Reentrant gas system for charged particle microscopes

Abstract

To provide gas delivery techniques for charged particle microscopes, and specifically, reentrant gas delivery systems that deliver a gas from a low voltage potential to a high potential that allow flexible design while minimizing or eliminating gas breakdown due to high electric fields.SOLUTION: A system comprises: a focused ion beam column 106 coupled to receive a gas and generate an ion beam with or from the gas; and a fluid delivery conduit 130 extending at least between first and second electrical potentials. The fluid delivery conduit 130 is formed into a tilted helical shape, so that a fluid flowing through the fluid delivery conduit 130 experiences an electric field reversal through each winding of the fluid delivery conduit 130.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates generally to gas delivery techniques for charged particle microscopes, and more particularly to a re-entrant gas delivery system that delivers gas from a low voltage potential to a high potential, allowing for flexible design while minimizing or eliminating gas breakdown due to high electric fields. [Background technology]

[0002] Many industrial and high-tech fields use gas systems to process materials. In some of these systems, gas may be delivered from ground or low voltage to a high voltage, for example, where the gas is used to form a plasma. The delivery of gas in such systems may need to adhere to strict constraints to avoid undesirable effects, such as gas decomposition in the delivery system. These constraints help reduce or prevent such decomposition, but also reduce flexibility in designing gas delivery systems. Therefore, alternative gas delivery technologies that offer greater design flexibility while still providing reduction / prevention of gas decomposition are desired. Summary of the Invention

[0003] Disclosed herein are devices and systems for re-entrant fluid delivery techniques. An exemplary system includes a fluid delivery conduit extending between at least a first electric potential and a second electric potential, the fluid delivery conduit formed in a tilted helical shape, such that fluid flowing through the fluid delivery conduit experiences an electric field reversal through each winding of the fluid delivery conduit.

[0004] Another exemplary system includes at least a focused ion beam column coupled to receive a gas and generate a focused ion beam with or from the gas, the focused ion beam column receiving the gas at a second potential, and a gas delivery system coupled to supply gas to the focused ion column, the gas being at a first potential at a first location within the gas delivery system. The gas delivery system includes a fluid delivery conduit extending between at least the first and second potentials, the fluid delivery conduit formed in a tilted helical shape, whereby fluid flowing through the fluid delivery conduit experiences an electric field reversal through each winding of the fluid delivery conduit. [Brief explanation of the drawings]

[0005] [Figure 1] 1 is an exemplary dual beam microscope including a re-entrant gas delivery system in accordance with one or more embodiments of the present disclosure. [Figure 2] 1 is an exemplary reentrant system according to an embodiment of the present disclosure. [Figure 3A] 1 is an exemplary gas conduit according to an embodiment of the present disclosure. [Figure 3B] 1 is an exemplary mandrel according to an embodiment of the present disclosure. [Figure 4] 1 is an exemplary reentrant system according to an embodiment of the present disclosure. [Figure 5A] 1 is an exemplary re-entrant gas delivery conduit according to an embodiment of the present disclosure. [Figure 5B] 10 is an exemplary plot illustrating the change in overall potential and field reversal in a gas delivery conduit, according to one embodiment of the present disclosure.

[0006] Like reference numerals refer to corresponding parts throughout the several views of the drawings. DETAILED DESCRIPTION OF THE INVENTION

[0007] Embodiments of the present invention are described below in the context of a charged particle microscope including a re-entrant gas delivery system for supplying gas from low to high voltages. The re-entrant gas system provides a flexible design while reducing gas breakdown progressing through the system. For example, a mandrel around which a gas conduit is wrapped in a slanted spiral shape provides a path for the fluid to undergo multiple electric field reversals, which can prevent gas breakdown from propagating through the conduit. Such a gas delivery system allows for flexible conduit designs, including lengths and shapes. However, it should be understood that the techniques described herein are generally applicable to a wide range of gas delivery systems and devices and are not limited to any particular device type disclosed herein.

[0008] As used in this application and the claims, the singular forms "a," "an," and "the" include the plural forms unless the context clearly dictates otherwise. Additionally, the term "includes" means "comprises." Furthermore, the term "coupled" does not exclude the presence of intermediate elements between the coupled items.

