle column 300 may include the same or similar components as the column 200 and is shown as generating a charged particle beam 320 that is directed toward the sample 330 through an opening in a column cap 310. During a processing operation in which the charged particle beam is directed to strike the sample 330, a negative voltage may be applied to the column cap 310 that is sufficient to repel emitted secondary electrons 340 toward the sample 330. In this manner, the charged particle column 300 may avoid forming a strong positive charge across the surface of the sample 330.

[0022] In practice, however, the column cap 310 and the detector (e.g., secondary electron detector) are each spaced a distance X1 away from the upper surface of the sample 330 that may be several millimeters or more. For example, in a typical machine processing operation, the column cap 310 may be spaced about 10-15 mm away from the sample surface, and the secondary electron detector may be spaced a similar distance away on one side of the machined area. Thus, as shown in FIG. 3, even when a negative voltage is applied to the column cap 310, the relatively large spacing (in the millimeter range) between the column cap 310 and the sample may cause bounced secondary electrons 340 to be returned to the sample 330 in a region having a radius of approximately Y1 that may be several millimeters or more away from the area where the ion beam strikes the sample 330. When the ion beam is directed toward the sample with micron-scale precision, the bounced electrons may not counteract the buildup of positive charge in the immediate vicinity of the beam, and thus this may still produce undesirable effects during the machine processing process. Furthermore, to efficiently repel electrons from such distances requires a relatively strong electric potential which can interfere with the optics of the primary ion beam emerging from the column.

[0023] Applying a negative voltage to structures in close proximity to the area to be machined According to some embodiments disclosed herein, a negative bias voltage may be applied to conductive structures in close proximity to the machined region to bounce secondary electrons back onto the surface of the sample in roughly the same area as the secondary electrons were emitted from the sample. As used herein, "close proximity" refers to a distance between about 5 microns and less than 5 millimeters. Also, in various embodiments, a negative bias voltage is applied to conductive structures that are 2 millimeters or less from the machined region, between 5 microns and 1.5 millimeters from the machined region, and / or between 5 microns and 700 microns from the machined region, which are essentially distances at least several times closer (and in many cases a full order of magnitude closer) to the machined region than the column cap.

[0024] As described below, in some embodiments, the conductive structure may be one or more of a gas injection nozzle, a voltage pin, a nanomanipulator, and / or any suitable conductive structure, and the conductive structure may be positioned within close proximity (as defined above) of the area to be machined without interfering with the ion beam while a negative bias voltage is applied to the conductive structure.

[0025] 1. Gas injection nozzle Reference is now made to Figure 4, which is a simplified diagram of a focused ion beam (FIB) characterization system 400, according to some embodiments. System 400 may be similar to system 100 and includes a FIB column 410 capable of directing an ion beam 420 towards a sample 430 disposed on a sample support 440. System 400 may also include a secondary electron or secondary ion detector 450 that detects secondary electrons or ions 425 generated during machine processing operations.

[0026] The FIB characterization system 400 further includes a gas injection nozzle 460 disposed between the distal end of the FIB column 410 and the sample 430. In some embodiments, the gas injection nozzle 460 may be in a fixed relationship in the X and Y planes relative to the FIB column 410 and movable in the Z plane to allow the nozzle to get in close proximity (e.g., as close as 300 microns in some embodiments) of the upper surface of the sample 430. In some embodiments, the gas injection nozzle 460 may include holes or channels formed therethrough that allow the ion beam 420 to pass through the gas injection nozzle and impact the sample 430 at a location directly below the nozzle, as described below with respect to FIGS. 6A-6C.

[0027] However, before discussing Figures 6A-6C, reference is made to Figure 5, which is a simplified flow chart illustrating steps associated with a method 500 of mechanically processing a sample, according to some embodiments. Method 500 begins by placing a sample, such as a semiconductor wafer having a non-conductive layer formed thereon, in a processing chamber of an exemplary characterization system (step 510). The processing chamber, which may be, for example, chamber 405, may include a focused ion beam (FIB) column, such as FIB column 410, and a gas injection nozzle, such as nozzle 460. Step 510 may include placing the sample in the vacuum chamber on a sample support, such as support 440.

[0028] A negative bias voltage may then be applied to the gas injection nozzle (step 520), and the FIB column may be activated to generate an ion beam (step 530), which is focused and scanned across a region of interest on the sample (step 540). The ion beam may be focused by a focusing lens (not shown in FIG. 4) and scanned across a region of the substrate by one or more deflection lenses (also not shown in FIG. 4).

[0029] A negative bias voltage is applied to the gas injection nozzle while the ion beam is scanned over the region. The negative bias voltage should be high enough to repel secondary electrons escaping from the surface of the sample back into the sample, but the negative bias voltage should not be so high as to affect the trajectory of the ion beam 420, which would adversely affect the mechanical treatment process. While the negative bias voltage is applied to the gas injection nozzle and while the ion beam is scanned over the region, secondary electrons emitted from the sample are repelled back into the sample, thus maintaining a relatively neutral charge in the region being mechanically treated. Thus, although FIG. 5 shows steps 520-550 as separate, consecutive steps, in practice steps 520-550 can occur simultaneously with one another.

[0030] In some embodiments, the negative bias voltage may be the minimum voltage required to repel a given percentage of secondary electrons. A suitable value for the negative bias voltage will depend in part on the geometry of the gas injection nozzle, the spacing of the nozzle relative to the sample, and the given percentage of secondary electrons that should be repelled into the sample. Thus, a suitable negative bias voltage may be determined by simulation or by experiment, as may be readily determined by one of ordinary skill in the art. In some embodiments, the bias voltage may be between -50 and -1000 volts, and in other embodiments, the bias voltage may be between -100 and -500 volts.

[0031] 5 describes a method in connection with mechanical processing operations of a non-conductive layer, it should be understood that in other embodiments, Additionally, while FIG 5 describes an embodiment in which a negative voltage is applied to a gas injection nozzle, it should be understood that the same or similar techniques may be used in connection with other conductive structures described herein for such purposes, including voltage pins, nanomanipulators, etc.

[0032] Reference is now made to FIG. 6A, which is a simplified diagram of the gas injection nozzle 460 shown in FIG. 4, and FIG. 6B, which is a simplified plan view of a portion of the gas injection nozzle 460. As shown, the gas injection nozzle 460 includes a channel 615 that extends all the way through the nozzle 460 from an upper surface of the nozzle 460 to a lower surface of the nozzle. The channel 615 may have a circular cross-section and may be centered about the ion beam 420 such that the ion beam traverses through the channel 615 of the gas injection nozzle 460 before striking the sample 430 (e.g., as shown in FIG. 6B as region 675). The nozzle 460 also includes an opening 620 at a bottom surface of the nozzle adjacent the upper surface of the sample 430. Gas flowing through the nozzle 460 may be delivered to the surface of the sample 430 through the opening 620. 6B, the opening 620 may also have a circular cross-section and may surround the channel 615 and symmetrically surround a region 675 on the sample where the ion beam 420 contacts and machines the sample 430. In this manner, gas provided by the nozzle 460 may be provided directly to the region 675 of the sample 430 being machined.

[0033] 4 and 6A, the gas injection nozzle 460 is much closer to the sample 430 than either the column tip 610 or the secondary ion detector (not shown). For example, the nozzle 460 may be an order of magnitude or more closer to the area on the upper surface of the sample 430 being machined than the nearest portion of the focused ion beam column is to said machined area.