[0009] The systems, devices, and methods described herein should not be construed as limiting in any way. Instead, the present disclosure is directed to all novel and non-obvious features and aspects of the various disclosed examples, alone and in various combinations and subcombinations with one another. The disclosed systems, methods, and devices are not limited to any particular aspect or feature or combination thereof, and the disclosed systems, methods, and devices do not require that any one or more particular advantages be present or problems be solved. While any theory of operation is for ease of explanation, the disclosed systems, methods, and devices are not limited to such theory of operation.

[0010] Although some operations of the disclosed methods are described in a particular sequential order for convenience of presentation, it should be understood that this description style encompasses rearrangement unless a specific order is required by specific language described below. For example, operations described sequentially may in some cases be rearranged or performed simultaneously. Moreover, for simplicity, the accompanying figures may not show the various ways in which the disclosed systems, methods, and apparatuses can be used in conjunction with other systems, methods, and apparatuses. Additionally, this specification sometimes uses terms such as "generate" and "provide" to describe the disclosed methods. These terms are high-level abstractions of the actual operations that are performed. The actual operations that correspond to these terms will vary depending on the particular implementation and will be readily recognized by those skilled in the art.

[0011] In some instances, values, procedures, or devices are referred to as "lowest," "best," "smallest," etc. It will be understood that such descriptions are intended to indicate that choices can be made from among many functional alternatives used, and that no such choice is necessarily better, smaller, or otherwise more preferable than other choices.

[0012] There are many industrial applications, both focused and broadband, that require gases to establish a process medium, such as a plasma or ion beam. In such applications, gases may be delivered to chambers or components at high potentials, such as tens of kilovolts. However, such gases are typically at very low voltages before reaching the high-voltage region, and this change in potential can cause problems such as gas decomposition within the delivery system. If a gas decomposes during transport, the decomposition can cause a cascade effect that progresses through all gases in the delivery system. Such decomposition can cause process interruptions, equipment failure, and physical injury to nearby personnel. Gas decomposition is well understood and is generally described by the Pachen curve for various gases. Those skilled in the art generally understand that the Pachen curve provides guidance on the minimum gas conduit length to prevent gas decomposition for a given delivery voltage. Unfortunately, in high-voltage applications, this requires long delivery lines, especially for gases delivered at low pressures, and such solutions offer little design flexibility in both physical and operational parameters. Therefore, new solutions are desirable.

[0013] One technique for addressing this problem is a reentrant gas delivery system, in which any fluid traveling through the system is subjected to multiple field reversals, providing a deterrent to any decomposition that occurs. A reentrant gas system can include a conduit formed in a tilted helix, with each turn of the helix containing both forward and reverse travel. The conduit is shaped so that, in a simple analogy, the fluid moves two steps forward and one step backward with each turn. Such systems allow for design flexibility, as the overall shape of the conduit can be compressed and varied. For example, the shape can be cylindrical or conical. This flexibility allows designers to design with fewer constraints.

[0014] 1 is an exemplary dual-beam microscope 100 including a re-entrant gas delivery system according to one or more embodiments of the present disclosure. The microscope 100 can be used to image and prepare samples using a focused ion beam with gas provided by the re-entrant gas delivery system. The re-entrant gas delivery system provides flexibility in gas delivery design while reducing or eliminating some gas decomposition mechanisms.

[0015] The microscope 100 includes an electron column 104, a plasma-based focused ion beam (PFIB) column 106, a movable stage 112, and a detector 108, all housed in or coupled to a vacuum chamber 102. The electron column 104 is a scanning electron column (SEM) in some instances, but may be omitted in other instances, such that the microscope 100 includes only a PFIB column. The electron column 104 provides an electron beam 114 to a sample 110 disposed on the stage 112 to image the surface of the sample 110. The detector 108 detects secondary electrons and / or backscattered electrons emitted or reflected from the sample 110 in response to the electron beam 114.

[0016] The PFIB column 106 generates and directs an ion beam 116 toward the sample 110 for imaging and / or processing the sample. For imaging, the detector 108 detects secondary and / or backscattered electrons emitted or reflected from the sample 110 in response to the ion beam 116. In some examples, the ion beam 116 can interact with a precursor gas present at the surface of the sample 110 to etch the sample or deposit material on the surface of the sample. Such precursor gases can be supplied by a gas injection system (not shown), as is known in the art.