[0034] In previously known systems, the substrate support 440 and the gas nozzle 460 are typically electrically grounded. However, some embodiments disclosed herein apply a negative voltage to the gas injection nozzle 460 to repel secondary electrons generated from the mechanical processing operation back to the sample in a manner similar to that described above with respect to the column tip 310 (FIG. 3). For illustration, reference is made to FIG. 6C, which is a simplified diagram of a portion of the gas injection nozzle 460 positioned above the sample 430 being mechanically processed. Because the gas nozzle 460 is much closer to the area being mechanically processed than the column tip 310 (or column tip 610), applying an appropriate negative voltage level to the gas nozzle 460 will repel the secondary electrons 640 to an area of ​​the sample that has a much smaller radius, and is therefore much closer to the area being mechanically processed, than the secondary electrons repelled by the column tip 310 to the sample 330. In some embodiments, the lower surface of the nozzle 460 may be spaced a distance X2 away from the upper surface of the sample 430, measured in tens or hundreds of microns. As a non-limiting example, in some machine processing operations, the lower surface of the nozzle 460 can be spaced approximately 200-700 microns away from the sample surface.

[0035] The design of the gas nozzle 460 to completely and symmetrically surround the machined area as shown in Figure 6B, and the extremely close spacing between the gas nozzle 460 and the sample (in the micron range) can result in the bounced secondary electrons 640 being returned to the sample 430 in a region centered on the machined area and having a radius of approximately Y2, measured in tens of microns as opposed to millimeters (and thus at least one or two orders of magnitude smaller than Y1). Thus, the secondary electrons can be bounced to an area on the sample that is generally within the same vicinity (as measured in microns) as the machined area, which allows the machined area to maintain a neutral charge even when the material being machined is non-conductive.

[0036] 2. Electrically insulating the gas injection nozzle In order for the gas nozzle 460 to be charged with a negative voltage, the nozzle needs to be electrically isolated from the rest of the system 400, which is grounded. FIG. 7 is a simplified diagram of a gas nozzle connection system 700, according to some embodiments, that can electrically isolate the gas nozzle from the rest of the system 400. As shown, the nozzle connection system 700 can allow a gas injection nozzle 710, which may represent the gas injection nozzle 460, to be charged with its own potential by applying a negative voltage to the gas nozzle 710. As shown in FIG. 7, the gas nozzle 710 includes an end portion 712 that can extend through a wall 720. The gas nozzle 710 and the wall 720 can be made of a conductive material, such as a metal. In some embodiments, the wall 720 can be a wall of a vacuum chamber, such as chamber 105 or 405, of a FIB evaluation system, such as system 100 or 400. In other embodiments, wall 720 may be the wall of a gas box that includes various valves and pipes (not shown) for controlling the flow of one or more gases into gas nozzle 710, the gas box being located within a vacuum chamber such as chamber 105 or 405. In either case, gas is piped through nozzle 710 in the direction indicated by arrow 715, and wall 720 may be electrically grounded.

[0037] An insulated electrical feedline 730 may extend through the wall 720 and be electrically coupled to a thermally conductive electrode 740. When a voltage is applied to the feedline 730, the electrode 740 transmits the applied voltage to the gas nozzle.

[0038] In some applications, it is important to heat the nozzle 460 to avoid deposition of material from the gas flowing through the nozzle, which may interfere with gas flow to the area being machined or clog the nozzle entirely. To this end, the gas nozzle 460 may be electrically insulated from the chamber walls and / or other components within the chamber by an electrically insulating but thermally conductive O-ring 750 or similar structure (e.g., an electrically insulating, thermally conductive paste). A heater element (not shown) may be operatively connected to the wall 720 and the gas nozzle 710 to heat both the wall and the nozzle to a temperature sufficient to prevent or otherwise reduce deposition within the gas nozzle. The electrically insulating but thermally conductive O-ring 750 allows heat to transfer between the two components while allowing the potential of the gas nozzle 710 to be isolated from the potential of the wall 720.

[0039] 3. Voltage pins / nanomaniipulators In some embodiments, in addition to or instead of applying a negative voltage to a gas injection nozzle or similar structure located in close proximity (e.g., less than a millimeter) of the area to be machined, a voltage pin (e.g., a structure whose sole or primary purpose is to apply a voltage in the vicinity of the area being machined or imaged), nanomanipulator, or similar structure may be included in the system, which may be moved to a position in close proximity of the area to be machined. Figures 8A and 8B are simplified diagrams of focused ion beam (FIB) characterization systems 800a and 800b, respectively, according to some embodiments. Each of the FIB characterization systems 800a and 800b is similar to the systems 100 and 400 described above and may include a FIB column 810 that can direct an ion beam 820 toward a sample 830 disposed on a sample support 840. Systems 800a and 800b may also include a secondary ion detector (not shown in either FIG. 8A or FIG. 8B) that detects secondary ions generated during the mechanical processing operation, and a gas injection nozzle 860 positioned to introduce one or more gases to the area being mechanically processed.

[0040] As shown in Figures 8A and 8B, system 800a does not include a gas injection nozzle, while system 800b includes a gas nozzle 860 that directs gas from a remote location to the side of the area to be machined, as opposed to gas nozzle 460 (Figure 4), which introduced gas directly above the area to be machined. Each of systems 800a and 800b further includes a voltage application structure 850 that may be positioned in close proximity to (e.g., less than a millimeter away from) the area on sample 830 being machined by ion beam 820. In some embodiments, the voltage application structure may be positioned less than 100 microns from the area to be machined, and in some embodiments, the voltage application structure may be positioned within tens of microns of the area to be machined. In some embodiments, the voltage application structure 850 may be freely moved within the processing chamber independent of the FIB column and other components, and in some embodiments, the voltage application structure 850 may be physically connected to and moved with the gas injection nozzle.

[0041] The voltage application structure 850 may be operatively coupled to a voltage source and, when properly positioned, may apply a negative voltage in close proximity to the area to be machined. In this manner, the voltage application structure 850 may repel secondary electrons escaping the sample back to the sample surface during the machine process, as described above with respect to FIG.

[0042] 8C, in yet another embodiment, the voltage application structure 870 can include a conductive ring-shaped structure 875 at its tip, which includes an inner aperture 880 through which the ion beam can pass. The aperture 880 can be very small (e.g., less than 1 mm in diameter) and the structure 875 can be positioned very close to the upper surface of the sample 830, such that when an appropriate negative voltage is applied to the structure 875, secondary electrons can be repelled onto the surface of the sample 830 in the same manner as described above in FIG. 6C with respect to the gas nozzle 460.

[0043] Examples of samples that will be machine processed As mentioned above, embodiments of the present disclosure may be used to machine or image many different types of samples, including electronic circuits formed on semiconductor structures, solar cells formed on polycrystalline or other substrates, nanostructures formed on various substrates, and the like. As one non-limiting example, FIG. 9 is a simplified diagram of an area on a semiconductor wafer that may be machine processed, according to some embodiments. In particular, FIG. 9 includes a top view of the wafer 900 along with two close-ups of certain portions of the wafer 900. The wafer 900 may be, for example, a 150 mm, 200 mm, or 300 mm semiconductor wafer and may include multiple integrated circuits 905 (52 in the illustrated example) formed thereon. The integrated circuits 905 may be in an intermediate stage of manufacture, and the machine processing techniques described herein may be used to evaluate and analyze one or more regions 910 of the integrated circuits, including two or more sections adjacent to one another that exhibit different machine processing speeds. For example, close-up A of FIG. 9 shows multiple regions 910 of one of the integrated circuits 905 that may be evaluated and analyzed according to the techniques described herein. Close-up B shows one of these regions 910, including the various electronic structures formed within the region.

[0044] Embodiments of the present disclosure can analyze and evaluate region 910, for example, using method 500 described above with respect to Figure 5. Evaluation can be performed by scanning an SEM beam back and forth within region 910 according to a raster pattern, such as scan pattern 920 shown in a simplified format in close-up B of Figure 9.

[0045] The above description, for the purpose of explanation, used specific names to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that specific details are not required to practice the described embodiments. Thus, the above description of the specific embodiments described herein is presented for the purpose of illustration and description. The above description is not intended to be exhaustive or to limit the embodiments to the precise form disclosed. Also, although different embodiments of the present disclosure have been disclosed above, the specific details of the specific embodiments may be combined in any suitable manner without departing from the spirit and scope of the embodiments of the present disclosure. Moreover, it will be apparent to one skilled in the art that many modifications and variations are possible in light of the above teachings.