[0017] The PFIB 106 includes a plasma-based ion source 120 that receives one or more gases from a gas reservoir 128. The one or more gases interact with the generated plasma to form an ion beam 116. The one or more gases can be reactive, non-reactive, or a mixture thereof. Gases from the gas reservoir 138 are supplied to a re-entrant gas delivery system 122 via pipes / tubes 124. Gases are typically received by the re-entrant gas delivery system at ground potential, while the ion source 120 is typically at tens of kilovolts. This change in potential can cause the gases to decompose, which can be reduced or eliminated by the re-entrant gas system 122.

[0018] The reentrant gas system 122 includes a reentrant gas conduit 130, or conduit 130 for short, supported by a structure 126, and an ion source 120. Generally, the reentrant gas conduit 130 includes a conduit formed in a tilted helix, with each turn of the helix tilted back a portion of the distance traveled. As used herein, reentrant suggests that the fluid delivered by the conduit travels from one end to the other through a path that travels forward and backward in voltage by different amounts or lengths for each turn of the tilted helix. As used herein, the fluid sequentially advances a certain amount of voltage, re-enters with a smaller amount of voltage, then advances to a larger amount of voltage, followed by appropriate smaller re-entry steps, progressing from a lower voltage to a higher voltage, and so on. In some examples, the amount of forward and backward travel may be determined based on the strength of the electric field through which the conduit travels, the electric field establishing a gradient of equipotential lines between two electrodes. For example, the pathway may provide for the fluid to advance through X equipotential lines and return through Y equipotential lines during one revolution / winding of the inclined helix, where Y is less than X. In some examples, X is 2 and Y is 1, although other combinations are contemplated herein and encompassed by this disclosure. Generally, the pathway, which may be related to the angle of inclination, may be based on the strength of the gradient, with a higher gradient increasing the difference between X and Y, while a lower gradient decreasing the difference. By moving the gas back and forth through the equipotential lines, the gas therein undergoes at least one field reversal. Another example includes, when equipotential lines are established between two potentials, each winding of the fluid delivery conduit advances through at least two equipotential lines and returns through at least one equipotential line, traveling via an adaptive configuration along equipotential lines of any shape. Field reversal allows for the reduction or elimination of the possibility of gas decomposition when traveling from a low voltage potential (e.g., ground) to a high voltage potential (e.g., approximately 35 kV). Additionally, the angled helix shape also provides flexibility in the design and sizing of the re-entrant gas delivery system 122 .

[0019] In some examples, the conduit 130 may be wrapped around a support mandrel or other shaped structure (see, e.g., FIGS. 2 and 4), which extends between the support 126 and the ion source 120. The support mandrel may be a rod formed from an insulating material with grooves formed in its outer surface for holding the conduit 130. In addition to rod-shaped mandrels, the support structure may have a conical shape with various height-to-radius ratios.

[0020] 2 is an exemplary re-entrant system 222 according to an embodiment of the present disclosure. Re-entrant gas system 222, or system 222 for short, is an example of re-entrant gas system 122. System 222 provides flexibility in design and sizing, providing a fluid, such as a gas, from a low voltage potential to a higher voltage potential while reducing or eliminating the possibility of fluid breakdown due to a high voltage field. While system 222 may be used in a microscope setting, system 222 may be used in any system that uses gas at high voltage but is provided to high voltage components from a lower voltage. An exemplary system is a plasma arc welding system.

[0021] System 222 includes support 226, electrode 220, and re-entrant gas conduit 230, or conduit 230 for short. Support 226 may provide physical support for conduit 230 and, in some instances, may be electrically conductive so that it can act as an electrode. Electrode 220 may be part of a high-voltage ion or plasma generation system to which gas is supplied by conduit 230. In some instances, support 226 may be at a lower voltage, such as ground, than electrode 220, which may be several tens of kV. For example, electrode 220 may be at a voltage in the range of 10 kV to 60 kV. The voltage difference between support 226 and electrode 220 generates an electric field that forms equipotential lines 236. The rate of change of the electric field, as well as the spacing and potential value of the equipotential lines, are established by the distance between support 226 and electrode 220 and their relative voltage levels.