[0046] Also, any reference in this specification above to a method should apply mutatis mutandis to a system capable of performing said method, and should apply mutatis mutandis to a computer program product storing instructions which, when executed, result in the performance of said method. Similarly, any reference in this specification above to a system should apply mutatis mutandis to a method which may be performed by said system, and should apply mutatis mutandis to a computer program product storing instructions which may be executed by said system, and any reference in this specification to a computer program product should apply mutatis mutandis to a method which may be performed upon execution of instructions stored in said computer program product, and should apply mutatis mutandis to a system configured to execute instructions stored in said computer program product.

[0047] Because the illustrated embodiments of the present disclosure can be implemented for the most part using electronic components and equipment known to those skilled in the art, details of such will not be described more extensively than is deemed necessary for an understanding and appreciation of the concepts underlying the present disclosure, and in order not to obscure or detract from the teachings of the present disclosure, as described above.

[0048] Additional Embodiments Any reference in this specification above to a method should apply mutatis mutandis to a system capable of performing said method, and should apply mutatis mutandis to a computer program product storing instructions which, when executed, result in the performance of said method. Similarly, any reference in this specification above to a system should apply mutatis mutandis to a method which may be performed by said system, and should apply mutatis mutandis to a computer program product storing instructions which may be executed by said system, and any reference in this specification to a computer program product should apply mutatis mutandis to a method which may be performed upon execution of instructions stored in said computer program product, and should apply mutatis mutandis to a system configured to execute instructions stored in said computer program product.

[0049] While the illustrated embodiments of the present disclosure can be implemented for the most part using electronic components and circuits known to those skilled in the art, details of such will not be described more extensively than is deemed necessary for an understanding and appreciation of the concepts underlying the present disclosure, and in order not to obscure or detract from the teachings of the present disclosure, as described above.

[0050] The above description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one of ordinary skill in the art that specific details are not required to practice the described embodiments. For example, while various embodiments are described above with respect to applying a negative voltage to a gas nozzle or voltage application structure during machine processing operations, the same concepts may be beneficially applied to imaging operations in which secondary ions are collected while an ion beam is directed toward a substrate. In such operations, when a non-conductive material is exposed to the ion beam during the imaging process, the embodiments described herein may prevent or significantly reduce the buildup of positive charge in the area being imaged by repelling secondary electrons back to the sample.

[0051] Thus, the above description of the specific embodiments described herein is presented for purposes of illustration and description. The above description is not intended to be exhaustive or to limit the embodiments to the precise form disclosed. Also, although different embodiments of the present disclosure have been disclosed above, the specific details of the specific embodiments can be combined in any suitable manner without departing from the spirit and scope of the embodiments of the present disclosure. Moreover, it will be apparent to one skilled in the art that many modifications and variations are possible in light of the above teachings.

Claims

1. 1. A method of processing an area of ​​a sample, the method comprising: Placing a sample in a vacuum chamber; generating an ion beam with a focused ion beam (FIB) column; focusing the ion beam on the sample and scanning the focused ion beam across the region of the sample, thereby generating secondary electrons within the region that are emitted from a surface of the sample; applying a negative bias voltage to a conductive structure proximate to the region during the scan to change the trajectory of the secondary electrons and repel the secondary electrons toward the sample surface, the conductive structure being one of a gas injection nozzle, a voltage pin, or a nanomanipulator; A method comprising:

2. The method of claim 1 , wherein the conductive structure is positioned no more than 5 millimeters away from the region during the scanning.

3. The method of claim 1 or 2, wherein the conductive structure comprises a gas injection nozzle disposed between a column cap of the FIB column and the sample.

4. The method of claim 3 , further comprising heating the gas injection nozzle while applying a negative bias voltage to the gas injection nozzle.

5. 5. The method of claim 4, wherein during the scanning step, a first end of the gas injection nozzle is positioned adjacent to the region and a second end of the gas injection nozzle extends through, is electrically insulated from, and is thermally coupled to a conductive wall of a component of the vacuum chamber.

6. 3. The method of claim 1 or 2, wherein the conductive structure comprises a voltage pin operable to be moved adjacent to within 100 microns of the region.

7. 7. The method of claim 1, wherein the sample includes a non-conductive layer formed on an upper surface of the sample, and the focusing step scans the focused ion beam across the region of the sample to machine a portion of the non-conductive layer.

8. 7. The method of claim 1, wherein the sample comprises a semiconductor substrate, and wherein during the scanning, the conductive structure is positioned between 5 microns and 1.5 millimeters away from the region.

9. 1. A system for processing an area of ​​a sample, the system comprising: A vacuum chamber; a sample support configured to hold a sample within the vacuum chamber during processing operations; a focused ion beam (FIB) column configured to direct an ion beam into the vacuum chamber toward the region of the sample during the processing operation; a conductive structure movable into position adjacent the region of the sample when the sample is disposed on the sample support, the conductive structure being one of a gas injection nozzle, a voltage pin, or a nanomanipulator; a voltage source operable to apply a negative bias voltage to the conductive structure; A system comprising:

10. 10. The system of claim 9, wherein the conductive structure is positioned no more than 1.5 millimeters away from the region of the sample.

11. and a processor and a memory coupled to the processor, the memory including a plurality of computer readable instructions that, when executed by the processor, cause the system to: Placing a sample in a vacuum chamber; generating an ion beam with a focused ion beam (FIB) column; focusing the ion beam on the sample and scanning the focused ion beam across the region of the sample, thereby generating secondary electrons within the region that are emitted from a surface of the sample; applying a negative bias voltage to the conductive structure proximate the region of the sample during the scan to change the trajectory of the secondary electrons and repel the secondary electrons toward the sample surface; The system of claim 9 ,

12. The system of claim 9 , wherein the conductive structure is a gas injection nozzle.

13. The system of claim 12 , further comprising heating the gas injection nozzle while applying a negative bias voltage to the gas injection nozzle.

14. 13. The system of claim 12, wherein during the scanning step, a first end of the gas injection nozzle is positioned adjacent to the region and a second end of the gas injection nozzle extends through, is electrically insulated from, and is thermally coupled to a conductive wall of a component of the vacuum chamber.

15. 15. The system of claim 9, wherein the sample includes a non-conductive layer formed on an upper surface of the sample, and the focusing step scans the focused ion beam across the region of the sample to machine a portion of the non-conductive layer.

16. A non-transitory computer-readable memory comprising a plurality of computer-readable instructions that, when executed by one or more processors, cause the processors to: Placing a sample in a vacuum chamber; generating an ion beam with a focused ion beam (FIB) column; focusing the ion beam on the sample and scanning the focused ion beam across the region of the sample, thereby generating secondary electrons within the region that are emitted from a surface of the sample; applying a negative bias voltage to a conductive structure proximate to the region during the scan to change the trajectory of the secondary electrons and repel the secondary electrons toward the sample surface, the conductive structure being one of a gas injection nozzle, a voltage pin, or a nanomanipulator; A non-transitory computer-readable memory that causes

17. 20. The non-transitory computer readable memory of claim 16, wherein the computer readable instructions cause the conductive structures to be positioned no more than 1.5 millimeters away from the region.

18. 18. The non-transitory computer readable memory of claim 16 or 17, wherein the conductive structure comprises a gas injection nozzle disposed between a column cap of the FIB column and the sample.

19. 20. The non-transitory computer readable memory of claim 18, wherein the computer readable instructions further comprise instructions that cause the one or more processors to heat the gas injection nozzle while a negative bias voltage is applied to the gas injection nozzle.

20. 20. The non-transitory computer-readable memory of claim 18, wherein a first end of the gas injection nozzle is disposed adjacent to the region and a second end of the gas injection nozzle extends through, is electrically insulated from, and is thermally coupled to a conductive wall of a component of the vacuum chamber.

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