[0022] The conduit 230 is formed from a mandrel 234 and a gas conduit 232. The mandrel 234, as the term mandrel suggests, is rod-shaped and may be made from an insulating material. Additionally, the mandrel 234 may have a groove formed in its exterior surface sized to receive the conduit 232. The groove is optional and may be used to hold the conduit 232 in a desired position and shape. The conduit 232 may be formed from a flexible tube that can be wrapped around the mandrel 234 with a desired radius of curvature. Additionally, the conduit 232 may be formed from a material that will not degrade from the gas or fluid delivered therethrough. Alternatively, the groove formed in the mandrel 234 may be encapsulated so that the groove itself forms the conduit 232, or the conduit 232 may be cast into the mandrel 234. Furthermore, once formed through the mandrel 234, the conduit 232 can be used independently of the mandrel 234. Additionally, conduit 232 used independently from mandrel 234 may be used to deliver gas to a moving electrode, for example, where the spacing between electrode 226 and electrode 220 is dynamically changing. Any of these options are possible, and the use of separate conduits and mandrels is for illustrative purposes only and is not a limitation of the technology disclosed herein.

[0023] As described above with respect to reentrant systems, conduit 232 is wound around mandrel 234 in a slanted helix, so that as fluid flowing through conduit 232 travels from inside to outside, it travels forward a distance and then backs away a portion of that distance in one winding before beginning the next. For example, if fluid enters winding A (into the page), it exits at position A', two pitches after A. As used herein, pitch is the distance between adjacent grooves in mandrel 234. The pitch, or more specifically, the number of pitches the conduit travels in each winding, is based on the distance between adjacent equipotential lines 236. Continuing with this example, fluid entering point B exits at B', and similarly for C and C', D and D'. Thus, fluid traveling through conduit 232 travels forward through two or more equipotential lines and backs away one equipotential line per winding. This process of increasing the potential and decreasing it with each expansion causes the fluid within the conduit 232 to experience a field reversal at each winding, which helps inhibit or prevent fluid breakdown in high field applications. The 2-to-1 equipotential change is only one example, and other variations are contemplated herein. It should also be noted that the conduit 232 can be used without the mandrel 234 used to provide physical support for the conduit.

[0024] 3A is an exemplary gas conduit 332 according to one embodiment of the present disclosure. The conduit 332 illustrates the angled helical shape of the conduit 232, which can be used as a re-entrant gas conduit. As seen in FIG. 3A, the conduit 332 is in a rotated view from that shown in FIG. 2, as indicated by the inward and outward arrows.

[0025] 3B is an exemplary mandrel 334 according to one embodiment of the present disclosure. The mandrel 334 exhibits grooves, their spacing, and amount of tilt such that a conduit wound thereon provides a desired field reversal for a given range of equipotential intervals.

[0026] 4 is an exemplary re-entrant system 422 according to an embodiment of the present disclosure. System 422 is similar to system 222 in many respects, such as support 426, electrode 420, and will not be discussed again for the sake of brevity. System 422 includes a support structure 434 around which a conduit 432 is wrapped. In contrast to mandrel 234, support structure 434 is cone-shaped with a radius r and a height h. Different ratios of h and r can be used to design the length, base width, and angle of the cone, providing design flexibility.

[0027] FIG. 5A illustrates an exemplary re-entrant gas delivery conduit 530 according to an embodiment of the present disclosure. Conduit 530 is a detailed version of conduit 230, showing the voltage levels of cells 8-20 and equipotential lines 236. The cell numbers indicate the associated winding locations on the top and bottom of mandrel 534 on which conduit 532 is placed. As seen in FIG. 5A, each winding is separated by at least two equipotential lines 536, as indicated by the matching top and bottom cell numbers. Furthermore, when one winding transitions to the next, the change from, say, top cell 10 to bottom cell 11, indicates that conduit 532 travels through three to four equipotential lines before returning through two equipotential lines in top cell 11. This repeated forward and reverse travel through equipotential lines establishes field reversal.

[0028] 5B is an exemplary plot 501 showing the change in overall potential and field reversal of a gas delivery conduit 530, according to one embodiment of the present disclosure. The left axis shows the voltage on the cells as the conduit 532 progresses from 5 kV to approximately 19 kV. As can be seen, the voltage change from cell 10 to cell 20 exhibits a step-like pattern as the cells progress back and forth through the equipotential lines. The right axis shows the field reversal as the conduit 532 progresses between the same potentials. As shown, each cell experiences a field change from approximately -1 kV / cm to approximately 3 kV / cm.

[0029] The embodiments discussed herein to illustrate the disclosed technology should not be considered limiting and merely provide examples of implementation. For example, a conduit can be wrapped around a structure of any shape, such as a pyramid, shear, hexagon, etc., so long as a field reversal occurs in any fluid flowing therethrough. Those skilled in the art will recognize myriad other ways in which the disclosed technology can be implemented that are contemplated herein and within the scope of this disclosure.

Claims

1. 1. A fluid delivery system comprising:

1. A fluid delivery system comprising: a fluid delivery conduit extending between a first electric potential and a second electric potential, the fluid delivery conduit formed in a tilted helical shape whereby fluid flowing through the fluid delivery conduit is subjected to an electric field reversal through each winding of the fluid delivery conduit.

2. 10. The fluid delivery system of claim 1, further comprising a mandrel extending between a first electrode and a second electrode, the fluid delivery conduit wrapped around the mandrel, and the first and second electrodes at the first and second potentials.

3. The fluid delivery system of claim 2 , wherein the mandrel is rod-shaped.

4. The fluid delivery system of claim 2 , wherein a groove is formed in the mandrel, the groove being positioned such that the fluid delivery conduit fits within the groove.

5. The fluid delivery system of claim 1 , wherein the first potential is a low voltage and the second potential is a high voltage.

6. The fluid delivery system of claim 5, wherein the low voltage is ground and the high voltage is in the range of 10 kV to 50 kV.

7. The fluid delivery system of claim 1 , further comprising a conical support structure extending between the first electrode and the second electrode, the fluid delivery conduit wrapping around the conical support structure.

8. 2. The fluid delivery system of claim 1, wherein equipotential lines are established between the first potential and the second potential, and each winding of the fluid delivery conduit advances through at least two equipotential lines and returns through at least one equipotential line.

9. 9. The fluid delivery system of claim 8, wherein equipotential lines are established between the first potential and the second potential, and each winding of the fluid delivery conduit advances through at least two equipotential lines and returns through at least one equipotential line that travels through an adaptive configuration along equipotential lines of any shape.

10. The fluid delivery system of claim 1 , wherein the fluid delivery conduit is disposed within a charged particle column.

11. The fluid delivery system of claim 10 , wherein the charged particle column is a plasma focused ion beam column.

12. 1. A system comprising: a focused ion beam column coupled to receive a gas and generate a focused ion beam with or from the gas, the focused ion beam column receiving the gas at a second potential; a gas delivery system coupled to supply the gas to the focused ion beam column, the gas being at a first potential at a first position, the gas delivery system a fluid delivery conduit extending between the first potential and the second potential, the fluid delivery conduit formed in a tilted helix shape whereby fluid flowing through the fluid delivery conduit experiences an electric field reversal through each winding of the fluid delivery conduit.

13. 13. The system of claim 12, wherein the gas delivery system further includes a mandrel extending between a first electrode and a second electrode, the fluid delivery conduit wrapped around the mandrel, and the first and second electrodes at the first and second potentials.

14. The system of claim 13 , wherein a groove is formed in the mandrel, the groove being positioned such that the fluid delivery conduit fits within the groove.

15. 13. The system of claim 12, wherein the first potential is a low voltage and the second potential is a high voltage.

16. 16. The system of claim 15, wherein the low voltage is ground and the high voltage is in the range of 10 kV to 50 kV.

17. The system of claim 12 , wherein the gas delivery system further includes a conical support structure extending between the first electrode and the second electrode, the fluid delivery conduit wrapping around the conical support structure.

18. 13. The system of claim 12, wherein equipotential lines are established between the first potential and the second potential, and each winding of the fluid delivery conduit advances through at least two equipotential lines and returns through at least one equipotential line that travels via an adaptive configuration along equipotential lines of any shape.

19. The system of claim 12 , wherein the focused ion beam column is part of a dual beam charged particle microscope.

20. The system of claim 12 further comprising a gas container coupled to the gas delivery system, the gas container storing the gas.

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